TEXTILE DYES

By Mansoor Iqbal M.Sc (Applied Chemistry) Senior Research Associate, Textile PCSIR Laboratories complex Karachi Ministry of Science & Technology Government of Pakistan.

REHBAR PUBLISHERS KARACHI

COPY RIGHT

Cover story: Original specimen of Mauvein, the first organic dye ever synthesized, made by W.Perkin in 1856.Some yarn colored by this dye and ALIZARINE, another important dye.courtesy of M.Holford of material in the science museum, London.

Dedicated to my Father (Late)

Mr. Nabi Hussain

FOREWORDS

It is indeed a matter of much pleasure to write the forewords of the book written by my student Mr.Mansoor Iqbal.I always please my student in writing such monographs. I do also understand, writing a technical book is a difficult task.Mr.Mansoor has performed an outstanding example, which definably follow up and continuation. Looking at the topics and contents of the book it was much needed book for industry and academia, Textile industry needs such books to upgrade the skills and knowledge of the people involved in processing, teaching and research and development activities. I am sure this book will fulfill the reader’s to their highest degree of satisfaction. However improvements are always possible. I must request the readers to indicate the improvements and suggestion to the author so that he can incorporates the same in the later edition. (Dr.Syed Ishrat Ali) Professor & Chairman

Dept of Applied Chemistry & Chemical Technology University of Karachi

April 26, 2008

PREFACE

Textile industry is the backbone of our country economy. During last few years a wide net of the professional textile institutes both in private and Government sector have been established that shows the present demand and interest of our peoples in this field. The textile books available in our country are very rare and beyond the scope of our student both from purchasing and understanding point of view. Textile dyes is the first attempt of its kind ever published in Pakistan. Dyes are coloured organic compounds, which impart colour to the fabric. Most important classes of dyes for textile application are discussed in a simple and easy style. Discussions are lead from fundamental concepts to the fastness properties evaluations of dyes. Interactions of dye molecule with different fiber polymer system have also been discussed. A chapter Banned Amines also included, which will helpful to understand the modern ecological issues of dyestuffs and textile industry. The book will be a handy and reliable source of information for textile students, teachers of textile chemistry, sales executives in dyes, dye house laboratories, dyeing department of textile mills, research workers and many others. Reference departments in the libraries will find this volume an essential addition to their offerings. Suggestions are welcome for the improvement in book in next edition. I offer my warm welcome to book lovers, please feel free to contact me to share knowledge, literature and books regarding textile.

MANSOOR IQBAL Senior Research Associate, Textile

E-mail: mansoorprocessing @ hotmail.com Cell: 0344 - 3046460

March 25, 2008

CONTENTS

Chapter # 1 DYES & COLOUR (1-6)

Dyes and colour Modern theory of colour Otto Witt theory of colour Valence bond approach to colour Bathochromic effect

Chapter # 2 HISTORY OF DYESTUFFS (7-21)

Chapter # 3 CLASSIFICATION OF DYES (22-46)

Classification of Dyes Classification according to chemical structure Nitro Dye Azo Dyes Aniline Yellow Butter Yellow Chrysoidine Methyl Orange Orange II Para Red Resorcin Yellow Disperse Red 1 Congo Red Diphenlymethane Dyes Auramine O

Triphenylmethane Dyes Malachite Green Pararosaniline Rosaniline Crystal Violet Xanthene Dyes Fluorescene Eosin Rhodamine B Phthaeleins Phenolphthalein Indigoid and Thioindigoid Dyes Preparation of Indigo Structure of Indigo Tyrian Purple Thioindigo Anthraquinoid Dyes Alizarin Structure of Alizarin Classification according to method of application Direct Dyes Mordant Dyes Vat Dyes Ingrain Deys Disperse Dyes

Chapter # 4 DYES AND FIBRE POLYMER SYSTEM (47-62)

Wool Fibres Silk Fibres Cellulosic Fibres Monoazso Dyes Dyes with Mixed Chromophores Cellulose Acetate Fibres Cellulose Triacetate Fibres Poyamide Fibres Polyester Fibres Polypropylene Fibres Polyurethane Fibres Polyacrylonitrile Fibres How do dyes stick to fibres?

Chapter # 5 REACTIVE DYES (63-86)

Nucleophilic substitution systems Vinylsulphone dyes Evidence for chemical combination Commercial popular reactive dyes Cold Dyeing Brands Hot dyeing brands Bifunctional Dyes (Sumitomo Chemicals Japan) Reactive dyes in pakistan Sumitomo chemicals (Osaka, Japan) Kyung-in synthetic corporation Reaffix dyestuffs Korea P.T.Sinar (Indonesia)

Meghmani dyes & intermediates India Jay chemicals India Dyestar (Germany) Sunfix Chemdyes Corporation Everzol dyes (Taiwan) Clarient dyes Switzerland

Chapter # 6 DIRECT DYES (87-91)

Direct dyes

Chemical constitution of direct dyes

Classification according to dyeing behavior

Class A

Class B

Class C

Chapter # 7 DISPERSE DYES (92-100)

Azo Dyes Anthraquinone Disperse Dyes Miscellaneous Disperse Dyes Methine or Styryl Dyes Quinphthalone dyes Coumarin Dyes

Chapter # 8 VAT DYES (101-109)

Indigoid Dyes Thioindigoid Dyes Anthraquinone Vat Dyes

Chapter # 9 SULPHUR DYES (110-116)

Sulphurised Vat Dyes

Ready-reduced and Solubilised Sulphur Dyes

Recent Developments

Examples of Important Commercial Sulphur Dyes

Chapter # 10 ACID (ANIONIC) DYES (117-123)

Acid or anionic dyes

Acid dyes can be divided into four groups

Dyeing Process

Dyeing of Nylon Carpets

Application of Acid Dyes to Silk

Dyeing of Modified Acrylic and Polypropylene

Chapter # 11 BASIC (CATIONIC) DYES(124-126)

Basic or cationic dyes

Dyeing of Acrylic Fibres

Chapter # 12 BANNED AMINES (127-142)

What are banned amines?

What is Eco-Labeling of Textiles?

Name the agencies, which have accredited Textiles

Committee Laboratories?

what are the advantages of testing of textiles in an

accredited laboratory?

State the list of dyes banned by Government?

Ecomark criteria for textiles

Product specific requirement

Jute and jute products

Silk and silk products

Pesticide registered for use on cotton

Coupled Amines released from Azo-dyes

Chapter # 13 FASTNESS PROPERTIES OF DYES (143-166)

Colour fastness

Acids and Alkalies

Evaluation and Classification

Colourfastness to Bleaching with Chlorine

Evaluation and Classification

Colourfastness to Bleaching with Peroxide

Carbonizing (AATCC 11-1975)

Crocking (AATCC 8-1974/116-1974)

Degumming (AATCC 7-1975)

Dry cleaning (AATCC 132-1976)

Fulling (AATCC 2-1975)

Dry Heat (Excluding hot Pressing)

Hot Pressing (AATCC 133-1976)

Light fastness

Lightfastness (General Method) (AATCC 16-1974)

Lightfastness-Carbon Arc (AATCC –16-A-1974)

Sunlight-Fastness (AATCC 16B-1974)

Daylight Fastness (AATCC 16C-1974)

Lightfastness Carbon Arc Alternate Light Darkness

(16D-1974)

Lightfastness-Xenon Lamp-Continuous Light

Lightfastness-Xenon Lamp-Alternate Light-Darkness

(AATCC 16F-1974)

Carbon-Arc Lamp (Fade-Ometer)

Exposure Cabinet

Black-Panel Thermometer

Lightfastness Standards

Xenon-Arc Lamp

Alternate Wash-and-Light (AATCC 83-1974)

Phototropism (AATCC 139-1975)

Ozone in the Atmosphere Under Low Humidity

Wash fastness

Prespiration (AATCC 15-1976)

Steam Pleating (AATCC 131-1974)

Stoving (AATCC 9-1975)

Water Spotting (AATCC 104-19756)

Dispersibility of Disperse Dyes

Dyestuff Migration (AATCC 140-1976)

Dyes & Colour

1 Any coloured compound is not a Dye or Dyestuff. A dye is a

coloured organic compound that absorbs light strongly in the visible region and can firmly attach to the fiber by virtue of chemical and physical bonding between group of the dye and group on the fiber. To be of commercial importance a dye should be fast to light, rubbing and water.

Colour and dye have always played an important role in the life of man from time immemorial. Preparation of a colour and dyeing of cloth date back to antiquity. Fabrics dyed in indigo were found in the tombs of predyanstic Egypt. Let us now try to understand how we get sensation of colour. Modern theory of colour:

Colour is a physiological sensation associated with the wavelength of light striking the retina of the eye. The sensation of colour is produced when light having a wavelength within the visible region of electromagnetic spectrum strikes the retina of the eye. The visible region of the spectrum extends from 4000 to 7500 Å in wavelength.

4000 4500 5000 5500 6000 7000 Ultra Viole

Violet Blue Green Yellow Orange Red Infra red

High Increasing Energy Low When white light falls on a substance, the light may be completely reflected and in this case substance will appear white. If it is completely absorbed, the substance will appear black. If a substance absorbs all visible light except that corresponding to e.g. yellow, it will transmit or reflect only yellow colour and will be seen as yellow. However, it is 1

generally seen that, light of only one colour is absorbed in which case the substance will appear to have the complementary colour. Thus, if the light is absorbed from the violet region of spectrum, the substance will be seen as yellow. If light is absorbed from the red region, the substance will appear green.

Wavelength absorbed (Å)

Colour absorbed Visible colour (complementary colour)

4000 – 4350 Violet Yellow Green 4350 – 4800 Blue Yellow 4800 – 4900 Green blue Orange 4900 – 5000 Blue green Red 5000 –5600 Green Purple 5600 – 5800 Yellow green Violet 5800 – 5950 Yellow Blue 5950 – 6050 Orange Green blue 6050 – 7500 Red Blue green

Otto Witt theory of colour (1876): An early theory of dyes first formulated by O. Witt provided a basis for understanding the reaction between colour and structure of the molecule. According to the O. Witt colour theory a dye is made up of two essential kinds of parts, Chromophores and Auxochromes. He designated a group that produces colour as a chromophore (Gr, Kuroma. colour + Phors carrier). Chromophores are unsaturated groups. Presence of at least one such group is essential to produce a colour in an organic compound and a molecule containing such a group is called as chromogen. Some most effective chromophores are

0 00

O

-N=N--N=0

Azo

Nitroso

N+

0

0

OP-Quinad O-Quinad

2

Thus for example nitrobenzene is pale yellow, azobenzene is orange-red, p-quinones are yellow and o-quinones are orange or red.

Certain other unsaturated groups produce colour only when several of them are present in a molecule and when they are conjugated. They are

Thus though acetone is colourless, biacetyl colour.

C = C

Ethylene

C = O

Carbonyl

C = N -

Azomethine

O || CH3 – C – CH3 Acetone Colourless O O || || CH3 – C – C – CH3 Biacetyl Yellow O O || || CH3 – C – CH3 – C – CH3 Acetonyl Colourless

Acetone O. Witt also observed that certain groups, while not producing colour themselves, are able to intensify the colour when present in a molecule together with a chromophore. These are called auxochromes (Gr, auxanein = to increase). The most effective auxochromes

H

| –OH –OR –NH2 –N–R –NR2 Hydroxyl Alkoxy Amino Alkylated Amines Thus nitrophenols and nitroanilines are more intensely coloured than nitrobenzene and aniline and are deep yellow to orange. Further auxchoromes are salt forming groups, i.e., they are basic or acidic and makes the coloured compound to attach itself to the fabric, so that it is fast to light, soap and water. Acidic auxochromes like – OH, --COOH and – SO2H give acidic dyes and basic auxochromes like – NH2 3

– NHR and – NR2 gives basic dyes. Auxochromes like – SO3H group has little value as auxochrome but it has a solublishing effect. The halogen atom also functions as auxochrome and the relative order of colour intensifying effect is I>Br>Cl. It can be observed that all the auxochromic groups contain atoms with unshared pair of electrons. According to Witt theory of colour and constitution chromogen is a compound which contains a chromophore –N=N. It is a bright red compound but not a dye.

C6H5 – N = N – C6H5 On the other hand p-hydroxy-azo benzene is acid dye because

H2O – C6H4 – N = N – C6H5It contains – OH group, an acid, auxochrome, and p-amino azobenzene is a basic dye, as it has basic auxochrome – NH2. Azobenzene, anthraquinone, dinitro benzene are chromogens O O || || and are coloured due to the presence of –N=N, --C--C, --NO2, groups respectively. The chloromogens, on reduction give the colourless compounds, for examples azobenzene, a bright red compound, on reduction forms the colourless hydrazobenzene.

H2 C6H5 – N = N – C6H5 C6H5 – NH – NH –C6H5 Azobenzene Hydrazobenzene Sometimes the conversion is reversible. In this case the reduction products are called “Lecuo compounds”. H2 Azobenzene Red Hydrazobenzene (colourless)

Oxidation

H2 Indigo Blue Indigo white (colourless)

Oxidation Sometimes reduction completely decomposes the coloured compound, such reduction products are called “Leuco compounds”. 4

Valence bond approach to colour: Valence bond approach to colour: Like many other theories, the Witt theory has also been replaced by modern electronic theory. According to this theory, it is the resonance stabilization of excited states that is responsible for the absorption in the visible region. When ultraviolet or visible light is absorbed by a molecule, an electron is excited, that is, it is promoted to an orbital of higher energy. The wavelength of light absorbed depends on the energy difference between the excited and ground states of the molecule. The smaller difference between the two states, the longer is the wavelength of the light absorbed.

Like many other theories, the Witt theory has also been replaced by modern electronic theory. According to this theory, it is the resonance stabilization of excited states that is responsible for the absorption in the visible region. When ultraviolet or visible light is absorbed by a molecule, an electron is excited, that is, it is promoted to an orbital of higher energy. The wavelength of light absorbed depends on the energy difference between the excited and ground states of the molecule. The smaller difference between the two states, the longer is the wavelength of the light absorbed. The energy required to promote an electron depends upon the environment of the electron. Sigma (σ) bond electrons are firmly held and very high energy (or short wavelength) is necessary to promote electrons and may at times break the molecule and form free radical.

The energy required to promote an electron depends upon the environment of the electron. Sigma (σ) bond electrons are firmly held and very high energy (or short wavelength) is necessary to promote electrons and may at times break the molecule and form free radical. Pi (π) electrons are less firmly held and require less energy (or longer wavelength) to excite. Electrons belonging to conjugated systems required even less energy (still longer length). Conjugation and resonance stabilize the excited state by sharing and delocalizing higher energy of the excited electron. As conjugation and resonance increases, the wavelength of light absorbed also increases and when the wavelength is long enough to be in the visible region, we observe colour. This can be explained with the help of following example.

Pi (π) electrons are less firmly held and require less energy (or longer wavelength) to excite. Electrons belonging to conjugated systems required even less energy (still longer length). Conjugation and resonance stabilize the excited state by sharing and delocalizing higher energy of the excited electron. As conjugation and resonance increases, the wavelength of light absorbed also increases and when the wavelength is long enough to be in the visible region, we observe colour. This can be explained with the help of following example. Ethylene absorbs light in the ultraviolet part of the spectrum 1800 Å. Butadiene, with two conjugated double bonds, absorbs at 8170 Å (a wavelength closer to visible region) and hexatriene, with three conjugated double bonds, absorbs at 2580 Å (a wavelength still closer to visible region). But all the three compounds are colourless. However, as the number of conjugated double bonds increases, the absorption falls in the visible region, for example in β-carotene there are eleven conjugated double bonds and absorbs at 4510 Å, that is, in the visible region. The light absorbed is blue and we see the complementary orange colour.

Ethylene absorbs light in the ultraviolet part of the spectrum 1800 Å. Butadiene, with two conjugated double bonds, absorbs at 8170 Å (a wavelength closer to visible region) and hexatriene, with three conjugated double bonds, absorbs at 2580 Å (a wavelength still closer to visible region). But all the three compounds are colourless. However, as the number of conjugated double bonds increases, the absorption falls in the visible region, for example in β-carotene there are eleven conjugated double bonds and absorbs at 4510 Å, that is, in the visible region. The light absorbed is blue and we see the complementary orange colour.

5

CH2=CH–CH = CH21: 3 Butadiene (Colourless)

CH2 = CH – CH = CH – CH = CH2 1: 3: 5 Hexantriene 1: 3: 5 Hexantriene CH2 = CH – CH = CH – CH = CH2

(Colourless) (Colourless)

H2C + CH2Ethylene

(Colourless)

H

H

2

22

2

23

C

C

H

H

H

H3 3C

C

H

H H32

CCH

H3 3C

C

H3 3 3 3

CCH=CHC=CHCH=CHC=CHCH=CHCH=CCH=CHCH=CCH=CHC

H H H H

Β-CAROTENE Benzene absorbs light at 2550 Å and is colourless. Aniline, which absorbs light at about 3000 Å, is also colourless; nitrobenzene absorbing light slightly above 4000 Å is pale yellow and p-nitro aniline absorbing light at 4500 Å is a yellow compound. Bathochromic effect:

In this case benzene ring may be considered to be chromophore, while amino group and nitro group auxochromes. When they are conjugated, the longer resonance system decreases the energy gap between the ground state and excited state transitions, thus producing visible colour. All these groups, which lengthen wavelength of absorption, are bathochrome groups. Thus displacements (or shift) to longer wavelength are known as bathochromic effects or bathochromic shift and displacements to shorter wavelength are hypsochromic. Hypsochromes are groups which decrease resonance. This is done by forcing the pi (π) orbitals out of planarity. For example when alkayl group on benzene ring is ortho to adjacent rings or chains, the molecule is distorted out of planarity and resonance is decreased. As the number of fused rings increases, the absorption in the visible region also increases e.g. naphthacene absorbs in blue region and is yellow. Pentacene absorbs in orange region and is blue. Graphite, which is a sheet of benzene rings is black, it absorbs all colours almost completely.

6

History of Dyestuff

2 The historical development of the synthetic dyestuffs dates back to 1856, when eighteen year old, W.H. Perkin discovered the synthesis of Mauveine, a basic dye, by accident, while he was engaged in the study of the action of potassium dichromate on aniline sulphate. He successfully converted the process he had developed in laboratory to a large-scale production, and demonstrated the application of the dye on silk. The intermediates nitrobenzene and aniline required in the production were also made commercially by him. Nitrobenzene was earlier prepared by Mansfield in 1847.

7

This historical discovery of the first synthetic dye was followed by the syntheses of numerous dyestuffs made for the first time in their laboratories by the individuals or the group of scientists putting in constant efforts and getting due credit for their discoveries. Earlier discoveries worth mentioning include the synthesis of Magenta, a basic dye (Verguin, 1859), Aniline blue, a basic dye (Girard and de Laire, 1860), Aurine, a basic dye (Runge and then Kolbe and Schmitt, 1861), Methyl Violet, a basic dye (Bardy, 1866), Induline, a basic dye (Dale and Caro, 1863), Bismark Brown, an azo dye (Martius, 1863), Aniline Black, an ingrain dye (Light foot, 1963) Alizarin, an anthraquinone dye (Graebe and Libermann, 1868), Fluorescein, a basic dye (Bayer, 1871), Eosin, a basic dye (Caro, 1871) Orange II and Orange IV, azo dyes, (Roussin, 1876,) Methylene Blue, a basic dye (Caro, 1876), Malachite Green, a basic dye (O’Fischer, 1877), Indigo, an indigoid vat dye (Bayer, 1880), Para red, an azo dye (Read, Holiday and Sons, 1880), Crystal Violet, a basic dye (Kern, 1883), Auramine, a basic dye (Kern, 1883), Congo Red, an azo dye (Boettiger, 1884), Tartrazine, an azo dye (Ziegler, 1884), Indigo, an indigoid vat dye by newer syntheses (Heumann, 1890 and Sandmeyer, 1899), Indanthrene blue, a vat dye (Bohn, 1901), Benzo fast scarlet 4 BS, an azo dye (Israel and Kolthe, 1900), Indanthrene Dark Blue BO, Green B, and Black BB, vat dyes (Bally and Isler, 1904), Indanthrene Golden Orange G, a vat dye (Scholl, 1905), Indanthrene

8

Brown GR, olive R and Khaki GG, vat dyes (MLB, 1908 to 1911), Indanthrene violet RN, Red BN and Red Violet RRN, vat dyes (Ullmann and coworkers, 1909 and 1910), Hydron Blue R, a sulphurised vat dye (Hass, 1908), Naphtol AS, a coupling component for azoics (Grieshei-Elektron,1912), Alizarin Direct Blue A, an anthraquinone dye (Herzberg 1913) and Brilliant take colours from basic dyes (BASF, 1913) and Brilliant lake colours from basic dyes (BASF, 1913). All these discoveries required requisite intermediates for the production as large-scale ventures and the technology for the production of the intermediates suitable for the dyes was naturally made available. These discoveries were made before the First World War (1914 to 1918) and until about 1920, as the effect of the war, the progress of chemical industry became stagnent. All the discoveries made during the period mentioned above (1856 – 1914) came into picture as a result of certain other auxiliary discoveries made and certain important theoretical suggestions initiated by pioneers of organic chemistry. There is a likelihood that as an error, the invaluable work of many individuals and organizations might not have been recorded Griess discovered diazotisation in 1858 and the coupling of diazonium salts subsequently in 1864 and his work is so valuable even today, that based on his discoveries, the azo dyes were developed and today they cover partically half the quantum of the total quantity of dyestuffs under commercial use. All the chemists, including the colour chemists are also indebted to the grand services rendered by Kekule in the field of organic chemistry by suggesting his institutional benzene and allied aromatic hydrocarbons. A large number of organic reactions were investigated by various scientists during the period and nitration, sulphonation, oxidation, reduction, alkylation, quaternization, alkali fusion, thionation etc., were developed probably without the sufficient background of the knowledge of organic chemistry since the exact nature of an the action of variety of reagents was not well established. The study of the correlation of colour and chemical nature of the compounds had been attempted which no doubt helped many other scientists to choose the right tracks. The discoveries of the organic compounds like Bnaphthol H-acid J-acid, Primuline Base, various anthraquinone derivatives, etc., worked as intermediates and led to the discoveries of then novel dyestuffs which are popular even today.

9

During the First World War, Neolan colours (metal complex dyes) were discovered by the Society of Chemical Industry at Basle (1915). An important dyestuff intermediate phthalic anhydride was also discovered by air oxidation of naphthalene using vanadium pentoxide as catalhyst by Gibbs in 1917. After the first world war, the major discoveries made were in the anthraquinonoid vat dyes such as caledon Jade Green (Davas and cowlorkers, 1920), Golden yellow GK (Kranzlein and coworkers 1922), Indanthrene Navy Blue R (Wilke, 1931), etc. Thje azoic colours made by the combination of diazonium salts from fast bases and coupling components naphtols, picked up market since 1921 to early 1930s as a result of the discoveries of other members of naphtol AS series and naphtol ASG as well as a number of fast bases. Indigosols, which are the soluble vat colours, and Cyanine dyes which are useful sensitisers for photography and dyeing and printing were developed by the German industry. With the discovery of man-made fibre cellulose acetate, obtained by acetylation of the hydroxyl group present in natural fibre (cotton), newer dyestuffs were searched and Ionamines (Green and Saunders, 1922) and S.R.A. colours (Baddiley and Shepherdson, 1923) making use of aqueous dispersons of the insoluble colours for dyeing of cellulose acetate were developed. Light fast Chlorantine colours for cotton with the use of Cynuric chloride intermediate were developed by Ciba in 1924. ICI in 1934 developed a process of manufacture of copper phthalocyanine as Monostral Fast Blue BS, which was actually observed in 1928 by Dandridge as a surprise, during the manufacture of phthalimide in an iron pan. The corresponding water-soluble dyes were also marketed by ICI in 1947 and by IG which were sulphonated copper phthalocyanines. The chlorination of copper phthalocyanine afforded green pigment.

The Second World War, which broke out in 1939 once again, disturbed the progress of the dyestuff industry. Until 1945, whatever discoveries made during the World War II, were kept in dark or unpublished. It was only after 1945, except German industries, the dyestuff industries, in other developed countries started taking shape with revival of interest in earlier discoveries. Many new organizations came up and started establishing their products in the world market, for

10

which a lot of efforts were made to introduce newer products for colouration of textile fibres. With the result, a great number of new members in already established classes of dyes such as direct cotton dyes, acid dyes, vat dyes, etc. were introduced. Newer series of dyes for cellulose acetates fibre were also discovered. Pigment emulsion techniques for printing of textile materials were developed. Optical brighteners for whitening of textile fibres were introduced in the market in 1940. The first firm, Arlabs, manufacturing dyestuffs and allied products in India, began in 1940 and various firms made further progress of manufacturing various intermediates and dyes in India after the independence.

With the discoveries and exploitation of newer synthetic fibres such as polyester and polyamide, it became necessary to design new structures of dyestuffs, which could suit the dyeing of these hydrophobic fibres. There was a revival of interest to check the suitability of earlier known dyes for these fibres also, for example, acid dyes were applicable to the polyamide fibre and the series of metal complex dyes were brought in the field. The dyestuffs suitable for cellulose acetate were found to be applicable to polyester. However, they being inferior to this fibre due to its compact structure, it was necessary to modify the original cellulose acetate dyes from their fastness and dyeing character point of view. Various newer techniques were developed in the application of the dyestuffs on polyester and in one of such developments, the application of the insoluble dyes in the form of microfine disperions called as disperse dyes were brought into commercial practice which is being followed even today.

The first reactive dye, the dye which reacts with the fibre during dyeing process forming a chemical covalent bond with the fibre structure as against the conventional dyes which are physically bound to the fibre structure, was discovered by Rattee and coworkers of ICI in a sensational way, while examining the dyeing character of certain dyes containing active chlorine attached to triazine ring, and earlier known to give fast dyeing especially to washing on cotton. A reactive dye after dyeing by a suitable method remains attached to the fibre because of chemical bondage and its washing fastness is of high standard. After a series of triazinyl class of reactive dyes was introduced by ICI, many dyestuff

11

firms concentrated their research and development investigating novel systems for the production of reactive dyes. Dyestuffs containing several groups of reactive systems were patented and few of them were commercially exploited. Hoechst introduced B-sulphato ethyl sulphone called as vinyl sulphone reactive dyes, which were superior in their dyeing properties to triazine class. The progress was constantly made in the fields of pigments, fluorescent brighteners, and azo dyes from novel diazonium salts, etc, as a result of the advancements in the chemistry of heterocyclic compounds. The introduction of heterocyclic moities in the dyestuff structures modifies their property in many ways. Smaller heterocyclic systems can restrict the molecular weight of the dye changing its dyeing character, certain heterocyclic systems effect the shift of the absorption maximum of wavelength to higher wavelength in the visible range of spectrum, generally most of the heterocyclic systems in dyestuff help to increase the fastness properties such as sublimation fastness in disperse dyes. A pouring number of patents were filed worldwide on the subject, exploiting usage of many heterocyclic systems. With the advances in newer analytical techniques such as visible, ultra violet and infrared spectra, it became possible to detect the properties of dyes. Newer tools in modern organic chemistry such as Nuclear Magnetic Resonance and Mass Spectra surpassed all the conventional methods of elucidating the structure of complex organic molecules. Chromatographic methods helped to separate various dyestuffs from their isomers, etc. These techniques and the overall growth of the technology and chemical engineering sciences made it possible for the colour chemists to broaden their ideas and grow fast. With the advent in the polymer chemistry, newer polymers such as plastic materials and fibres were put into the market. Polypropylene and polyacrylic fibres are important discoveries for a colour chemist. Polypropylene finds industrial and restricted domestic applications. Polyacrylic commonly known as PAN Polyacrylonitrile fibre has partially replaced wool because of the matching of its properties with other synthetic fibres especially polyester required for obtaining the blends. The dyestuffs were synthesised by examining the properties and characteristic groupings or side chains is quite adament to known dyes for the synthetic hydrophobic fibre polhyester, and therefore, special

12

dyes had to be searched. Cationic dyes which are similar to basic dyes (both the classes carry a +ve charge on the main structure of the dye,) were soon developed for polyacrylic fibre. It was suggested to modify both these newer synthetic fibres by addition of certain metal additives during their manufacture so as to increase the sites for dye attachments on the fibres. Modacrylates came in the market, which were copolymers of acrylonitrile and similar monome5rs having side chains present in the other monomers after copolymerisation provided better sites for dye attachment to the fibre. Astrazon class of dyes earlier developed were found to be the most suitable for dyeing of polyacrylic fibres and constitute even today an important class of cationic dyes. The optical brighteners initially synthesised for brightening cotton, wool, etc. were extended by suitably modifying the structures to brighten polyamide, polyester, etc. In the recent years a rapid growth of all the classes of dyestuffs is being made, the technology is being innovated, short-cuts are being followed, the basic raw materials are being newly examined and novel intermediates are being searched in more systematic manner. The colour and chemical constitution study based on the modern concepts has helped to strike the right targets of researches in the field. It is, however, possible to find several gaps and combinations of isolated facts in the further addition to known types of dyes. Some of the discoveries made recently were based on the logical thinking in appropriate direction based on certain published or exploited facts elsewhere. For example, the combination of disperses dyes and reactive dyes, suitable for polyamide and they are better than acid dyes or disperse dyes in their dyeing properties. The insertion reactions of the azides and carbenes in organic chemistry are applied by introducing azido group in the dyestuff molecule and applying them on polyester by insertion technique as a reactive dye for polyester which of course has not been commercialised as yet. Fluorescent dyestuffs could be said to be a bridge joining fluorescent brighteners and dyestuffs.

Our country, in the present days has become almost self-sufficient in the production of dyestuffs, though certain items are still being imported. The earlier trend of importing many intermediates as well as dyestuffs from developed countries have practically stopped because of our restricted import policy. This policy was whole heartedly supported

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by organised sectors as well as small scale industries which took a bold step in making larger quantity and better quality of variety of products which are direct requirements for dyestuff industries. The export market possibilities in the recent years have also increased the horizon of many ambitious dyestuff firms to enter in the worldwide competition in the dyestuffs and intermediates. The main threatening problem in the industrial world facing today and applicable to dyestuff field is the pollution problem. The dyestuff industrial waste in the form of atmospheric gases and wastewaters pollutes the neighbouring area. The handling of hazardous chemicals like solvents, cyanides, lead salts, mercury salts, etc, which are often required in the dyestuffs and their intermediates production is posing problems. The handling and production of carcinogenic intermediates regularly involved in the production, such as benzidine and its derivatives, a- and B-napthylamines, diphenylamine, etc., has created setbacks. For the pollution control, newer techniques have been introduced and are further being developed by absorbing the Industrial gases and giving appropriate treatments to waste waters to minimise pollution. An exaustive study has been made on careful handling of solvents, chyanides, etc. The processes where lead salts, mercury salts, etc., were essential are abondoned or replaced by new safer methods. These developments are notable from ecology point of view. Benzidine and its derivatives are important for the production of many dyestuffs consumed in huge quantities, however, because of the carcinogenic nature of these intermediates they are being banned all over the world and are being replaced by new comparatively much safer diamines. The use of β-nahthylamine for making its derivatives is no more in practice, the methods are abondoned or modified by using a much safer sulphonic acid, Tobias acid (β-naphthylamine – &-sulphonic acid). Many such examples can be cited in the dyestuff chemistry. It is rightly said that the development made in any field has to face major setbacks. It is hoped that the future development of intermediates and dyes to be exploited commercially will be thoroughly investigated first from the point of view of ecology and safety of human beings and animal as well as plant kingdom.

Ever since primitive people could create, they have been endeavoring to add color to the world around them. They used natural

14

matter to stain hides, decorate shells and feathers, and paint their story on the walls of ancient caves. Scientists have been able to date the black, white, yellow and reddish pigments made from ochre used by primitive man in cave paintings to over 15,000 BCE. With the development of fixed settlements and agriculture around 7,000-2,000 BCE man began to produce and use textiles, and would therefore add color to them as well. Although scientists have not yet been able to pinpoint an exact time where adding color to fibers first came into practice, dye analysis on textile fragments excavated from archaeological sites in Denmark have placed the use of the blue dye woad along with an as yet unidentified red dye in the first centuryCE.

In order to understand the art and history of dyeing, we must first understand the process of dyeing itself. According to Webster’s dictionary, dyeing is “the process of coloring fibers, yarns or fabrics by using a liquid containing coloring matter for imparting a particular hue to a substance.” There are three basic methods of “imparting a particular hue” to a substance. The first is by staining an item, a temporary means of coloration where the color is rubbed or soaked into an item without the benefit of some sort of chemical fixative to preserve the color. The next is the use of pigmentation, wherein the color is fixed to the surface of an object by another adhesive medium. A true dye is when the color of a substance is deposited on another substance in an insoluble form from a solution containing the colorant.

Natural dyes can be broken down into two categories: substantive and adjective. Substantive or direct dyes become chemically fixed to the fiber without the aid of any other chemicals or additives, such as indigo or certain lichens. Adjective dyes, or mordant dyes, require some sort of substance, (usually a metal salt) to prevent the color from washing or light bleaching out. Most natural dyes are adjective dyes, and do require the application of a mordant (the metal salt) solution to the fibers at some point in the dyeing process. Aluminum and iron salts were the most common traditional mordants, with copper, tin and chrome coming into use much later. In rural areas where these metals were not widely available, plants were also used as mordants, especially those that have a natural ability to extract such minerals from the earth, such as club moss. Most ancient and medieval dyers mordanted their yarns and fabrics before dyeing them. Alum and Iron were used as mordants in Egypt,

15

India and Assyria from early times, as there are many alum deposits in the Mediterranean region. Medieval dyers used alum, copper and iron as mordants, and cream of tartar and common salt were used as to assist in the dyeing process.

Different fibers also have different tendencies to absorb natural and synthetic dyes. Protein and cellulose fibers (the two main divisions for fibers used historically in spinning and dyeing) need to be mordanted differently because of their structural and chemical composition. Mordants to cellulose fibers such as cotton and linen usually involve the use of washing soda or tannins to create an alkaline dyebath. Tannins (plantstuffs, such as oak galls containing tannic acid) are widely used in dyeing cellulose fibers as they attach well to the plant fibers, thus allowing the dyes to attach themselves to the tannins, whereas they might not be able to adhere to the fibers themselves (Tannins are sometimes classified as mordants in and of themselves, but are usually considered a chemical to assist in the dyeing process.) Mordants for protein fibers, like wool and silk, are usually applied in acidic dyebaths. Alum with the assistance of cream or tartar is the most common mordant used to assist the dyes in taking to the fibers.

Since the difference in mordanting different fibers has been mentioned, it would be remiss not to spend a moment on the historic nature of the fibers themselves. Wool, a protein-based fiber, has been found in Europe dating back to 2000 BCE. It was a common medieval fabric in both dyed and natural colors, and was processed by both professional manufacturers and housewives. Silk, another protein-based fiber, was imported from China to Persia as early as 400-600 BCE. It became quite popular in the Late Middle Ages, and major silk manufacturing centers were set up in France, Spain and Italy. These silk production centers also became centers of dye technology, as most silk was dyed and required the highest quality dyes available. Cotton was considered a luxury fabric, as it was imported all the way from India and usually dyed or painted before it was shipped. Cotton was also valued because of the brightness and colorfastness of the dyes used to color it, and also for its use in making candlewicks. Samples of cotton fabrics have been found in India and Pakistan dating to 3000 BCE, but it did not appear in Europe until the 4th century. Cotton waving establishments were formed in Italy in the 13th & 14th centuries but they did not make a

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significant economic impact on the industry as they produced a coarser quality of fabric than the imported fabric, and therefore had difficulty in obtaining a good supply of cotton fiber.

Scientists are almost certain that dyeing was practiced throughout the world, but it is difficult to obtain proof on this for two reasons. First, not all cultures left written records of their practices. Second, because of the wide variance of environmental conditions and degree of geological disturbance, it is not easy to find well-preserved evidence of dyed textiles in many archaeological sites. A Chinese text from 3,000 BCE lists dye recipes to obtain red, black and yellow on silks. Ancient Indian texts describe several different yellow dyestuffs, how to obtain reds from the wood and bark of certain trees, and also notes the use of indigo to create blues on cotton. In Central and South America they dyed bast fibers (plant fibers) in shades of red and purple with the bodies of the cochineal insects (Dactylopius coccus).

A Greek artifact known as the Stockholm Papyrus details dyestuffs and techniques in almost a recipe fashion as it was practiced Egypt in the third and fourth centuries CE. The great detail in which the preparation of the fibers and the dyeing materials and the dyeing process itself are recorded has led scholars to believe that it had to have been practiced for thousands of years previously in order to raise the process to such a science and art. It discusses mordanting the fibers using alum, copper and iron oxides to darken or “sadden” the red, blue, green and purple dyes, as well as the occasional use of tin and zinc. It describes over ten different recipes for using alkanet (Anchusa tinctoria) root as a dye employing camel and sheep urine, lentils, vinegar, wild cucumber and barley malt among others as aids to producing color. It also gave recipes on obtaining purple hues by overdyeing the alkanet with woad (Isatis tinctoria), madder (Rubia tinctorum), kermes (made from the dried bodies of the female shield louse or scale insect (Kermes ilicis)) and the heliotrope plant (Heliotropium arborescens). Excavated coptic textiles dating from the fourth to the sixth century CE show use of weld (Reseda luteola) to produce yellow, madder and woad for dark purple, and blue from indigo (Indigofera tinctoria). Scientists have been able to date a red obtained from Egyptian madder root from the fourteenth century BCE. In the Mediterranean before the advent of Christianity, a whole dyeing industry arose around Tyrian purple. Tyrian purple is produced from the

17

mucous gland adjacent to the respiratory cavity within some species of Purpura and Murex species of shellfish. The shells were crushed to extract this fluid, which only turns purple once it has been applied to the fiber and exposed to light and oxidation with the air. The Phoenicians, skillful shipbuilders and sailors that they were, scoured the coastlines for sight of these whelk shells, and established a dyeworks and trading station wherever they found a plentiful population of these shellfish. Coastal Indians of Mexico were also using shellfish, but their delicate method involved blowing and tickling the shellfish to get them to spit out the dye precursor directly onto the cotton fibers. Even Ireland can produce archaeological evidence of dyeing with the native dog-whelk shells in the seventh century CE. Both Discorides, the Greek physician and Pliny the Elder, the Roman naturalist, mention in their first century works the preparation and dyeing of wool with various shellfish to produce colors of red, blue, purple and violet after first being mordanted with soapwort (Saponaria officinalis), oxgall or alum. (Schetky, 4) Both authors also mention the use of Indigo from the Orient to obtain blues, and Herodotus describes its use in a 450 BCE text. Dioscorides also mentions other dye plants of the ancient world, including madder, saffron (Crocus sativus) and weld for yellow, and woad for blue. Walnut shells (Juglans nigra), oak bark (Quercus sp.), pomegranate flowers (Punica granatum) and broom (Genista tinctoria) were also used in conjunction with various mordants; but galls formed on trees could mordant themselves, being high in tannic acid.

In Europe the art of dyeing rose to new heights with the diversity of climate, culture and migration/invasion waves. This was further influenced by the direct impact of trade instigated by the Crusades and furthered by the growing cultural awareness of the Renaissance period - everyone in Europe wanted the exotic, colorful dyestuffs from the Orient, and later from the Americas. Caravans of camels would cross the Gobi desert for centuries bringing goods from China to the Mediterranean. By the 12th century the two main trade routes for imported dyestuffs headed through Damascus: the first led from Baghdad to Damascus to Jerusalem and Cairo, the other went to Damascus to Mosul to the Black Sea to Byzantium (Istanbul).

Venice was one of the major early centers for imported dyestuffs, supplying Brazilwood (Caesalpinia sappan) from the East, lac (another

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insect dye) and indigo from India from the fifteenth century CE onward. Dyers of Italy soon became adept in their use; in 1429 the Venetian dyer’s guild wrote a book for its members containing a number of different dye recipes, including Brazilwood and lac. The Plictho de Larti de Tentori by Venetian author Giovanni Ventur Rosetti (sp - also listed as Giovanventura Rosetti) in the 1540s lists instructions for using both lac and indigo, as well as 217 other recipes for dyeing cloth, linen, cotton and silk with many varieties of dyestuffs. It would remain the best source for dyeing instruction for the next 200 years.

From Venice the dyestuffs were traded by ship around the coast of France to Flanders, Southampton and London; in the Mediterranean at Florence, Pisa and Genoa; and northward on the continent to the distribution centers of Basle and Frankfurt (Schetky, 6). Basle was a noted center of trade for saffron, the expensive yellow obtained from certain species of crocus. In later years crocus were grown in that area directly, and the crop became such a vital part of the local economy that they crocus was featured on the city’s coat of arms. Frankfurt housed trade fairs from the twelfth to fourteenth centuries that dominated the trade of many dyestuffs, but mainly that of locally grown woad, the only blue dyestuff available to European dyers before the coming of indigo. Many regions in Germany specialized in growing and processing the woad through its complex fermentation process, and strict legislation was placed on every aspect of the trade.

The government of Spain controlled the trade of cochineal, the red dye from the bodies of the Cochineal bugs of Central America. In 1587 approximately 65 tons were shipped to Spain, and from there northward throughout Europe. Italian dyers shunned cochineal in favor of the already established dye kermes, made from the dried bodies of the female shield louse or scale insect (Kermes ilicis) (Schetky, 4). It’s use was first recorded in 1727 BCE and it was long the standard red dye for silk, wool and leather, but the intense colorific value and relative cheapness of cochineal soon eliminated most of the kermes use in England, so Spain hung on to control of their lucrative monopoly.

European dyers reached their height of skill in the thirteenth century, mainly due to the guild systems who vigilantly maintained a high standard of quality. In many countries dyers were graded by the guild system, the master dyers being allowed to use the major “fast” dyes

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while their lesser colleagues were restricted to the slower, “fugitive” dyes. In some places it was forbidden to possess, let alone use, major dyestuffs unless you were a member of a guild. In Germany, the dyers and woad workers were regulated by the guilds, each grower having to present his crop to a “sworn dyer” to determine its quality, weight and condition before it could be sold. (Grierson, 8-9) English producers of woad had fewer restrictions, mainly that of a proclamation in 1587 to restrict growers to certain field size and ensure that no woad mills were sited within three miles of a royal residence, market town or city because of the highly offensive odor they emit. Even the local doctors in Venice in 1413 city fathers to prohibit dyeing with either woad or ox-blood after March first because of the “unhealthy smell.” France had developed an extensive and efficient textile industry by the 13th century and also increased the dyers craft by developing varied techniques to achieve additional colors from the basic dyestuffs. At the end of the 16th century, there were over 220 master dyers listed in Paris alone.

While the powerful guild system had numerous dyestuffs with which to blend their color palates of fiber for the bluebloods and wealthy merchants, dyeing in the lower classes was a bit more restrictive. Without the money (or connetions) to buy indigo, cochineal and turmeric, clothing in the country tended to natural colors – whites, blacks, browns, grays, and tans of the natural colors of the fibers themselves, with the reds, greens and yellows of local plants used for both food, medicine and dyes. In short, home dyers used any plants they could lay their hands on that would give a good color. Some colors were even derived accidentally. Washing beehives in preparation for making mead could yield yellows and golds. Blackberries and Bilberries that stained the fingers of pickers could also be used to achieve pale blues and purples, although these were not often color or lightfast. In England, the multitudinous variety of lichens and mosses produced greens, grays and browns.

By the seventeenth century a worldwide shipping and trading network was in place, allowing dyestuffs from all parts of the world to be brought to Europe. Legislation from earlier centuries to protect the growers and users of specific dyestuffs was overturned in favor of new demands and standards set by the growing consumer-focused society who wanted more colors and better quality. In the eighteenth and

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nineteenth centuries the practice of colonialism insured that there would always be a supply of foreign dyestuffs, and the Industrial Revolution met the demands of large-scale productions while finding new ways to make the colors brighter and longer-lasting to wear and washing.

As textile weaving technology advanced with the advent of machines to spin, design and weave fabric, dyers were forced to be able to produce dyes with exact shades, matching color lots and most importantly, ones that would stand “fast” to the new mechanical and chemical processing. In addition, exporters wanted colors that would stand up to tropical sunlight and still be exotic enough for foreign tastes. Dyers in turn demanded from their supplier’s purer chemicals and dyestuffs of consistent quality. Hand in hand, dyers, manufacturers, chemists, and dyestuff producers worked hand in hand to keep up with the progress of technology. Chemists in many countries had found a means of extracting highly concentrated powders or pastes from traditional dyestuffs that made stronger colors, such as cochineal carmine and madder garancine. Other procedures were used to extract indigo that gave us sulphonated indigo and Saxon blue. A few novel dyes (precursors of future chemical dyes) such as the yellow obtained from picric acid also made an appearance. With the tremendous rise in the interest of Chemistry in the mid nineteenth century, several important innovations in dyeing came about. W.H. Perkin, a student of celebrated European scientist Wilhelm von Hoffman, accidentally discovered the first synthetic dye in an attempt to synthesize quinine. The 18-year old student’s purple precipitate, later called mauviene, was quickly put into industrial application, allowing the young Perkin to start his own factory in London to commercially produce his dyestuff. Two years letter a synthetic red dye called magenta or fuchsine was patented in France, and hardly a year passed until the end of the century without a new synthetic dye being patented.

Eventually, the old natural dyes lost popularity in favor of the newer synthetic ones. By the end of the nineteenth century a few Scottish tweed producers were the only ones still using natural dyes, and now the use of natural dyes on a commercial scale barely exists, mainly in remote areas where people have either little access to synthetic dyes or a vested interest in retaining their ancient dyeing customs. Use of natural dyes is gaining popularity again with the renaissance in hand crafting, most

21

notably in the fields of spinning and weaving, basketry, papermaking and leather craft. There is also renewed scientific and historic interest in natural dyeing, both to help identify dyestuffs in recently discovered archaeological finds and to preserve the dyed textiles housed in museums and private collections.

As Su Grierson says in her book Dyeing and Dyestuffs, “Whilst the dyeing industry of today keeps pace with modern science, the future use of natural dyes will also follow a new path, but one firmly.

Classification of Dyes

3 Dyes may be classified in two ways. The organic chemist classifies them according to a common parent structure (Chemical Classification). The dyer, who is only interested in fixing the dye to the fibre, classifies them according to the method of application.

CLASSIFICATION ACCORDING TO CHEMICAL STRUCTURE

(1) Nitro Dyes:

Nitro dyes are polynitro derivatives of phenols containing at least one nitro group ortho or para to the hydroxyl group. They are of relatively little importance industrially, because the colours are not very fast. Examples of this class are picric acid (2,4,6-trinitrophenol), Maritus yellow (2, 4-dinitro-1-naphthol), and Naphthol yellow S (2,4-dinitro-1-naphthol-7-sulphonic acid).

OHO2N

NO2

NO2

OH

NO2

NO2

OH

NO2

NO2

HO3S

MARITUS YELLOWPICRIC ACID NAPHTHOL YELLOW S

Naphthol yellow S can be used to dye wool, and is one of the colours permitted in foods. (2) Azo Dyes:

The azo dyes represent the largest and the most important group of dyes. They are characterised by the presence of one or more azo groups (–N=N–), which form bridges between two or more aromatic rings. Preparation of azo dyes involves the following two steps.

22

Step 1. Conversion of primary aromatic amines into diazonium compounds by treatment with sodium nitrite in excess hydrochloric acid (Diazotisation).

NH2 HNO2 HCl N2Cl+ + + -+ 2H2O

A PRIMARY AROMATIC AMINE

A DIAZONIUMCOMPOUND

Step2. Coupling of diazonium compounds with phenols,

naphthols, or other aromatic amines. Coupling with phenols and naphthols is carried out in basic solution; coupling with amines is carried in acid solution.

N2Cl H

OH(-NH2,-NR2)

-HClN=N

+ -A DIAZONIUMCOMPOUND

+

OH(-NH2, -NR2)

A PHENOL, NAPHTHOL or AMINE

A DYE

The above reactions are carried out at low temperatures (0 – 5o) because diazonium compounds are usually unstable. In the resulting dyes an aromatic system joined to the azo group is the chromophore, and the hydroxyl group or amino group is an auxchrome. To simplify the description of azo dyes, only the coupling step will be shown. It will be assumed that the diazonium compound was obtained by diazotisation of the corresponding amine.

(a) Aniline Yellow: Solvent Yellow 1. It is p-aminoazobenzene. Aniline yellow is the simplest azo dye and is obtained by coupling benzenediazonium chloride with aniline in acidic medium

N2Cl H NH3 N=N NH2+ - + + HCl

BENZENEDIAZONIUMCHLORIDE ANILINE YELLOW

(P-aminoazobenzene)

Aniline yellow is used as a dye for oils and lacquers, and is also an intermediate for other dyes. 23

(b) Butter Yellow: It is p-N, N-dimethylaminoazobenzene. Butter yellow is obtained by coupling benzenediazonium chloride with N, N-dimethylaniline.

N2Cl H NCH3

CH3

N=N NCH3

CH3

+ -+

BenzenediazoniumChloride

N,N-Dimethylaniline Butter Yellow(p-N,N-dimethylaminoazobenzene)

Butter yellow has been used for colouring butter, margarine and oils.

(c) Chrysoidine: Basic Orange 2. It is 2, 4-diaminoazobenzene. Chrysoidine is prepared by coupling benzenediazonium chloride with m-phenylenediamine.

N2Cl H

NH2

NH2

NH2

NH2 HCl+ -

+ N=N +

BenzenediazoniumChloride

m-phenylediamine Chrysoidine(2,4-diaminoazobenzene)

Chrysoidine is an orange-red dye. It is used for dyeing paper,

leather, and jute.

(d) Methyl Orange. It is prepared by treatment of helianthine with sodium hydroxide, whereas helianthine is obtained by coupling diazotised sulphanilic acid with N, N-dimethylaniline.

N2Cl+ -

HO3S + H NCH3

CH3

NCH3

CH3

NCH3

CH3

N=N

N=N

HO3S NaOH

NaO3S

Methyl Orange

Helianthine

N,N-methylanilineDiazotised sulphanilic acid

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Methyl orange is not a satisfactory dye for textiles because it is sensitive to acids. It is used as an indicator in acid-base titrations. It is yellow in basic solutions (above pH 4.4), while red in acidic solutions (below pH 3.1). This change in the colour is attributed to change in the structure of its ion. Under alkaline conditions the ion contains the azo chromophore, while under acidic conditions it contains p-quinoid chromophore.

NCH3

CH3

H+

-OHN=N -O3S NH N N CH3

CH3

+

Yellow(Alkaline Solution)

RedAcidic Solution

AzoCompound

p-QuinoidChromophore

(e) Orange II: It is obtained by coupling diazotised sulphanilic acid with β-naphthol is basic medium.

HO3S N2Cl

OH

H+ -

+

HO

HO3S N=N HCl+

Orange 2-Naphthol

DiazotisedSulphanilic Acid

Orange II is used to dye wool, silk, nylon, paper and leather. (f) Para Red: It is prepared by coupling p-nitrobenzenediazonium chloride with β-naphthol.

N2ClO2N

OH

H

OH

O2N HCl+ -

+ N=N +

-Nitobenzenediazonium Chloride

-NaphtholPara Red

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(g) Resorcin Yellow: It is made by coupling diazotised sulphanilic acid with resorcinol.

N2ClHO3S H

OH

OH

HO3S

OH

OH HClN=N +

+ -+

DiazolisedSulphanilic acid

Reaoroinol

Reaoroinol Yellow Resorcin yellow is used for dyeing silk. (h) Disperse Red 1: It is obtained by coupling p-nitrobenzenediazonium chloride with N-ethyl-N- (β-hydroxyethyl) aniline in acidic medium.

N2ClO2N NCH2CH3

CH2CH2OHH

O2N NCH2CH3

CH2CH2OHHCl

+ -+

N=N +

Disperse Red 1

-Nitrobenzenediazonium Chloride

N-Ethyl-N-( -hydroxyethyl)aniline

(i) Congo Red. It is a diazo dye, that is, it contains two azo groups. Congo red is made by coupling tetrazotised benzidine with two molecules of naphthionic acid.

NH2

H

SO3H

+ Cl N2- +

N2Cl+ -

+

NH2

H

SO3H

NH2

SO3H

NH2

SO3H

2HCl

N=N N=N

+

Congo Red

Naphthionic Acid

Tetrazotised Benzidine

Bismark brown is used for dyeing leather, wool, and cotton. 26

(3) Diphenlymethane Dyes: Auramine O: It is one of the most valuable of the

diphenylmethane dyes. It is obtained by heating Michler’s ketone with ammonium chloride and zinc chloride at 160oC.

C N (CH3)2

ZnCl2

O

+ NH4Cl

(CH3)2N C

NH3

N(CH3)2

+

Cl-

AURAMINE O

MICHLERS KETONE

(CH3)2

Auramine O is used to dye wool, silk, silk, nylon, rayon and paper. (4) Triphenylmethane Dyes: Triphenylmethane dyes can be identified by common structural cature shown below. Notice that the central carbon atom is joined to two benzene rings and to p-quinoid group.

C

O Triphenylmethane dyes are not fast to light or washing, however,

except when applied to acrylic fibres. They are used in large quantities

27

for colouring paper, and typewriter ribbons where fastness to light is not so important.

(a) Malachite Green: It is obtained by condensing benzaldehyde (1 molecule) with N, N-dimethylaniline (2 molecules) in the presence of concentrated sulphuric acid to give a leuco base (Gr. Leuco, colourless). Oxidation of the leuco base with lead peroxide followed by treatment with hydrochloric acid yields the dye.

N (CH3)2

N (CH3)2

C

HN (CH3)2

N (CH3)2

Benzaldehyde N,N-Dimethyle aniline

HH

HC==O

Leuco base Melachite green

C

N(CH3)2

N(CH3)2

HCl c

N(CH3)2

N(CH3)2

Cl

MALACHITE GREEN

+

-

Malachite green takes its name from the fact that it has a deep blue-green colour resembling that a malachite (Copper ore). It is used as a dye for acrylic fibres, leather, paper, and lacquers. (b) Pararosaniline: It is the simplest triphenylmethane dye. Pararosaniline is obtained by consdensinig p-toluidine (1 molecule) with aniline (2 molecules) in the presence of nitrobenzene to give a colourless carbinol. Nitrobenzene serves both as a solvent and an oxidising agent. Treatment of the carbinol with hydrochloric acid yields the dye.

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H2N C

H

H

H

H NH2

H NH2

H2N

OH

CNH2

NH2

3[O]

-2H2O+

p-toludine Aniline Colourless carbinol

HCl

-H2O

+

H2N CNH2

NH2

PARAROSANILINE

Cl-

Pararosaniline has been used to dye cotton, wool and silk.

(c) Rosaniline: Fuchsine, magenta. It is closely related to pararosaniline. Rosaniline is prepared by condensing one molecule each of aniline, p-toluidine, and o-toluidine in nitrobenzene to give a carbinol. Treatment of the carbinol with hydrochloric acid yields the dye.

H2N C

H

H

H

H NH2

H NH2

H2N

OH

CNH2

NH2

3[O]

-2H2O+

p-toludineColourless carbinol

HCl

-H2O

+

H2N CNH2

NH2

PARAROSANILINE

Cl-

CH3

O-Toluidine

CH3

CH3

29

Rosaniline has a greenish metallic lustre. It dissolves in water to give a deep-red colour. Rosaniline is used for dyeing cotton, silk and wool. Addition of sulphur dioxide to the dye solution produces the colourless Schiff’s reagent, which is used to test the presence of aldehydes. (d) Crystal Violet: It is obtained by condensing Michler’s ketone with N, N-dimethylaniline in the presence of phosphorous oxichloride (POCl3) or phosgene (COCl2). If phosgene is used, then crystal violet can be prepared directly by heating phosgene and N, N-dimethylaniline, since these two react to give Michler’s keton.

(CH3)2N O

N(CH3)2

C + H (NCH3)2

POCl3

or COCl2

c N(CH3)2Cl

-

+

CRYSTAL VIOLET

MICHLERS KETONE

N,N-DIMETHYLE ANALINE

Crystal violet has a greenish-brown metallic lustre. It dissolves in water to give a deep-blue colour. Crystal violet is used in the manufacture of inks, stamping pads, and typewriter ribbons. It is also used as an indicator for the determination of hydrogen-ion concentration of solutions. (5) Xanthene Dyes:

Xanthene dyes can be identified by a common structural feature shown below. They are obtained by condensing phenols with phthalic anhydride in the presence of zinc chloride, sulphuric acid, or anhydrous oxalic acid. Examples of this class are fluorescein, eosin, and rhodamine B.

C

O O

H 30

(a) Fluorescene. It is prepared by heating resorcinol (2 molecules) and phthalic anhydridge (1 molecule) with zinc chloride at 190oC

HOOH

H

OH

H

OH

CH2

O

C O

O ZnCl2

2H2O

C

O OH

OC

HO

NaOH

OOH O

COONa+

PATHALIC ANHYDRIDE

FLUORESCEIN

URANINE Fluorescein is of no value as a dye. It is red powder, which is insoluble in water. A dilute solution of fluorescein in sodium hydroxide gives a strong yellow-green fluorescence when exposed to light. It is used to trace pollution of water supplies by sewerage, since if a small quantity of it is put in at the suspected source of pollution, the colour will be detectable at some distance from the source, even after extensive dilution. During World War II, fluorescein was used as a sea marker for airmen who had to bail out from aeroplanes over water. It also aided searchers in locating them. Fluorescein is also used as a mild purgative. The sodium salt of fluorescein is called Uranine. It is used to dye wool and silk.

(b) Eosin: It is the sodium salt of tetrabromofluorescein. Eosin is obtained by brominating fluorescein in glacial acetic acid to give tetrabromofluorescein. Treatment of this with sodium hydroxide yields the dye.

31

C

O OH

OC

HO

ONao O

COONa+BrBr

NaOH

Br Br

Br Br

C

O OH

OC o

HO

Br2

FLUORESCEIN

CH3COOH

EOISNE

BrBr

Tetrabromofluricine

o

Eosin is a red solid, which is soluble in water. Alkaline solutions of eosin show a yellow-green fluorescence. Eosin is used for dyeing wool, silk, and paper; for making red ink and as the colouring matter in lipsticks and nail polishes.

(c) Rhodamine B: It is prepared by condensing phthalic anhydride with N,N-diethyl-m-aminophenol in the presence of zinc chloride, and treating the product with hydrochloric acid.

OH

H

H-O

H

CO

OC

O

C=OOZnCl2

C

COOH

HCl

Cl

(C2H6)2N+

N(C2H6)2

C=O

PATHALIC ANHYDRIDE

2H2O-

(C2H6)2N N(C2H6)2

N(C2H6)2(C2H6)2N

+

-

RHODAMINE B

----

Rhodamine B is used for dyeing silk, wool and cotton. 32

(6) Phthaeleins: Phthaleins are related to xanthene dyes and are made in the same

way. Phenolphthalein: It is prepared by condensing phenol (2 molecules) with phthalic anhydride (1 molecule) in the presence of zinc chloride at 120oC.

OCC O

OHOH

H HO ZnCl2

-H2O C

HO OH

C=OO

Phthalic Anhydride Phenolphthalein (Colourless)

Phenollphthalein is not a dye. It is colourless solid, mp 261oC. Phenolphthalein is insoluble in water, but dissolves in alkalis to form deep red solutions. This is due to the formation of a disodium salt, the ion of which is coloured because of resonance. When excess of strong alkali is added, the solution of phenolphthalein becomes colourless. This is attributed to the formation of a trisodium salt, the ion of which is colourless because of loss of resonance and quinoid structure.

33

C

HO OH

C OO

Phenolphthalein (Colourless)

-OH

H+

O

C

-ONa+

COONa+- C

O

COONa

NaO+ -

+ -

-OHH+

COONa+O

+NaO--ONa+

OH

Trisodium Salt (Colourless)

Sodium Salt (Red)

Because of the colour changes shown above, phenolphthalein is used as an indicator in acid-base titrations. Phenolphthalein is an extremely powerful laxative, and this accounts for its widespread use as a denaturant for laboratory alchohol. (7) Indigoid and Thioindigoid Dyes: Indigoid. It is the parent compound of indigoid dyes and has been used in this country from times immemorial. Egyptian mummy clothes, which are 5000 years old, were dyed with it. Indigo was originally obtained from plants of indigofera group. The leaves from these plants were covered with water and allowed to stand for several hours. Enzymes present in the plants brought about fermentation, as a result of which the β-glucoside of indoxyl (known as indican) in the leaves was converted into indoxyl and glucose. Upon exposure to air the indoxyl was oxidised to indigo.

HOH

OHH

OH

HCH2OH

H

OH

H

H

O

N

C

CH

H

OHOH

OHH

CH2OH

H

OH

HFermentation

-Link

+N

CH2

CO

H-D-Glucose Indoxyl

NCH2

CO

HIndoxyl

Oxidation

O

CC

H

C

NC

O

H

N

Indigo(Indican)

Natural indigo contains an isomer of indigo known as indirubin (Indigo Red), and other impurities in varying proportions. Most of the indigo used at the present time is a synthetic product. It has replaced the natural stuff because of cheapness, purity, and uniformity of the manufactured dye. 34

Preparation of Indigo. It may be obtained: (1) By Heumann’s First Indigo Synthesis (1890). This involves the condensation of aniline with chloroacetic acid to give N-phenylglycine. The phenylglycine is then fused with sodium hydroxide and sodamide at 250oC to form indoxyl, which on oxidation by air yields the dye.

H

N

H

H+

+C O

CH2

HO

Cl N

H

CH2

CO

H

HO

HaOH + NaNH2

NCH2

C

H

O

O2

NC

C NC

C

H

O

O

H

Aniline Chloro Acetic Acid

N-Phenylolycine

Indoxyl

Indigo(Indigotin)

N-Phenylglycine is now obtained in much higher yield by interaction of aniline and the bisulphite compound of formaldehyde at 50-60oC, followed by treatment with aqueous sodium cyanide, and hydrolysis of the resulting nitrile.

35

H C H NaHSO3

O

+ H C H

OH

SO3Na+-An Addition Product

Sodium Bisulphite

Formaldehyde

N

H

H

N

H

CH2

N

H

+C HHO

H

SO3Na- +

50 70OC

SO3Na- +

NaCN

-Na2SO3

N

H

CH2

C NH+

H2O CH2

CHO O

N-Phenylglycine

(2) By Heumann’s Second Indigo Synthesis (1896): This involves the condensation of anthranilic acid with chloroacetic acid to form N-phenyl-o-carboxylic acid. This is then fused with sodium hydroxide and sodamide to produce unstable indoxylic acid, which decarboxyhlates to give indoxyl. Oxidation of indoxyl by air yields the dye.

C

OH

O

N H

H

+CH2 COOH

Cl

C

N

H

O

OH

CH2 COOH

NaOH, NaNH2,

-H2O

NC

COH

COOH

H

CO2

NCH2

C

H

OO2 Indigo

Indoxyl(2 molecules)

Indoxylic acid (unstable)

N-Phenylglycine-o-carboxylic acid

Chloroacetic acid

Anthranilic Acid

(3) From Aniline and Ethylene Oxide (1943): This involves treatment of aniline with ethylene oxide to form N-phenyl-2-hydroxyethylamine with sodium hydroxide and sodamide at 200oC produces its disodium derivative. The sodium derivative is heated rapidly to 300oC and then cooled to 240oC to yield the sodium salt of indoxyl. This on treatment with water and oxidation by air give indigo.

NH2Aniline

O

H2C CH2

Ethylene Oxide

+

NCH2

CH2

H

OHNaOH + NaNH2

200 0C

N-Phenyl-2-hydroxyethylamine

NCH2

CH2

Na+-

ONa+-(1) 300 OC(2) 240 OC

NCH

C ONa+-

H

H2ON

CH

C OH

H Indoxyl(Enol form)Sodium Salt of indoxyl

36

NCH2

C

H

O

Indigo

Indoxyl(Keto form) Indigo is a dark-

blue crystalline compound, mp 390-2o. It is insoluble in water and most organic solvents, but soluble in aniline, nitrobenzene, and chloroform. It can be sublimed under reduced pressure to deep red vapours, which on cooling yield prismatic crystals. Indigo is used very extensively for dyeing cotton by the Vat Process, and in printing inks. Structure of Indigo: The structure of indigo has been deduced from consideration of facts and conclusions such as the following. 1. Elemental analysis and molecular weight determinations show that the molecular formula of indigo is C16H10O2N2. 2. Fusion of indigo with sodium hydroxide at low temperature produces anthranilic acid. This indicates the presence of a benzene ring attached to one carbon atom and one nitrogen atom in the ortho position.

NH2

Indigo NaOHC

O

OH

Anthranilic Acid 3. Oxidation of indigo with nitric acid yields only two molecules

of isatin. This indicates that the indigo molecule contains two identical units joined together, and that each unit on oxidation produces a molecule of isatin.

37

N

H

INDIGO2[O] C=O

C=O

Isatin

The following two possible structures of indigo meet this requirement.

NC

H

OC C

N

O

C

H

(A)

NC

H

C C

NC

H

O O

(B)

4. Oxidation of indoxyl by air yields indigo.

NC

H

OC C

N

O

C

H

N

H

C

INDIGO

O2

CH2

INDOXYL

O

From above, it follows that (A) represents the structure of indigo. This has been confirmed by the following synthesis by Baeyer (1872).

NC

C

O

O

H

NC

C

OH

O

NC

C

Cl

OPCl5

Isatin(Keto form)

Isatin(Enol form)

Isatin chloride

CH3COOHZn

NCH2

CO

H Indoxyl(Two Molecules)

O2

NC

CO

C

CN

O

HHIndigo

Two geometrical isomers are possible for (A)

N

C

C C

C

N

H

O O

H

N

C

C N

C

C

H

OH

O

= =

Cis-form Trans-form

38

X-Ray analysis shows that mostly indigo exist in the more stable trans-form. However, derivatives of both are known. (a) Tyrian Purple. It is 6, 6’-dibromoindigo. Its discovery was later than that of indigo but it is believed to have been known in 1600 BC.

N

C

C

O

H

N

C

C

H

OBr

Br

2 2'

3

3'

1' 7'

6'

5'4'

4

76

Tyrian Purple(6,6' - Dibromoindigo)

Tyrian purple occures naturally in the purple snail, Murex

Brandaris. It takes about 12000 snails to produce 1.4 g of the dye. This explains its rarity and why the colour of mercial value.

(b) Thioindigo. It is analogues to indigo in which the two –NH– groups are replaced by sulphur atoms. Thioindigo may be obtained by the reaction of thiosalicylic acid, with chloroacetic acid, followed by fusion with sodium hydroxide and oxidation by air. Thiosalicylic acid itself is made by diazotisation and reaction with hydrogen sulphide.

S

CH

C

OH

S

CH2

C

O

O2

S

C

C

O

S

C

C

OThioindoxyl(Enol-Form)

Thioindoxyl(Keto-Form) THIOINDIGO

COOH

NH2

Anthranilic Acid

1. Diazotize2. H2S

COOH

SHThiosalicylic Acid

ClCH3COOH COOH

COOH

S CH2

HaOH200 0C

Thioindigo is used to dye cotton, wool and polyesters.

39

(8) Anthraquinoid Dyes: Anthraquinoid dyes can be identified by a common structural

feature shown below. Notice that a p-quinoid group is fused to two other benzene rings.

O

O Anthraqluinoid dyes are used for dyeing wool, silk, nylon, cotton, leather and paper. The most important dye in this group is alizarin. Alizarin. It is 1,2-dihydroxyanthraquinone. Alizarin derives its name from the fact that it was first obtained from the roots of the madder plant (Fr. Alizari, madder). It is now prepared from phthalic anhydride by the following six steps. Step 1. Phthalic anhydride is treated with benzene in the presence of AlCl3 to give o-benzoylbenzloic acid. (Friedel-Crafts Reaction)

c

o

cAlCl3

C

C

O

O

OH

O-Benzoyl-Benzoic Acid

o

o

Step 2. O-Benzoylbenzoic acid is cyclized by treatment with

concentrated sulphuric acid to form anthraquinone.

C

C

O

O

OH

H

H2SO4

O

OAnthraquinone

Step 3. Anthraquinone is heated with fuming sulphuric acid at 180oC to give anthraquinone-2-sulphonic acid. 40

O

O

O

O

SO3H

Anthraquinone

+ H2SO4Fuming

Anthraquinone

Anthraquinone-2-sulphonic acid Step 4. Anthraquinone-2-sulphonic acid is converted into its

sodium salt by treatment with sodium hydroxide. O

O

SO3HNaOH

O

O

SO3Na

AnthraquinoneAnthraquinone-2-sulphonic acid Sodium salt of

anthraquinone-2-sulphonic acid Step 5. Sodium salt of anthraquinone-2-sulphonic acid is fused with sodium hydroxide in the presence of potassium chlorate at 200oC under pressure to give sodium salt of 1, 2-dihydroxyanthraquinone. The purpose of potassium chlorate is to provide oxygen for the oxidation of the carbon atom at C-1.

O

O

SO3Na

O

O

ONa

ONa

10

2

345

6

78 9 - + - +

- +

+ Na2SO4

+ 2H2O

Sodium salt of1, 2-dihydroxyanthraquinone

Step 6. Sodium salt of 1,2-dihydroxyanthraquinone is treated with sulphuric acid to yield 1,2-dihydroxyanthraquinone (Alizarin).

O

O

ONa

ONa

H+

O

O

OH

OH

Alizarin(1, 2-dihydroxyanthraquinone)

Alizarin can also be made by condensing phathalic anhydride with catechol in the presence of sulphuric acid at 180oC (See Below).

41

Alizarin forms ruby red crystals, mp 290oC. It is insoluble in water and ethanol. It dissolves in alkalis to give purple solutions. Alizarin is used to dye cotton and wool. It is also used for making printing inks. Structure of Alizarin:

The structure of Alizarin has been deduced as follows: 1. Elemental analysis and molecular weight determinations show that

the molecular formula of alizarin is CI4H3O4: 2. Reduction of alizarin with zinc dust at 400oC produces anthracene.

This indicates that it has the same carbon skeleton as that of anthracene.

3. Alizarin reacts with acetic anhydride to form a diacetate. This

indicates the presence of two hydroxyl groups in the molecule. 4. Alizarin can be prepared by condensing phthalic anhydride and

catechol in the presence of sulphuric acid at 180oC. This shows that alizarin is a dihydroxy derivative of anthraquinone and both – OH groups are substituted in the same benzene ring.

C

O

C

O

O OH

OHO

O

OH

OHH2SO4+

Phthalic anhydride

Catechol Alizarin(1,2-dihydroxyanthraquinone)

The above facts limit our choice to two structural formula for alizarin.

O

O

O

O

OH

OH OH

OH

(A) (B) 42

5. Alizarin on nitration yields two isomeric mononitro derivatives, both of which on oxidation give phthalic acid. This shows that in each of these derivatives, the – NO2 group is substituted on the hydroxylated benzene ring.

Let us now write down the possible mononitro derivatives from (A) and (B). Mononitro derivatives from (A):

O

O

OH

OH

O

O

OH

OH

NO2

NO2DIFFERENT

O

O

NO2

OH

OH

O

O

OH

OH

NO2

IDENTICAL

MONO TRO DERIVATIVES FROM (B)

Since only formula (A) permits the formation of two isomeric mononitro derivatives, it represents the structure of alizarin.

(A) CLASSIFICATION ACCORDINGTO METHOD OF APPLICATION:

Methods for dyeing vary with the chemical structure of the fibre to be dyed. A dye suitable for wool or silk may be entirely unsatisfactory for dyeing cotton or rayon. Wool and silk are protein substances. They contain many acidic and basic (polar) groups. These groups serve as points of attachment for a dye because it also has acidic or basic group. On the other hand, cotton and rayon fibres are composed of cellulose in quite pure form and provide only neutral ether linkages and hydroxyl groups as points of attachment for hydrogen bonds. Polyolefin fibres are formed from products of polymerisation of unsaturated hydrocarbons, for 43

44

example, propylene. They do not contain any polar groups and require still other techniques for dyeing.

As already mentioned, a dye must do more than simply colour the surface of the fibre. It should become part of the fibre, and wear and wash with the fibre. A dye should be fast to light and should show resistance to the action of various organic solvents used in dry-cleaning, dilute alkalis and acids, etc. A number of dyes satisfy these conditions very well when used on some material but not when used on others. In all cases chemical structure of the material determines the process and the dye to be used for dyeing it. A number of dyeing methods and dyes adaptable to each method are described below.

1) Direct Dyes:

These contain acidic or basic groups and combine with polar groups in the fibre. Such dyes colour a fabric directly when the fibre is immersed in a hot aqueous solution of the dye. Direct dyes are used to dye wool and silk. Two examples of this class are Naphthol Yellow S and Martius Yellow. Both compounds are acids and combine with the free amino groups present in wool and silk fibres. Synthetic polyamide fibres (Nylon) can also be dyed by this method.

2) Mordant Dyes: This class of dyes requires a pretreatment of the fibre with a mordant material designed to bind the dye. The mordant becomes attached to the fibre and then combines with the dye to form an insoluble coloured complex. This complex is called a lake. Commonly used mordant are the oxides of aluminium, iron and chromium. Mordant dyes may be used to dye wool, silk and cotton. Alizarin is an example of a mordant dye. It gives different colours when used with different mordants. It gives a red colour with aluminium and tin salts, brownish red tones with a chromium mordant, and black-violets with an iron mordant.

O

O

OH

OH O

O

Al

OH

oo

fibre

mordant dyes on fibre

Al3 + fibre+

Modarant dyes have been used for many centuries. They have lost their original importance because their use is no longer necessary. Equal or superior results can be obtained with other classes of dyes at less expense in time and labour.

3) Vat Dyes:

These dyes are insoluble in water, but on reductin with sodium hydrosulphite yield alkali soluble forms (Leuco-compounds) which may be colourless. It is in this form they are introduced into the fabric. The reducing operation was ormerly carried out in wooden vats, giving rise to the name ‘Vat Dyes’. After the reduced dye has been absorbed in the fibre, the original insoluble coloured dye is reformed by oxidation with air or chemicals. Vat dyes are used to dye cotton, and very fast because of their insolubility in water. Indigo is an example of a vat dye.

N

C

C

C

H

O

N

C

H

O

INDIGO BLUE WATER INSOLUBLE

N

C

C

H

OH

N

C

C

H

OH

INDIGO COLORLESS WATER SOLUBLE

Reduction

Oxidation

4) Ingrain Deys: These dyes are synthesised within the fa bric, and may be applied to any type of fibre. The azo dyes are good examples of ingrain dyes. The cloth to be dyed is first soaked in an alkaline solution

45

of a phenol (usually naphthol) and dried. It is then immersed in a cold alkaline solution of a diazonium salt. Coupling reaction takes place within the fabric. Since these dyes are insoluble in water, they are very fast.

5) Disperse Dyes: These are insoluble in water, but are capable of dissolving certain synthetic fibres. Disperse dyes are usually applied in the form of a dispersion of finely divided dye in a soap solution in the presence of some solublising agent such as phenol, cresol, or benzoic acid. The absorption into the fibre is carried out at high temperatures and pressures. Disperse dyes are used to dye acetate rayons, Dacron, Nylon and other synthetic fibres. Celliton Fast Pink B (1-amino-4-hydroxyanthraquinone) and Celliton Fast Blue B (1,4-N, N’ –dimethylaminoanthraquinone) are examples of disperse dyes.

ONH2

OHOCELLITON FAST PINK B

o

o

N-CH3

H

N-CH3

HCELLITON FAST BLUE B

46

Dyes & Fibre Polymer System

4 Wool Fibres: The wool fibre is composed of the protein keratin, which consists of long polypeptide chains built from eighteen different amino acids. Most of these acids have the general formula H2N.CHR.COOH, in which R is a side chain of varying character. The chain structure is of the type:

NHC

H

R1

CONH

C

H

CONH

CCO

H

R3

R2

And at intervals bridges derived from the amino acid cystine connect the chains. Some of the side chains end in amino groups and others in carboxyl groups; internal salts are therefore formed and the

H2N

HOOC

CH CH2 S S CH2 CHCOOH

NH2

Molecules are bound together by electrovalent linkages. The molecules of keratin are very large, with and average molecular weight estimated at about 60,000. The wool fibre is readily destroyed by alkali, but withstands acid conditions fairly well; some hydrolysis of peplide linkages occurs on prolonged boiling with acids, however. The carboxylic acid and amino groups in the keratin molecule confer affinity for basic and acid dyes. Basic dyes are now little used on wool since their fugitive properties render them unsuitable for such and expensive and durable fibre. Acid dyes, however, are extensively used, and the general characteristics of this large class and the related mordant and pre-metallised azo dyes are now described. 47

48

Since the bonds between dye anions and amino groups in the wool fibre are easily broken and re-formed, dyes attached in this way are liable to migrate. This property is advantageous, in that level dyeing is readily attained, but it leads to low fastness to wet treatments, and any undyed wool present during washing becomes stained. These characteristics are chiefly apparent in dyes of low molecular weight, and fastness to washing is in general much better in more complex dyes. The larger dye molecules are evidently attached the fibre by some means other than the ionic bonds mentioned above, and it is believed that6 they are held by non-polar van der Waals forces exerted between hydrophobic dye anions and hydrophobic regions of the wool fibre, their strength being proportional to the area of contact. From an application point of view acid dyes are classed as either Levelling or Milling types. The Levelling (sometimes called Equalizing) dyes have fairly simple chemical structures, migrate readily on wool, and are easily applied from strongly acid baths; their wet-fastness properties are low. The Milling dyes are structurally more complex, have high affinity, and must be applied form weakly acid baths for control of the rate of dyeing, but they show high fastness to milling and other wet treatments. Milling is a felting process applied to woolen cloth by squeezing or beating, usually in a soap solution. It sometimes follows dyeing, and the dyes used must then have high wet-fastness properties in order to withstand these severe conditions. The advantages of good levelling and high milling fastness cannot be fully combined in a single dye, but there are general purpose dyes with intermediate GTFVJ,./properties. The application classes can be correlated roughly with chemical types, as shown for monoazo and disazo dyes in Table 4 – 1, which provides a few typical examples. As might be expected from the foregoing generalizations, trisazo and other polyazo dyes are of the milling class, but since shades are usually dull and uneven they are seldom of technical value on wool. Silk Fibres: Cultivated silk is a natural fibre produced by larvae of the silkworm Bombyxmori, and wild silk is produced similarly by silkdworms of various species. Raw silk consists of the protein fibroin surrounded by silk gum (sericin), and the latter is removed in the process

of de-gumming or ‘boiling off’ which precedes dyeing. Fibroin consists of long parallel chain containing about 400 amino acid residues with a structure of the general type

.

NH CH

R

CO NH CH

R

CO NH CH

R

CO

The residues are derived mainly from the amino acids glycine (R = H), alanine (R = CH3), serine (R=CH2OH) and tyrosine (R= --CH2---OH), but there are numerous others in small quantities. Fibroin differs from keratin in that it contains no sulphur. Its chemical properties are similar to those of keratin, but it is more sensitive to acids than the latter and less sensitive to milk alkalis. Silk can be dyed with dyes of almost every class, but some restrictions arise from the common practice of weighting the fibre with tin salts, which is carried out in order to improve handling properties and reduce cost. So far as azo dyes are concerned the main classes applied to silk are the acid dyes and pre-metallised dyes already described as wool dyes, the direct dyes described in Chapter and the reactive dyes described in Chapter. Mordant dyes applied to silk are mainly of the anthraquinone type. It has never been necessary to develop dyes especially for silk. Cellulosic Fibres: The earliest cellulosic fibres were lines and cotton, both of which have been used since remote antiquity. Linen, or flax, is derived from ‘bast’ fibres of plants of the Linum family, especially Linum usitatissimum. After removal of glutinous and pectinous matter the fibre has cellulose content of 82 – 83%. Cotton, which is fine hair attached to seeds of various species of plants of the Gossypium genus, has a cellulose content which may reach 96%. Cellulose is a polymer of high molecular weight consisting of long chains of D-glucose units connected by B-1, 4- glucosidic bonds, and its structure may be represented as follows:

49

Each glucose unit contains three alcoholic hydroxyl groups, of which two are secondary and one is primary. The degree of polymerisation of cellulose varies from a few hundred to 3500 or more. Regenerated cellulose fibres were introduced during the last two decades of the 19th century. The first process was that Chardonnet (1884), who produced a fibre by spinning a solution of nitrocellulose in a mixture of alcohol and ether and subsequently removing nitro groups. The cuprammonium process followed (1890), and in 1891 Cross and Bevan introduced the viscose process whereby wood pulp cellulose is treated with caustic soda and carbon disulphide to form sodium cellulose xanthate, which, after a ‘ripening’ stage, is spun into an acid coagulating bath. The nitrocellulose process is now obsolete, but the cuprammonium process, which has the advantage of giving an exceptionally fine filament, is still used. The viscose process is of much greater importance, but it is declining in consequence of the development of the newer synthetic fibres. The dyeing properties of the various cellulosic fibres are broadly similar, but application conditions are affected by differences in physically properties. Thus lines, which has a harder structure than cotton, is less readily penetrated by dyes. There are also differences in dyeing properties between the several types of regenerated cellulose fibres; cuprammonium rayon, for example, having fine filaments, is more easily dyed than viscose. Dyes of many chemical classes are applied to cellulosic fibres. Azo dyes, which predominate numerically, are described here, and others are dealt with in the appropriate chapters. The first substantive or ‘direct’ dyes discovered in 1884 were diazo dyes obtained from tetrazotised benzidine, but other structure have since been found to confer affinity for cellulose. The azo group itself favours substantivity but for adequate effect either a second azao group or another favourable group must also be present in the dye molecule.

50

The structures which are chiefly important in substantive dyes are as follows:

N NCONH

NaO3SNH2

HO

NH2

HO

NaO3S

CHS

CH

NCH

=

AZO

J-ACID

CH=CH

STILBENE

CARBOXYAMIDEDIPHENYLE

GAMMA ACID

THAIZOLE

All of the other groupings listed find used in conjunction with the azo chromophore to give a great variety of dyes for cellulosic fibres. Others of smaller importance, such as the residues of pyrazol-5-one, resorcinol and m-phenylenedianine, also confer a measure of cellulose affinity. Apart from the presence of one or more of the favourable components there are other structure requirements for substantivity. Typical substantive azo dyes of the various chemical classes are now described. Monoazso Dyes: About 35 monoazo direct dyes are in use, most of them containing either a thiazole or a J acid residue. Examples are CI Direct Yellow 8 (CI 13920), CI Direct Brown 30 (CI 17630) and CI Direct Red 118 (CI 17780) (diazotised and developed on the fibre with B-naphtol or 3-methy-1-phenylpyrazol-5-one), with the structures shown:

51

NC

SH3C

C-CH3

CONHPh

HONaO3S

N=N-C

CI DIRECT YELLOW 8

NC

S

NN=N

H3C

HO

NHPh

NaO3S

C

S

NaO3S

CI DIRECT BROWN 30

N=N

NHCO

NH2

HO

NaO3S

CI DIRECT RED 118

Congo Red, the first direct dye manufactured, which was discovered by Bottiger in 1884, has the constitution benzidine (naphthionic acid) and is therefore included under this heading. Many other dyes of the same. Dyes with Mixed Chromophores: Polyazo dyes normally contain a single chromophoric system, and a conjugated chain runs through the whole molecule. It is possible, however, for a dye molecule to contain two or more independent chromophoric systems electronically insulated from each other. Such dyes were first introduced by CIBA, who utilized the triazinyl ring as a chromophoric block. This ring serves as a convenient link since it can be introduced by reaction of cyanuric chloride with two or three amino-containing dyes in succession. Substitution of the first chlorine atom 52

takes place easily in presence of alkali at atmospheric temperature. The second chlorine atom is less easily removed, and reaction with an amino compound may require a temperature of 55o – 60oC, the optimum conditions varying with the basicity of the amine. Replacement of the clorine atom calls for still more vigorous conditions, and a temperature of 90o – 100oC may be suitable; much higher temperature are needed, however, in the case of weakly basic compounds. The progressive loss of activity at each stage enables condensation to be carried out with three different components to give a substantially homogeneous product. The residues of three dyes (Dye 1)-NH2, (Dye 2)-NH2 and (Dye 3)-NH2 may be linked by a series of reactions in alkaline medium, as shown:

N

N

N

Cl

Cl

Cl

N

N

N

Cl

Cl

+NH2(Dye 1)

NH(Dye 1)

N

N

N

Cl

NH

NH(Dye 1)

Low Temperature

Stage 1

Stage 2

N

N

N

Cl

Cl

NH(Dye 1) + (Dye 2) NH2Moderate Temperature (Dye 2)

Stage 3

N

N

N

Cl

NH(Dye 1)

NH (Dye 2)

+ (Dye 3) NH2 High Temperature

N

N

N

NH

NH

NH

(Dye 1)

(Dye 2)

(Dye 3) In the resulting product each dye residue contributes its own absorption characteristics; by combining yellow and blue components, green dyes can therefore be obtained that are much brighter than normal polyazo greens. Dyes containing three inde; pendent chromophoric system is of limited interest and the third condensation is often carried out with a suitably reactive colourless compound such as aniline or phenol.

53

An example of a commercial dye containing two electronically insulated chromophores is Chlorantine Fast Green BLL (CIBA) (CI Direct Green 26; CI 34045); it gives bluish green hue on cellulosic fibres. One of the aminoazo dye residues. A commercial dye containing both azo and anthraquinone residues is Chlorantine Fast 5 GLL (CIBA) (CI Direct Green 28; CI 14155), which has the structure (2) and gives bright yellowish green shades on cellulosic fibres.

OH

N

NaO3S

NaO3S

OMe

Me

NHNN

N

N

NHPh

NH N OH

COONa

N

(1)

H2N

O O

NaO 3S

NH HN

SO3Na

N

N

N

NHPh

COONa

OHNH- -N=N-

(2)

Cellulose Acetate Fibres: The D-glucose units in the cellulose polymer contain three hydroxyl groups, of which one is primary and two are secondary. By acetylating all of the hydroxyl group in cellulose a triacetate is obtained with a polymetric structure which may be represented thus:

O

oH

O

H

H

CH2

OAc

H OAc

OAc

H

H

O

H

H

OAc

OAc

H

H

CH2

OAc

n

54

55

The triacetate is soluble in chloroform, and a fibre known as Lustron was spun from chloroform solution in early small-scale American manufacture (1914-1924). If the triacetate is partially hydrolysed to give a mixture with an average of 2 ½ acetyl groups per glucose residue the product loses solubility in chloroform, but becomes soluble in acetone. A different product, which is insoluble in acetone, is obtained by direct introduction of 2 ½ acetyl groups; presumably the less accessible hydroxyl groups are the last to be acetylated and the last to be re-formed on hydrolysis.

During the First World War incompletely acetylated cellulose was produced on a large scale for use as a dope for aircraft fabric. After the war efforts to find a new use for it led to the production of cellulose acetate fibre by British Celanese Corporation. The commercial product contains an average of 2-3 acetyl groups per glucose residue, and is known as secondary acetate, or simply ‘acetate’. It is spun from acetone solution. In spite of an inconveniently low melting-point acetate fibre attained great success and is still extensively used, but in recent years it has been partly superseded by other synthetic fibres.

It was appreciated in the early days that the dyeing of acetae differs from that of the natural fibres and viscose in that fibre serves as a solvent for the dye. In 1923 work on dyes in the form of aqueous dispersions was carried out independently by British Celanese Corporation and British Dyestuffs Corporation. The SRA colours of British Celanese Corporation were dispersions of aminoazo or hydroxyazo dyes obtained by means of the surface-active agent sulphated ricinoleic acid. Other dispersing agents used included alkyl sulphates, alkaryl sulphonates and fatty alcohol-ethylene oxide condensates (a long alkyl chain being usually present in the molecule), and the dispersions obtained by applying them with various milling techniques were often so fine as to be easily mistaken for true solutions. British Dyestuffs Corporation marketed dispersed aminoazo and hydroxyazo dyes in their Dispersol range, and this is still maintained by ICI (formed in 1926 by a union of British dye stuffs Corporation with other firms). The Duranol range is a parallel range of dispersed dyes of the anthraquinone series.

Dyes of these types are now produced by many manufactures. Whereas the dyes were formerly supplied only as aqueous dispersions

56

they are now usually marketed in the form of re-dispersible powders which yield suitable dispersions on stirring with water. Hydroxyalkylamino groups impart a small degree of water-solubility and assist dispersibility; coupling components such as N-ethyl-N- B-hydroxyethylaniline or N, N-di (B-hydroxyethyl) aniline are therefore commonly used. Many of the earlier yellow and orange dyes proved to be phototropic, but it was found that this groublesome characteristic can be largely avoided by introducing nitro or other negative groups into the dye molecule; these substituents restrain trans cis isomerizatrion. Since dye molecules must be fairly small in order that they dissolve readily in the fibre monoazo dyes are commonly used, but a few disazo dyes are included in commercial ranges. Blacks are obtained by diazotising aminoazo dyes on the fibre and developing with a solution of 3-hydroxy-2-naphthoic acid. In 1936 a range of water-soluble dyes for acetate was marketed by ICI under the name Solacet. Their solubility was due to the presence of a sulphuric ester group (-- OSO3Na), usually introduced by sulphation of a B-hydroxyethlamino group, which did not seriously impair affinity for the fibre. The unsuitability of conventional water-soluble dyes for acetate fibres is apparently due to the presence of highly ionised – SO3-Na+ groups rather than their solubility in water. In consequence of the of the development of dispersed dyes with improved dyeing and fastness properties the Solacet range has now been superseded. Many dyes developed for acetate have now been applied to the newer synthetic fibres, and the manufactured ranges have been extended specially for these outlets. The term ‘Acetate dyes’ has therefore, been discarded in favour of ‘Disperse dyes’ so that all applications may be included. Disperse dyes for fibres other than acetate are described later. Examples of azo disperse dyes applied to acetate are shown in Table 4.6; violet and blue dyes are included, but disperse dyes of these shades are derived mainly from the anthraquinone series. Cellulose Triacetate Fibres: Cellulose triacetate was manufactured in the United States during the period 1914-24, but the process was unsatisfactory because the only suitable solvent then commercially available was chloroform, and this was both toxic and expensive. Methylene dichloride is a suitable solvent

57

of low toxicity, and it became available fairly cheaply about 1930, but by the eat time secondary acetate was fully established. Later, however, when the hydrophobic fibres nylon and ‘Terylene’ had achieved great success, the possibilities of triacetate as an inexpensive fibre sharing some of their good properties became apparent, and it has now been introduced as a commercial fibre under names such as Tricel (Courtaulds Ltd.), Armel (Celanese Corporation of America) and Trilon (Canadian Celanese Ltd.). It has good shrink- and crease-resistance, is quickdrying, shows good fastness to wet treatments and can be heat-set without loss of lustre. As it has a higher melting point the hazards associated with the ironing of fabrics of secondary acetate are largely avoided. Because of its hydrophobic character triacetate is less easily dyed than acetate, but suitable dyes can be selected from existing ranges of disperse dyes. Whereas acetate is dyed at 75o–80oC, triacetate requires a temperature at or near the boil. If the fabric is to be heat-set for pleats the dyes used must be stable at 200oC. Poyamide Fibres: Nylon 6,6 and Nylon 6 can be dyed by many disperse, acid and direct dyes. Since many suitable dyes are available, commercial ranges are usually selected from products already manufactured for other purposes, and (apart from the reactive dyes discussed later) new structures have not been required. It has proved very difficult to manufacture nylon with uniform dyeing properties, and for this reason dyes with good leveling properties are necessary. In this respect disperse dyes have a great advantage in that they conceal fibre irregularities. For high wet-fastness acid dyes are preferred, but very careful application is necessary in order to secure level dying. These dyes often show better wet-fastness properties on nylon than on wool because of the hydrophobic character of the former. Fastness to light, however, is often slightly lower on nylon than on wool. The affinity of acid dyes for Nylon 6 is higher than that for other types because polycaprolactam fibres contain a higher proportion of free amino groups Ranges of acid dyes for nylon are classified by the makiers so that users may select dyes with good leveling or good wet-fastness properties according to their requirements, there are also ranges with intermediate properties and others specially designed for fabric printing.

Polyester Fibres: In the course of the exploratory work that led to the development of nylon W.H. Carothers examined aliphatic polyesters but abandoned them in favour of the more promising polyamides. Subsequently, however, the late J.R. Whinfield and J.T. Dickson of The Calico Printers’ Association re-examined polyesters for the purpose. They extended the work to aromatic compounds and obtained a polymer with excellent fibre-forming properties from terephthalic acid and ethyleneglycol. This has the structure (3). The important fibre ‘Terylene’ was based on this

OC HHO CO.O.H2C.CH2.O

n Work, and was first prepared in the laboratory in 1941. Development and production of the fibre were carried out by ICI, and this fibre is now manufactured under various names on a very large scale in many parts of the world. Dimethyl terephthalate is now commonly used in place of the free acid so that the terminal carboxlic acid group is esterified. Since n has a value of about 80 the properties of the fibre are not greatly affected. The ester is preferred as starting material because it is more easily purified, and purity is essential in the manufacture of high polymers. ‘Terylene’ fibre is highly hydrophobic, withstands attack by bacteria, moulds, months, acid and alkali, has high strength even in wet conditions, is superior to nylon in resistance to light, can be heat-set and has glood di-electric properties. It is largely used for manufacture of net curtains, in blends with wool for suitings and other outerwer,k and for many industrial purposes.

The hydrophobic nature of ‘Terylene’, its tightly packed molecular structure and its lack of reactive groups all render it unreceptive to dye molecules. Certain disperse dyes can be applied, but under normal conditions adsorption is slow and only pale shades are

58

59

obtained. Much better penetration is obtained by dyeing at about 12oC under pressure, and the special dyeing machinery required is now in general use. Since diffusion is slow in conditions of normal use, dyeings obtained in this way have good wet-fastness properties. Suitable dyes must be selected for this process since not all will withstand the high temperature without change of shade. Disperse dyes can also be applied at temperatures below 100oC by the aid of ‘carriers’ added to the dyebath. These agents are supplied under various brand names, such as ‘Tumescal’ (ICI), and usually consist of compounds such as o- or p-hydroxydiphenyl. Their presence greatly facilitates the dyeing process, but the mode of action is not fully understood. This process enables dyeing to be carried out in standard machines, but it is somewhat expensive and has disadvantages in that the carriers are often difficult to remove completely; their presence may cause a noticeable odour and sometimes impairment of light-fastness. Polyester fibres can be dyed by the Thermosol process (DuPont), which consists in padding with disperse dye and a thickening agent, then drying and heating at 175o – 200oC for about one minute. Under such conditions the dye is absorbed rapidly; after scouring to remove loose colour the dyed material is finished in the usual way. Polypropylene Fibres: Polyethylene has many applications in the plastic industry, but its low melting-pointrenders it unsuitable for fibre formation. Its homologure polypropylene exists in various forms according to the disposition of the substituent methyl groups; the isotactic polymers, in which these groups are all attached on the same side of the main carbon chain, can be spun and drawn into fibres. Catalysts promoting formation of isolactic polymers were discovered by Zeigler, and the process was further developed by Natta and others Polyproplene fibres and hydrophobic and resist chemical attack, but they are not readily dyed. Certain disperse dyes can be applied, but only pale and medium shades are obtainable. Many methods have been described in the paten literature whereby the fibre may be modified to confer affinity for acid or basic dyes. Side chains carrying polar groups may be grafted to the main polymer chain, or basic substances may be included in the melt from which the fibre is spun. Much attention has been paid to a method whereby a compound of

a polyvalent metal such as nickel, zinc or aluminium is incorporated in the fibre, which can then be dyed with metalisable dyes. Polyurethane Fibres: Several elastomeric fibres developed in America are based on polymeric structures containing urethane (--NHCOO--) linkages. Full details of the processes used are not available but complex cross-linked polymers with rubber-like properties are obtained from polyesters or polyethers containing terminal hydroxyl groups by means of a series of reactions involving di-isocyanantes and diamines. Typical examples of such fibres are Lycra (Du Pont) and Vyrene (U.S. Rubber Co.), which are extensively used for foundation garments and swimsuits. These fibres have advantages over rubber in strength, resistance to oxidation, perspiration and cosmetic oils, also in whiteness and affinity for dyes. They are readily dyed by acid, basic and disperse dyes, but fastness properties are in general rather low. Polyacrylonitrile Fibres: The simplest, polyacrylonitrile fibres are straight polymers of

CH2-CH-

CN

n

acrylonitrile with structure where n varies from 600 to 2000. The first commercial fibre of this type was Orlon, introduced by DuPont in 1948. It can be dyed by basic dyes or by acid dyes in presence of copper sulphate. Various modified acrylic fibres (often called ‘modacrylic’ fibres) are now obtained by copolymerising acfrylonitrile with other substances, and dyeing properties are thereby improved; Orlon as now manufactured is a copolymer, but the identity of the second component has not been disclosed. Acrilan (Chemstrand Corporation), Dynel (Union Carbide Corporation) and courtelle (Courtaulds Ltd.) are other modified acrylic fibres. In general acid, disperse, basic and vat dyes can be applied to these fibres, but acid dyes are not recommended for Courtelle.

60

The older basic dyes often show better light fastness on acrylic fibres than on natural fibres, but new basic dyes have been developed with fastness properties on polyacrylonitrile that are fully compatible with modern standards. How do dyes stick to fibres?

This depends on the dye and the fibre to which the dye is attached. Protein-based fibres such as wool and silk have free ionisable CO2H and NH2 groups on the protein chains which can form an electrostatic attraction to parts of the dye molecule. For example the sulphonate group, SO3

-, on a dye molecule can interact with a NH3+ group on the

protein chain.

Cotton is a polymer with a string of glucose units joined together. Indigo which is used to dye denim jeans is a vat dye. Indigo is insoluble in water. The reduced form of indigo is soluble. Cotton is soaked in a colourless solution of the reduced form. This is then oxidised to the blue form of Indigo which precipitates in the fibres.

Direct dyes are applied to the cotton in solution and are held to the fibres by hydrogen bonds and instantaneous dipole-induced dipole forces. These are weak compared with covalent bonds hence these dyes are only fast if the molecules are long and straight.

Fibre reactive dyes actually form covalent bonds with fibre molecules and are therefore extremely colour fast. A dye molecule is reacted with the molecule trichlorotriazine:

61

Trichlorotriazine can react with either –OH groups (present in cotton) or –NH groups (present in wool and nylons), thus effectively bonding the dye to the fabric.

62

Reactive Dyes

5 A reactive dye, according to a useful definition by Rys and

Zollinger, is a coloured compound which has a suitable group enable of forming a covalent bond between a carbon atom of a hydroxy, an amino or a mercapto group respectively of the substrate. They point out that this definition excludes mordant dyes and 1: 1 chromium azo dye complexes, which are used in dyeing protein fibres, may form covalent bonds between metal ion and nucleophilic groups of the fibre. The idea that the establishment of a covalent bond between dye and substrate would result in improved wash fastness compared with that of ordinary dye-substrate systems where weaker forces were operative is an old one. Attempts were made by various dye firm s from about 1906 onwards to achieve this aim but it was not until 1956 that the first successful reactive dyes, the Procions, were introduced by ICI for the dyeing and printing of cellulose fibres, following the work of Rattee and Stephen from 1954 onwards. The invention consisted in the synthesis of dyes containing a reactive group, the 2,4,6-dichlorotriazinylamino group which has two labile chlorine atoms activated by the electron-withdrawing action of the three N atoms, and the

NCOH

NC

H2N

CDye NH

OH

NCCl

NC

H2N

CDye NH

Cl

NCOH

NC

H2N

CDye NHN

COR

NC

H2N

CDye NH

OR

RO-

HO-or

OR

R=Cellulose residue 63

Devising of dyebath conditions, which, while bringing about the formation of a covalent bond, were mild enough to avoid serious damage to the fibre. The dyeings were carried out at ordinary temperatures, ‘fixation’ being brought about by the addition of sodium bicarbonate, thus raising the pH. The reaction with cellulose may be represented as nucleophilic substitution by the attaching species RO- or HO- where R = cellulose moiety. Attach by HO-, derived from the water of the dyebath, occurs simultaneously, but that of cellulose onion predominates since the dye is absorbed by the cellulose fibres and dye-substrate reaction is therefore facilitated. It is necessary to remove hydrolysed unfixed dye by through soaping and washing otherwise inferior fastness to wet treatment results. An example of a Procion M dye is the following:

N

CN

CCl

C

SO3Na

N=N

NaO3S SO3Na

OH

Cl

HN

Procion red MX-2B(ICI) These dichlorotriazinyl dyes, being relatively easily hydrolysed,

tend to be unstable in storage. The Swiss Company CIBA had been interested from 1930 onwards in the introduction of triazinyl groups into dye molecules and had patented, manufactured and marketed monochlorotriazinyl dyes, though not as reactive dyes. In 1957 ICI and CIBA jointly introduced the Procion H and Cibacron ranges which require a higher temperature (60-90 oC) and a higher pH to bring about fixation, but are more stable in storage. An early example is:

64

N

CN

CNH2

C

SO3Na

N=N

NaO3S SO3Na

OH

Cl

HN

Cibcron brilliant red B The chlorotriazinyl reactive dyes are by far the most important class and have proved a serious rival to the vat dyes as regards wash-fastness and in other ways. The main chromogens employed are azo, metal-azo, anthraquinone and phthallocyanine systems. The question of cotton substantivity is an important one. It should be high enough to ensure a high ‘fixation-yield’ but at the same time a substantivity of the unfixed, hydrolysed dye should be low enough to permit easy removal by soaping and rinsing to ensure maximum fastness to wet treatments in the finished dyeing. Structural modifications to the molecule, which (a) inhibit coplanarity or (b) increase the water-solubility, tend to reduce substantivity. Since their introduction reactive dyes have been the subject of a very large number of patents comparable only with the numbers granted for inventions in the disperse dye field and in that of synthetic organic pigments. Most dye manufacturers have invested heavily in research programmes concerning new reactive systems and variations of molecular structure to achieve optimum fastness and other properties. Attention has naturally turned to reactive dyes for substrates other than cellulose and dyes have been developed which are suitable for wool and polyamides. Water-insoluble disperse dyes having reactive groups (Procynyl dyes, ICI) have been introduced principally for the dyeing of polyamide fibres on which they show improved washing and heat fastness. Reactive systems may be divided into two main types:

• Those involving nucleophilic substitution • Those involving nucleophilic addition

65

Nucleophilic substitution systems: The monochloro and dichlorotriazinyl dyes, of which early examples have already been given, account for 50% of all reactive dyes used in commerce. The dye:

C

NC

N

CN

Cl. .NH

Cl.

OH

SO3Na

NH.PhOH

N=N

NaO3S

As the 1: 2 chromium complex, is claimed in B.P. 938 125 (ICI) to dye cotton dark-green of excellent all round fastness. An example of a copper phthalocyanine dichlorotriazinyl dhye is afforded by:

C

NC

N

CN

. Cl

Cl.

NH.

SO2.NMe

SO2.NH

CuPC= (SO3H)2

Which, according to B.P. 948 256 (ICI), dyes cotton a bright greenish-blue of excellent fastness to wet treatments. The blue monochlorotriazinyl dye.

C

NC

N

CN

Cl

OPhNH

NaO3S

O

O

HN

SO3Na

.

66

B.P. 1230 722 (CGY) is said to have good light fastness and outstanding wet fastness. Dyes stemming from sulphonyl chloride derivatives of copper phthalocyanine by reaction with N- (β-hydroxyethyl) ethylenediamine, followed by condensation with 2,4-dichloro-6-methoxy-3-triazine are described in B.P. 1 227 538 (ICI). It should be noted that improved fixation can be obtained by introducing a second monochlorotriazinyl group into the reactive dye molecule. Such dyes from the basis of the Procion Supra range of ICI. Trichloropyrimidine dyes: These are derived from tetrachloropyrimidine:

CN

CN

C.Cl

C.Cl

Cl.

Cl . 2

3 5

61

4

The electron-withdrawing properties of the two nitrogen atoms render the chlorine atoms in position 2,4 and 6 labile; that in position 5 is unreactive. The trichloropyrimidine dyes do not equal the dichlorotriazines in reactivity and their fixation on the fibre requires temperatures. The dyes themselves are stated to be less sensitive to hydrolysis. Trichloropyrimidine dyes are marketed as Drimarenes (S) and Reactones (Gy) and are the general structure.

Fluorine atoms replace chlorine atoms in other pyrimidine systems e.g.

CC

C

N C

NDye NH

F

Cl F

DRIMALAN (S)VERAFIX(FBY)LEVAFIX(FBY)

Among other heterocyclic systems are the 2-chlorobenzthiazole system:

N

C

S

Cl REATEX (FRAN)CN

HDye

O

67

The chloropyridazine systems:

NNCl

ClCNH

O

SOLIDAZOL(FRAN)Dye

CNH

O

NN

Cl

Cl

DyeREATEX(FRAN)

Quinoxaline derivatives: The use of various qu8inoxaline derivatives is covfred by B.P. 995 796 (Fby):

N=C

N=C .X

.X

Where X = halogen, Y = H, Cl, Br, Qalk and other groups.

An example of a typical dye is given in B.P. 993 747 (F.By):

NC

CN

SO3H

SO3H

SO3H

SO3H

SO3HO

CuO

Cl.

Cl.

CO.NH

N=N

The acid chloride of the quinoxaline is condensed with the free amino group at position 6 in the monoazo copper at 40oC and pH 6.5-7-0 under which conditions neither chlorine atom undergoes hydrolysis. This class of reactive dyes is marketed as the Levafix E range (Fby).

68

Chloroacetyl and bromoacetyl derivatives: The Drimalan (S) dyes employ a – halogenoacetyl groups as reactive centre and this group occures (along with monochlorotriazinyl dyes) in the Cibalan Brilliant dyes (CIBA). In both cases the main application is in wool dyeing. The principal has been applied to disperse dyes as in B.P. 977 222 (S):

O

O

NH2

O

O

NH2

NH NH

CO.CH2.Br

Br2 in O - dichlorobenzene

CO.Me The resulting reactive disperse dye gives blue dyeings on polyamides of excellent fastness to wet treatments. Nuclear halogen, activated by electron, withdrawing groups such as – NO2 in o- or p-positions, can also serve as a reactive centre as in:

OH

HO3S

NH2

SO3H

N=N

HO3S NO2

Br

NH.CO

Which is claimed in B.P. 982 583 (CFM) as giving bluish-red prints on cotton of very good wet fastness and dischargeability. Vinylsulphone dyes:

The Removal (FH) dyes employ the vinylsulphone group as in Dye.SO2 CH=CH2 or compounds giving the vinyl group on treatment with alkali, i.e. under dyeing conditions:

Dye.SO2CH2.CH2OSO3Na+NaOH►Dye.SO2CH=CH2+Na2SO4+H2O

Or Dye.SO2

.CH2.Cl+NaOH ► Dye.SO2CH=CH2+Na2

.Cl+H2O The reaction mechanism leading to the formation of a covalent link with the substrate concerns the formation of a carbonium ion, facilitated by the electron-withdrawing properties of the sulphone group, followed by interaction with the anionic centre in the cellulose fibres: 69

70

Dye.SO2–CH=CH2+O–Cellulose Dye.SO2

.CH2–CH2.O–Cellulose

The mechanism is thus essentially one of nucleophilic addition. The Cavalites (DuP) also employe the vinylsulphonyl group (and also the chloroquinoxalines) while in the Levafix (Fby) range the vinylsulphonamides

Dye.SO2NHCH2CH2OSO3Na Are the relative groups, SO2NH.CH=CH2 being formed under the conditions of dyeing or printing. The ‘dye’ portion of the molecule is a water-insoluble pigment, the molecule of which contains no – SO3H or other solubilizing group. It is of interest also that β-thiosulphatoethylsulphones, ―SO2CH2CH2

.S.SO3H, are converted by bases into vinylsulphones. The Bunte sals or organic thiosulphate salts derived from dye molecules are capable of reacting directly with the thiol groups in wool fibres. –SH+SCH2CONH Dye SO3Na → –S.S.CH2CONH Dye Acrylamide dyes:

The Primazin (BASF) dyes embody the acrylamide group –NH.CO.CH=CH2 or a precursor such as –NH.CO.CH2CH2OSO3Na. As with the vinyl sulphones mechnism is primarily concerned with nucleophilic addition. The Procilan dyes for wool (ICI) embody the acryloylamino group attached to a 1: 2 nickel or cobalt azo complex. The Lanasol dyes (CGY) have as reactive centre the a – bromoacryloylamino group – NHCOC=CH2. Evidence for chemical combination Cellulose Stamm, zollinger and co-workers have endeavoured to obtain experimental evidence of the formation of a covalent link and to demonstrate its position in the D–glucose unit of cellulose. Cotton dyed with a Remazol dye was subjected to microbiological hydrolysis, a mixture of oligomers being formed. Further degradation, with dilute sulphuric acid, gave a glucose derivative in which one hydroxyl group was blocked by a dye molecule. Methylation of this under very mild conditions, followed by alkaline treatment to remove the dye molecule,

71

and then acid hydrolysis to remove the glucosidic methyl group gave finally a known trimethylglucose. Stamm later showed that a glucoside is normally formed by Remazol dyes acting on cellulose and concluded that the earlier findings were ambiguous. Cellulose dyed with a chlorotriazinyl reactive dye however will not dissolve in cuprammonium solution, whereas cellulose dyes with direct dyes will dissolve. Work on the attachment of reactive disperse dyes to polyamides has shown that both – CO.NH – groups and terminal – NH2 – groups are most probably involved. There is good evidence that chemical combination does not indeed occur in that polyamides dyed with reactive disperse dyes cannot be ‘stripped’ by solvents in contrasts to the same substrate dyed with conventional disperse dyes or azoic combinations, from which the colorant can be removed by solvents. Another striking demonstration is afforded by diluting a solution of dyed polyamide in o-chlorophenol. In the case of a reactive dye a coloured precipitate is obtained while the aqueous phase is colourless; with conventional dyes, coloration of the aqueous phase occurs. It is clear from the number of published patents relating to reactive dyes that this field is regard as being of the highest importance by the dye-maker and dye-user. Much work is also being done on the kinetics and physical chemistry of dyeing and printing processes in which reactive dyes are involved; in this, as in other fields of dye technology, progress is thereby accelerated.

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COMMERCIAL POPULAR REACTIVE DYES COLD DYEING BRANDS

# Commercial C.I.

Generic Name

Constitution Remarks Hue

1. Brill. Yellow AG

Reactive Yellow 4

Monoazo Reactive Dichlorotriazinyl

Bright Reddish yellow

2. Yellow RG Reactive Yello2w 7

Azo Reactive System –Dichlorotriazinyl

Bright Reddish Yellow

3. Yellow 4R Reactive Orange 14

Monoazo (Pyrazolone)

Bright Reddish Orange

4. Brill. Orange 2R

Reactive Orange 14

Azo Reactive System –Dichlorotriazinyl

Bright Reddish Orange

5. Brill. Red EB

Reactive Red 2

Monoazo Reactive System –Dichlorotriazinyl

Bright Blush Red

6. Brill. Rose 3B

Reactive Red 11

Azo Reactive System – Dichlorotriazinyl

Bright Blush Red

7. Brill. Pink B

Reactive Red 74

Azo Bright Bluish Pink

8. Brill. Magenta B

Reactive Violet 13

Azo Bright Reddish Violet

9. Brill. Violet RR

Reactive Violet 14

Azo Bluish Violet

10 Brill. Blue R

Reactive Blue 4 C.I.No.61205

Anthraquinone Reactive system –Dichlorotriazinyl

Bright Blue

11. Navy Blue 3R

Reactive Blue 9

Azo (copper complex) Reactive System –Dichlorotriazinyl

Reddish Navy

73

HOT DYEING BRANDS

# Commercial Name

C.I. Generic Name

Constitution Remark Hue

1. Brill. Yellow 4G-X

Reactive Yellow 18

Monoazo (pyrazolone) Monochlorotriazinyl

Bright Greenish Yellow

2. Yellow R-X Reactive Yellow 46

Azo Bright Reddish Yellow

3. Golden Yellow IR

Reactive Orange 12

Monoazo Yellowish Orange

4. Brill. Orange R

Reactive Orange 37

Azo Bright Reddish Orange

5. Brill. Orange 2R

Reactive Orange 13

Monoazo Reddish Orange

6. Brill. Red 6B

Reactive Red 76

Azo Bright Bluish Red

7. Brill. Red 8B

Reactive Red 31

Azo Bright Bluish Red

8. Brill. Violet 3R

Reactive Violet 1

Azo (copper complex) Reactive system – Monochlorotriazinyl

Bright Violet

9. Red Brown 4R

Reactive Brown 9

Monoazo(Chhromi-umcomplex)

Bordeaum

10. Turquoise Blue A

Reactive Blue 71

Phthalocyanine Greenish Blue

11. Turquoise Blue 2-G-X

Reactive Blue 3

Phthalocyanine Bright Greenish Blue

12. Turquoise Blue 25

Reactive Blue 25

Phthalocyanine Greenish Blue

13. Navy Blue R

Reactive Blue 59

Azo Reddish Navy

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BIFUNCTIONAL DYES (SUMITOMO CHEMICALS JAPAN)

No. Commercial Name C.I. Generic Name 1. Sumifix Supra

Yellow 3RF Reactive Y-145

2. Sumifix Supra Brill. Red 2BF

Reactive R-194

3. Sumifix Supra Brill. Red 3BF

Reactive R-195

4. Supra Navy Blue 2GF

Reactive B-194

5. Yellow FGS Reactive Y-115 6. Yellow GNS Reactive Y-115 7. Yellow GR Special Reactive Y-116 8. Brill. Scarlet R Reactive R-113 9. Brill. Red G Reactive R-112 10. Brill. Red BS Reactive R-111 11. Navy Blue GS 15% Reactive B-147 12. Turquoise Blue BF Reactive B-148

REACTIVE DYES IN PAKISTAN:

Cotton is the main crop of Pakistan so the main substrate for textile dyeing & processing purpose is cellulose or cotton. Cotton fabric can be dyed with a large number of dyes like vats, directs, sulphur etc In Pakistan the main consumable dyes for cotton are Reactive dyes. This is because of the following reasons:

1. In Pakistan a large number of reactive dyes class available. 2. It forms a co-valant linkage with cellulose so the fastness

properties achieved can satisfied the customers. 3. Can be applied both in Exhaust & Continuous process. 4. Most of the reactive dyes are economical. 5. A wide range of color is available. 6. From some of the manufacturer also available in granular form. The main classes of reactive dyes now available in Pakistan are

discussed below:

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SUMITOMO CHEMICALS (OSAKA, JAPAN):

BI-FUNCTIONAL DYES:1. SUMIFIX SUPRA YELLOW 3RF 2. SUMIFIX SUPRA RED 3BF 3. SUMIFIX SUPRA BLUE BRF 4. SUMIFIX SUPRA YELLOW EXF 5. SUMIFIX SUPRA RED EXF 6. SUMIFIX SUPRA BLUE EXF 7. SUMIFIX SUPRA YELLOW 3RS 8. SUMIFIX SUPRA RED 3BS 9. SUMIFIX SUPRA NAVY BLUE BS 10. SUMIFIX SUPRA NAVY BLUE BF 11. SUMIFIX SUPRA NAVY BLUE EXF 12. SUMIFIX SUPRA RED 2GF 125% 13. SUMIFIX SUPRA RED 3GF 150% 14. SUMIFIX SUPRA NAVY BLUE 3GF 15. SUMIFIX SUPRA RED BB 150% 16. SUMIFIX SUPRA YELLOW GN 150% 17. SUMIFIX SUPRA YELLOW GR 150% 18. SUMIFIX SUPRA YELLOW GL 150% SUMIFIX –HF DYES: 1. SUMIFIX HF YELLOW 3R 2. SUMIFIX HF RED 2B 3. SUMIFIX HF BLUE BG 4. SUMIFIX HF NAVY 2G SUMIFIX VS DYES: 1. SUMIFIX BLUE R 150% 2. SUMIFIX TURQ BLUE G 150% 3. SUMIFIX TURQ BLUE G 225% 4. SUMIFIX BLACK A 5. SUMIFIX BLACK B 150% 6. SUMIFIX YELLOW 4GL

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7. SUMIFIX BLACK EXF (A) 8. SUMIFIX ORANGE GRS 200% 9. SUMIFIX YELLOW 3GF 150%

KYUNG-IN SYNTHETIC CORPORATION (SEOUL, KOREA): 1. SYNOZOL BLACK HF-GR 130% 2. SYNOZOL BLACK SHF -RW 150% 3. SYNOZOL BLACK B 150% 4. SYNOZOL BLUE SHF-BRN 111150% 5. SYNOZOL BLACK HF- GR 130% 6. SYNOZOL BLUE SHF-BRS 150% 7. SYNOZOL BRILLIANT BLUE R 150% 8. SYNOZOL BRILLIANT BLUE R SPL 9. SYNOZOL BRILL BLUE R 150 % SPL 10. SYNOZOL BRILLIANT ORANGE 3R 150% 11. SYNOZOL GOLDEN YELLOW HF-2GR 150% 12. SYNOZOL GOLDEN YELLOW HF-4GR 13. SYNOZOL GOLDEN YELLOW SHF-RN 150% 14. SYNOZOL GREEN HF-GG 15. SYNOZOL NAVY BLUE HF-2GB150% 16. SYNOZOL NAVY BLUE RH 150% 17. SYNOZOL NAVY BLUE SHF-BR 18. SYNOZOL ORANGE SHF-RR 19. SYNOZOL RED HF-6BN 150% 20. SYNOZOL RED SHF-BN 150% 21. SYNOZOL RED SHF-EP CONC 22. SYNOZOL RED SHF-GD 23. SYNOZOL SCARLET SHF-2GN 150% 24. SYNOZOL TURQUOISE BLUE HF-G 165% 25. SYNOZOL VIOLET SHF-3B 26. SYNOZOL YELLOW HF-3GN 27. SYNOZOL YELLOW HF-4GL 150%

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REFAFIX DYESTUFFS (KOREA) : 1. REFAFIX LEMON YELLOW 4GL 2. REFAFIX ORANGE 2RN 3. REFAFIX GOLDEN YELLOW 3RN 4. REFAFIX RED 3BN 5. REFAFIX TURQUOISE BLUE G 170% 6. REFAFIX NAVY BLUE BF 7. REFAFIX VIOLET 5R 8. REFAFIX BLACK B 150% 9. REFAFIX BLACK GR P.T.SINAR (INDONESIA): 1. SINARCION RED BF 2B 150% 2. SINARCION YELLOW BF 4R 150% 3. SINARCION BLACK VBB 150% 4. SINARCION BLACK HF-GRPEX 5. SINARCION YELLOW BF 4GL 150% 6. SINARCION BLUE BFRF 150% 7. SINARCION NAVY BF2F 8. SINARCION NAVY BLUE RH 9. SINARCION ORANGE BF2B 150% 10. SINARCION RED HF 11. SINARCION YELLOW HF 12. SINARCION BLUE VR 150% 13. SINARCION BLUE VR SPL 14. SINARCION TURQUOISE BLUE VG 165% 15. SINARCION TURQUOISE BLUE GD

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MEGHMANI DYES & INTERMIDIATES (AHMEDABAD INDIA): BI- FUNCTIONAL TYPE DYES: 1. REACTOBOND YELLOW ME4GL 2. REACTOBOND YELLOW 3RX 3. REACTOBOND ORANGE 2RX 4. REACTOBOND RED 3GX 5. REACTOBOND RED 2BX 6. REACTOBOND RED 2GX 7. REACTOBOND RED 3BX 8. REACTOBOND RED 3BS 9. REACTOBOND RED 6BX 10. REACTOBOND BLUE 4GX 11. REACTOBOND BLUE RB 12. REACTOBOND BLUE BFN 13. REACTOBOND NAVY BLUE 3GX 14. RECTOBOND BLUE BRX 15. REACTOBOND BLACK GR 16. REACTOBOND BLACK GF 17. REACTOBOND BLACK GRD 18. REACTOBOND BLACK GRP HIGH EXHAUST TYPE DYESTUFFS: 1. REACTOBOND YELLOW HE6G 2. REACTOBOND YELLOW HE4G 3. REACTOBOND GOLDEN YELLOW HE4R 4. REACTOBOND ORANGE HER 5. REACTOBOND RED HE3B 6. RECTOBOND RED HE7B 7. REACTOBOND GREEN HE4B 8. REACTOBOND NAVY BLUE HER 9. REACTOBOND NAVY BLUE HE2R 10. REACTOBOND NAVY BLUE HERD

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11. RECTOBOND NAVY BLUE HEXL 12. REACTOBOND CRIMSON HEXL 13. REACTOBOND YELLOW HEXL

VINYL SULPHONE BASED DYESTUFFS: 1. REACTOBOND YELLOW 4GL 2. REACTOBOND YELLOW FG 3. REACTOBOND YELLOW GR 4. REACTOBOND YELLOW GL 5. REACTOBOND YELLOW RNL 100% 6. REACTOBOND YELLOW RNL 150% 7. REACTOBOND GOLDEN YELLOW G 8. REACTOBOND YELLOW GN 9. REACTOBOND YELLOW RI 10. REACTOBOND YELLOW RR 11. REACTOBOND ORANGE 3R 12. REACTOBOND RED C2G 13. REACTOBOND RED 5B 14. REACTOBOND RED FBN 15. REACTOBOND RED RB 16. REACTOBOND RED 5BX 17. REACTOBOND RED BB 150% 18. REACTOBOND RED BS 19. REACTOBOND RED 3B 20. REACTOBOND RED RR 21. REACTOBOND BORDAUX B 22. REACTOBOND VIOLET 5R 140% 23. REACTOBOND VIOLET 5R 180% 24. REACTOBOND NAVY BLUE GG 25. REACTOBOND BLUE BB 26. REACTOBOND NAVY BLUE RGB 150% 27. REACTOBOND BLUE 3R 28. REACTOBOND DARK BLUE HR 29. REACTOBOND BLUE R SPL 30. REACTOBOND TURQUOISE BLUE G 31. REACTOBOND BLUE RR

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32. REACTOBOND GREEN H6BL 33. REACTOBOND BROWN GR 34. REACTOBOND BLACK 100% 35. REACTOBOND BLACK B 150% 36. REACTOBOND BLACK RL HOT BRAND DYESTUFFS: 1. REACTOBOND YELLOW H5G 2. REACTOBOND YELLOW H4G 3. REACTOBOND GOLDEN YELLOW HR 4. REACTOBOND ORANGE H2R 5. REACTOBOND ORANGE HG 6. REACTOBOND RED 6BX 7. REACTOBOND RED H8B 8. REACTOBOND RED PB 9. REACTOBOND RED P3BN 10. REACTOBOND RED P3B 11. REACTOBOND RED P8BN 12. REACTOBOND PURPLE P3R 13. REACTOBOND MMEGENTA PB 14. REACTOBOND BLUE P5R 15. REACTOBOND BLACK PN 16. REACTOBOND TURQUOISE BLUE H5G 17. REACTOBOND TURQUOISE BLUE HA 18. REACTOBOND BLUE P3R 19. REACTOBOND NAVY BLUE P2R 20. REACTOBOND BLACK P2R 21. REACTOBOND BLACK PGR 22. REACTOBOND BLACK XLW COLD BRAND DYESTUFFS: 1. REACTOBOND YELLOW M8B 2. REACTOBOND YELLOW M4R 3. REACTOBOND ORANGE M2R 4. REACTOBOND RED M5B 5. REACTOBOND RED M8B

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6. REACTOBOND MEGENTA MB 7. REACTOBOND VIOLET C4R 8. REACTOBOND BLUE MR 9. REACTOBOND BLUE M2R 10. REACTOBOND BLUE M4GD REACTOBOND XL DYES: 1. REACTOBOND YELLOW XL 2. REACTOBOND RED XL 3. REACTOBOND RED XL3B 4. REACTOBOND BLUE XL 5. REACTOBOND NAVY BLUE XL 6. REACTOBOND BLACK XL REACTOBOND HEXL DYES: 1. REACTOBOND YELLOW HEXL 2. REACTOBOND CARAMINE HEXL 3. REACTOBOND CRIMSON HEXL 4. REACTOBOND RED HEXL 5. REACTOBOND NAVY BLUE HEXL

JAY CHEMICALS INDIA: 1. JAKAZOL BLACK B 150% 2. JAKAZOL BLACK GG 3. JAKAZOL BLACK GR CONC 4. JAKAZOL BLACK HF-GR 5. JAKAZOL BLACK HFGRPEX 6. JAKAZOL BLACK SJ 7. JAKAZOL BLUE JRF 8. JAKAZOL BLUE ME2RL 9. JAKAZOL BRILL BLUE R SPL 10. JAKAZOL BRILL RED RB 133% 11. JAKAZOL GOLDEN YELLOW MERL 150% 12. JAKAZOL GOLDEN YELLOW RNL 150% 13. JAKAZOL GREEN ME4BL

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14. JAKAZOL GREY MEN BF 15. JAKAZOL GREY MER VS 16. JAKAZOL NAVY BLUE ME2GL 17. JAKAZOL BLUE ME-BF 18. JAKAZOL NAVY BLUE ME-GFN 19. JAKAZOL ORANGE 3R 20. JAKAZOL ORANGE ME2RL 21. JAKAZOL RED ME4BL 22. JAKAZOL RED MEGF 23. JAKAZOL TURQ BLUE GD SPL 24. JAKAZOL TURQ BLUE PG 25. JAKAZOL VIOLET 5R 26. JAKAZOL VIOLET ME –B2 27. JAKAZOL YELLOW FG 28. JAKAZOL YELLOW GR 29. JAKAZOL YELLOW 4GL

DYESTAR (GERMANY) REMAZOL 1. GOLDEN YELLOW RGB 2. GOLDEN YELLOW RNL GRAIN 150% 3. RED RB GRAIN 133% 4. TURQ BLUE G 133% 5. BLACK B GRAIN 133% 6. DEEP BLACK N GRAIN 150% 7. BRILLIANT BLUE R SPL 8. YELLOW 3RS GRAIN 133% 9. NAVY GG GRAIN 133% 10. NAVY RGB GRAIN 150% 11. BRILLIANT BLUE RN GRAIN 12. BRILLIANT ORANGE 3R GRAIN 13. BRILLIANT RED 3BS GRAIN 14. BRILL VIOLET 5R 15. BRILL YELLOW GL GRAIN 16. RED RGB 17. DEEP RED RGB 18. YELLOW 3RS-A 150%

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19. BRILL RED 3BS-A 150% 20. BLACK GSA LEVAFIX: 1. ORANGE E3GA 2. BRILL RED E4BA GRAIN 3. BRILL YELLOW E3G GRAIN 4. YELLOW CA GRAIN 5. RED CA GRAIN 6. BLUE CA GRAIN 7. NAVY CA GRAIN 8. RUBINE CA GRAIN

SUNFIX (CHEMDYES CORPORATION) 1. SUNFIX RED S3B 150% 2. SUNFIX'YELLOWS3R 150% 3. SUNFIX RED SPD 150% 4. SUNFIX YELLOW SPD 150% 5. SUN FIX N.BI.UE SPD (SPL) 150% 6. SUN FIX BLUE SBR 7. SUN FIX RED SG (For pale shade) 8. SUN FIX. YELLOW SPR (For pale shade) 9. SUNFIX ORANGE S2R 150% 10. SUNFIX NAVY BLUE 150% 11. SUNFIX N/BLUE SB 12. SUNFIX YelJLDW S4GL 150% 13. SUNZOL BLACK B 150% 14. SUNZOL BLACK GR CONC 15. SUNZOL BIACK WN CONC 16. SUNZOL TURQ BLUE G 165% 17. SUNZOL BRILL BLUE-R (SPL) 18. SUNZOL ORANGE 3R (0RANGE-16) 19. SUNZOL VIOLET SR (VIOLET-5)

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20. SUNZOL BLUE BB (B-220) 21. SUNZOL GREEN GG 22. SUNZOL NAVY BLUE GG 23. SUNZOL YEIJLOW 2RN(SAME AS RAMAZOL YRNL) 24. SUNZOL RED RB 25. SUNZOL REDBB 26. SUNFIX YELLOW SS 27. SUNFIX RED SS 28. SUNZOL BLACK El3 (CONC) 29. SUNZOL NAVY BLUE GRH

EVERZOL DYES (TAIWAN) LX – DYES: 1. EVERZOL YELLOW LX 2. EVERZOL RED LX 3. EVERZOL BLUE LX EVERZOL ED-RANGE : 1. EVERZOL YELLOW ED 2. EVERZOL YELLOW EDR 3. EVERZOL YELLOW ED-2G 4. EVERZOL RED ED 5. EVERZOL RED ED 2B 6. EVERZOL RED ED-3B 7. EVERZOL BLUE ED 8. EVERZOL BLUE ED-G 9. EVERZOL NAVY ED 10. EVERZOL BLACK ED 11. EVERZOL BLACK ED-2R 12. EVERZOL RUBINE ED 13. EVERZOL ORANGE ED-2R

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EVRZOL BF/VS DYES: 1. EVERZOL BRILL RED F2B 2. EVERZOL BRILL. RED F3B 3. EVERZOL RED BS 4. EVERZOL BRILL RED 3BS H/C 5. EVERZOL RED RBN 6. EVERZOL RED BB 7. EVERZOL RED LF-2B 8. EVERZOL BLUE 3BR H/C 9. EVERZOL BLUE BB 133% 10. EVERZOL BLUE BRF 150% 11. EVRRZOL BRILL BLUE R S/P 12. EVERZOL BRILL BLUE R S/P H/C 13. EVERZOL TURQ. BLUE G 14. EVERZOL TURQ. BLUE VSG 133% 15. EVERZOL G. YELLOW 3RS H/C 16. EVERZOL L.YELLOW 3GL 17. EVERZOL BRILL YELLOW 4GL 18. EVERZOL YELLOW GR 19. EVERZOL YELLOW F3R H/C 20. EVERZOL G. YELLOW RNL 21. EVERZOL YELLOW PEG 22. EVERZOL NAVY BLUE BDF 23. EVERZOL NAVY BLUE GG 24. EVERZOL NAVY BLUE FBN 25. EVERZOL NAVY BLUE RGB 26. EVERZOL NAVY BLUE RGB H/C 150% 27. EVERZOL BRILL ORANGE 3R 28. EVERZOL BLACK B H/C 29. EVERZOL BLACK CRN 30. EVERZOL BLACK GSP 31. EVERZOL BLACK N 32. EVERZOL BLACK NR 33. EVERZOL BLACK GR 34. EVERZOL BLACK MW 35. EVERZOL BLACK GRB

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36. EVERZOL ORANGE ED-2R NEW RANGE: 1. EVERZOL YELLOW 2GR 150% 2. EVERZOL RED 6BN 150% 3. EVERZOL BLACK BFV

CLARIENT SWITZERLAND DYES K-DYES : 1. DRIMEREN RED K4BL 2. DRIMEREN BLUE K2RL 3. DRIMEREN TURQ BLUE K2B 4. DRIMEREN NAVY KGRL 5. DRIMEREN GOLDEN YELLOW K2RL 6. DRIMEREN ORANGE KGL 7. DRIMEREN ORANGE K3R 8. DRIMEREN ORANGE KR 9. DRIMEREN VIOLET K2R 10. DRIMEREN BLACK K3B 11. DRIMEREN YELLOW K2GLK 200% 12. DRIMEREN GREEN K5BL CL-DYES: 1. REACTIVE YELLOW CL3G 2. REACTIVE YELLOW CL2R 3. REACTIVE ORANGE CL3B 4. REACTIVE RED CL5B 5. REACTIVE CL3BL 6. REACTIVE BLUE CLRL 7. REACTIVE TURQ BLUE CLB 8. REACTIVE BLUE CLR

Direct Dyes

6 The direct dyes, also known as the substantive colours, differ from

the basic and acid dyes because cellulosic fibres have a strong affinity for them. Many of them will also dye the protein fibres and, as was explained in the previous chapter, the majority is sulphonated azo compounds very similar to the acid dyes in constitution, there being no clear demarcation between the two classes. Selected substantive dyes can be used to give solid shades on wool and cotton mixtures.

This was the first direct dye, and its discovery was quickly followed by the preparation of many similar colours, opening a new era in cotton dyeing. Before 1884 cellulosic fibres could only be dyed on a mordant or by means of indigo and a limited number of other naturally occurring vat dyes. Both of these methods were troublesome and expensive. Cotton was made in large quantities in the last century for markets where cheapness was a most important consideration. The direct dyes were inexpensive and easy to apply and, although of indifferent wet-fastness, their use spread with great rapidity because they fulfilled an outstanding demand. New members with improved fastness are still being added to this class. Chemical constitution of direct dyes: Most of the colours belonging to this class are sulphonated azo compounds. A simple monazo direct dye is Diazamine Scarlet B (C.I. Direct Red 118), formula (1):

87

N N

SO3Na NH.CO NH2

(1)

and the original Congo red (C.I.Direct red 28) formula 2

NH2 N N N N

SO3Na NaO3S

NH2(2)

Was a bisazo compound prepared by coupling benzidine diazotized at both amino groups with 2 molecules of naphthionic acid Diazo Brown 3RNA.CF (C.I. DIRECT BROWN 138), formula (3)

H2N NH2N N N N

NH2

N N

NH2NH2

SO3Na is a trisazo direct dye of comparatively simple structure and a polyazo or tetrakis azo member of the class is Chlorazol Brown GM (C.I. DIRECT BROWN 44), formula (4)

NaO3S

NH2NH2

SO3NaN=N- N=N-N=N-N=N-

An important group of the direct dyes is those derived from stilbene, formula (5), such as Diphenyl Chrysoine G (C.I. DIRECT YELLOW 19), formula (6)

CH

CH

(5)

CH

CH

N=N-

N=N-

NaO3S

NaO3S

OH

OH

(6) In 1887 Green prepared Primuline, formula (7), which was the fast of the Thiazole direct dyes.

88

N

C CS NH2

NaO3S

CH3S

N

(7)

89

CLASSIFICATION ACCORDING TO DYEING BEHAVIOUR It was appreciated by earlier workers that the behaviour of individual direct dyes varied considerably. This necessitated special care in selection, particularly in mixture, in order to achieve optimum results and to prevent the occurrence of faults, such as uneven or insufficiently penetrated dyeings on all types of materials and listing or ending with jig-dyed fabrics. As a result attention was given to devising suitable laboratory test methods to characterise the dyeing behaviour of individual direct dyes and thereby enable the best selection to be made for a particular dyeing method, highlighting the parameters to be observed in controlling the dyeing cycle. In the UK pioneer work in this area by C M Whittaker, John Boulton and their colleagues at Courtaulds in the 1940s was concerned with the dhyeing of viscose. A characteristic of individual direct dyes, described as the time of half dyeing (i.e. the time taken to reach 50% of the equilibrium absorption under specified conditions), is an indication of the rate at which a direct dye is absorbed by the fibre. In the direct dye range it varies from 0.72 to 280 min. Arising from this work, it was suggested that dyes exhibiting a similar time of half dyeing would be the preferred choice in mixtures. It was found later, however, that measurements of the so-called rate of dyeing, related to time of half dyeing, were inadequate to obtain a full understanding of the compatibility of direct dyes. Subsequently it was confirmed that rate of dyeing alone is insufficient to predict compatibility and that rate of migration and salt controllability are of greater importance. As a result of a detailed study of the subject by the Society of Dyers and Colourists’ Committee on the Dyeing Properties of Direct Cotton Dyes it was concluded that determination of four parameters was necessary, i.e., migration (or leveling power), salt controllability and the influence of temperature and of liquor ratio on exhaustion. Tests are prescribed for migration and salt controllability whilst a statement covers the influence of temperature and liquor ratio, no tests being prescribed. The aforementioned SDC committee recommended that direct dyes be classified as follows.

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Class A Dyes, which are self-levelling, i.e. dyes of good migration or leveling properties.

Class B Dyes which are not self-levelling, but which can be controlled by addition of salt to give level results; they are described as salt controllable.

Class C Dyes which are not self-levelling and which are highly sensitive to salt; the exhaustion of these dyes cannot adequately be controlled by addition of salt alone and they require additonal control by temperature; they are described as temperature controllable.

Widespread use is made of the SDC ABC classification and it is

included in many dye manufacturers’ pattern cards and other technical literature. A typical dye maker’s range of direct dyes would contain roughly 20% class A, 40% class B and 40% class C dyes. The prescribed tests were based on the use of unmercerised cotton and were found subsequently to be equally applicable to mercerised cotton, viscose and linen. Amplification and some modifications of the SDC ABC classification were undertaken by Beal and the results were given in the form of graphs covering gthe following factors: rate of exhaustion and degree of migration (which are characteristics properties of individual dyes), time and temperature of dyeing, electrolyte concentration and liquor ratio (all the last four being external factors capable of control); these graphs are now seldom used. A study of the migration properties of direct dyes was made by Cegarra to ascertain the effect of variations in temperature, electrolyte concentration, liquor ratio and agitation of the dye liquor. It was found that at low temperature an increase in temperature improved migration more effectively with classes A and B dyes than with class C direct dyes. An optimum electrolyte concentration for maximum migration is shown by classes A and B dyes but with class C dyes that migration diminishes steadily as the electrolyte concentration is increased. Increase in liquor ratio increases migration of classes B and C but not that of class A dyes. Agitation increases migration of all three classes of yes.

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Temperature-ranges tests are useful for determining the behaviour of individual dyes at various temperatures of dyeing and are of particular value in the selection of compatible dyes for mixtures. The percentage absorption of dye under standard conditions of electrolyte concentration, liquor ratio and time of dyeing at a variety of temperatures is estimated visually or colorimetrically and the results are given in the form of graphs. The selection of compatible dyes for padding and jig dyeing processes is not whooly covered by the SDC ABC classification and related tests. This can be done, however, by carrying out simple dip or strike tests in which fabric or yarn samples are dyed for short periods, e.g. for 1-2 min, removed from the dyebaths, replaced by fresh samples and the procedure repeated several times; the patterns are mounted in series and assessed visually for change of hue and depth. Marked changes of hue indicate incompatibility. The various tests described are simple to perform, required the minimum of apparatus and skill, and the results obtained are easy to interpret. They provide valuable information on the performance of individual direct dyes, either alone or mixtures.

Disperse Dyes

7 Disperse dyes include water insoluble dyes which could applied on synthetic fibres. The first disperse dyes were reported for cellulose acetate rayon by British Celanese Corpn. in 1920. None of the other classes of dyes had been good for dyeing cellulose acetate. Some dyes were reported which did not possess the solubilizing groups like SO3Na. These had been found to dye the cellulose acetate from a water dispersion. Green and Sanders in 1923 prepared temporarily solubilized dyes having –N–CH2SO3Na groups. These dyes were sold as ionamines e.g., ionamine orange CB

N=NO2N

C2H5

CH2SO3Na

N

This dye got hydrolysed in the dye-bath giving a finely divided

insoluble dye, which got dissolved in the fibre yielding a solid-sold solution. These dyes lost the solubilising CH2SO3Na group on hydrolysis. Several ionamine dyes had been marketed. These dyes were later replaced by acetate dyes which were aqueous disperse ions of insoluble dyes in a finely divided state (I to 4 u) and could be able to dye the fibre from aqueous dispersion.

Several dye manufacturers produced these dyes, which were named, disperse dyes by C.M. Whittaker in 1953. These dyes had been dispersed by several techniques such as precipitation, milling with surface-active agent, or milling with special kind of sand or glass. The disperse dyes should possess a slight solubility in water for proper dyeing. Dispersing agents are added to the dye to disallow aggregation but to enhance solubility. Several kinds of dispersing agents like alkyl sulphates, alkylaryl sulphonates. Fatty alcohol or amine+ethylene oxide condensation products, naphthalene sulphonic acid+formaldehyde condensation products, lignin sulphonate, etc. have been used with disperse dyes.

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Some of these dyes get sublimed during ironing. Hence a sublimation fastness rating has to be introduced. Some of these dyes with NH2, N-alkyl group are influenced by traces of nitrogen oxides in the city atmosphere resulting in change of shade. Fastness to burnt gas fumes provides rating of this capacity.

With the introduction of polyester fibres in 1950 there occurs the rapid development in this field to make dyes suitable for polyester fibres and several modifications have been carried out.

The dyeing could be carried out at about 100oC in presence of emulsified aromatic compounds like biphenyl, o-phenylphenol, di and tri chlorobenzene etc. The dyeing could be carried out of 130o in pressure vessels. Some new methods evolved are thermofixation, solvent dyeing and transfer printing. The chemical constitution of many of the disperse dyes is unknown. However, most of the disperse dyes belong to azo and anthraquine one class which will be described in the following pages. Azo Dyes: The monoazo disperse dyes have been reported to give almost a complete range of shades. These dyes are largely used for cellulose acetate (CA) and polyester (PE) fibres and their blends with cotton, polyamides (PA), polyacrylonitriles (PAN) and cellulose triacetate (CTA).

The CA dyes were mostly dyed red and yellow shades. They possess simple structures e.g. cibacet yellow GBA, C.I. disperse yellow 3, 11855.

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N=N

HO

CH3

H3CCOHN

CI disperse red 1,11110 possesses following structure:

N=NO2N

C2H5

N

C2H4OH

This dye is having lightfastness 5 but possesses poor sublimation fastness. Its chloro derivative possesses higher light fastness.

Cibacet diazo black B disperse black 2, 11255 is having following structure. It is applied to CA, then diazotised on the fibre coupled with 2, 3 hydroxy naphthaote to yield a good black:

N=NH2N NH2

OCH3

H3C

Manhy of these dyes are obtained from 4-aminophenylazobenzene substituted in various positions. The substitution of Br, Cl, NO2 and CN provides bathochromic shift i.e., the colour of dye moves from red to blue end of spectrum. It is possible to intensify colours by substitution on the nucleus as well as on the nitrogen. In the following example substitution of R1, R2 and R3 by electron withdrawing groups causes batho-chromic shift:

N=N NR2

R1

R3

C2H5

C2H4OCOC2H5

The dye BP 1351382 has been a bluish green dye for PE. Its structure is as follows:

SH3CCO

NO2

N=N

H3CCOHN

OCH3

H

N

C2H6OCOC2H6

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Another example of blue dye for PE is RP 1370034 whose structure is as follows:

N=N N

CN

O2N

BrH3CCOHN

CH3CH2OCH3

CH3CH2OCH3

For polyester fibres most of the cellulose acetate dyes could not be used due to poor fastness to sublimation. As the PE dyes are fixed at high temperatures, these dyes get sublimed to a large extent. Structural variations are being made to make more complex dye molecules having improved fastness for PE fibres. The following example provides the structure of a dye molecule and effect of some substitutents of fastness properties:

Cl

N=N NO2N

CH2CH2R2

CH2CH2R1

R2 = OH H CN CN CN

R1= H H OH OCOCH3 CN

Lightfastness 3 3.5 4.5 7 7

thermo fixation fastness

2.5 1.5 4 4 4.5

The cyanoethyl group tends to improve both light and thermo fixation fastness properties. The sublimation fastness has been improved by introducing acetylamino group in 3-position of coupling component.

The disazo dyes find use in dyeing CTA and PE fibres. The following examples are from patents BP 1171803 Orange PE, and B.P. 1805326 Navy, P. E.

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OH

N=N N=N-C-C-CH3

C N

N

B.P.1171803 ORANGE PE

Cl

OCH3

OCH3

NN=NNO2 N=NC2H4OCOCH3

C2H4OCOCH3

NHSO3CH3

B.P.1805326 NAVY PE

Anthraquinone Disperse Dyes: This group largely provides blue and violet dyes. The earliest known dye was Duranol Red 2B, C.I. Disperse Red 1560710. Another dye has been cellition Fast Pinki FF 3B, C.I. Disperse Red 11,

NH2

HOO

O

DURANOL RED 2B

NH2

NH2O

O

OCH3

CELLITON FAST PINK FF 3B

The 1, 4-diaminoathraquinone dyes provide red shades on CA. By the introduction of electron withdrawing groups it becomes possible to improve fastness by inhibition of nitrosation or diazotisation of amino group by nitrogen oxides. Cibacet Brilliant Blue BG C. I. Disperse Blue 361505 has been an important dye for CA, which is prepared from leucoquinizarin by condensing with a mixture of methylamine and 2-hydroxy ethylamine. 96

O

O NH2

O

O

OCH3

NHCH3

NHCH3CH2OH

H CH2CH2OH

N

Disperse Blue 7 62500 is as follows:

O

O

NHCH3CH2OH

NHCH3CH2OH

OH

OH

1, 3, 5, 8-tetra anthraquinone is also a CA dye Disperse Blue 1 60710. This 4-amino dye on partial methylation with methanol and sulphuric acid provides Celliton Blue Extra C. I. Disperse Blue 31. Many other anthraquinone dyes for PE fibres have been developed. For example, F.P. 1345377.

O

NH2O

OH2N

O

OR

H

H

R=H , ALKYLor COCH3

O

O

NH2

NH2

N - R

C=X

C=X

X=O or NH

R= ALKYLE,ALKYL ARYL HYDROXY ALKYLE or cyano alkyle group

97

By introducing phenoxy and other derivatives in 2-position of 1-amino 4-hydroxyanthraquinone, it becomes possible to improve thermofixation fastness.

NH2O

R

H

OO

R could be O OH

O

OH

O O

OCH2CH2OCH3

Cl

O SCH3, O SO3NHCH2CH2OC2H5

Miscellaneous Disperse Dyes: Nitro dyes find use of CA and PE fibres. The structure of Serilene golden yellow RFS is as follows:

NO2 NH

NO2

N=N OH

The following structure gives a nitro dye for PE having good

fastness properties according to BP 998918.

NH SO2

NO2

N

CH2CH2CH3

CH2CH2CH3

98

Methine or Styryl Dyes: Methine dyes provide yellow shades e.g., Celliton Fast Yellow 76, C.I. Disperse Yellow 31, 48000. It has excellent fastness properties. It is obtained by condensing 4-(N-n-butyl-N-chloroethyl amino)-benzaldehyde with ethylcyanoacetate.

CHO+CH2CNNC2H4Cl

COOC2H5

CH=C-CN

COOC2H5

NC2H4Cl

n-H9C4 n-H9C4

Quinphthalone dyes: These are used for PE providing yellow shades.

OH

HC

NC

C

O

O

Cl

Cl

Cl

Cl

C

C

O

O

N

OH

SO2C6H5

Naphthostyril dyes provide yellow orange shades. They are obtained from naphtho-styril by condensing with aniline derivatives e.g.,

99

HN CO

+ H2N NO2 POCl2

HN C NO2N

Coumarin Dyes: These dyes are used for polyester fibres and give flurescent yellow shade. A dye is obtained by condensing N, N-diethylamino-2-hydroxy-benzaldehyde and 2-cyanomethyl benzothiazole in a mixture of acetic acid and dimethy formamide.

N

C2H5

C2H5

CHO

OH

+

N

S

H2C-C

NC

24 HOURS

25 C

N

C5H2

C5H2NH

N

S

C

100

FORMAZINE DYESThese give blue disperse dyes which are suitable for nylon

N

O

C

O

N N

Ni

CN

C

Benzene ring has substituents such as NHCOCH3,SO2R,SO2NR1,R2

Vat Dyes

8 The term vat dyes relates to dyes of any chemical class that are applied by the vat process. The dyes are insoluble in water and cannot be used directly for dyeing, but on reduction to a leuco form they become soluble in presence of an alkali and acquire affinity for cellulosic fibres; a solution of a leuco compound can be applied by dyeing or printing and on reoxidation (usually be exposure to air) the original insoluble dye is formed witghin the structure of the fibre. A final treatment with hot soap or other detergent brings about aggregation or crystallization so that the particles of pigment become firmly fixed and the shade is fully developed.

One of the earliest vat dyes was indigo, which has been used in India from time immemorial. Another was Tyrian purple, obtained in Mediterranean countries from certain shell-fish, and known at the time of Moses. It may be conjectured that the vat process was developed as a result of observation of the effect of accidental fermentation on these natural dyes, the colour being destroyed by reduction during the process but restored on exposure to air. The name leuco compound (Greek ------ White) is somewhat misleading, since although indigoid reduction products are usually colourless they are applied as sodium salts which are yellow, and in the anthraquinone series the reduction products are coloured (but usually differing in hue from the oxidised dyes). All vat dyes contain a quinonoid system based on carbonyl groups, and in the vatting operation these are reduced to C-OH; since an alkaline medium is used salts of the type C- O Na are formed. On reduction anthraquinone forms a series of products, and vat dyes containing several anthraquinone residuces give rise to still more complex series. In the preparation of a vat reduction proceeds only to the hydroquinone stage, and in complex dyes it may be unnecessary to reduce all of the keto groups present.

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All vat dyes can be applied to cellulosic fibres, and some of them also to wool, silk, nylon and acetate fibres. The need for alkaline

application restricts their use on wool and acetate fibres, and in the case of many anthraquinjone dyes the necessary conditions are unduly severe. Protective agents such as glue are customarily used to minimise damage to wool. Most vat dyes have low affinity for nylon, and on that fibre their fastness to light is often lower than on wool. Dye of high molecular weight cannot usually be applied satisfactorily to acetate fibre. Air oxidation of leuco compounds is sometimes augmented by the used of acid dichromate, especially if the goods are in the form of loose cotton, cops, cheeses or pieces dyed on a ‘jigger’, when access of air is restricted. An aftertreatment with soap or another detergent is necessary for removal of loose pigment and promotion of crystallinity; it often results in a marked change in shade and improvement in fastness properties.

Some important vat dyes representing the chief chemical classes will now be described. Indigoid Dyes: Indigo Many plants of the genus Indigofera have been cultivated for production of indigo in India, China, Japan, Central America, West Indies, Brazil, South and Central Africa, Madagascar, Java and the Philippine Islands. The colouring principle is present as a glucoside of indoxyl known as indican, and this was hydrolysed to free indoxyl by enzyme action; indigo (also known as indigotin) was obtained by oxidation of indoxyl:

N

CH2

C

NC=

C NC

CH

O

O2

O

H

H

O

+ + H2O

INDOXYL INDIGO

2

Natural indigo contains a red isomer of indigo known as indirubin and other impurities in varying proportions. These constituents facilitate preparation of the vat, and were considered to have a desirable effect on the dyed shade, but the variable properties were a nuisance to the dyer. Woad, which was extracted from the plant Isatis tinctoria, and used in Western Europe over many centuries for colouring yarns, fabrics and the bodies of the inhabitants, contains a small amount of indigo. 102

After many years’ work Adolf Baeyer determined the structure of indigo in 1883. The ethylene linkage in its molecules leads to the possibility of stereoisomerism. It has been shown by X-ray crystallography that indigo normally exist in the trans form, but both cis rapidly reverts to the trans forms have been isolated; the cis rapidly reverts to the trans form during storage hower.

Early processes for manufacturing synthetic indigo were devised by Baeyer, Sandmeyer and Heumann, but the first commercially successful operation was achieved by BASF in 1897 using a process based on the fusion of o-carboxyphenylaglycine with caustic potash and oxidation of the resulting indioxyl. In 1901 it was found by the Deustshe Gold-un Silber-Scheideanstalt that good yield are obtained at a lower temperature by using a fusion mixture containing sodamide, caustic potash and caustic soda. Originally phenylglycine was obtained by condensing aniline with chloroacetic acid, but in consequence of shortage of acetic acid during World War I another route was introduced, and it is still generally preferred. The whole process is represented as follows:

N

CH2

C

N

C

C

NH2

CH2O+

NaHSO3 NHCH2SO2Na

NaCN

NHCH2CN

NaOH +H2O

fusion with

NaNH2 + NaOH+KOH

O

H

NHCH2COONa + NH3

N

C=

CO

H

H

O

OXIDATION

INDIGO After the introduction of synthetic indigo, cultivation of the natural product declined rapidloy and is now negligible. The synthetic product

103

was produced in vast quantities for many years and is still extensively used, but it has lost much of its former importance.

For application of indigo to cellulosic fibres vats of various types have been used. The hydrosulphite process is now the most important, and the others (zinc-lime, ferrous sulphate, bisulphite-zinc-lime and the traditional fermentation process) are chiefly of historical interest. The hydrosulphite process has advantages over the others in simplicity, speed and ease of control. It depends on the use of sodium hydrosulphite (Na2S2O4) in conjunction with caustic soda. Indigo is easily reduced at room temperature, giving a yellow alkaline solution of the leuco compound. Cellulosic materials are treated in the resulting vat either cold or at about 50o C, salt being added to improve exhaustion. Since the leuco compound has low affinity for cellulose several impregnations (each followed by air oxidation) may be needed for deep shades. The dyed material is rinsed, treated with acid, rinsed again, then soaped at the boil. The dyed shade is often modified by ‘bottoming’ or ‘topping with dyes of other application classes.

Indigo is applied to wool by a broadly similar process, using mildly alkaline conditions with an addition of glue or other suitable colloid to protect the fibre. Since the affinity of reduced indigo is low wool is usually dyed at 40o – 60o C. Several makes have marketed ready-reduced indigo, which can be applied to wool from a bath containing ammonia and glue.

Many textile-printing processes are available for application of indigo to natural or synthetic fibres by means of direct, discharge or resist styles.

Attempts to simplify the applicaltion of indigo were made by several workers, and these culminated in the introduction of stable disulphuric ester of leuco indigo by Bader and Sunder in 1921. This product, having the structure, was placed on the marked by Durand and Huguenin

104

N

C

CN

C -

C

H

H

NaO3SO

OSO3Na

under the name Indigosol O; equivalents are now made by many other firms and sold under different names. Indigosol O was originally obtained by treating leuco indigo in pyridine solution with chlorosulphonic acid, and converting the disulphuric ester into its disodium salt. An improved process was later discovered by Morton Sundour Fabrics Ltd., whereby unreduced vat dyues, including indigo and its derivatives, are treated with sulphur trioxide, chlorosulphonic acid or methyl chlorosulphonate in presence of pyridine and a metal such as copper, iron or zinc; an intermediate compound of the type

C OSO3

2

Cu.C5H5N

is formed, and on reaction with caustic soda the disodium salt of the disulphuric Easter is obtained.

Indigosol O is readily soluble in water, has affinity for cellulose and can be rapidly and quantitatively oxidised on the fibre with formation of indigo. Since the affinity is somewhat low and the cost relatively high this product is used mainly for pale shades; it is also especially suitable for wool since it has good affinity for that fibre and can be applied from a weakly acid bath. Development of dyed cellulose or wool is carried out either by means of sodium nitrite (often added to the dyebath) followed by acid treatment, or by an aftertreatment with acid dichromate. Indigosol O can be applied to acetate fibre from a strongly acid bath and developed by the nitrite method.

Although indigo has only moderately good fastness to light (approximately grade 4 on cotton, or 4–5 on wool) it has a great advantage over many other dyes in that as fading proceeds there is little or no change in hue. 105

Thioindigoid Dyes: Thioindigoid dye is analogues of indigo and its derivatives in which the two – NH – groups are replaced by sulphur atoms. The first of these, Thioindigo Red, was discovered by Friedlander in 1906.

S

C =

C S

C

CO

As indicated by its name, this dye gives bluish red shades. Derivatives with a very much wider range of shades than those available in the indigoid series can be obtained by suitable substitution. The effect of substituents may be either hypsochromic or bathochromic, and examples quoted later included dyes giving orange, red, violet and brown shades. The dyes have good fasgtness properties, and on account of their versatility they have surpassed those of the indigoid class (except indigo itself) in importnce. It will be seen from the following account of their manufacture, however, that the processes required are somewhat complex, and the resulting high cost has caused these dyes to lose favour as cheaper products with comparable fastness properties have been introduced.

It is not practicable to include a full account of the chemistry of the thioindigoid dyes here, but the following examples illustrate two of the more important industrial processes.

Example of such dyes is illustrated below. CI Vat Blue 8 (CI 73800) gives blue or heavy shades, and is applied to cellulosic fibres, silk and wool.

106

C

C

N

Cl

OMe

H

O

=

O

Me

CI VAT BLUE 8

CI Vat Red 45 (CI 738690) gives bright scarlet shades, and is applied to cellulosic fibres, also to wool.

CO

C

C

C

S

=

O

CI VAT RED 45 Indanthren Printing Black B (FH) (CI Vat Black 2; CI 73830) is manufactured by a condensation of a different type. Isatin a-anilide reacts with 4-hydroxy-10-methylbenzo [a ] carbazole in presence of acetic anhydride and formic acid with elimination of aniline to yield the dye with structure (98). It is applied to cellulosic fibres by printing processes to give bluish gray or bluish black shades. This dye is of little interest for application by dyeing methods.

N C

C

N

O O

H

MeH

Anthraquinone Vat Dyes: Over 200 anthraquinone vat dyes are at present in commercial use, and the constitutions of about 130 of them have been disclosed. They represent a wide variety of chemical types, and provide shades ranging from yellow to black. Many of the dyes are very complex, and their structures may contain up to nineteen condensed rings. They are often

107

built up by means of reactions between components containing several reactive positions, and in consequence some of the commercial products are mixtures. Anthraquinone vat dyes are chiefly important in application to cellulosic fibres by dyeing and printing processes. The conditions used for vatting very considerably but the only reducing agent to practical importance is alkaline sodium hydrosulphite.

The first anthraquinone vat dye was obtained by R. Bohn in 1901 in the course of an attempt to prepare an analogue of indigo by caustic fusion of 2-anthraquinonylglycine. The expected reaction did not take place, but a blue vat dye was formed which proved to have the structure. The same product was obtained by caustic fusion of 2-aminoanthraquinone. Bohn called his product

NH

NH

O

O

O

O

Indanthren (the name being derived from Indigo and anthracene), and later it was marketed by BASF as Indanthren Blue R. It will be seen that the dye is a dihydrodianthraquinlonylazine, and it was later given the chemical name indanthrone, thereby avoiding the trade name and at the same time indicating the quinonoid structure.

The excellent fastness properties of Indanthren blue R encouraged further research, and many other vat dyes were developed and sold as

108

109

memebers of the Indanthren range. Other makers have marketed comparable products under their own brand names; these include the Algol (Fby), Alizanthrene (ICI) (British Alizarine Co., later ICI), Calcoid (ACY), and Caledon (ICI, Carbanthrene (NAC), Cibanone (CIBA), Paradone (LBH), Ponsol (DuP), Sandothrene (S), and Tinon (Gy) ranges of vat dyes

Sulphur Dyes

9 Although dyes of the sulphur class are used in substantial quantities, there appears to be no justification for providing more than a brief description here. In spite of their long history little known about the chemical structure of these dyes. In recent years their importance has declined, and little needs to be added to the excellent years their importance has declined, and little needs to be added to be added to the excellent accounts published during the period 1950 – 1958.

The first commercial sulphur dye was made in France by Croissant and Bretonniere in 1873. These workers prepared brown dyes for cotton by heating a variety of organic materials of animal or vegetable origin with aqueous sodium sulphide or polysulphide. They also used slightly more complex processes in which the initial products were baked at temperatures above 200oC; the shade obtained could often be varied by adjusting the temperature and duration heating. Of the many dyes examined the only one that attained importance was Cachou de Laval, obtained by heating sawdust with sodium sulphide. It was manufactured by several firms for many years, and is still included in the Color Index (CI Sulphur Brown 1; CI 53000). It may be applied to cotton from a sodium sulphide bath and fixed on the fibre by aftertreatment with aqueous potassium dichromate; the resulting shades vary from yellowish brown to brownish olive.

110

It was not until 1893 that a sulphur dye was made from intermediates of known structure. The sulphurisation process was then applied by Vidal to a great variety of organic substances, and dyes were obtained that could be fixed on cotton by oxidation. The most important of these was Vidal Black (CI Sulphur Black 3; CI 53180), obtained from p-aminophenol or p-phenylenediamine by means of a sullphur melt. In 1897 a better black sulphur dye was manufactured by heating 4-gydroxy-2’,4. –dinitrodiphenylamine with sodium polysulphide, and this was marketed by Cassella as Immedial Black V (CI sulphur Black 9; CI 53230). Two years later a further improvement was obtained sulphurisation

111

of the cheap intermediate 2,4-dinitrophenol, and the resulting dye was produced by AGFA as Sulophur Black T (CI Sulphur Black 1;CI 53185). Many equivalent products were made by other firms, and the dye is still of importance. It gives blacks of good fastness to washing and light. During the years 1897-1902 a great deal of experimental work was carried out on sulphur dyes, and every available intermediate was subjected to sulphurisatic. This work led to an extensive patent literature and the manufacture of many competing ranges of dyes. An almost complete range of shades was produced, lacking a true red, however. After 1902 the rate of expansion of this field slackened, but the occasional introduction of new dyes continued until in 1950s. Table 9.1 gives details of some of the more important sulphur dyes.

Since so little is known of their structures, sulphur dyes are usually classified according to the chemistry of their starting materials. The manufacturing processes are chiefly of three types:

1. A dry mixture of the organic starting material (or material)

with sulphur is heated (the temperature usually exceeding 200o C).

2. As 1, but using sodium polysulphide instead, sulphur. The baking temperature varies widely.

3. The starting material is heated with aqueous sodium polysulphide, either under reflux or in a closed vessel under pressure. Some or all of the water may be replaced by butanol.

The shade and properties of the resulting dyes may vary

considerably with the reaction temperature and duration of heating. In all cases hydrogen sulphide is evolved during reaction and it is absorbed in aqueous caustic soda. The dyes are usually isolated from alkaline solution by air oxidation. Many of them are subject to deterioration during prolonged storage.

The chemistry of sulphur dyes has been studied by many workers, and although it has not been possible to assign definite structures the presence in certain dyes of chromophoric systems of the thiazole (1) thiazone (2) and thianthrene (3) types has been established. These

N

N

1

S

N

2

S

S

3 and other aromatic nuclei are linked by disulphide or disulphoxide bridges, which are broken on treatment with sodium sulphide with formation of –SNa groups, and on reoxidation the disulphide bridges, are re-formed on the fibre.

The properties of sulphur dyes are intermediate between those of direct dyes and vat dyes. As already stated, reds are poorly represented, only dull Bordeaux shades being available. Other hues are plentiful, but almost all sulphur dyes are somewhat dull. Wet fastness properties are usually good, but resistance to bleaching is poor. With some notable exceptions, as in sulphur black T and its equivalents, light-fastness is only fair or moderate (rarely exceeding SDC grade 5). The great demand for sulphur dyes is due to their moderately good properties and low cost.

They are applied almost exclusively to cellulosic fibres, the alkaline batch required being unsuitable for wool and silk. The process consists in dissolving the dye in a solution of sodium sulphide, whereby it is reduced to a leuco compound with affinity for the fibre, carrhying out dyeing just below the boil, then exposing the dyed material to air so that oxidation and development of the shade take place. Sometimes the dyeings are aftertreated with a mixture of a dichromate and copper sulphate for improvement in fastness to light and wet treatments, but this is liable to result in tendering of the fibre by slow liberating of sulphuric acid. Cotton dyed with sulphur colours acquires affinity for basic dyes, and there are sometimes applied as ‘topping’ colours in order to brighten the shades. Sulphur blacks can also be topped with aniline Black to give very deep black shades with increased fastness to milling. A bright green sulphur dye with excellent fastness properties was formerly included in the ICI range under the name Thionol Ultra Green B (CI sulphur Green 14). It was a derivative of copper pathalocyanine containing thiocyano groups which gave a water-soluble mercaptide on reduction with sodium sulphide. Cotton dyed with this leuco compound

112

is grey, but oxidation in air yields a bright green shade with very good fastness to light, washing and chlorine. With the advent of green reactive dyes this product has been superseded. Sulphurised Vat Dyes: The sulphurised vat dyes from a small but important group of products which resemble sulphur dyes in that they are manufactured by sulphurisation processes but they are applied from a hydrosulphite vat in the manner of vat dyes. The first of these was introduced by Cassella in 1909 under the name Hydron Blue R (CI Vat Blue 43; CI 53630). It is obtained by condensing p-nitrosophenol with carbazole in sulphuric acid medium to form the indophenol and refluxing this (or its leuco

N

N O

H

Compound) with dodium polysulphide in butanol. This dye gives reddish blue shades, and is valuable in that it has better fastness properties than most blue sulphur dyes and is valuable in that it has better fastness properties than most blue sulphur dyes and is used as an inexpensive substitute for indigo. It cannot be completely reduced by sodium sulphide, and a vat it usually prepared by using a mixture of sodium sulphide and hydrosulphite. A greener blue is manufactured similarly by sulphurisation of the indophenol obtained from N-ethylcarbazole and p-nitrosophenol; this is Hydron Blue G (Cassella) (CI Vat Blue 42; CI 53640). Several related dyes have been made by modified processes and by using mixtures of indophenols.

Attempts have been made to assign a constitution to Hydron Blue R but its structure has not been firmly established. 113

114

Ready-reduced and Solubilised Sulphur Dyes: Many sulphur dyes have been manufactured in a reduced or partly

reduced from and supplied either as solutions or powders, which easily dissolve in the dyebath with a small amount of sodium sulphide.

Sulphur dyes are also solubilised in the unreduced state by introducing thisulphonic acid groups, and the resulting derivatives give clear stable aqueous solutions. They lack substantivity for cellulose until they have been reduced, but show advantages in freedom from insoluble matter (especially important in package dyeing), By application of such products to the fibre from a sodium sulphide bath and exposure to air dyeings are obtained with the same properties are those of the corresponding conventional sulphur dyes. Recent Developments The Inthion (FH) and Dykolite (Southern Dyestuff Co.) ranges are sometimes regarded as sulphur dyes, but as their properties differ in several respects from those of sulphur dyes they are treated separately.

115

Table 9.1 : Examples of Important Commercial Sulphur Dyes CI Generic CI Consti-

tution No. Commercial Name

Intermediates Outline of Manjufracturing Process

CI Sulphur Yellow 2

CI 53120 Eclipse Yellow G (Gy)

N,N –Diformyl-m-tolylene-diamine +benezidine

Heat with sulphur at 140o – 150o C and rise during 15 hr. to 218o – 220o C (ref. 3)

CI Sulphur Yellow 4

CI 53160 Immedial Yellow GG (Cassella)

2-(p-Amino-pheny)-6 met6hylbenzo- thiazole + benezidine

Heat with sulphur at 190o – 220o C then reflux with aq. NaOH and oxidise with air. (ref.4)

CI Sulphur Orange 1

CI 53050 Immedial Orange C Extra (Cassella)

m-Tolylene-diamine

Heat with sulphur at 215o-220o C then treat with NaOH (ref. 5)

CI Sulphur Red 6

CI 53720 Immedial Red Brown 3B Extra (Cassella)

3-Amino-2-methyl-6-hydroxy-phonazine

Heat with sodium polysulphide at 115o – 116o C (ref. 6)

CI Sulphur Blue 7

CI 53440 Immedial Indone RR Extra (Cassella)

4-Amino-4 – hydroxy-3-methyldi-phenylamine

Heat with aq. Sodium poly-sulphide at106o – 112o C, then oxidise with air (ref. 7)

CI Sulphur Green 3

CI 53570 Thional Brilliant Green 3G (S)

8-Phenylamino- 5-p-hydroxy-

Reflux with aq. Sodium poly-sulphide in presence of

116

phenylamino-naphthalene-1-sulphonic acid

CuSO4, then oxidise with air (ref. 8)

CI Sulphur Brown 10

CI 53055 Immedial Yellow Brown G (Cassella)

m-Tolyene-diamine

Heat with sulphur at 210o rising to 250oC. Dissolve the product in eq. Na2S + NaOH, heat at 240o and evaporate (ref. 9)

CI Sulphur Black 1

CI 53185 Immedial Black AT (Cassella) and many other brands

2,4-Dinitrophenol or 2,4-dichloronitro-benzene

Heat with eq. Sodium poly-sulphide under reflux (110o – 120o C), dillute and oxidise with air (ref. 10)

Acid (Anionic) Dyes

10 The most common fiber types to be dyed with acid dyes are polyamide, wool, silk, modified acrylic, and polypropylene fibres as well as blends of the aforementioned fibres with other fibres, such as cotton, rayon, polyester, regular acrylic, etc. Approximately 80-85% of all acid dyes sold to the U.S. textile industry are used for dyeing nylon, 10-15% for wool and the balance for those fibres mentioned above. Acid dyes are organic sulfonic acids; the commercially available forms are usually their sodium salts, which exhibit good water solubility. According to their structure, acid dyes belong to the following chemical groups: azo; anthraquinone; triphenylmethane; pyrazolone; azine; nitro; and quinoline. Azo dyes represent the largest and most important group and are followed by antraquinone and traylmethane dyes. Of the other dye groups, very few products are of any commercial value. Acid dyes can be divided into four groups: (1) These are the level dyeing acid dyes with one sulfinic acid group.

They offer excellent leveling, migration and, coverage of barre properties. Fastness to light is very good, while the wetfastness properties in heavier shades generally are only marginal. The latter can be improved with an aftertreatment of either tannic acid/tartar emetic or any other synthetic aftertreating agent. The dyes of this group should be used when wetfastness properties are of no major concern and when emphasis is put on good dyeing performance, such as coverage of barre. Typical representatives are CI Acid Yellow 49, CI Acid Red 337 and CI Acid Blue 40. They can be used for dyeing of apparel, knit goods, carpet, upholstery, etc.

117

(2) These are the neutral-dyeing acid dyestuffs. They are also monosulfonated and are very similar in their leveling, migration, and coverage of barre properties to group 1; however, because of

118

their chemical structure (larger molecular size), these dyes exhibit superior wetfastness properties. Since these dyestuffs have excellent neutral affinity and good build up properties, they are suited especially for dyeing of medium to heavy shades. CI Acid Yellow 159 and CI Acid Red 299 are typical dyes of this class.

(3) These are the milling type acid dyes. They are disulfonated dyes

and provide dyeing with highest wetfastness properties. The leveling and migration properties of these products are much inferior than those of the monosulfonated dyes in groups 1 and2. Coverage of barre is also very poor. CI Acid Yellow 79 is an example of this groups. It is obvious that there are no acid dyes that combine all desirable properties. Those which offer the excellent dyeing characteristics such as good leveling, migration and coverage of barre, have only marginal wetfastness properties; those that provide high wetfastness do not level very well. The dyes in group 2 represent the best compromise. When the fabric is aftertreated with a synthetic aftertreating agent, wetfastness – in most instances – will be equal or similar to dyeings obtained from milling dyes.

(4) These are the premetallized dyes which also include mono-and

disulfonated types. Premetallized dyes exhibit are rather high dyeing strike rate even at pH values of 7-8 and, therefore, are extremely difficult to dye level. Their wetfastness properties are either comparable or superior to milling-type acid dyes. CI Acid Yellow 151 is a representative of this group.

Dyeing Process:

The two major polyamide types commercially available today are nylon 6 and nylon 66. Nylon 6 represents a polycondensate of caprolactam, and nylon 66 is a polycondensation product of two individual components, adipic acid and hexamethylendiamine. Both fibre types are very receptive to acid dyes under certain conditions.

A direct relationship exits between the chemical structure of an

acid dyes and its dyeing and wetfastness properties. The dyeing of

119

polyamide fibres depends on a great number of variables. Nylon 6 has greater affinity for dyes than nylon 66 and this may affect fastness properties of the final dyeing. Heat history of the fibre influences dye affinity; for instance, heat used during the texturizing process of the fibre may sometimes vary. Barfre develops as a result. Barre may also be caused by differences in knitting tension. Antisoil and antistatic fibre has become increasingly important and it is quite common that these modified fibres show a reduced dyeability. The dyeing process is influenced by a number of additional parameters, such as: (a) dyestuff selection, (b) type and quantity of auxiliaries, (c) ph, (d) temperature, and (e) time.

(a) Dyes are selected according to the intended use of the fabric to be

dyed. The needed fastness properties and / or dyeing characteristics determine whether mono or disulfonated acid dyes are used. It is not advisable to mix these two dyestuff types in a given formulation, especially not in medium to heavy shades. The monosulfonated dyes exhaust more rapidly and block the disulfonated dye from exhausting into the fibre, especially if the depth of shade is close to the saturation point of the fibre. At tention also has to be paid to the K value of the individual dyes within a combination. K values give the dyer an indication of the sequence in which the dyes of a combination will exhaust onto the fibre. Since it is most desirable to use on-tone exhausting combination, the K value of acid dyes in a formulation should not differ by more than + 0.5-1.0 unit.

(b) When a polyamide is dyed with acid dyes, dyeing assistants are

usually employed. They can fulfill three functions: increase the leveling and migration properties of acid dyes, help to cover barre, and improve the compatibility of acid dyes in combinations.

Anionic products show a relatively high affinity for the nylon fibre

at temperatures below the boil and temporarily block dyesites, slowing down the exhaustion of the dyes and thereby helping to achieve a level dyeing.

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Nonionic anionic auxiliaries not only show affinity for the fibre, but also form complexes with dyes. In this way, they slow down the exhaustion process and also achieve level dyeing by affecting the compatibility of the dyes. By proper use of such auxiliaries, normally incompatible combinations (dyes with substantially different K values) can become compatible (similar K values, i.e., compatible in presence of the auxiliary).

(c) The pH is one of the most important factors in dyeing polyamide

with acid dyes. The dyestuff binding groups in a polyamide fibre are the amino end groups (NH2-). The enable the dissolved and ionized dye to react with these amino end groups, the latter must be activated. A very low pH of 3-3.5 provides many activated NH2 groups and results in a rapid, almost instant, exhaust of all the dye present in the bath. In shuch a case leveling and migration would be rather poor. At the optimum pH, 85-95% of the dye in the bath is exhausted onto the fibre at the end of the dyeing cycle. The most effective pH can be calculated for certain dye combinations.

(d) The dyeing temperature for dyeing polyamide fibres with acid

dyes should be as close to the boil as possible. The higher the final temperature is, the better are the chances of obtaining a good dyeing, since the temperature has a great influence on the leveling and migration properties of acid dyes. Best results in leveling out fault lots are obtained if the goods are treated at elevated temperatures of 105-110o C.

Even more critical than the end temperature is the rate of

temperature increase. Depending on the type of dyes used, exhaustion starts at 25-35o C when using level dyeing acid dyes, or only 50-65o C when certain milling-types dyes are in the bath. If the correct pH has been chosen, the dyebath will be exhausted before the boil has been reached. This also means that it is not always necessary to start a dyeing at room temperature because there would be, in many instances, a considerable dead time before the actual exhaustion starts to take place.

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(e) The dyeing time represents a considerable cost factor in any process and should be as short as possible without jeopardizing the quality of the dyeing. Common practice is to sample after 40-45 min at the boil. If dyed under optimum conditions, the dyeing time at the boil is reduced to 10-20 min.

Dyeing of Nylon Carpet: A great percentage of acid dyes used in the textile industry is used

in dyeing of nylon and wool carpets. Nylon carpet fibres can be dyed in many different ways, eg., in raw stock from, where usually highest wetfastness dyes are applied, in yarn form and in piece form. The latter is divided into piece or beck dyeing and continuous dyeing. For the continuous dyeing process, the most popular machine is the Kuesters carpet-dyeing range, which consists of a wet-out-padder, a dye applicator, a loop steamer, and 3-4 wash boxes. Usually drying oven is used after a dyeing range.

Continuous dyeing of nylon carpet became of great interest when tufted wall-to-wall carpet gained in appeal. The ever-increasing demand for larger and larger yardages of one particular colour led to the developments of continuous dyeing ranges which, theoretically, can dye 85 x 103 m2 (1 x 105 yd2) of carpet within 24 hours with no shade difference from the method used for dyeing solid shades, many additional dye application techniques have been developed to create the very popular multicoloured carpet styles. The TAK and Multi-TAK machines are the most important units which have been added to the Kuester dyeing range to make it more versatile. Both the TAK and Multi-TAK represent machines that enable the dyer to apply different dye liquors in the form of drops or lines or any variation thereof onto the carpet. Usually, the ground shade is applied first by either padding or use of the blade; then, before the carpet enters the steamer, additional colour drops (2-4 different shades) are applied on top of the unifixed ground shade by either the TAK of Multi – TAK machine. These droplets form a variety of patterns depending upon the viscosity of the ground shade colouration, of the TAK droplets and / or of the machine settings. Some Kuester continuous dyeing machines also are set up in line with rotary print heads, thereby further widening the styling possibilities.

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Dyeing of Wool: Wool has lost its former importance and represents, today, only a minor factor in fibre dyeing. Dyeing of wool may be carried out in the various stages of processing. Dyestuff selection depends upon the specific end uses of the fabric or yarn as well as on the stage of manufacture. Wool fabrics are dyed primarily by exhaust dyeing methods. Although continuous dyeing of wool has been discussed for some time, it has not become very important. Only a few units are running today which continuously dye wool top and raw stock. Wool is dyed as: (1) raw stock, (2) yarn and (3) piece goods. (1) When dyeing raw stock or top the levelness of dyeing is of minor

importance, but the highest possible wetfastness properties for further processing are required. This does not mean than unlevel dyeings will be accepted, but that a certain shade variation in the dyeings can be counter balanced during the blending processes. According to the requirements for the manufacturing processes, dye classes with highest wet-fastness premetallized and milling colours.

(2) For yarn dyeing, the dye selection is governed mainly by the end –

use of the material. However, the subsequent manufacturing processes influence the selection of dyes as far as fastness properties are concerned.

(3) For dyeing on piece goods, the performance of the dyes in the

dyebath is very important because a level-dyed piece of fabric is required above all other aspects. The dye selection for piece dyeing is, therefore, based on the performance of the dyes as well as on the fastness requirements for the specific end-uses.

Applicaltion of Acid Dyes to Silk:

Because of economic reasons, very little pure silk is being processed these days. Blends of silk with other fibres (eg, polyester) are more common. For fastness reasons, fibre reactive dyes are used quite frequently, however, when top wetfastness is not needed, selected acid and neutral premetallized dyes may be utilized. Dyeing is carried out at a pH 5.0-5.5 with acetic acid and with 0.5% of an ethyxylated fatty acid

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derivative in the bath. Best exhaustion of acid dyes on silk is achieved at about 85o C. Dyeing of Modified Acrylic and Polypropylene:

These fibres in their modified acid dyeable form are of very minor importance. Regarding acid dyeable acrylic fibres, dyeing procedures are very specific for the few fibre types available and should be requested from the fibre producer. With acid-dyeable polypropylene, dyeing is usually is important to select the proper dyes for modified fibres because most of them are rather poor in either wetfastness or lightfastness properties.

Basic (Cationic Dyes)

11 The first basic dye, mauve, was synthesized by Perkins in 1856;

and shortly afterward fuchsine, methyl violet, aniline blue, and other classical basic dyes were developed. For years these dyestuffs were primarily used for dyeing brilliant shades on silk and cellulosic fibres that had been treated with a mordant; however, usage of cationic dyes for these fibres was limited due to very poor washfastness and lightfastness. Basic dyes did not achieve prominence until the polyacrylonitrile fibres were introduced in the early 1950s. Initially, acrylic fibres were very difficult to dye and, until acidic groups were incorporated as dye sites in the fiber, basic dyestuffs were of little interest. Cationic dyes are currently used in large quantities to dye acrylics (Orlon, Acrilan, Creslan, Zefran) and modified acrylics (Verel). Subsequent developments led to the introduction of acidic groups to polyester and polyamide fibres, further increasing the market for these dyes. Dyeing of Acrylic Fibres:

Basic dyes are water-soluble and dissociate into anions and coloured cations. The cations have a strong affinity for the acidic group (sulfonic or carboxylic) and form salts. Because of these strong bonds, washfastness is usually outstanding, and lightfastness varies considerably, depending on the dyestuff. Basic dyes are usually applied in a batch process with skein, stock, and package dyeing more prevalent than piece dyeing on becks or jet machines.

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The fundamental steps in the acrylic dying mechanism are: absorption of the basic dyestuff at the fiber surface, which occurs only when the glass transition point of the fiber is exceeded; diffusion of the dye into the fiber as the fiber molecules acquire enough energy to move; formation of the dye-fiber bond; and migration of dyestuff from the dyesite to another or from within the fiber to the surface. The degree of migration varies considerably, depending on the dyestuff, but generally basic dyes do not migrate well.

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Leveling of basic dyestuffs can be a major problem which often can be traced partially to differing exhaustion rates of individual dyestuffs which may occur in combination shades. One method for measurement of exhaustion rates is the time of half-dyeing or the time in minutes required for the fibre to absorb half as much dye as will be absorbed if dyed to equilibrium. Half-dyeing times do not adequately describe the behaviour of basic dyestuffs in combinations where the individual dyestuffs could interfere with each other’s exhaustion rate. A method has been developed for determining compatibility of K values. Dyeings of the basic dyestuffs, which are to be rated, are made in succession for a specified period of time with dyes having a known strike rate or K value. Five groups (K-1 through K-5) are used to classify dyes, with K-1 dyes being exhausted first when dyed in combination with dyes of any other group; dyes with a K-2 are taken up preferentially when combined with dyes of K-3 to K-5. For optimum leveling, the K values of basic dyes in a combination shade should be as close to each other as possible. Every basic dyeable fiber has a saturation value, i.e, it has given number of acidic dyesites, which limit the quantity of basic dyestuff that can be fixed. The dyestuff also has a saturation factor, which is a measure of the relative molecular weight per caution in the dye. These two values determine the depth of shade obtainable with a given dye and fibre. Acrylic fibres also vary considerably in their rate of dyeing, depending on whether they are of a dry-spun or a wet-spun fibre. Wet-spun fibres dye at a higher rate than dry spun fibres. To overcome the high affinity of some basic dyestuffs and to prevent unlevel dyeings, often a cautionic retarder is used. Cationic-dyeable polyester has achieved a moderat3e degree of success because it lends itself to two-or three colour effects in blends with regular dispense-dyeable polyester, cellulosic fibres, or wool. Typical basic-dyeable polyester fibres are Dacron T-64 and T-92, Fortrel 402, and Trevira 640. The dyeing rate of cationic-dyeable polyester is much lower than that of acrylic; however, an even greater difference exists in the diffusibility associated with each, which is estimated for the cationhic-dyeable polyester to be only 10% of that for acrylics. This has to be overcome by dyeing at higher temperatures (110-130o C) and by using a

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carrier to improve penetration. Another use for the carrier is the prevention of cross-staining the disperse-dyeable protion of the blend by the basic dyestuffs. Nonionic products must be present to act as antiprecipitants or to suspend particles resulting from the reaction between the cationic dyes and anionic dyestuffs when blends of basic-dyeable and disperse-dyeable polyester are dyed.

Banned Amines

12Q.1 What are banned amines? Q.2 What is Eco-Labeling of Textiles? Q.3 Name the agencies, which have accredited Textiles Committeee

Laboratories? Q.4 What are the advantages of testing of textiles in an accredited

laboratory? Q.5 State the list of dyes banned by Government? Q1. What are banned amines? Banned amines are the chemicals which are released from some of the azo dyes on reductive clevage. Following is the list of amines banned by Germany.

• 4-Amino biphenyl (CAS-No.:92-67-1) • Benzidine (CAS-No.:92-87-5) • 4-Chlor-o-toluidine(CAS-No.95-69-2) • 2-Naphthylamine (CAS-No.:91-59-8) • p-Chloroaniline(CAS-No.106-47-8) • 2,4-Diaminoanisole(CAS-No.615-05-4) • 4,4'-Diamino diphenyl methane (CAS No.:101-77-9) • 3,3'-Dichloro benzidine (CAS-No.:91-94-1) • 3,3'-Dimethoxy benzidine(CAS-No.:119-90-4) • 3,3'-Dimethyl benzidine(CAS-No.:119-93-7) • 3,3'-Dimethyl-4,4'-diamino diphenyl methane (CAS-No.:838-88-0) • p-Cresidine (CAS-No.:120-71-8)

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• 4,4'-Methylene-bis-(2-chloraniline) (CAS No.:101-14-4) • 4,4'-Oxydianiline (CAS-No.:101-80-4) • 4,4'-Thiodianiline (CAS-No.:139-65-1) • o-Toluidine(CAS-No.:95-53-4) • 2,4-Diamino toluene(CAS-No.:95-80-7) • 2,4,5-Trimethyl aniline (CAS-No.:137-17-7) • o-aminoazotoluene (CAS-No.:97-56-3) • 2-amino-4-nitrotoluene (CAS No.:99-55-8) • p-amino azo benzene • 2-methoxy aniline

These are suspected to be carcinogenic and are being banned.

Apart from Germany, Netherlands has also banned the presence of

these amines and this is applicable to clothing, bed linen and footwear. As per the latest information received, the European Commission has circulated a working document relating to the restrictions on the marketing and use of dangerous substances and preparation (azo dyes), for the consideration of the European parliament and the Council. The draft proposal aims to restrict the use of 22 amines in textiles and leather articles. Q2. What is Eco-Labeling of Textiles?

In order to promote the concept of eco-friendly textiles, a

comprehensive system of eco labels is advocated by European and other Western countries. For the purpose of issuing eco labels, certain norms/criteria are stipulated in respect of textile products, on the basis of Cradle-to-Grave approach. i.e. These criteria are developed on analysing the product's entire life cycle commencing with extraction of raw materials, progressing through the stages of production, distribution and utilisation and disposal after use. The norms are also referred to as Eco Standards. By and large, these standards are voluntary in nature.

While formulating eco-norms for the issuance of eco labels, at present the use of 7 different classes of chemicals in textile production and processing are taken into consideration. These are:

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• Formaldehyde • Toxic pesticides • Pentachlorophenol (PCP) • Heavy metal traces • Azo dyes which release carcinogenic amines • Halogen carriers • Chlorine Bleaching The eco standards stipulated by (i) MST, the German Textile

Association, (ii) OTN 100, the famous OEKOTEX Institute from Austria, (iii) Clean fashion and (iv) Steilmann, the two private eco-label issuing organisations in Germany are popular in European countries. In addition to the four-eco labels specified above, a number of private and national labels are operating in Europe. In some cases these labels are used solely as a marketing instrument and have little factual and technical substance. In the face of the proliferation of eco labels, the Coordination Committee for the Textiles Industries in the EEC (COMITEXTIL), supports a single European label. Further, it is learnt that the European Union is finalizing the criteria for a common "European Community Eco label" (EC-Eco label) after taking into consideration the criteria specified by other eco labels.

The Government has also evolved eco standards for the eco labeling

of the textile items in consultation with the Indian Textile Trade and Industry. The criteria for the environmentally friendly textiles including Cotton, Woolen, Man-made, Jute and Silk products were notified in the Gazette on October 8, 1996 by Ministry of Environment and Forests. The eco labeling of textiles notified in the Gazette is a voluntary scheme. This scheme aims at distinguishing through the agency of Eco-Mark, any product which is made, used or disposed of in a way that significantly reduces the adverse effect; it would otherwise have on the environment. The Earthen Pot is being used as the logo of this scheme.

A comparison of the norms/criteria stipulated for eco parameters in

the popular eco labels operating in Europe and in the Indian Eco Mark Scheme for textiles are as under:

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Criteria/Norms stipulated in ppmS.# Eco ParameterM.S.T OTN

100Clean Fashion

Steil-mann

COMIT-EXTIL

Indian Eco Label

Formaldehyde (i) Baby Clothing (ii) Close to skin (iii) Outer wear

20 75 300

20 75 300

20 75 300

50 300 500

20 75 300

20 75 300

Toxic Pesticides 1 5 1 1 0.1 to 1 1 Pentachlorophenol 0.5 -- 0.5 Ban 0.05 to 0.5 0.5 Heavy Metals

(i) Arsenic (ii) Lead (iii) Cadmium (iv) Mercury (v) Copper (vi) Chromium (vii) Cobalt (viii) Zinc (ix) Nickel

0.001 to 0.01 0.004 to 0.04 0.0005 to 0.005 0.0001 to 0.1 0.3 to 100.0 1 to 20 2 to 20 0.5 to 5.0 0.02 to 10.0

10.0 (for all heavy metals)

Azo dyes containing carcinogenic amines

Ban BanBan Ban Ban 50.0

Halogen Carriers Ban --- --- Ban Ban 200.0 Chlorine

Bleaching ___ ___ ___ To avoid Ban ___

Q3. Give the name of agencies, which have accredited Textiles

Committee Laboratories? Accreditation is a formal recognition that a Testing /Calibration

Laboratory is competent to carry out specific test/s. Such an accreditation is granted only after the accrediting body (Govt. /non Govt. body or any third party) is satisfied with a particular laboratory seeking Accreditation.

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In India, the National Accreditation Board for Testing and Calibration Laboratories (NABL) is accrediting the laboratories. Apart from this there are a number of accrediting bodies operating at international level including A2LA (American Association for Laboratory Accreditation, USA) and RvA (Raad Voor Accreditate), Dutch Accreditation Council, Netherlands.

Textiles Committee Laboratories, Mumbai is accredited by Raad Voor Accreditate, the Dutch Accreditation Council, Netherlands and National Accreditation Board for Testing and Calibration Laboratories (NABL) on the basis of its compliance to the relevant criteria which are based on ISO /IEC Guide 25 and EN-45001. This is the first Textile Laboratory in India accredited by a reputed Accreditation Board from abroad. Q4. What are the advantages of testing of textiles in an accredited

laboratory? In an accredited laboratory, a documented Quality System is

implemented and its effectiveness is assured. Consequently, the test reports/certificates issued by the laboratory is readily accepted by the trade, industry and exporters. The testing services rendered by the laboratory is qualitatively better than a non-accredited laboratory due to the following reasons:

The accuracy, repeatability and reproducibility of the test results are assured;

Qualified and trained manpower is employed for the testing

various parameters; Standard and validated methods only are used for testing; The accuracy and precision of the equipments used is ascertained

by periodical calibration using devices traceable to National Standards; and, the testing of various parameters is carried out under conditions, which does not affect the accuracy and precision of the test results.

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Q5. State the list of dyes banned by Government?

The Ministry of Environment and Forests, Government has prohibited the handling of benzidine based dyes vide the notification published in the Gazette in January, 1990. As per this notification, handling of all the 42 benzidine-based dyes is prohibited from 1993 onwards. These are related to banned amines.

The Ministry of Environment and Forests has further prohibited the handling of 70 more azo dyes, which came under the banned category as per the notification, published in the Gazette on 26th March, 1997. Thus, the Ministry of Environment and Forests has prohibited the handling of 42+70=112 dyes which are capable of releasing any of the harmful amines.

LIST OF 42 BENZIDINE BASED DYES PROHIBITED FROM 1993

S.No. CI Generic Name CI Constn. No.

1. Acid Orange 45 22195 2. Acid Red 85 22245 3. Acid Black 29 - 4. Acid Black 94 30336 5. Azoic Diazo Compo.112 37225 6. Direct Yellow 1 22250 7. Direct Yellow 24 22010 8. Direct Orange 1 22370 9. Direct Orange 8 22130

10. Direct Red 1 22310 11. Direct Red 10 22145 12. Direct Red 13 22153 13. Direct Red 17 22150 14. Direct Red 28 22120 15. Direct Red 37 22240 16. Direct Red 44 22500 17. Direct Violet 1 22570 18. Direct Violet 12 22550

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19. Direct Violet 22 22480 20. Direct Blue 2 22590 21. Direct Blue 6 22610 22 Direct Green 1 30280 23. Direct Green 6 30295 24. Direct Green 8 30315 25. Direct Green 8:1 -- 26. Direct Brown 1 30045 27. Direct Brown 1:2 30110 28. Direct Brown 2 22311 29. Direct Brown 6 30140 30. Direct Brown 25 36030 31. Direct Brown 27 31725 32. Direct Brown 31 35660 33. Direct Brown 33 35520 34. Direct Brown 51 31710 35. Direct Brown 59 22345 36. Direct Brown 79 30056 37. Direct Brown 95 30145 38. Direct Brown 101 31740 39. Direct Brown 154 30120 40. Direct Black 4 30245 41. Direct Black 29 22580 42. Direct Black 38 30235

LIST OF 70 AZO DYES PROHIBITED FROM JUNE 1997.

S.No. CI Generic Name CI Constn. No.1 Acid Red 4 14710 2 Acid Red 5 14905 3 Acid Red 24 16140 4 Acid Red 26 16150 5 Acid Red 73 27290

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6 Acid Red 114 23635 7 Acid Red 115 27200 8 Acid Red 116 26660 9 Acid Red 128 24125 10 Acid Red 148 26665 11 Acid Red 150 27190 12 Acid Red 158 20530 13 Acid Red 167 -- 14 Acid Red 264 18133 15 Acid Red 265 18129 16 Acid Red 420 -- 17 Acid Voilet 12 18075 18 Acid Brown 415 -- 19 Acid Black 131 -- 20 Acid Black 132 -- 21 Acid Black 209 -- 22 Basic Red 111 -- 23 Basic Red 42 -- 24 Basic Brown 4 21010 25 Developer 14 = Oxidation Base 20 76035 26 Direct Yellow 48 23660 27 Direct Orange 6 23375 28 Direct Orange 7 23380 29 Direct Orange 10 23370 30 Direct Orange 108 29173 31 Direct Red 2 23500 32 Direct Red 7 24100 33 Direct Red 21 23560 34 Direct Red 22 23565 35 Direct Red 24 29185 36 Direct Red 26 29190 37 Direct Red 39 23630 38 Direct Red 46 23050 39 Direct Red 62 29175 40 Direct Red 67 23505

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41 Direct Red 72 29200 42 Direct Violet 21 23520 43 Direct Blue 1 24410 44 Direct Blue 3 23705 45 Direct Blue 8 24140 46 Direct Blue 9 24155 47 Direct Blue 10 24340 48 Direct Blue 14 23850 49 Direct Blue 15 24400 50 Direct Blue 22 24280 51 Direct Blue 25 23790 52 Direct Blue 35 24145 53 Direct Blue 53 23860 54 Direct Blue 76 24411 55 Direct Blue 151 24175 56 Direct Blue 160 -- 57 Direct Blue 173 -- 58 Direct Blue 192 -- 59 Direct Blue 201 -- 60 Direct Blue 215 24115 61 Direct Blue 295 23820 62 Direct Green 85 30387 63 Direct Blue 222 30368 64 Direct Black 91 30400 65 Direct Black 154 -- 66 Disperse Yellow 7 26090 67 Disperse Yellow 23 26070 68 Disperse Yellow 56 -- 69 Disperse Orange 149 -- 70 Disperse Red 151 26130

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ECOMARK CRITERIA FOR TEXTILES

1. GENERAL REQUIREMENTS: 1.1 The entire textile products manufactured shall meet relevant

standards of Bureau of Indian Standards. 1.2 The product manufacturer must produce the consent clearance

as per the provisions of Water (Prevention and Control of Pollution) Act 1974 and Air (Prevention and Control of Pollution) Act 1981, Water (Prevention and Control of Pollution) Cess Act, 1977 respectively, along with the authorisation, if required under Environment (Protection) Act, 1986 and the rules made thereunder to BIS while applying for Ecomark. Additionally, the manufacturer shall produce documentary evidence on compliance of the provisions related to noise level and occupational health under the provisions of Factories Act, 1948 and Rules made thereunder.

1.3 The product packaging may display in brief the criteria based on which the product has been labelled environment friendly.

1.4 The material used for product packaging shall be reusable or made from recyclable or biodegradable materials.

1.5 Polyhalogenated based phenolic fire retardants shall not be used.

PRODUCT SPECIFIC REQUIREMENTS: A COTTON, WOOL, MAN-MADE FIBRE & BLENDS

S. # Parameters* Max. Limit, mg/kg (ppm) Baby

Clothing Close to Skin

Outer Fabrics

1 2 3 4 5 1. Free & Releasable

Formaldehyde 20 75 300

2. Extractable artificial sweat/salvia Heavy Metals Mercury

0.1 0.1 0.1

3. Chromium III 0.1 0.1 0.1 4. Chromium VI Nil Nil Nil

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Below detectable limit

5. Sum Parameters (as lead) 10.0 10.0 10.0 6. Pentachlorophenol (PCP) 0.5 0.5

(Detectable limit using GC.MS)

0.5

7. Volatile Hydrocarbons (non-halogens)

150 150 150

8. Volatile Halogenated Organics

200 200 200

9. Pesticides (Sum Parameter)**

1.0 1.0 1.0

10. Banned Pesticides Nil Nil (Below detectable limit)

Nil

11. pH of aqueous extract 4.0-7.5 4.0-7.5 4.0-7.5 12. Coupled Amines released

from Azo-dyes (Sum parameters)***

50 50 (Detectable limit using GC-MS)

50

* The methods of tests for Eco-parameters are being developed by BIS and Textiles Committee. Till the methods of test are standardised, the manufacturer shall declare conformance taking into consideration the chemicals, auxiliaries and dyes used. ** The list of Pesticides used on cotton, banned restricted or withdrawn is appended at Appendix A. *** The list of Coupled Amines released from Azo dyes is appended as Appendix-B.

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B. JUTE AND JUTE PRODUCTS S. # Parameters* Max. Limit, mg/kg

Home Textiles & Clothing

Hessians & Sockings

1 2 3 4 1. Free and Releasable

Formaldehyde

Close to skin 75 NA Outer Fabrics 300 NA

2. Extractable artificial sweat/salvia

Heavy Metals Mercury 0.1 NA Chromium III 0.1 NA Chromium VI Nil

(Below detectable limit)

NA

Sum parameters(as lead) 10.0 NA 3. Non-halogenated

Hydrocarbon NA 3%

4. Fatty esters based oil 2% NA 5. Pesticides (Sum

Parameter)** 1.0 1.0

Banned Pesticides Nil (Below detectable limit)

Nil

6. PH of aqueous extract 6.0-7.0 6.0-7.0 7. Coupled amines released

from Azo-dyes (Sum parameters)***

50 50 (Detectable limit using GC-MS)

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* The methods of tests for Eco-parameters are being developed by BIS and Textiles Committee. Till the methods of test are standardised, the manufacturer shall declare conformance taking into consideration the chemicals, auxiliaries and dyes used. ** The list of Pesticides used on jute, banned restricted or withdrawn is appended as Appendix A. *** The list of Coupled Amines released from Azo-dyes is appended as Appendix-B.

C. SILK AND SILK PRODUCTS S. # Parameters* Max. limit, mg/kg (ppm)

Baby Clothing

Close to Skin

Outer Fabrics

1 2 3 4 5 1. Free & Releasable

Formaldehyde 20 75 300

2. Extractable artificial sweat/salvia Heavy Metals Mercury

0.1 0.1 0.1

Chromium III 0.1 0.1 0.1 Chromium VI Nil Nil

Below detectable limit

Nil

Sum Parameters (as lead) 10.0 10.0 10.0 3. Pentachlorophenol (PCP) 0.5 0.5

(Detectable limit using GC.MS)

0.5

4. Volatile Hydrocarbons (non-halogens)

150 150 150

5. Pesticides (Sum Parameter)**

1.0 1.0 1.0

Banned Pesticides Nil Nil Nil

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(Below detectable limit)

6. pH of aqueous extract 4.0-7.5 4.0-7.5 4.0-7.5 7. Coupled Amines released

from Azo-dyes (Sum parameters)***

50 50 (Detectable limit using GC-MS)

50

* BIS and Textiles Committee are developing the methods of tests for Eco-parameters. Till the methods of test are standardised, the manufacturer shall declare conformance taking into consideration the chemicals, auxiliaries and dyes used. ** The list of Pesticides used on Silk Worm rearing, banned restricted or withdrawn is appended as Appendix A. *** The list of Coupled Amines released from Azo dyes is appended as Appendix-B.

APPENDIX-A 1. PESTICIDES REGISTERED FOR USE ON COTTON Herbicides:

Alachlor, Diuron, Fluchlosalin, Monosodium methanearsonate (MSMA), Paraquat Dichloride, Trifluralin.

Fungicides:

Carbendazim, Cuprous oxide, Streptomycin & Oxytetracycline, Thiram.

Insecticides:

Acephate, BHC, Carbaryl, Carbofuran, Chlorpyriphos, Cypermethrin, Decamethrin, Dicofol, Diflubenzuron, Dimenthoate, Endosulfan, Fenitrothion, Fenthion, Fenvalerate, Fluvalinate, Lindane,

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Malathion, Methyl parathion, Monocrotophos, Nicotine sulphate, Oxydemeton methyl, Permethrin, Phenthoate, Phorate, Phosalone, Phosphamidon, Pyrethrum, Quinalphos, Alphamethrin, Methomyl, Triazophos, Cartap hydrochloride, Neem based products, Carbosulfan (for cotton seed), Fenpropathrin, Bacillus thuringensis.

Plant Growth Regulators:

Chlorocholine Chloride (CCC) or Chlormequat Chloride. 2. PESTICIDES REGISTERED FOR USE ON JUTE IN INDIA HERBICIDES: Dalapon FUNGICIDES: Carbendazim INSECTICIDES: Carbaryl, Carbofuran, Endosulfan, Lindane, and

Phosalone. 3. PESTICIDES USED DURING REARING OF SILK WORM INSECTICIDES: Dichlorvos FUNGICIDES: Carbendazim DITHIANON:

Extract from list of pesticides not approved, restricted use, withdrawn or banned in the country as on 10.04.1992. (i) Pesticides not approved for use:

2, 4, 5-T (ii) Pesticides restricted for use:

Use of DDT in agriculture is banned. In very special circumstances warranting the use of DDT for plant protection, the State or Central Government may purchase it directly from M/s. Hindustan

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Insecticides Ltd. to be used under expert Government supervision. Use of DDT for public health programme upto 10,000 MT per annum, except in case of any major outbreak, is restricted.

Use of Lieldrin shall be restricted for Locust Control in desert areas by Plant Protection Adviser to the Govt. of India. (iii) Pesticides banned/withdrawn:

Pentachlorophenol, Toxaphene and Aldrin

APPENDIX-B Coupled Amines released from Azo dyes

1. 4-Aminodiphenyl 2. 2-Amino-1-nitrotoluene 3. Benzidine 4. 4-Chloro-o-toluidine 5. 2-Naphthylamine 6. O-Aminoazotoluene 7. p-Chloraniline 8. 2, 4’-Diaminoanisole 9. 4, 4’-Diaminodiphenylmethane 10. 3, 3’-Dichlorobenzidine 11. 3, 3’-Dimethoxy-benzidine 12. 3, 3’-Dimethylbenzidine 13. 3, 3’-Dimethyl-4, 4’-diaminodiphenylmethane 14. P-kresidin (2-Methoxy 5-methylaniline) 15. 4, 4’-Methylene-bis-(2-chloraniline) 16. 4, 4’-Oxydianiline 17. 4, 4’-Thiodianiline 18. 0-Toluidine 19. 2, 4-Toluyendiamine 20. 2, 4, 5-Trimethylaniline 21. p-Amino-azobenzene 22. 2-Methoxyaniline

Fastnes Properties of Dyes

13 In an age of consumer activism and increasing international trade, test methods and procedures assume more and more importance.

Generally accepted tests, instruments, and standards provide a common basis for the evaluation of quality aspects of dyed textiles.

In the development of text methods, an attempt is made to make them broad in scope and related to actual process in use. Such tests are generally of an accelerated nature, i.e., they reveal the fastness properties exhibited by the material over a lengthy period of time in a test of short duration.

Fastness of dyed textiles is evaluated in regard to natural destructive agents, such as daylight, weather, and atmospheric gases, as well as to various treatments the material is likely to undergo, such as washing, drycleaning, ironing, steaming, etc.

The international body active in test method development is the ISO (International Standards Organization). Fastness tests for dyed textiles fall under the jurisdiction of ISO Technical Committee 38 Textiles / Subcommittee 1 “Tests for Coloured Textiles and Colorants.” The United States is represented in ISO through the American National Standards Institute (ANSI). In the field of interest here, ANSI relies on the American Association of Textile Chemists and Colourists (AATCC) for test development and expert guidance. The AATCC currently has 15 active research committees concerned with colourfastness properties.

The purpose of these Organizations in this area is solely to provide useful test methods. The setting of specifications on the basis of such test methods is a matter to be resolved between buyer and seller. COLOURFASTNESS:

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Described below are the essential features of generally accepted tests (from the AATCC 1976 Technical Manual) used in evaluating fastness proper;ties of dyed, printed or otherwise colored textiles. For

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complete details and for sources of the specialized materials and equipment used in some of these test procedures, reference should be made to the current AATCC Technical Manual. Acids and Alkalies:

This test method is designed to reveal the colourfastness of dyed or printed textiles to acid fumes, sizes, alkaline sizes, alkaline cleaning agents, and alkaline street dirt, by steeping the textile material in or spotting with the required solutions. The tested specimens are examined for changes in colour. Procedure:

Acid tests: (1) The coloured material is spotted with hydrochloric acid solution (100 ml 35 wt % HCI soin) at 21o C and allowed to dry at room temperature without rinsing; and (2) The coloured material is spotted 56% acetic acid and allowed to dry at room temperature without rinsing. Alkaline tests: (1) The coloured material is steeped for two minutes at 21o C in ammonium hydroxide solution (28 wt% NH3) and dried at room temperature without rinsing; (2) The coloured material is steeped for two minutes at 21o C in a 10% sodium carbonate solution and dried at room temperature without rinsing, (3) The coloured material is hung in a 4-L bell jar placed on a glass plate over a 7.6-cm evaporating dish containing 10 ml of concentrated ammonium hydroxide (28 w% NH3). A 24-h exposure is made; and (4) The coloured material is spotted with a freshly prepared calcium hydroxide paste, allowed to dry, and then brushed to remove the dry power.

EVALUATION AND CLASSIFICATION:

The effect on the colour of the test specimens is expressed and defined by reference to the Gray Scale for Evaluating Change in Colour. The results are reported as to class with respect to the specified test.

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Colourfastness to Bleaching with Chlorine (AATCC 3-1975) ANSI L 14.57-1973/R 1963):

This test method is used to determine the effect of sodium hypochlorite containing up to 0.3% available chlorine on dyed or printed cotton or linen textiles. Procedure:

The specimens are washed in sodium hypochlorite solutions under controlled conditions at pH 11-0 = 0.2 and temperatures of 27+-3o C for 60 min.

Test I I III IV Available chlorine, %

0.01 0.1 0.2 0.3

Controls:

The correct test performance is checked with the aid of two control dyeings: Control 1 is a dyeing on cotton cloth of 4% of Vat Violet VN [4424-87-7] (CI Vat Violet 13), 10% paste`; and Control 2 is a dyeing on cotton of 40% Vat Brilliant Violet RK [3076-87-7] (CI Vat Violet 17), 10% paste. EVALUATION AND CLASSIFICATION:

Five classes of fastness are established with the help of the Gray Scale for Evaluating Change in Colour. Control 2 fabric, when exposed to the four tests under satisfactory conditions well shows the following classifications:

Test I I III IV Classification 4 4-3 3 3-2

Colourfastness to Bleaching with Peroxide (AATCC 101-1975) (ANSI L 14.146-1973):

This test is applicable to textiles of all kinds in all forms, with the exception of polyamides.

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Procedure A test specimen is placed between two 10.2 x 3.8 cm white test cloths, one of which is made of the same fabric as the specimen and the other of which varies as follows: If the first piece is wool, silk, linen, or rayon, the second piece should be cotton or multifiber fabric, if the first piece is cotton, or acetate, the second piece should be viscose rayon or multifiber fabric. The coloured swatch is placed between the two white cloths and sewn on all four sides, then subjected to the required test is rolled loosely and place in a test tube with the appropriate solution for the indicated time. In test IV, the swatch is placed in saturated steam (99-101o C) for 1 hour.

TABLE: 3

CONDITIONS IN TESTING FOR COLOURFASTNESS TO BLEACHING AND PEROXIDE

Test Conditions Wool, I Silk, II Cotton, III Cotton, IV 35% hydrogen peroxide, mL / L H2Oa

15.4 (17.5g)

8.8 (10.Og)

8.8 (10.Og)

8.8 (10.Og)

Sodium silicate; 1.41 sp gr (42o Be) mL / L H2Oa

5.1 (7.2g)

4.2 (6.Og)

7.0 (10.Og)

Sodium pyrophosphate, g / L H2Oa

0.5

Sodium hydroxide, g / L H2Oa,b

0.5 0.5

Wetting agent, mL/L H2Oa

2.0

pH, initial 9.0-9.5 10.5 10.5 10.5

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Table 3 Cont.

Test Conditions Wool, I Silk, II

Cotton, III

Cotton, IV

Time, h 2 1 2 1 liquor / cloth ration

20:1 30:1 30:1 1:1

• Distrilled water. • Doubly sulfonate coaster oil. EVALUATION AND CLASSIFICATION:

Staining and / or mark-off evaluated using either the AATCC Chromatic Transference Scale, or the Gray Scale for Evaluating Staining. Change of shade is evaluated by means of the Gray Scale for Evaluating Change in Colour.

Carbonizing (AATCC 11-1975) (AMSI L 14.3-1973/R 1960):

Carbonizing is the process to which wool is subjected in order to remove impurities (such as burrs, bark, grass and cotton fibres) by soaking in a strongly acid solution. The stock or fabric is then dried and baked, after which the cellulosic material may be beaten or washed out. This test method reproduces any colour change encountered in the carbonizing operation, and inapplicable to dyed wool textiles.

Procedure:

Four specimens of worsted test cloth (containing 12-effect floats of accetate, Acrilan 36, Arnel, cotton, Creslan 61, Dacron 54, Dacron 64, nylon 66, Orlon 75, silk, Verel A and viscose) are dyed. One is kept for comparison, and each of the other three is stirred and squeezed for 10 min at 24oC in 100 ml of sulfuric acid solution (50% g/L, or 6o Twad). The specimens are wrung to allow 60-80% pickup, dried at 80% pickup, dried at 80o C for 15 min, and then baked for 15 min at 110o C.

At this point, one sample is saved to show any change in shade while still strongly acid. A second sample is rinsed in running water for 30 min, and the third sample is rinsed twice in distilled

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water, then in a dilute soda ash solution, and finally in running water (rinsing is continued until the sample is neutral or slightly alkaline to litmus paper).

EVALUATION AND CLASSIFICATION:

The test specimens are examined by comparison with dyed standards and classified as follows: Class 1. Poor fastness – a colour which changes seriously in the acid bath and does not return to shade on rinsing; Class 3. Good fastness-a colour which changes materially in the acid bath but returns to shade on rinsing, and Class 5. Excellent fastness – a colour which is unaffected by the entire process of carbonization.

Evaluation may also be based on the Gray Scale for Evaluating Change in Colour. Standards:

Standards for Classes 1,3, and 5 are dyed with the following dyes: Class 1.2% Alizarine Red S (topchrome) [130-22-3] (CI 58005); class 3.2% Acid Cyanine (dyed acid) [6488-97-1] (CI 50230); and Class 5.2% Alizarine Irisol R (dyed acid) [4430-18-6] (CI 60730). Crocking (AATCC 8-1974/116-1974) (ANSIL 14.74-1973/ASSIL 14.212-1973):

This test determines the fastness of a dyestuff to either wet or dry rubbing. Procedure:

The test specimen is placed on the base of the Crockmeter and a square of white test cloth is rubbed on the coloured specimen by means of the Crockmeter finger (dry test cloth for dry crocking; test cloth wet out in distilled water for wet test; wet pickup 65+-5%). The sample is rubbed twenty times; after this the staining of the white cloth is determined.

CLASSIFICATION AND EVALUATION:

Staining is graded by use of the AATCC Chromatic Transference Scale or the Gray Scale for Evaluating Staining.

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Degumming (AATCC 7-1975) (ANSI L 14.4-1973): This test is applicable to dyed silk yarn which may be subjected to

a degumming operation (boil-off in soap solution) during manufacture. Procedure:

The dyed yarn in braided with undyed gum-silk yarn and boiled for 2 h in 0.5% soap solution at a constant 100: 1 liquor ratio, then rinsed cold, and air dried.

EVALUATION AND CLASSIFICATION:

Alterations in colour or staining of undryed silk are observed and rated by comparison with dyed standards or by use of the Gray Scale for Evaluating Staining or the AATCC Chromatic Transfer Scale. Standards:

The standards are dyed as follows: Class 3.5% Indigo MLB/6B Power [6417-56-7] (CI 73075). Class 5.5% Indigo MLK / 4B Powder [2475-31-2] (CI 73065). Drycleaning (AATCC 132-1976) (ANSI L 14.241-1970):

This test indicates the effect of repeated commercial drycleanings, using prechloroethylene as solvent, on dyed and printed fabrics. It is applicable for evaluating the colourfastness of all fibres, fabrics, and yarns which are intended for apparel or household use, and which are likely to be commercially drycleaned. The test is not intended to evaluate the resistance of colours to spot or stain – removal procedures. Procedures:

Samples (10 cm X 4 cm) are placed in a 10 cm X 10 cm bag of undyed cotton twill fabric together with 12 stainless steel disks 30+ 2 mm diameter and 3 + 0.5 mm thickness. Samples are run with 200 ml. Percloroethylene for 30 min at 30 + 20o C, after which they are blotted and air-dried.

EVALUATION AND CLASSIFICATION:

Sample are evaluated for colour change by comparison with the Gray Scale for Evaluating Change in Colour.

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Fulling (AATCC 2-1975): Fulling is a finishing process for woolen cloth involving the effect

of heat, moisture, soap, and mechanical pounding. The purpose of this process is to shrink the cloth by felting action and thus make it firmer and thicker. The fulling test is devised for evaluating the colourfastness of dyed wool fabrics or yarns to mill fulling. Procedure:

Two gram dyed wool and two-gram white test cloth are formed into a bag, dyed sample inside. Then 6.3 mm steel balls are placed inside the bag. Tests are carried out under controlled conditions as shown in Table 4, in the Launder-Ometer using 20-cm steel tubes and 8 ml of solution. Yarns may be braided with white wool or other yarn.

TABLE: 4 TEST CONDITION IN THE FULLING TEST

Test Temp. o

C Soap conc,

wt% Na2CO3

conc, wt% Time, h

I 32 3.75 1.5 0.5 II 38 3.75 1.5 1.5 III 43 3.75 1.5 4.5

EVALUATING & CLASSIFICATION:

The specimens are evaluated by running comparative tests against standard dyeings which represent minimum fastness for each class with respect to alteration of colour staining. As an alternative, the Gray Scale for Evaluating Staining or the AATCC Chromatic Transference Scale may be used. Standards:

Class1. 1% Alizarine Sky Blue B [6424-75-5] (CI 62105). Class 3.2% Brilliant Milling Blue B [5863-46-7] (CI 42645), and Class 5.2% Eriochrome Azurole B [1796-92-5] (CI 43830).

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Dry Heat (Excluding hot Pressing) (AATCC 117-1976) (Based On ISO R 105/IV Part 2):

This method assesses the resistance of the colour of textiles of all kinds and forms to the action of dry heat, but excludes hot pressing. Procedure:

The material under test is standwiched between a piece of undyed material of the same type as the test sample and a piece of multifiber test fabric No.10A. The composite test sample is exposed for 30s to one of the temperature conditions listed in Table 5 in a heating device such as the Scorch Tester.

EVALUATION AND CLASSIFICATION:

The change in colour of the test specimen is rated with the help of the Gray Scale for Evaluating Colour Change. The staining of the undyed fabric (s) is evaluated using the Gray Scale for Staining or the AATCC Chromatic Transference Scale. Hot Pressing (AATCC 133-1976):

Coloured samples are tested for dry, damp and wet pressing under controlled conditions. Procedure:

A 12 cm x 4 cm piece of material is exposed in a Scorch Tester. The bottom plate of the heating device is covered with asbestos sheeting, wool flannel, and dry, undyed cotton fabric. In case of dry pressing, the dry sample is placed on top of the cotton fabric. The top plate of the deveice is lowered for 15 at either 110 + 2o C, 150 + 2o C. In damp pressing, the sample is covered with a piece of undyed cotton fabric that has been soaked in distilled water and squeezed to contain its own weight of water. In wet pressing, both the test sample and a piece of undyed cotton are soaked in distilled water and squeezed to contain their own weight in water. The wet test sample is placed on top of the dry cotton cloth and covered with the wet cotton cloth.

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TABLE: 5

TEMPERATURE CONDITIONS FOR COMPOSITE TEST SAMPLE

Test Temperature, o C AATCC I 149 + 2 II 163 + 2 III 177 + 2 IV 191 + 2 V 205 + 2 VI 219 + 2

ISO I 150 + 2 II 180 + 2 III 210 + 2

EVALUATION AND CLASSIFICATION: For determining change in colour, samples are evaluated immediately

and after the sample have been allowed to condition for 4 hours at 20o C, using the gray Scale for Evaluating Colour Change, and staining is graded by comparison with the AATCC Chromatic Transference Scale the Gray Scale for Evaluating Staining. Lightfastness:

The 1976 edition of The AATCC Technical Manual lists six tests for lightfastness: sunlight, daylight; carbon arc, alternate light and darkness; water-cooled xenon arc, continuous; and alternate light and darkness for both carbon arc and xenon arc. Lightfastness (General Method) (AATCC 16-1974):

Samples and standards are properly mounted, partially covered, and exposed for the appropriate number of hours under specified conditions.

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CLASSIFICATION AND EVALUATION: Samples can be evaluated by three methods: 1. Based on AATCC blue-wool standards L2 through L9, as shown

in Table 6. Lightfastness is evaluated in terms of colour-change comparison with standard.

2. Based on standard sample. When an agreed-upon standard on

sample are exposed until the standard shown a change equal to step 4 on the Gray Scale for Evaluating Colour Change, the sample is considered satisfactory if no greater break appears, and unsatisfactory if a greater break is apparent.

3. AATCC Standard Fading Units. Samples may be classified

according to the number of Standard Fading Units necessary to products a change equal to step 4 on the Gray Scale for Evaluating Change in Colour.

TALE: 6

CLASSIFICATION BY LIGHTFASTNESS

Colour change Less than

Equal More than Class

L2 1 L2 L3 2

12 L3 2-3 L3 L4 3

L3 L4 3-4 L4 L5 4

L4 L5 4-5 L5 L6 5

L5 L6 5-6 L6 L7 6

L6 L7 6-7 L7 L8 7

L7 L8 7-8

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L8 L9 8 L8 L9 8-9

L9 9 Either the single step or the two step method can be used. In the

single step method, the sample is faded to a step 4 break of the Gray Scale. In the two-step-method, a preliminary judgement is made when a step 4 break is obtained, then the sample is exposed further until step 3 break is obtained. If the two result differ, both are reported. Lightfastness-Carbon Arc (AATCC –16-A-1974):

Partially covered sample and standards are exposed and examined after periods as are necessary to produce a “just appreciable fading” Classification may be by any method given under General Method in this procedure. Sunlight-Fastness (AATCC 16B-1974):

Partially covered samples and standards are exposed in a glass covered exposure cabinet and are allowed to remain in the cabinet only on sunny days during the hours between 9 am 3 am (Standard time); they are removed for inspection at frequent intervals. As such standard, beginning with L2, shows a change equal to step 4 on the Gray Scale for Evaluating Change in Colour, all samples that show an equal change are removed from the cabinet. Samples are classified as in the carbon arc method, using AATCC standards or a standard sample. When desired, a standard agreed upon by the buyer and seller may be used in place of the AATCC standards. In this case, exposure is continued until the sample agreed upon shows a change equal to step 4 on the Gray Scale for Evaluating Change in Colour. Exposure time may be based on a mutually agreed upon number of langleys (4.184 x 104 J/m2) of radiation. When a stated number of langleys are used, classification is based on the Gray Scale for Evaluating Change in Colour. A sample that shows no greater change than step 4 is considered satisfactory. Classification may also be used on the required number of langleys (4.184 x 104 J/cm2) necessary to cause a

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change equal to step 4 on the International Geometric Gray Scale. The report should include the method used as well as the date and location of testing. Daylight Fastness (AATCC 16C-1974):

Tests are conducted as for sunlight-fastness except that exposed samples are allowed to remain in the exposure cabinet 24 hours a day, and are removed only for inspection. Classification is as for sunlight testing. Lightfastness Carbon Arc Alternate Light Darkness (16D-1974):

This method requires a carbon arc machine that is equipped with an atomizer, and which automatically controls the turning on and off the lamp. A cam producing 1 h of darkness and 3.8 h of light is used. The apparatus is adjusted so that during the light-on period the black panel temperature is 63 + 3o C, and the rh 35 + 5%. During the 1-h period the relatively humidity is 90 + 5%. Classification and evaluation are based on AATCC blue wool standards or on a standard sample. Lightfastness-Xenon Lamp-Continuous Light (AATCC 16E-1976): Sample are exposed in the same manner as in the carbon arc machine with the black-panel temperature at 63 + 3o C and rh of 30 + 5%. Evaluation and classification are based on AATCC blue-wool standards or on a standard sample. Lightfastness-Xenon Lamp-Alternate Light-Darkness (AATCC 16F-1974):

This method uses a cam as in Method 16D-1974 and follows the same procedure with the xenon tube replacing the carbon arc as a light source. Carbon-Arc Lamp (Fade-Ometer):

The Fade-Ometer is operated on arc at 15-17 A and 125-145 V across the arc. The are is enclosed in a heat-resistant glass globe. The samples are mounted 25 cm from the arc and are on a frame that revolves about the arc 2 + 1 times per minute. A blower unit in the base provides as flow of air through the machine allowing for temperature control,

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which is measured by use of black-panel thermometer. The humidity in the chamber is automatically controlled. EXPOSURE CABINET:

The exposure cabinet for sunlight or daylight tests is constructed so as to face due sought in the Northern Hemisphere, and due north in the Southern Hemisphere, with a slant approximately equal to the degree of latitude at which the cabinet is located. It allows free access of air to the samples and is covered with window glass at least 8 cm above the exposure area. Black-Panel Thermometer:

The unit consists of bimetallic diatype thermometer mounted on a suitable frame with the face (plate) of the frame and stem of the thermometer sprayed with a head resistant black enamel. Lightfastness Standards:

Eight lightfastness L2 through L9 are available from AATCC. These standards are prepared by blending very proportions of wool dyed with a very fugitive colour, Eriochrome Azural B (1796-92-5] (CI 43830), and wool dyed with a fast colour. Indigosol Blue AGG [4086-05-9] [CI 173801], in such a manner that each numbered standard is approximately twice as fast the preceding numbered standard. Xenon-Arc Lamp:

The apparatus uses a 1quartz-xenon burner tube which is water-cooled, with an inner Pyrex (Corning Glass Works) filter glass and an outer filter of clear glass. Samples are mounted at the required distance from the arc and are supported on a frame which revolves about the arc 2 + 1 times per minute. Testing temperatures are measured by the black-panel thermometer, and moisture is added by controlled methods. Alternate Wash-and-Light (AATCC 83-1974):

This test is designed to provide a consumer end-use test which will simulate an average of five exposure to sunlight (duration, 6 h) followed by a washing without chlorine.

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Procedure:

A 6 cm X 15 cm specimen is exposed for twenty Standard Fading Units and is followed by a Wash IIIA.

EVALUATION:

The effect on the colour is greater and expressed by comparison with the Gray Scale for Evaluating Change in Colour. Phototropism (AATCC 139-1975):

This test is designed to show colours that are changed impermanently when exposed to strong light. This change takes place after a short exposure, but the colour returns to its original shade when placed in the dark.

Procedure: Dyed samples 6 cm X 3 cm are exposed in the xenon arc fading apparatus for 1/25 of the time necessary to obtain a step 4 Gray Scale Fade on an L-2 blue-wool standard. The sample is immediately inspected for a contrast between the original and the exposed portions. If the contrast is equal to or less than a step 4 of the Gray Scale for Evaluating Change in Colour, the sample is considered not phototropic. If the contrast is greater than step 4, the specimen is left in the dark for one hour at 20 + 2o C and a rah 65 + 2o C. If the contrast has not disappeared, the sample is exposed for 15 to steam at 101 kPa (1atm) and reinspected. If the disappears, the sample is considered to be phototropic. If the contrast remains, the sample is not considered phototropic and the contrast is due to low lightfastness. Fastness to light should be assessed in a parallel test.

OZONE IN THE ATMOSPHERE UNDER LOW HUMIDITY (AATCC 109-1975) (ANSI L 14174-1973):

It has been found that ozone can destroy dyes applied to textiles. This test has been devised to expose and determine the fastness of dyed textiles to ozone at rh not exceeding 65%.

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Procedure: A specimen 10 cm x 6 cm and a swatch of Control No.109, are suspended in a exposure chamber at 18-28o C with rh <65%. Ozone should be present in concentrations that produce one cycle of fading 1.5-6 h of test. Samples are exposed for the number of cycles necessary to cause a change of shade. A cycle is considered complete when the control matches the Standard for Fading. Usually two cycles will cause a change in an ozone-sensitive dye.

EVALUATION AND CLASSIFICATION:

Sample are granted by comparison with the Gray Scale for Evaluating Change in Colour and the report will include the number of cycles to which the sample has been subjected. Ozone in the Atmosphere Under High Humidity (AATCC 129-1975):

This test is analogus to the pregious test except that the test specimen is exposed in a chamber at 40 + 5o C and 85 + 5% rh, together with control sample No.129. Bumed Gas fumes (AATCC 23-1975) (ANSIL 14.56-1973):

This method accesses the resistance of coloured textiles when exposed to atmospheric oxides of nitrogen as derived from the combustion of heating gas. Procedure:

Test specimens (5 cm X 10 cm) are exposed together with a strip of Control Sample, No.1, in a gas-fading apparatus, until the control sample shows a change in colour corresponding to that of the standard of fading. The gas-fading apparatus contains an open flame from combustion of illuminating gas or butane.

EVALUATION:

After each exposure cycle the specimens are compared with unexposed samples. The effect, if any, is classified with the aid of the Gray Scale for Evaluating Change in Colour. The class number and the number of exposure cycles are reporte.

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Washfastness: Washing, Domestic and Laundering, Commercial: Accelerated (AATCC 61-1975) (ANSI L 14.81-1973): These accelerated laundering tests are designed for evaluating the washfastness of textiles. One 45 min test approximates the colour loss and/or abrasive action of five average hand, commercial, or home launderings.

The conditions of the four different tests are given in Table-7. Procedure:

Samples (5 cm X 10 cm (Test IA) or 5 cm X 15 cm (all other tests)) to which a 5 cm X 5 cm piece of multifiber fabric has been seen or stapled along one side are filled one each into 7.5 cm X 12.5 cm or 9 cm X 20 cm stainless-steel cylinders. The wash liquor and the steel balls as per Table 7 are added. The detergent used is AATCC Standard Detergent WOB. The containers are closed and subjected for 45 min at the required temperature in a Launder Ometer (Atlas Electric Devices Inc.). At the end of the cycle, the containers are removed and the samples rinsed twice in 100 ml of water for 1 min at 40o C. They are scoured in 100 ml of 0.014% soln of acetic acid for 1 min at 27o C and rinsed again for 1 min at 27o C in water. The sample are then hydroextractred and dried by pressing with an iron at 135-150o C.

TABLE: 7

TEST CONDITIONS

Test No.

Temp, oC

Total liquor volume mL

Detergent of Total

volume,%

Available Chlorine of total

volume %

Number of steel balls

Time, min

IA 40 200 0.5 10 45 IIA 49 150 0.2 50 45 IIIA 71 50 0.2 100 45 IVA 71 50 0.2 0.015 100 45

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EVALUATION: Test IA conforms to five careful hand launderings at 40o C. Test

IIA conforms to five commercial launderings at 38o C or five home-machine launderings at medium or warm temperature setting. Test IIA conforms to five commercial launderings at 49o C or five home launderings at 60o C. Test IVA conforms to five commercial launderings at 71o C or five home launderings at 60-66o with chlorine present. Samples are evaluated for change in colour with the corresponding Gray Scale and for staining with the aid of the AATCC Chromatic Transference Scale or the Gray Scale for Evaluating Staining.

MISCELLANEOUS FASTNESS PROPERTIES Prespiration (AATCC 15-1976):

Prespiration may cause an undesirable change in shade or staining or both. This test is applicable to dyed, printed or otherwise coloured fabrics. Procedure:

A 5.7 cm x 5.7 cm swatch backed with No.10 multifiber test cloth is immersed in the test solution for15-30 min and squeezed to 2-2 ½ times its original weight. The samples are placed between glass or plastic plates and stacked in the AATCC. Prespiration Tester or in Prespirometer. A 3.63 kg weight is added to the Prespiration Tester or 69-kPa (10 psi) pressure is adjusted on the Prespirometer. The loaded specimen unit is heated in an oven at 38 + 1o C > 6 h.

The acid solution (pH 3.5) is made up of 10.00g sodium chloride;

1.00 g of 85% lactic acid (USP); 1.00 g disodium hydrogen phosphate anhydrous, Na2HPO4; and 0.25 g histidine monohydrochloride; the solution is brought to one litre with distilled water. EVALUATION AND CLASSIFICATION:

Samples are evaluated for colour change by comparison with the Gray Scale for Evaluating Change in Colour. Four evaluation of staining, either the AATCC Chromatic Transference Scale or the Gray Scale for Staining may be used.

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Steam Pleating (AATCC 131-1974): This test is applicable to textile intended to be used in pleated

clothing. It is designed to measure the change in shade of dyed textiles that are subjected to a steam treatment, as in pleating. Procedure:

A 4 cm X 5 cm specimen is placed between two 4 cm X 5 cm pieces of undyed scoured fabric of the same type of fiber used in the test specimen and sewn along one side. The specimen is then mounted on a special Specimen Holder and steamed under one of the following three conditions:

Test Time,

min Temperature,

o C Pressure,

kPa I mild 5 108 34

II intermediate

10 115 69

III sever 20 130 173

After exposure the samples are air dried below 60oC and conditioned for 4 h at 20 + 2o C and 65 + 2% rh. EVALUATION:

The change in colour of test specimen is evaluated with the Gray Scale for Evaluating Colour Change. The staining of the undyed fabric pieces is evaluated with the Gray Scale for Evaluating Staining. The type of test and the ratings figures are reported: Stoving (AATCC 9-1975) (ANSI L 14.9-1973):

Stoving is a method for bleaching wool by subjecting it to sulfur dioxide fumes. This test is applicable to dyed yarns of all kinds, which might be subjected to the sulfur dioxide stoving procedure. Procedure:

The dyed yarn is braided with undyed wool and undyed silk, soaked in 0.5% soap, hung in a bell jar with an excess amount of

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burning sulfur dioxide fumes for 16.h. After through rinsing in cold water and extraction, the sample is dried and evaluated.

EVALUATION AND CLASSIFICATION:

Samples are evaluated in comparison with dyed standards, or by comparison with the Gray Scale for evaluating Change of Colour. Staining of the undyed materials is evaluated with the AATCC Chromatic Transference Scale or the Gray Scale for Evaluating Staining. Standards:

Dyed on worsted wool yarn: Class 1. 1% Alizaring yellow R (2243-76-7] (CI 14030): Class 3. 1% Naphthochrome Violet R [7452-51-9](43565); and Class 5.1% Acid Alizarine Violet N [2092-55-9](CI 15670).

Water Tests (AATCC 105-1975, ANSI L14.149-1973; AATCC 106-1975, ANSI L 14.150-1973; AATCC 107-1975, ANSI L14.151-1973): Tests in fresh, sea, and chlorinated pool water are designed to measure the resistance in each of dyed printed, or otherwise coloured textile yarns and fabrics of all kinds. Procedure:

Distilled or demineralized water are artificial seawater are used because of the variables encountered in tap water or natural seawater. Seawater solution is made up of 30 g sodium chloride and 5 g magnesium chloride pool water solution is made up of 5 parts of 1% soln of available chlorine per 10.000 parts of distilled 2water (5ppm), adjusted to pH 8 with either sodium bicarbonate or acetic acid. Specimens for each type of water test are backed with multifiber test cloth.

For freshwater and seawater tests, the specimens are wet out in the

suitable solution for 15 min, placed in the AATCC Prespiration Tester or Perspirometer at 69 kPa (10psi) and placed in an oven at 38oC for 18h, after which the specimens are removed and dried at room temperature without pressing.

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Specimens for chlorinated-pool-water-tests are kept in 200 mL of solution at 27o C in a closed jar for 4 h, during, which time they are occasionally gently agitated. They are then placed in the Perspirometer and kept at 38o for 2 h. EVALUATION AND CLASSIFICATION:

All three water tests are graded for colour change by comparison with the Gray Scale for Evaluating Change in Colour; either the AATCC Chromatic Transference Scale or the Gray Scale Evaluating Staining is used for rating the staining of the multifiber test cloth. Water Spotting (AATCC 104-19756) (ANSI L 14.148-1963/R-1963/R-1969):

This simple test indicates the fastness of textiles to water spotting. It does not show whether or not the discolouration is removable. Procedure and Evaluation:

A coloured swatch is spotted with water. The colour change is evaluated after 2 min, and again after drying, using the Gray Scale for Evaluating Change in Colour.

APPLICATION PROPERTIES: Recently the AATCC has initiated a research program to develop test methods for the evaluation of application properties of dyes in dyeing processes. So far, three such test methods have been published and others are to follow shortly. Compatibility of Basic Dyes for Acrylic Fibers (AATCC 141-1976):

This test is intended of determine the behaviour of a basic dye concerning compatibility when applied to acrylic fibers in the presence of other basic dyes. Compatible dyes according to this definition are those that exhaust at same rate as the other dyes in the combination. Procedure:

The compatibility is determined is a so-called dip test where the dye under test is exhausted on several pieces of acrylic material in separate combinations with five basic dyes of established

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compatibility value. There are separate yellow and blue scales (AATCC) of five standard dyes each.

EVALUATION:

The compatibility value of the dye under test is that of the standard dye with which is produces on-tone dyeings throughout the sequence of dyeings. The compatibility value C ranges from 1 to 5 with half steps. Dispersibility of Disperse Dyes:

Filter Test (AATCC 146-1976): This test determines the dispersibility of disperse dyes as evaluated by filtering time in filter residue under standard conditions in aqueous media. Procedure:

Dye powder (2g of standard and sample) is pasted with 180ml water at 43-49o C. The pH is adjusted as shown in Table 8 and the volume brought to 200 ml. The dispersion is heated to 71o C and filtered it in warmed Buchner funeral through filter paper (as indicated in Table 9), under vacuum. The time it takes for the dispersion to pass through the filter is recorded. The filter paper is dried for evaluation.

EVALUATION:

The residue on the filter paper is evaluated visually against the Filter Residue Scale from 5 to 1 (AATCC). The results are rated according to filtering time as follows:

Class Filtering time, s A 0-24 B 25-49 C 50-74 D 75-120 E >120

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The type of test, the filtering-time class and the residue class are reported.

TABLE: 8 SELECTION OF APPLICABLE TEST

Test

Whatman Filter

combination

Application of dyes

pH of dispersion

I # 2 over # 4 Package dyeing of polyester

4.5-5.0

II # 4 over # 4 Beck dyeing of polyester

4.5-5.0

III # 4 over # 4 Dyeing of nylon carpet and apparel

7.0-10.0

Dyestuff Migration (AATCC 140-1976):

The purpose of the test is to evaluate particulate migration of dyes that have been padded on a textile fabric during drying as well as the influence of auxiliaries on the migration. Such migration cab is substantial cause of unlevelness. Procedure:

The dye under test alone or together with auxiliaries is padded in a concentration desired on a 5 cm X 30 cm swatch of fabric. The swatch is immediately placed on a horizontal glass plate. A 9 cm dia watch glass is place on a portion of the fabric. The fabric is dried at room temperature and watch glass is removed.

EVALUATION: The degree of particular migration is estimated by comparison of

the dye concentration in the area of fabric, which was covered by the watch glass to the dye concentration in the rest of the fabric. Three methods of evaluation are possible: (1) visual, by reference to the Gray Scale for Evaluating Change in Colour; (2) by reflectance measurement and calculation of colour difference; and (3) by quantitative extraction of the dye from disks of fabric of equal size from the covered and uncovered areas. Percent particulate migration (Mp) is calculated as follows:

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(1 – AA) M p = 100 ------------------ ABB

Where AA is the absorbance at the analytical wavelength of the extract from the covered area. AB is the absorbance at the analytical wavelength of the extract from the uncovered area.

B

REFERENCE

1. Technical manual of American Associatio0n of Textile Chemist & Colourist (AATCC).

2. The Chemistry of Synthetic Dyes by Venkataraman Academic

Press London. 3. Waston E.R Colour in relation to Chemical Constitution,

Longman Green London. 4. Fundamental of the chemistry and Application of dyes By P.Rys

& H. Zolinger Wiley – Inter Science London. 5. P.F Gordon, Organic Chemistry in Colour, Springer – Verlag,

New York. 6. K. Mac Laren, the Colour Science of Dyes & Pigments Adam

Hilger, Bristol. 7. A Glimpes on the experimental Textile Laboratory, Mahajan

Brothers Ahmedabad India. 8. The Colour Index, Society of Dyes & Colourist Bradford. 9. Colour Chemistry, Synthesis Properties & Application of Organic

dyes and Pigments 2nd edn, VCH, New York. 10. Colourant and Auxiliaries Vol-1 J.Shore Society of Dyers &

Colourist Bradford. 11. Kirk – Orthmer Encyclopedia of Chemical Technology, John

Wiley, New York. 12. The Chemistry of Polymers, J.W. Nicholson The Royal Society of

Chemistry Cambridg. 167