Dyeing Processes

5/21/2018 Dyeing Processes

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Documentation on different types of Dyeing Processes

Submitted by:

Chiranjib Sahoo-06

Chitrangada Roy- 07

Nairita Mondal- 11

BFTech (AP)

Semester- III

2011-2015


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Dyeing ProcessTypes

YarnDyeing

SkeinDyeing

Package

Dyeing

Warp BeamDyeing

SpaceDyeing

PieceDyeing

CrossDyeing

Union

Dyeing

BeckDyeing

JigDyeing

PadDyeing

BeamDyeing

Cold padbatch Dyeing

FoamDyeing

JetDyeing

SolventDyeing

VacuumImpregnation

DopeDyeing

GarmentDyeing

StockDyeing

TopDyeing


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1. Stock Dyeing

Stock dyeing refers to the dyeing of the fibers, or stock, before it is spun in to yarn. It is done by

putting loose, unspun fibres in to large vats containing the dye bath, which is then heated to the

appropriate temperature required for the dye application and dyeing process.

Stock-dyeing or yarn-dyeing is another, less expensive process textile mills use to colorize

fabrics. Due to the nature of this material it is unable to outperform solution-dyed materials.

In the stock-dyeing process, the color is applied after the basic white fibers have been spun and

tightly woven together. Once material has been fabricated, the coloring is then applied via force

to penetrate the porous fibers as deeply as possible.

This method, regardless of how much dye is used or the amount of pressure applied, is not able

to achieve consistent coloring throughout the fibers.

Material's that do not have through and through coloring, are unfortunately more susceptible to

fading and tearing, as the fabric weakens more rapidly when in intense sunlight.

In today's marketplace, most polyester materials are stock-dyed because the process to make it

is less costly than the solution-dying process.

Important features

Stock dyeing is the most costly method for dyeing because the level of production is

relatively low.

Also there is 10-15% waste of dyed fibers through subsequent manufacturing of yarn.

Stock dyeing usually results in excellent penetration of the dye into the fiber and

evenness of the color throughout.

There is a strong element of fashion risk in stock dyeing because the decision as to the

final color of a fabric has to be made at the earlier stage in this manufacturing.

Reason for use:

Stock dyeing is used mostly in woolen materials when heather like color effects are

desired. . Wool fibre dyed black, for example, might be blended and spun with un-dyed

(white) wool fibre to produce soft heather like shade of grey yarn.

Tweed fabrics with heather like color effects such as Harris Tweed are examples of stock dyed

material. Other examples include heather like colours in covert and woolen cheviot.


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2. Top Dyeing

Top dyeing is also the dyeing of the fibre before it is spun in to yarn and serves the same

purpose as stock dyeingthat is, to produce soft, heather like color effects. The term top refers

to the fibres of wool from which the short fibres have been removed. Top is thus selecting long

fibres that are used to spin worsted yarn. The top in the form of sliver is dyed and then blended

with other colors of dyed top to produce desired heather shades.

3. Yarn Dyeing

Yarn dyeing is the dyeing of the yarns before they have been woven or knitted into fabrics. Yarn

dyeing is used to create interesting checks, stripes and plaids with different-colored yarns in theweaving process. In yarn dyeing, dyestuff penetrates the fibers in the core of the yarn. There

are many forms of yarn dyeing- Skein (Hank) Dyeing, Package Dyeing, Warp-beam Dyeing,

and Space Dyeing.

A. Skein (Hank) Dyeing

Skein dyeing consists of immersing large, loosely wound hanks (skeins) of yarn into dye vats

that are especially designed for this purpose. Soft, lofty yarns, such as hand knitted yarns are

usually skein dyed. Skein dyeing is the most costly yarn-dye method.

In skein dyeing, one of two main methods used to dye carpet yarn, twisted and heat-set yarn is

turned a new solid color. It is hung loosely in 1,000-pound batches on a carrier that keeps it

from tangling and is plunged into a stainless steel vat filled with a dye mixture for about three

hours. The dyed yarn is then bulked up for texture, wrung of excess liquid, and spun ontocones.


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B. Package Dyeing

In package dyeing the yarn is wound on a small perforated spool or tube called a package.

Many spools fit into the dyeing machine in which the flow of the dye bath alternates from the

center to the outside, and then from the outside to the center of the package. Package dyed

yarns do not retain the softness and loftiness that skein-dyed yarns do. They are however

satisfactory and very widely used for most types of yarns that are found in knitted and woven

fabrics.

C. Warp Beam Dyeing

Beam dyeing is the much larger version of package dyeing. An entire warp beam is wound on

to a perforated cylinder, which is then placed in the beam dyeing machine, where the flow of the

dye bath alternate as in the package dyeing. Beam dyeing is more economical than skein or

package dyeing, but it is only used in the manufacture of woven fabrics where an entire warp

beam is dyed. Knitted fabrics, which are mostly produced from the cones of the yarn, are not

adaptable to beam dyeing.

D. Space dyeing


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Space dyeing is a technique used to give yarn a unique, multi-colored effect. While a typical

skein of yarn is the same colour throughout, a skein of space dyed yarn is two or more different

colours that typically repeat themselves throughout the length of the yarn. Space dyed yarn is

sometimes referred to as dip dyed yarn.

The secret to space dyeing yarn involves the use of a special chemical called a mordant. Thepurpose of a mordant is to help permanently fix the dye to the yarn after the space dyeing

process. Since different colours of dye require different types of mordants, this makes it

possible to dye the same skein of yarn many different colours.

Space dyed yarn can be dyed in either coordinating or contrasting shades. Space dyeing yarn

in coordinating colors, such as various neutral tones or assorted shades of blue, provides a

subtle yet sophisticated look. Space dyed yarn in contrasting shades, such as yarn that is

purple, red, and blue, offers a funkier feel.

Space dyed yarn is most commonly used for knitting and crocheting. When space dyed yarn ismade to make a knitted or crocheted item, the resulting project features uneven horizontal

stripes that produce a collage-like effect. However, the size of the stripes in the finished piece

depends on what size of yarn is used.

4. Piece Dyeing

The dyeing of cloth after it is being woven or knitted is known as piece dyeing. It is the most

common method of dyeing used. The various methods used for this type of dyeing include:

A. Beck dyeing

It is used for dyeing long yards of fabric. The fabric is passed in rope form through the dyebath.

This rope of the fabric moves over a rail onto a reel which immerses it into the dye and thendraws the fabric up and forward and brings it to the front of the machine. This process is

repeated many times until the desired color intensity is obtained.

Key Features of Beck Dyeing

Liquor Ratio- The ratio of the liquor to goods that is used in becks typically stands out at

15:l or sometimes even higher.

Dyeing Temperatures- Tempearures upto 100oC can be employed for dyeing withatmospheric Becks.


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Time Duration- Just as the dye is natural that does not guarantee that it is also

environmentally sustainable. For example pesticide may have been used to grow the crops etc.

Crucial role of pH- pH plays a vital role in the beck dyeing process. pH controls strike

rate, absorption rate of dye, dye exhaustion etc.

Advantages of Beck Dyeing

The greatest advantage of beck dyeing is the modest pricing, simplicity, and versatility.

In Beck dyeing fabrics are subjected to comparatively low lengthwise tension and helps

the development of fabric bulk and yarn crimp.

The process Beck dyeing is an effective way to totally rule out any risk of sidematch

problems a common problem with dyeing of carpets.

Beck dyeing is able to maintain a colour consistency.

In case of carpets, beck dyeing makes it feel fuller and softer.

B. Jig dyeing

It is similar to the process of beck dyeing with a slight variation. The fabric in jig dyeing is held

on rollers at full width rather than in rope form as it is passed through the dyebath.

C. Pad dyeing

Padding is also done while holding the fabric at full width. The fabric is passed through a trough

having dye in it. Then it is passed between two heavy rollers which force the dye into the cloth

and squeeze out the excess dye. Then it is passed through a heat chamber for letting the dye to

set. After that it is passed through washer, rinser and dryer for completing the process.


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D. Jet dyeing

Fabric is placed in a heated tube where jets of dye solution are forced through it at high

pressures. The fabric too moves along the tube. The solution moves faster than the cloth while

coloring it thoroughly.

E. Beam dyeing

The beam dyeing machine is suited to process a wide range of knitted and woven textiles. The

fabric in open width is rolled on to a perforated beam, then subsequently loaded into a vessel

that is closed and pressurized. The dye impregnates the fabric as the dye liquor is allowed to go

on circulating through the perforations (holes) in the beam. Usually the beam dyeing machines

are designed to hold a single beam.

The fabric is placed under controlled tension, and is wound on to a perforated beam. This

results in the elimination of creases on the fabric.

The fabric is restricted to non movement during the dyeing process. This means that there is

no mechanical application of action to the fabric, the actual dyeing process is motionless. The

fabric remains stationary in the vessel as the pressure of the pump forces the dye liquor through

the fabric roll.

F. Cold Pad Batch Dyeing

The technique or process used in pad-batch dyeing starts with saturating first the prepared

fabric with pre-mixed dye liquor. Then it is passed through rollers. The rollers, or padders,

effectively force the dyestuff into the fabric. In the process, excess dye solution is also removed.

After removal of excess dye stuff the fabric is subsequently "batched". This batching is done by

either storing it in rolls or in boxes. It takes a minimum of 4-12 hours. The batches are generally

enclosed by plastic films. This prevents absorption of carbon dioxide and water evaporation.

Finally as the reaction is complete the fabrics are washed. This is done by becks, beams, or any

other washing devices.

Special Features of Pad Batch Dyeing Process

Significant cost and waste reduction as compared to other conventional dyeing

processes.

Total elimination of the need for salt and other specialty chemicals. For example there is

no need for anti-migrants, leveling agents and fixatives that are necessary in conventional

dyebaths.


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Optimum utilisation of dyes that eliminates specialty chemicals, cuts down chemical costs

and waste loads in the effluent. All this results in a formidable reduction in wastewater treatment

costs.

Excellent wet fastness properties.

Pad batch dyeing cuts energy and water consumption owing to low bath ratio (dye:water)

required for the process. This is because unlike other dyeing processes it does not function athigh temperatures.

A uniform dye quality is achieved with even color absorbency and colour fastness.

As compared to rope dyeing, Pad batch dyeing produces much lower defect levels.

In pad batch dyeing, qualities like high shade reliability and repeatability are common.

This is because of high reactivity dyes with rapid fixation rate and stability.

Lastly Pad batch dyeing can also improve product quality. The fabric undergoing the cold

pad batch dyeing process is able to retain an uniformly coloured appearance. It shows added

luster and gives a gentle feel. The fabric gives a brighter look in shades.

G. Vacuum Impregnation

Based on certain important principles

One of these is that air entrapped in the substrate of the textile fibres in the fabric and in

the folds of the fabric itself hinders the passing of dye through to the fibre sites

Also normal atmospheric pressure can be substituted for the higher pressures generally

used

Here air is evacuated from the dye tank to near zero pressure

Fabric is then covered with the dye liquid while it is in this vacuum state, then the system

is opened to allow return to normal atmospheric pressure

As a result there is instantaneous wetting, virtually complete saturation of the fabric and

impregnation of the dye into the fibre

In effect, when vacuum condition is suddenly changed to normal or even a bit higher, the

pressure created is so comparatively great that the dyestuff is literally forced onto the fibre


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H. Foam Dyeing

Technique of applying dyestuff suspended in liquid that is formed with a special mixer

and applied to the fabrics

Primary motivation for this method is the desire to conserve energy in steaming and

dyeing, apart from reduced water consumption and pollution

Method is based on the fact that the foam, which has high volume and high viscosity

makes it possible to apply relatively small quantities of conc.dye liquid as compared to pad

dyeing

Foam dyeing is accomplished, by feeding, with the acid of a trough and a doctor blade, a

uniform layer of foam of exactly defined thickeners

Foam is pressed into the fabric as it comes in contact with the roll for about 180 degrees

Front and back are simultaneously dyed in one pass

Heavy pile fabrics and carpet also can be foam dyed

Maintaining uniformity of foam composition, air, liquor with constant temperature control

is a problem

I.Solution pigmenting or dope dyeing

This is a method applied for dyeing the synthetic fibers. Dye is added to the solution before it is

extruded through the spinnerets for making synthetic filaments. This gives a colorfast fiber as

the pigments are used which are the fastest known colors.

The process in which solution-dyed polyester is created has much to do with the fabric's ability

to perform well in many areas of its use.

Polyester in general is a synthetic fabric that begins as a polymer melt (liquid form). In the

solution-dyeing process, the color is added during the liquid stage, prior to being cooled and

spun into synthetic fibers.

The fiber, both inside and out, reflects that much like a carrot as pictured above.

Since the coloring goes through and through and is not just applied to the surface of the

material, the fabric then retains its properties more than a stock-dyed fabric would when

exposed to intense sunlight and air pollutants.

The process of solution-dying polyester gives this cover material high marks performance-wise

in fade and stain resistance as well as overall durability.


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5. Garment Dyeing

Garment dyeing is the dyeing of the completed garments. The types of apparel that can be dyed

are mostly non-tailored and simpler forms, such as sweaters, sweatshirts, T-shirts, hosiery, and

pantyhose. The effect on sizing, thread, zippers, trims and snaps must be considered. Tailored

items, such as suits or dresses, cannot be dyed as garments because the difference in

shrinkage of the various components and linings disort and misshape the article.

Garment dyeing is done by placing a suitable number of garments (usually about 24 sweaters

or the equivalent, depending on the weight) into large nylon net bag. The garments are loosely

packed. From 10 to 50 of the bags are placed in large tubs containing the dye bath and kept

agitated by a motordriven paddle in the dye tub. The machine is appropriately called a paddle

dryer.

This method is the last process of the dyeing of goods. However, the penetration of the dye

solution may not be completely passed to the fibers such as between the seams, buttons,

zippers etc. Normally, it is used for lingerie, socks, sweater dyeing etc.

A. Exhaustion Process

This method is using lot of water as shown in Liquor Ratio (ratio between water and goods)

This should immerge the goods into dye solution for a long time in order to let the dye penetrate

into the goods. This will lead to produce more waste water than the continuous process.

Advantage: inexpensive, no have to train the employee with take care of plus run them

correctly.

Disadvantage: many water required, rather slow task (60-120 mm/batch.)

B. Continuous Process

This method is designed by putting different machinery into a sequence so that it can produce

the dyed fabric in one pass.


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Advantage: very quick procedure (10-100 m/min), tiny amount of water inside the task.

Disadvantage: very pricey, should train the employee with take care of plus run them correctly.

Example of the open width shape cloth dyeing .

6. Cross dyeing

This is the process of dyeing fabrics made up of different fibers or yarns with different

colors.

Yarn, fabric or even garment made with two or more generic fiber types Blends having

different dyeing qualities is dyed in a single dye bath containing different classes of dyes.

It produces a multi-colored fabric in one operation by mixing dyes, each specific to one

fiber.

Plaids or stripes can be created in a fabric by alternating yarns of different fibers.

7. Union dyeing

Union dyeing is achieving single solid color on blended fabrics.

A fabric composed of rayon and acetate can be dyed a solid color of green by using a

direct dye for the rayon and disperse dye of the same color for the acetate.

This process includes compartments of pre treatment, pad dyeing, after treatment,

washing and rinsing.

The problem with union dyeing is the variation in the fastness properties of different dyes.

Use of pigments, which are not fiber specific, offers a cheap and easy way to produce

solid-colored fabrics.

It is limited to pastel colors because large amounts of binder will affect fabric hand.

Dyeing Processes

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