114 World Journal of Textile Engineering and Technology, 2019, 5, 114-122

E-ISSN: 2415-5489/19 © 2019 Scientific Array

Ecofriendly Specialty Fibres from Bio-Resources

Hitesh Das and K. Murugesh Babu*

Department of Textile Technology and Research Centre, Bapuji Institute of Engineering and Technology, Davangere – 577004, Karnataka, India

Abstract: In the present era of environmental consciousness, sustainable materials play a vital role in protecting public health and environment. The eco-problems in textile industry occur during some production processes and are carried forward right to the finished product. Controlling pollution is as vital as making a product free from the toxic effect. There is a need to produce the material which is eco-friendly. So, the materials can be considered ‘environmentally friendly for a variety of reasons’. Concerns for the environment and consumer demand are driving research into environmentally friendly fibres as replacements for part of the 38 million tonnes of synthetic fibres produced annually. The main problems with synthetic fibres are that they are non-biodegradable. In last few decades, the textile industry has witnessed introduction of many new fibres in the market. Recently, environmental concerns and the growing global waste problem have spurred much research into the development of bio-based materials and motivated governments to increase the legislation pressure. Many clothing companies are focussing on use of sustainable fibres for manufacturing textiles and garments. These fibres are eco-friendly and are extracted or manufactured from bio-resources. Many innovations have been reported in recent years regarding the sustainability of these fibres. In this paper production of some regenerated sustainable fibres from bio-resources such as Viscose rayon, Lyocell fibres, Cupro fibres, Casein fibres, Groundnut protein fibres, Zein fibres, Soya bean fibres, Silicate fibres and Alginate fibres have been discussed.

Keywords: Sustainable fibres, Lyocell, Soyabean fibre, Ground nut fibre, Milk fibre, Zein fibre, Alginate fibre.

1. INTRODUCTION

The environmental consciousness these days is resulting in wide demand for eco-friendly products. Textile and garment industry are one of the major polluting industries in the world. But the impacts of global environmental concerns have led to the development of major revolutions in garment industry. One such development is increase in demand and use of regenerated fibres which are eco-friendly and derived from bio-resources [2, 3]. Concerns for the environment and consumer demand are driving research into these fibres as replacements for part of the 38 million tons of synthetic fibres produced annually [1, 5, 6]. Regenerated fibres are made by transforming natural polymers through chemical based processes. These can be mainly classified into:

• Regenerated cellulosic fibres.

• Regenerated protein fibres.

• Regenerated fibres from other sources like silica.

Regenerated cellulosic fibres are finding applications everywhere in the textile industry, alone or blended with other natural or synthetic fibres. From sportswear to health care textiles, these are used abundantly owing to their characteristic properties such

*Address correspondence to this author at the Department of Textile Technology and Research Centre, Bapuji Institute of Engineering and Technology, Davangere – 577004, Karnataka, India.

as tensile strength, smoothness and antimicrobial qualities. Suits, jackets and blazers with high-quality appearance and moisture permeability are also manufactured from these fibres blended with wool, polyester or acrylic fibres [14]. While current research focuses on cellulosic fibres, importance of fibres derived from proteins and other various bio-resources should also be given importance. Regenerated protein fibres generally called “azlons” were commercially produced from the proteins in corn, soybean, peanuts, and milk and also poultry feathers during the early 1930s. Although currently there is very limited or no commercial-scale production of regenerated protein fibers, recent advances in biotechnology, increase in the availability of low-cost biofuel coproducts that contain proteins, environmental awareness on using nondegradable fibres, and distinct properties of protein fibres have renewed interests in regenerated protein fibres. Reproducing proteins through biotechnology, developing novel methods to dissolve proteins and improving the properties of fibres, and biomimicking are some of the approaches that are being considered to develop regenerated protein fibres. An attempt has been made in this paper to review some of the eco-friendly specialty fibres derived from bioresources.

2. REGENERATED CELLULOSIC FIBRES

2.1. Viscose Rayon

In 1892, method of making regenerated cellulose fibre was devised, in which the cellulose was converted

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to cellulose xanthate and dissolved to form the solution known as viscose. When fine jets of viscose are extruded into an acid coagulating bath, cellulose is regenerated in form of filaments. Figure 1 shows the viscose rayon produced from eucalyptus.

Figure 1: Viscose rayon fibre.

Production: Raw material used in production of viscose rayon will be cellulosic source either derived from cotton linters or wood pulp. The production involves following steps:

Steeping: Cellulose pulp is immersed in 17-20% aqueous NaOH at temperature in the range of 18-150C in order to swell the cellulose fibres and to convert cellulose to alkali cellulose.

Shredding: The pressed alkali cellulose is shredded mechanically to yield finely divided, fluffy particles called “crumbs”. This step provides increased

surface area of the alkali cellulose, thereby increasing its ability to react in the steps that follow.

Ageing: The alkali cellulose is aged under controlled conditions of time and temperature (18-300) in order to depolymerize the cellulose to the desired degree of polymerization. In this step the average molecular weight of the original pulp is reduced by a factor of two to three. Reduction of the cellulose is done to get viscose solution of right viscosity and cellulose concentration.

Xanthation: In this step the aged alkali cellulose crumbs are placed in vats and are allowed to react with carbon disulphide under controlled temperature (20 to 300) to form cellulose xanthate.

Dissolving: The yellow crumbs of cellulose xanthate are dissolved in aqueous caustic solution. Because the cellulose xanthate solution has a very high viscosity, it has been termed as “viscose”.

Ripening: The viscose is allowed to stand for a period of time to “ripen”. Two important processes occur during ripening: redistribution and loss of xanthate groups. The reversible xanthation reaction allows some of the xanthate groups to revert to cellulosic hydroxyls and free CS2. This free CS2 can then escape or react with other hydroxyl groups on other portions of the cellulose chain. In this way, the ordered or crystalline regions are gradually broken down and more complete solution is achieved. The CS2

that is lost reduces the solubility of cellulose and facilitates regeneration of the cellulose after it is formed into a filament.

Figure 2: Manufacturing process of Viscose Rayon.

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Filtering: The viscose is filtered to remove undissolved materials that might disrupt the spinning process or cause defects in the rayon filament.

Degassing: Bubbles of air entrapped in viscose must be removed prior to extrusion or they would cause voids, or weak spots, in the fine rayon filaments.

Spinning: It involves the regeneration and the simple recovery of cellulose from cellulose xanthate by acid decomposition reaction, upon entering the bath the viscose is coagulated and acid diffuses into the filament regenerating cellulose. During this time viscose fibre is also stretched to orient the cellulose molecules in the direction of fibre axis. Ingredients used are Na2SO4 (salting out agent), H2SO4 (regenerating agent), ZnSO4 (compound forming agent).

Washing: When the filaments are being formed, in the bath the sulphur is evolved and deposited on the surface of filaments. It should be washed and desulphurised by treating it with a solution of Na2S or sulphite. Then the filaments are finally dried. Figure 2 shows the complete line diagram of production of viscose rayon. Figure 3 shows the finished viscose filaments

Figure 3: Finished Viscose Rayon product.

2.2. Lyocell Fibres

Lyocell fibres probably represent one of the greatest innovations of the fibre industry since the production of nylon 66 by Carothers at the laboratories of dupont [12]. Lyocell is a generic name for a new class of regenerated cellulosic fibre, which is obtained by solvent spinning process without formation of a derivative of cellulose.

Manufacturing Process

The Lyocell process uses a direct solvent rather than indirect dissolution like the xanthation/-

regeneration route in the viscose process. Lyocell fiber is produced from dissolving pulp, which contains cellulose in high purity with little hemicellulose and no lignin. Hardwood logs (such as oak and birch) are chipped into squares about the size of postage stamps. The chips are digested chemically either with the prehydrolysis-kraft process or with sulfite process to remove the lignin and hemicellulose. The pulp is bleached to remove the remaining traces of lignin, dried into a continuous sheet and rolled onto spools. The pulp has the consistency of thick poster board paper and is delivered in rolls weighing some 500 lbs. (230 kg). Figure 4 shows the flow chart of lyocell production. N-Methylmorpholine N-oxide is a key solvent in the Lyocell Process.

Figure 4: Flow chart of Lyocell production.

At the Lyocell mill, rolls of pulp are broken into one-inch squares and dissolved in N-methylmorpholine N-oxide, giving a solution called “dope”. The filtered cellulose solution is then pumped through spinnerets. The spinneret is pierced with small holes rather like a showerhead; when the solution is forced through it; continuous strands of filament come out. The fibres are drawn in air to align the cellulose molecules, giving the Lyocell fibres its characteristic high strength. The fibres are then immersed into a water bath, where desolvation of the cellulose sets the fibre strands. The bath contains some dilute amine oxide in a steady state concentration. Then the fibres are washed with de-mineralized water. The Lyocell fibre next passes to a drying area, where the water is evaporated from it.

Manufacture then follows the same route as with other kinds of fibers such as viscose. The strands pass

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to a finishing area, where a lubricant, which may be a soap or silicone or other agent depending on the future use of the fibre, is applied. The dried, finished fibres are at this stage are in the form of a tow, which is a large untwisted bundle of continuous lengths of filament. The bundles of tow are taken to a crimper, a machine that compresses the fibre, giving it texture and bulk. The crimped fibre is carded by mechanical carders, which perform an action like combing, to separate and order the strands. The carded strands are cut and baled for shipment to a fabric mill. The entire manufacturing process, from unrolling the raw cellulose to baling the fibre, takes about two hours. After this, the Lyocell may be processed in many ways. It may be spun with another fibre, such as cotton or wool. The resulting yarn can be woven or knitted like any other fabric, and may be given a variety of finishes, from soft and suede-like to silky.

The amine oxide used to dissolve the cellulose and set the fibre after spinning is recycled. Ninety-eight percent of the amine oxide is typically recovered. Since there is little waste product, this process is relatively eco-friendly. Figures 5 and 6 shows Lyocell fibres and fabric respectively.

Figure 5: Lyocell fibres.

Figure 6: Lyocell fabric.

2.3. Cuprammonium Fibres (Cupro)

Cupro is a regenerated cellulosic fiber that comes from cotton linter that has been dissolved in a solution

of ammonia and copper oxide. Cupro is similar to rayon, but breathes and regulates body temperature like cotton. Often used as a silk substitute, cupro is noted for its ability to create beautifully draped clothing, except it can be machine-washed and dried. Cupro is an antistatic fabric that is resistant to stretching out of shape at higher temperature [11].

Manufacturing Process

Cupro is a regenerated cellulose fibre derived from cotton linter and its name comes from cuprammonium, which refers to the process of dissolving pure cellulose in an ammonium solution of copper oxide at low temperature in a nitrogen atmosphere, followed by extruding through spinnerets into a sulphuric acid solution necessary to decompose cuprammonium complex to cellulose. The cuprammonium is obtained from the aqueous cuprammonium hydroxide solvent and the 1st bath contains warm water where the filaments are stretched and the second bath containing dilute H2SO4 completes the coagulation. So Cellulose + Cuprammonium hydroxide = Cupro. Manufacture then follows the same route as with other kinds of fibers such as viscose. The strands pass to a finishing area, where a lubricant, which may be a soap or silicone or other agent depending on the future use of the fibre, is applied and fibers are finally dried.

Figure 6: Cupro fibres.

3. REGENERATED PROTEIN FIBRES

3.1. Casein-Fibres

Milk fiber is a blend of casein protein and the chemical acrylonitrile, which is used to make acrylic. It is made using a process that is similar to rayon/viscose, but because it’s a regenerated protein fiber and not a regenerated cellulose fiber, it reacts like wool. That means that it dyes like wool and even smells like wool when burnt [4].

118 World Journal of Textile Engineering and Technology, 2019, Vol. 5 Das and Babu

Raw material: Casein is obtained by acid treatment of skimmed milk. The casein coagulates as a curd which is washed and dried, and then ground to a fine powder. 35 litres of skimmed milk produce about 1kg of casein.

Mixing, filtration and deaeration: Casein is blended to minimize the effect of variations in quality, and is then dissolved in sodium hydroxide solution (caustic soda). The solution is allowed to ripen until it reaches a suitable viscosity, and is then filtered and deaerated.

Wet spinning: The spinning solution is wet spun by extrusion through spinnerets into a coagulating bath containing sulphuric acid, formaldehyde, glucose and water in the ratio 2:5:20:100 respectively. The jets of solution coagulate into filaments in a manner similar to the coagulation of viscose filaments. They are stretched to some degree during coagulation.

Hardening, washing and drying: The newly coagulated casein filaments are weak and soft, and will break easily if handled. The spinning process has aligned the casein molecules to some extent, but they are not organized in to crystal structures which enable the water to penetrate readily into the filament and swelling it. In order to increase the water resistance process called hardening is followed. It involves the collection of bunches of filaments into a tow as they leave the coagulation bath, and are then steeped in formaldehyde solution. After treatment, the tow is washed and dried, crimped mechanically, and then cut into staple.

3.2. Groundnut Fibres

Groundnuts are cultivated in India, China, West Africa, and southern states of U.S.A. After harvesting, the nuts are shelled or decorticated. The red skins are removed from the shelled nuts, together with foreign matter such as small stones and nails [9]. There are five main steps to produce Groundnut fibres:

Extraction of oil to obtain oil-free meal: The nuts, which contain about 50 % of oil, are crushed and pressed. About 80% of the available oil is squeezed out, leaving the oily groundnut meal which is reduced in breaker rolls and passed through flaking rolls. The thin flakes pass via a series of buckets on an endless chain into an extraction plant. As they pass through the plant, the buckets of the meal are subjected to a thorough washing with a solvent (Hexane) which removes the remainder of the Arachis oil.

Extraction of protein: The extracted meal is heated under low pressure in steam jacketed pans to remove residual solvent. It is then cooled, screened, weighed and bagged.

This special technique for removing oil from groundnut meal was devised to provide protein suitable for fiber production. The groundnut protein is extracted from the meal by dissolving it in caustic soda solution. The residue after extraction is a valuable cattle food. Then acidification of the protein solution precipitates the protein, which is the raw material from which fiber is spun.

Preparation of spinning solution: The spinning solution is prepared by dissolving the extracted protein in aqueous urea, ammonia, caustic soda and solutions of detergents. Caustic soda is used for dissolution. It is allowed to mature under controlled condition for 24

Figure 8: Flow chart of casein fibre production.

Figure 9: Phase diagram of casein fibre production.

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hours. During the maturation, the viscosity of the solution increases and attains the spinning characteristics. The solids content of the protein is between 12 -30 %.

Fiber formation: Groundnut fiber is formed by the wet spinning method. The solution of groundnut protein is filtered and pumped to spinnerets, through which it is extruded at a constant rate into an acid coagulating bath. The spinneret holes have a diameter of 0.07 – 0.10 mm.

The coagulating liquor consists of a solution containing sulphuric acid, sodium sulfate, and auxiliary substances. It is maintained at a temperature of 12-400C.

After treatments: As the filament is being spun, it is stretched to increase the alignment of the protein molecule. It coagulates to a filament that is weak and flabby when wet and brittle when dry. At this stage, the filament dissolves easily in dilute saline solution and in dilute acid and alkali. After leaving the coagulating bath it is treated with formaldehyde to harden and insolubilize it, and it is then dried and cut into staple fibres (Figure 10).

Figure 10: Groundnut fibres.

3.3. Soyabean Fibres

Soybeans have a high protein content (about 35 %) and they are grown in abundance in U S A and eastern countries. China has taken the world lead in the industrialized production of soybean protein fibre [2]. They provide a cheap and readily available source of protein for fibre production. Soybean fibre can be obtained from soybean. 100 kg of soybean residue can be extracted from 40 kg of protein. There are five main steps to produce soybean fiber.

Extraction of Oil to Obtain Oil-Free Meal

First the beans are cleaned, cracked, and decorticated. After a conditioning step at about 700C, the beans are steeped in hexane to remove the oil. The oil can be extracted by pressing and extraction. The hexane solution is drawn off and the oil is extracted from this solution. The oil free bean is known as meal. The oil is a valuable by-product and so it is separated out. The resulting oil-free soybean meal is passed through a steam–jacketed pipe for removal of the solvent.

Extraction of Protein

The separation of protein from the oil-free meal is accomplished by steeping the meal in dilute alkalis like 1% Sodium Sulphite for one hour to one half hour. The protein is dissolved by this treatment and can be filtered out to separate the protein. The protein is precipitated by means of acid. Sulphuric acid is added and the pH of the solution is made to 4.5. This is near the iso-electric point of Soybean protein, i.e. at its minimum solubility and therefore will be precipitated. This Soybean protein thus separated out is a creamy –white powder.

Preparation of Spinning Solution

The spinning solution is prepared by dissolving the extracted protein in an alkaline solution. Caustic soda is used for dissolution. The solution is filtered and deaerated by means of vacuum to remove all undissolved particles and air bubbles. After filtration, the solution is allowed to age at the requisite temperature .During the ageing period, the solution becomes more viscose and develops the proper consistency for spinning.

Fiber Formation

Soybean fiber is formed by wet spinning method. The spinning operation consists of forcing the spinning solution through spinneret. The spinneret consists of several holes and it is emerged in the coagulation bath. The solution emerging from the spinneret holes is referred as liquid jet. The liquid jet precipitated as fine filaments in the coagulating bath containing 2% sulphuric acid and 15% sodium sulphate or sodium chloride for dehydration.

After –Treatments

Further treatments are required for the development of properties of the fibres like stretching and hardening.

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Stretching can be done in a separate bath, while the filament is soft and it induces orientation by rearrangement of the molecules and it enhances strength and durability of the filaments. Hardening can be done with formaldehyde to enhance the filaments with more strength and elasticity. The fibre performance can also be stabilized through hydroformylation. It is dried under controlled humidity and temperature, after which it is cut into desired lengths. It is then ready for shipment (Figure 11).

Figure 11: Soybean fibres.

3.4. Zein Fibres

Corn meal is extracted with isopropyl alcohol, which dissolves out the zein. After evaporation of the alcohol, the zein is obtained as a pale yellow powder [10].

Figure 12: Raw material for Zein fibre.

Spinning solution: The zein is dissolved in caustic soda solution, which is then filtered and deaerated. The solution is allowed to mature by standing for several hours, when the coiled molecules of zein protein are able to uncoil and straighten themselves out. During the maturation period the viscosity of the solution increases as these long molecules become associated into larger molecular groups.

Spinning: When the zein solution has reached the correct viscosity for spinning, it is pumped to spinnerets and extruded into an acid coagulating bath containing formaldehyde. The filaments are stretched, and some cross-linking takes place by reaction between zein molecules and formaldehyde. After stretching the zein filaments are subjected to further hardening in formaldehyde, which creates additional cross-linkages between zein molecules. The filaments are washed, crimped, dried and cut into staple.

4. REGENERATED FIBRES FROM OTHER BIO-RESOURCES

4.1. Alginate Fibres

Alginate is a natural polymer that exists widely in many species of brown seaweed. The biological function of alginates is to give strength and flexibility to the algal tissue and regulate the water content in the seaweed. It is these properties along with the ability to produce fibres from its isomers, which make Alginate the ideal wound dressing [3].

Raw material: Seaweed is dried and milled to a fine powder in which form it may be stored without undergoing bacterial attack. The first step in the production of fibre is to convert the alginic acid in sea weed into sodium alginate. This is done by treatment of the powdered weed with a solution of sodium carbonate and caustic soda.

The solution of sodium alginate is allowed to stand and the undissolved constituents of the seaweed form a sediment which may be removed. The solution is then bleached and sodium hypochlorite is added to prevent bacterial attack.

Figure 12: Alginate fibres extracted from seaweed.

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Alginic acid is precipitated from the solution by acidification with hydrochloric acid, and the alginic acid is purified and dried.

Spinning solution: The alginic acid is neutralized with sodium carbonate forming sodium alginate. This is made up into solution containing about 9% of alginate, which is again sterilized and filtered.

Spinning: Sodium alginate solution is wet spun into a coagulating bath containing calcium chloride, hydrochloric acid and a small amount of surface active agent. The jets emerging from the spinneret are coagulated into filaments of calcium alginate. These are brought together, washed, oiled, dried and wound.

4.2. Silicate Fibres

Most of the fibre forming substances made available to us by nature are organic materials, in which the element carbon forms the backbone of a long polymer molecule, as in cellulose and the proteins. There are, however, many naturally occurring inorganic substances which are capable of being formed into fibres, and some of these have become of commercial importance. They include many minerals and mixture of the silicate type [7].

Fibres are spun from a variety of silicate type minerals and mixtures of minerals, including basalt, wollastonite, dolomite/clay mixtures, etc. The fibres produced from them are generally mixtures of silicates, e.g. calcium, aluminium and magnesium.

Production of Fibre

The process used in making silicate fibres vary in detail depending upon the nature of the minerals used as raw materials, but the general principles are alike in most cases. The raw material is mixed with coke and fed into a form of blast furnace trough which an air jet is blown. The coke burns, releasing heat that melts the charge of siliceous raw material. The molten mineral flows to the bottom of the furnace, from which it emerges to meet a blast of high pressure steam. The molten mineral is disintegrated into small droplets which are attenuated into viscous filaments as they are blown along by the steam jet. The filaments solidify as they cool, forming fibres which are collected on a moving belt as a blanket or batt of matted fibre. A binder of resin may be sprayed on to the batt, and the resin cured by passing the batt through a curing oven.

Alternatively, the batt may be sprayed with oil and then broken up into loose fibre.

5. CONCLUSION

The textile and fashion industry do not respond entirely to the threats presented by the world’s uncertain future, including climate change, resource scarcity, vulnerable economic conditions, changing consumer behaviour and so on. So, the future challenge is to understand these threats and take appropriate action to safeguard its future, protect the environment and improve the lives of its costumers, workers and suppliers around the world. In this aspect production and use of sustainable regenerated fibres plays an important role. Manufacturers, distributors and consumers all should promote the use of these fibres and many researches should be carried out to discover more sustainable processing methods to produce these fibres.

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Received on 10-8-2019 Accepted on 30-8-2019 Published on 17-9-2019

DOI: https://doi.org/10.31437/2415-5489.2019.05.12

© 2019 Das and Babu; Scientific Array This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.