Friday, October 26, 2007

ECO-FRIENDLY TEXTILES THROUGH APPLICATION OF BIO-TECHNOLOGY!!!!

ABSTRACT

As the regulated quota system comes to an end in 2004 and the free globalise market takes over, the priorities of textile manufacturers as well as consumer all over the globe are undergoing dramatic change. In this global competition ‘quality’ and ‘eco - friendliness of process and product‘ plays key role. In this paper a brief introduction of research in various fields of biotechnology to achieve the quality product through eco friendly processes is given. Advances in the field of fibre production and modification, use of different enzymes in the textile processing, and waste management using the biotechnology is also discussed.

1. INTRODUCTON:
Textile industries are facing a challenging condition in the field of quality and productivity, due to the globalization of the world market. The highly competitive atmosphere and as the ecological parameters becoming more stringent, it becomes the prime concern of the textile processor to be conscious about quality and ecology. Again the guidelines for the textile processing industries by the pollution control boards create concern over the environment-friendliness of the processes. This in turn makes it essential for innovations and changes in the processes. As a result, the research and development strategies of the textile processors will be highly focused and the challenges will force many changes in the textile industry. Biotechnology is one such field that is changing the conventional processing to eco friendly processing of the textiles.
Biotechnology is the application of living organisms and their components to industrial products and processes. In 1981, the European federation of Biotechnology defined biotechnology as “integrated use of Biochemistry, Microbiology, and chemical engineering in order to achieve the technological application of the capacities of microbes and cultured tissue cells. Defining the scope of biotechnology is not easy because it overlaps with so many industries such as the chemical industry or food industry being the majors, but biotechnology has found many applications in textile industry also, especially textile processing and effluent management. Consciousness and expectations for better quality fabric and awareness about environmental issues are two important drivers for textile industry to adopt biotechnology in its various areas.

2. BIOTECHNOLOGY IN TEXTILE PROCESSING
The major areas of application of biotechnology in textile industry are given below:
Improvement of plant varieties used in the production of textile fibres and in fibre properties
· Improvement of fibres derived from animals and health care of the animals
· Novel fibres from biopolymers and genetically modified microorganisms
· Replacement of harsh and energy demanding chemical treatments by enzymes in textile processing
· Environment friendly routes to textile auxiliaries such as dyestuffs
· Novel uses for enzymes in textile finishing
· Development of low energy enzyme based detergents
· New diagnostic tools for detection of adulteration and Quality Control of textiles
· Waste management­­1, 2

3. Improvements in Natural fibres:

Biotechnology can play a crucial role in production of natural fibres with highly improved and modified properties besides providing opportunities for development of absolutely new polymeric material. The natural fibres under study are cotton, wool and silk.
3.1 Cotton
Cotton continues to dominate the market of natural fibres. It has the greatest technical and economic potential for transformation by technological means. Genetic engineering research on the cotton plant is currently directed by a two-pronged approach
Solving the major problems associated with the cultivation of cotton crop, namely the improved resistance to insects, diseases and herbicides, leading to improved quality and higher yield.
The long – term approach of developing cotton fibre with modified properties, such as improved strength, length, appearances, maturity and colour.
3.1.1 Transgenic cotton
Each year, thousands of research hours and hundreds of thousands of dollars are spent to prevent cotton from caterpillars that love to eat cotton. Cotton growers fight to produce a saleable product using pheromones (insects mating hormones) and monitoring. Use of excessive pesticides is posing serious threats to the green image of cotton.
After years of research, a completely new kind of tool is available for cotton growers to ward off the pink bollworm, one of the major cotton pests. About ten years ago, Monsanto scientists obtained a toxin gene from the soil bacterium called Bt (which is the nickname for Bacillus thuringiensis) and inserted it into cotton plants to create a caterpillar-resistant variety. The gene is DNA that carries the instructions for producing a toxic protein. The toxin kills caterpillars by paralyzing their guts when they eat it. Plants with the Bt toxin gene produce their own toxin and thus can kill caterpillars throughout the season without being sprayed with insecticide. Because the toxin is lethal to caterpillars but harmless to other organisms, it is safe for the public and the environment.
Monsanto registered their Bt gene technology for transgenic cotton under the trademark Bollgard and authorized selected seed companies to develop cotton variety carrying the patented gene.
More stable, long lasting and more active Bts are now being developed for the suppression of loopers and other worms in cotton. Insect resistance is also being developed using a ‘wound- inducible promoter‘ gene capable of delivering a large but highly localized dose of toxin within 30-40s of an insect biting.
3.1.2 Coloured cotton
Developments of fibres containing desirable shades in deep and fast colours would change the face of the entire processing industry. Coloured cottons are also being produced not only by conventional genetic selection but also by direct DNA engineering.
Although several naturally coloured cotton varieties have been obtained by traditional breeding methods, no blue variety exists. As blue is in great demand in the textile industry, particularly for jeans production, synthetic fabric dyes are used. However, the ingredients of these synthetic dyes are often hazardous and their wastes are polluting.
Additionally, they take time and energy to work into the cloth. Natural blue cotton does not have these disadvantages and, therefore has great market potential. The genetic engineers plan to insert into production of blue dye, until a cheaper synthetic method is discovered. By 2005, Monsanto hopes to have this blue-coloured cotton commercially available.
3.1.3 Hybrid cotton
Another major breakthrough has been the ability to produce cotton containing natural polyester, such as polyhydroxybutyrate (PHB), inside their hollow core, thereby creating a natural polyester/cotton fibre. About 1% polyester content has been achieved and it has led to 8-9% increase in the heat retention of fabrics woven from these fibres. Other biopolymers, including proteins, may also be introduced into cotton core in a similar manner.
These customized fibres will be tailored to the need of the textile industry. New properties may include greater fibre strength, enhanced dyeability, improved dimensional stability, reduced tendency for shrinking and wrinkling and altered absorbency. Greater strength will allow higher spinning speeds and improved strength after wrinkle-free treatments. Improved reactivity will allow more efficient use of dyes. Thus reducing the amount of colour in effluents. To reduce the waste generated during scouring and bleaching processes, it would be interesting to have fibres with less of pectins, waxy materials and containing enzymes that can biodegrade environmental contaminants. These fibres would be placed in filters through which contaminated water is passed.

4. NOVEL FIBRES:
The use of biotechnology has the potential of control and specificity in polymer synthesis which is difficult, if not impossible, to achieve in chemical systems. New materials produced using advanced biologically – based approaches represent the textiles of the future.
4.1 Protein Polymers:
Biological systems are able to synthesize protein chains in which molecular weight, stereochemistry, amino acid composition and sequence are genetically determined at the DNA level. A current area of investigation is to understand those features of protein polymers that confer high tensile strength, high modulus and other advantageous properties. Once those features are understood, the tools of biotechnology will make possible entirely new paradigms for the synthesis and production of engineered protein polymers. If they can be made economically viable, these new approaches will help to reduce the dependence on petroleum and furthermore will enable the production of materials that are biodegradable. Use of transgenic plants for large-scale production of these and other synthetic proteins is being explored.
Efforts in biosynthesis have been directed towards the preparation of precisely defined polymers of three kinds (1) natural proteins such as silks, elastins, collagens and marine bioadhesives, (2) modified versions of these biopolymers, such as simplified repetitive sequence of the native protein, and (3) synthetic proteins designed de novo that have no close natural analogues. Although such syntheses pose significant technical problems, these difficulties have all been successfully overcome in recent years. Using this technology, a whole new class of synthetic proteins with advanced properties, known as bioengineered materials, is being created.
4.1.1 Spider silk:
Spider dragline silk is a versatile engineering material that performs several demanding functions. The mechanical properties of dragline silk exceed those of many synthetic fibres. Dragline silk is at least five times as strong as steel, twice as elastic as nylon, waterproof and stretchable. Moreover, it exhibits the unusual behavior that the strain required to cause failure actually increases with increasing deformation.

4.2 Other New Fibres Sources:
There are many more biopolymers, of particular interest in sanitary and wound healing applications, which include bacterial cellulose and the polysaccharides such as chitin, alginate, dextran and hyaluronic acid. Some of these are discussed below:
4.2.1 Chitins and Chitosans:
Chitins and chitosans both can form strong fibres. Chitin is found in the shells of crustaceans, such as crab, lobster, shrimps etc. Resembling cellulose, the chitin consists of long linear polymeric molecules of beta- (1-4) linked glycans. The carbon atom at position 2, however, is aminated and acetylated. Fabrics woven from them are antimicrobial and serve as wound dressing products and as anti-fungal stockings. Chitosan also has promising applications in the field of fabric finishing, including dyeing and shrink proofing of wool. It is also useful in filtering and recovering heavy and precious metals and dyestuffs from the waste streams.
Wound dressing based on calcium alginate fibres are marketed by Courtaulds under the trade name ‘Sorbsan’. Present supplies of this polysaccharide rely on its extraction from certain species of bacteria. Dextran, which is manufactured by the fermentation of sucrose by Leuconostoc mesenteroides or related species of bacteria, is also being developed as a fibrous nonwoven for specialty end uses such as wound dressings. Additional biopolymers, not previously available on a large scale, are now coming into the market, thanks to biotechnology.
4.2.2 Bacterial cellulose:
Cellulose produced for industrial purposes is usually obtained from plants sources or it can be produced by bacterial action. Acetobacter xylinium is one of the most important bacteria for cellulose production as sufficient amounts can be produced which makes it industrially viable. Cellulose produced by Acetobacter, which has the ability to synthesize cellulose from a wide variety of substrates, is chemically pure and free of lignin and hemicellulose. Cellulose is produced as an extra cellular polysaccharide in the form of ribbon like polymerization, high tensile strength and tear resistance and high hydrophilicity that distinguishes it from other forms of cellulose. This bacterial cellulose is being used by Sony Corporation of Japan in acoustic diaphragms for audio speakers. They are also being used in the production of activated carbon fibre sheets for absorption of toxic gas and as thickeners for niche cosmetic applications. In medical field, because of the hydrophilic and mechanical properties of bacterial cellulose, it is used temporarily as skin substitute and in wound healing bandages.
4.2.3 Corn fibre:
An entirely new type of synthetic fibre derived from a plant is Lactron. This environment – friendly corn fibre was jointly developed by Kanebo Spinning and Kanebo Gohsen of Japan. Lactron, the polylactic acid fibre is produced from the lactic acid obtained through the fermentation of corn starch. Strength stretchability and other properties of Lactron are comparable to those of petrochemical fibres such as nylon and polyester. As the material is compatible with human body, it is being used for sanitary and household applications. In addition to clothing the company is also promoting its non-clothing applications, e.g. construction, agricultural, papermaking, auto seat covers and household use.
The energy required for production of corn fibre is low and the fibre is biodegradable. Moreover, no hazardous gases are created when it is incinerated and the required calories for combustion are only one-third or half of those required by polyethylene or polypropylene. It safely decomposes into carbon dioxide, hydrogen and oxygen when disposed of in soil. Lactron is being marketed in various forms such as woven cloth, thread and non-woven cloth.
4.2.4 Polyester fibres:
It has been known since 1926 that certain polyesters are synthesized and intra-cellulose deposited in granules by many micro-organism. Some of these materials have been formed into fibres. Polyhydroxybutyrate (PHB) is an energy storage material produced by a variety of bacteria in response to environmental stress. It is being commercially produced from Alcaligenes eutrophus by Zeneca Bioproducts and sold under the trade name Biopol.
As PHB is biodegradable, there is considerable interest in using it for packaging purposes to reduce the environmental impact of human garbage. Thus it is already finding commercial application in specialty packaging uses. Because of its immunological compatibility with human tissue, PHB also has utility in antibiotics, drugs delivery, medical suture and bone replacement applications.

5. BIOFABRICS:
The development of biocidal fabrics was based on the idea of activating textiles with reactive chemicals to impart desirable properties. The latest research however is aimed at producing fabrics containing genetically engineered bacteria and cell strains to manufacture the chemicals within the textiles thereby making the chemical stores within the fabrics the self-replenishing materials.
A collaborative project is on between the textile science research team at University of Massachusetts, Dartmouth and the bio-engineers at Harvard medical to carry out research leading to the production of a class of fabrics with special properties called biofabrics. Biofabrics will contain micro-fabricated bio-environments and biologically activated fibres. These fabrics will have genetically engineered bacteria and cells incorporated into them that will enable them to generate and replenish chemical coatings and chemically active components.
Niche applications for bio-active fabrics exist in the medical and defense industries, e.g. drug producing bandages or protective clothing with highly sensitive cellular sensors, but biofabrics may form the basis of a whole new line of commercial products as well e.g. fabrics that literally eat odours with genetically engineered bacteria, self – cleaning fabrics, and fabrics that continually regenerate water and dust repellents.
For such an approach to be successful, technologies will have to be developed to micro-fabricate devices able to sustain cellular or bacterial life for extended periods, exhibit tolerance to extremes of temperature, humidity and exposure to washing agents, as well as tolerance to physical stress on the fabrics such as tension, crumpling and pressure2.

6. ENZYMES IN TEXTILE FINISHING:
Textile finishing sector requires different chemicals, which are harmful to the environment. Sometimes they may affect the textile material if not used properly. So instead of using such chemicals we can use the enzymes. The finishing of denim garments has been revolutionized by application of enzymes. Enzymes are very specific in action when they are used under the required conditions. The processes in which enzymes can be used are desizing, scouring, bleaching, biowashing, degumming etc.

Enzymes in Textile processing

Fig : Enzymes in Textile processing

Amylase, pectinase, and glucose oxidase are enzymes used for desizing, scouring, and bleaching respectively in enzymatic preparation processes. Desized samples show completely size removal using amylase enzyme. Samples scoured with pectinase are immediately and uniformly wet. Amount of pectin and other substances left on scoured samples from both conventional and enzymatic processes were measured along with sample strength and whiteness index. Samples bleached with glucose oxidase obtain whiteness index 15-20 degree improvement with low strength loss. Conventional preparation of cotton requires high amounts of alkaline chemicals and consequently, huge quantities of rinse water are generated. An alternative to this process is to use a combination of suitable enzyme systems. Amyloglucosidases, Pectinases, and glucose oxidases have been selected that are compatible concerning their active pH and temperature range. A process has been developed that allows the combination of two or all three preparation steps with minimal amounts of treatment baths and rinse water. Whiteness, absorbency, dyeability and tensile properties of the treated fabrics have been evaluated.
The use of biocatalyst in the textile industry is already state of the art in the cotton sector. Research and development in this sector is primarily concentrating on:
- Optimizing and making routine the use of technical enzymes in processes that are already established in the textile industry today.
- Replacing established conventional processes with the aid of new types of enzymes, particularly from extremophile micro-organisms, under stringent conditions (temperature of surfactant or organic components etc)
- Preparing enzyme-compatible dyestuff formulations, textile auxiliary agents and chemical mixtures.
- Producing new or improved textile product properties by enzymatic treatment.
- Providing biotechnological dyes and textile auxiliary agents, which are suitable for industrial use, and can possibly be synthesized in-situ (i.e. on-line for the application process).
6.1 Extremophile Micro-Organisms:
Numerous micro-organisms have learnt to live in very different and difficult environmental conditions, e.g. in high temperatures, in acid and alkaline conditions and in the presence of salt concentrations. These extremophile micro-organisms live in the most inhospitable and unspoilt environments on earth. Where other micro-organisms do not exist, they are to be found in the deepest oceans under pressures of more than 100 bar, in hot volcanic sources at over 100 C in cold regions at temperatures around freezing point, in salt lakes (up to 30% salt concentration) and also in surroundings with extreme pH values (pH <2,> 9). The cell components (enzymes, membranes) of extremophile are optimally adapted to extreme environmental conditions, and have characteristics (stability, specificity and activity), which make them interesting for biotechnological application.
At the Hamburg-Harburg (D) University of Technology, a comprehensive screening programmed for isolating exremophile micro-organisms (like starch, proteins, and hemicellulose for example) has been implemented which is able to produce enzymes for breaking down biopolymers, alkanes, polyaromatic carbohydrates (PAK) plus fats and oils. Within the framework of these studies, a range of biotechnologically relevant enzymes like amylases, xylanases, proteases, lipases and DNA polymerases for example have been enriched and characterized.
6.2. Conversion Of Natural Polymers By Extremozymes:
Starch is one of the most important biopolymers on this earth. The macromolecule built up from glucose units, plays an outstanding role in the food industry under the collective concept “modified starch” this is found in many foods. Amylases and branching enzymes for example are used for modifying starch. With the aid of thermostable starch-modifying enzymes, starch finishing can be carried out more purposefully and efficiently, since for example the space-time yield at high temperatures is significantly better due to improved starch solubility. Thermo-alkali-stable enzymes (active at pH >8 and 600C) are used in washing and harness rinsing agents in order to remove tenacious starch accumulations with simultaneous reduction in detergent quantity.
6.3. Cyclising Enzymes:
So-called cylodextrins can be produced from starch with the aid of cyclising enzymes (cyclodextringlycosyltransferase, CGTase) from the recently isolated thermoalkaliphile bacterium Anaerobranca gottschalkii. Hydrophobic active substances or volatile aromas can be encapsulated in these cyclodextrins. Cyclodextrins were isolated by Villiers as early as 1891. In those days, cyclodextrins were regarded as curiosities of no technical value.
The properties of cyclodextrins have been altered by chemical change (derivatives). The target of much research work is to fix a reactive cyclodextrin derivative on cellulosic or protein fibres by forming a new chemical bond on the fibre. The molecules have a hollow space, which is suitable for absorbing diverse substances like perfume for example. Many application possibilities and effects arise out of this complexing like for example:
-Increased water solubility
-Change of rheological characteristics
-Stabilization against UV radiation, thermal disintegration, oxidation and hydrolysis
-Reduction of unpleasant smells
-Absorption of microbe-eliminating products
6.4. Cellulose From Extremophile Micro-Organisms:
Cellulose is also a biopolymer built up of glucose units. It forms the framework of higher plants and is an important resource in the textile industry. The use of cellulases in detergents leads to colour revival (colour detergent) and the improved removal of vegetable soiling. Cellulases are also successfully used in ‘biostoning’. In contrast to conventional cellulases, which are obtained from mesophilic fungi as a rule, cellulose-hydrolyzing enzymes from extremophile micro-organisms have the advantage of being capable of use even at high temperatures and pH values.
6.5 Xylanolytic enzymes:
Xylanolytic enzymes form another group. Xylan is heterogeneous molecule (basic component: xylose sugar), which makes up the largest proportion of the polymeric vegetable cell wall component hemicellulose. Xylanophile micro-organisms have enormous biotechnological potential. Thermobile xylanases are already being produced on an industrial scale today, and are used as fodder and food additives. In past years, interest in xylanases was concentrated particularly on enzymatic paper bleaching. Current studies have shown that the enzymatic treatment of paper is an ecologically and economically sound alternative to the hitherto employed chlorine-based bleaching process.
Enzymes which can for example destroy the coloured attendant substances of cotton are of interest to the textiles industry. The quantity of caustic soda and salt required in peroxide bleaching could be reduced by this type of enzymatic bleaching.
Reuse of the bleaching liquor after hydrogen peroxide bleaching is already possible today by using the enzyme ‘catalase’ after bleaching. This enzyme destroys excess hydrogen peroxide, making use of the bleaching liquor for other finishing stages possible.
Windel Textil GmbH & Co. (D) already uses the so-called ‘Bleach-Cleanup’ process, in which bleaching agent residues are removed from textiles, resulting in a reduction of energy, time and water-intensive washing operations at high temperatures.
Research projects at the German Wool Research Institute (DWI) in Aachen (D) are devoted to the use of enzymes in wool processing, including the removal of vegetable residues from the wool, increasing the degree of whiteness, improving handle, improving dyeability by increasing intensity of colour and for felt-free finishing.
Already interesting in practice is the felt-free finishing of wool. An enzyme not previously employed in the textile industry modifies the scale-like surface of wool fibres preventing felting. The enzyme ‘Lanazym’ has hitherto been used only in discontinuous batch processing.3


7. DECOLOURISATION OF DYES BY USING BIOTECHNOLOGY:
The synthetic dyes are designed in such a way that they become resistant to microbial degradation under the aerobic conditions. Also the water solubility and the high molecular weight inhibit the permeation through biological cell membranes. Anaerobic processes convert the organic contaminants principally into methane and carbon dioxide, usually occupy less space, treat wastes containing up to 30 000 mg/l of COD, have lower running costs and produce less sludge4. Azo dyes are susceptible to anaerobic biodegradation but reduction of azo compounds can result in odour problems. Biological systems, such as biofilters and bioscrubbers, are now available for the removal of odour and other volatile compounds. The dyes can be removed by biosorption on apple pomace and wheat straw5. The experimental results showed that 1 gm of apple pomace and 1 gm of wheat straw, with a particle size of 600┬Ám, were suitable adsorbents for the removal of dyes from effluents. Apple pomace had a greater capacity to adsorb the reactive dyes taken for the study compared to wheat straw.


7.1 Decolourization Of The Dye House Effluent Using Enzymes:
The use of lignin degrading white-rot fungi has attracted increasing scientific attention as these organisms are able to degrade a wide range of recalcitrant organic compounds such as polycyclic aromatic hydrocarbons, chlorophenol, and various azo, heterocyclic and polymeric dyes. The major enzymes associated with the lignin degradation are laccase, lignin peroxidase, and manganese peroxidase. The laccases are the multicopper enzymes, which catalyze the oxidation of phenolic and non-phenolic compounds.
However, the substrate of the laccases can be extended by using mediators such as 2, 2’-azoinobis-(3-ethylthiazoline-6-sulfonate), 1-hydroxybenzotriazole. The following fungi have been used for laccase production and for the decolourization of synthetic dyes, Trametes Modesta, Trametes Versicolour, Trametes Hirsuta, and Sclerotium Rolfsii 6 From the results obtained it was clear that Trametes Modesta laccase showed the highest potential to transform the textile dyes into colourless products. The rate of the laccase catalyzed decolourization of the dyes increases with the increase in temperature up to certain degree above which the dye decolourization decreases or does not take place at all. The optimum pH for laccase catalyzed decolourization depends on the type of the dye used. Dyes with different structures were decolourized at different rates. From these results it can be concluded that the structure of the dye as well as the enzymes play major role in the decolourization of dyes and it is evident that the laccase of Trametes Modesta, may be used for decolourization of textile dyestuffs, effluent treatments, and bioremediation or as a bleaching agent.
Another study carried out by E. Abadulla et al, has shown that the enzymes Pleurotus ostreatus, Schizophyllum Commune, Sclerodium Rolfsii, Trametes Villosa, and Myceliophtora Thermiphilia efficiently decolourized a variety of structurally different dyes. This study also shows that the rate of reaction depends on the structure of the dye and the enzyme7.
Activated sludge systems can also be used to treat the dyehouse effluents. But the main difficulty with activated sludge systems is the lack of true contact time between the bacteria of the system and the suspended and dissolved waste present. Immobilized microbe bioreactors (IMBRs) address the need of increased microbial/waste contact, without concomitant production of excessive biosolids, through the use of a solid but porous matrix to which a tailored microbial consortium of organisms has been attached. This allowed greater number of organisms to be available for waste degradation without the need of a suspended population and greater increased contact between the organisms and the waste in question8.


8. CONCLUSION:
The advent of biotechnological applications in textile processing widens the already existing wide horizons to produce aesthetically colourful magnanimous and ecologically friendly textiles, ringing in a new era of synergetic application of life sciences. As of today the huge textile industry is open to welcome the immense possibility of the various biotechnological applications limited by the limitations of being eco friendly and not harming either the food web or the life cycle of any other living creature. Such awareness is gradually metamorphosing a tool that could be intelligently used to meet the demand of our fashion trends.
Enzymes, bacteria and insects could be biologically modified into a fashion promoter if engineered with great caution. A major breakthrough in the textile industry is eagerly awaited through these biotechnological applications.



REFERENCES:
Biotechnology, Edited by H. J. Rehm and G. Reed
Biotechnology application in textiles industry, Deepti Gupta, Indian Journal of Fibres & Textile Research Vol.26, March-June 2001.
Biotechnology: process and products, Andrea Bohringer, Jurg Rupp, International Textile Bulletin, June 2002.
The Biotechnology Approach to Colour Removal from Textile Effluent, by Nicola Willmott et al. J of Soc. Of Dyers and Col., 1998, 114, 38-41.
Removal of dyes from a synthetic textile dye effluent by Biosorption, by T. Robinson, et al, Water Research, 36, 2002, 2824-2830.
Decolourization of textile dyes by laccases, by G. S. Nyanhongo, et al, Water Research, 36, 2002, 1449-1456.
Enzymatic decolourization of Textile Dyeing Effluents, by E. Abadulla et al, Textile Res. J. 70 (5), 2000, 409-414
Improving Bio-treatment For Textile Waste Decolourization, by Caroline A. Metosh et al, American Dyestuff Reporter, July/August19

Wednesday, October 24, 2007

Biotechnology in Textiles


The rapid developments in the field of genetic engineering have given a new impetus to the biotechnology. This introduces the possibility of 'tailoring' organisms in order to optimize the production of established or novel metabolites of commercial importance and of transferring genetic material (genes) from one organism to another. Biotechnology also offers the potential for new industrial processes that require less energy and are based on renewable raw materials. It is important to note that biotechnology is not just concerned with biology, but it is a truly interdisciplinary subject involving the integration of natural and engineering sciences. Defining the scope of biotechnology is not easy because it overlaps with so many industries such as the chemical industry or food industry being the majors, but biotechnology has found many applications in textile industry also, especially textile processing and effluent management. Environmental protection is becoming a serious concern for textile wet processors. Dyes discharged from textile dyeing and finishing processes are a priority pollutant because of their visibility at low concentrations. Most dyes have low toxicity but their components and breakdown products can be more toxic. Physical and chemical treatment techniques are effective for colour removal but use more energy and chemicals than the biological processes. They also concentrate the pollution into solid or liquid streams requiring additional treatment or disposal. Biotechnological methods can completely mineralize pollutants and are usually cheaper.

Biotechnology in Textiles:
Biotechnology has its roots in the dawn of the history. It is not new to textile industry, it has been used in textile processing for the enzymatic removal of starch sizes from woven fabrics for most of this century and the fermentation vat is probably the oldest known dyeing process. The scope of enzymes in textile industry is very wide. This can be understood by looking at the wide spectrum of applications in textiles. The major areas of application of biotechnology in textile industry are Improvement of plant varieties used in the production of textile fibres and in fibre properties, Improvement of fibres derived from animals and health care of the animals, Novel fibres from biopolymers and genetically modified micro-organisms, Replacement of harsh and energy demanding chemical treatments by enzymes in textile processing, Environment friendly routes to textile auxiliaries such as dyestuffs, Waste management.
Textile processing industry is characterized by high consumption of energy and resources and time consuming processes. Lot of pollutants are generated by textile industry, especially textile processing sector produces most of the pollutants, mostly water pollutants. Waste water from textile industry, especially process houses, is characterized by high COD and BOD, suspended solids and intense color due to the extensive use of dyes. This type of water must be treated before discharging it into the environment. The water must be decolorized; harmful chemicals must be converted into harmless chemicals. . Biological treatments have been used to reduce the COD of textile effluents. Instead of using the chemical treatments various biological methods can be used to treat the waste water from the textile industry. These methods include, Biosorption, use of Enzymes, Aerobic and anaerobic treatments etc. Only biotechnological solutions can offer complete destruction of the dyestuff, with a co-reduction in biological oxygen demand (BOD) and chemical oxygen demand (COD). In addition, the biotechnological approach makes efficient use of the limited development space available in many traditional dyehouse sites
Many azo dyes and harmful chemicals, like p-chlorophenol have been banned from use. The area in which biotechnology is required exactingly is the treatments on waste water generated during textile processing. The presence of chemicals, like formaldehyde, salts, phenols, dyes, alkalis and acids, heavy metals, polyvinyl alcohol in waste water is very harmful to the environment. So these chemicals must be either removed or converted into harmless chemicals by treating them chemically or biologically.

Though the industrial Biotechnology is in the early stages of development but its innovative applications are increasing and spreading rapidly into all areas of manufacturing. It is already providing useful tools that allow for cleaner, more sustainable production methods and will continue to do so in the future. Adoption of biotechnology ensures the cleaner environment; also it cuts the cost of the processes. Textile industry, which is responsible for generation of lot of pollutants in all forms, must adopt the biotechnology, especially in the processing sector, to reduce the consumption of energy as well as other resources.


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Wednesday, October 17, 2007

INK JET PRINTING

Navanath Pingle, Laxmikant Jawale, Prashant Vispute.
Department of Fibres and Textile Processing Technology
University Institute of Chemical Technology
University Of Mumbai, India





Abstract

Whilst, the India has abolished the textile quota regime of textiles, one has to face tremendous amount of competition from producers of all over the world. One has to be very productive, economical, quality conscious, environment friendly with assured reproducibility. Modern technologies are going to play very major role in this. Ink jet printing is one such promising technique, which will be a critical tool in the hands of production units. In this article attempt is made to familiarize ink jet printing.

Introduction
Drastic changes are taking place in the textile printing; quick response, globalization and ecology impose substantial demands on the different components of the printing process. They force the textile printers to focus on: shortening and flexibility of the pre-print process; printing right first and the next time, reducing down time of the printing machine, short run production, and stock risks. Consumers are demanding a greater variety of colour and design. They want fabrics that express their individuality in their environments and in the clothes that they wear. Today's ecological stringent demands ask for eco processes minimizing waste of raw materials and pollution of the environment. In short these demands have common denominations: flexibility and versatility. Conventional printing lacks the above demands. The answer lies in digital printing. The jet-printing technology has yet to make the leap into mainstream. Although digital printing is already claimed as the most significant technological advancement to the textile printing industry in over 30 years, the adaptation of these new systems has been much slower than many had anticipated or expected, due to specific technological limitations (hardware, print head or nozzle, ink classes). These hurdles must be overcome for Commercial exploitation of these new technologies.

INKJET TECHNOLOGY


Ink-jet printing involves squinting droplets of ink, which make contact with substrate image. Ink-Jet can be divided into two major technology types: Continuous and Drop-on-Demand. Each of these subdivided further as shown in figure:


Fig 1. TYPES OF INK JET PRINTING





l.Continuous Ink-Jet Printing (CIJ):
As the name implies, in Continuous Ink-Jet systems a continuous stream of ink droplets is ejected from nozzle on to the substrate. Two designs are possible in the designing of this method. In the first design, charged ink droplets are deflected on to the paper to form the image and the uncharged droplets are collected in gutter. This is called as raster scan continuous Ink-Jet method. In the second design, the uncharged ink droplets form the image and the charged ink droplets are deflected into the gutter. This is the Binary Continuous Ink-Jet system. While in Hertz technology, fine mist of the uncharged droplets form the images. Hertz Technology is more suited to color printing than the previous two methods.1
Continuous Ink Jet printing is further divided into two main types viz; Piezoelectric and Thermal Excitation.

Fig 2. Principle of continuous stream ink-jet printing (raster scan method/the Sweet system)


A) Piezo-eleetric Technology
Piezo-electricity is a phenomenon of producing electricity by application of pressure on a crystal, which is capable of conducting electricity through it.4 This method has been suitably exploited for ink jet printing technology. Piezo ink jet printing relies on different principles for the expulsion of ink from the cartridge nozzles. In this technology, an electrical charge is applied to the cartridge nozzles which excites a small piezo crystal that is inside. As the piezoelectric crystals are stimulated, the crystals change shape and squeeze the ink chamber. This action is similar to the action of squeezing an oilcan, and forcefully expels the ink from the nozzle.



(a) Continuous ink jet-binary deflection. (left)
(b) Continuous ink jet- multiple deflection. (middle)
(c) Continuous ink jet - Hertz method (right)


After leaving the nozzle, the drops are electically charged by an amount that depends on the image to be printed. The drops then pass through an electric field to cause then to deflect. There are two ways of deflecting the drops in piezoelectric- driven Continuous Ink Jet. In the binary deflection method droplets are directed to a single pixel location in the medium or to the recirculation gutter. In the multiple deflection method the deflection is variable so the drops can address several pixels. These two concepts are illustrated in the Fig.3 (a) and (b).

In the Hertz method, the amount of ink deposited per pixel is variable. This is achieved by generating very small drops at the speed of 40m/s with excitation frequencies of over 1 MHz (see Fig 3 (c)). The drops not intended to reach the medium are charged ad deflected to the gutter. The printing drops are given the smaller charge to prevent them in merging in flight.

Since the piezoelectric process does not utilize heat, the cartridge life of these printers is greatly expanded, cartridges should last a minimum of one year under heavy usage. Piezoelectric print heads can use a wider range of inks than thermal inkjet printers because the heat is removed from the process. This means that solvent-based ink systems and pigmented-ink formulations will be more readily available, which increases the development capabilities for better inks in the future. Although piezo is currently the lesser-utilized technology, many experts predict that the long-term development of ink jet print devices will use the piezo technology because of the greater through-put speeds offered and the wider latitude with the types of inks that can be developed 6.

3. DROP ON DEMAND (DOD)
Drop-on-Demand, or impulse, inkjet systems differ in two major respects from continuous Ink-Jet systems. First, all the ink droplets are used to form the image none are wasted. Ink droplets are ejected only where a dot is required on the substrate, i.e. they are produced "on demand ". Secondly, the droplets are not charged. Hence there is no deflection involved. Drop on Demand Ink Jet systems may be subdivided into two broad types, namely piezo and thermal (or bubble jet). In DOD printing a significant proportion of the solid ink resides on the surface of the paper giving the print an embossed feel.(2,3,4)


Principle of Drop On Demand printing (5)


principle of bubblejet printing



BUBBLE JET PRINTING
Bubble-Jet or thermal technology is a well-known technology. The technology relies on a thermal pulse to generate the ink drop. This technology was the first of the drop on demand. The technique boils the water content of the ink and the resulting steam pressure forces a droplet of ink out of the nozzle. In these engines, the computer signal heats a resistor to a high temperature(>360 C) which creates a vapor bubble in a volatile component in the ink, the vapor bubble expands and exits the nozzle followed by a contraction of the bubble causing a drop of ink to be ejected on the textile substrate. The vapqur bubble must then cool and collapse allowing the ink chamber to refill from a reservoir. Cycle time is limited to approximately 10,000 drops per second and the volume per drop of ink is typically 150 to 200 Pico liters.

The main advantage of the thermal ink jet technology is the low cost of nozzle fabrication. It is made using the mass production technique based on the integrated circuits. The system restricts the use of binder containing pigment inks. The major problem with the thermal ink jet is the high nozzle and resistor failure rate resulting from rapid thermal cycling. As the heater to boil the water has to work in a semi-explosive way, the temperature can rise up to 360 C, which can cause the nozzle to burn out. The high temperatures cause often decomposition of ink components, which leads to poor heat transfer and / or nozzle clogging. Therefore only thermal stable inks can be used. These defects are unpredictable.


Principle of Bubble jet printing.