ENZYME SYSTEMS FOR PROCESSING CELLULOSIC TEXTILES                                  3/12/2004

1.0 INTRODUCTION
Since ancient times, housewives were known to remove starches, applied during weaving of saris, by soaking them in sour buttermilk. Dyers softened harsh fabrics by treating them in a bath of fermenting jaggery. These instances may be considered as an application of biotechnology in traditional wisdom. Crude enzymes from malt extract have been in use since 1860’s for desizing process. Widespread or systematic use of specific enzyme formulations in textile processing is of recent origin; say, from 1980 onwards. Enzymes are biocatalysts without which no life in plant or animal kingdom can be sustained. Their technological application can be considered as the ultimate aspect in eco-friendly concepts. As enzymes are effective over mild conditions of pH and temperatures and as they are easily biodegradable, they pose practically no threat to environment. The present rapid developments in industrial production of various enzymes for specific uses have been possible due to the progress in genetic engineering.

The salient features of enzyme application in textile process are:

1. Extremely specific nature of reactions involved, with practically no side effects
2. Low energy requirements, mild conditions of use, safe to handle, non-corrosive in their applications
3. On account of lesser quantities of chemicals used in process as well as ease of biodegradability of enzymes results in reduced loads on ETP plants
4. Enzymes under unfavorable conditions of pH or temperatures chemically remain in same form but their physical configuration may get altered i.e. they get “denatured” and lose their activity. For this reason live steam must never be injected in a bath containing enzymes and any addition of chemicals to the enzyme bath must be done in pre-diluted form
5. Compatibility with ionic surfactants is limited and must be checked before use. Nonionic wetting agents with appropriate cloud points must be selected for high working efficiency as well as for uniformity of end results
6. High sensitivity to pH, heavy metal contaminations and also to effective temperature range. Intense cautions are required in use

2.0 ENZYMES FOR CELLULOSIC TEXTILES

2.1 AMYLASES - To decompose Starches in sizing preparations
2.2 CATALASES - Act on Hydrogen Peroxide to decompose it into water & oxygen
2.3 PROTEASE, LIPASES & PECTINASE - When combined, act on Proteins, Pectins & natural waxes to effect scouring
2.4 LACCASES - Decompose Indigo molecules for wash-down effect on Denim
2.5 CELLULASES - Break down Cellulosic chains to remove protruding fibres by degradation & create wash-down effect by surface etching on Denims etc. In this communication, we primarily discuss few enzyme-based systems of processing cellulosic textiles that have been developed in our R&D laboratories and most are being successfully used on an industrial scale.

3.0 PRETREATMENT SYSTEMS

3.1 Desizing of woven cotton fabrics- Weaving yarn sizes are largely maize starch based, wherein the starch content can be as high as 7-10 % with fatty plasticizers, lubricants and preservatives etc. During the course of our investigations it was concluded that the preservatives used in sizing, though anti-microbial in nature, do not interfere in enzyme action on starch. However, Amylase types of enzymes were found to be ineffective on Tamarind Kernel Powder (TKP). They are amenable to Cellulase enzyme for their degradation Normal sizes can be economically removed in Jigger processing by use of specialties UNODESIZE and WETAL LFW at temperatures around 600 C. This combination can also be used for padding application from quenching box of singeing machines. WETAL LFW is an enzyme compatible wetting agent with practically low foaming characteristics. DESIZE LW, a specialty formulation with Lubricating, Wetting & Anti-Back-Staining properties finds application on garment processing in drum washers.

3.2 Scouring of Woven & Knitted Goods - Natural cotton fibers, on an average contain up to 1% Waxes, 5-6 % Pectins, Proteins etc. and 1% mineral matter, as primary impurities. Pectins can be broken down by pectinase, while lipase enzymes degrade waxy materials. In case of cotton knits, apart from these primary impurities other major contaminant is the knitting oils that are mineral oil based and are not degraded by normal lipase system. In our laboratory trials, a pretreatment for cotton knit goods was developed to give instantaneous absorbency. It consisted of two-stage treatment with wetting in UNOZIN NIT-L, 0.5 gm/lit followed by enzyme formulation ECOSCOUR 0.5 gm/lit at 600 C for 30 minutes in same bath with pH adjusted to 8.5 by soda ash. In second stage 3.0 gm/lit Hydrogen Peroxide with STABILIZER BBPS is added after raising the pH to 10.5 and heating was continued to temperature around 950 C. The treatment continued for 60 minutes to get excellent absorbency. The traces of mineral oils, which are normally difficult to remove even by using harsher conditions, create no problems under present treatment and they presumably get emulsified by degraded cotton waxes acting as co-emulsifier. In an interesting development combined Enzymatic Desizing and scouring action is under investigation, in which, combination of enzymes are being used to achieve a single bath pretreatment for woven cotton goods.

3.3 AQUAMIN PROCESS for Knits - The recent crisis regarding availability of water in certain areas of South India, prompted us to initiate a study to economize utilities in processing of yarns and cotton knit goods. Code-named AQUAMIN PROCESS, it shortens the total processing for dyeing by reducing number of washing cycles conventionally followed. The use of dyestuff compatible NEUTRASCAN PK for removing excess Hydrogen Peroxide, holds the key to success of the AQUAMIN PROCESS. Its use as a peroxide killer, in de-mineralizing cum neutralizing bath, results in reduction in number of washes without affecting dye uptake in further processing in same liquor. UNOQUEST SWN is the de-mineralizing agent that also has buffering action to give required pH for reactive dye bath.

4.0 FINISHING

4.1 Finishing for Garments - It has been predicted that future development and progress of textile industry in India would be driven by the demands from garment manufacturing industry which in turn would be influenced by export markets. Under these circumstances processing of garments also assumes an unprecedented importance. Qualitatively speaking, finishing enzymes find major application in textile processing, next only to desizing enzymes. The garment processing industry is almost exclusive consumer of these enzymes for producing novel effects. The denim sector of garment industry is very peculiar and articles made from denim have been popular over longer period than any other type of garment. The denim culture is likely to grow in future. Denims are warp faced twill fabrics, made from 6s-12s warp dyed yarns and undyed weft. Warp yarns are ring dyed, using indigo colour. The denim garments were subjected to abrasive action of pumice stones to achieve “vintage”, “worn out “ effects as a fashion. This process had many drawbacks such as damage to machinery, residual deposit of stone powder on garments, lack of uniformity etc. This was fully or partly replaced by use of cellulase enzymes that have degrading action on fibre surface to give faded effect. Faded effects are also achieved by treatment with Sodium Hypochlorite or Potassium Permanganate. Bleaching effects on indigo are also achieved by Laccase, an oxidase type of enzyme, to give characteristic effects of fading. Today fashion conscious denim markets constantly receive innovative products. These are produced by combination of processes involving mechanically or chemically abrasive techniques with bleaching chemicals which are popularly known as stonewash, ice wash, acid wash, frosted wash, moon wash etc.

In garment processing, apart from desizing with Amylase enzymes, Cellulase enzymes are widely used to impart:
a) Fading by surface degradation of cotton fibers in indigo dyed denims.
b) Clear finish by removing protruding fibers in cotton or blended garments in denim or non-denim category.
c) To achieve soft, smooth feel with combination of a variety of exhaustible softeners.

The finishing system based on cellulase enzymes can be divided into two basic categories. 1) Neutral Enzymes (Operative pH band of 6.5-7.0)
2) Acid Enzymes (Operative pH band of 4.0-4.5)

Neutral Enzymes include systems operating around neutral pH range, which give characteristic softness with minimal back staining in case of denims, with better contrast between dyed and undyed yarns.
Acid Enzyme systems are more economical in application, but give lesser clarity of denim pattern due to back staining. In case of other cotton garments dyed with reactive colours, hydrolysis of dye-cellulose linkages in acidic pH cannot be ruled out with the result, there is likely colour bleeding in enzyme bath. An anti-staining/anti-re-deposition specialty, CLEAROL DX can be added to bath to minimize this drawback of back staining. A number of formulations have been developed in our laboratories, and are being successfully used in denim processing industries, for certain consumer preferred fashions. The enzyme treated goods are more receptive to action of other finishing specialties due to opening of fiber structures and creation of more active sites. Judicious use of softeners in separate bath is recommended. Drum washers are the preferred machinery for garment processing. As the conditions require comparatively milder temperatures, mechanical agitation must be carefully controlled. The drums diameter should be around 100 cm, with baffles to give adequate agitation and uniform action. Drums should have rotation of around 30 rpm for woven garments and 10 rpm for knitted garments.

4.2 Finishing of Cotton Knit - Cellulase enzyme treatments increasingly find applications in cotton hosiery sector to enhance aesthetic feel as well as surface clarity. ULTRAZYME SUPER is an enzyme-based formulation, well suited for use in winches or high turbulence soft flow machines. Adequate caution must be exercised to deactivate residual enzyme by elevating temperatures to around 80-85deg C., otherwise the reaction would continue to take place resulting in loss of physical strength of goods.

5.0 GENERAL PRECAUTIONS

1. Avoid exposure to direct sunlight and extreme temperatures
2. Prevent contact with live steam and concentrated chemicals. It is advisable to preheat bath in Jigger, Winch or Drum Washers before addition of enzymes
3. Maintain recommended pH and temperature conditions in bath for optimum results
4. Avoid heavy metal contamination
5. Cellulase enzymes must be deactivated at end of process
6. Use the FIFO system of material management, i.e. first batch of enzymes received must be consumed first

CONCLUSION
Applications of appropriate enzymes under well-defined conditions offer better options in textile processing due to novel effects and also eco-friendliness. We are thankful to Mr. Sanjiv Seth for his guidance and valuable help in our investigations.

Note:

1. The products mentioned above are manufactured by M/s. Uno Specialities Pvt. Ltd. Mumbai
2. This communication is based on the paper presented at ‘National Seminar on Application of Enzymes in Textile Wet Processing’, held at S. S. M. Institute of Textile Technology and Polytechnic College, Komarapalayam – 638 183 on 28-29th February 2004.