New Technique for Treatment of Garments

Denim is a garment accepted by the world. A faded elegant look is achieved because of the ring dyeing of warp yarn of denim. These types of wash down results are brought into by removing dyes by rubbing the garments. New methods of biotechnology (enzymes) have replaced the conventional method of stone washing to acquire the faded effect in an environment-friendly manner. Here the wash down effect is obtained due to bio-abrasion where the enzymes make their effects on cellulose and by hydrolyzing, it provides the expected appearance.

To give a smooth handle and clean appearance to the garment, enzymatic treatment is given, apart from denims, on different casuals like shirt, bottom weights.

What is Enzyme?

Enzymes are macromolecules mostly made of protein nature constructed within the cells of all living creatures, plants, fungi, bacteria and microscopic single cell organisms. These three dimensional protein groups are made up of 200-250 amino acids competent of catalyzing specific chemical reactions. Enzymes only catalyse reactions and they do not go through any transformation after the reaction. The catalysts are extremely capable of enhancing the reaction rate of biochemical procedure. The conventional use of enzymes is in the process of fermentation to make beer, bread and cheese. Nevertheless, the industrial production and usage of enzymes is recent.

Commercial production of Enzyme

Fermentation broth is disinfected to create a nutrient medium. The nutrient is transformed into an expected enzyme by carefully chosen microorganism action in the presence of oxygen. The selection of microorganism, nutrients and operating circumstances decide the type and produce of enzyme. Once fermentation is accomplished, several centrifugal, filtration and precipitation processes remove the enzyme from the fermentation broth. The enzyme is further refined and formulated to gain the expected application.

Mode of action of Enzyme

The enzyme has an active zone, which has similar pattern as the zone of the substrate and fits like a key in a lock. The substrate then fits into the enzyme, which is activated with the enzyme's force. The enzyme substrate complex then decomposes. The transformed substrate disconnects itself from the enzyme making it ready to obtain another substrate.

The enzyme works as molecular scissors.

The reaction can be both in the same stage like a compound of starch and compound of alpha amylase or like the soluble protease and wool or silk fibre, which are a solid. Here the enzyme gets soaked on the wool surface and works towards the internal layers.

Contrary to inorganic catalysts, enzymes are precise in process. For instance, amylase, a digestive enzyme will affect only starch and not cellulose; cellulose will act only on cellulose and not on the other substance.

Enzymes for textiles

As most of the raw stuff used in textile industry is natural, new enzymatic formulations have greatly developed and broadened in the market of the industrial care of the fabrics over the last 10 years. Following are the spheres where enzymes are being used for textiles:

. Desizing . Bioscouring . Fading . Biopolishing . Print Washing . Silk Degumming

Enzymes for Biowashing Fading

Cellulase either alone or sometimes in association with pumice stones provide the wash down effect i.e. fading. Stonewashing makes the garment surface more evenly faded, however, it has various drawbacks, which give an edge to the enzyme wash.

Following are the drawbacks of stonewashing: . Process control is not easy because the change in size and quality of stones pave the way to inconstant quality of washed garments regarding the degree of fading, strength, etc.

. Sometimes stones turn into powder during the process of making the garment greyish in colour and rough too. . Stone washing provides rougher feel than enzyme wash. . Stone may lead the harm to the machine parts. . Stone sometimes creates harm to the accessories of garments.

Types of cellulases

Acid and Neutral: two types of cellulases

In chemical terms, cellulase enzyme has two spheres. The spherical leader is the centre catalytic region, whereas the tail ender is a CBD (cellulose binding domain). However, the effectiveness of the catalytic centre (to hydrolyse glycosidic linkages) relies heavily on the absorption by the CBD tail. Tightly fastened to the substrate, certain endoglucanases interrupt the crystalline configuration and induces defibrillation, an outcome of the mechano-chemical effect by the binding domains.

A cellulase enzyme has several actions, which are named as Endoglucanases EG I, EG II and CBH III (Exoglucanases or Cellobio hydrolysate), EG III and EG IV.

These several actions have diverse effect on the crystalline and amorphous areas of cellulose. Regular whole acid cellulases possess a superior CMCase (Carboxy methyl Cellulase activity) activity, therefore charge the amorphous areas by producing better cutting, good contracting effects but with higher back discoloration.

In case of engineered acid cellulases, the CBD is cut down considerably, therefore, these products get connected to the cellulose substrate with difficulty, and for this reason the cutting is not very aggressive as in the case of whole acid cellulases. In addition, these products are designed to reproduce top activity at near neutral pH.

The neutral enzyme does not possess a CBD and therefore, does not adhere itself to the cellulose surface. This is why we acquire a more surface cutting and not "cutting in" activity. These causes lower back staining, a more even effect on the surface of the fabric, which creates a rich and more engaging look.

Effects of cellulase enzymes on denims

. In fading, the expected effect is wash down look on the garment making the seams, hems, and pockets more noticeable.

. Apart from look, colour contrast, generally recognised as salt pepper effect is also one of the effects created by fading. Faded garment with acid cellulase enzyme provides less colour contrast in proportion to garment washed with neutral cellulase enzymes.

Guidelines Desizing Rexsize LHT 100 liquid 0.3-1.0% Kleenox PSF liquid 0.5-1.0g/l Fibrolube HML 0.5 g/l Greenpol A liquid 1.0-2.0 g/l Treat at 850C and pH 6.5 for 30 mins Fading Genecel GLA liq/Valzyme FP pdr 3.0-6.0 g/kg Genecel HA-CLS pdr Greenpol A liquid 1.0-2.0 g/l Treat at 550C and pH 4.5 - 5.0 for 60 mins. Bleaching Sodium Hypochlorite 3.0 g/l available Cl2 Treat at room temperature for 20 mins Soaping/OBA Soda ash to adjust pH 8.0 Hydrogen Peroxide 1.0-3.0 g/l Zystab SA Liquid 0.3-1.0 g/l Zycol PCSN Liquid 1.0 g/l OBA 0.8% Treat at 700C and pH 4.5-5.0 for 20 mins. Softening Zylon HSS Liquid - 0.5% Innersof ELASTO Liquid - 1.0% Treat at 500C and pH 4.5-5.0 for 20 mins.

Parameters affecting cellulase performance There are various criteria, which affect the performance of the cellulases for producing expected faded look.

. pH: pH of the bath should be maintained as per suggestion. Change in it decreases the activity of the enzyme, consequently imparting low-quality effect. The enzyme built on acid cellulase performs in the pH range of 4.5-5.5 and neutral cellulase performs in the range of 6.5-8.0 optimum affects at pH 6.5. . Temperature: Similarly, temperature of the bath too should be maintained as per suggestion and difference in it gives unexpected outcome. Most of the acid as well as neutral cellulases act best at 55øC temperature. . Time: The performance of the cellulase also relies on the time of processing. More time might create unfavourable result also. . Dose: To achieve expected effect, it is required to use the appropriate dose. . Mechanical action: This is a very significant aspect for obtaining the expected outcome since abrasion is an essential for achieving the best result in fading and it relies on the machinery used. . Subsidiaries: It is necessary to monitor the ionic nature of the subsidiaries used along with the enzyme. Only Non-ionic type of subsidiaries is chosen. It is not advisable to use Cationic and anionic type of subsidiaries. Since the presence of heavy metals can disturb the activity of enzymes, apart from subsidiaries, presence of heavy metals in the bath should also be monitored.

Biopolishing

Biopolishing is the enzymatic treatment given to cellulose and its blends to achieve the following effect:

. To wipe out the protruded fibre from the surface of the fabric by hydrolysing them. . No pilling and fluffiness after use. . Gives spotless look to the fabric. . Imparts smoothness to the fabric.

Cellulase with high filter paper activity (FPU activity or Endoglucanase activity) in proportion to Carboxyl methyl cellulase activity (CMCase activity or Exoglucanase activity) delivers outstanding biopolishing effect. Rossari's G-Zyme series are special Trichoderma Cellulase with high filter paper activity (FPU activity or Endoglucanase activity) in proportion to carboxy methyl.

Defibrillation is readily recognised as an operation of FPU activity as most micro fibrils are made of polymerised glucose monomers, shaped into micro crystals being fastened by Van der Waals force and hydrogen bonds.

Being more superficial and unique, dye cutting is more of an amorphous (with greater CMCase activity) business, but biopolishing products like G-Zyme series are not useful to it.

Various techniques for testing biopolishing:

. Under microscope . Random tumble pilling test . ICI/Hoechst pilling test . Martindale test

Summing up

Acid and neutral cellulases have all-round performance in providing different types of fashionable and appealing look to the garments. Various acid cellulase gives wash down effect and softens the garment relying upon its chemistry and thus meets the requisites of the customer.