Page-2
ENZYMES EFFECT ON COLOUR
Hydrolases and oxireductases constituted important class of enzymes which dealt with colour in textile application. Speaking about how the enzymes affected these applications one said that when looked at fading, especially of denim, one came across the three classes of cellulase viz. acid, neutral and engineering. The affect of cellulase on denim and the wash down effect was attributed to the yarn, which was ring dyed i.e. yarn dyed with indigo was present only on the outer ring of the denim. Due to affect of enzyme and physical aberration of cellulose, the exposed areas became white as well as indigo dyed. If it was non denim, it was ring dyed non denim containing vat, sulphur or pigments. This kind of effect on denim was called salt and pepper effect. The more contrast, better was the denim wash. Some of the denims had blue or greyer cast because they were woven with one up or two down and one of the yarn was coloured while the other wasn’t. thus, the effect was created with the combination of the hydrolysis of 1-4 glucose linkage in cellulose and the abrasion e.g. turbulence of friction of metal to metal or fiber to fiber led to denim appearance.
Combination of enzyme, sand blasting and bleach evolved a fashion recently. Sand blasting was enzyme treatments which subject the denim fabric to sand at high pressure with consequent exposure of white area while blowing off surface colour followed by a treatment of the fabric again with enzyme, leading to a salt and pepper effect and bleached to reduce the colour value. Furthermore, after sand blasting, treatment with enzyme followed by over dyeing of the abraded areas produced typical effects on denim.
BIO-POLISHING
It was perceived that bio-polishing and fading or bio-polishing and wash down were two different operations. But both of them basically employed the same action. They degraded the cellulose due to abrasion or friction between fiber to fiber or fiber to metal resulting in removal first from cellulose and then surface bleeding. It was reported in literature that bio-polishing before dyeing could increase depth apparently due to clarity of shade. Bio-polishing or cellulase enzyme treatment of lyocell type of regenerated cellulose could produce peach like
effect.
Bio-polishing gives cleaner appearance to the garment besides wash down effect. If it was sulphur or pigment dyed goods or ring dyed fabric, wash down effect as well as cleaning of fabric surface could be obtained. The result surface hair was removed, reduced pilling, better print registration and colour brightness. Size of cellulase enzyme was about 8nm as also the size of cellulose monomer, which was in similar region.
BIO-CARBONISING
Polyester / cellulosic blends after dyeing and/ or printing are occasionally treated with strong solution of sulphuric acid to dissolve cellulosic component. The resultant goods are soft and have a peculiar fluffy feel. This process is risky due to highly corrosive acid that is also difficult to treat in an ET plant.
The process developed at UNO, has none of the above drawbacks. It offers a safe and eco-friendly to the obnoxious practice of using sulphuric acid. The goods are treated with cellulose enzyme based formulation to achieve dissolution of cellulosic fibers.
DEGUMMING OF SILK
Silk is made up of two types of proteins like fibrin and ceresin. In the case of enzymatic treatment, a ceresin specific protein was used to degum the silk with out causing damage, impart softness and increase dye uptake of about 30%. If silk was degummed by alkaline treatment, there was damage to fibrin and heavy weight loss.
<<previous Page |
