Enzymatic degumming of slik

ENZYMATIC DEGUMMING OF SILK:

       Natural fibres are eco-friendly in nature, and are essential alternatives in the ever-expanding horizon of textile fire. They are non-toxic and bio-degradable. They do not disturb the ecological balance of the environment.

     Silk is one of the most ancient natural fibers, proteins in nature and highly hygienic. It is derived from the moth Bombyx mori , feeding on mulberry leaves, is known as mulberry silk. It is commonly known as the’ Queen of Textile’, due to its luster, elegance and versatility. Silk is only natural filament fibre. Silk is composed of fibroin and sericin. The filament is a double strand of fibroin, which is held together by gummy substances called sericin or silk gum.

     Degumming of silk to remove the sericin is an important step. Soda-ash and sulphides used in conventional degumming process not only reduces the fabric strength but also causes pollution problem. On the other hand enzymatic degumming is a very safe and simple method of degumming. Apart from sericin the silk fabric also contain about 2% oil to facilitate weaving. Enzymes not only dissolved the gummy portion but also dissolved the oil at the same time (43).

Pre-treatment process:

           Recipe:

                Wetting agent (Zywet-W)- 1%

                 Sodium carbonate- 1%

                 Temperature- 60c

                               Time- 30min

                                MLR- 1:20

                                   PH- 8 to 9

           Pre-treatment is carried out to remove the phosphorus compounds and the waxy substances ad-mixed with the sericin. Otherwise it is very difficult to get the maximum efficiacid of the enzyme for actual degumming. The pre-treatment is carried out by treating the material with the chemicals as names an recipe and working for 30min at 60c. After treatment the material is thoroughly washed and squeezed and put into the degumming bath containing the following chemicals and enzymes are mentioned of the recipe below,

          Recipe:

                Papen- 6%

               Sodium phosphate- 2%

                   Formic acid- 1%

                   Temperature- 60

                    Time- 1h

                        PH- 6

                     MLR- 1:20

  After treating the material is washed thoroughly and residual enzyme so present within the substrate is a deactivated. By boiling the material, further with plain water for a period of 10 to 15min followed by through washing and drying. The gum loss is found to be around 21-22% with a strength loss of about only 12%.

      After from Papen pepsin, tropism, pechiness may be used as a proteolytic enzymes for degumming of silk.

    Degumming of silk can also be carried out with the help of cellulolytic enzyme (cellulose).

     Recipe:

          Cellulase- 6%

    Sodium bi-carbonate- 7.5%

                    Temperature- 70

                                 Time- 2h

                                    PH- 8.5

                                  MLR- 1:20

   The material is with the liquor containing the chemicals as mentioned in the recipe for a period of 2 h followed by deactivation of the same by boiling with plain water for 10 min. Then the material is washed thoroughly and dried.

BIO-POLISHING:

      Surface modification of cellulose fabrics to improve their cleaner surface conferring cooler feel, brighter luminosity of colors, softer feel and more resistance to pilling using cellulars is often known as bio-polishing (55,56).This treatment can be applied to knit and woven cellulose fabrics such as cotton, viscose and linen and their blends (57-60). The elimination of superficial micro fibrils of the cotton fiber through the action of cellulose enzymes is obtained by the controlled hydrolysis of cellulose leaving the surface of the fibers free and conferring a more even look (61-63). The effect of cellulose enzymes on the fabric is hairiness. After enzyme treatment the fabric improved their permanent softness and smoothness property. Further the water regain is not decreased by the enzymatic treatment. Although bio-polishing may be carried out at any time during wet processing, it is most conveniently performed after bleaching. Fabric may be treated in either piece or garment form and the treatment can be combined with another process or kept as a single operation. Controlled finishing with cellulose enzymes optimists the surface properties of the fabric, but decrease in tensile strength (72).