Degummase treatment of spun silk fabric

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Indian Journal of Fibre & Textile Research Vol. 22, June 1997, pp. 119-123 Degummase treatment of spun silk fabric Department M L Gulrajani.

1 Indian Journal of Fibre & Textile Research Vol. 22, June 1997, pp Degummase treatment of spun silk fabric Department M L Gulrajani. Sangeeta Arora & Shalini Aggarwal of Textile Technology, Indian Institute of Technology, New Delhi , India Received 5 August 1996; revised received and accepted 8 October 1996 Treatment of spun silk fabric with the proteolytic enzyme Degummase improves the wettability and whiteness of the fabric without affecting its strength. The enzyme-treated fabric absorbs more dye as compared to untreated fabric. Dyeing of spun silk fabric under alkaline condition gives more uniformly dyed fabric as compared to that obtained on under neutral condition. However, dye uptake and dye fixation are higher under neutral condition. Keywords: Degummase, Reactive dyes, Relative unlevelness index, Spun silk fabric t Introduction Spun silk fabrics made from nail yarn are increasingly being exported to various western countries. This fabric, although coarse and rough, is popular because of its unique drape and good drapability, especially when used for upholstery and furnishing. Since spun silk is made from waste silk, it poses some problems during processing. It contains many impurities in the form of broken chrysalises, straw, lignin, hair and some cellulosic particles. Broken chrysalises appear as black spots in the fahric. Conventional processing such as scouring followed hy bleaching removes these impurities to a certain extent;the fabric, however, is not completely free of the impurities. With biotechnological processes finding wider applications in the textile industry, the use of various enzymes in processing of natural textiles has also increased. One such set of enzymes is the proteolytic enzymes or the proteases. These enzymes catalyse the hydrolysis of amide bonds in a protein molecule and are, therefore, used for silk degumming and in wool processing. Proteases have been reported to give softer handle and reduced lousiness to the fabric. Studies have been conducted in the past by Gulrajani and Gupta I to process the waste silk fabric in order to get a clean fahric with improved processing properties. The process sequence adopted was soaping with Marseiles' soap, cellulase treatment, Degummase treatment, and bleaching with hydrogen peroxide. It is reported that the treated spun silk fabric had softer handle, reduced lousiness and increased wettability. In the present study, spun silk fabric after scouring with non-ionic surfactant has been subjected to bleaching and protease enzyme treatment in tandem to obtain a clean fabric with a softer handle and increased wettability. The effect of the enzyme treatment on various properties like dye uptake and levelness of has also been studied. 2 Materials and Methods 2.1 Materials A plain woven spun silk fabric (procured from Bhagalpur) of the following specifications was used: Ends/cm, 25; picks/em, 22; area density, 172 g/rn"; warp tex, 2/50; and weft tex, 2/50. Degummase loool, a proteolytic enzyme, supplied by the Advanced Biochemicals Ltd, Bomhay, was used. This preparation contained 800 Anson's Units (AU) per mg. One unit of the Degummase enzyme activity is defined as the amount of enzyme required to liberate 1 mg of tyrosine from casein at the required ph at 45 C in 30 min. Sodium sulphate and sodium carbonate, both of AR grade, were used for the study. Following commercial dyes were used for : Remazol Blue 3R, Remazol Brilliant Blue BBD, Remazol Brilliant Blue R, Remazol Red C2G, Remazol Black B, Acidol Dark Blue FB-M-TR, Coloacid Blue RL, Procion Brilliant Red HE3B, Sumifix Supra Blue BRF, Sumifix Supra Yellow 3RF, Sumifix Supra Navy Blue BF, Sumifix Supra Scarlet 2GF, and Sumifix Supra Brilliant Red 3BF. 2.2 Methods Fabric Treatment The spun silk fabric was scoured by boiling for 90 min in a solution containing 5 gpl of Lissapol N, keeping the material-to-iiquor ratio at 1:30, and

2 120 INDIAN J. FIBRE TEXT. RES., JUNE 1997 then washed. The scoured fabric was then bleached by pad-batch method, using the following ingredients in soft water as padding solution: Hydrogen peroxide (30%): 30 gpl Sodium silicate Trisodium phosphate Lissapol N EDTA : 20 gpl : 20 gpl : 3 gpl : 1 gpl After padding, the fabric was batched at C for 2 h, washed, dried and then treated with Degummase under the following conditions: Enzyme :lo%owf Sodium bicarbonate :0.5% Lissapol N :0.1% Temperature : 50 C Time : 3 h MLR : 1:20 For dye uptake studies, enzyme-treated and untreated samples were dyed with reactive dyes using the following recipe: Dye :2% Glauber salt : 60 gpl MLR : 1:40 Temperature : 50 C Time : min The time period of was varied from 10 to 120 min (i.e. 10, 25, 40, 60, 90 and 120 min). The samples were dyed separately at neutral and alkaline ph for levelness studies. The dyebaths were prepared with dye only. The fabric was kept into the dye bath at 30 C and two instalments of Glauber salt, each of 30 gpl, were added at an interval of 15 min, raising the temperature from 30 to 90 C. The was further continued at,90 C for 60 min for neutral. For alkaline, the was first continued for 30 min I at 90 C after which sodium carbonate (5 gpl) was added and the was then further continued for 30 min. The material-to-liquor ratio was kept at I:40 during. The dyed fabric pieces were rinsed thoroughly in cold water followed by soaping with 2 gpl of Lissapol N at 8()OC for 15 min. Finally, the fabrics were rinsed in cold water and dried Measurement of Moisture Regain Fabric samples were conditioned in a desiccator containing saturated solution of sodium nitrite for 48 h and then moisture regain was measured on the Sartorius Moisture Analyzer, MA Determination ofwicking Time Fabric strips of 10x2 em size were cut and the time taken for water to travel to a distance of 2.5 em recorded Measurement of Strength The Instron universal testing machine (model no. 42(2) was used for assessing the breaking strength. The test was carried out using 25 kg load cell, keeping gauge length at 25 ern. The samples were cut into 30 x 5 ern size and then unravelled to 2.5 ern width by removing yarn from each end Measurement of Whiteness Index and Colour Value The ACS Spectrosensor II spectrophotometer interphased with IBM personal computer was used for whiteness index and colour measurement. The colour values were measured in terms of colour strength (K/S values). Since the fibres also absorb light, a correction was made for absorption of light by fibres by subtracting K/S value of undyed sample from that of dyed sample. Whiteness index was measured in terms of Hunter's Whiteness Index Measurement of Levelness of Dyeing Unlevelness of dyed fabric has been represented by Relative Unlevelness Index (RUI) based on the variation in reflectance at different locations of the fabric sample.'. Reflectance values of eight randomly selected spots on a dyed fabric sample were measured over visible spectrurn.l), = nm) at an interval of 10 nm. All the measurements were taken against white background. Standard deviation (5,.) of reflectance values measured at a specific wavelength was calculated using the following equation: where n is the number of spots measured at each wavelength; R i' the reflectance value of ith measurement for each wavelength; and R, the mean of reflectance values of n measurements for each wavelength.

3 GULRAJ ANI et al.: DEGUMMASE TREATMENT OF SPUN SILK FABRIC 121 The relative unlevelness index is then given by: RUI = L{SAIR) VA where VA is the photopic relative luminous efficiency function. 3 Results and Discussion The effectiveness of treatments was assessed by measuring wicking time, strength, moisture regain, whiteness index, dye uptake and levelness of. :to t Wicking Time The impurities consistmg of waxy substances are found to be removed by scouring itself, thus increasing the wettability of the fabric considerably. The results of the wicking time measurements (Table I) indicate that the untreated fabric has a wicking time of over 10 min. On scouring, the wicking time comes down to 95 s and on subsequent bleaching, it is further lowered to 48 S. The wicking time of the fabric does not improve much after enzyme treatment. 3.2 Strength Table I shows that on scouring the breaking strength increases marginally. This may be due to the shrinkage of fabric during the scouring treatment, as confirmed by the increase in weight per unit area. However, a loss in strength of fabric is observed on bleaching which may be due to oxidative degradation of the fabric during bleaching. There is no significant decrease.n strength after enzyme treatment as the protease action is primarily on the surface. 3.4 Hunter Whiteness Index 11 As expected, the whiteness index (WI) of the fabric increases on bleaching. The WI values further increase after treatment with enzyme (Table I). 3.5 Dye Uptake The dye uptake studies were carried out by the fabric for different time periods with four different dyes belonging to acid, metal complex and reactive dyes. The plots of K/S values (difference in K/S values of dyed and undyed fabrics) of enzyme-treated and untreated fabrics vs time period of are shown in Fig. 1. The dye uptake for all the dyes investigated has been found to be higher for enzyme-treated fabrics since the begining of the. This may be because the protease acts on the fabric surface, bringing about hydrolysis of chains and thereby increasing the number of amino groups for sorption of the dye. 7 Enzyme Ire~lcu --t>o-- Remazol Brlillanl Blue Bnn 8 -- Enzyme II!11rcalcd-~- Acrdol D:I1'k mile I'D-M-nt Rcll1MOI Bill"!R -<I- Coloacrd Blue Rl,q *--~ Moisture Regain Table 1 shows that the moisture regain of the fabric increases on scouring, bleaching and enzyme treatment, the increase being minimal in case of enzyme treatment. OL- -L ~ ~ ~ ~~--~ o 20 ~O Tim.) min Fig. I-Plots ofkls values of untreated and enzyme-treated fabrics vs time period of Fabric sample Scoured Bleached Table I-Properties of treated and untreated fabrics Wicking time Strength. kg Moisture regain Whiteness index s % Warp way Weft way >

4 122 INDIAN J. FIBRE TEXT. RES., JUNE 1997 Table 2-K/S values of the fabrics dyed at different ph Dye used K/Svalue Sumifix Supra Blue BRF SumifixSupra Yellow 3RF Sumifix Supra Scarlet 2GF Sumifix Supra Navy Blue BF SumifixSupra Brilliant Red 3BF Remazol Brilliant Blue R Remazol Red C2G Remazol Black B Procion Brilliant Red HE3B Neutral Alkaline Neutral Alkaline Dye used Table 3-RUI values of the fabrics dyed at different ph RU) value Neutral Alkaline Neutral Alkaline Sumifix Supra Blue BRF Sumifix Supra Yellow 3RF Sumifix Supra Scarlet 2GF Sumifix Supra Navy Blue BF Sumifix Supra Brilliant Red 3BF Remazol Brilliant Blue R Remazol Red C2G Remazol Black B Procion Brilliant Red HE3B Levelness of Dyeing Since the spun silk fabric has various kinds of cellulosic and other impurities, it gives uneven results on. As proposed by Chong and Yeung", RUI is taken as a measure of uniformity of. For assessing the levelness of untreated and enzyme-treated dyed fabrics, RUI was compared. The K/S and RUI values of untreated and enzyme-treated samples dyed with 9 reactive dyes under neutral and alkaline conditions are given in Tables 2 and 3 respectively. Of the 9 dyes, five dyes (i.e. Sumifix Supra) are heterobifunctional, two dyes (i.e. Remazol Black Band Procion Brilliant Red H E 3 B) are homobifunctional and the remaining two dyes are monofunctional reactive dyes. Table 2 shows that the KfS values of the samples dyed under neutral conditions are higher than those of dyed under alkaline conditions and thus confirm the earlier observation" that more dye is fixed on silk at neutral ph than at alkaline ph. On the other hand, the RUI values indicate that, in general, levelness is better when is carried out under alkaline condition. This may be due to the fact that cel1ulosic impurities present in the fabric get dyed at alkaline ph. The treatment of fabric with enzyme does not affect the levelness. 4 Conclusion Degummase treatment improves the whiteness of the fabric with no adverse effect on the wettability and strength. The enzyme treatment also increases the dye uptake without affecting the levelness of. Dyeing of spun silk fabric with reactive dye under alkaline conditions results in level dyed fabrics.

5 GULRAJANI et al.: DEGUMMASE TREATMENT OF SPUN SILK FABRIC 123 Acknowledgement The authors are thankful to the Department of Biotechnology, Ministry of Science & Technology, Government of India, for providing financial assistance to carry out this work. References 1 Gulrajani M L & Gupta Shailja Vaidya, Indian J Fibre Text Res, 20 (1995) Chong S Q Li & Yeung K W, J Soc Dyers Colour, 108 (1992) Agarwal Deepali, Kushal Sen & Gulrajani M L, J Soc Dyers Colour, 112 (1996) 321.

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