Enzymatic Desizing Research Articles

Development of new eco‐friendly options for cotton wet processing

AbstractA new approach was used to search for the optimal conditions for enzymatic scouring with an alkaline pectinase and to investigate the feasibility of performed combined bioscouring and H2O2 bleaching and combined bioscouring and reactive dyeing of unscoured cotton fabrics. The possibility of conducting enzymatic desizing, bioscouring, and H2O2 bleaching of starch‐sized cotton fabrics in a single bath was also examined. The results indicated that changes in the parameters of the bioscouring process, the types and concentrations of the treating bath components, and the sequence of the treatment and addition had pronounced effects on certain properties of the treated cotton substrates (e.g., the residual size, weight loss, wettability, yellowness and whiteness, and dyeability with reactive dyes). The optimal conditions for efficient bioscouring alone and in combination with H2O2 bleaching, reactive dyeing, and enzymatic desizing and H2O2 bleaching were determined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1825–1836, 2004

Optimization and Modification of Enzymatic Desizing of Starch-Size

A comprehensive study was carried out to attempt to find out the proper and optimal conditions for attaining a higher extent of enzymatic desizing of starch size, modifying the desizing formulations via incorporation of H2O2 or a neutral cellulase enzyme along with α-amylases, and evaluating the impact of these modified formulations on the performance properties of the desized cotton fabrics. Several factors affecting the starch-size removal were studied and are discussed in this article. The results detailed in this article indicate that: (a) the effectiveness of enzymatic desizing can be enhanced by raising the desizing temperature up to 70°C; prolonging the desizing time up to 60 min: adding CaCl2·2H2O, as an enzyme-stabilizer up to 0.5 g/L; increasing the material-to-liquor ratio up to 20:1; increasing the Aquazym® 240-L dosage up to 6 g/L; treating at pH 7; and/or increasing the agitation rate up to 40 rpm, irrespective of the used substrate; (b) the higher the extent of the size removal, the lower the retained strength of the desized fabric; (c) the extent of enzymatic desizing is governed by the type of wetting agent, i.e., nonionic > nonionic/anionic > anionic > none, as well the nature and activity of the α-amylase enzyme, i.e., Aquazym® Ultra 250L > Aquazym® 240L > none; (d) including H2O2 (4 mL/L–35%) along with Aquazym® 240L (6 g/L) improves the extent of the desizing, the degree of whiteness, as well as the dyeability with reactive dyes; and (e) incorporation of a neutral cellulase enzyme (2% owf, Denimax® 302S) along with Aquazym® 240L (6 g/L) gives rise to higher weight loss, better wettability, lower stiffness, and higher dye uptake along with a marginal improvement in the extent of desizing.

Enzymatic Desizing of Polyvinyl Alcohol from Cotton Fabrics

Enzymatic degradation of polyvinyl alcohol (PVA) was used for the desizing of cotton fabrics. A mixture of two different PVA-degrading enzyme activities, including PVA oxidizing, was partially purified from the culture filtrate of a PVA-degrading mixed culture by ionic exchange chromatography. Optimum conditions for PVA-degradation by using this enzyme mixture were pH 8·0 and temperatures ranging from 30°C to 55°C. Cotton fabrics sized with a PVA solution (25 g dm−3) were desized with the enzyme mixture after a 1 h treatment at 30°C and pH 8·0. In this case, similar amounts of residual PVA in fabrics were detected in comparison with the conventional desizing process which uses hot water (80°C, 30 min). Minimum amounts of residual PVA were found when the enzymatic desizing time was extended to 6 h. Also, the PVA content in the liquid waste from the enzymatic desizing carried out during 4 h was negligible with a 7·4-fold increase in the biochemical oxygen demand as compared with the initial value. © 1997 SCI.

Preparation procedures for woven cotton and polyester/cotton fabric. Part 2 — oxidative desizing with hydrogen peroxide

Oxidative desizing with sodium hydroxide in the presence of hydrogen peroxide has been investigated as a preparatory treatment for dyeing and printing cotton and polyester/cotton woven fabric. Using statistically designed experiments, the effect of time and temperature of treatment, and peroxide and sodium hydroxide concentrations on degree of desizing, whiteness, fabric absorbency and mote removal has been determined. The major factor determining desizing rate was sodium hydroxide concentration. As peroxide concentrations increased above 0.1% o.w.f. of 35% solution desizing was retarded. Desizing was thus seen to be a hydrolytic process initiated by hydrogen peroxide. Whiteness achieved during desizing was not correlated with sodium hydroxide concentration and adequate whiteness was not achieved with the 100% cotton fabric. Whiteness of the blend was significantly influenced by all the desizing factors, while absorbency was affected by treatment time and temperature. Pure cotton was not rendered absorbent at all at below 65°C, in contrast with enzymatic desizing. Treatment for a short time in the temperature range 65–95°C gave a generally unsatisfactory level of mote removal.

Preparation procedures for woven cotton and polyester/cotton fabric. Part 1 — enzymatic desizing

Factors influencing the enzymatic desizing of woven cotton and polyester/cotton fabric have been examined using a medium‐temperature‐stable enzyme or one with high thermal stability. The effect of variation in time, temperature and concentration on degree of desizing, fabric absorbency before bleaching, whiteness and degree of desizing after bleaching were assessed by regression analysis on the results of statistically designed experiments. The dominant factors were temperature and time, while variation in concentration often had no significant effect. The results show that more than brief treatment with a high‐temperature enzyme has a negative influence on final whiteness. The polyester/cotton fabric, sized with a mixture of starch and poly(vinyl alcohol), was poorly desized by the medium‐temperature enzyme, but after bleaching desizing was adequate. Improved correlations for absorbency were obtained using a logarithmic absorbency index.