Abstract:

Objective In order to fundamentally solve the severe environmental pollution problem caused by the existing chlorinated wool carpet mercerizing finishing, much research has been focused on ecological mercerizing. The protease method is a mild and green finishing process. However, the low hydrolysis efficiency of protease on wool keratin remains to be a technical bottleneck, and it is necessary to develop the protease method for the wool carpet mercerizing process with ecological characteristics. It is conducive to promoting green and sustainable development of the textile industry.

Method A protease-catalyzed system consisting of substrate activator LKZ-630 and protease Savinase 16L was constructed and used for mercerizing wool carpets by combining mechanical scraping and brushing. The role of LKZ-630 in the enzymatic degradation of wool was studied by measuring the sulfhydryl content on the wool surface, protease activity, protease adsorption, and degree of hydrolysis of wool. The structure of wool carpets before and after treatment was examined by scanning electron microscopy, Fourier infrared spectroscopy, and X-ray diffraction energy spectroscopy.

Results The results showed that LKZ-630 could open disulfide bonds in wool fibers and convert them to sulfhydryl groups. It facilitated the rapid degradation of high-sulfur wool tissues by proteases. By adding LKZ-630, the protease activity (substrate of wool fibers) increased by 1 575 times when the concentration of LKZ-630 was 2 g/L. Under the treatment conditions of LKZ-630 2 g/L, Savinase 16L 1 g/L, and 50 ℃, LKZ-630 increased the equilibrium adsorption of protease on wool fibers by 12.7 times and increased the hydrolysis rate by 36.3 times. Wool carpet mercerizing equipment with brushing and scraping functions was developed. A protease-catalyzed system (LKZ-630 2 g/L and Savinase 16L 1 g/L) combined with brushing and scraping was used for mercerizing pure wool carpets at 50℃ for 40 min. Brushing and scraping cause the mechanical force on the carpet fiber to gradually increase from the tail to the tip during treatment. As a result, the fineness of the treated wool fibers gradually became finer from the tail to the tip. The fiber tip fineness after treatment even reached 1 μm, giving the treated carpet a layered feeling and a soft touch. In addition, the surface of the upper and middle fibers of the treated carpet was exceptionally smooth compared to the untreated carpet. As a result, the treated carpet had a better gloss, with CIE brightness and whiteness values increased by 6.99 and 50.12, respectively, and the yellowness value reduced by 14.84. The surface group structure of the treated carpet was similar to that of the untreated. However, the crystallinity was reduced due to the destruction of the disulfide bond cross-linking in the scale proteins.

Conclusion The protease-catalyzed system consisting of the substrate activator LKZ-630 and Savinase 16L was constructed to degrade wool high-sulfur hard keratin. LKZ-630 could efficiently open the disulfide bond in the wool fiber and significantly increase the adsorption rate of the enzyme on wool fiber and the hydrolysis efficiency of the enzyme on wool high-sulfur keratin. The higher the concentration of LKZ-630, the higher the adsorption of wool to the protease, and the higher the reactivity of the protease to the wool. The protease-catalyzed system was combined with brushing and scraping to mercerize the wool carpet. Compared with the untreated carpet, the degree of exfoliation of keratin tissue of the treated carpet fibers was gradually strengthened from the tail to the tip, and the fineness was also gradually thinned. The treated carpet was soft to the touch and had a sense of hierarchy and a silk-like luster, realizing the ecological chlorine-free mercerization of wool carpet. Further studies on the dyeing and finishing properties of carpets treated with the protease-catalyzed system are necessary.

Key words: protease, wool, carpet, protease catalytic system, mercerization, substrate activation