Research On Enzymatic Desizing And Its Mechanism Of Cotton Yarn Dyed Fabric

Amylase (α-amylase) can break the α-1,4-glucosidic bond of starch molecules, then thestarch can be hydrolyzed into soluble substances and removed from the wrap without bringserious damage to the fabrics, and the color of the fabrics also can not be changed obviously.Therefore, amylase desizing is used in color fabrics desizing processes widely. But currentenzymatic desizing effect is not ideal, which causes serious impact on high-grade qualitycolor fabrics. In order to investigate and improve desizing performance of color fabrics,several methods have been used in this paper. Firstly, a qualitative detection methods of starchand PVA have been established, which residued on color fabrics after desizing. Secondly, thedifference of decomposition performance and desizing performance of different modifiedstarchs were revealed. The effect of PVA of different content on the decompositionperformance and desizing performance of original starch by determining their decompositionrate and desizing rate were also studied. Finally, the color fabric enzymatic desizing processwas studied to improve the desizing rate of color fabric.The results showed that reduction method was used to decolorize the extract liquid ofdesizing color fabrics to test wether PVA was residual and testing by potassium iodide andiodine method combined with fehling reagent method; active carbon adsorption to decolorizethe extract liquid of desizing color fabrics was used to test wether starch was residual andtesting by iodine-boric acid method.Different structures of the modified starches have different enzyme decompositiondesizing performance. The decomposition performance and desizing performance of modifiedstarch, in decreasing order, was esterified starch such as starch acetate and phosphate starch,oxidized starch and cationic starch. In addition, the adding of PVA caused the reduction of therate of decomposition desizing rate. The more the amount of PVA added, the more obviousthese change were.The starch paste on color fabrics was removed effectively by pretreatment and enzymetreatment, while a small amount of starch paste was done in water washing process. The maintask of water washing process was to remove the starch sizing which remained on the colorfabric. Compared with the untreated one, the rate of the starch desizing increased obviously,which showed that pretreatment was an essential step during desizing process. In order toimprove the desizing rate of starch slurry, saccharifying enzyme was added, the desizing rateof starch was close to100%, but the desizing rate of PVA was still only about87%. Althoughit seems that the starch paste was removed completely during the desizing process, PVAslurrywas not, which showed that more research were needed on enzymatic desizing of color fabricin the future. In addition, there was almost no change of the K/S value of the color fabric afterenzymatic desizing reaction, which showed that enzymatic desizing has no obvious influenceon the color of color fabric.