There are multiple oxidants available. Padding the fabric in a hydrogen peroxide alkaline solution with a concentration of 3 to 5 g / L and then steaming it for 2 to 3 minutes can promote the degradation of starch and polyvinyl alcohol and have a certain bleaching effect on the fabric. When desizing with sodium hyposulfite, the fabric is paddled with a sodium hyposulfite solution with a pH of 9.5 to 10.5 and an effective concentration of 0.5 to 1.5 W, and stacked at room temperature for about 20 minutes to protect the methyl fiber. The fabric sizing with plain, starch or polyvinyl alcohol has a good desizing effect. Hyaluronic acid persulfate salt or potassium salt also has a good desizing effect, but it is easy to make the cellulose fiber brittle.
Desizing is an important process before scouring and bleaching of fabrics. It can not only remove sizing from fabrics, but also remove some impurities from cotton fibers. Desizing should be selected according to the composition and product characteristics of the fabric on the fabric to improve the desizing effect. After the fabric is desizing, it is generally required that the desizing rate is above 80%, or the amount of residual pulp on the fabric is less than 1%.
Scouring can remove the symbiosis of cottonseed hull and cellulose and the residual slurry on the cloth, so that the cotton cloth can obtain a good appearance and water absorption, so as to facilitate post-processing. Viscous fiber and fiber-rich fabrics have less natural impurities due to the caustic soda and bleaching process in the manufacturing process, generally only need to be desizing and bleaching during processing to remove sizing and stains on the fabric to further improve whiteness , No need to practice. Vinylon, polyester and wax fiber do not need to be smelted. They are not required to be smelted with viscose, fiber-rich blended fabrics or polyester-wax blended fabrics, but blended fabrics with cotton need to be cooked because there are many cotton fibers practice. However, vinylon is yellowed and hardened after long-term treatment under the action of high temperature concentrated alkali; polyester fiber will undergo different degrees of etching on the fiber surface in high temperature concentrated alkali. After scouring, the semi-manufactured cotton requires capillary effect above 8 cm / 30min.
After scouring, Mianzhi generally remains natural pigments and some impurities, which affects the whiteness and vividness of the finished product. Therefore, except for some dyed dark products, bleaching is required. Bleaching can not only remove pigments, but also remove impurities such as cottonseed hulls and nitrogenous substances to varying degrees. The whiteness of semi-finished products after bleaching is generally required to reach
More than 85% (100% with BaSO4).