Dyeing and finishing process of pure cotton fabric

Dyeing and finishing process of pure cotton fabric
1、 Common Dyes for Cotton Fabrics and Their Dyeing and Printing Properties
Dyes used for dyeing pure cotton fabrics mainly include direct dyes, reactive dyes, vat dyes, soluble vat dyes, insoluble azo dyes, sulfide dyes, etc. Printing dyes mainly include reactive dyes, insoluble azo dyes, stable insoluble azo dyes, vat dyes, soluble vat dyes and printing pigments. Viscose fiber similar to cotton fiber can also be dyed and printed with the above-mentioned dyes. However, because viscose fiber is regenerated cellulose fiber with relatively loose structure, and compared with cotton fiber, it is not alkali resistant and sensitive to acid, etc., so when dyeing with this kind of dye, there should be some differences in process and other aspects. The following is a brief introduction to the dyeing and printing properties of common dyes for pure cotton fabrics.
1. Direct dyes Direct dyes can be soluble in water, and can be directly used to dye cotton fibers in neutral or weak alkaline solutions. Adding neutral electrolytes such as salt during dyeing can increase the amount of impurities on the dye. Direct dye chromatography is complete, the dyeing method is simple, and the price is relatively cheap. It was once the main beam material of cotton fabric. However, this kind of dye is not good enough to dye firmly, so it needs to be fixed in the post-treatment.
2. Reactive dyes Reactive dyes refer to soluble dyes containing reactive groups. Under appropriate conditions, it can be chemically combined with cellulose fiber and protein fiber to greatly improve the color fastness of the dyed fabric to washing and soaping. At the same time, it also has the advantages of simple dyeing and printing, bright color, complete color spectrum and low price. However, the fixation rate of general reactive dyes is not high, and it is easy to hydrolyze in alkaline solution, resulting in floating color. Therefore, the method of first dyeing and then fixing is adopted to improve the fixing rate of the dye. For printing, one phase method or two phase method shall be selected according to different types of dyes. Some reactive dyes have poor color fastness to chlorine bleaching and climate.