The whole process from yarn to weaving and dyeing

The whole process from yarn to weaving and dyeing

Pre-treatment of bad cloth

Singeing: Burn off the fluff on the cloth surface to make the surface of the cloth smooth and beautiful, and prevent uneven dyeing or printing defects due to the existence of fluff during dyeing or printing.

Desizing: Removing the sizing of the grey fabric and the added lubricant, softener, thickener, preservative, etc., is beneficial to the subsequent scouring and bleaching process.

Scouring: Remove natural impurities such as waxy substances, pectin substances, nitrogen-containing substances and some oil agents in grey fabrics, so that the fabric has a certain water absorption, which is convenient for the adsorption and diffusion of dyes during the printing and dyeing process.

Bleaching: removes natural impurities such as natural pigments and cottonseed husks on fibers, imparts the necessary whiteness to the fabric, and improves the vividness and effect of dyeing.

Mercerizing: Through concentrated caustic soda treatment, stable size, durable luster is obtained, and the adsorption capacity of dyes is improved, and the physical and mechanical properties such as strength, extension force and elasticity are improved.

Types of commonly used dyes

Direct dye: Direct dye refers to a dye that can directly dye cotton fibers by heating and boiling in a neutral or weak alkaline medium. It has high directness to cellulose fibers, and does not need to use dyes related to chemical methods to color fibers and other materials.

Reactive dye: It is a water-soluble dye with active groups in the molecule, which can covalently bond with the hydroxyl group on the cellulose molecule under weak alkaline conditions. The daily fastness of reactive dyes is generally good, and the soaping fastness and rubbing fastness are higher after sufficient washing and floating.

Acid dyes: It is a kind of water-soluble dyes with acidic groups on the structure, which are dyed in acidic medium. Most of the acid dyes contain sulfonic acid sodium salt, which is soluble in water, bright in color and complete in chromatogram. It is mainly used for dyeing wool, silk and nylon, and has no coloring power to cellulose fibers.

Vat dyes: Vat dyes are insoluble in water. When dyeing, they must be reduced and dissolved into leuco sodium salts in an alkaline strong reducing solution to dye fibers. After oxidation, they will be restored to insoluble dye lakes and fixed on the fibers. Generally, the fastness to washing and light fastness is high.

Disperse dyes: Disperse dyes have small molecules and do not contain water-soluble groups in structure. They are uniformly dispersed in the dye solution with the help of dispersants for dyeing. The polyester and cotton dyed with disperse dyes can be dyed with polyester fiber, acetate fiber and polyester amine fiber, and become a special dye for polyester.