The dyeing process of sulfur dyes

(1) The reduction of dyes is easier to dissolve sulfur dyes, and sodium sulfide is commonly used as a reducing agent, and it also plays the role of alkali agent. In order to prevent cryptochromatic bodies from being hydrolyzed, soda ash and other substances can be added appropriately, but the alkalinity of the reducing bath should not be too strong, otherwise the dye reduction rate will be slowed down.
(2) The dye cryptochromosome in the dye solution is adsorbed by the fiber, and the cryptochromatic body of the sulfur dye exists in the anion state in the dyeing solution, which has directness to the cellulose fiber, and can be adsorbed on the surface of the fiber and diffused into the fiber. The sulfide dye cryptochromosome has low directness to cellulose fibers, generally using a small bath ratio, while adding appropriate electrolyte, at a higher temperature, the upper dyeing rate can be increased, and the uniformity and permeability can be improved.
(3) After the oxidation treatment sulfur dye cryptochromatic body is dyed on the fiber, it must be oxidized to show the desired color. Oxidation is an important step after dyeing sulfur dyes. After dyeing the sulfur dyes that are easy to oxidize, they can be oxidized by air after washing and ventilation, that is, air oxidation; For some sulfur dyes that are not easy to oxidize, oxidant treatment is used to promote oxidation.
(4) Post-treatment and post-treatment include cleaning, oiling, anti-brittleness and color fixation. After dyeing the sulfur dye, it must be fully washed to reduce the residual sulfur on the fabric and prevent the fabric from being brittle, because the sulfur in the dye and the sulfur in the sulfide alkali are easy to oxidize in the air to generate sulfuric acid, which will cause acid hydrolysis and reduce the strength of the cellulose fiber, so that the fiber is brittle. Therefore, it can be treated with anti-brittle agents, such as: urea, trisodium phosphate, bone glue, sodium acetate, etc. In order to improve the fastness of sulfur dyes to sun exposure and soaping, the color can be fixed after dyeing. There are two methods of fixing treatment: metal salt treatment (such as: potassium dichromate, copper sulfate, copper acetate and a mixture of these salts) and cationic fixing agent treatment (such as: fixing agent Y), the actual production with fixing agent M treatment is better, fixing agent M is made of cationic fixing agent and copper salt compound, can reduce chromium pollution.