Vat dye yarn dyeing method, vat dye is a major category of cotton yarn dyeing of current colored fabrics. The dyed yarn is not only bright in color, but also has excellent fastness. Most of the light fastnesses are above level 6, and some varieties are as high as level 8. Therefore, all yarn-dyed fabrics that need finishing such as scouring, bleaching, mercerizing and heat setting can be dyed with vat dyes. There are many varieties of vat dyes, but they can be divided into indigo and anthraquinones according to their chemical structure. The vat dyes used in yarn dyeing are mostly anthraquinones.
Firstly, the basic method of dyeing is introduced: the vat dye with anthraquinone structure, its leuco sodium salt is easily absorbed by cotton yarn, and the dyeing rate is fast, so level dyeing is poor. The amount of caustic soda and sodium hydroxide required for the dye bath Also higher. In the process of yarn dyeing, 1g of anthraquinone vat dyes often consume 5~6g of caustic soda and sodium hydroxide in the dyeing bath. In addition, the dyeing bath also needs retarding agents such as bone glue and leveling to reduce the dye uptake rate. , It is helpful for the dye liquor to diffuse into the fiber and improve its levelling effect. The dosage is 0.2～0.5g/l. In daily dyeing, the dyeing time is generally 15～2omin.
In order to improve the levelness and color fastness of colored yarn, it is reasonable to extend the dyeing time to 20～3omin. For a small amount of vat dyes that need to be dyed at a lower temperature, after the leuco sodium salt is adsorbed by the yarn, it is not easy to oxidize in the air. You can choose an appropriate oxidation method and oxidant to promote the conversion and color development of the dye leuco , And then washed with water or treated with dilute acid solution to remove residual alkali and impurities, and finally soaped and washed to complete yarn dyeing. Since different vat dyes have different dyeing properties, when dyeing yarns, you can choose the appropriate reduction method and dyeing method according to the amount of caustic soda, sodium hydroxide, auxiliaries, dyeing temperature, time and other conditions required for yarn dyeing. .