What is dyeing method of vat dye？

Vat dyes can be used to dye cotton and polyester-cotton and virgin cotton blended fabrics. According to the different dyeing methods, it can be divided into leucochromic dyeing method and suspension pad dyeing method. There is also a leuco acid staining method, which is not used because it is not commonly used.

Leucochrome staining
Leuco dyeing is a dyeing method in which the dye is reduced to a leuco in advance, adsorbed by fibers in a dye bath, and then oxidized and soaped. It can be divided into dip dyeing, pad dyeing and pad dyeing, etc. It is mostly used for dip dyeing and pad dyeing. Leukochromic dip dyeing is suitable for yarn dyeing. The degree of penetration through the core dyeing method is poor, and there is a white core phenomenon. Depending on the nature of the dye, different reduction methods can be used.

(1) Dry-cylinder method: In the dyeing process, some dyes have a slower reduction rate. More drastic conditions must be used to increase the reduction rate of the dye. This reduction method is called dry-cylinder method.

Dry-cylinder method is to reduce the dye to a thin slurry with a small amount of water and Taikoo oil or powder, then add an appropriate amount of warm water and a specified amount of caustic soda and insurance powder, and reduce at the specified temperature for 10-15 minutes. After filtering, it is added to the dyeing tank containing caustic soda and insurance powder solution, and diluted to the required concentration for dyeing. Because the water consumption during the reduction is very small, which is equivalent to increasing the concentration of caustic soda and insurance powder, the reduction rate of the dye is accelerated, and the reduction reaction is completed normally.

(2) Full bath method: This reduction method is suitable for vat dyes with a faster reduction rate. The method is to directly put the dye in the dyeing tank, add a prescribed amount of caustic soda and insurance powder to reduce the dye, and then dye it after 10-15 minutes. If more severe reducing conditions are used for this type of dye, it will easily cause the hydrolysis or excessive reduction of the dye, which will affect the quality of the dyed product.
Suspension padding

The insoluble dye is formulated into a stable suspension, is dipped on the fabric, and is then subjected to a color fixing treatment.

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