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What are the vat dye dyeing methods


Release time:

2023-07-28

Vat dyes can be used for dyeing cotton and polyester-cotton and cotton blended fabrics. According to the different forms of dye, it can be divided into leuco dyeing method and suspension pad dyeing method. There is also a leuco acid staining method, which is not commonly used, so it is not discussed here. 1. leuco dyeing leuco dyeing is a dyeing method in which the dye is reduced to leuco in advance, adsorbed by the fiber in the dye bath, and then oxidized and soaped. It can be divided into dip dyeing, roll dyeing and pad dyeing, etc., and is currently mostly used for dip dyeing and roll dyeing. Leuchrome dip dyeing is suitable for yarn dyeing, but the dyeing method has poor core penetration and white core phenomenon. Depending on the nature of the dye, different reduction methods can be used.

Vat dyes can be used for dyeing cotton and polyester-cotton and cotton blended fabrics. According to the different forms of dye, it can be divided into leuco dyeing method and suspension pad dyeing method. There is also a leuco acid staining method, which is not commonly used, so it is not discussed here.

1. leuco dyeing leuco dyeing is a dyeing method in which dyes are reduced to leuco in advance, adsorbed by fibers in the dye bath, and then oxidized and soaped. It can be divided into dip dyeing, roll dyeing and pad dyeing, etc., and is currently mostly used for dip dyeing and roll dyeing. Leuchrome dip dyeing is suitable for yarn dyeing, but the dyeing method has poor core penetration and white core phenomenon. Depending on the nature of the dye, different reduction methods can be used.

(1) dry cylinder method: during dip dyeing, some dyes have a slow reduction speed, and more severe conditions must be used to improve the reduction rate of dyes. this reduction method is called dry cylinder method.

dry cylinder reduction is to first mix the dye with a small amount of water and swire oil or pull-open powder into slurry, then add a proper amount of warm water and a specified amount of caustic soda and sodium hydrosulfite, reduce for 10~15min at a specified temperature, and then filter the dye into a dye vat containing caustic soda and sodium hydrosulfite solution after the dye is fully reduced, and dilute to the required concentration for dyeing. Due to the reduction of water consumption is very small, equivalent to improve the caustic soda, insurance powder concentration, accelerate the reduction rate of the dye, so that the reduction reaction is completed normally.

(2) Full bath method: This reduction method is suitable for vat dyes with faster reduction rate. The method is to directly put the dye into the dye tank, add a specified amount of caustic soda and insurance powder, so that the dye reduction, reduction of 10 to 15min after dyeing. If the more severe reduction conditions are used for such dyes, it is easy to cause hydrolysis or excessive reduction of the dyes, affecting the quality of the dyed products.

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