1. Sulphur black dyes are water-resistant dyes, so the sulphur dyes do not have dyeing ability for cotton. However, it has good dyeing properties for cotton when the dye is reduced to leuco in alkali sulfide solution. The dyeing of sulfur dyes is carried out in sodium sulfide solution.

2. Operation of sulphur black dyes: dissolve the prepared sodium sulfide in 80℃ water for 5-10 minutes, and then put the sulphur black  in boiling water for 20 minutes. Soda for 1% sulphur black was added.

3. The function and dosage of each additive:

Sodium sulfide (Na2S): Solvent for dissolving sulfur black dyes. Its function is to reduce sulfur black to a leuco of dyes which have dyeing ability for cotton. It can reduce and dissolve sulphur black dye.

Dosage: The ratio of sulfur black and Na2S is 1-1.5:1

Sodium carbonate (Na2CO3): Sodium carbonate plays a role in improving the reduction stability of dye solution in black sulfide dyeing solution and preventing premature oxidation of dyes. It is also an alkali agent for degreasing. When dyeing in hard water,  calcium and magnesium salts in hard water can prevent the effect of dyeing. Generally, the amount of calcium and magnesium salts in hard water is about 2% of the fabric.Excessive dosage will make the fabric red-brown.

Sodium sulfide powder (Na2SO4): The dyeing rate of sulphur dyes is low. Adding sodium sulfate powder in dyeing solution is helpful to improve the dyeing rate, so sodium sulfate powder plays a role in promoting dyeing.

Degreaser: Remove grease from cloth and improve the permeability of germ cloth, improve dyeing rate and levelness.

Wrinkle-proof agent: to prevent creases and creases on the fabric surface.

Urea: It can prevent brittleness.

Soft Oil: It plays a softening role to make the cloth feel soft and comfortable.

Operational attentions

1.Dyestuff dissolution need to ensure time and temperature. Ensure that the dyes are fully reduced and dissolved.

2. The temperature and time of degreasing of embryonic cloth should be guaranteed to remove the grease stain on the cloth, improve the capillary effect and be conducive to even dyeing.

3.Oxidation in water is the key.

4 Over-soft: Soft oil should be converted with high water ratio (1:20 or more) in the auxiliary cylinder and pumped into the main cylinder for too soft in 5-10 minutes.

Note: Sulphur black br dye does not need oxidizer for oxidation, washing water can be fully oxidized.