Classification of sulfur dyes 1. Powder vulcanization
The general formula of the dye is D-S-S-D. Generally, it needs to be boiled with sodium sulfide and used after dissolution. This type of dye is insoluble in water. The dye can be reduced to a leuco body with an alkaline reducing agent and dissolved in water. The leuco body sodium salt can be absorbed by the fiber.
2. Water-soluble vulcanization The general formula of the dye structure is D-SSO3Na. The characteristic of this type of dye is that there are water-soluble groups in the molecular structure of the dye, which has good solubility and level dyeing. Common sulfur dyes are reacted with sodium sulfite or sodium bisulfite to generate thiosulfate of the dye, which has a solubility of 150g/L at 20°C and is used for continuous dyeing. Water-soluble sulfur dyes have a fast dissolution rate at room temperature, no insoluble matter, and the saturated dissolution amount is sufficient to meet all the dissolution requirements of the dyeing dosage. Water-soluble sulfur dyes have excellent high temperature resistance. However, the dye contains no reducing agent and has no affinity for fibers. It is necessary to add alkali sulfide during dyeing and transform it into a state that has affinity for cellulose fibers through nucleophilic and reduction reactions. Generally, it is applied to textiles by suspension pad dyeing.
3. Liquid curing The general formula of the dye is D-SNa, which contains a certain amount of sodium sulfide reducing agent to pre-reduce the dye into a water-soluble leuco body. Reduce ordinary sulfur dyes into water-soluble leuco body with reducing agent, add excess reducing agent as antioxidant, add penetrant, inorganic salt and water softener to make liquid dye, also known as pre-reduced dye. It can be used directly after diluting with water during use. Such dyes contain sulfur, such as Cassulfon dyes containing sodium sulfide, and some do not contain or contain a very small amount of sulfur, such as Immedial dyes, there is no sulfur-containing wastewater during dyeing.
4. Environmentally friendly vulcanization In the production process, it is refined into dyed leuco body, but the sulfur content and polysulfide content are far lower than ordinary sulfur dyes. The dye has high purity, stable reducibility, and good permeability. At the same time, glucose and sodium sulfonate are used as binary reducing agents in the dye bath, which can reduce sulfur dyes and play an environmental protection role.
5. Sulfide reduction
It is often made into powder, fine, ultra-fine powder or liquid dyes. It is suitable for dyeing polyester-cotton blended fabrics and disperse dyes in the same bath. It can be used for reduction of caustic soda, sodium sulfide (or thiourea dioxide) instead of sodium sulfide for reduction and dissolution, such as Hydron Indocarbon dye.
6. Disperse vulcanization Disperse sulfur dyes are based on sulfur dyes and sulfur vat dyes and are made according to the processing methods of disperse dyes. They are mainly used for pad dyeing of polyester-viscose or polyester-cotton blended fabrics in the same bath with disperse dyes.
