Sulfur dyes are one of the most widely used dye. It was reported that the production of sulfur dye reaches more than a hundred thousand of tons throughout the world, and one of the most important varieties are sulfur black dye. Currently, the sulphur black accounts for 75%~80% of the total sulfur dyes. It is by the favor of dyeing and printing factory for its synthesis simplicity, low cost, good fastness and no carcinogenic. It is widely used in the dyeing of cotton and other cellulose fibers. Sulphur dyes with more vivid color and the fastness to chlorine bleaching is relatively good. But some yellow and orange varieties have photosensitive tendering effect on fiber.
In recent years, liquid sulfur dyes, ultrafine dispersion sulfur dyes and environment-friendly sulfur dyes is developing rapidly. As the requirements to environment is higher, the ecological selection of sulphur dyes reductant and oxidant is necessary. It is widely used in the dyeing of cotton and other cellulose fibers. Sulphur dyes with more vivid color and the fastness to chlorine bleaching is relatively good. But some yellow and orange varieties have photosensitive tendering effect on fiber.
According to the different dyeing conditions, sulphur dye divided into two kinds: sodium sulfide is used as a reducing agent for dyeing of sulfur dyes; even two sodium sulfite is used as a reducing agent sulfur reduction dyes. For ease of use, the sulfur dyes use sodium metabisulfite or sodium formaldehyde sulfoxylate substituent sulfonic acids to get water-soluble sulfur dye, and the dye can directly dyeing without a reducing agent.
I. sulfur dyes that use sodium sulfide as a reducing agent
II. the curing VAT of hydrosulfite is used as a reducing agent
III. liquid sulfur dyes are developed in order to facilitate the processing and production of a new type of sulfur dyes.
Such dyes uses are similar to soluble VAT dye, the configurations can be directly add water according to proportional. It's no need to add a reducing agent, only partially light color dye should add some sodium sulfide, and such dye color spectrum is wide.
There are two mehods of industrial production of sulfur dyes:
I. Baking Raw materials of aromatic amines, phenols or nitro compounds with sulfur or polysulfide baking at a high temperature to produce yellow, Orange and Brown sulfur dyes.
II. Boiling Raw materials of aromatic amines, phenols or nitro compounds with sodium polysulfide heated to boiling in water or organic solvents to produce black, blue, green sulphur dyes.