Sulfur dye

Sulfur dyes are a class of sulfur-containing dyes with complex molecular structures. It is generally prepared by heating, such as vulcanization, an organic compound such as an aromatic amine or an aminophenol with sulfur or sodium polysulfide. Most of the sulphur dyes are insoluble in water. When dyeing, they need to be dissolved in sodium sulfide or alkaline powder solution to reduce them into leuco, and then oxidized by fibers to form color. They are classified into two types, sulphur dyes and sulfurized vat dyes, depending on the dyeing conditions required. The former is reduced with sodium sulfide as a reducing agent; the latter is reduced with a safety powder as a reducing agent, and its dyeing fastness and performance are between the sulphur dye and the vat dye, which is a higher-grade sulphur dye. In 1873, the polysulfide was melted by Groissant et al. to form the initial sulphur dye. China began to produce sulphur dyes in 1918. Mainly used for dyeing plant fibers. It is characterized in that it contains a sulfur atom in the molecule and reacts with a reducing agent such as sodium sulfide to form a colloid which is soluble in water, dyes the fiber, and is oxidized by air to become an insoluble dye. The color light is not very bright and can make the fiber brittle. But generally washable and light fast. There are also soluble sulphur dyes, which are soluble in water and are convenient to use. The resulting sulphur dye is a mixture of various reaction stages. After 1950, continuous dyeing of sulphur dyes began to appear. However, due to the emergence of reactive dyes and advanced direct dyes, especially light-resistant direct dyes, after the 1950s, sulphur dyes tend to be unsalable, but It is still used because of factors such as cheap. The sulphur dyes are simple in manufacturing process, low in cost, washable and light-resistant, but the color is not bright, can be dyed dark, suitable for plant fiber and counterstaining, and is more popular among rural users. In addition to the color is not bright, the dye is incomplete, lacking red and purple, and the coloring power is low, the amount is large, so it is limited in application, but it is still the largest and widely used dye in China.