The dyeing mechanism of sulfur dyes

Features

Sulfur dyes are a type of sulfur-containing dyes. The molecules contain sulfur bonds composed of two or more sulfur atoms. When used, they are reduced to leuco body, dissolved in water, and dyed fibers. The dyeing characteristics of sulfur dyes vary depending on the type of dye. Sulfur dyes have high washing fastness and strong applicability. Although the rubbing fastness and vividness are not as good as reactive dyes, their color fastness and light fastness are better than reactive dyes. Sulfur dyes use less salt and consume less water. less. Sulfur dyes are organic compounds containing nitro and amino groups, most of which are formed by reacting with sulfur and sodium sulfide at high temperatures. Many sulfur dyes do not have a certain chemical formula. The dyeing principle of sulfur dyes is similar to that of vat dyes. They form a water-soluble leuco body dyeing fiber with affinity through chemical reduction reaction, and then bind tightly to the fiber through an oxidation process.

Sulfur dyes are insoluble in water. Sodium sulfide or other reducing agents are needed to reduce the dyes to soluble leucos. It has affinity for fibers and dyes the fibers, and then restores its insoluble state after oxidation and color development and is fixed on the fibers. So sulfur dye is also a kind of vat dye. Sulfur dyes can be used for dyeing cotton, linen, viscose and other fibers. Its manufacturing process is simple and low in cost. It can dye single colors and can also match colors. It has good light fastness and poor abrasion fastness. The color spectrum lacks red and purple, and the color is dark, suitable for dyeing deep colors.

Dyeing mechanism

The sulphur dye is reduced and dissolved into a dye solution, and the dyed leuco body formed is absorbed by the cellulose fiber and subjected to air oxidation treatment to make the cellulose fiber show the desired color.

Sulfur dye matrix has no affinity for fibers, and its structure contains sulfur bonds, disulfide bonds or polysulfide bonds, which are reduced to sulfhydryl groups under the action of sodium sulfide reducing agent and become water-soluble leuco sodium salt. The reason why the leucosome has a good affinity for the cellulose fiber is that the dye has a larger molecule, which in turn produces a larger van der Waals force and hydrogen bond force with the fiber.