What are the functions of sulfur dyes？

What are the functions of sulfur dyes？

Sulfurized dyes are a kind of dyes which are made from aromatic or phenolic compounds, sulfurized with sulfur or polysulfide, and contain sulfur bonds (single sulfur bond, double sulfur bond, multi sulfur bond) in molecules.

1) Sulfurized dyes are insoluble in water. When dyeing, they are usually reduced with sodium sulfide to form leucosomes, which have affinity for cellulose fibers. The fibers are dyed by van der Waals force and hydrogen bonds, and then oxidized by air or oxidant. The original insoluble dyes are formed on the fibers and fixed on the fibers.



2) Sulfur dyes are cheap and easy to use. They are mainly used for dyeing cotton and other cellulose fibers. The main colors of dyes are yellow brown, grass green, red brown, blue and black. The dyed products are not resistant to chlorine and the fastness to sunlight is not as good as vat dyes. The polysulfide bonds in sulfide dyes can be oxidized by air to produce acid substances such as sulfuric acid. The fibers of dyed textiles will gradually become brittle during storage and transportation, so it is necessary to carry out anti embrittlement treatment. Sulfide dyes are mainly used for deep dyeing of cotton fabrics.



3) Sulfurized vat dyes are also insoluble sulfur-containing dyes made by sulfurization, and sodium hydrosulfite is used as reducing agent in dyeing. The chemical structure of sulfurized vat dyes is similar to that of sulfurized dyes, and the dyeing performance, color brightness and color fastness are between those of sulfurized dyes and vat dyes. Compared with sulfurized dyes, the sulfur bond in the molecular structure of sulfurized vat dyes is stronger and more stable than that of sulfurized dyes, and the color fastness is better than that of sulfurized dyes, especially the color fastness to chlorine bleaching. Sulfurized vat dyes are mainly dark blue, grass green, black, etc., which can match with vat dyes or sulfurized dyes.