Textile dyes are used for dyeing textiles. According to the properties and usage of dyes, they can be categorized into vat dyes, sulfur dyes, reactive dyes, azoic dyes, acid dyes, cationic dyes, direct dyes, and disperse dyes.
- Acid Dyes
Acid dyes contain acidic groups in their dye molecules and are also known as anionic dyes. They bind to the amino groups in protein fibers through ionic bonds. They are suitable for acidic, weakly acidic, or neutral conditions. These dyes are water-soluble and primarily used for dyeing wool, silk, and nylon. They exhibit bright colors but have poor wash and light fastness and come in a wide variety of types.
- Cationic Dyes (Basic Dyes)
Cationic dyes, also known as basic or alkaline dyes, dissolve in water in cationic form. In an aqueous solution, cationic dyes ionize to form positively charged colored ions. The cation of the dye can combine with the acidic groups of the third monomer in the fabric, thereby dyeing the fibers. They are suitable for acrylic, polyester, nylon, cellulose, and protein fibers.
- Direct Dyes
Direct dyes are dyes that can be heated and boiled in neutral and weakly binding media without the need for a mordant. Direct dyes form hydrogen bonds and van der Waals forces between the direct dye and cotton fibers. They can be directly used for dyeing various cellulosic fibers. They have poor wash fastness and varying light fastness, but the wash fastness of modified direct dyes can be improved.
- Disperse Dyes
Disperse dyes are small molecule textile dyes that do not contain water-soluble groups in their structure. When dyeing, a dispersant is needed to evenly disperse the dye in the dye solution in order to dye polyester and other fibers. Disperse dyes are mainly used for dyeing chemical fibers such as polyester, acetate, and polyamide fibers. They exhibit bright colors, good wash fastness, and have a wide range of applications.
- Reactive Dyes
Reactive dyes are a new type of water-soluble textile dyes. They contain active groups that can react with hydroxyl groups in cellulose and amino groups in protein fibers. During dyeing, they form covalent bonds with the fibers, creating “dye-fiber” compounds.
- Sulfur Dyes
Dyes dissolved in alkaline sulfides are suitable for fabrics made from cellulose rather than protein. They produce colors like gray, navy blue, black, and brown. They exhibit good light fastness, wash fastness, and chlorine bleach fastness. However, these fabrics may deteriorate over long-term storage.
- Vat Dyes
Vat dyes refer to the dyeing of fibers under alkaline conditions, reducing the color, and then converting the insoluble dye on the fiber into a water-soluble reduced dye, which is used for dyeing cellulose fibers. They have excellent light, wash, and chlorine bleach fastness.
