1. Classification according to chemical structure

Azo dyes, anthraquinone dyes, arylmethane dyes, indigo dyes, sulfur dyes, phthalocyanine dyes, nitro, and nitroso dyes.

  1. according to the application performance classification

Divided into direct dyes, acid dyes, cationic dyes, reactive dyes, insoluble azo dyes, disperse dyes, reducing dyes, sulfur dyes, condensation dyes, fluorescent whiteners, in addition, there are oxidation dyes used for textiles (eg, aniline black), solvent dyes, polypropylene dyes, as well as food pigments used for food, and so on.

  • Introduction to various dyes
Dye Name Characteristics of structural properties Dyeing Objects and Methods
direct dye Direct dyes are a class of water-soluble anionic dyes. Most of the dye molecules contain sulfonic acid groups, some have carboxylic acid groups, the dye molecules and cellulose molecules are combined with van der Waals forces and hydrogen bonding Direct dyes are mainly used for dyeing cellulose fibers, but can also be used for dyeing silk, paper and leather. When dyeing, the dyes are directly dyed on the fibers in the dye solution, and adsorbed on the fibers through van der Waals force and hydrogen bonding.
acid dye Acid dyes are a class of water-soluble anionic dyes. The dye molecule contains acidic groups such as sulfonic acid group and carboxyl group, usually in the form of sodium salt, which can be combined with amino group in protein fiber molecule by ionic bond in acidic dyeing bath, so it is called acidic dye. Commonly used in silk, wool and polyamide fibers and leather dyeing. Acid dyes, through its own affinity on the dyeing fiber, and ionic bonding and fiber binding; acid mordant dyes, its dyeing conditions and acid dyes are similar, but need to be through the role of certain metal salts, the formation of chelates in the fiber in order to obtain a good washing performance; acid-containing dyes with mordant dyes, there are a number of acid dyes with chelating metal ions in the molecule, the tendency of hydrolysis is small, dyeing fastness is good.
cationic dye Cationic dyes are soluble in water in a cationic state. Early dye molecules had basic groups such as amino groups, often in the form of acid salts. It is mainly used for the dyeing of polyacrylonitrile fibers, and can combine with the carboxyl negative ions in the protein fiber molecules, such as silk, in the form of salt bonds when dyeing.
reactive dye Reactive dyes are also known as reactive dyes. These dyes contain reactive groups in their molecular structure, which can covalently bond with hydroxyl and amino groups in the fiber molecules during dyeing and firmly adhere to the fibers. Reactive dyes are mainly used for dyeing and printing of cellulose fiber textiles, but can also be used for dyeing wool and nylon fibers. The dyestuffs stain the fibers by their own affinity, after which they are firmly bonded to the fibers by covalent bonds in the presence of an alkali agent.
Disperse dye Disperse dyes are a class of non-ionic dyestuffs with a simple structure, extremely low water solubility, and exist mainly as dispersions of tiny particles in the dye bath. The chemical structure of disperse dyes is dominated by azo and anthraquinones, and there are also heterocyclic disperse dyes. Disperse dyes are mainly used for dyeing and printing of polyester fibers, but can also be used for dyeing of acetate fibers and polyamide fibers. The dyes must be evenly dispersed in the dye solution with the aid of a dispersant, and then all types of synthetic fibers are dyed.
Vat Dye Most of the Vat dyes belong to polycyclic aromatic compounds, which do not contain water-soluble groups such as sulfonic acid and carboxylic acid groups in their molecular structure. Their basic feature is that they contain two or more carbonyl groups in the conjugated double bond system of the molecule, so that the carbonyl groups can be reduced to hydroxyl groups under the action of the insurance powder and become soluble sodium salts of cryptochromes in alkaline aqueous solutions. Vat dyes are mainly used for dyeing cellulose fibers. When dyeing, they are reduced to water-soluble sodium salt of cryptochrome in alkaline solution containing reducing agent (e.g., Na2S2O4, sodium dithionite, commonly known as insurance powder), and then oxidized to become insoluble dyes again and fixed on the fibers.

 

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