Classification of various dyes

1. Classified by chemical structure

Divided into: azo dyes, anthraquinone dyes, arylmethane dyes, indigo dyes, sulfur dyes, phthalocyanine dyes, nitro and nitroso dyes, in addition to other structural types of dyes, such as methyl and polymethine dyes , Stilbene dyes and various heterocyclic dyes, etc.

2. Classification by application performance

Divided into: direct dyes, acid dyes, cationic dyes, reactive dyes, insoluble azo dyes, disperse dyes, vat dyes, sulfur dyes, polycondensation dyes, fluorescent brighteners, in addition, there are oxidation dyes used in textiles (such as aniline black ), solvent dyes, polypropylene dyes and food colorings for food.

3. Introduction to various dyes

1). Direct dyes

Structural properties: Direct dyes are a kind of water-soluble anionic dyes. Most of the dye molecules contain sulfonic acid groups, and some have carboxyl groups. The dye molecules and cellulose molecules are combined by van der Waals forces and hydrogen bonds.

2). Acid dyes

Structural properties: acid dyes are a type of water-soluble anionic dyes. The dye molecule contains acidic groups such as sulfonic acid group and carboxyl group, which usually exists in the form of sodium salt. In the acid dye bath, it can bond with the amino group in the protein fiber molecule by ionic bond, so it is called acid dye.

3). Cationic dyes

Structural properties: Cationic dyes are soluble in water and are in a cationic state. Early dye molecules have basic groups such as amino groups, often in the form of acid salts.

4). Reactive dyes

Structural properties: reactive dyes are also called reactive dyes. The molecular structure of this type of dye contains active groups, which can covalently bond with the hydroxyl and amino groups in the fiber molecule during dyeing to firmly dye the fiber.

5). Insoluble azo dyes

Structural properties: in the dyeing process, this kind of dyes directly react on the fiber by the diazo component (color base) and the coupling component (chromanol) to form an insoluble lake and dye it. This dye is called an insoluble couple. Nitrogen dye.

6). Disperse dyes

Structure and properties: Disperse dyes are non-ionic dyes with simple structure and extremely low water solubility. They mainly exist as dispersions of tiny particles in the dye bath. The chemical structure of disperse dyes is mainly based on azo and anthraquinones, as well as heterocyclic disperse dyes.

7). Vat dyes

Structural characteristics: Vat dyes are mostly polycyclic aromatic compounds, and their molecular structure does not contain sulfonic acid groups, carboxylic acid groups and other water-soluble groups. Their basic feature is that they contain two or more carbonyl groups in the conjugated double bond system of the molecule, so they can reduce the carbonyl group to a hydroxyl group under the action of sodium hydroxide, and become a soluble hidden in the alkaline aqueous solution. Sodium salt of chromosome.

8). Sulfur dyes

Structural properties: Sulfur dyes are a type of water-insoluble dyes, which are generally prepared by mixing aromatic amines or phenolic compounds with sulfur or sodium polysulfide by heating. This process is called vulcanization.

9). Polycondensation dyes

Structural properties and characteristics: Condensation dyes are a type of dyes that can covalently bond between molecules of the dye itself or with compounds other than fibers during or after dyeing, thereby increasing the molecules. The polycondensation dye molecule contains thiosulfuric acid group (-SSO3Na), which can break off the sulfite from the thiosulfuric acid group under the action of sodium sulfide and sodium polysulfide, and form -S-S between the dye molecules. -Bond, which makes two or more dye molecules bind into an insoluble state and fixed on the fiber.

10). Fluorescent brightener

Structural properties: fluorescent brighteners can be regarded as a kind of colorless dyes. After they are dyed on fiber, paper and other substrates, they can absorb ultraviolet rays and emit blue light, thereby offsetting the excessive yellow light reflection on the fabric. The yellow feeling of the product produces a white and dazzling effect visually.