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Classification of dyes
Aug 14, 2018

l. Direct Dyes These dyes are named because they can be directly dyed on cotton, hemp, silk, wool and other fibers without relying on other chemicals. Its dyeing method is simple, complete with chromatogram and low cost. However, its washing fastness and light fastness are poor. For example, the proper post-treatment method can improve the fastness of the dyed product.

2. Insoluble Azo Dyes These dyes are essentially two intermediates of the dye which are coupled to the fabric to form an insoluble pigment. Because it is added during the printing and dyeing process, it is also called ice dye. Because of its good washing and light fastness, the chromatogram is relatively homogeneous, the color is rich, and the price is low, so it is widely used in the dyeing and printing of cellulose fiber fabric.

3. Reactive dyes Also known as reactive dyes. These dyes are new dyes that were developed in the 1950s. Its molecular structure contains one or more active genes that, under appropriate conditions, can chemically react with the fibers to form covalent bonds. It can be used for dyeing various textiles such as cotton, hemp, silk, wool, viscose, nylon and vinylon.

4. Reducing dyes These dyes are insoluble in water and are dyed by reduction and dissolution in a strong alkali solution by means of a reducing agent. After dyeing, the oxidation is reconverted into an insoluble dye and firmly fixed to the fibers. Due to the strong alkalinity of the dye liquor, it is generally not suitable for dyeing protein fibers such as wool and silk. These dyes are complete in chromatography, bright in color and good in color fastness, but they are expensive and difficult to dye uniformly.

5. Soluble vat dyes It is a dye that can be directly dissolved in water after it is made into a sucrose sodium salt of a vat dye. It is called a soluble vat dye and can be used as a dye for various fibers. This type of dye has complete chromatogram, bright color, convenient dyeing and good color fastness. However, its price is higher than that of vat dyes, and its affinity is lower than that of vat dyes, so it is generally only suitable for dyeing light-colored fabrics.

6. Sulfur dyes Most of these dyes are insoluble in water and organic solvents, but can be dissolved in an alkali sulfide solution. After dissolution, the fibers can be directly dyed. However, because the dyeing liquid is too alkaline, it is not suitable for dyeing protein fibers. These dyes are homogeneous in chromatography, low in price, and good in color fastness, but the color is not bright.

7. Sulfurized vat dyes The chemical structure and manufacturing method of the sulfurized vat dyes are the same as those of general sulphur dyes, and their dye fastness and dyeing properties are between the sulphide and vat dyes, so they are called sulphur reduction dyes. Dyeing can be done with caustic soda-safety powder or sodium sulfide-safety powder.

8. Phthalocyanine dyes Phthalocyanine dyes often act as a dye intermediate to form condensation on the fabric and metal atom complexation to form a lake. At present, the chromatograms of these dyes are only blue and green, but because of the high color fastness and vivid color, it is very promising.

9. Oxidation Dyes Some aromatic amine compounds undergo complex oxidation and condensation reactions on fibers, which become insoluble dyes called oxidation dyes. Essentially such dyes can only be said to be pigments that are firmly attached to the fibers.

10. Polycondensation dyes A different type of dye precursor is used to introduce a temporary dye containing a thiosulfate group in its structure. At the time of dyeing, the dye can be condensed into macromolecules and deposited in the fibers, thereby obtaining excellent color fastness.

11. Disperse dyes These dyes have low solubility in water, very fine particles, and are dispersions in dye liquors. They are nonionic dyes and are mainly used for dyeing polyester yarns.

12. Acid dyes These dyes are water-soluble and mostly contain water-soluble genes such as sulfonic acid groups and carboxyl groups. Protein fibers can be directly dyed in acidic, weakly acidic or neutral media, but the wet handling is poor.

13. Acidic media and acidic median dyes These dyes include two. A dye itself does not contain metal ions for mordant dyeing, and the fabric is treated with a mordant to obtain metal ions before or after dyeing; the other is to complex the dye with metal ions before the dye is produced to form a medium containing the medium. Complex dyes, which do not require mordant treatment before or after dyeing. These dyes have better light fastness and wash fastness than acid dyes, but they are darker in color and are mainly used for wool dyeing.

14. Alkaline and cationic dyes Basic dyes, formerly known as base-based dyes, are the first synthetic dyes. They are also called cationic dyes because they are positively dissolved in water. These dyes are bright in color, complete in chromatography, and have high color fastness, but are not easily leveled, and are mainly used for dyeing acrylic fibers.

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