What is Acidic Dye?

Acid dyes refer to the dye molecules containing acidic groups, also known as anionic dyes, which can be combined with amino groups in protein fiber molecules by ionic bonds, and are applicable under acidic, weakly acidic or neutral conditions. Mainly azo and anthraquinone structures, a few are aromatic methane structures. Dyes and colors are generally compounds that have their own color and can give other substances a clear and firm color in a molecular or dispersed state. ^[1]

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Acid dyes refer to the dye molecules containing acidic groups, also known as anionic dyes, which can be combined with amino groups in protein fiber molecules by ionic bonds, and are applicable under acidic, weakly acidic or neutral conditions. Mainly azo and anthraquinone structures, a few are aromatic methane structures. Dyes and colors are generally compounds that have their own color and can give other substances a clear and firm color in a molecular or dispersed state. ^[1]

The acid dye has complete chromatography and bright color. The fastness to sunlight and wet treatment vary greatly with different dyes. Compared with direct dyes, acid dyes have a simple structure and lack long conjugated double bonds and coplanarity structures, so they lack directness to cellulose fibers and cannot be used for cellulose fiber dyeing. Different types of acid dyes have different molecular structures, so they have different dyeing properties and different dyeing methods.

Acid dyes are divided into strongly acidic, weakly acidic, acidic mediators, acidic complex dyes, etc. according to their chemical structure and dyeing conditions.

Strong acid dye

One of the earliest developed acid dyes requires dyeing in a strong acid dyeing bath. Its molecular structure is simple, its molecular weight is low, and it contains sulfonic acid groups or carboxyl groups. It is uniform, so it is also called acid leveling dye, but the color is not deep, the washing fastness is poor, and the wool is damaged during dyeing, and the wool feel is poor after dyeing. Such as acid red G (CI acid red 1).

Weak acid dyes

Weak acid dyes are produced in strongly acidic dyes by increasing molecular weight, introducing groups such as arylsulfone groups, or introducing long carbon chains. The molecular structure is more complex, and it has a greater affinity for wool. It can dye wool in a weakly acidic medium, has no damage to wool, has a darker color, and has improved fastness, but uneven dyeing. Such as weak acid brilliant blue RAW (ie CI acid blue 80).

Acid dye

Acid dyes that form metal complexes on fabrics after treatment with certain metal salts (such as chromium salts, copper salts, etc.) as mordants. Mordling procedures are more complicated, but can get dyeing products with good properties such as lightfastness, washability and rubbing fastness, such as acid media black T (CI media black 11).

Acid dye

It is formed by complexing some acid dyes with metals such as chromium and cobalt. It is soluble in water, and its dyeing products have good light fastness and light fastness. Its dye precursor is similar to acid mordant dyes, but in the preparation of dyes, metal atoms have been introduced into azo dye molecules. The ratio of metal atoms to dye molecules is 1: 1, so it is also called 1: 1 metal complex dye. No further mordant treatment is required during dyeing. Such as acid complex yellow GR (ie CI acid yellow 99).

Another type of acid complex dye does not contain sulfonic acid groups, but contains hydrophilic groups such as sulfonylamino. The ratio of metal atom to dye molecule in the molecule is 1: 2, so it is also called 1: 2 metal complex dye. It is dyed in a neutral or weakly acidic medium, so it is called a neutral dye. Such as neutral gray 2BL (CI acid black 60).

Acid dyes include azo type, anthraquinone type, and triarylmethane type, but most of them belong to azo dyes. The production of acid complex dyes is similar to general dyes, but a step of complexing with metals must be added, such as neutral gray 2BL, which is first diazotized with 2-aminophenol-4-sulfonamide, and 1-acetylamino-7 -Naphthol coupling and complexation with sodium chromium salicylate.