Acid dyes refer to containing acidic groups in dye molecules, also known as anionic dyes, which can be combined with amino groups in protein fiber molecules by ionic bonds, and are suitable for acidic, weak acid or neutral conditions. The main ones are azo and anthraquinone structures, and a few are arylmethane structures. Dyes and colors are generally compounds that have their own color and can give other substances a bright and firm color in a molecular state or a dispersed state.

Strong acid dye

　　Basic Information

　　Chinese name: acid dye

　　Foreign name: Acid Dyes

　　Uses: Mainly used for dyeing wool, silk and nylon

　　Classification: divided into strong acid, weak acid,

　　Introduction

　　Acid dyes have complete chromatograms, bright colors, and the light fastness and wet fastness vary greatly with the variety of dyes. Compared with direct dyes, acid dyes have a simple structure and lack long conjugated double bonds and a homoplanar structure, so they lack directness to cellulose fibers and cannot be used for dyeing cellulose fibers. Different types of acid dyes have different dyeing properties and different dyeing methods due to different molecular structures.

　　Classification

　　Acid dyes are classified into strong acid, weak acid, acid medium and acid complex dyes according to their chemical structure and dyeing conditions.

　　Strong acid dye

　　One of the earliest developed acid dyes requires dyeing in a strong acid dye bath. Its molecular structure is simple, its molecular weight is low, it contains sulfonic acid or carboxyl groups, and it has little affinity for wool. It is uniform, so it is also called acid level dyeing dye, but the color is not deep, the washing fastness is poor, and the wool is damaged during dyeing, and the dyed wool feels poor. Such as acid red G (ie C.I. acid red 1).

　　Weak acid dye

　　In strong acid dyes, weak acid dyes are generated by increasing the molecular weight, introducing groups such as arylsulfone groups, or introducing long carbon chains. The molecular structure is more complex, and the affinity for wool is large. It can dye wool in weakly acidic medium without damage to wool. Such as weak acid brilliant blue RAW (ie C.I. acid blue 80).

　　Acid Mordant

　　Acid dyes that form metal complexes on fabrics after treatment with certain metal salts (such as chromium salts, copper salts, etc.) as mordant. Mordant dyeing procedures are more complicated, but dyeing products with better performance such as light fastness, washing fastness and rubbing fastness can be obtained, such as acid medium black T (ie C.I. medium black 11).

　　Acid complex dyes

　　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 excellent lightfastness and lightfastness. Its dye parent is similar to the acid mordant dye, but when preparing the dye, the metal atom has been introduced into the azo dye molecule, and the ratio of the metal atom to the dye molecule is 1:1, so it is also called 1:1 metal complex dye. No further mordant treatment is required for staining. Such as acid complex yellow GR (ie C.I. acid yellow 99).

　　Another type of acidic complex dyes do not contain sulfonic acid groups, but contain hydrophilic groups such as sulfonamido groups. The ratio of metal atoms to dye molecules in the molecule is 1:2, so it is also called 1:2 metal complex dyes. It is dyed in neutral or weak acid medium, so it is called neutral dye. Such as neutral gray 2BL (ie C.I. acid black 60).

　　Acid dyes include azo type, anthraquinone type, triarylmethane type, etc., but most of them belong to azo dyes. The production of acid complex dyes is similar to that of general dyes, but a process of complexing with metals must be added. - Naphthol coupling, and then complexed with sodium chromium salicylate.