Acid Dyestuff

An acid dye is a type of dye which contains a soluble group such as a sulfonic acid group, a carboxyl group or a hydroxyl group in the molecular structure and needs to be dyed in an acidic or neutral dye bath. According to the chemical structure, it can be divided into azo type, triphenylmethane type, hydrazine type, oxonium type, nitroso type and pyrazolone type. Acid dyes are widely used, mainly for the dyeing of protein fibers (such as wool, silk) and polyamide fibers, and are directly related to polyamide fibers, protein fibers, etc., and need to be dyed in an acidic solution. Mainly used for dyeing nylon, wool, leather, silk, etc. The use of acid dyes for dyeing paper is far less popular than direct dye or basic dyes. Acid dyes can be classified into strong acid dyes, weak acid dyes, acid medium dyes, acid metal complex dyes and neutral dyes depending on the molecular structure and dyeing conditions of the dye. Acid dyes are mainly used for dyeing wool, silk, leather and nylon, with bright color and complete chromatogram. Strong acid dyes are small types of dye molecules, have low affinity for wool fibers, and need to be dyed in a strong acid dye bath (pH ≤ 4), with bright color and good leveling. The chemical structure types mainly include azo type, hydrazine type, triarylmethane type and oxon type. For example: Acid Yellow 2G (CI Acid Yellow 17), Acid Indigo (CI Acid Blue 25), Acid Lake Blue A (CI Acid Blue 7), and Acid Rose B (CI Acid Red 52). The weak acid dye molecules are more complex with acid dyes, and the relative amount of water-soluble groups contained in the whole molecule is relatively small. The affinity for wool fibers is relatively large, and it can be dyed in weakly acidic or near-neutral dye baths. In addition to the ionic bonding of the anion of the acid dye to the cation of the wool molecule during dyeing, it is also combined by the non-polar van der Waals attraction between the two molecules. Therefore, the weak acid dye has poor leveling property and good washing fastness, so it is also called a fluff resistant dye. The chemical structure types are mainly azo type and 蒽醌 type. For example: weakly acidic black BR (CI Acid Black 24), weak acid blue RAW (CI Acid Blue 80). When the acid medium dye is dyed, the dye metal chromium compound is formed on the fiber after being treated with the metal mordant (chromium salt), thereby improving the light fastness and moisture fastness of the dye. However, the dyed products after treatment have a darker shade, the color shade is not easy to control, the color matching is difficult, and the dyeing procedure is cumbersome. Acid metal complex dyes are a class of acid dyes that form internal complexes with certain transition metal elements such as copper, complex, cobalt, and the like. The difference from the acidic medium dye is that the acid metal complex dye is a dye metal complex of the dye and the complexing agent, and then dyed, and the medium dye is dyed first, and then the dye metal complex is formed on the fiber. The former is easy to dye.