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A brief description of acid dyes

2021-04-01

A brief description of acid dyes

1: History and characteristics of acid dyes

1) History of acid dyes: In 1868, the earliest acid dye, triarylmethane acid dye, appeared, which had strong dyeing ability but poor fastness; In 1877, the first acid dye Acid Red A used for wool dyeing was synthesized, and its basic structure was determined; After 1890, acid dyes with anthraquinone structure were invented, and their chromatograms became more and more comprehensive; So far, there are nearly hundreds of acid dyes, which are widely used in the dyeing of wool, silk, nylon and other fibers. 2) Features of acid dyes:

The acidic groups in acid dyes are generally sulfonic acid groups (-SO3H), which exist on the dye molecule in the form of sodium sulfonate (-SO3Na). Some dyes also use sodium carboxylate (-COONa) as acid Group. It is characterized by good water solubility, bright color, complete chromatogram, simpler molecular structure than other dyes, lack of a long conjugated coherent system in the dye molecule, and low directness of the dye.

2. Classification of acid dyes 1) According to the molecular structure of the dye matrix: Azos (60%, extensive chromatogram) Anthraquinones (20%, mainly blue and green) Three aromatic methanes (10%, purple, green) Heterocyclic (10%, red and purple series) 2) Classified by dyeing pH: Strong acid bath acid dyes: dyeing pH value 2.5-4, good light fastness, but poor wet processing fastness, bright color, good level dyeing; Weak acid bath acid dyes: dyeing pH value is 4-5, the proportion of sulfonic acid groups in the dye molecular structure is slightly lower, so the water solubility is slightly worse, the wet processing fastness is better than the strong acid bath dyes, and the leveling property is slightly worse. Neutral bath acid dye: dyeing pH value is 6-7, the proportion of sulfonic acid group in the dye molecular structure is lower, the dye solubility is low, the level dyeing property is poor, the color is not bright enough, but the wet processing fastness is high.

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