Acid dyes are often sodium nitrate salts of aromatic compounds. Since this type of dyeing needle is usually dyed in an acidic solution, it is an acid dye. Acid dyes are mainly used for dyeing wool. They can also be used for dyeing silk, polyester and leather. They can also be used in the manufacture of ink, paper, soap and as color lakes.
According to differences in chemical structure, dyeing conditions, etc., acid dyes can be divided into strong acid dyes, weak acid dyes, and acid mordants. Dyes, acid metal complex dyes.
1. Strong acid dye
This is the earliest developed acid dye, which can dye wool and leather in acid medium. It is also called acid level dye.
Strong Acid dyes have a simple molecular structure, low molecular weight, contain sulfonic acid groups or cherry acid groups, and have little affinity for wool. , can migrate on wool, so the color can be evenly dyed.
When dyed with strong acid dyes, although the color is bright, The level dyeing property is good, but the dyeing is not deep, the fastness to moisture treatment is not good, and it is not resistant to shrinkage. When dyeing wool in a strong acidic medium, it will damage the strength of the wool. The wool feels bad after dyeing, and the acid fastness is also weaker than the former. In order to overcome the adverse effects of strong acid dyes on dyed fibers, industrial improvements have been made to produce weak acid dyes, metal mordant dyes and complex dyes.
2. Weakly acidic dyes
are based on strong acidic dyes and increase the molecular weight , which generates weakly acidic dyes, also known as acidic shrink-resistant dyes. The molecular structure of this type of dye is slightly complex. As the molecular weight increases, the affinity for wool is greater, so wool can be dyed in a weakly acidic medium. During dyeing, in addition to the salt bond between the dye molecules and the wool molecules, there is also non-polar van der Waals attraction between the two molecules. combined with each other. Therefore, the affinity between the dye molecules and wool molecules increases, the washing fastness of the dye increases, and the dyeing becomes darker. It has no effect on the strength of wool during dyeing, but the solubility of the dye in the dye bath is low.
3. Metal mordant and complex dyes
Metallic mordant refers to the treatment with metal mordant during the dyeing process, or the introduction of metal atoms during the manufacturing process of the dye to improve the performance of the dye. Any acid dye that can increase its fastness after being treated with a metallic mordant is called acid mordant dye.
Mordant is a method of dyeing A method of improving the light fastness of original acid dyes by adding metal salts (such as salt or copper salts) to the dye. This method can also be divided into three types: front mordant, post mordant, and co-mordant. The wool fiber is first treated with a mordant, and then treated with an acid mordant dye, which is called front mordant; after the wool is dyed with the acid dye first, then heavy dye is added. Those with acid mordant dyes are called post-mordants; wool dyed with acid mordant dyes and treated with heavy acid mordants at the same time are called co-mordanters.
The advantages of acid mordant dyes are lightfastness, washability and shrinkage resistance, and high dye fastness. The disadvantage is that the color is dark. The dyed material after treatment with mordant will change color, so it is not easy to match the color.
Acidic metal complex dyesrefers to When preparing dyes, metal atoms have been introduced into azo dye molecules to form metal complexes. The ratio of metal atoms to dye components in the molecules of this type of dye is 1:1. Therefore, it is also called 1:1 metal complex dye. When dyeing wool with 1:1 metal complex dyes, it still needs to be carried out in a strong acidic medium. Therefore, it still affects the strength and feel of wool fibers. However, because metal complex dye molecules can form complexes with wool fiber molecules, dyeing is The light fastness of the material is improved.
