How Does Acid Dye Dye?

2019-01-07

Acid dyestuff dyeing is an important dyestuff for nylon dyeing. If the PH value is low at the time of dyeing (PH<3=), the imino in the molecular chain can also be positively ionized (-n +H2-) to bind to the dye anion. In addition, hydrogen bond and van der Waals force also play an important role in the dyeing of acid dyes with weak acid or neutral bath dyeing. Because the amino content of the nylon end is higher than that of light music, when two or more dyes are used for color matching, dyestuff with better compatibility should be selected.

Nylon molecules are linear molecules, molecular chain without branch chain and large side group, but there are many groups can form hydrogen bonds. Dyestuff molecules are easy to interfere with fiber molecules, with a greater van der Waals force, dye and fiber easy to form hydrogen bonds, therefore, the affinity of acid dyes to nylon is generally higher than wool. The saturation value of strong acid dyestuff on nylon is 2.3%, and that of weak acid dyestuff is 5%~5.2%. Therefore, weak acid dyes are commonly used to dye nylon, with the help of van der Waals force and hydrogen bond to improve the dye on the rate.

Polyamide acid dyes with strong, is generally is not deep, this is because the group the proportion of different sexes (polyamide synthesis of acetic acid and benzoic acid is commonly used to adjust molecular weight, amino by acylation, part of the end of the macromolecular in the form of acetyl press and benzamide save big, amino content than the carboxyl content is low, also found ring amide group in PA6). Therefore, the typical levelling acid dye dyeing, that is, only by coulomb force dyeing, it is difficult to dye deep color.

Acid dyestuffs can also be used to dye polyurethane, because there are amides, ureas and carbamates in polyurethane molecules, and the binding forms are van der Waals force, hydrogen bond and ionic bond, but the dyeing effect is not ideal. In particular, strong acid dyes, dyes almost all fixed on the surface of the fiber, rarely able to infiltrate into the fiber, soapy fading is serious, solid color fastness is very poor. Weak coordination dyes than strong acid dyes dyeing percentage slightly higher, washing fastness is good, but the soapy fastness is still not ideal, the dye also can not infiltrate into the fiber, poor light fastness.

Neutral dyeing

Neutral dyes are 1:2 acid mordant dyes, metal atoms and dye molecules in 1:2 ratio. In the dye molecules do not contain sulfonic acid group and other water-soluble groups, but only water-soluble hydrophilic groups, such as sulfonylamino (-so2nhr), methyl sulfone group (-so2ch3), they are generally in neutral or weak acid medium dyeing, this is the origin of the name.

Nylon molecules have a large number of amino carboxyl terminal group, can be used in neutral dyes