Basic Understanding of Various Properties of Printing and Dyeing Auxiliaries

1. The solubility of dyeing auxiliaries and their stability to hard water and metal ions

It is necessary to have a basic understanding of the solubility of dyeing auxiliaries and their stability to hard water and metal ions. For example, the solubility of anionic surfactants in alkaline is greater than that in acids, while cationic surfactants are on the contrary. Amphoteric surfactants have both anionic and cationic characteristics, while nonionic surfactants have less effect. The solubility of the first three surfactants increases when the temperature rises, while the solubility of non-ionic surfactants decreases with the rise of temperature. Therefore, when there is a cloud point, the cloud point must be higher than the use temperature. Otherwise it will lose its efficiency and dyeing auxiliaries can't play a role.

The cloud point increases with the increase of EO number, the amount of anionic dyeing auxiliaries incorporated, but decreases with the increase of electrolyte content. If it is used to add high temperature and high pressure dyeing as a leveling agent or dispersant, it will cause precipitation in the dyeing solution because the use temperature greatly exceeds its cloud point (usually about 75~C), which will not work, but will condense the dye and cause color points. Silicone defoaming agent are emulsions of methyl silicone oil or ethyl silicone oil emulsified with white carbon black. If a silicon oil emulsifier with a low cloud point is used, the same problems mentioned above will occur, which is extremely harmful to textile dyeing factories.

2. Acid and alkali resistance of dyeing auxiliaries

The acid and alkali resistance of dyeing auxiliaries is extremely poor. Anionic surfactants are generally alkali resistant but not acid resistant. Among them, phosphate esters have the best alkali resistance, and carboxylic acids have the worst acid resistance. Cationic surfactants are generally acid resistant but not alkali resistant. Nonionic surfactants can withstand weak alkalis and weak acids, but can't withstand strong acids and strong alkalis.