The so-called tarification of dyes refers to the process in which dye particles and surfactants agglomerate into coal tar-like substances under high temperature conditions.
There are usually the following 4 factors that cause dye tarization
Poor pretreatment and insufficient purification. The oil (lubricant, emulsifier, antistatic agent, etc.) contained on the fabric and grease (sticky dirt during processing) are brought into the dyeing bath and brought into the dyeing bath under high temperature conditions. When dyeing, once these water-repellent oil stains come into contact with the dye particles, they will adsorb each other, accumulate more and more, and finally form a tar-like substance.
When using non-ionic auxiliaries whose cloud point is lower than the dyeing temperature or non-ionic and anionic composite auxiliaries (such as refining agents) for pretreatment, if the washing is not clean, a large amount of them will be brought into the dyeing bath. As the temperature rises, the non-ionic components gradually lose their water solubility, or separate from the anionic components to form hydrophobic oil particles. At this time, the dye particles in an unstable state in the dye bath facilitate the precipitation of these hydrophobic oil particles. At this time, the dye particles in an unstable state in the dye bath adsorb each other with these hydrophobic oil particles to form a thick colored tar that adheres to the fabric and produces color stains.
When dyeing with non-ionic and anionic composite auxiliaries such as high-temperature levelling agents, if the dosage is too high (above 2g/L) or mixed with the dye at a high concentration, and directly added to the water bath above 90 ℃, due to the non-ionic group The binding force between the anionic component and the anionic component is weak, and the cloud point of the non-ionic component is not high enough, which often causes the non-ionic component to liberate from the colloidal particles of the anionic component and aggregate with the dye into a tarified substance.
When anionic surfactants such as diffusing agents are used for dyeing, if the additives are poorly dissolved, the granular dyes and additives will adsorb each other. Once they are put into the pot, they will form a viscous paste that adheres to the fabric. Produce color stains.