How to choose dyeing auxiliaries for high temperature and high pressure dyeing polyester?

Domestic disperse dyes contain about 1/2 amount of anionic dispersants. The reason is: in the molecular structure of disperse dyes, there is no hydrophilic group (-SO3Na), so it has high hydrophobicity and low solubility. In water, due to the repulsion of water, the uncharged dye particles will naturally aggregate, from small particles to large particles, resulting in the so-called "crystal growth" or "agglomeration" phenomenon. A stable dye liquor cannot be prepared.

However, these anionic dispersants added in the commercialization process of domestic disperse dyes have the defect that the higher the water temperature, the worse the dispersing effect. That is, the "bonding method" (the cohesion of the two) between the dye particles (grains) and the dispersant molecules will gradually weaken with the increase of the water temperature.

The hydrophilic micelles formed by both dye dispersants at lower temperatures (<70°C) will be disintegrated to varying degrees under the action of high temperature and the shear force generated by the flow of dye liquor and the operation of the fabric, and even the entire The dispersion system will be destroyed. As a result, the dyes lose their stability in water, and lead to significant changes in dyeing properties (dyeing rate, balanced dyeing percentage, level dye penetration, color brightness, dyeing fastness), which cause serious harm to dyeing quality.

Therefore, the addition of dispersant is of great significance to the preparation of disperse dyes with good stability at lower temperature. However, it is powerless to maintain the dispersion stability of disperse dyes at high temperature (>100℃).

Therefore, when disperse dyes dye polyester light colors, due to the low concentration of dyes, the amount of dispersant introduced is not enough to ensure the stability of the dye liquor. Therefore, an appropriate amount (0.5gL) of dispersant should be added when dispersing dyes. This has a positive effect on the dispersion and stability of the initial dye solution, but has a weak effect on maintaining the dispersion stability of the dye solution in the warm stage. When disperse dyes dye polyester with dark colors, due to the high concentration of dyes, more dispersants are brought in, which can generally meet the needs of preparing disperse dyes (chemicals) at lower temperatures, so no additional dispersants are usually added. In order to ensure the dispersion stability of disperse dyes in the process of heating, heat preservation, and cooling, and effectively prevent dyestuffs from coagulating and causing dyeing defects, it is necessary to apply an appropriate amount (1-2g/l) of high-temperature dispersing and leveling agent for dyeing.

At present, most of the high-temperature dispersing and leveling agents available in the market belong to the complex of anionic surfactants and non-ionic surfactants. Use both in combination.