Disperse dyes are mainly used for dyeing hydrophobic fibers such as polyester, spandex, nylon, and acetate fibers. With the continuous advancement of fiber dyeing technology, various types of leveling agents have achieved significant development.
1.Leveling agent for high-temperature dyeing
When using disperse dyes for high-temperature and high-pressure dyeing, uneven dyeing often occurs due to factors such as poor dispersibility, leveling property, and migration property of the dyes, as well as improper control of the heating rate. In particular, fine-denier polyester fibers have a very small linear density and an increased surface area, which accelerates the dyeing rate of the dyes. Additionally, the tight fabric structure makes it difficult for the dyes to penetrate thoroughly, resulting in more prominent uneven dyeing compared to conventional polyester fibers. The use of high-temperature dispersing leveling agents during dyeing can improve the leveling effect of the fabric and enhance product quality.
Generally, for non-ionic disperse dyes, non-ionic surfactants can be used as leveling agents. The two can form a hydrophobic combination, which can slow down the dyeing rate to achieve the purpose of leveling. Among non-ionic dispersing leveling agent molecules, polyoxyethylene ester-type surfactants have better leveling properties than polyoxyethylene ether-type surfactants (the affinity of ester-type structures for polyester is greater than that of ether-type structures), and surfactants with benzene rings have better leveling properties than aliphatic surfactants.
However, non-ionic surfactants are prone to dehydration during high-temperature dyeing of polyester, and the combination between the oxyethylene chain and groups such as hydroxyl and amino in dye molecules is a physically loose adsorption, lacking intermolecular forces, resulting in poor dispersibility and solubilization. The use of low-cloud-point non-ionic surfactants can easily lead to dye aggregation. Since anionic surfactants can be adsorbed on the surface of dye particles to form a strong negative charge layer, there is a strong electrical repulsion between dye particles, forming a stable dispersed state. They have a strong dispersing ability for the associative polymers of disperse dyes, thereby reducing their aggregation and keeping the dyes stable in the dye bath, which can solve the problem of dye spots caused by dye aggregation due to the low cloud point of non-ionic surfactants.
High-temperature leveling agents with excellent performance are compounded by utilizing the synergistic and enhancing effects of non-ionic surfactants and anionic surfactants, where different structures of each component have different functions. There are many high-temperature leveling agent products compounded by anionic/non-ionic surfactants (some also add some carriers). The different structures of each component have different functions, which can be mainly divided into: 1) The ethoxy structure can capture disperse dyes during the dyeing process, increase the dyeing sites of the dyes, and delay dyeing; 2) When the dyeing temperature reaches a certain critical value, the aromatic compound structure can make the polyester fiber quickly plasticize and swell, reduce the glass transition temperature of polyester by 20-25℃, significantly increase the pores in the fiber, enable the dye to quickly and intensively dye the fiber, and at the same time, act as a solvent for the dye to make the dye in the fiber continuously desorb from the fiber and undergo obvious migration (dye migration) to achieve the leveling effect.
Some compound products of surfactants have high foaming properties, which can easily cause problems in rapid dyeing machines and low bath ratio dyeing. Therefore, low-foam leveling agents are required. The solutions include: adding defoamers, especially silicone defoamers, which are very effective at high temperatures; using the copolymerization method of ethylene oxide and propylene oxide to obtain low-foam products.
2.Leveling agent for thermosol dyeing
During the thermosol dyeing process of disperse dyes, migration often occurs, causing defects such as color spots, uneven shading, and streaks on the fabric surface, resulting in uneven dyeing. To solve this problem, anti-migration agents must be used. Currently, there are two types of anti-migration agents in application: one is sodium alginate; the other is acrylic copolymer. Sodium alginate has poor level-dyeing properties, while acrylic copolymer has good anti-migration ability and no dyeing defects.
Post time: Feb-11-2026