Views: 2 Author: Site Editor Publish Time: 2023-09-01 Origin: Site
I. Levelling agent for high temperature dyeing
In the process of high temperature and high pressure dyeing with disperse dyes, the uneven dyeing is often caused by the poor dispersibility, evenness, transference and improper control of temperature rise rate. In particular, the linear density of fine denier polyester fiber is very small, the surface area increases, the dyeing speed of the dye is accelerated, and the fabric structure is tight, the dye is not easy to dye through, and the dyeing irregularity is more prominent than that of conventional polyester fiber. The use of high temperature dispersion levelling agent during dyeing can improve the levelling effect of fabrics and improve the quality of products.
Generally, non-ionic surfactants can be used as levelling agents for non-ionic disperse dyes, which can form a hydrophobic combination and slow down the dyeing speed to achieve the purpose of levelling. Among the non-ionic dispersion levelling agent molecules, the levelling property of polyoxyethylene ester surfactant is better than that of polyoxyethylene ether surfactant (the affinity of ester structure to polyester is greater than that of ether structure), and the levelling property of surfactant with benzene ring is better than that of fatty surfactant.
However, non-ionic surfactants are easy to lose water when dyeing polyester at high temperature, and the combination of oxyethylene chain with hydroxyl, amino and other groups in dye molecules is physical loose adsorption, lack of ionic interforce, poor dispersion and solubilization, and it is easy to produce dye condensation when using low turbidity point non-ionic surfactants. Because the anionic surfactant can be adsorbed on the surface of the dye particles to form a strong negative charge layer, so that there is a strong electric repulsion between the dye particles to form a stable dispersion state, and has a strong dispersion ability for the association of dispersed dyes, thereby reducing its cohesion, so that the dye remains stable in the dye solution. It can solve the problem of staining due to the low turbidity point of non-ionic surfactants caused by dye condensation.
The high temperature levelling agent with good performance was synthesized by the synergistic effect and synergistic effect of non-ionic surfactant and anionic surfactant, and the different structure of each component had different effects. There are many high temperature levelling products with negative/non-ionic surfactants combined (some also add some carriers). The different structures of each component have different effects, which can be mainly divided into: 1) the ethoxy structure can capture disperse dyes, increase dye sites, and delay dyeing; 2) When the dyeing temperature reaches a certain critical value, the structure of aromatic compounds can make the polyester fiber rapidly plasticizing and swelling, reduce the glass transition temperature of the polyester fiber by 20 ~ 25℃, and significantly increase the pores in the fiber, so that the dye is rapidly and intensively dyed on the fiber. At the same time, it can be used as the solvent of the dye to make the dye in the fiber continuously desorption from the fiber and obvious swimming (shifting) to achieve the leveling effect.
Some of the compound products of surfactants have high foaming property, which is easy to cause problems in the rapid dyeing machine and small bath dyeing, so low foaming levelling agents are required. The solution is: add defoamer, especially silicone defoamer, which is very effective at high temperature; The low foaming product was obtained by the copolymerization of ethylene oxide and propylene oxide.
2. Levelling agent for hot melt dyeing
In the process of hot melt dyeing, disperse dyes often produce the phenomenon of swimming, which makes the cloth surface appear color spots, Yin and Yang, stripe shadow and other defects, resulting in uneven dyeing. To solve this problem, it is necessary to use anti-mobility agents. At present, there are two kinds of anti-swimming agents used: one is sodium alginate; The other is the copolymer of acrylic acid. The levelling property of sodium alginate is not good, while the acrylic copolymer has good anti-migration ability and no staining phenomenon.