Reduction cleaning belongs to the post-treatment process of polyester textile dyeing or printing. Generally, sodium hydroxide and insurance powder solution are used to treat the fabric to remove the disperse dyes and oligomers adsorbed by the fiber. When polyester fabric is dyed with disperse dyes at high temperature, there are always dyes only adsorbed on the fiber surface and not diffused into the fiber, which not only affects the color light after dyeing, but also seriously affects the water washing and friction fastness of the fabric. Therefore, the reduction of caustic soda and insurance powder is needed to decompose and eliminate the color of disperse dyes.
The polymerization mechanism of polyester belongs to stepwise polymerization (linear polycondensation), and the degree of polymerization increases gradually with the reaction, but there are still a small amount of monomers and oligomers in polyester polymer. The degree of polymerization of these oligomers is low and mainly exists in the form of ring. When the cyclic trimer is dyed with disperse dye at 130 ℃, its solubility is less than 2mg / L, so it is difficult to be removed in the process of polyester dyeing, and it is easy to deposit on the fabric to produce color spots and color differences. Reduction cleaning can not only improve the color fastness of the fabric, but also play a positive role in reducing oligomers.
In addition, there are many problems in the dyeing of polyester / spandex fabrics, mainly manifested in poor color fastness, especially poor washing fastness. Due to the loose structure of spandex soft chain segment and the high directness of disperse dyes to spandex fiber, the dyes are easy to diffuse into the spandex fiber during dyeing, and the dye uptake increases with the increase of temperature. However, the binding force between dyes and spandex is weak, resulting in a significant decrease in the water washing fastness of the fabric. In order to remove the disperse dyes on spandex fiber, multi-channel reduction cleaning is usually required, which requires a large amount of water and is difficult to treat wastewater.
The reduction cleaning process after dyeing of classic polyester and polyester / spandex fabrics uses caustic soda and insurance powder. Although it has good treatment effect, the insurance powder smells bad and has spontaneous combustion and toxicity, which is easy to cause fire hazard. Therefore, many scholars have explored safer alternative processes, mainly using safer reducing agents, such as thiourea oxide, sodium bisulfite, glucose derivatives, etc., which have less odor than insurance powder Low dosage. In addition, there are also reduction cleaning methods that cooperate with the use of anionic and non-ionic detergent aids, such as the reduction cleaning agent developed by zhkchem, and the use of borohydride compound surfactant can achieve safe and efficient cleaning effect. The acid reduction cleaning agent compounded by sodium bisulfite and AEO-9 in Wuyi University can also achieve good results without alkali neutralization. Many new reduction cleaning processes have been able to meet the requirements of safety and fastness, but for polyester blended products containing spandex, the soaping color fastness of high-efficiency reductant reduction cleaning process is half to one grade lower than that of traditional reduction cleaning process, which is difficult to meet the requirements of dyeing products such as high color fastness and white spell.
To sum up, many existing reduction cleaning processes can achieve the same bath of dyeing and washing, simplify the process and save energy, but can not achieve the fastness effect that can be achieved by the traditional process. Most of the recommended processes that can achieve the cleaning effect can not be controlled, reduce the production cost and can not be industrialized. In addition, the damage caused by industrial development to the environment makes people more and more aware of the importance of environment-friendly development. Therefore, how to improve polyester The reductive cleaning process of polyester / spandex fabric needs to be further studied.
