关键词: 涤纶, 碱减量, 促进剂, 生态染整, 促进机制

Abstract: Polyester fiber is currently the most widely used synthetic fiber. However, its poor moisture absorption, susceptibility to static electricity, and other issues have hindered its market prospects as a high-end textile material. Alkali reduction treatment can improve the inherent defects of polyester fiber, resulting in a soft and smooth texture, a pleasant sheen, good drapability, water retention, and other advantages. Meanwhile, this treatment makes it has the characteristics of imitated silk. Nevertheless, the traditional alkali reduction process for polyester involves excessive use of alkali, making it difficult to process. Finally, it requires a large amount of acid to neutralize. As a result, there are many problems, such as high energy consumption, serious environmental pollution, and serious damage to the fabric. Additionally, the liquid alkali is also a dangerous chemical, so safety problems should be considered. All these problems seriously restrict the sustainable development of the polyester textile industry. Therefore, reducing the amount of liquid alkali with promoters is currently the most convenient, environmentally friendly, and easily implementable improvement method in the alkali reduction technology.
Currently, promoters are widely used to improve alkali utilization, reduce the environmental hazards of excessive alkali, and impart exceptional performance to fabrics. Promoters can be roughly categorized into quaternary ammonium salts, gelatin protein promoters, cationic polymers, ionic liquids, amines, alcohols, and others. Among them, quaternary ammonium salts are widely used. In terms of effectiveness, most promoters can accelerate the hydrolysis of polyester and reduce the amount of alkali required. And different promoters have different promotion mechanisms. Quaternary ammonium cationic surfactants mainly utilize positively charged quaternary ammonium ions to attack the carbonyl carbon atoms by carrying the hydroxide ions, further promoting the rapid hydrolysis of ester bonds in polyester macromolecules. Gelatin has certain surface activity, infiltration, and colloidal protection. In the process of alkali reduction, gelatin can play a role in swelling fiber and reducing surface tension. Some new alkali reduction promoters are mainly cationic polymers. They mainly adsorb more hydroxide ions through water-soluble quaternary ammonium cation groups, so as to achieve the purpose of promoting the hydrolysis of polyester. Ionic liquid is a kind of compound ionic surfactant and it can completely ionize in water. The cationic part of the ionic liquid has a long carbon chain and strong adsorption capacity for polyester. Its mechanism is similar with quaternary ammonium salts. There are some other additives that can also promote polyester hydrolysis. For example, ammonia mainly generates an amide group at one end and a hydroxyl group at the other end to destroy the polymer chain through the diffusion of amine molecules in the polymer. Alcohol can realize the purpose of surface functionalization of polyester through the exchange reaction of ester and amine. 
The traditional alkali reduction treatment of polyester fiber has the following problems, such as high concentration of liquid alkali, great difficulty in processing, serious environmental pollution, and high energy consumption. All these problems seriously restrict the sustainable development of the polyester textile industry. The addition of promoters is an effective way to improve the utilization rate of alkali. The promoter can transfer and enrich the OH- in the solution on the fiber surface, and OH- is more likely to attack the carbon atoms in the carbonyl group with partial positive charge in the polyester molecule. As a result, the hydrolysis reaction of the polyester molecule becomes easy. Therefore, how to effectively use promoters to reduce the amount of liquid alkali has become a research hotspot to promote the sustainable development of polyester textiles.
The development of alkali reduction promoters can be started from the following perspectives: first of all, the new promoter is synthesized to increase the function of the fabric while effectively reducing the amount of liquid alkali and retaining the advantages of liquid alkali treatment. For example, the use of gelatin protein reagents can also play a certain role in fiber repair while improving the performance of fibers. By increasing the study of the combination of accelerators to explore the mechanism, the cost saving treatment formula with the best effect was obtained. The development of alkali reduction technology can also be applied to the alkali reduction dyeing one-bath system of polyester fabrics, which can reduce energy consumption and be more environmentally friendly and efficient. The use of promoters to reduce the alkali concentration provides more possibilities for the pH application range of some alkali-resistant disperse dyes, and development space for alkaline dyeing technology. This provides reference for promoting the industrialization development of polyester fabric alkali reduction technology and realizing the sustainable development of the textile printing and dyeing industry.

Key words: polyester, alkali reduction, promoter, ecological dyeing and finishing, promotion mechanism