How to classify the reduction and cleaning of polyester?

The reduction cleaning of polyester is divided into: reduction cleaning under alkaline conditions and reduction cleaning under acidic conditions

1. Reductive cleaning under alkaline conditions: soaping agent + reducing agent (sodium sulfide or thiourea dioxide) + alkali (caustic soda or soda ash), but many domestic dyeing factories do not use soaping agent. Soaping agent: non-ionic surface active agent, which is conducive to dissolving, dispersing, and preventing re-staining of floating color. The commonly used flat addition of O and nonylphenol polyoxyethylene ether Np10 works well. Cationic surfactant: It is especially suitable for completely removing disperse dyes adsorbed in spandex, and significantly improving the color fastness of polyester/spandex dyeing (especially dark colors) (black nylon staining can reach 4-5 levels). Compared with sodium hydroxide powder, thiourea dioxide has the advantages of small odor, low dosage and high durability (high unit price)

When used in overflow dyeing machine, the reducing cleaning liquid will be consumed by oxygen in the air and wasted when spraying, while the open-width washing can be used less. Foreign manufacturers have tried to remove the air in the overflow dyeing machine with nitrogen in advance, and found that it can greatly reduce the amount of insurance powder.

2. Reductive cleaning under acidic conditions: soaping agent (same as above) + reducing agent (sulfinic acid) + acid (acetic acid)

The advantages of reductive cleaning under acidic conditions: it can be reduced to 80-90°C after dyeing, without draining liquid, and directly reductive cleaning; compared with sodium hydroxide, the reducing agent used under acidic conditions is less consumed by air oxidation;

Reduction cleaning under acidic conditions is not a panacea. In fact, compared with alkaline reduction cleaning process, reduction cleaning under acidic conditions is more effective for azo disperse dyes, and sometimes it is not as good as traditional alkaline reduction cleaning for anthraquinone disperse dyes. This is the reason why many dyeing factories use acidic reducing agents and find that the effect is not as good as that of alkaline reduction cleaning.