What is the method of polyester reduction cleaning?

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

Reduction cleaning under alkaline conditions: soaping agent + reducing agent (sulfur powder or thiourea dioxide) + alkali (caustic soda or soda ash). However, many domestic dyeing factories do not use soaping agent. Soaping agent: non-ionic surfactant, which is beneficial to the dissolving and dispersing of floating color, preventing re-staining. The commonly used peregrine O and nonylphenol polyoxyethylene ether Np10 have good effect. Cationic surfactant: It is especially suitable for completely removing the disperse dyes adsorbed in spandex, significantly improving the color fastness of polyester/spandex dyeing (especially dark colors) (black nylon staining can reach grade 4-5) Reducing agent: Compared with sodium hydrosulfite, thiourea dioxide has the advantages of low odor, low dosage and high sustainability (high unit price)

When the hydrosulfite is used in the overflow dyeing machine, most of the reducing cleaning solution will be wasted by the oxygen in the air when it is sprayed, and the open-width washing can be used much less. Foreign manufacturers have tested and found that the amount of hydrosulfite can be greatly reduced after removing the air in the overflow dyeing machine with nitrogen in advance.

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

Advantages of reduction cleaning under acidic conditions: when the temperature is lowered to 80-90 °C after dyeing, reduction cleaning can be performed directly without draining; compared with hydrosulfite, 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 the alkaline reduction cleaning process, reduction cleaning under acidic conditions is more effective for azo disperse dyes, while for anthraquinone disperse dyes, it is sometimes not as good as traditional alkaline reduction cleaning. Many dye houses use acidic reducing agents to find reasons why they are not as effective as alkaline reducing cleaning.