1. Reduction and 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. Commonly used flat addition of O and nonylphenol polyoxyethylene ether Np10 have good effects.
Cationic surfactant: It is especially suitable for thoroughly 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)
Reducing agent: Compared with sodium sulfonate, thiourea dioxide has the advantages of small odor, low dosage and high sustainability (high unit price)
When the fusogenic powder is used in an overflow dyeing machine, most of the reducing cleaning liquid will be wasted by the oxygen in the air when it is sprayed, and 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. Reduction and 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℃ after dyeing, the reducing agent can be directly reduced and cleaned without draining; compared with the sodium hydroxide, the reducing agent used under acidic conditions is less consumed by air oxidation;
Reductive cleaning under acidic conditions is not a panacea. In fact, compared to alkaline reduction cleaning processes, reductive cleaning under acidic conditions is more effective for azo disperse dyes, and for anthraquinone disperse dyes, it is sometimes not as good as traditional alkaline reduction cleaning. Many dyeing factories use acidic reducing agents to find the reason why they are not as effective as alkaline reduction cleaning.