Preparation method of high-efficiency low-cost acidic color fixing agent

According to the preparation method, phenol, concentrated sulfuric acid and formaldehyde are used as raw materials to synthesize an intermediate, 4, 4'-dihydroxy diphenyl sulfone and 4-hydroxy benzenesulfonic acid are used as main mixtures, the pH value is adjusted to 8-9 by using an alkaline substance, a 37% formaldehyde solution is added for a condensation reaction to obtain the acidic color fixing agent, and acetic acid is used for adjusting the acid when the acidic color fixing agent is used. The acidic color fixing agent prepared by the method has the advantages of short synthesis route,no need of purification of the produced intermediate, low manufacturing cost, and satisfaction of market demands on use performance, can save cost for printing and dyeing enterprises, can greatly reduce sewage discharge, especially phenol-containing sewage discharge, and has the advantages of energy saving and emission reduction. The acid color fixing agent synthesized by the invention is small incolor change, the soaping