Method for producing thioglycollic acid

The invention discloses a method for producing thioglycollic acid, comprising the following steps: (1) continuously and uniformly mixing a sodium chloroacetate solution and a sodium hydrosulfide solution with the mol ratio of 1:1.2-2.5, reacting the mixture at the temperature of 30-90 DEG C and under the pressure of 0.5-2.6 Mpa; (2) adding dilute acid to the reaction solution for acidifying; and (3) carrying out multi-stage continuous extraction by using ethers extractant, distilling to remove the solvent and water at normal pressure, and carrying out multi-stage flash evaporation with an absolute vacuum degree of less than 0.01 Mpa and at the temperature of 100-130 DEG C, so as to obtain the thioglycollic acid with a purity of more than 99%. According to the invention, by adopting the reaction of high temperature and high pressure, the reaction is completed fully with high conversion rate; by adopting the multi-stage eddy current extraction, the product yield is raised; by using the multi-stage flash evaporation in extraction process, the purity of the product is improved.