Purification of amido-carboxylic acids

A process for purifying amido-carboxylic acids by liquid/liquid extraction from a reaction mixture containing an amido-carboxylic acid, said process comprising the steps of:

• (A) distilling impurities at a temperature of 120.degree. C. to 220.degree. C. under vacuum from a reaction mixture containing an amido-carboxylic acid under reduced pressure to form a distillate residue;
• (B) mixing the distillate residue from Step (A) with a nonpolar hydrocarbon solvent having 5 to 30 carbon atoms wherein the amount of the nonpolar hydrocarbon solvent is 1 to 5 times the weight of the distillate residue and the mixture of the hydrocarbon solvent and the distillate residue is maintained above the freezing point of the distillate residue;
• (C) allowing the hydrocarbon solvent and distillate residue to achieve phase separation of an organic phase containing the amido-carboxylic acid and an organic phase containing the nonpolar hydrocarbon solvent;
• (D) decanting the organic phase containing the nonpolar hydrocarbon solvent from the organic phase containing the amido-carboxylic acid;
• and
• (E) repeating Steps (B), (C) and (D) wherein the distillate residue is replaced with the organic phase containing the amido-carboxylic acid.