Patent ID: 7781600

Claim:
A continuous process for purifying a hydroxycarboxylic acid, comprising: a crystallization step of subjecting a hydroxycarboxylic acid aqueous solution to crystallization for purification, a separation step of separating a hydroxycarboxylic acid crystal from a mother liquid, and a washing step of washing the hydroxycarboxylic acid crystal for further purification with a washing liquid, wherein the washing liquid is a starting hydroxycarboxylic acid aqueous solution, a portion of the mother liquid separated from the hydroxycarboxylic acid crystal is discharged out of a system, and the remainder of the mother liquid and waste liquid after washing the hydroxycarboxylic acid crystal are recycled as the hydroxycarboxylic acid aqueous solution to be subjected to the crystallization step, thereby recovering refined hydroxycarboxylic acid at a yield of 95% or higher.