Recovery of caprolactam from nylon 6 oligomers

摘要

This invention is the method to recover caprolactam from a concentrated nylon 6 chip wash water containing water, cyclic oligomer, and caprolactam. The method comprises feeding the concentrated wash water to a wiped-film evaporator operated at a temperature of from about 200 DEG C. to 300 DEG C. and a pressure from about 10 to about 250 Torr, thereby separating the wash water into (a) an overhead stream of water and caprolactam and (b) a bottom stream of caprolactam and cyclic oligomers, then recovering the caprolactam from the overhead stream. The caprolactam in the bottom stream can also be recovered, and the cyclic oligomers depolymerized to caprolactam for recovery.