Allied Corporation

John W Wagner

William B Fisher

Lamberto Crescentini

Charles J Cole

Samuel L Yates

Joseph D DeCaprio

Roy J Lilley, Jr

Albert H Wiesner

Webb B Blackman, Jr

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.degree. C. to 300.degree. 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.

Recovery of caprolactam from nylon 6 oligomers

A two-stage hydrolysis process for polymerizing epsilon-caprolactam is disclosed comprising a first stage from a temperature of about 180.degree. C.-260.degree. C., a pressure of 20 to 150 psig, for a period of about 0.5 to 4 hours, then before equilibrium conditions are reached a second stage at a temperature of about 200.degree. C.-260.degree. C., a pressure of about 100-900 Torr for a period of about 2 to 15 hours, while continuously removing most of the water so that water is removed both during hydrolyzation and during the subsequent polycondensation, whereby the cyclic dimer content of the shaped polymer article is below 0.2 percent by weight.

Two-stage hydrolysis process for the preparation of nylon 6

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Petersburg, VA, United States of America

John W Wagner