Recovering caprolactam from polycaprolactam prepn - using reaction heat to concentrate aq extraction soln contg monomer and oligomers

摘要

Aqs. extraction solns. obtd during the purification of polycaprolactam, and contg. the monomer and oligomers, are treated to recover the monomer by (a) evaporating the water from the soln. in several stages, the necessary energy for the evaporation of the main part of the water being derived from the heat liberated during the transformation of the cyclohexanone oxime into caprolactam in sulphuric acid or oleum; and (b) distilling the residue obtd. after the evapn. of the water.