摘要 |
PROBLEM TO BE SOLVED: To obtain a recovered caprolactam with impurity content of a specified level or lower, by purifying anε-caprolactam, obtained by, e.g. depolymerization of Nylon 6, using an adequate process, e.g. enrichment, recrystallization, or distillation under specified pressure and temperature conditions, to remove impurities present in the rawε-caprolactam. SOLUTION: Thisε-caprolactam(CL) is recovered from a resin composition, containing Nylon 6 normally at 10 wt.% or more, preferably 30 wt.% or more, depolymerized under heating in the presence of a catalyst. The recovered CL normally contains impurities, e.g. water and adipimide shown by the formula, normally at 5 wt.ppm or higher for the latter, when enriched to 90% or higher. It is further purified by, e.g. distillation or recrystallization, to reduce the adipimide content to 3 wt.ppm or lower. It is recommended that the distillation is effected at a reduced pressure of 20 Torr. or lower and 150 deg.C or lower, and the recrystallization is effected in the presence of an organic or aqueous solvent.
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