Process for the recovery of very pure caprolactam from polyamide-6 carpet materials

摘要

Process for the recovery of very pure caprolactam from the aqueous caprolactam solution obtained by depolymerisation of polyamide-6 carpet materials by potassium permanganate refining up to a potassium permanganate consumption of less than 800 mg/l, the concentration of free permanganate at no time exceeding 0.4% by weight, relative to caprolactam, subsequent active carbon treatment, filtration and evaporation, and very pure caprolactam distillation in an evaporator system without rotating parts and with a pressure loss of at most 5 mbar at a pressure in the vacuum generator of less than 2 mbar, a wall temperature of less than 155 DEG C, a bottom temperature of less than 130 DEG C and a low temperature-time product.