Amide 6 obtd. from waste amide - by passing melt through shear filter, partly depolymerising with water at specified temp. under pressure, and post-condensing

摘要

Producing polyamide 6 (PA 6) from material (I) contg. PA 6 scrap and/or oligomer-contg. PA 6 scrap and/or oligomer-contg. lactam residues and/or oligomer contg. lactam comprises (i) melting (I) (ii) shear filtering and (iii) treating with water at 230-290 deg.C in pressure stage(s) to bring the melt to a uniformly low deg. of polymerisation (DP) with soln. viscosity above 1.5. Pref. after pressure treatment, the melt is subjected to post-condensn. stage(s) subjected to shear in a multilayer metal fibre web, fine-pore sintered filter or fine sand filter, and is pref. also shear-filtered after passing through the first pressure stage. USE/ADVANTAGE - PA 6 residue is converted into a low mol. wt. prod. which can be converted by relatively low-cost post-condnsn. into high mol wt. polyamide suitable for the prodn. of fibre, film etc. Process can also be integrated with the actual prodn. of PA6, and is cheap and more environmentally acceptable than total depolymerisationag