Application of coil tube evaporators for the production of polyamides

Abstract

Helical tube evaporators are used to concentrate aqueous extract solutions from the extraction of polyamides based on polyamide 6. A process for preparing polyamides based on polyamide 6 comprises the stages of b) monophasic or biphasic reaction of aqueous extract solutions from the extraction of polyamides based on polyamide 6, which may be enriched with caprolactam, aminocapronitrile, aminocaproic acid or mixtures thereof, in a prereactor at pressures in the range from 5 to 40 bar and temperatures in the range from 150 to 300° C., the gaseous phase formed being removable from the liquid phase in the case of the biphasic reaction, c) discharge of the reaction mixture from stage b) through a helical tube evaporator at a temperature in the range from 220 to 300° C. with pressure reduction to about atmospheric pressure and removal of a gaseous phase to obtain a liquid phase, d) further reaction of the liquid phase from stage c) at temperatures in the range from 240 to 300° C. and pressures in the range from atmospheric pressure to 2 bar with removal of a gaseous phase.

Dependencies are inferred from the claim text.