GB793598A - A process for recovering monomers from polyamides - Google Patents

Abstract

Aminocarboxylic acids, a :o - dicarboxylic acids and a :o -diamines are recovered from polyamides by treating the latter in water at an elevated temperature with a strongly acid ion exchanger and eluting the reaction products from the ion exchanger. The polyamide may be in the form of powder or chips and is preferably pre-treated with water at an elevated temperature until the greater part has been dissolved with partial depolymerization. Preferred temperatures are 50-150 DEG C., and preferred ion exchangers are those of the sulphated polystyrene type. The process may be carried out batchwise or continuously. With polyamides of the polylactam or polyaminoacid type the aminoacid products may be removed from the ion exchanger by elution with ammonia. With mixed polyamides derived from aminocarboxylic acids and dicarboxylic acids and diamines the products may be recovered separately by elution with selective solvents; thus the dicarboxylic acid may be washed from the ion exchanger with a solvent such as an alcohol and the aminoacid may be removed by subsequent elution with ammonia, the diamine remaining bound by the ion exchanger. The examples describe the recovery of e -aminocaproic acid from polycaprolactam; e -aminooenanthic acid from oenantholactam; o -aminoundecylic acid from the corresponding polyamide; and a mixture of adipic acid, e -aminocaproic acid and hexamethylenediamine from a polyamide derived from 50 per cent of aminocaproic acid and 50 per cent of an adipic acidhexamethylenediammonium salt.