Chemical conversion of polyamide waste to heat resistant monomers - by reacting with trimellitic anhydride in presence of fluid reaction medium to give bis-carboxy-phthalimido-acids and original di:acid(s) derived from polyamide

摘要

A process for the chemical utilisation of polyamide waste from the areas of fibres, textiles, plastics and household and industrial refuse. The polyamide is mixed with trimellitic anhydride in a fluid, thermally stable medium which is chemically inert to trimellitic anhydride and heated to above 170 deg.C, pref. 270 deg.C, under an inert gas for 1-60 mins. It is partly or completely converted to 5-carboxyphthalimido-alkane acid and/or a dicarboxylic/bis-(5- carboxyphthalimido)alkane mixt. and/or a dicarboxylic acid/bis-(carboxyphthalimido)benzene mixt., and opt. sepd. or purified. The polyamide may contain up to 60 mol.% of hetero groups such as ester, imide and/or ether gps. The polyamide may contain up to 80 bulk % of extraneous material. The molar ratio of amide gps. to trimellitic anhydride is less than 1. USE/ADVANTAGE - The prods. are useful for the prod. of thermoplastic polyamide-imides and polyester-imides, which are heat-resistant and themselves useful as wire insulation. The process is not conducted in the melt, meaning that infusible polyamides such as Aramids can be processed. There are no noteworthy side-reactions.