GB891579A - Improvements in the production of expandable polyamides - Google Patents

Abstract

Expandable polyamide compositions are prepared by heating polyamide-forming substances in the presence of (1) esters of carboxylic acids with 1-3 carbon atoms and polyhydric alcohols and (2) N-hydroxyalkyl diamines or their salts with dicarboxylic acids at temperatures at which condensation but no foam formation takes place, e.g. 180 DEG -240 DEG C., until the polyamide formed is still at least partly soluble in sulphuric acid. Specified reaction mixture components are:- polyamide-forming substances dicarboxylic acid salts of diamines, e.g. adipic acid hexamethylene diamine, sebacic acid hexamethylene diamine and suberic acid octamethylene diamine; omega-aminocarboxylic acids, e.g. omega-aminocaproic acid; and lactams, e.g. caprolactam, oenanthic lactam and caprylic lactam: esters ethylene glycol diformate, ethylene glycol oxalate, propylene glycol diformate, glycerine diformate and triformate, trimethylol-propane diformate and triformate, pentaerythritol formate, trimethylol cyclohexanol formate and diethanolamine diformate: N-hydroxyalkyl diamines the reaction products of alkylene oxides or aldehydes with aliphatic, cycloaliphatic or aromatic diamines or the dicarboxylic acid salts of these products, e.g. N-hydroxyethyl-hexamethylene diamine or its adipate. The reaction mixture may also include the carboxylic acid esters specified in the parent Specification or oxamic acid or esters as specified in Specification 858,254. The compositions are converted into powder form and expanded by further heating at 275 DEG -280 DEG C. by the decomposition of the ester.ALSO:Expandable polyamide compositions are prepared by heating polyamide-forming substances in the presence of (1) esters of carboxylic acids with 1-3 carbon atoms and polyhydric alcohols and (2)N-hydroxyalkyl-diamines or their salts with dicarboxylic acids at temperatures at which condensation but no foam formation takes place, e.g. 180-240 DEG C., until the polyamide formed is still at least partly soluble in sulphuric acid. Specified reaction mixture components are: polyamide-forming substances dicarboxylic acid salts of diamines e.g. adipic acid hexamethylene diamine, sebacic acid hexamethylene diamine and suberic acid octamethylene diamine; omega-aminocarboxylic acids e.g. omega-amino caproic acid; and lactams e.g. caprolactam, oenanthic lactam and caprylic lactam: esters ethylene glycol diformate, ethylene glycol oxalate, propylene glycol diformate, glycerine diformate, glycerine triformate, trimethylol-propane diformate, trimethylol-propane triformate, pentalrythritol formate, trimethylol cyclohexanol formate and diethanolamine diformate: N-hydroxyalkyl diamines the reaction products of alkylene oxides or aldehydes with aliphatic, cycloaliphatic or aromatic diamines or the dicarboxylic acid salts af these products, e.g. N-hydroxyethyl-hexamethylene diamine or its adipate. The reaction mixture may also include the carboxylic acid esters specified in the parent Specification or oxamic acid or esters as specified in Specification 858,254. The compositions are converted into powder form and expanded by further heating at 275-280 DEG C. by the decomposition of the ester.