GB857657A - Improvements in and relating to polyamides - Google Patents

Abstract

Linear polyamides containing recurring structural units -HN(CH2)6-CO- are made by heating at a temperature above 240 DEG C., a pre-polyamide made by heating an aliphatic, aralkyl or cycloaliphatic ester of 7-aminoheptanoic acid or mixtures thereof at a temperature below 280 DEG C. and a pressure of at least 50 pounds per square inch with at least a molar equivalent of water while passing a stream of inert gas through the reaction mixture. Specified esters are the ethyl, iso-propyl, n-propyl, 2-ethylbutyl, n-octyl, 1-phenylethyl, cyclopentyl and cyclohexyl esters of 7-aminoheptanoic acid. Specified inert gases are nitrogen, argon, helium and carbon dioxide. Viscosity stabilizers e.g. acetic, benzoic, stearic, p-toluic, adipic, sebacic and glutaric acid and ethyl 6-cyanohexanoate, ethyl 7-benzamidoheptanoate, ethyl 7-acetamidoheptanoate, and ethyl 7-toluamidoheptanoate may be present in the reaction mixture. In the examples, polyamides are made from:- (1) and (2) isopropyl 7-aminoheptanoate, (3) iso-ipropyl, 7-aminoheptanoate and oretic acid, (4) cyclohexyl 7-aminoheptanoate, (5) 2-ethyl butyl 7-aminoheptanoate, (6) 1-phenylethyl 7-aminoheptanoate and a prepolymer of isopropyl 7-aminoheptanoate, (7) butyl 7-aminoheptanoate and a prepolymer of isopropyl 7-aminoheptanoate, (8) ethyl 7-aminoheptanoate and a prepolymer of cyclohexyl 7-aminoheptanoate and (9) npropyl 7-aminoheptanoate and a prepolymer of 2-ethyl butyl 7-aminoheptanoate. Specification 857,062 is referred to.ALSO:Polyamide prepolymers comprising a mixture of unreacted 7-aminoheptanoic acid ester, 7-aminoheptanoic acid and a polyamide having a reduced viscosity lower than 0,7 at a concentration of 0,2 grams of the polyamide in solution in 100 mls. of a 3:2 by weight mixture of phenol and tetrachloroethane are made by heating an aliphatic, aralkyl or cycloaliphatic ester of 7-aminoheptanoic acid or mixtures thereof at a temperature below 280 DEG C. and a pressure of at least 50 lbs. per square inch with at least a molar equivalent of water while passing a stream of inert gas through the mixture. Specified esters are the ethyl, isopropyl, n-propyl, 2-ethyl butyl, n-octyl, 1-phenylethyl, cyclopentyl and cyclohexyl esters of 7-aminoeptanoic acid. Specified inert gases are nitrogen, argon, helium and cargon dioxide. In the Examples, polyamide propolymers are made from : (1) and (2) isopropyl 7-aminoheptanoate, (3) isopropyl 7-aminoheptanoate and acetic acid as viscosity stabiliser, (4) cyclohexyl 7-amino heptanoate and (5) 2-ethyl-butyl 7-aminoheptanoate. Specification 857,062 is referred to.