Transparent copolyamides from m-xylylene diamine, an aliphatic diamine and terephthalic acid

Claim 1

A polyamide having improved form stability at elevated temperature, said polyamide being of the general formula R.sub.3 --HN--R.sub.1 --NH--CO--R.sub.2 --CO ].sub.x R.sub.4 in which R 1 represents meta-xylylene units, para-xylylene units in an amount of from 0 to 50 mol % of the meta-xylylene units, and at least one, straight-chain bivalent aliphatic hydrocarbon unit containing from 4 to 20 carbon atoms, said meta-xylylene, para-xylylene and bivalent aliphatic hydrocarbon units being randomly distributed in the macromolecule and the proportion of the aliphatic hydrocarbon units being from 5 to 90 mol %, based on the sum of the xylylene and aliphatic hydrocarbon units, R 2 represents phenylene units selected from the group consisting of p--C 6 H 4 --, m--C 6 H 4 --, and mixtures thereof, and at least one bivalent aliphatic saturated hydrocarbon unit containing from 3 to 18 carbon atoms; said phenylene and aliphatic hydrocarbon units being randomly distributed over the macromolecule and the proportion of aliphatic units being from 10 to 90 mol %, based on the sum of the phenylene and aliphatic units, R 3 represents H or OC--R 2 --COOH and R 4 represents OH or NH--R 1 --NH 2 , and in which x indicates the degree of polymerization, measured as reduced specific viscosity within range of from 1.0 to 2.5 dl/g, determined in a solution of 1 g of the polyamide in 100 ml of a mixture of phenol/tetrachloroethane in a weight ratio of 60:40 at 25° C.