Linear polyesters based on n,n-heterocyclic dicarboxylic acids

Claim 1

A linear, thermoplastic polyester having a relative viscosity of 1.2 to 3.0, measured at 30° C. on a 1% strength solution consisting of equal parts of phenol and tetrachloroethane, which is characterised by the structural elements of the general formula I ##STR21## wherein R denotes a N,N-heterocyclic radical of the formula ##STR22## wherein R 1 and R 2 independently of one another each denote hydrogen or an alkyl having 1 to 3 C atoms, R 3 denotes hydrogen or methyl, A denotes an aliphatic radical having 2 to 6 C atoms, a N,N'-heterocyclic-aliphatic radical of the formula ##STR23## or the formula ##STR24## wherein R 1 and R 2 have the same meaning as above and R' and R" represent H, chlorine or bromine atoms or R' represents a H atom and R" represents a chlorine or bromine atom, D denotes meta- or para-phenylene and x and y represent integers, and the mol fraction x/(x + y) derived from x and y can have values from 0.05 to 1.0.