Thermoplastic polyesters possessing high stability in the molten state.

摘要

Thermoplastic aromatic polyesters possessing high resistance to degradation in the molten state, are obtained by a two-stage polycondensation process comprising: a) reacting an aromatic dicarboxylic acid, or a derivative thereof esterified with a volatile alcohol, with an excess of a diol, until the dicarboxylic acid diglycolester or a mixture of oligomers thereof is formed; b) polycondensing the dicarboxylic acid diglycolester to obtain the thermoplastic aromatic polyester; wherein in stage b) or preferably in both stages a) and b) of the process a salt or a saline complex, soluble in the reacting mixture, of a metal chosen from the group comprising lanthanides (or rare earths) having an atomic number equal to or greater than 62 is used as catalyst.