Process for the manufacture of linear polyesters which contain phosphites and/or phosphates

Claim 1

An improved process for the manufacture of high molecular weight linear homo- or copolyesters, which contain moieties selected from the group consisting of phosphites and phosphates, and which are derived from aromatic and/or cycloaliphatic, unsaturated aliphatic and optionally in addition aliphatic, dicarboxylic acids, hydroxycarboxylic acids and diols, and which are formed first by transesterification process in the presence of a catalyst followed by a preliminary precondensation to give a precondensate containing hydroxy groups and with an average minimum degree of polycondensation Pn of 50, wherein the improvement comprises adding from 1 to 25% by weight, based on the polyester precondensate, of a reaction catalyst of the general formula I, or mixtures thereof, ##STR2## wherein R 1 , R 2 and R 3 are the same or different, and represent linear or branched alkyl groups, aryl, aralkyl, cycloalkyl or cycloalkylalkyl; or said aryl, aralkyl, cycloalkyl or cycloalkylalkyl groups substituted by alkyl, cyclohexyl, phenyl or phenylalkyl, and x is 0 or 1, and completing the polycondensation in the melt or solid phase at a temperature between 170° C and 320° C until a minimum degree of polymerisation Pn of 100 is attained.