VERFAHREN ZUR KONTINUIERLICHEN HERSTELLUNG VON LINEAREN THERMOPLASTISCHEN POLYESTERN

Process for the continuous preparation of linear thermoplastic polyesters, in which a) a transesterification or esterification product of aliphatic and/or aromatic dicarboxylic acids having a molecular weight < 300 or ester- forming derivatives thereof with aliphatic and/or cycloaliphatic diols having a molecular weight < 250 which may additionally contain poly(alkylene oxide)glycols having a molecular weight from 400 to 4000 is passed from top to bottom at a temperature of above 240 DEG C and under reduced pressure through an essentially vertical tubular precondensation zone, forming a precondensate and vapour-form diols having a molecular weight < 250, b) the precondensate and the vapour-form diols are separated, and c) the precondensate is discharged from the bottom, characterised in that, in step a), a temperature of from 250 to 360 DEG C, a pressure of from 0.5 to 20 mm Hg and a residence time of from 3 to 10 minutes are observed, and the tubular precondensation zone is provided with internals which have a free surface area of from 0.3 to 1.5 m /l, and in step c), the precondensate is further condensed at a temperature of from 240 to 290 DEG C under a pressure of from 0.5 to 20 mm Hg and a residence time of from 10 to 40 minutes, giving polyesters which are suitable for granulation.