Patent ID: 7244806

Claim:
In a process for the continuous production of polyesters (PES) by esterification/transesterification of dicarboxylic acids, or esters of the dicarboxylic acids with diols, in at least one reaction stage, prepolycondensation of the esterification/transesterification product under vacuum by means of a reaction stage consisting of a vertical reactor, and polycondensation of the prepolycondensation product in at least one polycondensation stage, the improvement comprising the steps of: flowing the esterification/transesterification product into the vertical reactor and maintaining in the vertical reactor a pressure of 10 to 40% of the diol equilibrium pressure of the prepolycondensation product leaving the reactor and a process temperature of 268 to 274° C.; and successively passing the esterification/transesterification product in a free movement without stirring under limited heating first through at least one first reaction zone formed of an annular channel, then into the radially outer or the radially inner ring duct of at least one second reaction zone formed of an annular channel divided into a plurality of concentric ring ducts where the product passes successively through the ring ducts to the outlet and then into a stirred third reaction zone located at the bottom of the reactor.