Patent ID: 7153927

Claim:
A process of producing polyesters and copolyesters by continuous esterification of dicarboxylic esters and diols or by continuous transesterification of dicarboxylic esters with diols in n reaction pressure stages, where n=at least 2, connected in series, wherein the pressure in the first reaction pressure stage is higher than the pressure of the remaining reaction pressure stages, and the pressure successively decreases from reaction pressure stage to reaction pressure stage, the combined vapor flows of the individual reaction pressure stages are introduced into a rectifying column and rectified, and the diol component obtained at the bottom of the rectifying column is recirculated at least to the first reaction pressure stage, at least the last reaction pressure stage in the series has a vacuum, the pressure in the rectifying column is greater than that in the last reaction pressure stage, and vapors discharged from the last reaction pressure stage are condensed to the pressure existing in the rectifying column.