Continuous manufacture of unsaturated polyesters

Claim 1

A process for the continuous manufacture of an unsaturated polyester by polycondensation of one or more ethylenically unsaturated dicarboxylic acids, with or without dicarboxylic acid(s) free from olefinic unsaturation, and/or their anhydrides, with one or more diols, with or without monohydric and/or higher polyhydric alcohol(s), in a stirred kettle cascade, wherein (a) in a first reaction stage, the dicarboxylic acid or acids and/or its anhydride or their anhydrides are condensed with the alcohol(s) in the molar ratio COOH or 1/2 (CO) 2 O:OH of from 1:1.0 to 1:1.1, at from 190° to 250° C., with the proviso that the reaction mixture is boiling, the water of condensation is separated, from the vapors which distil off, by means of a vapor column, and the unconverted distilled-off or sublimed starting materials are recycled to the reaction mixture, the vapor column used being a two-part distillation column (i) in the upper part of which, at from 95° to 135° C., the diol/water of condensation mixture is separated by spraying it in counter-current with water of condensation, the spray density being from 0.5 to 5 m 3 /m 2 per hour and (ii) in the lower part of the column, at from 110° to 180° C., unconverted dicarboxylic acid(s) and/or anhydride(s) and part of the alcohol are absorbed, partially esterified and washed out by spraying in counter-current, at a spray density of from 20 to 80 m 3 /m 2 per hour, with a mixture of refluxing alcohol, freshly fed-in alcohol and circulated reaction medium, and are recycled to the reaction mixture, and (b) in a second stage of the reaction, the condensation of the resulting reaction mixture is completed at from 190° to 250° C.