Process for the preparation of polycarbonate copolyether polyols

A process for the preparation of polycarbonate copolyether polyols having formula (I):

• ##STR15## wherein R is an organic radical with a valence n varying from 2 to 6, selected from the following structures:
• --(CH.sub.2 --CH.sub.2 O).sub.x' --CH.sub.2 --CH.sub.2 --
• wherein x' varies from 0 to 4
• --(CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 O).sub.y' --CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 --
• wherein y' varies from 1 to 10 ##STR16## wherein y' varies from 1 to 5 ##STR17## wherein w' varies from 1 to 10 ##STR18## wherein z' varies from 1 to 3 and x" from 1 to 5 ##STR19## wherein w' varies from 1 to 10 R.sub.1, R.sub.2 . . . R.sub.n in formula (I), the same or different are divalent organic radicals in the group of those listed for R;
• x, y . . . z, represent the number of sequences, statistically distributed, of oligopolyether carbonates deriving from glycols whose organic radical corresponds to R.sub.1, R.sub.2 . . . R.sub.n respectively and said x, y . . . z, either singly or as a sum has a value, also fraction within the range of from 2 to 30;
• comprising reacting dimethylcarbonate (DMC) with one or more polyether diols whose organic radicals R, R.sub.1, R.sub.2, . . . R.sub.n have been previously defined and with one or more polyether diols with a molecular weight of between 100 and 200 as measured by the method of ASTM D2849, at a DMC/polyether diols ratio of between 0.5 and 1.35, at a temperature of between 130.degree. and 185 .degree. C., in the presence of a catalyst comprising an oxide, a carbonate or an alcoholate of a metal of the first or second group or a salt or an organometallic compound belonging to the third or fourth or fifth group with a concentration of between 0.0001 and 0.01% by weight.