Polyol esters, process for their preparation and use.

Process for the preparation of polyester polyols with functionalities of from 1.95 to 3.25 and OH numbers from 90 to 33 mg KOH / g, in which a) are reacted organic polycarboxylic acids having 4 to 12 carbon atoms and 2 to 4 carboxyl groups, their derivatives or mixtures thereof with b) organic polyols having functionalities of 2 to 4 and number average molecular weights of 62 to 400 g / mol at from 150 to 250 ° C and in vacuo to give polyester polyols Z-terminated groups hydroxyl, with a hydroxyl number from 100 to 40 mg KOH / g and a functionality of 1.95 to 3.25, and then c) are added to lower initial temperatures to 220 monomers of cyclic esters in a mass ratio between polyolester Z and monomer cyclic ester of 10: 1 to 1: 1, the temperature after at most 60 minutes or less at 175 ° C, and wherein the OH number of the polyester polyol Z is reduced by at least 5 mg KOH / g and the molar ratio of monomers cyclic esters and the hydroxyl groups of the polyester polyol Z is between 0.75: 1 and 10: 1.