Patent ID: 7763683

Claim:
An isocyanate-terminated prepolymer comprising the reaction product of one or more organic di- or polyisocyanates with one or more polyester polyols having functionalities of from 1.95 to 3.25 and OH numbers of from 90 to 33 mg KOH/g, wherein said polyester polyols comprise the reaction product of: 1) one or more hydroxyl group-terminated polyester polyols Z having a hydroxyl number of 100 to 40 mg KOH/g and a functionality of 1.95 to 3.25 which are prepared by reacting, at temperatures of from 150 to 250° C. under vacuum: a) one or more organic polycarboxylic acids having from 4 to 12 carbon atoms and from 2 to 4 carboxyl groups, derivatives thereof and/or mixtures thereof; with b) one or more organic polyols having functionalities of from 2 to 4 and number-average molecular weights of from 62 to 400 g/mol, with 2) one or more cyclic ester monomers, in a ratio by weight of polyester polyol Z to cyclic ester monomer of 10:1 to 1:1, at starting temperatures below 220° C., wherein the temperature is less than or equal to 175° C. after no more than 60 minutes, and the OH number of said polyester polyols Z is reduced by at least 5 mg KOH/g and the ratio of moles of the cyclic ester monomer to the hydroxyl groups of the polyester polyol Z ranging from 0.75:1 to 10:1.