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Abstract

The present invention relates to a process for preparing a moisture-curable, polyether urethane containing terminal cyclic urea/reactive silane groups by reacting at an NCO:OH equivalent ratio of 1.5:1 to 2.5:1 a) a hydroxyl component containing i) 20 to 100% by weight, based on the weight of component a), of a polyether containing two hydroxyl groups and one or more polyether segments, wherein the polyether segments have a number average molecular weight of at least 3000 and a degree of unsaturation of 0.04 milliequivalents/g, provided that the sum of the number average molecular weights of all of the polyether segments per molecule averages 6000 to 20,000, and ii) 0 to 80% by weight, based on the weight of component a), of a polyether containing one hydroxyl group and one or more polyether segments having a number average molecular weight of 1000 to 15,000, with b) an isocyanate component containing i) 20 to 100% by weight, based on the weight of component b), of a compound containing two isocyanate groups, and ii) 0 to 80% by weight, based on the weight of component b), of a compound containing one isocyanate group, provided that total percentages of a-ii) and b-ii) add up to at least 10, to form an isocyanate-containing reaction product and subsequently reacting this reaction product at an equivalent ratio of isocyanate groups to isocyanate-reactive groups of 0.8:1 to 1.1:1 with c) a compound containing an aspartate group and a reactive silane group to form an intermediate polyether urethane containing terminal non-cyclic urea/reactive silane groups and converting the non-cyclic urea groups to cyclic urea groups by reacting the intermediate polyether urethane in the presence of an acid catalyst and heat.

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