Patent ID: 6903167

Claim:
A polyurethane prepolymer comprising an NCO content of 2% by weight to 10% by weight (as determined by Spiegelberger's method, EN ISO 11909), an OH value of 0 and a monomeric polyisocyanate content of at most 2% by weight produced by the process of A) mixing I) at least one reactive component (I) containing urethane groups with II) at least one low-monomer polyisocyanate (II) containing urethane groups, the low-monomer polyisocyanate (II) containing urethane groups produced by reacting at least one monomeric polyisocyanate with at least one polyol in an NCO:OH ratio of 2:1 to 10:1 and subsequently removing unreacted monomeric polyisocyanate, wherein the percentage by weight of the reactive component (I) containing urethane groups in the mixture of component (I) and polyisocyanate (II) is in the range from 20 to 90% by weight, B) and, optionally reacting components (I) and (II); wherein component (I) contains at least one of: both NCO groups and isocyanate-reactive functional groups as component (Ia); NCO groups as component (Ib) and is characterized by: i) a molecular weight of 500 to 20,000 g/mol, as determined by gel permeation chromatography (GPC), ii) a Brookfield viscosity of 500 to 25,000 mPas (ISO 2555) at a temperature of 20° C. to 100° C., iii) an NCO content in the range from 1 to 10% by weight, as determined by Spiegelberger's method (EN ISO 11909), iv) an OH value of 0, and v) a monomer concentration of greater than 2% by weight; isocyanate-reactive functional groups as component (Ic) and is characterized by; i) a molecular weight of 500 to 20,000 g/mol, as determined by gel permeation chromatography (GPC), ii) a Brookfield viscosity of 500 to 25,000 mPas at a temperature of 20° C. to 100° C., as determined by ISO 2555 iii) an OH value as determined by ISO 4326 in the range from 5 to 50 and iv) an NCO content of 0.