Patent ID: 7985479

Claim:
A polyisocyanate mixture comprising: (A) 15 to 35 wt. % of diphenylmethane diisocyanate with 2 aromatic rings; (B) 10 to 30 wt. % of polymeric diphenylmethane diisocyanate with 3 or more aromatic rings; and (C) 40 to 75 wt. % of an isocyanate-functional polyurethane component; wherein the polyisocyanate mixture has an isocyanate content of 12 to 20 wt. %, an isocyanate functionality of >2.4, a viscosity of <10,000 mPa·s at 25° C., and a shear rate of 80 l/s, and wherein the isocyanate-functional polyurethane component comprises a mixture of prepolymers prepared by reacting: (i) a first mixture comprising: (a) at least one first aromatic polyisocyanate reactant mixture comprising diphenylmethane diisocyanate and having >38% of its isocyanate groups in the 4,4′ position and having 0 to 60% of its isocyanate groups in the 2,4′ position, 0 to 2% of its isocyanate groups in the 2,2′-position, an isocyanate content of >33 wt. % and a functionality of 2.0; and (b) at least one second aromatic polyisocyanate reactant mixture comprising diphenylmethane diisocyanate and having <50% of its isocyanate groups in the 4,4′ position, 10 to 15% of its isocyanate groups in the 2,4′ position, and 0.1 to 5% of its isocyanate groups in the 2,2′ position, an isocyanate content of 30 to 33 wt. % and a functionality of >2.0; with (ii) a second mixture comprising: (c) at least one amino group-free polyether based on propylene oxide having an OH number of 40 to 80 mg KOH/g and a functionality of at least 2.0; and (d) at least one amino group-containing polyether based on propylene oxide having an OH number of 40 to 80 mg KOH/g, a functionality of 4.0 and an amine content of 0.499 to 0.998 wt. %.