| 主权项 |
1. A process for the preparation of a polyurethane, comprising the process steps of:
i) providing a polyisocyanate prepolymer component comprising at least one polyisocyanates and a polyol wherein the said polyisocyanate prepolymer has a NCO content of 8 to 25 wt. %; ii) providing a polyol component comprising (a) a polyol and (b) a polyol ester of (bi) a polyol and (bii) a monocarboxylic acid, wherein the (a) polyol is selected from at least one polyether polyol having a hydroxyl number in a range of from 50 mg of KOH/g to 1,200 mg of KOH/g and a viscosity of from 2,000 to 8,000 mPas at 25° C., one polyester polyol having a hydroxyl number in a range of from 20 mg of KOH/g to 500 mg of KOH/g and a viscosity of from 2,000 to 15,000 mPas at 25° C., or a mixture of said polyether polyol and said polyester polyol and wherein said (bii) monocarboxylic acid is a short chain monocarboxylic acid comprising a C1 to C4 monocarboxylic acid or a C1 to C4 monocarboxylic acid derivative; iii) bringing of the polyisocyanate prepolymer component of step i) into contact with the polyol component of step ii) to form a mixture; and iv) foaming the mixture of step iii) wherein the viscosity of the polyol component is lower than the viscosity of said polyether polyol, said polyester polyol, or the mixture of said polyether polyol and said polyester polyol. |
