Patent ID: 8110704

Claim:
A process for the production of a stable NCO prepolymer having an NCO content of from 2.5 to 6 wt. % and a viscosity at 100° C. of 5000 mPas comprising: a) reacting (1) a polyisocyanate having a melting point greater than 70° C. with (2) one or more polyols, having an average molecular weight of 1000 to 3000 g/mol, a viscosity measured at 75° C. of 700 mPas and a functionality of 1.95 to 2.15, (3) optionally in the presence of auxiliary substances and additives, at a temperature of from 80° C. to 240° C. in a ratio of NCO to OH groups of from 1.55:1 to 2.35:1 to form a prepolymer, and b) rapidly cooling the prepolymer formed in a) in a manner such that the residence time of the prepolymer A) in the temperature range between the temperature at the end of a) to 130° C. does not exceed ½ hour and B) in the temperature range from the temperature at the end of a) to 110° C. does not exceed 1.5 hours and C) in the temperature range from the temperature at the end of a) to 90° C. does not exceed 7.5 hours and D) in the temperature range from the temperature at the end of a) to 70° C. does not exceed 72 hours, in which unreacted polyisocyanate still present after cooling is not removed and is present in an amount greater than 0.3 wt. % and less than 5 wt. %, based on the weight of the prepolymer.