LIQUID, LIGHT-COLORED POYLISOCYANATE MIXTURES AND A PROCESS FOR THEIR PRODUCTION

An isocyanate terminated prepolymer based upon diphenylmethane isocyanates. This prepolymer is the reaction product of a diphenylmethane isocyanate mixture having from about 75 to about 95 wt% binuclear isomers and from about 5 to about 25 wt% polymeric isocyanate with a polyether polyol. The binuclear isomer content is generally from about 15 to about 40 wt% 2,4'-isomer and from about 2 to about 10 wt% 2,2'-isomer. The polyether polyol has a functionality of from about 3 to about 8, an OH number of from about 350 to about 1000 mg KOH/g and a molecular weight of from about 150 to about 1000. These prepolymers are particularly useful as starting materials for the production of light-colored, dimensionally stable rigid polyurethane foams.