| abstract |
A process for the production of a low-hardness thermosetting polyurethane elastomer having a high curing rate, a low JIS A hardness of 10 to 40, a small compression set, a low moisture absorption, good dimensional stability and no bleeding property. In this process, a prepolymer formed from a difunctional polyol having a degree of total unsaturation of at most 0.01 meq/g and 4,4′-diphenylmethane diisocyanate alone or a polymethylene polyphenyl polyisocyanate containing 4,4′-diphenylmethane diisocyanate having an NCO content of 3 to 6% is reacted with a difunctional or trifunctional polyol having a degree of total unsaturation of at most 0.01 meq/g or a mixture thereof in the presence of a urethane reaction promoting catalyst. |