Non-catalytic process for preparing rapid-setting rigid polyurethanes

Claim 1

A non-catalytic process for preparing rapid-setting polyurethanes having a density of at least about 1 g/cc and a percent elongation of less than about 100, and are demoldable within about 15 minutes, which process comprises: A. admixing in the absence of a catalyst for urethane formation a first liquid component containing a polyol free of nitrogen atoms and having from about 2 to about 8 hydroxyl groups per molecule and an OH equivalent weight of less than about 200 with a second liquid component containing an aromatic polyisocyanate having an average of at least about 2 NCO groups per molecule with the proviso that when said first liquid component contains a polyol having an average of less than about 2.5 hydroxyl groups per molecule, then said second component contains an aromatic polyisocyanate or mixture of such polyisocyanates wherein the average number of NCO groups per molecule is at least about 2.5; B. placing the resultant mixture into a suitable mold wherein said mixture solidifies within about 15 minutes to a solid having a density of at least about 1 g/cc and an elongation of less than about 100; and C. subsequently demolding the resultant article from the mold; wherein the temperature of said first and second component at the time of mixture is such that the temperature of the resultant mixture is at least about 50° C. and is sufficient to provide a peak exotherm temperature of at least about 85° C. and less than about 200° C. and wherein said first and and second components are admixed in such proportions that the resultant NCO:OH equivalent ratio is from about 0.75:1 to about 1.5:1.