| abstract |
This invention relates to a process for preparing optionally reinforced rigid polyurethanes by the reaction, under resin transfer molding conditions at an isocyanate index of 90 to 130, of (a) an organic polyisocyanate, with (b) 15 to 80 percent by weight, based on the total of components (b), (c), and (d), of certain polyester polyols having long-chain fatty acid or fatty alcohol groups, a number average molecular weight of 500 to 3000, and a metal ion content below 100 ppm; and (c) 20 to 85 percent by weight, based on the total of components (b), (c), (d) and (e), of one or more crosslinkers, other than component (b), containing 3 to 8 hydroxyl groups and having a molecular weight of 92 to 1000 and a metal ion content below 100 ppm, (d) 0 to 60 percent by weight, based on the total of components (b), (c), and (d), of an isocyanate-reactive compound, other than a polyester polyol of component (b), having a metal ion content below 100 ppm, selected from (i) an isocyanate-reactive polyol containing 3 to 6 hydroxyl groups and having a number average molecular weight of more than 1000 to 10,000, (ii) an isocyanate-reactive diol having a number average molecular weight of 62 to 10,000, and (iii) mixtures thereof, and (e) 0.05 to 3 parts by weight, based on the total amount of components (b), (c), (d) and (e), of a delayed action catalyst. |