Polyurethanes prepared from hydroxymethyl isocyanurates

Process for preparing polyurethanes containing isocyanurate rings from a polyol containing one or more isocyanurate rings, this process being characterized in that said polyol selected from the group consisting of tris-hydroxymethyl isocyanurate, bis-hydroxymethyl isocyanurate, mixed hydroxymethylhydroxy (C.sub.2 - C.sub.6 alkyl) isocyanurates, derivatives of bis- or tris-hydroxymethyl isocyanurate or a mixed hydroxymethyl-hydroxy (C.sub.2 - C.sub.6 alkyl) isocyanurate in which one or more hydroxymethyl groups have been replaced by hydroxypolyoxymethylene groups containing 2-4 oxymethylene groups, oligomers obtained by intercondensation of the above-mentioned compounds during the preparation of the above-mentioned compounds, derivatives of said compounds in which the hydroxy groups are partly etherified and/or esterified, and mixtures of these compounds, is made to react with an organic polyisocyanate or a mixture of polyisocyanates, the ratio of isocyanate groups of said polyisocyanate or mixture to hydroxy groups of said polyol being between 1.0 and 1.5, in the presence of one or more compounds accelerating the reaction of isocyanate groups with hydroxyl groups, wherein said polyol contains at least 2% by weight of solvent.