| abstract |
Rigid, closed cell polyisocyanurate foams are prepared by reacting together a polyisocyanate and a polyester polyol or a mixture of a polyester polyol and at least one other isocyanate-reactive compound in the presence of (a) a hydrogen-containing blowing agent or a mixture of a hydrogen-containing blowing agent and at least one co-blowing agent and (b) a catalyst mixture comprising (i) a carboxylate salt of an alkali metal or an alkaline earth metal or mixtures thereof, (ii) a quaternary ammonium carboxylate salt, and (iii) optionally a tertiary amine, wherein the mole ratio of carboxylate metal salt: tertiary amine is a value greater than about 2:1, and the total moles of quaternary ammonium carboxylate salt are less than the combined moles of the carboxylate metal salt and the tertiary amine. |