Catalyst for polyisocyanurate foams made with alternative blowing agents

A closed cell, rigid polyisocyanurate foam which comprises the reaction product of (1) a polyisocyanate and (2) 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 catalytically effective amount of a catalyst mixture comprising (i) a salt of a carboxylic acid selected from the group consisting of an alkali metal salt and an alkaline earth metal salt and mixtures thereof, (ii) a tertiary amine, and (iii) a quaternary ammonium carboxylate salt, wherein the mole ratio of carboxylate metal salt:

• tertiary amine is a value less 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 teritary amine.