Isocyanurate groups containing polyisocyanate mixtures, process for their preparation and their use in the preparation of polyurethane foams.

摘要

Liquid polyisocyanate mixtures containing isocyanurate groups and having an NCO content of 15 to 30% by weight, obtainable by trimerisation of some of the isocyanate groups of polyisocyanate mixtures of the diphenylmethane series containing 80 to 100% by weight of diisocyanatodiphenylmethane isomers and 0 to 20% by weight of polyisocyanates of the diphenylmethane series which have a functionality greater than 2, the diisocyanatodiphenylmethane isomers being composed of 40 to 80% by weight of 4,4'-diisocyanatodiphenyl- methane, 20 to 60% by weight of 2,4'-diisocyanatodiphenylmethane and 0 to 8% by weight of 2,2'-diisocyanatodiphenylmethane and the stated percentages summing to 100, by carrying out the trimerisation up to the desired degree of trimerisation in the presence of a trimerisation-accelerating catalyst and optionally with the concomitant use of components containing hydroxyl groups, and then terminating the trimerisation by adding a catalyst poison. The liquid polyisocyanate mixtures thus obtained are used for the production of polyurethane foams.