Polyisocyanates, preparation and use thereof

摘要

The present invention relates to a process for the production of specific polyisocyanates by reacting diamines containing hydrogen atoms which are active in the context of the isocyanate addition reaction with excess quantities of organic diisocyanates. The invention also relates to a modification of the above process characterized in that the diamines are reacted first with excess quantities of a first diisocyanate after which the thus obtained reaction product which contains a urea group and a biuret group is reacted in a second stage with a second diisocyanate. The invention also relates to the use of polyisocyanates as the isocyanate component in the production of polyurethane plastics by the isocyanate-polyaddition process.