NOVEL SINGLE-COMPONENT REACTIVE SYSTEMS B ASED ON SOLID POLYISOCYANATES

Storage-stable polyurethane one-pack systems are usually cured either by moisture from the environment or by splitting off a blocking agent. The curing characteristics of moisture-curing isocyanate-prepolymers are strongly dependent on humidity and temperature whilst in the case of blocked isocyanate systems special care has to be taken to avoid ai r pollution. New heterogeneous systems on the basis of usual isocyanat e-reactive compounds and solid polyisocyanate particles, which are sur rounded by a diffusion-barrier-layer, are highly storage-stable und cu re even in thick layers without the need of humidity and without forma tion of volatile blocking agents or by-products. After curing the syst ems, preferably by heating, polyurethanes with very good overall mecha nical properties are obtained, which feature high temperature stabilit y und high dimensional stability under heat. The new systems with prac tically unlimited pot-life offer new applications so far unaccessible for polyurethane chemistry.