PROCESSO PARA PURIFICACAO DE POLIISOCIANATOS BRUTOS E OS POLIISOCIANATOS ASSIM PURIFICADOS

摘要

Crude polyisocyanates are purified by extraction at a temperature from 80 DEG to 180 DEG C. to form a two-phase system. The phases are separated and the phase made up of purified polyisocyanate and solvent is cooled to a temperature which is at least 50 DEG C. below the extraction temperature. Upon cooling, a second two-phase system forms. Purified polyisocyanate containing residual solvent is recovered upon separation of these phases. Solvent in which polyisocyanate is present that is reclaimed during this process may be reused in subsequent extractions. The purified polyisocyanates have a viscosity which is lower than that of crude polyisocyanates having substantially the same isocyanate content and average functionality. These purified polyisocyanates are useful in the production of polyurethane foams and moldings as well as adhesives and coatings.