VERFAHREN ZUR REINIGUNG UND ISOLIERUNG VON KONDENSIERTEN ISOCYANATEN DURCH EXTRAKTION MIT FLUESSIGEM ODER UEBERKRITISCHEM KOHLENDIOXID.

摘要

Polyisocyanates containing only trace amounts of free aromatic diisocyanates are recovered by purifying and isolating an isocyanate condensate containing free NCO groups from an impure admixture thereof, said isocyanate condensate impure admixture having been prepared by reacting a stoichiometric excess of an aromatic di- or polyisocyanate with a reactant compound containing at least two functional groups which are reactive with NCO groups, and such purification/isolation entailing extracting unreacted excess di- or polyisocyanate from said impure admixture with an inert gas, e.g., carbon dioxide, in either the liquid or supercritical state.