Abstract: A reactor for the thermal cleavage of monofunctional and/or polyfunctional carbamic esters into the corresponding isocyanate and hydroxyl components in the liquid phase having devices for introduction of heat into the reactor, where the devices are heat exchanger plates through which a heat transfer medium flows and have a geometry defined by the ratio of the degassing area to the volume and arrangement of the heating surfaces which makes it possible for the cleavage to be carried out in a two-phase mixture which has a gas content of over 50% by volume.

Abstract: A reactor for the thermal cleavage of monofunctional and/or polyfunctional carbamic esters into the corresponding isocyanate and hydroxyl components in the liquid phase having devices for introduction of heat into the reactor, where the devices are heat exchanger plates through which a heat transfer medium flows and have a geometry defined by the ratio of the degassing area to the volume and arrangement of the heating surfaces which makes it possible for the cleavage to be carried out in a two-phase mixture which has a gas content of over 50% by volume.

Abstract: In a process for preparing mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates having a reduced content of chlorinated by-products and a reduced iodine color number by two-stage reaction of the corresponding mixtures of diphenylmethanediamines and polyphenylpolymethylenepolyamines with phosgene in the presence of at least one inert organic solvent at elevated temperature, separation of the excess phosgene and solvent after the phosgenation is complete and thermal treatment of the reaction product, the mass ratios of phosgene to hydrogen chloride in the residence time apparatus of the second stage of the phosgenation are at the same time 10-30:1 in the liquid phase and 1-10:1 in the gas phase.

Abstract: Organic polyisocyanates are prepared by a process in which polyurethanes are thermally dissociated in a dissociation reactor, a distillation is subsequently carried out and the bottom fraction obtained here is recirculated, wherein the recirculated bottom fraction is firstly fed at least partly into a reaction region and subsequently into the dissociation reactor.