Abstract: The present invention comprises a process for purifying isocyanate-comprising residues.

Abstract: The invention provides a multistage process for continuously preparing organic polyisocyanates, preferably diisocyanates, more preferably aliphatic or cycloaliphatic diisocyanates, by reaction of the corresponding organic polyamines with carbonic acid derivatives and alcohols into monomeric polyurethanes of low molecular mass, and the dissociation of said polyurethanes. The invention further provides an associated preparation process in which at certain reaction stages the polyisocyanates prepared and unutilizable residues are removed and reusable by-products and intermediates are recycled to preliminary stages.

Abstract: The invention provides a multistage process for continuously preparing organic polyisocyanates, preferably diisocyanates, more preferably aliphatic or cycloaliphatic diisocyanates, by reaction of the corresponding organic polyamines with carbonic acid derivatives and alcohols into monomeric polyurethanes of low molecular mass, and the dissociation of said polyurethanes. The invention further provides an associated preparation process in which at certain reaction stages the polyisocyanates prepared and unutilizable residues are removed and reusable by-products and intermediates are recycled to preliminary stages.

Abstract: The present invention comprises a process for purifying isocyanate-comprising residues.

Abstract: The invention provides a multistage process for continuously preparing organic, distillable polyisocyanates, preferably diisocyanates, more preferably aliphatic or cycloaliphatic diisocyanates, by reacting the corresponding organic polyamines with carbonic acid derivatives and alcohols to low molecular mass monomeric polyurethanes, and thermally cleaving said polyurethanes, in which at defined reaction stages the polyisocyanates prepared and unusable residues are separated off, and reusable by products and intermediates are recycled to upstream stages.

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 the preparation of isocyanates from carbamic esters, (i) a mixture containing a monofunctional or polyfunctional carbamic ester is passed continuously into a cleavage reactor or a cascade of two or more cleavage reactors, (ii) the carbamic ester is subjected to a thermal cleavage to give isocyanate and alcohol, (iii) the cleavage gas escaping from the cleavage reactor or reactors and containing the isocyanate, the alcohol, any uncleaved and/or partly cleaved carbamic ester and byproducts is brought into contact with a liquid coolant and condensing agent, cooled and at least partly condensed and (iv) the isocyanate and the alcohol are obtained from the cooled cleavage gas and the condensate in a rectification column, a part-stream of the alcohol obtained being used as liquid coolant and condensing agent for cooling and condensing the cleavage gas.

Abstract: The present invention relates to a process for the dissociation of allophanates, in which a thermal dissociation is carried out in a reaction vessel and the gaseous dissociation products obtained are removed from the reaction vessel using an inert carrier gas or the vapor of a liquid as stripping medium and are condensed.

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.