Abstract: Isocyanates are prepared by a continuous process by reacting appropriate primary amines with phosgene in the presence of an isocyanate as solvent, the primary amine optionally dissolved in an inert organic solvent being reacted with phosgene, which is dissolved in the isocyanate, at temperatures of 60 to 150.degree. C. and at pressures of 1 to 30 bar (10.sup.5 to 3.10.sup.6 Pa) to obtain the corresponding isocyanate, wherein the molar ratio of phosgene to amine used is 4:1 to 1:1, and the isocyanate used as solvent is solids-free and has a value for hydrolysable chlorine of less than 2%.

Abstract: The present invention relates to an improved process for the production of monomeric and polymeric poly(O-alkylurethanes) of the diphenyl methane series. The process comprises the reaction of the corresponding amines with dialkyl carbonates in the presence of a catalyst, followed by the isolation of the products in a highly pure form. The invention also relates to the use of the produced monomeric and polymeric poly(O-alkylurethanes) for the production of the corresponding isocyanates.

Abstract: The present invention relates to a process for the preparation of a polyisocyanate comprising(a) thermally decomposing in a tube reactor a solution of an N-substituted carbamic acid ester corresponding to said polyisocyanate in a solvent used as decompositoin medium, wherein said solvent (i) is capable of dissolving the carbamic acid ester, (ii) is stable at the decomposition temperature and chemically inert towards the carbamic acid esters and the polyisocyanate product, (iii) can be distilled without decomposing under the conditions of decomposition of carbamic acid estes, and (iv) has at least one miscibility gap with an extracting agent used according to the extraction step (c), said solutions being carried along the internal wall of reactor;(b) separating the gaseous materials formed in the tube reactor by fractional condensation into a fraction I comprised mainly of the alcohol by-product and a fraction II comprised mainly of polyisocyanates, isocyanatourethanes, unreacted carbamic acid ester, and the s

Abstract: N-monosubstituted carbamic acid esters are thermally split on a continuous basis in a tube reactor. The carbamic acid ester which is flowed down or passed over the inner wall of a tube reactor is thermally split at a temperature of from 150.degree. to 450.degree. C. and under a pressure of from 0.001 to 20 bar into at least two fractions. One fraction is predominantly isocyanate and a second fraction is predominantly hydroxyl compound. These fractions may be separated by removing one as a gaseous fraction formed under the splitting conditions from the head of the reactor and collecting the second fraction as a liquid which accumulates at the base of the reactor. If both fractions are gaseous under the splitting conditions, they are both removed from the head of the reactor and subsequently separated by fractionating columns for example. This process is particularly advantageous in that isocyanate and hydroxyl fractions are obtained in high yield without using a solvent.

Abstract: Cycloaliphatic triisocyanates or isomer mixtures of such triisocyanates corresponding to the formula ##STR1## in which R represents hydrogen or a C.sub.1 -C.sub.4 alkyl group are produced by phosgenating the corresponding cycloaliphatic triamines or isomer mixtures of such triamines or a salt thereof.These triisocyanates are useful in the production of polyisocyanate addition products, particularly polyurethane coatings and lacquers.

Abstract: Triisocyanates and isomeric mixtures of triisocyanates corresponding to the formula ##STR1## in which R represents hydrogen or an alkyl group having from 1 to 4 carbon atoms are made by phosgenating the corresponding triamine. These triisocyanates are particularly useful in the production of polyurethanes, especially polyurethane lacquer coats.