Bayer Aktiengesellschaft

Rhein Chemie Rheinau Gmbh

Hans-Joachim Hennig

Dietrich Liebsch

Jurgen Lahrs

Andreas Hauner

Jorg Lussmann

Wolfgang Alter

A process for the production of aromatic carbodiimides by carbodiimidization of aromatic monoisocyanates in the presence of distillable organic phosphorus compounds as catalyst at 120.degree. to 220.degree. C. up to a maximum degree of carbodiimidization of 80% and subsequent removal by distillation of the unreacted starting isocyanate together with the catalyst from the reaction mixture, optionally together with subsequent preparation by distillation, together with the carbodiimides obtainable in accordance with this process.

Process for the production of aromatic carbodiimides

A process for the continuous catalyst-free production of polyisocyanates by thermal decomposition of the N-substituted carbamic acid esters corresponding to the polyisocyanates, in which the carbamic acid esters to be decomposed, in the form of a 5 to 90% by weight solution in an inert high-boiling solvent, are heated to a temperature of 100.degree. to 400.degree. C. and are subsequently introduced with expansion as a sidestream into a distillation column (4), in the sump of which a pressure of 0.001 to 5 bar and a temperature of 150.degree. to 400.degree. C. are maintained so that the high boiler is kept boiling in the sump, and the decomposition products are simultaneously condensed continuously and selectively at the head of the distillation column. The high boiler, which optionally contains impurities, is continuously removed via the sump outlet in a quantity substantially corresponding to the quantity of high boiler introduced into the column as solvent for the carbamic acid ester.

Process for the production of polyisocyanates

Organic mono- or poly-isocyanates are produced on a continuous basis by phosgenating the corresponding amines. A solution of the amine to be phosgenated is continuously sprayed through a smooth-jet nozzle into a solution of phosgene continuously flowing through a mixing chamber. The mixing chamber is maintained at a temperature of 120.degree.to 300.degree. C. and a pressure of from 10 to 1000 bars. The molar ratio of phosgene to primary amino groups is generally from 2:1 to 30:1.

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Leverkusen, Germany

Hans-Joachim Hennig