Process for the production of polyisocyanates

US5284969A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Andreas Hauner · Leverkusen, DE
• Hans-Joachim Hennig · Leverkusen, DE

Key dates

• Filing date: Nov 6, 1992
• Grant date: Feb 8, 1994
• Expiry date: Nov 6, 2012

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C263/04
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

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.