Process for the preparation of isocyanates

US5925783A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Klaus Jost · Hagen, DE
• Gunter Hammen · Dormagen, DE
• Rudolf Sundermann · New Martinsville, US

Key dates

• Filing date: May 12, 1997
• Grant date: Jul 20, 1999
• Expiry date: May 12, 2017

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C263/10
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

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%.