Preparation of mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates having a reduced iodine color number

US5207942A · kind A · utility

Assignee

• BASF SE

Inventors

• Dietrich Scherzer · Neustadt, DE
• Roland Minges · Havelsee, DE
• Werner Langer · Ludwigshafen, DE
• Bernd Bruchmann · Ludwigshafen, DE
• Wolfgang Heider · Neustadt, DE
• Peter Keller · Bruchmühlbach-Miesau, DE
• Arnold J. Schmitt · Beloit, US
• Willy van Pee · Neukirchen-Vluyn, DE

Key dates

• Filing date: Feb 8, 1991
• Grant date: May 4, 1993
• Expiry date: Feb 8, 2011

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C263/20
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

Mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates (crude MDI) having a reduced iodine color number are prepared by reacting the corresponding mixtures of diphenylmethanediamines and polyphenylpolymethylene-polyamines with phosgene in the presence of one or more inert organic solvents at elevated temperatures by a process in which low molecular weight alkanols, polyhydric alcohols, preferably dihydric to octahydric alcohols having a molecular weight of from 60 to 350, or mixtures thereof are incorporated in an effective amount, advantageously in an amount of from 0.01 to 5% by weight, based on the weight of crude MDI, into the reaction mixture after the end of the phosgenation, the phosgene and the inert organic solvent are then separated off, from 0 to 5% by weight, based on the weight of crude MDI, of one or more phenol-based antioxidants and/or aryl phosphite are added to the reaction product, and the reaction mixture is subjected to a thermal treatment.