Process for the production of polyisocyanates

US4597909A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Berthold Keggenhoff · Krefeld, DE
• Enno Mahlmann · Krefeld, DE
• Willi Eifler · Bensberg, DE
• Gunther Ellendt · Krefeld, DE

Key dates

• Filing date: Feb 21, 1985
• Grant date: Jul 1, 1986
• Expiry date: Feb 21, 2005

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C265/14
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

The present invention is directed to a process for the production of polyamines of the diphenylmethane series having a high diamine content and a low 2,2'-diamino-diphenylmethane content by condensing aniline with formaldehyde in the presence of hydrochloric acid as catalyst, neutralizing the acid catalyst at the end of the condensation reaction and working up the polyamine mixture thus obtained by distillation, characterized in that PA0 (a) in a first reaction stage, from 2.0 to 3.5 moles of aniline are reacted with 1 mole of formaldehyde in the presence of hydrochloric acid or a condensation product produced from 2.0 to 3.5 moles of aniline and 1 mole of formaldehyde in the absence of acid catalyst is reacted in the presence of hydrochloric acid at a degree of protonation maintained at 40 to 60% at temperatures below 50.degree. C., PA0 (b) more aniline is then added to the reaction mixture so that the molar ratio of amine nitrogen atoms in the form of free aniline and the reaction products formed in accordance with (a) to formaldehyde chemically bound in the form of methylene bridges in those reaction products rises to more than 10:1 and up to 20:1 with the degree of protonation …