Polyisocyanates of the diphenyl methane series

US4613687A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Hartmut Knofel · Odenthal, DE
• Michael Brockelt · Bensberg, DE

Key dates

• Filing date: Aug 17, 1981
• Grant date: Sep 23, 1986
• Expiry date: Aug 17, 2001

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C08G18/7664
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

A polyisocyanate or mixture of polyisocyanates in which the main component(s) correspond to the formula: ##STR1## in which R.sub.1, R.sub.2, and R.sub.3 each represent hydrogen or a saturated alkyl group containing from 1 to 12 carbon atoms, provided that at least two of these radicals represent hydrogen; and PA1 m, n, o and p each represent 0 or 1, provided that when m, n, o and/or p represent 0, the free valency is taken up by a hydrogen atom and that the sum of m+n+o+p is greater than 1 on a statistical average. Such polyisocyanate or mixture of polyisocyanates may be produced by first reacting a 4-nitrobenzyl halide, a 3-nitrobenzyl halide, a benzyl halide, a benzyl alcohol or a nitrobenzyl chloride isomer mixture with nitrobenzene, an alkyl-substituted nitrobenzene, an alkyl benzene or benzene in the presence of a Friedel-Crafts or an acid catalyst. This reaction product is then nitrated, the nitro groups are converted to amino groups by reduction or hydrogenation and the amino compound(s) subsequently phosgenated to form the polyisocyanate(s). The purity of the product polyisocyanate may be improved by distilling off secondary products before and/or after the phosgenation.