Bayer Aktiengesellschaft

Gunther Hammen

Klaus Konig

Hartmut Knofel

Theodor Engbert

Rudolf Sundermann

Peter Heitkamper

Stefan Penninger

Gernot Becker

Low molecular weight N- and O-substituted diurethanes and/or polyurethanes are prepared by reacting a diamine and/or polyamine containing a primary amino group with an N-aryl-0-alkyl urethane in the presence of at least one high boiling alcohol. This reaction may be carried out at a temperature of from 180.degree. to 350.degree. C. and a pressure of approximately 0.1 to 1,500 mbar. The arylamine corresponding to the N-ary-0-alkyl urethane which forms during this reaction is continuously removed from the reaction mixture.

Process for the preparation of N- and O-substituted diurethanes and/or

Polyisocyanates are prepared by thermally splitting a carbamate corresponding to the formula:

Process for the preparation of polyisocyanates

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Dormagen, Germany

Gunther Hammen