Basf Aktiengesellschaft

Willy Van Pee

Ulrich Penzel

Joachim Pfeffinger

Filip Nevejans

Hans Volkmar Schwarz

Frank Poplow

Friedrich Sauer

Eckhard Str&ouml;fer

Rainer Ohlinger

Peter Van Den Abeel

Volker Scharr

Jan Jacobs

Rudolf Schmidt

Dieter Starosta

Horst Brandtstaedter

Hans J Astheimer

Jaak Van Steen

Siegfried Krueger

J&uuml;rgen Dosch

Hilmar Boesel

Fritz N&auml;umann

In a process for preparing mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates having a reduced content of chlorinated by-products and a reduced iodine color number by two-stage reaction of the corresponding mixtures of diphenylmethanediamines and polyphenylpolymethylenepolyamines with phosgene in the presence of at least one inert organic solvent at elevated temperature, separation of the excess phosgene and solvent after the phosgenation is complete and thermal treatment of the reaction product, the mass ratios of phosgene to hydrogen chloride in the residence time apparatus of the second stage of the phosgenation are at the same time 10-30:1 in the liquid phase and 1-10:1 in the gas phase.

METHOD FOR PRODUCING MIXTURES CONSISTING OF DIPHENYLMETHANE DIISOCYANATES AND POLYPHENYLENE-POLYMETHYLENE-POLYISOCYANATES CONTAINING A REDUCED AMOUNT OF CHLORINATED SECONDARY PRODUCTS AND WITH A REDUCED IODINE COLOR INDEX

A process for the manufacture of 4,4'-diphenylmethane diisocyanate and a mixture of diphenylmethane diisocyanate isomers containing a controllable amount of uretdione and hydrolizable chlorine which comprises feeding crude MDI to an evaporator, condensing a head fraction in two stages in the presence of an inert gas, feeding the first stage condensate to a distillation column, producing a mixture of diphenylmethane diisocyanate isomers as an overhead, producing 4,4'-diphenylmethane diisocyanate as a side draw, and condensing each of the overhead and side draw in two stages in the presence of an inert gas.

Process for the manufacture of 4,4'-diphenyl-methane diisocyanate and a

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