Bayer Materialscience Ag

Covestro Deutschland Ag

Lars Padeken

Friedhelm Steffens

Wolfgang Lorenz

Bernd Pennemann

Fritz Pohl

Rainer Bruns

Klaus Biskup

Andreas Karl Rausch

Gerhard Wiechers

Lothar Weismantel

Meta-toluene-diisocyanate is produced by reacting meta-toluenediamine with phosgene in the gas phase. The meta-toluenediamine to be vaporized for use in this phosgenation process must contain less than 0.5 wt. % of toluenediamine residue, a total of less than 0.2 wt. % of ammonia and cycloaliphatic amines, and less than 20 ppm of heavy metals. At least 0.1 wt. % of the liquid meta-toluenediamine being to be vaporized must not be vaporized. This non-vaporized content of the meta-toluenediamine must not be fed to the phosgenation reactor.

Process for the preparation of isocyanates in the gas phase

Aromatic diisocyanates are produced by reacting in the gas phase the corresponding primary aromatic diamine with phosgene. The phosgene and the primary aromatic diamine are reacted within a mean residence time of from 0.05 to 15 seconds. The aromatic diamine used contains less than 0.05 mole % overall of aliphatic amine containing no keto groups, per mole of primary amino groups.

Process for the production of aromatic diisocyanates in the gas

The present invention relates to a process for the preparation of toluene-diisocyanate. In this process, toluenediamine is reacted with phosgene to give crude toluene-diisocyanate, the crude toluene-diisocyanate is purified by distillation, the distillation residue formed during the distillation is hydrolysed at temperatures of less than 230&#xb0; C. under absolute pressures of less than 30 bar, and the toluenediamine formed by this process is subsequently recycled into the reaction of toluenediamine and phosgene.

Process for the preparation of toluene-diisocyanate

The present invention relates to a process for the preparation of toluenediamine, in which dinitrotoluene is reacted with hydrogen in the presence of a catalyst. The dinitrotoluene required by this process has a content of carbon dioxide, in either physically dissolved or chemically bonded form, of not more than 0.175 mol %, based on the molar amount of the dinitrotoluene.

Process for the preparation of toluenediamines by catalytic hydrogenation of dinitrotoluenes

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Düsseldorf, Germany

Lars Padeken