Bayer Aktiengesellschaft

Chiraranjan Podder

Harro Schlesmann

Pramod Gupta

Wilfried Nolte

Hans-Wilhelm Engels

Christian Konig

Hans-Jurgen Rabe

The present invention relates to the use of nucleus-substituted 4-hydroxyphenyl propionic acid compounds for stabilizing organic polyisocyanates.

Stabilization of organic polyisocyanates

4-nitrodiphenylamines may be produced by an improved process from 4-halo nitrobenzenes and primary aromatic amines in the presence of potassium carbonate and copper compounds, wherein

Process for the production of 4-nitrodiphenylamines

The reaction of 4-nitrohalogenbenzenes with primary aromatic amines in the presence of potassium carbonate and copper compounds to 4-nitrodiphenylamines gives better yield of purer products when synthetic polyamides are added.

The reaction of 4-nitrohalobenzenes with primary aromatic amines in the presence of potassium carbonate and copper compounds to produce 4-nitrodiphenylamine results in products with improved purity and yield if (1) carbonic acid amides or their derivatives are added, (2) 3 to 5 mol of amine are used per mole of halonitrobenzene and (3) 1.2 to 2 mol of the amine are added before the beginning of the reaction and the remainder during the reaction at such a rate that the molar excessive amine over halonitrobenzene is always from 100 to 400%.

Process for the preparation of 4-nitrodiphenylamines

An improved process for the preparation of 4-nitrodiphenylamines by the reaction of 4-nitrohalobenzenes with primary aromatic amines in the presence of potassium carbonate and copper compounds is characterized in that sulpholane dimethylsulphone, dimethylacetamide, diethylacetamide, tetramethylurea, tetraethylurea or mixtures thereof are used as solvents and 3 to 5 mol of amine are used per mol of halogenated nitrobenzene, from 1.2 to 2 mol of said amine being added before the beginning of the reaction and the remainder during the reaction at such a rate that the molar excess of unreacted amine over unreacted halogenated nitrobenzene is constantly at least 100%.

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Dormagen, Germany

Chiraranjan Podder