The Dow Chemical Company

The Upjohn Co.

Nirad N Shah

Guo-shuh J Lee

Kirk D Anderson

V Rao Durvasula

Louis N Moreno

George E Hartwell

Richard A Prather

Howard R Steele

Richard Hatfield, Jr

Aromatic diamines, such as toluenediamine, are alkylated in the ortho position by heating the diamine in the presence of an aluminum alloy, aluminium chloride and, optionally, zinc, and then reacting with an alkene at elevated temperatures and pressures.

Ortho-alkylation of aromatic amines

A catalytic intermediate useful in the preparation of ortho-alkylated aromatic amines is prepared by heating an amine in the presence of aluminum metal, zinc metal and aluminum chloride. This catalytic intermediate is used to alkylate aromatic amines which may be the same as or different from the amine used in the catalytic intermediate preparation. In a preferred embodiment, toluenediamine is alkylated in the ortho positions to form diethyltoluenediamine.

'An improvement is described in the process of preparing polymethylene polyphenyl polyamines by condensing aniline and formaldehyde in the presence of an acid catalyst. The improvement entails adding a minor proportion of a polyamine mixture comprising di(aminophenyl)methanes and oligomeric polymethylene polyphenyl polyamines, collectively known as polymethylene polyphenyl polyamines or polymeric MDA, to an intermediate stage of the condensation reaction where the various intermediately formed aminobenzylamines are present. The process lends itself to either a batch or continuous method for preparing the polyamines. The improvement is actually observed in the polymethylene polyphenyl polyisocyanates derived from the polyamines which have substantially reduced color over those polyisocyanates prepared from polyamines prepared via a prior art method. Such color improvements invariably carry over to polyurethane products derived therefrom.

Process for polymeric MDA, recycle of finished polymeric MDA

An improvement is described in the process of preparing polymethylene polyphenyl polyamines by condensing aniline and formaldehyde in the presence of an acid catalyst in the initial condensation. The improvement enables the amount of acid which has to be neutralized at the end of the reaction to be substantially reduced or eliminated entirely. This is accomplished without sacrifice of the high level of 4,4'-isomer of di(aminophenyl)methane normally present in the diamine content of the polyamines when a mineral acid catalyst is employed in the condensation. The improvement comprises conducting the initial condensation of aniline and formaldehyde in the presence of a strong acid at a level normally employed to obtain high 4,4'-isomer content in the diamine component of the polyamine product, subjecting the reaction mixture, at the stage at which benzylamine formation is substantially complete, to solvent extraction after adjusting the aniline and water content of the reaction mixture to specified levels, recovering the mixture of benzylamine and excess aniline from the solvent extract and subjecting this mixture (optionally after removal of aniline) to rearrangement to the desired polyamine product in the presence of a catalyst which can be a strong acid (at a level substantially below that used in the initial condensation), or a solid catalyst (diatomaceous earth, clay, zeolite). The aqueous layer remaining after the solvent extraction contains aniline hydrochloride and a minor amount of benzylamine hydrochloride and is recovered and used as part of the reactants employed in a subsequent condensation.

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Houston, TX, United States of America

Nirad N Shah