The Upjohn Co.

The Dow Chemical Company

Floro F Frulla

Peter J Whitman

Henri Ulrich

Adnan A Sayigh

Fred A Stuber

Disclosed is an improved process for the preparation of carbamates by heating an organic carbonate and an aromatic urea or polyurea in the presence of aluminum as catalyst and a promoter comprising a combination of iodine and a mercury salt. High reaction temperatures are avoided by the process and conversions to carbamate products are high. Additionally, the process is economically attractive because even the common aluminum foil can be used as the catalyst. The products prepared by the process can be used in the production of insecticides, and, particularly, as intermediates in the preparation of organic mono- and polyisocyanates.

Preparation of carbamates from organic carbonates and aromatic ureas

Disclosed is an improved process for the preparation of carbamates by heating an organic carbonate and an aromatic amine in the presence of aluminum as catalyst and a promoter comprising a combination of iodine and a mercury salt. High reaction temperatures are avoided by the process and conversions to carbamate products are high. Additionally, the process is economically attractive because even the common aluminum foil can be used as the catalyst. The products prepared by the process can be used in the production of insecticides, and, particularly, as intermediates in the preparation of organic mono- and polyisocyanates.

Preparation of carbamates

A process is described for the preparation of polymethylene polyphenyl polyamines containing from 40 to 60 percent by weight of diamine and also containing markedly less high molecular weight polyamines than products hitherto available. Phosgenation of the polyamines gives the corresponding mixture of polymethylene polyphenyl polyisocyanates of markedly lower viscosity and lighter color than products hitherto available, and yielding polymer foams which are substantially white in color. The process comprises condensing aniline and formaldehyde (molar ratio 4-10:1) in the absence of catalyst, separating water from the resulting aminal mixture, contacting the aminals at 20.degree. C to 60.degree. C with a solid catalyst (diatomaceous earths, clays, zeolites) until formation of benzylamines is substantially complete, distilling aniline from the resulting benzylamines under reduced pressure and below 150.degree. C until the aniline content is 3 to 22 percent by weight, and contacting the resulting product with a solid catalyst (diatomaceous earths, clays, zeolites) at 100.degree. C to 190.degree. C until conversion to polymethylene polyphenyl polyamines is complete.

Polymethylene polyphenyl polyisocyanate

Process for preparing di(aminophenyl)methanes

Aniline and formaldehyde are condensed (2-10 moles aniline per mole of formaldehyde) at ambient temperature in the absence of acid catalysts to give a mixture of aminals (anilinoacetals) and aniline from which the water is removed. The anhydrous aminals are contacted with a solid catalyst (clays, zeolites, diatomaceous earth) using either batch or continuous operation initially at 20.degree. C to 55.degree. C until benzylamine formation is substantially complete, then at 50.degree. C to 65.degree. C until benzylamine conversion to methylene polyphenyl polyamines is 75 - 90% complete and finally at 80.degree. C to 100.degree. C. A polyamine mixture is obtained in which diaminodiphenylmethane is the major (order of 90 percent by weight or higher) component, the bulk of the higher oligomeric polyamines being triamine. The diaminodiphenylmethane component contains of the order of 85 percent of 4,4'-isomer, the rest being 2,4'-isomer except for very small amounts (order of 2 percent or less) of 2,2'-isomer. Advantages of the process include high yield of diaminodiphenylmethane with relatively high 4,4'-isomer content, low oligomeric polyamine content, low temperature operation (energy consumption lower), no acidic reactants to cause corrosion of equipment, and rapid rates of conversion.

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Wallingford, CT, United States of America

Floro F Frulla