Production of 4,4'-alkylidene diphenyl diisocyanate

Details Production of 4,4'-alkylidene diphenyl diisocyanate Production of 4,4'-alkylidene diphenyl diisocyanate

1978-07-10

1979-07-31

Torrence, Dolph H.

Chemistry of carbon compounds

Miscellaneous organic carbon compounds

C-metal

260453AM, 560 24, 560 25, C07C11800, C07C119048, C07C12506

Patent

active

041630190

ABSTRACT:
A process for the production of 4,4'-methylene diphenyl diisocyanate (4,4'-MDI) to the substantial exclusion of other position isomers and of higher oligomers comprises a coupling reaction in which formaldehyde is condensed with an N-phenyl alkylcarbamate under mild conditions to produce the dialkyl carbamate of 4,4'-methylene diphenyl diisocyanate, and a catalytic exchange reaction in which the latter is reacted with phenyl isocyanate to produce with extremely high selectivity 4,4'-methylene diphenyl diisocyanate as product and N-phenyl alkylcarbamate which is recycled to the coupling reaction. In the overall process, formaldehyde and phenyl isocyanate are selectively converted to 4,4'-MDI. By substituting a higher aldehyde or a ketone for formaldehyde, the process may also be employed to produce other 4,4'-alkylidene diphenyl diisocyanates.

REFERENCES:
patent: 3059021 (1962-10-01), Prill
patent: 3243448 (1966-03-01), Erner
patent: 3277098 (1966-10-01), Merten
patent: 3345395 (1967-10-01), Muller et al.
patent: 3719699 (1973-03-01), McClure et al.
Kirk-Othmer, "Encyclopedia of Chemical Technology", Second Edition, vol. 12, pp. 53-59.
Chemical Week, Nov. 9, 1977, pp. 57-58.
Wagner, J. Org. Chem., vol. 59, pp. 1862-1881 (1959).

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