Process for the preparation of methylene diphenylene diisocyanates and polymethylene polyphenylene poly (diisocyanates)
AssigneeArco Chemical Technology, L.P.
InventorsEdward T. Shawl, Haven S. Kesling, Jr.
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Abstract
An improved process is provided for the preparation of methylene diphenylene diisocyanates (MDI) and polymethylene polyphenylene poly (diisocyanates) by the thermal decomposition of a methylene diphenylene bis (dialkylurea) or a polymethylene polyphenylene poly (dialkylurea) in a solvent in the presence of a tertiary amine hydrohalide, such as pyridine hydrochloride, as a promoter for conversion of the urea groups to the corresponding isocyanate.
Claims12
A process for the preparation of a methylene diphenylene diisocyanate or a polymethylene polyphenylene poly (diisocyanate) which comprises heating at a temperature within the range of from about 50.degree. C. to about 220.degree. C. a methylene diphenylene bis (dialkylurea) having the formula ##STR3## or a polymethylene polyphenylene poly (dialkylurea) having the formula ##STR4## wherein at least one of the substituents u, w, x, y and z on the ring is a dialkylureido (--NHCONRR') group and the other substituents which may be the same or different on the ring, are hydrogen, an ether group or a nitro group, R and R' of the dialkylureido group which may be the same or different are an alkyl group having indepedently from 1 to 8 carbon atoms and n is an integer of from 1 to 8, dissolved or slurried in an organic solvent or mixture of solvents, in the presence of a tertiary amine hydrohalide as a promoter to convert the urea to the corresponding diisocyanate, and thereafter separating and recovering the diiscoayanate or poly (diisocyanate).
A process for the preparation of a methylene diphenylene diisocyanate which comprises heating at a temperature of from about 90.degree. C. to about 150.degree. C. a methylene diphenyl bis (dialkylurea) having the formula ##STR5## wherein at least one of the substituents, u, w, x, y and z on the ring is a dialkylureido (--NHCONRR') group and the other substituents which may be the same or different on the ring are hydrogen, an ether group or a nitro group and R and R' of the dialklureido group are an alkyl group having independently from 1 to 8 carbon atoms, dissolved in or slurried in an organic solvent or mixture of solvents in the presence of a tertiary amine hydrohalide as a promoter to convert the urea to the isocyanate and thereafter separating and recovering the isocyanate.
Dependencies are inferred from the claim text.