Preparation of liquid diphenylmethane diisocyanate compositions

Claim 2

Process as claimed in claim 1 wherein heating is carried out at a temperature of from 40* C. to 250* C.

Claim 3

Process as claimed in claim 6 wherein the temperature is from 50* to 200* C. and heating is carried out under a pressure of from 200 mm to 1 mm Hg.

Claim 4

Process for the manufacture of a liquid diphenylmethane composition which comprises heating a diphenylmethane diisocyanate which is solid or partially solid at 15* C., with an N,N''-disubstituted thiourea of the formula R-NHCS-NHR'' or an N1, N4-disubstituted-bis-thiourea of the formula R-NHCSNH-X-NHCSNHR'' wherein R and R'' represent phenyl radicals optionally substituted with a methyl, chloro, methoxy or nitro substituent, alkyl radicals with one to four carbon atoms, benzyl or a cyclohexyl radical and X represents a divalent alkyl radical containing two to six carbon atoms, in an amount of from 0.25 to 20 percent by weight of the diphenylmethane diisocyanate at a temperature within the range 40* to 250* C. and distilling out an isothiocyanate from the heated mixture.

Claim 5

A liquid diphenylmethane diisocyanate composition made by a process comprising heating at elevated temperature, a diphenylmethane -4,4''-disubstituted-bis-thiourea of the formula R-NHCSNH-X-NHCSNHR'' wherein R and R'' represent phenyl radicals optionally substituted with a methyl, chloro, methoxy or nitro substituent, alkyl radicals with one to four carbon atoms, benzyl or a cyclohexyl radical and X represents a divalent alkyl radical containing two to six carbon atoms, in an amount of from 0.25 to 20 percent by weight of the diphenylmethane diisocyanate and distilling out an isothiocyanate during the heating step.