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US 4,307,029 AGranted
Process for preparing polymethylene-polyphenyl polyisocyanates
AssigneeMitsui Toatsu Chemicals, Inc.
InventorsKoichi Takeuchi, Seiji Hasegawa, Shinobu Aoki
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Abstract
A process for preparing polymethylene polyphenyl polyisocyanates, in which N-phenyl carbamic acid esters are subjected to a condensation reaction with formaldehyde, and the reaction product containing polymethylene polyphenyl polycarbamic acid esters and unreacted N-phenyl carbamic acid esters is thermally decomposed to obtain polymethylene polyphenyl polyisocyanates.
Claims16
A process for preparing polymethylenepolyphenyl polyisocyanates which comprises subjecting N-phenyl carbamic acid esters having the formula (I):
- ##STR6## wherein R is a lower alkyl group having 1 to 4 carbon atoms, to condensation reaction with formaldehyde or a formaldehydeproducing compound in the presence of an acid catalyst, subjecting the reaction product containing the resulting polycarbamic acid esters having the formula (II):
- ##STR7## wherein R is as defined in the formula (I) and m is 0 or an integer from 1 to 5, and the unreacted N-phenyl carbamic acid esters to thermal decomposition in an organic solvent under a boiling pressure of the solvent at a temperature from 200.degree. to 350.degree. C., and separating the resulting alcohol and the unreacted N-phenyl isocyanates as vapor from the formed liquid polyisocyanates.
Dependencies are inferred from the claim text.