A METHOD FOR THE PREPARATION OF A MIXTURE OF DIPHENYL METHANE DICARBAMATES AND POLYMETHYLENE POLYPHENYL CARBAMATES

摘要

A method for increasing the 4,4' disubstituted isomer of the diphenylmethane dicarbamates produced by the acid catalyzed condensation of an N-aryl carbamic acid ester, such as ethylphenylcarbamate, with a carbonyl compound, such as formaldehyde, which comprises carrying out the condensation in a single phase system with a dilute solution of the N-aryl carbamic acid ester in an inert solvent having a dielectric constant of at least 20 at 20 DEG C. The solvent must have good solubility for the carbamates, which carbamates are employed in the solvent at concentrations of from about 0.1 to 50 weight percent to provide a product enriched with the 4,4'-diphenylmethane dicarbamate isomer.