Method for increasing the 4,4'dicarbamate isomer of the diphenylmethane dicarbamates during preparation thereof
AssigneeAtlantic Richfield Company
InventorsEdward T. Shawl, Gerald A. Bullano
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Abstract
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.degree. 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.
Claims13
A method for the preparation of diphenylmethane dicarbamates and polymethylene polyphenyl carbamates having an increased amount of 4,4'-diphenylmethane dicarbamate isomer in the total diphenylmethane dicarbamate produced which comprises reactng in a single phase system an N-aryl carbamic acid ester with a carbonyl compound selected from formaldehyde, para-formaldehyde or trioxane or mixtures thereof, at a temperature of from about ambient to about 170.degree. C. in the presence of a mineral acid condensation catalyst while said N-aryl carbamic acid ester is dissolved in an inert organic solvent having a dielectric constant of at least 20 at 20.degree. C. and at a concentration of N-aryl carbamic acid ester in said solvent of from 0.1 to 50 weight percent and recovering the desired carbamates.
A method for the preparation of a diphenylmethane dicarbamate, diethyl ester, and polymethylene polyphenyl carbamates, ethyl esters, having an increased amount of 4,4'-diphenylmethane dicarbamate, diethyl ester in the total diphenylmethane dicarbamate produced which comprises reacting in a single phase system at atmospheric pressure ethylphenylcarbamate with trioxane at a temperature of from about 50.degree. C. to 130.degree. C. in the presence of from 5.0 to 50 weight percent of the ethylphenylcarbamate employed of a sulfuric acid condensation catalyst while said ethylphenylcarbamate is dissolved in an inert organic solvent having a dielectric constant of at least 20 at 20.degree. C. and a concentration of ethylphenylcarbamate in said solvent of 0.75 to 20 weight percent and recovering the desired diphenylmethane dicarbamate.
Dependencies are inferred from the claim text.