Process for preparing isocyanate and carbamate ester products

Details Process for preparing isocyanate and carbamate ester products Process for preparing isocyanate and carbamate ester products

1992-10-15

1993-08-03

Welsh, Maurice J.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From reactant having at least one -n=c=x group as well as...

528 84, 560330, 560334, 560335, 560336, 560338, 560343, 560345, C08G 1872

Patent

active

052330109

ABSTRACT:
A process for preparing an isocyanate having at least two --N.dbd.C.dbd.O groups is provided which comprises preparing a substituted aromatic amine having at least two --NH.sub.2 groups, recovering the substituted aromatic amine having at least two --NH.sub.2 groups, and preparing an isocyanate from the substituted aromatic amine having at least two --NH.sub.2 groups by (1) contacting the substituted aromatic amine with CO.sub.2 under conditions sufficient to produce the corresponding ammonium carbamate salt, and reacting the ammonium carbamate salt with an electrophilic or oxophilic dehydrating agent under conditions sufficient to produce the corresponding isocyanate, or (2) contacting the substituted aromatic amine with CO.sub.2 under conditions sufficient to produce the corresponding ammonium carbamate salt, reacting the ammonium carbamate salt with a primary or secondary hydrocarbyl halide in a polar aprotic solvent under conditions sufficient to produce the corresponding carbamate ester, and cracking the carbamate ester under conditions sufficient to produce the corresponding isocyanate.

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