Process for the preparation of 4-oxo-4-((4-(phenylamino)phenyl)amino)-2-butenoic acid

1. A process for the preparation of 4-oxo-4-((4-(phenylamino)phenyl)amino)-2-butenoic acid which comprises: reacting p-aminodiphenyl amine and maleic anhydride in a reaction first mixture containing a volatile organic solvent under suitable reaction conditions to provide a second mixture containing 4-oxo-4-((4-(phenylamino)phenyl)amino)-2-butenoic acid product; subjecting the second mixture to vacuum distillation to remove the volatile organic solvent while simultaneously adding diluent oil to produce a dispersion of 4-oxo-4-((4-(phenylamino)phenyl)amino)-2-butenoic acid in the diluent oil.

2. The process of claim 1 wherein reaction conditions include a temperature of from about 50° C. to about 100° C.

3. The process of claim 1 wherein the reaction conditions include a temperature of from about 70° C. to about 80° C.

4. The process of claim 1 wherein the volatile organic solvent is acetone, methylethyl ketone, methyl isobutyl ketone, ethyl acetate, methyl acetate, butyl acetate, xylene, toluene, or N-methylpyrrolidinone.

5. The process of claim 1 wherein the diluent oil is a natural oil selected from the group consisting of animal, vegetable and mineral oils.

6. The process of claim 5 wherein the natural oil is a vegetable oil.

7. The process of claim 5 wherein the mineral oil is selected from the group consisting of paraffinic, naphthenic and mixed paraffinic-naphthenic oils.

8. The process of claim 1 wherein the diluent oil is a synthetic oil.

9. The process of claim 8 wherein the synthetic oil is a polyalphaolefin oil.

10. The process of claim 8 wherein the polyalphaolefin is derived from monomers having from about 4 to about 30 carbon atoms.

11. The process of claim 8 wherein the synthetic oil is an ester oil.

12. The process of claim 11 wherein the ester oil is derived from (i) an acid selected from the group consisting of phthalic acid, succinic acid, alkyl succinic acids, alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acid, and alkenyl malonic acid, and (ii) an alcohol selected from the group consisting of butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether and propylene glycol.

13. The process of claim 8 wherein the synthetic oil is selected from the group consisting of alkylaromatic compounds, polyphenyls and alkylated diphenyl ethers.