Poly(amic acid) synthesis and conversion to high molecular weight polyimide

1. A process for synthesis of a poly(amic acid), the process comprising:

reacting a dianhydride and a diamine in the presence of a higher monoamine comprising tertiary amine, tertiary ammonium salt, tertiary ammonium hydroxide, secondary amine, secondary ammonium salt, secondary ammonium hydroxide, quaternary ammonium salt, quaternary ammonium hydroxide, ammonium hydroxide, or a combination comprising at least one of the foregoing, in a reaction medium comprising at least 95 volume percent water, at a temperature of 80° C. to 180° C., under an inert atmosphere, with agitation, to produce an aqueous poly(amic acid).

2. The process of claim 1 ,

wherein the dianhydride is bisphenol A dianhydride, pyromellitic dianhydride, 3,3′,4,4′-biphenyl dianhydride, 3,3′,4,4′-benzophenone dianhydride, 3,3′,4,4′-oxydiphthalic dianhydride, 1,4-bis(3,4 dicarboxyl phenoxy)benzene dianhydride, 1,3-bis(2,3-dicarboxyphenoxy)benzene dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, or a combination comprising at least one of the foregoing.

3. The process of claim 1 , wherein the diamine is meta-phenylene diamine, para-phenylene diamine, 4,4′-diaminodiphenylene ether, oxydianiline, 4,4′-diamino-3,3′-dimethyl diphenyl methane, 1,4- bis(4-aminophenoxy) benzene, 2,2′-bis(4-(4-amino phenoxy)phenyl)propane, 3,3′-diaminodiphenylene sulphone, 4,4′-diaminodiphenylene sulphone, 3,4′-diaminodiphenylene sulphone, or a combination comprising at least one of the foregoing.

4. The process of claim 1 ,

wherein the higher monoamine is triethylamine, triethanolamine, tributylamine, dimethyldodecylamine, ammonium hydroxide, triallylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, dibutylamine, dimethylethanolamine, or a combination comprising at least one of the foregoing amines.

5. The process of claim 1 ,

wherein the higher monoamine content is greater than 0.3215 mole equivalent per mole equivalent of dianhydride.

6. The process of claim 1 ,

wherein an end-capping agent is present during the reacting.

7. The process of claim 1 , wherein the reacting is at a pressure of 0 to 685 kPa.

8. The process of claim 1 , wherein the reacting is in the absence of a halogenated solvent, a solvent having a boiling point greater than 105° C., or both.

9. The process of claim 1 , comprising combining the dianhydride, the water, and the higher monoamine; and then adding the diamine.

10. The process of claim 1 , comprising combining the diamine, the water composition and the higher monoamine; and then adding the dianhydride.

11. The process of claim 1 , comprising combining the higher monoamine with the water; and then adding the dianhydride, or the diamine, or both.

12. The process of claim 1 , wherein the aqueous poly(amic acid) is a homogenous solution.

13. The process of claim 1 , further comprising neutralizing the aqueous poly(amic acid) to precipitate the poly(amic acid).

14. The process of claim 1 , further comprising spray drying the aqueous poly(amic acid) to isolate a poly(amic acid) powder.

15. A process for producing a polyimide, comprising cyclizing the poly(amic acid) formed by the method of claim 1 .

16. The process of claim 15 , wherein the polyimide has at least one of a weight average molecular weight of greater than 10,000 Daltons, a polydispersity index of less than 3.0, or a residual amine content less than 10 ppm.

17. A process for producing a polyimide coating, comprising

contacting a substrate with the poly(amic acid) aqueous solution of formed by the method of claim 1 ; and

cyclizing the poly(amic acid) to form the polyimide coating.

18. The process of claim 17 , wherein the substrate is a fiber.