Direct dianhydride synthesis

1. A method for preparing an symmetrical aromatic diether dianihydride of structure I,

wherein Ar is a divalent aromatic radical; R 1 is a C 1 -C 6 , aliphatic radical, C 3 -C 6 cycloaliphatic radical; and n=1;

said method comprising contacting under reactive and substantially anhydrous conditions, a mixture comprising:

at least one halophithalic anbydride of structure II

wherein R 1 is a C 1 -C 6 , aliphatic radical, C 3 -C 6 a cycloaliphatic radical;

X is selected from the group consisting of chloro, fluoro, bromo, and iodo; and n=1;

at least one salt of an aromatic dibydroxy compound, said salt having structure III

[ − OArO − ][M a+ ] (2/a)   III

wherein Ar is a divalent aromatic radical; and M is independently at each occurrence an alkali metal cation, an alkaline earth metal cation, or a mixture thereof; and “a” is an integer having a value of 1 or 2;

at least one solvent selected from the group consisting of ortho-dichlorobenzen, para-dichlorobenzene, dichlorotoluene, 2,4-dichiorotoluene, 1,2,4-trichlorobenzene, diphenyl sulfone, phenetole, anisole, veratrole,

at least one phase transfer catalyst selected from the group consisting of:

guanidium salts having structure V

wherein R 3 -R 8 are independently, at each occurrence a C 1 -C 6 , aliphatic radical, a C 3 -C 6 cycloaliphatic radical, or and X − is an organic or inorganic anionic species,

(ii) aminopyridium salts having structure VI

wherein R 9 , R 10 and R 11 are independently at each occurrence a C 1 -C 6 , aliphatic radical, C 3 -C 6 cycloaliphatic radical, and wherein said R 9 and R 10 may be linked together form a cyclic structure comprising at least one nitrogen atom; and X − is an organic or inorganic anionic species,

wherein R 12 and R 13 are independently at each occurrence a C 1 -C 20 aliphatic radical, a C 3 -C 20 cycloaliphatic radical, or a C 2 -C 20 aromatic radical, or R 12 and R 13 may together form a cyclic structure comprising at least one nitrogen atom; and X − is an organic or inorganic anionic species; p is an integer ranging from 1 to 3.

2. The method according to claim 1 wherein the halophthalic anhydride is selected from the group consisting of 3-chlorophthalic anhydride, 4-chlorophthalic anhydride, 3-fluorophthalic anhydride, 4-fluorophthalic anhydride, and a mixture thereof.

3. The method according to claim 1 wherein M is sodium or potassium.

4. The method according to claim 1 wherein said aromatic dihydroxy compound is selected from the group consisting of bisphenols having structure IV

wherein R 2 is a halogen atom, a nitro group, a cyano group, a C 1 -C 6 , aliphatic radical, C 3 -C 6 cycloaliphatic radical, or a; and W is a bond, O, S, SO, SO 2 , Se, a C 1 -C 6 , aliphatic radical, C 3 -C 20 cycloaliphatic radical.

5. The method according to claim 1 wherein said aromatic dihydroxy compound is selected from the group consisting of 4,4′-biphenol, and bisphenol A.

6. The method according to claim 1 wherein the phase transfer catalyst is hexaethylguanidinium chloride.

7. The method according to claim 1 wherein a proportion of phase transfer catalyst in a range from about 0.2 mole percent to about 10.0 mole percent based on halophthalic anhydride is employed.

8. The method according to claim 1 wherein said contacting comprises heating at a temperature in a range from about 150° C. to about 300° C.

9. The method according to claim 8 wherein a temperature in a range from about 170 to about 250° C. is employed.

10. The method according to claim 8 wherein a temperature in a range from about 180 to about 200° C. is employed.

11. The method according to claim 1 wherein the reaction is conducted at atmospheric pressure.

12. The method according to claim 1 wherein said solvent comprises less than 20 ppm water.

13. The method according to claim 1 wherein said solvent comprises less than 5 ppm water.

14. A method for preparing a diether and dianbydride I,

wherein Ar is a divalent aromatic radical; R 1 is a C 1 -C 6 , aliphatic radical, a C 3 -C 6 cycloaliphatic radical, and n=1;

said method comprising contacting a mixture comprising 3-fluorophthalic anhydride and 4-fluorophthalic anhydride, with at least one salt of an aromatic dihydroxy compound of structure III

[ − OArO − ][M a+] (2/a)   III

wherein Ar is a divalent aromatic radical; and M is independently at each occurrence an alkali metal cation, an alkaline earth metal cation, or a mixture thereof, and “a” is an integer having a value of 1 or 2;

said contacting being carried out in the presence of a solvent selected from the group consisting of ortho-dichlorobenzene, para-dichlorobenzene, dichlorotoluene, 2,4-dichlorotoluene, 1,2,4-trichlorobenzene, diphenyl sulfone, phenetole, anisole, veratrole, a phase transfer catalyst under substantially anhydrous conditions at a temperature in a range from about 150 to about 300° C., said solvent having a boiling point greater than about 150° C., said phase transfer catalyst being selected from the group consisting of hexalkylguanidinium salts.

15. The method according to claim 14 wherein said phase transfer catalyst is hexaethylgnauidinium chloride.

16. A method for preparing a diether symmetrical dianhydride I,

wherein Ar is a divalent aromatic radical, R 1 is independently at each occurrence a C 1 -C 6 , aliphatic radical, a C 3 -C 6 cycloaliphatic radical, and n=1;

said method comprising contacting a mixture comprising 3-chlorophthalic anhydride and 4-chlorophthalic anhydride, with at least one salt of an aromatic dihydroxy compound of structure III

[ − OArO −][M a+ ] (2/a)   III

wherein Ar is a divalent aromatic radical, and M is independently at each occurrence an alkali metal cation, an alkaline earth metal cation, or a mixture thereof; “a” is an integer having a value of 1 or 2;

said contacting being carried out in the presence of a solvent selected from the group consisting of ortho-dichlorobenzene, para-dichlorobenzene, dichlorotoluene, 2,4-dichlorotoluene, 1,2,4-trichlorobenzene, dipheuyl sulfone, phenetole, anisole, veratrole, a phase transfer catalyst under substantially anhydrous conditions at a temperature in a range from about 150 to about 300° C., said solvent having a boiling point greater than about 150° C., said phase transfer catalyst being selected from the group consisting of hexalkylguanidinium salts.

17. The method according to claim 16 wherein said phase transfer catalyst is hexaethylguanidinium chloride

18. A method for preparing a diether symmetrically dianhydride I,

wherein Ar is a divalent aromatic radical, R 1 is a C 1 -C 6 , aliphatic radical, a C 3 -C 6 cycloaliphatic radical, and n=1;

said method comprising contacting a mixture comprising 3-chlorophtbalic anhydride and 4-chlorophthalic anbydride, with at least one salt of an aromatic dihydroxy compound of structure lII

[ − OArO − ][M 1 ] ( 21/a)   III

wherein Ar is a divalent aromatic radical; and M is independently at each occurrence an alkali metal cation, an alkaline earth metal cation, or a mixture thereof; “a” is an integer having a value of 1 or 2;

said contacting being carried out in the presence of a solvent selected from the aroup consisting of ortho-dichlorobenzene, para-dichtorobenzene, dichlorotoluene, 2,4-dichiorotoluene, 1,2,4-trichlorobenzene, diphenyl sulfone, phenetole, anisole, veratrole, a phase transfer catalyst under substantially aub.yclxous conditions at a temperature in a range from about 150 to about 300° C., said solvent having a boiling point greater than about 150° C., said phase transfer catalyst being selected from the group consisting of hexaethylguanidinium chloride, 1-neopentyl-4-(N,N-dibutylaniino)-pyridinium chloride, 1-neopentyl-4-piperidin-1-ylpyridinium chloride, 1-neopenryl-4-piperidin-1-ylpyridinium mesylate, 1-3-methylheptyl-4-(4-methyl)-piperidin-1-ylpyridinium chloride, and combinations thereof.