Method for purifying oxybisphthalic anhydrides
View Patent ↗A method for purifying dianhydrides is provided. In one aspect, purified oxybisphthalic anhydrides, intermediates useful in the preparation of polyetherimides are provided. In one embodiment, a first solution containing a dianhydride compound, a solvent, and a phase transfer catalyst is contacted with a solid inorganic adsorbent material having a total pore volume of about 0.5 milliliters/gram or greater and a cumulative pore volume distribution of about 20 percent or greater of particles having a pore diameter in a range between about 3 nanometers and about 20 nanometers. The solution containing the dianhydride compound is then separated from the solid inorganic adsorbent material to provide a purified dianhydride compound which is substantially free of the phase transfer catalyst. The purification technique is especially valuable for preparing high purity oxybisphthalic anhydrides, such as 4,4′-oxybisphthalic anhydride (4,4′-ODPA), which are substantially free of residual phase transfer catalyst.
1. A method for purifying an oxybisphthalic anhydride having structure (IV)
said method comprising the steps of:
a. providing a first solution comprising at least one oxybisphthalic anhydride (IV), at least one solvent, and at least one organic phase transfer catalyst; and
b. contacting the first solution with a solid inorganic adsorbent material, said solid inorganic adsorbent material having a total pore volume of about 0.5 milliliters/gram or greater, and a cumulative pore volume distribution of about 20 percent or greater of particles having a pore diameter in a range between about 3 nanometers and about 20 nanometers; to provide a second solution of the oxybisphthalic anhydride (IV), which is substantially free of the organic phase transfer catalyst.
2. The method of claim 1 , wherein said contacting is carried out at a temperature in a range between about 50° C. and about 250° C.
3. The method of claim 1 , further comprising crystallizing the oxybisphthalic anhydride (IV) from the second solution to provide a purified slurry of oxybisphthalic anhydride containing less than about 150 parts per million of an organic phase transfer catalyst.
4. The method according to claim 1 , wherein the oxybisphthalic anhydride is selected from the group consisting of 4,4′-oxybisphthalic anhydride; 3,3′-oxybisphthalic anhydride; and mixtures thereof.
5. The method according to claim 1 , wherein the oxybisphthalic anhydride is selected from the group consisting of 4,4′-oxybisphthalic anhydride; 3,4′-oxybisphthalic anhydride; and mixtures thereof.
6. The method according to claim 1 , wherein the oxybisphthalic anhydride is selected from the group consisting of 3,4′-oxybisphthalic anhydride; 3,3′-oxybisphthalic anhydride; and mixtures thereof.
7. The method according to claim 1 , wherein said oxybisphthalic anhydride has structure (V)
8. The method according to claim 1 , wherein said at least one solvent is selected from the group consisting of chlorobenzene, ortho-dichlorobenzene, para-dichlorobenzene, dichlorotoluene, 1,2,4-trichlorobenzene, diphenyl sulfone, phenetole, anisole, veratrole, toluene, xylene, mesitylene, and mixtures thereof.
9. The method according to claim 1 , wherein said at least one solvent is ortho-dichlorobenzene.
10. The method according to claim 1 , wherein said solid inorganic adsorbent material is selected from the group consisting of silica, alumina, zeolites, inorganic ion exchange compounds, and mixtures thereof.
11. The method according to claim 1 , wherein said solid inorganic adsorbent material is silica.
12. The method according to claim 1 , wherein said solid inorganic adsorbent material is alumina.
13. The method according to claim 1 , wherein said solid inorganic adsorbent material has a cumulative pore volume distribution of about 20 percent or greater of particles having a pore diameter in a range between about 10 nanometers and about 20 nanometers.
14. The method according to claim 1 , wherein said organic phase transfer catalyst is present in said first solution in an amount corresponding to between about 0.1 and 10 mole percent based on the amount of the oxybisphthalic anhydride initially present.
15. The method according to claim 1 , wherein said organic phase transfer catalyst is present in said second solution in an amount corresponding to from about 2 parts per million to about 120 parts per million.
16. A method for purifying an oxybisphthalic anhydride having structure (IV)
said method comprising the steps of:
a. providing a first solution comprising at least one oxybisphthalic anhydride (IV), ortho-dichlorobenzene solvent, and a hexaalkylguanidinium halide phase transfer catalyst; and
b. contacting the first solution with a silica, said silica having having a total pore volume of about 0.5 milliliters/gram or greater, and a cumulative pore volume distribution of about 20 percent or greater of particles having a pore diameter in a range between about 3 nanometers and about 20 nanometers; said contacting being carried out at a temperature in a range between about 50° C. and about 250° C. to provide a second solution of the oxybisphthalic anhydride (IV) which is substantially free of said phase transfer catalyst.
17. The method of claim 16 , further comprising crystallizing the oxybisphthalic anhydride (IV) from the second solution to provide a purified oxybisphthalic anhydride containing less than about 150 ppm of said phase transfer catalyst.
18. A method for the preparation of an oxybisphthalic anhydride having structure (IV)
said method comprising steps (a)-(e)
a. contacting in a reaction mixture at least one substituted phthalic anhydride in at least one solvent in the presence of at least one organic phase transfer catalyst and at least one inorganic carbonate salt to provide a first product mixture comprising at least one oxybisphthalic anhydride, at least one solvent, and at least one inorganic salt selected from the group consisting of alkali metal halide salts, alkaline earth metal halide salts, and mixtures thereof, said oxybisphthalic anhydride being present in said first product mixture in an amount corresponding to at least 25 percent by weight of a total weight of said first product mixture, said substituted phthalic anhydride having structure VI
wherein Z is O and X 1 is selected from the group consisting of fluoro, chloro, bromo, iodo, and nitro groups;
b. diluting said first product mixture with at least one solvent, to provide a second product mixture, wherein the oxybisphthalic anhydride is present in an amount corresponding to less than 25 percent by weight of a total weight of the second product mixture;
c. dissolving substantially all of the oxybisphthalic anhydride present in the second product mixture to provide a third product mixture, said third product mixture comprising less than 25 ppm water, and wherein said oxybisphthalic anhydride is present in an amount corresponding to less than 25 percent by weight of a total weight of the third product mixture; and
d. filtering the third product mixture at a temperature above the crystallization point temperature of the oxybisphthalic anhydride to provide a first solution of the oxybisphthalic anhydride; and
e. contacting the first solution with a silica, said silica having a total pore volume of about 0.5 milliliters/gram or greater, and a cumulative pore volume distribution of about 20 percent or greater of particles having a pore diameter in a range between about 3 nanometers and about 20 nanometers, said contacting being carried out at a temperature in a range between about 50° C. and about 250° C. to provide a second solution of the oxybisphthalic anhydride IV which is substantially free of said organic phase transfer catalyst.
19. The method of claim 18 , further comprising crystallizing the oxybisphthalic anhydride IV from the second solution to provide a purified oxybisphthalic anhydride containing less than about 150 ppm of said organic phase transfer catalyst.