Method for purifying oxybisphthalic anhydrides

Details Method for purifying oxybisphthalic anhydrides Method for purifying oxybisphthalic anhydrides

2006-11-22

2008-11-04

Saeed, Kamal (Department: 1626)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C502S167000

Reexamination Certificate

active

07446214

ABSTRACT:
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.

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Elliott P. Barrett et al., “The Determination of Pore Volume and Area Distributions in Porous Substances. I. Computations From Nitrogen Isotherms”, Contribution from the Multiple Fellowship of Baugh and Sons Company, Mellon Institute, vol. 73, pp. 373-380, Jan. 1951.

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