| CPC C08G 73/1071 (2013.01) [C07D 307/89 (2013.01); C08G 73/1032 (2013.01); C08G 73/1053 (2013.01)] | 10 Claims |
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1. A method for the purification of a biphenol dianhydride composition comprising
a biphenol dianhydride of the formula
![]() wherein Ra and Rb are each independently a halogen or a monovalent C1-6 alkyl group and p and q are each independently an integer of 0 to 4; and
at least one of sodium ions, potassium ions, calcium ions, aluminum ions, magnesium ions, phosphate ions, sulfate ions, or chloride ions, bromide ions, or nitrate ions;
the method comprising:
contacting the biphenol dianhydride composition with a halogenated aromatic solvent under conditions effective to form a solution, the conditions including heating the solution in a range from 150° C. to 250° C. with stirring; and
isolating a purified biphenol dianhydride composition from the solution, wherein the isolating the purified biphenol dianhydride comprises:
i. cooling the heated solution to less than 100° C. to induce crystallization to form a slurry,
filtering the slurry to form a wet cake comprising the purified biphenol dianhydride composition, and
washing the wet cake with water, a C1-6 alcohol, or a combination thereof; or
ii. filtering the heated solution followed by process i; or
iii. washing the solution with an aqueous alkaline solution at a temperature of 50° C. to less than 100 C followed by separation of solids; or
iv. adding an adsorbent to the solution to remove ionic species from the solution, and filtering the solution to remove the adsorbent and ionic species; or
a combination thereof,
with the proviso that the method does not include conversion back to a tetracarboxylic acid form of the biphenol dianhydride.
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