Purification of anhydrides
AssigneeHoechst Celanese Corporation
InventorsWerner H. Mueller, Suzanne Fontaine
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Abstract
Process for the purification of organic polyanhydrides to substantially-completely remove trace metals, such as for the production of metal-free electronic grade polymers. The process comprises decyclizing in an aqueous vehicle to form the polyacid, treating with an adsorption agent, crystallizing the polyacid, filtering and reconverting to the polyanhydride which is substantially free of trace metals. The purified polyanhydride can be reacted with other metal-free monomers to form metal-free polymers having excellent insulating properties for use in electrical components.
Claims17
Process for the purification of commercially-available aromatic anhydrides to substantially reduce the content of metal salt impurities therein, comprising the steps of:
- (1) dissolving a commercially-available aromatic anhydride in an aqueous vehicle at elevated temperatures to convert the anhydride to the corresponding polyacid and to ionize the metal salt impurities in the aqueous vehicle,
- (2) exposing the aqueous solution of the polyacid to an adsorption agent,
- (3) separating out the adsorption agent,
- (4) reducing the temperature of the aqueous solution of the polyacid to cause the polyacid to crystallize out of solution in purified form,
- (5) filtering the moist purified crystalline polyacid, and
- (6) cyclizing the crystalline polyacid to form the original aromatic anhydride in purified form.
Dependencies are inferred from the claim text.