Metal residues are extracted from poly(ether ketone ketones) with aliphatic alpha-hydroxycarboxylic acids or aromatic ortho-hydroxycarboxylic acids in a liquid phase, either neat or in an aqueous or a nonaqueous solution. Extraction of metal residues, which usually derive from the catalysts used in the preparation of poly(ether ketone ketones), improves both the color and the thermal stability of these polymers.
There is provided a method of removing metal residues from a polymer cement, the method comprising polymerizing a monomer with a metal-based polymerization initiator to give a polymer cement having metal polymerization initiator residue; adding an organic-soluble acid having a pKa no greater than about 4.5 to the polymer cement, thereby forming an acid containing organic phase; mixing the organic phase with an aqueous phase containing a mineral acid; and recovering the polymer cement substantially free of metal residue.
