R12 is a hydrogen atom, a halogen atom, a hydrocarbon group or an alkoxy group, n is an integer of 0 to...http://www.google.com/patents/US4661581?utm_source=gb-gplus-sharePatent US4661581 - Process for producing aromatic polyether ketones and polythioether ketonesAdvanced Patent SearchPublication numberUS4661581 APublication typeGrantApplication numberUS 06/656,325Publication dateApr 28, 1987Filin