rbon atoms, ##STR25## --SO.sub.2 --, --O--, or 13 S-- wherein each R independently represents a hydrogen atom or a lower alkyl group having from 1 to 4 carbon atoms, and n is an integer of 1 or over.The improved polyarylate resin, polyamide resin and epoxy resin used in the third embodiment of the invention are, respectively, those defined above.The polyethylene terephthalate resin used in the thi