Copolymers of polyarylates with polyethylene arylates and process for their preparation

A process for the preparation of a copolymer which comprises reacting at a temperature of about 265.degree.-270.degree. C. for a period of about 60 minutes under a vacuum of less than one mm. mercury, or under an inert atmosphere, a mixture of (1) a high molecular weight polyethylene arylate having an intrinsic viscosity of at least about 0.5 dl/g and (2) a low or high molecular weight bisphenol A-isophthalate-terephthalate polyarylate or bisphenol A-isophthalate-terephthalate-carbonate polyarylate, said low molecular weight polyarylate having an intrinsic viscosity of about 0.1-0.3 dl/g and said high molecular weight polyarylate having an intrinsic viscosity of at least about 0.5-0.6 dl/g, in the proportion of 10 percent to 70 percent of (1) to 90 percent to 30 percent of (2), the resulting polymer being transparent, tough, soluble in chlorinated solvents, capable of maintaining its dimensional stability over a wide range of temperatures, and possessing a single glass transition temperature said intrinsic viscosity being as measured in a 60:40 mixture of phenol and tetrachloroethane at 25.degree. C.