Nos. 220550/1984, 236828/1984, 236829/1984, 242336/1984 and 95906/1986, it had previously been found by the present applicant that cycloolefin random copolymers obtained by copolymerization of ethylene and cycloolefins such as tetracyclodecene are synthetic resins which are excellent in transparency and also are well balanced among such properties as heat resistance, heat aging resistance, chemica