| 摘要 |
PURPOSE:To produce a copolymer excellent in dielectric breakdown characteristic, long-term performance retention and flexibility and containing no metallic catalyst residues, by polymerizing ethylene containing N-vinylimidazole. CONSTITUTION:Ethylene containing 0.001-4mol%, based on the total, N- vinylimidazole is polymerized at a reaction temperature >=120 deg.C and a reaction pressure >=500kg/cm<2> in the presence of a free radical generating catalyst. With respect to the polymer structure of the ethylene copolymer, a random copolymer or a graft copolymer obtained by grafting a monomer of the formula onto an ethylene polymer skeleton is preferable. This ethylene copolymer may contain other monomers for modification of resin in addition to ethylene and N-vinyl-imidazole, and the modifying monomer can be contained in an amount of 10mol% or below. This ethylene copolymer should have a number-average MW>=1,000. When the MW is smaller than 1,000, the long-term performance is lowered. It is preferable that the MW is higher than 3,000. |
