| 摘要 |
PROBLEM TO BE SOLVED: To obtain an ethylene-α-olefin copolymer excellent in transparency by selecting one which has specified MFR and density and of which K1 and K2 , each given by a certain formula, are each in a specified range. SOLUTION: A prepolymn, catalyst is prepd. by polymerizing ethylene, etc., in the presence of a catalyst which is a mixture of a transition metal compd. of a metallocene type, an ion-exchanging layer compd. (e.g. salt-treated mica), and if necessary an organoaluminum compd. and then removing a polymer from the polymn. system. The prepolymn. catalyst is used for copolymerizing ethylene and a 3-12Cα-olefin (e.g. 1-butene) at -50 to +250 deg.C under normal pressure to 2,000kgf/cm<2> , thus giving an ethyene-α-olefin copolymer which has an MFR (190 deg.C, 2.16kg-load) of 0.1-5g/10min, a density of 0.890-0.960g/cm<3> , and such K1 and K2 that when FR<=Mw/Mn+4.4, then K1 giving by formula I (wherein MT is the melt tension; and FR is the ratio of the MFR at 190 deg.C under 10kg-load to the MFR at 190 deg.C under 2.16kg-load) satisfies the relation: 0.2<=K1 <=10.0 and that when FR>Mw/Mn+4.4, then K2 given by formula II satisfies the relation: 0<K2 <=8.
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