Patent ID: 6313240
Filing Date: 2001-11-06
Classification: C08F,Y10S

Abstract:
A process for producing an ethylene/.alpha.-olefin copolymer by copolymerization of ethylene with an .alpha.-olefin having three or more carbons by use of an olefin polymerization catalyst at a polymerization temperature of not lower than 120.degree. C., the olefin polymerization catalyst comprising, a) a metallocene compound, b) an ionizing ionic compound, and c) an organoaluminum compound: the metallocene compound (a) being a hafnium compound represented by the general formula (1): ##STR3##wherein Cp.sup.1 and Cp.sup.2 are independently a substituted or unsubstituted cyclopentadienyl group; a substituted or unsubstituted indenyl group, or a substituted or unsubstituted fluorenyl group; R.sup.1 is a substituted or unsubstituted lower alkylene group or a dialkylsilanediyl group, R.sup.1 crosslinking Cp.sup.1 and Cp.sup.2 together; R.sup.2 and R.sup.3 are independently halogen atoms, the ionizing ionic compound (b) being a compound which is capable of changing the metallocene compound (a) into a cationic form; andthe organoaluminum compound (c) being represented by the general formula (3): ##STR4##wherein R.sup.4, R.sup.4 ' and R.sup.4 "" are independently an alkyl group,wherein said ionizing ionic compound is a salt of an anion and a cation;said cation is selected from the group consisting of tri(n-butyl)ammonium, N,N-dimethylanilinium, triphenylcarbenium, tropylium and lithium; andsaid anion is selected from the group consisting of tetrakis(p-tolyl)borate, tetrakis(m-tolyl)borate, tetrakis(2,4-dimethylphenyl)borate, tetrakis(3,5-dimethylphenyl)borate and tetrakis(pentafluorophenyl)borate.