Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1994-02-18
2001-11-06
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S132000, C526S160000, C526S943000
Reexamination Certificate
active
06313240
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing an ethylene/&agr;-olefin copolymer with an olefin polymerization catalyst constituted of a metallocene compound, an organoaluminum compound, and an ionizable ionic compound.
2. Description of the Related Art
The low-pressure Ziegler process for polymerization of ethylene or an &agr;-olefin is well known in the related technical fields. The catalyst for the process is generally prepared by treating a mixture of an organometallic compound or hydride of a metal of Group 1A to 3A of Periodic Table with a compound of a transition metal (Group 3B to 2B of Periodic Table) in a suspension or a solution, or in the absence of a solvent or a diluent.
In recent years, special kinds of catalysts are being developed which are active in olefin polymerization. Examples of the catalyst are combination of a cyclopentadienyl derivative of a metal such as titanium, zirconium, and hafnium (Group 4B of Periodic Table) with aluminoxane. (See, for example, J. Boor: “Ziegler-Natta Catalyst and Polymerization”, Academic Press, New York (1979), and H. Sinn and W. Kaminsky: Adv. Organomet. Chem. 1899 (1980).) These catalysts have ability of forming a stereospecific olefin polymer with high catalyst activity.
Nevertheless, such catalysts have not been used industrially mainly because of the following reasons: the aluminoxane cannot readily be produced in a reproducible form, hindering preparation of the catalyst and the polymer with required reproducibility, and the expensive aluminoxane has to be used in a considerably high ratio to the transition metal compound to achieve sufficient activity.
To offset the above disadvantages, Japanese Patent Laid-Open No. 3-207704 discloses ionic metallocene compound prepared by reacting a metallocene with an ionizing ionic compound. PCT Patent Application WO 92/01723 discloses a process of &agr;-olefin polymerization by use of a catalyst system prepared by reacting a halogenated metallocene with an organometallic compound and then bringing the reaction product into contact with an ionizing ionic compound. This catalyst system is advantageous in olefin polymerization. However, when ethylene and &agr;-olefin are copolymerized by use of such a catalyst at a high temperature, the resulting copolymer has a low molecular weight disadvantageously.
Japanese Patent Application Laid-Open No. 60-217209 discloses production of a high-molecular-weight olefin polymer by use of a catalyst comprising a hafnium compound as the metallocene component. In copolymerization of ethylene with &agr;-olefin, however, this catalyst is much less active than the catalyst having zirconium as the ligand, and is disadvantageous in production efficiency of the copolymer.
The inventors of the present invention made comprehensive studies to solve the above problems, and found that an ethylene/&agr;-olefin copolymer is obtained with a high catalyst activity by copolymerizing ethylene with &agr;-olefin by use of a specific ionic metallocene catalyst at a temperature of not lower than 120° C. The present invention has been accomplished based on the above findings.
SUMMARY OF THE INVENTION
The present invention intends to provide a process for producing ethylene/&agr;-olefin copolymer of high molecular weight with high efficiency at a high temperature.
The present invention provides a process for producing an ethylene/&agr;-olefin copolymer by copolymerization of ethylene with an &agr;-olefin having three or more carbons by use of an olefin polymerization catalyst at a polymerization temperature of not lower than 120° C., the olefin polymerization catalyst comprising, as constitutional components, 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) or (2):
wherein Cp
1
and Cp
2
are independently a substituted or unsubstituted cyclopentadienyl group; idenyl group or fluorenyl group; R
1
is a substituted or unsubstituted lower alkylene group, a dialkylsilanediyl group, a dialkylgermanediyl group, an alkylphosphinediyl group, or an alkylimino group, R
1
crosslinking Cp
1
and Cp
2
together; R
2
and R
3
are independently a hydrogen atom, a halogen atom, a hydrocarbon group an alkoxy group, or an aryloxy group of 1 to 12 carbons, the ionizing ionic compound (b) being a compound which is capable of changing the metallocene compound (a) into a cationic form and does not further react the cationic form of the metallocene compound, and the organoaluminum compound (c) being represented by the general formula (3):
wherein R
4
, R
4′
, and R
4″
are independently a hydrogen atom, a halogen atom, an amino group, an alkyl group, an alkoxy group, or an aryl group, at least one thereof being an alkyl group.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The metallocene compound (a) used in the present invention is a hafnium compound represented by the general formula (1) or (2). The metallocene compound is exemplified specifically by
bis(cyclopentedienyl)hafnium dichloride,
bis(methylcyclopentedienyl)hafnium dichloride,
bis(butylcyclopentedienyl)hafnium dichloride,
ethylenebis(indenyl)hafnium dichloride,
dimethylsilanediylbis(2,4,5-trimethylcyclopentadienyl)hafnium dichloride,
dimethylsilanediylbis(3-methylcyclopentadienyl)hafnium dichloride,
dimethylsilanediylbis(4-t-butyl,2-methylcyclopentadienyl)hafnium dichloride,
diethylsilanediylbis(2,4,5-trimethylcyclopentadienyl)hafnium dichloride,
diethylsilanediylbis(2,4-dimethylcyclopentadienyl)hafnium dichloride,
diethylsilanediylbis(3-methylcyclopentadienyl)hafnium dichloride,
diethylsilanediylbis(4-t-butyl,2-methylcyclopentadienyl)hafnium dichloride,
isopropylidene(cyclopentadienyl)(fluorenyl)hafnium dichloride,
diphenylmethylene(cyclopentadienyl)(fluorenyl)hafnium dichloride,
methylphenylmethylene(cyclopentadienyl)(fluorenyl)hafnium dichloride,
isopropylidene(cyclopentadienyl)(2,7-di-t-butylfluorenyl)hafnium dichloride,
diphenylmethylene(cyclopentadienyl)(2,7-di-t-butylfluorenyl)hafnium dichloride,
methylphenylmethylene(cyclopentadienyl)(2,7-di-t-butylfluorenyl)hafnium dichloride,
isopropylidenebis(cyclopentadienyl)hafnium dichloride,
diphenylmethylenebis(cyclopentadienyl)hafnium dichloride,
methylphenylmethylenebis(cyclopentadienyl)hafnium dichloride,
isopropylidene(cyclopentadienyl)(tetramethylcyclopentadienyl)hafnium dichloride,
diphenylmethylene(cyclopentadienyl)(tetramethylcyclopentadienyl)hafnium dichloride,
isopropylidenebis(indenyl)hafnium dichloride,
diphenylmethylenebis(indenyl)hafnium dichloride,
methylphenylmethylenebis(indenyl)hafnium dichloride, and the like, but is not limited thereto.
The ionizing ionic compound (b) used in the present invention is a compound which is capable of making the aforementioned metallocene compound (a) cationic, and does not reacts further the formed cationic metallocene compound. The ionizing ionic compound is exemplified specifically by boron compounds such as
tri(n-butyl)ammonium tetrakis(p-tolyl)borate,
tri(n-butyl)ammonium tetrakis(m-tolyl)borate,
tri(n-butyl)ammonium tetrakis(2,4-dimetylphenyl)borate,
tri(n-butyl)ammonium tetrakis(3,5-dimethylphenyl)borate,
tri(n-butyl)ammonium tetrakis(pentafluorophenyl)borate,
N,N-dimethylanilinium tetrakis(p-tolyl)borate,
N,N-dimethylanilinium tetrakis(m-tolyl)borate,
N,N-dimethylanilinium tetrakis(2,4-dimetylphenyl)borate,
N,N-dimethylanilinium tetrakis(3,5-dimethylphenyl)borate,
N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate,
triphenylcarbenium tetrakis(p-tolyl)borate,
triphenylcarbenium tetrakis(m-tolyl)borate,
triphenylcarbenium tetrakis(2,4-dimetylphenyl)borate,
triphenylcarbenium tetrakis(3,5-dimethylphenyl)borate,
triphenylcarbenium tetrakis(pentafluorophenyl)borate,
tropylium tetrakis(p-tolyl)borate,
tropylium tetrakis(m-tolyl)borate,
tropylium tetrakis(2,4-dimetylphenyl)borate,
tropylium tetrakis(3,5-dimethylphenyl)borate,
tropylium tetrakis(pentafluorophenyl)borate,
lithium tetrakis(pentafluorophenyl)borate
Hasegawa Saiki
Sone Makoto
Yano Akihiro
Yasuda Hisami
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Rabago R.
Tosoh Corporation
Wu David W.
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