Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1998-05-27
2001-07-03
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...
C526S126000, C526S127000, C526S943000
Reexamination Certificate
active
06255417
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improved method for preparing an olefinic polymers by polymerizing an olefinic monomer in an aliphatic hydrocarbon solvent using a metallocene catalyst in the presence of a cocatalyst.
DESCRIPTION OF THE PRIOR ART
A metallocene compound refers to a transition metal complex having coordinated cyclopentadienyl ligands. Many studies on various catalysts based on metallocene compounds have been carried out since Kaminsky and Sinn reported that a metallocene compound, when used together with a condensation product of water and methylaluminum (e.g., methylaluminoxane, MAO), exhibits a high catalytic activity in olefin polymerization [H. Sinn and W. Kaminsky,
Adv. Organomet. Chem.,
18, 99 (1980); and H. Sinn, W. Kaminsky, H. J. Vollmer and R. Woldt,
Angew. Chem.,
92, 396 (1980)]. Such studies have shown that may metallocene catalysts exhibit high activities in polymerizing olefins, diolefins, styrenes, and others (see WO 91/14713).
When a metallocene catalyst is used in olefin polymerization, the structure and properties of the polymer produced can be better controlled than when a conventional Ziegler-Natta catalyst is used together with an alkylaluminum compound as a cocatalyst. For example, the molecular weight distribution of the polymer becomes narrower, and when used in a copolymerization, the distribution of the comonomer in the copolymer is much more uniform.
However, one drawback of metallocene catalysts is that although they readily dissolve in aromatic hydrocarbons such as benzene, toluene and substituted benzene, they are almost insoluble in aliphatic hydrocarbons. Bisindenyl zirconium dimethyl, for example, is completely soluble in toluene whereas it does not dissolve in heptane and this difference in solubility is reflected on its catalytic activity, i.e., its catalytic activity in toluene is greater than that in heptane by a factor of 7 or more (see
J. Polym. Sci; Polym. Chem. Ed.,
123, 2117 (1985)). Because the use of an aromatic hydrocarbon solvent in a polymerization process is not advantageous due to its toxicity and unfavorable process economics in recovering a high-boiling aromatic solvent, it is desirable to develop an efficient polyolefin manufacture process using a metallocene catalyst in an aliphatic hydrocarbon solvent. Accordingly, there exists a need to develop a new metallocene catalyst that exhibits a high activity in an aliphatic hydrocarbon solvent.
Karol et al. have reported on the effects of introducing such substituents as methyl, n-butyl and t-butyl to the cyclopentadienyl ligands of biscyclopentadienyl zirconium dichloride on the rate of copolymerization of ethylene and 1-hexene in hexane[Karol et al., “Catalyst Design for Tailor made Polyolefins”,
Studies in Surface Science and Catalysis
, B. Delmon and J. T. Yates Ed., Vol. 89, p. 389 (1994)]. However, the results were inconclusive in terms of the above mentioned purpose, and there still remained the need to develop a more effective method for the preparation of polyolefins.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an improved method for the preparation of an olefinic polymer in an aliphatic hydrocarbon solvent by way of using a modified metallocene catalyst having at least one C
5-20
alkyl substituent so as to increase its solubility in the aliphatic hydrocarbon solvent, thereby increasing the activity of the catalyst.
In accordance with the present invention, there is provided an improved process of preparing an olefinic polymer of the type in which an olefinic monomer is polymerized alone or with a comonomer in a hydrocarbon solvent using a metallocene catalyst of formula(I) in the presence of a cocatalyst; wherein the improvement comprises: preparing the olefinic polymer in an aliphatic hydrocarbon solvent using a modified metallocene catalyst which is obtained by introducing at least one C
5-20
alkyl substituent into the &pgr;-ligand, the alkylene bridge or silicon bridge of the metallocene catalyst of formula (I):
L
1
L
2
MX
2
(I)
wherein,
M is Ti, Zr or Hf;
X is a halogen, or a C
1-3
alkyl group; and
L
1
and L
2
are each a &pgr;-ligand selected from the group consisting of cyclopentadienyl, indenyl, fluorenyl and derivatives thereof, and are optionally linked together by a C
1-4
alkylene bridge optionally substituted with a C
1-3
hydrocarbyl group or by a silicone bridge optionally substituted with a C
1-3
hydrocarbyl group.
DETAILED DESCRIPTION OF THE INVENTION
The catalyst that may be used in practicing the present invention is a metallocene compound having one or more C
5-20
alkyl substituents in the ligand moiety and the bridge between ligands. Examples of particularly preferred catalysts of the present invention are the compounds of formula (II) to (X):
wherein R
1
is a C
5-20
alkyl group.
The introduction of long chain hydrocarbon substituents imparts many desirable properties to the metallocene catalyst, e.g., improved solubilities and high polymerization activities in aliphatic hydrocarbon solvent, and easier activation due to improved interactions with cocatalysts.
As the cocatalyst, alkylaluminoxane of formula (XI) and/or alkyl metal compound of formula (XII) may be used:
wherein:
m is an integer of 2 or more; and
R
2
, R
3
, R
4
and R
5
, are each C
1-20
hydrocarbyl group or a halogen.
Representative examples of an alkylaluminoxane of formula (XI) which may be used in the present invention include: methylaluminoxane, ethylaluminoxane, propylaluminoxane, butylaluminoxane, i-butylaluminoxane and the like.
Representative examples of an alkyl metal compound of formula (XII) which may be used in the present invention include: trimethylaluminum, triethylalminum, tripropylaluminum, triisopropylaluminum, tributylaluminum, triisobutylaluminum, triisoprenylaluminum and the like.
The olefinic monomer which can be used in the present invention includes ethylene, &agr;-olefin, cyclic olefin, dienes, trienes and the like. The preferred are ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, cyclopentene, 1,3-cyclopentadiene, norbonene, norbonadinene, ethyliden norbonene, vinyl norbonene, dicyclopentadiene, 1,3-butadiene, 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, styrene, &agr;-methylstyrene, divinylbenzene, 3-chloromethylstyrene and the like. The monomer can also be copolymerized with one or more other monomers.
The preferred solvent which may be used in the present invention includes a C
3-10
aliphatic hydrocarbon solvent, for example, propane, butane, isobutane, pentane, hexane, heptane, octane, nonane, decane and a mixture thereof. It is also possible to use one of the olefinic monomers mentioned above as the solvent in practicing the present invention.
The catalyst which may be used in practicing the present invention is a metallocene compound obtained by introducing at least one C
5-20
alkyl substituent to the compound of formula (I) and it may be prepared by employing a conventional method, e.g., by a process which comprises: dissolving a metal salt (e.g., Na, K etc) of a C
5-13
ring compound containing a cyclopentadienyl moiety; adding a C
5-20
alkyl derivatives, e.g., a halide thereto to conduct a substitution reaction. The cyclopentadiene moiety having a C
5-20
substituent thus obtained can be used in preparing the catalyst of the present invention in accordance with the procedure described in
Organometallics,
12, 2140 (1993).
The polymerization of the present invention can be conducted in a conventional manner. For example, a suitable amount of an inert organic solvent and a small amount of cocatalyst are added to a glass reactor. At this stage, if a liquid monomer is to be employed, it is introduced into the reactor together with a suitable solvent. In case of a gaseous monomer, it is charged to the reactor to a preset pressure. Then, a catalyst solution is added thereto e.g., by employing a syringe to initiate the polymerization.
The polymerization m
Jeong Sang-Won
Lee Bun-Yeoul
Oh Jae-Seung
Park Tai-Ho
Anderson Kill & Olick PC
LG Chemical Ltd.
Rabago R.
Wu David W.
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