Aluminum-based lewis acid cocatalysts for olefin polymerization

Details Aluminum-based lewis acid cocatalysts for olefin polymerization Aluminum-based lewis acid cocatalysts for olefin polymerization

2000-07-20

2002-11-05

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...

C526S348500, C526S348600, C526S943000, C502S155000

Reexamination Certificate

active

06476166

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the preparation of olefin polymers using ionic catalyst systems based on transition metal compounds activated by Lewis acids that are capable of providing stable polymerization catalysts.
BACKGROUND OF THE INVENTION
Group 13 based Lewis acids having three fluorinated aryl substituents are known to be capable of activating transition metal compounds into olefin polymerization catalysts. Trisperfluorophenylborane is demonstrated in EP 0 427 697 and EP 0 520 732 to be capable of abstracting a ligand for cyclopentadienyl derivatives of transition metals while providing a stabilizing, compatible noncoordinating anion. See also, Marks, et al, J. Am. Chem. Soc. 1991, 113, 3623-3625. The term “noncoordinating anion” is now accepted terminology in the field of olefin polymerization, both by coordination or insertion polymerization and carbocationic polymerization. See for example, EP 0 277 004, U.S. Pat. No. 5,198,401, and Baird, Michael C., et al,
J. Am. Chem. Soc.
1994, 116, 6435-6436, and U.S. Pat. No. 5,668,234. The noncoordinating anions are described to function as electronic stabilizing cocatalysts, or counterions, for cationic metallocene complexes which are active for olefin polymerization. The term noncoordinating anion as used herein applies both to truly noncoordinating anions and coordinating anions that are at most weakly coordinated to the cationic complex so as to be labile to replacement by olefinically or acetylenically unsaturated monomers at the insertion site. The synthesis of Group 13-based compounds derived from trisperfluorophenylborane are described in EP 0 694 548. These Group 13-based compounds are said to be represented by the formula M(C
6
F
5
)
3
and are prepared by reacting the trisperfluorophenylborane with dialkyl or trialkyl Group 13-based compounds at a molar ratio of “basically 1:1” so as to avoid mixed products, those including the type represented by the formula M(C
6
F
5
)
n
R
3−n
, where n=1 or 2. Utility for the tris-aryl aluminum compounds in Ziegler-Natta olefin polymerization is suggested.
Perfluorophenylaluminum (toluene) has been characterized via X-ray crystallography. See, Hair, G. S., Cowley, A. H., Jones, R. A., McBurnett, B. G.; Voigt, A., J. Am. Chem. Soc., 1999, 121, 4922. Arene coordination to the aluminum complex demonstrates the Lewis acidity of the aluminum center. However, perfluorophenyl-aluminum complexes have been implicated as possible deactivation sources in olefin polymerizations which utilize Trityl
+
B(C
6
F
5
)
4
−
/alkylaluminum combinations to activate the catalysts. See, Bochmann, M.; Sarsfield, M. J.; Organometallics 1998, 17, 5908. Bochmann and Sarsfield have shown that Cp
2
ZrMe
2
reacts with Al(C
6
F
5
)
3
0.5(toluene) with transfer of the C
6
F
5
— moiety forming metallocene pentafluorophenyl complexes. These complexes were reported having very low activity compared to the corresponding metallocene dimethyl complexes when activated with B(C
6
F
5
)
3
or Trityl
+
0
B(C
6
F
5
)
4
−
.
Supported non-coordinating anions derived from trisperfluorophenyl boron are described in U.S. Pat. No. 5,427,991. Trisperfluorophenyl boron is shown to be capable of reacting with coupling groups bound to silica through hydroxyl groups to form support bound anionic activators capable of activating transition metal catalyst compounds by protonation. U.S. Pat. No. 5,643,847 discusses the reaction of Group 13 Lewis acid compounds with metal oxides such as silica and illustrates the reaction of trisperfluorophenyl boron with silanol groups (the hydroxyl groups of silicon) resulting in bound anions capable of protonating transition metal organometallic catalyst compounds to form catalytically active cations counter-balanced by the bound anions.
Immobilized Group IIIA Lewis acid catalysts suitable for carbocationic polymerizations are described in U.S. Pat. No. 5,288,677. These Group IIIA Lewis acids are said to have the general formula R
n
MX
3−n
where M is a Group IIIA metal, R is a monovalent hydrocarbon radical consisting of C
1
to C
12
alkyl, aryl, alkylaryl, arylalkyl and cycloalkyl radicals, n=0 to 3, and X is halogen. Listed Lewis acids include aluminum trichloride, trialkyl aluminums, and alkylaluminum halides. Immobilization is accomplished by reacting these Lewis acids with hydroxyl, halide, amine, alkoxy, secondary alkyl amine, and other groups, where the groups are structurally incorporated in a polymeric chain. James C. W. Chien, Jour. Poly. Sci.: Pt A: Poly. Chem, Vol. 29, 1603-1607 (1991), describes the olefin polymerization utility of methylalumoxane (MAO) reacted with SiO
2
and zirconocenes and describes a covalent bonding of the aluminum atom to the silica through an oxygen atom in the surface hydroxyl groups of the silica.
In view of the above there is a continuing need for an activating cocatalyst compound that improves the industrial economics and provides a simpler method of synthesis and preparation of.suitable activating compounds for ionic catalyst systems. Additionally, improvements in gas phase and slurry polymerization of olefins, where supported catalysts are typically used, are sought to meet the demanding criteria of industrial processes.
SUMMARY OF THE INVENTION
This invention relates to a process for the preparation of polyolefins from one or more olefinic monomers comprising combining the olefinic monomers with the reaction product of i) a transition metal organometallic catalyst compound and ii) a neutral, aluminum-based Lewis acid compound wherein the aluminum contains at least one, preferably two, halogenated aryl ligands and one or two additional monoanionic ligands not including halogenated aryl ligands.
The invention is also directed to an ethylene copolymer having a relatively narrow molecular weight distribution with an unexpected improvement in melt strength as compared to equivalent density and melt index polymers having the same melt flow ratio as expressed as I
21
/I
2
. As a result, the polymers of this invention have better bubble stability. In particular, the invention is to an ethylene copolymer having a density greater than 0.900 g/cc, and a I
21
/I
2
in the range of from about 15 to about 25, and a melt strength in the range of from 6 to about 11 cN or higher. In a preferred embodiment, the polymer is made in a gas phase polymerization process using the supported catalyst of the invention.
DESCRIPTION OF THE INVENTION
The invention provides a process in which a Lewis acid activator and the organometallic catalyst precursor compounds can be combined to form an active catalyst for olefin polymerization. The invention further provides for the subsequent contacting, or in situ catalyst formation, with insertion polymerizable monomers, those having accessible olefinic unsaturation, or with monomers having olefinic unsaturation capable of cationic polymerization. The catalyst according to the invention is suitable for preparing polymers and copolymers of two or more olefinically unsaturated monomers.
The Lewis acid compounds of the invention include those olefin catalyst activator Lewis acids based on aluminum and having at least one bulky, electron-withdrawing ancillary ligand such as the halogenated aryl ligands of tris(perfluorophenyl)borane or tris(perfluoronaphtyl)borane. These bulky ligands are those sufficient to allow the Lewis acids to function as electronically stabilizing, compatible noncoordinating anions. Stable ionic complexes are achieved when the anions will not be a suitable ligand donor to the strongly Lewis acidic cationic organometallic transition metal cations used in insertion polymerization, i.e., inhibit ligand transfer that would neutralize the cations and render them inactive for polymerization. The Lewis acids fitting this description can be described by the following formula:
R
n
Al(ArHal)
3−n
,
where R is a monoanionic ligand and ArHal is a halogenated C
6
aromatic or higher carbon number polycyclic aromatic hydrocarbon or aromatic ring assembly in w

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