Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-02-17
2001-05-29
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...
C526S172000, C526S348000, C502S102000, C502S103000, C502S150000, C502S123000, C502S125000
Reexamination Certificate
active
06239239
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the single-site catalysts useful for olefin polymerizations. In particular, the invention relates to improved catalysts that contain a Group 4 transition metal, at least one quinolinoxy or pyridinoxy ligand, and at least one benzyl ligand.
BACKGROUND OF THE INVENTION
Interest in metallocene and non-metallocene single-site catalysts (hereinafter all referred to as single-site catalysts) continues to grow rapidly in the polyolefin industry. These catalysts are more reactive than Ziegler-Natta catalysts, and they produce polymers with improved physical properties. The improved properties include narrow molecular weight distribution, reduced low molecular weight extractables, enhanced incorporation of &agr;-olefin comonomers, lower polymer density, controlled content and distribution of long-chain branching, and modified melt rheology and relaxation characteristics.
Recent attention has focused on developing improved single-site catalysts in which a cyclopentadienyl ring ligand of the metallocene is replaced by a heteroatomic ring ligand. For example, U.S. Pat. No. 5,554,775 discloses catalysts containing a boraaryl moiety such as boranaphthalene or boraphenanthrene. U.S. Pat. No. 5,539,124 discloses catalysts containing a pyrrolyl ring, i.e., an “azametallocene.” In addition, U.S. Pat. No. 5,902,866 discloses azaborolinyl heterometallocenes wherein at least one aromatic ring includes both a boron atom and a nitrogen atom.
U.S. Pat. No. 5,637,660 discloses single-site catalysts that contain a Group 4 transition metal (such as titanium or zirconium) and at least one quinolinyl (or “quinolinoxy”) or pyridinyl (or “pyridinoxy”) group. In addition to the quinolinoxy or pyridinoxy group, these catalysts contain two “X” ligands, where X is halogen, alkyl, alkoxy, or dialkylamino, and one “L” ligand, where L is X, cyclopentadienyl, substituted cyclopentadienyl, indenyl, or fluorenyl. (Benzyl is not taught as an X or L ligand.) When combined with an activator such as MAO or an ionic borate, these catalysts efficiently polymerize olefins such as ethylene or mixtures of ethylene and &agr;-olefins. The ready availability of quinolinols and pyridinols and ease of preparation make these catalysts an attractive alternative to other heterometallocenes.
Copending appl. Ser. No. 08/872,659, filed Jun. 10, 1997 as a continuation-in-part of the '660 patent, discloses single-site catalysts that contain a Group 3-10 transition or lanthanide metal and at least one quinolinyl or pyridinyl group. In addition to the quinolinyl or pyridinyl groups, these catalysts include an optional polymerization-stable ligand (such as a cyclopentadienyl group), and at least one “X” ligand, where X can be “halogen, C
1
to C
6
alkyl, C
6
to C
14
aryl, C
7
to C
20
alkaryl, C
7
to C
20
aralkyl, C
1
to C
6
alkoxy, or —NR
2
.” All of the examples in the '659 application show catalysts that contain one or two quinolinoxy or pyridinoxy groups and two or three chlorides (as “X”). The application gives a skilled person no reason to expect that any one X group (other than, perhaps, chloride) will give a significantly better catalyst than the other listed X groups. For example, a skilled person has no reason to believe that any one ligand within “C
6
to C
14
aryl, C
7
to C
20
alkaryl, C
7
to C
20
aralkyl” will give a significantly better catalyst than the rest.
On the other hand, it would be valuable to identify particular quinolinoxy and pyridinoxy-substituted single-site catalysts with exceptionally high activities. Ideally the catalysts could be prepared inexpensively and in short order, and they would give high yields of olefin polymers.
SUMMARY OF THE INVENTION
The invention is an olefin polymerization catalyst. The catalyst comprises a Group 4 transition metal, at least one quinolinoxy or pyridinoxy ligand, and at least one benzyl ligand. The invention includes a catalyst system comprising the catalyst and an effective amount of an activator.
I surprisingly found that catalyst systems based on quinolinoxy and pyridinoxy complexes of Group 4 transition metals that contain at least one benzyl ligand have exceptional activities for polymerizing olefins. Compared with similar catalysts that contain other C
6
-C
8
aryl, alkaryl, or aralkyl groups, the benzyl group-containing single-site catalysts are far more active.
DETAILED DESCRIPTION OF THE INVENTION
Catalysts of the invention include a Group 4 transition metal, i.e., titanium, zirconium, or hafnium. Preferably, the Group 4 metal is titanium or zirconium. The catalysts also include from one to three benzyl (—CH
2
Ph) ligands. Preferred catalysts contain three benzyl groups.
The catalysts also include at least one quinolinoxy or pyridinoxy ligand. Preferred catalysts contain only one quinolinoxy or pyridinoxy group. Preferably, the oxygen on the quinolinoxy or pyridinoxy ligand is attached to a carbon that is one or two atoms away from the nitrogen of the quinolinyl or pyridinyl ring. For example, the ligand is preferably an 8-quinolinoxy, 2-quinolinoxy, or 2-pyridinoxy group.
In addition to the benzyl and pyridinoxy or quinolinoxy ligands, the catalysts can include up to 2 additional ligands, which may be labile or polymerization-stable. “Labile” ligands have the ability to dissociate from the metal, particularly during an olefin polymerization, often leaving behind a cationically active species. Suitable labile ligands include, for example halide, dialkylamino, alkoxy, hydrocarbyl, siloxy, hydrido, and the like. “Polymerization-stable” ligands normally stay bonded to the metal during olefin polymerization. Suitable polymerization-stable ligands include, for example cyclopentadienyl and substituted cyclopentadienyl, indenyl, fluorenyl, azaborolinyl, borabenzyl, pyrrolyl, indolyl, and the like.
Catalysts of the invention can be prepared by numerous methods that are generally known to those skilled in the art. The starting material is any convenient source of the Group 4 transition metal. The required ligands can be introduced in any desired order. For example, the quinolinoxy or pyridinoxy ligand or ligands can be introduced either before or after the benzyl ligand or ligands.
Suitable Group 4 transition metal sources include, for example, halides, alkyls, alkoxides, acetates, amides, or the like. Because of their ready availability, halides are particularly preferred. Examples of suitable Group 4 transition metal sources: titanium tetrachloride, titanium tetrabromide, zirconium tetrachloride, zirconium tetrabromide, tetrakis(dimethylamino) hafnium, zirconium tetraacetate, zirconium dichloride diacetate, titanium dimethyl dichloride, and the like.
In one convenient method, a Group 4 transition metal tetrahalide is first reacted with one equivalent of a quinolinol or pyridinol in a hydrocarbon solvent as described in U.S. Pat. No. 6,020,493, the teachings of which are incorporated herein by reference. Thus, for example, the quinolinol or pyridinol is dissolved or suspended in the hydrocarbon at or slightly above room temperature and is stirred under an inert atmosphere such as nitrogen or argon. The Group 4 transition metal tetrahalide is then preferably added, usually as a solution or suspension in more of the hydrocarbon. After stirring the reaction mixture awhile, preferably at room temperature, solvents are removed, and the residual product is recovered, washed, and recrystallized if desired from a suitable solvent. Example 1 below illustrates this method of preparing the trihalide.
The reaction product is then conveniently combined with from 1 to 3 equivalents of an alkali metal benzyl compound (e.g., benzyl lithium) or a benzyl Grignard reagent (e.g., benzylmagnesium chloride) to replace from 1 to 3 of the remaining halides with benzyl ligands. For example, reaction of titanium tetrachloride with one equivalent of 8-quinolinol, followed by reaction of the product with 3 equivalents of benzylmagnesium chloride, gives 8-quinolinoxytitanium tribenzyl (see Example 2 below). The reaction product can be
Choi Ling-Siu
Equistar Chemicals L.P.
Schuchardt Jonathan L.
Wu David W.
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