Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-07-20
2001-08-07
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...
C526S127000, C526S943000, C526S348000, C502S117000, C502S152000, C502S155000, C556S009000, C556S011000, C556S013000, C556S019000, C556S020000, C556S051000, C556S052000, C556S053000
Reexamination Certificate
active
06271322
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to monocyclopentadienyl transition metal catalysts. The present invention further relates to a monocyclopentadienyl transition metal catalyst system and a method to produce polyolefins such as polyethylene and polypropylene.
BACKGROUND OF THE INVENTION
Many catalytic processes exist for the polymerization or copolymerization of olefins such as ethylene and propylene. These processes have traditionally utilized a Ziegler-Natta catalyst system. These catalyst systems contain a transition metal compound (typically a titanium, zirconium, or vanadium halide or alkoxide) and a main group metal alkyl (usually an aluminum alkyl). The Ziegler-Natta catalyst systems are heterogeneous and possess a number of different active catalyst sites. Each different active site has different characteristics and produces a different polymer, and as a result, Ziegler-Natta catalyst systems produce polyolefins with broad molecular weight distributions and copolymers with broad compositional distributions.
Recent developments in the field of olefin polymerization have focused on the use of transition metal compounds having at least one n-bound cyclopentadienyl ligand. The cyclopentadienyl ligand can be substituted or unsubstituted, and generally includes fused ring derivatives such as indenyl and fluorenyl. These cyclopentadienyl transition metal compounds are often referred to as metallocenes, though the term was initially used to describe biscyclopentadienyl compounds such as dicyclopentadienyliron (ferrocene).
Olefin polymerization systems using metallocenes differ from Ziegler-Natta catalyst systems in important ways. With metallocene catalysts there is generally only one catalytically active species responsible for the polymerization of the monomers. The metallocenes, therefore, produce uniforms chains of polymer having narrower molecular weight distributions and narrower compositional distribution. Metallocene catalysts are also typically much more active on a weight basis than Ziegler-Natta catalysts. Metallocene catalysts can be 10 to 1,000 times more active than the best Ziegler-Natta catalysts.
Metallocene catalysts are often classified into two separate groups, those possessing one cyclopentadienyl ligand, and those possessing two cyclopentadienyl ligands. The monocyclopentadienyl metallocenes are generally known in the art as good styrene polymerization catalysts and poor olefin polymerization catalysts, whereas biscyclopentadienyl metallocenes are generally known in the art as good olefin polymerization catalysts and poor styrene polymerization catalysts. Representative examples of these various catalysts are disclosed in U.S. Pat. Nos. 4,978,730; 5,023,222; 5,045,517; 5,066,741; 5,196,490; and 5,340,892 disclosing monocyclopentadienyl metallocenes. Examples of biscyclopentadienyl metallocenes are disclosed in U.S. Pat. Nos. 4,404,344; 4,542,199; 4,752,597; 5,198,401; 5,278,119; and 5,453,475.
Despite the utility of the catalysts disclosed above, a need still exists to discover more useful and efficient catalysts to polymerize olefins.
SUMMARY OF THE INVENTION
According to the present invention, a novel composition is provided that comprises a monocylopentadienyl transition metal compound of the formula:
Wherein,
M is a Group IV metal selected from the group consisting of titanium, zirconium, and hafnium;
m is one, two, or three, depending on the valency and oxidation state of M;
R′ is each independently selected from the group consisting of hydrogen, substituted hydrocarbyl groups, unsubstituted hydrocarbyl groups, silyl groups, germyl groups, and stannyl groups, including wherein two or more R′ groups can be joined to form a ring;
L is a covalent bridging group containing a main group element from Group 14 selected from the group consisting of carbon, silicon, germanium, and tin.
E is datively bonded to M, and is a main group element from Group 15 selected from the group consisting of nitrogen, phosphorous, arsenic, and antimony;
R is each independently selected from the group consisting of substituted hydrocarbyl groups, unsubstituted hydrocarbyl groups, and silyl groups, wherein two R-groups can be joined to form a ring, and wherein an L group and R can be joined to form a ring;
X is each independently selected from the group consisting of hydrogen, halides, substituted hydrocarbyl groups, unsubstituted hydrocarbyl groups, silyl groups, alkoxides, aryloxides, amides, arylamides, phosphides, arylphosphides, carboxylates , and sulfonates;
D is a neutral Lewis base; and
n is 0, 1, or 2.
The present invention is also directed towards a catalyst system that comprises (A) a monocyclopentadienyl compound described above, and (B) an activator chosen from (1) alumoxanes, (2) a salt of a labile, relatively non-coordinating anion that is able to abstract one substituent X from the monocyclopentadienyl compound, and (3) a neutral Lewis acid that can abstract one substituent X from the monocyclopentadienyl compound.
The present invention is also directed towards a polymerization process incorporating the above catalyst system for producing polyolefins comprising the steps of (i) contacting an olefin monomer at a temperature and pressure sufficient to produce a polymer with the catalyst system described above, and (ii) recovering a polyolefin.
DETAILED DESCRIPTION OF THE INVENTION
The applicants have unexpectedly discovered a novel monocyclopentadienyl transition metal compound that is very useful in catalyst systems for the polymerization of polyolefins. These catalyst systems employing the monocyclopentadienyl transition metal compound are unexpectedly active for the polymerization of olefins. This is particularly unexpected since monocyclopentadienyl transition metal compounds are generally useful for the polymerization of bulky monomers such as styrene, and are poor olefin polymerization catalysts. These monocyclopentadienyl transition metal compound catalyst systems are unexpectedly active in the polymerization of olefins, comparable to, or better than some biscyclopentadienyl transition metal catalyst systems.
It is generally accepted that the active species in both the monocyclopentadienyl transition metal compounds and biscyclopentadienyl transition metal compounds is a cation. These cations are strong Lewis acids, capable of coordinating Lewis bases, such as ethers or amines. U.S. Pat. No. 5,198,401 teaches this, and further states that the coordination of Lewis bases is undesirable and leads, at best, to catalysts of very low activity. It is therefore very unexpected that the intramolecular coordination of a Lewis base would produce a catalyst system of high activity, which is the exact result of the presently claimed compound and process.
The monocyclopentadienyl transition metal compound of the present invention entails:
Wherein,
M is a Group IV metal selected from the group consisting of titanium, zirconium, and hafnium;
m is one, two, or three, depending on the valency and oxidation state of M;
R′ is each independently selected from the group consisting of hydrogen, substituted hydrocarbyl groups, unsubstituted hydrocarbyl groups, silyl groups, germyl groups, and stannyl groups, including wherein two or more R′ groups can be joined to form a ring;
L is a covalent bridging group containing a main group element from Group 14 selected from the group consisting of carbon, silicon, germanium, and tin.
E is datively bonded to M, and is a main group element from Group 15 selected from the group consisting of nitrogen, phosphorous, arsenic, and antimony;
R is independently selected from substituted hydrocarbyl groups, unsubstituted hydrocarbyl groups, and silyl groups, wherein two R-groups can be joined to form a ring, and wherein an R-group and L can be joined to form a ring;
X is each independently selected from the group consisting of hydrogen, halides, substituted hydrocarbyl groups, unsubstituted hydrocarbyl groups, silyl groups, alkoxides, aryloxides, amides, arylamides, phosphides, arylphosphides, carboxylat
Chien James C. W.
Flores Juan Carlos
McCullough Laughlin Gerard
Rausch Marvin D.
Choi Ling-Siu
Graves Bernard J.
Wood, Esq. Jonathan D.
Wu David W.
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