Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
1998-09-16
2001-02-13
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C502S202000, C526S134000, C526S170000, C526S901000
Reexamination Certificate
active
06187712
ABSTRACT:
The present invention relates to a catalyst composition useful for the polymerization of olefins. The catalyst composition comprises a mono- or biscycloalkadienyl catalyst precursor comprising at least one protected hydride or protected hydrocarbyl ligand bound to a metal atom and a cocatalyst.
BACKGROUND OF THE INVENTION
A variety of catalyst compositions containing single site catalyst precursors have been shown to be highly useful in the preparation of polyolefins, producing relatively homogeneous copolymers at good polymerization rates and allowing one to tailor the properties of the finished polymer closely. In contrast to traditional Ziegler-Natta catalyst compositions, single site catalyst compositions comprise catalytic compounds in which each catalyst composition molecule contains one or only a few polymerization sites.
The most well known category of single site catalyst precursors is metallocenes of the general formula Cp
2
MX
2
wherein Cp is a cycloalkadienyl ligand, typically cyclopentadienyl or indenyl, M is a metal, usually from Group 4, and X is a halogen or alkyl group.
Other types of single site catalyst precursors have more recently been reported. Wolczanski et al.,
Organometallics,
1:793 (1982) describes the synthesis of Cp*Zr(BH
4
)
3
and a related dimer, [Cp*Zr(BH
4
)H(&mgr;-H)]
2
, wherein Cp* is pentamethylcyclopentadienyl. The authors state on page 794, the dimer “appears to polymerize ethylene; however, the low rate of oligomerization may indicate trace impurities are responsible.”
The present invention revolves around the discovery that single site catalyst precursors comprising at least one protected hydride or protected hydrocarbyl ligand bound to a metal atom combined with a cocatalyst are particularly effective for the polymerization of olefins. Protected hydride or hydrocarbyl ligands are quite stable when attached to the metal of ligated catalyst precursor. In contrast to the findings of Wolczanski et al., this unique combination of precursor and cocatalyst provides an extremely active catalyst composition.
SUMMARY OF THE INVENTION
The invention provides a catalyst composition for the polymerization of olefins comprising: a) a catalyst precursor of the formula L
x
M
n+
(A)
y
[R
z
Z]
(n−x−y)
, wherein each L is a cycloalkadienyl ligand; M is an element selected from Groups 3 to 10 and the Lanthanides; each A is an anionic group; each R is carbon or hydrogen; each Z is a protecting moiety containing an element from Group 13 through which Z is bridged to M via R; x is 0, 1 or 2; n is the valence of M; y is an integer from 0 to 7; and Z is an integer from 1 to 4 and b) a cocatalyst.
The invention also provides a process for preparing the above catalyst precursor, as well as processes for the polymerization of olefins which comprise contacting olefins under polymerization conditions with the above catalyst composition.
DETAILED DESCRIPTION OF THE INVENTION
Olefin polymers that may be produced according to the invention include, but are not limited to, ethylene homopolymers, homopolymers of linear or branched higher alpha-olefins containing 3 to about 20 carbon atoms, and interpolymers of ethylene and such higher alpha-olefins, with densities ranging from about 0.86 to about 0.96. Suitable higher alpha-olefins include, for example, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, and 3,5,5-trimethyl-1-hexene. Olefin polymers according to the invention may also be based on or contain conjugated or non-conjugated dienes, such as linear, branched, or cyclic hydrocarbon dienes having from about 4 to about 20, preferably 4 to 12, carbon atoms. Preferred dienes include 1,4-pentadiene, 1,5-hexadiene, 5-vinyl-2-norbornene, 1,7-octadiene, vinyl cyclohexene, dicyclopentadiene, butadiene, isobutylene, isoprene, ethylidene norbornene, norbornadiene and the like. Aromatic compounds having vinyl unsaturation such as styrene and substituted styrenes, and polar vinyl monomers such as acrylonitrile, maleic acid esters, vinyl acetate, acrylate esters, methacrylate esters, vinyl trialkyl silanes and the like may be polymerized according to the invention as well. Specific olefin polymers that may be made according to the invention include, for example, polyethylene, polypropylene, ethylene/propylene rubbers (EPR's), ethylene/propylene/diene terpolymers (EPDM's), polybutadiene, polyisoprene and the like.
The catalyst precursor has the formula L
x
M
n+
(A)
y
[R
z
Z]
(n−x−y)
Each L is an unsubstituted or substituted cycloalkadienyl ligand, i.e., cyclopentadienyl, indenyl, or fluorenyl groups optionally substituted with one or more hydrocarbyl groups containing 1 to 20 carbon atoms. Examples of L include cyclopentadienyl, indenyl, fluorenyl, methylcyclopentadienyl, 1,2-dimethylcyclopentadienyl, 1,3-dimethylcyclopentadienyl, 2,3,4,5-tetramethylcyclopentadienyl, pentamethylcyclopentadienyl, trimethylsilylcyclopentadienyl, phenylcyclopentadienyl, indenyl, fluorenyl, trimethylsilylindenyl, 2-methylindenyl, 2-arylindenyl, and trimethylsilylfluorenyl. Preferably, L is selected from methylcyclopentadienyl, 1,3-dimethylcyclopentadienyl, indenyl, fluorenyl, and 2-arylindenyl. More preferably, L is selected from methylcyclopentadienyl, 1,3-dimethylcyclopentadienyl, indenyl, and fluorenyl. Most preferably, L is methylcyclopentadienyl.
M is an element selected from Groups 3 to 10 and the Lanthanides. Preferably, M is selected from Groups 3, 4, 5, 6 and the Lanthanides. More preferably, M is a Group 4 element. Zirconium in particular is preferred.
Each A is an anion, and may be multifunctional. Preferably, each A is selected from hydrogen, an aryl, alkyl, alkenyl, alkylaryl, or arylalkyl radical having 1-20 carbon atoms, a halogen, chalcogen or pnictogen. More preferably, each A is selected from hydrogen, aryl or alkyl. Most preferably, A is hydrogen.
The group [R
z
Z] is a protected hydride or hydrocarbyl group wherein Z is linked to M via R. Preferably, each R is hydrogen or carbon. Most preferably, R is hydrogen. Each Z is a protecting moiety containing an element from Group 13 through which the group Z is connected to M via R. More preferably, each Z is boron or aluminum. Most preferably, each Z is boron. In a preferred embodiment of the invention, the [R
z
Z] group is a borohydride group of the formula [BH
4
].
In the above formula, x is 1 or 2; n is the valence of M; and y is an integer from 0 to 7 and Z is an integer from 1 to 4.
In a preferred embodiment of the invention, the catalyst precursor has the formula: L
x
M
n+
(BH
4
)
n−x
wherein L, M, n have the meanings above, and x′ is 1 or 2.
More preferably, the catalyst precursor has one of the formulas:
The catalyst precursor may be made by any means, and the invention is not limited thereby. For example, a preferred method of making the catalyst precursor is by reaction of a compound containing at least two protected hydride or hydrocarbyl ligands bound to a metal atom with an anionic donor. In this reaction the anion of the anionic donor is substituted for one of the protected hydride or hydrocarbyl ligands to form the catalyst precursor.
The compound containing at least two protected hydride or hydrocarbyl ligands bound to a metal atom is preferably a homoleptic metal ligand complex, more preferably a homoleptic Group 4, 5, or 6 metal ligand complex. Most preferably, the compound containing at least two protected hydride or hydrocarbyl ligands bound to a metal atom is a homoleptic Group 4 metal ligand complex, such as zirconium tetraborohydride.
The anionic donor may be an atom or group of atoms capable of donating an anion to the compound containing at least two protected hydride or hydrocarbyl ligands bound to a metal atom. Examples include anionic fragments of oxygen-, nitrogen-, sulfur- and phosphorus-containing compounds such as alkoxides, amides, thiolates, or phosphides as well as hydrocarbyl, or aryl groups bearing a negative charge. Additionally, the anionic donor may
Bell Mark L.
Jones Lisa Kimes
Pasterczyk J.
Sher Jaimes
Univation Technologies LLC
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