Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Reexamination Certificate
1997-01-21
2001-06-12
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S104000, C502S115000, C526S943000
Reexamination Certificate
active
06245705
ABSTRACT:
The invention relates to cocatalysts used in polymerization and copolymerization of ethylene, undertaken in the presence of catalyst systems comprising metallocenes of transition metals. The invention relates to metallocene catalysts which do not require alumoxane to activate the catalysts or alumoxane co-feed to the polymerization reactor.
BACKGROUND OF THE INVENTION
Metallocene compounds of transition metals are used as catalyst precursors for polymerization and copolymerization of ethylene and in the stereospecific polymerization of olefins. Metallocenes can be described by the empirical formula (CP
m
MLB
1
)
n
(R
2
)
p
. These compounds in combination with an alumoxane such as methylalumoxane (MAO) have been used to produce olefin polymers and copolymers, such as ethylene and propylene homopolymers, ethylene-butene and ethylene-hexene copolymers, e.g., see Kaminsky et al, U.S. Pat. No. 4,542,199 and Sinn et al, U.S. Pat. No. 4,404,344.
MAO has been used as a co-catalyst with various metallocenes. It comprises mixtures of oligomeric linear and/or cyclic alumoxanes with an average molecular weight of about 1200 represented by the formulas: R—(Al(R)—O)
n
—AlR
2
for linear alumoxanes and (—Al(R)—O—)
m
for cyclic alumoxanes wherein n is 1-40, m is 3-40, and R is preferably methyl.
Use of MAO has presented problems in the development of catalysts formed from metallocenes. Because of the varying chemical makeup of the material itself, as reflected by its its formula above, it is often difficult to obtain reproducable catalyst synthesis results. If supported catalysts are prepared with combinations of metallocenes and MAO, MAO is not uniformly distributed within catalyst particles. The resulting non-homogeneous polymerization catalysts have low activity and produce resins with less attractive properties.
SUMMARY OF THE INVENTION
The invention provides cocatalyst systems for metallocenes which require no alumoxanes in catalyst synthesis or in the polymerization reactor.
The invention relates to an activated catalyst composition which comprises mixtures of:
(1) a metallocene compound,
(2) an inorganic aluminum compound Al(OH)
x
O
y
, wherein x is a number from 0 to 3, wherein x+2y=3
(3) trimethylaluminum (TMA),
wherein Al(OH)
x
O
y
is used in an amount sufficient to provide an Al(OH)
x
O
y
:metallocene molar ratio of 5 to 10,000,
wherein TMA is used in an amount sufficient to provide a TMA:metallocene molar ratio of 50 to 10,000, and
wherein the two aluminum compounds, (2) and (3), are used in amounts to provide a molar ratio of TMA to Al(OH)
x
O
y
in the range of from 0.1 to 100.
The invention includes the catalysts described herein, polymerizations and copolymerizations achieved thereby, and the product(s) thereof.
DETAILED DESCRIPTION OF THE INVENTION Catalyst Composition
The catalysts may be unsupported or supported, and comprise
(1) a metallocene compound,
(2) an inorganic aluminum compound Al(OH)
x
O
y
, wherein x is a number from 0 to 3, wherein x+2y=3, and
(3) trimethylaluminum (TMA),
wherein Al(OH)
x
O
y
is used in an amount sufficient to provide an Al(OH)
x
O
y
:metallocene molar ratio of 5 to 10,000,
wherein TMA is used in an amount sufficient to provide a TMA:metallocene molar ratio of 50 to 10,000, and
wherein the two aluminum compounds, (2) and (3), are used in amounts to provide a molar ratio of TMA to Al(OH)
x
O
y
in the range of from 0.1 to 100.
The metallocene compound has the formula CP
m
M(R
1
)
n
(R
2
)
p
in which Cp is an unsubstituted or substituted cyclopentadienyl group, m is 1 or 2, M is titanium, zirconium or hafnium, and R
1
and R
2
belong to the group including a halogen atom, a hydrogen atom or an alkyl group. In the above formula of the metallocene compound, the preferred transition metal atom M is zirconium. In the above formula of the metallocene compound, the Cp group is an unsubstituted, a mono- or a polysubstituted cyclopentadienyl group. The substituents on the cyclopentadienyl group can be preferably straight-chain C
1
-C
6
alkyl groups. The cyclopentadienyl group can be also a part of a bicyclic or a tricyclic moiety such as indenyl, tetrahydroindenyl, fluorenyl or a partially hydrogenated fluorenyl group, as well as a part of a substituted bicyclic or tricyclic moiety. In the case when m in the above formula of the metallocene compound is equal to 2, the cyclopentadienyl groups can be also bridged by alkyl groups, such as —CH
2
—, —CH
2
—CH
2
—, —CR′R″— and —CR′R″—CR′R″—, where R′ and R″ are short alkyl groups or hydrogen atoms; or dialkylsilane groups, such as —Si(CH
3
)
2
—, Si(CH
3
)
2
—CH
2
—CH
2
—Si(CH
3
)
2
— and similar bridge groups. Bridged cyclopentadienyl complexes are used for stereospecific polymerization of propylene. If the R
1
and R
2
substituents in the above formula of the metallocene compound are halogen atoms, they belong to the group of fluorine, chlorine, bromine or iodine. If the substituents R
1
and R
2
in the above formula of the metallocene compound are alkyl groups, they are preferably straight-chain or branched C
1
-C
8
alkyl groups, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, n-hexyl or n-octyl.
Suitable metallocene compounds include bis(cyclopentadienyl)metal dihalides, bis(cyclopentadienyl)metal hydridohalides, bis(cyclopentadienyl)metal monoalkyl monohalides, bis(cyclopentadienyl)metal dialkyls and bis(indenyl)metal dihalides; wherein the metal is titanium, zirconium or hafnium, halide atoms are preferably chlorine, and the alkyl groups are C
1
-C
6
. Illustrative, but non-limiting examples of metallocenes include bis(cyclopentadienyl)zirconium dichloride, bis(cyclopentadienyl)hafnium dichloride, bis(cyclopentadienyl)titanium dichloride bis(cyclopentadienyl)zirconium dimethyl, bis(cyclopentadienyl)hafnium dimethyl, bis(cyclopentadienyl)zirconium hydridochloride, bis(cyclopentadienyl)hafnium hydridochloride, bis(n-butylcyclopentadienyl)zirconium dichloride, bis(n-butylcyclopentadienyl)hafnium dichloride, bis(n-butylcyclopentadienyl)zirconium dimethyl, bis(n-butylcyclopentadienyl)hafnium dimethyl, bis(n-butylcyclopentadienyl)zirconium hydridochloride, bis(n-butylcyclopentadienyl)hafnium hydridochloride, bis(pentamethylcyclopentadienyl)zirconium dichloride, bis(pentamethylcyclopentadienyl)hafnium dichloride, bis(pentamethylcyclopentadienyl)titanium dichloride, cyclopentadienylzirconium trichloride, cyclopentadienyltitaniun trichloride, bis (indenyl) zirconium dichloride, bis(4,5,6,7-tetrahydro-1-indenyl) zirconium dichloride, and ethylene- [bis(4,5,6,7-tetrahydro-1-indenyl)]zirconium dichloride. The metallocene compounds utilized within the embodiment of this art can be used as crystalline solids, as solutions in aromatic hydrocarbons or in a supported form.
If the metallocene is supported, the support carrier material is a particulate, porous, solid such as an oxide of silicon and/or of aluminum, or a crosslinked polymer, e.g. polystyrene. Preferably, it is an inorganic material. The carrier material is used in the form of a dry powder having an average particle size of from about 1 mircons to about 150 microns.
The surface area of the carrier is preferably at least about 50 m
2
/g up to about 350 m
2
/g. The carrier material should be dry, that is, free of absorbed water. Drying of the inorganic carrier material can be effected by heating at about 100° C. about 1000° C., preferably at about 600° C. When the carrier is silica, it is heated to at least 200° C., preferably about 200° C. In the most preferred embodiment, the carrier is silica which, prior to the use thereof in the catalyst synthesis, has been dehydrated by fluidizing it with nitrogen and heating at about 600° C. for about 4 to 16 hours. The silica of the most preferred embodiment is a high surface area, amorphous silica with a (surface area of 300 m
2
/g and a pore volume of 1.65 cm
3
/g.
In accordance with the invention, the metallocene compound is supported on the carrier. Supporting of a metallocene compound on a carrier i
Univation Technologies
Wood Elizabeth D.
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