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
1999-09-10
2002-11-05
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...
C502S152000, C502S155000, C556S011000, C556S053000, C526S134000, C526S160000, C526S943000
Reexamination Certificate
active
06475947
ABSTRACT:
BACKGROUND OF THE INVENTION
Metallocenes have been found to be useful for the polymerization of olefins. In order for metallocenes to be particularly useful in slurry type polymerization processes, it has generally been found necessary to form a catalyst system in which the metallocene and the cocatalyst are insoluble during the polymerization. Various approaches have been taken to provide insoluble heterogeneous catalyst systems that would be applicable. One technique involves the employment of metallocenes containing unsaturated substituents which can be prepolymerized in the presence of a cocatalyst to produce a solid insoluble catalyst system. An example of such a process is disclosed in U.S. Pat. No. 5,498,581. Another approach for preparing such an insoluble heterogeneous catalyst system involves the employment of a special type of metallocene referred to as a metallocycle metallocene. A metallocycle type metallocene is one in which one of the cyclodienyl groups that is pi bonded to the metal of the metallocene also contains a substituent which is sigma bonded to the metal of the metallocene. An example of such a metallocene is disclosed in U.S. Pat. No. 5,654,454. In that case, the metallocycle was produced by a hydrozirconation type reaction. Such compounds are often referred to as metallocycles for the reason that there is what can be viewed as a cyclic structure comprising the cyclic dienyl group pi bonded to the zirconium and the substituent on the cyclic dienyl group being sigma bonded to the metal.
In accordance with the present invention, there is provided a process for producing a new type of metallocene which could be called an oligomeric metallocycle metallocene. The term oligomeric metallocene as used herein refers to a metallocene which has a plurality of repeating units which are bridged metallocenes wherein each unit is connected to the other through a cyclic structure connecting the bridge of one unit to the metal of the next unit.
An object of the present invention is to provide catalyst systems using such oligomeric metallocenes and polymerization processes using such catalyst systems.
Another object of the present invention is to provide a metallocene which can be prepolymerized to form a solid particulate catalyst system suitable for use in slurry polymerization processes.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a process for producing oligomeric metallocenes which involves reacting a first bridged metallocene having an alkenyl group attached to the bridge with an alkali metal alkyl. Still further in accordance with the present invention, there is provided a process for polymerizing olefins using such metallocenes. Still further in accordance with the present invention, there is provided a process for employing such metallocenes to produce catalyst systems useful for the polymerization of olefins. In a particularly preferred process, the metallocenes are used to form a prepolymerized heterogeneous catalyst that is suitable for use in a slurry type olefin polymerization process.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the present invention, the new metallocenes are prepared by reacting a first bridged metallocene having an alkenyl group attached to the bridge group with about two molar equivalents of an alkali metal alkyl having at least 4 carbon atoms. Preferably the alkenyl group is an &ohgr;-alkenyl group with terminal unsaturation having 3-10 carbon atoms.
It is contemplated that the process can be applied to any metallocene in which there is a cyclodienyl group which has the required type of alkenyl substituted bridging radical. The currently preferred metallocenes are those of the transition metal compounds Ti, Zr, and Hf. Examples of such metallocenes would include those of the formula
wherein L and L′ are the same or different radicals having a cyclodienyl skeleton, examples of which would include cyclopentadienyl, indenyl, fluorenyl, and benzo indenyl, both substituted and unsubstituted; Y is a structural unit connecting L to L′, Y being further characterized by having a substituent with olefin unsaturation, preferably having 3 to 20 carbons, and M is a transition metal, preferably Zr, Hf, or Ti. Examples of Y include alkylidene and silylene divalent radicals preferably having 4 to 20 carbon atoms. Some specific examples of Y would be —CR
2
—, —SiR
2
—, and the like, wherein one R is a hydrocarbyl radical having olefinic functionality and 3 to 8 carbon atoms and the other R is selected from hydrogen and hydrocarbyl radicals having 1 to 10 carbon atoms. Each X can be the same or different and is selected from halogens and organo radicals having 1 to 20 carbon atoms. Preferably X is selected from halogens, alkyl, aryl, alkaryl, and alkoxy radicals.
The substituents on L and L′, if any, are preferably hydrocarbyl substituents having 1 to 20 carbon atoms, more preferably 1 to 5 carbon atoms.
The reaction of the first metallocene and the alkali metal alkyl can be conducted in any suitable manner. Typically the reaction would be carried out by forming a solution of the metallocene in a hydrocarbon, for example toluene, and then adding a solution of the alkali metal alkyl. The temperature employed can vary widely; however, temperatures below 0° C. are generally preferred for the combining the metallocene and the alkali metal alkyl, for example 0 to −90° C., more typically −20° C. to −80° C.
The resulting oligomeric metallocycle metallocene can be used for polymerization reactions. The inventive catalyst systems are particularly useful for the polymerization of alpha-olefins having 2 to 10 carbon atoms. Examples of such olefins include ethylene, propylene, butene-1, pentane-1, 3-methylbutene-1, hexene-1, 4-methylpentene-1, 3-methylpentene-1, heptene-1, octene-1, decene-1, 4,4-dimethyl-1-pentane, 4,4-diethyl-1-hexene, 3,4-dimethyl-1-hexene, and the like and mixtures thereof. The catalysts are also useful for preparing copolymers of ethylene and propylene and copolymers of ethylene or propylene and a higher molecular weight olefin. Monomers such as styrene and butadiene are also useful.
Polymerizations with the inventive catalyst can be carried out under a wide range of conditions depending upon the particular metallocene employed and the particular results desired. The inventive catalyst systems are considered useful for polymerization conducted under solution, slurry, or gas phase reaction conditions. Typically the inventive metallocene would be used with a suitable cocatalyst.
Examples of suitable cocatalysts include generally any of those organometallic cocatalysts which have in the past been employed in conjunction with transition metal containing olefin polymerization catalysts. Some typical examples include organometallic compounds of metals of Groups IA, IIA, and IIIB of the Periodic Table. Examples of such compounds have included organometallic halide compounds, organometallic hydrides and even metal hydrides. Some specific examples include triethylaluminum, triisobutylaluminum, diethylaluminum chloride, diethylaluminum hydride, and the like. Other examples of known cocatalysts include the use of a stable non-coordinating counter anion cocatalyst, an example of such is disclosed in U.S. Pat. No. 5,155,080, e.g. using triphenyl carbenium tetrakis(pentafluorophenyl)boronate. Another example would be the use of a mixture of trimethylaluminum and dimethylfluoroaluminum such as disclosed by Zambelli et al,
Macromolecules
22, 2186 (1989). In such counter anion systems, the cocatalyst can be viewed as an ion-exchange compound comprising a cation which will irreversibly react with at least one ligand contained in the metallocene and a non-coordination anion which is either a single coordination complex comprising a plurality of lipophilic radicals covalently coordinated to and shielding a central formally charge-bearing metal or metalloid atom or an anion comprising a plurality of boron atoms such as polyhedral boranes, carboranes, and metallacarborane
Alt Helmut G.
Hauger Bryan E.
Licht Erik
Welch M. Bruce
Phillips Petroleum Company
Wood Elizabeth D.
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