Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-03-13
2003-03-18
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...
C526S126000, C526S128000, C526S170000, C526S064000, C526S943000, C526S348000, C526S127000, C502S152000, C502S104000, C502S108000, C502S116000, C502S103000
Reexamination Certificate
active
06534609
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a new type of solid particulate metallocene catalyst system useful for the polymerization and/or copolymerization of olefins. The invention is also related to a process for conducting polymerization of olefins using the inventive solid metallocene catalyst system.
BACKGROUND OF THE INVENTION
The term “Metallocene” as used herein refers to a derivative of cyclopentadienylidene which is a metal derivative containing at least one cyclopentadienyl component which is bonded to a transition metal. The transition metal is selected from Groups IVB, VB, and VIB, preferably IVB and VIB. Examples include titanium, zirconium, hafnium, chromium, and vanadium. A number of metallocenes have been found to be useful for the polymerization of olefins. Generally, the more preferred catalysts are metallocenes of Zr, Hf, or Ti.
Generally, in order to obtain the highest activity from metallocene catalysts, it has been necessary to use them with an organoaluminoxane cocatalyst, such as methylaluminoxane. This resulting catalyst system is generally referred to as a homogenous catalyst system since at least part of the metallocene or the organoaluminoxane is in solution in the polymerization media. These homogenous catalysts systems have the disadvantage that when they are used under slurry polymerization conditions, they produce polymer which sticks to reactor walls during the polymerization process and/or polymer having small particle size and low bulk density which limits the commercial utility.
Some attempts to overcome the disadvantages of the homogenous metallocene catalyst systems are disclosed in U.S. Pat. Nos. 5,240,894, 4,871,705; and 5,106,804. Typically, these procedures have involved the prepolymerization of the metallocene aluminoxane catalyst system either in the presence of or in the absence of a support. An evaluation of these techniques has revealed that there is still room for improvement, particularly when the catalyst is one which is to be used in a slurry type polymerization where the object is to produce a slurry of insoluble particles of the end product polymer rather than a solution of polymer which could result in fouling of the reactor. In the operation of a slurry polymerization in a continuous loop reactor it is extremely important for efficient operations to limit polymer fouling of the internal surfaces of the reactor. The term “fouling” as used herein refers to polymer buildup on the surfaces inside the reactor.
An improved type of solid metallocene catalyst composition that can be used in a slurry polymerization process was revealed in U.S. Pat. No. 5,498,581, the disclosure of which is incorporated herein by reference. That catalyst composition was prepared by combining a cocatalyst with a metallocene that had an olefinically unsaturated substituent, subjecting that mixture to prepolymerization with an olefin in the presence of a liquid to produce a solid prepolymerized catalyst, and separating the resulting prepolymerized catalyst from the liquid and the components dissolved in the liquid. Some specific variations of producing such catalysts are disclosed in WO 99/29738 and WO 98/52686, the disclosures of which are also incorporated herein by reference.
An object of the present invention is to provide yet further improvements for the making of solid catalyst systems of the type disclosed in U.S. Pat. No. 5,498,581. In accordance with another aspect of the present invention, there is provided a method for polymerizing olefins using the new improved version of such solid prepolymerized metallocene catalyst systems.
SUMMARY OF THE INVENTION
In accordance with the present invention, a solid particulate metallocene-containing catalyst system is produced by (a) combining an organoaluminoxane and at least one metallocene having at least one olefinic unsaturated substituent in an aliphatic liquid to form a liquid catalyst system, (b) conducting prepolymerization of at least one olefin in the presence of said liquid catalyst system, optionally in multiple steps, to produce a prepolymerized solid catalyst, and (c) separating the resulting solid from the liquid and the components dissolved in the liquid, said solid being the solid particulate metallocene catalyst system. The phrase “liquid catalyst system” as used herein refers to the combination of the aluminoxane, the metallocene, and the aliphatic liquid, irrespective of whether the aluminoxane and/or the metallocene are dissolved in the liquid.
In accordance with another aspect of the present invention, the resulting inventive solid particulate metallocene-containing catalyst system is employed in the polymerization of an olefin by contacting the olefin with the inventive solid particulate metallocene-containing catalyst system under suitable reaction conditions.
DETAILED DESCRIPTION OF THE INVENTION
A wide range of metallocenes are considered to be applicable to the present process. The essential feature is that the metallocene be one wherein at least one cyclopentadienyl-type ligand has a substituent having a polymerizable olefinic group. Some examples of such olefin-containing metallocenes are disclosed in U.S. Pat. No. 5,169,818 and published European Application No. 574,370. The invention is considered applicable to both bridged and unbridged metallocenes. The unbridged metallocenes can even include bridged ligands which contain two cyclopentadienyl-type radicals connected by a suitable bridging structure but wherein only one of the cyclopentadienyl-type radicals of that ligand is bonded to the transition metal. Alternatively the olefinic substituent can be on the bridge connecting the two cyclopentadienyl-type groups.
The metallocenes of the type contemplated as useful for the present invention include those represented by the formula R
x
(Z)(Z)MQ
k
wherein each Z bound to M and is the same or different and is a cyclopentadienyl-type ligand selected from substituted or unsubstituted cyclopentadienyl, indenyl, tetrahydroindenyl, octahydrofluorenyl, and fluorenyl ligands; R is a structural bridge linking the Z's and M is a metal selected from the group consisting of IVB, VB, and VIB metals of the periodic table, each Q is the same or different and is selected from the group consisting of hydrogen, halogens, and organoradicals; x is 1 or 0; k is a number sufficient to fill out the remaining balances of M; further characterized by the fact that at least one Z has at least one olefinically unsaturated substituent attached. In bridged metallocenes this olefinically unsaturated substituent can be a branch on the bridging unit or on one or both of the cyclopentadienyl-type groups of the bridged ligands.
When a Q is an organo radical it can be selected from any of the organo radicals known to be suitable for metallocenes that are useful as polymerization catalysts. Some examples include aryl, alkyl, alkenyl, alkylaryl, and arylalkyl radicals. Preferably, if Q is an argano radical, the organo radical has 1 to 20 carbon atoms.
A particularly preferred type of bridged metallocene includes those in which the olefinically unsaturated substituent has the formula
wherein R″ is a hydrocarbyl diradical having 1 to 20 carbon atoms; more preferably 2 to 10; n is 1 or 0, and each R′ is individually selected from the group consisting of organo radicals having 1 to 10 carbon atoms and hydrogen. Most preferably R″ has at least two carbons in its main alkylene chain, i.e. it is a divalent ethylene radical or a higher homolog thereof.
Some olefinic branched bridged ligands useful for making metallocenes suitable for the present invention can be prepared by reacting a dihalo olefinic compound with an alkali metal salt of a suitable cyclopentadiene-type compound to produce a compound of the formula Z—R—Z where R is a bridge having olefinic unsaturation and wherein each Z is the same or alternatively to first produce a compound of the formula Z—R—X wherein X is a halogen and then reacting that compound with an alkali metal salt of another different cyclopentadiene-type com
Ford Leigh A.
Glass Gary L.
Kirchman L. Matthew
Mitchell Kent E.
Muninger Randall S.
Chevron Phillips Chemical Company LP
Choi Ling-Siu
Kilpatrick & Stockton LLP
Wu David W.
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