Bridged metallocenes for olefin copolymerization

Details Bridged metallocenes for olefin copolymerization Bridged metallocenes for olefin copolymerization

2002-03-07

2003-01-14

Shaver, Paul F. (Department: 1621)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

Reexamination Certificate

active

06506857

ABSTRACT:

TECHNICAL FIELD
This invention relates to aryl-substituted-bridge containing organometallic catalyst compounds suitable for olefin polymerization processes.
BACKGROUND ART
Olefin polymers comprising ethylene and at least one or more &agr;-olefin and optionally one or more diolefin make up a large segment of polyolefin polymers and will be addressed as “ethylene copolymers” herein. Such polymers range from crystalline polyethylene copolymers such as High Density Polyethylene with a density in excess of 0.94, to slightly crystalline polyethylene such as Linear Low Density Polyethylene with a density between 0.915 to 0.94, to largely amorphous elastomers with a density down to 0.85 and a relatively high molecular weight and with a new area of semi-crystalline “plastomers” with a density of between 0.915 and 0.86 and a moderate molecular weight. In particular, ethylene copolymer plastomers are now a well established class of industrial polymers having a variety of uses associated with their unique properties, such as elastomeric properties and their thermo-oxidative stability. Uses of the plastomers include general thermoplastic olefins, films, wire and cable coatings, polymer modification, injection molding, foams, footwear, sheeting, functionalized polymers and components in adhesive and sealant compounds.
Commercially prepared ethylene copolymers have been traditionally been made via Ziegler-Natta polymerization with catalyst systems largely based on vanadium or titanium. Newer metallocene catalyst compounds have received attention due to their ease of larger monomer incorporation and potential increases in polymerization activities. U.S. Pat. No. 5,324,800 describes metallocenes having substituted and unsubstituted cyclopentadienyl ligands which are suitable for producing high molecular weight olefin polymers, including linear, low density copolymers of ethylene with minor amounts of &agr;-olefin.
The utility of bridged metallocene-based ionic catalysts in olefin polymerization is described in U.S. Pat. Nos. 5,408,017 and 5,767,208, EP 0 612 768, and EP 0 612 769. Each addresses suitable bridged metallocene catalysts for high temperature processes for olefin copolymerization. Substituted single carbon, or methylene, bridging groups for metallocenes suitable as olefin polymerization catalysts is described in U.S. Pat. Nos. 4,892,851, 5,155,080 and 5,132,381. Isopropylidene, mono- and diaryl methylene groups are identified as particularly suitable.
Olefin solution polymerization processes are generally conducted in aliphatic solvents that serve both to maintain reaction medium temperature profiles and solvate the polymer products prepared. However, aryl-group containing metallocenes, those having cyclopentadienyl derivatives and other fused or pendant aryl-group substituents, are at best sparingly soluble in such solvents and typically are introduced in aryl solvents such as toluene. Solution polymerization processes in aliphatic solvents thus can be contaminated with toluene that must be removed to maintain process efficiencies and to accommodate health-related concerns for both industrial manufacturing processes and polymer products from them. Alternatively, relatively insoluble catalysts can be introduced via slurry methods, but such methods required specialized handling and pumping procedures that complicate and add significant costs to industrial scale plant design and operation. Low solubility can also become disadvantageous should the process involve low temperature operation at some stage such as in typical adiabatic processes run in areas subject to low ambients temperatures. Additionally, separating or counteracting the build up in the recycle system of special catalyst solvents may become another problem. At the same time means of maintaining high molecular weights in olefin polymers while operating at economically preferable high polymerization reaction temperatures and high polymer production rates is highly desirable. It is therefore desirable to provide a metallocene catalyst which is active for polyethylene polymerization particularly at elevated temperatures which nevertheless has increased solubility in aliphatic solvents.
BRIEF SUMMARY OF THE INVENTION
The invention thus addresses specifically substituted, bridged metallocene catalyst complexes comprising a solubilizing covalent bridge comprising at least one hydrocarbylsilyl substitutent. It can be described as a Group 4 organometallic compound comprising two ancillary monanionic ligands, each of which independently may be substituted or unsubstituted, wherein the ligands are bonded by a covalent bridge containing a substituted single Group 14 atom, the substitution on said Group 14 atom comprising aryl groups at least one of which contains at least one hydrocarbylsilyl substituent group sufficient to provide increased solubility in aliphatic solvents. Additionally, the invention relates to solution polymerization processes for ethylene copolymers having a density of about 0.850 to about 0.940 comprising contacting, under supercritical or solution polymerization conditions at reaction temperatures of 40° C. to 300° C., ethylene and one or more comonomers capable of insertion polymerization with a metallocene catalyst complex derived from A) a metallocene compound having a covalent bridge connecting a cyclopentadienyl ligand to another ancillary anionic metal ligand group, said bridge containing a substituted single Group 14 atom, the substitution on said Group 14 comprising aryl groups at least one of which contains at least one hydrocarbylsilyl substituent group of the formula R
2
n
SiR
1
3−n
, where each R
1
is independently a C
1
-C
20
hydrocarbyl, hydrocarbylsilyl, hydrofluorocarbyl substitutent, R
2
is a C
1
-C
10
linking group between Si and the aryl group, and n=0, 1 or 2. Where n=0, the Si atom is covalently bound directly to an aryl group ring carbon atom.
DETAILED DESCRIPTION OF THE INVENTION
The bridged metallocene compounds of the invention are those having a single substituted carbon or silicon atom bridging two ancillary monanionic ligands, such as substituted or unsubstituted cyclopentadienyl-containing (Cp) ligands and/or substituted and unsubstituted Group 13-16 heteroatom ligands, of the metallocene metal centers. The bridge substituents are substituted aryl groups, the substituents including at least one solubilizing hydrocarbylsilyl substituent located on at least one of the aryl group bridge substituents. Substituents present on the cyclopentadienyl and/or heteroatom ligands include C
1
-C
30
hydrocarbyl, hydrocarbylsilyl or hydrofluorocarbyl groups as replacements for one or more of the hydrogen groups on those ligands, or those on fused aromatic rings on the cyclopentadienyl rings. Aromatic rings can be substituents on cyclopentadienyl ligand and are inclusive of the indenyl and fluorenyl derivatives of cyclopentadienyl groups, and their hydrogenated counterparts. Such typically may include one or more aromatic ring substituent selected from linear, branched, cyclic, aliphatic, aromatic or combined structure groups, including fused-ring or pendant configurations. Examples include methyl, isopropyl, n-propyl, n-butyl, isobutyl, tertiary butyl, neopentyl, phenyl, n-hexyl, cyclohexyl, benzyl, and adamantyl. For the purposes of this application the term “hydrocarbon” or “hydrocarbyl” is meant to include those compounds or groups that have essentially hydrocarbon characteristics but optionally contain not more than about 10 mol. % non-carbon heteroatoms, such as boron, silicon, oxygen, nitrogen, sulfur and phosphorous. Additionally, the term is meant to include hydrofluorocarbyl substitutent groups. “Hydrocarbylsilyl” is exemplified by, but not limited to, dihydrocarbyl- and trihydrocarbylsilyls, where the preferred hydrocarbyl groups are preferably C
1
-C
30
substituent hydrocarbyl, hydrocarbylsilyl or hydrofluorocarbyl substitutents for the bridging group phenyls. For heteroatom containing catalysts see WO 92100333. Also, the use of hetero-atom containing rings o

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