WO1995016716A1 - Process for producing elastomers with an indenyl metallocene catalyst system - Google Patents

Abstract

A process for producing a high Mw EPDM or ethylene propylene elastomer having low crystallinity using a bridged bis-metallocene-alumoxane catalyst wherein the metallocene component of the catalyst has formula (I), wherein 'M' is titanium, zyrconium or hafnium; R?1 and R2¿ are each independently a C¿1? to C20 linear, branched or cyclic alkyl group; 'X' independently is a halogen, hydride, alkyl, aryl or chelating group; and 'y' and 'z' are integer numbers of 0 to 2.

Description

Title: PROCESS FOR PRODUCING ELASTOMERS WITH AN

INDENYL METALLOCENE CATALYST SYSTEM

FIELD OF THE INVENTION This invention relates to a process for the production of elastomers, particularly high molecular weight (Mw) elastomers such as ethylene-α-olefin diene-elastomers (EODE) of low crystallinity or ethylene-propylene elastomers using a bisindenyl metaUocene catalyst system which provides medium to high levels of comonomer incorporation at high catalyst activity.

BACKGROUND OF THE INVENTION

Olefin-based elastomeric polymers may be produced by the proper copolymerization of ethylene, an α-olefin and optionally a diene monomer. The most common such elastomers are copolymers of ethylene and propylene (EP elastomers) and terpolymers of ethylene, propylene, and diene, generally referred to as EPDMs. While ordinary EP elastomers can be cured through use of curatives such as organic peroxides, for cures using sulfur and sulfur-containing compounds, the presence of a diene is required. Hence, EPDM elastomers find use in numerous cured applications for which the EP copolymers are not suitable. Currently, EPDMs are commonly produced with vanadium cόmpound-organoaluminum catalyst systems.

While demonstration of this invention is made specifically with EPDM and EP copolymers, the scope includes co- and terpolymers incorporating other α-olefins in place of propylene, and the comments should be understood to include ethylene-α-olefin-diene elastomers (EODE) containing 1-butene, 1-pentene and other α-olefins including 1- hexene and 1-octene, either alone or in combinations, as well as propylene. These related materials are referred to herein as EODEs.

EPDMs have many properties which make them desirable for applications for which other types of elastomers are not as well suited. EPDMs have outstanding weather and acid resistance, and high and low temperature performance properties. Such properties particularly suit EPDMs as an elastomer for use in hoses, gaskets, belts, bumpers; as blending components for plastics and for tire side walls in the automotive industry; and for roofing applications. Additionally, because of their dielectric properties, EPDMs are particularly well suited for use as wire and cable insulation.

Desirably, an EPDM elastomer should have a reasonably fast cure rate and high state of cure; hence its diene content should be relatively high, preferably above three weight percent. The cure rate for an EPDM elastomer and the final properties of the cured article depend upon the type of diene incorporated. For example, on a comparable diene weight percent basis, an EPDM produced with 5-ethylidene-2-norbomene (ENB) as the diene will have a faster cure rate in sulfur cures than an EPDM produced with dicyclopentadiene (DCPD), or 1 ,4-hexadiene (HD), whereas EPDMs with hexadiene as the termonomer are known to exhibit good heat resistance. For many commercial applications an EP or EPDM elastomer should also have a low degree of crystallinity, measured by Differential Scanning Calorimetry (DSC) as a heat of fusion of 9 cal/g or less, preferably less than 3 cal/g, according to the technique described herein. For an EPDM material to be useful for most elastomer applications, it should have a weight-average Mw of at least about 100,000, or expressed in terms of the Mooney viscosity (ML-, ₊4 at 125°C), at least 5; and more preferably a Mw of at least about 110,000 or, expressed in terms of the Mooney viscosity (ML-, ₊4 at 125°C), at least 10. In many applications it is further desirable that the molecular weight distribution (MWD) of an EPDM should be characterized by a ratio of weight average Mw to number average molecular weight (Mn), Mw/Mn, less than 5, preferably less than 3.

The heat of fusion of an EPDM is a commonly-used measure of its degree of crystallinity. This property is important because the degree of crystallinity is correlated with physical properties, such as the tensile strength, and also the processibility and tack of the EPDM material. Since, in most commercial uses, elastomers are generally significantly higher in Mw than plastics, too much crystallinity makes an EPDM material very difficult to process at ordinary temperatures. Also, although good physical properties are desirable (e.g., in applications such as hose and tubing, or wire and cable), again, an excess of crystallinity causes an EPDM material to exhibit high hardness and stiffness and a surface with a "plastic-like" rather than a "rubbery" feel, and poor surface tack.

In most current EPDM production processes, the catalysts used for production of high Mw EPDM elastomers are soluble catalysts formed from vanadium compounds such as VCI4, VOCI3, V(AcAc)3, or VO(OR)3 (where R is an alkyl group) in conjunction with an organoaluminum compound. The activity of vanadium compound catalysts are generally low, e.g., 80-120 g polymer/mmol V. In current commercial grades of EPDMs, crystallinity is a function of the ethylene content of the polymer and the catalyst system used for its production. For a given polymer composition, the catalyst system controls the fraction of ethylene units present in long ethylene sequences (long runs of ethylene units), which are capable of crystallizing. On the other hand, when a given catalyst system is used in a given reactor configuration, polymers with higher ethylene content will always have more long ethylene sequences, hence will be more crystalline. For current commercial EPDMs based on vanadium catalysts, the nature of this relationship is such that polymers are completely amorphous (non- crystalline) at ethylene contents below approximately 55 wt% and possess significant crystallinities (i.e., heat of fusion greater than approximately 0.05 cal/g) at ethylene contents of approximately 55 wt% or greater. The degree of crystallinity exhibits less dependence on the diene content of the EPDM material than on the percentage of ethylene. For an EP or EPDM produced by the vanadium catalyst system, VOCI- ethylaluminum sesquichloride for example, a heat of fusion (HOF) of roughly 3 cal/g is obtained at 67 wt% ethylene, while HOF is as high as 9 cal/g at 78 wt% ethylene. The HOF of an EPDM at a given ethylene content may be used to compare the crystallinity of polymers produced by a given catalyst system. In order for the catalyst system to be useful for commercial production of an EPDM elastomer, it is desirable for the crystallinity of the polymers to be roughly comparable to that of currently available commercial grades of EPDM for most applications, although higher levels are acceptable in some applications. Since the recent advent of metallocene-alumoxane catalyst systems for the production of polyethylene and copolymers of ethylene and α-olefins (e.g., linear low density polyethylene), some effort has been made to determine the suitability of particular metallocene-alumoxane catalyst systems for the production of EPDM elastomers. For a metallocene-alumoxane catalyst system to be useful for the production of EPDM elastomers, it should produce high yields of EPDM in a reasonable polymerization time, and provide for adequate incorporation of a diene monomer, and provide a nearly statistically random distribution of monomers, while enabling good control of Mw over a wide range while yielding a relatively narrow MWD. To date two publications have addressed the production of EPDM elastomers by processes using particular metallocene-alumoxane catalyst systems. Kaminsky, J_ Polv. Sci.. Vol. 23, pp. 2151-64 (1985) reports upon the use of a soluble bis(cyclopentadienyl) zirconium dimethyl- alumoxane catalyst system for toluene solution polymerization of elastomers containing ethylene, propylene, and ENB. Kaminsky employed this catalyst at low zirconium concentrations, high AI:Zr ratios and long reaction times to prepare, in low yields, high Mw EPDM elastomers having high ENB incorporation. The method by which Kaminsky reports such EPDM elastomers to be producible with a bis(cyclo- pentadienyl)zirconium dimethyl-alumoxane catalyst system is not commercially suitable. In particular, the long induction times required for Kaminsky's catalyst system to reach its full activity, a period on the order of hours without diene present, and longer with diene present, precludes commercial operation. Japanese Kokai 62-121 ,711 illustrates the use of a soluble bis(cyclopentadienyl) zirconium monohydride monochloride-alumoxane catalyst system for toluene solution polymerization of ethylene and butene-1 wherein, variously, 5-ethylidene-2-norbomene (ENB), 5- vinylidene-2-norbornene (VNB), and dicyclopentadiene (DCPD) were employed as the diene. This reference further suggests, but does not illustrate, that the zirconocene component of the catalyst system may be a bis(indenyl) zirconium hydride or bis(tetrahydroindenyl) zirconium hydride rather than a bis(cyclopentadienyl) zirconium hydride. Though the reference suggests that α-olefins other than 1-butene can be employed, it illustrates only the production of an ethylene-butene-1 -diene elastomer (EBDM) material of high ethylene content in a continuous flow atmospheric pressure reaction. The low product yield in view of the high monomer requirements for such process renders it undesirable for commercial utilization.

A number of European Patent Applications (EP) describe supported and prepolymerized metallocene-alumoxane catalysts useful for ethylene and ethylene-α-olefin polymerization. See EP Publication Nos. 0279863; 0287666; 0285443; 0294942; and 0295312. Each identifies as examples of metallocenes which may be utilized in the preparation of a supported form of metallocene-alumoxane catalyst a broad list of zirconocenes, titanocenes, and hafnocenes, among which are a few species, bridged and unbridged, of bis(indenyl)metallocenes. The examples of each illustrate the supported catalyst, which may be in prepolymerized form, only with reference to bis(cyciopentadienyl) transition metal components. It appears that the described supported catalyst compositions are limited to the production of plastics and would not be suitable to the production of a commercially useful ethylene-α- olefin-diene elastomer.

Recently, patents and applications have appeared from our labs describing the use of certain metallocene/alumoxane catalysts for slurry polymerization of ethylene-α-olefin copolymers (U.S. patent 4,871 ,705, EP 347,128) to make high Mw elastomers. The metaUocene components taught in those cases were specifically with cyclopentadienyl ligands having saturated substituents on the ring. Also, the products taught were specifically copolymers, not diene-containing terpolymers. The use of certain of the class of metallocenes covered by the above mentioned patents and applications for synthesis of high Mw elastomers of the ethylene-α-olefin-diene type was described in EP 347,129 and in commonly owned copending U.S. 5,229,478. The class found to be effective for high Mw, low crystallinity EPDM synthesis were all of the bridged cyclopentadienyl type with saturated substituents on the ring. In contrast, the use of an unbridged analogue

(bis(tetrahydroindenyl) zirconium dichloride) gave products with undesirable higher crystallinity, lower incorporation of diene, or lower Mw.

Ethylene-propylene elastomers find many end-use applications due to their resistance to weather, good heat aging properties and their ability to be compounded with large quantities of fillers and plasticizers. Typical automotive uses are radiator and heater hose, vacuum tubing, weather stripping and sponge doorseals. Typical industrial uses are for sponge parts, gaskets and seals.

Due to their different properties and end uses, it is important to distinguish between those factors affecting elastomeric or plastic properties of α-olefin polymers. While such factors are many and complex, a major one is that related to sequence distribution of the monomers throughout the polymer chain. For polyolefin plastics, sequence distribution is of little consequence in determining polymer properties since primarily one monomer is present in the chain. Accordingly, in plastic copolymers the majority monomer will be present in the form of long monomeric blocks. While sequence distribution is thus of little concern with respect to polymeric plastics, it is a critical factor with respect to elastomers. If the olefinic monomers tend to form long blocks which can crystallize, elastic properties of the polymer are poorer than in a polymer with short monomer sequences in the chain.

Titanium catalysts, which can produce stereoregular propylene sequences, are particularly disadvantageous since creating blocks of either ethylene or propylene will lead to crystallinity in the elastomer. At a given comonomer composition, sequence distribution is primarily a function of the catalyst. It is important to exercise care in selecting a catalyst system for making elastomers, with their critical dependency on sequence distribution and stereoregularity. On the other hand, no such restrictions apply to the selection of a catalyst system for making plastic polymer.

To avoid crystallinity in copolymers, it is also necessary to use a catalyst that produces a material with a narrow compositional distribution so that fractions containing a high content of one monomer are not present. Furthermore, when making ethylene-α-olefin copolymers it is well known that the α-olefin may act as a chain transfer agent. For essentially crystalline copolymers with low α-olefin content, the Mw modifying effect of the α-olefin may be insignificant. However, when making copolymers with compositions in the elastomer range, catalysts that give high Mw plastic copolymers may produce low Mw polymers unsuitable for elastomer applications. In a similar fashion, undesirable MWD changes can occur or the compositional distribution can change. Furthermore, commercially useful plastics of polyethylene or polypropylene need not have as high a Mw as commercially useful elastomers of ethylene-α-olefin type.

In view of the complicated and poorly understood relationship between polymer composition and catalyst performance, it is difficult to predict the behavior of a catalyst for the production of an elastomer if it has only been used previously to make plastic.

EP 206,794 discloses that certain supported metallocene/alumoxane complexes, particularly bis(cyclopentadienyl) transition metal metallocenes, in which the cyclopentadienyl ligands are unsubstituted or substituted with alkyl groups and may be bridged by an alkylene or a silanylene group, are useful for polymerizing ethylene to a copolymer with an α-olefin for purposes of modifying the clarity or impact properties of the polyethylene product. The art has also indicated that amorphous ethylene-propylene copolymers (EPC) may be produced by metallocene/alumoxane catalyst systems in which the metaUocene component is a particular species of metaUocene. As used herein the term "EPC" means a copolymer of ethylene and an α-olefin which exhibits elastomeric properties as defined in ASTM D1566 under rubber. However, prior to the work reported herein and in U.S. 4,571 ,705 and U.S. 5,001 ,205, the EP copolymers so produced have been too low in Mw to be suitable for use as a commercial elastomeric material, especially when the elastomer has more than 20 wt% incorporated propylene. Also, the activities of the catalysts employed have been too low for production of products with low residues of catalyst in a reasonable time.

In EP 128,046 it is indicated that an alumoxane complex with dimethylsilanyienedicyclopentadienyl zirconium dichloride or bis(cyclopentadienyl) titanium diphenyl will catalyze production of a low Mw EPC, and that such catalyst complexes may be employed in conjunction with other distinct metallocene/alumoxane catalyst complexes to produce reactor blends of an EPC with high density polyethylene (HDPE) and linear low density polyethylene (LLDPE) such as, HDPE/EPC, LLDPE/EPC, HDPE/LLDPE/EPC reactor blends or the like. The EPC component of the blends so produced -- which by itself by reason of its low Mw is not a commercially useful — is useful in the context of a modifier blend component for the base HDPE or LLDPE with which it is coproduced.

Japanese Kokai 62-119,215; 62-121 ,707; and 62-121 ,709 disclose production of soft copolymers variously of ethylene-α-olefin, propylene-α- olefin, butylene-α-olefin, using a metallocene/alumoxane catalyst complex wherein the metaUocene is a metal salt of a lower alkylene bridged - bis(cyclopentadienyl), -bis(indenyl) or -bis(tetrahydroindenyl) compound. The Japanese Kokai represent that copolymer products may be produced by a gas or liquid phase reaction procedure to have a wide range of properties such as crystallinities from 0.5-60%, while having a MWD less than 3 with low levels of boiling methyl acetate soluble components. The Japanese Kokai represent that such copolymerization may be carried out in the presence of such catalysts at temperatures from -80 to 50°C under pressures ranging from ambient to 30 kg/cm². Yet in the examples of the first two Japanese Kokai, which illustrate actual production of such materials, the reaction conditions illustrated are temperatures of -10 to - 20°C at reaction times of from 5 to 30 hours using solution polymerization with toluene as the solvent. A process as illustrated by the operating examples of the first two Japanese Kokai is not commerically attractive since the long reaction times, low temperatures and need to separate polymer product from the reaction solvent impose severe increases in production cost. The process of Japanese Kokai 62-121 ,709 is also unattractive due to the use of toluene as a solvent and the expense of separating and recycling the large volume of solvent. A number of references have recently appeared which describe specific forms of metallocene/alumoxane catalysts useful for ethylene and supported and prepolymerized ethylene-α-olefin polymerization. See EPs: 0279863; 0287666; 0285443; 0294942; and 0295312. Each identifies as examples of metallocenes which may be utilized in the preparation of a supported form of metallocene/alumoxane catalyst a broad list of zirconocenes, titanocenes and hafnocenes, among which are a few species of bis(indenyl) metallocenes. The examples of each illustrate the supported catalyst, which may be in prepolymerized form, only with reference to bis(cyclopentadienyl) transition metal components. From the information presented, it would appear that the described supported catalyst compositions are limited to the production of plastics and, whether or not in prepolymerized form, would not be suitable to the production of ethylene-α-olefin elastomer.

For an EPC elastomer to be considered to have commercially acceptable properties, it should have a Mooney viscosity (ML₁₊ at 125° C) no less than 10, a weight-average Mw no less than 100,000, a glass transition temperature below -40 to -60°C and a degree of crystallinity no greater than 25%. Such EPC elastomer should also have a MWD of 5 or less. The range of reaction conditions most economical under which EPC elastomers should be produced is a temperature ranging from 0 to 80°C at reaction residence times of from 30 minutes to 6 hours. The reaction conditions should minimize or eliminate the number of extrinsic treatment steps needed to isolate the polymer product in final form. Hence, it is desirable for the production method to employ as a reaction diluent one or more of the monomers rather than an inert solvent from which the polymer product must later be separated. It is also desirable that the product be produced in granular form in the slurry reactor for ease of isolation and subsequent processing. Finally, it is desirable that the catalyst be sufficiently active that deashing from the product is not needed. Preferably, the catalyst productivity should be greater than 500 grams of polymer per gram of ash (catalyst and cocatalyst residues) per hour.

More preferably, the productivity should be greater than 1000 grams of polymer per gram of ash per hour; and most preferably, the productivity should be greater than 2000 grams of polymer per gram of ash per hour.

Before the discovery described in my U.S. Patent 4,871 ,705 that highly substituted bis(cyclopentadienyl) Group IVB transition metal compounds, particularly bis(tetrahydroindenyl) and more preferably bridged bis(tetrahydroindenyl) Group IVB metal compounds, can be used with an alumoxane in a supported form of catalyst to produce EPC elastomers, the production of EPC elastomers with a metallocene/alumoxane catalyst under conditions suitable for commercial practice had not been demonstrated. As my U.S. Patent 4,871 ,705 describes, supported bis(tetrahydroindenyl) Group IVB metal compounds are a class of metallocenes that particularly useful in forming a catalyst system for commercial production of EPC elastomers. Nevertheless, it is still desirable to develop catalyst systems, particularly metallocene-alumoxane catalysts, with which EPC elastomers may be produced wherein the expense associated with catalyst production is reduced compared to that required for production of a bis(tetrahydroindenyl) Group IVB metal compound based catalyst systems.

SUMMARY OF THE INVENTION

In the present invention, the use of the unsaturated, unbridged bis(indenyl) ligand provides products with intermediate crystallinity and other properties of interest for commercial elastomers.

The suitability of unbridged bis(indenyl) metallocenes for production of commercially interesting EOD elastomers was unexpected in light of the poor performance of bridged bis(indenyl) ligand metallocenes for copolymer synthesis as described in commonly owned U.S. Patent No. 4,871 ,705 and in light of the performance of the unbridged saturated ligand as described above. The invention provides process for producing an ethylene-α-olefin elastomer optionally containing a diene which may comprise as process steps: supplying an α-olefin monomer to a reactor vessel to provide a liquid monomer and diluent medium and optionally supplying a diene monomer to said reactor vessel; supplying to ethylene in an amount to maintain desired relative monomer ratios; adding to said diluent a metallocene-cocatalyst catalyst system . The metaUocene component of the catalyst is of the formula:

wherein "M" is titanium, zirconium or hafnium; R¹ and R² may be the same or different and are each independently an electron donating group, preferably of a C-| to C20 linear, branched or cyclic alkyl group; each "X" is an anionic group, preferably a halogen, hydride, alkyl, aryl or hetero atom containing group or chelating group or the two X's form a divalent group, preferably an alkylene group, and "y" and "z" are integer numbers of 0, 1 , or 2; two R1 or R2 groups may be fused on the respective ligands. This invention thus comprises a method for producing high Mw ethylene-α-olefin-diene elastomers by slurry polymerization of ethylene, propylene or other α-olefin, and optionally a non-conjugated diene monomer in the presence of a metallocene-alumoxane catalyst system in which the metaUocene component is as above indicated and in which the same process steps may be used.

Such metaUocene catalyst complex is preferably supported on a silica gel support, in the presence of the alumoxane cocatalyst, and is employed for the production of an ethylene-α-olefin-diene elastomer in a slurry polymerization procedure wherein propylene or other α-olefin monomer serves as the polymerization diluent, in the presence or absence of additional alumoxane in the liquid phase beyond that which is already present on the support. An ethylene-α-olefin-diene elastomer material produced by the process of this invention is characterized by a narrow MWD of less than 3, a Mooney viscosity within the range of 5 to 100 or greater, and a heat of fusion generally of less than 5 cal/g at ethylene contents up to 70 wt%. The invention, in the case of EP elastomers comprises a process employing a metallocene/alumoxane catalyst system in which the metaUocene is a specific class of zirconocene, titanocene or hafnocene which provides for the production of high Mw ethylene-α-olefin elastomers under reaction conditions suitable for commercial practice. Employment of one of the specified metallocenes, preferably a zirconocene, in the metallocene/alumoxane catalyst in a slurry reaction process results in the production of high Mw ethylene-α-olefin elastomers which typically have a low ash content (where ash refers to the catalyst and cocatalyst residue in the polymer), so that deashing is not required. The most preferred catalysts are those wherein M is zirconium. Utilizing the defined metaUocene in the metallocene/alumoxane catalyst with which the process is practiced, the process may be practiced with the catalyst in non-supported form by adding the metaUocene of the description given above and alumoxane in hydrocarbon solutions to the polymerization diluent. Preferably, the metallocene/alumoxane catalyst system is used in a heterogeneous form on a catalyst support, such as a silica gel support, and polymerization is carried out by a slurry polymerization technique in which an α-olefin monomer is used in excess and maintained in the liquid state to serve as the polymerization diluent. Most preferably, the supported metallocene/alumoxane catalyst is prepolymerized with ethylene or an α-olefin to control EPC granule size and size distribution for the direct production of granular EPC products from the slurry process.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a graphic presentation of Yield v. Reaction Time, Ex. 25-30.

Figure 2 is a graphic presentation of Average wt.% C2 v. Reaction Time, Ex. 25-30. Figure 3 is a graphic presentation of wt.% C2 v. Cumulative wt.%,

Ex. 28-30.

Figure 4 is a graphic presentation of Ethylene Content Distribution Profiles.

Figure 5 is a graphic presentation of Compositional Distribution, Ex. 31-32.

Figure 6 is a graphic presentation of the Compositional Distribution, Ex. 14.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FOR AN EPDM TYPE ELASTOMER

This invention relates to a process for producing ethylene-α-olefin-

EODE of high Mw and greater than about 0.3 weight percent diene content, preferably greater than 2.0 weight percent diene content. In particular it relates to a catalyst system comprising a bis(indenyl) Group IVB transition metal compound-alumoxane which is highly active for the production of high Mw-high diene-high ethylene content ethylene-α-olefin- diene elastomeric polymers having a low heat of fusion.

As used herein the term "EODE" encompasses elastomeric polymers comprised of ethylene, an α-olefin, and one or more non- conjugated diene monomers. The non-conjugated diene monomer can be a straight chain, branched chain or cyclic hydrocarbon diene having from about 6 to about 15 carbon atoms. Examples of suitable non-conjugated dienes are straight chain acyclic dienes such as 1 ,4-hexadiene and 1 ,6- octadiene; branched chain acyclic dienes such as 5-methyl-1 ,4- hexadiene; 3,7-dimethyl-1 ,6-octadiene; 3,7-dimethyl-1 ,7-octadiene and mixed isomers of dihydro myricene and dihydroocinene; single ring alicyclic dienes such as 1 ,4-cyclohexadiene; and 1 ,5-cyclododecadiene; and multi-ring alicyclic fused and bridged ring dienes such as tetrahydroindene, methyl tetrahydroindene, dicyclopentadiene; bicyclo- (2,2,1)-hepta-2,5-diene; alkenyl, alkylidene, cycloalkylidene norbornenes such as 5-methylene-2-norbornene (MNB); 5-propenyl-2-norbornene, 5- isopropylidene-2-norbomene,5-(4-cyclopentenyl)-2-norbomene, 5- cyclohexylidene-2-norbornene, 5-vinyl-2-norbornene and norbornadiene.

Of the dienes typically used to prepare EPDMs, the particularly preferred dienes are 1 ,4-hexadiene (HD), 5-ethylidene-2- norbornene (ENB), 5-vinylidene-2-norbornene (VNB), 5-methylene-2- norbomene (MNB), and dicyclopentadiene (DCPD). The especially preferred dienes are 5-ethylidene-2-norbomene (ENB) and 1 ,4-hexadiene (HD). The preferred EOD elastomers may contain about 20 up to about 90 weight percent ethylene, more preferably about 30 to 85 weight percent ethylene, most preferably about 35 to about 80 weight percent ethylene.

The α-olefin suitable for use in the preparation of elastomers with ethylene and dienes are preferably α-olefins. Illustrative non-limiting examples of such α-olefins are propylene, 1-butene, 1-pentene, 1- hexene, 1-octene and 1-dodecene. The α-olefin is generally incorporated into the EODE polymer at about 10 to about 80 weight percent, more preferably at about 20 to about 65 weight percent. The non-conjugated dienes are generally incorporated into the EODE at about 0.5 to about 20 weight percent; more preferably at about 1 to about 15 weight percent, and most preferably at 3 to about 12 weight percent. If desired, more than one diene may be incorporated simultaneously, for example HD and ENB, with total diene incorporation within the limits specified above.

DETAILED DESCRIPTION FOR AN EP RUBBER TYPE ELASTOMER This invention relates to a process for producing in high yield EPC elastomers of high Mw, low crystallinity, and low ash. In particular, it relates to a catalyst system comprising an indenyl metallocene/alumoxane complex which is highly active for the production of high Mw EPC elastomers in a slurry polymerization process. As used herein the term "EPC" means a copolymer of ethylene and an α-olefin, not necessarily propylene, which exhibits the properties of an elastomer. The α-olefins suitable for use in the preparation of elastomers with ethylene are preferably C₃-C₁₆ α-olefins. Illustrative non-limiting examples of such α-olefins are propylene, 1-butene, 1-pentene, 1- hexene, 1-octene and 1-dodecene. If desired, more than one α-olefin may be incorporated.

The EPC elastomers may contain about 20 up to about 90 weight percent ethylene, more preferably about 30 to 85 weight percent ethylene, and most preferably about 35 to about 80 weight percent ethylene.

DESCRIPTION OF THE CATALYST SYSTEM

The catalyst employed in the method of this invention is preferably a metallocene-alumoxane system as described above. The metaUocene is preferably a zirconocene, i.e. "M" is zirconium. The preferred zirconocene is bis(indenyl)zirconium dichloride.

The alumoxane component of the catalyst system is an oligomeric aluminum compound represented by the general formula (R-AI-O)_n+2, which is a cyclic compound, or R(R-AI-O-)_nAIR, which is a linear compound. In the general alumoxane formula "R" is a C-C alkyl radical, for example, methyl, ethyl, propyl, butyl or pentyl and "n" is an integer from 1 to about 25. Most preferably, "R" is methyl and "n" is at least 4. Alumoxanes can be prepared by various procedures known in the art. For example, an aluminum alkyl may be treated with water contained in a moist inert organic solvent, or it may be contacted with a hydrated salt, such as hydrated copper sulfate suspended in an inert organic solvent, to yield an alumoxane. Generally, however prepared, the reaction of an aluminum alkyl with a stoichiometric amount of water yields a mixture of the linear and cyclic species of the alumoxane. Usually there are also residual aluminum alkyl species associated with the alumoxane.

The catalyst employed in the method of the invention comprises a system formed upon admixture of a metaUocene, as specified, with an alumoxane. The catalyst complex may be prepared as a homogeneous catalyst by addition of the requisite metaUocene and alumoxane to a solvent in which polymerization will be carried out by solution polymerization procedures. However, in the context of the present invention, the catalyst complex is preferably prepared and employed as a heterogeneous catalyst by adsorbing and complexing the requisite metaUocene, preferably zirconocene, and alumoxane components on a catalyst support material such as silica gel, alumina or other inorganic support material. When prepared in heterogeneous or supported form, it is preferred to use silica gel as the support material. The heterogeneous form of the catalyst complex is employed in a slurry polymerization procedure with or without additional alumoxane present in the liquid phase. In the production of EOD in accordance with this invention, it is preferred to utilize the α-olefin monomer in excess in liquified state as the polymerization diluent.

The support material for preparing a heterogeneous catalyst may be any finely divided inorganic solid porous support, such as talc, silica, alumina, silica-alumina and mixtures thereof. Other inorganic oxides that may be employed either alone or in combination with silica or silica- alumina are magnesia, titania, zirconia, and the like. The preferred support material is a silica gel.

The metaUocene and alumoxane are utilized in the form of a heterogeneous supported catalyst by deposition on the support material. While it should not be construed that the invention is limited in any way by the following mechanistic interpretation, it is considered that for optimal effectiveness of the alumoxane deposited on the support, it is desirable that the unbound water initially present on the support should be essentially wholly removed. Suitably surface hydroxyl groups of the silica or inorganic oxide can also be removed or reduced by suitable thermal or chemical treatment. For example, silica gel may be dehydrated by heating or otherwise treating it to remove its water content, or its water content may be converted to a derivate which is conducive to the formation the metallocene-alumoxane catalyst system, water and most of the surface hydroxyl groups. The residual surface hydroxyl groups in the inorganic solid porous support may be removed by reaction with agents such as lithium alkyls, silyl chlorides, aluminum alkyls, or preferably with alumoxane, thus producing surface bound alumoxane. Hence, a preferred catalyst support is a dehydrated inorganic oxide treated with an alumoxane, more preferably methylalumoxane. A suitable support material is a dehydrated silica gel treated with methylalumoxane. The normally hydrocarbon soluble metaUocene and alumoxane are prepared as a heterogeneous supported catalyst by deposition on a support material, such as a dehydrated silica gel. The silica gel may be prepared in dehydrated form by heating or otherwise treating it to remove its water content or to convert same to a derivate which is clement to the formation of the metallocene/alumoxane catalyst complex. The residual surface hydroxyl groups can be removed by reaction with alumoxane, thus producing surface bound alumoxane. A suitable silica gel would have a particle diameter in the range of 1 or 10-600 microns, preferably 30-100 microns; a surface area of 50-1000 m/g, preferably 100-500 m²/g; and a pore volume of 0.5-3.5 cm/g. The silica gel may be heat treated at 100- 1000°C, preferably 200 or 300-800°C for a period of 1-100 hours, preferably 3-24 hours, to insure removal of unbound water from its surfaces. The residual surface hydroxyl groups may be subsequently removed by reaction with the alumoxane or with the associated alkylaluminum compounds.

The order of addition of the metaUocene and alumoxane to the support material can vary. For example, the metaUocene (dissolved in a suitable hydrocarbon solvent) can be first added to the support material followed by the addition of the alumoxane; the alumoxane and metaUocene can be added to the support material simultaneously, either separately or premixed together, or the alumoxane can be first added to the support material followed by the addition of the metaUocene.

The treatment of the support material, as mentioned above, is conducted in an inert solvent. The same inert solvent or a different inert solvent can be employed to dissolve the metaUocene and alumoxanes. Preferred solvents include mineral oils and the various hydrocarbons which are liquid at reaction temperatures and in which the individual adsorbates are soluble. Illustrative examples of useful solvents include alkanes such as pentane, iso-pentane, hexane, heptane, octane and nonane; cycloalkanes such as cyclopentane and cyclohexane; and aromatics such as benzene, toluene, xylenes, ethylbenzene and diethylbenzene. The support material may be present by itself, which is preferred, or may be slurried in the inert solvent in which the zirconocene and alumoxane are dissolved prior to the addition of the support material. The supported catalyst is prepared by adding the adsorbates in a suitable solvent, e.g., toluene, to the support material which is by itself or in a slurry. Preferably, the dried support material is added to a solution of the adsorbate. Most preferably, a silica support is added to a toluene solution of the adsorbate. In accordance with the preferred embodiment of this invention, a toluene solution of the zirconocene is added to the alumoxane dissolved in toluene, then the silica support is added to the solution, and the treated solid is dried. In both of these steps, the conditions for addition of the adsorbates are not particularly critical. The amount of solvent to be employed should be sufficient to provide adequate heat transfer away from the catalyst components during reaction and to permit good mixing. The temperature maintained during the contact of the reactants can vary widely, such as, for example, from about 0° to about 100°C. Greater or lesser temperatures can also be employed. Although the reaction between the alumoxane and the support material is rapid, it is desirable that the alumoxane be contacted with the support material for about one half hour up to eighteen hours or greater. Preferably, the reaction is maintained for about one hour.

At all times, the individual ingredients as well as the recovered catalyst components must be protected from oxygen and moisture. Therefore, the reactions must be performed in an oxygen and moisture free atmosphere and recovered in an oxygen and moisture free atmosphere. Preferably, therefore, the reactions are performed in the presence of an dry, inert gas such as, for example, nitrogen. The recovered solid catalyst is maintained in a nitrogen atmosphere.

Upon completion of the deposition of the zirconocene and alumoxane on the support, the solid material can optionally be treated with a small amount of monomer, e.g. ethylene, to prepolymerize the solid catalyst materials to a weight increase of from about 50 to about 1000% preferably from 100 to 500 percent based on initial weight of catalyst and support material. Prepolymerization of the solid catalyst material aids in obtaining an EOD or EP elastomer produced therefrom during slurry polymerization in well defined particle form. The solid material, as such or as prepolymerized, can be recovered by any well-known technique. For example, the solid catalyst material can be recovered from the liquid solvent by vacuum evaporation or decantation. The solid is thereafter dried under a stream of pure dry nitrogen or dried under vacuum. Careful rinsing of the prepolymerized catalyst provides the best granular particle form. Prepolymerization also greatly reduces the requirement for alumoxane. For example, an AI:Zr ratio of 1000:1 or greater for alumoxane:zirconocene is needed for high activity when the alumoxane is added to the liquid phase of the reactor, but a ratio less than 100:1 is often sufficient when the alumoxane is incorporated into the prepolymerized catalyst. For a prepolymerized catalyst the ratio of aluminum to zirconium may range from about 1:1 to 500:1, preferably from about 20:1 to 200:1 , and high activities will still be obtained.

Most preferably, the supported catalyst is prepared by 1 ) addition of a solution, toluene for example, of zirconocene to the alumoxane solution and stirring for 5-30 minutes; 2) adding the dry support to the solution and stirring at 25-80° for 15-60 minutes; 3) removal of toluene by vacuum with heating to leave a dry powder; 4) adding a light hydrocarbon, pentane for example, to slurry the powder; 5) prepolymerizing with ethylene or other olefin in the pentane slurry and then collecting, rinsing and drying the catalyst. For best particle form, it is preferred to add no alumoxane to the reactor beyond what is on the prepolymerized catalyst. Sufficient aluminum alkyl, such as triethylaluminum or triisobutylaluminum, to scavenge impurities in the feeds may be added, but not an excess.

The catalyst complex obtained through contacting of the metaUocene and the alumoxane cocatalyst may be formed prior to introduction of these components into the reactor, e.g., on the support surface, or, alternatively, it may be formed in the reactor. In the case that the active complex is formed in the polymerization reactor, the molar ratio of Al to Group IVB transition metal in the reactor is desirably in the range of 10-5000, preferably 20-4000 and most preferably 20-1000. In the case that the active complex is formed outside the reactor, the preferred molar ratio of Al to Group IVB transition metal is in the range 1 -1000, desirably 20-200. In the latter case, additional alumoxane cocatalyst may be used in the reactor so that the total ratio of Al to Group IVB transition metal is in the range 1-5000, preferably 20-4000 and most preferably 20-1000. Likewise, in this case, a small amount of another aluminum compound may be added to the reactor together with, or instead of, additional alumoxane, for the purposes of scavenging any impurities which may be present in the reactor.

Description of polymerization step

In accordance with the preferred procedure of this invention an EOD or EP elastomer is produced by slurry polymerization utilizing α- olefin monomer, preferably propylene, as the polymerization diluent in which a supported and prepolymerized zirconocene-alumoxane catalyst complex is suspended, in an amount sufficient to yield a polymer with the desired comonomer such as diene content, generally greater than or equal to 0.3 wt%. For the EOD elastomer, the concentration of diene in the reactor as a volume percentage of total diluent present will range from 0.1 to 25 vol%, with 0.5 to 10 vol% preferred and 1 to 5 vol% especially preferred. Diene monomer is supplied to the polymerization diluent. Ethylene is added to the reaction vessel in an amount to maintain a differential pressure in excess of the combined vapor pressure of the α- olefin and diene monomers. The ethylene content of the polymer is determined by the ratio of ethylene differential pressure to the total reactor pressure. Generally the polymerization process is carried out with a differential pressure of ethylene of from about 0.7 atm to about 70 atm (about 10 to about 1000 psi), most preferably from about 2.7 atm to about 27 atm (about 40 to about 400 psi); and the polymerization diluent is maintained at a temperature of from about -10°C to about 90°C; preferably from about 20°C to about 70°C, and most preferably from about 30°C to about 60°C. Under the conditions as indicated above the ethylene, α-olefin and diene polymerize to an EOD elastomer. The polymer product Mw is controlled, optionally, by controlling other polymerization variables such as the temperature, or by a stream of hydrogen introduced to the gas or liquid phase of the reactor, as is well known in the art.

It has been found that the purity of the 1 ,4-hexadiene is important to carrying out the polymerization. 1 ,4-hexadiene as received typically contains 500 parts per million by weight of various organic chlorides, of which a representative species is 3-chloro-1 -butene. These chlorides were found to be very severe poisons for the catalyst, even at very high Al/Zr. In addition, smaller amounts of hydrocarbons, including conjugated 1,3- and sometimes 2,4-hexadienes are contained in the 1 ,4-hexadiene as received. The 2,4-hexadienes also cause activity loss in the catalyst, particularly at low Al/Zr, but their effect is much less severe than that of the chlorides. The chlorides can be removed by, for example, passing over several columns of Basic Brockmann Activity 1 alumina used either as received or with a mild heat treatment. The chloride impurities should be removed to the detectability limit (using a GC Hall detector) of less than 2 parts per million, for use with prepolymerized catalysts.

The purification of ENB is also useful for successful polymerization with these catalysts. The best method found to purify ENB requires passage through a 1 meter bed of 800°C dried aluminum (12 x 32 granular La Roche A201 Alumina was used) followed by a 0.5 meter bed of dry 3A molecular sieves.

The polymerization may be carried out as a batchwise slurry polymerization or as a continuous process slurry polymerization. The procedure of continuous process slurry polymerization is preferred, in which event ethylene, α-olefin, diene, hydrogen, and catalyst are continuously supplied to the reaction zone in amounts equal to the ethylene, α-olefin, diene and catalyst removed from the reaction zone with the polymer in the product stream.

In accordance with the preferred procedure of this invention, an EPC elastomer is produced by slurry polymerization utilizing the α-olefin monomer or mixture of monomers as the polymerization diluent in which a supported zirconocene/alumoxane catalyst system is suspended. For EP elastomers the catalyst system may be unsupported, e.g. for solution polymerization or concentrated solution may be used for slurry polymerization. The catalyst selection and use may follow the general lines indicated above. Ethylene is added to the reaction vessel in an amount sufficient to produce the desired ethylene content in the EPC product. The differential pressure of ethylene, in excess of the vapor pressure of the α-olefin monomer, required to produce a given ethylene content depends on the structure of the zirconocene used. Generally the polymerization process is carried out at an ethylene differential pressure of from about 0.7 atm (about 10 to about 1000 psi), most preferably from about 3 atm to about 41 atm (about 40 to about 600 psi); and the polymerization diluent is maintained at a temperature of from about -10°C to about 100°C; preferably from about 10°C to about 70°C, and most preferably from about 20°C to about 60°C. Under the conditions as above indicated the ethylene and α-olefin monomers copolymerize to an EPC elastomer. The polymerization may be carried out as a batchwise slurry polymerization or as a continuous slurry polymerization. The procedure of continuous process slurry polymerization is preferred, in which event ethylene, liquid α-olefin, and catalyst are continuously supplied to the reaction zone in amounts equal to the ethylene, α-olefin, and catalyst removed from the reaction zone, with the EPC polymer, in the product stream.

The heterogeneous form of catalyst system is employed in a suspension or slurry polymerization procedure. For the production of EPC or EPDM elastomers in accordance with the method of this invention, it is preferred to utilize the α-olefin monomers in liquified state as the polymerization diluent. As a practical limitation, slurry polymerization takes place only in solvents which are not solvents for the product. This may limit the choice of α-olefin solvent to those with less than 5 carbon atoms. Otherwise the above referred to conditions can be used to prepare the supported catalyst.

Without limiting in any way the scope of the invention, one means for carrying out the process of the present invention is as follows: in a stirred-tank reactor liquid propylene monomer is introduced continuously together with diene monomer. The reactor contains a liquid phase composed substantially of liquid propylene and diene monomers together with dissolved ethylene and hydrogen gases, and a vapor phase containing vapors of all monomers and hydrogen. Feed ethylene gas and hydrogen are introduced either into the vapor phase of the reactor, or sparged into the liquid phase as is well known in the art. Catalyst and any additional cocatalyst and scavenger, if employed, are introduced via nozzles in either the vapor or liquid phase, with polymerization occurring substantially in the liquid phase. The reactor temperature and pressure may be controlled via reflux of vaporizing α-olefin monomers (autorefrigeration), as well as by cooling coils, jackets etc. The polymerization rate is controlled by the rate of catalyst addition. The ethylene content of the polymer product is determined by the ratio of ethylene to propylene in the reactor, which is controlled by manipulating the respective feed rates of these components to the reactor. The polymer product which leaves the reactor is recovered by flashing off gaseous ethylene and propylene at reduced pressure, and, if necessary, conducting further devolatilization to remove residual olefin and diene monomers in equipment such as a devolatilizing extruder. In a continuous process the mean residence time of the catalyst and polymer in the reactor generally is from about 10 minutes to 12 hours, preferably 20 minutes to 8 hours, and more preferably 30 minutes to 6 hours, and most preferably 1 to 4 hours.

The final properties of the elastomer produced by the process of the invention are related to the reaction conditions, particularly the ethylene-α-olefin ratio, the concentration of diene monomer, the catalyst residence time and concentration of hydrogen, if present. Longer catalyst residence time will result in a higher yield of an

EOD elastomer when other conditions are constant, providing a product with low residues of aluminum, Group IVB transition metal and support material. Higher diene monomer concentrations will provide an EODE having a higher weight percentage of incorporated diene. As mentioned previously, the Mw of the polymer product can be controlled by methods well known in the art, such as by addition of hydrogen to the polymerization system. However, the weight-average Mw of the EODE polymers according to the present invention is greater than or equal to 100,000 and generally greater than 110,000. Alternatively, in terms of the Mooney viscosity, the polymer ML_{1 +} at 125°C is greater than or equal to 5 and generally greater than 10. The polymer product Mw is controlled, optionally, by controlling other polymerization variables such as the temperature, or more desirably by a stream of hydrogen introduced to the gas phase of the reactor, as is well known in the art. Hydrogen is very effective for Mw control with these catalysts. Usually, less than 1000 mole ppm is sufficient to provide 10- 100 ML₁₊₄, 125°C products, with the precise amount required depending on temperature and pressure in the reactor. In the absence of hydrogen, the catalysts of this invention give products with about 2-3 times the Mw obtained with the tetrahydroindenyl catalysts of my U.S. Patent 4,871 ,705. Surprisingly, we find that use of more TEAL (triethylaluminum) than required for scavenging impurities can also reduce Mw as illustrated in the Examples. The polymer product which leaves the reactor is recovered by flashing off gaseous ethylene and propylene at reduced pressure, and, if necessary, conducting further devolatilization in equipment such as a devolatilizing extruder. In a continuous process the residence time of the catalyst in the reactor generally is from about 10 minutes to 12 hours, preferably 20 minutes to 8 hours, and more preferably 30 minutes to 6 hours, and most preferably 30 minutes to 4 hours. The final properties of the EPC elastomer produced by the process of the invention are related to the zirconocene structure and the reaction conditions, particularly the ethylene/propylene ratio and reaction temperature.

Examples

In the Examples which illustrate the practice of the invention, the analytical techniques described below were employed for the analysis of the resulting EOD or EPC elastomer products.

The heat of fusion was determined by DSC according to the following technique. Approximately 0.5 g of polymer was placed between two sheets of Mylar® film and pressed in a 20 mil mold at 150°C for 30 minutes. The resulting pad was annealed for at least 1 day at room temperature. The DSC analysis was run under a helium atmosphere on a Perkin-Elmer DSC-7, using about 10-15 mg of test sample from the pad. The cycle consisted of loading at room temperature, cooling to about -125 °C, followed by heating to about 200°C at a rate of 20°C per minute. The heat of fusion was obtained by summing the area of well-defined peaks occurring above the glass transition temperature, at which a baseline change occurred. In general, a well-defined melting peak is observed at around 40°C, and occasionally an additional peak is observed at 100°C - 110°C.

Polymer ethylene content was determined by infrared analysis according to ASTM D3900. The diene content was determined by ¹H nuclear magnetic resonance (NMR), according to the following technique. H spectra at 400 MHz were recorded on a Varian L-400 NMR spectrometer operating in Fourier Transform mode, with the following instrument conditions: pulse angle, 40°; acquisition time, 0.7 sec; pulse delay, 5.0 sec; spectral width, 12,000 Hz, and number of transient accumulated, 200. Samples were dissolved in deuterated chloroform at room temperature, at a concentration of 1-2 wt%. When the diene is 1 ,4- hexadiene, the diene content was determined from the integral of the peak for olefinic protons occurring at 5.48 ppm, and the methylene, methyl and methine regions were corrected for the presence of hexadiene incorporated in the polymer. In addition, unincorporated hexadiene, if present, was distinguished by the presence of vinyl protons appearing at 5.7-5.8 ppm. When the diene is ENB, the diene content was determined from the integral of the peak for olefinic protons occurring at 5.28 and 5.02 ppm (for cis- and trans- methine protons of =CH-CH, respectively) and the methylene, methyl and methine regions were corrected for the presence of incorporated ENB. In addition, unincorporated ENB, if present, was distinguished by the presence of vinyl protons appearing at

6.01 ppm. In this way, the proton NMR analysis was capable of yielding unambiguous values for the content of diene incorporated in the polymer.

Mw determinations for the elastomer products were made by gel permeation chromatography (GPC) according to the following technique. Mws and MWDs were measured using a Waters 150 gel permeation chromatograph equipped with a differential refractive index (DRI) detector and a Chromatix KMX-6 on-line light scattering photometer. The system was used at 135°C with 1 ,2,4-trichlorobenzene as the mobile phase. Shodex (Showa Denko America, Inc.) polystyrene gel columns 802, 803, 804 and 805 were used. This technique is discussed in "Liquid Chromatography of Polymers and Related Materials III", J. Cazes editor, Marcel Dekker, 1981 , p. 207 which is incorporated herein by reference.

No corrections for column spreading were employed; however, data on generally accepted standards, e.g., National Bureau of Standards

Polyethylene 1484 and anionically produced hydrogenated polyisoprenes, which are alternating ethylene-propylene copolymers, demonstrated that such corrections on Mw/Mn were less than 0.05 units.

The MWD, expressed by Mw/Mn, was calculated from an elution time -

Mw relationship whereas Mz/Mw was evaluated using the light scattering photometer. The numerical analyses were performed using the commercially available Beckman/CIS customized LALLS software in conjunction with the standard Gel Permeation package, run on a HP 1000 computer.

The Mooney viscosity, ML_{1 +4} at 125°C, was measured in a Monsanto Mooney Viscometer according to ASTM standard D1646.

Diene Purification

1 ,4-hexadiene (about 93% trans) was purified by passage through several feet of basic Brockmann activity I alumina to remove allylic chloride impurities to less than 2 ppm. Ethylidene norbomene (ENB) was purified for examples 3 and 4 by passing 600 mL through three 2.5 cm (1 inch) diameter columns, each containing 23 cm (9 inches) of silica gel dried at 240°C and 2.5 cm (1 inch) of dry 4A molecular sieves. For examples 5-13, the ENB was purified by passage at 50 cc/min through an 8 mm ID column, 1.5 meter long, containing 1 meter of 12 x 32 granular La Roche A201 alumina (dried at 800°C for 4 hours) followed by 0.5 meter of dry 3A molecular sieves. This last treatment gave runs with the best activity.

Examples 1-4 Synthesis of Prepolymerized Catalyst A mND1₂ZrCl_z/MAO/SiO₂.

10 g of Davison 948 silica gel (dried at 800°C for 4 hours) was added slowly to 250 mL of methylalumoxane in toluene (from Ethyl corporation, reported 1 M in aluminum) in a 500 mL flask equipped with a magnetic stir bar. The toluene was removed under vacuum, while heating at 80°C for 1 hour, to yield 18 g of white powder. To 2 g of the solid residue in a pressure bottle, magnetically stirred under nitrogen in 50 mL of dry pentane, was added 40 mg of bis(indenyl)zirconium dichloride dissolved in 3 mL of dry toluene. The slurry was then stirred at room temperature for 15 minutes. With water bath cooling of the reaction flask, ethylene was added at 6 mmol/min for 40 min. The powder was then collected on a fritted glass funnel in the dry box, washed five times with 40 mL of dry pentane, and dried. Collected was 7.06 g of prepolymerized catalyst as a tan powder with several larger pieces of polymer from the flask walls. Catalyst A was nominally 13 wt% methylalumoxane, 0.57 wt% zirconocene (0.13 wt% Zr), and 71 wt% polyethylene. The molar ratio of AI:Zr was about 150: 1.

Examples 5-13 Synthesis of Prepolymerized Catalyst B friND1₂ZrCI /MAO/SiO₂

200 g of Davison 948 silica gel (dried at 800°C for 4 hours) was added slowly to 5000 mL of methylalumoxane in toluene (Ethyl Corporation, reported 1 M in aluminum) under a nitrogen atmosphere in an 8 liter reactor equipped with a helical stirrer and a water jacket for heating and cooling. The toluene was removed under vacuum, with stirring and nitrogen sparging while heating at 66°C for 2.5 hours, to yield a white powder. The powder was reslurried in 6 liters of isopentane and 5.0 g of bis(indenyl)zirconium dichloride ([IND^ZrCI^) slurried in 750 mL of dry toluene was added over 15 minutes with good stirring. The reactor was closed in and polymer grade ethylene was added at a rate to maintain less than about 1 atm (about 15 psig) pressure in the reactor while cooling the reactor with 10-15°C water to maintain a temperature in the reactor below 30°C. After 1.5 hours, the ethylene feed was stopped, and the slurry was stirred 15 minutes to react with the last of the ethylene and bring the reactor to room temperature. The slurry was allowed to settle and the isopentane was decanted. The slurry was then rinsed three times with 4 L of isopentane, allowing it to settle and decanting the liquid after each rinse. The slurry was then transferred to a dry box where it was sieved through an ASTM 14 mesh sieve with pentane, collected on a fritted funnel, washed with 4 L of pentane, and dried under vacuum. The collected yield of catalyst B was 1020 g of fine tan powder. The bulk density of the catalyst in settled isopentane slurry was 0.43 g/mL and analysis of the powder gave 0.074% Zr, 4.58% Al, 8.74% Si and 72% polyethylene. The molar ratio of AI:Zr was 209:01.

Polymerization

A clean, dry 2 L autoclave was flushed with propylene and then charged with 0.25 mL of 25% TEAL and the appropriate amount of the diene (see Table). If hydrogen was used, it was added next by adding the appropriate amount of 1 % hydrogen in ethylene from a 527 cc feed bomb system charged to about 41 atm (about 600 psig) (see Table). Next the reactor was charged with 1000 mL of liquid propylene. The reactor was then brought to the desired temperature, and pressurized with ethylene to the desired pressure. The catalyst was injected into the reactor as a slurry in 3 mL of pentane using nitrogen pressure. The reaction was allowed to run with temperature controlled, and with pressure maintained by the ethylene feed regulator. Ethylene uptake was monitored by pressure drop in the feed bomb. After the desired reaction time, the monomers were quickly flashed from the reactor and the product was removed and soaked overnight in isopropyl alcohol/acetone mixture containing 0.5% BHT antioxidant. The product was then rinsed with isopropyl alcohol and dried in a vacuum oven at 50°C overnight.

Discussion of Examples

The EOD elastomers presented in the Table are commercially useful products with properties similar to commercial EPDMs produced with vanadium catalysts. In contrast, prior art teaches that metallocene/alumoxane catalysts produce EPDMs with properties deficient for commercial use. Specifically, Japanese Kokai 62-121 ,711 teaches the synthesis of ethylene-1-butene-diene terpolymers in toluene solution, requiring a high AI:Zr molar ratio of 500:1 for methylalumoxane: bis-(cyclopentadienyl)zirconium monochloride monohydride, and only achieves a catalyst activity of 30 Kg/g-Zr/h. Invention catalyst A has a molar ratio of AI:Zr of only 150 and catalyst B has a molar ratio of only 209, yet both catalysts achieve activities 10-70 times greater than the best run reported in the Kokai, and slurry polymerization avoids the expense of toluene purification and recycle. Furthermore, the examples reported in the Kokai are all high ethylene content materials (all greater than 84 mol% ethylene) whereas the examples in the Table for this invention are all in the more useful elastomeric range of 50-75 wt% ethylene. Another deficiency of the product taught by this Kokai is the rather low Mw. The reported intrinsic viscosities were all below 1.5 dL g (in decalin at 135°C), which is equivalent to about 70,000 weight average Mw and is too low for commercial elastomers. In contrast, the products in the Table show that this invention can provide elastomers with Mooney viscosities throughout the most useful of 10-100 range with suitable adjustment of hydrogen addition.

Kaminsky also teaches, in J. Poly. Sci. Vol. 23, pp. 2151-2164 (1985), the synthesis of EPDM in toluene solution. In this case, the catalyst is bis(cyclopentadienyl)zirconium dichloride/methylalumoxane. In the Kaminsky paper, the process also requires a very large AI:Zr ratio, 19,000:1 and 38,000:1 were reported. Even with such a large ratio, the highest activity reported was only 23 Kg/g-Zr/h, about 10 times less than that observed in the examples illustrating the invention of this patent. Although the products are in the interesting composition range of 50-82 wt% ethylene, another problem with the Kaminsky process is that they suffer from low Mw for all but the highest ethylene content products. Only those products with ethylene content greater than 70 wt% gave an estimated Mw above 100,000 and the highest Mws reported would only provide a Mooney viscosity of about 20-30 (ML_{1 +4}, 125°C).

Example 14 Catalyst Preparation

Catalyst C was prepared like Catalyst B.

Example 14 Polymerization

Catalyst C was used for a continuous polymerization in a 760 I.

(200 gallon) autorefrigerated CSTR reactor. The reactor was maintained at 45°C and 525 psig, while adding about 57 kg/hr (125 Ibs/hr) of propylene, about 2.3 kg/hr (5 Ibs/hr) of purified ENB, and maintaining pressure with ethylene added at about 22 - about 24 kg/hr (about 48-52 Ibs/hr). The gas phase ethylene concentration under these conditions was measured to be 49-51 mol% and the nominal residence time was 2.8 hours. The catalyst was added to the reactor as a 12 wt% slurry in mineral oil at a rate of 885 mg/min (106 mg/min, dry catalyst weight). The other feeds were 5 cc/min of 11 wt% TEAL in isopentane (scavenger) and hydrogen at about 0.5 g/hr (adjusted to maintain desired hydrogen level in reactor gas phase). Product granules of EPDM were removed from the reactor on level control via solenoid valve-controlled let-down to a section of tubing near the bottom of the reactor. From the tubing section, the product slurry was flashed into a cyclone where the granules were separated from the ethylene and propylene gases. The product was finished by melting and extrusion as pellets. A total of 175 lbs of EPDM was produced during 16 hrs of operation, for an average production rate of 11 lbs per hour, and an average catalyst productivity of 780 g-EPDM/g- cat, which is equivalent to 280 g-EPDM/g-cat/hr, or about 380 Kg- EPDM/g-Zr/hr.

The product was 73-78 wt% ethylene and 4-5 wt% ENB. Mw was controlled by addition of very small amounts of hydrogen to the reactor. With hydrogen in the vapor phase ranging from 600 to 100 mole ppm, products were obtained with Mooney viscosities ranging from 16 to 78 (ML-j +4, 125°C).

This example illustrates the use of the catalyst of this invention in a continuous polymerization process. The bis(indenyl)zirconium dichloride based catalyst produces high quality EPDM which meets the needs of the rubber industry.

As in the case of ethylene-α-olefin copolymers prepared with the bis(indenyl)-zirconium dichloride derived catalysts, as described in copending application USSN 08/166,758 filed December 14, 1993, the terpolymer products also show much broader compositional distributions than EPs derived from commercial vanadium catalysts in solution processes. Figure 6 shows the ethylene contents of fractions obtained by fractional precipitation with isopropanol from cyclohexane solutions of both the product from Example 14 and of a sample of commercial VISTALON® 7000 (available from Exxon Chemical Company). One advantage of the broad compositional distribution of the current invention is that products can be obtained from slurry polymerization with less agglomeration and fouling. The higher ethylene composition at the surface of the growing particles is semicrystalline and helps prevent agglomeration. A disadvantage is the higher average crystallinity of the product relative to conventionally solution-produced EPDM from vanadium catalysts. But the higher crystallinity is not a problem in many applications and may even be useful in certain applications requiring green strength.

Examples 15-20

Synthesis of Prepolymerized Catalyst A

(riNDI ZrCU/MAO/SiOy⁾

10 g of Davison 948 silica gel (dried at 800°C for 4 hours) was added slowly to 250 mL of toluene (from Ethyl Corporation, reported 1 M in aluminum) in a 500 mL flask equipped with a magnetic stir bar. The toluene was removed under vacuum, while heating at 80°C for 1 hour, to yield 18 g of white powder. To 2 g of the solid residue, magnetically stirred under nitrogen in 50 mL of dry pentane, was added 40 mg of bis(indenyl)zirconium dichloride (INDZ) dissolved in 3 mL of dry toluene. The slurry was then sirred at room temperature for 15 minutes.

With water bath cooling of the reaction flask, ethylene was added at 6 mmol/min for 40 minutes. The powder was then collected on a fritted glass funnel in the dry box, washed five times with 40 mL of dry pentane, and dried. Collected was 7.06 g of prepolymerized catalyst as a tan powder with several larger pieces of polymer from the flask walls. The catalyst was nominally 13 wt% methylalumoxane, 0.57 wt% zirconocene (0.13 wt% Zr), and 71 wt% polyethylene, Since catalyst A was prepolymerized to 346% of its original weight, this is labeled PP(346)INDZ in the Table.

Comparative Examples 21-22

Synthesis of Prepolymerized Catalysts B and C

(Me_?SirTHn₂ZrCI /MAO/SiO2. To 10 g of Davison 948 silica gel (dried at 800°C for 4 hours) in a

500 mL flask equipped with a magnetic stir bar, was added 200 mL of 1 M MAO in toluene (from Ethyl Corporation, reported 1 M in aluminum). The toluene was removed under vacuum, after heating at 80°C for 1 hour. To

2 g of the solid residue, magnetically stirred under nitrogen in 35 mL of dry pentane, was added 40 mg of dimethylsilanylene bis(tetra- hydroindenyl)zirconium dichloride (STHIZ) dissolved in 3 mL of dry toluene. The slurry was then stirred at room temperature for 15 minutes.

With water bath cooling of the reaction flask, ethylene was added at 6 mmol/min for 30 minutes. The powder was then collected on a fritted glass funnel in the dry box, washed three times with 30 mL of dry pentane, and dried. Collected was 6.17 g of prepolymerized catalyst B as a tan powder with several larger pieces of polymer from the flask walls. The catalyst was nominally 12 wt% methylalumoxane, 0.65 wt% zirconocene (0.13 wt% Zr), and 67 wt% polyethylene. Since catalyst B was prepolymerized to 302% of its original weight, this is labeled PP(302)STHIZ in the Table. Catalyst C was prepared in a similar manner, was prepolymerized to 330% of its original weight, and is reported as PP(330)STHIZ in the Table.

Comparative Example 23 Synthesis of Prepolymerized Catalyst D (Me₂SiriNP1 ZrCI₂/MAO/SiO₂i

To 8 g of Davison 948 silica gel (dried at 800°C for 4 hours) in a 500 mL flask equipped with a magnetic stir bar, was added 200 mL of 1 M MAO in toluene (from Ethyl Corporation, reported 1 M in aluminum). The toluene was removed under vacuum, after heating at 80°C for 1 hour, to yield 13 g of MAO/SiO₂. To 2 g of the solid residue, magnetically stirred under nitrogen in 35 mL of dry pentane, was added 40 mg of dimethylsilanylene-bis(indenyl)zirconium dichloride (SINDZ) dissolved in

3 mL of dry toluene. The slurry was then stirred at room temperature for 10 minutes.

With water bath cooling of the reaction flask, ethylene was added at 6 mmol/min for 40 minutes. The powder was then collected on a fritted glass funnel in the dry box, washed three times with 30 mL of dry pentane, and dried. Collected was 6.59 g of prepolymerized catalyst D as an orange powder with several larger pieces of polymer from the flask walls. The catalyst was nominally 12 wt% methylalumoxane, 0.61 wt% zirconocene (0.12 wt% Zr), and 69 wt% polyethylene. Since catalyst D was prepolymerized to 323% of its original weight, this is labeled PP(323)SINDZ in the Table.

Comparative Example 24

Synthesis of Prepolymerized Catalyst E fCH₂CH₂riND1₂ZrCI₂/MAO/SiO₂

To 2 g of Davison 948 silica gel (dried at 800°C for 4 hours) in a 200 mL flask equipped with a magnetic stir bar, was added 50 mL of 1 M MAO in toluene (from Ethyl Corporation, reported 1 M in aluminum). The toluene was removed under vacuum, after heating at 80°C for 1 hours, to yield a white solid MAO/SIO₂ residue containing about 1.25 g MAO. To this solid residue, magnetically stirred under nitrogen in 50 mL of dry pentane, was added 40 mg of ethylene-bis(indenyl)zirconium dichloride (EINDZ) dissolved in 3 mL of dry toluene. The slurry was then stirred at room temperature for 10 minutes.

With water bath cooling of the reaction flask, ethylene was added at 6 mmol/min for 35 minutes. The powder was then collected on a fritted glass funnel in the dry box, washed three times with 30 mL of dry pentane, and dried. Collected was 6.72 g of prepolymerized catalyst E as a light yellow powder with several larger pieces of polymer from the flask walls. The catalyst was nominally 19 wt% methylalumoxane, 0.60 wt.% zirconocene (0.13 wt% ZR), and 51 wt% polyethylene. Since catalyst E was prepolymerized to about 204% of its original' weight, this is labeled PP(204)EINDZ in the Table.

Examples 15-23, 25-32 Polymerization

A clean, dry one liter autoclave was flushed with propylene. The reactor was then charged with 500 mL of liquid propylene and a measured quantity of 25% TEAL in hexane was added by syringe. Hydrogen, if used, was added at this point. Thereafter, the liquid propylene was brought to the temperature for reaction, where the pressure in the autoclave was measured. The pressure in the reactor was then increased by a measured incremental pressure by addition of ethylene. To start the run, a measured quantity of the supported catalyst injected as a slurry in 3 ml of pentane was injected into the autoclave. Ethylene was supplied to maintain the initial total pressure in the autoclave. After reaction for the desired length of time, the monomers were flashed off, and the temperature was brought to 25°C. The polymer product was recovered from the reactor and dried in a vacuum oven at 50 °C overnight. Amounts and types of catalysts used and the results of the polymerizations are reported in the Table.

Discussion of Examples Examples 15 and 16 in the Table illustrate the excellent activity and product Mw obtained with the unbridged bis(indenyl)zirconium dichloride based PP(346)INDZ catalyst prepared according to this invention. Examples 17 to 18 illustrate the control of product Mw by use of hydrogen or TEAL, allowing for the production of EPC with commercially useful Mooney viscosities in the range of 10-100 (ML₁₊₄, 125°C).

For comparison, Examples 20 and 21 illustrate the performance of the dimethylsilanylene-bridged bis(tetrahydroindenyl)zirconium dichloride based catalyst described in my U.S. patent 4,871 ,705. This catalyst is in the class of zirconocene/alumoxane catalysts containing alkyl substituted (but not olefinic or aromatic substituted) cyclopentadienyl ligands which were found to be useful for making high Mw elastomers. In the absence of hydrogen, the catalyst of the present invention gives products with somewhat lower Mw than the catalyst in Examples 20 and 21 , but still high enough for commercial applications. In contrast to the catalysts of my U.S. Patent 4,871 ,705, the bridged analogues of the present invention do not provide high Mw products under the conditions of the slurry polymerization used for these examples. This is illustrated by the comparative examples 22 and 23 in the Table, which also shows the much lower activity obtained with the dimethylsilanyiene- and ethylene- bridged bis(indenyl)zirconium dichloride based catalysts. Table I Laboratory Propylene Slurry Polymerizations Using Prepolymerized Catalysts

25% Product ML

C a t a l y s t TEAL C2 T ΔT Yield Activity -ivity c₂ M_w 1+4,

Example Catalyst Zirc MAO mg mi psi C _c q/min Kα/α-Zr/h α/α-cat/h wt% 103 MWD 125°c

Invention Examples

15 A:PP(346)INDZ 0.57 13 100 0.2 150 45 1.2 40/12 1520 2000 73 217 2.52 94

16 A:PP(346)INDZ 0.57 13 100 0.2 200 35 0.8 44/23 870 1150 71 238 2.43 112

Examples of Molecular Weight Control:

17^a A:PP(346)INDZ 0.57 13 100 1.0 150 45 1.1 43/53 373 490 73 141 2.27 32

18^b A:PP(346)INDZ 0.57 13 100 0.2 150 45 0.5 49/26 860 1130 67 171 2.48 49

19^c A:PP(346)INDZ 0.57 13 100 0.2 150 45 0.2 36/50 250 430 60 108 2.65 10

Comparative Examples

20 B:PP(302)STHIZ 0.65 12 100 ^" 0.1 250 40 0.8 62/30 950 1230 51 285 2.22 147

21 C:PP(330)STHIZ 0.61 11 100 0.1 250 40 0.5 58/30 940 1150 53 302 2.22 98

22 D:PP(323)SINDZ 0.61 12 200 0.2 250 40 0.1 45/98 110 138 42 52 2.81 <10

23 E:PP(204)EINDZ 0.60 19 200 0.2 250 40 0.2 70/86 190 245 44 103 5.48 <10

Note: Used 500 mL propylene.

Used 1.0 ml of 25 wt% TEAL in hexane to reduce Mw Used 0.85 mmol of hydrogen to reduce Mw Used 1.7 mmol of hydrogen to reduce Mw

Run Zirconocene Catalyst Component

bis(indenyl)zirconium dichloride [INDZ]

B,C dimethylsilanylene bridged bis(tetrahydroindenyl)zirconium dichloride [STHIZ]

D dimethylsilanylene bridged bis(indenyl)zirconium dichloride [SINDZ]

ethylene bridged bis(indenyl)zirconium dichloride [EINDZ]

Definitions for Tables

Catalyst: PP(nnn)INDZ is a (INDZ)ZrCI containing catalyst prepolymerized with ethylene to nnn % of its nonprepolymerized weight.

Catalyst Zirc: wt % zirconocene in the supported or prepolymerized catalyst

MAO: wt % methylalumoxane in the supported or prepolymerized catalyst

mg: weight of catalyst used in the run

25% TEAL ml: quantity of triethylaluminum (25 wt% in hexane) used as a scavenger or for Mw control C2 psi: incremental pressure of ethylene, above the vapor pressure of propylene, used for the run

T °C: reaction temperature

ΔT °C: magnitude of the temperature exotherm observed upon injection of catalyst

Yield g/min: weight of polymer, after drying, recovered from the reaction/minutes of reaction

Activity Kg/g-Zr/h: Kg of polymer obtained per gram of zirconium per hour of reaction

Productivity g/g-cat/h: g of polymer obtained per gram of catalyst per hour of reaction

C₂ wt%: weight % ethylene in the polymer product as per ASTM D3900

M_w 10 3. weight average Mw of the product as determined from DRI (in thousands)

MWD: MWD as expressed by the ratio of the weight average to number average Mws

ML₁₊₄, 125°C: Mooney viscosity as per ASTM D1646 Example 24

Preparation of Prepolymerized Catalyst F

A clean, dry, glass catalyst preparation vessel of two gallon capacity was charged with 3 L of 9.5 wt% Sherex MAO in toluene. 200 g of Davison 948 silica gel (which had been dried at 800°C for 4 hours) was added, under nitrogen atmosphere, with good stirring by an anchor/helix combination stirrer. The reactor was heated to 50-60°C, subjected to about 635 mm (25 inches) of mercury vacuum, and sparged with nitrogen from the bottom to help remove the toluene. After five hours, the solid MAO/Siθ2 was a dry, free-flowing powder. The reactor was then cooled to 28°C and about 8 liters of dry isopentane was added. Next, 5.0 grams of bis(indenyl)zirconium dichloride slurried in 700 mL of toluene was added with good stirring over 10 minutes and the mixture was stirred for 15 minutes more. The reactor vent was blocked in and polymer grade ethylene was added from the bottom, with strong agitation, at a rate of about 7 g/min. The reactor pressure was maintained below about atm (15 psig) by cooling the reactor to maintain a temperature below 28°C during addition. The total ethylene addition time was about 1 hours. About 20 minutes further stirring, the slurry was allowed to settle and the supernatant liquid was decanted. The slurry was washed by adding 4 L of isopentane, stirring a few moments, letting the solids settle, and decanting. This was repeated twice more with 4 L of isopentane. The slurry was then removed from the reactor, and collected in a dry box on a filter. The solids were washed on the filter three times with 2 L of isopentane, dried by pulling nitrogen through the filter until no more liquids were obtained, and then dried under vacuum. A total of 815 grams of prepolymerized catalyst were obtained as a tan powder. This catalyst is identified as Catalyst F, and is nominally 0.61 wt% zirconocene (0.14 wt% Zr).

Example 24 Polymerization

Catalyst F was used for a continuous polymerization in a 200 gallon autorefrigerated CSTR reactor. The reactor was maintained at 35° C and about 34 atm to about 36 atm (510-530 psig), while adding about 52 kg/hr (115 Ibs/hr) of propylene and maintaining pressure with ethylene added at about 41-45 kg/hr (about 90-100 Ibs/hr). The gas phase ethylene concentration under these conditions was measured to be 63-65 mol% and the nominal residence time was 2 hours. The catalyst was added to the reactor as an 18 wt% slurry in mineral oil at a rate of 200 mg/min (37 mg/min, dry catalyst weight). The other feeds were 15 cc/min of 2 wt% TEAL in isopentane (scavenger) and hydrogen at about 0.5 g/hr (adjusted to maintain desired hydrogen level in reactor gas phase). Product granules of EP were removed from the reactor on level control via solenoid valve-controlled let-down to a section of tubing near the bottom of the reactor. From the tubing section, the product slurry was flashed into a cyclone where the granules were separated from the ethylene and propylene gases. The product was finished by melting and extrusion as pellets. A total of 608 lbs of EP was obtained during 55.5 hrs of operation, for an average production rate of 11 lbs per hour, and average catalyst productivity of 2250 g-EP/g-cat, which is equivalent to 1125 g- EP/g-cat/hr, or about 800 Kg-EP/g-Zr/hr.

The product was 70-72 wt% ethylene. Mw was controlled by addition of very small amounts of hydrogen to the reactor. With hydrogen in the vapor phase ranging from 500 to 250 mppm, products were obtained with Mooney viscosities ranging from 42 to 66 (ML ₊₄, 125°C).

This example illustrates the use of the catalyst of this invention in a continuous polymerization process. The bis(indenyl)zirconium dichloride based catalyst produces high quality EP which meets the needs of the rubber industry. Analysis of the EP produced by the bis(indenyl)zirconium dichloride derived catalyst has revealed that the product is significantly different from that produced by the dimethylsilanylene-bridged- bis(tetrahydroindenyl)zirconium dichloride derived catalysts described in our U.S. 4,871 ,705 and U.S. 5,001 ,205 patents. The reactivity for ethylene incorporation is much higher than that for propylene. A consequence of this high reactivity ratio is a broader compositioned distribution for the products of this invention than for those previously described. This is due to preferential reaction of ethylene in the particles which is faster than diffusion can maintain equilibrium. In the growing particles of EP there is a lower ethylene/propylene feed ratio at sites in larger particle sizes and at sites farther from the particle surface. Thus the incorporation of ethylene into the polymer is less at longer reaction times.

This can be seen in several results. Figures 1 and 2 show that under the same conditions of polymerization with Catalyst A, except for total reaction time, the yield is proportional to reaction time, but the average ethylene content of the product drops from about 89 wt% after five minutes to 64 wt% after 60 minutes (Examples 28-30). A second indication is shown in Figures 3 and 4, where the distribution of ethylene composition of the products after 20, 40 and 60 minutes (as determined by stepwise precipitation from cyclohexane solution with isopropanol) is plotted. For comparison, such broad distributions are not found in products from conventional soluble single-species vanadium catalysts (which typically show less than 1 % compositional variation), nor from the dimethylsilanylene-bhdged-bis(tetrahydroindenyl)zirconium dichloride derived catalysts of our previous patents. This is illustrated in Figure 5, which shows the compositional distribution of products with the same average ethylene content (59%) made from both Catalyst A (Example 31 ) and Catalyst C (Comparative Example 32).

One advantage of the broad compositional distribution of the current invention is that products can be obtained from slurry polymerization with less agglomeration and fouling. The higher ethylene composition at the surface of the growing particles is semicrystalline and helps prevent agglomeration. A disadvantage is the higher average crystallinity of the product relative to conventionally solution produced EP from vanadium catalysts, but the higher crystallinity is not a problem in many applications and may be useful in certain applications requiring green strength. Table II Additional Examples from Laboratory Slurry Polymerizations

While all test examples (for all Examples, 1-32 above) were performed using an alumoxane cocatalyst, the metaUocene catalyst, particularly the alkylated forms, should accomplish similar results when incorporated into an ionic catalyst system or when any other suitable activator is used. Such ionic activators include, for example, those now known in the art such as those described in EP A 277 003, EP A 277 004, and U.S. 5,153,157 which are incorporated by reference.

Such catalyst systems, either with cocatalysts or ionic activators, will also be functional when supported on an inert medium including those described in U.S. 5,240,894, 5,006,500, 4,808,561 and 5,124,418, all of which are incorporated by reference.

The scope of this invention is to be interpreted to include those modifications of the catalyst system.

Although the invention has been described with reference to its preferred embodiment, those of ordinary skill in the art may appreciate different modes for practice which do not depart from the scope and spirit of the invention as described above or claimed hereafter.

Claims

CLAIMS:

A process for producing an ethylene-α-olefin elastomer optionally containing a diene comprising: supplying an α-olefin monomer to a reactor vessel to provide a liquid monomer and diluent medium and optionally supplying a diene monomer to said reactor vessel; supplying to ethylene in an amount to maintain desired relative monomer ratios; adding to said diluent a metallocene-cocatalyst catalyst system wherein the metaUocene component of the catalyst is of the formula:

wherein "M" is titanium, zirconium or hafnium; R¹ and R² may be the same or different and are each independently an electron donating group, preferably of a C→. to C₂o linear, branched or cyclic alkyl group; each "X" is an anionic group, preferably a halogen, hydride, alkyl, aryl or hetero atom containing group or chelating group or the two X's form a divalent group, preferably an alkylene group, and "y" and "z" are integer numbers of 0, 1 , or 2; two R¹ or R² groups may be fused on the respective ligands reacting the mixture at e temperature and for a time sufficient to permit polymerization of said ethylene, alhpa olefin and optional diene monomers. 2. Process according to claim 1 in which the alpha olefin is propylene and/or 1-butene, the desired polymer is not soluble in the liquid medium, and an EPC elastomer results the process being performed preferably at 0-80°C.

Process according to claim 1 in which diene is present, the total pressure in the reaction vessel is in excess of the the combined vapour peressure of the alpha olefin and diene monomers; the polymerisation is maintained at from -10°C to +100°C to produce an EOD elastomer having either a weight average Mw greater than 100 000 preferably greater than 110 000 or a Mooney viscosity (ML_{1 +}4 at 125°C) greater than 5 preferably greater than 10.

Process according to claim 3 in which the alpha olefin is 1-butene and /or the diene is one or more of the following 1 ,4 hexadiene; 5- ethylidene-2-norbomene; 5-methylene-2-norbomene;5-vinylidene- 2-norbomene; or dicyclopentadiene.

5. The process according to any of the preceding claims, wherein said metaUocene component of the catalyst is a zirconocene preferably with y and z being zero and preferably bis(indenyl) zircomium dihalide or dialkyl.

Process according to any of the preceding claims in which the metaUocene component is of the formula:

wherein "M" is titanium, zirconium or hafnium; R¹ and R² are each independently is a C-_j to C20 linear, branched or cyclic alkyl group; each "X" is a halogen, hydride, alkyl, aryl or chelating group, and "y" and "z" are integer numbers of 0, 1 , or 2.

7. The process according to any of the preceding claims in which the cocatalyst is a Lewis base and preferably an alumoxane.

8. The process according to any of the preceding claimsw wherein said catalyst system is partially or wholly present on a catalyst support material, optionally prepolymerised to a degree of at least 50 percent based on the total weight of the catalyst and support material.

9. The process of claim 8, wherein said catalyst support material is a silica gel preferably treated with an alumoxane especially methylalumoxane.

10. The process according to any of the preceding claims , wherein there exists in the reactor vessel a mole ratio of aluminum to zirconium in the range of 10 to 5,000.

11. The process according to any of the preceding claims , wherein the polymerization diluent is subjected to an amount of ethylene to maintain a total pressure in the reaction vessel in the range of about 0.7 atm to about 70 atm in excess of the combined vapor pressure of the α-olefin and optional diene monomers.

12. The process according to any of the preceding claims, wherein the α-olefin monomer is propylene or 1-butene or a mixture thereof and/or the optional diene monomer is one or more of the following, 1 ,4 hexadiene; 5-ethylidene-2-norbomene; 5-methylene-2- norbornene; 5-vinylidene-2-norbomene; or dicyclopentadiene.

13. A prepolymerized catalyst for producing elastomers in liquid olefin slurry polymerization, comprising: an inorganic support which has been dried and treated with an alumoxane followed by: addition of metaUocene of structure:

wherein each R¹ and R² are independently a C1-C20 linear, branched or cyclic alkyl group; X is a an alkyl, aryl, halide, hydride, or oxygen bridge of a metaUocene dimer; and "y" and "z" are independently numbers 0, 1 or 2; followed by a prepolymerization treatment with ethylene or an α-olefin to increase the weight of the catalyst by at least 50 wt%.

14. A prepolymerized catalyst according to claims 13, wherein the inorganic support is a silica gel dried at 100 to 1000°C.

15. The prepolymerized catalyst according to claims 13 or 14 in which the support is pretreated with methylalumoxane and the ratio of alumoxane with the silica gel is in the range of 1 :1 to 1:10 on a weight basis.

16. The prepolymerized catalyst accoprding to any of claims 13 to 15 wherein the mole ratio of aluminum to metaUocene transition metal is in the range of 1 to 500 and/or the prepolymerization weight gain is in the range of 50 to 500 wt%. The prepolymerized catalyst according to any of claims 13 to 17 wherein the prepolymerized catalyst is washed with a hydrocarbon to remove soluble materials following prepolymerization.