Method for the preparation of metallocene catalysts

ES 2 248 481 T3

DESCRIPTION

Method for the preparation of metallocene catalysts.

Many catalyst systems for use in the polymerization of ethylenically unsaturated monomers are based on metallocenes. Metallocenes can generally be characterized as coordination compounds that incorporate one or more cyclopentadienyl (Cp) groups (which may be substituted or unsubstituted) coordinated with transition metal through π bonding. When certain metallocene compounds are combined with an activator or cocatalyst such as methylaluminoxane (MAO) and optionally an alkylating / scavenging agent such as trialkylaluminum compounds, highly active polymerization catalysts are formed. Various types of metallocenes are known in the art. As described, for example, in US Patent No. 5,324,800 to Wlberon et al, they include monocyclic (one single cyclopentadienyl group), bicyclic (two cyclopentadienyl groups, as shown in formula 1), or tricyclic groups. (Three cyclopentadienyl groups coordinated with a central transition metal. Homogeneous or unsupported metallocene catalysts are known for their high catalytic activity especially in olefin polymerizations. Under polymerization conditions where the polymer is formed as solid particles, these homogeneous (soluble) catalysts form polymer deposits on the reactor walls and stirrers. These deposits must be removed frequently as they impede efficient heat exchange, necessary to cool the reactor contents, and cause excessive wear on moving parts. In addition, solid particles formed by these homogeneous catalysts have undesirable particle morphologies with low mass densities that make them difficult to circulate in the reactor, limiting performance and are difficult to convey outside the reactor. In order to overcome these difficulties, various supported metallocene compounds have been proposed. As described in Welborn, et al, typical supports include inorganic oxides such as silica, alumina, or polymeric materials such as polyethylene.

Metallocene compounds, supported or unsupported, can be characterized in terms of stereoregular catalysts that result in the polymerization of alpha olefins, such as propylene, to produce crystalline stereoregular polymers, the most common of these being isotactic polypropylene and syndiotactic polypropylene. In general, stereospecific metallocene catalysts possess at least one chiral center and the ligand structure (usually based on cyclopentadienyl) are conformationally restricted. Due to the nature of Cp-type ligands it is common for at least one Cp ligand to be appropriately substituted to impart some measure of stereorigidity. These stereospecific metallocenes can include unbridged bicyclic compounds of bicyclic coordination compounds of the general formula:

(Cp)₂MeQn (1) which are characterized by isospecific metallocenes as described below and dicyclopentadienyl compounds of the general formula:

CpCp'MeQn (2) characterized by the syndiospecific metallocenes described below. In the above formulas, Me denotes a transition metal element and Cp and Cp 'denote a cyclopentadienyl group that may be substituted unsubstituted, Cp' being different from Cp, Q is an alkyl or other hydrocarbyl or a halogen group and n is a number in the range 1-3. In these cases the stereorigidity can be provided through substituent groups that result in steric hindrance between the two cyclopentadienyl moieties, as described, for example, in US Patent No. 5,243,002 to Razavi. Alternatively, the cyclopentadienyl groups are in a conformationally restricted relationship provided by a bridged structure between the metallocene rings (not shown in formulas (1) and (2) set forth above). It is sometimes advantageous to use metallocene compounds where the two cyclopentadienyl moieties (the same or different) are covalently linked by a so-called bridging group such as a dimethylsilylene group. The bridging group limits the spin of the two cyclopentadienyl moieties and in many cases improves catalytic performance. Metallocenes containing such a bridging group are often referred to as stereorigids. While bridged metallocenes normally incorporate two cyclopentadienyl groups (or substituted cyclopentadienyl groups), bridged metallocenes that incorporate a single cyclopentadienyl group that is bridged to an aromatic heteroatom group (both being coordinated with a transition metal) are also known in the art. . For example, US Patent No. 5,026,798 to Canich describes bridged cyclopentadienyl-anilino dimethylsilyl or other heteroatom ligand structure with coordination being provided to the transition metal through the nitrogen atom of the anilino group as well as the cyclopentadienyl group. Other common bridging groups include CRiR₂, CR₁R₂CR₂R₃, SiRiR₂ and SiRiR₂SiRiR₂ where the substituents R₁ can be chosen independently from H or a hydrocarbyl radical C₁ -C₂₀. Alternate bridging groups can also contain nitrogen, phosphorus, bromine, or aluminum.

As previously indicated isospecific and syndiospecific metallocene catalysts are useful in the stereospecific propagation polymerization of monomers. Stereospecific structural relationships of syndiotacticity and isotacticity can be implicated in the formation of stereoregular polymers of various monomers. Stereospecific propagation can be applied in the polymerization of ethylenically unsaturated monomers such as alpha olefins C₃ to C₂₀ which can be linear, branched or cyclic 1-dienes, such as 1,3-butadiene, com2

ES 2 248 481 T3 substituted vinyl positions such as vinyl aromatics, for example styrene, vinyl chloride, vinyl ethers such as alkyl vinyl ethers, for example isobutyl vinyl ether, or even aryl vinyl ethers. Stereospecific polymer propagation is probably of greater significance in the production of polypropylene of isotactic or syndiotactic structure.

The isotactic polypropylene structure can be described as one having the methyl groups attached to the tertiary carbon atoms of successive monomer units that fall on the same side of a hypothetical plane through the main chain of the polymer, for example, the groups methyl are all above or below the plane. Using the Fischer projection formula the stereochemical sequence of isotactic polypropylene can be described as follows:

<img file="ES2248481T3_D0001.tif" />

In formula 3 each vertical segment indicates a methyl group on the same side of the polymeric backbone. In the case of isotactic polypropylene most of the inserted propylene units have the same relative configuration in relation to their neighboring propylene unit. Another way to describe the structure is through the use of NMR. The Bovey NMR nomenclature for an isotactic sequence as shown above is ... mmmm ... each "m" representing a "meso" diad in which there is a mirror plane of symmetry between two adjacent monomer units, or successive pairs of methyl groups in the same plane mentioned in the polymer chain. As is known in the art, any deviation or inversion in the chain structure lowers the degree of isotacticity and subsequently the crystallinity of the polymer.

In contrast to the isotactic structure, syndiotactic propylene polymers are those in which the methyl groups attached to the tertiary carbon atoms of successive monomer units in the chain meet on alternate sides of the plane of the polymer. In the case of syndiotactic polypropylene, most of the inserted propylene units have the opposite relative configuration with respect to their neighboring monomeric unit. Syndiotactic polypropylene using Fisher's projection formula can be indicated by racemic dyads showing syndiotactic rrr as follows:

<img file="ES2248481T3_D0002.tif" />

The Bovery NMR nomenclature for a syndiotactic sequence as shown above is ... rrrr ... with each "r" representing a "racemic" diad where successive pairs of methyl groups are on opposite sides of the plane of the polymer chain . Similarly, any deviation or inversion in the chain structure lowers the degree of syndiotacticity and subsequently the crystallinity of the polymer. The vertical segments in the preceding example indicate methyl groups in the case of syndiotactic or isotactic polypropylene. Other end groups, for example ethyl, in the case of polybutene, chloride, in the case of polyvinyl chloride, or phenyl groups in the case of polystyrene, etc. it can also be described in this way as isotactic or syndiotactic.

Polypropylene resins can also be obtained in which the propylene units are inserted in a more or less random configuration. These materials are referred to as atactic and as such these polymers lack any sign of crystallinity as determined by common X-ray diffraction (XRD) methods, heat, or fusion by Differential Scanning Calorimetry, or density. These atactic polymers also tend to be more soluble in hydrocarbon solvents than polymers which possess some crystallinity. Syndiotactic polymers with sufficiently high levels of syndiotacticity and isotactic polymers with sufficiently high levels of isotacticity are semi-crystalline. Similarly this can be established with any technique known to those skilled in the art such as XRD, DSC or density measurements. It is common for polymers to be obtained as a mixture of highly stereoregular polymer and atactic polymer. In these cases it is often useful to carry out the solubility test, such as mass fraction soluble in boiling xylene or heptane for example to establish the amount of atactic polymer present. In many cases atactic polymers are more soluble than stereoregular counterparts and therefore the hydrocarbon soluble mass fraction provides an indirect indication of the amount of atactic polymer present. While several other stereoregular or quasi-stereoregular polymer structures are known, such as hemiisotactic or stereoisoblock structures, the major stereoregular polymer configurations of interest are predominantly isotactic and predominantly syndiotactic polymers.

Catalysts that produce isotactic polyolefins are described in US Patent Nos. 4,794,096 and 4,975,403. These patents describe chiral stereorigid metallocene catalysts that polymerize olefins to form isotactic polymers and are especially useful in the polymerization of highly isotactic polypropylene. As described, for example, in the aforementioned US Patent No. 4,794,096, stereorigidity in a metallocene ligand is imparted via a structural bridge that spans between cyclopentadienyl groups.

ES 2 248 481 T3

Specifically described in this patent are stereoregular hafnium metallocenes that can be characterized by the following formula:

R ”(C₅(R ') 4bHfQp

In the formula (5) (C₅(R ')₄) is a cyclopentadienyl or substituted cyclopentadienyl group, R 'is independently hydrogen or a hydrocarbyl radical having 1-20 carbon atoms, and R "is a structural bridge spanning between the cyclopentadienyl rings. Q is a halogen or a hydrocarbon radical, such as an alkyl, aryl, alkenyl, alkylaryl or arylalkyl with 1-20 carbon atoms and p is 2.

Catalysts that produce syndiotactic polypropylene or other syndiotactic polyolefins and methods for the preparation of these catalysts are described in US Pat. 4,892,851 to Ewen et al and 5,807,800 to Shamshoum et al. These catalysts are also bridged stereorigid metallocene catalysts, but, in this case, the catalysts have a structural bridge that spans between chemically dissimilar cyclopentadienyl groups and can be characterized by the formula:

R ”(CpR_n) (CPR '_m) MeQ (6)

In formula (6) Cp represents a cyclopentadienyl or substituted cyclopentadienyl ring, and R and R 'represent hydrocarbyl radicals having 1-20 carbon atoms. R "is a structural bridge between the rings that impart stereorigidity to the catalyst. Me represents a transition metal, and Q is a hydrocarbyl or halogen radical. R '_mis chosen so that (CpR '_m) is a sterically substituted cyclopentadienyl ring other than (CpR_n). In formula (6) n varies between 0-4 (0 does not designate hydrocarbyl groups, that is, no additional substitution other than the bridging substituent on the cyclopentadienyl ring), m varies from 1-4, and k is 0-3 . Sterically different cyclopentadienyl rings produce a predominantly syndiotactic polymer rather than an isotactic polymer.

Like their isospecific counterparts, syndiospecific metallocenes are used in combination with cocatalysts. A particularly useful class of cocatalysts is based on organoaluminum compounds which can take the form of an alumoxane, such as methylalumoxane or a modified alkylaluminoxane compound. Alumoxane (also referred to as an aluminoxane) is an ilogomeric or polymeric aluminum oxy compound containing alternating aluminum chains and oxygen atoms, whereby aluminum carries a substituent, preferably an alkyl group. The exact structure of aluminoxane is not known, but it is generally considered to be represented by the following general formula - (Al (R) -O-)_m for a cyclic alumoxane, and R₂Al-O- (Al- (R) -O)_m-AlR₂for a linear compound, where R independently of each occurrence is a hydrocarbyl QC₁₀, preferably alkyl, or halide and m is an integer ranging from 1 to about 50, preferably at least about 4. Alumoxanes are typically the reaction products of water and an aluminum alkyl, which in addition to a alkyl group may contain halide or alkoxide groups. Reaction of several different alkyl aluminum compounds, such as, for example, trimethylaluminum and tri-isobutyl aluminum, with water provides so-called modified or mixed alumoxanes. Preferred alumoxanes are methylalumoxane and methylalumoxane modified with minor amounts of other higher alkyl groups such as isobutyl. Alumoxanes generally contain minor to substantial amounts of the starting alkyl aluminum compound (s). Other cocatalysts include trialkylaluminum, such as triethylaluminum (TEAL) or triisobutylaluminum (TIBAL), or mixtures thereof. Methylalumoxane and triethylaluminum (TEAL) are specifically described in the '851 patent.

Metallocene ligands bridged with a dissimilar cyclopentadiene groups can result from the reaction of 6,6-dimethyl fulvene with a substituted cyclopentadiene such as fluorene or substituted fluorene derivative to produce a ligand characterized by an isopropylidene bridging structure. Preferably this ligand structure is characterized as having bilateral symmetry as indicated by the isopropylidene (cyclopentadienyl fluorenyl) structure as shown in Formula 9 of the aforementioned Patent No. 5,807,800. As described in the Shamshoum et al '800 patent, the bilateral symmetry of the ligand structure is indicated by the balanced orientation around the dashed line representing a plane of symmetry that extends generally through the bridging structure and the transition metal atom.

As described in the aforementioned Welborn Patent No. 5,324,800, supported catalysts can be prepared by converting a soluble metallocene to a heterogeneous catalyst by depositing the metallocene on an appropriate catalyst support. Other supported catalysts are described in US Patent Nos. 4,701,432 and 4,808,561, both to Welborn, US Patent No. 5,308,811 to Suga et al., Patent No. 5,444,134 to Matsumoto, Patent No. 5,719,241 to Razavi, and the aforementioned patent No. 5,807 .800 of Shamshoum et al.

As described in the Welborn '432 patent, the support can be any support such as talc, an inorganic oxide, or a resinous support material such as a polyolefin. Specific inorganic oxides include silica and alumina, used alone or in combination with other inorganic oxides such as magnesium, titanium, zirconium, and the like. Non-metallocene transition metal compounds, such as titanium tetrachloride, are also incorporated into the supported catalyst component. The inorganic oxides used as support are characterized by having an average particle size ranging between 30-600 microns, preferably 30-100 microns, a surface area of ​​50-1,000 square meters per gram, preferably 100-400 square meters per gram, a pore volume

ES 2 248 481 T3 of 0.5-3.5 cc / g, preferably about 0.5-2 cc / g. In general, particle size, surface area, pore volume, and number of surface hydroxyl groups are not considered critical to the Welborn procedure. Silica is often the support material of choice. A catalyst is specifically described in Welborn in which bis (cyclopentadienyl) zirconium dichloride (non-bridged metallocene) is supported on a high surface area silica dehydrated in dry nitrogen at 600 ° C and characterized by Davison 952. The Welborn '561 patent describes a heterogeneous catalyst that is formed by the reaction of a metallocene and an alumoxane in combination with the support material. The support in Welborn '561 is similarly described as the support in the Welborn' 432 patent. Several other catalyst systems involving supported metallocene catalysts are described in US Patent Nos. 5,308,811 to Suga et al and 5,444,134 to Matsumoto. In both patents the supports are characterized as various high surface area inorganic oxides or clay materials. In the Suga et al patent, support materials are characterized as clay minerals, layered ion exchange compounds, diatomaceous earth, silicates or zeolites. As explained in Suga, high surface area support materials must have pore volumes with radii of at least 20 Angstroms. Clay and clay minerals such as montmorillonite are specifically described and preferred in Suga. The catalyst components in Suga are prepared by mixing the support material, the metallocene and an organoaluminum compound such as triethylaluminum, trimethylaluminum, various alkylaluminum chlorides, alkoxides or hydrides or an alumoxane such as methylalumoxane, ethylalumoxane or the like. The three components can be mixed together in any order, or they can be contacted simultaneously. The Matsumoto patent similarly describes a supported catalyst wherein the support may be provided by inorganic oxide vehicles such as SiO₂, To the₂O, MgO, ZrO₂, Uncle₂, Faith₂OR₃, B₂OR₂, CaO, ZnO, BaO, ThO₂ and mixtures thereof, such as silica, alumina, zeolite, ferrite, and glass fibers. Other vehicles include MgCl₂, Mg (O-Et)₂, and polymers such as polystyrene, polyethylene, polypropylene, substituted polystyrene and polyacrylate, starches, and carbon. The vehicle has a surface area of ​​1-1000 m²/ g, preferably 50-500 m²/ g, 0.1-5 cm pore volume³/ g, preferably 0.3-3 cm³/ g, and a particle size of 20-100 microns.

Of the various inorganic oxides used as support, silica, in one form or another, is widely described as a support material for metallocene catalysts. The aforementioned patent No. 5,719,241 to Razavi, while describing a wide range of inorganic oxides and resinous support materials, identifies the preferred support as a silica having a surface area between about 200 and 600 µm.²/ g and a pore volume between 0.5 and 3 ml / g. A support identified as Grace '952 having a surface area of ​​322 m is specifically described.²/ g. In preparing supported metallocenes as described by Razavi, silica is dried under vacuum for three hours to remove water and then suspended in toluene where it is reacted with methylalumoxane for three hours at reflux temperature. The silica is washed three times with toluene to remove unreacted alumoxane after which a solution of two metallocenes is added and the mixture is stirred for one hour. The supernatant liquid is then removed and the solid support containing the metallocene is washed with toluene and then dried under vacuum. Silica characterized as Davison D-948 or Davison D-952 also appears as a conventional metallocene support. For example, US Patent No. 5-466,649 to Jejelowo describes the use of dehydrated Davison D-948 silica as a support for various unbridged metallocenes used in connection with supported cocatalysts. Welch et al. Patent No. 5,498,581 describes silica for use as a support for bridged or unbridged metallocenes wherein the silica is treated with carbon monoxide, water, and hydroxyl groups. Silica, Davison D-948, which has a mean particle size of 50 microns, is specifically described. Other silica-based supports are described in US Patent Nos. 5,281,679 to Jejelowo, 5,238,892 to Chang, and 5,399,636 to Alt. The Chang and Jejelowo patents describe the use of a silica support identified as Davison D948, which is characterized as an amorphous silica gel containing about 9.7% by weight of water. As described in the Chang and Jejelowo patents, alumoxane is formed directly on the surface of silica gel by direct reaction of an aluminum alkyl with silica gel which is dehydrated so as to ensure the conversion of the amount of aluminum alkyl to a alumoxane having a high degree of oligomerization. The gel impregnated with water is characterized as having a surface range of 10-700 m²/ g, a pore volume of about 0.5-3 cc / g, and an absorbed water content of about 10-50% by weight in the case of the Jejelowo patent and about 6-20% in weight in the case of the Chang patent. The mean particle size for silica is described in Chang as 0.3-100 microns and in Jejelowo as around 10-100 microns. After the alumoxane silica gel component has been formed, the metallocene can be added to the wet suspension.

Other supported catalyst systems are described in European Patent No. 96111719.9 (EPO 819706A1) by Shamshoum et al. Here a silica support as described above is pretreated with an alumoxane, such as methylalumoxane followed by the addition of a syndiospecific metallocene on the MAO-treated silica. The supported metallocene is used in connection with an organo-aluminum cocatalyst such as a monoalkyl or dialkyl aluminum halides as previously described, or trialkylaluminum such as trimethylaluminum, triethylaluminum or tri-isobutyl aluminum (TIBAL). In the supported catalyst described in EP0819706, the silica support is a small pore size, high surface area silica that is first dried, suspended in an apolar solvent, and then contacted with methylalumoxane in a solvent. The metallocene was then dissolved in an apolar solvent, particularly the same one that was used as the solvent for the alumoxane. The metallocene supported on the alumoxane-treated silica is then recovered from the solvent, dried, and then incorporated into the carrier liquid such as mineral oil. Shamshoum's EPA application also describes a pre-polymerization step that can be used to decrease the aging time of the catalyst in aluminum trialkyl or other aluminum cocatalyst.

Still other supported catalyst systems incorporating bridged metallocene catalysts are described in US Patent No. 5,968,864, Shamshoum et al. Here the efficiency of the catalyst is improved by a preparation process wherein a support such as silica is treated with alumoxane in an apolar solvent such

ES 2 248 481 T3 as toluene and contacted with a solution of a metallocene at reduced temperature, preferably in the range of 0 ° C to -20 ° C. The resulting solid is then washed with hexane and dried overnight at room temperature.

Summary of the invention

In accordance with the present invention there is provided a process for the preparation of a silica supported metallocene catalyst wherein the metallocene and cocatalyst components can be adjusted relative to the particulate silica support to provide a supported catalyst system that can be isolated and stored in a mineral oil suspension for extended periods of time and then used in the production of stereoregular polymers while alleviate or eliminate problems associated with reactor fouling and undesirable polymer fines. The resulting supported catalyst provides good activity that can be maintained when the process is used to produce an isospecific or syndiospecific supported catalyst.

In the practice of the invention there is provided a particulate catalyst support material comprising silica particles impregnated with an alumoxane cocatalyst with at least half of the cocatalyst disposed within the internal pore volume of the silica. The support material is contacted with a dispersion of a metallocene catalyst in an aromatic hydrocarbon solvent. The metallocene solvent dispersion and the support containing alumoxane are mixed at a temperature of about 10 ° C or less for a period sufficient to facilitate the metallocene to reactively support and permeate into the alumoxane-impregnated silica particles. . After the mixing time, which can typically range from a few minutes to a few hours, the supported catalyst is recovered from the aromatic solvent and then optionally washed with an aromatic hydrocarbon and then sequentially with a paraffinic hydrocarbon solvent in order to remove substantial amounts of aromatic solvent of the supported catalyst. These washing procedures are carried out at a low temperature of around 10 ° C or less. The washed catalyst is then dispersed in a viscous mineral oil having a viscosity that is substantially higher than the viscosity of the paraffinic hydrocarbon solvent. Typically mineral oil is a viscosity at 40 ° C of at least 65 centistokes (units) as measured by ASTM D 445. This can be contrasted with the viscosity of the paraffinic hydrocarbon solvent which will usually not be greater than 1 centipoise under the reduced temperature conditions. . No steps should be taken to dry the washed catalyst, and typically the washed catalyst at the time of dispersion will contain a substantial residual amount of the paraffinic hydrocarbon solvent. Preferably after recovering the supported catalyst from the aromatic solvent and before washing with the paraffinic hydrocarbon solvent, a further washing step with an aromatic solvent is carried out to separate the unsupported metallocene from the supported catalyst.

In another aspect of the invention there is provided a particulate catalyst support comprising spheroidal silica particles having a mean particle size within the range of 10-100 microns and a mean effective pore diameter within the range of 200-400 Angstroms. . Typically the silica will be dried at an elevated temperature for a period of time to moderately dehydrate the silica. Often a mild heat treatment such as 100 to 160 ° C is sufficient, although higher temperatures can be used. The silica support is then contacted with an alumoxane cocatalyst in an aromatic carrier liquid. The alumoxane support, carrier liquid and cocatalyst mixture is heated to an elevated temperature for a period of time to fix the alumoxane on the silica support with at least half of the alumoxane disposed internally within the silica support. For example the mixture can be heated under reflux conditions of about 100 ° C or more for a period between one hour and several hours. The mixture is then cooled and the support containing alumoxane is separated from the carrier liquid. The support material containing alumoxane is then washed with an aromatic hydrocarbon solvent in order to remove excess unsupported or free alumoxane (or alkyl aluminum residues) so that substantially all of the alumoxane is bound to the support. The support material containing alumoxane is then cooled to a reduced temperature of about 10 ° C or less, and a dispersion of metallocene in an aromatic solvent is added with mixing as described above at a temperature of about 10 ° C or less to allow the metallocene to become reactively supported on and impregnated within the alumoxane impregnated silica particles. The supported catalyst is then recovered, washed with a low viscosity paraffinic hydrocarbon solvent at a reduced temperature of about 10 ° C or less as described above and then dispersed in a viscous mineral oil. Alternatively, the catalyst is washed with mineral oil and a non-paraffinic hydrocarbon solvent is used. Polyolefin catalysts prepared in this way have superior performance qualities such as superior activity.

Brief description of the drawings

Figure 1 is a front elevational view showing an idealized representation of a generally spherical catalyst particle that can be used to carry out the present invention.

Figure 2 is a cross-sectional elevation view of the catalyst particle of Figure 1.

Figure 3 is a front elevational view of an idealized representation of a modified form of a catalyst particle corresponding to the catalyst particle of Figures 1 and 2.

Figures 4, 5 and 6 are photographs of catalyst support particles that generally conform to the support particles ideally set forth in Figures 1, 2 and 3.

ES 2 248 481 T3

Figure 7 is a graphical representation showing the relationship between catalytic activity and time of catalysts.

Detailed description of the invention

The present invention involves processes for the preparation of supported metallocenes that are generally carried out under low temperature conditions for the deposition of metallocene catalysts on the support containing alumoxane and wherein the supported metallocene, once obtained, is dispersed directly in a mineral oil vehicle. These supported catalysts are suitable for use in the polymerization of ethylene, propylene, and higher olefins, including the homopolymerization of these olefins or their copolymerization, such as in the preparation of ethylene / propylene copolymers. The process is in contrast to the prior art process, as described in the aforementioned Welborn patents where the metallocene and alumoxane are generally added at room temperature conditions, and regardless of the order of addition used, the final catalyst particles they are dried for extended periods of time in order to remove volatile materials. Similarly, in procedures such as described in the aforementioned Razavi '241 patent where alumoxane is added first and mixed with the support at reflux temperature, the final supported catalyst is dried under vacuum. In contrast to the prior art process, the present invention proceeds, once the alumoxane is fixed on the silica support, to carry out the metallocene support reaction under low temperature conditions, typically within the range of about -20 ° -10 ° C followed by washing the catalyst with hydrocarbons and directly supplying the washed catalyst in a viscous mineral oil without involving a drying step. The washes and dispersions of the catalysts in the mineral oil are carried out under sub-ambient temperature conditions.

The supported catalyst produced in accordance with the present invention provides several important characteristics. The metallocene and alumoxane loading on the support material can be controlled to desired levels. This is particularly significant in the case of the preferred silica supports for use in the present invention where it is desired to control the alumoxane / silica ratios to levels that can vary depending on the nature of the metallocene component. Particularly, in the case of stereospecific metallocenes, the alumoxane / silica ratio is controlled to lead to desired ratios for effective characteristics of the final catalyst in terms of metallocene activation, polymer fines, fouling during the polymerization process and imperfections sometimes referred to. as "fish eyes" in finished products produced from olefinic polymer. Furthermore, for metallocenes and support materials other than the stereospecific metallocenes and preferred silica supports, the invention still provides a process wherein charging of the metallocene and an alumoxane-containing support can be carried out at relatively low temperatures and with direct dispersion of the catalyst. supported on a viscous mineral oil dispersion without involving a drying step as is common practice in prior art techniques. The resulting catalyst systems have generally higher activities with very little activity decay, that is, long "shelf life" during storage prior to use especially when the catalyst is stored cold.

The catalysts are further subjected to activity enhancement by aging with an alkylaluminum compound, such as triisobutylaluminum (TIBAL) in accordance with an aging procedure as described in US Patent No. 09 / 086,080, filed May 28, 1998, by Edwar Shamshoum et al, entitled "Procedure for the syndiotactic propagation of Olefins". In summary the improvement of catalyst activity can be carried out by aging the supported metallocene in an organoaluminum compound, specifically TIBAL, in mineral oil overnight (about 12 hours) or for additional periods, for example for one or two days, of in accordance with the following procedure. A specific aging procedure involves contacting equal parts of the supported metallocene and equal parts of the TIBAL in a mineral oil suspension and allowing them to stand at room temperature, 25 ° C for an overnight period (about 12 hours) before polymerization. A typical master batch of the syndiospecific catalyst or isospecific catalyst can be prepared from a 180 mg suspension. of the supported metallocene (the metallocene and the support), 8.3 ml of mineral oil, and 180 mg of TIBAL in a concentration of 25% by weight in hexane. After the overnight aging process, a 1.0 ml aliquot of the master suspension is used for each propylene polymerization. For further description of the aging process, reference is made to the aforementioned patent Serial No. 09 / 086,080, the entire description of which is incorporated herein by reference.

The particulate silica support used in the present invention comprises generally spheroidal silica particles having a mean diameter within the range of 20-60 microns, preferably 20-30 microns, and pore sizes that accommodate the internal support of the alumoxane and metallocene. The preferred form of silica support is characterized by generally spheroidal silica particles having generally axial depressions, sometimes fully extended through the particle, to provide a toroidal configuration to the particle. A silica support of this nature is available from Fuji Silysia Chemical Company, Ltd., under the designation P-10. The P-10 silica support has a mean diameter of about 22 to 25 microns and a pore volume of 1.4 millimeters per gram. The metallocene catalyst and alumoxane cocatalyst are mainly supported within the pore surface area of ​​the silica, in contrast to the external surface area, with the amount of externally supported metallocene of the silica particle comprising a smaller fraction, usually not greater than 10% by weight of the total metallocene found on the silica support. In other words, a larger fraction of more than 50% and preferably at least 90% by weight of the metallocene is contained within the internal pore volume of the silica support. An improved polymer is observed characterized

ES 2 248 481 T3 in terms of reduced gel defects for catalysts supported on relatively high surface areas, small particle size spheroidal silica particles. Although the petitioner's invention is not limited by theory, it is postulated that these spheroidal silica particles used in the present invention fracture highly during the polymerization process. Not only does the breakdown of the spheroidal silica particles continually expose more transition metal sites to the monomer insertion mechanism during the polymerization process, it ultimately reduces the silica particles to a size such that it does not result in significant numbers of gel defects. Thus, toroidal silica particles, while initially having a mean particle size of around 20-21 microns, possibly increasing to 24 microns after the alumoxane loading reaction, are considered to eventually fracture during the process of polymerization to a size of about five microns or less, usually about three microns or less, with a corresponding highly significant reduction in gel blemishes. Silica particles of a spheroidal configuration that can be used to carry out the present invention are shown schematically and in highly idealized form in Figures 1, 2 and 3.

As shown in Figure 1 a generally spherical silica particle 12 is characterized by a central hole 14 such that the silica particle is of a spherical annular configuration. When viewed from the front elevation of Figure 1 the silica particle is generally depicted in the likeness of a donut and is therefore referred to as having a "toroidal type" configuration. As shown in Figure 2, when viewed from an elevation the central hole is not apparent, and the silica particle 12 appears to generally conform to a solid spherical configuration. Figure 3 is a view corresponding to Figure 1 and shows a "toroidal" configuration where the central hole does not extend completely through the catalyst particle 16 but instead forms a pronounced depression 17 so that when it is viewed from the side of the depression the silica particle still has the reminiscence of a "toroidal" configuration. Other suitable silica supports may be used to carry out the present invention. These must be characterized as having a pore volume in excess of 1 millimeter per gram in order to provide an internal arrangement within the pore volume of the support.

As previously stated the present invention provides a process for loading a metallocene catalyst precursor onto an alumoxane-containing support material with subsequent dispersion in a mineral oil carrier liquid as well as a preferred process for loading alumoxane onto a support material that is particularly applicable to certain silica supports. Support materials that can be used to carry out the present invention are described in the aforementioned patents nos. 5,719,241 to Razavi, 5,308,811 to Suga et al, and 5,444,134 to Matsumoto, the entirety of the descriptions being included here for reference.

The metallocenes used in the present invention include metallocene compounds that are known to be useful in olefin polymerization processes and include monocyclic, bicyclic, or tricyclic fractions as described in the aforementioned Welborn Patent No. 5,324,800 and Patent No. 5,719 .241 of Razavi et al. The metallocenes used in the present invention include stereospecific metallocene compounds, specifically isospecific and syndiospecific metallocenes. As discussed below, different parameters in terms of alumoxane loading and metallocene content are applicable in the formation of isospecific and syndiospecific supported metallocenes and the present invention easily accommodates tight control of alumoxane and metallocene loading within relatively narrow.

Stereorigid metallocenes, which are preferred for use in the present invention, can be characterized as metallocenes that incorporate a ligand structure having at least one appropriate substituent on at least one cyclopentadienyl ring coordinated with a central transition metal. At least one of the cyclopentadienyl rings is substituted and provides an orientation relative to the transition metal, which is sterically different from the orientation of the other cyclopentadienyl group. Thus, both of the cyclopentadienyl groups are in a relationship to each other that provides a stereorigid relationship to the coordinating transition metal atom to substantially prevent rotation of the ring structures. The sterically dissimilar ring structures can be chemically identical as in the case of certain isospecific metallocenes or chemically different as in the case of syndiospecific metallocenes. However, if two chemically identical cyclopentadienyl groups are involved in the ligand structure they must be sterically different, as in the case of racemic bis (indenyl) structures, rather than sterically equal with respect to the transition metal, as in the case of meso bis (indenyl) ligand structures.

Bridged isospecific metallocenes can be characterized as chiral stereorigid metallocenes defined by the following formula:

R ”(Cp (R ') 4)₂MeQ_p where each (Cp (R ')₄) is a substituted cyclopentadienyl ring; each R 'is the same or different and is a hydrogen or hydrocarbyl radical with 1-20 carbon atoms; R ”is a structural bridge between the two rings (Cp (R ')₄ that imparts stereorigidity to said catalyst, having the two rings (C₅ (R ')₄) a racemic configuration with respect to Me, and R "is selected from the group consisting of a substituted or unsubstituted alkylene radical having 1-4 carbon atoms, a silicon hydrocarbyl radical, a germanium hydrocarbyl radical, a phosphorous hydrocarbyl radical , a hydrocarbyl radical of nitrogen, a hydrocarbyl radical of boron, and a hydrocarbyl radical of aluminum; Is me a

ES 2 248 481 T3 metal of group 4b, 5b or 6b as designated in the Periodic Table of Elements; each Q is a hydrocarbyl radical having 1-20 carbon atoms or is a halogen; and 0 &lt;p &lt;3.

A particularly preferred class of isospecific metallocenes is based on racemic bis (indenyl) ligand structures. Indenyl groups can be substituted or unsubstituted and include aromatic indenyl groups as well as saturated indenyl groups, such as also substituted or unsubstituted tetrahydroindenyl groups. Specific examples of suitable isospecific metallocenes for use in the present invention include isopropylidene bis- (2,3-dimethylcyclopentadineyl) zirconium dimethyl, isopropylidene bis (tetramethylcyclopentadienyl) zirconium dimethyl, and isopropylidene bis (2,4-dimethylcyclopentadienyl) zirconium dimethyl racemic and the corresponding dichlorides. Other metallocenes include ethylene bis (2-methyl indenyl) zirconium dichloride, methyl silyl bis (2-methyl indenyl) zirconium dichloride, diphenyl silyl bis (2-methyl indenyl) zirconium dichloride, diphenyl silyl bis (2-methyl -4-phenyl-indenyl) zirconium and diethyl silyl bis (2-methyl-4-phenyl-indenyl) -zirconium dichloride, benzo indenyl metallocenes.

Syndiospecific bridged metallocenes can be characterized by metallocenes exhibiting bilateral symmetry and are defined by the formula

R ”(Cp_toR_n) (Cp_b R '_m ) MeQp (8) where Cpa_to is a substituted cyclopentadienyl ring, Cp_b is an unsubstituted or substituted cyclopentadienyl ring; each R is the same or different and is a hydrocarbyl radical with -120 carbon atoms; each R 'm is the same or different and is a hydrocarbyl radical having 1-20 carbon atoms; R "is a structural bridge between the cyclopentadienyl groups that impart stereorigidity to the catalyst and is selected from the group consisting of a substituted or unsubstituted alkylene radical having 1-4 carbon atoms, a silicon hydrocarbyl radical, a germanium hydrocarbyl radical , a hydrocarbyl radical of phosphorus, a hydrocarbyl radical of nitrogen, a hydrocarbyl radical of boron and a hydrocarbyl radical of aluminum; Me is a metal of group 4b, 5b, or 6b of the Periodic Table of Elements; each Q is a hydrocarbyl radical having 1-20 carbon atoms or is a halogen; 0 S p S 3; 0 S 4; 1 S n S 4; and where R '_m is chosen so that (Cp_bR '_m) is a different ring from (Cp_toR_n). Syndiospecific bridged metallocenes that can be used in the present invention include isobutylidene (cyclopentadienyl-1-fluorenyl), dimethyl zirconium, dimethyl isopentylidene (cyclopenta-dienyl-1-fluorenyl) zirconium, dimethyl isopropylidene- (cyclopenta-dienyl) (2,7- di-t-butyl-fluorenyl) zirconium, dimethyl isopropylidene (cyclopentadienyl-1-flurenyl) -zirconium, dimethyl diphenyl methylene (cyclopentadienyl-1-flurenyl) zirconium and the corresponding dichlorides or methylchlorides.

As previously indicated with reference to US Patent No. 5,807,800 the bilateral symmetry of a bridged metallocene ligand structure is indicated by the balanced orientation around the dashed line representing a plane of symmetry generally extending through through the bridging structure and the transition metal atom. The concept of bilateral symmetry is useful in illustrating metallocene structures that are useful for the invention. However other metallocene compounds lacking bilateral symmetry can also be used as long as the surrounding environment of the metal is such that the two coordination sites on the transition metal possess opposite anantifacial selectivity. To illustrate this point consider MePhC - cyclopentadienyl fluorenyl zirconium dichloride. This metallocene grows out of bilateral symmetry by virtue of the asymmetric bridge and would still be suitable for use in the invention. Similarly, I₂C (2-Me-Cp) (Flu) ZrCl₂ it would also give a syndiospecific catalyst although it lacks bilateral symmetry. The key requirement of a transition metal catalyst precursor is that the reaction sites possess opposite antifacial selectivity to olefin insertion. Visually this can be illustrated below. The antifacial selectivity of the metallocene catalytic precursor is established by an environment organization of the metal where R₂ and R₃ are sterically greater than the R groups₆ and R₇ or conversely, R₆ and R₇ are sterically greater than R₂ and R₃. In the case of Me₂CpFluZrCl₂, R₂ and R₃ are hydrogen atoms and R₆and R₇ they are hydrocarbyl radicals that are clearly larger than hydrogen.

<img file="ES2248481T3_D0003.tif" />

ES 2 248 481 T3

Condition for syndiospecific polymerizations

R₂ and R₃ are sterically greater than R₆ and R₇ or

R₆ and R₇ are sterically greater than ^R2 ^{and R}3

Conditions for isospecific polymerizations

R₂ is sterically greater than R₆ and R₇ is sterically greater than R₃ or

R₆ is sterically greater than R₂ and R₃ is sterically greater than R₇

Usually, in the metallocenes used in the present invention, Me is titanium, zirconium, hafnium or vanadium; Q is preferably methyl or halogen, more preferably chlorine; and k is normally 2 but can vary with the valence of the metal atom. Exemplary hydrocarbyl radicals include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, isoamyl, hexyl, heptyl, octyl, nonyl, decyl, cetyl, phenyl, and the like. Other hydrocarbyl radicals include other alkyl, aryl, alkenyl, alkylaryl, or arylalkyl radicals. For metallocenes where the oxidation state is not stable during use or storage (eg group 5 based metallocenes) it is often useful to use halogenated substances such as carbon tetrachloride, chloroform, etc. in order to maintain good catalytic performance.

While different loading factors are preferred for syndiospecific and isospecific catalysts, the same general procedure is to load the alumoxane first and then the metallocene onto the support material is applicable for both isospecific and syndiospecific metallocenes, as well as other metallocenes. The invention can be described generally without regard to the particular metallocene as follows. The particulate silica support is dried to remove a substantial amount of its water content. The drying procedure can be carried out under nitrogen overnight (about 12 hours) at a temperature of about 100 ° -160 ° C. The silica should be dried to the point where the amount of weight loss on ignition (LOI) at 300 ° C is less than 4%, preferably less than 2% and more preferably within the range of about 0.1- 1.5% by weight. The dried silica is then suspended in toluene or other similar aromatic hydrocarbon solvent. A solution of an alumoxane, preferably methylalumoxane (MAO), although other alumoxanes can be used, in toluene (or another aromatic solvent) is then added to the silica / toluene mixture, and as the MAO silica the resulting suspension is mixed together it is heated to a temperature of about 100 ° C or more and then heated over a period of several hours. By way of example when toluene is used as the aromatic solvent, the MAO / toluene silica mixture can be heated to the reflux temperature of toluene, about 115 ° C, for a period of about 4 hours. The resulting product where the MAO is fixed on the support is then cooled to room temperature, about 25 ° C, over a period of several hours and then allowed to settle so that the particulate silica with the supported MAO settles out of solution. without mixing or other agitation. The liquid is separated by decantation and the particulate material is filtered off and subjected to several toluene washes in order to remove excess alumoxane or other aluminum compounds not fixed on the support. Typically 2-4 toluene washes at room temperature conditions will be used in this phase of the process.

At this point the support containing alumoxane is mixed with toluene cooled to about 10 ° C or less. Typically the temperature in this phase and in subsequent phases will be within the range of about 0 ° to 10 ° C. Substantially cooler temperatures can be used but are often unnecessary. At this temperature the metallocene dispersed in the toluene or other aromatic solvent, again at reduced temperature, is added to the MAO / silica suspension and the resulting mixture is stirred for a period of time to allow the metallocene to reactively support on the support material with the alumoxane. While the predominant part of the reaction of the metallocene with the support takes place over an initial period of several minutes, it will usually be desirable to maintain the mixture of the support and metallocene for a period of one or more hours. If desired, the mixing time can be up to several hours.

At the end of the support reaction, the solid material is filtered from the liquid and then washed with a cold toluene solution, typically 0-10 ° C, and filtered and washed several times with a paraffinic hydrocarbon solvent such as hexane, new at a temperature of about 10 ° C or less. Three sequential hexane washes can be performed in order to substantially reduce the amount of toluene on the support material to a low level typically less than a few percent. In this stage cold mineral oil is added to the supported catalyst in the filtrate in order to form a dispersion of the catalyst in the mineral oil. There is no need, as described above, for a drying step so that the resulting mineral oil dispersion will contain a minor amount of the hexane or other paraffinic solvent and still a minor amount of the toluene or other aromatic solvent. However, a drying step can be applied immediately prior to the addition of the mineral oil.

The mineral oil must have a sufficient viscosity to keep the supported catalyst in a dispersive suspension with gentle agitation when used in a polymerization reaction. The mineral oil will obviously have a viscosity substantially higher than the viscosity of the paraffinic hydrocarbon solvent. Typically a paraffinic mineral oil will have a viscosity of about 10 centistokes or more at 10 ° C, while the viscosity of 10

The value of the paraffinic hydrocarbon solvent again at 10 ° C will be about one centistoke or less. The final liquid dispersing agent will contain a minor amount of the volatile paraffinic solvent used in the toluene wash of the supported catalyst and an even less amount of the aromatic solvent itself. Typically the aforementioned residual aromatic and paraffinic solvent will be present in about 1-15% by weight of the mineral oil and will be about 1-13% by weight of the hexane or other paraffinic solvent and less than 2% by weight of the toluene or another aromatic solvent. Optionally the oil can be evacuated or sparged with inert gas to remove residual paraffinic and aromatic solvent. As previously indicated the present invention can be used to incorporate the alumoxane metallocene cocatalyst or a wide variety of supports.

Characteristic of silica supports, such as those described above, is that the alumoxane is deposited primarily within the pore volume of the support with usually only a minor portion of the outer surface of the support particles. The metallocene is then applied over the alumoxane to provide a configuration where the alumoxane forms a liner on the pore walls of the support by contacting the metallocene and generally overlapping the alumoxane liner. On the outer surface of the support the alumoxane in a minor amount forms an intermediate shell that encompasses the support particle and the metallocene forms an outer shell that overlaps the alumoxane. Treatment with toluene or other aromatic solvent subsequent to the reaction of the alumoxane support removes the excess alumoxane that does not bind on the support so that together with the associated metallocene applied later it is not released from the support during the polymerization reaction. Similar considerations apply with respect to the subsequently applied metallocene. The metallocene, as indicated above, enters the pore space of the support and is also supported on the external surface as an external shell surrounding the organoaluminum cocatalyst. Because the support particles break down during polymerization, excess metallocene is easily subject to being dislodged during the polymerization reaction with corresponding production of fouling within the polymerization reactor. By initial cold temperature washings with toluene or other aromatic solvents on the freshly prepared supported catalyst, the excess metallocene is separated, not only from the external surface but also from the pore space of the support, to produce the final product where substantially all of the metallocene is attached to the support. In order to avoid any metallocene desorption by residual toluene, subsequent cold washings with hexane or other hydrocarbon removes the large preponderance of metallocene desorption.

As indicated above the invention is particularly applicable to silica supports having a mean particle size within the range of about 10-100 microns wherein organoaluminum compounds and later metallocene are internally supported within the space of pore of the support particles. As described below the relative amount of the alumoxane on the support, will be present, in preferred embodiments, in an amount to provide a weight ratio of 0.6-2.0 parts of alumoxane in the starting reaction mixture on the one hand. of support material, but amounts can vary within this range depending on whether an isospecific or syndiospecific metallocene is involved. Preferred alumoxane ratios for isospecific and syndiospecific are between 0.5 and 1.5 parts of alumoxane in the starting reaction mixture per one part of support material. Metallocene loadings will normally range between about 0.1-6% by weight of the MAO / support material, with optimal loadings being between 1.0 and 1.5% by weight. Although the activity appears to increase with the metallocene loading, it tends to level out with loads of around 1.0-2.0% by weight with very little increase, if any, in the activity achieved for loads above this range.

With syndiospecific or isospecific metallocenes, substantial improvements are observed as a result of the practice of the present invention over the typical prior art processes described above. The catalytic activity is substantially higher for isospecific and syndiospecific metallocenes, increasing by as much as twice the activity of the catalyst prepared following the practice of the prior art. The syndiospecific and isospecific catalysts shown increase in activity when a TIBAL aging procedure is followed. The polymeric product produced with the catalysts formed in accordance with the present invention has a higher bulk density, typically increased within the range of about 125-20% for isospecific metallocenes. For isospecific and syndiospecific catalysts the shelf life of the catalyst dispersed in mineral oil without the conventional intermediate drying step is much longer than the catalyst produced with conventional techniques. Shelf life can be characterized on the order of 3 months or more versus a matter of weeks shelf life for catalysts produced with conventional techniques.

Experimental work on the present invention was carried out using three bridged isospecific catalysts and two bridged syndiospecific catalysts. The isospecific catalysts were all racemic substituted bis (indenyl) zirconium dichlorides, including racemic dimethylsilyl bis (2-methyl-4-phenyl-indenyl) zirconium dichloride (referred to herein as Catalyst 1), dimethylsilyl bis (2-methyl- racemic indenyl) zirconium (catalyst 2), and racemic bis (2-methyl-4,5-benzoindenyl) zirconium dichloride (catalyst 3). To illustrate the invention with a syndiospecific catalyst the following metallocene was used: diphenyl methylene (cyclopentadienyl) (fluorenyl) zirconium dichloride (catalyst 4). To further illustrate that the invention is useful in the production of broad molecular weight distribution resins, a catalyst was prepared containing 1.6% by weight of diphenyl methylene (cyclopentadienyl) (fluorenyl) zirconium dichloride and 0.4% by weight of isopropylidene (cyclopentadienyl) (2,7-di-tert-butylfluorenyl) -zirconium dichloride (Catalyst 5). These isospecific and syndiospecific metallocenes were supported on MAO / silica using the process of the present invention and were also supported according to the current technique carried out at room temperature or above and wherein the catalyst component was dried according to conventional procedure. In general, the supported isospecific catalyst prepared with the current technique has activities ranging from about 3,000-6,000 grams of polymer per grams of catalyst per

ES 2 248 481 T3 hour (g / g / h) versus activities for the catalyst produced in accordance with the present invention within the range of about 8,000-13,500 g / g / h. The bulk density of the polymer produced from the prior art catalyst ranged from about 0.3-0.36 g / ml while the bulk density of the polymer produced from the catalyst of the present invention ranged from about 0. 35-0.4 g / ml. In addition, following the present invention the shelf life increased from about two weeks to twelve weeks or more. Lastly, the catalyst produced in accordance with the present invention can be stored as a non-pyrophoric suspension, in contrast to the pyrophoric solid produced with prior art techniques.

The following examples illustrate the practice of the present invention in the preparation of silica-supported metallocenes based on the aforementioned catalyst 1, 2, 3,4 and 5.

General procedure for polymerization of syndiotactic polypropylene (sPP)

Polymerizations were carried out in a 4L Autoclave Engineers Zipperclave reactor equipped with a pitch vane impeller operating at 800 rpm. The reactor is jacketed to keep the polymerization temperature within 1 ° C of a melting point of 60 ° C. The dried and deoxygenated reactor was charged under ambient conditions (25 ° C) with 750 g of liquid propylene and 41.2 mmol of hydrogen. The catalyst / oil suspension (containing 36 mg of catalyst) was added to a stainless steel cylinder with 109 mg of triisobutylaluminum. The catalyst / cocatalyst were precontacted for approximately 3 minutes and then introduced into the reactor with an additional 750g aliquot of propylene. The reactor was heated to 60 ° C for about 3 minutes and then the reaction was allowed to proceed for 60 minutes. The contents of the reactor were rapidly aerated and the polymer was allowed to dry overnight in a ventilated enclosure.

General procedure for polymerization of isotactic polypropylene (miPP)

Polymerizations were carried out in a 4L Autoclave Engineers Zipperclave reactor equipped with a Magnedrive pitch vane impeller operating at 800 rpm. The reactor is jacketed to keep the polymerization temperature within 1 ° C of a melting point of 60 ° C. The dried and deoxygenated reactor was charged under ambient conditions (25 ° C) with 750 g of liquid propylene and 10 mmol of hydrogen. The catalyst / oil suspension (containing 36 mg of catalyst) was added to a stainless steel cylinder with 72 mg of triisobutylaluminum. The catalyst / cocatalyst were precontacted for approximately 3 minutes and then introduced into the reactor with an additional 750g aliquot of propylene. The reactor was heated to 67 ° C for about 3 minutes and then the reaction was allowed to proceed for 60 minutes. The contents of the reactor were rapidly aerated and the polymer was allowed to dry overnight in a ventilated enclosure.

Mass density measurement

Mass density measurements were carried out by weighing the unpackaged contents of a 100 ml graduated cylinder containing the polymer powder.

Melt flow index measurement

The melt flow of the polymer was recorded on a Tinius-Olsen extrusion plastometer at 230 ° C with a mass of 2.16 kg. The polymer powder was stabilized with approximately 1 mg of 2,6-di-tert-butyl-4-methylphenol (BHT). Preparation of silica supported by methylaluminoxane

Silica gel (Fui Silysia, P-10) was dried in an oven at 150 ° C for 18 hours, then transferred to a glove box for storage. 15 g of dry silica were placed in a round bottom flask and 3 necks of 1 L in a glove box with a condenser attached. The flask was sealed and removed from the glove box and attached to a Schlenk manifold under a slight positive pressure of nitrogen. To this was added 150 ml of dry deoxygenated toluene. The suspension was stirred briefly and 41 mls of MAO at 30% by weight of toluene were added. The reaction mixture was heated to 115 ° C and refluxed for 4 hours using a magnetic stirrer. The suspension was allowed to cool to room temperature and settled. The toluene supernatant was removed via cannula and the wet product was washed sequentially with three 150 ml portions of toluene followed by three 150 ml portions of dry deoxygenated hexane. The MAO was then dried over silica in vacuo to obtain the white solid. Drying the MAO on silica in this case provides convenience in the laboratory evaluation of different catalysts. Example 1

MiPP catalyst preparation

5 g of MAO on P-10 silica was added to a 100 ml round bottom flask with 30 mls of toluene and the flask was cooled to 15 ° C. Rac-Me was discontinued₂Yes (2-Me-4-PhInd)₂ZrCl₂ (65 mg) in 10 ml of toluene in a 20 ml Wheaton vial. The metallocene suspension was added to a stirred solution of MAO on silica. The metallocene transfer was completed with a second 10 ml portion of toluene. The metallocene and MAO / silica were allowed to react for a period of 1 hour at 15 ° C. The solids were allowed to settle and the supernatant was separated via cannula. The wet supported catalyst was washed with a 50 ml portion of toluene and again

ES 2 248 481 T3 the solids were allowed to settle and the supernatant was removed via cannula. The wet supported catalyst was then washed sequentially with 3 x 50 ml portions of hexane at 0 ° C. After the third decantation of the hexane, the wet catalyst suspension was diluted with 45 g of mineral oil. The miPP supported catalyst was isolated as an 8.2% solids slurry.

Example 2

MiPP Catalyst Preparation

4 g of MAO on P-10 silica was added to a 100 ml round bottom flask with 30 mls of toluene and the flask was cooled to 15 ° C. Rac-Me was discontinued₂Yes (2-Me-4,5-BzInd)₂ZrCl₂ (65 mg) in 10 ml of toluene in a 20 ml Wheaton vial. The metallocene suspension was added to a stirred solution of MAO on silica. The metallocene transfer was completed with a second 10 ml portion of toluene. The metallocene and MAO / silica were allowed to react for a period of 1 hour at 0 ° C. The solids were allowed to settle and the supernatant was separated via cannula. The wet supported catalyst was then washed sequentially with 3 x 50 ml portions of hexane at 0 ° C. After the third decantation of the hexane, the wet catalyst suspension was diluted with 45 g of mineral oil. The miPP supported catalyst was isolated as a 7.0% solids slurry.

Example 3

MiPP catalyst preparation

5 g of MAO on P-10 silica was added to a 100 ml round bottom flask with 30 mls of toluene and the flask was cooled to 15 ° C. Rac-Me was discontinued₂Yes (2-Me-MeInd)₂ZrCl₂ (65 mg) in 10 ml of toluene in a 20 ml Wheaton vial. The metallocene suspension was added to a stirred solution of MAO on silica. The metallocene transfer was completed with a second 10 ml portion of toluene. The metallocene and MAO / silica were allowed to react for a period of 1 hour at 0 ° C. The solids were allowed to settle and the supernatant was separated via cannula. The wet supported catalyst was washed with a 50 ml portion of toluene and again the solids were allowed to settle and the supernatant was removed via cannula. The wet supported catalyst was then washed sequentially with 3 x 50 ml portions of hexane at 0 ° C. After the third decantation of the hexane, the wet catalyst suspension was diluted with 45 g of mineral oil. The miPP supported catalyst was isolated as a 7.5% solids slurry.

Example 4

SPP catalyst preparation

5 g of MAO on P-10 silica were added to a 100 ml round bottom flask with 50 ml of toluene. Diphenyl methylene (cyclopentadienyl) - (fluorenyl) zirconium dichloride (80 mg) and isopropylidene (cyclopentadienyl) (2,7-bis-tert-butylfluorenyl) zirconium dichloride (20 mg) were suspended in 10 mls of toluene in a Wheaton vial. of 20 ml. The metallocene suspension was added to a stirred solution of the MAO on silica. The metallocene and MAO / silica were allowed to react over a period of 1 hour. The solids were allowed to settle and the supernatant was separated via filtration through a sintered glass frit. The wet supported catalyst was washed with a 50 ml portion of toluene followed by 3 50 ml portions of hexane (sequentially) at 0 ° C while on the glass frit. After the third filtration of the hexane, the wet catalyst suspension was dried under vacuum for 2 hours, then diluted with 43 g of mineral oil. The sPP supported catalyst was isolated as a 9.5% solids suspension.

Comparative Example 1

MiPP catalyst preparation

5 g of MAO on P-10 silica was added to a 200 ml round bottom flask with 100 mls of toluene and the flask was cooled to 0 ° C. Rac- Me was added₂Yes (2-MeInd)₂ZrCl₂ (100 g) to a stirred solution of the MAO on silica. The metallocene and MAO / silica were allowed to react for a period of 1 hour at 0 ° C. The solids were allowed to settle and the supernatant was removed via cannula. The supported catalyst was washed sequentially with three 100 ml portions of hexane and again the solids were allowed to settle and the supernatant was removed via cannula. The wet supported catalyst was washed sequentially with 10 100 mL portions of toluene followed by three additional washes using 100 mL hexane. The catalyst was then vacuum dried for 30 minutes.

Comparative Example 2

Preparation of SPP catalyst

5 g of MAO on P-10 silica was added to a 500 ml round bottom flask with 50 ml of toluene and the flask was cooled to 0 ° C. Diphenyl methylene (cyclopentadienyl) (fluorenyl) zirconium dichloride (100 mg) was suspended in toluene. The metallocene suspension was added to the stirred solution of MAO on silica. The metallocene and MAO / silica were allowed to react over a period of 1 hour. The solids were allowed to settle and the supernatant was separated via cannula. The wet supported catalyst was washed sequentially with three 50-100 ml portions of hexane.

ES 2 248 481 T3

After the third filtration of the hexane, the wet catalyst suspension was dried under vacuum for 1 hour.

The polymerization results are summarized in Table 1. The modified procedure described here results in a substantial increase in catalytic activity (see Example 1 and Comparative Example 1).

TABLE 1

Polymerization results of the catalysts of the invention compared to current methods

<td>Catalyst</td><td>Preparation method</td><td>Activity g / g / h</td><td>BD (g / cc)</td><td>MF (g / 10) min.</td><td>XS (%)</td><td>T_m(° C)</td><td>M_w /1000</td><td>D (Mw / M_n)</td>

<td>Ex. 1</td><td>modified</td><td> 11.200</td><td> 0,46</td><td> 1,4</td><td> 0,4</td><td> 150,1</td><td> 431</td><td> 2,8</td>

<td>Ex. 2</td><td>modified</td><td> 11.700</td><td> 0,46</td><td> 25</td><td> 1,0</td><td> 145,5</td><td> 152</td><td> 2,6</td>

<td>Ex. 3</td><td>modified</td><td> 20.000</td><td> 0,48</td><td> 49</td><td> --</td><td> --</td><td> --</td><td> --</td>

<td>Ex.4</td><td>modified</td><td> 13.500</td><td> 0,45</td><td> 4,9</td><td> 4,3</td><td> 129,7</td><td> 141</td><td> 5,2</td>

<td>Comp 1</td><td>current</td><td> 5.000</td><td> 0,46</td><td> 8,1</td><td> 1,0</td><td> 151,2</td><td> 230</td><td> 3,0</td>

<td>Comp. 2</td><td>current</td><td> 4.000</td><td> 0,30</td><td> 1,4</td><td> 3,1</td><td> 129,6</td><td> 188</td><td> 2,5</td>

Shelf life was also surprisingly improved using the process of the invention. For example in Figure 7 described below the activity of two catalysts was measured under standard miPP conditions. The results indicate that dry catalysts are much more susceptible to catalytic deactivation leading to reductions in catalytic activity and that catalysts produced using the process of the invention exhibited significantly longer shelf life with activities observed for much longer than the catalytic processes of the invention. drying streams.

Figure 7 illustrates the catalytic activity (AC) in grams per gram per hour plotted on the ordinate versus the life of the catalyst (A) in days plotted on the abscissa for the isospecific metallocene catalyst formulated in accordance with the present invention (♦ data points) and in accordance with the current prior art procedure (data points). As indicated by curve 7a for the supported catalyst in accordance with the present invention, the catalytic activity declined only moderately over aging times of up to 400 days. Curve 7a indicates a vast improvement over the rapid decline in catalytic activity indicated by the conventional support procedure as indicated by Curve 7b.

The specific embodiments of the present invention having been described, it will be understood that modifications may be suggested to those skilled in the art, and it is understood that all such modifications will be covered as they come within the scope of the appended claims.