Method for preparing a supported metallocene alumoxane catalyst

Abstract: This invention relates to a process for preparing a supported metallocene alumoxane catalyst for use in the slurry, gas or liquid phase polymerization of olefins. The invention particularly relates to the use of silica gel containing from about 10 to about 50 per cent by weight adsorbed water as the catalyst support material. It has been found that such silica gel may be safely added to an aluminum trialkyl solution to form by direct reaction with the adsorbed water content of the silica gel catalyst support material the alumoxane component of the catalyst system. An alumoxane coated silica gel is formed to which a metallocene may be added. The resulting material can either be used in this slurry state for slurry polymerization or can be used for liquid phase polymerization of olefins.

Description: Field of the Invention This invention relates to a Liquid or slurry olefin polymerisation process. The invention particularly relates to the use of silica gel containing from above 10 to 50 percent by weight absorbed water as the catalyst support material. It has been found that such silica gel may be safely added to an aluminum trialkyl solution to form, by direct reaction with the absorbed water content of the silica gel catalyst support material, the alumoxane component of the catalyst system. Background to the Invention EP 260 130 discloses a polymerisation catalyst using amongst others, a metallocene, a support and an alumoxane. The components are reacted in the presence of a support but the alumoxane is prepared in a separate step prior to the reaction. No water containing support is added to diluted aluminum trialkyl to form alumoxane. German Patent 3,240,382 discloses a method for producing a filled polyolefin composition which utilises the water absorbed or adsorbed on an inorganic filler material to directly react with an aluminum trialkyl and produce thereon an active metallocene alumoxane catalyst complex. The absorbed water may be crystal water. Polymer is produced by solution or gas phase procedures to uniformly coat the filler particles and provide a filled polymer composition. German Patent 3,240,382 does not illustrate use of less than 1 % of filler or of supported catalysts using inorganic oxide supports used in low amounts appropriate to the catalytic function. German Patent 3,240,382 does not describe an inorganic filler material having absorbed or adsorbed water which has surface area or pore volume properties suitable for service as a catalyst support for a liquid or slurry phase polymerisation procedure. European Patent 0,170,059 discloses a process for polymerisation olefins using alumoxanes as part of the catalyst. Specifically, it discloses adding a finely divided porous solid, e.g., silicon dioxide or aluminum oxide, to a non-aqueous medium, adding water to that medium and then mixing in aluminum trialkyl to form alumoxane. After the alumoxane is formed, a transition metal compound (metallocene) is added, followed by the monomer. Since water and porous solid are added separately into the reactor, this technique basically involves adding aluminum trialkyl to water which yields a catalyst not being attached to any solid support. EP 315324 uses a solid material containing water to produce alumoxane separate from the solid material. There is no suggestion that the solid material left over after alumoxane preparation has utility as a catalyst system or forms a supported catalyst. EP 323716 produces a supported catalyst with undehydrated silica. The actual water contents disclosed range from 6 to 10 weight percent. The invention uses undehydrated materials with higher water contents. It would be desirable to devise an economical, reproducible, and clean process whereby an active supported metallocene/alumoxane catalyst could be produced for use in liquid or slurry phase polymerization. To be economical the process should dispense with the requirement of producing the alumoxane component as a separate component apart from the procedure by which the catalyst itself is prepared. To be reproducible, the procedure should specify the exact procedure of producing the porous solid material which contains the right amount of water absorbed or absorbed on its surface so that it could generate alumoxane with a high degree of catalytic activity. To be clean, the catalyst produced in the polymerization system should not cause the fouling of the reactor during the polymerization so that it could be applied to commercial production. Summary of Invention According to the invention, there is provided a liquid or slurry olefin polymerization process conducted in a reactor in the presence of a catalyst prepared by reacting aluminum trimethyl and water in the presence of silica at a mole ratio of aluminum trimethyl to water of from 10:1 to 1:1, and adding a transition metal metallocene to the reacted mixture, wherein the water is absorbed by the silica prior to the reactions in an amount of from above 10 to 50 weight percent, the silica is added to the aluminium trimethyl diluted in a solvent and the mole ratio of aluminium to metallocene transition metal is from 1000:1 to 1:1 with the aluminium trimethyl, the water impregnated silica, metallocene, comonomer and ethylene feed being added continuously into the reactor while polymer product is continuously removed from the reactor. The process may utilize as the catalyst support material silica particles, especially those having a surface area in the range of 10 m 2 /g to 700 m 2 /g, preferably 100-500 m 2 /g and desirably 200-400 m 2 /g, a pore volume of 3 to 0.5 ml/g and preferably 2-1 ml/g and an absorbed water content of from above 10 to 50 weight percent, preferably from 20 to 40 weight percent, and most preferably 35 weight percent. Such silica particles are referred to hereafter as a "water-impregnated" silica gel. The silica gel supported metallocene alumoxane catalyst is prepared by adding the water-impregnated silica gel to a stirred solution of aluminium trialkyl in on amount sufficient to provide a mole ratio of aluminum trialkyl to water of from 10:1 to 1:1, preferably 5:1 to 1:1; thereafter adding to this stirred solution a metallocene in an amount sufficient to provide an aluminium to transition metal ratio from 1000:1 to 1:1, preferably from 300:1 to 10:1, most preferably from 150:1 to 30:1. The contact of the water-impregnated material with aluminum trialkyl forms an alumoxane compound attached to the surface of the support. The reaction between the supported alumoxane with metallocene compound produces a supported catalyst with high catalytic activity in a liquid medium. The supported catalyst greatly reduces the reactor fouling during the polymerization due to the formation of granular polymer particle. The catalyst complex formed by this process can be used for polymerization of olefins by conventional liquid or slurry phase polymerization procedures. In both cases aluminum trialkyl, water-impregnated silica, metallocene, comonomer, as well as ethylene feed is added continuously into the reactor while polymer product is continuously removed from the reactor. Detailed Description of the Preferred Embodiments The present invention is directed toward a process for the liquid or slurry phase polymerization of olefins, particularly lower alpha-olefins, such as ethylene, propylene, and butene-1, hexene-1 and oxtene-1. The catalyst is especially useful for the production of linear low density polyethylene (LLDPE). The polymers are intended for fabrication into articles by extrusion, injection molding, thermoforming or rotational molding. In particular, the polymers prepared with the catalyst complex and by the method of this invention are homopolymers or copolymers of ethylene with higher alpha-olefins having up to 10 carbon atoms. Illustrative of the higher alpha-olefins are hexene-1 and octene-1. In the process of the present invention, ethylene, either alone or together with alpha-olefins having up to 10 carbon atoms, is polymerized in the presence of a silica gel supported catalyst system comprising at least one matallocene and an alumoxane. In accordance with this invention, olefin copolymers, particularly copolymers of ethylene and higher alpha-olefins having from 3-10 carbon atoms, can also be produced. The active catalyst complex prepared by the process of this invention comprises a metallocene and an alumoxane adsorbed onto the surface of a silica gel support material. Alumoxanes are oligomeric aluminum compounds represented by the general formula (R-Al-O) y which is believed to be a cyclic compound and R-(R-Al-O-) y AlR 2 , which is a linear compound. In the general formula, "R" is a C 1 -C 10 alkyl group such as, for example, methyl, ethyl, propyl, butyl, and pentyl and "y" is an integer from 2 to 30 and represents the degree of oligomerization of the alumoxane. Preferably, "R" is methyl and "y" is 4 to 25 and most preferably 8-25. Generally, in the preparation of alumoxanes from, for example, the reaction of aluminum trimethyl and water, a mixture of linear and cyclic compounds is obtained. Generally, an alumoxane having a higher degree of oligomerization will, for a given metallocene, produce a catalyst complex of higher activity than will an alumoxane having a lower degree of oligomerization. Hence, the procedure by which alumoxane is produced by direct reaction of an aluminum trimethyl with a water-impregnated silica gel should ensure the conversion of the bulk quantity of the aluminum trimethyl to an alumoxane having a high degree of oligomerization. In accordance with this invention the desired degree of oligomerization is obtained by the order of addition of reactants as described hereinafter. The metallocene may be any of the organometallic coordination compounds obtained as a cyclopentadienyl derivative of a transition metal. Metallocenes which are useful for preparing an active catalytic complex according to the process of this invention are the mono, bi and tri cyclopentadienyl or substituted cyclopentadienyl metal compounds and most preferably, bi-cyclopentadienyl compounds. The metallocenes particularly useful in this invention are represented by the general formulas: wherein Cp is a cyclopentadienyl ring, M is a Group 4b or 5b transition metal and preferably a Group 4b transition metal, R is a hydrocarbyl group or hydrocarboxy group having from 1 to 20 carbon atoms, X is a halogen, and m is a whole number from 1 to 3, n is a whole number form 0 to 3, and q is a whole number from 0 to 3, wherein (C 5 R' k ) is a cyclopentadienyl or substituted cyclopentadienyl, each R' is the same or different and is hydrogen or a hydrocarbyl radical such as alkyl, alkenyl, aryl, alkylaryl, or arylalkyl radicals containing from 1 to 20 carbon atoms, a silicon-containing hydrocarbyl radical, or a hydrocarbyl radical wherein two carbon atoms are joined together to form a C 4 -C 6 ring, R'' is C 1 -C 4 alkylene radical, a dialkyl germanium or silicon, or an alkyl phosphine or amine radical bridging two (C 5 R' k ) rings, Q is a hydrocarbyl radical such as aryl, alkyl, alkenyl, alkylaryl, or arylalkyl having 1-20 carbon atoms, hydrocarboxy radical having 1-20 carbon atoms or halogen and can be the same or different, Q' is an alkylidene radical having from 1 to 20 carbon atoms, s is 0 or 1, g is 0, 1 or 2; when g is 0, s is 0; k is 4 when s is 1 and k is 5 when s is 0 and M is as defined above. Exemplary hydrocarbyl radicals are methyl, ethyl, propyl, butyl, amyl, isoamyl, hexyl, isobutyl, heptyl, octyl, nonyl, decyl, cetyl, 2-ethylhexyl or phenyl. Exemplary alkylene radicals are methylene, ethylene or propylene. Exemplary halogen atoms include chlorine, bromine and iodine and of these halogen atoms, chlorine is preferred. Exemplary of the alkylidene radicals is methylidene, ethylidene and propylidene. Of the metallocenes, zirconocenes and titanocenes are most preferred. Illustrative but non-limiting examples of these metallocenes which can be usefully employed in accordance with this invention are monocyclopentadienyl titanocenes such as, cyclopentadienyl titanium trichloride, pentamethylcyclopentadienyl titanium trichloride; bis(cyclopentadienyl) titanium diphenyl; the carbene represented by the formula Cp 2 Ti = CH 2 · Al(CH 3 ) 2 Cl and derivatives of this reagent such as Cp 2 Ti = CH 2 · Al(CH 3 ) 3 , (Cp 2 TiCH 2 ) 2 , Cp 2 Ti = CHCH 2 CH 3 , Cp 2 Ti = CH 2 · AlR''' 2 Cl, wherein Cp is a cyclopentadienyl or substituted cylopentadienyl radical, and R''' is an alkyl, aryl, or alkylaryl radical having from 1-18 carbon atoms; substituted bis(Cp)Ti(IV) compounds such as bis(indenyl)Ti diphenyl or dichloride, bis(methylcyclopentadienyl)Ti diphenyl or dihalides and other dihalide complexes; dialkyl, trialkyl, tetra-alkyl and penta-alkyl cyclopentadienyl titanium compounds such as bis(1,2-dimethylcyclopentadienyl)Ti diphenyl or dichloride, bis(1,2-diethylcyclopentadienyl)Ti diphenyl or dichloride and other dihalide complexes; silicon, phosphine, amine or carbon bridged cyclopentadiene complexes, such as dimethyl silyldicyclopentadienyl titanium diphenyl or dichloride, methylenedicyclopentadienyl titanium diphenyl or dichloride and other dihalide complexes. Illustrative but non-limiting examples of the zirconocenes which can be usefully employed in accordance with this invention are, cyclopentadienyl zirconium trichloride, pentamethylcyclopentadienyl zirconium trichloride, bis(cyclopentadienyl)zirconium diphenyl, bis(cyclopentadienyl)zirconium dichloride, the alkyl substituted cyclopentadienes, such as bis(ethyl cyclopentadienyl)zirconium dimethyl, bis(β-phenylpropylcyclopentadienyl)zirconium dimethyl, bis(methylcyclopentadienyl)zirconium dimethyl, and dihalide complexes of the above; di-alkyl, tri-alkyl, tetra-alkyl, and penta-alkyl cyclopentadienes, such as bis(pentamethylcyclopentadienyl)zirconium dimethyl, bis(1,2-dimethylcyclopentadienyl)zirconium dimethyl, bis(1,3-diethylcyclopentadienyl)zirconium dimethyl and dihalide complexes of the above; silicon, phosphorus, and carbon bridged cyclopentadiene complexes such as dimethylsilyldicyclopentadienyl zirconium dimethyl or dihalide, methylphosphine dicyclopentadienyl zirconium dimethyl or dihalide, and methylene dicyclopentadienyl zirconium dimethyl or dihalide, carbenes represented by the formulae Cp 2 Zr = CH 2 P(C 6 H 5 ) 2 CH 3 , and derivatives of these compounds such as Bis(cyclopentadienyl)hafnium dichloride, bis(cyclopentadienyl)hafnium dimethyl and bis(cyclopentadienyl)vanadium dichloride are illustrative of other metallocenes. Generally the use of a metallocene which comprises a bis(substituted cyclopentadienyl) zirconium will provide a catalyst complex of higher activity than a corresponding titanocene or a mono-cyclopentadienyl metal compound. Hence bis(substituted cyclopentadienyl) zirconium compounds are preferred for use as the metallocene. Heretofore the alumoxane component of the active catalyst complex has been separately prepared then added as such to a catalyst support material which is then treated with a metallocene to form the active catalyst complex. One procedure heretofore employed for preparing the alumoxane separately is that of contacting water in the form of a moist solvent with a solution of aluminum trialkyl in a suitable organic solvent such as benzene or aliphatic hydrocarbon. This procedure is attendant with fire and explosion hazards which requires the use of explosion-proof equipment and carefully controlled reaction conditions. In an alternative method heretofore employed for the separate production of alumoxane, an aluminum alkyl is contacted with a hydrated salt, such as hydrated copper sulfate. The method comprised treating a dilute solution of aluminum alkyl in, for example, toluene, with a copper sulfate pentahydrate. A slow, controlled hydrolysis of the aluminum alkyl to alumoxane results which substantially eliminates the fire and explosion hazard but with the disadvantage of the creation of hazardous waste products that must be disposed of and from which the alumoxane must be separated before it is suitable for use in the production of an active catalyst complex. Separate production of the alumoxane component by either procedure is time consuming and costly. Correspondingly, the use of a separately produced alumoxane greatly increases the cost of producing a metallocene alumoxane catalyst. In accordance with the present invention the alumoxane component of the catalyst complex is prepared by direct reaction of an aluminum trialkyl with the material utilized as the catalyst support, namely a water-impregnated silica gel. Silica useful as the catalyst support is that which has a surface area in the range of 10 to 700 m 2 /g, preferably 100-500 and desirably 200-400 m 2 /g, a pore volume of 3 to 0.5 ml/g and preferably 2-1 ml/g, and an absorbed water content of from above 10 to 50 weight percent, preferably from 20 to 40 weight percent, and most preferably 35 weight percent. The particle size of the silica should be from 10µ to 100µ, and preferably from 30µ to 60µ (1µ = 10 -6 m). Hereafter, silica having the above identified properties is referred to as water-impregnated silica gel. Water-impregnated silica gel may be formed by adding sufficient water to commercially available silica gel (Davidson 948) to create an aqueous slurry. Because silica gel possesses many fine pores, it is extremely adsorbent and will rapidly become saturated. Once the aqueous slurry is formed, excess water can be removed by filtration, followed by air drying, or only air drying, to a free flowing powder state. Drying at elevated temperatures is not recommended because it could substantially decrease the amount of absorbed water. Water-impregnated silica gel, as defined above, is added over time, about a few minutes, to a stirred solution of trimethyl aluminum, in an amount sufficient to provide a mole ratio of aluminum trimethyl to water of from 10:1 to 1:1, preferably 5:1 to 1:1. The solvents used in the preparation of the catalyst system are inert hydrocarbons, in particular a hydrocarbon that is inert with respect to the catalyst system. Such solvents are well known and include, for example, isobutane, butane, pentane, hexane, heptane, octane, cyclohexane, methylcyclohexane, toluene or xylene. Also suitable for use as the aluminum trialkyl are tripropyl aluminum, tri-n-butyl aluminum tri-isobutyl aluminum, tri(2-methylpentyl) aluminum, trihexyl aluminum, tri-n-octyl aluminum, and tri-n-decyl aluminum. Upon addition of the water-impregnated silica gel to the solution of aluminum trimethyl, the water content of the silica gel controllably reacts with the aluminum trimethyl to produce an alumoxane which is deposited onto the surface of the silica gel particles. Although the reaction of the aluminum trimethyl with the water content of the silica gel proceeds relatively quickly, that is, it is generally completed within the time of 5 minutes, it does not occur with the explosive quickness of that which occurs with free water. The reaction may be safely conducted in conventional mixing equipment under a mantle of inert gas. Thereafter a metallocene is added to the stirred suspension of alumoxane silica gel product in an amount sufficient to provide a mole ratio of aluminum to transition metal of from 1000:1 to 1:1, preferably from 300:1 to 10:1 and most preferably from 150:1 to 30:1. The mixture is stirred for about 1 minute to 10 minutes at ambient or an elevated temperature of 85°C to permit the metallocene to undergo complete complexing reaction with the adsorbed alumoxane. For a continuous polymerization process in liquid medium, it is important to minimize the reactor fouling in order to minimize the interruption of the operation. The major source of reactor fouling is the formation of polymer on the surface of process equipment such as reactor vessel, agitator, and transfer lines. The cause of polymer formation on equipment surface is mainly due to the very fine catalyst particles. These fine particles are attracted on the equipment surfaces due to the static charge. The attracted catalyst particles catalyze the formation of polymer on the equipment surface. In order to minimize the reactor fouling, it is important to minimize the formation of very fine catalyst particles in the reactor. One effective approach of minimizing the formation of very fine catalyst particles in a liquid medium is to attach the catalyst on a support material. It was observed that the catalyst formed by reacting aluminum trialkyl with water in liquid hydrocarbon followed by metallocene can cause severe reactor fouling. This reactor fouling can be minimized by using this invention. The order of addition between the water-impregnated silica gel and the aluminum trimethyl is important with regards to the activity of the supported catalyst which results upon addition of the metallocene. A supported catalyst composition of little or no activity results when an aluminum trimethyl is added to a stirred solvent suspension of water-impregnated silica gel. It has been found that to prepare a supported catalyst composition of acceptable or high activity the order of mixing must be one wherein the water-impregnated silica gel is added to a stirred solution of the aluminum trimethyl. It is believed that this order of mixing forces the aluminum trimethyl to undergo reaction in the context of a transient localized excess of aluminum trimethyl compared to a transient localized deficiency of water. Under a mixing condition which slowly adds water-impregnated silica gel to a stirred solution of aluminum trimethyl, the bulk content of the aluminum trimethyl converts to an alumoxane with a degree of oligomerization of 6-25 (y = 6-25). Production of an alumoxane with this degree of oligomerization results in a final metallocene alumoxane catalyst complex of useful or high activity. A reverse order of mixing, that is, addition of an aluminum trimethyl to a stirred solvent suspension of water-impregnated silica gel yields a catalyst which has a poor degree of catalytic activity. In addition to the importance of proper mixing order in achieving a supported catalyst of useful activity, it has also been observed that the water content of the water-impregnated silica gel influences final catalyst activity. Hence the water-impregnated silica gel should have an absorbed water content of from above 10 to 50 weight percent. Preferably the absorbed water content should be from 20 to 40 weight percent. Maximum catalyst activity for a given metallocene component is generally observed wherein the absorbed water content of the water-impregnated silica gel used as a support is 35 weight percent. Further influencing the degree of activity attained in the final supported catalyst complex is the mole ratio of aluminum to the absorbed water content of the water-impregnated silica gel. The quantities of aluminum trimethyl employed should, in comparison to the quantity of water-impregnated silica gel of specified adsorbed water content, be selected to provide a mole ratio of aluminum to water of from 10:1 to 1:1, preferably from 5:1 to 1:1, more preferably from 3:1 to 1:1. It has been observed that for a given metallocene, a maximum catalyst activity is generally observed in the aluminum to water mole ratio range of 5:1 to 1:1. Commercially acceptable catalyst activities are exhibited in the aluminum to water mole ratio range of 3:1 to 1:1. Also influencing the cost of production and the level of catalytic activity obtained in the final supported catalyst complex is the mole ratio of aluminum to transition metal of the metallocene component. The quantity of metallocene added to the alumoxane adsorbed silica gel solids should be selected to provide an aluminum to transition metal mole ratio of from 1000:1 to 1:1, preferably from 300:1 to 10:1, and most preferably from 150:1 to 30:1. From the standpoint of economic considerations it is desirable to operate in the lower ranges of the aluminum to transition metal mole ratio in order to minimize the cost of catalyst production. The procedure of this invention is one which provides the maximum conversion of the aluminum trialkyl component to the most efficacious form of alumoxane, hence permits the safe production of a supported metallocene alumoxane catalyst of useful activity with low quantities of the costly aluminum trialkyl component. By appropriate selection of the type and relative counts of the metallocene and the aluminum trimethyl cocatalyst precursor, one can attain by the present method the particular active catalyst complex desired for any particular application. For example, higher concentrations of alumoxane in the catalyst system generally result in higher molecular weight polymer product. Therefore, when it is desired to produce a high molecular weight polymer a higher concentration of aluminum trimethyl is used, relative to the metallocene, than when it is desired to produce a lower molecular weight material. For most applications the ratio of aluminum in the aluminum trimethyl to total metal in the metallocene can be in the range of from 300:1 to 20:1, and preferably 200:1 to 50:1. The molecular weight of the polymer product can be controlled by the judicious selection of substituents on the cyclopentadienyl ring and use of ligands for the metallocene. Further, the comonomer content can be controlled by the judicious selection of the metallocene. Hence, by the selection of catalyst components it is possible to tailor the polymer product with respect to molecular weight and density. Further, one may tailor the polymerization reaction conditions over a wide range of conditions for the production of polymers having particular properties. In the examples following, the melt index (MI) and melt index ratio (MIR) were determined in accordance with ASTM test D1238. Example 1 Water-impregnated silica gel was employed in accordance with the procedure of this invention to prepare a silica gel supported (nBuCp) 2 ZrCl 2 methyl alumoxane catalyst complex which was used in a slurry phase polymerization process as follows: One hundred (100) grams of silica gel (Davison 948) was treated with enough water to form a slurry mixture. This slurry was air dried at room temperature to a free flowing state to form water-impregnated silica gel. The water content of this material measured by weight loss on ignition at 1000°C was 37 wt.%. A freshly cleaned 2.2 liter autoclave was heated to 60°C and flushed with purified N 2 for 30 minutes. It was cooled to room temperature, and eight hundred (800) milliliters of dried, oxygen free hexane was charged into the autoclave followed by the addition of five (5) milliliters of trimethylaluminum/heptane solution (2.62 M). The autoclave was heated to 85°C, and one hundred thirty (130) milligrams of water-impregnated Davison 948 silica gel was injected into the autoclave using a dry injection tube. The resulting mixture was allowed to react for five (5) minutes. One (1) milligram of (n-C 4 H 9 C 5 H 4 ) 2 ZrCl 2 dissolved in one (1) milliliter toluene was injected into the autoclave to form the catalyst in situ. One hundred (100) milliliters of butene-1 was pushed into the reactor by ethylene pressure, and the reactor was pressurized to 150 psi (10.33 bar) with ethylene. The reaction was allowed to proceed for 20 minutes, and it yielded 39 grams of resin with 2.8 MI and 20.1 MIR and a density of 0.936. Example 2 The catalyst was prepared in the same manner as the catalyst in Example 1 except that ten (10) milliliters of trimethylaluminum/heptane solution were used during the co-catalyst preparation. Polymerization of ethylene and 1-butene was performed as in Example 1. After the reaction, 49 grams of resin was recovered with 1.7 MI and 20.8 MIR and a density of 0.937. Example 3 The catalyst was prepared in the same manner as the catalyst in Example 1 except that fifteen (15) milliliters of trimethylaluminum/heptane solution were used during the co-catalyst preparation. Polymerization of ethylene and 1-butene was performed as Example 1. The reaction lasted 40 minutes yielding 46 grams of resin with 5.4 MI and 24.8 MIR and a density of 0.945. Example 4 The catalyst was prepared using the same quantities of ingredients as in Example 1. However, the wet silica was first contacted with the metallocene, dried to a free flowing solid (silica contained 37 wt.% water) and thereafter contacted with TMA. On polymerizing in the manner of Example 1, one (1) gram of resin was recovered. Example 5 Example 4 was repeated identically with the exception that fifteen (15) milliliters of TMA/heptane solution were used during the co-catalyst preparation. Upon polymerization in the manner of Example 1, two grams of resin were recovered. Example 6 Example 2 was repeated with the exception that one (1) milligram of (C 5 H 5 ) 2 ZrCl 2 dissolved in one (1) milliliter of toluene was used during the catalyst preparation. After 40 minutes of polymerization, forty-five (45) grams of resin were recovered. The resin manifested an MI of 9.1 and an MIR of 28.5. Example 7 Example 2 was repeated with the exception that bis(cyclopentadienyl)titanium dichloride was substituted for the zirconocene. After 20 minutes of polymerization, two grams of resin were recovered. Example 8 The catalyst was prepared in the same manner as Example 2 with the exception that one-hundred thirty (130) milligrams of Al(OH) 3 with a water content of 39 wt.% were substituted for the silica. The polymerization resulted in forty-one (41) grams of resin being recovered with an MI of 1.0 and an MIR of 18.4. Example 9 Example 8 was repeated with the exception that five (5) milliliters of trimethyl aluminum/heptane solution were employed in the catalyst preparation. The polymerization resulted in forty-one (41) grams being recovered with an MI of 0.9 and an MIR of 22.7. Example 10 A catalyst was prepared in the same manner as in Example 2 with the exception that one-hundred thirty (130) milligrams of Mg(OH) 2 with a water content of 31 wt.% were substituted for the silica. After 40 minutes of polymerization, six (6) grams of resin were recovered. Example 11 A catalyst was prepared in the same manner as Example 10 with the exception that five (5) milliliters of trimethyl aluminum/heptane solution were used during the catalyst preparation. After polymerization, one (1) gram of resin was recovered. Example 12 A catalyst was prepared in the same manner as in Example 11 with the exception that ten (10) milliliters of triethyl aluminum/heptane solution were used during the catalyst preparation. After polymerization in the manner of Example 1, one (1) gram of resin was recovered. Example 13 A catalyst was prepared in the same manner as in Example 12 with the exception that five (5) milliliters of triethyl aluminum/heptane solution were employed for the catalyst preparation. Upon polymerization in the same manner as Example 12, one (1) gram of resin was recovered. Table 1 summarizes the result obtained in the preceding examples: Example 14 A continuous gas fluidized bed reactor was used to carry out the polymerization. The catalyst prepared in Example 2 and a triethyl aluminum with Al/Zr ratio in the range of 30:1 to 600:1 were injected continuously into the fluidized bed reactor at 63°C; 300 psi (20.67 bar) total pressure: butene-1 as comonomer; and the hydrogen as chain transfer agent. A molar ratio of 1-butene to ethylene of 0.17:1 and a molar ratio of hydrogen to ethylene of 0.00001:1 were maintained during the polymerization. The reaction was run continuously and smoothly at a space time yield of 3-6 lb/hour/ft 3 (1.36 - 2.72 kg/hour/28.3 liters) while producing a low density polyethylene butene-1 copolymer with a 0.892-0.897 g/cc gradient density, MI of 3.5 - 3.0 dg/min, and bulk density of 22 lb/ft 3 (352 kg/m 3 ).

Claims: A liquid or slurry olefin polymerization process conducted in a reactor in the presence of a catalyst prepared by reacting aluminum trimethyl and water in the presence of silica at a mole ratio of aluminum trimethyl to water of from 10:1 to 1:1, and adding a transition metal metallocene to the reacted mixture, wherein the water is absorbed by the silica prior to the reactions in an amount of from above 10 to 50 weight percent, the silica is added to the aluminium trimethyl diluted in a solvent and the mole ratio of aluminium to metallocene transition metal is from 1000:1 to 1:1 with the aluminum trimethyl, the water impregnated silica, metallocene, comonomer and ethylene feed being added continuously into the reactor while polymer product is continuously removed from the reactor. The process according to claim 1 or claim 2, wherein the metallocene is represented by the general formula: wherein Cp is cyclopentadienyl ring, M is a Group 4b or 5b transition metal, R is a hydrocarbyl group or hydrocarboxyl group having from 1 to 20 carbon atoms, X is a halogen, m is a whole number from 1 to 3 and n and q are whole numbers from 0 to 3. The process according to claim 1 or claim 2, wherein the metallocene is represented by the general formula: wherein (C 5 R' k ) is a cyclopentadienyl or substituted cyclopentadienyl, each R' is the same or different and is hydrogen or hydrocarbyl radical containing from 1 to 20 carbon atoms, a silicon-containing, hydrocarbyl radical or a hydrocarbyl radical wherein two carbon atoms are joined together to form a C 4 -C 5 ring, R' is C 1 -C 4 alkylene radical, a dialkyl germanium or silicon or an alkyl phosphine or amine radical bridging two (C 5 R' k ) rings, Q is a hydrocarbyl radical having 1-20 carbon atoms, hydrocarboxyl radical having 1-20 carbon atoms or halogen and can be the same or different, s is 0 or 1, g is 0, 1 or 2, s is o when g is 0, k is 4 when s is 1, k is 5 when s is 0, and M is a Group 4b or 5b transition metal. The process according to any of claims 1 to 3 wherein the metallocene is represented by the general formula: wherein (C 5 R' k ) is cyclopentadienyl or substituted cyclopentadienyl, each R' is the same or different and is hydrogen or hydrocarbyl radical containing from 1 to 20 carbon atoms, a silicon-containing hydrocarbyl radical, or a hydrocarbyl radical wherein two carbon atoms are joined together to form a C 4 -C 5 ring, R'' is C 1 -C 4 alkylene radical, dialkyl germanium or silicon, or an alkyl phosphine or amine radical bridging two (C 5 R' k ) rings, Q' is an alkylidene radical having from 1 to 20 carbon atoms, s is 0, and M is a Group 4b or 5b transition metal. The process according to any of the preceding claims wherein the metallocene is selected from the group consisting of zirconocenes, titanocenes, hafnocenes and vanadocenes. The process according to any of the preceding claims wherein the mole ratio of aluminium trimethyl to water is from 5:1 to 1:1 and/or wherein the mole ratio of aluminium to transition metal is from 300:1 to 10:1, preferably from 150:1 to 30:1. A process according to any of the preceding claims further characterized in that: (a) less than 33 wt% of water is absorbed by the silica (b) the trimethyl aluminum solution is stirred during contacting with the water containing silica and has a concentration of 0.1 to 5M, optionally the water containing silica being added, free of diluent, in powder form; and/or (c) the metallocene is a substituted cyclopentadiene derivative.

Inventors: CHANG MAIN, CHANG, MAIN
Applicants: EXXON CHEMICAL PATENTS INC, EXXON CHEMICAL PATENTS INC.
Application year: 1989
Main classification: C08F4
IPC codes: C08F4, C08F10