OLEFIN POLYMERIZATION CATALYST FROM TRIALKYLALUMINUM MIXTURE, SILICA GEL AND A METALLOCENE

Abstract: A high activity alumoxane-metallocene supported catalyst for the polymerization of 1-olefins prepared by reacting undehydrated silica gel with a mixture of trimethylaluminum and triisobutylaluminum to produce a silica-alumoxane product which is then reacted with a Group IVB and/or Group VB metallocene to produce an active catalyst which may be obtained in powder form, suitable for use in gas or slurry phase reactors, by a removal of solvents and drying.

Description: OLEFIN POLYMERIZATION CATALYST FROM TRI ALKYLALUMINUM MIXTURE , SILICA GEL AND A METALLOCENE SPECIFICATION This application Is a cont1nuat1on-1n-part of copendlng application Serial No. 263,572 filed October 27, 1988 which Is n turn a contlnuatlon- n-part of U.S. Serial No. 134,413 filed December 17, 1987. Background of the Invention 1. Field of the Invention This invention relates to a supported metallocene-alumoxane catalyst and a process for preparing th s catalyst for use In polymerization of oieflns and especially n the gas phase or liquid phase polymerization of oieflns. The nvention particularly relates to the substitution of trllsobutylalualnua for tr1meth laluminum In 10 the production of those -metallocene-alumoxane catalysts which are il supported on silica gel containing froa about 6 to about 20 percent 12 by weight adsorbed water. The resulting Material s dried to a 13 free-flowing powder to yield a supported catalyst which Is active for 14 the homo or copolymerlzatlon of polymerlzable-oleflns. 2. Background to the Invention 15 Olef.n polymerization catalysts comprising a metallocene and 16 an aluminum alkyl component were first proposed In about 1956. 17 Australian patent 220436 proposed for use as a polymerization 18 catalyst a bls-(cyclopentadlenyl) titanium, zirconium, or vanadium 19 salt as reacted with a variety of halogenated or unhalogenated aluminum alkyl compounds. Although capable of catalyzing the polymerization of ethylene. such catalytic complexes, especially those made by reaction with a trlalkyl aluminum, had an Insufficient level of catalytic activity to be employed commercially for production of polyethylene or copolyaers of ethylene. Later t was found that certain metallocenes such as b1s-(cydopenta lenyl) titanium, or zirconium dlalkyls n combination with aluminum alkyl/water cocatalyst formed catalyst systems for the polymerization of ethylene. Such catalysts are discussed In German Patent Application 2,608,863 which discloses a polymerization catalyst for ethylene consisting of bis-(cydopentadlenyl) titanium dl lkyl, trlalkyl aluminum and water. German Patent Application 2.608.933 discloses an ethylene polymerization catalyst consisting of a cydopentadlenyl zirconium salt, a trlalkyl aluminum cocatalyst and water. European Patent Application No.0035242 discloses a process for preparing ethylene and atactlc propylene polymers in the presence of a cydopentadlenyl transition metal salt and an alusoxane. Such catalysts have sufficient activity to be comerdally useful and enable the control of polyolefln molecular weight by means other than hydrogen addition — such as by controlling the reaction temperature or by controlling the amount of cocatalyst alumoxane as such or as produced by the reaction of water with an aluminum alkyl. To realize the benefits of such catalyst systems, one must use or produce the required alumoxane cocatalyst component. An alumoxane Is produced by the reaction of an aluminum alkyl with water. The reaction of an aluminum alkyl with water Is very rapid and highly exothermic. Because of the extreme violence of the reaction the alumoxane cocatalyst component has, heretofore, been separately prepared by one of two general methods. Aluoxanes may be prepared by adding an extremely finely divided water, such as In the form of a humid solvent, to a solution of aluminum alkyl In toluene or other aromatic hydrocarbons. The production of an alumoxane by such procedure requires use of explosion-proof equipment and very close control of the reaction conditions n order to reduce potential fire and explosion hazards. Also, fine solid particles are generated in the head space of the reactor which can plug the vent and the transfer tube and cause the shut down of the process. For this reason. It has been preferred to produce alumoxane by reacting an aluminum alkyl with a hydrated salt, such as hydrated copper sulfate. In such procedure a slurry of flntly divided copper sulfate pentahydrate and toluene Is formed and mantled under an inert gas. Aluminum alkyl 1s then slowly added to the slurry wth stirring and the reaction mixture 1s maintained at room temperature for 24 to 48 hours during which a slow hydrolysis occurs by which alumoxane 1s produced. Although the production of alumoxane by a hydrated salt method significantly reduces the explosion, fire hazard, and fine generation Inherent In the wet solvent production method, production of an alumoxane by reaction with a hydrated salt must be carried out as a process separate from that of producing the metallocene-alumoxane catalyst Itself, Is slow, and produces hazardous wastes that create disposal problems. Further, before the alumoxane can be used for the production of an active catalyst complex the hydrated salt reagent must be stparattd from the alumoxane to prevent It from becoming entrained In the catalyst complex and thus contaminating any polymer produced therewith. U. S. Patent 4,431,788 discloses a process for producing a starch filled polyolefln composition wherein a trlalkyl aluminum Is first reacted with starch particles. The starch particles are then treated with a (cydopentadlenyl)-chrom1ua, titanium, vanadium or zirconium alkyl to form a metallocene-alumoxane catalyst complex on the surface of the starch particles. An olefln Is then polymerized about the starch particles by solution or suspension polymerization procedures to form a free-flowing composition of polyolefIn-coated starch particles. German Patent 3,240,382 likewise discloses a method for producing a filled polyolefln composition which utilizes the water content of an Inorganic filler material to directly react with a trlalkyl aluminum and produce thereon an active metallocent alumoxane catalyst complex. Polymer Is produced by solution or gas phase procedures at the filler surface to uniformly coat the filler particles and provide a filled polymer composition. German Patent 3,240,382 notes that the activity of a metallocene-alumoxane catalyst Is greatly Impaired or lost when prepared as a surface coating on an Inorganic material . Although German Patent 3,240,382 suggests that an Inorganic material containing absorbed or adsorbed water may be used as a filler material from which the alumoxane cocatalyst component may be prepared by direct reaction with a trlalkyl aluminum, the only water containing Inorganic filler materials which art Identified as capable of producing the alumoxane without adversely affecting the activity of the metal locene alumoxane catalyst complex are certain Inorganic materials containing water of crystallization or bound water, such as gypsum or mica. German Patent 3,240,382 does not Illustrate the production of a catalyst coated Inorganic filler material wherein the Inorganic material Is one having absorbed or adsorbed water. Nor does German Patent 3,240,382 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 gas phase polymerization procedure. All these publications also teach that only methyl alumoxane formed by reacting trl methyl aluminum with water, has high enough activity for polyolefln polymerization. Other trlalkyl aluminum compounds do not form high activity alumoxane when react with water. My copendlng U.S. Patent Application Serial No. 134,413 discloses a method by which the requisite alumoxane cocatalyst component for a supported metal locene gas phase polymerization catalyst may be safely and economically prepared by addition of an "undehydrated" silica gel to a trlalk- yl aluminum solution. My co-pending application Illustrates the production of highly active silica gel supported metal locene-alumoxane catalyst wherein trl methyl aluminum 1s utilized to form the alumoxane. Although the reaction product of trl ethyl aluminum with water Is known to form an Ineffective cocatalyst, a highly active catalyst system Is formed In accordance with the method disclosed In ay co-pending application Serial No. 268.834. by reacting trl ethyl aluminum with undehydrated silica gel followed by reacting with metallocene. y copendlng U.S. application Serial No. 263,572 teaches the use of a mixture of TEAL and TMA to produce the alumoxane component of a metal locene-alumoxane catalyst In a less expensive process than the use of TMA alone. The use of this TEAL/TMA mixture produces an alumoxane which, In combination with a metal locene, provides a catalyst more active for olefln polymerization than those metal locene-alumoxane catalysts using only TEAL. Furthermore, It has been found that the TEAL/TMA mixture-based aetal locene-alumoxane catalyst reduces the amount of solid waste particles that accumulate In the head space of reactors thereby eliminating or reducing vent-line plugging and costly reactor down time. The TEAL In the mixture also tends to reduce the violence of the reaction produced when TMA alone Is contacted with water to product in alumoxane component. Thus, the TEAL/TMA based catalysts provide Mgh activity, lower cost catalysts which are safer to product and which offer reduced operating costs due to lower reactor down times. OespUe the activity and cost mprovements already achieved In processes for polymerizing oieflns using aetal locene-alxtd alumoxane catalysts , It Is yet desirable to product even higher activity catalysts. Summary of the Invention The Invention provides a supported aetal locene-aluaoxane catalyst effective for the homo or copolyaerlzatlon of oieflns. The alumoxane cocatalyst component Is formed by reacting a mixture of triisobutylaluminum (TIBA) and trlmethylalualnua (TMA) with undehydrated si lica gel . The metal locene component, which Is selected from the metal locenes of the Group IVB and/or VB metals, Is then added to the trl alkyl aluminum-silica gel complex to form tht active supported catalyst. Solvents used n the preparation of the catalyst may be evaporated to produce a dry catalyst In powder form useful In gas or slurry phase 1-olefln polymerization. It has been surprisingly discovered that by replacing TEAL with equivalent amounts of TIBA obtains a more active catalyst for the polymerization of oieflns. As the catalyst support, this Invention utilizes silica particles having a surface area In the range of about 10 m/g to about 700 m/g, preferably about 100-500 m/g and desirably about 200-400 m/g, a pore volume of about 3 to about 0.5 cc/g and preferably 2-1 cc/g and an adsorbed water content of from about 6 to about 20 weight percent, preferably from about 9 to about 15 weight percent. The novel silica gel supported metallocene-alumoxane catalyst Is prepared by adding the undehydrated silica gel to a stirred solution of a mixture of TIBA and TMA n an amount sufficient to provide a mole ratio of TIBA plus TMA to water of from about 3:1 to about 1:2, preferably 1.2:1 to about 0.8:1; thereafter mixing this stirred solution with a metallocene In an amount sufficient to provide an aluminum to transitional metal ratio of froa about 1000:1 to 1:1, preferably froa about 300:1 to 10:1, most preferably froa about 150:1 to about 30:1; removing the solvent and drying the solids to a free-flowing powder. Drying can be obtained by modest heating or vacuum. The dried, free-flowing powder comprises a metallocene-alumoxane catalyst complex adsorbed upon the surface of the silica gel support particles. The supported catalyst complex has an activity sufficient for use as a catalyst for polymerization of oieflns by conventional gas or slurry phase polymerization procedures. This nvention further provides for the use of TIBA to produce a substantial portion of the alumoxane cocatalyst component required to produce a highly active supported aetallocene-alumoxane catalyst. The undehydrated silica gel support material Is added to a stirred solution of TMA and TIBA, the mole ratio of THA.TIBA 1n coπmon solution being from about 1:1 to about 10,000:1 prefereably 2:1 to about 1000:1 and the mole sum of TMA and TIBA being selected to provide a mole ratio of Al to transition metal In the final catalyst composition of from about 1000:1 to about 1:1. Thereafter, the metallocene Is added to the stirred solution after which the solvent Is removed and the solids dried to a free-flowing powder. D ailad Description of the Preferred Embodiments The present Invention Is directed toward a supported catalyst system for use In polymerization of oieflns and especially i the gas or slurry phase homo and copolymerlzatlon of oieflns. The supported catalyst Is particularly useful for the gas phase copolymerlzatlon of ethylene to high molecular weight polytthylenes such as linear low density polyethylene (LLOPE) and high density polyethylene (HOPE). The novel catalyst complex Is particularly suitable for the production of the homopolymers of ethylene and copolyaers of ethylene with higher alpha-oleflns and dloltflns having from 3 to about 10 carbon atoms and preferably 3 to 8 carbon atoms. Illustrative of the oieflns art butenβ-1. hexene-1, octene-1, 3-aethylpentenβ-l, 4-mβthylpβntene-1, l,4-hβxad1βne, 1,4-pentadlene, 1,3-butadlene, 4 aethyl-1,4-pentad1ene, 1.5-heptadlene, 1,4-heρtad1ene. In the process of the present Invention, a 1-oltfn or a mixture of 1-oieflns Is polymerized In the presence of a silica gel supported catalyst system comprising at least one metallocene and an alumoxane produced from reacting a mixture of TIBA and TMA with the water contained In an undehydrated silica gel. The Invented catalyst system Includes a metallocene and an alumoxane cocatalyst formed onto the surface of a silica gel support material. Alumoxanes art ollgoaerlc alualnua compounds represented by the general formula (R-A1-0 which Is believed to be a cyclic 0 compound and R(R-Al-0-) y AlR, which Is a linear compound. In the i general formula, "R" Is a C-C alkyl group such as, for example, 2 methyl, ethyl, propyl, butyl, and pentyl and "y" Is an Integer from 2 3 to about 30 and represents the degree of ollgomerlzatlon of the 4 alumoxane. Preferably, the degree of ollgomerlzatlon, "y," Is about 5 4 to about 25 and most preferably 6-25. Generally, In the 6 preparation of aluaoxanes froa, for example, the reaction of 7 trlmethyl aluminum and water, a mixture of linear and cyclic 8 compounds Is obtained. Generally, an alumoxane having a higher 9 degree of ollgomerlzatlon will, for a given aetallocene, product a 0 catalyst complex of higher activity than will an alumoxane having a 1 lower degree of ollgoaerlzatlon. Hence, the procedure by which 2 alumoxane Is produced by direct reaction of a trlalkyl alualnua with 3 an undehydrated silica gel should Insure the conversion of the bulk 4 quantity of the trlalkyl alualnua to an alumoxane having a high 5 degree of ollgoaerlzatlon. In accordance with th s Invention the 6 desired degree of ollgoaerlzatlon Is obtained by the order of 7 addition of rtactants as described hereinafter.. The metallocene may be any of the organometalllc coordination compounds obtained as a cydopentadlenyl derivative of the Group IVB and/or Group VB transition metals. Metallocenes which are useful for preparing an active catalytic complex according to the process of this Invention are the mono, bl and trl cydopentadlenyl or substituted cydopentadlenyl aetal compounds and most preferably, bl-cydopentadlenyl compounds. The aetallocenes particularly useful In this Invention are represented by the general formulas: wherein Cp Is a cydopentadlenyl ring, M Is a Group IVB or VB transition metals and preferably a Group IVB transition metal, R Is a hydrogen, 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 form0 to 3, and "q" Is a whole number from 0 to 3, with a+n+q-4 wherein CC # R' fc > Is a cydopentadlenyl or substituted cydopentadlenyl, each R' Is the same or different and Is hydrogen or a hydrocarbyl radical such as alkyl, alkenyl, aryl, alkylaryl, or arylalkyl radicals containing froa 1 to 20 carbon atoas, a silicon-containing hydrocarbyl radical, or a hydrocarbyl radical wherein two carbon atoas are joined together to form a C 4 -C ring, R" Is C χ -C 4 alkylene radical, a d1alkyl geraanluaor s111cone, or an alkyl phosphlne or aalne radical bridging two ι R V r1n 9 s * 0 Is a hydrogen, 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 1 1s an alkylldene radical having from 1 to about 20 carbon atoms, s Is 0 or 1, g 1s 0, 1 or 2; when g Is 0, s Is 0; k Is 4 to 0 when s Is 1 and k Is 5 to 0 when s 1s 0 and M Is as defined above. - 9 - 1 Exemplary hydrocarbyl radicals are methyl , ethyl , propyl , butyl , a yl , Isoamyl , hexyl , Isobutyl , heptyl , octyl , nonyl , decyl , 3 cetyl , 2-ethyl exyl , phenyl , and the like. Exemplary alkylene 4 radicals are methylene, ethylene, propylene, and the like. Exeaplary 5 halogen atoas Include chlorine, bromine and odine and of these 6 halogen atoms, chlorine Is preferred. Exemplary of the alkyl 1 dene 7 radicals 1 methyl 1 dene, ethyl 1 dene and propyl 1 dene. 8 Of the metal locenes, hafnocenes, zlrconocenes and 9 tltanocenes are most preferred. Illustrative but -non- Halting 10 examples of the metal locenes which can be usefully employed In il accordance with this Invention are aonocyclopentadlenyl tltanocenes 12 such as, cydopentadlenyl titanium trichloride, 13 pentamethyl cydopentadlenyl titanium trichloride; 14 b s (cydopentadlenyl) titanium dlphenyl ; the carbene represented by 15 the formula Cp.TI-CH. • AKCH t )_C1 and derivatives 16 of this reagent such as Cp .-CH, • A1(CH.) $ , 17 (Cp ICH.)., Cp t T1CH a CH(CH t )CN a , 18 Cp_T1.CHCH a CH t • AIR' • • .Cl , wherein Cp Is a 19 cydopentadlenyl or substituted cydopentadlenyl radical , and R* " Is 20 an alkyl , aryl , or alkylaryl radical having from 1-18 carbon atoms; 21 substituted bls(Cp)TKIV) compounds such as blsdndenyDTI dimethyl , 22 dlhallde, or methyl hallde. bl s (methyl eye 1opentad1βnyl)T1 dimethyl , 23 dlhalldes, methyl hallde, or other dl alkyl or alkyl hallde complexes; 24 di lkyl , trlalkyl , tetra-alkyl and penta-alkyl cydopentadlenyl 25 titanium compounds such as b1s(1,2-d1methy1cyc1opentad1enyl)T1 26 dimethyl , dlphenyl , dlchlorlde, methyl chloride, or phenyl chloride, 27 b1s(l ,2-d1ethy1cyclopentad1eny1)T1 dimethyl , dlphenyl , dlchlorlde, 28 methyl chloride, phenyl chloride, or othtr dlalkyl , alkyl hallde or 29 aryl hallde complexes; si 11 cone, phosphlne, aalne or carbon bridged 30 eye 1 open tad ene complexes, such as dimethyl sllyldl cydopentadlenyl 31 titanium dimethyl, dlphenyl , or dlchlorlde, 32 methyl enedl cydopentadlenyl titanium dimethyl , dlphenyl , dlhallde, or 33 other dlalkyl , dlaryl , alkyl hallde, or aryl hallde complexes. 34 Illustrative but n . on-limiting examples of the zlrconocenes 35 which can be usefully employed In accordance with this Invention are. cydopentadlenyl zl rconlua trichloride, pen tame thy 1 cydopentadlenyl zi rconium trichloride, bis (cy opentadlenyl ) zirconium dlphenyl , b1s(cydopentad1eny1)z1rcon1ua dlchlorlde, the alkyl substituted eye 1 open tad 1enβs, such as b1s< ethyl cydopentadlenyl) zirconium dimethyl , b1s(-pheny1propy1cyclopentad1eny1 ) z1rcon1ua dlaethyl , b1s(aethy1cydopentad1eny1)z1rcon1ua dlaethyl , and dlhallde coapltxts of the above; d1 -alkyl , trl-alkyl , tttra-alkyl , and pβnta-alkyl cydopentadlenes, such as b1 s ( pen taaethyl cydopentadlenyl ) zirconium dlaethyl , b1s(1 ,2-d1aethy1cyc1optntad1tny1)z1rcon1ua dlaethyl , b1s(1 ,3-d1ethy1cydopentad1eny1)z1rcon1ua dlaethyl and dlhallde complexes of the above; $111 cone, phosphorus, and carbon bridged cyclopentadlene complexes such as d1methyls11yld1cydopentad1enyl zi rconium dimethyl or dlhallde, methyl phosp ne dl cydopentadlenyl zirconium dimethyl or dlhallde, and methyl ene dl cydopentadlenyl zirconium dimethyl or dlhallde, carbenes represented by the formulae Cp a Zr-CH 1 P(C β H f ) t CH t . and derivatives of these compounds such as Cp a ZrCH a CH(CH | )CH a . B1s( cydopentadlenyl ) hafnium dlchlorlde, b1s(cydopentad1eny1)hafn1um dl .methyl , b1s(cydopentad1eny1)vanad1ua dlchlorlde b1s(n-butyl cy opentadlenyl) hafnium dlchlorlde, or dimethyl , bis (methyl cydopentadlenyl ) hafnium dlchlorlde, or dimethyl , b1s(1ndeny1)hafn1ua dlchlorlde, or dimethyl and the like are Illustrative of other aetal locenes. Generally the use of a aetal locene which comprises a bi s (substituted cydopentadlenyl) zlrconlua trill provide a catalyst complex of higher activity than a corresponding tltanocene or a aono cydopentadlenyl metal compound. Hence, bi s (substituted cydopentadlenyl) zirconium compounds are preferred for use as tht metal locene. The alumoxane component of the Invention catalyst complex Is prepared by direct reaction of a TMA and TIBA mixture with the Material utilized as the catalyst support, namely an undehydrated si lica gel . Silica useful as the catalyst support Is that which has a surface area In the range of about 10 to about 700m 1 /g, preferably about 100-500 and desirably about 200-400a s /g, a port volume of about 3 to about 0.5 cc/g and preferably 2-1 cc/g, and an adsorbed water content of froa about 6 to about 20 weight percent, preferably froa about 9 to about 15 weight percent. The average particle slzt (APS) of tht silica may bt froa about 0.3μ to about 100μ, and for a gas phast catalyst preferably froa about 30μ to about 80μ (lμ - 10 " *a). For a catalyst Intended for hgh pressure polymerization (10,000 to 30,000 pslg) tht particle size of the silica should range froa about 0.3 to no greater than about 10. Silica having the above Identified properties Is referred to as "undehydrated silica gel." To produce the Invention catalyst, undehydrated silica gel 1s added over time, about a few minutes to one hour, to a stirred solution of a mixture of TMA and TIM, In an amount sufficient to provide a mole ratio of trlalkyl aluminum to water of from about 3:1 to 1:2, preferably about 1.2:1 to 0.8:1. The temperature of reaction Is from -196*C to 150*C. The solvents used 1n 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, cydohexane, methylcydohexane, toluene, xylene and the like. The less toxic aliphatic hydrocarbon solvents are preferred. Upon addition of the undehydrated silica gel to the solution of TIBA and TMA In an Inert solvent, the water content of the silica gel controllably reacts with the TMA and TIM to produce an alumoxane which 1s deposited onto the surface of the silica gel particles. Although the reaction of the TIBA and TMA with the water content of the silica gel proceeds relatively quickly, that Is, t s generally completed within the time of about 5 minutes, It does not occur with the explosive quickness of that which occurs with fret wattr. Tht reaction may be safely conducted In conventional mixing equipment under a mantle of Inert gas. After the TMA/TIBA mixture has been reacted with the water contained In the undehydrated silica gel, and the alumoxane formed, a Group IVB and/or VB metallocene or mixture of such metallocene Is added to the stirred suspension of alumoxane-s llca gel product n an amount sufficient to provide a mole ratio of aluminum to transition metal of from about 1000:1 to about 1:1, preferably from about 300:1 to about 10:1 and most preferably from about 150:1 to about 30:1. The mixture 1s stirred for about 30 minutes to about one hour at ambient or an elevated temperature to permit the metallocene to undergo complete reaction with the adsorbtd alumoxane. Upon completion of the metallocene-alumoxane reaction, tht solvent 1s removed and the residual solids art dried, preferably at a teaperature of 25*C or greater, to a free-flowing powder. The free-flowing powder comprises a silica gel-supported metallocene-alumoxane catalyst complex of sufficiently high catalytic activity for use 1n the polymerization of oieflns by conventional gas or slurry phase polymerization procedures. The order of addition of the undehydrated silica gel to the TIBA and TMA solution Is Important and directly Impacts the activity of the resultant supported catalyst when the aetallocene Is added. A supported catalyst composition of little or no activity results when the TMA and TIBA solution Is added to a stirred suspension of undehydrated silica gel In a solvent. 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 undehydrated silica gel Is added to a stirred solution of TIBA and TMA. It has been found that under alxlng conditions which slowly add undehydrated silica gel to a stirred solution of TIBA and TMA, the bulk content of the trlalkyl alualnua converts to an alumoxane with a degree of ollgoaerlzatlon of about 6-25 (y - 6-25). Production of an alumoxane with this degree of ollgoaerlzatlon results In a final metallocene alumoxane catalyst complex of useful or high activity. As mentioned before, a reverse order of mixing, that Is, addition of a trlalkyl aluminum to a stirred solvent suspension of undehydrated silica gel Is not recommended and yields a catalyst which has a low 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 undehydrated silica gel influences final catalyst activity. Hence, the undehydrated silica gel should have an adsorbed water content of from about 6 to about 20 weight percent. Preferably the adsorbed water content should be from about 9 to about 15 weight percent. Further Influencing tht degrtt of activity attained In tht final supported catalyst complex Is the mole ratio of trlalkyl aluminum (I.e. TMA plus TIBA) to tht adsorbtd wattr content of tht undehydrated silica gel. The quantities of TMA plus TIBA employed should, In comparison to the quantity of undehydrated silica gel of specified adsorbed water content, be selected to provide a .mole ratio of total trlalkyl aluminum to water of froa about 3:1 to about 1:2, preferably from about 1.5:1 to about 0.8:1, more preferably froa about 1.2:1 to about 0.8:1. It has been observed that for a given metallocene, a maximum catalyst activity Is generally observed In the TMA plus TIBA to water mole ratio range of about 1.2:1 to about 0.8:1. Depending upon the particular trlalkyl alualnua selected for use, commercially acceptable catalyst activities are exhibited In the trlalkyl alualnua to water mole ratio range of about 3:1 to about 1:2. Also Influencing the cost of production and the level of catalytic activity obtained In the final supported catalyst coapltx 1s the mole ratio of aluminum to transition metal of the metallocene component. The quantity of metallocene added to the alumoxane adsorbed onto the silica gel solids should be selected to provide an aluminum to transition metal mole ratio of from about 1000:1 to about i: t preferably from about 300:1 to about 10:1, and most preferably from about 150:1 to about 30:1. From the standpoint of economic considerations. It 1s desirable to operatt In tht lowtr rangts of tht aluminum to transition metal mole ratio 1n order to minimize the cost of catalyst production. The procedure of this Invention Is one which provides the maximum conversion of the trlalkyl alualnua component (I.e. the TMA and TIBA) to the tost efficacious form of alumoxane, hence peraltlng the safe production of a supported metallocene alumoxane catalyst of useful activity with minimum quantities of the costly trlalkyl aluminum component. The present Invention now provides a method by which substantial quantities of TIBA can be used In replacement of the more expensive TMA to produce a methyl aluoxane-butylalumoxane alxtd cocatalyst component which, when combined with a Group IVB and/or Group VB metallocene or mixtures thereof, produces a final supported catalyst having a high degree of catalytic activity and surprisingly higher activity than catalyst produced froa TEAL and TMA. In this embodiment of the Invention, the trlalkyl aluminum solution to which the undehydrated silica gel Is added Is a alxtd solution of TMA and TIBA, In the mole ratio TMA:TIBA of froa about 1:1 to about 10,000:1, In quantities sufficient to provide the amount of total aluminum necessary to achieve the mole ratio of Al to transition aetal desired In the final supported catalyst composition. By appropriate selection of the type and relative amounts of the Group IVB and/or Group VB metallocene and the relative quantities of TIBA and TMA 1n the cocatalyst precursor mixture, one can attain by the present method the particular active catalyst complex desired for a specific 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 trlalkyl aluminum 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 alkyl to total metal In the metallocene can be 1n the range of from about 300:1 to about 20:1, and preferably about 200:1 to about 50:1. Following the addition of the metallocene to the alumoxane adsorbed on the silica gel solids, the catalyst Is dried to a free-flowing powder. Drying of the catalyst may be conducted by filtration or evaporation of solvent at a temperature up to about 85*C. The dried free-flowing powder comprises a metallocene-alumoxane complex adsorbed upon the surface of tht silica gei support particles. The dried state composition exhibits a level of catalytic activity useful for polymerization of oieflns by a gas or slurry phase procedure as are known In tht art. As disclosed In copendlng application Serial No.728,111 filed April 29, 1985, Call the metallocenes disclosed therein being usefully employed In this Invention, said disclosure being Incorporated herein by reference] the molecular weight of the polymer product can be controlled by the judicious selection of substituents on the cydopentadlenyl ring and use of llgands for the metallocene. Further, the coαonoaer content can be controlltd by tht judicious selection of the aetallocene. Henct, by tht selection of catalyst components It Is possible to tailor the polymer product with respect to molecular weight and density. Further, one aay tailor tht polymerization reaction conditions over a wide range of conditions for the production of polymers having particular properties. [In the examples following, the aelt Index (MI) and melt Index ratio (MIR) were determined In accordance with ASTM test Dl238.3 Example 1 A catalyst was prepared by adding 90 al of TIBA In a heptane (0.9 M) solution, 160 al of TMA 1n heptane (1.4 M) solution, and 200 al of heptane solvent to a dry and oxygen-free one-liter reactor equipped with a magnetic stirring bar. A 50 g of undehydrated silica gel (Davlson 948) containing 12.81 of water was slowly added to the flask. After the addition was complete, the mixture was stirred at ambient temperature for one hour. A 1.25 g of d1-(n-buty1cydopentad1enyl)z1rcon1um dlchlorlde slurrled In 50 ml of heptane was then added to the reactor and the mixture was allowed to react at ambient temperature for 30 minutes. The reactor was then heated to 65*C while purging nitrogen gas through the flask to remove the solvent and produce a free-flowing powder. Example 2 Example 1 was repeated except that 130 al of TIBA and 135 al of TMA solution were added to the reactor to react with the undehydrated silica. Exarolt 3 Example 1 was repeated except that 170 ml of TIBA and 110 ml of TMA solution were added to the reactor to react with the undehydrated silica. Example 4 (Comparative) Exaaplt 1 was repeated except that 335 al of TIBA solution was added to the reactor to react with the undehydrated silica. Example 5 (Comparative) Example 1 was repeated except that 220 al of TMA solution was added to the reactor to react with the undehydrated silica. Example 6 (Comparative) Example 1 was repeated except that 60 al of trlethylaluminum (TEAL) (1.6 M In heptane) and 140 al of TMA solution were added to the reactor to react with the undehydrated silica which contained 12.31 water. Example 7 (Comparative) Example 6 was repeated except that 120 al of TEAL (1.6 H In heptane) and 70 al of TMA solution were added to the reactor to react with the undehydrated silica which contained 12.31 water. Example 8 Polymerization Uslno The Catalysts of Examples 1 - 7 The activity of the catalyst of Examples 1 - 7 was determined at ambient temperature and 5 pslg ethylene pressure by the following procedure. A 150 al vial containing a .magnetic stirring bar was charged with 2.0 g of catalyst. Ethylene was fed Into the vial at ambient teaperature and a total pressure of 5 pslg was maintained for 30 minutes. Thereafter, the residual ethylene gas was vented froa the via. and the polyethylene formed Inside tht vial was weighed. Theyield of polyethylene obtained with each catalyst Is listed In Table 1. The Invention has been described with reftrtnct to Its preferred embodiments. From this description, a person of ordinary skill In the art may appreciate changes that could be made In tht Invention which do not depart from the scope and spirit of the Invention as described above and claimed hereafter.

Claims: CLAWS : 1. A catalyst for the polymerization of 1-oieflns comprising the reaction product of: (a) undehydrated silica gel; (b) a alxture of trlaethylalualnua and triisobutylaluminum; and (c) a metallocene component selected from the group consisting of Group IVB metallocenes, Group VB aetallocenes and mixtures thereof. 2. The catalyst of claim 1 wherein the mole ratio of TMA to TIBA 1s froa about 2:1 to about 1000:1. 3. The catalyst of claim 1 wherein the aetallocene Is a tltanocene, zlrconocene, hafnocene or mixtures thereof. 4. The catalyst of claim 1 wherein the wattr content of the undehydrated silica gel ranges from about 6 to about 20 wt.l based on the total weight of silica gel and water. 5. The catalyst of claim 1 wherein the aetallocene Is a tltanocene, hafnocene, zlrconocene or mixtures thereof; the mole ratio of TMA to TIBA Is from about 2:1 to about 1000:1; and the moisture content of the undehydrated silica gel Is froa about 6 wt.X to about 20 wt.l based on the total weight of silica gel and water. 6. A method of preparing a catalyst active for tht polymerization of 1-oieflns comprising: (I) reacting a alxture of trlIsobutylalualnua and trlaethylalualnua with an undehydrated silica gel to fora a reaction product; (II) contacting the reaction product with a metallocene component selected froa the group consisting of Group IVB metallocenes. Group VB metallocenes and mixtures thereof to produce a catalytic composition. 7. The method of claim 6 further comprising removing solvents and drying the catalytic composition to produce a catalyst In powder fora. 8. The method of claim 6 wherein the aole ratio of TMA to TIM Is froa about 2:1 to about 1000:1. 9. The method of claim 6 wherein the metallocene Is a tltanocene, zlrconocene, hafnocene or mixtures thereof. 10. The method of claim 6 wherein the water content of the undehydrated silica gel ranges froa about 6 to about 20 wt.l based on the total weight of silica gel and water. 11. The method of claim 6 wherein the metallocene Is a tltanocene, hafnocene, zlrconocene or mixtures thereof; the mole ratio of TMA to TIM Is from about 2:1 to about 1000:1; -and the moisture content of the undehydrated silica gel Is from about 6 wt.l to about 20 wt.l based on the total weight of silica gel and water.

Inventors: CHANG MAIN, CHANG, MAIN
Applicants: EXXON CHEMICAL PATENTS INC, EXXON CHEMICAL PATENTS INC.
Application year: 1990
Main classification: C08F4
IPC codes: C08F4, C08F10