AU652363B2 - Catalyst composition and process for polymerizing polymers having multimodal molecular weight distribution - Google Patents

Description

AUSTRALIA

Patents Act6 4 M"=EE SPECIFICATICW

(ORIGINAL)

Class Int. Class Application Nvmber: Lodged: Complete Specification 'Lodged: Accepted: Published: a Priority :Related Art: Name of Applicant: *Mobil Oil Corporation Actual Inventor(s): Fr ederick Yip-Kwai Lo, Thomas Edward Nowlin, Pkadup Pandurang Shirodkar Address for Service: PHILLIPS 0RMODE FI11?Z;R2CK Patent and Trade Hark Attorneys 367 Collins Street *X Helbourne-3000 AUSTRALIA Invention Title: CATALYST COMPOSITION AND PROCESS FOR POLYHERIZING POLYMERS HAVING HULTIHODAL MOLECULAR WRIGHT DISTRIBUTION our Ref'- 216971 POP Code: 14E,2/1462 The folidvilng statement is a full description of this invention, including the best method of performing it knovi to applicant(s): 6006" F-5629-L CATALYST COMPOSION AND PRCESS FOR POLYMERIZING POLYMERS HAVING MULTIMODAL MOLECULAR WEIGHT DISIRIUTION This invention relates to catalyst precursor compositions; to catalyst compositions; and to processes for Spolymerizing alpha-olef ins to form polymers having multimodal molecular weight distributions. More particularly, this invention relates to a catalyst, and a method for preparation thereof, which produces high density polyethylene (HDPE) having a multimodal molecular weight distribution. The invention is also e: directed to an olefin polymerization process carried out with the catalyst of the invention which produces polymers of multimodal molecular weight distribution in a single polymerization reactor under steady state polymerization conditions.

Various processes have been proposed for the production of polymers having multimodal molecular weight distribution. The term 'multimodal molecular weight distribution" means that two or 000 more peaks are readily discernible in a plot of molecular weight as a function of 1,raction of the polymer having the given molecular weight, such as that obtained by gel permeation .chromatography (GPC) analysis of the polymer. One such process known to us utilizes tandem reactors operated in series, wherein in the first reactor the olefin is polymerized in the presence of a catalyst and substantially in the absence of hycirogen as a chain transfer agent. The product is transferred to the second, downstream reactor wherein polymerization is conducted in the presence of relatively large amounts of hydrogen. The first reactor produces the high molecular weight component, and the second reactor the low molecular weight caomnent of tho final polymer product. Such a method of producing multimodal molecular

I

F-5629-L -2- C S

S.

S

S S

S.

555 SSSS 55 S S 55

S.

S S 5

S

weight distribution polymers is expensive, cumbersome, and time consuming.

The present invention seeks to provide an olefin polymerization catalyst capable of producing polymers of multimodal molecular weight distribution in a single polymerization reactor under steady state polymerization conditions.

In the drawings: Figure 1 represents a Gel Petrzeation Ohromatograiphy (GPC) chromatogram of molecular weight distribution of a commercially-produced bimodal polymer (Cain L5005, obtained from Cain Chemicals, Inc.).

Figure 2 represents a GPC graph of molecular weight distribution of a polymer produced with the catalyst and the process of this invention discussed in Example 2.

Figure 3 represents a GPC graph of a molecular weight distribution of a polymer produced with the catalyst and the process of this invention discussed in Example 4.

S

C

S

According to the present invention, there is provided an olefin polymerization catalyst precursor composition supported on i) a ma -ium compound; ii) a zirconi compound; and iii) a titanium and/or a vanadium compound, wherein, during preparation of the catalyst precursor canposition, the titanium compound and/or vanadium compound is add rior to the zirconium compound.

The catalyst precursor is supported on a ier. The TicZrg s It) 81341 -2aa porous carrier containing active OH groups, including: i) a magnesium compound having the formula: Mg(OR) 2 R MgR2n or RMgX(2-k) wherein: 1 2 3 R, R R 2 and R which may be the same or different, each represent an alkyl group X represents a halogen atom; and k, m and n each represent 0, 1 or 2, providing that m n equals the valency of Mg; ii) a zirconium compound having the formula: CPmZrYnX(2-n) wherein: Cp represents a cyclopentadienyl group; m represents 1, 2 or 3; Y and X, which may be the same or different, each represent a halogen atom, a C 1 to C6 alkyl group or a hydrogen atom; and n represents 0 or 1; and 20 iii) a titanium compound and/or a vanadium compound; wherein the magnesium compound is contacted with the porous carrier to form reaction product and the titanium and/or vanadium compound is contacted with the reaction product before the zirconium compound.

25 The catalyst precursor is supported on a carrier.

The carrier materials used herein are usually inorganic, solid, particulate porous materials. These carrier materials include such inorganic materials as oxides of silicon and/or aluminum. Preferably the carrier materials are used as dry powders having an average particle size from 1 micron to 250 microns, more preferably from microns to 150 microns. The carrier materials are also porous and preferably have a surface area of at least 3 square meters per gram, and more preferably at least square meters per gram. Preferably the carrier material should be dry, that is, free of absorbed water. Drying of the carrier material can be effected by heating at a temperature from 100 0 to 00C, and preferably at about 600 0 C. When the carrier is silica, it can be 4 heated at a temperature of at /4 '2 F-5629-L -3such inm c materials as oxides of silicon and/or aluminum.

The carrier terials are used as dry powders having an average particle size fr 1 micron to 250 microns, preferably from microns to 150 micro The carrier materials are also porols and have a surface area o t least 3 square meters per gram, and preferably at least 50 square ters per gram. The carrier material should be dry, that is, f of absorbed water. Drying Sof the carrier material can be eff heating at a temperature from 1000 to 100000, and prefer at about 6000C.

e-Whpn hbe cnrrir is milica, it is heated a aa mperature of at least 200°C, preferably from 2000 to 8500C, and most preferably at about 600 0 C. The carrier material must contain at least some active hydroxyl (OH) groups to produce the catalyst composition of this invention. The term "active OH groups" means hydroxyl groups that react chemically with metal-alkyl compounds, such as magnesium and/or aluminum alkyls.

.9 In the most preferred embodiment, the carrier is silica which, prior to the use thereof in the first catalyst synthesis step, has been dehydrated by fluidizing with nitrogen and heating at about 600 0 C for about 16 hours to achieve a surface hydroxyl concentration of about 0.7 mmols/gm. The silica of the most preferred embodiment is a high surface area, amorphous silica (surface area 300m /gm; pore volume of 1.65 cm3/gm), and it is a material marketed under the tradenames of Davison 952 or Davison 955 by the Davison Chemical Division of W.R. Grace and Company. Th silica has the shape of spherical particles, e.g., as obtained by a spray-drying process.

The carrier material is suitably slurried in an organic solvent for, and the resulting slurry is contacted with, at least 0 one magnesium compound. The slurry of the carrier material in the solvent is prepared by introducing the carrier material into the solvent, preferably while stirring, and heating the mixture I F-5629-L -4to a temperature from 50° to 90 0 C, preferably from 50° to 85 0

C.

The slurry is then contacted with the magnesium compound, while the heating is continued at the aforementioned temperature.

The magnesium compound .peferab y has the formula

R

wherein o 3 R, R, R 2 and R 3 which may be the same or different, each represent an alkyl group, such as a C to C 12 alkyl, preferably a C 4 to C 8 alkyl, more preferably a C 4 alkyl; k, m and n each represent 0, 1, or 2, providing that m n is equal to the valency of Mg; and X represents a halogen, preferably a chlorine, atom.

Mixtures of such compounds may be utilised. The magnesium compound must be soluble in the organic solvent and capable of being deposited onto the carrier containing the active OH groups.

suitable magnesium compounds are Grignard reagents, e.g., methylmagnesium bromide, chloride or iodide, ethylmagnesium bromide, chloride or iodide, propylmagnesium chloride, bromide or iodide, isopropylmagesium chloride, bromide or iodide, n-butylmagiiasium chloride, bromide or iodide, isobutylmagnesium chloride, bromide or iodide; magnesium alkoxides, such as '1 3 r F-5629-L magnesium methoxide, magnesium ethoxide, magnesium propoxide, magnesium butoxide, magnesium pentoxide, magnesium hexoxide, magnesium heptoxide, magnesium octoxide; dialkylmagnesium carmpounds, wherein the alkyl groups may be the same or different, such as dimethylmagnesium, diethylmagnesium, dipropylmagnesium, dibutymagnesium, dipentylmagnesium, dihexynlmagnesium, diheptylmagnesium, dioctylbagnesiUm, dinonylmagnesium, methyl-ethylmagnesium, methyl-propylmagnesium, methyl-butylmagnesium, or propyl-butymagnesium; and magnesium dihalides, such as magnesium dichloride. Dibutylmagnesium was found to be particularly preferred in one embodiment of the invention.

Subsequently, at least one organic compound may be optionally added to the slurry. Suitable organic coupronds include an alcohol of the formula, R-OH; a ketone of the formula, RcO-R'; an Ester of the formula, R00R'; an acid of the formula, RODOH; or an organic silicate of the formula, Si(OR) 4 where R and R 1 which may be the same or different, each represents a linear, branched or cyclic alkyl group of 1 to 12 carbon atoms, such as methyl, ethyl, propyl, butyl, isobutyl, cyclopropyl, decyl or dodecyl. In each of the organic compounds R may also be a mixture of any of the aforementioned alkyl groups. Alcohols, such as 1-butanol, are preferred.

Subsequently, a titanium and/or a vanadium compound is suitably added to the slurry and heating the mixture is continued at the aforementioned teperature, fraom 50 to 90 0

C,

preferably from 50 to 85 0 C. Suitable titanium or vanadium compounds used herein are such cocpunds which are soluble in the organic solvents used in the synthe4is. IManples of such copounds include a titanium halide titanium oxyhalide or a mixture thereof, for exarWe titanium tetrachloride or titanim 4 I F-5629-L -6oxytrichloride; a vanadium halide, a vanadium oxyhalide or a mixture thereof, for example vanadium tetrachloride or vanadium oxytrichloride; and a titanium or vanadium alkoxide, wherein the alkoyxide moiety comprises a branched or unbranched alkyl group from 1 to 20 carbon atoms, preferably from 1 to 6 carbon atoms.

Titanium compounds, and particularly tetravalent titanium compounds, are preferred. The most preferred titanium compound Sis titanium tetrachloride. However, if vanadium alkoxides alone, without any other titanium or vanadium compounds containing e Schlorine (Cl) or bromine (Br) atoms are used in this step of the 0* catalyst synthesis, such vanadium alkoxides must be chlorinated or brominated in the mannee I?;own to those skilled in the art to p-oduce an active catalyst.

The aforementioned titanium or vanadium compounds may be used individually <r mixtures of such titanium or vanadium compounIs may also be used and generally no restrictions are imposed on the titanium or vanadium compounds which may be included. Any titanium or vanadium compound that may be used .GOO alone may also be used in conjunction with other titanium or vanadium compounds.

Subsequently, at least one zirconium compound is suitably introduced into the slurry desirably together with a t promoter. The zirconium compound has the formula CPmZrYnX (2-n) uherein Cp represents a cyclopentadienyl group, m represents 1, 2 or 3; Y and X, which may be the same or different, each represent a halogen atom, particularly a chlorine atomn, a C 1 to C 6 alkyl group or a hydrogen atom; and n represents 0 or 1.

-1i.

-Ir F-5629-L -7 Suitable zirconium comCounds are dicyclopentadienyl zirconium dihalide or dicyclopentadienyl zirconium monoalkyl monohalide, wherein the halide atoms are chlorine, bromine or iodide preferably chlorine, and the alkyl groups are C 1 to C 6 alkyl groups. Mixtures of the zirconium compounds may also be used.

Dicyclopentadienyl zirconium dichloride is particularly preferred in one embodiment of the invention.

The Ipromoter is at least one aluminoxane compound of the i formula

R

**0 i m represents an integer from 3 to n represents zero or an integer from 1 to 50; and jj R represents a linear, branched or cyclic C 1 to C12 12 i alkyl group, such as methyl, ethyl, propyl, butyl, isobutyl, cyclohexyl, decyl or dodecyl.

Each of the aluminoxane compounds may contain different R groups and mixtures of the aluminoxane compounds may also be used. Methylaluminoxane is a particularly preferred promoter in one embodiment of the invention. The promoter is used to impregnate the zirconium compound onto the carrier. Without wishing to be bound by any theory of operability, it is believed usdVehllmnxn sapriual rfre rmtri F-5629-L -8that the promoter enables the zirconium compound to be deposited L,0Wreoote prue-s eonto the carrier. 4 amount of the promoter is such that it will promote the deposition of the entire amount of the zirconium compound onto the carrier. In apreerred mbodiment, the amount of the promoter is sulc that all of it will be deposited onto the carrier, and substantially none will remain in the solvent. The slurry is stirred for about 1 to about 5 hours at the aforementioned temperature and the solvent is removed by filtration or distillation under vacuum, so that the temperature does not exceed 90 0 C. All of the catalyst synthesis steps must be conducted at the aforementioned temperature of about 50 to about 90 0 C, preferably about 50 about 85°C, because, it is believed, higher teaperatures may destroy titanium as the active polymerization site. For examplr, maintaining the mixture of all of the aforementioned compounds in the solvent at 1150 for several hours is believed to destroy titanium as thi active polymerization site.

Suitable organic solvents are materials in which all of the reactants used herein, the magnesium compound, the titanium and/or vanadium compounds, the zirconium compound, the promoter and the optional organic compounds are at least partially soluble and which are liquid at reaction temperatures.

Preferred organic solvents are benzene, toluene, ethylbenzene, or xylene. The most proferred solvent for one embodiment of the invention is toluene. Prior to use, the solvent should be purified, such as by percolation through silica gel and/or molecular sieves, to remove traces of water, oxygen, polar copunds, and other materials capable of adversely affecting catalyst activity,

I

F-5629-L 9 In the most preferred embodiment of the synthesis of this catalyst it is inportant to add only such amounts of all of the catalyst synthesis reactants, the magnesium, zirconium, titanium and/or vanadium compounds, the, promoter and the optional organic compounds, that will be deposited physically or chemically onto the support since any excess of the reactants in the solution ay react with other synthesis chemicals and Sprecipitate outside of the support. The carrier dryij,-g temperature affects the number of sites on the carrier available for the reactants the higher the drying temperature the lower the number of sites. Thus, the exact molar ratios of the magnesium, zirconium, titanium and/or vanadium compounds, the 'Oe) c' k, Spromoter and the optional organic compounds to the hydroxyl groups will vary and must be determined on a case-by-case basis Q..to assure that only so much of each of the ceactants is added to the solution as will be deposited onto the support from the solvent without leaving any excess thereof in the solution.

Thus, the molar ratios given below are intended to serve only as an approximate guideline and the exact amount of the catalyst synthesis reactants in this embodiment must be controlled by the functional limitation discussed abO\e, it must not he greater than that which can be deposited onto the support. If greater than that amount is added to the solvent, the excess may react with other reactants, thereby forming a precipitate outside of the support which is detrimental in the synthesis of our catalyst and must be avoided. The amount of the various reactants which is not greater than that deposited onto the support can be determined in any conventional manner, by I 4.

44 4e 0 J 4 4

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404 404444 4 t4 04 4. A 40 b. 4 44. 4 a 444444 4

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44 a F-56?9-L 10 adding the reactant, such as the magnesium compound, to the slurry of the carrier in the solvent, while stirring the slurry, until the may.nesium compound is detected as a solution in the solvent.

For example, for the silica carrier heated at about 200 to about 850°C, the amount of the magnesium compound added to the slurry is such that the molar ratio of Mg to the hydroxyl groups (OH) on the solid carrier is about 0.1 to about 3, preferably about 0.5 to about 2, more preferably about 0.7 to about most preferably about 0.8 to about 1.2, depending upon the temperature at which the carrier material was dried. The magnesium compound dissolves in the solvent to form a solution.

For the same silica carrier, subjected to the aforementioned heat treatment, if a titanium compv'd is used in the synthesis, the molar ratio of the Ti to OH groups on the carrier is about 0.1:1 to about 10:1, preferably about 1:1; if a vanadium compound is used in the synthesis, the molar ratio of V to the OH groups is about 0.1:1 to about 10:1, preferably about 1:1, and if a mixture of titanium and vanadium compounds is used, the molar ratio of the sum of V and Ti to the OH groups on the solid carrier is xptr us ao) about 0.1:1 to about 10:1, preferably about 1:1. 'Xhekamount of the promoter added to the slurry is such that the molar ratio of Al, derived from the promoter, to the OH groups on the solid P re-f morecarrier islabout 0.1 to about 3,/,preferably about 0.5 to about 2, more preferably about 0.7 to about 1.5, and most preferably about 0.8 to Kbout 1.2, depending upon the temperature at which the Iarrier material was dried. 9ei-Ti:Zr or V:Zr molar ratios in the final catalyst composition are about 1:1 to about 50:1, 4 i~ir-~XTi~iB~iUj;W*:- C(i. L i i.

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F-5629-L 11 preferably about 10:1 to about 20:1. If optional organic ccmpounds are used in the synthesis, the amount thereof will be such that they will react with substantially all of the magnesium compounds deposited up to that point in the catalyst synthesis onto the carrier.

It is also possible to add the amounts of the various reactants which are in excess of those which will be deposited 'onto the support and then remove, by filtration and washing, any excess of the reactants. However, this alternative is less deairable than the most preferred embodiment described above. Thus, in the preferred embodiment, the amount of the maqgesium, zirconium, titanium and/or vanadium compounds, the /prcmoter and the optional organic compounds, used in the synthesis is not greater than that which can be deposited onto the carrier. The exact molar ratios of Mg to Zr, Ti and/or V and of Mg, Zr, Ti and/or V to the hydroxyl groups of the carrier will therefore vary (depending, on the carrier drying S temperature) and must be determined on a case-by-case basis.

The resulting solid, referred to herein as a cat&.yst precursor, is combined with a catalyst activator. The activator is a mixture of a conventional olefin polymerization catalyst co-catalyst used to activate the titanium or vanadium sites, and an activator suitable to activate the zirconium sites, The conventional co-catalyst used herein is any one or a combinatioh of any of the material, commonly employed to activate Ziegler-N tta olefin polymerization catalyst components containig at least one compound of the elements of Groups IB, IIA, IIB, IIIB, or IVB of the Periodic Chart of the Elements, published by Fisher Scientific Company, Catalog Number 5-702-10, I/ i

I

F-5629-L 12 1978. Examples of such co-catalysts are metal alkyls, hydrides, alkylhydrides, and alkylhalides, such as alkyllithium compounds, dialkylzinc compounds, trialkylboron compounds, trialkylaluminum compounds, alkylaluminum halides and hydrides, and tetraalkylgermanium compounds. Mixtures of the co-catalysts may also be employed. Specific examples of useful co-catalysts include n-butyllithium, diethylzinc, di-n-propylzinc, triethylboron, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, ethylaluminum dichloride, dibromide, and dihydride, isobutyl aluminum dichloride, dibromide, and dihydride, diethylaluminum chloride, bromide, and hydride, di-n-propylal*minum chloride, bromide, and hydride,* diis-n-propylaluminum chloride, bromide and hydride, diisobutylaluminum chloride, bromide and hydride, tetramethylgermanium, and tetraethylgermanium. Organometallic a'So co-catalysts which are preferred in this invention are Group IIIB 0 metal alkyls and dialkylhalides having 1 to about 20 carbon atoms S per alkyl radical. More preferably, the co-catalyst is a trialkylaluminum compound having 1 to 6, preferably 1 to 4 carbon atoms per alkyl radical. The most preferred co-catalyst is trimethylaluminum. Other co-catalysts which can be used herein are disclosed in Stevens et al, U.S. Patent No. 3,787,384, column S4, line 45 to column 5, line 12 and in Strobel et al, U.S. Patent 4,148,754, column 4, line 56 to column 5, line 59, the entire contents of both of which are incorporated herein by reference.

The co-catalyst is employed in an amount which is at least effective to prancte the polymerization activity of the titanium and/or vanadium sites of the catalyst of this invention.

Preferably, at least about 10 parts by weight of the co-catalyst are employed per part, by weight, of the V or Ti in the catalyst F-5629-L 13 precursor, although higher weight ratios of the co-catalyst to the V or Ti in the catalyst precursor, such as 15:1, 30:1, 50:1 or higher, are also suitable and often give satisfactory results.

The activator suitable for activating the zirconium sites is distinct from the conventional activators described above.

The zirconium sites activator is a linear and/or cyclic aluminoxane species prepared from the interaction of R Al and water, where R is a C C alkyl, with the amount of water ontrolling the average molecular weight of the aluminoxane molecule. As is known to those skilled in the art, the rate of addition of the water to !Al, the concentration of the R Al and S water, and the temperature of the reaction may control catalyst properties, such as catalyst activity, molecular weight and molecular weight distribution of the polymers made with the S.catalyst having its zirconium sites activated with the zirconium S• sites activator.

The zirconium sites activator is preferably an aluminoxane of the fcrmula

R

I

:j O) R (A-O)n-I

S

Sfora linear aluminoxane, whereniso, 1, 2 or13, and/or F- (Al -0)jjfor a cyclic aluminoxane, wherein m is an integer from 3 to and R for both the linear and the cyclic aluminoxane is the same or different linear, Ixanched or cyclic alkyl group of 1 12 carb-wcn such as methyl, ethyl, propyl, butyl, isobutyl, cyclopropyl, decyl or dodecyl. Each of the aluminoxane cmpounds may contain different R groups and mixtures of the aluminoxane caedounds may also be used.

F-5629-L 14- The most preferred activator for the zirconium sites is methylaluminumoxane. since the commercially-available methylaluminumoxane is believed to contain trimethylaluminum, in the most preferred embodiment the addition of such a commercial methylaluminumoxane to the catalyst precursor is sufficient to of activate both the zirconium sites and the titanium and/or e• vanadium sites.

The catalyst precursors of the present invention are prepared in the substantial absence of water, oxygen, and other catalyst poisons. Such catalyst poisons can be excluded during the catalyst preparation steps by any well known methods, e.g., by carrying out the preparation under an atmosphere of nitrogen, argon or other inert gas. An inert gas purge can serve the dual purpose of excluding external contaminants during the preparation and removing undesirable reaction by-products resulting from the preparation of catalyst precursor. Purification of the solvent employed in the catalyst synthesis is also helpful in this regard.

The precursor may be activated in situ by adding the precursor and the mixture of the activators separately to the polymerization medium. It is also possible to combine the S. e o* precursor and the activators before the introduction thereof into the polymerization medium, for up to about 2 hours pior to the introduction thereof into the polymerization medium at a temperature of from about -40 to about 100 0

C.

Olefins, especially alpha-olefins, are polymerized with the catalysts prepared according to the present invention by any suitable process. Such processes include polymerizations carried out in suspension, in solution, or in the gas phase. Gas phase polymerization reactions are preferred, those taking place in stirred bed reactors and, especially, fluidized bed reactors.

F-5629-L 15 Because of the unique nature of the catalyst of this invention, relatively low amounts of hydrogen are added intentionally to the reaction medium during the polymerization reaction to control molecular weight of the polymer product.

hydrogen ethylene (C 2 molar gas phase ratios in h (Hrp the reactor are between about 0.01 and about 0.2, ,preferably about 0.02 to about 0.05. The reaction ature isjkbut to about 100 0 C, residence time isobout 1 to about 5 hours, and P, eme t the amounts of olefins used in the reactor are such that the ethylene partial pressure in the reactor is about 50 to about 250 psi, when ethylene alone or in conjunction with higher alpha-olefins is polymerized. At these polymerization process conditions polymers having miltimodal molecular weight distribution are obtained. Tae polymerization carried out in a single polymerization reactor in the presence of the catalyst of this invention produces polymers having bimodal molecular weight distribution, having polymer chains whose molecular weight ranges from about 1,000 to about 1,000,000. Without wishing to be bound by any theory of operability, it is believed that the bimodal molecular weight distribution is obtained because the zirconium (Zr) catalytic sites under certain polymerization conditions, S".i the amounts of hydrogen specified herein, produce relatively short polymer chains, having relatively low molecular weight. In contrast the titanium (Ti) and/or vdiura (v) catalytic sites, under the same polymerization conditions, produce relatively long polymer chaJns, of relatively high molecular weight. The polymer product, thexrefore, contains both types of polymer chains, resulting in the multimodal molecular weight distribution. The multimodal molecular weight distribution is :inortant because the resins having such F-5629-L 16 molecular weight distribution are relatively easily processed, in an extruder, and because such risins produce 'ilms having good strength properties.

The molecular weight distribution of the polymers prepared in the presence of the catalysts of the present invention, as expressed by the melt flow ratio (MFR) values, :o varies from about 50 to about 300, preferably about 100 to about 200, for medium density polyethylene (MDPE) products having a density of about 0.930 to about 0.940 g/cc, and an 12 (melt index) of about 0.01 to about 1 g/10 min. Conversely, HDPE products, produced with the catalysts of this invention, have a density of about 0.940 to about 0.960 g/cc, flow index (I21) of about 1 to about 100, preferably about 4 to about 40, MFR values of about 50 to about 300, preferably about 100 to about 200. As is known to those skilled in the art, at the aforementioned flow index values, these MFR values are indicative of a relatively broad molecular weight distribution of the polymer. As is also known to those skilled in the art, such MFR vaJue are indicative of the polymers specially suitable for high density polythylene (HDPE) film and blow molding applications. The gel permeation chraatography (GPC) traces of polymers produced with the mixed C metal catalyst of this invention show broad and bimodal molecular weight distriution (MWD). The details of the MWD are controlled by catalyst composition and reaction conditions. The bimodal MWD can be exploited t produce the proper balance of mechanical properties and processability.

The catalysts prepared according to the present invention are highly active and may have the activity of at least about 1. 0 to about 10.0 kilograms of polymer per gram of catalyst per 100 psi of ethylene in about 1 hour.

F-5629-L 17 The linear polyethylene polymers prepared in accordance with the present invention are hc0opolymers of ethylene or copolymers of ethylene with one or more C 3 -C0 alpha-olefins.

Thus, copolymers having two monomeric units are possible as well as terpolymers having three monomeric units. Particular examples of such polymers include ethylene/propylene copolymers, ethylene/1-butene copolymers, ethylene/1-hexene copolymers, S" ethylene/1-octene copolymers, ethylene/4-methyl-l-pentene copolymers, ethylene/l-butene/1-hexene terpolymers, ethylene/propylene/l-hexene terpolymers and ethylene/propylene/1-butene terpolymers. Ethylene/l-hexene is the most preferred copolymer polymerized in the process of and with the catalyst of this invention.

The polyethylene polymers produced in accordance with the present invention preferably contain at least about 80 percent by weight of ethylene units.

A particularly desirable method for producing polyethylene polymers according to the present invention is in a fluid bed reactor. Such a reactor and means for operating it are described by Levine et al, U.S. Patent No. 4,011,382, Karol et al, V,S. Patent 4,302,566 and by Nowlin et al, U.S. Patent 4,481,301, the entire contents of all of which are incorporated herein by reference. The polymer produced in such a reactor contains the catalyst particles because the catalyst is not separated from the polymer.

The following Examples illustrate the invention.

The properties of the polymers produced in the Examples and any calculated process parameters were determined by the following test methods: -e F-5629-L -18- Density: ASIM D 1505-A plaque is made and conditioned for one hour at 10000 to approach equilibrium crystallinity.

Measu~rement for density is then made in a density gradient colum; reported as gins/cc.

Mlt Index (MI),11 2 ASIM D-1238-Condition E-Mbasured at 190 0 C-reported as grans per 10 minutes.

C:..*:High Ioad Melt Index (Ht4l), 121: ASIM D-1238--Condition F-Measured at 10 times the weight used in the melt index test S* Melt Flowi Ratio (MFR) =I121/12 Productivity: A sample of the resin prtJuct is ashed, and the weight parcent of~ ash iz determined; ',-,ince the ash is substantially cmposed of the oatalyst, the productivity is thus the pounds of polymer produced per pound of total catalyst consumed. The amount of TiI Mg, V an Al in the' ash is determined 1by elemental analyscis.

EXAMPLE 1 too Ctiy.-t Precursor Synthesis) All procedures were performed under a dizy ntrgq n atz~ophere.

SO=ON0~ 0.317 gram of zirconium dicyclopentadienyl dichl.oride (Cp 2 ZrCl 2 was trnfex to a 100 so rl round-bottom flask and then 50 mis of dry toluene were added.

The flask was placed into a 50 0 C oil bath until a clear solution was formed.

SCOAWON 50 mis of, dry toluend- and 12 mis of mathylaluminumoxane (MA~O) (4.6 Al in toluene) were added to a 200 cc pear flask. The pear flask was placed into an oil bath go O 0 a.

00 *s S 0@ 0e 0 a 0 S 0 0* 0 f F-45629-L 19 set to 50°C. Next, 20 mis of solution was added to the pear flask to yield a clear light yellow solution.

CATALYST PREPARATION SOLUTION: 10.095 grams of Davison Chemical Company's grade 955 silica which had been heated at 600°C for about 16 hours under a dry nitrogen purge was weighed into a 500 cc pear flask containing a magnetic stirring bar. The flask was placed into a 80°C oil bath and 50 mls of dry toluene was adde, to the flask. Next, 7.2 mls of dibutylnagnesium (0.973 mmol/ml) was added to the silica/toluene slurry. The contents of the flask were stirred for 50 minutes. Then, 0.80 mis of neat titanium tetrachloride was added to the flask. The slurry turned a dark brown color and stirring was continued for 60 minutes.

Finally, the entire contents of solution were siphoned into the catalyst preparation flask and the slurry was stirred for minutes. After this time, all solvents were removed by evaporation under a nitrogen purge. Catalyst yield was 12.805 grams of a dark-brown free-f lowing powder.

EXAMPLE 2 (Polvmerizat.n Process) An ethylene/1-hexene copolyirer was prepared with the catalyst precursor of Example 1 in the following representative procedure.

A 1.6 liter stainless steel autoclave, maintained at about 50 0 C, was filled with 0.750 liiers of dry hexane, 0.030 liters of dry 1-hexene, and 5,1 mAls of methylaluminnumoxane (MAD) while under a slow nitrogen purge. The reactor was closed, the stirring rate was set at about 900 rpmt, the internal temperature was increased to 70 0 C, and the internal pressure was raised from 8 psi to 11 psi with hydrogen. Ethylene was introduced to maintain the pressure at about 114 psi. Next, 0.0349 grams of the Example 1 catalyst precursor was introduced into the reactor with ethylene over-pressure ani the teperature was increased and held at 85 0 C. The polyinerizet on was -ittinued a 0 00 S 00 0* iiL ,I I- S i F-5629-L 20 for 60 minutes, and then the ethylene supply was stopped and the reactor allowed to cool to room temperature. 110 grams of polyethylene were collected.

The MWD of the polymer was examined by GPC, and the results clearly showed that the polymer had a bimodal MWD (Figure 2).

EXAMPLE 3 SIatalyst Precursor Synthesis) "191.4 grams of Davison grade 955 silica which was previously dried at 600 0 C for 16 hours was added to a nitrogen purged, 4-neck, 3-liter round-bottom flask fitted with an overhead stirrer. Toluene (800 mls) was added to the flask and the flask was placed into an oil bath maintained at 60 0 c. Next, 129 mis of dibutylmage.si,,m (1.04 Molar solution in heptane) was added to the silica/toluene slurry. The solution was stirred for 35 minutes. Then, 15.0 mis of neat TiCl was diluted with 50 mis 5 5 4 of dry toluene and added to the flask. The solution was stirred for 60 minutes. Finally, 93 mis of methyl aluminoxane (4.6 wt% Al) and 2.41 g of Cp 2 ZrCl 2 were added to a 125 ml addition funnel to yield a clear yellow solution. This solution was added to the silica/toluene slurry and the oil bath temperature was increased :I to 80-85 0

C.

The slurry was heated for 3 hours. After this time, the oil bath temperature was lowered to 50 0 C and stirring was stopped to allow the silica to settle. The supernatant liquid was decanted and the silica was washed three times with 1500 mis of dry hexane. The silica was dried under a nitrogen purge to yield about 233 grams of dry, free-flowing powder.

(Polymrization rocess he catalyst precursor ccposition of Example 3 was used to prepar an ethylene/1-hexne co-polymer in a fluid bed, pilot plant reactor operated substantially in the manner dislosed by We i I I F-5629-L 21 Nowlin et al, U.S. Patent 4,481,301. A steadystate operation was obtained by continuously feeding the catalyst precursor, MAO activator, and reactant gases (ethylene, 1-hexene and hydrogen) to the reactor while also continuously withdrawing polymer product from the reactor. The reactor operating conditions were as follows:

S.*

o 5. 0 S 0

S.*

*q 0« *5 4 5 0

S

S

*4 9* Ethylene (C6/C2 vapor mole ratio

(H

2

/C

2 v:.por mole ratio Production Rate Catalyst Productivity Residence Time Temperature MAO feed 210 psi 0.039 0.050 24.9 lbs/hr 3000 grams polymer/gm catalyst 2.5 hours 270 mls/hr (1.0 wt% Al in toluene) The polymer had the following properties: Density Flow Index (121) 0.942 gms/cc 16.3 gs/10 Min The molecular weight distribution of the polymer was examined by GPC and the results clearly showed that the polymer had a bimodal MWD (Figure 3).

Claims (8)

1. An olefin polymerization catalyst precursor composition supported on a porous carrier containing active OH groups, including i) a magnesium compound having the formula: Mg (OR) 2 R 1 mMgR 2 n or R 3 kMgX( 2 wherein R, R 2 and R 3 which may be the same or different, each represent an alkyl group X represents a halogen atom; and k, m and n each represent 0, 1 or 2, providing that m n equals the valency of Mg; ii) a zirconium compound having the formula: CpmZrYIX(2-n) wherein Cp represents a cyclopentadienyl group; m represents 1, 2 or 3; Y and X, which may be the same or different, each represent a halogen atom, a C l to C 6 alkyl group or a hydrogen atom; and n represents 0 or 1; and iii) a titanium compound and/or a vanadium compound; S wherein the magnesium compound is contacted with the porous carrier to form reaction product and the titanium and/or S vanadium compound is contacted with the reaction product before the zirconium compound and wherein the Ti:Zr or V:Zr molar ratio ranges from 1:1 to 50:1.

2. A precursor composition accor:ding to claim 1, wherein the titanium compound includes a titanium halide, a titanium oxyhalide, or a mixture there-' and the vanadium compound includes a vanadium halide, a vanadium oxyhalide, or a mixture thereof. S

3. A precursor composition according to claim 1 or 2 S which has a Ti:Zr molar ratio from 1:1 to 50:1.

4. 4. A precursor composition according to claim 1, 2 or 3 i I S* *S F-5629-L 23 which additionally includes an alcohol of the formula R-OH; a ketone of the formula RCO-R'; an ester of the formula RCOOR 1 an acid of the formula RCOOH; or an organic silicate of the formula Si(OR) 4 where R and R I which may be the same or different, each represents a linear, branched, or a cyclic alkyl group of 1 to 12 carbon atoms, A catalyst composition which includes, the precursor of any preceding claim and a catalyst activator which is a mixture of a co-catalyst containing at least one compound of the elements of Group IB, IIA, IIB, IIIB, or IVB of the Periodic Chart of the Elements and a zirconium sites activator which is an aluminoxane of the formula R (Al-0),-AlR2 or: -(Al wherein m represents an integer from 3 to n represents zero or an integer from 1 to.50; and R represents a linear, branched or cyclic Ci to C12 alkyl grc,'p. S6. A catalyst composition according to claim 5 wherein the co-catalyst is a Group IIIB metal alkyl or dialkylhalide having 1 to 20 carbon atoms per alkyl group.

7. A process of polymerizing at least one C 2 to CI0 alpha- olefin to produce a polymer having a multimodal molecular weight distribution, which process includes conducting the polymerization in the presence of a supported catalyst composition as defined in claim 5 or 6.

8. A prooess according to claim 7 wherein the alpha- I Li \L *1~ F-5629-L -24 olef in feed includes a mixture of ethylene and at least one C 3 to CIO aipha-olef in.

9. A process according to claim 7 or 8 which is conducted the presence of such amounts of hydrogen that the molar ratio of hydrogen: ethylene is from 0.01 to 0.2. A precursor composition according to claim 1 substantially as hereknbefbre described with reference to any one of the Exam ples.

11. A process according tzn claim 7 substantially as hereinbefiore described with reference to any one of the Examples. S S S SS S 5* S. S S S S S SSS* DATED :10 JUNE 1994 PHILLIPS ORMONDE FITZPATRICK Attorneys For: MOBIL OIL CORPORATION MOT'" F-5629-L 26 ABSTRACT OS a C C SC. cs) *9 'C C.* Sr, CU C S. S There is disclosed a supported olefin polymerization catalyst composition comprising a precursor and a catalyst activator. The precursor ccmprises a magnesium compound, e.g., dibutylmagnesium, a cyclopentadienyl group containing zirconium campound, and a titanium and/or a vanadium compound, TiCl 4 and an organic compound, an alcohol. The catalyst activator is a mixture of a conventional Ziegler/Natta co-catalyst and a zirconium sites activator, e.g., methylaluminumoxane. The catalyst is used in the presence of small amounts of hydrogen to produce polymers having multimodal molecular weight distribution in a single reactor. j i