CA2042961C - Catalyst composition and process for polymerizing polymers having multimodal molecular weight distribution - Google Patents

Abstract

There is disclosed a supported olefin polymerization catalyst composition comprising a precursor and a catalyst activator. The precursor comprises a magnesium compound e.g., dibutylmagnesium, a cyclopentadienyl group - containing zirconium compound, and a titanic and/or a vanadium compound e.g., TiCl4, and an organic compound, e.g., 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 preserve of small amounts of hydrogen to produce polymers having multimodal molecular weight distribution in a single reactor.

Description

CATALYST POSITION AND PI~~SS FOR POLYMERIZING
POLYN~iS HAVING MULTIhfODAL MOLEICIJLAR WEIGHT DTSrRIH~TI'ION
ion relates to catalyst precursor ~positians; to catalyst compositions; and to processes for ~l~izit~g alpi~a-olefins to form polymers having multimodal molecular weight distributions. More particularly, this invention relates to a catalyst, and a method for preparati~
f, ~~ proc~oes high density polyethylene (FmPE) having a multimodal molecular weight distribution: The ir~ntion is also directed to an olefin polymerization p~ooess carried out with the ~~~ of the invention which produces polymers of mu.7.timodal ~lweight distributiari in a single polymerizatiar~ reactor ur~er 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 a pegs are readily disG~ernible in a plat of molecular weight as a function of fraction of the polymer having the given molecular r~aeight, such as that obtained by gel permeation chraaat.~raphy (GPC) analysis of the polymex. One such process own to us utilizes tandem reactors operated in series, wherein in the first reactor the olefin is polymerized in the presence of a catalyst arid substantially in the absence of hydrogen as a chain'trar~sfer a~tt~ ~ ~ ~ ~ferred to the second, ~~ ~~, wherein polymerization is cnr~ducted in the prese~ooe of relatively large amounts of hydrogen. The first the high molecaxlar weight component, and the second reaG~tOr the low molecular weight c~onent of the final polymer p1~oduct. Such a method of producing aaxltinadal molecular

- 2 -weight distribution polymers is expensive, c~nnberscene, and time consumixyg.
She present invention seeks to provide an olefin polymerization catalyst capable of producing polymers of multimodal molecular weight distribution in a side polymerization reactor un3er steady state polymerization conditions.
In the drawings:
Figure 1 represents a Gel Permeation Qzroanatography (GPC) chrcanatogram 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 distrilxztion of a polymer produced with the catalyst and the process of this invention discussed in ale 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 ale 4.
According to the present invention, there is providecT an olefin polymerization catalyst precursor com~sition supported on a porous carrier prising:
i) a magnesium odd;
ii) a zirconium ~o~.u~d; arr3 ~ ) a titaniimm candor a vanadimn oc~oond.
wherein, during the preparation of the catalyst precursor composition, the titanium oc~ound and/or vanadilnn d is added prior to the zirconium ~e catalyst precursor is supported on a carrier. 'Ihe carrier materials used herein are usually inorganic, solid, * Trademark

- 3 -particulate porous materials. Zhe_se carrier materials include such inorganic materials as oxides of silicon and/or alumirnmm.
~e carrier materials are used as dry powders having an average particle size from 1 micron to 250 microns, preferably frcan 10 microns to 150 microns. Zhe carrier materials are also porous and have a surface area of at least 3 square meters per gram, and preferably at least 50 square meters per gram. 'I3~e carrier material should be dry, that is, free of absorbed water. Drying of the carrier material can be effected by heating at a temperature frcan 100° to 1000°C, and preferably at about 600°C.
i~en the carrier is silica, it is heated at a temperature of at least 200°C, preferably frcan 200° to 850°C, and most preferably at about 600°C. the carrier material nnlst contain at least scene active hydroxyl (OH) groups to produce the catalyst ition of this invention. 'Ihe term "active OH groups" means hydroxyl groups that react chemically with metal-alkyl cc~paunds, such as magnesium and/or almnirnnn alkyls.
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°C for about 16 hours to achieve a surface hydroxyl concentration of about 0.7 mmols/c~n. 'Ihe silica of the most preferred embodiment is a hick surface area, amorphous silica (surface area = 300m2/gm; pane volume of 1.65 csn3/gm), and it is a material marketed under the trademarks of "Davison 952" or "Davison 95S" bY ~ ~~.~ .cal Division of W.R. c~aoe and ~~ s~~ ~s ~ of spherical particles, e.g., as obtained by a sp~raY-drying process.
'Ihe carrier material is suitably slurried in an organic solvent for, and the resulting slurry is contacted with, at least ors mag~~sium o~.md. ~e slurry of the carrier material in the solvent is prepared by introducing the carrier material into the solvent, preferably while stirring, and heating the mi~tbzre F-5E>29-L

- 4 -to a t~exature from 50° to 90°C, preferably froan 50° to 85°C.
The slurry is then contacted with the magnesiwn cue, while the heating is continued at the aforementioned te~rature.
The magnesium oc~o~urri preferably has the form0.zla ~J(~)2. R m~2n. ~' R3(2 k) ~
R, RZ, R2 and R3, which may be the same or different, each represent an alkyl group, such as a C2 to C~ alkyl, preferably a C4 to C8 alkyl, more preferably a C4 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 oar~cx~nds may be utilised. The magnesium ootapotmd nest be soluble in the organic solvent and capable of being deposited onto the carrier containing the active OH groups.
Stx3.table limn con~wrxls are Grignard reagents, e.g., methyium l~aaide, cfiloride or iodide, ethy7magnesium snide, chloride or iodide, propylmagnesium chloride, xrcanide or iodide, isopropylmagnesium chloride, brcanide or iodide, n-butylmag~sivn chloride, broanide or iodide, isobutylmagnesium chloride, bromide or iodide; magnesium alkoxides, such as 2~~2961

- 5 -magnesium methoxide, magnesium ethoxide, magnesium propoxide, magnesium butoxide, magnesium pentoxi.de, magnesium hexoxide, magnesium heptoxide, magnesium octoxide; dialkylmlgnesium co~npour~ds, wherein the alkyl groups may be the same or different, such as dimethyium, diethylmagnesium, dip~y7magnesium, dibutyhaagnesium, dipenty7magnesium, dihexylmagnesium, dihepty7.magnesium, dioctylmagnevsium, dinonylmagnesium, methyl-ethylmagnesium, methyl-propy7magnesium, methyl-butylmagnesium, or propyl-butylmagnesiamn; and magnesium dihalides, such as magnesium dichloride. Di.buty7magnesium was found to be particularly preferred in one embodiment of the invention.
Subsequently, at least one organic e~ound may be optionally added to the slurry. Suitable organic oc~ocnds include an alcohol of the formula, R-OH; a ketone of the forrm~la, Ra0--R'; an ester of the fla, ROOOR'; an acid of the formula, l~Ii; or an organic silicate of the formula, Si (fit) 4, where R
and R1, which may be the same or different, each represents a .
linear, bandied or cyclic alkyl grcxzp of 1 to 12 carbon atcans, such as methyl, ethyl, propyl, butyl, isobutyl, cyclopropyl, decyl or dodecyl. In each of the organic aompOUnds R may also be a mixture of any of the aforementioned alkyl groups. Aleohols, such as 1-butaryol, are preferred.
Subsequently, a titanium and/or a vanadium c~o~nd is suitably added to the slurry and heating the mixture is continued at the afararnemiomed t.~exature, i.e., frcen 50 to 90°C, preferably from 50 to 85°C. Suitable titanium or vanadium c~npau~ds used herein are such compouryds which are soluble in the organic solvents used in the synthesis. R~les of such onds include a titanium halide, titanium oxyhalide or a mixtt~e thereof, for example titanium tetrachloride or titanium 2~~2;~61

- 6 -oxytrichloride; a vanadium halide, a vanadiwn oxyhalide or a mixture thereof, for example vanadium tetrachloride or vanadium oxytrichloride; and a titanium or vanadium alkoxide, wherein the alkoxic'~ moiety o~ises a branched or unbrarached alkyl group frcan 1 to 20 carbon atoms, preferably from 1 to 6 carbon atoms.
Titani~n ocar~ounds, and particularly tetravalent titanitun oca~ounds, are preferred. The most preferred titanium ~
is titaniinn tetrachloride. Haa~evex, if vanadimn alkoxides alone, without any other titaniwn or vanadimn founds containing chlorine (C1) or b~nine (Hr) ataens are used in this step of the catalyst synthesis, such vanadiwn alkoxides mast be chlorinated or b~roaninated in the manner known to those skilled in the art to produce an active catalyst.
The aforementioned titanium or vanadium compout~s may be used individually or mixtures of such titaniwn or vanaditun Cnmpaands may also be used and generally no restrictions are in~osed on the titanium or vanadium ors which may be included. Ar~y titanium or vanadium ~ that may be used alone may also be used in conjunction with other titanium or vanadium compounds.
Subsequently, at least one zirconium oampawnd is suitably irrtroduoed into the slurry desirably together with a prcmater. The zirconium o~ound has the fornwl.a CpmZrYnX(2-n) wherein Cp repra cycldienyl group, m represents 1, 2 or 3; Y and X, which may be the same or different, each represent a halogen atoan, particularly a chlorine at~n, a C1 to C6 alkyl group or a hydrogen atcan; and n represents 0 ar 1.

F-5629-L 20~2~~~
5liitable zirconium ends are dicyclopentadienyl zirconium dihalide ar~ dicyclopentadierryl zirconium monoalkyl nanohalide, wherein the halide atc~ns are dzlorine, b~aine or iodide preferably chlorine, and the alkyl groups are C1 to C6 alkyl Mixtures of the zirconium c~au~ds may also be used.
Dicyclapentadienyl zirconium dichloride is particularly preferred in one embodiment of the invention.
Zhe is at least ~e aluminoacane oonq~au~d of the formula R
R2A1-O-(Al-O)ri A1R2 (~ (R) 0) m wherein m represents an integer fran 3 to 50;
n represents zero or an integer from 1 to 50; and R represents a linear, branched or cyclic C1 to C~
alkyl group, such as methyl, ethyl, propyl, butyl, isobutyl, cyclohexyl, decyl or dodeLyl.
Each of the alwninrnrar~e canpounds may oomtain different R
and mixtures of the aluminoacane compounds may also be used. M~ethylaluminohcar~e is a particularly preferred prosmoter in one embodiment of the irnrention. 'Ihe prodnatex is used to impregnate the zirconium compound onto the carrier. Without wishing to be bound by any theory of operability, it is believed _ g _ that the prcanater enables the zirconium cnd to be deposited onto the carrier. The amount of the pxna~ater is stx"h that it will prcmate the deposition of the entire amount of the zirconium compound onto the carrier. In a preferred embodiment, the amount of the p~oter is such that all of it will be deposited onto the carrier, arid substantially none will remain in the solvent. The slurry is stirred for about 1 to about 5 hours at the aforem~eotioned temperature and the solvent is removed by filtration or distillation under vacuum, so that the te~~erature does not exceed 90°C. All of the catalyst synthesis steps must be conducted at the aforementioned temperature of about 50 to about 90°C, preferably about 50 to about 85°C, because, it is believed, higher temppxatures may destroy titanium as the active polymerization site. For example, maintaixiing the mixture of all of the aforementioned ooanpaunds in the solvent at 115°C for several hours is believed to destroy titanium as the active polymerization site.
Suitable organic solvents are materials in which all of the reactants used herein, i.e., the magnesium cx~pound, the titanium and/or vanadium ecanpo~u~ds, the zirconium cxm~ound, the promoter and the optional organic ooanpwnds are at least partially soluble and which are liquid at reaction terrpexatures.
Preferred organic solvents are benzene, toluene, ethylbenzene, or xylene. The most preferred solvent far one embodiment of the invention is toluene. Prior to use, the solvent should be purified, such as by percolation silica gel arul/or molecular sieves, to remove traces of water, oxygen, polar eats, and other materials capable of adversely affecting catalyst activity.

20~2~0~
_ g _ In the most preferred embodiment of the synthesis of this catalyst it is important to add only such amounts of all of the catalyst synthe'Sis reactants, i.e., the magnesium, zirconium, titanium and/or vanadium ends, the p~:~anoter and the optional organic compounds, that will be deposited - physically or chemically - onto the support since any excess of the reactants in the solution may react with other synthesis d~emicals and precipitate outside of the support. the carrier drying te~perature affects the rnm~ber of sites on the carrier available for the reactants -- the higher the drying t~rrperature the lower the rnnnber of sites. Thus, the exact molar ratios of the ~~agnesium, zirconium, titanium and/or vanadium c~OUnds, the p~rx~c~ter and the optional organic oo~qaoiuxls to the hydroxyl grrx~ps will vary and must be determined on a case-by-case basis to assure that only so much of each of the reactants 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 of the catalyst synthesis reactants in this embodiment must be controlled by the functional limitation discussed above, i.e., it xm~st not be 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 moust be avoided. The amount of the various reactants which is mat greater than that deposited onto the support can be detxrmined in any oorxvventional manner, e.g., by adding the reactant, such as the magnesium C~o~d, to the slurry of the carrier in the solvent, while stirring the slurry, until the magnesitun c~owxl is detected as a solution in the solvent.
Four example, for the silica carrier heated at about 200 to about 850°C, the amt of the magnesi~n ooh added to the slurry is such that the molar ratio of Mg to the hydroxyl (OH) o~ the solid carrier is about 0.1 to about 3, preferably about 0.5 to about 2, more preferably about 0.7 to about 1.5, most preferably about 0.8 to about 1.2, depexydixig upon the trature at which the carrier material was dried. The magnesium voa~u~d dissolves in the solvent to farm a solution.
For the same silica carrier, subjected to the aforementioned heat treatment, if a titanium odd is used in the synthesis, the molar ratio of fine Ti to OH on the car~°ier is about 0.1:1 to about 10:1, preferably about 1:1; if a vanadiwn o~ow~d is used in the synthesis, the molar ratio of V to the OH groups i.a about 0.1:1 to about 10:1, preferably about 1:1, and if a mixture of titanium and vanadium coa~uryds is used, the molar ratio of the sum of V and Ti to the OH groups on the solid carrier is about 0.1:1 to about 10:1, preferably about 1:1. The amount of the ~ added to the slurry is such that the molar ratio of A1, derived fraan the praanater, to the OH groups 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 1.5, and most preferably about 0.8 to about 1.2, deperyding upon the temperature at which the carrier material was dried. The Ti:Zr or V:Zr molar ratios in the final catalyst c~OSition are about 1:1 to about 50:1, -11- 2~~2~~~.
preferably about 10:1 to about 20:1. If optional organic grids are used in the synthesis, the amount thereof will be such that they will react with substantially all of the magnesium ~s 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 kited aaito the support and then re~mve, e.g., by filtration and washing, any e~aoess of the reactants. However, this alternative is less desirable than the most preferred embodiment described above. Thus, in the preferred embodiment, the amamt of the magnesium, ziro~ium, titanium aixl/o~r vanadium oompau~ds; the pratadter and the optional oceanic ocxnpouryds, used in the synthesis i.s not greater than that which can be deposited onto the c~rriex. 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, e.g., on the carrier drying Mature) and trust be determined on a case-by-case basis.
The resulting solid, referred to herein as a catalyst p~eca~z~sar, is combined with a catalyst activator. The activator is a mixture of a conventional olefin polymerization catalyst ao-catalyst used to activate the titanium or vanadium sites, and an activator suitable to activate the zirconium sites.
~ ~,~.~i~l ~talyst used herein is any one or a combi,rsation of any of tip materials commonly employed to activate .
Ziegler-Natta olefin polymerization catalyst ocmponents i n; ng at least one oa~c~.u~d of the elements of Gds 7B, IIA, IIB, IIIB, ar IVB of the Periodic cW art of the Elements, publi.ahed by Fisher Scientific Oon~ax~y, Catalog Number 5-702-10, 1978. E~les of such co-catalysts are metal alkyls, hydrides, alkyl.hydr-ides, and alkylhalides, such as alkyllithium c~ounds, dialkylzinc ~otu~ds, trialkylboron compounds, trialkylaluminum cc~po~ux3s, alkylaluminum halides and hydrides, arr3 tetraalkylgermanium onds. Mixtures of the oo-catalysts may also be employed. Specific examples of useful co-catalysts include n-Lxxtyllithium, diethylzinc, di n prapylzinc, triethylbomn, triethylaluzai.num, triisokutylalumi.rnun, tri-n-hexylahmtiin~n, ethylahm~i~n dichloride, dib~nide, and dihydride, isobutyl alimtirnun dichloride, dibrornide, arid dihydride, diethylaluminum chloride, bromide, and hydride, di-n-propylaluminum chloride, hromide, arid hydride, diisobutylaluminum chloride, bromide and hydride, tetramethylgPrman i tan, and tetraethylgPr~n i tun. Organcenetallic co-catalysts which are preferred in this invention are C~a~zp IIIB
metal alkyls and dialky7halides having 1 to about 20 carbon atoms per alkyl radical. Mare preferably, the oo-catalyst is a trialkylaluminum d having 1 to 6, preferably 1 to 4 carbon at~ans 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 4, 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 oo-catalyst is employed in an apt which is at least effective to pate 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 oo-catalyst are employed per part, by weight, of the V ar Ti in the catalyst -13 - 2~~~961 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 activatar suitable for activating the ziraonimn sites is distinLrt fray the co~m~entional activators described above.
The ziiroo~iwn sites activator is a linear and/or cyclic alumihoocane species pr~ared frcria the interaction of R3A1 and water, where R is a C1 - C~ alkyl, with the amount of water controlling the average molecular weight of the aluminoxane molecule. As is Jmaan to those skilled in the art, the rate of ackliti~ of tt~e water to R3Al, the concentration of the R3A1 and water, and the temperature of the reaction may control catalyst pzroperties, sudr'as catalyst activity, molecular,weight and nalecular weight distribution of the polymers made with the ~talyst having its zirc~iiaa sites activated with the zirconimn sites activator.
The zirconiwn sites activator is preferably an aha~nrn~ne of the formula R
~'°_ ~1~7.~°) ri ~1R2 four a linear alwninoxar~e, where n is 0, 1, 2 or 3, and/or (Al (R) -0~
far a,cyclic aluminoxane, wherein m is an integer frcam 3 to 50, a~ R for both the linear and fine cyclic aluminoxane is the same or different linear, branched or cyclic alkyl group of 1 - 12 carboys, swch as methyl, ettryl, prc~yl, butyl, isobutyl, ill, decyl ar dodecyl~ Each of the aluminoxane com~u~ds may voa~t2~in different R groups and mixtures of the alumihoxane ca~po~u~ds may also be used.
a The most preferred activator for the zirconium sites is methylalumirnm~o~car~e. Sinve the ocrmnercially-available methylahani~oocane is believed to contain trimethylaluminum, in the most preferred embodiment tl~ addition of such a oo~nnercial ~Y~.umi~no~cane to the catalyst precursor is sufficient to activate both the zirconium sites and the titanium and/or vanadiW n sites.
~talyst precursors of the present irnrention are in the substantial abser~oe of water; oxygen, and other ~talyst poisons: Such catalyst poisons can be excluded during the catalyst preparation steps by ar~y well lam methods, e:g., bY ~'Y~! ~ ~ ati.o~n under an atmosphere of nitrogen, argon or attier inert 9~. ~ inert ,gas put~ge can serve the dual p~pose of excludiryg external coiataininants during the Preparation and r~maving undesirable reacti~ by-products resulting from the preparation of catalyst precursor. Purification of the solvent e~loyed in the catalyst synthesis is also helpful in this regard.
The far' may be activated in situ by adding the ~~ and the mixture of the activators separately to the polymerization mediwn. It is also possible to carbine the ~ar and the activators before the introduction thez°eDf into ~ pal~~,zation medium, e.g., for up to about 2 hours prior to the introductioa~ thereof irito the polymerization medium at a tune of fran about _40 to about 100°C.
Olefins, especially alpha--olefins, are polymerized with the catalysts pr~ared aooomdi.ng to the present invention by any ~~le process: S~h processes include polymerizations carried out in suspension; in solution; or in the gas phase. Gas phase polymerization reactions are preferred, e.g., those taking place ~ a ~ and, especially, fluidized bed reactars.

~fl429~~.

Because of the uniqe~e nature of the catalyst of this invention, relatively low amo~~nts of hydrogen are added intentionally to the reaction medium during the polymerization reaction to ooaztrol moleGVlar weic~t of the polymer product.
Typical hydrogen (H2): ethylene (C2 ) molar gas phase ratios in the reactor are between about 0.01 and abort 0.2, preferably chart 0.02 to about 0.05. The reactiari te~erature is about 70 ~, 100°C, residence time is about l to about 5 hours, and the a~ma~u~.s of olefins used in the reactor are such that the ethylene partial a in the reactar~ is about 50 to about 250 hsi. ~Ylene aloe or in oonjunctiari with higher alpha-olefins is polymerized. At these polymerization process condithons polymers having multimodal molecular weight thstribution are obtained. The polymerizatioa~ carried out in a sirygle polymerizathon reactor in the p~esenoe of the catalyst of this invetnthon ~ polymers having bimodal molecular weight distribution, having polymer chains whose molecular weight ranges from about 1,000 to about 1,000,000. Without whshing to be bound ' by any theory of operability, it is believed that the bimodal molecular w~ehght distribution is obtained because the zirconium (Zr) catalytic sites under certain polymerization conditions, h.e:, the amo~mts of hydrogen specified herein, pmduae relatively short polymer dzains, having relatively low molecular weight: In c~txast the titaniwn (Ti) and/or vanadium (V) catalytic sites, undex the same polymerization conditions, pzroduoe relatively lomg polymer drains, of relatively high molecular weight. The polymer product, therefore, contains bath types of polymer drains, resulting in the mu7.timodal molecular The mu7.timodal molecular weight distribution is important because the resins having such 2~4~961 molecular weight distritutio~n are relatively easily processed, e.g., in an extruder, and because such resins produce films having good strength proppxties.
The molecular weight distribution of the polymers p~aZ~ed in the p~esenoe of the catalysts of the p~sent inccrentiaa~, ~ ~~ ~ melt flaw ratio (1~'R) values, varies fraa about 50 to about 300, preferably about 100 to about 200 for medium density polyethylene (1~PE) products having a ~i~ of about 0:930 to abaft 0.940 g/oc, arid an I2 (melt ) of 0.01 to about 1 g/10 min: Cbn~xsely, I~PE
~. ~ with the catalysts of this in~ntiari, have a density of about 0.940 to about 0:960 g/oc, flow index (I21)' of about 1 to about 100, preferably about 4 to about 40, 1~'R values of about 50 to about 300, preferably about 100 to abaft 200. As is la~aan to those skilled in the art, at the aforementioned flora 'values, these 1~'R values~are indicative of a relatively b~oa~d molecular weight distribution of the polymer. As is elso lo~aan to those skilled in the Wit, such 1~R values are indicative of the polymers specially suitable for high density polyethylene (I~PE) film arid blaa molding applications. The gel permeation ~y (~) trays of polymers produced with the mixed metal catalyst of this inventi~ show bn~oad and bimodal molecular w~aight distributiah (1~1D) : The de~tai.ls of ttie 1~1D are controlled by catalyst vompositiari arid reaction vo~ditions. The bimodal 1~1D
be'exploited to pmodcoe the proper balance of merhanic~7.
pip; ~ p~ooes.,gabirity:
The catalysts pared aoooxdi~ to the present invention are highly active arid may ~~ the activity of at least about l.o too about 10.0 kilograms of polymer per gram of catalyst per 100 psi of: e~thyler~e in about 1 hour.

Zhe linear polyethylene polymers prepared in accordance with the present invention are homapolymers of ethylene ar-oopolymers of ethylene with one or more C3-C10 alpha-°lefins' 'mss. ~lY~ having two moncmPxic units are possible as well as terpolymers having three moncaneric units. Particular examples of such polymers include ethylene/propylene copolymers, ethylene/1-butane copolymers, ethylene/1-hexane copolymers, ethylene/1-octane copolymers, ethylene/4~nethyl-1 pentane copolymers, ethylene/1-but~ne/l~exene texpolymers, ethylene/propylene/1-hexane terpolymers and ethylene/pmpylene/1-k~ztene terpolymers. Ethylene/1-hexane is the most preferred copolymer polymerized in the process of and with the catalyst of this invention.
'Ihe polyethylene polymers produced in accordance with the present invention preferably contain at least about 80 percent by weic~t 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 de'saibed by Levine et al, U.S. Patent No. 4,011,382, Karol_et al, U.S. Patent 4,302,566 and by Nowlin et al, U.S. Patent 4,481,301. The polymer produced in such a reactor cor~tains the catalyst particles because the catalyst i.s not separated frcan the polymer.
'Ihe following ales illustrate the invention.
~e properties of the polymers produced in the ales arid any calculated process parameters were determined by the following test methods:

-1~ - 2~~2~~6~.
Density: AS~I D 1505 A plaque is made and conditioned for one hour at 100°C to approach equilibrium crystallinity.
Measur~aeat far density is then made in a density gradient cohutai; reported as gue;/oc.
Melt Irydex (1~) ~ I2: AS'~i D-1238--Oondition E--Measured at 190°C-reported as ~an~ per 10 minutes.
High Load Melt Irydex (HIl~) . I21. ASIM D-1238--Condition F--Measured at 10 times tl~ weight used in tl~ melt index test above.
Melt Flow Ratio (MFR)=I21/I2 Productivity: A sample of the resin p~duct is asked, and the meight percent of ash is determined; since the ash is substantially coal of the catalyst, 'the prod~tivity is thus the pads of polymer psroduoed per pow~d of total catalyst ooa~sumed: The amount of Ti, Mg. V an Al in the ash is determined by elemental analysis.
F~(~LE 1 ~(CatalVSt Precursor Syr~esisJ~
All procedures were performed under a dry nitrogen atmosphere.
9pIl~ION (A) : 0.317 groans of zirconium dicyclopentadienyl dichloride (Cp2ZrC12) was transferred to a 100 ~, f~ ~ then 50 mls of dry toluene were added.
flask was placed into a 50°C oil bath until a clear solution was formed:
gp~pN (B): 50 mls of dry toluene and 12 mls of methylalum3rnm~oocane (MAID) (4.6 wt% A1 in toluene) were added to a 200 cc pear flask. The pear flask was placed into an oil bath set to 50°C. Next, 20 mls of solution (A) was added to the pear flask to yield a clear light yellow solution.
CYST fREPARATIC~1 90IlJFION: 10.095 grams of Davison Cynical ~a~apany'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 oc pear flask cantainirg a etic stirring bar., the flask was placed into a 80°C oil bath and 50 mls of dry toluene was added to the flask. Next, 7.2 mls of dibutylmagnesium (0.973 1/~~ ~ ~ ~e silica/toluene slurry. The contents of the- flask w~exe stirred for 50 minutes. den, p,80 mls of neat ~taniwin tetrachloride was added to the flask. The slurry turned a dark blown color and stirring was- oo~xtirn~ed far 60 mirn~tes.
Finally, the eWire oo~ntems of solution (B) ~ siphohed into the catalyst preparation flas)c, arid the slurry was stirred for 60 .~~ all solvents were removed by evaporation under a nitrogen purge. Catalyst yield was 12.805 of a dark-b~ac~m free-flaaing powder.
F.~~AI~'i~ 2 .(~3~'iza~ion Process) An athylene~l-hexane copolymer, was prepares with the catalyst fox of Ele 1 in the following representative A 1.6 liter stainless steel autoclave, maintained at about :50°C, was filled with 0.750 literss of dry he~car~e, 0.030 liters of dry 1-he~cene, and 5.1 mmols of methylalwnirnunoxane (1~D) while under a slag nitrogen purge. The reactor was closed, the stirring rate was set at about 900 rpm, the internal attire was increased to 70°C, and the internal pressure was raised fran 8 psi to ll psi with hydrogen. Ethylene was int~roduoed to maintain the pressure at about 114 psi. Next, 0:0349 gr~ of the Fle 1 catalyst precursor was introduced into the reactor with ethylene over pressure and the te~erature Was increased and held at 85°C. The polymerization was cantirn~ed for 60 minutes, arid then the ethylene supply was s~t~ed and the rector allowed to cool to rocen temperature. 110 grams of polyethylene wexe collected.
The Nd~ID of the polymer was examined by GPC, and the results clearly showed that the polymer had a bimodal 1~5~1D (Figure 2) .
F~~LE 3 ~Catal~st Pr~ursor Synthesis) 191.4 grams of Davison grade 955 silica which was previously dried at 600°C for 16 hours was added to a nitrogen pied, 4-neck, 3-liter round-bottcen flask fitted with an overhead stirrer. Toluene (800 mls) was added to the flask and the flask was placed into an ail bath maintained at 60°C. Next, 129 mls of dibutyiwn (1.04 Molar solution in heptane) was added to the silica/toluene slurry. The solution was stirred for 35 minutes. Then, 15.0 mls of neat TiCl4 was diluted with 50 mls of dry toluene and added to the flask. The solution was stirred for 60 mirmtes. Finally, 93 mls of methyl aluminoxane (4.6 wt%
A1) and 2.41 g of Cp2ZrCl2 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 t.~erature was i.nGreased 'to 80-85°C.
The slurry was heated far 3 hours. After this time, the oil bath te~erature was lowexed to 50°C and stirrixig was stopped to allay the silica to settle. The supernatant liquid was decanted and the silica was washed three times with 1500 mls of dry hexane. The silica was dried under a nitrogen purge to yield about 233 of dry, free-flowing powder.
E~A,T~~'LE 4 SPol~m~rization Pmoess) The catalyst precursor v~sition of ale 3 was used to prepare an ethylene/1 hexane co-polymer in a fluid bed, pilot plant reactor operated substantially in the manner dislosed by F-5629 L 20~~9~~

Nowlin et al, U.S. Patent 4,481,301. A steadystate operation was obtained by contirnmusly feeding the catalyst precursor, 1~0 activator, and reactant gases (ethylene, 1-l~xene and hydrogen) to the reactor while also continuously withdrawing polymer product from the reactor. The reactor operating conditions were as follows:
Ethylene 210 psi (C6:/C2 ) vapor mole ratio 0.039 (Ii2/C2 ) vapor mole ratio 0.050 Production Rate 24.9 lbs/hr Catalyst Productivity 3000 grams polym x/cpn catalyst Resic~enoe Time 2.5 twhrs ~ 90C

1~0 feed 270 mls/hr (1.0 wt%

Al in toluene) The polymer had the following properties:
Density 0. 942 c, fms/cc Flaw Index (I21) 16.3 c~ns/lo min The molecular weight distribution of the polymer was exaomined by GPC and the results clearly showed that the polymer had a bimodal I~7D (Figure 3).

Claims (11)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An olefin polymerization catalyst precursor composition supported on a porous carrier containing active OH groups comprising:
i) a magnesium compound soluble in the organic solvent employed for the preparation of the catalyst precursor composition and capable of being deposited onto the carrier containing the active OH groups;
ii) a zirconium compound of the formula:
Cp mZrY nX(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 represents a halogen atom, a C1-6 alkyl group or a hydrogen atom; and n represents 0 or 1;
iii) a titanium compound and/or a vanadium compound;
wherein, during the preparation of the catalyst precursor composition, the titanium compound and/or vanadium compound is added prior to the zirconium compound.

2 . A precursor composition according to claim 1 wherein the magnesium compound has the formula:
Mg(OR)2, R1 mMgR2n or R3k MgX(2-k) wherein R, R1, R2, and R3, which may be the same or different, each represent an alkyl group X a halogen atom; and k, m and n each represent 0, 1 or 2, providing that m + n equals the valency of Mg.

3. A precursor composition according to any preceding claim wherein the titanium compound comprises a titanium halide, a titanium oxyhalide, or a mixture thereof and the vanadium compound comprises a vanadium halide, a vanadium oxyhalide, or a mixture thereof.

4 . A precursor composition according to any preceding claim which has a Ti:Zr molar ratio from 1:1 to 50:1.

. A precursor composition according to any preceding claim which additionally comprises an alcohol of the formula R-OH; a ketone of the formula RCO-R1; an ester of the formula RCOOR1; an acid of the formula RCOOH; or an organic silicate of the formula Si(OR)4, where R and R1, which may be the same or different, each represents a linear, branched, or a cyclic alkyl group of 1 to 12 carbon atoms.

6. A catalyst composition which comprises 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 or:

wherein:
m represents an integer from 3 to 50;
n represents zero or an integer gram 1 to 50; and R represents a linear, branched or cyclic C1 to C12 alkyl group.

7. A catalyst composition according to claim 6 wherein the co-catalyst Group IIIB metal alkyl or dialkylhalide having 1 to 20 carbon atoms per alkyl group.

8. A method of synthesizing an olefin polymerization catalyst precursor composition, which method comprises contacting a solid, porous carrier containing active OH
groups with a magnesium compound that is soluble in the organic solvent employed for the preparation of the catalyst precursor composition and capable of being deposited onto the carrier containing the active OH groups; a zirconium compound of the formula:

Cp mZrY nX(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 represents a halogen atom, a C1-6 alkyl group or a hydrogen atom; and n represents 0 or 1;
and a compound selected from the group consisting of titanium compounds, vanadium compounds and mixtures thereof, wherein the titanium compound and/or vanadium compound is added prior to the zirconium compound.

9. A process of polymerizing at least one C2 to C10 alpha-olefin to produce a polymer had a multimodal molecular weight distribution, which process comprises conducting the polymerization in the presence of a supported catalyst composition as defined in claim 6 or 7.

10. A process according to claim 9 wherein the alpha-olefin feed comprises a mixture of ethylene and at least one C3 to C10 alpha-olefin.

11. A process according to claim 9 or 10 which is conducted in the presence of such amounts of hydrogen that the molar ratio of hydrogen: ethylene is from 0.01 to 0.2.