WO1997024380A1

WO1997024380A1 - High efficiency catalyst systems

Info

Publication number: WO1997024380A1
Application number: PCT/US1996/020609
Authority: WO
Inventors: Donald E. Gessell; Leonard V. Cribbs
Original assignee: Lyondell Petrochemical Company
Priority date: 1995-12-28
Filing date: 1996-12-24
Publication date: 1997-07-10
Also published as: AU1567297A

Abstract

A catalyst system containing a magnesium siloxide support and a catalyst on the support exhibits high activity. The invention is further drawn to a catalyst system composition containing a halogenating agent and the catalyst system. The catalyst of the catalyst system is a mixture of two organometallic compounds. One of the organometallics is of the formula M(R)x, wherein M is titanium, vanadium, chromium or zirconium; x is 3 or 4; and each R is independently selected from halogen, a C1C20 alkyl, C1 to C20 alkoxide; or an amide. The second organometallic is a mono-, bi- or tricyclopentadienyl or substituted cyclopentadienyl metal compound represented by the general formula: (C5R1m)pR2s(C5R1m)M1Q3-p; and R2s(C5R1m)2M1Q1 wherein (C¿5R?1m) is a cyclopentadienyl or substituted cyclopentadienyl; each R1 is the same or different and is hydrogen or a hydrocarbyl radical such as alkyl, alkenyl, aryl, alkylaryl or arylalkyl radical containing from 1 to 20 carbon atoms or two carbon atoms are joined together to form a C¿4?-C6 ring; R?2¿ is a C¿1?-C4 alkylene radical, a dialkyl germanium or silicon or an alkyl phosphine or amine radical bridging two (C5R?1¿m) rings; Q is a hydrocarbyl radical such as aryl, alkyl, alkenyl, alkylaryl or arylalkyl radical having from 1-20 carbon atoms or halogen and can be the same or different; Q1 is an alkylidene radical having from 1 to about 20 carbon atoms; s is O or 1; p is O, 1 or 2; provided that when p is O, s is O; m is 4 when s is 1; m is 5 when s is O; at least one R1 is a hydrocarbyl radical when Q is an alkyl radical and M1 is a Group 4b, 5b or 6b metal.

Description

TITLE: HIGH EFFICIENCY CATALYST SYSTEMS

SPECIFICATION

Field of the Invention

This invention relates to a catalyst system containing a mixture of organometallic compounds, one of which is a metallocene, on a magnesium siloxide support. In practice, the catalyst system is used in combination with a halogenating agent. The combination of catalyst system and halogenating agent is referred to as the catalyst system composition. The catalyst system comprises a magnesium siloxide support and a catalyst which is a mixture of (1) a compound of the formula M(R)_X wherein M is titanium, vanadium, chromium or zirconium; x is 3 or 4; and R is halogen, a C,-C₂₀ alkyl, a C₁-C₂₀ alkoxy, a C,-C₂₀ siloxy group or an amide containing from 1 to 20 carbon atoms; and (2) derivatives of mono, bi or tricyclopentadienyl coordination complexes with a Group 4b, 5b or 6b metal. Background of the Invention

Until relatively recently, polyolefms have been made with conventional Ziegler catalysts. For example, polyethylene has been made using such

Ziegler catalysts as titanium trichloride and diethylaluminum chloride as well as a mixture of titanium tetrachloride, vanadium oxytrichloride and triethylaluminum.

While Ziegler catalysts are inexpensive, they have low activity and thus must be used at high concentrations. As a result, it is often necessary to remove catalyst residue from the resulting polymer. Such removal adds to production costs. Neutralizing agents and stabilizers must further be added to the polymer to overcome the deleterious effects of the catalyst residue. Failure to remove catalyst residue leads to polymers having a yellow or grey color and poor ultraviolet and long term stability. Furthermore, Ziegler catalysts produce polymers having a broad molecular weight distribution, which is undesirable for some applications such as injection molding. Catalysts that exhibit very high activity are therefore desirable since they can be used at low concentrations.

The polyethylene manufacturing industry has therefore advanced towards the use of metallocene containing catalysts. Such catalysts typically contain a transition metal compound which has one or more cyclopentadienyl ring ligands. Metallocene catalysts typically produce polymers of high molecular weight and narrow molecular weight distribution. Further, metallocene catalysts exhibit high activity. Catalyst residues therefore need not be removed from the polymer. While the metallocene catalysts of the prior art are higher in activity than Ziegler catalysts, the need continues to develop catalyst systems which exhibit even higher activity. Although much improvement has been observed with metallocene catalysts, deficiencies are still observed in catalysts of the prior art. In general, metallocene catalysts of the prior art render polymers which exhibit poor powder morphology. Further, they often produce fouling in the polymerization zone. Fouling is detrimental to the process since heat transfer is lost and the reactors typically must be shut down for a difficult cleaning process. Similarly, catalysts of the prior art also produce polymer particles of very small size. These small particles can also lead to poor heat transfer and are difficult to handle in slurry and gas-phase processes. It is also desirable to produce polymers over a wide molecular weight range for product such as film or bottles to injection molded articles. Typically, more than one catalyst is required to produce a wide range of molecular weights, but with the catalyst of the present invention, the addition of hydrogen to the reactor allows for the production of polymer over a very wide range of molecular weights. Typically, metallocenes require the use of very expensive co-catalysts such as methylalumoxane (MAO) to achieve desirable properties such as high activity. With the catalyst of the present invention, extremely high activity is observed with inexpensive co-catalysts such as triethylaluminum. Optionally, even higher activity can be observed with MAO if this is desired. Summary of the Invention The invention is drawn to a catalyst system containing as catalyst a mixture of two organometallic compounds, one of which is a metallocene. The first compound is of the formula:

M(R)- (I)

wherein M is titanium, vanadium, chromium or zirconium; x is 3 or 4; and R is independently selected from the group consisting of halogen, a C₁-C₂₀ alkyl, a

C C₂₀ alkoxy group, a C^C_jo siloxy group and an amide containing from 1 to

20 carbon atoms.

The second organometallic of the catalyst is a metallocene. The metallocene, an organometallic coordination complex, is a cyclopentadienyl derivative of a Group 4b, 5b or 6b metal of the Periodic Table. The metallocene includes those compounds represented by the general formulae

(C₅R¹ _m)_pR² _s(C₅R¹ M¹Q₃._p (II); and

wherein M¹ is a Group 4b, 5b or 6b metal of the Periodic Table, C₅R _m is a cyclopentadienyl or substituted cyclopentadienyl, each R\ which can be the same or different, is hydrogen or a hydrocarbyl radical such as alkyl, alkenyl, aryl, alkylaryl or arylalkyl having from 1 to 20 carbon atoms or two carbon atoms are joined together to form a C₄-C₆ ring, R² is a C_rC₄ alkyiene radical, a dialkyi germanium or silicon, or an alkyl phosphine or amine radical bridging two (C₅R¹ _m) rings, Q is a hydrocarbon radical such as aryl, alkyl, alkenyl, alkylaryl, or arylalkyl radical having from 1 to 20 carbon atoms or halogen and can be the same or different, Q¹ is an alkylidene radical having from 1 to about 20 carbon atoms, s is 0 or 1 , p is 0, 1 or 2; when p is 0, s is 0; m is 4 when s is 1 ; and m is 5 when s is 0 and at least one R¹ is a hydrocarbyl radical when Q is an alkyl radical.

The catalyst systems of the invention exhibit an activity which is five to six times higher than the activity exhibited by a catalyst system containing only the metallocene compound as catalyst. In other words, the presence of the (first) organometallic compound of the formula M(R)₄ synergistically enhances the activity of the metallocene compound of the catalyst of the catalyst system. Brief Description of the Figure

Fig. 1 illustrates the secondary activation period exhibited by the catalysts of the invention. Description of the Preferred Embodiments

The catalyst system of the invention contains two organometallic compounds as catalyst and a magnesium siloxide support. In practice, the catalyst system is used in conjunction with a halogenating agent. (The catalyst system and halogenating agent is herein referred to as the "catalyst system composition".)

The catalyst of the catalyst system of the invention is a mixture of two different organometallic compounds; one of which is a metallocene. The first metallic compound has the general formula:

M(R)_X (I)

wherein M is titanium, vanadium, chromium or zirconium; preferably titanium, vanadium, or zirconium; and most preferably titanium. Further, x is 3 or 4 and each R of the formula is independently selected from the group consisting of halogen (preferably chlorine or bromine, most preferably chlorine); a CΓC-_JO alkyl group, preferably a C,-C₁₀ alkyl, most preferably a C_rC₆ alkyl group; a C₇-C₂₀ alkaryl or aralkyl group preferably a 0,-0,₅ group such as benzyl and neophyl; an alkoxy group of the formula OR³ wherein each R³ is independently selected from a C,-C₂₀ alkyl group, preferably a C C,₀ alkyl, most preferably a C,-C₄ alkyl group; a silyl or siloxy group of the formula -SiR³ wherein each R³ is independently selected from hydrogen or a C,-C₂₀ alkyl, preferably a C_rC₁₀ alkyl, most preferably a C,-C₄ alkyl group; and an amide group of the formula CONHR" wherein R⁴ is a 0,-0₂-. alkyl group, preferably a C,-C,₀ alkyl, most preferably a C,-C₄ alkyl group. Specific examples of the first organometallic compound of the catalyst system of the invention are titanium tetrachloride, titanium tetraisopropoxide, tetramethyl titanium, tetra-n-butyl titanium, tetraisopropyltitanate, tetra-n- butyltitanate, tri-n-butyl vanadate, tera-n-propylzirconate and tetra-n- butylzirconate as well as such vanadyl halides as VCI₃ and VCl₄ and dialkoxyvanadium dihalides. Further, mixtures of any of these compounds may further be used.

Particularly preferred as the R group of the first organometallic compound are chlorine and those alkoxy substituents of the formula OR³ where R³ is a C, to C₅ alkyl group; isopropoxide and chlorine being particularly preferred. The second organometallic member of the catalyst system of the invention is one which contains π-bonded ligands, preferably a mono, bi or tricyclopentadienyl or substituted cyclopentadienyl metal compound. Such compounds may be represented by the general formulae:

(C₅R¹ _pR² _s(C₅ ¹ _m)M¹Q₃._p (II); and

wherein

(C₅R¹ is a cyclopentadienyl or substituted cyclopentadienyl; each R¹ is the same or different and is hydrogen or a hydrocarbyl radical such as alkyl, alkenyl, aryl, alkylaryl or arylalkyl radical containing from 1 to 20 carbon atoms or two carbon atoms are joined together to form a C₄-C₆ ring;

R² is a C,-C₄ alkyiene radical, a dialkyi germanium or silicon [such as silyl or a compound of the formula -SiR₃ wherein each R₃ is -H, a 0,-0,₀ (preferably a C,-C₄) alkyl group, an aryl such as benzyl or phenyl or a benyzl or phenyl group substituted with one or more C,-C₄ alkyl groups] or an alkyl phosphine or amine radical bridging two (C₅R _m) rings;

Q is a hydrocarbyl radical such as aryl, alkyl, alkenyl, alkylaryl or arylalkyl radical having from 1-20 carbon atoms or halogen and can be the same or different,

Q¹ is an alkylidene radical having from 1 to about 20 carbon atoms, s is 0 or 1 ; provided that when p is 0, s is 0; m is 4 when s is 1 ; m is 5 when s is 0; at least one R¹ is a hydrocarbyl radical when Q is an alkyl radical and

M¹ is a Group 4b, 5b or 6b metal, preferably Ti or Zr, most preferably Ti.

Such compounds are disclosed in U.S. Patent No. 5,324,800, herein incorporated by reference.

Of the metallocenes, zirconocenes and titanocenes are most preferred. Illustrative but non-limiting examples of these metallocenes are monocyclopentadienyl titanocenes such as cyclopentadienyl titanium trichloride, pentamethylcyclopentadienyl titanium trichloride; bis(cyclopentadienyl) titanium diphenyl, the carbene represented by the formula Cp₂Ti=CH₂-AI(CH₃)₂CI and derivatives of this reagent such as Cp₂Ti=CH₂-AI(CH₃)₃, (Cp₂TiCH₂)₂,

Cp₂TiCH₂CH(CH₃)CH₂, Cp₂Ti=CHCH₂CH₂, and

Cp₂Ti=CH₂'AIR'"₂CI wherein Cp is a cyclopentadienyl or substituted cyclopentadienyl radical and R'" is an alkyl, aryl or alkylaryl radical having from 1-18 carbon atoms; substituted bis(Cp)Ti(IV) compounds such as bis(indenyl)Ti diphenyl or dichloride, bis(methylcyclopentadienyl)Ti diphenyl or diahalides and other dihalide complexes; dialkyi, trialkyl, tetraalkyl and pentaalkyl cyclopentadienyl titanium compounds such as bis(1 ,2- dimethylcyclopentadienyl)Ti diphenyl or dichloride, bis(1 ,2- diethylcyclopentadienyl)Ti diphenyl or dichloride and other dihalide complexes silicone, phosphine, amine or carbon bridged cyclopentadiene complexes such as dimethyl silyldicyclopentadienyl titanium diphenyl or dichloride, methyl phosphine dicyclopentadienyl titanium diphenyl or dichloride, methylenedicyclopentadienyl titanium diphenyl or dichloride, ethylene bis(4,5,6,7-tetrahydroindenyl) titanium dichloride and other dihalide complexes and the like.

Illustrative but non-limiting examples of the zirconocenes which can be employed in accordance with this invention are cyclopentadienyl zirconium trichloride, pentamethylcyclopentadienyl zirconium trichloide, bis(cyclopentadienyl)zirconium diphenyl, bis(cyclopentadienyl)zirconium dimethyl, the alkyl substituted cyclopentadienes such as bis(ethyl cyclopentadienyl)zirconium dimethyl, bis(β-phenylpropylcyclopentadienyl) zirconium dimethyl, bis(methylcyclopentadienyl) zirconium dimethyl and dihalide complexes of the above; dialkyi, trialkyl, tetraalkyl, and pentaalkyl cyclopentadienes such as bis(pentamethylcyclopentadienyl)zirconium dimethyl, bis(1 ,2-dimethylcyclopentadienyl)zirconium dimethyl, bis(1 ,3- diethylcyclopentadienyl)zirconium dimethyl and dihalide complexes of the above; silicone, phosphorous, and carbon bridged cyclopentadiene complexes such as dimethylsilyldicyclopentadienyl zirconium dimethyl or dihalide, methylphosphine dicyclopentadienyl zirconium dimethyl or dihalide and methylene dicyclopentadienyl zirconium dimethyl or dihalide, carbenes represented by the formulae Cp₂Zr=CH₂P(C₆H₅)₂CH₃ and derivatives of these compounds such as

In a preferred embodiment, the second organometallic of the catalyst system may be described by the formulae (II) and (III) above wherein p is 0 or 1 and R² is independently selected from the group consisting of methylene, ethylene, 1 ,2-phenylene, dimethyl silyl, diphenyl silyl, diethyl silyl and methyl phenyl silyl. Examples of alkyl substituted (C₅R¹ _m) rings include cyclopentadienyl, butyl cyclopentadienyl and methyl cyclopentadienyl. Particularly preferred as the second organometallic of the catalyst system of the invention is dicyclopentadienyl titanium dichloride and cyclcopentadienyl titanium trichloride. The mixture of the two organometallic compounds consist of about 1 to about 99 wt% of the first organometallic to about 99 to about 1 wt% of the (second) metallocene. The preferred mixture is about 25 to about 75 wt% of the first organometallic to about 75 to about 25 wt% of the metallocene. Especially preferred is the ratio of about 40 to about 60 wt% of the first organometallic and from about 60 to about 40 wt% of the metallocene. The magnesium siloxide catalyst support and its preparation are described in U.S. Patents Nos. 4,518,706 and 4,699,961, herein incorporated by reference. The magnesium siloxide catalyst support has the general formula

wherein each R⁵ is independently selected from hydrogen; halogen (preferably chlorine or bromine, most preferably chlorine); a O,-C₂₀ , preferably a C, to C,₀, alkyl group, preferably a C,-C₆ alkyl, most preferably a C,-C₄ alkyl group; a C₄ to C₂₀, preferably a C₄-C,₀, cycloalkyl ring; a radical containing an aryl ring, optionally substituted with one or more C,-C_β alkyl groups; and an alkoxy group of the formula OR⁶ wherein R⁶ is a C,-C₂₀ alkyl group, preferably a C,-C,₀ alkyl, most preferably a C,-C₆ alkyl group, each of which can be further substituted with one or more chlorine or bromine atoms.

Further, "n" is 0 or greater and refers to the average of the

units. While varying from molecule to molecule, averages for n typically are between about 0.05 to about 50, preferably between from about 0.1 to about 5.

Preferably, each R⁵ is independently selected from hydrogen, alkyl, silyl and chloride.

The magnesium siloxide support can be prepared by reacting a polysiloxane or silanol, such as polymethylhydrosiloxane, with a dialkyi magnesium compound, such as dibutylmagnesium or butylethylmagnesium. The reaction is exothermic and is allowed to proceed up to a temperature of about 70° C. The support is prepared so that its silicon to magnesium atomic ratio is such that substantially all of the dialkyi magnesium compound is converted into magnesium siloxides. Typically, the atomic ratio of Si to Mg in the magnesium siloxide catalyst support is between about 0.5 to about 20, preferably from about 2:1 to about 10:1. Especially preferred is a ratio of about 5:1. Polyolefins produced in the presence of catalyst systems containing such magnesium siloxide supports exhibit an improved hydrogen response producing higher melt index polymers, greater comonomer incorporation and greater catalyst activity. Lower atomic ratios of Si:Mg of 0.5:1 are detrimental to catalyst efficiency of the resulting polyolefin. In addition, the expressed atomic ratio of Si:Mg serves to increase the concentration of metallocene which is adfixed to the magnesium siloxide support.

The catalyst system of this invention may further be combined with a halogenating agent to create the catalyst system composition. The halogenating agent reacts with the magnesium siloxide to form a magnesium containing reaction product which is insoluble in hydrocarbons.

Representative but non-exhaustive examples of halogenating agents useful in the present invention are agents of the formula (R⁶)₃._qAI(CI)_q wherein q is 1 to 2 and R⁶ is hydrogen or a C,-C₂₀ alkyl group, preferably a C, to C₄ alkyl group (preferably methyl, ethyl, or isobutyl) as well as SnCI₄, SiCI₄, HC1 , HSiCI₃, aluminum trichloride, ethylboron dichloride, boron chloride, diethylboron chloride, HCCI₃, methyl trichlorosilane, phosphorous trichloride, phosphorous oxytrichloride, acetyl chlorides, thionyl chloride, sulfur chloride, vanadium oxytrichloride, vanadium oxytetrachloride and dimethyl dichlorosilane.

Preferred are methylaluminum dichloride, methylaluminum sesquichloride, isobutylaluminum dichloride, isobutylaluminum sesquichloride, ethylaluminum dichloride, diethylaluminum chloride and ethylaluminum sesquichloride. Most preferred are diethylaluminum chloride and ethylaluminum dichloride.

The amount of support, catalyst and halogenating agent are chosen such that the atomic ratio of Mg:M+M¹ in the catalyst system is from about 1 to about 50, preferably from about 5 to about 20, when the halogenating agent does not contain a transition metal and is from about 0.1 to about 100 when the halogenating agent does contain a transition metal. The atomic ratio of halogen to magnesium (X:Mg) in the catalyst system is from about 1 to about 50, preferably from about 3 to about 12, when the halogenating agent does not contain a transition metal and is from about 0.4 to about 40, preferably from about 0.4 to about 20, when the halogenating agent does contain a transition metal.

The catalyst system of the invention may optionally contain an aluminum containing co-catalyst. Typically the co-catalysts for use in the invention are aluminum alkyls or alumoxanes. Representative but non- exhaustive examples of aluminum alkyl co-catalysts are those of the formula AI(R⁷)₃ where R⁷ independently denotes a C,-C₈ alkyl group, hydrogen or halogen. Such co-catalysts include triethylaluminum, trimethylaluminum and tri-isobutylaluminum. The alumoxanes are polymeric aluminum compounds typically represented by the cyclic formulae (R^β-AI-0)_s and the linear formula R^β(R"-AI-0)_tAIR^β wherein R⁸ is a C,-C₅ alkyl group such as methyl, ethyl, propyl, butyl and pentyl and s is an integer from 1 to about 20. Preferably, R⁸ is methyl and s is about 4. Representative but non-exhaustive examples of alumoxane co-catalysts are (poly)methylalumoxane (MAO), ethytalumoxane and diisobutylalumoxane. The preferred co-catalyst is MAO.

It is preferably not to premix the catalyst and the co-catalyst as this may result in lower catalyst activity. Rather, the catalyst and co-catalyst are preferably injected separately into the reactor containing the monomer(s) to be polymerized. The molar ratio of co-catalyst to the catalyst system of the invention may range from about 1 :1 to about 15,000:1 , preferably from about 1 :1 to about 1 ,000:1 , most preferably from about 5:1 to about 200:1. The concentration of co-catalyst is such that the AI:M+M' atomic ratio is from 0 to about 10,000. Where the co-catalyst is a trialkylaluminum, the AI:M+M¹ atomic ratio is preferably from about 5 to about 200. Slurry polymerization is particularly useful in such instances. When the co-catalyst is an alumoxane, the ALM+M¹ atomic ratio is generally from about 10 to about 1 ,000.

Catalyst system compositions having a halogen:Mg atomic ratio of 8:1 and a Si:Mg atomic ratio of about 2.1 to about 2.5 have been observed to produce, via slurry polymerization techniques, a polyolefin having broad molecular weight distribution. The catalytic efficiency of the catalyst system is very high.

Generally, catalyst system compositions employing higher atomic ratios of halogen:Mg (typically between about 8:1 to about 20:1) and a trialkylaluminum co-catalyst render polymers of broader molecular weight distribution. The use of lower atomic ratios of halogen:Mg (typically between about 2: 1 to about 6: 1 ) render polymers of narrower molecular weight distribution.

It further has been observed that polymers of narrow molecular weight distribution are produced by the catalyst system compositions of this invention when the halogenating agent is of the formula (R⁶)₃^AI(CI)_q or is a metallic halide, such as silicon tetrachloride (SiCI₄) or tin tetrachloride (SnCI₄). This is the case even where the atomic ratio of halogen to magnesium in the catalyst systems is high. Lastly, narrower molecular weight distribution is obtained in those polyolefins produced in the presence of catalyst system compositions having a low atomic ratio of halogen:magnesium, i.e. less than 8:1 (generally less than 3:1), and alumoxane co-catalysts.

The catalyst system compositions of the invention may further contain a sufficient amount of organic solvent to render them stirrable. Aliphatic C₄- 0,₂ hydrocarbons such as isohexane, isooctane, butane, and octane are preferred; isobutane, hexane, and heptane being especially preferred. When present, the solvent constitutes about 1 to about 99 wt%, preferably between from about 50 to about 99 wt. %, of the total weight of the catalyst system composition. In the most preferred embodiment, the catalyst system composition includes an organic solvent.

Normally, the magnesium siloxide support per se (without the solubilizing agent) is insoluble in organic solvent as is the combination of magnesium siloxide support and catalyst. While the halogenating agent per se is soluble in the organic solvent, the reaction product of the magnesium siloxide support with catalyst and halogenating agent is not soluble in the organic solvent. The solvent renders to the catalyst system a slurry consistency.

In order to more closely control the particle size distribution of the resulting polymer, the magnesium siloxide support may further be solubilized by a trialkylaluminum compound of the formula AI(R⁹)₃ wherein R⁹ independently is selected from hydrogen or a C,-C₈ alkyl or aryl group. Trialkylaluminum compounds are more preferred. Representative but non- exhaustive examples of solubilizing agent useful in the invention are triethylaluminum, tributylaluminum, triisobutylaluminum, diethylaluminum hydride, isopropylaluminum and trimethylaluminum.

The solubilizing agent may be added before or after the formation of the magnesium siloxide as well as during the formation of the magnesium siloxide. Preferably, the solubilizing agent is added before the formation of the magnesium siloxide. Normally, from about 0.02 to about 2, preferably from about 0.05 to about 0.5, moles of solubilizing agent per mole of magnesium siloxide is employed. The resulting solution is generally too viscous if less solubilizing agent is used.

Normally, the catalyst system compositions of this invention are prepared by contacting the (solubilized) magnesium silicon support with the (first) organometallic compound of the catalyst and then the metallocene compound. The resulting solution is then reacted with the halogenating agent. The reaction with halogenating agent may occur prior to introduction of the catalyst system composition to the polymerization reactor vessel. Alternatively, the solution may be reacted with the halogenating agent in the reactor in the presence of the polymerizable olefιn(s). In a preferred embodiment, the dialkyi magnesium compound is reacted with the siloxane or silanol to produce the magnesium siloxide support. This occurs at a temperature from about 25° C to about 30° C. After thoroughly stirring, the (first) organometallic component of the catalyst is added. The act of adding the halogenating agent to the catalyst system results in the formation of a solid, presumably MgCI₂. The metallocene catalyst systems of the invention are useful in the production of homo- and co- polymers of olefins. Preferred as olefins are ethylene, propylene, butene and octene. Most preferred as olefin is ethylene. The catalyst is particularly useful in the production of copolymers of ethylene and unsaturated monomers such as 1 -butene, 1-hexene, 1 -octene; mixtures of ethylene and di-olefins such as 1 ,3-butadiene, 1 ,4-hexadiene, 1 ,5- hexadiene; and mixtures of olefins and unsaturated comonomers such as norbornene, ethylidene norbornene, and vinyl norbornene.

The catalyst systems of the invention can be utilized in a variety of different polymerization processes. For instance, they can be used in a liquid phase polymerization process (slurry, solution, suspension, bulk or a combination), or gas phase polymerization process. The processes can be used in series or as individual single processes. The pressure in the polymerization reaction zones can range from about 15 psia to about 50,000 psia. The temperature can range from about 40°C to about 300°C. Gas phase and slurry polymerizations of olefins are typically conducted at about 70°C to about 105° C. Solution, suspension and bulk phase polymerizations of olefins is normally conducted at temperatures of about 150°C to about 300°C.

The catalysts of the present invention exhibit unusually high thermal stability, enabling their use over a very wide range of temperatures. Catalysts of the prior art usually are suitable for use in a single process such as slurry or solution since their activity or polymer products may only be suitable for the conditions of a given process. Due to the high thermal stability and hydrogen sensitivity of the catalysts of the present invention, they are suitable for use in slurry and solution processes, covering process temperatures of about 60° C to about 300° C.

The molecular weight of the resultant polymers can be controlled by utilizing hydrogen as is known in the art. In addition, molecular weight can be controlled by reactor temperature or a combination of hydrogen and reactor temperature in both slurry and solution polymerization processes. Normally, higher temperatures will reduce molecular weight, although this effect is seen more acutely in solution polymerization systems than in slurry polymerization systems.

A further distinguishing characteristic of the catalyst system composition of the invention is its ability to demonstrate a secondary activation period. Normally, catalysts used in the production of polyolefins exhibit their strongest activity when initially introduced into the reactor vessel. An ongoing decay in activity is then evidenced such that catalysts often need to be replenished during the polymerization process. It has been observed that the catalyst system compositions of the invention undergo a second period of activation in that a peak of increased activity occurs long after the introduction of the initial catalyst system into the polymerization reactor. This is illustrated in Fig. 1.

The following examples will illustrate the practice of the present invention in its preferred embodiments. The examples are provided to illustrate the invention and not to limit it. Other embodiments within the scope of the claims herein will be apparent to one skilled in the art from consideration of the specification and practice of the invention as disclosed herein. It is intended that the specification, together with the examples, be considered exemplary only, with the scope and spirit of the invention being indicated by the claims which follow.

EXAMPLES

All catalyst preparations were conducted either in a vacuum atmosphere glovebox filled with nitrogen treated to eliminate moisture and oxygen or using Schlenk type glassware using standard airless techniques and a nitrogen purge. The aluminum alkyls, ethylaluminum dichloride (EADC) in hexane, polymethylalumoxane in toluene (PMAO S2) and triethylaluminum (TEAL) in hexane, were obtained from Akzo Chemical. Dibutylmagnesium in heptane (DBM) was obtained from FMC Corp. and butylethylmagesium (BEM)/heptane was obtained from Akzo Chemical. Hexane, ethylene, butene, hydrogen and nitrogen were purified by passing over 13X Linde molecular sieves and Q-5 oxygen scavenger, a product of the Dow Chemical Company. Polymethylhydrosiloxane (PMHS) with a molecular weight of 2270 and 30 cSt viscosity was obtained from HύLs America. Titanocene dichloride, titanium tetrachloride and titanium isopropoxide (TiPt) were obtained from Aldrich.

The melt index (Ml) of the resulting polymers was measured according to ASTM D-1238, Condition E and Condition F. Ml is the melt index measured with a 2.16 kg weight (Condition E). HLMI is the melt index measured with a 21.6 kg weight (Condition F). MFR is the ratio of HLMI to Ml. Polymer density was measured according to ASTM D-1505. Catalyst efficiency is defined as the number of g of polyolefin per gram of Ti in slurry in one hour. Example 1

In a glovebox, 73.64 ml of 0.68 M DBM in heptane were added to a flask equipped with a mechanical stirrer. While stirring, 3.27 ml of a 1.53 M solution of TEAL were added to the flask. Using an addition funnel, 9.09 ml of PMHS and 14.00 ml of hexane were added dropwise to the solution in the flask. The addition rate was controlled to maintain a temperature of less than 75° C. The solution was then stirred for an extra 60 min. While stirring the solution, 0.12 g of titanocene dichloride were added yielding a dark blue solution. Using the addition funnel, 133.33 ml of 1.5 M EADC were added dropwise to the flask. The mixture was then stirred for 120 minutes. The mixture was then treated with 18.00 ml of 0.25 M titanium tetrachloride/ hexane and stirred 16 hours. The slurry contained 20.13 mM Ti; the molar ratio of Mg:Ti was 9.89; the molar ratio of Al.Ti was 38.95; and the molar ratio of Mg:AI was 0.25. The molar ratio of Ti in the resulting metallocene to the Ti in the slurry was 0.11. Example 2

In a glovebox, 73.64 ml of 0.68 M DBM in heptane were added to a flask equipped with a mechanical stirrer. While stirring, 3.27 ml of 1.53 M TEAL in heptane were added to the flask. Using an addition funnel, 13.64 ml of PMHS and 9.46 ml of hexane were added dropwise to the solution in the flask. The addition rate was controlled to maintain the temperature to be less than 75° C. The solution was then stirred for 60 minutes after the addition was completed. While stirring, 0.622 g of titanocene dichloride were added to the solution. Using an addition funnel, 100.0 ml of 1.5 M EADC were added dropwise to the flask. The mixture was next stirred for 120 minutes and 51.0 ml of hexane added. The mixture was then treated with 10.0 ml of 0.25 M TiCI₄/hexane and stirred for 16 hours. The resulting slurry was analyzed yielding 15.78 mM Ti. The molar ratio of Mg:Ti was 12.24. The molar ratio of AI:Ti was 34.21. The molar ratio of Mg/AI was 0.36. The molar ratio of Ti in the resulting metallocene catalyst component to the Ti in the slurry was 1.00. Polymerization Procedure

In the examples which follow, ethylene was polymerized in a 1.7 I stirred reactor. The reactor was heated and thoroughly purged with dry, oxygen free nitrogen to remove oxygen and moisture from the system. The reactor was then charged with 0.850 I of high purity n-hexane, an appropriate volume of the catalyst, hydrogen and co-catalyst. The reactor was then heated to the desired temperature and constant temperature maintained. Ethylene was then admitted to 150 lbs/in² and the pressure maintained by a pressure regulator. The catalyst system composition was then charged to a vessel above the reactor and forced into the reactor by a nitrogen over- pressure. The olefin pressure was maintained by feed on demand. The polymerization was allowed to proceed for 60 minutes.

Examples 3-13 Polyethylene was produced in accordance with the "Polymerization Procedure" above. All polymerizations were conducted at 80° C. The co- catalyst was TEAL. The molar ratio of TEAL:Ti in the catalyst system composition (slurry) was 100. Process parameters and results are set forth in Table II.

TABLE I

The catalyst of Example 2 was seen to exhibit increased melt index with increasing hydrogen content over the catalyst of Example 1. The catalyst of Example 2 has a 1 :1 molar ratio of metallocene:TiCI₄ versus a 1 :9 ratio in the catalyst of Example 1. The catalyst of Example 2 also exhibits a greater activity at a given melt index over the catalyst of Example 1.

Examples 14-16 Catalysts were prepared analogously to Example 1 with the formulations as described in Table III. Polyethylene was then produced in accordance with the "Polymerization Procedure" above. All polymerizations were conducted at 80° C for 60 minutes. The molar ratio of TEAL:Ti in the catalyst system composition (slurry) was 100. Process parameters and results are further set forth in Table IV.

TABLE IV

Example H₂, Δ psi Amount of Ti in Ml HLMI MFR Density Catalyst Efficiency

Slurry Injected,

Moles

14 35 1.5 x 10-° 0.1071 3.66 34.17 0.9535 2,421 ,016 15 35 1.5 X 10^"6 0.2155 7.12 33.04 0.9554 1 ,361 ,169 16 35 1.5 x 10^"° 0.11296 3.51 31.07 0.9537 947,112

Example 17 In a glovebox, 73.64 ml of 0.68 M DBM in heptane were added to a flask equipped with a mechanical stirrer. While stirring, 3.27 ml of a 1.53 M solution of co-catalyst were added to the flask. An additional 65 ml of hexane were added to the flask. Using an addition funnel, 15.15 ml of PMHS were added dropwise to the solution in the flask. The addition rate was controlled to maintain a temperature of less than 60° C. The solution was then stirred for an extra 60 min. The addition funnel was then charged with 8.93 ml of 1.4 M EADC and added to the flask dropwise. While stirring the solution, 0.62 g of titanocene dichloride was added yielding a dark blue solution. Stirring was maintained for 60 minutes during which the solution color changed dramatically. The funnel was then charged with 23.15 ml of 0.11 M titanium tetraisopropoxide (TiPt). Using the addition funnel, 62.50 ml of 1.4 M EADC was added in a dropwise fashion to the flask. The mixture was then stirred for 16 hr. The slurry was analyzed yielding 12.13 mM Ti. The molar ratio of Mg:Ti was 12. The molar ratio of AI.Ti was 29. The molar ratio of Mg:AI was 0.42.

Example 18 A copolymer of ethylene and 1 -butene was produced in accordance with the "Polymerization Procedure" above; however 20 g of butene was added to the reactor prior to the start of admittance of ethylene. The polymerization was conducted at 80° C using the catalyst system composition of Example 17. The co-catalyst was TEAL. The molar ratio of TEAL:Ti in the catalyst system composition (slurry) was 100. Process parameters and results are set forth in Table V. The secondary activation period is exhibited in Fig. 1.

TABLE V

A catalyst was prepared similar to that of Example 17 except for the changes shown in Table VI and the components were added in the order: A B C E D F G. Catalyst analysis revealed a slurry titanium concentration of 14.68 mM. The molar ratio of Mg:Ti was 11.49. The molar ratio of AI:Ti was 25. The molar ratio of Mg:AI was 0.46.

Example 20 A catalyst was prepared similarly to that of Example 19 except for the changes shown in Table VI and the components were added in the order: A B C D E F G. Analysis of the catalyst indicated the concentration of Ti to be

12.17 mM. The molar ratio of Mg:Ti was 14. The molar ratio of AI:Ti was 29. The molar ratio of Mg:AI was 0.48. Example 21 A catalyst was prepared similarly to that of Example 19 except for the changes shown in Table VI and the components were added in the order: A B C D E F G. Catalyst analysis revealed the concentration of Ti to be 5.49 mM. The molar ratio of Mg:Ti was 16. The molar ratio of AI:Ti was 34. The molar ratio of Mg.AI was 0.47.

Copolymers of ethylene and butene were produced in accordance with the procedures set forth in "Polymerization Procedure" (except for the addition of 20 g of butene) to the reactor prior to the admittance of the ethylene) using the catalysts of Examples 17 and 21. The results are compiled in Table VII.

Catalysts prepared with titanocene dichloride often experience difficulties due to the formation of soluble species resulting from the reaction products of titanocene dichloride with alkyl aluminum components. Comparison of catalysts in Table VIII indicate catalysts of the present invention have eliminated this problem. Samples of these catalysts were analyzed by separating the solid and liquid components and measuring the elemental composition of each phase. The data from Table VIII indicates improvement in support of the metallocene component by increasing the Si/Mg ratio. The co-catalyst in all Examples was TEAL.

Table V M

Polyethylene was prepared in accordance with "Polymerization Conditions" at several hydrogen concentrations. Table IX illustrates the ability to control polyolefin molecular weight with the catalysts of the present invention.

10

Example 40 In a glovebox, 500 ml of BE was added to a flask equipped with a mechanical stirrer. 32.7 ml of TEAL was added to the solution and heated to 50° C. Using an addition funnel, 41.8 ml of PMHS and 25 ml of hexane were added dropwise to maintain the temperature less than 70° C. The mixture was stirred for one hour.

Example 41 90.9 ml of the solution was then added to a flask equipped with a mechanical stirrer. While stirring, 0.55 g of titanocene trichloride was added to the flask. After the addition was complete, the mixture was stirred for one hour. Using an addition funnel, 87 ml of 1.15 M EADC was added dropwise to the flask. 2.5 ml of 1.0 M TiPt was then added dropwise and the mixture stirred for one hour. Analysis of the catalyst slurry revealed the concentration of Ti to be 18.54 mM. The molar ratio of Mg:Ti was 12.3. Polyethylene was then prepared in accordance with "Polymerization

Conditions" in the presence of the catalyst. The results are compiled in Table X.

The use of PMAOS2 as the polymerization co-catalyst increases the catalyst activity, the molecular weight of the polymer (at a given hydrogen concentration) and the polymer molecular weight distribution over that observed with TEAL as the co-catalyst.

Example 48 90.0 ml of the solution prepared in Example 40 was added to a flask equipped with a mechanical stirrer. While stirring, 0.73 g of zirconocene dichloride was added to the flask. By dropwise addition from an addition funnel, 87.0 ml of 1.15 M EADC were added to the solution in the flask. 25 ml of 0.1 M TiCI₄ in hexane was then added dropwise to the flask. The mixture was then stirred for one hour. Example 49

90.0 ml of the solution prepared in Example 40 was added to a flask equipped with a mechanical stirrer. While stirring, 0.15 g of zirconocene dichloride was added to the flask. By dropwise addition from an addition funnel, 174 ml. of 1.15 M EADC were added to the solution in the flask. 45 ml. of 0.1 M TiCI₄ in hexane was then added to the flask. The mixture was then stirred for one hour. Examples 50-52 Polyethylene was prepared in accordance with "Polymerization Conditions" using the catalyst of Example 48. The results are shown in Table XI.

Examples 53-55 Polyethylene was prepared in accordance with "Polymerization Conditions" using the catalyst of Example 49. The results are shown in Table XII.

From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the true spirit and scope of the novel concepts of the invention.

Claims

CLAIMS What is claimed is: 1. A catalyst system comprising (A) a magnesium siloxide support; and (B) a catalyst comprising (1) a mixture of a first trivalent or tetravalent metallic compound having the general formula M(R)_X, where M is titanium, vanadium, chromium or zirconium and x is either 3 or 4 and further wherein each R is independently selected from halogen, a 0,-0₂₀ alkyl, a C₇-C₂₀ alkaryl or aralkyl, a C^C_j. alkoxy, a silyl, a C^C-,- siloxy and an amide; and (2) a mono, bi or tricyclopentadienyl or substituted cyclopentadienyl metal compound represented by the formula (C₅R¹ _pR² _s(C₅R¹ _m)M¹Q₃._p or

wherein (C₅R¹--) is a cyclopentadienyl or substituted cyclopentadienyl; each R¹ is the same or different and is hydrogen or a hydrocarbyl radical containing 1 to 20 carbon atoms or two adjacent carbon atoms are joined together to form a C₄-C₆ ring; R² is a C,^ alkyiene radical, a dialkyi germanium or silicon or an alkyl phosphine or amine radical bridging two (C₅R¹ _m) rings; each Q is the same or different and is a hydrocarbyl radical having from 1 to 20 carbon atoms or halogen; at least one R¹ being a hydrocarbyl radical when Q is a hydrocarbyl radical; Q is an alkylidene radical having from 1 to about 20 carbon atoms, s is O oM ; p is 0, 1 , or 2; provided that when p is 0, s is 0; m is4when s is 1; and m is 5when s is 0; and M¹ is a Group 4b, 5b or 6b metal.

2. A catalyst system composition comprising a halogenating agent and the catalyst system of claim 1.

3. The catalyst system of claim 1 wherein M is titanium.

4. The catalyst system of claim 1 wherein M¹ is titanium.

5. The catalyst system of claim 1 wherein M and M¹ are both titanium.

6. The catalyst system of claim 1 wherein each R of the trivalent or tetravalent metallic compound is halogen, C_rC₃ alkoxy or C_rC₄ alkyl.

7. The catalyst system of claim 1 wherein M¹ is Zr.

8. The catalyst system of claim 1 wherein x is 4.

9. A process for polymerizing one or more olefins which comprises conducting the polymerization in the presence of the catalyst system composition of claim 2.

10. The catalyst system composition of claim 2 further comprising an aluminum containing co-catalyst selected from (i) compounds of the formula AI(R⁷)₃ where R⁷ is independently selected from the group consisting of 0,-0₂₀ alkyl, hydrogen and halogen; and (ii) an alumoxane.

11. The catalyst system composition of claim 10 wherein said aluminum containing co-catalyst is selected from the group consisting of triethylaluminum, trimethylaluminum, tri-isobutylaluminum, methylalumoxane, ethylalumoxane and diisobutyl alumoxane.

12. The catalyst system composition of claim 2 wherein the halogenating agent does not contain a transition metal and further wherein the Mg:M+M¹ atomic ratio is about 1 to about 50.

13. The catalyst system composition of claim 2 wherein the halogenating agent contains a transition metal and further wherein the Mg:M+M¹ atomic ratio is about 0.1 to about 100.

14. The catalyst system composition of claim 12 wherein the atomic ratio of halogen to magnesium in the catalyst system is about 3 to about 12.

15. The catalyst system composition of claim 13 wherein the atomic ratio of halogen to magnesium is about 0.4 to about 40.

16. The catalyst system composition of claim 2 which further comprises a hydrocarbon solvent.

17. The catalyst system composition of claim 2 wherein the halogenating agent is a metallic halide or is of the formula (RβkcrAKCI)., wherein R₆ is a 0,-0₄ alkyl group and q is 1 to 2.

18. The catalyst system composition of claim 10 wherein the co- catalyst is an alumoxane and further wherein the atomic ratio of halogen:Mg is less than 8:1.

19. The catalyst system of claim 1 wherein the atomic ratio of Si:Mg is between from about 2:1 to about 10:1.

20. The catalyst system composition of claim 10 wherein the co- catalyst is a compound of the formula AI(R⁷)₃ and further wherein the atomic ratio of halogen:Mg is between from about 8:1 to about 20:1.

21. A catalyst system comprising (A) a magnesium siloxide support having the general formula

where each R⁵ is independently selected from hydrogen, halogen, 0,-0₂₀ alkyl, C₄-C₂₀ cycloalkyl, aryl, and C,-C₂₀ alkoxy; and "n" is from about 0.05 to about 50; and (B) a catalyst, comprising a mixture of

(1) a mixture of a first trivalent or tetravalent metallic compound having the general formula M(R)_X, where M is titanium, vanadium, chromium or zirconium and x is either 3 or 4 and further wherein each R is independently selected from halogen, a C,-C₂₀ alkyl, a C₇-C₂₀ alkaryl or aralkyl, a C,-C₂₀ alkoxy, a silyl, a 0,-0^ siloxy and an amide; and

(2) a mono, bi or tricyclopentadienyl or substituted cyclopentadienyl metal compound represented by the formula (C₅R¹ _pR² _s(C₅R¹ M^,Q₃._p or

wherein (C₅R¹ _m) is a cyclopentadienyl or substituted cyclopentadienyl; each R¹ is the same or different and is hydrogen or a hydrocarbyl radical containing 1 to 20 carbon atoms or two adjacent carbon atoms are joined together to form a C₄-C₆ ring; R² is a C,-C₄ alkyiene radical, a dialkyi germanium or silicon or an alkyl phosphine or amine radical bridging two (C₅R¹ rings; each Q is the same or different and is a hydrocarbyl radical having from 1 to 20 carbon atoms or halogen; at least one R¹ being a hydrocarbyl radical when Q is a hydrocarbyl radical; Q¹ is an alkylidene radical having from 1 to about 20 carbon atoms, s is O oM ; p is 0, 1 , or 2; provided that when p is 0, s is 0; m is 4 when s is 1 ; and m is 5 when s is 0; and M is a Group 4b, 5b or 6b metal.

22. A catalyst system composition comprising a halogenating agent and the catalyst system of claim 21.

23. The catalyst system composition of claim 22 wherein the halogenating agent does not contain a transition metal and further wherein the atomic ratio of Mg:M+M¹ is from about 1 to about 50.

24. The catalyst system composition of claim 22 wherein the halogenating agent contains a transition metal and further wherein the atomic ratio of MgM+M¹ is from about 0.1 to about 100.

25. The catalyst system composition of claim 23 wherein the atomic ratio of halogen to magnesium is about 3 to about 12.

26. The catalyst system composition of claim 24 wherein the atomic ratio of halogen to magnesium is about 0.4 to about 40.

27. The catalyst system composition of claim 22 further comprising an aluminum containing co-catalyst selected from (i) compounds of the formula AI(R⁷)₃ where R⁷ is independently selected from the group consisting of C,-C₂₀ alkyl, hydrogen and halogen; and (ii) an alumoxane.

28. The catalyst system composition of claim 27 wherein the co- catalyst is an alumoxane and further wherein the atomic ratio of halogen:Mg is less than 8:1.

29. The catalyst system of claim 21 wherein the atomic ratio of Si:Mg is between from about 2: 1 to about 10: 1.

30. The catalyst system composition of claim 27 wherein the co- catalyst is a compound of the formula AI(R⁷)₃ and further wherein the atomic ratio of halogen: Mg is between from about 8:1 to about 20:1.

31. A process for polymerizing one or more olefins which comprises conducting the polymerization in the presence of the catalyst system composition of claim 22.

32. The process of claim 31 wherein the olefin is ethylene.

33. A catalyst system comprising:

(A) a magnesium siloxide support having the general formula

where each R⁵ is independently selected from hydrogen, halogen, C,-C₂₀ alkyl, C₄-C₂₀ cycloalkyl, aryl, and C,-C₂₀ alkoxy; and "n" is from about 0.05 to about 50; (B) a catalyst comprising a mixture of

(1 ) about 25 to about 75 wt. % of a mixture of a first trivalent or tetravalent metallic compound having the general formula M(R)₄, where M is titanium, vanadium, chromium or zirconium and x is 3 or 4 and further wherein each R is independently selected from halogen, a C,-C₂₀ alkyl, a C₇-C₂₀ alkaryl or aralkyl, a C,-C₂₀ alkoxy, a silyl, a C,-C₂₀ siloxy and an amide; and

(2) about 75 to about 25 wt. % of a mono, bi or tricyclopentadienyl or substituted cyclopentadienyl metal compound of the formula

(C₅R¹ _pR² _s(C₅R¹ _m)M¹Q₃._p or

wherein

(C₅R¹ is a cyclopentadienyl or substituted cyclopentadienyl; each R¹ is the same or different and is hydrogen or a hydrocarbyl radical containing 1 to 20 carbon atoms or two adjacent carbon atoms are joined together to form a C₄-C₆ ring; R² is a C,-C₄ alkyiene radical, a dialkyi germanium or silicon or an alkyl phosphine or amine radical bridging two (C₅R¹ rings; each Q is the same or different and is a hydrocarbyl radical having from 1 to 20 carbon atoms or halogen; at least one R¹ being a hydrocarbyl radical when Q is a hydrocarbyl radical; Q¹ is an alkylidene radical having from 1 to about 20 carbon atoms, s is 0 or 1 ; p is 0, 1 , or 2; provided that when p is 0, s is 0; m is 4 when s is 1 ; and m is 5 when s is 0; and M¹ is a Group 4b, 5b or 6b metal.

34. A catalyst system composition comprising a halogenating agent and the catalyst system of claim 33.

35. The catalyst system of claim 33 wherein M and M¹ are both titanium.

36. The catalyst system composition of claim 34 wherein the halogenating agent is of the formula

wherein R⁶ is an C,-C₄ alkyl group and q is 1 to 2.

37. The catalyst system composition of claim 34 wherein the halogenating agent does not contain a transition metal and further wherein the Mg:M+M¹ atomic ratio is from about 1 to about 50.

38. The catalyst system composition of claim 34 wherein the halogenating agent contains a transition metal and further wherein the Mg:M+M¹ atomic ratio is from about 0.1 to about 100.

39. The catalyst system composition of claim 34 further comprising an aluminum containing co-catalyst selected from (i) compounds of the formula AI(R⁷)₃ where R⁷ is independently selected from the group consisting of C,-C₂₀ alkyl, hydrogen and halogen; and (ii) an alumoxane.

40. The catalyst system composition of claim 39 wherein the co- catalyst is an alumoxane and further wherein the atomic ratio of halogen:Mg is less than 8:1.

41. The catalyst system of claim 33 wherein the atomic ratio of Si:Mg is between from about 2:1 to about 10:1.

42. The catalyst system composition of claim 39 wherein the co- catalyst is a compound of the formula AI(R⁷)₃ and further wherein the atomic ratio of halogen:Mg is between from about 8:1 to about 20:1.

43. A process for polymerizing one or more olefins which comprises conducting the polymerization in the presence of the catalyst system composition of claim 34.