WO1995006672A1

WO1995006672A1 - Improved catalysts for polymerizing olefins

Info

Publication number: WO1995006672A1
Application number: PCT/US1994/006656
Authority: WO
Inventors: Donald Earl Gessell
Original assignee: Occidental Chemical Corp
Current assignee: Occidental Chemical Corp
Priority date: 1993-09-03
Filing date: 1994-06-14
Publication date: 1995-03-09
Anticipated expiration: 1996-03-03

Abstract

Catalysts useful in preparing olefin polymers of a more uniform particle size distribution are disclosed. The catalysts are made by reacting a magnesium siloxide support with a portion of the chlorinating agent to be used, followed by a transition metal compound and then the remaining chlorinating agent.

Description

IMPROVED CATALYSTS FOR POLYMERIZING OLEFINS

Background of the Invention

This invention relates to catalysts useful in preparing polyolefins that have a more uniform particle size distribution. More specifically, this invention relates to a method of preparing such catalysts from a magnesium siloxide support where the addition of a chlorinating agent is made partly before and partly after the addition of a transition metal compound.

U.S. Patent No. 4,511,669, herein incorporated by reference, discloses a catalyst for polymerizing olefins. That catalyst has many advantages. However, polyethylene and copolymers of ethylene and other α-olefins, such as propylene, 1-butene, 1-hexene, and 1-octene, produced using that catalyst have a wide distribution of particle sizes. When the polymer particles are transferred in a tube using a gas, i.e., blowing the powder through a tube, and the polymer particles have a wide particle size distribution, the powder tends to separate according to particle size with the finer particles plugging filters and gas recycle compressors used to prevent the escape of the polymer powder and transfer gas to the atmosphere. In addition, the powder does not freely flow out the bottom of storage silos when the powder has a wide particle size distribution. This uneven powder flow results in non-uniform blending of the powder with powder additives such as calcium stearate and anti-oxidants commonly used to stabilize polyolefins. For these reasons, a polymer powder of more uniform particle size would be desirable.

Summary of the Invention

I have discovered that if one of the components used in making the catalyst (the chlorinating agent) is added partly before and partly after another of the components (the transition metal compound) , polyethylene made using the catalyst is of much more uniform particle size. It is remarkable and as yet unexplained how this change in the method of preparing the catalyst would affect the particle size distribution of polymers made using it.

Description of the Preferred Embodiments The catalysts of this invention are prepared in an aliphatic hydrocarbon from a polysiloxane or silanol, a dialkyl magnesium compound, a solubilizing agent, a transition metal compound, and a chlorinating agent.

Aliphatic Hydrocarbon The media in which the catalyst is prepared is preferably the same media or carrier solvent used in the polymerization reactor or reactors. Typically, a slurry polyolefin process uses an aliphatic hydrocarbon such as isobutane, hexane, or heptane. These hydrocarbons are therefore preferred because the solvent recycle distillation system in the production plant is less complex. However, solvents such as isohexane, isooctane, butane, octane or mixtures of these solvents could also be used.

Polysiloxane or Silanol The siloxane is preferably a hydropolysiloxane that can be described by the general formula

where each R is independently selected from hydrogen, alkyl containing from 1 to 20 carbon atoms, or aryl, aralkyl, or alkaryl containing from 6 to 20 carbon atoms, "a" and "b" are each greater than 0, where the sum of "a" and "b" does not exceed 3, and "m" is one or more. A preferred hydropolysiloxane utilized in the preparation of the catalyst of this invention has an "a" value of from 0.1 to 2, and a ^Mb" value of 1, 2, or 3, where the sum of "a" and "b" does not exceed 3. More preferably, the hydropolysiloxane has the formula

where "m" is 2 to 1000 and is preferably 10 to 50.

Representative but non-exhaustive examples of hydropolysiloxanes useful in the practice of the instant invention are polymethylhydridosiloxane (PMHS) , polyethylhydrosiloxane, polyethoxyhydrosiloxane, polymethylhydro-dimethylsiloxane copolymer, polymethylhydro- methyloctylsiloxane copolymer, polyethoxyhydrosiloxane, tetramethyldisiloxane, diphenyldisiloxane, trimethylcyclotrisiloxane, tetramethylcyclotetrasiloxane, polyphenylhydrosiloxane, polyeicosylhydrosiloxane, polychlorophenylhydrosiloxane, and mixtures of these. PMHS is preferred because it is a relatively inexpensive polysiloxane, commercially available, and reacts readily with dialkylmagnesium compounds.

When preparing a magnesium siloxide having only two siloxane groups, silanols of the formula (R³)₈Si(OH)₄.₈ can be used, where each R³ is independently selected from alkyl having from 1 to 20 carbon atoms or cycloalkyl, aralkyl, aryl, or alkoxy1 having 6 to 20 carbon atoms and "s" is 1, 2, or 3. Representative but non-exhaustive examples of these organic silanols are trimethylhydroxysilane, triethylhydroxysilane,

- A - triphenylhydroxysilane, diethyldihydroxysilane, dipropyldihydroxysilane, triethoxyhydroxysilane, dicyclohexyldihydroxysilane, diphenyldihydroxysilane, butyltrihydroxysilane and phenyltrihydroxysilane.

-?. Dialkyl Magnesium Compound

The dialkyl magnesium compound has the general formula RMgR. Representative but non-exhaustive examples of dialkyl magnesium compounds useful in preparing the catalysts of the present invention are dibutylmagnesium, n-butyl- secbutylmagnesium, but_lethylmagnesium, butyloctylmagnesium, dieicosylmagnesium, di-n-hexylmagnesium, di-n-butylmagnesium, di-n-butylmagnesium, dibutylmagnesium, dibutylmagnesium, butyloctylmagnesium, butylethylmagnes um, and m:. _ures of these. The preferred dialkyl magnesium compounds are dibutyl magnesium and butylethyl magnesium because they are commercially available. Small amounts of trialkylaluminum compound such as trimethylaluminum, triethylaluminum, or triisobutylaluminum can be added to render the dialkylmagnesium compound hydrocarbon soluble at concer rations of about 1 mole magnesium per liter of solution. Solubilizing Agent The magnesium siloxide formed in the first step of the process of this invention is solubilized in the aliphatic hydrocarbon by the addition of a trialkylaluminu or aluminum alkoxide compound in order to more closely control the particle size distribution of the polymer produced. Solubilizing agents can be added either before or after the reaction that produces the magnesium siloxide is carried out. However, the solubilizing agent is preferably added before the reaction as less is then required. Normally, about 0.02 to about 2 moles, and preferably about 0.05 to about 0.5 moles, of solubilizing agent per mole of magnesium siloxide is used as the solution is too viscous if less is used and more is unnecessary. Trialkylaluminum compounds having the formula A1(R²)₃ and aluminum alkoxides having the formula Al(OR²)₃ are useful as solubilizing agents in this invention, where each R² is independently selected from hydrogen and alkyl having from 1 to 20 carbon atoms; preferably, at least two of the R² groups are alkyl. Trialkylaluminum compounds are preferred as less is required. Representative but non-exhaustive examples of aluminum alkyls useful in the practice of the present invention are triethylaluminum, tributylaluminum, triisobutylaluminum, diethylaluminum hydride, isoprenylaluminum, and trimethylaluminum. Triethylaluminum is particularly preferred because it is readily available. Transition Metal Compound The transition metal compound is preferably a titanium alkoxide. Representative but non-exhaustive examples of titanium alkoxides useful in the preparation of the present invention are tetraisopropyltitanate, tetra-n-butyltitanate, tetrabiε(2-ethylhexyl)titanate, isopropyltitanate decamer, i.e. , iso-C₃H₇-0[Ti(O-iso-C₃H₇)₂-0]₁₀isoC₃H₇, butyl(triisopropoxy)-titanium, tetraeicosyltitanate, and mixtures thereof. The transition metal compound can also be a chloride such as TiCl₄, VC1₄, VOCl₃, or mixtures thereof. A titanium alkoxide chloride represented by the formula:

TiCl_x(OR)₄._x where x is a value greater than zero and less than four, and each R is independently selected from an alkyl containing 1 to 20 carbon atoms, or aryl, aralkyl, or alkaryl containing 6 to 20 carbon atoms, is also useful in the preparation of the present invention. Mixtures of the aforementioned compounds can also be used in this invention. If the transition metal compound contains a chloride, the chloride in the transition metal compound should be less than 10 mole percent of the total chloride in the catalyst after all the chlorinating agent is added. Chlorinating Agent The chlorinating agent is a compound that reacts with the magnesium siloxide hydrocarbon solution to form a hydrocarbon insoluble magnesium containing reaction product. The chlorinating agent does not contain a transition metal and is either a liquid or a gaseous material that is soluble in the aliphatic hydrocarbon. Transition metal chlorinating agents are not permitted for the purpose of the present invention because transition metal chlorides provide an excess of transition metal to the reaction, which is not fully reduced and decreases catalytic activity. A transition metal chloride compound is not considered to be a chlorinating agent if the transition metal compound contributes less than 10 mole percent chloride of the total chloride content used in the catalyst preparation.

Representative but non-exhaustive examples of chlorinating agents useful in the present invention are methylaluminum dichloride, methylaluminum sesquichloride, isobutylaluminu dichloride, isobutylaluminum sesquichloride, ethylaluminum dichloride, diethylaluminum chloride, ethylaluminum sesquichloride, SnCl₄, SiCl₄, HCl, HSiCl₃, aluminum chloride, ethylboron dichloride, boron chloride, diethylboron chloride, HCC1₃, methyl trichlorosilane, and dimethyl dichlorosilane. Of these, alkylaluminum sesquichloride, dialkyl aluminum chlorides and alkylaluminum dichlorides, where the alkyl group is methyl, ethyl, or isobutyl, are preferred because, in addition to the narrow particle size distribution described in this invention, the polymer molecular weight distribution can be controlled as described in Examples 12 to 17 of U.S. Patent No. 4,511,669. The most preferred chlorinating agents are diethylaluminum chloride, ethylaluminum dichloride, ethylaluminum sesquichloride and methyl and isobutyl analogs of these.

When a silicon compound such as silicon tetrachloride is used as the chlorinating agent, a narrow molecular weight distribution polymer is produced even at high Cl/Mg atomic ratios. Using a tin chloride such as tin tetrachloride as the chlorinating agent results in a polymer having substantially no broadened molecular weight distribution at high Cl/Mg atomic ratios.

Catalyst Preparation - First Step

The catalyst of the present invention is prepared by first reacting the polysiloxane or silanol with the dialkyl magnesium compound. The reaction is exothermic and is allowed to proceed up to a temperature of about 70°C. The magnesium siloxide reaction product has the general formula

Mς.- OO

where each R¹ is independently selected from hydrogen, halogen, alkyl, cycloalkyl, alkaryl, aralkyl, aryl, or alkoxy containing from 1 to 20 carbon atoms, each of which can be further substituted with halogen, and "n" is 0 or greater, usually 0.05 or higher. In the formula, ^Mn" refers to an average of these units in the total magnesium siloxide such that while the value of "n" can vary from molecule to molecule, the average value will be at 0 or greater. Preferably, "n" is from 0 to about 50. The catalysts of the present invention are prepared so that the silicon to magnesium atomic ratio is such that substantially all of the dialkyl magnesium compound is converted into magnesium siloxides. It should be noted that an excess of some silicon compounds, such as polymethylhydridosiloxane, is not detrimental except to catalyst cost and, in fact, sometimes has advantages such as in slurry powder bulk densities. The atomic ratio of Si to Mg is about 2 to about 3. A ratio of 3 is preferred as it gives an improved hydrogen response, a higher melt index, and higher catalyst activity. The silicon to magnesium atomic ratio can be much higher, the excess silicon being free silicon polymers as described in the present specification, or a polymeric siloxide bound to the magnesium. Lower atomic ratios are detrimental to catalyst efficiency and higher ratios show no significant improvement. Increasing the Si/Mg molar ratio in the catalyst improves the catalyst efficiency. A catalyst having a Cl/Mg mole ratio of 8:1, prepared while increasing the Si/Mg atomic ratio from 2.1 to 2.5 or higher produces a broad molecular weight distribution polyethylene at increased catalyst efficiencies in slurry polymerization. This increase in Si/Mg atomic ratio results in about a two-fold increase in catalyst efficiency.

Catalyst Preparation - Second Step The next step of the process of this invention is critical to achieving a catalyst capable of making a polymer having a more uniform particle size. In this step only part of the chlorinating agent is reacted with the magnesium siloxide. Sufficient chlorinating agent should be added in this step to obtain an atomic ratio of chlorine to magnesium of about 0.4 to about 2. This should be done at a temperature of about 10 to about 30°C (and preferably about 20 to about 25°C) , as higher temperatures may produce a polymer having a smaller average particle size and lower temperatures may decrease the activity of the catalyst.

Catalyst Preparation - Third Step After the chlorinating agent that was added in the second step has reacted, the transition metal compound is added. This preferably done within the same temperature range (10 to 30°C) for the same reasons. The magnesium to transition metal atomic ratio can be about 1 to about 200, but is preferably about 5 to 100. The most preferred molar ratio of magnesium to transition metal is about 5 to about 20 as higher ratios may result in a polymer having a smaller particle size and lower ratios may result in lower catalyst activity. As the magnesium to transition metal atomic ratio increases, polymer bulk density goes down while catalyst efficiency rises so a balance between catalyst efficiency and lowered polymer bulk density must be achieved.

Catalyst Preparation - Fourth Step In the next step of the process, after the transition metal compound has reacted, the remaining chlorinating agent is added at about the same temperature (10 to 30°C) . The total atomic ratio of chlorine to magnesium is about 3 to about 12 and the highest catalyst activity is at a ratio of 4 to 8. A ratio of 4 gives a polymer having a narrow molecular weight distribution. The catalyst activity tends to decrease as the ratio of chlorine to magnesium is increased. If an aluminum chloride compound is used as the chlorinating agent, polymer molecular weight distribution broadening is most significant at Cl/Mg atomic ratios of 6 to 12 and a Cl/Mg atomic ratio of about 8 is most preferred. Slurry polymerization catalysts having a Cl/Mg mole ratio of 6 or more give a catalyst having a decreased catalyst efficiency when an aluminum chloride compound is the chlorinating agent. In yet another preparation method, titanium chloride is used at sufficiently high Mg/Ti molar ratios that the titanium present does not chlorinate significant portions of the MgO-Si bonds to Mg-Cl bonds and maintains the Cl/Mg ratio below 0.5. Once the catalyst has been prepared, it can be used in the solvent if desired. Alternatively, the solvent can be decanted from the catalyst slurry to remove the hydrocarbon soluble chloride species. However, decanting provides no advantage over use in the solvent unless a large excess of halogenating agent has been used as excess chlorine in the catalyst may make the polymer corrosive.

Co-Catalvst The catalyst of this invention is typically used with a co-catalyst, typically a trialkyl aluminum compound, as is known in the art for these types of catalysts. High co- catalyst to catalyst ratios are preferred to scavenge impurities. However, high ratios are detrimental in effect, in that the co-catalysts tend to over reduce the transition metal and render the catalyst less active. Preferred molar ratios of cocatalyst to catalyst transition metal are 1 to about 1000, and most preferred are ratios of about 10 to about 100.

Representative but non-exhaustive examples of aluminum alkyl co-catalysts useful in the practice of the present invention are aluminum triethyl, aluminum tributyl, triisobutylaluminum, diethylaluminum chloride, isoprenylaluminum, trimethylaluminum, dimethylaluminum chloride, trioctylaluminum, diethylaluminum ethoxide, tridecylaluminum, trioctylaluminum, trihexylaluminum, and diethylaluminum propoxide. Polymerization The catalysts of the present invention are effective in slurry polymerization systems. They will normally be effective when residence time parameters are observed. In slurry polymerization systems the residence time preferably range from about 30 minutes to about 10 hours, usually from about 1 to 5 hours.

While the instant invention can be carried out in either continuous or batch polymerization, for commercial use continuous polymerizations are preferred. The reactor can be a tube or a stirred tank reactor as is commonly used, and any reactor can be used which intimately contacts ethylene with the catalyst.

Control of molecular weight can be accomplished by utilizing hydrogen or a combination of hydrogen and temperature as is known in the art. Normally, higher temperatures will reduce molecular weight.

In slurry polymerization reactions, the catalyst is useful under conditions known to those skilled in this art, normally at 40°C to about 90°C and at total reactor pressures up to about 40,000 psig, including the use of hydrogen to control molecular weight. These catalysts can generally be used in place of prior art catalysts without modification.

The invention is more concretely described with reference to the examples below wherein all parts and percentages are by weight unless otherwise specified. Examples are provided to illustrate the instant invention and not to limit it. In the examples which follow, dibutyl magnesium was obtained as a solution in heptane from the Lithium Corporation of America. Polymethylhydridosiloxane (PMHS) was obtained from Petrarch Systems, Inc. Triethyl aluminum and ethyl aluminum d_~chloride were obtained as hexane solutions from Texas Alkyls, Inc. Hexane was obtained from the Phillips Petroleum Company and purified with molecular sieves and nitrogen to remove oxygen and water. All catalyst preparations were carried out in an inert atmosphere. The catalysts were stirred at least one hour after preparation before taking a sample for testing.

Catalyst Preparation Reactor The catalyst preparation reactor was a 10-gallon jacketed vessel. Water was circulated through the jacket and an external heat exchanger. Chilled water or steam could be applied to the heat exchanger to provide the necessary temperature control. The agitator entered through the top of the reactor with a double mechanical seal to prevent air from getting into the reactor. The agitator was a four bladed, 5 inch diameter, 45-degree downward thrust turbine turning at 100 revolutions per minute. The inside of the reactor was 15 inches from tangent to tangent and 14 inches in diameter. There were four equally spaced baffles having a width of 1.4 inches inside the reactor. Each catalyst component was added through a separate addition port, except dibutylmagnesium and triethylaluminum which used the same port. The ethylaluminum dichloride was added through a dip tube with the exit nozzle located one impeller width above and one impeller width inside the tip of the agitator blade. The ethylaluminum dichloride was discharged parallel to the agitator shaft at an exit velocity of 1.5 times the tip speed of the impeller.

Comparative Example 1 Polymethylhydridosiloxane (1.038 ml, 17.02 moles silicon) was uniformly added over a period of about 3 hours to a stirred solution of 6.0 liters of 0.946 molar dibutylmagnesium, 0.390 liters of 0.877 molar triethylaluminum, and 5 liters of hexane heated to 70°C. The reactor temperature was maintained at 70°C during the addition of the polymethylhydridosiloxane and for a period of about one hour after the addition. The resultant solution was quite viscous because the Al/Mg atomic ratio was only 0.06. The viscous solution was cooled to 25°C and 0.169 liters of tetraisopropyltitanate (0.568 moles titanium) was added followed by 1 liter of hexane. At a controlled temperature of 25°C, 19.24 liters of 1.18 molar ethylaluminum dichloride was added continuously over a period of about 5 hours for a Cl/Mg atomic ratio of 8. The catalyst was stirred overnight before taking a sample for testing. Example 2

The catalyst preparation of Example 1 was repeated except

1.20 liters of 1.18 molar ethylaluminum dichloride was added before the tetraisopropyltitanate. The remainder of the 19.24 liters of ethylaluminum dichloride was then added as in

Example 1.

Example 3 Polymethylhydridosiloxane (1.038 ml, 17.02 moles silicon) was uniformly added over a period of about 3 hours to a stirred solution of 6.0 liters of 0.946 molar dibutylmagnesium, 0.646 liters of 0.877 molar triethylaluminum, and 5 liters of hexane heated to 70°C. The reactor temperature was maintained at 70°C during the addition of the polymethylhydridosiloxane and for a period of about one hour after the addition. The resultant solution was quite fluid because the Al/Mg atomic ratio was 0.10. The clear solution was cooled to 25°C and 0.962 liters of 1.18 molar ethylaluminum dichloride was added to give a cloudy solution having a Cl/Mg atomic ratio of 0.40. Then 0.169 liters of tetraisopropyltitanate (0.568 moles titanium) was added followed by 1 liter of hexane. At a controlled temperature of 25°C, a solution of 1.18 molar ethylaluminum dichloride was added continuously over a period of about 5 hours until the total volume of 1.18 molar ethylaluminum dichloride added to the reactor was 19.24 liters for a Cl/Mg atomic ratio of 8. The catalyst was stirred overnight before taking a sample for testing.

Example 4 The procedure of Example 3 was repeated except 4.81 liters of 1.18 molar ethylaluminum dichloride was added at the first addition to give a Cl/Mg atomic ratio of 2.0 before the tetraisopropyltitanate was added.

Example 5

The procedure of Example 3 was repeated except ethylaluminum dichloride was added to give a Cl/Mg atomic ratio of 0.5 before the tetraisopropyltitanate was added and the volumes of the components was different because the concentration of the dibutylmagnesium and ethylaluminum dichloride solutions were slightly different. The atomic ratios of the total components added was the same as Example

3.

Polymethylhydridosiloxane (1.136 liters, 18.63 moles silicon) was uniformly added over a period of about 3 hours to a stirred solution of 6.0 liters of 1.035 molar dibutylmagnesium, 0.708 liters of 0.877 molar triethylaluminum, and 5 liters of hexane heated to 70°C. The reactor temperature was maintained at 70°C during the addition of the polymethylhydridosiloxane and for a period of about one hour after the addition. The resultant solution was quite fluid because the Al/Mg atomic ratio was 0.10. The clear solution was cooled to 25°C and 1.30 liters of l.ll molar ethylaluminum dichloride was added to give a cloudy solution having a Cl/Mg atomic ratio of 0.50. Then, 0.185 liters of tetraisopropyltitanate (0.622 moles titanium) was added followed by 1 liter of hexane. At a controlled temperature of 25°C, a solution of 1.11 molar ethylaluminum dichloride was added continuously over a period of about 6 hours until the total volume of 1.11 molar ethylauminum dichloride added to the reactor was 20.53 liters for a Cl/Mg atomic ratio of 8. The catalyst was stirred overnight before taking a sample for testing.

Comparative Example 6 The procedure of Example 5 was repeated except that all of the ethylaluminum dichloride was added after the tetraisopropyltitanate. The volume was different because the concentration of the ethylaluminum dichloride solutions was slightly different. The atomic ratios of the total components added was the same as Example 5.

Polymethylhydridosiloxane (1.136 ml, 18.63 moles silicon) was uniformly added over a period of about 3 hours to a stirred solution of 6.0 liters of 1.035 molar dibutylmagnesium, 0.708 liters of 0.877 molar triethylaluminum, and 5 liters of hexane heated to 70°C. The reactor temperature was maintained at 70°C during the addition of the polymethylhydridosiloxane and for a period of about one hour after the addition. The resultant solution was quite fluid because the Al/Mg atomic ratio was 0.10. The clear solution was cooled to 25°C and 0.185 liters of tetraisopropyltitanate (0.622 moles titanium) was added followed by 1 liter of hexane. At a controlled temperature of 25°C, 22.56 liters of a 1.12 molar ethylaluminum dichloride solution was added continuously over a period of about 5 hours for a Cl/Mg atomic ratio of 8.

Example 7 Laboratory reactor polymerizations were conducted using each of the catalysts prepared in the previous examples and the following procedure.

A portion of the catalyst slurry was diluted with hexane. An aliquot of this dilute catalyst slurry containing 0.002 millimoles of titanium was added to a nitrogen purged stirred 1.8 liter reactor containing 600 ml of dry oxygen free hexane and 2.0 ml of 0.10 molar triethylaluminum. The reactor was pressured to 50 pounds per square inch gauge (psig) with hydrogen and vented to 0 psig. This procedure was repeated three times. The reactor pressure was adjusted to 55 psig with hydrogen and then 100 psig with ethylene. The reactor contents were heated to 80°C. Ethylene was added to maintain a constant reactor pressure of 150 psig. After one hour the reactor was cooled and vented. The reactor contents were filtered and the polyethylene powder was dried in a vacuum oven at 40°C until free of hexane. The particle size distribution of the polyethylene powder was determined by screening a portion of the powder in a series of standard mesh size screens and weighing the powder on each screen to determine the weight percent polyethylene powder on each screen. The data obtained is summarized in the following table.

The table shows that the particle size distribution of the polyethylene was more uniform for polyethylene prepared using a catalyst according to this invention.

Claims

I CLAIM:

1. A method of making an olefin polymerization catalyst comprising the following separate steps:

(A) forming a solution in an aliphatic hydrocarbon of a trialkylaluminum or aluminum alkoxide solubilizing agent and magnesium siloxide having the general formula

where each R¹ is independently selected from hydrogen, halogen, alkyl, cycloalkyl, alkaryl, aralkyl, aryl, or alkoxy from C, to C₂₀, or halogen substitutions thereof, and "n" is 0 or greater;

(B) reacting said magnesium siloxide with a chlorinating agent at a temperature of about 10 to about 30°C and an atomic ratio of chlorine to magnesium of about 0.4 to about 2, where said chlorinating agent is soluble in said aliphatic hydrocarbon and is selected from the group consisting of chlorides of aluminum, silicon, and boron; (C) reacting said magnesium siloxide at a temperature of about 10 to about 30°C with a transition metal compound at an atomic ratio of magnesium to transition metal of about 5 to about 20, where said transition metal is selected from the group consisting of titanium and vanadium; and

(D) reacting said magnesium siloxide at a temperature of about 10 to about 30°C with additional said chlorinating agent at a total atomic ratio of chlorine to magnesium of about 3 to about 12.

2. A method according to Claim 1 wherein said magnesium siloxide is made by reacting at a temperature up to about 70°C a hydropolysiloxane with a dialkyl magnesium compound, where the Si to Mg atomic ratio is about 2 to about 3.

3. A method according to Claim 2 wherein said hydropolysiloxane has the formula

where "a + b" is less than 3, "m" is at least one, and each R is independently selected from hydrogen, alkyl from C, to C₂₀, and aryl or aralkyl from C₆ to C₂₀.

4. A method according to Claim 2 wherein said hydropolysiloxane as the formula

where each R is independently selected from hydrogen, alkyl from C, to C₂₀, and aryl or aralkyl from C₆ to C₂₀, and "m" is 2 to..1000.

5. A method according to Claim 2 wherein said hydropolysiloxane is polymethylhydridosiloxane.

6. A method according to Claim 2 .wherein said dialkyl magnesium compound is dibutyl magnesium or butylethyl magnesium.

7. A method according to Claim 1 wherein said solubilizing agent is a trialkylaluminum.

8. A method according to Claim 1 wherein said chlorinating agent is ethylaluminum dichloride.

9. A method according to Claim 1 wherein said magnesium siloxide is prepared by reacting at a temperature up to about 70°C a dialkyl magnesium compound with a silanol having the formula (R³)₈Si(OH)₄._β, where each R³ is independently selected from alkyl from C₁ to C₂₀ or cycloalkyl, ara? :yl, aryl, or alkoxyl from C₆ to C₂₀ and "s" is 1, 2, or 3.

10. A method of making an olefin polymerization catalyst comprising the following separate steps:

(A) forming a magnesium siloxide having the formula

Mg

where each R, is independently selected from hydrogen, halogen, alkyl, cycloalkyl, alkaryl, aralkyl, aryl, and alkoxy from C, to C₂₀ and "n" is 0 or greater, by reacting at a temperature up to about 70°C a hydropolysiloxane with a dialkyl magnesium compound in a solution of an aliphatic hydrocarbon in the presence of about 0.02 to about 2 moles per mole of said magnesium siloxide of a trialkylaluminum compound, where the Si to Mg molar ratio is about 2 to about 3; (B) reacting said magnesium siloxide with an aluminum chloride chlorinating agent at a temperature of about 10 to about 30°C and at an atomic ratio of halogen to magnesium of about 0.4 to about 2, where said chlorinating agent is soluble in said aliphatic hydrocarbon solvent;

(C) reacting therewith at a temperature of about 10 to about 30°C a titanium alkoxide at an atomic ratio of magnesium to titanium of about 5 to about 20; and

(D) reacting therewith at a temperature of about 10 to about 30°C additional said aluminum chloride chlorinating agent at a total atomic ratio of halogen to magnesium of about 3 to about 12.

11. A method according to Claim 10 wherein said hydropolysiloxane has the formula

12. A method according to Claim 10 wherein said hydropolysiloxane as the formula

where each R is independently selected from hydrogen, alkyl from C, to C₂₀, and aryl or aralkyl from C₆ to c₂₀ and "m" is 10 to 50.

13. A method according to Claim 10 wherein said hydropolysiloxane is polymethylhydridosiloxane.

14. A method according to Claim 10 wherein said dialkyl magnesium compound is dibutyl magnesium or butylethyl magnesium.

15. A method according to Claim 10 wherein said chlorinating agent is ethylaluminum dichloride.

16. A method according to Claim 10 wherein said transition metal compound is tetraisopropyltitanate.

17. A method according to Claim 10 wherein said solubilizing agent is triethylaluminum.

18. A method of making an ethylene polymerization catalyst comprising the following separate steps:

(A) forming a magnesium siloxide by reacting at a temperature up to 70°C polymethylhydridosiloxane with butyl ethyl magnesium or dibutyl magnesium in a solution of hexane or heptane in the presence of about 0.05 to about 0.5 moles per mole of said magnesium siloxide of a trialkylaluminum solubilizing agent, where the Si to Mg atomic ratio is about 2 to about 3;

(B) reacting said magnesium siloxide with ethylaluminum dichloride at a temperature of about 10 to about 30°C and at an atomic ratio of chlorine to magnesium of about 0.4 to about 2; (C) reacting said magnesium siloxide at a temperature of about 10 to about 30°C with a titanium isopropoxide at an atomic ratio of magnesium to titanium of about 5 to about 20; and (D) reacting said magnesium siloxide at a temperature of about 10 to about 30°C with additional ethylaluminum dichloride to a total atomic ratio of chlorine to magnesium of about 3 to about 12.

19. A catalyst made according to the method of Claim 1.

20. A polyolefin polymerized using a catalyst according to Claim 19.