CA2145538A1 - Process for polymerizing alpha-olefin - Google Patents

Abstract

A process for polymerizing one or more .alpha.-olefins of up to 10 carbon atoms which comprises contacting the one or more .alpha.-olefin under polymerization conditions with a catalyst system comprising: (a) a titanium halide-containing magnesium, con-taining procatalyst component wherein the component is obtained by contacting a magnesium compound of the formula MgR'R", wherein R' and R" are, independently, alkoxide group, aryloxide group or halogen, with a halogenated tetravalent tita-nium compound in the presence of a halohydrocarbon and an alkyl ester of a polycarboxylic acid electron donor, (b) an orga-noaluminum cocatalyst component, and (c) an organosilane selectivity control agent represented by general formula (I) wherein R1, R2 and R3, are, independently, alkyl group of 1 to 12 carbon atoms; aryl group of 1 to 12 carbon atoms, alkaryl group of 1 to 12 carbon atoms, aralkyl of 1 to 12 carbon atoms or halogen; and R4 is hydrocarbyloxy of 1 to 2 carbon atoms. The pro-cess affords high catalyst productivity and produces polymer products that have broad molecular weight distribution while retaining low oligomer content properties.

Description

214~538 W O 94/07926 PC~r/US93/09009 DESCRIPTION
PROCESS FOR POLYMERIZING ALPHA-OLEFIN
~- Technical Field This invention relates to a process for producing highly stereospecific ~-olefin polymers. More particularly, the invention relates to a process that utilizes a novel high activity stereoregular polymerization catalyst system to produce ~-olefin polymers having improved properties.
Background Art The use of a solid, transition-metal based, olefin polymerization catalyst system including a magnesium-containing, titanium halide-based catalyst component to produce a polymer of an ~-olefin such as ethylene, propylene, and butene-1, is well known in the art. Such polymerization catalyst systems are typically obtained by the combination of a titanium halide-based catalyst component, an organoaluminum compound and one or more electron donors. For convenience of reference, the solid titanium-containing catalyst component is referred to herein as "procatalyst", the organoaluminum compound, as "cocatalyst", and the electron donor compound, which is typica~ly used separately or partially or totally complexed with the organoaluminum compound, as "selectivity control agent" (SCA). It is also known to incorporate electron donor compounds into the procatalyst. The electron donor which is incorporated with the titanium-containing compounds serves a different purpose than the electron donor modifier referred to as the selectivity control agent. The compounds which are used as the electron donor may be ~he same or different compounds which are used as the selectivity control agent. The above-described stereoregular high activity catalysts are broadly conventional and are described in numerous patents and other references including Nestlerode et al, U. S. Patent 4,728,705, which is incorporated herein by reference.
Although a broad ra~ge of compounds are known generally as selectivity control agents, a particular

-2-catalyst component may have a specific compound or groups of compounds with which it is specially compatible. For any given procatalyst and/or cocatalyst, discovery of an appropriate type or selectivity control agent can lead to significant increases 5 in catalyst efficiency, lower hydrogen demand as well as the improvement in polymer product properties.
Many classes of selectivity control agents have beer. disclosed for possible use in polymerization catalysts.
One class of such selectivity control agents is the class of 10 organo-silanes. For examples, Hoppin et al, U.S. Patent 4,990,478, describes branched C3 - Clo alkyl-t-butoxydimethoxysilanes. Other aliphatic silanes are described in Hoppin et al, U.S. Patent 4,829,038. EP-A-0459009 discloses the use of a solid catalyst prepared under special conditions 15 from diethoxy magnesium, titanium tetrachloride and phthaloyl chloride along with a specific silicon compound and a specific organoaluminium compound.
Although many methods are known for producing highly stereoregular ~-olefin polymers, it is still desired to 20 improve the activity of the catalyst and produce polymers or copolymers that exhibit improved properties such as broad molecular weight distribution, and low zylene solubles.
Further, it is desired to produce polymers or copolymers that exhibit a reduction in the amount of volatiles, e.g. smoke 25 and/or oil, liberated during subsequent processing, e.g.
extrusion.
Disclosure of the Invention The invention relates to a process for the production of homopolymers or copolymers that have improved 30 polymer properties.
More particularly, the present invention is a process for the production of polymers using a high activity olefin polymerization catalyst system which comprises (a) a titanium halide-containing procatalyst components obtained by 35 halogenating a magnesium compound, typically of the formula 2~R'R'', wherein R' and R'' are, independently, an alkoxide, aryloxide or hydrocarbyl carbonate group or halogen, especially -214S~38 -2a-alkoxide groups of 1 to 10 carbon atoms with a halogenated tetravalent titanium compound in the presence of a polycarboxylic acid ester electron donor, and a - halohydrocarbon, (b) an organoaluminum cocatalyst 21~5~8 Jmponent, and (c) an organosilane selectivity control agent naving the general formula:
Rl R3 \si/
R2/ \R4 wherein Rl, R2 and R3 are, independently, alkyl of 1 to 12 - carbon atoms, aryl of 1 to 12 carbon atoms, alkaryl of 1 to.
12 carbon atoms, aralkyl of 1 to 12 carbon atoms or halogens and R4 is a hydrocarbyloxy Gf 1 to 2 carbon atoms. The preferred selectivity control agents are t-butyld imethylmethoxys i lane, ( 2 -methyl-2 -butyl) dimethylmethoxysilane, (3-ethyl-3-pentyl) -dimethylmethoxysilane and mixtures thereof.
Best Mode for Carryinq Out the Invention lS Although a variety of chemical compounds are useful for the production of the procatalyst, a typical procatalyst of the invention is prepared by halogenating a magnesium compound of the formula MgR'R", wherein R' is an alkoxide or aryloxide group and R" is an alkoxide, hydrocarbyl carbonate or aryloxide group or halogen, with a halogenated tetravalent titanium compound in the presence of a halohydrocarbon and an electron donor.
The magnesium compound employed in the preparation of the solid catalyst component contains alkoxide, aryloxide, 25 hydrocarbyl carbonate or halogen. The alkoxide, when present, generally contains from 1 to 10 carbon atoms. Alkoxides containing from 1 to 8 carbon atoms are preferable, with 2 to 4 carbon atoms being more preferable. The aryloxide, when present, generally contains from 6 to 10 carbon atoms, with 6 30 to 8 carbon atoms being preferred. When halogen is present, it is preferably present as bromine, fluorine, iodine or chlorine, with chlorine being more preferred. Preferred magnesium compounds are magnesium dialkoxides.
Suitable magnesium compounds are magnesium 35 chloride, ethoxy magnesium bromide, isobutoxy magnesium chloride, phenoxv magnesium iodide, cumyloxy magnesium bromi~e magnesium diethoxide, magnesium iscpropcxide, ~ 2145~38 magnesium ethyl carbonate and naphthoxy magnesium chloride.
The preferred magnesium compound is magnesium diethoxide.
Halogenation of the magnesium compound with the halo-genated tetravalent titanium compound is usually effected by employing an excess of the titanium compound. At least 2 moles o~ the titanium compound should ordinarily be employed per mole o~ the magnesium compound. Preferably from 4 moles to 100 moles of the titanium compound are employed per mole of the magnesium compound, and most preferably from 4 moles to 20 moles of the titanium compound are employed per mole of the magnesium compound.
Halogenation of the magnesium compound with the halogenated tetravalent titanium compound is typically effected by contacting the compounds at an elevated temperature in the range from about 60~C to about 150~C, preferably from about 70~C to about 120C. Usually the reaction is allowed to proceed over a period of 0.1 to 6 hours, preferably between 0.5 to 3.5 hours. The halogenated product is a solid material which is isolated from the liquid reaction medium by filtration, decantation or a suitable method.
The halogenated tetravalent titanium compound employed to halogenate the magnesium compound contains at least two halo~en atoms, and preferably contains ~our halogen atoms. The halogen atoms are chlorine atoms, bromine atoms, iodine atoms or fluorine atoms. The halogenated tetravalent titanium compounds generally has up to two alkoxy and/or aryloxy groups. Examples of suitably halogenated tetravalent titanium compounds include diethoxytitanium dibromide, isopropoxytitanium triiodide, dihexoxytitanium dichloride, phenoxytitanium trichloride, titanium tetrachloride and titanium tetrabromide. The preferred halogenated tetravalent titanium compound is titanium tetrachloride.
Halogenation of the magnesium compound with the halogenated tetravalent titanium compound, as noted, is con-ducted in the presence of a halohydrocarbon and an electrondonor. If desired, an inert hydrocarbon diluent or solvent may also be present, although Ihis is not necessary.

The halohydrocarbon employed is an aromatic or aliphatic including cyclic and alicyclic compounds.
Preferabl~ the halohydrocarbon contains 1 or 2 halogen atoms, although more may be present if desired. It is preferred that the halogen, independently, is chlorine, bromine or fluorine. Suitable aromatic halohydrocar~ons include chlorobenzene, bromobenzene, dichl~robenzene, dichlorodibromobenzene, o-chlorotoluene, chlorotoluene, dichlorotoluene, chloronaphthalene. Chlorobenzene, o-chlorotoluene and dichlorobenzene are the preferredhalohydrocarbons, with chlorobenzene and o-chlorotoluene being more preferred.
The aliphatic halohydrocarbons which can be employed suitably of 1 to 12 carbon atoms. Preferably such halohydrocarbons of 1 to 9 carbon atoms and at least 2 halogen atoms. Most preferably the halogen is present as chlorine. Suitable aliphatic halohydrocarbons include dibromomethane, trichloromethane, 1,2-dichloroethane, trichloroethane, dichlorofluoroethane, hexachloroethane, trichloropropane, chlorobutane, dichlorobutane, chloropentane, trichloro-fluorooctane, tetrachloroisooctane, dibromodi-fluorodecane. The preferred aliphatic halohydrocarbons are carbon tetrachloride and trichloroethane.
Aromatic halohydrocarbons are preferred, particularly those of 6 to 12 carbon atoms, and especially those of 6 to 10 carbon atoms.
Typical electron donors that are incorporated within the procatalyst include esters, particularly aromatic esters, ethers, particularly aromatic ethers, ketones, phenols, amines, amides, imines, nitriles, phosphines, phosphites, stibines, arsines, phosphoramides and alcoholates. Alkyl esters of aromatic polycarboxylic acids are frequently incorporated into electron donors.
Illustrative of such electron donors are methyl benzoate, ethyl benzoate, diethyl phthalate, diisoamyl Phthalate, ethyl p-ethoxybenzoate, methyl p-ethoxybenzoate, diisobutyl - 2115~38 phthalate, dimethyl napthalene-dicarboxylate, diisobutyl maleate, diisopropyl terephthalate, and diisoamyl phthalate.
Diisobutyl phthalate is the preferred alkyl ester of aromatic carboxylic acid.
After the solid halogenated product has been separated frcm the liquid reaction medium, it is usually treated one or more times with additional halogenated tetravalent titanium compound in order to remove residual al~oxy and/or aryloxy grGups and ~xi~ize catal~yst activity. Preferably, the halogenated product is treated multiple times with separate portions of the halo-genated tetravalent titanium compound. Better results are obtained if the halogenated product is treated twice with separate portions of the halogenated tetravalent titanium compound. As in the initial halogenation, at least 2 moles of the titanium compound should ordinarily be employed per mole of the magnesium compound, and preferably from 4 moles to 100 moles of the titanium compound are employed per mole of the magnesium compound. Most preferably from 4 moles to 20 moles of the titanium compound per mole of the magnesium compound.
Optionally, the solid halogenated product is treated at least once with one or more acid chlorides after washing the solid halogenated product at least once with additional amounts of the halogenated tetravalent titanium 2S compound. Suitable acid chlorides include benzoyl chloride and phthaloyl chloride. The preferred acid chloride is phthaloyl chloride.
The reaction conditions employed to treat the solid halogenated product with the titanium compound can be the same as those employed during the initial halogenation of the magnesium compound.
After the solid halogenated product has been treated one or more times with additional halogenated tetravalent titanium compound, it can be separated from the liquid reaction medium, washed at least once with an inert hydrocarbon of up to 10 carbon atoms to remove unreacted titani~lm compounds, zn~ dried Exemplary of ~he inert 2~4~38 hydrocarbons that are suitable for the invention are isopentane, isooctane, hexane, heptane and cyclohexane.
~ he final washed product usually has a titanium content of from 0 . 5 percent by weight to 6 . 0 percent by weight, 5 preferably from 2 . 0 percent by weight to 4 . 0 percent by weight The atomic ratio of titanium to magnesium in the rinal product is usually between 0 . 01:1 and 0 . 2 :1, preferably between 0 . a2 :1 and 0 . 0 :1.
The cocatalyst is an organoaluminum compound which 10 is tvpically an alkylaluminum compound. Suitable alkylaluminum compounds include trialkylaluminum compounds, such as triethyl-aluminum or triisobutylaluminum; includinq dialkylaluminum halides such as diethylaluminum chloride and dipropylaluminum chloride; and dialkylaluminum alkoxides such 15 as diethylaluminum ethoxide. Trialkylaluminum compounds are preferred, with triethylaluminum being the preferred trialkylaluminum compound.
The organosilane selectivity control agents in the catalyst system contain at least one silicon-oxygen-carbon 20 lin~age Suitable organosilane compounds includes compounds having the following general formula:
Rl R3 \si/
R2 / \ R4 25 wherein Rl, R2 and R3 are, independently, alkvl of I to 12 carbon atoms, aryl group of 1 to 12 carbon atoms, alkaryl group of 1 to 12 carbon atoms, aralkyl group of from 1 to 12 carbon atoms or halogen; and R4 is a hydrocarbyloxy group of to 2 carbon atoms . It is pref erred that Rl, R2, and R3 are

3 0 alkyl groups and R4 is a alkoxy group . It is further preferred that R4 is a methoxy group. Examples of suitable organosilane selectivity control agents include t-butyldimethyl-methoxys i lane, ( 2 -methyl-2 -butyl) dimethylmethoxysilane, (3-ethyl-3-pentyl) -35 dimethylmethoxysilane and mixtures thereof. The preferredorgznosilane selectivity control agent is t-butvldi;nethylmethoxysilane The invention also contemplates 21~5538 the use of mixtures of two or more selectivity control agents. The selectivity control agent is provided in a quantity such that the molar ratio or the selectivity control agent to the titanium present in the procatalyst is ~rom about 2 to about 60. Molar ratios rrom about 8 to about 45 are pre~erred, with molar ratios from about 10 to about 35 being more preferred.
The hig~ activity stereoregular polymerization cata-lyst is employed in a chemical reaction to effect lo polymerization by contacting at least one ~-olefin under polymerization condi-tions. In accordance with the invention, the procatalyst component, organoaluminum cocatalyst, and selectivity control agent can be in~roduced into the polymerization reactor separately or, i~ desired, two or all of the components may be partially or completely mixed with each other before they are introduced into the reactor. In any event, the organoaluminum cocatalyst is employed in sufficient quantity to provide from, say, 1 mole to about 150 moles of aluminum per mole of titanium in the procatalyst It is preferred that the cocatalyst is present in sufficient quantities to provide from 10 moles to about 100 moles of aluminum per mole of titanium in the procatalyst.
The particular type of polymerization process utilized is not critical to the operation of the present invention and the polymerization processes now regarded as conventional are suitable in the process of the invention.
The polymerization is suitably conducted under polymerizatiOn conditions as a liquid phase or a gas-phase process employing a fluidized catalyst bed.
The polymerization conducted in the liquid phase usually employs as reaction diluent an added inert liquid diluent or alternatively a liquid diluent which comprises the olefin, such as propylene or 1-butene, undergoing polymerization. If a copolymer is prepared wherein ethylene is one of the monomers, ethylene is introduced by conventional means. Typical polymerization conditions include a reaction 214~538 temperature from about 2SC to about 125C, with temperatures from about 35C to about 90C being preferred and a pressure su~icient to maintain the reacliOn mixture in a liquid phase. Such pressures are from about 150 psi to about 1200 S psi, with pressures from about 2S0 psi to about 900 psi are preferred. The liquid phase reaction is operatea in a batchwise manner or as a continuous or semi-con~inuous process. Subsequent to reaction, the polymer product is recovered by conventional procedures. The precise controls of the polymerization conditions and reaction parameters of the liquid phase process are within the skill of the art.
As an alternate embodiment of the invention, the polymerization may be conducted ir. a gas phase process in the presence of a fluidized catalyst bed. One such gas phase process polymerization process is described in Goeke et al, U.S. Patent 4,379,7S9, incorporated herein by reference. The gas phase process typically involves charging to reactor an amount of preformed polymer particles, gaseous monomer and separately charge a lesser amount of each catalyst component.
Gaseous monomer, such as propylene, is passed through the bed of solid particles at a high rate under conditions of temperature and pressure sufficient to initiate and maintain polymerization. Unreacted ole~in is separated and recovered and polymerized olefin particles are separated at a rate substantially equivalent to its production. The process is conducted in a batchwise manner or a continuous or semi-continuous process with constant or intermittent addition of the catalyst components and/or ~-olefin to the polymerization reactor. Typical polymerization temperatures for a gas phase process are from about 30C to about 120C and typical pressures are up to about 1000 psi, with pressures from about 100 to about S00 psi being preferred.
In both the liquid phase and the gas-phase poly-merization processes, molecufar hydrogen is generally added to the reaction mixture as a chain transfer agent to regulate the molecular weight of the polymeric product. Hydrcgen is typically employed for this purpose in a manner well known to ~ 21~5538 persons skilled in the art. The precise control of reaction conditions, the rate of addition of feed component and molecular hydrogen is broadly within the skill of the art.
The present invention is useful in the polymerization of ~-olefins of up to 10 carbon atoms, including mixtures thereof. It is preferred that ~-olefins of 3 carbon atoms to 8 carbon atoms, such as propylene, butene-l and pentene-1 and hexane-l, are polymerized. If ~-olefins are to be copolymerized, the preferred ~-olefins include ethylene.
The polymers produced according to this invention are predominantly isotactic. Polymer yields are high relative to the amount of catalyst employed. The process of the invention produces homopolymer and copolymers including both random and impact copolymers, that have a relatively broad molecular weight distribution while maintaining a relatively low oligomers content (determined by the weight fraction of C2l oligomer) of less than 180 ppm. The production of polymers having an oligomers content of less than 130 ppm is preferred, with an oligomers content of less than 115 ppm being more preferred.
Other features, advantages and embodiments of the invention disclosed herein will be readily apparent to those exercising ordinary skill after reading the foregoing disclosure. In this regard, while specific embodiments of the invention have been described in detail, variations and modifications of these embodiments can be effected without departing from the spirit and scope of the invention as described and claimed.
The invention described herein is illustrated, but not limited by the following Illustrative Embodiments and the Comparative Example. The following terms are used throughout the Illustrative Embodiments and Comparative Example:
SCA (selectivity control agent) PEEB (ethyl p-ethoxybenzoate) TBDMMS (t-butyldimethylmethoxysilane) NPTMS (n-propyltrimethoxysilane) DIBDMS (diisobutyldimethoxysilane) DIBDES (diisobutyldiethoxysilane) W094/07926 2 1 ~ 5 5 3 8 PCT/US93/09009 ILLUSTRATIVE EMBODIMENT I
(a) Preparation of Procatalyst Component The procatalyst was prepared by adding magnesium diethoxide (2.17 g, 19 mmol) to 55 ml of a 50/50 (vol/vol) mixture of TiCl4/chlorobenzene. After adding diisobutyl phthalate (0.66 ml, 2.50 mmol), the mixture was heated in an oil bath and stirred at 110C for 60 minutes. The mixture was filtered hot and slurried in 55 ml of a 50/50 (vol/vol) mixture of TiCl4/chlorobenzene. Phthaloyl chloride (0.13 ml, 0.90 mmol) was added to the slurry at room temperature. The resulting slurry was stirred at 110C for 60 minutes, filtered, and slurried again in a fresh 50/50 mixture of TiCl4/chlorobenzene. After stirring at 110C for 30 minutes, the mixture was filtered and allowed to cool to room temperature. The procatalyst slurry was washed 6 times with 125 ml portions of isooctane and then dried for 120 minutes, at 25C, under nitrogen.
(b) Polymerization of Propylene Various catalysts were produced using several organosilanes as the selectivity control agent, some of which are within the scope of the invention (TBDMMS) and others that are not within the scope of the invention (NPTMS, DIBDES
and DIBDMS). Propylene (2700cc) and molecular hydrogen were introduced into a 1 gallon autoclave. The temperature of the propylene and molecular hydrocarbon was raised to 67C. An organosilane selectivity control agent, triethylaluminum, and the procatalyst slurry produced above were premixed for about 20 minutes and then the mixture was introduced into the autoclave. The amount of silane utilized in the polymerization also varied. The amount of triethylaluminum (0.56 mmoles) and the amount of the procatalyst slurry (sufficient quantity of procatalyst to provide 0.008 mmoles of titanium to the autoclave) remained constant. The autoclave was then heated to about 67C and the polymerization was continued at 67C for one hour. The polypropylene product was recovered from the resulting mixture by conventional methods and the weight of the product wo 94/07922 ~ 4~S 3 8 PCI`/US93/09009 was~used to calculate the reaction yield in millions of grams of polymer product per gram (MMg/g) of titanium in the procatalyst. The term "Q" was calculated as the quotient of the weight average molecular weight (Mw) and the number 5 average molecular weight (Mn)~ determined by gel permeation chromatography. The term ''Mz'' as defined in "Encyclopedia of Polymer Science and Engineering, 2nd Edition", Vol. 10, pp.
1-19 (1987) incorporated herein by reference, is the z-average molecular weight. The term "R";was calculated as the 10 quotient of Mz and Mw. "Melt Flow" is determined according to ASTM D-12~8-73, condition L. "Xylene Solubles" were determined in accordance with U.S. Food and Drug in;stration Regulations, 21 CFR 177.1520. The results of a series of polymerizations are shown in TABLE I.
TABLE I
H2 Yield XS3 SCA MFmmoles MMq/g Mzx 10-3 f% wt) Q R
TBDMMS 3.527 1.2 1560 5.0 9.9 4.3 TBDMMS 2.327 1.0 1570 3.8 9.6 3.9 NPTMSl 2.234 0.88 1510 2.4 7.3 3.9 20DIBDES 5.223 0.87 2070 lo.o 8.0 5.4 DIBDMSI 3.534 1.10 1560 3.8 8.2 4.3 l Comparison 2 mmoles of hydrogen added to the liquid phase reactor system 3XS = Xylene solubes by % weight To further illustrate the advantages obtained using the catalyst system of the invention, viscosity ratio values were taken for polymers having a melt flow of about 3 dg/min using the smooth curves (viscosity ratio vs. melt flow).
"Viscosity Ratio" was determined by cone and plate rheometry (dynamic viscosity measurements) as a ratio of the viscosity of the product at a frequency of 0.1 Hz divided by the viscosity of the product at a frequency of 1.0 Hz. As the viscosity ratio of polymer product increases, the molecular W094/07926 2 1 ~ 5 5 3 8 PCT/US93/09009 weight distribution increases. The values are shown in TABLE
II.
Table II

- SCA Viscosity Ratio at 3 dq/min TBDMMS 1.75 NPTMSI 1.56 DIBDMSI 1.56 ~For comparison It is seen from TABLE II that the catalyst systems of the invention direct a higher viscosity ratio and therefore a broader molecular weight distribution than a conventional catalyst systems using NPTMS as the selectivity control agent.
ILLUSTRATIVE EMBODIMENT II
Injection Molding of Polypropylene Product Some of the polypropylene products, produced according to Illustrative Embodiment I, were recovered by conventional means. Each recovered product was mixed and pelletized with the following additives package: 1000 ppm of Irganox~ 1010 hindered phenolic primary antioxidant, 1000 ppm of Irgafos~ 168 phosphite secondary antioxidant and 500 ppm of Calcium stearate as an acid acceptor. The pelletized polymer products were injection molded in an Arburg Injection Molder. The final "melt temperature" (Tmt, C) is obtained from a differential scanning calorimetry curve for each polymer product produced. A higher melt temperatu~e correlates to higher isotacticity of the polymer product.
The "Oligomers Content" was determined by the overnight extraction of a polypropylene sample in a~ 30 chloroform solution containing hexadecane (n-CI6) as an internal standard. An aliquot of the extract is shaken in , methanol and filtered to remove trace amounts of atactic material. The filtered liquid is then injected onto a capillary column which uses a flame ionization gas W094/07926 2 1 4 5 5 3 ~ PCT/US93/09oO9--chromatograph. Relative amounts of the extracted components are calculated based on the weight of polymer extracted using the internal standard quantitation against the C2l oligomer groups. The oligomers content is an indicator of the amount of volatiles, e.g. smoke and/or oil that will be liberated by the polymer during extrusion. For instance, a lower oligomers content for a polymer product translates into lower smoke generation during further processing (e.g. extrusion) of the polymer product for film and tèxtile applications.
The results of the various analysis of polymer products are shown in Table IV.
Comparative Example (a) Preparation of Procatalyst Component The procatalyst was prepared by adding magnesium diethoxide (50 mmol) to 150 ml of a 50/50 (vol/vol) mixture of chlorobenzene/TiCl4. After adding ethyl benzoate (16.7 mmol), the mixture was heated in an oil bath and stirred at 110C for approximately 30 minutes. The resulting slurry was filtered and slurried twice with 150 ml of a fresh 50/50 (vol/vol). Benzoyl chloride (0.4 ml) was added to the final slurry. After stirring at 110C for approximately 30 minutes, the mixture was filtered. The slurry was washed six times with 150 ml portions of isopentane and then dried for 90 minutes, at 30C, under nitrogen.
(b) Polymerization Using the above-described procatalyst (section a), propylene was polymerized as described in Illustrative Embodiment II, section (b), except the selectivity control agent was PEEB.
The resulting polypropylene product was mixed, pelletized and injection molded as described in Illustrative Embodiment III. The results are furnished in TABLE III.
, ,~

W094/07926 2 1 ~ 5 ~ 3 8 PCT/US93/09009 TABLE III

21 Carbon Melt Oligomer Count Flow SCA Tmt(C)l (pPm) dq/min - TBDMMS 170.8 102 2.3 NPTMS2 160.3 54 2.4 NPTMS3 169.5 76 3.3 DIBDMS2 169.2 80 2.3 PEEB3 169 260 2.9 ~Final melt temperature (C) was obtained by differential scanning calorimetry (DSC) according to ASTM D-3417-83.
2For comparison 3Comparative catalyst system

Claims (19)

1. A process for polymerizing one or more .alpha.-olefins of up to 10 carbon atoms which comprises contacting the one or more .alpha.-olefins under polymerization conditions with a catalyst system comprising:
(a) a titanium halide-containing procatalyst component obtained by halogenating a magnesium compound with a halogenated tetravalent titanium compound, in the presence of a halohydrocarbon and an alkyl ester of a polycarboxylic acid electron donor;
(b) an organoaluminium cocatalyst component; and (c) an organosilane selectivity control agent having the formula;

wherein R1, R2 and R3 are, independently, an alkyl group of 1 of 12 carbon atoms, an aryl group of up to 12 carbon atoms, an alkaryl group of up to 12 carbon atoms, an aralkyl group of up to 12 carbon atoms or halogen; and R4 is a hydrocarbyloxy group of 1 to 2 carbon atoms.

2. A process according to class 1, wherein said organosilane selectivity control agent is present in a quantity such that the molar ratio of the selectivity control agent to titanium present in the procatalyst component is from 1:1 to 70:1.

3. A process according to claim 1 or 2, wherein R1, R2 and R3 are alkyl groups and R4 is an alkoxy group.

4. A process according to claim 3, wherein R4 is a methoxy group.

5. A process according to claim 4, wherein the organosilane selectivity control agent is t-butyldimethyl-methoxysilane, (2-methyl-2-butyl)dimethylmethoxysilane or (3-ethyl-3-pentyl)dimethyl-methoxysilane or a mixture thereof.

6. A process according to claim 5, wherein the organosilane selectivity control agent is t-butyldimethyl-methoxysilane.

7. A process according to claim 6, wherein t-butyl-dimethylmethoxysilane is present in a quantity such that the molar ratio of t-butyldimethylmethoxysilane to the titanium present in the procatalyst component is from 2:1 to 60:1.

8. A process according to any one of claims 1 to 7 wherein the halogenated tetravalent titanium compound is titanium tetrachloride.

9. A process according to any one of claims 1 to 8 wherein the magnesium compound has the formula MgR'R"
wherein R' and R" are, independently, an alkoxide, aryloxide or hydrocarbyl carbonate group or halogen.

10. A process according to claim 9 wherein R' and R" are alkoxide of 1 to 10 carbon atoms.

11. A process according to claim 10, wherein the magnesium compound is magnesium ethoxide.

12. A process according to any one of claims 1 to 11 wherein the polycarboxylic acid ester electron donor is diisobutyl phthalate.

13. A process according to any one of claims 1 to 12 wherein the .alpha.-olefin is propylene and/or ethylene.

14. An olefin polymerization catalyst system comprising:
(a) a titanium halide-containing procatalyst component obtained by halogenating a magnesium compound with a halogenated tetravalent titanium compound, in the presence of an alkyl ester of a polycarboxylic acid compound and a halogenated hydrocarbon.
(b) an organoaluminum cocatalyst component, and (c) an organosilane selectivity control agent having the formula wherein R1, R2 and R3 are, independently, an alkyl group of 1 to 12 carbon atoms; an aryl group of up to 12 carbon atoms, an alkaryl group of up to 12 carbon atoms, an aralkyl group of up to 12 carbon atoms or halogen; and R4 is a hydrocarbyloxy group of 1 to 2 carbon atoms.

15. The olefin polymerization catalyst system according to claim 17, wherein the molar ratio of the selectivity control agent to the titanium present in the procatalyst is from 1:1 to 70:1.

16. The olefin polymerization catalyst system according to claim 14 or 15, wherein the selectivity control agent is t-butyldimethylmethoxysilane, (3-methyl-3-pentyl)-dimethylmethoxysilane, or (2-methyl-2-butyl)dimethylethoxy-silane or a mixture thereof.

17. the olefin polymerization catalyst system according to claim 16, wherein the selectivity control agent is t-butyldimethylmethoxysilane.

18. The olefin polymerization catalyst system according to anyone of claims 14 to 17, wherein the magnesium compound is a magnesium dialkoxide, the halogenated tetravalent titanium compound contains at least two halogen atoms, and the organoaluminum cocatalyst component is a trialkylaluminum compound.

19. The olefin polymerization catalyst system according to claim 18, wherein the magnesium compound is magnesium diethoxide, the alkyl ester of the polycarboxylic acid compound is diisobutyl phthalate, and the halohydrocarbon is chlorobenzene or o-chlorotoluene.