ALPHA-OLEFIN POLYMERIZATION CATALYSTS COMPRISING SUPPORTED CYCLOPENTADIENYL GROUP 6b METAL OXO, THIO, IMIDO AND PHOSPHIDO COMPOUNDS AND PROCESS FOR POLYMERIZING ALPHA-OLEFINS

Abstract: Disclosed is a catalyst system for the homopolymerization and copolymerization of alpha-olefins having 2-8 carbon atoms, said catalyst system comprising a cyclopentadienyl Group 6b metal compound having at least one oxo, thio, imido or phosphido group bonded directly to the Group 6b metal, and at least one organic radical bonded to the Group 6b metal through a carbon atom, said Group 6b metal compound being supported on an inorganic support. The catalyst system may also contain a Group 2 or Group 3 metal alkyl compound cocatalyst.

Description: 01 ALPHA-OLEFIN POLYMERIZATION CATALYSTS COMPRISING SUPPORTED 02 CYCLOPENTADIENYL GROUP 6b METAL OXO, THIO, IMIDO AND 03 PHOSPHIDO COMPOUNDS AND PROCESS FOR POLYMERIZING 04 ALPHA-OLEFINS 05 OC FIELD OF THE INVENTION 07 08 The present invention relates to catalyst systems for 09 polymerizing alpha-olefins and processes for polymerizing 10 alpha-olefins using such catalysts. 11 12 BACKGROUND OF THE INVENTION 13 14 Chromium-based catalysts are used in the commercial 15 polymerization of small alpha-olefins such as ethylene and 1* propylene. One such catalyst is prepared by depositing 17 chromocene (bis(cyclopentadienyl) chromium (II)) on an 18 inorganic metal oxide support, as disclosed in British 19 Patent No. 1,253,063 to Karapinka. U.S. Patent 0 No. 4,015,059, issued March 29, 1977 to Karol, describes the 1 use of bis(indenyl)- and bis(flourenyl)-chromium (II) 2 compounds supported on activated inorganic oxide supports as 3 catalysts for the polymerization of ethylene. 24 5 U.S. Patent No. 4,530,914, issued July 23,1985 to E en 6 et al., discloses a catalyst system for the polymerization 7 of alpha-olefins which comprises two or more metallocenes, 28 each having different propagation and termination rate 9 constants, and aluminoxane. The metallocenes are 30 cyclopentadienyl derivatives of a transition metal of 31 Group 4b, 5b, and 6b metals of the Periodic Table. They are 32 described by the formulas (C 5 R' m ) p R M 8 (C 5 R' m )MeQ 3 _ p and 33 R" β (C5R , m ) 2 MeQ' where (C 5 R , m ) is a cyclopentadienyl or 34 01 substituted cyclopentadienyl, each R' is hydrogen or a 02 hydrocarbyl radical, R" is an alkylene radical, a dialkyl 03 germanium or silicon or an alkyl phosphine or amine radical 04 bridging two (C5R' m ) rings, Q is a hydrocarbon radical, Me 05 is a Group 4b, 5b, or 6b metal, s is 0 or 1, p is 0, 1, 0< or 2; when p=0, s=0; m is 4 when s is 1 and is 5 when ε 0 is o. 08 09 U.S. Patent No. 4,939,217, issued July 3, 1990 to Stricklen, 10 also discloses a process for polymerizing olefins where the 11 polymerization is conducted in the presence of hydrogen, and 12 a catalyst system is used which contains aluminoxane and at 13 least two metallocenes, each having different olefin 14 polymerization termination rate constants. The metallocenes 15 disclosed are similar to those described in aforementioned lβ U.S. Patent No. 4,530,914. 17 18 U.S. Patent No. 4,975,403, issued December 4, 1990 to Ewen, 19 discloses a catalyst system for use in the polymerization of 20 olefins. The catalyst system includes at least two 21 different chiral, stereo-rigid metallocene catalysts of the 22 formula R" (C5(R') )2MeQ p (where Me is a Group 4b, 5b or 6b 23 metal and (C 5 (R , ) 4 ) is a cyclopentadienyl or substituted 24 cyclopentadienyl ring) and an aluminum compound. 25 C Canadian Patent Application No. 2,000,567, published 7 April 13, 1990, discloses a process for producing 8 polyethylene using a composite catalyst made up of a solid 9 catalyst component typified by a selected chromium compound, 0 a modified aluminum compound typified by a trialkylaluminum, 1 and an alkylaluminum alkoxide compound. The chromium 2 compound may be chromium oxide, and the modified aluminum 3 4 01 compound may be the reaction product of an organoaluminum 02 compound and water. 03 04 European Patent Application Publication No. 416,784 by 05 Dawkins, published March 13, 1991, discloses an olefin 0< polymerization catalyst obtainable by depositing on a dry 07 inorganic oxide support a mononuclear chromium complex to 08 produce a catalyst precursor and thereafter by thermally 09 activating the catalyst precursor. The mononuclear chromium 10 complex is representable by the general formula: 11 12 Z-CR-L χ 13 ** wherein Z is a cyclopentadienyl ligand substituted with 4 or 15 5 hydrocarbon groups containing 1 to 3 carbon atoms; *' x is an integer from l to 4, and 17 L is either a four- or five-substituted cyclopentadienyl 18 ligand, or (CO) 3 R in which R is H, methyl or ethyl. 19 20 The catalyst is used to polymerize olefins, particularly 21 ethylene optionally with C 3 -C 8 alpha-olefins. The catalyst 22 is said to produce polyolefins having a relatively high 23 molecular weight and a broad molecular weight distribution. 24 25 European patent Application Publication No. 416,785 by 2C Dawkins, published March 13, 1991, also describes an olefin 27 polymerization catalyst obtainable by depositing on a dry 28 inorganic oxide at least one mononuclear chromium complex 29 having the general formula: 30 31 Z-Cr-L 32 33 34 01 wherein Z is a cyclopentadienyl ligand substituted with 4 or 02 5 hydrocarbyl groups containing 1 to 3 carbon atoms; and 03 L is one or more hydrocarbyl ligands which are sufficiently 04 reactive to enable the complex to react with the inorganic 05 oxide without thermal activation. oc 07 The catalyst can be used without thermal activation for 08 polymerizing olefins, particularly ethylene optionally with 09 C 3 -C 8 alpha-olefins. The catalyst is said to produce 10 polyolefins having a broad molecular weight distribution. 11 12 U. S. Patent No. 4,424,139, issued January 3, 1984 to 13 McDaniel et al., discloses a catalyst system containing (a) ** a catalyst comprising a bis-(cyclopentadienyl)-chromium (II) 15 compound and a phosphate-containing support and (b) a lβ cocatalyst selected from trihydrocarbyl borane compounds and 17 aluminum compounds. These catalyst are said to be useful as 18 olefin polymerization catalysts, and are said to be capable 19 of giving narrow molecular weight distribution polymer. 20 21 A tetrameric chromium (II) compound useful as an alpha- 22 olefin polymerization catalyst is disclosed in U. S. Patent 23 No. 4,806,513, issued February 21, 1989 to McDaniel et al. 4 The compound, octakis-(μ-trimethylsilylmethyl)tetrachromium, 5 is not, however, cyclopentadienyl-containing. ( 7 U. S. Patent No. 4,587,227, issued May 6, 1986 to Smith et 8 al., discloses octakis-(μ-trimethylsilylmethyl)tetrachromium 9 on an inorganic oxide as a catalyst to make linear low 0 density polyethylene with specific short chain branching. 1 2 3 4 1 SUMMARY OF THE INVENTION 2 3 it has now been discovered that when cyclopentadienyl Group 4 6b metal compounds having at least one oxo, thio, imido or 5 phosphido group bonded directly to the Group 6b metal and at β least one organic radical bonded to the Group 6b metal 7 through a carbon atom are supported on an inorganic support, 8 high productivity alpha-olefin polymerization catalysts are 9 produced. In addition, the use of a cocatalyst improves the 0 productivity of many of these compounds. Also, these 1 catalysts produce linear polyethylenes. 2 3 in accordance with the present invention, there is provided 4 a catalyst system for the homopolymerization and 5 copolymerization of alpha-olefins having 2-8 carbon atoms, * said catalyst system comprising a cyclopentadienyl Group 6b 7 metal compound having at least one oxo, thio, imido or 8 phosphido group bonded directly to the Group 6b metal, and 9 at least one organic radical bonded to the Group 6b metal 0 through a carbon atom, said Group 6b metal compound being 1 supported on an inorganic support. 2 3 Also provided in accordance with this invention is a 4 catalyst system for the homopolymerization and 5 copolymerization of alpha-olefins having 2-8 carbon atoms, < said catalyst system comprising (a) a cyclopentadienyl Group 7 6b metal compound having at least one oxo, thio, imido or 8 phosphido group bonded directly to the Group 6b metal, and 9 at least one organic radical bonded to the Group 6b metal 0 through a carbon atom; and (b) a cocatalyst selected from 1 Group 2 or 3 metal alkyl compounds. 2 3 Further, provided in accordance with the present invention is 4 a process for the homopolymerization or copolymerization of 01 alpha-olefins having 2-8 carbon atoms comprising 02 polymerizing said alpha-olefin, or copolymerizing two or 03 more alpha-olefins in the presence of a catalyst system 04 comprising a cyclopentadienyl Group 6b metal compound having 05 at least one oxo, thio, imido or phosphido group bonded 0 β directly to the Group 6b metal, and at least one organic 07 radical bonded to the Group 6b metal through a carbon atom, 08 said group 6b metal compound being supported on an inorganic 09 support. 10 11 The present invention also provides a process for the 12 homopolymerization or copolymerization of alpha-olefins 13 comprising polymerizing said alpha-olefin, or copolymerizing 14 two or more alpha-olefins in the presence of a catalyst 15 system comprising (a) a cyclopentadienyl Group 6b metal 1* compound having at least one oxo, thio, imido or phosphido 17 group bonded directly to the Group 6b metal, and at least 18 one organic radical bonded to the Group 6b metal through a It carbon atom, said group 6b metal compound being supported on 20 an inorganic support, and (b) a Group 2 or 3 metal alkyl 21 compound cocatalyst. 22 23 in the above catalyst systems and processes, chromium is a 24 preferred Group 6b metal, silica, aluminum phosphate and 25 alumina aluminum phosphate are preferred supports, and 2C aluminoxanes and trialkylaluminum compounds are preferred 27 Group 2 or 3 metal alkyl compounds. 28 29 Among other factors, the present invention is based on the 30 discovery that the catalyst systems of the present invention 31 have high activity (in terms of amount of polymer produced 32 per amount of chromium per hour) , produce ethylene 33 homopolymers with a high degree of linearity, and produce 34 polymers with a variety of molecular weight distributions. 1 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 2 3 The present invention provides catalyst systems for use in 4 the polymerization (either homopolymerization or 5 copolymerization) of C 2 -C 8 alpha-olefins, including 8 ethylene, propylene, 1-butene, 1-hexene, 7 4-methyl-l-pentene, and 1-octene. 8 8 It has quite surprisingly been found that, even though the 0 productivity of many cyclopentadienyl Group 6b metal 1 compounds is quite low when employed as catalyst in the 2 homogeneous polymerization of alpha-olefins, when these 3 compounds are supported on an inorganic support, such as a 4 solid inorganic metal oxide or inorganic phosphate, their 5 productivity increases dramatically, especially when * cocatalysts are used. 7 8 While the catalyst systems of the present invention can be 9 used to polymerize a variety of alpha-olefins, they are 0 especially useful in the polymerization of ethylene. These 1 catalysts produce linear polyethylene, i.e., polyethylene 2 with substantially no side chain branches, in high yield. 3 In addition, the catalyst systems of this invention produce 4 polyethylene with a variety of molecular weight 5 distributions, depending on the support used. C 7 The catalyst systems of the present invention comprise at 8 least one cyclopentadienyl Group 6b metal compound having at 9 least one oxo, thio, imido or phosphido group bonded 0 directly to the Group 6b metal, and at least one organic 1 radical bonded to the Group 6b metal through a carbon atom, and which is catalytically active when deposited on an 3 inorganic support, such as a solid inorganic metal oxide or 4 1 inorganic metal phosphate. As used herein, the term 2 N cyclopentadienyl" refers to unsubstituted cyclopentadienyl 3 as well as substituted derivatives of cyclopentadienyl in 4 which the cyclopentadienyl ring contains one or more 5 substituents which do not interfere with the Group 6b metal C compound's ability to function as an alpha-olefin 7 polymerization catalyst. Examples of substituted 8 cyclopentadienyl include pentamethylcyclopentadienyl, 9 ethyltetramethylcyclopentadienyl, methylcyclopentadienyl, 0 t-butylcyclopentadienyl, and pentaphenylcyclopentadienyl, as 1 well as compounds where the substituent forms a multi-cyclic 2 ring with the cyclopentadienyl ring. Examples of these 3 multi-cyclic rings include indenyl and fluorenyl rings. For 4 the sake of simplicity, the abbreviation Cp* will be used 5 herein to refer to pentamethylcyclopentadienyl, and the C abbreviation Cp' will be used herein to refer to ethyltetramethylcyclopentadienyl. Cp* is a preferred 8 cyclopentadienyl group as it stabilizes the organometallic 9 compound of this invention. 0 1 The Group 6b metal compounds useful in the present invention 2 include compounds wherein the metal is chromium, molybdenum 3 or tungsten. Compounds in which the metal is chromium are 4 preferred. The Group 6b metal atom in the compound has an 5 oxidation state of +4, +5, or +6. β 7 The Group 6b metal compounds useful in this invention have 8 at least one oxo, thio, imido or phosphido group(s) bonded 9 directly to the Group 6b metal. As used herein, the term 0 "oxo" refers to divalent radicals having the formula =0 or 1 -o- (i.e., the oxygen atom is bonded exclusively to the Group 6b metal) , the term H thio n refers to divalent radicals 3 having the formulas =S or -S- (i.e., the sulfur atom(s) is 4 bonded exclusively to the Group 6b metal) , the term "imido" 1 refers to divalent radicals having the formula =N-R or =N-H, 2 and the term "phosphido" refers to divalent radicals having 3 the formula =P-R or =P-H where R is as defined below. 4 5 The Group 6b metal compounds also have, in addition to one C cyclopentadienyl group, at least one organic radical bonded 7 to each Group 6b metal atom through a carbon atom. As used 8 herein, the term "organic radical" refers to hydrocarbyl 9 radicals such as alkyl, alkenyl, aryl, aralkyl and alkaryl 0 radicals and the like. Exemplary hydrocarbyl radicals 1 include, but are not limited to, methyl, ethyl, propyl, 2 butyl, amyl, isoamyl, hexyl, neopentyl, isobutyl, heptyl, 3 octyl, nonyl, decyl, cetyl, phenyl, benzyl and other similar 4 groups. Additionally, organosilyl groups which are bonded to 5 the Group 6b metal atom(s) through a carbon atom can be used * as the organic radical. Trimethylsilyl methyl, i.e., 7 (CH J β SiC^-, and the like are examples of such organosilyl 8 groups. If more than one hydrocarbyl group is bonded to the 9 metal atom, they can be independent or linked, i.e., they 0 can form a 3-, 4-, 5-, 6-, or 7-membered metallocycle. 1 One object of this invention is to provide a catalyst and a 2 process for producing linear, high density polyethylene with 3 high molecular weight and narrow molecular weight 4 distribution, using the Group 6b metal compounds of this 5 invention. C 7 Examples of the Group 6b metal compounds useful in this 8 invention include, but are not limited to, compounds having 9 the following general formulas: 0 1 2 3 4 (I) (II) 08 .. wherein M is a Group 6b metal such as chromium, molybdenum 10 and tungsten; 11 12 (C 5 (R , ) 5 ) is an unsubstituted or substituted 13 cyclopentadienyl ring; 14 15 R' is at each independent occurrence hydrogen, a hydrocarbyl lβ radical having 1-20 carbon atoms, or adjacent R' groups may 17 together form one or more hydrocarbyl rings; 18 19 X is at each independent occurrence O, S, N-R, N-H, P-R or 20 P " H ' * 21 22 R1 is a hydrocarbyl radical having 1-20 carbon atoms (for 23 example, a monov lent saturated aliphatic or alicyclic 2 radical or a monovalent aromatic radical, or combinations 25 thereof) , or an organosilyl group, such as 2c tri ethylsilylmethyl; 27 2 8 R is at each independent occurrence hydrogen or a 29 hydrocarbyl radical having 1-20 carbon atoms (such as a 3 0 monovalent saturated aliphatic or alicyclic radical or a 31 monovalent aromatic radical) ; 32 33 a = l or 2, b = l or 2, c = l or 2 with the proviso that 34 when b = 1 then a + c = 3 <and when b = 2 then a + c = 2; and d = 1 or 2, e = 1 or 2 and d + e = 3. Examples of compounds having formula (I) above include, but are not limited to, Cp*Cr(0) 2 CH 3 , Cp*Cr(0) (CH 3 ) 2 , and [Cp*Cr(CH 3 ) 2 ] 2 0. In part, the choice of Group 6b metal compound is based on the thermal stability of the compound and its ease of preparation. Of the Group 6b metal compounds useful in this invention, the organochromium compounds are preferred. The Group 6b metal compounds of this invention may be prepared in a manner similar to that described in Noh, S. et al., J. Am. Chem. Soc.. 1992, 114 1892-1893. In the catalyst systems of the present invention, the Group 6b metal compound is deposited on an inorganic support. Suitable inorganic metal oxide supports include silica, alumina, silica-alumina mixtures, thoria, zirconia, magnesium oxide and similar oxides. Suitable inorganic metal phosphates include aluminum phosphate, zirconium phosphate, magnesium-containing alumina phosphate and alumina aluminum phosphate. Silicas, aluminum phosphates and alumina aluminum phosphates are preferred. Suitable silica supports include Davison 952, Davison 955, Crosfield EP-10 and Crosfield EP17MS. Further examples of useful supports are the following: alumina aluminum phosphates with aluminum to phosphorus ratios of about 5:1 to 1:1 as disclosed in U.S. Patents Nos. 4,080,311 and 4,219,444; magnesia-alumina-aluminum phosphates as described in U.S. Patent No. 4,210,560; zinc oxide-cadmium oxide-alumina- aluminum phosphates such as those disclosed in U.S. Patent No. 4,367,067; and the calcium, barium, and/or strontium oxide-alumina-aluminum phosphates described in U.S. Patent Nos. 4,382,877 and 4,382,878. The acidity of these supports can be adjusted by judicious inclusion of basic metals such as alkali and alkaline earth metals (Ca, Be, Mg, K, Li) to counteract excessive acidity. Other useful supports include magnesium halides, particularly magnesium chloride, such as those described in "Transition Metals and Organometallics as Catalysts for Olefin Polymerization" (1988, Springer-Verlag) edited by . Kaminsky and H. Sinn and "Transition Metal Catalyzed Polymerizations-Ziegler-Natta and Metathesis Polymerizations" (1988, Cambridge University Press) edited by R. Quirk. The supports useful in this invention should have a high surface area. In general, these supports should have the characteristics listed in the following table: Property Broad Ranσe Preferred Ranσe Surface area 25-600 m 2 /g 100-370 m 2 /g Pore volume 0.25-4 cm 3 /g 0.7-3 cm 3 /g Mean particle 30-200 microns 60-140 microns diameter Preferably, the pore size distribution is broad, with a significant percentage of the pores in the acropore range (>500 Angstroms) . Preferably, at least 50% of the pores are acropores. It is also desirable that the support be substantially anhydrous before the Group 6b metal compound is deposited on it. Thus, it is desirable to calcine the support prior to deposition of the Group 6b metal compound. The supported catalysts of this invention are readily prepared by techniques well known in the art. For example, a solution of the Group 6b metal compound in aliphatic, aromatic or cycloaliphatic hydrocarbons, or ethers such as diethyl ether or tetrahydrofuran can be stirred with the support until the Group 6b metal compound is adsorbed on or reacted with the support. The amount of Group 6b metal compound relative to the amount of support will vary considerably depending upon such factors as the particle size of the support, its pore size and surface area, the solubility of the Group 6b metal compound in the solvent employed, and the amount of Group 6b metal compound which is to be deposited on the support. However, in general the amount of Group 6b metal compound used is adjusted so that the final metal content (calculated as the element) , relative to the support, is in the range of from about 0.01 to about 10 weight percent. In most cases, the most desirable level is in the range of about 0.1 to about 5 weight percent. Activities for the catalyst systems of the present invention are greater than 3,000 grams of polymer per gram of chromium metal per hour ("g/g Cr/hr"), preferably greater than 30,000 g/g Cr/hr. it has been found that the activity of many of the supported Group 6b metal compounds of this invention is significantly increased when they are employed in conjunction with a co-catalyst. The co-catalysts useful in the practice of the present invention are Group 2 and Group 3 metal alkyIs. As used herein, the term "Group 2 and Group 3 metal alkyIs" refers to compounds containing a metal from Group 2 or Group 3 of the Periodic Table (such as Mg, Zn, B, or Al) to which is bonded at least one alkyl group, preferably a C l to C 8 alkyl group. Suitable Group 2 and Group 3 metal alkyls 1 include dialkyl magnesium, dialkyl zinc, trialkylboranes, 2 and aluminum alkyls. Suitable aluminum alkyls include 3 trialkylaluminums (such as trimethylaluminum, 4 triethylaluminum, triisobutylaluminum and trioctylaluminum) . 5 Trialkylaluminums with alkyl groups of four carbons or 6 greater are preferred. Other aluminum alkyls useful in the 7 practice of the present invention include alkylaluminum 8 alkoxides (such as diethylaluminum ethoxide and 9 ethylaluminum diethoxide) , and alkylaluminum halides (such 0 as diethylaluminum chloride, diethylaluminum bromide, 1 diethylaluminum iodide, diethylaluminum fluoride, ethyl 2 aluminum dichloride, ethyl aluminum dibro ide, ethyl 3 aluminum diiodide, ethyl aluminum difluoride, and ethyl 4 aluminum sesquichloride) . 5 6 Other suitable aluminum alkyls are aluminoxanes, including 7 those represented by the general formula (R-Al-0) n for the β cyclic form and R(R-Al-0) n -AlR 2 for the linear form. In 9 these formulas, R is, at each independent occurrence, an 0 alkyl group (such as methyl, butyl, isobutyl and the like) 1 preferably with more than two carbon atoms, more preferably with 3-5 carbon atoms, and n is an integer, preferably from 3 1 to about 20. Most preferably, R is an isobutyl group. 4 Mixtures of linear and cyclic aluminoxanes may also be used. 5 Examples of aluminoxanes useful in this invention include, β but are not limited to, ethyl aluminoxane, isobutyl 7 aluminoxane, and methyl aluminoxane. Aluminoxanes (also 8 known as "alumoxanes") suitable for use in this invention 9 are described in Pasynkiewicz, "Alumoxanes: Synthesis, 0 Structure, Complexes and Reactions," Polyhedron 9, p. 429 1 (1990) , which is incorporated by reference herein in its entirety. 3 4 The preferred Group 2 and Group 3 metal alkyls are the aluminoxanes and the trialkylaluminums. When used, the Group 2 and Group 3 metal alkyls are used in a Group 2 or 3 metal alkyl to Group 6b metal compound mole ratio of from about 1:1 to about 1000:1. The preferred mole ratio is from about 10:1 to about 200:1. The catalyst systems of the present invention may be used in either slurry or gas phase polymerization processes. After the catalysts have been formed, the polymerization reaction is conducted by contacting the monomer charge with a catalytic amount of the catalyst at a temperature and at a pressure sufficient to initiate the polymerization reaction. if desired, an organic solvent may be used as a diluent and to facilitate materials handling. The polymerization reaction is carried out at temperatures of from about 30°C or less up to about 200°C or more, depending to a great extent on the operating pressure, the pressure of the entire monomer charge, the particular catalyst being used, and its concentration. Preferably, the temperature is from about 30°C to about 125°C. The pressure can be any pressure sufficient to initiate the polymerization of the monomer charge, and can be from atmospheric up to about 1000 psig. As a general rule, a pressure of about 20 to about 800 psig is preferred. when the catalyst is used in a slurry-type process, an inert solvent medium is used. The solvent should be one which is inert to all other components and products of the reaction system, and be stable at the reaction conditions being used. it is not necessary, however, that the inert organic solvent medium also serve as a solvent for the polymer produced. The inert organic solvents which may be used include saturated aliphatic hydrocarbons (such as hexane, heptane, pentane, isopentane, isooctane, purified kerosene and the like) , saturated cycloaliphatic hydrocarbons (such as cyclohexane, cyclopentane, dimethylcyclopentane, methylcyclopentane and the like) , aromatic hydrocarbons (such as benzene, toluene, xylene and the like) , and chlorinated hydrocarbons (such as chlorobenzene, tetrachloroethylene, o-dichlorobenzene and the like) . Particularly preferred solvents are cyclohexane, pentane, isopentane, hexane and heptane. When the catalyst is used in a gas phase process, it is suspended in a fluidized bed with, e.g., ethylene. Temperature, pressure and ethylene flow rates are adjusted so that to maintain acceptable fluidization of the catalyst particles and resultant polymer particles. Further descriptions of such a fluidized bed may be found in British Patent No. 1,253,063, to Karapinka, which is incorporated by reference herein. The term molecular weight distribution ("MWD") , as used herein, is the weight average molecular weight ("M^,") divided by the number average molecular weight ("M JJ ") , i.e., M w /M n . The polymers produced in accordance with the present invention using silica supported catalysts have a MWD greater than 10, preferably greater than 15, and more preferably greater than 20. These polymers, which have high MWD's, have improved ease of processing, better melt behavior, and other desirable properties such as impact resistance and environmental stress crack resistance. Large blow molded products are superior when made with high MWD polymers. Additionally, film is more puncture resistant when made from polymer with a high MWD. The polymers made in accordance with this invention using alumina aluminum phosphate supported catalysts possess high molecular weight and a more narrow MWD, making them useful in such applications as injection molding. it has quite surprisingly been found that when the catalyst systems of this invention are used to produce ethylene homopolymers, the resulting polyethylenes are highly linear, whereas ethylene homopolymers prepared using similar catalyst systems contain significant amounts of side chain branching. This is demonstrated by 13 C NMR analysis where, for example, polyethylene prepared in accordance with the present invention has essentially no side chain branches ("SCB") per 1000 carbon atoms in the polyethylene. In contrast, polyethylene prepared using bis - (cyclopentadienyl) chromium (II) (chromocene) supported on A1 2 0 3 'A1P0 4 are reported to contain 0.6 to 0.7 mole percent of side chain branches (see U.S. Patent No. 4,424,139). The following examples are intended to further illustrate the present invention, and are not intended to limit its scope. EXAMPLE 1 PREPARATION OF SUPPORTED CATALYSTS Silica supports were purchased from W. R. Grace & Co., and included Davison 952 and Davison 955 silicas. These silicas have the following properties: Property Davison 952 Davison 955 Surface area 340 m 2 /g 300 m 2 /g Pore volume 1.68 cm 3 /g 1.60 cm 3 /g Mean particle 110 microns 40 microns diameter The alumina aluminum phosphate supports used in the following examples were prepared by the procedure of Example 1 in U.S. Patent No. 4,080,311, issued March 21, 1978 to Kehl, which patent is incorporated by reference herein. The product had an A1 2 0 3 to A1P0 4 ratio of 1:2. All catalysts were prepared in a similar manner. Details for Cp*Cr(0)CH 3 ) 2 are as follows: Cp*Cr(0) (CH 3 ) 2 (0.025g) was dissolved in 10 ml of pentane and treated all at once with 0.750g of A1 2 0 3 *A1P0. The resulting solution was stirred for 15 minutes resulting in a solid and a clear supernatant. The solid was collected, washed with 2 x 10 ml of pentane and dried under vacuum to a free-flowing powder. EXAMPLE 2 ETHYLENE POLYMERIZATION USING SUPPORTED CATALYST Polymerization runs were conducted in 1 or 2 liter autoclave reactors under particle form (slurry) conditions using between 300 and 500 ml heptane as diluent, and a weighed amount of catalyst (typically 0.050 to 0.250 g) . Run times of 0.5 to 2.0 hours were normally employed. For example, in a typical run, 0.075 g of the supported catalyst of Example l was charged to a one-liter autoclave along with 300 ml of heptane. Polyisobutylaluminoxane (0.3 ml of a 1.0 M heptane solution, prepared by slow hydrolysis of triisobutylaluminum with 1.0 equivalents of H 2 0 as in Example 3 of U.S. Patent No. 4,665,208, issued May 12, 1987 to Welborn et al., which patent is incorporated by reference herein) was added to the stirred reactor as cocatalyst. The reactor temperature and pressure were adjusted to 80°C and 550 psi (with ethylene) , respectively. The ethylene was supplied on demand from a pressurized reservoir. After 2.0 hours, the reaction was stopped by rapidly cooling the reactor and venting the pressure. The polymer produced was washed with isopropanol and acetone, and dried under vacuum to yield 38 g of white, granular solid. The results of these polymerizations are indicated in Tables I-VI. Mole ratio b Activity is expressed in g. polymer/g. Cr/hr. c ALPO - Al 2 θ3»λlP0 4 dehydrated at 400°C for 24 hours. d IBAO * Isobutylaluminoxane "Determined by GPC TABLE V POLYMERIZATION DATA FOR Cp Cr (Q) 2 CH 3 Run Support u mol Co¬ Al : Cr C2H 4 Temp, Activity Cr catalyst psig β C ALPO 26 IBAO 20 550 80 58, 000 ALPO 26 IBAO 20 550 80 50, 000 EXAMPLE 3 GAS PHASE POLYMERIZATION The procedure of Example 2 is repeated in a 2 liter, stirred autoclave using the supported catalysts of this invention, except that heptane is not added to the autoclave. The reactor temperature and pressure are adjusted to 85°C and 550 psi (with ethylene) , respectively. A white, granular polymer is produced.

Claims: WHAT IS CLAIMED IS: 1. A catalyst system for the homopolymerization and copolymerization of alpha-olefins having 2-8 carbon atoms, said catalyst system comprising a cyclopentadienyl Group 6b metal compound having at least one oxo, thio, imido or phosphido group bonded directly to the Group 6b metal, and at least one organic radical bonded to the Group 6b metal through a carbon atom, said Group 6b metal compound being supported on an inorganic support. 2. The catalyst system of Claim 1 wherein the cyclopentadienyl is substituted cyclopentadienyl. 3. The catalyst system of Claim 2 wherein the substituted cyclopentadienyl is pentamethylcyclopentadienyl. 4. The catalyst system of Claim 1 wherein the Group 6b metal compound is a chromium compound. 5. The catalyst system of Claim 4 wherein the chromium compound has an oxo.group bonded directly to the chromium. 6. The catalyst system of Claim 5 wherein the chromium compound is selected from Cp*Cr (0) 2 CH 3 Cp*Cr (0) (CH 3 ) 2 and [Cp*Cr (CH 3 ) 2 ] 2 0 1 where Cp* is pentamethylcyclopentadienyl. 2 3 7. The catalyst system of Claim 1 wherein the Group 6b 4 metal compound has the formula: 5 7 (C 5 (R')57-afflM -b(R l .) c (I) 8 2 3 wherein M is a Group 6b. metal; 4 5 (C 5 (R') 5 ) is an unsubstituted or substituted 8 cyclopentadienyl ring; 7 8 R' is at each independent occurrence hydrogen, a 9 hydrocarbyl radical having 1-20 carbon atoms, or 0 adjacent R' groups may together form one or more * hydrocarbyl rings; 2 3 X is at each independent occurrence O, S, N-R, N-H, P-R < or P-H; 5 8 R 1 is a hydrocarbyl radical having 1-20 carbon atoms, 7 or an organosilyl group; 8 9 R is at each independent occurrence hydrogen or a 0 hydrocarbyl radical having 1-20 carbon atoms; 1 2 3 4 a = l or 2, b = l or 2, c = l or 2 with the proviso that when b = 1 then a + c = 3 and when b = 2 then a + c = 2; and d = 1 or 2, e = 1 or 2 and d + e = 3. 8. The catalyst system of Claim 7 wherein (C 5 (R , ) 5 ) is pentamethylcyclopentadienyl. 9. The catalyst system of Claim 7 wherein X is O. 10. The catalyst system of Claim l wherein the support is an inorganic metal oxide or inorganic metal phosphate. 11. The catalyst system of Claim 10 wherein the support is selected from the group consisting of alumina, silica, silica-alumina, aluminum phosphate, zirconium phosphate, and alumina aluminum phosphate. 12. The catalyst system of Claim 11 wherein the support is alumina aluminum phosphate. 13. The catalyst system of Claim 6 wherein the support is selected from the group consisting of alumina, silica, silica-alumina, aluminum phosphate, zirconium phosphate, and alumina aluminum phosphate. 14. The catalyst system of Claim 13 wherein the support is alumina aluminum phosphate. 15. The catalyst system of Claim 4 wherein the chromium of said chromium compound is present in an amount within the range of 0.1 to 10 weight percent based on the weight of said inorganic support. 16. A catalyst system for the homopolymerization and copolymerization of alpha-olefins having 2-8 carbon atoms, said catalyst system comprising: (a) a cyclopentadienyl Group 6b metal compound having at least one oxo, thio, imido or phosphido group bonded directly to the Group 6b metal, and at least one organic radical bonded to the Group 6b metal through a carbon atom, said Group 6b metal compound being supported on an inorganic support; and (b) a cocatalyst selected from Group 2 or 3 metal alkyl compounds. 17. The catalyst system of Claim 16 wherein the cyclopentadienyl is substituted cyclopentadienyl. is. The catalyst system of Claim 17 wherein the substituted cyclopentadienyl is pentamethylcyclopentadienyl 19. The catalyst system of Claim 16 wherein the Group 6b metal compound is a chromium compound. 20. The catalyst system of Claim 19 wherein the chromium compound has an oxo group bonded directly to chromium. 21. The catalyst system of Claim 20 wherein the chromium compound is selected from Cp*Cr(0) 2 CH 3 Cp*Cr(0) (CH 3 ) 2 and [Cp*Cr(CH 3 ) 2 ] 2 0 where Cp* is pentamethylcyclopentadienyl. 22. The catalyst system of Claim 16 wherein the Group 6b metal compound has the formula: (C 5 (R')5 7 - a (Mli-bfR. 1 ), (I) [ (II) wherein M is a Group 6b metal; (C 5 (R') 5 ) is an unsubstituted or substituted cyclopentadienyl ring; R' is at each independent occurrence hydrogen, a hydrocarbyl radical having 1-20 carbon atoms, or adjacent R' groups may together form one or more hydrocarbyl rings; x is at each independent occurrence 0, S, N-R, N-H, P-R or P-H; 01 R 1 is a hydrocarbyl radical having 1-20 carbon atoms, 02 or an organosilyl group; 03 04 R is at each independent occurrence hydrogen or a 05 hydrocarbyl radical having 1-20 carbon atoms; 06 87 a = l or 2, b = l or 2, c = l or 2 with the proviso 08 that when b = 1 then a + c = 3 and when b = 2 then a + 09 c = 2; and 10 11 d = 1 or 2, e = 1 or 2 and d + e = 3. 12 13 23. The catalyst system of Claim 22 wherein (C 5 (R , ) 5 ) is * 8 pentamethylcyclopentadienyl. 15 24. The catalyst system of Claim 16 wherein the support is 1 an inorganic metal oxide or inorganic metal phosphate. 18 19 25. The catalyst system of Claim 24 wherein the support is 20 selected from the group consisting of alumina, silica, 21 silica-alumina, aluminum phosphate, zirconium 22 phosphate, and alumina aluminum phosphate. 23 24 26. The catalyst system of Claim 25 wherein the support is alumina aluminum phosphate. 26 27 27. The catalyst system of Claim 21 wherein the support is 28 selected from the group consisting of alumina, silica, 29 silica-alumina, aluminum phosphate, zirconium 30 phosphate, and alumina aluminum phosphate. 31 32 28. The catalyst system of Claim 27 wherein the support is alumina aluminum phosphate. 34 29. A catalyst system according to Claim 19 wherein the chromium of said chromium compound is present in an amount within the range of 0.1 to 10 weight percent based on the weight of said inorganic support. 30. The catalyst system of Claim 16 wherein the Group 2 or Group 3 metal alkyl compound is an alkylaluminum compound. 31. The catalyst system of Claim 30 wherein the alkylaluminum compound is selected from the group consisting of trialkylaluminum compounds, alkylaluminum alkoxides, alkylaluminum, halides and aluminoxanes. 32. The catalyst system of Claim 31 wherein the alkylaluminum compound is an aluminoxane or trialkylaluminum compound. 33. A catalyst system according to Claim 32 wherein the alkylaluminum compound is isobutylaluminoxane. 34. A process for the homopolymerization and copolymerization of alpha-olefins having 2-8 carbon atoms, comprising polymerizing said alpha-olefin, or copolymerizing two or more of said alpha-olefins, in the presence of a catalyst selected from the catalysts of Claims 1-33.

Inventors: BEACH DAVID L, CARNEY MICHAEL J, BEACH, DAVID, L., CARNEY, MICHAEL, J.
Applicants: CHEVRON RES & TECH, CHEVRON RESEARCH AND TECHNOLOGY COMPANY
Application year: 1993
Main classification: C08F10
IPC codes: C08F2, C08F4, C08F10