MXPA97007680A - Metalalcalino metal ciclopentadienilo catalysts of group 6b for polymerization of alpha-olefin and its use in processes depolimerizac - Google Patents

Abstract

The present invention relates to a catalyst system for the homopolymerization of alpha-olefins having 2-8 carbon atoms, said catalyst system comprising a multi-valent metal dimer precursor catalyst compound of Group 6b, characterized in that a metal metallic atom of said metal of Group 6b is a cyclopentadienyl hydrocarbyl complex of Group 6b metal in which the Group 6b metal has a 3+ oxidation state and characterized in that a metal atom is an alkaryl cyclopentadienyl complex in which the Group 6b metal is supported on an inorganic support. The process for the polymerization of alpha-olefin having 2-8 carbon atoms, characterized in that it comprises contacting said alpha-olefin under polymerization reaction conditions in the presence of contact of a catalyzed system.

Description

CATALYSTS OF GROUP 6B METAL CYLINDERS FOR ALPHA-OLEFINE POLYMERIZATION AND PROCESS FOR THE POLYMERIZATION OF ALPHA-OLEFINS FIELD OF THE INVENTION The present invention relates to catalyst systems for the polymerization of alpha-olefins and processes for the polymerization of alpha olefins using such catalysts.

BACKGROUND OF THE INVENTION Chromium-based catalysts are used in the commercial polymerization of small alpha-olefins such as ethylene and propylene. Such a catalyst is prepared by depositing chromium (chromium bis (cyclopentadienyl) (II)) on an inorganic metal oxide support, as set forth in British Patent No. 1,253,063 by Karapinka. In U.S. Pat. No. 4,015,059, published March 29, 1977 by Karol, discloses the use of bis (indenyl) - and bis (fluorenyl) - chromium (II) compounds supported on activated inorganic oxide supports as catalysts for the polymerization of ethylene. Recently, new synthetic methods have been described for the preparation of organometallic compounds of Cr3t. Theopold, J. A. Chem Soc. (1988), na, 5902 entitled "Cationic Chromium (III) Alkyls as Olefin Polymerization Catalyst," Theopold, Acc. Chem. Res. (1990), 23, 263 entitled "Organochromium (III) Chemistry: A Neglected Oxidation State "and Thomas et al., J. Am. Chem. Soc. (1991), 113, sec et. discloses that certain pentamethylcyclopentadienyl alkyls of chromium (III) can be prepared and that they can be used to make polyethylene homogeneously in CH2C12. However, this homogeneous polymerization with chromium (III) catalysts has several deficiencies. These include low polymer productivity, rapid deactivation and the need to use non-coordinating polar solvents. Additionally, since they are homogeneous catalysts, they are unsuitable for gas phase olefin polymerizations. U.S. Patent No. 4,530,914, published July 23, 1985 by Ewen et al., Discloses a catalyst system for the polymerization of alpha-olefins comprising two or more metallocenes, each having different rate constants of propagation and termination, and aluminoxane. The metallocenes are cyclopentadienyl derivatives of a metal transition metal of groups 4b, 5b, and 6b of the Periodic Table. They are described by means of the formulas (CsR 'pR * * B. {C5R "Me03.py R" .. (CsR' 2MeQ 'where (C5R' is a substituted cyclopentadienyl or cyclopentadienyl, each R1 is hydrogen or a radical hydrocarbyl, R "is an alkylene radical, a dialkyl germanium or silicon or an alkyl phosphine or amino radical joining two rings of (C5R ', Q is a hydrocarbon radical, Me is a metal of group 4b, 5b or 6b, s is 0 or 1, p is 0, 1 or 2, when p = 0, s = 0, m is 4 when s is 1 and m is 5 when s is 0. US Patent No. 4,939,217, published July 3, 1990 Stricklen also discusses a process for the polymerization of olefins wherein the polymerization is carried out in the presence of hydrogen, and a catalyst system containing aluminoxane and at least two metallocenes, each having different olefin polymerization rate constants, is used. The exposed metallocenes are similar to those described in US Patent No. 4,530,914 mentioned above.

U.S. Patent No. 4,975,403, published on 4 December, 1990 by Ewen, exposes a catalyst system to be used in the polymerization of olefins. The catalyst system includes at least two different stereo-rigid chiral metallocene catalysts of the formula R1 '(C5 (R') 4) .MeQp (where Me is a Group 4b, 5b or 6b metal and (C5R ') 4 ) is a . cyclopentadienyl or substituted cyclopentadienyl ring) and an aluminum compound.

Canadian Patent Application No. 2,000,567, published on April 13, 1990, discloses a process for the production of polyethylene using a composite catalyst made of a solid catalyst component typified by a compound selected from chromium, a modified aluminum compound typified by a trialkylaluminum, and an alkylaluminum alkoxide compound. The chromium compound could be chromium oxide, and the modified aluminum compound could be the reaction product of an organoaluminum compound and water. European Patent Application 0,509,294 A2 published on October 21, 1992 Bulletin 92 43, discloses a catalyst system for the homopolymerization and copolymerization of alpha-olefins having from 2-8 carbon atoms. The catalyst system comprises a cyclopentadienyl hydrocarbyl metal compound of Group 6b in which the metal has an oxidation state of 3+, the metal compound of Group 6b is supported on an inorganic support. Page four of the European Patent Application discloses dimer compounds having the formula: [C5 (R »)?). Xb] e where M is a Group 6b metal such as chromium, molybdenum or tungsten; (CS (R *) S) is a substituted cyclopentadienyl or cyclopentadienyl ring; R 'is in each existing independent hydrogen, a hydrocarbyl radical having 1-20 carbon atoms, or adjacent groups R' could together form one or more rings; X is a hydrocarbyl radical having 1-20 carbon atoms (eg, a saturated monovalent or alicyclic aliphatic radical or a monovalent aromatic radical or combinations thereof); a = 1 or 2, b = l or 2 where a + b = 3; c = l or 2 with the proviso that when c = 2 then x is alkyl. When c is i, the catalyst is a monomer and X is defined as a hydrocarbyl radical having 1-20 carbon atoms. When c is 2, the catalyst is a dimer and X is alkyl. On page 4, lines 21-22, the term "hydrocarbyl" refers to "alkyl, alkenyl, aryl, aralkyl, and alkaryl radicals and the like." On page 5, lines 3 and 4 indicate that [Cp'Cr (CH3) 3] - is the preferred dimeric compound. In all cases, the metal atom of Group 6b in the compound has an oxidation state of 3+. U.S. Patent No. 5,240,895 published August 31, 1993 by Michael J. Carney and David L. Beach discloses a catalyst system for the homopolymerization and copolymerization of alpha-olefins having 2-8 carbon atoms. The catalyst system comprises a dimeric or tetrameric cyclopentadienyl compound of Group 6b metal, in which the metal has an oxidation state of 2+, the metal compound of Group 6b is supported on an inorganic support. In column 5, 10 sec lines, examples of compounds of Group 6b metals having the formula: [C5 (R ') 5) XJa where M is a Group 6b metal such as chromium, molybdenum and tungsten; (C5 (R ') 5) is a substituted cyclopentadienyl ring; R 'is in each independent presence hydrogen, a hydrocarbyl radical having 1-20 carbon atoms, or adjacent groups R' could together form one or more hydrocarbyl rings with the proviso that at least one R1 is alkyl; a = 2 or 4; X is in each independent presence, a hydrocarbyl radical having 1-20 carbon atoms (for example a saturated aliphatic or alicyclic monovalent radical or a monovalent aryl, alkaryl radical or combinations thereof), or an organosilyl group, such as trimethylsilylmethyl , where a = 2 or hydrogen when a = 4. Examples of compounds having the formula (I) included above, but are not limited to, [Cp * Cr (CH3)] 3, [Cp * Cr (Bile)] J ([Cp'Cr (Ph)], [Cp'Cr (TMSM)] 2 f Where Bcilo is benzyl, Ph is phenyl, and TMSM is trimethylsilylmethyl It is also indicated in Patent '895, Column 5, line l sec et, that the strong chromium-chromium multiple bond present in [Cp'Cr (CH3)], makes it virtually unreactive with respect to ethylene (the reference is made to an article by Heinzt, RA et al; A-. gew. Chem. (1992), 104. 1100) The invention in the '895 patent was the discovery that by depositing [Cp'Cr (CH3) ] 2 on a solid support, generates a highly active catalyst in the polymerization of ethylene (See column 5, lines 5-7) In all cases, the metal compounds of Group 6b in the reference '895 have the metal in the oxidation state 2+ Thus, the prior art discloses the preparation of several cyclopentadienyl type catalysts Group 6b for the polymerization of alpha-olefins and especially ethylene The Group 6b metal, exemplified by chrome, is in all cases in the oxidation state of 2+ or 3+. This is not easy or reliably predictable if a given catalyst system based on chromium-cyclopentadienyl will be catalytically active for the polymerization of ethylene in homogeneous type reactions or heterogeneous type reactions where the catalyst is deposited on an inorganic support. In addition, tarnüoco is easy or reliably predictable, regarding the nature of the polymer, if any, will occur, p. ex. , whether it will be of a low or high molecular weight or will have a reduced or broad molecular weight distribution. The type of sigma ligands bound to cyclopentadienyl-Cr are also important. European Patent Application 0,509,294 A2, referred to above, indicates that the ligand ("X") is alkyl, e.g. ex. , CH3 where a dimeric compound with chromium is used in the oxidation state 3+ while the teaching of U.S. Pat. No. 5,240,895 indicates above that the ligand ("X") is hydrocarbyl when the chromium is in the oxidation state 2+.

BRIEF DESCRIPTION OF THE INVENTION It has now been discovered that when cyclopentadienyl cyclopentadienyl dimeric compounds of Cr3 * -CrL * which are supported on an inorganic support, catalysts with high productivity of alpha-olefin polymerization are produced. In addition, using a co-catalyst improves the productivity of these compounds. Also, these catalysts produce linear polyethylenes. According to the present invention, there is provided a catalyst system for the homopolymerization of alpha-olefins having 2-8 carbon atoms, said catalyst system comprising a multivalent metal cyclopentadienyl dimer precursor catalyst compound of Group 6b wherein a metal atom of Group 6b is a metal cyclopentadienyl hydrocarbyl complex of Group 6b, wherein the metal of group 6b is in the oxidation state of 3+ and a metal atom of Group 6b is a cyclopentadienyl alkaryl complex in which the Group 6b metal is in the oxidation state 1+, said metal dimeric compound of Group 6b is supported on an inorganic support. The above catalyst system is improved by the addition of a co-catalyst selected from alkyl metal compounds of Group 2 or 3. In the above catalyst systems and processes, chromium is a preferred Group 6b metal, preferred supports are aluminum phosphate. and alumina-aluminum phosphate, and aluminoxane and trialkylaluminum compounds are preferred Group 2 or 3 alkyl metal compounds. Among other factors, the present invention is based upon the discovery that the catalyst systems of the present invention have high activity (in of amount of polymer produced by amount of chromium per hour) and produces ethylene homopolymers with a high degree of linearity.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The present invention provides catalyst systems for use in the homopolymerization of C2-Ca alpha-olefins, including ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1- octene. It has been found quite surprisingly that, although the productivity of many cyclopentadienyl compounds of Group 6b metal is very low when used as a catalyst in the homogeneous polymerization of alpha-olefins, when these compounds are supported on an inorganic solid support for example a Inorganic solid phosphate support, its productivity increases dramatically, especially when co-catalysts are used. It has been found very surprisingly that cyclopentadienyl dimeric compounds of Group 6b multi-valent metal, wherein one metal atom is in the oxidation state 3+ and the other metal atom is in the oxidation state 1+, have substantially the same activity as mononuclear compounds where the metal is exclusively in the oxidation state 3+. While the catalyst systems of the present invention can be used to polymerize a variety of alpha-olefins, they are useful especially in the polymerization of ethylene. These catalysts produce linear polyethylene, e.g. ex. , polyethylene in high production without substantially lateral branches.

The catalyst systems of the present invention comprise at least one cyclopentadienyl dimeric compound of multi-valent metal of Group 6b in which a metal atom of Group 6b is in the oxidation state 3+ and in which the other metal atom is in the oxidation state 1+, in which the catalyst precursor is catalytically active when deposited on an inorganic support such as an inorganic metal phosphate support. In addition, the multi-valent Group 6b metal cyclopentadienyl dimer precursor catalyst compounds of this invention are ferromagnetically coupled. As used herein, the term "cyclopentadienyl" refers to the same cyclopentadienyl or substituted cyclopentadienyl derivatives wherein the cyclopentadienyl ring contains one or more substituents that do not interfere with the ability of Group 6b metal compounds to function as a catalyst. polymerization of alpha-olefins. Examples of substituted cyclopentadienyl include pentamethylcyclopentadienyl, ethyltetramethylcyclopentadienyl, methylcyclopentadienyl, t-butylcyclopentadienyl and pentaphenylcyclopentadienyl, in addition to compounds where the substituent forms a multicyclic ring with the cyclopentadienyl ring. Examples of these multicyclic rings include indenyl and furanyl rings. For some simplicity, the abbreviation Cp * will be used here to refer to pentamethylcyclopentadienyl. Cp * is a preferred cyclopentadienyl group since it stabilizes the organometallic compounds of this invention. The Group 6b metal compounds useful in the present invention include compounds wherein the metal is chromium, molybdenum or tungsten. Compounds in which the metal is chromium are preferred. The metal atoms of Group 6b in the dimeric compound before deposition on the inorganic support have a multivalent oxidation state wherein one metal atom of Group 6b is in the oxidation state 1+ and the other metal atom is in the state of oxidation 3+. The metal dimers of Group 6b also have a cyclopentadienyl group for each metal atom, at least one hydrocarbyl group bonded to each metal atom. The metal atom of Group 6b in the oxidation state 3+ could be appropriately bonded to at least one hydrocarbyl group having 1-20 carbon atoms. The metal atom of Group 6b in the oxidation state 3+ is pi-linked to the cyclopentadienyl group; sigma bond to a hydrocarbyl group and sigma bond to the alkyl portion of an alkaryl group which is, in turn, linked coordinately through the aryl portion of the alkaryl group to the metal of Group 6b in the oxidation state? +. The metal of Group 6b in the oxidation state 1+ is also, of course, pi-linked to the cyclopentadienyl group. In effect, the sigma bond of Group 6b metal in the 3+ oxidation state to the alkyl portion of the alkaryl group is a bridge between the Group 6b atoms in the 1+ and 3+ oxidation states from which the The aryl of the alkaryl group is coordinately linked to the metal atom of Group 6b in the oxidation state I +. The effect of the bridge is shown diagrammatically below, where Cr is used as Group 6b metal and benzyl is used as the hydrocarbyl or alkaryl group only for simplicity.

[Cp'-Cr ^ -Bzyl] [Cp * -Cr *, - Bzyl] As used herein, the term "hydrocarbyl" refers to alkyl, alkenyl, aryl, arylkyl radicals and the like. Exemplary hydrocarbyl radicals include, but are not limited to, methyl, ethyl, propyl, butyl, amyl, isoamyl, hexyl, neopentyl, isobutyl, heptyl, octyl, nonyl, decyl, cetyl, phenyl, benzyl and other similar groups. Additionally, organosilyl groups that link to chromium atom (s) through a carbon atom can be used. Trimethylsilyl methyl, p. ex. , (CH3) 3SiCH2, and the like are examples of such organosilyl groups. If more than one hydrocarbyl group is linked to the metal atom, it may be independent or linked, eg. ex. , can form a member metallocyclo 3-, 4-, 5-, 6- or 7-. It is necessary in accordance with the findings of this invention that the metal atom of group 6b in the oxidation state 1+ be coordinately linked to the aryl portion of an alkaryl radical. As used herein, the term "alkaryl" refers to alkaryl radicals having from 7-20 carbon atoms. The simplest alkaryl radical is benzyl. Examples of alkaryl radicals useful in this invention include, but are not limited to, compounds having the following general formula: R -'_ C-R- where R "; R '' 'and R1V can in each independent presence be hydrogen or an alkyl group having from 1-4 carbon atoms with the proviso that the sum of the carbon atoms in R ", R' '' and Rlv is 0-14.

The preferred alkaryl radical having the above formula is benzyl. It is very surprising that the multi-valent Group 6b metal dimer precursor catalyst compounds of this invention have no chromium to chromium metal bond. U.S. Patent No. 5, 240,895, the teachings are incorporated herein by reference, indicates that there are strong chromium-chromium multiple bonds present in [Cp'Cr (CH3)] 2 that make it virtually -non-reactive with respect to ethylene. It has been found in accordance with this invention that when at least one of the hydrocarbyl groups is attached to the metal in an alkaryl group, this makes it possible to prepare a multi-valent metal precursor catalyst compound without metal-to-metal bond, which precursor is catalytically active. when it is deposited on an inorganic support. Examples of Group 6b metal compounds in this invention include, but are not limited to, compounds having the following general formula: [(Cs? R ') s) M * 3X] [(Cs íl') ¡) M + lX '] where M is a Group 6b metal such as chromium, molybdenum and tungsten; (C5 (R ') 5) is a cyclopentadienyl ring, R 'is in each independent presence hydrogen, a hydrocarbyl radical having 1-20 carbon atoms, or adjacent R1 groups which can together form one or more hydrocarbyl rings; X is a hydrocarbyl radical having 1-20 carbon atoms (for example, a saturated aliphatic or alicyclic monovalent radical or a monovalent aryl O alkaryl radical or combinations thereof), or an organosilyl group, such as trimethylsilylmethyl; and X 'is an alkaryl radical having from 7-20 carbon atoms. Preferably, multi-valent metal precursor catalyst compounds of Group 6b of this invention have the general formula: [(C5 (R ') J) M + JX1 [(C5 (R') J) M *, X '] I I where M; (C5 (R ') 5); and X 'are as defined above. Examples of compounds that have the formulas included above, but are not limited to, [Cp'Cr3 * (Bcil)] [Cp'Cr1 * (Bcil)]; [Cp * Cr3'CH3] [Cp'Cr3 * (Bcil)]; and [Cp'Cr3 * CH2Si (CH3) 3] [Cp'Cr1 *. { Bcil)] where Bcil is benzyl and Cr is in a multi-valent state where one Cr atom is in the 1+ oxidation state and one Cr atom is in the 3+ oxidation state and where Cr is bonded as described above. In part, the choice of the metal compound of the Group 6b is based on its ease of preparation. Of the Group 6b metal compounds useful in this invention, organochromium compounds are preferred. In the catalyst systems of the present invention the metal compound of Group 6b 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, alumina containing magnesium phosphate and aluminum phosphate alumina. Silicas, aluminum phosphates, alumina silica from aluminum phosphates and alumina from 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: aluminum phosphate alumina with aluminum to phosphorus ratio of about 5: 1 to 1: 1 as set forth in U.S. Pat. Nos. 4,080,311 and 4,219,444; magnesium-alumina-aluminum phosphates as described in U.S. Pat. No. 4,210,560; Zinc-cadmium oxide-alumina-aluminum oxide phosphates such as those disclosed in U.S. Pat. No. 4,367,067; and calcium, barium, and / or strontium alumina-aluminum oxide phosphates disclosed in U.S. Pat. Nos. 4,382,877 and 4,382,878. The acidity of these supports can be adjusted by judicious inclusion of base metals such as alkaline 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 Catalyst for Olefin Polymerization" (1988, Springer-Verlag) edited by W. 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 General Rank Preferred Rank Surface area 25-600 m2 / g 100-370 m2 / g Pore volume 0.25-4 cm3 / g 0.7-3 cm3 / g - Diameter of 10-200 micras 60-140 micras average particle Preferably, a significant percentage of the pores in the macropore range (> 500 Angtroms). Preferably, at least 50% of the pores are macropores. It is also desirable that the support be substantially anhydrous before the Group 6b metal compound is deposited thereon. In this way, it is desirable to calcinate the support before the Group 6b metal compound is deposited. The support 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 on or reacts with the support. The amount of the metal compound of Group 6b related to the amount of support will vary considerably depending on factors such as the particle size of the support, its pore size and surface area, the solubility of the metal compound of Group 6b which is going to be deposited on the support. However, in general the used amount of the Group 6b metal compound is adjusted so that the final metal content (calculated as the element), related to the support is in the range of about 0.01 to about 5 weight percent. Preferably the catalyst is made at room temperature. The 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, and more preferably higher of 200,000 g / g Cr / hr. It has been found that the activity of the metal dimers supports of Group 6b of this invention is significantly increased when used in conjunction with a co-catalyst. Co-catalysts useful in the practice of the present invention are Group 2 and Group 3 metal alkyls. As used herein, the term "Group 2 and Group 3 metal alkyls" refers to compounds containing a metal of the Group 2 or Group 3 of the Periodic Table (such as Mg, Zn, B, or Al) which binds to at least one alkyl group, preferably an alkyl group of Cj. to C ". Suitable Group 2 and Group 3 metal alkyls include dialkyl magnesium, dialkyl zinc, trialkylboranes, and aluminum alkyls. Suitable aluminum alkyls include trialkylaluminums (such as trimethylaluminum, triethylaluminum, triisobutylaluminum, and trioctylaluminum).

Trialkylaluminums with alkyl groups of four carbons or more are preferred. Other aluminum alkyls useful in the practice of the present invention include alkylaluminum alkoxides (such as diethylaluminum ethoxide and ethylaluminum dietoxide), and alkylaluminum halides (such as diethylaluminum chloride, diethylaluminum bromide, diethylaluminum iodide, diethylaluminum fluoride , ethyl aluminum dichloride, ethyl aluminum dibromide, ethyl aluminum diiodide, ethyl aluminum difluoride and ethyl aluminum sesquichloride). Other suitable aluminum alkyls are aluminoxanes, including those represented by the general formula (R-A1-0), for the cyclic form and R (R-A1-0) "- AlR2 for the linear form. In these formulas, R is, in each independent presence, an alkyl group (such as methyl, butyl, isobutyl and the like) preferably with more than two carbon atoms, more preferably with 3-5 carbon atoms and n is an integer, preferably of 20. More preferably, R is an isobutyl group. Mixtures of linear and cyclic aluminoxanes can also be used. Examples of aluminoxanes useful in this invention include, but are not limited to, ethyl aluminoxane, isobutyl aluminoxane, and methyl aluminoxane. Aluminoxanes (also known as "alumoxanes") suitable for use in this invention are described in Pasynkiewicz, "Alumoxanes: Synthesis, Structures, Complexes and Reactions," Polyedron 9. p. 429 (1990), which is incorporated herein by reference in its entirety. The preferred Group 2 and Group 3 metal alkyls are the aluminoxanes and the trialkylaluminums. When used, Group 2 and Group 3 metal alkyls are used in a Group 2 or 3 metal alkyl to a Group 6b metal compound in a molar ratio of about 1: 1 to about 1,000: 1. The preferred molar ratio is from about 10: 1 to about 200: 1. The catalyst systems of the present invention could be used in solution, suspension or gas phase polymerization processes. After the catalyst has been formed, the polymerization reaction is carried out 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 could be used as a thinner and facilitate the handling of materials. The polymerization reaction is carried out at temperatures of about 30 ° C or less to about 200 ° C or more, depending on the degree of operating pressure, the pressure of the entire monomer charge, the particular catalyst that is used, and its concentration. Preferably, the temperature is from about 30 ° C to about 125 ° C. The pressure may be any pressure sufficient to initiate the polymerization of the monomer charge, and may be from atmospheric to about 1,000 psig. As a general rule, a pressure of about 20 to 800 psig is preferred. When the catalyst is used in a suspension type process, a diluent is used in an inert medium. The diluent should be a diluent that is inert to all other compounds and products of the reaction system, and stable under the reaction conditions that are used. This is not necessary, however, this inert organic diluent also serves as a solvent for the polymer produced. Inert organic diluents that could 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, tetrachlorobenzene, o-dichlorobenzene and the like). Particularly preferred diluents 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. ex. , ethylene. Temperature, pressure and ethylene flow rates are adjusted to maintain acceptable fluidization of the catalyst particles and resulting in the polymer particles. Further descriptions of such a fluidized bed could be found in British Patent No. 1,253,063, by Karapinka, which is incorporated herein by reference. The term "molecular weight distribution" (MWD), as used herein, is the average molecular weight ("M,") divided by average molecular weight number ("M ,,"), p. ex. , M "/ Mn. In general, polymers having broad MWDs have improved processability, improved melting behavior, and other desirable properties such as impact resistance and environmental resistance to cracking. Wide blow molding products are superior when made with broad MWD polymers. Additionally, the film is more resistant to perforation when made with broad MWD polymers. The polymers made in accordance with this invention using aluminum phosphate supported catalysts possess high molecular weight and a more reduced MWD, making them useful in such applications as injection molding. When H2 is used in the reaction, the resulting polymers have a broad MWD. It has been found quite surprisingly that when the catalyst systems of this invention are used to produce ethylene homopolymers, the resulting polyethylenes are highly linear, while ethylene homopolymers prepared using similar catalyst systems contain significant amounts of chains with side branches. This is demonstrated by means of C13 NMR analysis. Here, for example, the polyethylene prepared according to the present invention using [Cp'Cr3 * (Bcilo)] [Cp'Cr1 * (Bcilo)] supported on A1P04 with co-catalyst IBAO has chains with 0 side branches ("SCB"). ") per 1,000 carbon atoms in the polyethylene. (See Table I below.) In contrast, polyethylenes made using chromium (II) bis (cyclopentadienyl) (eg, chromocene) supported on A1P04 are reported to contain 0.6 to 0.7 mol percent of chains with side branches (see Patent No. 4,424,139). In addition, it has been found that, in contrast to catalysts supported on C4 (TMSM) β which produces polymer with extremely broad molecular weight distributions (MWD = 140, see Run 7 in Comparative Example A of US Patent 5,240,895), the catalysts of The present invention produces polymers with extremely reduced MWD (see Examples 5-10 in Table I below). This is surprisingly below the unpredictable nature of organochromium support catalysts and their polymerization products.

The following examples are intended for further illustration of the present invention, and are not intended to limit its scope. All manipulations of compounds were carried out by means of standard Schelenk techniques, vacuum and glove box. All solvents were thoroughly dried over Na / benzophenoria or calcium hydride and distilled before use. LiCp * and [Cp * CrCl] 2 were synthesized by literature procedures, p. ex. , for the LiCp * see R.S. Threlkel, et al, J. Organomet. Chem. (1977), 137, 1; and the [Cp * CrCl] 2 see R.A. Keintz et al, J. Organomet. Chem. Soc. 1994, 116, xxxx.

EXAMPLE 1 PREPARATION OF [Cp'Cr3 (n'-Bcil) (μ-r .: n6-Bcil) Cr ^ Cp '] 0.375 g (0.84 mmol) of (CP'CrCl), was dissolved in 50 ml of pentane and it was cooled to -4 ° C. 1.68 ml (2 eq., 1.68 mmol) of benzyl magnesium chloride was slowly added to this solution. This reaction was allowed to stir for four hours and then filtered to remove the MgCl2 formed. Crystallization of a mixture of Et20 and pentane gave 0.349 g (75% yield) of [Cp'Cr3 * (n1-Bcil) (μ-n3: n6-Bcil) Cr ^ Cp *] as brown needles. Anal, caled, for C34H44Cr2: C, 73.35; H, 7.97; N, O. Found: C, 73.51; H, 8.06; DO NOT.

EXAMPLE 2 PREPARATION OF DIMERIC CATALYSTS SUPPORTED IN A1P04 The multi-valent chromium dimer compound (0.031 g, 5.57 x 10"5 moles) prepared as described in Example 1 was dissolved in. 20 ml of pentane, giving a brown solution for which 0.5 g of A1P04 purchased from Grace-Davison Company. The A1P04 was dehydrated for 16 hours at 400 ° C before use. The resulting mixture was stirred for 5 minutes. The resulting solid catalyst was washed with pentane, and dried under vacuum in a fluid free powder.

EXAMPLE 3 PREPARATION OF Cp'Cr (Bcil) 2 (Pir) (Monomeric Catalyst) A THF solution (50 mL) of [Cp'CrCl2] 2 was formed by stirring CrCl3 (THF), (1.003 g, 2.67 mmol) and Cp ' Li (0.382 g, 2.69 mmol) for one hour. 2.67 ml (2.00 eq.) Of BcilMgCl (2.0 M in THF, 5.3 mmol) was slowly added to this solution. Pyridine (2 ml) was added after another hour and the solution allowed to stir for an additional 20 minutes. Then 1,4-dioxane (3 ml) was added to facilitate the precipitation of MgCl 2. After removing all volatiles, the solid was extracted with Et20 and crystallized from the same solvent at -40 ° C.

Total yield: 0.801 g (67%). Anal, caled, for C29H34NCr: C, 77.65; H, 7.64; N, 3.12. Found: C, 77.78; H, 7.85 and N, 3.17. Cr is in the oxidation state 3+.

EXAMPLE 4 PREPARATION OF MONOMERIC CATALYST SUPPORTED IN AlPO, The monomeric chromium compound (0.046 g) was prepared as described in Example 3 above, dissolved in 20 ml of pentane to give a brown solution to which 0.5 g of A1P04 purchased from Grace-Davison Company was added. The A1P04 was dehydrated at 400 ° C for 16 hours before use. The resulting mixture was stirred for 5 minutes. The resulting solid catalyst was washed with pentane, dried under vacuum in a fluid free powder.

COMPARATIVE EXAMPLE A A solution of 30 mg (5.39 x 10"5 mol) of catalyst of Example 1 in 50 ml of pentane was exposed to ethylene at room temperature and atmospheric pressure for 2 hours and 115 mg of insoluble polymer was recovered. Polymer GPC gave average molecular weights as follows: M "= 3140; M" = 5120 with an MWD of 1.63.

EXAMPLE 5 ETHYLENE POLYMERIZATION USING SUPPORTED CATALYST The polymerization runs were carried out in 2 liter autoclave reactors under particulate (suspension) conditions using 300 ml of heptane as the diluent, and an amount of catalyst (typically 0.050-) was weighed. 0.250 g). Running times were normally used from 0.5 to 1.0 hours. For example, in a typical run, 0.050 g of the catalyst prepared in Example 2 was charged to a 2 liter autoclave together with 300 ml of heptane and 0.3 ml of a 1.0 M heptane solution of isobutylaluminoxane purchased from AKZO. The temperature and pressure of the reactor were adjusted to 80 ° C and 200 psi (with ethylene), respectively except in run 8 where a partial pressure of 10 psig of hydrogen was used. The ethylene was supplied according to the pressurized reserve. 1.0 hour later, the reaction was stopped by deactivating the agitator and releasing the pressure. The polymer produced was washed with isopropanol and acetone, and dried under vacuum to yield the indicated amounts of granular white solid. In the run for this example, the supported catalyst was as the preparation in Example 2 above and the results are summarized in Table I below. It is to be observed that the aluminum phosphate support was pretreated at 400 ° C for 16 hours before the chromium dimer compound of Example 1 was added thereto. The dehydration occurred under fluidized bed type conditions.

EXAMPLE 6 Example 5 was repeated giving substantially the same results as shown in Table I below.

EXAMPLE 7 Example 5 was repeated except that the concentration of chromium doubled and 40 ml of 1-butene were added to the reactor. The results are summarized in Table I below. Referring to Table I, a comparison of the Examples 5 and 7 show that the activity of the catalyst decreases and it was observed that there were no chains with lateral branches indicating that co-polymers of ethylene and 1-butene were not produced.

EXAMPLE 8 Example 5 was repeated again except that hydrogen was used at a partial pressure of 10 psi to determine the sensitivity of the hydrogen to this catalyst. The results are summarized in Table I below. Referring to Table I, a comparison of Examples 5 and 8 shows that the molecular weight of the resulting product is considerably reduced indicating that this catalyst is highly sensitive to the effect of hydrogen.

EXAMPLE 9 Example 7 was repeated except that co-catalyst was not used and co-monomer was not used. The results are shown in Table I below. Referring to Table I, a comparison of Examples 7 and 9 shows that in the absence of a co-catalyst, the activity of the catalyst system is reduced.

EXAMPLE 10 ETHYLENE POLYMERIZATION USING SUPPORTED MONOMER CATALYST Example 5 was repeated except that the catalyst of Example 4 was used. The results are summarized in Table I below. A comparison of Examples 5 and 10 shows that the concentration of the chromium was approximately the same, e.g. ex. , approximately 11 μmol. However, all the chromium in the catalyst for Example 10 was in the oxidation state 3+, while the chromium in the catalyst for Example 5 was 50% in the oxidation state 3+ and 50% in the state of oxidation l +. This was surprising, therefore, that the multi-valent chromium dimer compound was as active as the monomeric chromium catalyst known in which chromium is all in the 3+ oxidation state. This was surprising especially since a chromium dimer similar to that of Example 1 above, except where the chromium atoms both in the oxidation state l +, was, under homogeneous conditions, totally inactive for the polymerization of ethylene as shown in Example 12 below.

EXAMPLE 11 PREPARATION OF DIME Cr1 * A portion (0.275 g) of brown crystals of Example 1 was dissolved in 20 ml of toluene. This solution was sealed in a tight bulb with a Teflon cap. The ampoule was then heated to 50 ° C in an oil bath for two days. During this period, the color of the solution changed from brown to orange. The ampule was then closed and the toluene was removed by means of rotovaporization. The NMR analysis showed the product to be [Cp'Cr1 *), (μ-n6: n6-Bcil-Bcil)].

EXAMPLE 12 Comparative Example A was repeated except that the catalyst prepared as described in Example 11 above was used. Polyethylene was not recovered. 3b TABLE I ETHYLENE POLYMERIZATION1 USING SUPPORTED CATALYSTS3 1 Examples were made at S5 ° C and 200 psig. C2. except in Example 2 that used 190 psig? e C2H «and 10 pcig ce Ha. At Sjeflo 7 faiceeiite ce adicionare ?, ii pl of I-Meno 3 Supported on A1P04 dehydrated at íCO ° C for 16 hours 3IBAO = Isobut? Lalua? HQ? Ar.0 4g / g cat / hr = polyatum graaos per grain of catalyst per hour &g / g Cr / h - polyester grams per gram of chromium per hour% = Molecular Weight Preceded; Ha is the source of the Molecular Peq c and Arijos were determwaron by G? C 7S B = Lateral Eapification Chain ßTn - Melting Temperature, determined by DSC 9MI = Melt Index by ASTH D-1238, Condition E l0EL I - Fusion Index for High Load by ASIA D-123S, Condition F

Claims (20)

1. A catalyst system for the homopolymerization of alpha-olefins having from 2-8 carbon atoms, said catalyst system comprises a multi-valent metal dimer precursor catalyst compound of Group 6b, characterized in that a metal atom of said Group 6b metal is a cyclopentadienyl hydrocarbyl complex of Group 6b metal in which the Group 6b metal has a 3+ oxidation state and, characterized in that a metal atom is an alkaryl cyclopentadienyl complex in which the Group 6b metal is supported on a inorganic support.

2. The catalyst system of Claim 1, characterized in that the Group 6b metal is chromium. The catalyst system of Claim 1, characterized in that the metal compound of Group 6b has the formula: [(C5 (R ')

3) Nr3XpC3 (R') 5) M * lX '] where M is a tn < = Group 6b lime such as chromium, molybdenum and tungsten; (C5 (R ') S) is a cyclopentadienyl ring, R1 is in each independent presence hydrogen, a hydrocarbyl radical having 1-20 carbon atoms, or adjacent R' groups could together form one or more rings. hydrocarbyl. X is a hydrocarbyl radical having 1-20 carbon atoms; and X 'is an alkaryl radical having 7-20 carbon atoms.

4. A catalyst system according to claim 3, characterized in that it is chromium; X is an alkyl radical having from 7-20 carbon atoms and (C5 (R ') S) is pentamethylcyclopentadienyl.

5. A catalyst system according to claim 4, characterized in that X and X 'are benzyl.

6. A catalyst system according to claim 3, characterized in that X is methyl and X 'is benzyl.

The catalyst system of Claim 5, characterized in that the support is an inorganic metal oxide or inorganic metal phosphate.

8. The catalyst system of Claim 5, characterized in that the support is an aluminum phosphate.

The catalyst system of Claim 1, characterized in that it also contains an alkyl metal compound of Group 2 or 3.

10. The catalyst system of claim 9, characterized in that the metal of Group 6b is chromium.

The catalyst system of Claim 10, characterized in that the cyclopentadienyl hydrocarbyl complex of Group 6b metal is a cyclopentadienyl alkaryl complex of chromium.

The catalyst system of Claim 11, characterized in that each alkaryl group is a benzyl group.

The catalyst system of Claim 3, characterized in that it also contains an alkyl metal compound of Group 2 or 3.

14. The catalyst system of claim 13, characterized in that X is alkaryl, M is chromium and the metal of Group 2 or 3 is an aluminum alkyl compound.

The catalyst system of Claim 14, characterized in that X and X1 are benzyl and the inorganic oxide support is aluminum phosphate.

16. The catalyst system of Claim 15, characterized in that the aluminum alkyl compound is selected from the group consisting of trialkylaluminum compounds, alkyl aluminum alkoxides, alkyl aluminum halides and aluminoxanes.

17. The catalyst system of Claim 16, characterized in that the aluminum alkyl compound is an aluminoxane.

18. The process for the polymerization of alpha-olefin having from 2-8 carbon atoms, characterized in that it comprises contacting said alpha-olefin under polymerization reaction conditions in the presence of the contact of a catalyst system according to any of claims 1-17.

19. A process according to claim 18, characterized in that the alpha-olefin is ethylene.

20. A process according to claim 19, characterized in that the process is operated in the presence of hydrogen added.