BORABENZENE BASED OLEFIN POLYMERIZATION CATALYSTS

Abstract: Disclosed is a catalyst having general formula (I), where Q is a ligand containing the ring (II), R is hydrogen, N(R')2, OR', or R', each R' is independently selected from alkyl from C1 to C10, aryl from C6 to C15, alkaryl C7 to C15, and aralkyl from C7 to C15, each X is independently selected from hydrogen, halogen, alkoxy from C1 to C10, dialkylamino from C1 to C10, methyl, (III), each R1 is independently selected from halogen, alkoxy from C1 to C10, and R', L is (IV), (V), (VI), (VII), (VIII), Q, or X, where L can be bridged to Q, B is an optional base, "n" is 0 to 5, and M is titanium, zirconium, or hafnium.

Description: BORABENZENE BASED OLEFIN POLYMERIZATION CATALYSTS Background of the Invention This invention relates to catalysts useful in homo- and co-polymerizing ethylene and other olefinic hydrocarbons. In particular, it relates to catalysts containing a transition metal ir-bonded to a ligand that contains a borabenzene ring. Until recently, polyolefins have been primarily made with conventional Ziegler catalyst systems. These catalysts typically consist of transition metal-containing compounds and one or more organometallic compound. For example, polyethylene has been made using Ziegler catalysts such as titanium trichloride and diethylaluminum chloride, or a mixture of titanium tetrachloride, vanadium oxytrichloride, and triethylaluminu . These catalysts are inexpensive but they have low activity and therefore must be used at high concentrations. As a result, it is sometimes necessary to remove catalyst residues from the polymer, which adds to production costs. Neutralizing agents and stabilizers must be added to the polymer to overcome the deleterious effects of the catalyst residues. Failure to remove catalyst residues leads to polymers having a yellow or grey color and poor ultraviolet and long term stability. For example, chloride- containing residues can cause corrosion in polymer processing equipment. Furthermore, Ziegler catalysts produce polymer having a broad molecular weight distribution, which i undesirable for some applications such as injection molding They are also poor at incorporating α-olefin co-monomers Poor co-monomer incorporation makes it difficult to contro the polymer density. Large quantities of excess co-monome may be required to achieve a certain density and many highe α-olefins, such as 1-octene, may be incorporated at only ver low levels, if at all. Although substantial improvements in Ziegler catalys systems have occurred since their discovery, these catalyst are now being replaced with the recently discovere metallocene catalyst systems. A metallocene catalys typically consists of a transition metal compound which ha one or more cyclopentadienyl ring ligands. They have lo activities when used with organometallic compounds, such a aluminum alkyls, which are used with traditional Ziegle catalysts, but very high activities when used wit aluminoxanes as cocatalysts. The activities are generally s high that catalyst residues need not be removed from th polymer. Furthermore, they produce polymers with hig molecular weights and narrow molecular weight distributions. They also incorporate α-olefin co-monomers well. However, at higher temperatures metallocene catalysts tend to produce lower molecular weight polymers. Thus, they are useful for gas phase and slurry polymerizations of ethylene, which are conducted at about 80°C to about 95°C, but they do not generally work well in solution polymerizations of ethylene, at about 150°C to about 250°C. The polymerization of ethylene in solution is desirable because it allows great flexibility for producing polymers over a wide range of molecular weights and densities as well as the use of a large variety of different co-monomers. One can produce polymers that are useful in many different applications. For example, high molecular weight, high density polyethylene (PE) film useful as a barrier film for food packaging and low density ethylene co-polymers with good toughness and high impact strength. Summary of the Invention We have found a new class of catalysts based on a bora- benzene ring structure and containing a transition metal. The catalysts of this invention have unusually high activities, which means that they can be used in very small quantities. They are also very good at incorporating co-monomers into the polymer. They have good activity at higher temperatures and are therefore expected to be useful in solution polymerizations of ethylene. Finally, some of the catalysts within the scope of this invention contain tertiary amine groups. It is surprising that these catalysts are effective because many amine-containing compounds are known to be catalyst poisons. Description of the Preferred Embodiments The catalysts of this invention have the general formula In the formula, Q is a ligand containing a bora-benzen ring. A bora-benzene ring has the structure where R can be hydrogen, N(R' ) 2 , OR' , or R' , where each R' is independently selected from alkyl from C, to C 10 , aryl from C β to C 15 , alkaryl from C 7 to C 15 , and aralkyl from C 7 to C 15 . The R group is preferably -N(R' ) 2 or phenyl, as those catalysts have the best properties and, if R is -N(R' ) 2 , then the R' in -N(R' ) 2 is preferably methyl. Examples of Q ligands include (bora-benzene) (bora-naphthalene) (bora-naphthalene) (bora-anthracene) (bora-phenanthrene) where "m" is 0 to the maximum number of substitutable positions, and is preferably 0 as those catalysts are easier to make. Each R, is independently selected from halogen, alkoxy from C, to C 10 , and R' . The preferred Q ligands are bora-benzene, bora-naphthalene, and bora-anthracene because those catalysts are easier to prepare. In the general formula, each X is independently selected from hydrogen, halogen, alkoxy from C. to C 10 , dialkylamino from C. to C 10 , methyl, J@-«V n . - -CH 2 -@- (Rl ^ where M n" is 0 to 5 and preferably is 0. The X group is preferably chlorine or methyl, as those catalysts are easy to prepare and have good properties. Also, L in the general formula can be Q, or X. Preferably, L is Q, cyclopentadienyl, or chlorine because those catalysts are easiest to prepare and have good properties. Optionally, L can be bridged to Q. Groups that can be used to bridge two ligands include methylene, ethylene, 1,2- phenylene, dimethyl silyl, diphenyl silyl, diethyl silyl, and methyl phenyl silyl. Normally, only a single bridge is used in a catalyst. It is believed that bridging the ligand changes the geometry around the catalytically active transition metal and improves catalyst activity and other properties, such as comonomer incorporation and thermal stability. The M group in the general formula can be titanium, zirconium, or hafnium, but is preferably zirconium as those catalysts have a good combination of high activity and good stability. In the general formula, B is an optional Lewis base. Up to an equimolar amount (with H) of base can be used. The use of a Lewis base is generally not preferred because it tends to decrease catalyst activity. However, it also tends to improve catalyst stability, so its inclusion may be desirable depending upon the process in which it is being used. The base can be residual solvent from the preparation of the catalyst, or it can be added separately in order to enhance properties of the catalyst. Examples of bases that can be used in this invention include ethers such as diethyl ether, dibutyl ether, tetrahydrofuran, and 1,2-dimethoxyethane, esters such as n-butyl phthalate, ethyl benzoate, and ethyl p- anisate, and phosphines such as triethylphosphine, tributylphosphine, and triphenylphosphine. Preparation of the Q ligand portion of the catalyst can be found in the literature. See, for example, "Borabenzene Derivatives 21.2,4-Pentadienylboranes as Key Intermediates of a Novel Route to Boracyclohexadienes and Boratabenzenes. Structure of [Li(TMEDA)] (C 5 H 3 BNMe 2 )" by Gerhard E. Herberich et al., Orσanometallics (1993), pages 2891-2893, herein incorporated by reference. In that article, 2,4- pentadienylborane is reacted with a lithium amide in tetrahydrofuran in the presence of tetramethylethylenediamine (TMEDA) to form a dimethylamino borabenzenyl lithium TMEDA complex having the formula (CH 3 ) 2 N(CH2) 2 N(CH 3 ) 2 - Li - OJ B See also, "Reactions of the 9-Mesityl-9-boraanthracene Anion by R. Van Veen and F. Bickelhaupt, Journal of Orσanometalli Chemistry. (1974), pages 153-165, which describes th formation of 9-mesityl-9-boraanthracenyllithium. Other Q ligands can be prepared in an analogous manner or b other processes. The catalyst can be made from the Q ligan by adding a suspension of an appropriate tetravalent meta compound to a solution of the Q ligand. This reaction ca occur at about -78 to about 50°C, but is preferably performe below 0°C. Since the catalyst is normally used in conjunction wit an organometallic co-catalyst, it is preferable to dissolv the catalyst in a solvent in which the co-catalyst is also soluble. For example, if methylaluminoxane (MAO) or polymethylaluminoxane (PMAO) is the co-catalyst then toluene, xylene, benzene, or ethylbenzene could be used as the solvent. Other suitable co-catalysts include aluminum alkyls having the formula AIR' X (R 2 ) 3 . X , where 1 ≤ x <3 and Rj is hydrogen, halide, or alkyl or alkoxide from C, to C 20 , such as triethylaluminum and ethylaluminum dichloride. The preferred co-catalyst is MAO as it results in high activity and a polymer having a narrower molecular weight distribution. The mole ratio of the organometallic cocatalyst to catalyst when used in a polymerization is generally in the range 0.01:1 to 100,000:1, and preferably ranges from 1:1 to 10,000:1. To enhance its properties, the catalyst can be used with an acid salt that contains a non-coordinating inert anion (see U.S. Patent No. 5,064,802). The acid salt is generally a non- nucleophilic compound that consists of bulky ligands attached to a boron or aluminum atom, such as lithium tetrakis(penta- fluorophenyl) borate, lithium tetrakis(pentafluorophenyl)- aluminate, anilinium tetrakis(pentafluorophenyl)borate, and mixtures thereof. The anion which results when these compounds react with the catalyst is believed to be weakly coordinated to the metal-containing cation. The mole ratio of acid salt to catalyst can range from about 0.01:1 to about 1000:1, but is preferably about 1:1 to 10:1. While there is no limitation on the method of preparing an active catalyst system from the catalyst and the acid salt, preferably the are mixed in an inert solvent at temperatures in the range o about -78°C to about 150°C. They can also be mixed in th presence of monomer if desired. The acid salt can be used i combination with the organometallic cocatalysts describe earlier. The catalyst and co-catalyst can be used on a suppor such as silica gel, alumina, silica, magnesia, or titania, bu supports are not preferred as they may leave contaminants in the polymer. However, a support may be required dependin upon the process being utilized. For example, a support i generally needed in gas phase polymerization processes an slurry polymerization processes in order to control the particle size of the polymer being produced and in order to prevent fouling of the reactor walls. In order to use a support, the catalyst and co-catalyst are dissolved in the solvent and are precipitated onto the support material by, for example, the evaporation of solvent. The co-catalyst can also be deposited on the support or it can be introduced into the reactor separately from the supported catalyst. Once the catalyst has been prepared it should be used as promptly as possible as it may lose some activity during storage. Storage of the catalyst should be at a low temperature, such as -100 to about 20°C. The catalyst is used in a conventional manner in the polymerization of olefinic hydrocarbon monomers. While unsaturated monomers such as styrene can be polymerized using the catalysts of this invention, it is particularly useful for polymerizing α- olefins such as propylene, 1-butylene, 1-hexene, 1-octene, and especially ethylene. The catalyst is also useful for copolymerizing mixtures of ethylene with unsaturated monomers such as 1-butene, 1- hexene, 1-octene, and the like; mixtures of ethylene and di- olefins such as 1,3-butadiene, 1,4-hexadiene, 1,5-hexadiene, and the like; and mixtures of ethylene and unsaturated comono ers such as norbornene, ethylidene norbornene, vinyl norbornene, and the like. The catalysts of this invention can be utilized in a variety of different polymerization processes. They can be utilized in a liquid phase polymerization process (slurry, solution, suspension, bulk phase, or a combination of these) , in a high pressure fluid phase, or in a gas phase polymerization process. The processes can be used in series or as individual single processes. The pressure in the polymerization reaction zones can range from about 15 psia to about 50,000 psia and the temperature can range from about - 100°C to about 300°C. The catalyst can be used in a conventional manner in the co-polymerization of olefin monomers such as ethylene, propylene, 1-butene, 1-octene, l- hexene, norbornene, and norbornadiene. The following examples further illustrate this invention. Example 1 This example describes the synthesis of (B-dimethylamino borabenzene) cyclopentadienylzirconium dichloride, which ha the formula where Cp is cyclopentadienyl and Me is methyl. To a suspension of 0.56 grams (2.13 mmole) o cyclopentadienylzirconium trichloride (purchased from Strem Chemicals) in 15 ml of absolute ether, a solution of 0.61 g (2.51 mmole) of dimethylamino borabenzenyl lithium tetramethylethylenediamine complex, (prepared according to the hereinabove cited article by G. E. Herberich) in 10 ml of ether was added at -78°C. The mixture was warmed to room temperature and was stirred for an additional 1 hour. After the volatiles had been removed in vacuo. the residue was washed with 30 ml of hexane and extracted with 30 ml of toluene. The toluene was evaporated under reduced pressure to give 0.23 grams of a black solid. Proton NMR spectrum indicated the presence of some impurities in the product. Example 2 This example describes the synthesis of cyclopentadienyl ( 9-mes itylboraanthracenyl ) z irconium dichloride, which has the formula A solution of 9-mesitylboraanthracenyllithium in diethyl ether was prepared by adding 1.0 mL of 1.6 M n-butyllithium in hexanes to a solution of 0.47 g (1.6 mmol) of 9- mesitylboraanthracene in 18 mL diethyl ether at -78°C, warming to room temperature, and stirring for an additional 2 hours. The solution was cooled to -10°C and 0.42 g (1.6 mmol) of cyclopentadienylzirconium trichloride (Strem Chemicals) was added. The bath was then allowed to reach room tmperature, and the reaction mixture was stirred overnight. The volatiles were removed in vacuo to give a reddish brown powder. To this was added 20 mL dry toluene and the mixture ws filtered to give a clear yellow-orange filtrate which was concentrated to give a brown foam. This was treated with dry hexane (20 mL) and the mixture filtered to give 0.26 g of a light tan solid Proton NMR spectrum of the product indicated the presence o some impurities. Examples 3 to 17 Ethylene was polymerized using the catalysts of Example 1 and 2. (Examples 3 through 13 and Example 20 used th catalyst prepared in Example 1 and Examples 14 through 19 use the catalyst prepared in Example 2. ) The polymerizations were conducted in a stirred 1.7 liter autoclave at 80 or 110°C. Dry, oxygen-free toluene (840 ml) was charged to a clean, dry, oxygen-free reactor. MAO from Ethyl Corporation (10 wt% in toluene) was used in some of the polymerizations. Other polymerizations were conducted using PMAO from Akzo Chemical (25 wt% in toluene) . The desired amount of MAO or PMAO to give the ratio shown in the table which follows was added by syringe at 30°C. The reactor was heated to the desired temperature and sufficient ethylene was added to bring the reactor pressure to 150 psig. The reactor was allowed to equilibrate at the desired temperature and pressure. A solution of catalyst was prepared by dissolving 0.100 grams of product in 100 ml of toluene. The amount of this solution needed to give the amount of catalyst shown in the table was used to start a polymerization. Ethylene flowed into the reactor as needed in order to keep the pressure constant at 150 psig as polymer was produced. At the end of 1 hour (less, if the activity was very high) the ethylene flow was stopped and the reactor was rapidly cooled to room temperature. The reactor was opened and the polymer was filtered from the toluene. The product was dried overnight in a vacuum oven and weighed. The following tables give the reaction conditions and the results of polymerizations. u. Wt. PE Cat Prod MI2 MI20 Density (fl) (kg/o/hr) (dg/ain) (dg/ain) MFR (g/«D Mw/Mn 3 77.1 93.9 0.17 2.37 13.9 0.9574 2.00 4 81.3 198.1 0.14 2.57 18.0 0.9587 1.75 5 92.5 225.4 10.28 333 32.4 0.9720 . β 71.7 174.7 1.11 24.92 22.5 0.9323 . 7 70.4 171.5 1.10 22.64 20.6 0.9616 1.70 8 80.1 195.2 1.50 35.81 23.9 0.9637 1.84 9 105.0 511.7 18.40 539 29.3 0.9714 4.194 10 96.5 235.1 7.92 152 19.2 0.9448 . 11 110.0 536.1 41.94 1202 28.7 0.9521 . 12 138.9 676.9 16.27 588 36.1 0.9584 4.85 13 65.0 158.4 9.29 185 19.9 0.9515 . 14 31.8 145.7 549 . . . . 15 34.5 316.1 <0.01 2.89 . . . 16 44.5 203.8 106 . . . . 17 83.6 383.0 25.8 588 22.8 . . 18 66.1 908.4 <0.01 49.1 . . . 19 33.2 253.5 <0.01 31.9 . . . 20 | 49.1 179.4 0.07 1.18 17.1 0.9415 - The melt index of the polymer was measured according to ASTM D-1238, Condition E and Condition F. MI2 is the melt index measured with a 2.16 kg weight (Condition E) . MT20 is the melt index measured with a 21.6 kg weight (Condition F) . MFR is the ratio of MI20 to MI2. The polymer density was measured according to ASTM D-1505. The molecular weight distribution of the polymer was measured using a Waters 150C gel permeation chro atograph at 135°C with 1,2,4-trichlorobenzene as t solvent. Both weight average molecular weight (M and rati of M, to H, (number average molecular weight) are used t characterize the molecular weight distribution. The tabl shows a high activity at 80°C and little or no decline i activity at 110°C (Examples 9 vs. 2). The catalyst has excellent comonomer incorporatio properties. Note the unusually high butene-1 incorporation i Examples 6 and 10 which produced relatively low polyme densities. In addition, the catalyst readily incorporate comonomers which are usually difficult to copolymerize. Thi is exemplified by the copolymerization of ethylene and 5 vinyl-2-norbornene in Example 20. In Example 3, the ratio o the weight average molecular weight to the number averag molecular weight, which is an indication of the molecula weight distribution, was measured as 2.00. An Mw/Mn of 2.0 indicates a very narrow molecular weight distribution.

Claims: WE CLAIM: 1. A catalyst having the general formula where Q is a ligand containing the ring R is selected from the group consisting of hydrogen, N(R' ) 2 , OR' , and R' , each R' is independently selected from the group consisting of alkyl from C- to c 10 , aryl from C β to C 15 , alkaryl from C 7 to C 15 , and aralkyl from C 7 to C 15 , each X is independently selected from hydrogen, halogen, alkoxy from C, to C 10 , dialkylamino from C, to C 10 , methyl, each R. is independently selected from the group consisting of halogen, alkoxy from C, to C 10 , and R' , L is selected from the group consisting of Q, and X, where L can be bridged to Q, B is an optiona Lewis base, "n" is 0 to 5, and M is selected from th group consisting of titanium, zirconium, and hafnium. 2. A catalyst according to Claim 1 wherein M is zirconium. 3. A catalyst according to Claim 1 wherein each X i chlorine. 4. A catalyst according to Claim 1 wherein each X is methyl 5. A catalyst according to Claim 1 wherein L i cyclopentadienyl. 6. A catalyst according to Claim 1 wherein L is chlorine. 7. A catalyst according to Claim 1 wherein Q is and R is -N(R' ) 2 or phenyl. 8. A catalyst according to Claim 7 wherein Q is 9. A catalyst according to Claim 1 wherein Q is where "m" is 0 to 7. 10. A catalyst according to Claim 1 wherein Q is where "m M is 0 to 9, 11. A catalyst according to Claim 1 in combination with about 0.01 to about 100,000 moles of an organometallic cocatalyst per mole of said catalyst. 12. A catalyst according to Claim 11 wherein sai organometallic cocatalyst is methylaluminoxane o polymethylalu inoxane. 13. A catalyst according to Claim 1 in combination with abou 0.01 to about 1000 moles per mole of said catalyst of a acid salt that contains a non-coordinating inert anion. 14. A catalyst according to Claim 13 wherein said acid sal is selected from the group consisting of lithiu tetrakis (pentafluorophenyl) borate, lithiu tetrakis(pentafluorophenyl) aluminate, aniliniu tetrakis(pentafluorophenyl)borate, and mixtures thereof. 15. A method of polymerizing an α-olefin comprising heating said α-olefin in the presence of a catalyst according to Claim 1. 16. A catalyst having the general formula where Q is each X is independently selected from the group — ., — - « . . .. .. ^ _ I R or chlorine, R is -N(CIi j ) 2 or alkyl substituted phenyl from C 7 to C 1S , and B is an optional Lewis base. 17. A catalyst having the general formula CI I I Q - ZZrr - Cp I I CI where Cp is cyclopentadienyl, Q is and R is -N(01 3 ) 2 or alkyl substituted phenyl from C 7 t -15" 18. A catalyst according to Claim 17 wherein R is -N(CH g ) 2 . 19. A catalyst according to Claim 17 wherein R is trimethy phenyl. 20. A catalyst according to Claim 17 which comprises B dimethylamino-borabenzene cyclopentadienylzirconiu dichloride. 21. A catalyst according to Claim 17 which comprise cyclopentadienyl(9-mesitylboraanthracenyl) zirconiu dichloride.

Inventors: ETHERTON BRADLEY P, KRISHNAMURTI RAMESH, NAGY SANDOR, ETHERTON, BRADLEY, P., KRISHNAMURTI, RAMESH, NAGY, SANDOR
Applicants: OCCIDENTAL CHEM CO, OCCIDENTAL CHEMICAL CORPORATION
Application year: 1995
Main classification: C08F
IPC codes: C07F17, C08F4, C08F10, C08F110, C08F210