TRIS-(3,5-DIMETHYLPYRAZOLYL)CHROMIUM BORATE DICHLORIDE AS COMPONENT OF CATALYTIC SYSTEMS FOR THE POLYMERIZATION OF OLEFINS AND POLYMERIZATION PROCESS USING IT

Abstract: Tris-(3,5-dimethylpyrazolyl)chromium borate dichloride as component of catalytic systems for the polymerization of olefins.

Description: TRIS- (3, 5-DIMETHYLPYRAZOLYL) CHPOMIUM BORATE DICHLOPIDE AS COMPONENT OF CATALYTIC SYSTEMS FOP THE POLYMERIZA ¬ TION OF OLEFINS AND POLYMERIZATION PROCESS USING IT. The present invention relates cc tns-,2,5- dimethylpyrazolyl) chromium bcra e dichlcπde when used as component of catalytic systems for the polymerization of olefins, as well as the polymerization process consisting in polymerizing the clefin (s; in question in the presence of a catalytic system comprising the above component and a suitable cocatalyst. It is known that olefins can be polymerized using soluble compounds of transition metals combined with organic derivatives of aluminum, either alkyl- or al- kyl-halogen derivatives, or oxy-derivatives . Typical compounds of transition metals (e.g. Ti, Zr, Hf) are those in which the metal is complexed with a polydentate organic ligand, which does not partici ¬ pate in the polymerization reaction but contributes to blocking some of the coordination sites of the metal, the others being occupied by ligands which are released at the right moment for making the coordination site available for the polymerization reaction. With reference to these complexes, patent appli- cation WO 97/17379 expressly indicates ligands such as hydride-tris (pyrazolyl) borates or cyclopentadienyls which complex metals such as titanium and zirconium. This patent application, in turn, refers to catalysts for the polymerization cf olefins comprising a component consisting of a metal complexed by pyrazolyl groups substituted in position 3 by organic radicals containing at least three carbon atoms and attributes to these catalytic systems the property of modifying (or predetermining) the molecular weight distribution of the polymerization reaction products, thus disclosing an advantage with respect to the complexes cf the known art (e.g. EP 482,931; U.S. 5,312,794). The catalytic system according to patent applica ¬ tion WO 97/17379, however, seems to be limited only to the use of methylaluminoxane as cocatalyst which, in turn, combined with complexes of chromium in accordance with the definition mentioned above, does not seem to be particularly effective in the polymerization of ethylene. The Applicant has now found that a particular py- razolyl complex of chromium can be used as component of catalytic systems for the polymerization of olefins with all the advantages and without the limits of the analogous compounds described in the art mentioned above . In fact, an object of the present invention relates to a component of catalytic systems for the polymerization cf olefins consisting of tris-(3,5- di ethylpyrazolyl) -chromium borate dichloride which, when suitably combined with a compound of aluminum, is capable of favoring the preparation of polymers cf olefins with a good productivity, these polymers being characterized by a low poly-dispersion. A great advantage deriving from the use of the above component lies in the fact that there is no restriction as to the selection of cocatalyst, even if from the point of view of efficiency, it is sometimes preferable to use the less expensive aluminum alkyls; this is an additional advantage in the possible industrial embodiment of the polymerization process according to the present invention. A second object of the present invention there ¬ fore relates to a process for the preparation of poly ¬ mers and copolymers of olefins which comprises polym- erizing at least one olefin in the presence of a cata- lytic system comprising: a) tris- (3, 5-dimethylpyrazolyl) chromium borate di- chloride, and b) a cocatalyst consisting of a compound of alumi- num, selected from alkyl-halide and alkyl derivatives thereof in which the alkyl group contains from 1 to 6 carbon atoms, and aluminoxane . The aluminoxane cocatalyst consists of a mixture which can contain linear or cyclic structures, as well as possible cage structures. The linear structure has general formula (I) : Al —O— [—f\\—O—] m —Al whereas the cyclic structure has general formula (II -{-Λ\—O—] m wherein m represents an integer ranging from 1 to 40 and Ri a Cι-C 2 o, preferably Cτ.-C , alkyl radical; a Cs- C 20 preferably Cό-Ci.;, aryl radical; a C--C 2 _., prefera ¬ bly C7-C 1 , arylalkyl or alkylaryl radical; or a C;-C_., preferably C3-C 10 cycloalkyl radical; or an O-R' ' radi- cal, wherein R' ' represents a Ci-C;, preferably C1-C , alkyl radical; a C 0 -C preferably Cs-C— aryl radical; or a halogen atom, such as chlorine, fluorine or bromine, provided not all the R : radicals are contempora ¬ neously O-R' ' or halogens. The cocatalysts mentioned above, having general formulae (I) and (II), are known in literature and de ¬ scribed, for example, in European patent applications 272,584 and 421,659 or in U.S. patent 4,978,730. The preferred cocatalyst having general formulae (I) and (II) is methylaluminoxane (MAO ' ! with a number average molecular weight (Mn) ranging from 400 to 2000. The cocatalyst is generally used in such quantities that the molar ratio Al/Cr ranges from 10 to 5000, preferably from 10 to 1000. According to the process object of the present invention, the catalytic system described above, as already mentioned, can comprise as cocatalyst, instead of aluminoxane, an aluminum alkyl or an aluminum al- kyl-halide in which the alkyl group contains from 1 to 6 carbon atoms, for example aluminum trimethyl, aluminum triethyl, aluminum triisobutyl, aluminum diethyl ¬ chloride, in such quantities as to give the molar ra ¬ tio Al/Cr specified above: of all these, the use of aluminum diethylchloride has proved to be particularly ef fective . The term "α-olefins", as used in the present description and claims, essentially refers to ethylene, propylene, 1-butene, 4-methyl-l-pentene, 1-hexene, 1- octene. The catalytic system cf the process object of the present invention can be used in suspension processes at low, medium or high pressure and at temperatures ranging from 0 to 300 °C. Alternatively, it can be used in solution processes, in the presence cf an inert diluent such as toluene, operating at pressures ranging from 1 to 150 bar and at temperatures ranging from 0- 100°C. Some illustrative but non-limiting examples are provided hereunder for a better understanding of the present invention and for its embodiment. Hereafter tris- (3, 5-dimethylpyrazolyl) chromium (III) borate dichloride is referred to as Tp*CrCi_. The structure of this compound is the following: Example 1 Synthesis of tris- (3, 5-dimethylpyrazolyl) chromium (III) borate dichloride Tp*CrCl 2 from tris- (3,5- dimethylpyrazol-yl) potassium borate (Tp*K) and CrCl-*6H 2 0 0.500 g of CrCl*»6H_0 (MW = 266; 1.87*10 "' moles, in 150 ml of methanol are put into a flask and a suspension of 0.630 g of Tp*K (MW = 316; 1.87*10 " ' moles) in 50 ml of methanol are then added. After 1 night, the solvent is evaporated, chloroform is added and the mixture is filtered. 0.74 g cf green complex are obtained. (Yield: 47%) mass (negative ions) : 419 elemental analysis: Cl 16.53% (calc. Iό.88° 0 ); Cr 12.01°o (calc. 12.38%) . Example 2 Synthesis of tris- [ 3 , 5-dimethylpyrazolyl ■ chromium (III) borate dichloride Tp*CrCl„ from Tp*Tl and CrCl 3 »6H : 0 0.501 g of Tp*Tl (MW = 501; 1*10 "~ moles) in 150 ml of ethanol are put into a flask equipped with a cooler and 0.267 g of CrCl 3 »6H^0 (MW = 266; 1*10 "' moles) are added. The mixture is refluxed for 30 minutes. The solvent is evaporated and ethyl ether is added and after filtering the TlCl and evaporating the solvent, 0.355 g of green complex are obtained. ( Yield : 85% ) mass (negative ions) : 419 EPR: only Cr (III) Comparative example 3 11.6 mg of Tp*CrCl , prepared as described in ex ¬ ample 1 (MW = 420; 2.7*10 " moles) and 30 ml of degassed, anhydrous toluene are introduced, under argon, into a 100 ml four-necked flask equipped with a cooler. 1 ml of MAO 1.57 M (55 eq. ) is added to the green suspension. The yellow solution obtained is put under ethylene and heated to 55°C for 2 hours. The formation of the polymer is observed on the walls of the reactor. The solution is treated with methanol and HC1 6N. After filtration, washing and drying, 0.603 g of polymer are obtained. Activity = 22.07 gPE/1 mmole of Cr Comparative example 4 6.4 mg of Tp*CrCl , prepared as described in exam ¬ ple 2 (MW = 420; 1.5*10 " " moles) and 30 ml of degassed, anhydrous toluene are introduced, under argon, into a 100 ml four-necked flask. 8 ml of MAO 1.57 M (400 eq.) are added to the green suspension. The yellow solution obtained is put under ethylene and maintained at room temperature for 2 hours. The polymer is formed on the walls of the reactor. The solution is treated with methanol and HC1 6N. The polymer, after filtration, washing with acetone and drying, weighs 0.53 g. Activity = 34.70 gPE/mmole Cr Comparative example 5 12.6 mg of Tp*CrCl , prepared as described in ex ¬ ample 1 (MW = 420; 3*10 "^ moles) and 30 ml cf degassed, anhydrous toluene are introduced, under argon, into a 100 ml four-necked flask equipped with a cooler. 1.65 ml of MgBu; 1 M (55 eq. ) are added to the green suspension. The solution, put under ethylene, is heated to 55°C for 2 hours. The solution is treated with metha ¬ nol and HCl 6 N. After extraction with methylene chlo ¬ ride and evaporation of the solvent, 0.243 g of poly- mer are obtained. Activity = 8.10 g PE/mmole Cr Comparative example 6 2.8 mg of Tp*CrCl 2 (MW = 420; 6.2*10 "' moles), prepared as described in example 1 in 100 ml of de- gassed, anhydrous toluene are introduced, under argon, into a 250 ml four-necked flask. 2.5 ml of TIBAL 1 M (400 eq. ) are added to the green solution. The yellow- solution obtained is put under ethylene and maintained at room temperature for 2 hours. The suspension is treated with methanol and HCl 6N; the polymer, after filtration, washing with acetone and drying, weighs 0.12 g. Activity = 19.38 gPE/mmole Comparative example 7 11.9 mg of Tp*CrCl_, prepared as described in ex ¬ ample 2 (MW = 420; 2.8*10 " ' moles) and 30 ml of degassed, anhydrous toluene are introduced, under argon, into a 100 ml four-necked flask equipped with a cooler. 5.66 ml of MgBu- 1 M (200 eq. ) are added to the green suspension. The solution, put under ethylene, is heated to 55°C for 2 hours. The solution, quenched with methanol and HCl 6 N, is extracted with methylene chloride to give, after evaporation of the solvent and drying, 0.255 g of polymer. Activity = 9.00 g PE/mmole Cr Comparative example 8 6.4 mg of Tp*CrCl 2 , prepared as described in exam ¬ ple 2 (MW = 420; 1.5*10 "5 moles) and 100 ml of de ¬ gassed, anhydrous toluene are introduced, under argon, into a 250 ml four-necked flask. 0.3 ml of EtMgBr 1 M (20 eq. ) are added to the green solution, put under ethylene. The yellow solution obtained is put under ethylene and maintained at room temperature for 1 hour. After treating the solution with HCl 6 N and methanol, no polymer is formed. Activity = 0 g PE/mmole Cr Example 9 4.2 mg of Tp*CrCl_, prepared as described in example 2 (MW = 420; 1*10 "" moles! and 100 ml of degassed, anhydrous toluene are introαuced, under argon, nto a 250 ml four-necked flask. 2.22 ml of Et A1C1 1.8 M ^0 eq.) are added to the green solution. The yellow solution obtained is put under ethylene and maintained at room temperature for 2 hours. The polymer is formed on the walls of the reactor. The suspension is treated with methanol and HCl 6N; the polymer, after filtration, washing with acetone and drying, weighs 2.513 g. Activity = 251.30 gPE/mmole Cr Example 10 6.4 mg of Tp*CrCl_, prepared as described in example 2 (MW = 420; 1.5*10 "" ' moles) and 100 ml of degassed, anhydrous cyclohexane are introduced, under argon, into a 250 ml four-necked flask. 2.50 ml of EtcAlCl 1.8 M (400 eq. ) are added to the green solution. The yellow solution obtained is put under ethylene and maintained at room temperature for 2 hours . The polymer is formed on the walls of the reactor. The suspension is treated with methanol and HCl 6N; the polymer, after filtration, washing with acetone and drying, weighs 0.355 g. Activity = 23.66 gPE/mmole Cr T ( °C) Mw Mw/Mn 140.2 n.d. n.d. Example 11 6.4 mg of Tp*CrCl ^ , prepared as described in exam- pie 2 (MW = 420; 1.5*10 " - moles) and 90 ml of degassed, anhydrous toluene are introduced, under argon, into a 250 ml four-necked flask. 1.66 ml of EtAiCl 1.8 M (2G0 eq.) are added to the green suspension. The yellow so ¬ lution obtained is put under ethylene and maintained at 25°C for 2 hours. The suspension is treated with methanol and HCl 6N; the polymer, after filtration, washing with acetone and drying, weighs 2.44 g. Activity = 162.66 gPE/mmole Cr Example 12 6.4 mg of Tp*CrCl_, prepared as described in example 2 (MW = 420; 1.5*10 " ^ moles) and 80 ml of degassed, anhydrous toluene are introduced, under argon, into a 250 ml four-necked flask. 0.46 ml of Et.AlCl 1.8 M ;53 eq. ) are added to the green solution. The yellow solution obtained is put under ethylene and maintained at room temperature for 2 hours. The polymer is formed on the walls of the reactor. The suspension is treateo with methanol and HCl 6N; the polymer, after filtra ¬ tion, washing with acetone and drying, weighs 1.332 g. Activity = 83.80 gPE/mmole Cr Example 13 6.4 mg of Tp*CrCl , prepared as described in example 2 (MW = 420; 1.5*10 "? moles) and 30 ml of degassed, anhydrous toluene are introduced, under argon, into a 100 ml four-necked flask. 0.46 ml of Et ; AlCl 1.8 M (55 eq.) are added to the green suspension. The yellow solution obtained is put under ethylene and maintained at room temperature for 2 hours. The suspension is treated with methanol and HCl 6N; the polymer, after filtration, washing with acetone and drying, weighs 0.864 g and has a Tm of 128.5°C. Activity = 57.60 gPE/mmole Cr. Example 14 6.4 mg of Tp*CrCl_, prepared as described in example 2 (MW = 420; 1.5*10 " moles) and 30 ml of degassed, anhydrous toluene are introduced, under argon, into a 100 ml four-necked flask equipped with a cooler. 0.4c ml of Et;AlCl 1.8 M (55 eq.) are added to the green sc- lution. The yellow solution obtained is put under ethylene and heated to 65°C for 2 hours. The suspension is treated with methanol and HCl 6N; the polymer, after filtration, washing with acetone and drying, weighs 0.410 g. Activity = 26.91 gPE/1 mole of Cr Example 15 6.4 mg of Tp*CrCl 2/ prepared as described in example 2 (MW = 420; 1.5*10 ~b moles) and 100 ml of de ¬ gassed, anhydrous toluene are introduced, under argon, into a 250 ml four-necked flask. 0.17 ml of EtAlCl 1.8 M (20 eq. ) are added to the green solution, which turns yellow. The yellow solution is put under ethyl- ene and maintained at room temperature for 2 hours . The suspension is treated with methanol and HCl 6N; the polymer, after filtration, washing with acetone and drying, weighs 0.643 g. Activity = 42.86 gPE/mmole Cr Table 1: Polymerization tests catalyzed by tris- (3, 5-dimethyl pyrazolyl) chromium borate dichloride Tp*CrCl 2 obtained by varying the activators and experimental conditions.

Claims: CLAIMS 1. Tris- (3, 5-dimethylpyrazolyl) chromium borate dichloride as component of catalytic systems for the polymeriza ¬ tion of olefins. 2. A process for the (co) polymerization of olefins comprising polymerizing at least one olefin in the presence of a catalytic system comprising tris- (3,5- dimethylpyrazolyl) chromium borate dichloride and a cocatalyst consisting of a compound of aluminum selected from alkyl-halide or alkyl derivatives thereof, and aluminoxane . 3. The process for the (co) polymerization of olefins according to the previous claim wherein the catalyst is preferably methylaluminoxane . 4. The process for the (co) polymerization of olefins according to claim 2 wherein the catalyst is preferably aluminum diethylchloride. 5. The process for the (co) polymerization of olefins according to claim 2, characterized in that the polym- erization reaction is carried out in suspension at a temperature of up to 300 °C. 6. The process for the (co) polymerization of olefins according to claim 2, characterized in that the polymerization reaction is carried out in solution at a temperature of up to 100°C. 7. The process for the (co) polymerization of olefins according to claim 6, characterized in that the polymerization reaction is carried out at a pressure ranging from 1 to 150 bar. 8. The process for the (co) polymerization of olefins according to any of the previous claims wherein the cocatalyst is used in such quantities that the Al/Cr ra ¬ tio ranges from 10 to 5000.

Inventors: GRANDE MANUELA, ROMANO ANNA MARIA, SANTI ROBERTO, SOMMAZZI ANNA, GRANDE, MANUELA, ROMANO, ANNA, MARIA, SANTI, ROBERTO, SOMMAZZI, ANNA
Applicants: ENICHEM SPA, GRANDE MANUELA, ROMANO ANNA MARIA, SANTI ROBERTO, SOMMAZZI ANNA, ENICHEM S.P.A., GRANDE, MANUELA, ROMANO, ANNA, MARIA, SANTI, ROBERTO, SOMMAZZI, ANNA
Application year: 2000
Main classification: C08F10
IPC codes: C08F4, C08F110