Patent Application
20070173400
The present invention relates to a catalyst system comprising a single site catalyst component containing a transition metal, supported on an adduct containing magnesium halide, and an organoaluminum compound.
Single site catalyst components are well known in the art and are usually used in conjunction with alumoxanes or boron compounds as cocatalysts in polymerization processes. The catalyst systems so obtained can be used supported on an inert support in order to control the morphology of the obtained polymer and to avoid fouling in the reactor, especially in a gas-phase or slurry polymerization processes.
The drawback of the catalyst systems so obtained is that since alumoxanes need to be used in large excess with respect to the single site catalyst components, the resulting catalyst is very expensive. Therefore it is desirable to reduce or eliminate the use of alumoxanes.
When boron compounds are used as cocatalyst, a large excess is not required. However they have the drawback of being more expensive than alumoxanes and dangerous to handle.
Magnesium chloride is a well-known support for classic Ziegler Natta catalyst systems based on TiCl4 or TiCl3. The use of this compound as a carrier for single-site catalysts could be very advantageous, in view of its chemical and structural simplicity, and the possibility to finely control the porosity of this support and, therefore, to easily tune the porosity of the final catalyst system.
Adducts containing magnesium chloride and an organoaluminum compound have already been proposed as supports for metallocene-based catalyst components in which the central atom is zirconium, titanium or hafnium. For example, in Macromol. Chem. Phys. 195, 1369-1379 (1984), MgCl2 in combination with a zirconocene catalyst and trialkylaluminum is used. More recently, In Macromolecules 1993, 26, 4712, mixtures of MgR2 and AlR2Cl (generating MgCl2 and AlR3) as cocatalyst components for olefin polymerization using various metallocenes have been used. In various papers, namely, Korean J. Chem. Eng. 16(5) 562-570, Journal of Applied Polymer science Vol 70, 1707-1715, Korean J. Chem. Eng. 19(4) 557-563 and J. Molec. Catal A 191, 2003, 155-165, Lee and co-workers proposed a metallocene-based catalyst system in which alcohol and anhydrous MgCl2 are reacted to form an adduct MgCl2-alcohol. The adduct, further reacted with trialkylaluminum, is used for supporting zirconocene compounds. The obtained catalyst system can be used without a further addition of alumoxanes.
However, there is still the need to find alternative, easily obtainable supports for other kinds of single site catalyst system allowing elimination of the use of alumoxanes or boron compounds.
An object of the present invention is therefore a supported catalyst system comprising the product obtainable by contacting:
The partially dealcoholated adduct of formula MgT2.wUOH used in step a) can be obtained by partial dealcoholation of adducts of MgT2 with alcohols, said adducts contains from 1 to 6 mol of alcohol. It is possible that two adducts having the same content of alcohol, i.e. having the same empirical formula, are different in porosity and surface area for the reason that one adduct is partially dealcoholated.
The dealcoholation can be carried out according to known methodologies such as those described in U.S. Pat. No. 5,698,487. Depending on the extent of the dealcoholation treatment, partially dealcoholated adducts can be obtained having an alcohol content generally ranging from 0.1 to 3 moles of alcohol per mole of MgT2, preferably from 2.9 to 0.5; more preferably from 2.9 to 1.
Said partially dehalcoholated magnesium adduct is then contacted with an organo-aluminium compound of formula HeAlQ13-e or HeAl2Q16-e in an inert solvent with methods common known in the art, such as the method described in EP-A-553 806.
In step b) of the process of the present invention at least one compound of formula (II), (III), and (IV) can be supported on the carrier obtained in step a) according to known methods by bringing the product of step a) into contact, for example, with a solution of the said compound, operating at temperatures between room temperature and 120° C. The hydrocarbon radical, preferably R7 is a linear or branched, cyclic or acyclic, C1-C20-alkyl, C6-C20-aryl, C7-C20-alkylaryl or C7-C20-arylalkyl radical; more preferably R7 is a C1-C20-alkyl radical, such as a methyl or an ethyl radical; preferably A1 is a NR72 group;
The adduct of formula (I)
MgT2.yAlQj(OU)3-j (I)
generally has a surface area (BET) higher than 30 m2/g; more preferably higher than 38 m2/g; even more preferably higher than 200 m2/g; but it can reach values higher than 300 m2/g. It can be obtained with methods commonly known in the art. For example the adduct MgT2.wUOH, wherein w ranges from 0.1 to 6, is contacted with an aluminum compound of formula HeAlQ13-e or HeAl2Q16-e, in an inert solvent; where each Q1 substituent, same or different, is hydrogen atom, halogen atom, or a hydrocarbon radical containing from 1 to 20 carbon atoms optionally containing silicon or germanium atoms; with the proviso that at least one Q1 is different from halogen, and e ranges from 0 to 1, being also a non-integer number; preferably said hydrocarbon radicals is a linear or branched, cyclic or acyclic, C1-C20-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C20-aryl, C7-C20-alkylaryl or C7-C20-arylalkyl radical optionally containing silicon or germanium atoms; preferably Q1 is a linear or branched C1-C20-alkyl radical; more preferably Q1 is an ethyl, a n-propyl, an iso-propyl, a n-butyl, an iso-butyl, a tert-butyl, a hexyl or an octyl radical. Examples of this reaction can be found in U.S. Pat. No. 4,399,054 and U.S. Pat. No. 5,698,487.
Preferably the adduct of formula MgT2.wUOH is partially dealcoholated as described in U.S. Pat. No. 5,698,487. Therefore a further object of the present invention is a supported catalyst system obtainable by the process comprising the following steps:
The amount of said compounds supported on the adduct of formula (I) is generally between 1000 μmol/g of support and 1 μmol/g of support; preferably said amount ranges from 500 μmol/g of support to 2 μmol/g of support; more preferably from 200 μmol/g of support to 2 μmol/g of support.
Preferably, the compound of formula (II) has formulas (IIa) or (IIb)
wherein R1, T1, M1, X, m and n are as described above;
Preferred compounds belonging to formula (IIc) are compounds of formula (IIca) and (IIcb)
wherein:
Compounds belonging to formulas (II), (III), and (IV) are well known in the art. They are described for example in WO 96/23010, WO 97/02298, WO 98/40374, U.S. Pat. No. 5,707,913 and Organometallics 2000, 19, 388.
The catalyst system object of the present invention can be used for (co)polymerizing one or more olefins. Therefore a further object of the present invention is a process for (co)polymerizing olefins containing from 2 to 20 carbon atoms comprising contacting one or more of said olefins under polymerization conditions in the presence of the catalyst system described above. Preferably alpha-olefins containing from 2 to 20 carbon atoms are used.
Examples of alpha-olefins that can be used with the process of the present invention are: ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 4,6-dimethyl-1-heptene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene. Preferred olefins are propylene, ethylene 1-butene, 1-hexene and 1-octene.
The catalyst system object of the present invention are particularly suitable for the production of ethylene polymers having very high molecular weight. Thus a further object of the present invention is a process for polymerizing ethylene comprising contacting one or more of said olefins under polymerization conditions in the presence of the catalyst system described above.
Preferably the ethylene polymer obtainable with the catalyst system object of the present invention has a molecular weight Mw higher than 500,000; more preferably higher than 700,000; even more preferably higher than 1,000,000; still more preferably Mw can be higher than 1,300,000.
The following Examples are given for illustrative purpose and do not intend to limit the invention.
All manipulations were performed under an argon atmosphere using A glove box (Braun MB-150 GI or LM-130) and Schlenk techniques. Solvents were distilled from Na (toluene) or Na/benzophenone (heptane) and freeze-thaw degassed twice before use.
The vanadium aminidinate complexes 1 and 2 were prepared according to Eur. J. Inorg. Chem. 1998, 1867. The analogous titanium amidinate complexes 3 and 4 were prepared as follows:
[{PhC(NSiMe3)2}TiCl2(THF)2] (3) was prepared by adding [PhC(NSiMe3)2]Li(THF) (1.1 g, 4.07 mmol) to a suspension of TiCl3(THF)3 (1.50 g, 4.05 mmol) in THF (ca. 100 mL) cooled to −78° C., The mixture was allowed to warm to room temperature while stirring, affording a dark green-brown solution. After stirring overnight, the volatiles were removed in vacuo and the residue was “stripped” twice (2×10 mL) with petroleum ether (40-70 distillates). The residue was then extracted with hot toluene (ca. 40 mL) and cooled to −30° C., yielding 3 as dark-green needles (0.77 g, 37%).
[(Me3SiNC(Ph)NCH2CH2NMe2)TiCl2(THF)] (4) was prepared by adding [(Me3SiNC(Ph)NCH2CH2NMe2)Li] (1.0 g, 3.69 mmol) to a suspension of TiCl3(THF)3 (1.37 g, 3.70 mmol) in THF (ca. 100 mL) cooled to −78° C. Further steps were as described for (3), yielding 4 as brown-green needles (0.54, 32%).
The chromium complex 5 [η1:η5-Me2NCH2CH2C5Me4)CrCl2] was prepared according to A. Döring, J. Göhre, P. W. Jolly, B. Kryger, J. Rust, G. P. J. Verhovnik, Organometallics 2000, 19, 388.
The nickel complexes 6-9 (R=isopropyl) were prepared according to procedures reported in: L. J. Johnson, C. M. Killian, M. Brookhart, J. Amer. Chem. Soc. 1995, 117, 6414, and R. J. Maldanis, J. S. Wood, A. Chandrasekaran, M. D. Rausch, J. C. W. Chien, J. Organometal. Chem. 2002, 645, 158.
AlMe3 (2M in hexane), AlEt3 (25 wt.-% solution in toluene) and AlnOct3 (25 wt-%, ca. 0.5M in hexanes) were obtained from Aldrich. AliBu3 (1M solution in hexane) was purchased from Fluka.
Ethylene (3.5 grade supplied by Air Liquide) was purified by passing over columns of 4 Å Molecular Sieves and BTS copper catalyst.
The Al and transition metal contents were determined by ICP/atomic absorption.
Surface area (BET) is determined according to BET methods (apparatus used: SORPTOMATIC 1800 from Carlo Erba).
The ethoxide content in the magnesium adducts was determined by GC analysis of the ethanol content of a solution obtained by dissolving 100 mg support in 5 mL n-BuOH containing a known quantity of n-PrOH as internal standard.
Preparation of Partially Dealcoholated Adduct of Formula MgCl2.wUOH
The adduct MgCl2.3EtOH was prepared according to the procedure described in Example 2 of U.S. Pat. No. 4,399,054, operating at 3,000 rpm instead of at 10,000 rpm.
The adduct was partially dealcoholated by heating in a stream of nitrogen at temperatures increasing from 30° C. to 180° C.
Preparation of the Support MgCl2/AlQj(OEt)3-j
10-50 mL n-heptane were added to 1-5 g of a spherical adduct of magnesium chloride and ethanol under argon and the mixture was cooled to 0° C. A 25-28 wt-% solution of AlR3 was then added gradually, over 5-10 min., to give a mol ratio AlR3/EtOH=2, the reaction being carried out in a standard Schlenk vessel equipped with a pressure release valve. The mixture was allowed to warm slowly to room temperature and the reaction was continued with occasional agitation for a further 1 day (AlMe3), 2 days (AlEt3), 3 days (AliBu3) or 4 days (AlnOct3). The solid support was isolated by filtration, washed with heptane and petroleum ether (40-70) and then dried under a flow of argon and subsequently in vacuum. The compounds so obtained are reported in Table 1.
Preparation of the Catalyst System—General Procedure
A solution containing 1 μmol of the relevant transition metal complex (reported in Table 2) in toluene (1 mL) was added to 100 mg of support prepared as described above. The mixture was heated to 50° C. and kept at this temperature for 4 h. The toluene was then removed by decantation and the solid was reslurried in petroleum ether.
Polymerization—General Procedure
Ethylene polymerization was carried out in a 1 L Premex autoclave equipped with a vortex stirrer. Petroleum ether (40-70, 450 mL) was introduced via a canulla. The reactor contents were stirred and heated to 50° C. Triisobutylaluminium (TIBAL, 1 mmol) in petroleum ether (40-70, 10 mL) was introduced via the catalyst injection system. An ethylene overpressure of 0.5 MPa was applied and stirring continued for 5-10 min. A slurry of the immobilized catalyst (100 mg) in petroleum ether (40-70, 10 mL) was introduced through the catalyst injection system, which was then flushed with a further 50 mL petroleum ether (40-70). The ethylene pressure was increased to 1 MPa and kept constant for 2 h at a polymerization temperature of 50° C., the stirrer speed being ca. 1000 rpm. After venting the reactor, the polymer slurry was mixed with 20 mL of acidified methanol, 50 mL demineralised water and 10 mL HCl (10%). The polymer was recovered by filtration, washed with water (3×200 mL) and ethanol (2×30 mL) and dried in vacuo overnight at 70° C. The polymerization results are reported in Table 2.
*= (30 min. polymerization)
n.a. = not available
| Number | Date | Country | Kind |
|---|---|---|---|
| 04075578.7 | Feb 2004 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP05/01539 | 2/14/2005 | WO | 8/24/2006 |
