WO2002004468A1

WO2002004468A1 - Metallocene polymerization catalyst

Info

Publication number: WO2002004468A1
Application number: PCT/US2000/018905
Authority: WO
Inventors: Raisa Kravchenko
Original assignee: E.I. Du Pont De Nemours And Company
Priority date: 2000-07-12
Filing date: 2000-07-12
Publication date: 2002-01-17
Also published as: AU2000262096A1

Abstract

A dimethylsilylene (2,4-dimethylcyclopentadienyl)-(fluorenyl) zirconocene-type compound polymerizes olefins. The resulting polyolefins may be used as molding resins and for films.

Description

TITLE METALLOCENE POLYMERIZATION CATALYST

FIELD OF THE INVENTION A dimethylsilylene (2 ,4 -dimethylcyclopentadienyl) -

(fluorenyl) zirconocene-type compound may be used to catalyze (co) polymerization of olefins such as ethylene, propylene, and 4 -methyl-1-pentene. The resulting polyolefins sometimes have structures different from polymers produced using closely related metallocene-type catalysts.

TECHNICAL BACKGROUND Polyolefins, such as polyethylene and polypropylene, are important items of commerce, many billions of kilograms being produced each year. These polymers are produced by a variety of methods, probably the most common being use of a transition metal containing polymerization catalyst. Recently, there has been much interest in so-called metallocene-type catalysts, and some of these are now used in commercial polymerization processes.

Metallocene catalysts are most often cyclopentadienyl complexes of early transition metals such as titanium, zirconium and hafnium. Usually used in combination with an alkylaluminum compound such as methylaluminoxane, they (co) polymerize various olefins such as ethylene and α- olefins . However it is well known in the art that the productivity of these catalysts and the structure of the polymers they produce with any particular monomer (s) often critically depends on the exact structure of the metallocene compound used. In at least some cases, small changes in the metallocene compound produce unexpected and/or unpredictable changes in the polyolefins produced.

US5627118, US5571880, US5436305 and US5401817; C. J. Schaverien, et al . J^". Mol . Catal . A : Chem. 1998, 128, 245- 256; K. Patsidis, et al . J^". Organomet . Chem . 1996, 509, 63- 71; Y.-X. Chen, et al . J. Organomet . Chem. 1995, 497, 1-9; J. A. Ewen, et al . , Makromol . Chem . , Macromol . Symp . 1991, 48-49, 253-295; all describe various metallocene-type compounds in which a cyclopentadienyl and a fluorenyl groups complexed to a zirconium atom are connected by a bridging group . None of these references describes the compounds or processes claimed herein.

All of the above references are incorporated by reference herein for all purposes as if fully set forth.

SUMMARY OF THE INVENTION This invention concerns a compound of the formula

(I) wherein each X is independently a monoanion.

This invention also concerns a process for the polymerization of olefins, comprising the step of contacting, under polymerizing conditions, a compound of the formula

(I) and optionally one or more cocatalysts, with one or more olefins of the formula H₂C=CHR¹, wherein: each X is independently a monoanion; and R is hydrogen or alkyl . Also disclosed herein is the compound (dimethylcyclopentadienyl) (9-fluorenyl) dimethylsilane .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The catalyst zirconocenes described and used herein are typical metallocene-type catalysts, and may be used for polymerizations under conditions usually used in such polymerizations. Also the Examples herein describe how the claimed catalysts may be made and used.

By "under polymerizing conditions" is meant, for instance, that the polymerization may be run as gas phase, solution or slurry processes, and/or may be run as continuous, batch or semibatch processes, under such conditions to polymerize the monomers. The zirconocene may be supported on a heterogeneous support such as a metal halide, silica gel, alumina or an organic polymer, or may just be suspended or dissolved in a liquid. Polymerization processes using metallocenes are described in previously US5627118, US5571880, US5436305 and US5401817, and reference may be had thereto for further details on such processes. For instance, the polymerization may be run at a temperature of about 0°C to about 70°C, typical for metallocene-type catalysts. Hydrogen may be used as a chain transfer agent. The zirconocene described herein may be used as part of a mixed polymerization catalyst system, for example with another metallocene (such as described in the aforementioned incorporated references) , a Ziegler-Natta-type catalyst

(see, for instance, J. Boor Jr. , Ziegler-Natta Catalysts and Polymerizations , Academic Press, New York, 1979) , or a late transition metal catalyst (see, for instance, US5714556, US5880241, US5955555, WO98/30609, WO98/30610, O98/30612, W098/38228, O99/02472 and 099/12981 (all incorporated by reference herein for all purposes as if fully set forth) ) , or any combination thereof.

In (I) it is preferred that X is halide, more preferably chloride, bromide or alkyl, and especially methyl . By monoanionic is meant that each anion has a single negative charge. (I) may be made by methods analogous to those known for other structurally similar metallocenes, for instance see Examples 1 and 2 herein for such a synthesis. It is preferred that one or more cocatalysts be used. Such cocatalysts are known in the art, and are typically able to alkylate the zirconium atom (if not already alkylated) , and/or abstract X^" from (I) to form a cationic Zr species and a relatively noncoordinating anion. A preferred cocatalyst is an alkylaluminum compound, that is an aluminum compound containing at least one alkyl group bound to an aluminum atom. This compound may also contain other groups such as oxygen between Al atoms, alkoxide, halide, etc.

Preferred alkylaluminum compounds are alkylaluminoxanes, and methylaluminoxane is especially preferred.

Preferred olefin monomers are those in which R¹ is hydrogen (ethylene), n-alkyl, especially methyl (propylene) , and 2-methylpropyl (4-methyl-l-pentene) , and combinations thereof. An especially preferred copolymer is ethylene/4- methyl-1-pentene . The polymers made by the polymerization process described herein are useful as molding resins, and for films and packaging. If elastomeric, they are useful as elastomers.

The zirconocene of the present invention has been found to produce, for example, a copolymer of ethylene and 4- methyl-1-pentene which is a random copolymer. It has also been found to produce a highly isotactic homopolymer from 4- methyl -1-pentene, and a high molecular weight partially isotactic (homo) polypropylene . This is in contrast to other structurally close zirconocenes that produce polyolefins with different structures with these same monomers.

In the Examples, certain abbreviations are used: ΔH_m - heat of fusion

Cp - cyclopentadienyl

DSC - differential scanning calorimetry

GPC - gel permeation chromatography

MAO - methylaluminoxane Mn - number average molecular weight

Mw - weight average molecular weight

MWD - Mw/Mn

RT - room temperature

Tg - glass transition temperature THF - tetrahydrofuran

Tm - melting point

All organometallic reactions were conducted using standard Schlenk and drybox techniques. Unless otherwise specified all reagents were purchased from commercial suppliers and used without further purification. Isopropylidene (3 -methylcyclopentadienyl) (fluorenyl) zirconium dichloride (II) (J. A. Ewen, et al . , Makromol . Chem. , Macromol . Symp. 1991, 48 -49, 253-295); dimethylsilylene- bis (fluorenyl) zirconocene dichloride (III) (L. Resconi, et al . , Organomet llies 1996, 15, 998-1005); ethylene- bis (indenyl) zirconium dichloride (IV) (G. M. Diamond, et al., Organom tallies 1995, 14 , 5-7); and 1,3- dimethylcyclopentadiene (A. L. McKnight and R. M. Waymouth Macromolecules 1999, 32, 2816-2825) ; were prepared according to the literature procedures. Anhydrous hexane, toluene, pentane and methylene chloride were filtered through basic alumina in the dry box. Tetrahydrofuran, diethyl ether and 1-methyl-4 -pentene were distilled from sodium/benzophenone under nitrogen and filtered through basic alumina in the dry box. Chloroform-d₃ and methylene chloride-d₂ were distilled from calcium hydride and benzene-d_e was distilled from sodium benzophenone . Polymethylaluminoxane (PMAO-IP, 12.7-13.5 wt % Al in toluene) was purchased from Akzo and either used as received or dried in vacuo prior to use and is referred to as "MAO" or "dry MAO" in the Examples. Propylene was passed through a VWR moisture trap. Polymer molecular weights and molecular weight distributions were determined by high temperature gel permeation chromatography using polypropylene and polyethylene GPC calibration standards. ¹³C NMR measurements were performed on a Varian Unity 400 instrument at 120°C in 1, 1, 2, 2-tetrachloroethane-d₂ using no delay (polypropylene and poly-4-methyl-l-pentene) or 13 s delays between pulses with gated proton decoupling (ethylene-4-methyl-l-pentene copolymers) and 1 s acquisition times. All spectra were referenced to the solvent resonance. It was assumed that the relaxation times and NOE's of all carbon atoms of a similar nature were the same (Segre, A. L.; et al . Macromolecules 1983, 16, 1207-1212) . Melting and glass transition points and heats of fusion were determined by differential scanning calorimetry. The DSC scans were obtained by first heating the polymer samples to above their melting temperature for 5 min, cooling them down to -50 °C at 10°C/min and then reheating them to above their melting point at 10°C/min. All reported DSC values are reheat values .

In all cases wherein (I) is used in the examples, X is chloride. Some of the Examples use the following compounds:

(II) (III)

(IV) Example 1 Preparation of (2 , 4-dimethylcyclopentadienyl) - (fluorenyl) dimethylsilane

A solution of Me₂SiCl₂ (4.5 g, 35 mmol) in THF (30 mL) was cooled to 0°C and treated dropwise with a solution of l,3-Me₂CpLi (1.16 g, 11.6 mmol) in THF (20 mL) . The resulting yellow solution was warmed to room temperature and stirred overnight. After volatiles were removed, the yellow paste was extracted with pentane (3x10 mL) . The combined pentane washings were evaporated to dryness to give a yellow solid (2 , 4-dimethylcyclopentadienyl) chlorodimethylsilane, 1.28 g, 6.90 mmol) which was dissolved in Et₂0 (30 mL) and treated with a solution of fluorenyllithium (1.18 g, 6.90 mmol) in Et₂0 (30 L) at 0°C dropwise. The resulting yellow solution was warmed to room temperature and stirred overnight. After volatiles were removed, the yellow paste was extracted with toluene (3x10 mL) and filtered. The solvent was removed in vacuo to yield a yellow oil (1.80 g) containing a mixture of isomers of (dimethylcyclo- pentadienyl) (9-fluorenyl) dimethylsilane according to """H NMR.

Example 2 Preparation of Me₂Si(l,3- dimethylcyclopentadienyl) (fluorenyl) ZrCl₂

The dilithio salt of (dimethylcyclopentadienyl) - (fluorenyl) dimethylsilane (1.75 g, 5.34 mmol) and ZrCl₄ (1.244 g, 5.34 mmol) were mixed in toluene (60 mL) at room temperature to form a yellow-red suspension. The reaction mixture was allowed to stir at room temperature overnight. A clear red solution was collected after filtration and concentrated in vacuo to give an orange paste which was subsequently dissolved in toluene (5 mL) and kept in a -30°C freezer overnight. The yellow-red powder was collected and redissolved in CH₂C1₂ (4 mL) . Yellow powder of the desired product was collected after storing this solution at -30°C overnight (0.5 g, 19%). ^XH NMR (CD₂C1₂, 20°C, 500 MHz): δ 8.10 (t, J^" = 8.3 Hz, 2H) , 7.70 (d, J^" = 8.6 Hz, 1H) , 7.59 (m, 2H) , 7.53 (d, J^" = 8.6 Hz, 1H) ,7.28, (t, J = 7.7, 1H) , 7.24 (t, J = 7.7, 1H) , 6.11 (d, J^" = 2.1 Hz, 1H) , 5.33 (d, J^" = 2.1 Hz, 1H) , 2.11 (s, 3H) , 1.96 (s, 3H) , 1.29 (s, 3H) , 1.10 (s, 3H) . ¹³C H} NMR (CD₂C1₂, 20°C, 125 MHz): 5137.78, 132.51, 131.40, 130.84, 129.43, 128.59, 128.47, 127.20, 126.75, 126.62, 126.11, 125.39, 125.23, 124.21, 111.76, 100.31, 17.97, 16.05, 0.98. Elemental analysis was consistently low in C: Anal. Calcd (Found) for C₂₂H₂₀Cl₂SiZr : C 55.44 (54.48); H 4.65 (4.54) .

Examples 3-5 and Comparative Examples A-B Propylene Polymerization

A 600 mL Hastelloy® Parr autoclave equipped with a mechanical stirrer was charged with methylaluminoxane and toluene (150 mL) . The mixture was allowed to equilibrate under reaction temperature and pressure until no more propylene flow into the reactor was registered. Metallocene solution in toluene (50 mL) was injected from a 50-mL pressure tube under propylene pressure set at 35-70 kPa above the reactor equilibrium pressure. After 1 h the reaction was quenched by injecting methanol (40 mL) . Polypropylene was precipitated by pouring its toluene solution into acidified MeOH (5 % HCl) , filtered, washed with MeOH and dried in a vacuum oven at 50°C to constant weight .

Example 3 Propylene polymerization with (I) /MAO A 600 mL Hastelloy® Parr autoclave equipped with a mechanical stirrer was charged with methylaluminoxane (13.4 wt % Al in toluene, 3.5 mL) and toluene (146.5 L) . The mixture was allowed to equilibrate at 25°C and 620 kPa until no more propylene flow into the reactor was registered. A solution of (I) (2.5 μmol) in toluene (50 mL) was injected from a 50-mL pressure tube under 655 kPa of propylene. After 1 h the reaction was quenched by injecting methanol (40 mL) . Polypropylene was precipitated by pouring its toluene solution into acidified MeOH (5 % HCl) , filtered, washed with MeOH and dried in a vacuum oven at 50°C to constant weight (tough white polymer, yield 8.92 g) .

Details for all these polymerizations are found in Table 1.

Table 1

a) Zr, μmol = 2 . 5 , [Al] .- [Zr] = 2 570 , t^ = 1 h b) kg^'PP/ (mol'Zr^'h) c) Determined from high temperature GPC, using universal calibration curve for polypropylene d) Determined by DSC e) Determined from ¹³C NMR f) Unusual crystallization behavior: no crystallization occurs after initial melt in the cooling run, however, in the second heating run a sharp crystallization peak occurs just below 40°C and then the sample melts. g) Hemi-isotactic pattern

Examples 6-7 and Comparative Examples C-E 4 -Methyl -1 -pentene Polymerizations In a nitrogen filled dry box, 4-methyl-l-pentene and MAO/toluene were combined in a 20 mL vial equipped with a stir bar. Polymerization was initiated by adding the solution of the corresponding zirconocene in toluene via syringe . After 1 h the vial was taken out of the dry box and the reaction mixture was poured into MeOH/10 vol % HCl to precipitate the polymer. Poly-4-methylpentene was then collected by filtration, washed with copious amounts of methanol and dried in a vacuum oven at 50°C to constant weight . Example 6

4 -Methyl -1 -pentene Polymerization with (I) /MAO In a nitrogen filled dry box, 4-methyl-l-pentene (25 mL) , MAO solution in toluene (12.7 wt % Al, 1.1 mL) and toluene (4.4 mL) were combined in a 20 mL vial equipped with a stir bar. Polymerization was initiated by adding a solution of (I) (4.5 μmol) in toluene (2 mL) via syringe. After 1 h the vial was taken out of the dry box and the reaction mixture was poured into MeOH/10 vol % HCl to precipitate the polymer. Poly-4-methylpentene was then collected by filtration, washed with copious amounts of methanol and dried in a vacuum oven at 50 °C to constant weight (polymer yield 715 mg) .

Results of all these polymerizations are given in Table 2. Table 2

a) [cat] = 0.15 mM; [Al] = 0.15 M; [Al] : [Zr] = 1 000; t -p,ol = 1 h; [4MP] = 6.1 M, 25°C b) determined by high temperature GPC c) determined by DSC d) Determined from ¹³C NMR as an integral ratio for peaks at 45.4 and 45.7 ppm

Examples 8-11 and Comparative Example F 4-Methyl-1-pentene Copolymerization with Ethylene In a nitrogen filled dry box, methylaluminoxane and 4- methyl-1-pentene were measured into a 100 mL Schlenk tube equipped with a stir bar. The reaction flask was then placed under an atmospheric pressure of ethylene on a vacuum line with or without prior removal of nitrogen. The reaction was initiated by injecting the metallocene solution in toluene (2 mL) . After a certain time the reaction was quenched by injecting methanol (5 mL) and/or pouring the reaction mixture into MeOH/10 vol % HCl. The polymer was isolated by filtration, washed with copious amounts of methanol and dried in a vacuum oven at 50°C to constant weight .

Example 13 Ethylene-propylene copolymerization with catalyst (I) /MAO In a nitrogen filled dry box, methylalμminoxane (13.5 wt % Al in toluene, 0.96 mL) and 4-methyl-l-pentene (10 mL) were measured into a 100 L Schlenk flask equipped with a stir bar. The reaction flask was then connected to a vacuum line. Its contents were frozen in liquid N₂ and the head space was evacuated to remove nitrogen. The flask was then refilled with 1 atm of ethylene at 25°C. The reaction was initiated by injecting the solution of (I) (4 μmol) in toluene (2 mL) . Ethylene was constantly fed into the reaction through a bubbler. After 1 h the reaction was quenched by injecting methanol (5 mL) and the reaction mixture was poured into MeOH/10 vol % HCl. The white rubbery polymer was isolated by filtration, washed with copious amounts of methanol and dried in a vacuum oven at 50°C to constant weight (yield 1.563 g) .

Table 3

K->

a) [cat] = 0.31 mM; [Al] : [Zr] = 1 000; t_pol = 1 h; b) kg^'PP/ (mol^'Zr^'h) ; c) determined by quantitative ¹³C NMR e) determined by high temperature GPC d) determined by DSC

Claims

CLAIMS What is claimed is: 1. A compound of the formula

(I) wherein each X is independently a monoanion.

2. The compound as recited in claim 1 wherein each X is independently halide or alkyl .

3. The compound as recited in claim 1 wherein both of X are chloride.

4. A process for the polymerization of olefins, comprising the step of contacting, under polymerizing conditions, a catalyst composition with one or more olefins

Of the formula H₂C=CHR , wherein R is hydrogen or alkyl, and wherein said catalyst composition comprises a compound of the formula

wherein each X is independently a monoanion.

5. The process as recited in claim 4 wherein a cocatalyst is present .

6. The process as recited in claim 5 wherein said cocatalyst is an alkylaluminum compound.

7. The process as recited in claim 6 wherein said alkylaluminum compound is methylaluminoxane .

8. The process as recited in claim 4 wherein each X is independently halide or alkyl.

9. The process as recited in claim 8 wherein both of X are halide.

10. (Dimethylcyclopentadienyl) (9-fluorenyl) - dimethylsilane.