Metallocenes with silyl-substituted bridges and their use for olefin polymerization

The invention relates to novel metallocenes and their use as catalysts in olefin polymerization.

Metallocenes of the metals of IV. Subgroup of the Periodic Table of the Elements are highly active catalysts for the polymerization of olefins. The resulting polyolefins have new property combinations and complement the product spectrum of the polyolefins previously produced with known conventional Ziegler-Natta catalysts.

It is known that catalysts based on unbelted, substituted and unsubstituted biscyclopentadienyl metallocenes can be used in conjunction with aluminoxanes as cocatalyst for the production of polyethylene and ethylene / α-olefin copolymers (EXXON, EP 128 046 A).

Furthermore, it is known that stereoregular polyolefins can be prepared with bridged, chiral metallocenes. For a bridging of the ligand systems are mainly dimethylsilanediyl groups (CHISSO, EP 316 155 A), methyl-phenylsilanediyl groups (HOECHST, EP 320 762 A), ethylene groups (Brintzinger et al, J. Organomet. Chem., 288 (1985) 63-67) and isopropylidene bridges (Mitsui Toatsu, EP 459 264 A). Depending on the ligand type and the substituents, isotactic, syndiotactic, hemi-isotactic, stereoblock-like and atactic homo- and copolymers with aliphatic or cyclic structures can be prepared.

Preferred ligands are substituted and unsubstituted cyclopentadienyl units (CHISSO, EP 316 155 A), substituted and unsubstituted indenyl units (Hoechst, EP 302 424 A, Hoechst, EP 485 823 A) and substituted and unsubstituted cyclopentadienyl units in combination with unsubstituted fluorenyl groups (Mitsui Toatsu, EP 412 416 A) used.

It is also known that bridged metallocenes having a cyclopentadienyl system and a constrained geometry catalyst can be used for the polymerization of olefins (EXXON, US Pat. No. 5,096,867 A).

Of these different metallocene types, the bridged, chiral, substituted bisindenyl systems gained particular importance. Thus, it has been demonstrated that the nature of the substituents and the position of the substituents on the ligand of the metallocene exert a significant influence on the reactivity of the catalyst system and the stereoregular structure of the resulting polyolefins. Especially two substitution possibilities proved to be advantageous. The first possibility is based on a substitution on the indenyl ligand in 2, 4 and / or 6 position (Hoechst, EP 485 823 A, Angew. Chem., 10 (1992) 1373), the second possibility describes the annulation on the benzene ring of the indenyl ligand (Organometallics 1994, 13, 964-970). Both types of catalysts can be used for the preparation of isotactic polypropylenes and ethylene / α-olefin copolymers.

Repeatedly substituted indenyl ligands can be produced only with considerable effort. Relatively simple systems with good activity containing indenyl, 2-methylindenyl or 2-methylbenzene [e] indenyl ligands provide products and in particular polypropylene with relatively low molecular weights, which are too low for many applications and the lower limit for the represent technical application.

It was therefore the object of finding further structural variants of bridged metallocenes as catalysts for the polymerization of olefins, which provide polyolefins, in particular polypropylenes with higher molecular weights.

Surprisingly, it has now been found that silyl-substituted, diyl-bridged metallocene systems are suitable catalysts for the preparation of polyolefins and in particular of polypropylenes having relatively high molecular weights.

The present invention accordingly metallocenes of the formula I.

<img file="AT403376B_D0001.tif" />

wherein M is a metal from the group Ti, Zr, Hf, V, Nb, Ta or an element from the group of lanthanides,

AT 403 376 Β

X, and X2 are the same or different and a Ci - Ci 0-alkyl group, a Ci - Ci₀Alkoxy group, a C₆ Cw aryl group, a C₆ - Ci₀- aryloxy group, a C₂ - Ci₉ Alkenyl group, a C₇ - C₂₀Arylalkyl group, a C₇ - C₂₀Alkylaryl group, a C_8th - C₂₀ Arylalkenyl group, hydrogen or a halogen atom,

Li and L2

a) are identical or different and denote an optionally mono- or polysubstituted mononuclear or polynuclear hydrocarbon radical having at least one cyclopentadienyl unit, which may form a sandwich structure with M, or

b) Li is an optionally mono- or polysubstituted mono- or polynuclear hydrocarbon radical having at least one cyclopentadienyl unit which can form a sandwich structure with M and L₂ a radical of the formula containing N, P or As

E-D \ is where D is nitrogen, phosphorus or arsenic and E is Bedeutung_Ί and X2 has,

R is carbon, silicon, germanium or tin,

A and B are the same or different and silyl radicals of the formula

<img file="AT403376B_D0002.tif" />

in which Q, S, T are the same or different and are a Ci - Ci₀Alkyl group, a Ci - Ci₀Alkoxy group, a C₆ - Ci₀-Aryl group, a C₆ -Ci 0 aryloxy group, a C₂ - Cio-alkenyl group, a C₇ - C₂₀-Arylalkylgruppe, a C₇ - C₂o-alkylaryl group, a C_8th - C20-Arylalkenylgruppe, hydrogen, a halogen atom or other silyl radicals, where B is also the meaning of Xi or X.₂ may have.

Preferred as substituents A and / or B are trialkylsilyl radicals, particularly preferred are trimethylsilyl radicals.

As ligands Li and / or L₂ substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl radicals are preferred. Particularly preferred are cyclopentadienyl, tetramethylcyclopentadienyl, indenyl, 2-methylindenyl, 2-methyl-4,5-benzoindenyl, fluorenyl units and ferrocene and ruthenocene-substituted units, as described, for example, in DE-A-44 17 542 are described.

According to the invention, the following metallocenes are particularly preferred: bis (trimethylsilyl) silanediyl-dicyclopentadienylzirconium dichloride, Bis (trimethylsilyl) silanediylbis diindenyl dichloride, Bis (trimethylsilyl) silanediyl-bis (2-methylindenyl) zirconium dichloride, Bis (trimethylsilyl) silanediyl-bis (2-methyl-4,5-benzoindenyl) zirconium dichloride, silanediyl-bis zirconium dichloride bis (trimethylsilyl) (2-methyl-4-phenylindenyl) silanediyl-bis zirconium dichloride bis (trimethylsilyl) (2-methyl-4-naphthylindenyl) Bis (trimethylsilyl) silanediylbis difluorenyl dichloride, Bis (trimethylsilyl) silanediyl (fluorenyl) (cyclopentadienyl) zirconium dichloride, Bis (trimethylsilyl) silanediyl (fluorenyl) (indenyl) zirconium dichloride and bis (trimethylsilyl) silanediyl (tetramethylcyclopentadienyl) (indenyl) zirconium dichloride.

Another object of the invention is a process for the preparation of metallocenes I, which is characterized in that a compound of formula II

AT 403 376 Β

<img file="AT403376B_D0003.tif" />

(Μ ·)₂ (Η) where Li, L₂, Α, Β and Ft have the meaning described in formula I and M 'is an alkali metal, preferably lithium, with a compound of formula III

M (X ')₂XiX2 (III), wherein M, Xi and X2 has the meaning given in formula I and X 'represents a halogen atom, preferably chlorine.

By way of example, the metallocenes I can be prepared according to the following reaction scheme:

X-R-X + butyl Li -► H-Ln Li

H

H.

L2 + butyl Li -► H-L2 Li

H

A

I

H-L_rR ~ X + H-L₂ Li -

I

B

A

HL_rRX

I

B

A

I

H-L | -RL₂-H

I

B

A

H-L | -RL₂ -H

I

B

Butyl Li -► Li-Lir - ^ - Li

I

B

A

I

Li-Ljr-Li-Li + I

B

M Cl₂ Xi X₂ *&gt;

<img file="AT403376B_D0004.tif" />

lv

<img file="AT403376B_D0005.tif" />

Xi

X2

X = F; CI; Br; J

Xi, X₂, Li and L₂ have the above meaning.

In the case of unsymmetrical metallocenes, the ligands L₂ in addition, variously substituted or unsubstituted cyclopentadienyl, indenyl, fluorenyl or amido, phosphido and arsenido radicals can be used, the substituents of these ligands being the meaning of Xi and X.₂ own or

AT 403 376 Β but are ferrocenyl- or ruthenocenyl-substituted or -annelated.

Another object of the invention is the use of the metallocenes of the invention as

Polymerization catalysts in the polymerization of olefins, and a Olefinpolymerisationsverfahren in which the metallocenes of the invention are used as catalysts.

In the polymerization of olefins, preference is given to a cocatalyst, for example an aluminoxane of the formula IV for the linear type:

K

R

Γ ^R1

Al-O-Al-O-Al (IV) and / or of the formula V:

| - ^R_l -O-Aln + 2 (V) used for the cyclic type, wherein in the formulas IV and V, the radicals may be identical or different and denote a C1-C6-alkyl group and n is an integer 1-50. The radicals are preferably identical and are methyl, isobutyl, phenyl or benzyl, particularly preferably methyl. The aluminoxane can be prepared in various ways by known methods. One possibility is, for example, the reaction of aluminum alkyls with aluminum sulfate containing water of crystallization (Hoechst, EP 302 424 A). In the present invention, commercially available MAO (methylaluminoxane, Fa. Witco, FRG).

It is also possible to mix the metallocene of formula I with an aluminoxane of the formula IV and / or V before use in the polymerization reaction. The mixing is preferably carried out in solution. The metallocene is preferably dissolved in an inert hydrocarbon and then mixed with the aluminoxane solution. As an inert hydrocarbon, an aliphatic or aromatic hydrocarbon is suitable. Preferably, toluene is used.

The concentration of the aluminoxane in the solution is in the range of 5-30% by mass based on the total solution. The metallocene is preferably added in an amount of 10 "⁴ - 1 mol per mole of aluminoxane used. The mixing time is about 5 minutes to 24 hours, preferably 5 to 60 minutes. It usually works at a temperature of -10 to + 70 * C, especially at 10 to 40'C.

The metallocene may also be applied to a support. Suitable carriers are, for example, the inorganic oxides of the metals of II-IV main group of the Periodic Table. Preferably, the oxides of the metals magnesium, calcium, aluminum, silicon, boron and mixtures thereof, for example, the commercially available Al-oxides Alumina type C (Degussa) and Si oxides of the type Davis Davison grade 952-957 "or of the type Aerosil (Degussa), as well as mixtures of AI2O3 and SiO2. Particular preference is given to catalyst supports according to EP 685494 A.

The polymerization can be carried out in solution, suspension or gas phase processes continuously or discontinuously at a temperature of -10 to + 200 ° C., preferably + 20 to + 80 ° C. Olefins of the formula R are polymerized or copolymerized^a-CH = CH-R^b, In this formula, R^a and R^b identical or different and denote a hydrogen atom or an alkyl radical having 1 to 20 C atoms. R^a and R^b however, they can also form a ring with the carbon atoms connecting them. For example, such olefins as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, cyclopentene, norbornene or norbornadiene are polymerized or copolymerized. In particular, ethylene, propylene and 1-butene are polymerized or copolymerized.

As molecular weight regulator, if necessary, hydrogen is added. The total pressure of the polymerization is 0.5-150 bar. The polymerization is preferably in the pressure range from 1 to 40 bar.

It has proved advantageous to react the monomers in the presence of the metallocene catalyst system at a molar ratio of aluminum of the oligomeric aluminoxane compound to the transition 5

AT 403 376 metal of the metallocene compound of 10⁶ : 1 to 10¹ : 1, preferably 10⁴ : 1 to 10²: 1 to perform.

When the polymerization is carried out as a suspension or solution polymerization, an inert solvent is used. For example, aliphatic or cycloaliphatic hydrocarbons such as pentane, hexane or cyclohexane can be used. Also useful is toluene. Preference is given to polymerizing in the liquid monomer.

In the copolymerization of ethylene with propylene is polymerized according to the invention in liquid propylene or in hexane as a suspending agent. Preferably, in the polymerization in liquid propylene, the ethylene is added in the amount such that a partial pressure ratio Pc 2 / Pc 3 of greater than 0.5, in particular greater than 1.0, is established above the liquid phase (P c z = partial pressure of the ethylene in the gas phase Above the suspension; P_C3 = Partial pressure of propylene in the gas phase over the suspension). In the copolymerization in hexane as a suspending agent, an ethylene / propylene gas mixture having a propylene content of one to 50 mol%, preferably 5 to 30 mol% is added. The total pressure is kept constant during the polymerization by subsequent addition. The total pressure is 0.5 to 40 bar, preferably 1 to 20 bar.

The duration of the polymerization is generally about 10 minutes to 6 hours, preferably 30 minutes to 2 hours.

The catalysts used in the invention expand the range of polymerization-effective metallocenes for the preparation of polyolefin homo- and copolymers. In particular, the metallocenes according to the invention are distinguished by the fact that they produce polymers and copolymers with high, technically relevant molar mass and narrow molar mass distribution in the industrially interesting temperature range between 20 and 80 ° C.

The following examples are intended to explain the invention in more detail.

It means:

M_w = weight average molecular weight in g / mol,

M_n = number average molar mass in g / mol,

Μ * / Μ_η = Molecular weight distribution, determined by gel permeation chromatography,

MS mass spectroscopy

1H-NMR

13Q-NMR ¹ H nuclear magnetic resonance spectroscopy

Elucidation of the catalyst structure ¹3c Kernresonanzspektroskopi§,

EXAMPLE I:

Bis (trimethylsilyl) silanediyl dicyclopentadienyl zirconium

<img file="AT403376B_D0006.tif" />

CI

CI g (16.4 mmol) of bis (trimethylsilyl) -dicyclopentadienyl-silane (K. Hassler, K. Schenzel, J. Organomet. Chem., 484, C1-C4, {1994)) are dissolved in 20 ml of diethyl ether. The solution is cooled to -78 * C and treated with 21 ml of a 1.55 molar solution of n-butyllithium in n-pentane. The solution is warmed to room temperature, the bis (trimethylsilyl) siiandiyl-dicyclopentadienyldilithium is filtered off and dried in vacuo. The yield is 3.7 g (71.4% of theory).

1.1 g (3.5 mmol) of bis (trimethylsilyl) silanediyl-disyclopentadienyl-dilithium are initially charged in 50 ml of toluene. The suspension is cooled to -40.degree. C. and admixed with 1.3 g (3.5 mmol) of zirconium tetrachloride bis (tetrahydrofuran). After warming to room temperature, the solution is kept at room temperature for 24 hours

AT 403 376 und ratur and then filtered. The solvent is removed in vacuo, the residue is extracted with n-pentane and the extract is concentrated to dryness to leave bis (trimethylsilyl) silanediyl-dicyclopentadienylzirconium dichloride.

The yield is 600 mg (37.2% of theory).

MS (El, 70 eV, 200 'C): m / z = 464 (100%) molecular peak; 354 (95%) 1-methylsilyl-3-silyi-2-silanediyl-2-dicyclopentadienyl zirconium chloride radical cation; 318 (49%) 1-methylsilyl-3-silyl-2-silanediyl-2-dicyclopentadienylzirconium radical cation¹H-NMR (C₆P₆): 0.14 ppm (18H, d); 5.87 ppm (4H, t); 6.75 ppm (4H, t)¹³C-NMR (THF-d_8th) .0.19 ppm; 103.97 ppm; 118.30 ppm; 125.90 ppm; 128.35 ppm

EXAMPLE II:

Bis (trimethylsilyl) silanediyl-dinindenyl-zirconium dichloride (mixture of diastereomers)

<img file="AT403376B_D0007.tif" />

Cl

Cl g (20.4 mmol) 2,2-dichlorohexamethyltrisilane (G. Kolliger, Dissertation 1993, Graz University of Technology) are presented in 50 ml of n-pentane. The solution is cooled to -78 ° C and mixed with 5 g (40.8 mmol) Indenyllithium. After warming to room temperature, the solution is stirred for 24 hours, then filtered, cooled again to -78 ° C., and 21 ml of a 1.58 molar solution of n-butyllithium in n-pentane are added dropwise. After warming to room temperature, the reaction mixture is filtered and the residual bis (trimethylsilyl) silanediyl-diindenyl-dilithium dried in vacuo. The yield is 3.5 g (40.9% of theory). Th.).

A solution of 3.5 g (8.4 mmol) of bis (trimethylsilyl) silanediyl-diindenyl-dilithium in 50 ml of toluene is cooled to -30 ° C. To the suspension is added 3.1 g (8.3 mmol) of zirconium tetrachloride bis (tetrahydrofuran). After warming to room temperature, the reaction mixture is heated to 50 ° C. in a water bath for 5 hours and then filtered. The solvent is removed in vacuo, the residue taken up in n-pentane and the solution filtered. After removal of the solvent in vacuo, the bis (trimethylsilyl) silanediyl-diindenyl-zirconium dichloride remains. The yield is 1.2 g (25.5% d. Th.).

MS (El, 70 eV, 200 ° C): m / z = 564 (100%) Mol peak; 453 (29%) 1-trimethylsilyl-2-silanediyl-2-diindenylzirconium chloride radical cation;

389 (36%) 1-methylsilyl-2-silanediyl-2-diindenyl zirconium radical cation; 289 (58%)

1-Methylsilyl-2-silanediyl-2-diindenyl radical cation ¹H-NMR (THF-ds): -0.0917 ppm (18 H, t); 5.65 ppm (2H, d); 6.73 ppm (2H, d); 7.13ppm (8H, m)

AT 403 376 Β

EXAMPLE III:

Bis (trimethylsilyl) silanediyl-bis (2-methylindenyl) zirconium dichloride

<img file="AT403376B_D0008.tif" />

A solution of 3 g (20 mmol) of 2-methylindene (CF Koelsch, PR Johnsen, J. Am. Chem. Soc., 65, 567, (1943)) in 50 ml of diethyl ether is cooled to -78.degree. Added 6 ml of a 1.58 molar solution of n-butyllithium in n-pentane. The solution is warmed to room temperature, the resulting 2-methylindenyllithium is filtered off and dried in vacuo. The yield is 2.5 g (91.9% of theory).

To 2.2 g (9.2 mmol) of 2,2-dichlorohexamethyltrisilane in 50 ml of n-pentane at -78 'C, a solution of

2.5 g (18.4 mmol) of 2-methylindenyl-lithium in 50 ml of diethyl ether. After warming to room temperature, the reaction mixture is heated for 4 hours at 50 'C in a water bath, then warm filtered, cooled again to -78' C and treated with 11.6 ml of a 1.58 molar solution of n-butyllithium in n-pentane. After warming to room temperature, the solution is filtered and the residual bis (trimethylsilyl) silanediylbis (2-methylindenyl) -dilithium dried in vacuo. The yield is 2.6 g (63.4% d. Th.).

To 2.2 g (4.9 mmol) of bis (trimethylsilyl) silanediylbis (2-methylindenyl) dilithium in 50 ml of toluene are added at -30 'C 1.8 g (4.9 mmol) of zirconium tetrachloride bis ( tetrahydrofuran). After warming to room temperature, the reaction mixture is heated for 4 hours at 50 'C in a water bath, then filtered and the toluene removed in vacuo. The residue is washed with n-pentane. After decanting the n-pentane, the bis (trimethylsilyl) silanediylbis (2-methylindenyl) zirconium dichloride is dried in vacuo. The yield is 800 mg (27.6% d. Th.).

MS (El, 70 eV, 200 ° C): m / z = 596 (0.5%) Mol peak; 483 (4.7%) 1-trimethylsilyl-3-silyl-2-silanediyl-2-bis (2-methylindenyl) zirconium radical cation; 441 (10.6%) 1-methylsilyl-3-silyl-2-silanediyl-2-bis (2-methylindenyl) zirconium radical cation; 383 (62.4%) 1-trimethylsilyl-3-silyl-2-silanediyl-2-bis (2-methylindenyl) radical cation; 348 (26%) 1-dimethylsilyl-2-bis (2-methylindenyl) silyl radical cation; 129 (100%) bis (2-methylindenyl) radical cation; 115 (61.3%) 2-methylindenyl radical cation

Ή-NMR (THF-dg): -0.0621 ppm (18H, t); 2.26 ppm (6H, s); 5.878 ppm (2H, s); 6.4069 ppm (2H, d); 7.17.2 ppm (8H, m)

Polymerization:

example 1

After stirring at room temperature, a 2 l stirred reactor is filled with 6.6 g of 10% MAO and 300 g of liquid, purified propylene, and the mixture is stirred for 15 minutes.

mg of bis (trimethylsilyl) silanediyl-dicyclopentadienylzirconium dichloride are dissolved in 2.4 ml of toluene and mixed with 6.6 g of 10% MAO. Subsequently, the catalyst solution is pressed into the reactor with a further 200 g of propylene and the batch is heated to the polymerization temperature of 70 ° C., which is kept constant for a period of two hours. The reaction is stopped by flashing the propylene after one hour. There were 106.3 g of polypropylene with a molecular weight M_w = 25 000 g / mol and a distribution width M_w/ M_n = 2.9.

AT 403 376 Β

Example 2

In a 2 l stirred reactor, after inerting under nitrogen, 3.9 g of 10% MAO and 1 dm³metered n-hexane and stirred for 15 minutes. After degassing of the suspending agent and heating of the reactor to the reaction temperature of 70 'C, the polymerization is initiated by pressing the catalyst solution with an ethylene / propylene mixture containing 11.3 mol% of propylene.

The catalyst solution is prepared by dissolving 3 mg of bis (trimethylsilyl) silanediyldicyclopentadienylzirconium dichloride in 1.4 ml of toluene and mixing with 4.0 g of 10% MAO.

The pressure in the reactor is kept constant during the entire polymerization time to 2 bar by metering in the gas mixture. The stirrer speed is 700 revolutions per minute, the polymerization time is 2 hours.

There were 14.8 g of ethylene / propylene copolymer with one molecular weight M_w = 134 000 g / mol and a distribution width Μ? Μ_η = 6.3. The propylene content is 2.7 mol%.

Example 3

The experiment is carried out analogously to Example 1. There is no MAO presented in the reactor. The catalyst solution is prepared by dissolving 5 mg of bis (trimethylsilyl) silanediyl-diindenyl-zirconium dichloride in

3.6 ml of toluene and mixed with 9.2 g of 30% MAO.

There were 45.7 g of polypropylene with a molecular weight M_w = 42,000 g / mol and a distribution width Mw / M_n= 2.0.

Example 4

In a 2 l stirred reactor after inerting under nitrogen 1 dm³ Purified n-hexane dosed. After degassing of the suspending agent and heating of the reactor to the reaction temperature of 70 'C, the polymerization is carried out by pressing the catalyst solution with ethylene.

The catalyst solution is prepared by dissolving 2 mg of bis (trimethylsilyl) silanediyldiindenylzirconium dichloride in

1.7 ml of toluene and mixing with 3.7 g of 30% MAO.

The pressure in the reactor is kept constant during the entire polymerization time to 2 bar by metering in the monomer. The stirrer speed is 700 revolutions per minute, the polymerization time 1 hour.

There were 25.4 g of polyethylene with a molecular weight M_w = 445,000 g / mol and a distribution width M_w/ M_n= 5.8 received.

Example 5

The experiment is carried out analogously to Example 1. There is no MAO presented in the reactor. The catalyst solution is prepared by dissolving 6 mg of bis (trimethylsilyl) silanediylbis (2-methylindenyl) zirconium dichloride in 3.2 ml of toluene and mixing with 10.5 g of 30% MAO. The reaction time is 2 hours.

There were 48.3 g of polypropylene with a molecular weight M_w = 336 000 g / mol and a distribution width M_w/ M_n = 2.2.

Example 6

The experiment is carried out analogously to Example 1. There is no MAO presented in the reactor. The catalyst solution is prepared by dissolving 5 mg of bis (trimethylsilyl) silanediylbis (2-methylindenyl) zirconium dichloride in 26.2 g of 30% MAO. The reaction time is 2 hours.

There were 92 g of polypropylene with a molecular weight M_w = 248 000 g / mol and a distribution width Μν / Μ_η= 2.0.

Example 7

A 2 l Ruhr reactor is filled after inerting at room temperature with 500 g of liquid, purified propylene and then heated to 70 'C. 5 mg of bis (trimethylsilyl) silanediyl-bis (2-methylindenyl) -zirkoniumdichlorid be dissolved in 2.8 ml of toluene and mixed with 8.7 g of 30% MAO. The catalyst solution is forced into the reactor with ethylene. Over the reaction time of 2 hours becomes one

AT 403 376 Β

Maintained ethylene partial pressure of 1 bar. The reaction is stopped by flashing the monomers. There were 174.4 g of an ethylene / propylene copolymer with a molecular weight M_w = 101 000 g / mol and a distribution width Μ * / Μ_η = 2.7. The propylene content is 16.6 mol%.