Metallocenes and their use as catalyst component

The present invention relates to a new metallocene compound which is suitable as a catalyst component for olefin polymerization. The invention also relates to a process for the preparation of this metallocene compound. The invention also relates to a process for the preparation of polyolefins using the metallocene compound according to the invention.

Metallocene compounds of subgroup 4 are suitable in the presence of methylaluminoxane (MAO) for the polymerization of olefins. Examples of bridged and unbridged metallocene compounds are described in the literature which, in combination with aluminoxanes or other cocatalysts, have catalyst systems with, for. T. very high activity and stereospecificity represent (Chem. Of our time (1994) 28, 197; J. Organomet. Chem. (1994) 479, 1). Metallocene-containing catalysts are increasingly being used for the copolymerization and terpolymerization of linear and cyclic olefins and also diolefins (EP 399 348).

Mononuclear metallocene dichloride complexes are suitable in the presence of MAO for the polymerization of ethylene and propylene (EP 129 368).

Also known are dinuclear ansa-metallocene dichloride complexes in which the bridge atoms are part of a hydrocarbon ring system and which are suitable for the syndiospecific polymerization of 1-olefins in the presence of MAO (EP 528 041). Binuclear metallocenes are also known from EP 632 063.

Only those examples of unbridged binuclear metallocene dichloride complexes with metals of subgroup IV are known which contain a divalent hydrocarbon radical or a dimethylsilyl group as the connecting element (J. Chem. Soc., Chem. Comm. (1994) 727; Organometallics (1991) 10, 2191; Organometallics (1989) 8, 2107; Organometallics (1989) 8, 547; J. Organomet. Chem. (1989) 264, 105).

A disadvantage of using soluble (homogeneous) metallocene-methylaluminoxane catalyst systems in processes in which the polymer formed is a solid is the formation of heavy deposits on the reactor walls and stirrer. These deposits arise from agglomeration of the polymer particles if the metallocene, or aluminoxane, or both are present in solution in the suspension medium. Such deposits in the reactors must be removed regularly, since these quickly reach considerable strengths, have high strength and prevent heat exchange with the cooling medium.

Metallocenes can be supported to avoid reactor deposits. Methods for this are known (EP 578 838). However, the detachment of the supported catalyst from the particle surface ("leaching") cannot yet be completely prevented.

The object was to find a metallocene compound which avoids the disadvantages of the prior art and in particular produces polyolefins, such as polyethylene, with high activity and high molecular weight. Another object was to find a metallocene compound which, due to multiple fixation on the carrier surface, has a much more favorable "leaching" behavior.

The present invention thus relates to a polynuclear metallocene compound of the formula I<chemistry id="chem0001" num="0001"><img file="EP0723971A2_D0001.tif" /></chemistry> where M¹ is a tetravalent metal, L¹ independently of one another, identical or different, are a substituted cyclopentadienyl group, L² and L³ independently of one another are identical or different π ligands, B independently of one another are identical or different each are a divalent bridging unit, X independently of one another are identical or different and for a hydrogen atom, a halogen atom, a C.₁-C₁₀Fluorocarbon residue or a hydrocarbon-containing residue with 1-40 C atoms, and k is an integer from 0 to 10.

M are preferred¹ is titanium, zirconium, hafnium, vanadium, niobium, tantalum, scandium, yttrium or a rare earth metal, titanium or zirconium are particularly preferred. L¹ are the same or different, preferably the same, and a substituted cyclopentadienyl group. L² are the same or different, preferably the same, and preferably a cyclopentadienyl group, which is preferably substituted. L³ are the same or different, preferably the same, and preferably a cyclopentadienyl group, which is preferably substituted. The term cyclopentadienyl group means unsubstituted and substituted cyclopentadienyl groups, such as methylcyclopentadienyl, indenyl, 2-methylindenyl, 2-methyl-4-pnenylindenyl, 2-ethyl-4-naphthylindenyl, 2-methyl-4,6-diisopropylindenyl, 4,5- Benzoindenyl, 2-methyl-4,5-benzoindenyl, fluorenyl or 2,7-di-tert-butyl-fluorenyl.

The unsubstituted or substituted cyclopentadienyl groups can be monovalent (L²), divalent substituted cyclopentadienylidene groups (L¹) mean, or also tridentate unsubstituted or substituted cyclopentadienyl-ylidene groups (L.³) mean. X are preferably the same and stand for a hydrogen atom, a halogen atom, a C.₁-C₁₀-Fluorocarbon residue like CF.₃, or a hydrocarbon-containing radical with 1-40 C atoms such as C₁-C₂₀-Alkyl, C₆-C₃₀-Aryl, a residue OR¹ or NO¹₂, where R¹ are the same or different, and hydrogen, a C₁-C₃₀-hydrocarbon-containing residue such as C₁-C₂₀-Alkyl, C₆-C₃₀-Aryl or a C₁-C₂₀- Halogenated hydrocarbon residue mean.

B is a divalent C₁-C₄₀-hydrocarbon-containing bridged unit and preferably has the formula II         -HE²)_n-K_m-HE²)_n- (II) where E is the same or different and stands for a hetero atom (ie an atom not equal to carbon and hydrogen), preferably E stands for an element of the fourth main group of the periodic table of elements other than carbon, or for an element of the fifth or sixth main group of the periodic table Elements, particularly preferred for silicon and germanium.

R² stands for a hydrocarbon-containing radical with one to forty carbon atoms such as C₁-C₂₀-Alkyl or C₆-C₃₀-Aryl. The leftovers R² can also be cyclically linked to one another. n corresponds to the valence of E minus 2, for example, n is 2 if E is an element of the fourth main group, n is preferably one if E is an element of the fifth main group, and n is zero if E is an element of the sixth main group represents. K represents a bridging unit between the two heteroatoms E and is preferably a hydrocarbon-containing divalent radical with one to forty carbon atoms, preferably 2 carbon atoms. m is one or - if the two elements E are directly connected to each other - zero. k is an integer from 0 to 10, preferably 0, 1 or 2.

Examples of L¹ are: Methylcyclopentadienylidene, tert-butylcyclopentadienylidene, dimethylcyclopentadienylidene, 1H-inden-1-ylidene, 4-phenyl-1H-inden-1-ylidene, 4-naphthyl-1H-inden-1-ylidene, 2,4,7-trimethyl-1H- inden-1-ylidene, 2-methyl-1H-inden-1-ylidene, 2-methyl-4,6-diisopropyl-1H-inden-1-ylidene, 2-methyl-4-phenyl-1H-indene-1- ylidene, 2-methyl-4,5-benzo-1H-inden-1-ylidene, 4,5-benzo-1H-inden-1-ylidene, 9H-fluorene-9-ylidene, 2,7-dibromo-9H- fluoren-9-ylidene, 4,5-dimethyl-9H-fluoren-9-ylidene, 3-tert-butyl-9H-fluoren-9-ylidene, 7H-Benzo [c] fluoren-7-ylidene.

Examples of L² are: Cyclopentadienyl, methylcyclopentadienyl, dimethylcyclopentadienyl, tert-butylcyclopentadienyl, pentamethylcyclopentadienyl , pentaethylcyclopentadienyl, pentaphenylcyclopentadienyl, indenyl, 1,2,3-trimethylindenyl, 9H-fluorenyl, 2,7-diphenyl-9H-9-fluoro-9H-fluorenyl , 5-dimethyl-9H-fluorenyl and 3-tert-butyl-9H-fluorenyl.

Examples of L³ are: Cyclopentadien-1-yl-2,4-ylidene, 9H-fluoren-9-yl-2,7-ylidene, 1H-inden-1-yl-4,7-ylidene, 1H-inden-1-yl-3, 7-ylids.

Examples of polynuclear metallocene compounds of the formula I are: [1,1,2,2-tetramethyl-1,2-bis (1H-indenyl-1-ylidene) disilane] bis (cyclopentadienyltitanium dichloride) [1,4-disila-1,4-bis (1H-indenyl-1-ylidene) -1,1,4,4-tetramethylbutane] bis (cyclopentadienyltitanium dichloride) [1,5-disila-1,5-bis (1H-indenyl-1-ylidene) -1,1,5,5-tetramethylpentane] bis (cyclopentadienyltitanium dichloride) [1,6-disila-1,6-bis (1H-indenyl-1-ylidene) -1,1,6,6-tetramethylhexane] bis (cyclopentadienyltitanium dichloride) [1,8-disila-1,8-bis (1H-indenyl-1-ylidene) -1,1,8,8-tetramethyloctane] bis (cyclopentadienyltitanium dichloride) [1,10-disila-1,10-bis (1H-indenyl-1-ylidene) -1,1,10,10-tetramethyldecane] bis (cyclopentadienylzirconium dichloride) [1,12-disila-1,12-bis (1H-indenyl-1-ylidene) -1,1,12,12-tetramethyldodecane] bis (cyclopentadienylzirconium dichloride) [1,4-disila-1,4-bis (1H-indenyl-1-ylidene) -1,1,4,4-tetramethyl-2-butyne] bis (cyclopentadienylzirconium dichloride) 1,4-bis [dimethyl- (1H-indenyl-1-ylidene) silyl] benzene-bis (cyclopentadienylzirconium dichloride) 1,4-bis [2- [dimethyl- (1H-indenyl-1-ylidene) silyl] ethyl] bis (cyclopentadienylzirconium dichloride) [1,1,2,2-tetramethyl-1,2-bis (9H-fluorenyl-9-ylidene) disilane] bis (cyclopentadienylzirconium dichloride) [1,4-disila-1,4-bis (9H-fluorenyl-9-ylidene) -1,1,4,4-tetramethylbutane] bis (cyclopentadienylzirconium dichloride) [1,5-disila-1,5-bis (9H-fluorenyl-9-ylidene) -1,1,5,5-tetramethylpentane] bis (cyclopentadienylzirconium dichloride) [1,6-disila-1,6-bis (9H-fluorenyl-9-ylidene) -1,1,6,6-tetramethylhexane] bis (cyclopentadienylzirconium dichloride) [1,8-disila-1,8-bis (9H-fluorenyl-9-ylidene) -1,1,8,8-tetramethyloctane] bis (cyclopentadienylzirconium dichloride) [1,10-disila-1,10-bis (9H-fluorenyl-9-ylidene) -1,1,10,10-tetramethyldecane] bis (cyclopentadienyl hafnium dichloride) [1,12-disila-1,12-bis- (9H-fluorenyl-9-ylidene) -1,1,12,12-tetramethyldodecane] bis- (cyclopentadienyl hafnium dichloride) [1,4-disila-1,4-bis (9H-fluorenyl-9-ylidene) -1,1,4,4-tetramethyl-2-butyne] bis (cyclopentadienyl hafnium dichloride) 1,4-bis [dimethyl- (9H-fluorenyl-9-ylidene) silyl] benzene-bis (cyclopentadienyl hafnium dichloride) 1,4-bis [2- [dimethyl- (9H-fluorenyl-9-ylidene) silyl] ethyl] bis (cyclopentadienyl hafnium dichloride) [1,1,2,2-tetramethyl-1,2-bis (1H-indenyl-1-ylidene) disilane] bis (pentamethylcyclopentadienyltitanium dichloride) [1,4-disila-1,4-bis (1H-indenyl-1-ylidene) -1,1,4,4-tetramethylbutane] bis (pentamethylcyclopentadienyltitanium dichloride) [1,5-disila-1,5-bis (1H-indenyl-1-ylidene) -1,1,5,5-tetramethylpentane] bis (pentamethylcyclopentadienyltitanium dichloride) [1,6-disila-1,6-bis (1H-indenyl-1-ylidene) -1,1,6,6-tetramethylhexane] bis (pentamethylcyclopentadienylzirconium dichloride) [1,8-disila-1,8-bis (1H-indenyl-1-ylidene) -1,1,8,8-tetramethvloctane] bis (pentamethylcyclopentadienyl zirconium dichloride) [1,10-disila-1,10-bis (1H-indenyl-1-ylidene) -1,1,10,10-tetramethyldecane] bis (pentamethylcyclopentadienylzirconium dichloride) [1,12-disila-1,12-bis- (1H-indenyl-1-ylidene) -1,1,12,12-tetramethyldodecane] bis (pentamethylcyclopentadienylzirconium dichloride) [1,4-disila-1,4-bis (1H-indenyl-1-ylidene) -1,1,4,4-tetramethyl-2-butyne] bis (pentamethylcyclopentadienyl hafnium dichloride) 1,4-bis [dimethyl- (1H-indenyl-1-ylidene) silyl] benzene-bis (pentamethylcyclopentadienyl hafnium dichloride) 1,4-bis [2- [dimethyl- (1H-indenyl-1-ylidene) silyl] ethyl] bis (pentamethylcyclopentadienyl hafnium dichloride) [1,1,2,2-tetramethyl-1,2-bis (9H-fluorenyl-9-ylidene) disilane] bis (pentamethylcyclopentadienylzirconium dichloride) [1,4-disila-1,4-bis (9H-fluorenyl-9-ylidene) -1,1,4,4-tetramethylbutane] bis (pentamethylcyclopentadienyl zirconium dichloride) [1,5-disila-1,5-bis (9H-fluorenyl-9-ylidene) -1,1,5,5-tetramethylpentane] bis (pentamethylcyclopentadienyl hafnium dichloride) [1,6-disila-1,6-bis (9H-fluorenyl-9-ylidene) -1,1,6,6-tetramethylhexane] bis (pentamethylcyclopentadienyl hafnium dichloride) [1,8-disila-1,8-bis (9H-fluorenyl-9-ylidene) -1,1,8,8-tetramethyloctane] bis (pentamethylcyclopentadienyl hafnium dichloride) [1,10-disila-1,10-bis- (9H-fluorenyl-9-ylidene) -1,1,10,10-tetramethyldecane] bispentamethylcyclopentadienyltitanium dichloride) [1,12-disila-1,12-bis- (9H-fluorenyl-9-ylidene) -1,1,12,12-tetramethyldodecane] bis (pentamethylcyclopentadienyltitanium dichloride) [1,4-disila-1,4-bis (9H-fluorenyl-9-ylidene) -1,1,4,4-tetramethyl-2-butyne] bis (pentamethylcyclopentadienyltitanium dichloride) 1,4-bis [dimethyl- (9H-fluorenyl-9-ylidene) silyl] benzene-bis (pentamethylcyclopentadienylzirconium dichloride) 1,4-bis [2- [dimethyl- (9H-fluorenyl-9-ylidene) silyl] ethyl] bis (pentamethylcyclopentadienylzirconium dichloride) [1,4-disila-1,4-bis (3-tert-butyl-2,4-cyclopentadien-1-ylidene) -1,1,4,4-tetramethylbutane] bis (indenyltitanium dimethyl) [1,5-disila-1,5-bis (1H-indenyl-1-ylidene) -1,1,5,5-tetramethylpentane] bis (indenyltitanium dimethyl) [1,6-disila-1,6-bis (4,7-dimethyl-1-indenyl-1-ylidene) -1,1,6,6-tetramethylhexane] bis (indenyl zirconium dimethyl) [1,8-disila-1,8-bis (2-ethyl-4-phenyl-1H-indenyl-1-ylidene) -1,1,8,8-tetramethyloctane] bis (indenyl zirconium dichloride) [1,10-disila-1,10-bis (2,7-dimethyl-9H-fluoren-9-ylidene) -1,1,10,10-tetramethyldecane] bis (cyclopentadienylzirconium dichloride) [1,12-disila-1,12-bis- (2,4-dimethyl-2,4-cyclopentadien-1-ylidene) -1,1,12,12-tetramethyldodecane] bis (cyclopentadienylzirconium dichloride) [1,4-disila-1,4-bis (4,5-dimethyl-9H-fluoren-9-ylidene) -1,1,4,4-tetramethyl-2-butyne] bis (pentamethylcyclopentadienylzirconium dimethyl) 1,4-bis [dimethyl- (2,7-di-tert-butyl-9H-fluorenyl-9-ylidene) silyl] benzene-bis (cyclopentadienylzirconium dichloride) 1,4-bis [2- [dimethyl- (4-naphthyl-1H-indenyl-1-ylidene) silyl] ethyl] bis (cyclopentadienylhafniumdimethyl] [1,8-disila-1,8-bis (2-methyl-1H-indenyl-1-ylidene) -1,1,8,8-tetraethyloctane)] bis [(2-methyl-4-phenyl-1H- indenyl) zirconium dichloride] [1,6-disila-1,6-bis (4,5-benzo-1H-indenyl-1-ylidene) -1,1,6,6-tetraethoxyoctane)] bis [(2-methyl-4-naphthyl- 1H-indenyl) zirconium dichloride] [1,8-disila-1,8-bis (2,3-dimethyl-1H-indenyl-1-ylidene) -1,1,8,8-tetraethyl-3,4-dibutyl-3-octene]] to [(2-methyl-4,7-diisopropyl-1H-indenyl) zirconium dichloride] [1,7-distanna-4-oxa-1,7-bis (tetramethylcyclopenta-2,4-dienyl-1-ylidene) -1,1-dimethyl-7,7-dibutylheptane] bis [(2,7-dimethyl -9H-fluorenyl) zirconium dichloride] [1,8-disila-1,8-bis (3-methylcyclopenta-2,4-dien-1-ylidene) -1,1,8,8-tetramethyloctane)] bis [(4-phenyl-1H-indenyl) zirconium dichloride] The procedures for making the ligand systems of the Metallocene compounds according to the invention are known in principle (Angew. Chem. (1989) 101, 1536).

The present invention further relates to a process for the preparation of a metallocene compound of the formula I. Here, a ligand precursor of the formula III is replaced by a suitable reagent of the formula IV M.²R³ (k + 2) times deprotonated and reacted with a compound of formula V to a compound of formula VI.<chemistry id="chem0002" num="0002"><img file="EP0723971A2_D0002.tif" /></chemistry> L¹In Formula III, B and k have the same meaning as in Formula I. In Formula IV M stands for² for an alkali metal such as lithium, sodium or potassium and R³ represents a hydrocarbon-containing radical with 1 to 16 carbon atoms or hydrogen. Process for the preparation of compounds of formula L.²M¹Y₃ (V) are known (Chem. Ber. (1994) 127, 3; Macromolecules (1993) 26, 5822; J. Organomet. Chem. (1988) 340, 37; Inorg. Chem. (1982) 21, 1277). In formula V, Y represents a halogen atom, in particular chlorine, L.² and M¹ have the same meaning as in formula I. In formula VII, M is² an alkali metal such as lithium, sodium or potassium and X has the same meaning as in formula I.

The reaction is preferably carried out in an aprotic solvent, for example toluene, hexane, diethyl ether or tetrahydrofuran. The temperature can be between -78 and 140 ° C, preferably 0 to 110 ° C. The compound VI can be used in excess, preferably 2 to 3 equivalents of the compound VI, based on the ligand precursor III, are used.

The present invention also relates to a process for the preparation of an olefin polymer by polymerizing at least one olefin in the presence of a catalyst which comprises at least one metallocene compound and at least one cocatalyst, characterized in that the metallocene is a compound of the formula I.

Olefins of the formula R are preferred^a-CH = CH-R^b homo- or copolymerized, wherein R^a and R^b are identical or different and represent a hydrogen atom or a hydrocarbon radical having 1 to 20 carbon atoms, in particular 1 to 10 carbon atoms, or R^a and R^b form one or more rings together with the atoms connecting them. Examples of such olefins are 1-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene or 1-octene, styrene, dienes such as 1,3-butadiene or 1,4 -Hexadiene and cyclic olefins such as norbornene, tetracyclododecene, norbornadiene or vinyl norbornene. Ethylene is preferably homopolymerized in the process according to the invention, or ethylene is copolymerized with one or more 1-olefins having 3 to 20 carbon atoms, such as propylene, and / or one or more dienes having 4 to 20 carbon atoms, such as 1,4-butadiene . Examples of such copolymers are ethylene / propylene copolymers and ethylene / propylene / 1,4-hexadiene copolymers.

The polymerization is preferably carried out at a temperature of from -60 to 300.degree. C., particularly preferably from 50 to 200.degree. The pressure is preferably 0.5 to 64 bar.

The polymerization can be carried out in solution, in bulk, in suspension or in the gas phase, continuously or batchwise, in one or more stages. A preferred embodiment is gas phase polymerization.

The catalyst used in the process according to the invention preferably contains a metallocene compound of the formula I. Mixtures of two or more metallocene compounds of the formula I, or mixtures of metallocene compounds of the formula I with other bridged or unbridged metallocenes can also be used, for example for the preparation of polyolefins having a broader range or multimodal molecular weight distribution.

In principle, any compound is suitable as a cocatalyst in the process according to the invention which, because of its Lewis acidity, can convert the neutral metallocene into a cation and stabilize it ("unstable coordination"). In addition, the cocatalyst or the anion formed from it should not undergo any further reactions with the metallocene cation formed (EP 427 697). An aluminum compound and / or a boron compound is preferably used as the cocatalyst.

The boron compound preferably has the formula R.³_xNH_4-xBR⁴₄, R³_xPH_4-xBR⁴₄, R³₃CBR⁴₄ or BR⁴₃, wherein x is a number from 1 to 4, preferably 3, the radicals R³ are the same or different, are preferably the same, and C₁-C₁₀-Alkyl- or C₆-C₁₈- Aryl residues, or two residues R³ form a ring together with the atoms connecting them, and the radicals R⁴ are the same or different, are preferably the same, and C₆-C₁₈Are aryl, which can be substituted by alkyl, haloalkyl or fluorine. In particular, R³ for ethyl, propyl, butyl or phenyl and R⁴ for phenyl, pentafluorophenyl, 3,5-bistrifluoromethylphenyl, mesityl, xylyl or tolyl (EP 277 003, EP 277 004 and EP 426 638).

An aluminum compound such as aluminoxane and / or an aluminum alkyl is preferably used as the cocatalyst.

An aluminoxane, in particular of the formula VIIIa for the linear type and / or of the formula VIIIb for the cyclic type, is particularly preferably used as cocatalyst,<chemistry id="chem0003" num="0003"><img file="EP0723971A2_D0003.tif" /></chemistry> where in the formulas VIIIa and VIIIb the radicals R⁵ are the same or different and are hydrogen or a C.₁-C₁₈-Alkyl group or a C₆-C₁₈-Aryl group or benzyl, and p is an integer from 2 to 50, preferably 10 to 35.

The radicals R are preferred⁵ the same and mean hydrogen, methyl, isobutyl, phenyl or benzyl, particularly preferably methyl.

The processes for the preparation of the aluminoxanes are known (DE 4 004 477).

The exact spatial structure of the aluminoxanes is not known (J. Am. Chem. Soc, 115 (1993) 4971). For example, it is conceivable that chains and rings combine to form larger two- or three-dimensional structures.

Regardless of the type of production, all aluminoxane solutions have in common a changing content of unreacted aluminum starting compound, which is present in free form or as an adduct.

It is possible to preactivate the metallocene compound according to the invention before use in the polymerization with a cocatalyst, in particular an aluminoxane. This significantly increases the polymerization activity. The preactivation of the metallocene compound is preferably carried out in solution. The metallocene compound is preferably dissolved in a solution of the aluminoxane in an inert hydrocarbon. An aliphatic or aromatic hydrocarbon is suitable as the inert hydrocarbon. Toluene is preferably used.

The concentration of the aluminoxane in the solution is in the range from about 1% by weight to the saturation limit, preferably from 5 to 30% by weight, based in each case on the total amount of solution. The metallocene can be used in the same concentration, but it is preferably used in an amount of 10^-4 up to 1 mol per mol of aluminum. The preactivation time is 5 minutes to 60 hours, preferably 5 to 60 minutes. The process is carried out at a temperature of from -78 to 100.degree. C., preferably from 0 to 70.degree.

The metallocene compound is preferably in a concentration, based on the transition metal, of 10^-3 until 10^-8, preferably 10th^-4 until 10^-7 mol of transition metal per dm³ Solvent or per dm³ Reactor volume applied. The aluminoxane is preferred in a concentration of 10^-6 until 10^-1 mol, preferably 10^-5 until 10^-2 mol per dm³ Solvent or per dm³ Reactor volume used. The other cocatalysts mentioned are used in approximately equimolar amounts to the metallocene compound. In principle, however, higher concentrations are also possible.

To remove catalyst poisons present in the olefin, cleaning with an aluminum compound, preferably an aluminum alkyl, such as trimethyl aluminum or triethyl aluminum, is advantageous. This cleaning can take place both in the polymerization system itself, or the olefin is brought into contact with the aluminum compound before being added to the polymerization system and then separated off again.

Hydrogen can be added as a molecular weight regulator and / or to increase the activity in the process according to the invention. As a result, low molecular weight polyolefins such as waxes can be obtained.

In the process according to the invention, the metallocene compound is preferably reacted with the cocatalyst outside the polymerization reactor in a separate step using a suitable solvent. Carrying can be carried out.

In the process according to the invention, prepolymerization can be carried out using the metallocene compound. The prepolymerization preferably uses the (or one of the) olefin (s) used in the polymerization.

The catalyst used in the process according to the invention can be supported. The support allows, for example, the grain morphology of the polyolefin produced to be controlled. The metallocene compound can be reacted first with the support and then with the cocatalyst. The cocatalyst can also first be supported and then reacted with the metallocene compound. It is also possible to support the reaction product of the metallocene compound and cocatalyst. Suitable carrier materials are, for example, silica gels, aluminum oxides, solid aluminoxane or other inorganic carrier materials such as magnesium chloride. A suitable carrier material is also a polyolefin powder in finely divided form. The supported cocatalyst can be prepared, for example, as described in EP 567 952.

If the polymerization is carried out as a suspension or solution polymerization, an inert solvent customary for the Ziegler low-pressure process is used. For example, one works in an aliphatic or cycloaliphatic hydrocarbon; such as propane, butane, hexane, heptane, isooctane, cyclohexane, methylcyclohexane. A gasoline or hydrogenated diesel oil fraction can also be used. Toluene can also be used. Polymerization is preferably carried out in the liquid monomer.

If inert solvents are used, the monomers are added in gaseous or liquid form.

The duration of the polymerization is arbitrary, since the catalyst system to be used in the process according to the invention shows only a slight time-dependent drop in the polymerization activity.

The polymers produced by the process according to the invention are particularly suitable for the production of moldings such as foils, plates or large hollow bodies (for example pipes).

The metallocene compound according to the invention can advantageously be used for the production of copolymers, in particular ethylene-containing copolymers, with low density such as LLDPE. In particular, the metallocene compound according to the invention is suitable for the production of copolymers, in particular ethylene-containing copolymers, with low density using low comonomer concentrations. This is particularly advantageous if, for technical or economic reasons, a low comonomer concentration has to be maintained, for example if comonomers in gas phase polymerization condense when the saturation concentration is exceeded and cause technical difficulties. The use of the metallocene compound according to the invention is particularly advantageous in the copolymerization with higher-boiling comonomers in gas phase polymerization.

Examples:

The production and handling of organometallic compounds was carried out with the exclusion of air and moisture under an argon protective gas (Schlenk technique). All required solvents were absolute before use by boiling for several hours over suitable desiccants and then distilling under argon.

The connections were made with ¹Characterized by H-NMR spectroscopy.

example 1

[1,4-disila-1,4-bis- (9H-fluorenyl-9-ylidene) -1,1,4,4-tetramethylbutane] bis (cyclopentadienylzirconium dichloride) (1):

5.0 g (10.5 mmol) of 1,1,4,4-tetramethyl-1,4-difluorenyl-1,4-disilabutane are suspended in 100 ml of diethyl ether and mixed with 13.0 ml (21 mmol) of n-butyllithium (1.6 molar in hexane) implemented. The yellow suspension is stirred for 8 hours at room temperature and then cooled to 0 ° C. Then 5.5 g (21 mmol) of cyclopentadienylzirconium trichloride are added, the mixture is stirred at 0 ° C. for 30 minutes and at room temperature for one hour. The orange suspension is freed from the solvent in vacuo, the residue is extracted with methylene chloride and filtered through a glass frit. At -30 ° C, a total of 4.25 g (4.6 mmol, 44%) of the binuclear complex 1 crystallize out in the form of yellow crystals.¹H-NMR (300 MHz, CDCl₃, 25 ° C, δ (ppm) rel. CH₂Cl₂): 8.14-8.08 (m, 4H, c₁₃H₈), 7.77-7.68 (m, 4H, c₁₃H₈), 7.47-7.40 (m, 8H, c₁₃H₈), 5.73 (s, 10H, C₅H₅), 0.77 (s, 4H, CH₂CH₂), 0.59 (s, 12 H, Si (CH₃)₂).

Example 2

[1,4-disila-1,4-bis (1H-indenyl-1-ylidene) -1,1,4,4-tetramethylbutane] bis (cyclopentadienylzirconium dichloride) (2):

4.0 g (10.7 mmol) of 1,1,4,4-tetramethyl-1,4-diindenyl-1,4-disilabutane are dissolved in 80 ml of diethyl ether and mixed with 13.5 ml (21.4 mmol) of n-butyllithium (1.6 molar in hexane) implemented. The yellow solution is stirred for 4 hours at room temperature and then mixed with 5.65 g (21.6 mmol) of cyclopentadienylzirconium trichloride. A red, initially oily suspension is formed within minutes, which changes into a yellow suspension within 3 hours. The solvent is separated off on a glass frit, the residue is washed with 50 ml of diethyl ether and dried in vacuo. The residue is extracted with methylene chloride, filtered through a glass frit and crystallized at -30 ° C. The yield of finely crystalline 2 is 2.8 g (3.4 mmol, 32%).¹H-NMR (300 MHz, CDCl₃, 25 ° C, δ (ppm) rel. CH₂Cl₂): 7.76-7.66 (m, 4H, c₉H₆), 7.38-7.26 (m, 4H, c₉H₆), 6.98 (d, 2H, C₉H₆), 6.84 (d, 2H, C₉H₆), 6.05 (s, 10 H, C₅H₅), 0.72 (m, 4H, CH₂CH₂), 0.46 (s, 6H, SiCH₃), 0.40 (s, 6H, SiCH₃).

Example 3

[1,4-disila-1,4-bis (1H-indenyl-1-ylidene) -1,1,4,4-tetramethylbutane] bis (pentamethylcyclopentadienylzirconium dichloride) (3):

6.0 g (16.0 mmol) of 1,1,4,4-tetramethyl-1,4-diindenyl-1,4-disilabutane are dissolved in 250 ml of diethyl ether and mixed with 20.0 ml (31.0 mmol) of n-butyllithium (1.6 molar in hexane) implemented. The light yellow solution is stirred at room temperature for 8 h and then 10.3 g (31.0 mmol) of pentamethylcyclopentadienylzirconium trichloride are added. A yellow suspension forms within minutes and is stirred for a further three hours at room temperature. The lithium chloride is separated off via a glass frit and the residue is washed with 200 ml of diethyl ether. The combined ethereal solutions are concentrated to 150 ml and brought to crystallization at -20 ° C. The yield of 3 is 4.5 g (4.7 mmol, 29%).¹H-NMR (300 MHz, CDCl₃, 25 ° C, δ (ppm) rel. CHCl₃): 7.92 (m, 2H, c₉H₆), 7.65 (m, 2H, c₉H₆), 7.44 (m, 4H, c₉H₆), 6.46 (s, 4H, C₉H₆), 2.18 (s, 30 H, C₅Me₅), 0.82 (m, 4H, CH₂CH₂), 0.58 (s, 6H, SiCH₃), 0.52 (s, 6H, SiCH₃).

Polymerization example 1

0.20 mg of the metallocene from Example 1 were dissolved in 1.25 ml of MAO solution in toluene and stirred for 15 minutes. In parallel, an inertized 1.5 dm³ Stirring reactor filled with 750 ml of diesel oil (boiling point 100 to 120 ° C) and 3.75 ml of MAO solution in toluene and heated to 70 ° C. The catalyst solution is metered in and polymerized at 750 rpm with 7 bar ethylene for 1 hour. The reactor is then depressurized, the polymer is filtered off from the suspension, washed with acetone and dried in a vacuum drying cabinet for 12 hours. The result is 14 g of polyethylene, with a VN of 711 ml / g.

Polymerization example 2

Polymerization was carried out with 0.6 mg of the metallocene from Example 2 as in Polymerization Example 1. The result is 29.4 g of polyethylene, with a VN of 874 ml / g. GPC analysis finds Mw = 551000 g / mol and Mw / Mn = 5.2.

Polymerization example 3

Polymerization was carried out analogously to polymerization example 2 with 0.5 mg of the metallocene from Example 2, initially introducing 0.5 bar of hydrogen and then supplementing it with ethylene to 7 bar. The result is 42.3 g of polyethylene, with a VN of 113 ml / g.

Polymerization example 4

Polymerization was carried out with 2.0 mg of the metallocene from Example 3 as in Polymerization Example 1. The result is 25 g of polyethylene, with a VZ of 224 ml / g. GPC analysis finds Mw = 121400 g / mol and Mw / Mn = 7.1.