Metallocene catalyst for preparing olefin polymer

[0002] 1. Field of the Invention

[0003] The present invention relates to a novel metallocene complex, and more particularly to a novel metallocene complex in which the cyclopentadienyl group is substituted with an alkanediyl silyl group. Such a metallocene complex is suitable for preparing olefin polymers.

[0004] 2. Background of the Invention

[0005] Olefin-based polymers have been used in a wide range of applications. One group of commonly used olefin-based polymers is polyolefins, that is, homopolymers or copolymers of olefins. These polyolefin plastics are typically used in such applications such as blow and injection molding, extrusion coating, film and sheeting, pipe, wire and cable.

[0006] An example of a polyolefin is ethylene-propylene elastomer (ethylene-propylene rubbers, EPR). It has many end-use applications due to its resistance to weather, good heat aging properties and its ability to be compounded with large quantities of fillers and plasticizers. Typical automotive uses are radiator and heater hoses, vacuum tubing, weather stripping and sponge doorseals. Typical industrial uses are sponge parts, gaskets and seals.

[0007] Another group of commonly used olefin-based polymers is terpolymers of ethylene, propylene, and a non-conjugated diene, which are generally referred to as EPDM elastomers. EPDM elastomers have outstanding weather and acid resistance, and high and low temperature performance properties. Such properties particularly suit EPDM elastomers for use in hoses, gaskets, belts, bumpers, as blending components for plastics and for tire side walls in the automotive industry; and for roofing applications. Additionally, because of their electrical insulation properties, EPDMs are particularly well suited for use as wire and cable insulation.

[0008] To date, many catalyst systems have been developed for olefin polymerization, these mainly being classified into two types: Ziegler-Natta catalyst systems and metallocene catalyst systems.

[0009] Ziegler et. al. in U.S. Pat. No. 3,113,115 uses TiCl₄/AlEtCl₂catalyst system to produce EPR. Natta et. al. in U.S. Pat. No. 3,300,459 uses VOCl₃/Al(C₆H₁₃)₃catalyst system to produce EPR.

[0010] Floyd and Hoel in U.S. Pat. Nos. 5,001,205; 4,871,705; and 5,229,478 use metallocenes such as biscyclopentadienyl compounds to produce olefin polymers. The Dow Chemical Company in WO 9,308,221 and European Patent No. 0,416,815 A2 developed monocyclopentadienyl compounds, in which the cyclopentadienyl group is substituted with a constrain-inducing moiety, such as dimethylsilyl. However, synthesis of this particular constrained geometry catalyst (CGC) has a low yield, about 30%.

[0011] A need still exists for discovering a metallocene complex with a better yield that can be used as a catalyst in olefin polymerization.

[0012] The object of the present invention is to provide a metallocene complex with a high yield of up to 80%.

[0013] Another object of the present invention is to provide a metallocene complex capable of producing a high molecular weight olefin polymer with high catalytic activity.

[0014] To achieve the above-mentioned object, a metallocene complex is developed in the present invention which is represented by the following formula (I)

[0015] wherein:

[0016] M is a Group IVB transition metal with an oxidation state of +4;

[0017] Z is a Group IVA element;

[0018] R¹is a divalent unsubstituted or substituted C_3-6alkanediyl group which forms a ring system with Z, wherein the substituent is selected from the group consisting of C_1-20alkyl, C_1-20alkenyl, C_6-20aryl, C_7-20alkylaryl, and C_1-20arylalkyl;

[0019] R²can be the same or different and is H, a C_1-20linear, branched or cyclic hydrocarbyl. group, or a silyl group, or two adjacent R²groups combine together to form with the carbon atoms to which they are attached a C_4-6fused ring system;

[0020] X is independently an anionic ligand with a −1 valence;

[0021] Y is a Group VA element or a Group VIA element;

[0022] q is 1 when Y is a Group VA element, and q is 0 when Y is a Group VIA element; and

[0023] R³is H, or a C_1-20linear, branched or cyclic hydrocarbyl group.

[0024] The present invention provides another novel metallocene complex which is represented by the following formula (II):

[0025] wherein:

[0026] M is selected from the group consisting of a Group IIIB transition metal, a lanthanide, and Ti with an oxidation state of +3;

[0027] Z is a Group IVA element;

[0028] R¹is a divalent unsubstituted or substituted C_3-6alkanediyl group which forms a ring system with Z, wherein the substituent is selected from the group consisting of C_1-20alkyl, C_1-20alkenyl, C_6-20aryl, C_7-20alkylaryl, and C_7-20arylalkyl;

[0029] R²can be the same or different and is H, a C_1-20linear, branched or cyclic hydrocarbyl group, or a silyl group, or two adjacent R²groups combine together to form with the carbon atoms to which they are attached a C_4-6fused ring system;

[0030] X is independently an anionic: ligand with a −1 valence;

[0031] Y is a Group VA element or a Group VIA element;

[0032] q is 2 when Y is a Group VA element, and q is 1 when Y is a Group VIA element; and

[0033] R³is H, or a C_1-20linear, branched or cyclic hydrocarbyl group.

[0034] FIG. 1 shows the ¹H NMR spectrum of a metallocene complex of the present invention.

[0035] FIG. 2 is a computer generated model of a metallocene product based on single crystal X-ray data.

[0036] The present invention provides two similar metallocene complexes, i.e., complexes of the formulae (I) and (II).

[0037] In formula (I), M is a Group IVB transition metal with an oxidation state of +4, such as titanium(+4), zirconium(+4), and hafnium(+4). Z is a Group IVA element, such as carbon, silicon, and germanium. R¹can be a divalent unsubstituted or substituted C_3-6alkanediyl group. The substituent can be C_1-20alkyl, C_1-20alkenyl, C_6-20aryl, C_7-20alkylaryl, or C_7-20arylalkyl. Preferably, R¹is a divalent unsubstituted C_3-6alkanediyl group which forms a ring system with Z. Representative examples of R¹include trimethylene, tetramethylene, pentamethylene, and hexamethylene.

[0038] R²can be the same or different and is independently H, a C_1-20linear, branched or cyclic hydrocarbyl group, or a silyl group. The silyl group can be an alkyl silyl, a dialkyl silyl, a trialkyl silyl, a cycloalkyl silyl. Representative examples include methyl silyl, dimethyl silyl, trimethyl silyl, and methyl ethyl silyl. Alternatively, two adjacent R²groups can combine together to form with the carbon atoms to which they are attached a C_4-6fused ring system.

[0039] Specifically, the C_1-20linear, branched or cyclic hydrocarbyl group can be C_1-20alkyl, C_1-20alkenyl, C_6-20aryl, C_7-20alkylaryl, or C_7-20arylalkyl. Representative examples of R²include H, methyl, ethyl, propyl, butyl, isobutyl, amyl, isoamyl, hexyl, 2-ethylhexyl, heptyl, octyl, vinyl, allyl, isopropenyl, phenyl, and tolyl.

[0040] Specifically, when two adjacent R²groups are combined together to form with the carbon atoms to which they are attached a C_4-6fused ring system, R²can form with the cyclopentadienyl moiety on which they are attached to give a saturated or unsaturated polycyclic cyclopentadienyl ligand such as an indenyl, tetrahydroindenyl, fluorenyl or octahydrofluorenyl group.

[0041] Representative examples of C₅(R²)₄include η⁵-cyclopentadienyl, η⁵-methylcyclopentadienyl, η⁵-ethylcyclopentadienyl, η⁵-tetramethylcyclopentadienyl, η⁵-pentamethylcyclopentadienyl, η⁵-n-butylcyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, and octahydrofluorenyl.

[0042] R³can be H, C_1-20alkyl, C_1-20alkenyl, C_6-20aryl, C_7-20alkylaryl, and C_1-20arylalkyl.

[0043] Suitable examples of Group VA elements for Y are nitrogen, phosphorus, and arsenic, and suitable examples of Group VIA elements for Y are oxygen, sulfur, and selenium.

[0044] q is 1 when Y is a Group VA element, and q is 0 when Y is a Group VIA element. Representative examples of Y(R³)_qinclude —NH—, —N(CH₃)—, —N(t-butyl)—, —PH—, —P(CH₃)—, —P(t-butyl)—, —O—, and —S—.

[0045] Another metallocene complex developed by the present invention is represented by formula (II), which has a structure similar to formula (I), except that the bonding between M and Y is different and M in formula (II) is a transition metal with an oxidation state of +3.

[0046] In formula (II), M can be a Group IIIB transition metal such as scandium and yttrium, a lanthanide, or titanium. The bonding between M and Y is not a covalent bonding, rather, a dative bonding, in which Y donates two electrons to M. The definitions of the rest of the symbols including Z, R¹, R², X, Y and R³in formula (II) are the same as in formula (I).

[0047] For formula (II), representative examples of Y(R³)_qinclude OH, OCH₃, SH, SCH₃, NH₂, N(CH₃)₂, PH₂, and P(CH₃)₂.

[0048] In the present invention, the metallocene complex can be combined with an activating coatalyst to form a catalyst composition which can be used for preparing olefin polymers having a high molecular weight.

[0049] The activating cocatalyst can be a methyl aluminoxane (MAO), a trialkyl aluminum, a dialkyl aluminum halide, a salt of an inert and non-coordinating anion, or a mixture thereof.

[0050] The trialkyl aluminum can be selected from the group consisting of trimethyl aluminum, triethyl aluminum, tripropyl aluminum, trisopropyl aluminum, tributyl aluminum, and triisobutyl aluminum (TIBA).

[0051] The inert and non-coordinating anion can be a borate Borates that are suitable for use in the present invention include N,N-dimethyl anilinium tetrakis(pentafluorophenyl)borate, triphenyl carbenium tetrakis(pentafluorophenyl)borate, trimethyl ammonium tetrakis(pentafluorophenyl)borate, ferrocenium tetrakis(pentafluorophenyl)borate, dimethyl ferrocenium tetrakis(pentafluorophenyl)borate, and silver tetrakis(pentafluorophenyl)borate.

[0052] Preferably, the activating cocatalyst is methyl aluminoxane, or a mixture of a trialkyl aluminum and a borate.

[0053] By using the catalyst composition of the present invention (containing the metallocene complex and the activating cocatalyst), an olefin polymer can be synthesized. In the presence of a catalytically effective amount of the metallocene complex catalyst of the present invention under polymerizing conditions, an olefin can be polymerized (i.e., homopolymerized), or an olefin together with another monomer can be polymerized (i.e., copolymerized).

[0054] Suitable olefin monomers can be ethylene or α-olefins. The polymers to be prepared by the process of the present invention can be homopolymers of ethylene, homopolymers of α-olefins, copolymers of α-olefins, and copolymers of ethylene and α-olefins. Examples of the α-olefins include those olefins having 3 to 12 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene.

[0055] More particularly, the catalyst system disclosed in the present invention can be advantageously used to prepare ethylene homopolymers, including high density polyethylene (HDPE) having broad, bimodal, or multimodal, molecular weight distributions for applications such as high molecular weight films and blow molding.

[0056] Furthermore, the catalyst system disclosed in the present invention can be advantageously used to prepare a copolymer of ethylene and propylene (EPR). Also, a copolymer of ethylene, a C_3-12α-olefin, and a non-conjugated diene can be prepared. More particularly, when the C_3-12α-olefin used is propylene, a copolymer of ethylene, propylene, and a non-conjugated diene can be prepared, which is referred to as EPDM. Suitable non-conjugated dienes can be 5-ethylidene-2-norbornene (ENB), 5-methylene-2-norbornene, 5-vinylidene-2-norbornene, 1,4-hexadiene (HD), or dicyclopentadiene (DCPD).

[0057] The polymerization can also be carried out in the presence of hydrogen together with the catalyst composition. Thus, the molecular weight of the resulting polymer can be controlled to any desired range.

[0058] The catalyst system disclosed in the present invention can be used in slurry reaction conditions, gas phase, and solution polymerization reaction conditions. Polymerization is typically carried out at a temperature of 0° to 250° C., and an atmospheric pressure up to 3,000 psi.

[0059] The following examples are intended to illustrate the process and the advantages of the present invention more fully without limiting its scope, since numerous modifications and variations will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percents, ratios and the like are by weight.

[0060] Preparation of (C₅Me₄H)Li

[0061] Tetramethylcyclopentadiene (8.57 g, 70.2 mmole) was placed in a 300 ml round bottom flask with 150 ml of diethyl ether. This clear solution was cooled to −78° C. before 1 equivalent of n-butyl lithium (n-BuLi) was injected into it with a syringe. The mixture turned yellow immediately and the color of it faded away gradually. This mixture was allowed to warm to room temperature (about 20-30° C.) and stirred overnight. The mixture was filtered to collect 4.83 g of a lithium salt.

[0062] Preparation of (C₅Me₄H) (C₃H₆)SiCl

[0063] The lithium salt (4.8 g, 0.0375 mole) obtained from Example 1 was suspended in a toluene/THF mixed solvent (2:1 by volume). This slurry was cooled to −78° C. before an excess amount of trimethylenesilyl dichloride was injected into it. The mixture was allowed to warm to room temperature and stirred overnight. Then, the mixture was stripped under vacuum to remove solvent and excess silyl dichloride. Some pentane was added to remove LiCl. The yellow filtrate was stripped again to a light oil (8.05 g).

[0064] Preparation of (C₅Me₄H) (C₃H₆)Si(t-Bu)NH

[0065] (C₅Me₄H) (C₃H₆) SiCl (8 g, 35.3 mmole) obtained from Example 2 was dissolved in 30 ml of toluene. The solution was cooled to −78° C. before an excess amount of t-butyl amine (2.1 equivalents) was injected into it. The thick slurry was filtered to remove white insolubles. The yellow filtrate was concentrated to obtain 8.10 g of product.

[0066] Preparation of (C₅Me₄) (C₃H₆)Si(t-Bu)NLi₂

[0067] The ligand (8.1 g, 30.78 mmole) obtained from Example 3 was added to 200 ml of diethyl ether. This solution was cooled to −78° C. before 2 equivalents of n-BuLi were injected into it with a syringe. No obvious change was observed. The mixture was stripped to reduce the solvent level to one third of the original amount and the mixture was stirred overnight. It was filtered to collect 7.5 g of a white solid.

[0068] Preparation of (C₅Me₄) (C₃H₆)Si(t-BuN)TiCl₂[trimethylenesilylcyclopentadienyl-t-butylamido dichloro titanium]

[0069] The dilithium salt (2.07 g) obtained from Example 4 and TiCl₃(thf)₃, comprising an adduct of tetrahydrofuran with TiCl₃, were suspended in 25 ml of THF (tetrahydrofuran) and cooled to −30° C. separately. These two solutions were mixed and stirred. The mixture turned black after 1 hour and turned into a clear solution with a very dark blue color after 3 hours. Then, an excess amount of AgCl (2.1 g) was added to this dark blue solution in a flask wrapped by aluminum foil and stirred overnight in dark.

[0070] The reaction mixture was orange-red and clear. The reaction mixture was filtered to remove Ag salts.

[0071] The red filtrate was stripped to dryness and the residue was redissolved in 40 ml of toluene. The solution was filtered to remove LiCl, concentrated again to induce a yellow solid to come out, filtered, and collected to give a yellow solid (2.2 g). The yield was about 80%, which was much higher than that of a conventional constrained geometry catalyst (CGC). The ¹H NMR spectrum of the solid is shown in FIG. 1.

[0072] FIG. 2 is a computer generated model of the metallocene product based on single crystal X-ray data.

[0073]

[0074] 1.9 g of cyclopentadienyl-Li (CpLi) (26.8 mmol) was dissolved in 50 ml of THF, stirred and cooled to −30° C. 3 g of trimethylsilyl chloride (TMSCl) (27.6 mmol) was diluted with 10 ml of THF and this diluted TMSCl was cooled to −30° C. The diluted TMSCl was gradually dropped into the CpLi solution at room temperature and the reaction was allowed to proceed for 24 hours. Then, the mixture was stripped under vacuum to remove solvent. Some pentane was added to remove LiCl. The filtrate was stripped again to afford 2.1 g of C₅H₅SiMe₃as a yellow liquid.

[0075]

[0076] C₅H₅SiMe₃(1.9 g) obtained from Example 6 was dissolved in 20 ml of THF. 0.65 g of KH was suspended in 30 ml of THF. These two solution were cooled to −30° C. for more than 30 minutes. The C₅H₅SiMe₃solution was added to the KH solution and the mixture was allowed to warm up to room temperature and stirred overnight. The mixture was filtered to remove excess KH and the filtrate was cooled to −30° C. for use in Example 8.

[0077]

[0078] The filtrate of potassium salt obtained from Example 7 was diluted in THE and cooled to −30° C. 1.5 g of TMSCl was diluted with 10 ml of THF and then cooled to −30° C. The TMSCl solution was dropped into the potassium salt solution and the mixture was allowed to warm to room temperature and stirred overnight. Then, the mixture was stripped by vacuum to remove THF. Some pentane was added to remove KCl. The filtrate was stripped again to afford 2.15 g of C₅H₄(SiMe₃)₂.

[0079]

[0080] 2.15 g of C₅H₄(SiMe₃)₂obtained from Example 8 and 0.42 g of KH were diluted with 30 ml. THF separately and then were cooled to −30° C. The C₅H₄(SiMe₃)₂solution was added dropwise into the KH solution and the mixture was allowed to warm to room temperature and stirred overnight. Then, the mixture was filtered to remove KH. The filtrate was stripped under vacuum to afford 2.457 g of a potassium salt.

[0081]

[0082] The potassium salt (2.457 g) obtained from Example 9 was dissolved in a 50 ml of THF/pentane mixed solvent (1:1 by volume). This slurry was cooled to −78° C. with liquid nitrogen before an excess amount of trimethylenesilyl dichloride (2.8 g) was injected into it. The mixture was allowed to warm to room temperature and stirred overnight. Then, the reaction mixture was stripped under vacuum to remove the solvent, filtered, and washed with pentane. The filtrate was stripped to a yellow liquid (2.38 g, yield=77%).

[0083]

[0084] The yellow liquid (C₅H₃) (SiMe₃)₂(C₃H₆)SiCl (2.38 g) obtained from Example 10 and NMe₂Li (0.385 g) were dissolved in 20 ml of toluene separately and cooled to −30° C. for about 2 hours. The (C₅H₃) (SiMe₃)₂(C₃H₆)SiCl solution was added dropwise to the Nme₂Li solution and the mixture was allowed to warm to room temperature and stirred overnight. The reaction mixture was filtered, stripped under vacuum, and washed with pentane. The filtrate was distilled at 80° C. under vacuum. The 0.74 g of distillate was recovered as a yellow clear liquid (yield=60.5%).

[0085]

[0086] The amine (0.74 g) obtained from Example 11 and KH (0.1 g) were dissolved in 20 ml of THF separately and cooled to −30° C. for 30 minutes. The amine solution was added dropwise to the KH solution and the mixture was allowed to warm to room temperature and stirred overnight. The reaction mixture was filtered, stripped, and washed with pentane. The 0.69 g of distillate was recovered as a pale yellow liquid.

[0087]

[0088] The potassium salt (0.69 g) obtained from Example 12 and TiCi₃(thf)₃(0.707 g) were dissolved in THF separately and cooled to −30° C. The potassium salt solution was added dropwise to the TiCl₃(thf)₃solution and the mixture was allowed to warm to room temperature and stirred for 3 hours. The reaction mixture was stripped, washed with toluene and filtered. The filtrate was stripped to dryness and was recrytallized with toluene/pentane to afford a green solid.

[0089] Synthesis of ethylene-propylene rubber (EPM)

[0090] The reactor vessel was heated to 105° C., nitrogen gas was introduced for 5 minutes to purge oxygen from the reactor. The reactor was then evacuated for about 2 hours to ensure complete removal of moisture and oxygen. The reactor temperature was adjusted to 80° C., and 500 ml of toluene was charged into the reactor. After the temperature was stabilized, 8 ml (1.2×10⁻²mole) of MAO was charged into the reactor and stirred. After 5 minutes, 2 ml (4×10⁻⁶mole) of the metallocene catalyst obtained from Example 5 in toluene was charged and stirred. After stirring at 80° C. for 1 minute, ethylene and propylene gas (ratio by volume: 40/50) at 100 psi were introduced into the reactor.

[0091] After the completion of the polymerization reaction, the solution was cooled and methanol was added to precipitate the product. The product was filtered and dried for various tests. The results obtained are shown in Table 1 below.

[0092] The same procedures as described in Example 14 were employed, except that the reaction temperature was changed. The results obtained are shown in Table 1.

[0093] Synthesis of ethylene propylene diene rubber (EPDM)

[0094] The reactor vessel was heated to 105° C., nitrogen gas was introduced for 5 minutes to purge oxygen from the reactor. The reactor was then evacuated for about 2 hours to ensure complete removal of moisture and oxygen. The reactor temperature was adjusted to 80° C., and 500 ml of toluene was charged into the reactor. After the temperature stabilized, 8 ml (1.2×10⁻²mole) of MAO was charged into the reactor and stirred. After 5 minutes, 2 ml (4×10⁻⁶mole) of the metallocene catalyst obtained from Example 5 in toluene was charged and stirred. After stirring at 80° C. for 5 minute, 10 ml of 5-ethylidene-2-norbornene (ENB) was charged and stirred. After 1 minute, ethylene and propylene gas (ratio in volume: 40/50) at 100 psi were introduced into the reactor.

[0095] After the completion of the polymerization reaction, the solution was cooled and methanol was added to precipitate the product. The product was filtered and dried for various tests. The results obtained are shown in Table 1.

[0096] The same procedures as described in Example 17 were employed, except that the ethylene/propylene feed ratio was changed to 50/40 in volume. The results obtained are shown in Table 1.

[0097] The same procedures as described in Example 14 were employed, except that the metallocene catalyst used was replaced by C₅Me₄(Me₂Si-N-tert-Bu)TiCl₂[dimethylsilyl-cyclopentadienyl-t-butylamidodichloro titanium], which is a constrained geometry catalyst (CGC), the reaction temperature was changed, and the feed ratio of ethylene and propylene gas by volume was changed to 50/50. The results are shown in Table 2 below.

[0098] From the results in Tables 1 and 2 above, it can be seen that the catalyst of the present invention has a higher catalytic activity than that of a conventional CGC. Moreover, the olefin polymer obtained by the catalyst of the present invention has a relatively high molecular weight.

[0099] The foregoing description of the preferred embodiments of this invention has been presented for purposes of illustration and description. Obvious modifications or variations are possible in light of the above teaching. The embodiments chosen and described provide an excellent illustration of the principles of this invention and its practical application to thereby enable those skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.