阅读说明：本技术 负载型茂金属催化剂的制备方法及使用由此制备的催化剂制备聚丙烯的方法 (Method for preparing supported metallocene catalyst and method for preparing polypropylene by using catalyst prepared by same ) 是由 金炳奭 李仁羨 金祏焕 李惠京 朴喜廣 洪大植 全相珍 于 2018-12-14 设计创作，主要内容包括：本发明涉及一种制备负载型茂金属催化剂的方法,以及使用由此制备的催化剂制备聚丙烯的方法。根据本发明,提供了一种负载型茂金属催化剂,其能够制备具有低二甲苯可溶物含量的等规聚丙烯聚合物,同时具有优异的催化活性。(The present invention relates to a method for preparing a supported metallocene catalyst, and a method for preparing polypropylene using the catalyst prepared thereby. According to the present invention, there is provided a supported metallocene catalyst capable of preparing an isotactic polypropylene polymer having a low xylene solubles content while having excellent catalytic activity.)

1. A method of preparing a supported metallocene catalyst, the method comprising the steps of:

preparing a mixture of a racemic form of the following chemical formula 1 and a meso isomer of the following chemical formula 2;

dissolving the mixture in a solvent comprising toluene and hexane;

filtering the mixture dissolved in the solvent to remove the solidified meso-isomer of chemical formula 2; and

removing the solvent from the filtered mixture and then loading the resulting product on a carrier:

[ chemical formula 1]

[ chemical formula 2]

In the chemical formulae 1 and 2,

X¹and X²Each of which is independently a halogen, is,

R¹and R¹' each independently is an aryl group having 6 to 20 carbon atoms substituted with an alkyl group having 1 to 20 carbon atoms,

R²、R³、R⁴、R²’、R³' and R⁴' are each independently hydrogen, halogen, alkyl having 1 to 20 carbon atoms, alkenyl having 2 to 20 carbon atoms, alkoxy having 1 to 20 carbon atoms, aryl having 6 to 20 carbon atoms, alkylaryl having 7 to 20 carbon atoms, or arylalkyl having 7 to 20 carbon atoms,

a is carbon, silicon or germanium, and

R⁵and R⁶Each independently an alkyl group having 1 to 20 carbon atoms.

2. The method for preparing a supported metallocene catalyst according to claim 1, wherein R in chemical formulas 1 and 2¹And R¹' is tert-butyl substituted phenyl.

3. The method for preparing a supported metallocene catalyst according to claim 1, wherein R in chemical formulas 1 and 2²、R³、R⁴、R²’、R³' and R⁴' is hydrogen or an alkyl group having 1 to 20 carbon atoms.

4. The method for preparing a supported metallocene catalyst according to claim 1, wherein R in chemical formulas 1 and 2⁵And R⁶Is methyl.

5. The method for preparing a supported metallocene catalyst according to claim 1, wherein the weight ratio of toluene and hexane is 1:0.01 to 1: 100.

6. The method of preparing a supported metallocene catalyst according to claim 1, wherein the step of dissolving the mixture in the solvent comprising toluene and hexane is performed at a temperature of-78 ℃ to 70 ℃ for 1 hour to 128 hours.

7. The method of preparing a supported metallocene catalyst according to claim 1, wherein the concentration of toluene and hexane is each independently 0.05M to 2.0M.

8. The method of preparing a supported metallocene catalyst according to claim 1, wherein the step of dissolving the mixture in the solvent comprising toluene and hexane comprises the steps of: toluene was first added to the mixture to dissolve the mixture, and then hexane was added thereto at a temperature lower than the toluene dissolution temperature to dissolve the mixture.

9. The method of preparing a supported metallocene catalyst according to claim 8, wherein the step of dissolving the mixture in the solvent comprising toluene and hexane is performed by: toluene was first added to the mixture to dissolve the mixture at 30 ℃ to 70 ℃ for 0.1 hour to 3 hours, and then hexane was added thereto to hold the mixture at-30 ℃ to 30 ℃ for 6 hours to 96 hours.

10. The method for preparing a supported metallocene catalyst according to claim 1, wherein the step of dissolving the mixture in the solvent comprising toluene and hexane is performed two or more times.

11. The process for producing a supported metallocene catalyst according to claim 1, wherein the molar ratio of racemic form to meso isomer (rac: meso) in the mixture dissolved in the solvent is 7 or more.

12. A process for preparing polypropylene comprising the step of polymerizing monomers comprising propylene in the presence of the supported metallocene catalyst prepared by the process of claim 1.

Technical Field

Cross Reference to Related Applications

The present application is based on and claims priority from korean patent application nos. 10-2017-0180263 and 10-2018-0161297, filed on 26/2017 and 12/2018 and 13/2018, respectively, the entire disclosures of which are incorporated herein by reference.

The present invention relates to a method for preparing a supported metallocene catalyst, and a method for preparing polypropylene using the catalyst prepared thereby.

Background

Catalysts for olefin polymerization can be classified into ziegler-natta catalysts and metallocene catalysts, and both catalysts have been developed according to their characteristics.

Ziegler-natta catalysts have been widely used in existing commercial processes since the development of the fifties of the twentieth century. However, since the ziegler-natta catalyst is a multi-active site catalyst in which a plurality of active sites are mixed, a polymer prepared using the same has a broad molecular weight distribution. Also, since the comonomer composition distribution is not uniform, there is a limitation in securing desired physical properties. In particular, since polypropylene produced using a ziegler-natta catalyst has a high xylene solubles content (e.g., greater than 5 wt%), there is a limitation in that it is difficult to obtain polypropylene having a low melting point (Tm) when using a ziegler-natta catalyst.

The metallocene catalyst comprises a combination of a main catalyst and a cocatalyst, wherein the main component of the main catalyst is a transition metal compound, and the main component of the cocatalyst is aluminum. Such catalysts are single site catalysts that are homogeneous composite catalysts. Thus, metallocene catalysts can produce polypropylene with narrow molecular weight distribution and uniform comonomer composition distribution. In addition, the metallocene catalyst has characteristics that the tacticity, copolymerization property, molecular weight, crystallinity, etc. of polypropylene can be changed by changing the ligand structure and polymerization conditions.

Wherein the ansa-metallocene catalyst is an organometallic catalyst comprising two ligands interconnected by a bridging group. The bridging group prevents ligand rotation and determines the activity and structure of the metal center. In particular, in the polymerization of polypropylene, the ansa-metallocene catalyst can form a polymer having a low xylene solubles content, and thus is advantageous in the production of polypropylene having a low melting point.

Meanwhile, during the preparation of the ansa-metallocene catalyst, both the racemic form and the meso isomer are produced. Therefore, in order to prepare an isotactic polymer having high crystallinity and melting point as well as high specific gravity and mechanical strength, it is necessary to separate a metallocene compound having a racemic form with high purity from a mixture of a meso isomer and a racemic form.

However, the racemic form and the meso isomer do not have much difference in solubility with respect to a general recrystallization solvent, and thus the pure racemic form cannot be easily separated.

Therefore, there is a need to develop a method capable of obtaining a metallocene compound in a highly pure racemic form in a simpler manner than existing methods.

Disclosure of Invention

Technical problem

The present invention provides a method for preparing a catalyst comprising a metallocene compound in a highly pure racemic form to provide a supported metallocene catalyst capable of polymerizing a desired isotactic polypropylene having a high stereoregularity.

In addition, the present invention provides a method for preparing polypropylene using the supported metallocene catalyst.

Technical scheme

According to the present invention, there is provided a process for preparing a supported metallocene catalyst, the process comprising the steps of:

preparing a mixture of a racemic form of the following chemical formula 1 and a meso isomer of the following chemical formula 2;

dissolving the mixture in a solvent comprising toluene and hexane;

filtering the mixture dissolved in the solvent to remove the solidified meso isomer of chemical formula 2; and

the solvent was removed from the filtered mixture and the resulting product was then loaded on a carrier:

[ chemical formula 1]

[ chemical formula 2]

In the chemical formulae 1 and 2,

X¹and X²Each of which is independently a halogen, is,

R¹and R¹' each independently is an aryl group having 6 to 20 carbon atoms substituted with an alkyl group having 1 to 20 carbon atoms,

R²、R³、R⁴、R²’、R³' and R⁴' each independently is hydrogen, halogen, alkyl having 1 to 20 carbon atoms, alkyl having 2 to 20An alkenyl group of carbon atoms, an alkoxy group of 1 to 20 carbon atoms, an aryl group of 6 to 20 carbon atoms, an alkylaryl group of 7 to 20 carbon atoms or an arylalkyl group of 7 to 20 carbon atoms,

a is carbon, silicon or germanium, and

R⁵and R⁶Each independently an alkyl group having 1 to 20 carbon atoms.

Further, according to the present invention, there is provided a method for preparing polypropylene, comprising the steps of: polymerizing monomers comprising propylene in the presence of the supported metallocene catalyst.

Advantageous effects

According to the method for preparing the supported metallocene catalyst of the present invention, the supported metallocene catalyst including a highly pure racemic form can be prepared in a simpler manner.

Therefore, when the supported metallocene catalyst prepared by the method is used, an isotactic polypropylene polymer having a low xylene solubles content can be prepared while exhibiting excellent catalytic activity.

Detailed Description

Unless otherwise described throughout the specification, technical terms are directed to particular embodiments and are not intended to limit the present invention.

Also, as used herein, the singular includes the plural unless it is clearly contradicted. Furthermore, the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but does not preclude the presence or addition of other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

As used herein, the term "racemic form" means that the same substituents on both cyclopentadienyl moieties are present on opposite sides of a plane containing zirconium and the center of the cyclopentadienyl moiety.

As used herein, the term "meso-isomer," which is a stereoisomer of the racemic form, means that the same substituents on both cyclopentadienyl moieties are present on the same side relative to a plane containing zirconium (Zr) and the center of the cyclopentadienyl moieties.

According to one embodiment of the present invention, there is provided a method of preparing a supported metallocene catalyst, the method comprising the steps of:

preparing a mixture of a racemic form of the following chemical formula 1 and a meso isomer of the following chemical formula 2;

dissolving the mixture in a solvent comprising toluene and hexane;

filtering the mixture dissolved in the solvent to remove the solidified meso isomer of chemical formula 2; and

the solvent was removed from the filtered mixture and the resulting product was then loaded on a carrier:

[ chemical formula 1]

[ chemical formula 2]

In the chemical formulae 1 and 2,

X¹and X²Each of which is independently a halogen, is,

R¹and R¹' each independently is an aryl group having 6 to 20 carbon atoms substituted with an alkyl group having 1 to 20 carbon atoms,

R²、R³、R⁴、R²’、R³' and R⁴' are each independently hydrogen, halogen, alkyl having 1 to 20 carbon atoms, alkenyl having 2 to 20 carbon atoms, alkoxy having 1 to 20 carbon atoms, aryl having 6 to 20 carbon atoms, alkylaryl having 7 to 20 carbon atoms, or arylalkyl having 7 to 20 carbon atoms,

a is carbon, silicon or germanium, and

R⁵and R⁶Each independently an alkyl group having 1 to 20 carbon atoms.

The metallocene compound of chemical formula 1 has an ansa-metallocene structure comprising two indenyl groups as ligands and zirconium (Zr) as a metal atom, thereby exhibiting high catalytic activity.

In addition, the ligand is a bulky group (R)¹And R¹') provides steric hindrance and, therefore, substantially prevents the formation of the metallocene compound of the meso isomer during the synthesis of the catalyst. However, it is difficult to suppress the formation of the meso isomer below 30 mol%.

However, as described above, since the metallocene compound of the meso isomer forms atactic polypropylene, it is necessary to purify only the metallocene compound in a racemic form with high purity in order to produce isotactic polypropylene.

The basic method for separating the racemic form from the meso isomer is based on the fact that the racemic form generally has poorer solubility than the meso isomer, and is isolated by solidifying the racemic form by recrystallization using the solubility difference. However, for the metallocene compound of chemical formula 1, the racemic form and the meso isomer do not show a great difference in solubility to DCM (dichloromethane) which is generally used as a recrystallization solvent, and thus, it is not easy to isolate the pure racemic form. In addition, there is a problem that the total yield is low because a large amount of racemic form is present in the filtrate remaining after removing the solidified racemic form.

Thus, the present inventors have found conditions under which the racemic form shows a higher solubility than the meso isomer. Under these conditions, a mixture of racemic form and meso isomer is dissolved (recrystallized) to separate racemic form in liquid form and meso isomer in solid form is removed, whereby racemic form can be separated in high purity by purification, thereby completing the present invention.

Hereinafter, the preparation method of the supported metallocene catalyst of the present invention will be described in more detail.

First, a metallocene mixture including a racemic form of the following chemical formula 1 and a meso isomer of the following chemical formula 2 is prepared.

[ chemical formula 1]

[ chemical formula 2]

In the chemical formulae 1 and 2,

X¹and X²Each of which is independently a halogen, is,

R¹and R¹' each independently is an aryl group having 6 to 20 carbon atoms substituted with an alkyl group having 1 to 20 carbon atoms,

R²、R³、R⁴、R²’、R³' and R⁴' are each independently hydrogen, halogen, alkyl having 1 to 20 carbon atoms, alkenyl having 2 to 20 carbon atoms, alkoxy having 1 to 20 carbon atoms, aryl having 6 to 20 carbon atoms, alkylaryl having 7 to 20 carbon atoms, or arylalkyl having 7 to 20 carbon atoms,

a is carbon, silicon or germanium, and

R⁵and R⁶Each independently an alkyl group having 1 to 20 carbon atoms.

According to one embodiment of the present invention, in chemical formulas 1 and 2, X¹And X²May each independently be a halogen, preferably Cl.

In chemical formulas 1 and 2, R¹And R¹' may be each independently an aryl group having 6 to 20 carbon atoms substituted with an alkyl group having 1 to 20 carbon atoms, preferably a phenyl group substituted with a tert-butyl group, and more preferably a 4-tert-butylphenyl group.

In chemical formulas 1 and 2, preferably, R²、R³、R⁴、R²’、R³' and R⁴' may each independently be hydrogen or an alkyl group having 1 to 20 carbon atoms, and more preferablyIs hydrogen.

In chemical formulas 1 and 2, a may be carbon, silicon or germanium, and is preferably silicon.

In chemical formulas 1 and 2, R⁵And R⁶May each independently be an alkyl group having 1 to 20 carbon atoms, and is preferably a methyl group.

According to one embodiment of the present invention, representative examples of the racemic form compound of chemical formula 1 are as follows:

representative examples of the meso-isomer compound of chemical formula 2 are as follows:

the metallocene mixture including the racemic form of chemical formula 1 and the meso isomer of chemical formula 2 may be prepared by the following method, but the present invention is not limited thereto.

First, a compound of the following chemical formula 1-2 is reacted with a compound of the following chemical formula 1-3 to prepare a compound of the chemical formula 1-4. The reaction can be carried out using an alkyllithium (e.g., n-butyllithium) as a catalyst at a temperature of-200 ℃ to 0 ℃.

Next, the compounds of the following chemical formulae 1 to 4 are reacted with the compounds of the following chemical formulae 1 to 5 to prepare compounds of the chemical formulae 1 to 6. The reaction can be carried out using an alkyllithium (e.g., n-butyllithium) as a catalyst at a temperature of-200 ℃ to 0 ℃. At this time, the organic layer is separated from the product, and after the separated organic layer is vacuum-dried, it is preferable to remove the excess reactant therefrom.

Next, the compounds of the following chemical formulae 1 to 6 are reacted with the compounds of the chemical formulae 1 to 7. Through this reaction, a metallocene compound in the form of a mixture of a racemic form of chemical formula 1 and a meso isomer of chemical formula 2 may be obtained.

[ chemical formulas 1-2]

[ chemical formulas 1-3]

Cl₂AR⁵R⁶

[ chemical formulas 1 to 4]

[ chemical formulas 1 to 5]

[ chemical formulas 1 to 6]

[ chemical formulas 1 to 7]

Cl₂ZrRX¹X²

In chemical formulae 1-2 to 1-7, X¹、X²、A、R¹、R¹’、R²、R³、R⁴、R²’、R³’、R⁴’、R⁵And R⁶As defined in chemical formulas 1 and 2.

The molar ratio of the racemic form of chemical formula 1 to the meso isomer of chemical formula 2 in the mixture (racemic: meso) may be about 1:1 to about 3:1, but varies depending on reaction conditions, and it is difficult to increase the molar ratio of the racemic form to more than the above range in the synthesis step.

Next, the mixture was dissolved in a solvent comprising toluene and hexane.

The weight ratio of toluene and hexane may be 1:0.01 to 1:100, 1:0.1 to 1:10 or 1:0.5 to 1: 2.

Furthermore, the dissolution temperature may be in the following range: -78 ℃ or higher, -30 ℃ or higher, or-25 ℃ or higher, and 70 ℃ or lower, 60 ℃ or lower, or 25 ℃ or lower, preferably-30 ℃ or higher and 70 ℃ or lower, preferably-25 ℃ or higher and 70 ℃ or lower, and more preferably-25 ℃ or higher and 60 ℃. When the dissolution temperature is within the above range, the molar ratio of the racemic form to the meso isomer may be further increased.

In addition, the dissolution may be performed for 1 hour or more, 24 hours or more, or 48 hours or more, and 128 hours or less, 96 hours or less, 72 hours or less, or 60 hours or less.

Further, the concentrations of toluene and hexane may each independently be 0.05M or more, 0.1M or more, or 0.2M or more, and 2.0M or less, 1.5M or less, 1.0M or less, or 0.5M or less.

Further, the mixture may be dissolved by mixing the mixture with toluene and hexane sequentially or simultaneously.

When the mixture is sequentially dissolved in toluene and hexane, toluene is first added to the mixture, and hexane is sequentially added thereto, so that the mixture can be dissolved at a temperature lower than the dissolution temperature of toluene. As described above, by adopting both the cooling method and the solvent use method utilizing the solubility difference between the solvents, in which toluene is first added to dissolve the mixture and then hexane is added at a lower temperature to dissolve the mixture, it is possible to expect recrystallization which further increases the molar ratio of the racemic form.

According to one embodiment of the present invention, toluene is first added at a temperature of 30 ℃ to 70 ℃ or 40 to 70 ℃ to dissolve the mixture for 0.1 hour to 3 hours, and then hexane is added at a temperature of-30 ℃ to 30 ℃ or-25 ℃ to dissolve the mixture for 6 hours to 96 hours.

According to an embodiment of the present invention, when the weight ratio of toluene and hexane solvents and the dissolution temperature and time satisfy the above ranges, the solubility of the racemic form with respect to the meso isomer is further increased, thereby obtaining a racemic form of higher purity.

In other words, when the mixture is dissolved under the above conditions, the racemic form exhibits a much higher solubility than the meso isomer. As a result, in a mixture dissolved in a solvent including toluene and hexane, the molar ratio of the racemic form to the meso isomer (racemic: meso) may be 7 or more, 8 or more, or 9 or more, and 30 or less, 25 or less, 20 or less, or 18 or less, the content of the racemic form may be greatly increased, and the meso isomer having relatively low solubility may be precipitated as a solid.

Further, according to an embodiment of the present invention, the step of dissolving the racemic form/meso-isomer mixture in a solvent including toluene and hexane may be performed two or more times. When the dissolution step is carried out more than twice, the molar ratio of the racemic form to the meso isomer in the second dissolution step may be further increased, since the molar ratio of the racemic form to the meso isomer in the previous dissolution step has been increased.

Next, the mixture dissolved in the solvent is filtered using a filter or the like, thereby removing the solidified meso-isomer of chemical formula 2. From the mixture from which the solidified meso isomer is removed, the solvent including toluene and hexane is removed by distillation under reduced pressure, thereby obtaining a metallocene catalyst having a much higher content of the racemic form of chemical formula 1. Thereafter, the metallocene catalyst having a higher content of racemic form is dissolved in a non-polar solvent (e.g., hexane, heptane or pentane), and impurities are additionally removed by filtration using a filter or the like, thereby finally obtaining a racemic form with high purity.

Subsequently, the metallocene catalyst is supported on the carrier according to a conventional supporting method.

As the carrier, a carrier having a hydroxyl group on the surface thereof can be used. Specifically, the support may be a support containing highly reactive hydroxyl groups or siloxane groups, the surface of which is dried and the moisture is removed. By way of non-limiting example, the support includes silica, silica-alumina, and silica-magnesia dried at high temperature. The support may comprise an oxide (e.g. Na)₂O), carbonates (e.g. K)₂CO₃) Sulfates (e.g. BaSO)₄) And nitrates (e.g. Mg (NO)₃)₂) And (4) components.

According to one embodiment of the present invention, the supported metallocene catalyst may further include one or more cocatalysts selected from the group consisting of compounds represented by the following chemical formulas 3 to 5, in addition to the metallocene compound:

[ chemical formula 3]

-[Al(R⁷)-O]_c-

In the chemical formula 3, the first and second,

c is an integer of 2 or more,

R⁷each independently is a halogen, a hydrocarbyl group having 1 to 20 carbon atoms, or a halogen-substituted hydrocarbyl group having 1 to 20 carbon atoms;

[ chemical formula 4]

D(R⁸)₃

In the chemical formula 4, the first and second organic solvents,

d is aluminum or boron, and the metal is aluminum or boron,

R⁸each independently is a halogen, a hydrocarbyl group having 1 to 20 carbon atoms, or a halogen-substituted hydrocarbyl group having 1 to 20 carbon atoms;

[ chemical formula 5]

[L-H]⁺[Q(E)₄]^-

In the chemical formula 5, the first and second organic solvents,

l is a neutral Lewis base,

[L-H]⁺is a Bronsted acid and is a Bronsted acid,

q is boron or aluminum in the +3 oxidation state, and

each E is independently an aryl group having 6 to 20 carbon atoms or an alkyl group having 1 to 20 carbon atoms, wherein one or more hydrogen atoms are unsubstituted or substituted with a halogen, hydrocarbyl having 1 to 20 carbon atoms, alkoxy, or phenoxy functionality.

Specifically, the compound represented by chemical formula 3 may include alkylaluminoxane, such as methylaluminoxane, ethylaluminoxane, butylaluminoxane, isobutylaluminoxane, etc. In addition, the compound represented by chemical formula 3 may include Modified Methylaluminoxane (MMAO) obtained by substituting a part of methyl groups of methylaluminoxane with other alkyl groups. For example, the modified methylaluminoxane may be a compound obtained by substituting 40 mol% or less or 5 mol% to 35 mol% of a methyl group of methylaluminoxane with a linear or branched alkyl group having 3 to 10 carbon atoms. Examples of commercially available modified methylaluminoxanes may include MMAO-12, MMAO-3A, MMAO-7, and the like.

In addition, the compound represented by chemical formula 4 may include trimethylaluminum, triethylaluminum, triisobutylaluminum, tripropylaluminum, tributylaluminum, dimethylaluminum chloride, dimethylaluminum isobutyl, dimethylethylaluminum, diethylaluminum chloride, triisopropylaluminum, triisobutylaluminum, tri-sec-butylaluminum, tricyclopentylaluminum, tripentylaluminum, triisopentylaluminum, trihexylaluminum, ethyldimethylaluminum, methyldiethylaluminum, triphenylaluminum, tri-p-tolylaluminum, dimethylmethoxyaluminum, dimethylethoxyaluminum, trimethylboron, triethylboron, triisobutylboron, tripropylboron, tributylboron, and the like.

Further, the compound represented by chemical formula 5 may include triethylammonium tetraphenylboron, tributylammonium tetraphenylboron, trimethylammonium tetraphenylboron, tripropylammonium tetraphenylboron, trimethylammonium tetrakis (p-tolyl) boron, tripropylammonium tetrakis (p-tolyl) boron, triethylammonium tetrakis (o, p-dimethylphenyl) boron, trimethylammonium tetrakis (o, p-dimethylphenyl) boron, tributylammonium tetrakis (p-trifluoromethylphenyl) boron, trimethylammonium tetrakis (p-trifluoromethylphenyl) boron, tributylammonium tetrapentafluorophenylboron, N-diethylanilinium tetraphenylboron, N-diethylanilinium tetrapentafluorophenylboron, diethylammonium tetrapentafluorophenylboron, triphenylphosphonium tetraphenylboron, trimethylphosphonium tetraphenylboron, triethylammonium tetraphenylaluminum, tributylammonium tetraphenylaluminum tetraphenylboron, triphenylphosphonium tetraphenylboron, tri-ethylphenylammonium tetraphenylboron, tri-propylaluminum, Trimethylammoniumtetraphenylaluminum, tripropylammoniumtetraphenylaluminum, trimethylammoniumtetrakis (p-tolyl) aluminum, tripropylammoniumtetrakis (p-tolyl) aluminum, triethylammoniumtetrakis (o, p-dimethylphenyl) aluminum, tributylammoniumtetrakis (p-trifluoromethylphenyl) aluminum, trimethylammoniumtetrakis (p-trifluoromethylphenyl) aluminum, tributylammoniumtetrapentafluorophenylaluminum, N-diethylphenylammonium tetraphenylaluminum, N-diethylphenylammonium tetrapentafluorophenylaluminum, diethylammonium tetrapentafluorophenylaluminum, triphenylphosphoniumtetraphenylaluminum, trimethylphosphoniumtetraphenylaluminum, triphenylcarbonium tetraphenylboron, triphenylcarbonium tetraphenylaluminum, triphenylcarbonium tetrakis (p-trifluoromethylphenyl) boron, triphenylcarbonium tetrapentafluorophenylboron, and the like.

Specifically, as the co-catalyst, one or more compounds selected from trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, ethylaluminum sesquichloride, diethylaluminum chloride, ethylaluminum dichloride, methylaluminoxane and modified methylaluminoxane may be preferably used.

Further, the content of the co-catalyst can be determined by taking catalytic activity and the like into consideration. According to an embodiment of the present invention, the cocatalyst may be included in a molar ratio of 1:1 to 1:10000, 1:1 to 1:5000, or 1:1 to 1:3000, relative to the total weight of the metallocene compound.

Meanwhile, in this case, the supported metallocene catalyst may be prepared in any order by first supporting the cocatalyst on the support and then supporting the metallocene compound on the cocatalyst-supported support, or by first supporting the metallocene compound on the support and then supporting the cocatalyst thereon.

In the preparation of the supported catalyst, a hydrocarbon solvent such as pentane, hexane, heptane or the like, or an aromatic solvent such as benzene, toluene or the like may be used.

According to the preparation method, the content of the metallocene compound in a racemic form in the catalyst can be increased in a simple manner, and when a supported metallocene catalyst prepared by supporting it on a carrier is used, a high-quality isotactic propylene polymer can be obtained.

Meanwhile, according to another embodiment of the present invention, there is provided a method for preparing polypropylene, which includes the step of polymerizing a monomer including propylene in the presence of the supported metallocene catalyst prepared by the above-mentioned preparation method.

The process for the preparation of polypropylene can be carried out in the presence of the supported metallocene catalyst described above by applying ordinary apparatus and contact techniques using a monomer comprising propylene as a raw material.

By way of non-limiting example, the process for preparing polypropylene can be carried out by homopolymerization of propylene or random polymerization of propylene and a comonomer using a continuous slurry polymerization reactor, a loop slurry reactor, a gas phase reactor or a solution reactor. The comonomer may include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-eicosene, and the like.

In the preparation method, the supported metallocene catalyst may be used in a state of being dissolved or diluted in a solvent such as pentane, hexane, heptane, nonane, decane, toluene, benzene, dichloromethane, chlorobenzene, or the like.

Further, the method of preparing polypropylene may be at a temperature of 20 ℃ to 500 ℃ or 20 ℃ to 200 ℃ and 1kgf/cm²To 100kgf/cm²Or 1kgf/cm²To 70kgf/cm²Is carried out for 1 to 24 hours, or 1 to 10 hours. The polymerization may be carried out with or without hydrogen added thereto, as required.

Further, the production method can be suitably applied to the production of desired isotactic polypropylene.

Hereinafter, preferred embodiments will be provided to better understand the present invention. However, the following examples are provided only for illustrating the present invention, and the present invention is not limited thereto.

< example >

Preparation of crude mixture of racemic and meso isomers

Synthesis example 1

(4- (4- (tert-butyl) phenyl) -2-isopropyl-1H-inden-1-yl) dimethyl (2-methyl-4-phenyl-1H-inden-1-) Preparation of silyl) silanes

2-iPr-4-tBuPh indene (1 eq) was dissolved in toluene/THF (10/1, 0.5M) and then n-butyllithium (1.05 eq) was added slowly thereto at-25 deg.C, followed by stirring at room temperature for 3 hours. Thereafter, dichlorodimethylsilane (1.05 eq) was added at-10 ℃ and then stirred at room temperature overnight. In another reactor, 2-Me-4-tBuPh indene (1 eq) was dissolved in toluene/THF (5/1, 0.7M) and n-butyllithium (1.05 eq) was added slowly at-25 ℃ and then stirred at room temperature for 3 hours. Thereafter, CuCN (2 mol%) was added, followed by stirring for 30 minutes. Thereafter, a first reactant monosilicon (mono-Si) solution was added, followed by stirring at room temperature overnight. Post-treatment with water and then drying to obtain the ligand.

Dimethylsilyl- (4- (4-tert-butylphenyl) phenyl) -2-methyl-1H-inden-1-yl) (4- (4-tert-butylphenyl) Preparation of yl) phenyl) -2-isopropyl-1H-inden-1-yl) zirconium dichloride (mixture of racemic and meso)

The ligand was dissolved in toluene/ether (2/1, 0.53M) and n-butyllithium (2.05 equiv.) was added thereto at-25 ℃ and then stirred at room temperature for 5 hours. Preparation of ZrCl₄(1 eq) slurry in toluene (0.17M) and added to the flask, which was then stirred at room temperature overnight.

When the reaction was complete, the solvent was dried in vacuo and DCM was added again and the LiCl was removed by filter etc. The filtrate was dried in vacuo to obtain a metallocene compound in the form of a mixture of racemic form and meso isomer (rac: meso ═ 2:1, molar ratio).

Process for preparing rac-dimethylsilyl- (4- (4-tert-butylphenyl) phenyl) -2-methyl-1H-inden-1-yl) (4- (4-tert-butylphenyl) phenyl) -2-isopropyl-1H-inden-1-yl) zirconium dichloride¹H NMR(500MHz,CDCl₃,7.26ppm):0.89(6H,t),1.19(3H,d),1.34(9H,s),1.35(9H,s),1.47(3H,d),1.50(3H,s),2.38(3H,s),3.20(1H,m),6.88(2H,m),6.94(2H,d),7.14(2H,d),7.44(4H,t),7.52(4H,d),7.65(2H,t)