Metallocene catalysts for polymerizing polyethylene, methods of making polyethylene copolymers using the same, and films made using the polyethylene copolymers

Abstract

The present invention relates to a metallocene catalyst for polymerizing polyethylene, a method for preparing a polyethylene copolymer using the same, and a film prepared using the polyethylene copolymer. According to the present invention, a polyethylene having a high molecular weight can be prepared. Furthermore, according to the present invention, a film having improved transparency can be prepared.

Description

Technical Field

[0001] This invention relates to a metallocene catalyst for polymerizing polyethylene, a method for preparing polyethylene copolymers using the same, and a membrane prepared using the polyethylene copolymer.

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2023-0169843, filed on November 29, 2023, the entire contents of which are incorporated herein by reference. Background Technology

[0003] Global demand for polyolefins, especially polyethylene, is close to 100 million metric tons per year and continues to grow at a rate of 3-5% annually.

[0004] Polyethylene continues to evolve based on its existing product portfolio. For example, the production of low-density linear polyethylene using metallocene catalysts is increasing to enhance membrane properties, and efforts are ongoing to diversify the product portfolio and produce specialty products. Within this product portfolio, the demand for ultra-high molecular weight polyethylene (UHMWPE), which requires high physical properties, has been steadily increasing recently. Summary of the Invention

[0005] The present invention aims to provide a catalyst for preparing polyethylene copolymers with increased molecular weight.

[0006] Furthermore, the present invention aims to provide a film with excellent transparency prepared from a polyethylene copolymer.

[0007] An embodiment of the present invention provides a metallocene catalyst for polymerizing polyethylene comprising: a transition metal compound A; a cocatalyst compound B; and a support C supporting the transition metal compound A and the cocatalyst compound B, wherein the transition metal compound A may be a mixture of a first metallocene catalyst compound represented by the following chemical formula 1 and a second metallocene catalyst compound represented by the following chemical formula 2.

[0008] [Chemical Formula 1]

[0009]

[0010] In the above chemical formula 1,

[0011] M 1 Is it titanium (Ti), zirconium (Zr), or hafnium (Hf)?

[0012] X 1 It is a halogen group, (C1-C 20 )alkyl, (C2-C 20 )alkenyl, (C2-C 20 ) ynyl group, (C6-C20 )Aryl, (C1-C 20 )alkyl (C6-C 20 )Aryl, (C6-C 20 )Aryl(C1-C 20 )alkyl, (C1-C 20 )alkylamide group, (C6-C 20 ) aryl amide group or (C1-C 20 ) alkylidene group,

[0013] R 1 and R 2 It is a (C1-C6) alkyl group.

[0014] n and k are each integers between 0 and 2, and at least one of them is not 0.

[0015] [Chemical Formula 2]

[0016]

[0017] In the above chemical formula 2,

[0018] M 2 Is it titanium (Ti), zirconium (Zr), or hafnium (Hf)?

[0019] X 2 It is a halogen group, (C1-C 20 )alkyl, (C2-C 20 )alkenyl, (C2-C 20 ) ynyl group, (C6-C 20 )Aryl, (C1-C 20 )alkyl (C6-C 20 )Aryl, (C6-C 20 )Aryl(C1-C 20 )alkyl, (C1-C 20 )alkylamide group, (C6-C 20 ) aryl amide group or (C1-C 20 ) alkylidene group,

[0020] Q is carbon (C), silicon (Si), germanium (Ge), or tin (Sn).

[0021] R 3 To R 7 Each is independently either substituted or unsubstituted (C1-C) 20 )alkyl, substituted or unsubstituted (C2-C 20 Alkenyl, substituted or unsubstituted (C6-C) 20 ) aryl, substituted or unsubstituted (C1-C 20 )alkyl (C6-C 20) aryl, substituted or unsubstituted (C6-C 20 )Aryl(C1-C 20 )alkyl, substituted or unsubstituted (C1-C 20 Heteroalkyl, substituted or unsubstituted (C3-C) 20 ) heteroaryl, substituted or unsubstituted (C1-C 20 )alkylamide group, substituted or unsubstituted (C6-C 20 ) aryl amide group, substituted or unsubstituted (C1-C 20 ) alkylidene or substituted or unsubstituted (C1-C 20 )silyl,

[0022] R 3 To R 7 Each can independently connect with adjacent groups to form substituted or unsubstituted saturated or unsaturated C4-C groups. 20 ring,

[0023] m, l, and y are each integers from 0 to 4.

[0024] In another embodiment of the metallocene catalyst for polymerizing polyethylene, in the above chemical formula 1, M is zirconium (Zr), X is a halogen, and R... 1 and R 2 It is a (C1-C6) alkyl group, where n and k are each 1 or 2. In the above chemical formula 2, M is zirconium (Zr), X is a halogen, Q is carbon (C), and R... 3 To R 5 It is unsubstituted (C1-C) 20 )alkyl, R 6 and R 7 It is unsubstituted (C6-C) 20 )Aryl, m, l and y can each be 1.

[0025] In another embodiment of the present invention, in a metallocene catalyst for polymerizing polyethylene, the first metallocene catalyst compound represented by the above-described chemical formula 1 can be represented by the following chemical formula 1-1, and the second metallocene catalyst compound represented by the above-described chemical formula 2 can be represented by the following chemical formula 2-1.

[0026] [Chemical Formula 1-1]

[0027]

[0028] [Chemical Formula 2-1]

[0029]

[0030] According to one embodiment of the present invention, the cocatalyst compound B may be at least one selected from the following chemical formulas 3 to 5.

[0031] [Chemical Formula 3]

[0032]

[0033] In the above chemical formula 3,

[0034] p is an integer greater than 2.

[0035] Ra is a halogen group; or a group that is substituted or unsubstituted with a halogen group (C1-C2). 20 ) hydrocarbon group,

[0036] [Chemical Formula 4]

[0037]

[0038] In the above chemical formula 4,

[0039] Q is aluminum or boron.

[0040] Rb may be the same as or different from each other, each being an independent halogen group; or may be substituted or unsubstituted by halogen groups (C1-C2). 20 ) hydrocarbon group,

[0041] [Chemical Formula 5]

[0042]

[0043] In the above chemical formula 5,

[0044] [W] + It is a cationic Lewis acid; or a cationic Lewis acid bonded to a hydrogen atom.

[0045] Z is a Group 13 element.

[0046] Rc may be the same as or different from each other, and each is independently selected from halogen groups, (C1-C2). 20 ) substituted with one or more of the following groups: hydrocarbon group, alkoxy group, and phenoxy group (C6-C) 20 ) aryl; or selected from halogen groups, (C1-C 20 ) substituted with one or more of the following groups: hydrocarbon group, alkoxy group, and phenoxy group (C1-C2). 20 )alkyl.

[0047] In one embodiment of the present invention, in a metallocene catalyst for polymerizing polyethylene, the first metallocene catalyst compound and the second metallocene catalyst compound may be present in a molar ratio of 10:1 to 50:1.

[0048] According to one embodiment of the present invention, the carrier C may be silica (SiO2), alumina (Al2O3), magnesium chloride (MgCl2), or a mixture thereof having micropores on its surface or inside.

[0049] According to one embodiment of the present invention, a method for preparing a polyethylene copolymer can be carried out by reacting ethylene with an olefin monomer in the presence of a metallocene catalyst used for polymerizing polyethylene.

[0050] According to one embodiment of the present invention, the olefin monomer may be selected from (C2-C4) 20 α-olefins, (C4-C) 20 (C3-C) dienes, (C3-C) 20 ) cyclic olefins, (C3-C 20 Among cyclodienes, styrene and styrene derivatives.

[0051] According to another embodiment of the invention, the olefin monomer may be an (C3-C8) α-olefin.

[0052] According to one embodiment of the polyethylene copolymer of the present invention, the Mz / Mn value of the polyethylene copolymer may be 4.5 or more and 6 or less, and the density may be 0.90 g / cm³. 3 Above and 0.935 g / cm 3 The following, according to ASTM D1238, can be melt flow rate ratio (MFRR) of 10 or higher and 40 or lower.

[0053] In one embodiment of the present invention, the membrane can be prepared using a polyethylene copolymer.

[0054] According to one embodiment of the present invention, the elastic index calculated by the following mathematical formulas 1 to 4 can be 20 or more and 40 or less, and the BOCD index calculated by the following mathematical formula 5 can be 0 or more and 3.0 or less.

[0055] [Mathematical Expression 1]

[0056] Elasticity index = RSS × 1000

[0057] In the above mathematical formula 1, RSS is the recovered shear strain (γ∞) and is calculated by mathematical formula 2.

[0058] [Mathematical Expression 2]

[0059]

[0060] In the above mathematical formula 2, γ∞ is the RSS (Recovery Shear Strain), η *G is the complex viscosity, calculated by the following mathematical formula 3; G' is the storage modulus, calculated by the following mathematical formula 4; and ω (Rad / s) is the angular frequency and is an arbitrary variable.

[0061] [Mathematical Expression 3]

[0062]

[0063] In the above mathematical formula 3, η0 (Pa·s) is the zero shear viscosity, λ (s) is the relaxation time, ω (Rad / s) is the angular frequency, n is the shear thinning index, and a is the fitting index.

[0064] [Mathematical Expression 4]

[0065]

[0066] In the above mathematical formula 4, n is the number of Maxwell's equation patterns, and g i (Pa) is the platform modulus, λ i (s) is the relaxation time, and ω(Rad / s) is the angular frequency.

[0067] [Mathematical Expression 5]

[0068] BOCD index = (Short-chain branching content in high molecular weight component - Short-chain branching content in low molecular weight component) / (Short-chain branching content in low molecular weight component)

[0069] According to the present invention, the BOCD (Broad Orthogonal Comonomer Distribution Index) value of polyethylene copolymers can be increased.

[0070] Furthermore, according to the present invention, the transparency of films prepared using polyethylene copolymers can be improved. Attached Figure Description

[0071] Figure 1 This is a graph showing the molecular weight distribution and SCB distribution of the polyethylene copolymer prepared in Example 1.

[0072] Figure 2 This is a graph showing the molecular weight distribution and SCB distribution of the polyethylene copolymer prepared in Comparative Example 1.

[0073] Figure 3 This is a graph showing the RSS (Recovery Shear Strain) of Example 1, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0074] The preferred embodiments of the present invention will now be described. However, the embodiments of the present invention can be modified in many other ways, and the scope of the present invention is not limited to the embodiments described below.

[0075] The term "alkyl" as used in this invention refers to a monovalent straight-chain or branched saturated hydrocarbon free radical consisting only of carbon and hydrogen atoms. Examples of such alkyl free radicals include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, octyl, dodecyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and cyclodecyl.

[0076] Furthermore, the term "alkenyl" as used in this invention refers to a straight-chain or branched hydrocarbon free radical containing one or more carbon-carbon double bonds, including vinyl, propenyl, butenyl, pentenyl, etc., but not limited thereto.

[0077] Furthermore, the term "alkynyl" as used in this invention refers to a straight-chain or branched hydrocarbon free radical containing one or more carbon-carbon triple bonds, including, but not limited to, methynyl, ethynyl, propynyl, butynyl, pentyynyl, hexynyl, hepynyl, octyynyl, etc.

[0078] Furthermore, the term "aryl" as used in this invention refers to an organic radical derived from an aromatic hydrocarbon by removing a hydrogen atom, including monocyclic or fused-ring systems. Specific examples include, but are not limited to, phenyl, naphthyl, biphenyl, anthracene, fluorenyl, phenanthrene, triphenylene, pyrene, peryl, thionyl, tetraphenyl, fluoranyl, etc.

[0079] Furthermore, the term "alkylaryl" as used in this invention refers to an organic group in which one or more hydrogen atoms of an aryl group are replaced by an alkyl group, including, but not limited to, methylphenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, n-butylphenyl, isobutylphenyl, tert-butylphenyl, etc.

[0080] Furthermore, the term "arylalkyl" as used in this invention refers to an organic group in which one or more hydrogen atoms of an alkyl group are replaced by aryl groups, including phenylpropyl, phenylhexyl, etc., but not limited thereto.

[0081] Furthermore, the term "amide group" as used in this invention refers to an amino group (-NH2) bonded to a carbonyl group (C=O), "alkylamide group" refers to an organic group in which at least one hydrogen atom in the -NH2 group of an amide group is replaced by an alkyl group, and "arylamide group" refers to an organic group in which at least one hydrogen atom in the -NH2 group of an amide group is replaced by an aryl group. The alkyl group in the alkylamide group and the aryl group in the arylamide group may be the same as the aforementioned examples of alkyl and aryl groups, but are not limited thereto.

[0082] Furthermore, the term "alkylidene" as used in this invention refers to a divalent aliphatic hydrocarbon group from which two hydrogen atoms are removed from the same carbon atom of an alkyl group, including ethoxylide, propyleneide, isopropyleneide, butylidene, pentoxylide, etc., but is not limited thereto.

[0083] Furthermore, the term "acetal" as used in this invention refers to an organic group formed by the combination of an alcohol and an aldehyde, that is, a substituent having two ether (-OR) bonds on one carbon atom, including methoxymethoxy, 1-methoxyethoxy, 1-methoxypropoxy, 1-methoxybutoxy, 1-ethoxyethoxy, 1-ethoxypropoxy, 1-ethoxybutoxy, 1-(n-butoxy)ethoxy, 1-(isobutoxy)ethoxy, 1-(sec-butoxy)ethoxy, 1-(tert-butoxy)ethoxy, 1-(cyclohexyloxy)ethoxy, 1-methoxy-1-methylmethoxy, 1-methoxy-1-methylethoxy, etc., but not limited thereto.

[0084] Furthermore, the term "ether" as used in this invention refers to an organic group having at least one ether bond (-O-), including, but not limited to, 2-methoxyethyl, 2-ethoxyethyl, 2-butoxyethyl, 2-phenoxyethyl, 2-(2-methoxyethoxy)ethyl, 3-methoxypropyl, 3-butoxypropyl, 3-phenoxypropyl, 2-methoxy-1-methylethyl, 2-methoxy-2-methylethyl, 2-methoxyethyl, 2-ethoxyethyl, 2-butoxyethyl, 2-phenoxyethyl, etc.

[0085] Furthermore, the term "silyl" as used in this invention refers to a -SiH3 radical derived from silane, wherein at least one hydrogen atom in the silyl group can be replaced by various organic groups such as alkyl or halogen groups, specifically including trimethylsilyl, triethylsilyl, tert-butyldimethylsilyl, vinyldimethylsilyl, propyldimethylsilyl, triphenylsilyl, diphenylsilyl, phenylsilyl, trimethoxysilyl, methyldimethoxysilyl, ethyldiethoxysilyl, triethoxysilyl, vinyldimethoxysilyl, triphenoxysilyl, etc., but not limited thereto.

[0086] Furthermore, the term "alkoxy" as used in this invention refers to an -O-alkyl radical, where "alkyl" is as defined above. Examples of such alkoxy radicals include, but are not limited to, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tert-butoxy, etc.

[0087] Furthermore, the term "halogen" as described in this invention refers to fluorine, chlorine, bromine, or iodine atoms.

[0088] Furthermore, the term "C" described in this invention n "" refers to the number of carbon atoms being n.

[0089] The present invention relates to a metallocene catalyst for polymerizing polyethylene, comprising: a transition metal compound A; a cocatalyst compound B; and a support C supporting the transition metal compound A and the cocatalyst compound B, wherein the transition metal compound A is a mixture of a first metallocene catalyst compound represented by the following chemical formula 1 and a second metallocene catalyst compound represented by the following chemical formula 2.

[0090] The transition metal compound is the main catalyst for metallocene catalysts used in the polymerization of polyethylene.

[0091] [Chemical Formula 1]

[0092]

[0093] In the above chemical formula 1,

[0094] M 1 It can be titanium (Ti), zirconium (Zr), or hafnium (Hf). Specifically, M can be zirconium (Zr).

[0095] X 1 It can be a halogen group, (C1-C) 20 )alkyl, (C2-C 20 )alkenyl, (C2-C 20 ) ynyl group, (C6-C 20 )Aryl, (C1-C 20 )alkyl (C6-C 20 )Aryl, (C6-C 20 )Aryl(C1-C 20 )alkyl, (C1-C 20 )alkylamide group, (C6-C 20 ) aryl amide group or (C1-C 20 Alkyl groups, specifically, X can be a halogen, more specifically, X can be chlorine (Cl).

[0096] R 1 and R 2 It can be a (C1-C6) alkyl group.

[0097] n and k can each be an integer from 0 to 2, and at least one of them is not 0. Specifically, n and k can each be 1 or 2.

[0098] [Chemical Formula 2]

[0099]

[0100] In the above chemical formula 2,

[0101] M 2It can be titanium (Ti), zirconium (Zr), or hafnium (Hf). Specifically, M can be zirconium (Zr).

[0102] X 2 It can be a halogen group, (C1-C) 20 )alkyl, (C2-C 20 )alkenyl, (C2-C 20 ) ynyl group, (C6-C 20 )Aryl, (C1-C 20 )alkyl (C6-C 20 )Aryl, (C6-C 20 )Aryl(C1-C 20 )alkyl, (C1-C 20 )alkylamide group, (C6-C 20 ) aryl amide group or (C1-C 20 Alkyl groups, specifically, X can be a halogen, more specifically, X can be chlorine (Cl).

[0103] Q can be carbon (C), silicon (Si), germanium (Ge), or tin (Sn). Specifically, Q can be carbon (C).

[0104] R 3 To R 7 Each can be independently substituted or unsubstituted (C1-C) 20 )alkyl, substituted or unsubstituted (C2-C 20 Alkenyl, substituted or unsubstituted (C6-C) 20 ) aryl, substituted or unsubstituted (C1-C 20 )alkyl (C6-C 20 ) aryl, substituted or unsubstituted (C6-C 20 )Aryl(C1-C 20 )alkyl, substituted or unsubstituted (C1-C 20 Heteroalkyl, substituted or unsubstituted (C3-C) 20 ) heteroaryl, substituted or unsubstituted (C1-C 20 )alkylamide group, substituted or unsubstituted (C6-C 20 ) aryl amide group, substituted or unsubstituted (C1-C 20 ) alkylidene or substituted or unsubstituted (C1-C 20 )silyl group, specifically, R 3 To R 7 Each can be independently substituted or unsubstituted (C1-C50) with an acetal or ether group. 20 )alkyl, acetal or ether substituted or unsubstituted (C2-C 20 Alkenyl, acetal or ether substituted or unsubstituted (C6-C) 20) aryl, acetal or ether substituted or unsubstituted (C1-C 20 )alkyl (C6-C 20 ) aryl, acetal or ether substituted or unsubstituted (C6-C 20 )Aryl(C1-C 20 )alkyl, acetal or ether substituted or unsubstituted (C1-C 20 Heteroalkyl groups, substituted or unsubstituted (C3-C4) acetal or ether groups 20 Heteroaryl, substituted or unsubstituted (C1-C5) acetal or ether group 20 Alkyl amide group, substituted with acetal or ether group or unsubstituted (C6-C) 20 ) aryl amide group, substituted or unsubstituted with acetal or ether group (C1-C 20 Alkyl groups, substituted with or unsubstituted acetal or ether groups (C1-C4) 20 )silyl,

[0105] Specifically, R 3 It can be (C1-C) 20 )alkyl, more specifically, R 3 It can be (C1-C6) alkyl, more specifically, R 3 It can be n-butyl.

[0106] Specifically, R 4 and R 5 Each can be (C1-C) 20 )alkyl, more specifically, R 4 and R 5 Each can be a (C1-C6) alkyl group, more specifically, R 4 and R 5 Each can be a tert-butyl.

[0107] Specifically, R 6 and R 7 Each can be (C6-C) 20 )Aryl, more specifically, R 6 and R 7 Each can be a phenyl group.

[0108] R 3 To R 7 They can be connected to form a ring, specifically, R 3 To R 7 Each can independently connect with adjacent groups to form substituted or unsubstituted saturated or unsaturated C4-C groups. 20 The ring, more specifically, R 3 To R 7 Each can independently connect with adjacent groups to form saturated or unsaturated C4-C groups that are substituted or unsubstituted with acetal or ether groups.20 ring,

[0109] m, l, and y can each be an integer from 0 to 4, specifically, m, l, and y can each be 1.

[0110] The first metallocene catalyst compound represented by the above chemical formula 1 can be represented by the following chemical formula 1-1.

[0111] [Chemical Formula 1-1]

[0112]

[0113] The second metallocene catalyst compound represented by the above chemical formula 2 can be represented by the following chemical formula 2-1.

[0114] [Chemical Formula 2-1]

[0115]

[0116] The cocatalyst compound B may be at least one selected from chemical formulas 3 to 5 below.

[0117] [Chemical Formula 3]

[0118]

[0119] In the above chemical formula 3,

[0120] p is an integer greater than 2.

[0121] Ra is a halogen group; or a group that is substituted or unsubstituted with a halogen group (C1-C2). 20 ) hydrocarbon group,

[0122] [Chemical Formula 4]

[0123]

[0124] In the above chemical formula 4,

[0125] Q is aluminum or boron.

[0126] Rb can be the same as or different from each other, each being an independent halogen group; or substituted or unsubstituted (C1-C2) halogen groups. 20 ) hydrocarbon group,

[0127] [Chemical Formula 5]

[0128]

[0129] In the above chemical formula 5,

[0130] [W] +It is a cationic Lewis acid; or a cationic Lewis acid bonded to a hydrogen atom.

[0131] Z is a Group 13 element.

[0132] Rc may be the same as or different from each other, and each is independently selected from halogen groups, (C1-C2). 20 ) substituted with one or more of the following groups: hydrocarbon group, alkoxy group, and phenoxy group (C6-C) 20 ) aryl; or selected from halogen groups, (C1-C 20 ) substituted with one or more of the following groups: hydrocarbon group, alkoxy group, and phenoxy group (C1-C2). 20 )alkyl.

[0133] The cocatalyst compound, together with the transition metal compound, is included in the catalyst composition to activate the transition metal compound. Specifically, in order to make the transition metal compound an active catalyst component for olefin polymerization, ligands (Q1Q2) in the transition metal compound can be extracted to cationize the central metal (M), while compounds containing units represented by chemical formula 3, compounds represented by chemical formula 4, and compounds represented by chemical formula 5, which act as counterions (i.e., anions) with weak binding forces, work together as cocatalysts.

[0134] The “unit” represented by the above chemical formula 3 is a structure in the compound in which n structures are connected within [ ]. As long as it contains a unit represented by chemical formula 3, there are no special restrictions on other structures in the compound. It can be a cluster-type compound formed by the interconnection of repeating units of chemical formula 3, such as a spherical compound.

[0135] Compounds containing a unit represented by Formula 3 are not particularly limited, but alkylaluminoxanes are preferred. Non-limiting examples include methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, butylaluminoxane, etc. Methylaluminoxane is preferred due to the reactivity of the transition metal compounds.

[0136] Furthermore, the compounds represented by the above-mentioned chemical formula 4 are alkyl metal compounds, and there are no particular limitations. Non-limiting examples include trimethylaluminum, triethylaluminum, triisobutylaluminum, tripropylaluminum, tributylaluminum, dimethylaluminum chloride, triisopropylaluminum, trisec-butylaluminum, tricyclopentylaluminum, tripentylaluminum, triisopentylaluminum, trihexylaluminum, trioctylaluminum, ethyldimethylaluminum, methyldiethylaluminum, triphenylaluminum, tri-p-tolylaluminum, dimethylmethoxyaluminum, dimethylethoxyaluminum, trimethylboron, triethylboron, triisobutylboron, tripropylboron, tributylboron, etc. Considering the activity of the aforementioned transition metal compounds, it is preferable to use one or more of trimethylaluminum, triethylaluminum, and triisobutylaluminum.

[0137] Considering the reactivity of the transition metal compounds, in the compound represented by chemical formula 5, when the [W] + When it is a Lewis acid with a cationic bond to a hydrogen atom, [W] + It is a dimethylphenylamine cation; when [W] + When it is a cationic Lewis acid, [W] + [(C6H5)3C] + ; and the aforementioned [Z(Rc)4] - The preferred option is [B(C6F5)4] - .

[0138] There are no particular restrictions on compounds represented by chemical formula 5, but when [W]... + When it is a cationic Lewis acid that bonds to a hydrogen atom, non-limiting examples include: triethylammonium tetraphenylborate, tributylammonium tetraphenylborate, trimethylammonium tetraphenylborate, tripropylammonium tetraphenylborate, trimethylammonium tetra(p-tolyl)borate, tripropylammonium tetra(p-tolyl)borate, trimethylammonium tetra(o-,p-dimethylphenyl)borate, triethylammonium tetra(o-,p-dimethylphenyl)borate, tributylammonium tetra(p-trifluoromethylphenyl)borate, and trimethylammonium tetra(p-trifluoromethylphenyl)borate. Tributylammonium tetra(pentafluorophenyl)borate, phenylammonium tetraphenylborate, phenylammonium tetra(pentafluorophenyl)borate, N,N-dimethylphenylammonium tetra(pentafluorophenyl)borate, N,N-diethylphenylammonium tetraphenylborate, N,N-diethylphenylammonium tetrapentafluorophenylborate, diethylammonium tetrapentafluorophenylborate, triphenylphosphine tetraphenylborate, trimethylphosphine tetraphenylborate, triphenylcarbamonium tetra(p-trifluoromethylphenyl)borate, triphenylcarbamonium tetrapentafluorophenylborate, dimethylphenylammonium tetra(pentafluorophenyl)borate, etc.

[0139] In the metallocene catalyst for polymerizing polyethylene of the present invention, the first metallocene catalyst compound and the second metallocene catalyst compound may be present in a molar ratio of 10:1 to 50:1.

[0140] On the other hand, in this invention, a transition metal compound represented by chemical formula 1, or a transition metal compound and a cocatalyst compound, can be loaded onto a support. As the support, inorganic or organic materials commonly used for preparing catalysts can be used without restriction, such as silica (SiO2), alumina (Al2O3), magnesium oxide (MgO), magnesium chloride (MgCl2), calcium chloride (CaCl2), zirconium oxide (ZrO2), titanium oxide (TiO2), boron trioxide (B2O3), calcium oxide (CaO), zinc oxide (ZnO), barium oxide (BaO), thorium dioxide (ThO2), silica-alumina (SiO2-Al2O3), silica-magnesium oxide (SiO2-MgO), silica-titanium oxide (SiO2-TiO2), silica-vanadium pentoxide (SiO2-V2O5), silica-chromium oxide (SiO2-Cr2O3), silica-titanium oxide-magnesium oxide (SiO2-TiO2-MgO), bauxite, zeolite, starch, cyclodextrin, synthetic polymers, etc. Preferably, the carrier can be silica (SiO2), alumina (Al2O3), magnesium chloride (MgCl2), or a mixture thereof, which have micropores on their surface or inside and a large surface area. Alternatively, the carrier can be a carrier containing hydroxyl groups on its surface, and can be one or more carriers selected from silica, silica-alumina, and silica-magnesium oxide.

[0141] Methods for loading transition metal compounds and cocatalyst compounds onto a support may include: directly loading the transition metal compound onto a dehydrated support; pretreating the support with the cocatalyst compound before loading the transition metal compound; loading the transition metal compound onto the support and then performing post-treatment with the cocatalyst compound; or reacting the transition metal compound with the cocatalyst compound before adding the support for further reaction.

[0142] The solvents that can be used in the loading method can be aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, halogenated aliphatic hydrocarbon solvents, or mixtures thereof. Non-limiting examples of aliphatic hydrocarbon solvents include: pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, etc. Non-limiting examples of aromatic hydrocarbon solvents include: benzene, monochlorobenzene, dichlorobenzene, trichlorobenzene, toluene, etc. Non-limiting examples of halogenated aliphatic hydrocarbon solvents include: dichloromethane, trichloromethane, dichloroethane, trichloroethane, etc.

[0143] Furthermore, the process of loading the transition metal compound and the cocatalyst compound onto the support can be carried out at a temperature of -70 to 200°C, preferably -50 to 150°C, and more preferably 0 to 100°C, which is beneficial to the efficiency of the loading process.

[0144] In the transition metal catalyst composition of the present invention, the transition metal compound can be used as a homogeneous catalyst or a supported catalyst. That is, it can be used as a homogeneous catalyst in which the transition metal compound and the reactants react in the same phase, or it can be used as a heterogeneous catalyst in which the transition metal compound and the reactants react in different phases. In the transition metal catalyst composition, the transition metal compound is supported on a support and used as a supported catalyst in a dispersed form.

[0145] The method for preparing polyolefins according to the present invention includes the step of polymerizing olefin monomers in the presence of a transition metal catalyst composition containing the transition metal compound.

[0146] The transition metal catalyst composition containing the aforementioned transition metal compound is the same as described above.

[0147] The olefin monomer may be ethylene, propylene, 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, norbornene, norbornediene, ethylidene norbornene, phenyl norbornene, vinyl norbornene, dicyclopentadiene, 1,4-butadiene, 1,5-pentadiene, 1,6-hexadiene, styrene, α-methylstyrene, divinylbenzene, 3-chloromethylstyrene, or mixtures thereof.

[0148] In this invention, the polymer generated by a polymerization process involving direct contact between olefin monomer compounds can be prepared via olefin polymerization under conditions where the catalyst site is relatively insoluble and / or immobilized, thereby allowing the polymer chains to be rapidly immobilized based on this information. This immobilization can be achieved, for example, by using a solid insoluble catalyst, conducting polymerization in a medium in which the resulting polymer is typically insoluble, and maintaining the polymerization reactants and products at the polymer's crystallization temperature (Tc). c The following will proceed.

[0149] The aforementioned catalyst can preferably be used for the copolymerization of olefin monomers, and more preferably for the copolymerization of ethylene or propylene. The following describes a method for preparing polyethylene that includes the step of polymerizing olefin monomers under the aforementioned catalyst.

[0150] Olefin polymerization processes are well known in the art, including liquid-phase polymerization, solution polymerization, slurry polymerization, and low-pressure gas-phase polymerization. Metallocene catalysts are particularly suitable for known operating methods using fixed-bed, moving-bed, or slurry processes in single, series, or parallel reactors.

[0151] When the polymerization reaction is carried out in a liquid phase or a slurry phase, a solvent or the propylene or ethylene monomer itself can be used as a medium.

[0152] The solvents that can be used in the polymerization reaction can be aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, halogenated aliphatic hydrocarbon solvents, or mixtures thereof. Non-limiting examples of aliphatic hydrocarbon solvents include: butane, isobutane, pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, cyclopentane, methylcyclopentane, cyclohexane, etc. Non-limiting examples of aromatic hydrocarbon solvents include: benzene, monochlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, chlorobenzene, etc. In addition, non-limiting examples of the halogenated aliphatic hydrocarbon solvents may include: dichloromethane, trichloromethane, chloroethane, 1,2-dichloroethane, etc.

[0153] In this invention, polyolefins can be prepared by polymerizing olefin monomers in the presence of the catalyst. In this case, the transition metal compound and the co-catalyst component can be added to the reactor separately, or the components can be pre-mixed before being added to the reactor; there are no particular restrictions on the order of addition, temperature, concentration, or other mixing conditions. In this invention, the polyolefin can be, for example, polyethylene.

[0154] On the other hand, in the polymerization reaction of the present invention, the amount of catalyst added can be determined within a range that allows the monomer polymerization reaction to occur sufficiently, depending on whether the process is slurry-phase, liquid-phase, gas-phase, or solution-phase, and therefore there is no particular limitation. However, based on the concentration of the central metal (M) of the transition metal compound in a unit volume (L) of monomer, the amount of catalyst added is preferably 10. -8 ~1 mol / L, more preferably 10 -7 ~10 -1 mol / L, more preferably 10 mol / L -7 ~10 -2 mol / L.

[0155] Furthermore, the polymerization reaction of the present invention can be a batch type, a semi-continuous type, or a continuous type reaction, preferably a continuous type reaction.

[0156] In this invention, the temperature and pressure conditions of the polymerization reaction can be determined based on the type of reaction and reactor used, taking into account the efficiency of the polymerization reaction. The polymerization temperature can be 40~150℃, preferably 60~100℃, and the pressure can be 1~100 atmospheres, preferably 5~50 atmospheres.

[0157] More specifically, the polyethylene preparation method of the present invention involves reacting ethylene with one or more olefin monomers in the presence of a metallocene catalyst used for polymerizing polyethylene to prepare a polyethylene copolymer. The olefin monomers may be selected from (C2-C4) 20 α-olefins, (C4-C) 20 (C3-C) dienes, (C3-C) 20 ) cyclic olefins, (C3-C 20 The olefin monomer can be a cyclodiene, styrene, or styrene derivative thereof. More specifically, the olefin monomer may be an (C3-C8) α-olefin.

[0158] According to the present invention, a film prepared using polyethylene with improved transparency is provided. Specifically, a film having an elasticity index of 20 or higher and improved transparency is provided. More specifically, a mLLDPE film having an elasticity index of 20 or higher and less than 40 and improved transparency is provided.

[0159] RSS (Recovery Shear Strain) is a rheological property obtained by quantifying the elasticity of a rubber-like liquid. RSS is a rheological property relating to the recovery characteristics of a substance, and its value can be measured through recovery experiments. For example, an approximation of RSS can be obtained through a Small Amplitude Oscillation Shear (SAOS) experiment. The RSS (Recovery Shear Strain, γ∞) can be approximated in the low-shear region using the Cox-Merz rule and the following mathematical formula 2. To minimize the error of this approximation, a value in the low-shear region (ω = 0.01~0.05) can be taken. By adjusting ω to 0.01~0.05, a γ∞ value of 0.01~0.1 can be obtained.

[0160] [Mathematical Expression 2]

[0161]

[0162] Complex viscosity (η)* The energy modulus (η) and storage modulus (G') can be measured using a rheological property analysis device called a rotation rheometer via the SAOS (Small Amplitude Oscillation Shear) test. The SAOS test provides data for η(ω) and G' in the form of a graphical function based on angular frequency (ω).

[0163] Complex viscosity (η) * The Complex Viscosity is fitted using the following mathematical formula 3 (Carreau-Yasuda model). The Carreau-Yasuda model is a graphical model formula for η(ω) based on angular frequency (ω).

[0164] [Mathematical Expression 3]

[0165]

[0166] η(ω): viscosity function; η0(Pa·s): zero shear viscosity; λ(s): relaxation time; ω(Rad / s): angular frequency; n: shear thinning index; a: fit index.

[0167] By fitting the mathematical formula 3 based on angular frequency (ω) and the graphical data to the model formula using Excel's solver function, the variables λ, n, and a can be obtained.

[0168] The storage modulus (G') value was fitted using the following mathematical formula 4 (Maxwell model). The Maxwell model is a model formula that matches well with the graph of G' based on angular frequency (ω).

[0169] [Mathematical Expression 4]

[0170]

[0171] n: the number of Maxwell equation modes; g i (Pa): Platform modulus; λ i (s): Relaxation time; ω(Rad / s): angular frequency.

[0172] By fitting the mathematical formula 4 based on angular frequency (ω) and the graphical data to the model formula using Excel's solver function, g can be obtained. i and λ i (i=1~7).

[0173] The elasticity index is the value of the RSS (Recovery Shear Strain) multiplied by 1000. In this invention, the value of the RSS multiplied by 1000 is used as the elasticity index, which is used as an indicator to predict the elasticity and film processing properties (haze) of the corresponding resin.

[0174] [Mathematical Expression 1]

[0175] Elasticity index = RSS × 1000

[0176] The RSS multiplied by 1000 equals the elasticity index, which ranges from 10 to 100 for the corresponding membrane product group. As the RSS value increases, the melt elasticity of the resin increases. Therefore, during membrane molding, it exhibits a fibrous crystalline structure rather than a spherulitic crystalline structure, thus reducing the surface roughness of the membrane. Consequently, it is known that increasing the RSS value reduces haze, thereby improving molding quality.

[0177] The haze of a membrane represents its turbidity and can be measured using an instrument called a haze meter. The elasticity index is inversely correlated with haze. Therefore, the elasticity index can also be used as a method to predict haze.

[0178] Example

[0179] The present invention will now be described in more detail through examples of the synthesis and polymerization of metallocene catalysts. However, the following examples are merely one illustration of the invention, and the invention is not limited thereto.

[0180] <Examples of metallocene catalyst preparation>

[0181] All synthetic reactions were carried out in an inert atmosphere, such as nitrogen or argon, using standard Schlenk techniques and glove box techniques.

[0182] After purchasing anhydrous grade toluene from Sigma-Aldrich, it is further dried by passing it through an activated molecular sieve (4A) or an activated alumina layer before use.

[0183] MAO (methylaluminoxane) was prepared using a 10% toluene solution (HS-MAO-10%) purchased from Albemarle; silica was prepared using Grace's XPO24O2, used directly without any additional treatment.

[0184] In addition, bis(1-butyl-3-methylcyclopentadienyl)zirconium dichloride and diphenylmethylene(n-Butyl-Cyclopentadienyl)(2,7-di-t-Butyl-9-Fluorenyl)zirconium dichloride are purchased and used directly without purification.

[0185] Bis(1-butyl-3-methylcyclopentadienyl)zirconia dichloride is shown in Formula 6, and diphenylmethylene(n-butyl-cyclopentadienyl)(2,7-di-tert-butyl-9-fluorenyl)zirconia dichloride is shown in Formula 7.

[0186] [Chemical Formula 6]

[0187]

[0188] [Chemical Formula 7]

[0189]

[0190] Bis(1-butyl-3-methylcyclopentadienyl)zirconia was purchased from W.RGrace, and diphenylmethylene(n-butyl-cyclopentadienyl)(2,7-di-tert-butyl-9-fluorenyl)zirconia was purchased from MCN.

[0191] [Synthesis example 1]

[0192] Inside a glove box, 1 g of silica was placed into a round-bottom flask and then removed from the glove box. 10 mL of toluene was added at room temperature to prepare a silica slurry. After cooling the silica slurry to 0°C, 8 mL of MAO (methylaluminoxane) was slowly added to the silica slurry, and the mixture was stirred for 1 hour. The temperature was then raised to 70°C and reacted for another 4 hours to prepare a silica slurry. The resulting silica slurry was then cooled to 0°C again.

[0193] Inside a glove box, a mixture was prepared by mixing bis(1-butyl-3-methylcyclopentadienyl)zirconia dichloride and diphenylmethylene(n-butyl-cyclopentadienyl)(2,7-di-tert-butyl-9-fluorenyl)zirconia dichloride at a molar ratio of 30:1. 100 µmol of the mixture was placed into a Schlenk flask, and after being removed from the glove box, 10 mL of toluene was added to the Schlenk flask to completely dissolve it, yielding a catalyst compound solution.

[0194] The obtained catalyst compound solution was slowly added to the silica slurry at room temperature, and then the temperature was raised to 70°C and reacted for 1 hour. Afterward, the temperature was lowered to room temperature, stirring was stopped, the toluene layer was separated and removed, and then the mixture was washed three times with n-hexane before all solvents were removed under vacuum.

[0195] This yielded a pale yellow, free-flowing powder catalyst 1. The Zr loading of the obtained catalyst 1 was confirmed to be 0.4 wt%, and the Al loading was 13.0 wt%.

[0196] [Synthesis example 2]

[0197] Catalyst 2 was obtained by the same method as in Synthesis Example 1, except that bis(1-butyl-3-methylcyclopentadienyl)zirconia dichloride was used alone instead of the mixture of bis(1-butyl-3-methylcyclopentadienyl)zirconia dichloride and diphenylmethylene(n-butyl-cyclopentadienyl)(2,7-di-tert-butyl-9-fluorenyl)zirconia dichloride mixed in a molar ratio of 30:1.

[0198] <Preparation of Polyethylene Copolymers>

[0199] [Example 1]

[0200] The catalyst 1 was loaded into a thoroughly dried, dedicated catalyst loading tank (1.5L, SUS) and transported to the pilot plant under a nitrogen atmosphere. Then, it was pushed into a catalyst tank (V-2400, a pilot-scale metallocene catalyst tank) containing a measured amount of mineral oil, diluted to 1.5 wt%. The mineral oil used was Shell Ondina 68 from Yeosu Oil, Korea. The catalyst delivery operation was carried out by repeatedly purging the Teflon pipelines and valves to ensure it was conducted under a high-purity nitrogen (HPN) atmosphere.

[0201] Operating conditions were set at a reactor temperature of 85℃, a total pressure of 22 K / G, and an ethylene partial pressure of 12.1 K / G (ethylene concentration of 55 mol%). Polyethylene copolymer production was achieved by adjusting the input ratios of C6 / C2 and H2 / C2. The catalyst input was adjusted by monitoring the output to maintain a bed weight of 45-50 kg and a powder discharge rate of 7-8 kg / hr.

[0202] [Comparative Example 1]

[0203] The polyethylene copolymer was prepared using the same method as in Example 1, except that catalyst 2 was used instead of catalyst 1.

[0204] [Comparative Example 2]

[0205] Commercially available polyethylene copolymer (DL Chem, XP9200E) was used.

[0206] <Analytical Methods for Polyethylene Copolymers>

[0207] The physical properties of polyethylene copolymers were measured according to the following method and are shown in [the figure]. Figure 1 , Figure 2 And in Table 1.

[0208] (1) Molecular weight (Mn, Mw, Mz), molecular weight distribution (MWD), Mz / Mn ratio (MZD)

[0209] Number-average molecular weight (Mn), weight-average molecular weight (Mw), and z-average molecular weight (Mz) were measured using an Agilent PL-GPC220 gel permeation chromatography (GPC) instrument.

[0210] The molecular weight distribution (MWD) is calculated by dividing the weight-average molecular weight (Mw) by the number-average molecular weight (Mn).

[0211] The Mz / Mn value (Molecular z-Averageweight Distribution, MZD) is calculated by dividing the z-average molecular weight (Mz) by the number-average molecular weight (Mn).

[0212] (2) Melting point (Tm), crystallization temperature (Tc), and enthalpy of fusion (ΔH)

[0213] Melting point (Tm), crystallization temperature (Tc), and enthalpy of fusion (ΔH) were measured using a TA Q-200 differential scanning calorimeter (DSC).

[0214] (3) Melt index (MI) and melt flow rate ratio (MFRR)

[0215] According to ASTM D1238, the melt flow index (MI) is measured at 190°C and a load of 2.16 kg. 2.16 The high-load melt flow index (MI) was measured at 190℃ and 21.6kg load. 21.6 ).

[0216] The high load melt index (MI) 21.6 Divide by the melt flow index (MI) 2.16 Calculate the melt flow rate ratio (MFRR).

[0217] (4) Content of low molecular weight components and high molecular weight components

[0218] The content of components is obtained from the molecular weight distribution obtained by GPC using a peak fitting analysis program.

[0219] (5) BOCD Index and Short Chain Branch (SCB) Content

[0220] The weight-average molecular weight and SCB content of the copolymer were measured using a cross-fractionation chromatography (CFC) instrument from PolymerChar. Based on the weight-average molecular weight (Mw), the SCB (short-chain branching content in the high molecular weight component) in the top 30% and the SCB (short-chain branching content in the low molecular weight component) of the copolymer weight were substituted into Equation 5 below to calculate the BOCD index (Broad Orthogonal Comonomer Distribution Index). SCB represents short-chain branching.

[0221] [Mathematical Expression 5]

[0222] BOCD index = (Short-chain branching content in high molecular weight component - Short-chain branching content in low molecular weight component) / (Short-chain branching content in low molecular weight component)

[0223] [Table 1]

[0224]

[0225] Compared to Comparative Example 1, it can be confirmed that the number-average molecular weight (Mn) and weight-average molecular weight (Mw) of Example 1 are higher. In particular, the z-average molecular weight (Mz) of Comparative Example 1 is only 201,953 g / mol, while the z-average molecular weight (Mz) of Example 1 is 223,006 g / mol. Furthermore, the MZD of Comparative Example 1 is only 4.28, while the MZD of Example 1 is significantly higher at 5.02. The BOCD index of Example 1 is 0.08, while the BOCD index of Comparative Example 1 is 0.03. In Example 1, it can be confirmed that the increase in the content of comonomers in the high molecular weight region due to the change in catalyst leads to an increase in the BOCD index.

[0226] <Preparation and Property Analysis of Membranes>

[0227] Films were prepared using the polyethylene copolymers of Example 1, Comparative Example 1, and Comparative Example 2. The physical properties of the films were measured according to the methods described below and are shown in Tables 2 and 3. Figure 3 middle.

[0228] (1) Calculation of RSS (Recovery Shear Strain, γ∞) value

[0229] The RSS (Recovery Shear Strain, γ∞) value is obtained through the following mathematical formula 2, using the complex viscosity (η). * The physical properties of Complex Viscosity (G', Storage Modulus) and Storage Modulus (G', Storage Modulus) are calculated.

[0230] [Mathematical Expression 2]

[0231]

[0232] Complex viscosity (η) * The energy storage modulus (G') and the energy storage modulus (η) were measured using a rheological property analysis device called a rotation rheometer via a SAOS (Small Amplitude Oscillation Shear) test. The SAOS test yielded data for η(ω) and G' in the form of a graph based on the angular frequency (ω).

[0233] Complex viscosity (η) * The Complex Viscosity is fitted using the following mathematical formula 3 (Carreau-Yasuda model). The Carreau-Yasuda model is a graphical model formula for η(ω) based on angular frequency (ω).

[0234] [Mathematical Expression 3]

[0235]

[0236] η(ω): viscosity function; η0(Pa·s): zero shear viscosity; λ(s): relaxation time; ω(Rad / s): angular frequency; n: shear thinning index; a: fit index.

[0237] By fitting the mathematical formula 3 based on angular frequency (ω) and the graphical data to the model formula using Excel's solver function, the variables λ, n, and a can be obtained.

[0238] The storage modulus (G') value was fitted using the following mathematical formula 4 (Maxwell model). The Maxwell model is a model formula that matches well with the graph of G' based on angular frequency (ω).

[0239] [Mathematical Expression 4]

[0240]

[0241] n: the number of Maxwell equation modes; g i (Pa): Platform modulus; λ i (s): Relaxation time; ω (Rad / s): Angular frequency

[0242] The mathematical formula 4 based on angular frequency (ω) and the graphical data were fitted to the model formula using Excel's solver function to obtain g. i and λ i (i=1~7).

[0243] For Example 1, Comparative Example 1, and Comparative Example 2, when ω = 0.03 Rad / s, the values ​​of η and G' were calculated using mathematical formulas 3 and 4, respectively, and are shown in Table 3. The values ​​of η and G' were calculated using their respective formulas. * The results of calculating the RSS value of Formula 1 using the G' value confirm that Example 1, Comparative Example 1, and Comparative Example 2 have RSS values ​​of 0.0227, 0.0106, and 0.0125, respectively. The elasticity index corresponding to multiplying the RSS value by 1000 is shown in Table 3.

[0244] [Mathematical Expression 1]

[0245] Elasticity index = RSS × 1000

[0246] (2) Density

[0247] According to ASTM D1505, the density gradient tube method is used for measurement.

[0248] (3) Resin pressure, speed, and load

[0249] Extrusion data during film forming was measured using Shin Kwang's LLDPE blown film forming equipment.

[0250] (4) Tensile strength (Break) and elongation

[0251] Using Instron equipment, measurements were taken in the machine direction (MD) and width direction (TD) according to ASTM D638.

[0252] (5) Elemendorf tear strength

[0253] Elemendorf measuring equipment was used in both the machine direction (MD) and width direction (TD) to perform measurements according to ASTM D1922.

[0254] (6) Dart Impact

[0255] Measurements were taken using a dart impact tester according to ASTM D1709 Method A.

[0256] (7) Haze

[0257] After the film is formed to a thickness of 30 μm, it is measured using a haze meter according to the ASTM D1003 test method. Specifically, the haze can be calculated using the following formula.

[0258] [Mathematical Expression 6]

[0259] Haze (%) = T d (diffuse transmission light) / T t (Total transmitted light) × 100%

[0260] [Table 2]

[0261]

[0262] [Table 3]

[0263]

[0264] It can be confirmed that the haze value of the film prepared by Example 1 is significantly low, at 20%. The polyethylene copolymer of Example 1 has a high molecular weight and molecular weight distribution (MWD), and it is believed that this increase in molecular weight leads to the improvement in film transparency.

Claims

1. A metallocene catalyst for polymerizing polyethylene, comprising: Transition metal compound A; Co-catalyst compound B; as well as The support C on which the transition metal compound A and the cocatalyst compound B are loaded. The transition metal compound A is a mixture of a first metallocene catalyst compound represented by the following chemical formula 1 and a second metallocene catalyst compound represented by the following chemical formula 2. [Chemical Formula 1] In the above chemical formula 1, M 1 Is it titanium (Ti), zirconium (Zr), or hafnium (Hf)? X 1 It is a halogen group, (C1-C 20 )alkyl, (C2-C 20 )alkenyl, (C2-C 20 ) ynyl group, (C6-C 20 )Aryl, (C1-C 20 )alkyl (C6-C 20 )Aryl, (C6-C 20 )Aryl(C1-C 20 )alkyl, (C1-C 20 )alkylamide group, (C6-C 20 ) aryl amide group or (C1-C 20 ) alkylidene group, R 1 and R 2 It is a (C1-C6) alkyl group. n and k are each integers between 0 and 2, and at least one of them is not 0. [Chemical Formula 2] In the above chemical formula 2, M 2 Is it titanium (Ti), zirconium (Zr), or hafnium (Hf)? X 2 It is a halogen group, (C1-C 20 )alkyl, (C2-C 20 )alkenyl, (C2-C 20 ) ynyl group, (C6-C 20 )Aryl, (C1-C 20 )alkyl (C6-C 20 )Aryl, (C6-C 20 )Aryl(C1-C 20 )alkyl, (C1-C 20 )alkylamide group, (C6-C 20 ) aryl amide group or (C1-C 20 ) alkylidene group, Q is carbon (C), silicon (Si), germanium (Ge), or tin (Sn). R 3 To R 7 Each is independently either substituted or unsubstituted (C1-C) 20 )alkyl, substituted or unsubstituted (C2-C 20 Alkenyl, substituted or unsubstituted (C6-C) 20 ) aryl, substituted or unsubstituted (C1-C 20 )alkyl (C6-C 20 ) aryl, substituted or unsubstituted (C6-C 20 )Aryl(C1-C 20 )alkyl, substituted or unsubstituted (C1-C 20 Heteroalkyl, substituted or unsubstituted (C3-C) 20 ) heteroaryl, substituted or unsubstituted (C1-C 20 )alkylamide group, substituted or unsubstituted (C6-C 20 ) aryl amide group, substituted or unsubstituted (C1-C 20 ) alkylidene or substituted or unsubstituted (C1-C 20 )silyl, R 3 To R 7 Each can independently connect with adjacent groups to form substituted or unsubstituted saturated or unsaturated C4-C groups. 20 ring, m, l, and y are each integers from 0 to 4.

2. The metallocene catalyst for polymerizing polyethylene according to claim 1, wherein, In the above chemical formula 1, M is zirconium (Zr), X is a halogen, and R... 1 and R 2 It is a (C1-C6) alkyl group, where n and k are 1 or 2 respectively. In the above chemical formula 2, M is zirconium (Zr), X is a halogen, Q is carbon (C), and R is... 3 To R 5 It is unsubstituted (C1-C) 20 )alkyl, R 6 and R 7 It is unsubstituted (C6-C) 20 )Aryl, m, l and y are each 1.

3. The metallocene catalyst for polymerizing polyethylene according to claim 1, wherein, The first metallocene catalyst compound represented by the above chemical formula 1 is represented by the following chemical formula 1-1. The second metallocene catalyst compound represented by the above chemical formula 2 is represented by the following chemical formula 2-1. [Chemical Formula 1-1] [Chemical Formula 2-1] 。 4. The metallocene catalyst for polymerizing polyethylene according to claim 1, wherein, The cocatalyst compound B is selected from at least one of the following chemical formulas 3 to 5. [Chemical Formula 3] In the above chemical formula 3, p is an integer greater than 2. Ra is a halogen group; or a group that is substituted or unsubstituted with a halogen group (C1-C2). 20 ) hydrocarbon group, [Chemical Formula 4] In the above chemical formula 4, Q is aluminum or boron. Rb may be the same as or different from each other, each being an independent halogen group; or may be substituted or unsubstituted by halogen groups (C1-C2). 20 ) hydrocarbon group, [Chemical Formula 5] In the above chemical formula 5, [W] + It is a cationic Lewis acid; or a cationic Lewis acid bonded to a hydrogen atom. Z is a Group 13 element. Rc may be the same as or different from each other, and each is independently selected from halogen groups, (C1-C2). 20 ) substituted with one or more of the following groups: hydrocarbon group, alkoxy group, and phenoxy group (C6-C) 20 ) aryl; or selected from halogen groups, (C1-C 20 ) substituted with one or more of the following groups: hydrocarbon group, alkoxy group, and phenoxy group (C1-C2). 20 )alkyl.

5. The metallocene catalyst for polymerizing polyethylene according to claim 1, wherein, The first metallocene catalyst compound and the second metallocene catalyst compound exist in a molar ratio of 10:1 to 50:

1.

6. The metallocene catalyst for polymerizing polyethylene according to claim 1, wherein, The carrier C is silica (SiO2), alumina (Al2O3), magnesium chloride (MgCl2), or a mixture thereof that has micropores on its surface or inside.

7. A method for preparing a polyethylene copolymer, wherein ethylene is reacted with an olefin monomer in the presence of a metallocene catalyst for polymerizing polyethylene as described in any one of claims 1 to 6 to prepare the polyethylene copolymer.

8. The method for preparing polyethylene copolymer according to claim 7, wherein, The olefin monomer is selected from (C2-C4). 20 α-olefins, (C4-C) 20 (C3-C) dienes, (C3-C) 20 ) cyclic olefins, (C3-C 20 Among cyclodienes, styrene and styrene derivatives.

9. The method for preparing polyethylene copolymer according to claim 7, wherein, The olefin monomer is an (C3-C8) α-olefin.

10. A polyethylene copolymer prepared by the preparation method of claim 7.

11. The polyethylene copolymer according to claim 10, wherein the Mz / Mn value of the polyethylene copolymer is 4.5 or more and 6 or less, and the density is 0.90 g / cm³. 3 Above and 0.935 g / cm 3 The following are melt flow rate ratios (MFRR) of 10 or higher and 40 or lower according to ASTM D1238.

12. A membrane prepared using the polyethylene copolymer of claim 10.

13. The membrane according to claim 12, wherein the elastic index calculated by the following mathematical formulas 1 to 4 is 20 or more and 40 or less, and the BOCD index calculated by the following mathematical formula 5 is 0 or more and 3.0 or less. [Mathematical Expression 1] Elasticity index = RSS × 1000 In the above mathematical formula 1, RSS is the recovered shear strain γ. ∞ And calculated by mathematical formula 2, [Mathematical Expression 2] In the above mathematical formula 2, γ ∞ It is the recovery of shear strain RSS, η * G is the complex viscosity, calculated by the following mathematical formula 3; G' is the storage modulus, calculated by the following mathematical formula 4; ω is the angular frequency and is an arbitrary variable, wherein the unit of ω is Rad / s. [Mathematical Expression 3] In the above mathematical formula 3, η0 is the zero shear viscosity, λ is the relaxation time, ω is the angular frequency, n is the shear thinning index, and a is the fitting index, wherein the units of η0, λ, and ω are Pa·s, s, and Rad / s, respectively. [Mathematical Expression 4] In the above mathematical formula 4, n is the number of Maxwell equation patterns, and g i It is the platform modulus, λ i It is the relaxation time, ω is the angular frequency, where g i The λ i The units of ω are Pa, s, and Rad / s, respectively. [Mathematical Expression 5] BOCD index = (short-chain branching content in high molecular weight component - short-chain branching content in low molecular weight component) / (short-chain branching content in low molecular weight component).

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