Polyethylene resin composition and biaxially stretched film comprising the same

Abstract

The present invention provides a polyethylene resin composition and a biaxially-stretched film comprising the same, which can prevent surface defects by improving melt fracture when manufacturing a biaxially-stretched film.

Description

Cross-references to related applications

[0001] This application is based on and claims priority to Korean Patent Application Nos. 10-2024-0044703 and 10-2025-0041093, filed on April 2, 2024 and March 31, 2025, respectively, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0002] The present invention relates to a polyethylene resin composition and a biaxially stretched film comprising the composition, wherein the composition can prevent surface defects by improving melt fracture during the manufacture of the biaxially stretched film. Background Technology

[0003] Shrink films made of linear low-density polyethylene (LLDPE) or high-density polyethylene (HDPE) are widely used in packaging such as shopping bags, food and specialty packaging, and industrial liners. In these applications, shrink films, which can wrap products and maintain their shape, are primarily used to protect products from touch during display.

[0004] In particular, among these shrink films, biaxially oriented polymer films possess excellent mechanical properties, production efficiency, and printability, thus finding widespread application in packaging. Commercially available packaging films typically use biaxially oriented polypropylene (BOPP), biaxially oriented polyethylene terephthalate (BOPET), or biaxially oriented polyamide (BOPA) as the printing layer and LLDPE as the sealing layer. These composite materials are not recyclable, and due to regulations on recycling packaging materials, the demand for single-material packaging films is growing. Therefore, research and development is underway to manufacture single-material packaging films by replacing the printed layer films with biaxially oriented polyethylene (BOPE) films.

[0005] However, commercially available polyethylene (PE) resins lack sufficient tensile stability, exhibiting cracking and melting during stretching, making them unsuitable for biaxial stretching processes. Therefore, to ensure tensile stability, a polyethylene resin composition containing a low-density, high melt index resin has been developed. However, this composition is unsuitable for use as a PE resin for biaxially stretched films due to its low stiffness, shrinkage, and impact resistance.

[0006] Therefore, it is necessary to develop a PE resin with a molecular structure that is conducive to stretching, thereby exhibiting excellent tensile stability when manufacturing biaxially stretched films, while also improving the surface properties of the film. Summary of the Invention

[0007] [Technical Issues] The present invention provides a polyethylene resin composition and a biaxially stretched film comprising the composition, wherein the composition can prevent surface defects by improving melt fracture during the manufacture of the biaxially stretched film.

[0008] [Technical Solution] The present invention provides a polyethylene resin composition comprising one or more polyethylenes and satisfying the following requirements (a1) to (a4): (a1) Melt flow rate ratio (MI) 21.6 / MI 2.16 (ASTM D1238, 190℃): 60 to 120; (a2) Density (ASTM D1505): 0.920 g / cm³ 3 Up to 0.950 g / cm 3 ; (a3) Molecular weight distribution: 5.50 to 15.00; (a4) When the logarithm of the weight-average molecular weight (Mw) (g / mol) obtained by gel permeation chromatography is used as the x-axis and the molecular weight distribution (dW / dlogMw) relative to the logarithm is used as the y-axis, the molecular weight distribution type is: single peak.

[0009] In addition, the present invention also provides a biaxially stretched film comprising the above-described polyethylene resin composition.

[0010] The polyethylene resin composition and biaxially stretched film according to embodiments of the present invention will now be described in detail.

[0011] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the invention.

[0012] The singular form is also intended to include the plural form, unless the context clearly indicates otherwise.

[0013] In this specification, terms such as “comprising,” “including,” or “having” are used to describe the features, quantities, steps, components, or combinations thereof, and do not preclude the addition of one or more other features, quantities, steps, components, or combinations thereof.

[0014] Furthermore, in this specification, degree terms such as “about” or “substantially” are used in accordance with corresponding numerical values ​​or to indicate approximation to values ​​where there are inherent manufacturing and material tolerances in the meaning described, in order to prevent irresponsible infringers from illegally using the disclosed content (including numerical values ​​interpreted as precise or absolute) to aid in understanding the invention.

[0015] Furthermore, in this specification, (co)polymer refers to both homopolymers and copolymers.

[0016] Unless otherwise defined herein, “copolymer” can mean block copolymer, random copolymer, graft copolymer or alternating copolymer, and “polymer” can mean block copolymer, random copolymer, graft copolymer or alternating copolymer.

[0017] Furthermore, as used herein, “parts by weight” refers to a relative concept of the weight ratio of said materials based on the weight of a specific material. For example, in a mixture containing 50g of material A, 20g of material B, and 30g of material C, the amounts of material A, material B, and material C, based on 100 parts by weight, are 40 parts by weight and 60 parts by weight, respectively.

[0018] Meanwhile, "weight%" refers to an absolute concept that expresses the weight of a specific material as a percentage based on the total weight. In the above mixture, based on 100% of the total weight of the mixture, the contents of materials A, B, and C are 50% by weight, 20% by weight, and 30% by weight, respectively.

[0019] This invention can be modified and has various forms, and specific embodiments will be described in detail below. However, it should be understood that the description is not intended to limit the invention to the specific forms disclosed, but rather to cover all modifications, equivalents, and alternatives that fall within the spirit and scope of this invention.

[0020] (Polyethylene resin composition) This invention relates to a polyethylene resin composition having improved melt fracture characteristics, particularly sharkskin melt fracture characteristics.

[0021] Melt fracture, or melt cracking, refers to the phenomenon where extruded materials exhibit irregular surfaces during the extrusion process of polyethylene resin compositions as the processing linear speed increases. Specifically, as the processing linear speed increases, shear stress increases; when the shear stress exceeds a critical value, the surface contact between the polymer melt and the processing device (such as a die) deteriorates, leading to cohesive failure. When this phenomenon occurs, defects appear on the product surface.

[0022] The inventors discovered that melt fracture occurs when the viscosity of the resin composition in the processing area is high, which can represent the shear stress when the processing line speed increases. The inventors improved the melt fracture characteristics, especially the sharkskin melt fracture characteristics, by controlling the molecular structure within the resin composition.

[0023] Specifically, the polyethylene resin composition according to the present invention comprises one or more polyethylenes and satisfies the following requirements (a1) to (a4): (a1) Melt flow rate ratio (MI) 21.6 / MI 2.16 (ASTM D1238, 190℃): 60 to 120; (a2) Density (ASTM D1505): 0.920 g / cm³ 3 Up to 0.950 g / cm 3 ; (a3) Molecular weight distribution: 5.50 to 15.00; (a4) When the logarithm of the weight-average molecular weight (Mw) (g / mol) obtained by gel permeation chromatography is used as the x-axis and the molecular weight distribution (dW / dlogMw) relative to the logarithm is used as the y-axis, the molecular weight distribution type is: single peak.

[0024] Specifically, the melt flow rate ratio (MFRR, MI) of the polyethylene resin composition according to the present invention 21.6 / MI 2.16 The MFRR is between 60 and 120. When the MFRR is less than 60, the physical properties, especially the stiffness in the MD direction, may deteriorate during the production of the stretch film; while when the MFRR is greater than 120, the toughness and transparency of the stretch film may deteriorate. More specifically, the MFRR of the polyethylene resin composition can be 60 or more, or 70 or more, or 75 or more, or 79 or more, or 80 or more, or 85 or more, or 88 or more, and is less than 120, or less than 100, or less than 95, or less than 90, or less than 89.5, or less than 89.

[0025] In this invention, the MFRR of the polyethylene resin composition is determined by measuring the MFRR at 190°C according to ASTM D1238 standard. Melt index (MI) was measured at a temperature of C and a load of 21.6 kg. 21.6 ) and at 190 Melt index (MI) was measured at a temperature of C and a load of 2.16 kg. 2.16 Then the measured MI 21.6 Divide by MI 2.16 It is used for calculation.

[0026] In addition to possessing the aforementioned melt properties, the polyethylene resin composition has a density of 0.920 g / cm³. 3 Up to 0.950 g / cm 3 When the density is less than 0.920 g / cm³ 3 During the production of stretch film, physical properties, especially stiffness in the TD direction, may deteriorate; when the density is greater than 0.950 g / cm³, the physical properties may also deteriorate. 3 At this point, the processability and tensile properties of the film may deteriorate due to excessively high density. More specifically, the density of the polyethylene resin composition can be 0.920 g / cm³. 3 Above, or 0.930 g / cm 3Above, or 0.932 g / cm 3 Above, or 0.935 g / cm 3 The above, and 0.950 g / cm³ 3 Below, or 0.945 g / cm 3 Below, or 0.940 g / cm 3 the following.

[0027] In this invention, the density (g / cm³) of the polyethylene resin composition can be measured according to the American Society for Testing and Materials (ASTM) standard D1505. 3 Detailed measurement methods are described in the experimental examples below.

[0028] Simultaneously, when the viscosity is low at the linear velocity in the processing zone, melt fracture is suppressed. The viscosity in the processing zone can be reduced by introducing long-chain branches (LCBs) into the polymer or by broadening the molecular weight distribution (PDI) of the resin composition to a certain level. Typically, methods for broadening the PDI include controlling the polymerization process or using methods of mixing with the polymer. In this invention, the resin composition has a broad PDI by mixing two or more polymers. Specifically, the molecular weight distribution (PDI) of the polyethylene resin composition according to the invention is 5.50 to 15.00. When the PDI is less than 5.50, the viscosity in the processing zone increases significantly due to the narrow molecular weight distribution; while when the molecular weight distribution exceeds 15.00, the viscosity in the processing zone decreases significantly, thereby deteriorating the processability and tensile properties of the film. More specifically, the PDI of the polyethylene resin composition is 5.50 or more, or 5.54 or more, or 5.60 or more, or 6.00 or more, or 6.40 or more, and is 15.00 or less, or 10.00 or less, or 7.00 or less, or 6.70 or less, or 6.65 or less.

[0029] In this invention, the molecular weight distribution (PDI) of the polyethylene resin composition can be calculated by dividing the weight-average molecular weight (Mw) (g / mol) by the number-average molecular weight (Mn) (g / mol). Both the weight-average and number-average molecular weights can be determined by gel permeation chromatography (GPC), and both are values ​​converted from standard polystyrene. Detailed determination methods and conditions are described in the experimental examples below.

[0030] In addition to having the wide molecular weight distribution described above, when a molecular weight distribution curve is plotted based on GPC analysis results, with the logarithm of the weight-average molecular weight (Mw) (g / mol) (logMw) as the x-axis and the molecular weight distribution relative to the logarithm (dW / dlogMw) as the y-axis, the polyethylene resin composition according to the present invention also has a unimodal molecular weight distribution curve.

[0031] In traditional polyethylene resin compositions, selectively increasing the distribution (or content) of low-molecular-weight polymers and high-molecular-weight polymers enhances the molecular structure that favors biaxial stretching, while simultaneously improving physical properties. Therefore, in gel permeation chromatography (GPC) analysis, the molecular weight distribution curve exhibits a bimodal pattern.

[0032] In contrast, the polyethylene resin composition according to the present invention exhibits a unimodal molecular weight distribution.

[0033] Bimodal polyethylene resin compositions are known to exhibit a different melt fracture tendency than unimodal polyethylene resin compositions due to differences in molecular structure depending on the ratio of high to low molecular weight polymers (J Rheol., 57, 393(2013)). Increased low molecular weight polymer content improves processability, which is advantageous in terms of melt fracture tendency. Furthermore, even with the same level of low molecular weight polymers, unimodal molecular weight distributions exhibit a delayed melt fracture tendency compared to bimodal molecular weight distributions due to the good miscibility between high and low molecular weight polymers.

[0034] Because the polyethylene resin composition according to the invention has a unimodal molecular weight distribution and a wide PDI, melt fracture will not occur even under high shear stress.

[0035] Meanwhile, in this invention, the molecular weight distribution curve of the polyethylene resin composition is plotted as follows: Gel permeation chromatography analysis was performed as described above, and then the logarithm of the weight-average molecular weight (Mw) (g / mol) (logMw) was used as the x-axis, and the molecular weight distribution relative to the logarithm (dW / dlogMw) was used as the y-axis. Detailed analytical methods are described in the experimental examples below.

[0036] Furthermore, the weight-average molecular weight (Mw) of the polyethylene resin composition can be from 110,000 g / mol to 130,000 g / mol, and it has the aforementioned molecular weight distribution characteristics.

[0037] The Mw of the polyethylene resin composition affects tensile properties and physical properties. Since the Mw of the polyethylene resin composition is within the above-mentioned range, it exhibits excellent tensile properties during film production and improves the physical properties of the produced film, particularly its stiffness. More specifically, the Mw of the polyethylene resin composition can be 110,000 g / mol or more, or 110,500 g / mol or more, or 115,000 g / mol or more, or 117,000 g / mol or more, and is less than 130,000 g / mol, or less than 125,000 g / mol, or less than 121,000 g / mol, or less than 120,900 g / mol.

[0038] Furthermore, when measured using a rotational rheometer at 230°C and 500 rad / s, the complex viscosity of the polyethylene resin composition can be less than 400 Pa·s. More specifically, when measured under the above conditions, the complex viscosity of the polyethylene resin composition can be less than 400 Pa·s, or less than 350 Pa·s, or less than 345 Pa·s, and greater than 300 Pa·s, or greater than 330 Pa·s, or greater than 340 Pa·s, or greater than 344 Pa·s.

[0039] In addition, at 230℃ and 1000s -1 Under the conditions specified, the shear viscosity of the polyethylene resin composition, measured using a capillary rheometer, can be below 300 Pa·s. More specifically, under the aforementioned conditions, the shear viscosity of the polyethylene resin composition is below 300 Pa·s, or below 295 Pa·s, or below 293 Pa·s, and above 200 Pa·s, or above 250 Pa·s, or above 270 Pa·s, or above 272 Pa·s, or above 285 Pa·s, or above 289 Pa·s.

[0040] The complex viscosity of a polyethylene resin composition refers to its viscosity under oscillatory deformation, while the shear viscosity refers to its viscosity under unidirectional deformation. By having complex viscosity and / or shear viscosity within the above-mentioned ranges, the resin compositions of the present invention can exhibit excellent film stretchability.

[0041] Polyethylene resin compositions that meet the above-mentioned property requirements exhibit improved melt fracture characteristics, wherein the melt fracture initiation shear rate is delayed and melt fracture does not occur even under high shear stress.

[0042] Specifically, when the shear viscosity of the polyethylene resin composition was measured using a capillary rheometer at 230°C with varying shear rates, melt fracture (melt fracture initiation) occurred at 1000 s. -1 At the above shear rates, as mentioned earlier, the shear rate at which melt fracture begins is defined as the shear rate. 熔体破裂起始 (Shear rate)onset of M.F The shear rate of the polyethylene resin composition according to the present invention 熔体破裂起始 For 1000s -1 That's all. Due to the shear rate 熔体破裂起始 The higher the value, the better; therefore, there is no particular upper limit, for example, it can be 100,000s. -1 Below, or 10,000s -1 the following.

[0043] The melt fracture initiation stress (MF) of the polyethylene resin composition was measured using a capillary rheometer at 230°C. 起始 (MF) on_set The stress is above 265,000 Pa. Due to MF... 起始 The higher the stress value, the better, so there is no particular upper limit. For example, it can be below 1,000,000 Pa or below 500,000 Pa.

[0044] Meanwhile, in this invention, the shear rate of the polyethylene resin composition... 熔体破裂起始 and MF 起始 Stress can be measured using a capillary rheometer, and the detailed measurement methods and conditions are described in Experimental Example 1 below.

[0045] Furthermore, GPC analysis determined that the bimodal triangular region (BMTA) of the polyethylene resin composition according to the present invention can be from 0.05 to 0.15.

[0046] BMTA corresponds to the triangular region formed by connecting three coordinates on the GPC curve measured according to ASTM D6474 standard, where these three coordinates are defined as: the maximum peak in the low molecular weight fraction where the logMw of the peak maximum intensity is less than 5.0 (Peak). low The maximum intensity coordinates (X-axis: a, Y-axis: d); the maximum peak in high molecular weight fractions with a maximum intensity logMw of 5.0 or higher. high The maximum intensity coordinates (X-axis: b, Y-axis: e) of Peak; and the coordinates containing Peak low Low molecular weight fractions and those containing Peak high The coordinates of the intersection points of the high molecular weight fractions (X-axis: c, Y-axis: f). In other words, the area of ​​the BMTA, i.e., the area connecting the peaks. low Maximum intensity coordinates (X-axis: a, Y-axis: d), Peak high The area of ​​the triangle formed by the maximum intensity coordinates (X-axis: b, Y-axis: e) and the coordinates of the intersection of these two coordinates (X-axis: c, Y-axis: f) can be determined by the following formula 1.

[0047] [Formula 1]

[0048] In Formula 1, ae represents the product of the maximum intensity X-axis coordinate value of the low molecular weight fraction and the maximum intensity Y-axis coordinate value of the high molecular weight fraction. bf represents the product of the maximum intensity X-axis coordinate value of the high molecular weight fraction and the Y-axis coordinate value of the intersection point. cd represents the product of the X-axis coordinate value of the intersection point and the Y-axis coordinate value of the maximum intensity of the low molecular weight fraction. db represents the product of the maximum intensity Y-axis value of the low molecular weight fraction and the maximum intensity X-axis value of the high molecular weight fraction. ec represents the product of the maximum intensity Y-axis value of the high molecular weight fraction and the X-axis value of the intersection point. fa represents the product of the Y-axis coordinate of the intersection point and the X-axis coordinate of the maximum intensity of the low molecular weight fraction.

[0049] A higher BMTA value indicates a greater degree of bimodal separation between the low-molecular-weight and high-molecular-weight fractions on the GPC curve, which means a larger low-molecular-weight region and indicates excellent processability. Specifically, the BMTA value of the polyethylene composition according to the invention can be 0.06 or higher, or 0.07 or higher, or 0.08 or higher, or 0.09 or higher. However, when the BMTA value is too high, it is difficult to form a crystalline framework during the manufacture of biaxially stretched films, thereby reducing their mechanical properties. Therefore, the BMTA value is preferably 0.3 or lower, or 0.25 or lower, or 0.2 or lower, or 0.15 or lower, or 0.12 or lower.

[0050] Meanwhile, in this invention, for BMTA, the weight-average molecular weight (Mw, g / mol) is determined by gel permeation chromatography according to the American Society for Testing and Materials (ASTM) D6474 standard. On the logarithmic plot of the weight-average molecular weight (Mw) of the polyethylene resin composition measured in this way, i.e., with logMw on the x-axis... W The area of ​​BMTA can be determined on the GPC curve with y-axis as dw / dlogMw. The method for determining BMTA is described in the experimental examples below.

[0051] Meanwhile, the melt index (MI) of the polyethylene resin composition 2.16 The melt index affects the processability and stretchability of the film. When the melt index of the polyethylene resin composition is too low, there is concern that the processability and stretchability of the film may deteriorate due to the low melt index. Conversely, when the melt index is too high, there is concern that processability may deteriorate, and the physical properties of the prepared stretched film may also deteriorate.

[0052] The polyethylene resin composition according to the present invention exhibits a melt index (MI) 2.16The melt index is 0.10 g / 10 min to 2.00 g / 10 min. Therefore, the composition exhibits excellent film processability and stretchability, and the physical properties of the stretched film to be prepared are also improved. In particular, the polyethylene resin composition can exhibit even better biaxial stretchability by simultaneously meeting the following density requirements. More specifically, the melt index of the polyethylene resin composition according to the invention can be 0.10 g / 10 min or more, or 0.30 g / 10 min or more, or 0.50 g / 10 min or more, and is 2.00 g / 10 min or less, or 1.00 g / 10 min or less, or 0.80 g / 10 min or less, or 0.70 g / 10 min or less, or 0.65 g / 10 min or less, or 0.60 g / 10 min or less.

[0053] Meanwhile, in this invention, the melt index (MI) of the polyethylene resin composition is... 2.16 It can be measured according to ASTM D1238 (Condition E) at 190°C and a load of 2.16 kg. Detailed measurement methods are described in the experimental examples below.

[0054] The above-mentioned polyethylene resin composition comprises one or more ethylene-α-olefin copolymers, and more specifically, comprises one or more ethylene-α-olefin copolymers.

[0055] Specifically, the polyethylene resin composition includes: (a) Density is 0.870 g / cm³ 3 Up to 0.920 g / cm 3 The first ethylene-α-olefin copolymer with a number-average molecular weight Mn of 20,000 g / mol or higher, and (b) Density is 0.945 g / cm³ 3 Up to 0.960 g / cm 3 A second ethylene-α-olefin copolymer with a number-average molecular weight Mn of 10,000 g / mol or more and less than 20,000 g / mol; The first ethylene-α-olefin copolymer and the second ethylene-α-olefin copolymer are different from each other.

[0056] Furthermore, by mixing the first and second ethylene-α-olefin copolymers in appropriate amounts, the polyethylene resin composition according to the present invention can satisfy the above-mentioned excellent overall physical properties.

[0057] Specifically, based on the total weight of the polyethylene resin composition according to the present invention, the content of the first ethylene-α-olefin copolymer may be from 10% to 40% by weight, and the content of the second ethylene-α-olefin copolymer may be from 60% to 90% by weight.

[0058] More specifically, based on the total weight of the polyethylene resin composition, the content of the first ethylene-α-olefin copolymer may be more than 10% by weight, or more than 15% by weight, or more than 17% by weight, and less than 40% by weight, or less than 35% by weight, or less than 30% by weight, or less than 20% by weight.

[0059] Furthermore, based on the total weight of the polyethylene resin composition, the content of the second ethylene-α-olefin copolymer may be 60% or more by weight, or 65% or more by weight, or 70% or more by weight, or 80% or more by weight, and is less than 90% by weight, or less than 85% by weight, or less than 83% by weight.

[0060] Furthermore, in the polyethylene resin composition, both the first and second ethylene-α-olefin copolymers are copolymers of ethylene with α-olefins containing 3 to 20 carbon atoms, more specifically, copolymers of ethylene with 1-butene, 1-hexene, or 1-octene. In this respect, the α-olefins contained in the first and second ethylene-α-olefin copolymers are different from each other.

[0061] More specifically, the first ethylene-α-olefin copolymer can be an ethylene / 1-octene copolymer, and the second ethylene-α-olefin copolymer can be an ethylene / 1-hexene copolymer.

[0062] (a) First ethylene-α-olefin copolymer First, in the polyethylene composition according to the invention, the first ethylene-α-olefin copolymer has excellent flowability, thereby providing properties suitable for manufacturing biaxially stretched films, such as excellent tensile stability and high shrinkage resistance.

[0063] Specifically, the density of the first ethylene-α-olefin copolymer is 0.870 g / cm³. 3 Up to 0.920 g / cm 3 The number-average molecular weight Mn is above 20,000 g / mol.

[0064] More specifically, the density of the first ethylene-α-olefin copolymer can be 0.880 g / cm³. 3 Above, or 0.890 g / cm 3 Above, or 0.895 g / cm 3 Above, or 0.900 g / cm 3 The above, and 0.915 g / cm³ 3 Below, or 0.910 g / cm 3 Below, or 0.905 g / cm 3 the following.

[0065] Furthermore, the number-average molecular weight Mn of the first ethylene-α-olefin copolymer may more specifically be 20,000 g / mol or more, or 22,000 g / mol or more, or 25,000 g / mol or more, or 28,000 g / mol or more, or 30,000 g / mol or more, and less than 34,000 g / mol, or less than 33,000 g / mol, or less than 32,000 g / mol.

[0066] In addition, the melt index (MI) of the first ethylene-α-olefin copolymer 2.16 ASTM D1238, 190 C, under a 2.16 kg load, has a molecular weight of 3.0 g / 10 min to 10.0 g / 10 min, a weight-average molecular weight Mw of 60,000 g / mol or more and less than 95,000 g / mol, and a molecular weight distribution Mw / Mn of 2.0 or more and less than 3.5, while simultaneously meeting the above requirements for density and number-average molecular weight.

[0067] More specifically, the melt index (MI) of the first ethylene-α-olefin copolymer 2.16 ASTM D1238, 190 C, under a load of 2.16 kg, can be 3.5 g / 10 min or more, or 4.0 g / 10 min or more, or 4.5 g / 10 min or more, or 6.0 g / 10 min or more, and is less than 9.0 g / 10 min, or 8.0 g / 10 min or less, or 7.0 g / 10 min or less.

[0068] Furthermore, the weight-average molecular weight Mw of the first ethylene-α-olefin copolymer may more specifically be 60,000 g / mol or more, or 62,000 g / mol or more, or 64,000 g / mol or more, or 65,000 g / mol or more, or 68,000 g / mol or more, and less than 95,000 g / mol, or less than 90,000 g / mol, or less than 80,000 g / mol, or less than 70,000 g / mol.

[0069] Furthermore, the molecular weight distribution Mw / Mn of the first ethylene-α-olefin copolymer can more specifically be 2.0 or more, or 2.1 or more, or 2.2 or more, or 2.3 or more, and less than 3.5, or less than 3.2, or less than 3.0, or less than 2.8, or less than 2.5.

[0070] The first ethylene-α-olefin copolymer may have at least one of the above-mentioned properties, and may have all of the above-mentioned physical properties, to exhibit excellent mechanical strength.

[0071] Here, the method for measuring each physical property of the first ethylene-α-olefin copolymer is the same as the method described for the polyethylene composition, therefore a detailed description will be omitted.

[0072] Meanwhile, the first ethylene-α-olefin copolymer comprises ethylene and one or more α-olefins selected from 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, and mixtures thereof.

[0073] Furthermore, the first ethylene-α-olefin copolymer can be a copolymer of ethylene and 1-octene.

[0074] When the first ethylene-α-olefin copolymer is the copolymer described above, the above physical properties can be achieved more easily. However, the type of the first ethylene-α-olefin copolymer is not limited to the types described above, and various types known in the art to which this invention pertains can be provided as long as they can exhibit the above physical properties.

[0075] Meanwhile, the first ethylene-α-olefin copolymer with the above-mentioned physical properties can be prepared in the presence of a metallocene catalyst.

[0076] Specifically, the first ethylene-α-olefin copolymer can be prepared by copolymerizing ethylene and comonomers in the presence of a catalyst composition comprising a first metallocene compound represented by the following chemical formula 1.

[0077] [Chemical Formula 1]

[0078] In chemical formula 1, M 1 It is a group 4 transition metal; X 1 and X 2 They may be the same as or different from each other, and each can be independently a halogen, nitro, amide, phosphin, phosphine anion group, C1 to C30 hydrocarbon group, C1 to C30 hydrocarbon oxy group, C2 to C30 hydrocarbon oxy hydrocarbon group, -SiH3, C1 to C30 hydrocarbon (oxy) silyl group, C1 to C30 sulfonate group or C1 to C30 sulfone group. Z represents -O-, -S-, -NR a -or-PR a -; R a It can be any one of hydrogen, C1 to C20 hydrocarbon group, C1 to C20 hydrocarbon (oxy)silyl group, or C1 to C20 silyl hydrocarbon group; T is or , T 1It can be C, Si, Ge, Sn, or Pb. Q 1 and Q 2 They may be the same as or different from each other, and each independently consists of hydrogen, C1 to C30 hydrocarbon group, C1 to C30 hydrocarbon oxygen group, C2 to C30 hydrocarbon oxygen hydrocarbon group, -SiH3, C1 to C30 hydrocarbon (oxy) silicon group, halogen-substituted C1 to C30 hydrocarbon group, and -NR. b R c any one of them, R b and R c Each can be an independent hydrogen atom and any one of C1 to C30 hydrocarbon groups, or they can be connected to each other to form an aliphatic ring or an aromatic ring; C 1 It is any one of the ligands represented by the following chemical formulas 1a to 1d. [Chemical Formula 1a]

[0079] [Chemical Formula 1b]

[0080] [Chemical Formula 1c]

[0081] [Chemical formula 1d]

[0082] In chemical formulas 1a to 1d, Y is O or S, and R 1 To R 6 They may be the same as or different from each other, and each is independently any one of hydrogen, C1 to C30 hydrocarbon group and C1 to C30 hydrocarbon group.

[0083] Unless otherwise specified herein, the following terms may be defined as follows.

[0084] A hydrocarbon group is a monovalent functional group obtained by removing a hydrogen atom from a hydrocarbon, and can include alkyl, alkenyl, alkynyl, aryl, aralkyl, aryl-alkenyl, arylynyl, alkylaryl, alkenylaryl, alkynylaryl, etc. C1 to C30 hydrocarbon groups can be C1 to C20 or C1 to C10 hydrocarbon groups. For example, the hydrocarbon group can be a straight-chain, branched, or cyclic alkyl group. More specifically, C1 to C30 hydrocarbon groups can be linear, branched, or cyclic alkyl groups, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, cyclohexyl, etc.; or aryl groups, such as phenyl, biphenyl, naphthyl, anthraceneyl, phenanthrene, or fluorenyl, etc. Furthermore, it can also be an alkylaryl group, such as methylphenyl, ethylphenyl, methylbiphenyl, methylnaphthyl, etc., or an aryl group, such as benzyl, phenethyl, biphenylmethyl, naphthylmethyl, etc. It can also be alkenyl, such as allyl, allyl, vinyl, propenyl, butenyl, pentenyl, etc.

[0085] An alkyl group is a functional group formed by the combination of a hydrocarbon group and an oxygen atom. Specifically, C1 to C30 alkyl groups can be C1 to C20 or C1 to C10 alkyl groups. For example, an alkyl group can be a straight-chain, branched, or cyclic alkyl group. More specifically, C1 to C30 alkyl groups can be straight-chain, branched, or cyclic alkoxy groups, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy, n-hexoxy, n-heptoxy, and cyclohexoxy; or aryloxy groups, such as phenoxy and naphthoxy.

[0086] A alkyloxyalkyl group is a functional group formed by replacing one or more hydrogen atoms on a hydrocarbon group with one or more alkyloxy groups. Specifically, C2 to C30 alkyloxyalkyl groups can be C2 to C20 or C2 to C15 alkyloxyalkyl groups. For example, alkyloxyalkyl groups can be straight-chain, branched, or cyclic alkyl groups. More specifically, C2 to C30 alkyloxyalkyl groups can be alkoxyalkyl groups, such as methoxymethyl, methoxyethyl, ethoxymethyl, isopropoxymethyl, isopropoxyethyl, isopropoxyhexyl, tert-butoxymethyl, tert-butoxyethyl, tert-butoxyhexyl, etc.; or aryloxyalkyl groups, such as phenoxyhexyl, etc.

[0087] A hydrocarbon (oxy)silyl group is a functional group obtained by substituting one to three hydrogen atoms in SiH3 with one to three hydrocarbon or hydrocarbon oxygen groups. Specifically, C1 to C30 hydrocarbon (oxy)silyl groups can be C1 to C20, C1 to C15, C1 to C10, or C1 to C5 hydrocarbon (oxy)silyl groups. More specifically, C1 to C30 hydrocarbon (oxy)silyl groups can be alkylsilyl groups, such as methylsilyl, dimethylsilyl, trimethylsilyl, dimethylethylsilyl, diethylmethylsilyl, or dimethylpropylsilyl; alkoxysilyl groups, such as methoxysilyl, dimethoxysilyl, trimethoxysilyl, or dimethoxyethoxysilyl; or alkoxyalkylsilyl groups, such as methoxydimethylsilyl, diethoxymethylsilyl, or dimethoxypropylsilyl.

[0088] C1 to C20 silyl hydrocarbon groups are functional groups obtained by replacing one or more hydrogen atoms on a hydrocarbon group with a silicon group. The silicon group can be -SiH3 or a hydrocarbon (oxy)silyl group. Specifically, C1 to C20 silyl hydrocarbon groups can be C1 to C15 or C1 to C10 silyl hydrocarbon groups. More specifically, C1 to C20 silyl hydrocarbon groups can be silyl alkyl groups, such as -CH2-SiH3; alkylsilyl alkyl groups, such as methylsilylmethyl, methylsilylethyl, dimethylsilylmethyl, trimethylsilylmethyl, dimethylethylsilylmethyl, diethylmethylsilylmethyl, or dimethylpropylsilylmethyl; or alkoxysilyl groups, such as dimethylethoxysilylpropyl.

[0089] Halogens can be fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).

[0090] The structure of the sulfonate group is -O-SO2-R d , where R d It can be a C1 to C30 hydrocarbon group. Specifically, the C1 to C30 sulfonate groups can be methanesulfonate groups, benzenesulfonate groups, etc.

[0091] The structure of C1 to C30 sulfone groups is -R e' -SO2-R e” , where R e' and R e” They can be the same or different, and each can be any one of the C1 to C30 hydrocarbon groups. Specifically, the C1 to C30 sulfone groups can be methylsulfonylmethyl, methylsulfonylpropyl, methylsulfonylbutyl, or phenylsulfonylpropyl, etc.

[0092] In this disclosure, "two adjacent substituents connected to each other to form an aliphatic or aromatic ring" means that the atoms of the two substituents and the atoms attached to these two substituents are connected to each other to form a ring. Specifically, -NR b R c or -NR b' R c'R in b and R c or R b' and R c' Examples of compounds that connect to form aliphatic rings include piperidinyl groups, etc.; -NR b R c or -NR b' R c' Chinese R b and R c or R b' and R c' Examples of compounds that connect to form aromatic rings include pyrrole groups, etc.

[0093] Furthermore, the Group 4 transition metal can be titanium (Ti), zirconium (Zr), hafnium (Hf) or ruthenium (Rf), specifically titanium (Ti), zirconium (Zr) or hafnium (Hf), more specifically zirconium (Zr) or hafnium (Hf), but is not limited thereto.

[0094] In addition, Group 13 elements can be boron (B), aluminum (Al), gallium (Ga), indium (In) or thallium (Tl), specifically boron (B) or aluminum (Al), but are not limited to these.

[0095] Within the range of exhibiting the same or similar effects as desired, the above substituents may optionally be replaced by one or more substituents selected from the group consisting of: hydroxyl; halogen; hydrocarbon group; hydrocarbon oxygen group; hydrocarbon group or hydrocarbon oxygen group containing heteroatoms of group 14 to 16; silyl group; hydrocarbon (oxy)silyl group; phosphin group; phosphine anionic group; sulfonate group; and sulfone group.

[0096] In this disclosure, It refers to a bond that is attached to another substituent.

[0097] Specifically, in chemical formula 1, Z is -NR a -, where R a It can be a C1 to C10 hydrocarbon group. Specifically, R a It can be a straight-chain or branched C1 to C6 alkyl group, more specifically, tert-butyl.

[0098] Furthermore, in chemical formula 1, T is... T 1 For carbon (C) or silicon (Si), Q 1 and Q 2 Each can be independently hydrogen, a C1 to C30 hydrocarbon group, or a C1 to C30 hydroxyl group. Specifically, Q 1 and Q 2 Each can be a C1 to C10 hydrocarbon group or a C2 to C12 hydroxyl group. More specifically, Q 1 and Q 2Each of the C1 to C6 alkyl groups may be substituted with a C1 to C6 alkyl group or a C1 to C6 alkoxy group. For example, Q 1 and Q 2 Each of these hexyl groups can be independently substituted with hydrogen, methyl, ethyl, or tert-butoxy groups. More specifically, T 1 For silicon (Si), Q 1 and Q 2 All are methyl, or Q 1 and Q 2 One of them is a methyl group, and the other is a tert-butoxy-substituted hexyl group.

[0099] Specifically, the metallocene compounds represented by chemical formula 1 can be represented by any one of the following chemical formulas 1-1 to 1-4.

[0100] [Chemical Formula 1-1]

[0101] [Chemical Formula 1-2]

[0102] [Chemical Formulas 1-3]

[0103] [Chemical Formulas 1-4]

[0104] In chemical formulas 1-1 to 1-4, M 1 X 1 X 2 R a T 1 Q 1 Q 2 Y and R 1 To R 6 Same as the definition in Chemical Formula 1.

[0105] Furthermore, in chemical formula 1, R 1 To R 4 Each can be hydrogen or a C1 to C10 hydrocarbon group, R 5 and R 6 Each can be a C1 to C10 hydrocarbon group. Specifically, R 1 To R 4 Each can be hydrogen or C1 to C10 alkyl, R 5 and R 6 Each can be a C1 to C10 alkyl group. More specifically, R 1 To R 4 Each can be either hydrogen or methyl, R 5 and R 6 It can be methyl.

[0106] In chemical formula 1, M 1 It can be titanium (Ti), zirconium (Zr) or hafnium (Hf), with titanium (Ti) being preferred.

[0107] Furthermore, in chemical formula 1, X 1 and X 2 They can each be halogen, C1 to C10 alkyl or C1 to C6 alkyl, specifically chlorine or methyl.

[0108] Furthermore, in chemical formula 1, the second metallocene compound can be represented by any of the following structural formulas.

[0109]

[0110] The metallocene compounds represented by the above structural formulas can be synthesized by applying known reactions. More detailed synthesis methods can be understood by referring to the examples and synthesis examples.

[0111] As described above, the transition metal compound represented by Formula 1 used in this invention controls the degree of introduction of α-olefin monomers during copolymerization due to the structural characteristics of the catalyst, and exhibits the aforementioned density, resulting in excellent flowability and stretch processability.

[0112] In this invention, the polymerization reaction can be carried out by continuously polymerizing ethylene and α-olefin monomers in the presence of a catalyst composition containing one or more transition metal compounds represented by Formula 1, while hydrogen is being continuously introduced. Specifically, the polymerization reaction can be carried out while hydrogen is being introduced at a rate of 5 cc / min to 100 cc / min.

[0113] Hydrogen gas inhibits the rapid reaction of transition metal compounds in the early stages of polymerization and is used to terminate the polymerization reaction. Therefore, by using hydrogen gas and adjusting its amount, ethylene / α-olefin copolymers with narrow molecular weight distributions can be effectively prepared.

[0114] For example, the hydrogen introduction rate can be 5 cc / min or higher, or 7 cc / min or higher, or 10 cc / min or higher, or 15 cc / min or higher, or 19 cc / min or higher, but not exceeding 100 cc / min, or not exceeding 50 cc / min, or not exceeding 45 cc / min, or not exceeding 35 cc / min, or not exceeding 29 cc / min. When hydrogen is introduced under the above conditions, the prepared ethylene / α-olefin copolymer can achieve the aforementioned physical properties.

[0115] When the hydrogen introduction rate is below 5 cc / min, the polymerization reaction cannot terminate uniformly, making it difficult to prepare ethylene / α-olefin copolymers with the desired physical properties. When the hydrogen introduction rate is above 100 cc / min, the termination reaction occurs too quickly, raising concerns about the potential formation of ethylene / α-olefin copolymers with extremely low molecular weights.

[0116] Furthermore, the polymerization reaction can be carried out at 100°C to 200°C, and by controlling the polymerization temperature and the amount of hydrogen introduced, the crystallization distribution and molecular weight distribution of the ethylene / α-olefin copolymer can be more easily controlled. Specifically, the polymerization reaction can be carried out at 100°C to 200°C, or 120°C to 180°C, or 130°C to 170°C, or 140°C to 160°C, but is not limited to these temperatures.

[0117] In this invention, a co-catalyst may also be used in the catalyst composition to activate the transition metal compound of formula 1. The co-catalyst is an organometallic compound containing a group 13 metal, specifically, it may include one or more compounds selected from formulas 2 to 4.

[0118] [Chemical Formula 2] R8-[Al(R7)-O] n -R9 In chemical formula 2, R7, R8, and R9 are each independently hydrogen, halogen, and carbon. 1-20 C with hydrocarbon or halogen substitution 1-20 hydrocarbon groups, and n is an integer greater than or equal to 2. [Chemical Formula 3] D(R 10 )3 In chemical formula 3, D is aluminum or boron. R 10 Each is independently a halogen, C 1-20 hydrocarbon group, C 1-20 C with alkyl or halogen substitution 1-20 hydrocarbon group, [Chemical Formula 4] [LH] + [W(A)4] - Or [L] + [W(A)4] - In chemical formula 4, L is a neutral or cationic Lewis base. H is a hydrogen atom. W is the 13th element, and A is independent and C is independent. 1-20 hydrocarbon group; C1-20 alkyloxy groups; and one or more hydrogen atoms of these substituents are selected from halogens, C 1-20 alkyl groups and C 1-20 Substituents obtained by replacing one or more substituents of a hydrocarbon (oxy)silyl group.

[0119] Specifically, in chemical formula 4, [LH] + It is Brønsted acid.

[0120] For example, [LH] + It is trimethylammonium; triethylammonium; tripropylammonium; tributylammonium; diethylammonium; trimethylphosphine; or triphenylphosphine, wherein [L] + It is N,N-diethylaniline; or triphenylcarbium.

[0121] Furthermore, in chemical formula 4, W can be B. 3+ Or Al 3+ .

[0122] Compound represented by chemical formula 2 can function as an alkylating agent and an activator, compound represented by chemical formula 3 can function as an alkylating agent, and compound represented by chemical formula 4 can function as an activator.

[0123] More specifically, the compounds of Formula 2 can be alkylaluminoxane-based compounds, wherein the repeating units are linked in a linear, cyclic, or network manner, and specific examples may include methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane, or tert-butylaluminoxane, etc. Non-limiting examples of compounds represented by Formula 2 may include methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, or tert-butylaluminoxane, etc.

[0124] In addition, non-limiting examples of compounds represented by Formula 3 may include trimethylaluminum, triethylaluminum, triisobutylaluminum, tripropylaluminum, tributylaluminum, dimethylaluminum chloride, triisopropylaluminum, trisec-butylaluminum, tricyclopentylaluminum, tripentylaluminum, triisopentylaluminum, trihexylaluminum, trioctylaluminum, ethyldimethylaluminum, methyldiethylaluminum, triphenylaluminum, tri-p-tolylaluminum, dimethylmethoxyaluminum, dimethylethoxyaluminum, etc.

[0125] In addition, non-limiting examples of compounds represented by Formula 4 may include: trimethylammonium tetra(pentafluorophenyl)borate, triethylammonium tetra(pentafluorophenyl)borate, N,N-dimethylaniline tetra(pentafluorophenyl)borate, N,N-dimethylaniline n-butyltri(pentafluorophenyl)borate, N,N-dimethylaniline benzyltri(pentafluorophenyl)borate, N,N-dimethylaniline tetra(4-(tert-butyldimethylsilyl)-2,3,5,6-tetrafluorophenyl)borate, N,N-dimethylaniline tetra(4-(triisopropylsilyl)-2,3,5,6-tetrafluorophenyl)borate, N,N-dimethylaniline pentafluorophenoxytri(pentafluorophenyl)borate, and N,N-dimethyl-2,4,6-trimethylaniline tetra(pentafluorophenyl)borate. Aniline tetra(pentafluorophenyl)borate, trimethylammonium tetra(2,3,4,6-tetrafluorophenyl)borate, N,N-dimethylaniline tetra(2,3,4,6-tetrafluorophenyl)borate, hexadecyl dimethylammonium tetra(pentafluorophenyl)borate, N-methyl-N-dodecylaniline tetra(pentafluorophenyl)borate, methyl di(dodecyl)ammonium tetra(pentafluorophenyl)borate, etc.

[0126] In the above compounds, the cocatalyst can more specifically be an alkylaluminoxane-based cocatalyst, such as methylaluminoxane.

[0127] The amount of catalyst can be adjusted appropriately according to the physical properties or effects required by the hybrid supported metallocene catalyst.

[0128] The co-catalyst can be used in an appropriate amount to ensure sufficient activation of the transition metal compound of Formula 1. The amount of co-catalyst can be adjusted appropriately according to the desired physical properties or effects of the hybrid supported metallocene catalyst.

[0129] In this disclosure, the transition metal compound of Formula 1 can be used in a state supported on a support.

[0130] When a transition metal compound of Formula 1 is supported on a support, the weight ratio of the transition metal compound to the support can be from 1:10 to 1:1000, more specifically, from 1:10 to 1:500. When the support and the transition metal compound are included within the above weight ratio range, the optimal shape is observed. Furthermore, when a co-catalyst and the support are co-supported, the weight ratio of the co-catalyst to the support can be from 1:1 to 1:100, more specifically, from 1:1 to 1:50. When the co-catalyst and the support are included within the above weight ratio range, the catalyst activity can be improved and the microstructure of the prepared polymer can be optimized.

[0131] Meanwhile, the support can be silica, alumina, magnesium oxide, or a mixture thereof, or it can be used in a state where highly reactive hydroxyl or siloxane groups are present on its surface after the material has been dried at high temperature to remove moisture. Furthermore, the high-temperature dried support can also contain oxides, carbonates, sulfates, or nitrates, such as Na₂O, K₂CO₃, BaSO₄, and Mg(NO₃)₂.

[0132] The drying temperature of the support is preferably 200°C to 800°C, more preferably 300°C to 600°C, and most preferably 300°C to 400°C. When the drying temperature of the support is below 200°C, the surface moisture may react with the cocatalyst due to excessive moisture. When the drying temperature is above 800°C, the pores on the support surface may merge, reducing the surface area, and the surface may lose a large number of hydroxyl groups, leaving only siloxane groups, thereby reducing the reaction sites with the cocatalyst, which is disadvantageous.

[0133] Furthermore, the content of hydroxyl groups on the carrier surface is preferably from 0.1 mmol / g to 10 mmol / g, more preferably from 0.5 mmol / g to 5 mmol / g. The content of hydroxyl groups on the carrier surface can be controlled by the preparation method and conditions of the carrier, or by the drying conditions (e.g., temperature, time, vacuum or spray drying, etc.).

[0134] Furthermore, organoaluminum compounds can be introduced during the polymerization process to remove moisture from the reactor, allowing the polymerization to proceed in the presence of these compounds. Specific examples of such organoaluminum compounds include trialkylaluminum, dialkylaluminum halides, alkylaluminum dihalides, dialkylaluminum hydrides, or alkylsesquihalides. More specific examples include Al(C2H5)3, Al(C2H5)2H, Al(C3H7)3, Al(C3H7)2H, Al(iC4H9)2H, and Al(C8H5)2H. 17 3. Al(C) 12 H 25 3. Al(C2H5)(C 12 H 25 )2、Al(iC4H9)(C 12 H 25 )2, Al(iC4H9)2H, Al(iC4H9)3, (C2H5)2AlCl, (iC3H9)2AlCl or (C2H5)3A l2 Cl3, etc. These organoaluminum compounds can be continuously introduced into the reactor, and can be added in amounts of about 0.1 mol to about 10 mol per 1 kg of reaction medium introduced into the reactor to fully remove moisture.

[0135] In addition, the polymerization pressure can be approximately 1 kgf / cm. 2 Approximately 100 kgf / cm2 The preferred value is approximately 1 kgf / cm³. 2 Approximately 50 kgf / cm 2 More preferably about 5 kgf / cm 2 Approximately 30 kgf / cm 2 .

[0136] Furthermore, when the transition metal compound is used in a supported state, it can be dissolved or diluted in an aliphatic hydrocarbon solvent (e.g., pentane, hexane, heptane, nonane, decane and their isomers), an aromatic hydrocarbon solvent (e.g., toluene and benzene), or a chlorinated hydrocarbon solvent (e.g., dichloromethane and chlorobenzene) having 5 to 12 carbon atoms before introduction. The solvent used here is preferably treated with a small amount of alkylaluminum to remove trace amounts of water or air that act as catalyst poisons. The aforementioned co-catalyst may also be used further.

[0137] As previously mentioned, the first ethylene-α-olefin copolymer can be prepared by copolymerizing ethylene and α-olefin using the aforementioned metallocene catalyst.

[0138] The first ethylene-α-olefin copolymer with the above physical properties can be prepared by the above preparation method.

[0139] (b) Second ethylene-α-olefin copolymer The polyethylene resin composition according to the present invention can control the balance between mechanical properties and tensile characteristics by blending the above-mentioned first ethylene-α-olefin copolymer with a second ethylene-α-olefin copolymer having excellent flowability, superior tensile stability and shrinkage resistance, thereby imparting properties suitable for the production of biaxially stretched films, maintaining mechanical properties, production efficiency and tensile stability comparable to or better than those of the prior art, and having high shrinkage resistance, printability and excellent transparency.

[0140] Specifically, the second ethylene-α-olefin copolymer can be high-density polyethylene (HDPE) that meets the requirement of 0.945 g / cm³ at 23°C as measured according to ISO 1183-2. 3 Up to 0.960 g / cm 3 The density requirement. More specifically, the density of the second ethylene-α-olefin copolymer can be 0.945 g / cm³. 3 Above, or 0.946 g / cm 3 The above, and 0.960 g / cm³ 3 Below, or 0.958 g / cm 3 Below, or 0.956 g / cm 3 Below, or 0.955 g / cm 3 Below, or 0.952 g / cm 3 Below, or 0.948 g / cm3 the following.

[0141] Furthermore, the number-average molecular weight Mn of the second ethylene-α-olefin copolymer can be 10,000 g / mol or more, and less than 20,000 g / mol. More specifically, the number-average molecular weight Mn of the second ethylene-α-olefin copolymer can be 10,000 g / mol or more, or 11,000 g / mol or more, or 11,500 g / mol or more, and less than 20,000 g / mol, or less than 20,000 g / mol, or less than 18,000 g / mol, or less than 15,000 g / mol, or less than 14,500 g / mol, or less than 14,100 g / mol.

[0142] In addition, in 190 Under loads of C and 2.16 kg, the melt index (MI) of the second ethylene-α-olefin copolymer, measured according to ASTM D1238, is... 2.16 The molecular weight can be from 0.10 g / 10 min to 2.00 g / 10 min, and the weight-average molecular weight Mw can be from 100,000 g / mol to 200,000 g / mol, and the molecular weight distribution Mw / Mn can be from 7.0 to 20.0.

[0143] More specifically, the melt index (MI) of the second ethylene-α-olefin copolymer 2.16 The concentration can be above 0.10g / 10min, or above 0.20g / 10min, above 0.30g / 10min, or above 0.35g / 10min, or above 0.36g / 10min, and below 2.00g / 10min, or below 1.50g / 10min, or below 1.00g / 10min, or below 0.50g / 10min, or below 0.40g / 10min, or below 0.39g / 10min.

[0144] This means that the second ethylene-α-olefin copolymer has a high weight-average molecular weight and a high content of high molecular weight components, thus exhibiting excellent mechanical properties, such as high tensile strength. Because the second ethylene-α-olefin copolymer has a low melt index as described above, the polyethylene resin composition of the present invention containing said copolymer can meet excellent processability and crack resistance requirements when manufactured for pipe applications.

[0145] Furthermore, the weight-average molecular weight Mw of the second ethylene-α-olefin copolymer may more specifically be 100,000 g / mol or more, or 120,000 g / mol or more, or 140,000 g / mol or more, or 145,000 g / mol or more, or 149,200 g / mol or more, and less than 200,000 g / mol, or less than 180,000 g / mol, or less than 170,000 g / mol, or less than 165,000 g / mol, or less than 161,000 g / mol.

[0146] Furthermore, the molecular weight distribution of the second ethylene-α-olefin copolymer can be 7.0 or more, or 10.0 or more, or 11.0 or more, or 11.4 or more, and is 20.0 or less, or 18.0 or less, or 15.0 or less, or 13.0 or less, or 12.9 or less.

[0147] Since the second ethylene-α-olefin copolymer of the present invention has a relatively high molecular weight and a narrow molecular weight distribution relative to a low melt index as described above, it can simultaneously satisfy excellent mechanical properties and tensile strength characteristics.

[0148] Meanwhile, in this invention, the number-average molecular weight (Mn), weight-average molecular weight (Mw), and molecular weight distribution of the second ethylene-α-olefin copolymer can be determined by measuring the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polyethylene using gel permeation chromatography (GPC), and the molecular weight distribution can be calculated as the ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn).

[0149] Specifically, polyethylene samples were tested using a Polymer Laboratories PLgel MIX-B 300 mm column and a Waters PL-GPC220 instrument. The test temperature was 160°C, 1,2,4-trichlorobenzene was used as the solvent, and the flow rate was 1 mL / min. Samples were prepared at a concentration of 10 mg / 10 mL and then loaded in 200 μL volumes. Mw and Mn values ​​were obtained using a calibration curve formed using polystyrene standards. Nine polystyrene standards were used, with molecular weights of 2,000 / 10,000 / 30,000 / 70,000 / 200,000 / 700,000 / 2,000,000 / 4,000,000 / 10,000,000.

[0150] In addition, the second ethylene-α-olefin copolymer may include ethylene and one or more α-olefins selected from the group consisting of 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, and mixtures thereof.

[0151] More specifically, the second ethylene-α-olefin copolymer can be a copolymer of ethylene and 1-hexene.

[0152] The second ethylene-α-olefin copolymer can be prepared by, but is not limited to, the following method: copolymerizing ethylene and α-olefin comonomers in the presence of a catalyst composition, while introducing hydrogen gas at a concentration of 150 ppm to 200 ppm based on the total weight of ethylene, wherein the catalyst composition comprises a first metallocene compound represented by Chemical Formula 5 and a second metallocene compound represented by Chemical Formula 6. In this case, the amount of α-olefin comonomer introduced can be from 1% to 3% by weight based on the total weight of ethylene.

[0153] [Chemical Formula 5] (Cp 1 R a ) m (Cp 2 R b M 2 Z 2 3-m In chemical formula 5, M 2 It is a group 4 transition metal; Cp 1 and Cp 2 All are cyclopentadienyl groups, which are either unsubstituted or C-shaped. 1-20 Hydrocarbon substitution; R a and R b They may be the same or different from each other, and each is independently hydrogen or carbon. 1-20 Alkyl, C 1-20 Alkoxy, C 2-20 Alkoxyalkyl, C 6-20 Aryl, C 6-20 aryloxy group, C 2-20 alkenyl, C 7-40 alkylaryl, C 7-40 Aryl alkyl, C 8-40 Arylene, C 2-20 Alkyne group, or a substituted or unsubstituted C group containing one or more heteroatoms selected from N, O, and S. 2-20 heteroaryl, provided that R a and R b At least one or more of them are not hydrogen; Z2 Each is independently a halogen, C 1-20 Alkyl, C 2-20 alkenyl, C 7-40 alkylaryl, C 7-40 Aryl alkyl, C 6-20 aryl, substituted or unsubstituted C 1-20 Alkylidene, substituted or unsubstituted amino groups, C 2-20 Alkoxyalkyl or C 7-40 arylalkoxy groups; and m is 1 or 0; [Chemical Formula 2]

[0154] In chemical formula 6, M 3 It is a group 4 transition metal. T 2 Is it carbon, silicon, or germanium? X 3 and X 4 They may be the same as or different from each other, and each is independently a halogen or C. 1-20 alkyl, R 11 To R 14 They may be the same or different from each other, and each is independently hydrogen or carbon. 1-20 Alkyl, C 2-20 alkenyl, C 6-20 Aryl, C 7-20 alkylaryl, C 7-20 Aryl alkyl, or R 11 To R 14 Two or more adjacent groups are connected to each other to form substituted or unsubstituted aliphatic or aromatic rings, or contain any one or more heteroaromatic rings selected from N, O and S.

[0155] Q 3 and Q 4 C represents those that are the same as or different from each other and are independent of each other. 1-20 Alkyl, C 2-20 alkenyl, C 6-30 Aryl or C 2-20 Alkoxyalkyl, and R 15 It is C 1-20 Alkyl, C 2-20 alkenyl or C 6-30 Aryl.

[0156] In addition, unless otherwise specified herein, the following terms may be defined as follows.

[0157] Halogens can be fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).

[0158] C 1-20 Alkyl groups can be straight-chain, branched, or cyclic. Specifically, C 1-20 Alkyl groups can be C 1-15 Straight-chain alkyl; C 1-10 Straight-chain alkyl; C 1-5 Straight-chain alkyl; C 3-20 Branched or cyclic alkyl groups; C 3-15 Branched or cyclic alkyl groups; or C 3-10 Branched or cyclic alkyl groups. More specifically, C 1-20 Alkyl groups can be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, cyclohexyl, etc.

[0159] C 2-20 The alkenyl group can be straight-chain, branched, or cyclic. Specifically, C 2-20 The alkenyl group can be C 2-20 Straight-chain alkenyl, C 2-10 Straight-chain alkenyl, C 2-5 Straight-chain alkenyl, C 3-20 Branched alkenyl, C 3-15 Branched alkenyl, C 3-10 Branched alkenyl, C 5-20 Cyclic alkenyl or C 5-10 Cyclic alkenyl groups. More specifically, C 2-20 The alkenyl group can be vinyl, propenyl, butenyl, pentenyl, cyclohexenyl, etc.

[0160] C 6-20 Aryl refers to monocyclic, bicyclic, or tricyclic aromatic hydrocarbons, including monocyclic or fused aryl groups. Specifically, C 6-20 The aryl group can be phenyl, biphenyl, naphthyl, anthracene, phenanthryl, or fluorene, etc.

[0161] C 7-40 Alkyl aryl refers to a substituent obtained by replacing one or more hydrogen atoms on an aryl group with an alkyl group. Specifically, C 7-40 The alkyl aryl group can be methylphenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, n-butylphenyl, isobutylphenyl, tert-butylphenyl, or cyclohexylphenyl, etc.

[0162] C 7-40 Aryl groups can refer to substituents obtained by replacing one or more hydrogen atoms on an alkyl group with aryl groups. Specifically, C 7-40 Aryl groups can be benzyl, phenylpropyl, or phenylhexyl, etc.

[0163] C 6-20 The aryloxy group can be phenoxy, biphenoxy, naphthoxy, etc., but is not limited to these.

[0164] C1-20 Alkoxy groups can be methoxy, ethoxy, phenoxy, cyclohexyloxy, etc., but are not limited to these.

[0165] C 2-20 Alkoxyalkyl is a functional group obtained by substituting one or more hydrogen atoms of an alkyl group with an alkoxy group. Specifically, it may include, but is not limited to, alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, isopropoxymethyl, isopropoxyethyl, isopropoxyhexyl, tert-butoxymethyl, tert-butoxyethyl, tert-butoxyhexyl, etc.

[0166] C 1-20 Alkylsilyl or C 1-20 Alkoxysilyl is a functional group obtained by substituting one to three hydrogens of -SiH3 with one to three of the above-mentioned alkyl or alkoxy groups. Specifically, it may include alkylsilyl groups, such as methylsilyl, dimethylsilyl, trimethylsilyl, dimethylethylsilyl, diethylmethylsilyl or dimethylpropylsilyl; alkoxysilyl groups, such as methoxysilyl, dimethoxysilyl, trimethoxysilyl or dimethoxyethoxysilyl; or alkoxyalkylsilyl groups, such as methoxydimethylsilyl, diethoxymethylsilyl or dimethoxypropylsilyl, but is not limited thereto.

[0167] C 1-20 Silyl groups are functional groups obtained by substituting one or more hydrogen atoms of an alkyl group with a silicon group. Specifically, they may include -CH2-SiH3, methylsilylmethyl, or dimethylethoxysilylpropyl, but are not limited to these.

[0168] The sulfonate group has the structure -O-SO2-R', where R' can be C 1-20 Alkyl groups. Specifically, C 1-20 The sulfonate group can be a methanesulfonate group, a phenylsulfonate group, etc., but is not limited to these.

[0169] Heteroaryl groups are C groups containing one or more of N, O, and S. 2-20 Heteroaryl groups include monocyclic heteroaryl groups or fused heteroaryl groups. Specific examples may include xanthonyl, thioxanthonyl, thiophene, furanyl, pyrrolyl, imidazolyl, thiazolyl, oxazolyl, oxadiazolyl, triazolyl, pyridyl, bipyridyl, pyrimidinyl, triazinyl, acridinel, pyridazinyl, quinolinyl, quinazolinyl, quinoxolinyl, phthalazinyl, pyridopyrimidinyl, pyridopyrazinyl, pyrazinopyrazinyl, isoquinolinyl, indolyl, carbazole, benzoxazolyl, benzoimidazolyl, benzothiazolyl, benzocarbazole, benzothiaphene, dibenzothiaphene, benzofuranyl, phenanthrololinyl, isoxazolyl, thiadiazolyl, phenothiazinyl, dibenzofuranyl, etc., but are not limited thereto.

[0170] Within the range of effects that are the same as or similar to the desired effect, the above-mentioned substituents may optionally be replaced by one or more substituents selected from the group consisting of: hydroxyl; halogen; alkyl or alkenyl, aryl, alkoxy; alkyl or alkenyl, aryl, alkoxy containing one or more heteroatoms of groups 14 to 16; silyl; alkylsilyl or alkoxysilyl; phosphin; phosphine anionic group; sulfonate group; and sulfone group.

[0171] Furthermore, "two adjacent substituents connecting with each other to form an aliphatic or aromatic ring" refers to the atoms of two substituents and the atoms attached to these two substituents connecting with each other to form a ring. Specifically, -NR9R 10 R9 and R 10 Examples of compounds that can connect to form aliphatic rings include piperidinyl groups, while -NR9R 10 R9 and R 10 Examples of compounds that connect to form aromatic rings include pyrrole groups, etc.

[0172] In the catalyst composition, the first metallocene compound represented by formula 5 is a compound containing Cp. 1 and Cp 2 Non-crosslinked compounds of ligands are advantageous for the production of low molecular weight copolymers with low SCB (short chain branching) content.

[0173] Specifically, in chemical formula 5, Cp 1 and Cp 2 The ligands may be the same or different from each other, and each may be cyclopentadienyl and constituting one or more, or one to three C ions. 1-10 Alkyl substitution. Due to Cp 1 and Cp 2 The ligands possess unshared electron pairs capable of functioning as Lewis bases, thus enabling high polymerization activity. In particular, due to Cp... 1 and Cp 2 The ligands are cyclopentadienyl groups with relatively low steric hindrance, which exhibit high polymerization activity and low hydrogen reactivity, thus enabling highly active polymerization of low molecular weight polyethylene.

[0174] In addition, Cp 1 and Cp 2 The properties of the prepared polyethylene, such as chemical structure, molecular weight, molecular weight distribution, mechanical properties, and transparency, can be easily controlled by adjusting the degree of steric hindrance effect according to the type of substituted functional groups. Specifically, Cp 1 and Cp 2 The ligands were respectively R a and R b Replace, where R a and R b They are the same or different from each other, and R a and Rb They can each be independently hydrogen or C 1-20 Alkyl, C 2-20 Alkoxyalkyl, C 7-40 Aryl alkyl groups, substituted or unsubstituted, containing one or more heteroatoms selected from N, O, and S 2-12 heteroaryl, more specifically C 1-10 Alkyl, C 2-10 Alkoxyalkyl, C 7-20 Aryl alkyl groups, substituted or unsubstituted, containing one or more heteroatoms selected from N, O, and S 4-12 Mixed aromatic compounds.

[0175] In addition, Cp 1 and Cp 2 There is M between ligands 2 Z 2 3-m And M 2 Z 2 3-m This can affect the storage stability of metal complexes. To more effectively ensure this effect, Z... 1 Each can be independently halogen or C 1-20 Alkyl groups, more specifically, F, Cl, Br, or I. Additionally, M 2 It can be Ti, Zr, or Hf; Zr or Hf; or Zr.

[0176] For the first metallocene compound, in formula 5, Cp 1 and Cp 2 Each can be an unsubstituted or substituted cyclopentadienyl group, R a and R b They can each be independently hydrogen or C 1-10 Alkyl, C 2-10 Alkoxyalkyl or C 7-20 Aryl alkyl group, wherein R a and R b At least one of them is an alkoxyalkyl group, such as tert-butoxyhexyl, and more specifically, -(CH2). p -OR c Substituents (where R) c It is a straight-chain or branched alkyl group having 1 to 6 carbon atoms (p is an integer from 2 to 4). In the preparation of polyethylene using comonomers, this situation shows a low comonomer conversion compared to other Cp-based catalysts without the above-mentioned substituents, thus producing low molecular weight polyethylene in which the degree of copolymerization or comonomer distribution is controlled. Furthermore, when a first metallocene compound having the above structure is supported on a support, the -(CH2) substituent... p -OR cThe functional groups can form covalent bonds through close interaction with silanol groups on the silica surface used as a support. Therefore, stable supported polymerization can be carried out.

[0177] The first metallocene compound represented by chemical formula 5 can be a compound represented by, for example, one of the following structural formulas, but is not limited thereto.

[0178] .

[0179] The first metallocene compound represented by chemical formula 5 can be synthesized by applying known reactions; more detailed synthesis methods can be understood by referring to the examples.

[0180] Meanwhile, in one embodiment of the present invention, the second metallocene compound represented by Formula 6 comprises an aromatic ring compound containing a cyclopentadienyl group or a derivative thereof and a nitrogen atom, and the aromatic ring compound and the nitrogen atom are connected by a bridging group T in its structure. 2 Q 3 Q 4 Crosslinking. Second metallocene compounds with this specific structure exhibit high activity and copolymerization ability when applied to the polymerization reaction of polyethylene, and can provide high molecular weight olefin copolymers.

[0181] In particular, due to the well-known confined geometry catalyst (CGC) structure of the second metallocene compound represented by Formula 6, the introduction of comonomers is highly effective, and the distribution of comonomers is controlled by the electronic and spatial properties of the ligands. These properties control the average ethylene sequence length (ASL) to increase the proportion of medium- to high-molecular-weight regions in the molecular weight distribution, thereby increasing the fraction of chain-linked molecules and the degree of polymer chain entanglement. Therefore, polyethylene resins exhibiting long-term stability, processability, and excellent pipe pressure resistance are readily prepared.

[0182] M of the metallocene compound represented by chemical formula 6 3 It can be a Group 4 transition metal, and preferably titanium (Ti), zirconium (Zr) or hafnium (Hf).

[0183] Preferably, T in chemical formula 6 2 It can be silicon.

[0184] Preferably, X in chemical formula 6 3 and X 4 They can each be methyl or chlorine (Cl) independently.

[0185] Preferably, R in chemical formula 6 11 To R 14 They may be the same as or different from each other, and each can be methyl or phenyl independently.

[0186] Preferably, the adjacent Rs in chemical formula 611 To R 14 Two or more groups in a compound form a substituted or unsubstituted aliphatic or aromatic ring, or contain one or more heteroaromatic rings selected from N, O, and S. For example, in Formula 6, adjacent R groups... 11 To R 14 Two or more groups in the compound are linked together to form an aliphatic ring, an aromatic ring, or a heteroaromatic ring, thereby forming an indole, fluorenyl, benzothiophene, or dibenzothiophene group fused with cyclopentadiene. Furthermore, the indole, fluorenyl, benzothiophene, and dibenzothiophene groups can be substituted by one or more substituents.

[0187] Preferably, R in chemical formula 6 15 To R 16 They can be the same as or different from each other, and each can be methyl, ethyl, phenyl, propyl, hexyl or tert-butoxyhexyl.

[0188] Preferably, R in chemical formula 6 17 It can be methyl, ethyl, n-propyl, isopropyl, n-butyl, or tert-butyl.

[0189] As a second metallocene compound capable of providing polyethylene resin with excellent long-term stability and processability due to the increased medium and high molecular weight regions, as well as pipe internal pressure resistance, the metallocene compound of Formula 6 can be any one selected from the group consisting of compounds, but the invention is not limited thereto: .

[0190] The second metallocene compound represented by Formula 6 can be synthesized using known reactions. Specifically, it can be prepared by connecting a nitrogen compound and a cyclopentadiene derivative with a bridging compound to prepare a ligand compound, followed by a metal precursor compound to undergo a metallization reaction. However, this method is not limited to this; more detailed synthetic methods can be understood by referring to the examples.

[0191] The second metallocene compound of formula 6 exhibits excellent activity and can polymerize high molecular weight polyethylene resin. In particular, it still exhibits high polymerization activity even when used by loading onto a support, thereby preparing polyethylene resin with ultra-high molecular weight.

[0192] Furthermore, even when using hydrogen for polymerization to prepare polyethylene resin with high molecular weight and a wide molecular weight distribution, the second metallocene compound represented by Formula 6 according to the present invention exhibits low hydrogen reactivity, thus enabling highly active polymerization of polyethylene resin with ultra-high molecular weight. Therefore, even when used in combination with catalysts possessing other properties, polyethylene resin satisfying the high molecular weight characteristics can be prepared without reducing activity, thus making it easy to prepare polyethylene resin containing high molecular weight polyethylene resin and having a wide molecular weight distribution.

[0193] As described above, in the catalyst composition, the first metallocene compound represented by Formula 5 primarily contributes to the preparation of low molecular weight copolymers with low SCB content, while the second metallocene compound represented by Formula 6 primarily contributes to the generation of high molecular weight copolymers with high SCB content. More specifically, the catalyst composition exhibits a high comonomer incorporation rate of the second metallocene compound relative to the comonomers in the high molecular weight region of the copolymer, while exhibiting a low comonomer incorporation rate of the first metallocene compound relative to the comonomers in the low molecular weight region of the copolymer. Therefore, polyethylene resins exhibiting excellent mechanical properties and excellent heat resistance due to their bimodal molecular weight distribution can be prepared.

[0194] Specifically, by controlling the content ratio of the first and second metallocene compounds in the catalyst composition of the present invention, the above-mentioned physical properties can be achieved and the improvement effect can be further enhanced. Specifically, the second metallocene compound is included in the catalyst composition at a higher content than the first metallocene compound to increase the medium and high molecular weight regions in the molecule, thereby increasing the fraction of chain-linked molecules and the degree of polymer chain entanglement, and optimizing the ratio of high molecular weight regions to low molecular weight regions.

[0195] Specifically, the first and second metallocene compounds should be contained in a molar ratio of 1:1 to 1:8. Preferably, the first and second metallocene compounds can be contained in a molar ratio of 1:1 to 1:7, 1:1 to 1:6, or 1:1 to 1:5.5. When the first and second metallocene compounds are contained in the above molar ratios, the balance between the mechanical and tensile properties of the polyethylene resin prepared using the compounds can be controlled. Therefore, the resin maintains mechanical properties, production efficiency, and tensile stability comparable to or better than conventional resins, and its shrinkage resistance, printability, and transparency can be improved.

[0196] Meanwhile, the first and second metallocene compounds possess the aforementioned structural characteristics, thus allowing them to be stably loaded onto the support.

[0197] In this configuration, the first and second metallocene compounds are used in a supported state. When used as a supported catalyst, the prepared polymer exhibits excellent particle shape and packing density, and the catalyst is suitable for conventional slurry polymerization or bulk polymerization as well as gas-phase polymerization processes.

[0198] Specific examples of supports may include silica, alumina, magnesium oxide, silica-alumina, or silica-magnesium oxide, and they typically also contain oxides, carbonates, sulfates, or nitrates, such as Na₂O, K₂CO₃, BaSO₄, and Mg(NO₃)₂. Among these supports, when silica is used, very little catalyst is released from the support surface during propylene polymerization because the transition metal compounds are fixed to the support by chemical bonds with active functional groups (e.g., siloxane groups) present on the silica support surface. Therefore, when preparing polypropylene using slurry polymerization or gas-phase polymerization, scaling that adheres to the reactor walls or to each other can be minimized.

[0199] Furthermore, the surface of the support can be modified by calcination or drying processes to improve its loading efficiency and minimize leaching and scaling. Through the surface modification steps described above, moisture on the support surface that inhibits reaction with the components can be removed, and the content of active functional groups (e.g., hydroxyl and siloxane groups) capable of chemically bonding with the loaded components can be increased.

[0200] Specifically, the calcination or drying process of the support can be carried out within a range covering the temperature from the disappearance of moisture from the support surface to the temperature at which the active functional groups (specifically hydroxyl (OH groups)) present on the surface are completely eliminated. Specifically, the temperature can be 150°C to 600°C, or 200°C to 500°C. When the temperature during the calcination or drying process of the support is low, below 150°C, the moisture removal efficiency is low, and therefore, there is concern that residual moisture on the support may react with the co-catalyst, reducing the loading efficiency. Conversely, when the drying or calcination temperature is too high, above 600°C, the pores on the support surface may merge together, reducing the specific surface area, and many reactive functional groups on the surface (e.g., hydroxyl or silanol groups) may be lost, leaving only siloxane groups. Therefore, there is concern that the number of reactive sites with the co-catalyst will be reduced.

[0201] When the first and second metallocene compounds are supported on a support, for example, when the support is silica, the total loading of the first and second metallocene compounds based on 1 g of silica can be 40 μmol or more, or 80 μmol or more, and less than 240 μmol or less, or less than 160 μmol. When loaded within the above range, suitable supported catalyst activity can be exhibited, which is beneficial for maintaining catalyst activity and economic feasibility.

[0202] Furthermore, the catalyst composition may further include a co-catalyst to improve high activity and process stability. The co-catalyst is as described above.

[0203] Furthermore, the amount of co-catalyst can be appropriately controlled according to the desired properties or effects of the catalyst and resin composition. For example, when silica is used as a support, the loading of the co-catalyst can be above 8 mmol, or above 10 mmol, and below 25 mmol, or below 20 mmol, based on the weight of the support, such as 1 g of silica.

[0204] Furthermore, the catalyst composition can be used alone in the polymerization reaction, or it can be contacted with ethylene monomers before being used in the polymerization reaction to be used in a prepolymerized state. In this case, the preparation method according to embodiments of the present invention may further include a prepolymerization step of contacting the catalyst composition with ethylene monomers before preparing polyethylene by polymerization.

[0205] Furthermore, the catalyst composition can be dissolved or diluted in an aliphatic hydrocarbon solvent having 5 to 12 carbon atoms (e.g., pentane, hexane, heptane, nonane, decane and their isomers); an aromatic hydrocarbon solvent (e.g., toluene and benzene); or a chlorinated hydrocarbon solvent (e.g., dichloromethane and chlorobenzene), and then introduced into the polymerization reaction described below. The solvent is preferably used after treatment with a small amount of alkylaluminum to remove trace amounts of water or air that act as catalyst poisons. A co-catalyst may also be used further.

[0206] Simultaneously, the polymerization process can be carried out by contacting ethylene and comonomers in the presence of the aforementioned catalyst composition. In particular, the polymerization reaction can be carried out in a single polymerization reactor.

[0207] Typically, in conventional bimodal polymerization, two or more reactors are used depending on the amount of catalyst, and the catalyst is injected into each of these reactors separately for polymerization, thereby generating polymers with different molecular weights, which are then mixed. However, a problem arises in this approach: the difference in molecular weight leads to reduced uniformity. Therefore, in this invention, two catalysts are co-loaded on the same support and subjected to unimodal polymerization in a single reactor, thereby simultaneously polymerizing low-molecular-weight and high-molecular-weight polymers. This allows for the preparation of polymers with excellent uniformity.

[0208] Furthermore, the polymerization temperature can range from 25°C to 500°C, preferably from 25°C to 200°C, and more preferably from 50°C to 150°C. Additionally, the polymerization pressure can be 1 kgf / cm². 2 Up to 100 kgf / cm 2 1kgf / cm 2 Up to 50 kgf / cm 2 .

[0209] Furthermore, during the polymerization process, the amount of α-olefin comonomer added can be from 1% to 3% by weight, based on the total weight of ethylene.

[0210] The amount of α-olefin comonomer added, along with the catalyst structure and the amount of hydrogen added, collectively affects the molecular weight and molecular structure of the final prepared second ethylene-α-olefin copolymer. In this invention, when the α-olefin comonomer is introduced within the above-mentioned amount range, a second ethylene-α-olefin copolymer with high molecular weight and a wide molecular weight distribution can be easily achieved. More specifically, based on the total weight of ethylene, the amount of α-olefin comonomer added can be 1% by weight or more, or 1.2% by weight or more, or 1.5% by weight or more, or 1.6% by weight or more, and is less than 3% by weight, or less than 2.5% by weight, or less than 2% by weight, or less than 1.8% by weight.

[0211] Furthermore, polymerization can be carried out by continuously polymerizing ethylene and α-olefin monomers in the presence of a catalyst composition while continuously introducing hydrogen.

[0212] Hydrogen gas inhibits the rapid reaction of transition metal compounds in the early stages of polymerization and is used to terminate the polymerization reaction. Therefore, by using hydrogen gas and controlling its amount, ethylene / α-olefin copolymers with controlled molecular weight distributions can be prepared efficiently.

[0213] Specifically, in this invention, the amount of hydrogen input can be from 150 ppm to 200 ppm based on the total weight of ethylene. When hydrogen is input within the above range, a second ethylene-α-olefin copolymer with a high molecular weight and a wide molecular weight distribution can be easily achieved. More specifically, the amount of hydrogen input can be 150 ppm or more, or 155 ppm or more, or 160 ppm or more, and less than 200 ppm, or less than 180 ppm, or less than 170 ppm, or less than 165 ppm based on the total weight of ethylene.

[0214] The above preparation method can be used to prepare a second ethylene-α-olefin copolymer with the above physical properties.

[0215] (Biaxial stretch film) The polyethylene resin composition having the above-described physical properties can be used to manufacture biaxially stretched films that exhibit excellent surface properties by improving melt fracture. Therefore, the present invention provides a biaxially stretched film comprising the aforementioned polyethylene resin composition.

[0216] In addition to using the above-mentioned polyethylene resin composition, biaxially stretched films can be manufactured using conventional film manufacturing methods.

[0217] For example, to manufacture the biaxially stretched film according to this disclosure, a polyethylene resin composition sheet with a thickness of 0.75 mm can be produced using a Bruckner'slab extrusion line (L / D ratio: 42, screw diameter: 25 mm, melt / T-die temperature: 220°C). The polyethylene biaxially stretched film can then be manufactured using a KARO 5.0 apparatus by biaxially stretching the polyethylene resin composition sheet having dimensions of 90 mm × 90 mm. Detailed methods and conditions for film manufacturing are described in the experimental examples described later.

[0218] In addition to the aforementioned polyethylene resin composition, the biaxially stretched film according to this disclosure may also contain additives known in the art. Specifically, the additives may include solvents, heat stabilizers, antioxidants, UV absorbers, light stabilizers, metal passivators, fillers, reinforcing agents, plasticizers, lubricants, emulsifiers, pigments, optical brighteners, flame retardants, antistatic agents, foaming agents, etc. There are no particular limitations on the type of additives; common additives known in the art may be used.

[0219] The polyethylene biaxially stretched film manufactured using the above method according to one embodiment of the present invention exhibits excellent surface properties.

[0220] Beneficial effects The polyethylene resin composition according to this disclosure can prevent surface defects during the manufacture of biaxially stretched films by improving melt fracture. Therefore, biaxially stretched films with excellent surface properties can be manufactured using the polyethylene resin composition. Attached Figure Description

[0221] Figure 1 The molecular weight distribution diagrams were obtained by gel permeation chromatography analysis of the polyethylene resin compositions of Examples 1 and 2 and Comparative Example 2. Figure 2 This is a graph showing the ARES analysis results of the polyethylene resin compositions of Examples 1 and 2, and Comparative Example 2; Figure 3 This is a graph showing the observations of the temperatures at the onset of melt fracture for the polyethylene resin compositions of Examples 1 and 2, and Comparative Example 2. Detailed Implementation

[0222] The embodiments of the present invention will be described in more detail below. However, the following embodiments are merely illustrative of the embodiments of the present invention and are not intended to limit the present invention.

[0223] <Preparation of Metallocene Compounds> Synthesis Example 1 (1) (1) Preparation of ligand compounds A 1-benzothiophene solution was prepared by dissolving 4.0 g (30 mmol) of 1-benzothiophene in THF. Then, 14 mL of n-BuLi solution (36 mmol, 2.5 M hexane) and 1.3 g of CuCN (15 mmol) were added to the 1-benzothiophene solution. Subsequently, 3.6 g of crotonyl chloride (30 mmol) was slowly added to the above solution, which was at -80 °C, and the resulting solution was stirred at room temperature for approximately 10 hours. Afterward, the reaction was terminated by adding 10% HCl to the above solution, and the organic layer was separated with dichloromethane to obtain a pale yellow solid (2E)-1-(1-benzothiophene-2-yl)-2-methyl-2-buten-1-one.

[0224]

[0225] 1 H NMR(CDCl3): 7.85-7.82(m, 2H), 7.75(m, 1H), 7.44-7.34(m, 2H), 6.68(m, 1H), 1.99(m, 3H), 1.92(m, 3H).

[0226] 34 mL of sulfuric acid was slowly added to a solution obtained by dissolving 5.0 g of (2E)-1-(1-benzothiophene-2-yl)-2-methyl-2-buten-1-one (22 mmol) prepared above in 5 mL of chlorobenzene, and the mixture was stirred vigorously. The solution was then stirred at room temperature for about 1 hour. Afterward, ice water was poured into the solution, and the organic layer was separated with diethyl ether to give 4.5 g of 1,2-dimethyl-1,2-dihydro-3H-benzo[b]cyclopentano[d]thiophene-3-one as a yellow solid (91% yield).

[0227]

[0228] 1 H NMR(CDCl3): 7.95-7.91(m, 2H), 7.51-7.45(m, 2H), 3.20(m, 1H), 2.63(m, 1H), 1.59(d, 3H), 1.39(d, 3H).

[0229] At 0 °C, 570 mg NaBH4 (15 mmol) was added to a solution obtained by dissolving 2.0 g of 1,2-dimethyl-1,2-dihydro-3H-benzo[b]cyclopenta[d]thiophene-3-one (9.2 mmol) in a mixed solvent of 20 mL THF and 10 mL methanol. The solution was then stirred at room temperature for approximately 2 hours. Subsequently, HCl was added to adjust the pH to 1, and the organic layer was separated with diethyl ether to obtain the alcohol intermediate.

[0230] An alcohol intermediate was dissolved in toluene to prepare a solution. Then, 190 mg of p-toluenesulfonic acid (1.0 mmol) was added to the solution and the mixture was refluxed for about 10 minutes. The resulting reaction mixture was separated by column chromatography to give 1.8 g of 1,2-dimethyl-3H-benzo[b]cyclopentano[d]thiophene (ligand A) in orange-brown liquid form (9.0 mmol, 98% yield).

[0231]

[0232] 1 H NMR(CDCl3): 7.81(d, 1H), 7.70(d, 1H), 7.33(t, 1H), 7.19(t, 1H), 6.46(s, 1H), 3.35(q, 1H), 2.14(s, 3H), 1.14(d, 3H).

[0233] Weigh 4.65 g of the compound prepared above (15.88 mmol) into a 100 mL Schlenk flask and add 80 mL of THF. Add tBuNH2 (4 equivalents, 6.68 mL) at room temperature and react for 3 days at room temperature. After the reaction, remove the THF and filter the resulting product together with hexane. After drying the solvent, 4.50 g of N-tert-butyl-1-(1,2-dimethyl-3H-benzo[b]cyclopentano[d]thiophen-3-yl)-1,1-dimethylsilane (86% yield) in the form of a yellow liquid.

[0234] 1 H-NMR (500 MHz, CDCl3): δ 7.99 (d, 1H), 7.83 (d, 1H), 7.35 (dd, 1H), 7.24 (dd, 1H), 3.49 (s, 1H), 2.37 (s, 3H), 2.17 (s, 3H), 1.27 (s, 9H), 0.19(s, 3H), -0.17(s, 3H).

[0235] (2) Preparation of metallocene compound (1) The ligand compound (1.06 g, 3.22 mmol / 1.0 equivalent) and 16.0 mL of MTBE (0.2 M) were added to a 50 mL Schlenk flask and stirred. n-BuLi (2.64 mL, 6.60 mmol / 2.05 equivalent, 2.5 M THF solution) was added at -40 °C, and the reaction was allowed to proceed overnight at room temperature. Then, MeMgBr (2.68 mL, 8.05 mmol / 2.5 equivalent, 3.0 M diethyl ether solution) was slowly added at -40 °C, followed by TiCl4 (2.68 mL, 3.22 mmol / 1.0 equivalent, 1.0 M toluene solution), and the reaction was allowed to proceed overnight at room temperature. The reaction mixture was then filtered through diatomaceous earth with hexane. After drying the solvent, 1.07 g of a brown solid (82% yield) was given.

[0236] 1 H-NMR (500 MHz, CDCl3): δ 7.99 (d, 1H), 7.68 (d, 1H), 7.40 (dd, 1H), 7.30 (dd, 1H), 3.22 (s, 1H), 2.67 (s, 3H), 2.05 (s, 3H), 1.54 (s, 9H), 0.58(s, 3H), 0.57 (s, 3H), 0.40 (s, 3H), -0.45 (s, 3H).

[0237] Synthesis Example 2 (2) tert-butyl-O-(CH2)6-Cl was prepared using 6-chlorohexanol according to the method described in the literature (Tetrahedron Lett. 2951 (1988)), and reacted with Na(C5H5) [NaCp] to give tert-butyl-O-(CH2)6-C5H5 (60% yield, bp 80°C / 0.1 mmHg).

[0238] Furthermore, tert-butyl-O-(CH2)6-C5H5 was dissolved in tetrahydrofuran (THF) at -78°C, and n-BuLi was slowly added to it, followed by heating to room temperature and reacting for 8 hours. The synthesized lithium salt solution was then slowly added to a suspension of ZrCl4(THF)2 (170 g, 4.50 mmol) / THF (30 mL) at -78°C, and reacted further at room temperature for 6 hours. All volatile substances were dried under vacuum, and the resulting oily liquid material was filtered by adding hexane. After vacuum drying of the filtrate, hexane was added to induce precipitation at low temperature (-20°C). The resulting precipitate was filtered at low temperature to give the white solid [tert-butyl-O-(CH2)6-C5H4]2ZrCl2 compound (92% yield).

[0239] 1 H-NMR (300 MHz, CDCl3): δ 6.28 (t, J=2.6 Hz, 2H), 6.19 (t, J=2.6 Hz,2H), 3.31 (t, 6.6 Hz, 2H), 2.62 (t, J=8 Hz), 1.7 - 1.3 (m, 8H), 1.17 (s, 9H).

[0240] 13 C-NMR (CDCl3): δ 135.09, 116.66, 112.28, 72.42, 61.52, 30.66, 30.31, 30.14, 29.18, 27.58, 26.00.

[0241] Synthesis Example 3 (3) 50 g of Mg was added to a 10 L reactor at room temperature, followed by 300 mL of THF. 0.5 g of I₂ was then added, and the reactor temperature was maintained at 50 °C. After the reactor temperature stabilized, 250 g of 6-tert-butoxyhexyl chloride was added to the reactor at a rate of 5 mL / min using a feed pump. It was observed that the reactor temperature increased by 4 °C to 5 °C with the addition of 6-tert-butoxyhexyl chloride. The addition of 6-tert-butoxyhexyl chloride was continued while stirring for 12 hours. After 12 hours of reaction, a black reaction solution was obtained. 2 mL of the black reaction solution was taken, and water was added to obtain an organic layer, which was obtained by... 1 H-NMR analysis identified it as 6-tert-butoxyhexane, indicating that the Grignard reaction was successfully carried out. Thus, 6-tert-butoxyhexyl magnesium chloride was synthesized.

[0242] 500 g of MeSiCl3 and 1 L of THF were added to a reaction vessel, and the reaction vessel was then cooled to -20°C. 560 g of the synthesized 6-tert-butoxyhexyl magnesium chloride was added to the reaction vessel using a feed pump at a rate of 5 mL / min. After the Grignard reagent was added, the mixture was stirred for 12 hours while the temperature was slowly increased to room temperature. After 12 hours of reaction, a white MgCl2 salt was observed to form. 4 L of hexane was added, and the salt was removed using a labdori filter to obtain a filtrate. The resulting filtrate was added to the reaction vessel, and the hexane was removed at 70°C to obtain a pale yellow liquid. 1 The liquid obtained by H-NMR identification was the target compound methyl(6-tert-butoxyhexyl)dichlorosilane.

[0243] 1H-NMR (300 MHz, CDCl3): δ 3.3 (t, 2H), 1.5 (m, 3H), 1.3 (m, 5H), 1.2(s, 9H), 1.1 (m, 2H), 0.7 (s, 3H).

[0244] 1.2 mol of tetramethylcyclopentadiene (150 g) and 2.4 L of THF were added to a reactor, and the reactor temperature was then cooled to -20°C. 480 mL of n-BuLi was added to the reactor using a feed pump at a rate of 5 mL / min. After the addition of n-BuLi, the mixture was stirred for 12 hours while slowly heating to room temperature. After 12 hours of reaction, 1 equivalent of methyl(6-tert-butoxyhexyl)dichlorosilane (326 g, 350 mL) was rapidly added to the reactor. The mixture was stirred for 12 hours while slowly heating to room temperature. Then, the reactor temperature was cooled to 0°C again, and 2 equivalents of t-BuNH2 were added. The mixture was stirred for 12 hours while slowly heating to room temperature. After 12 hours of reaction, THF was removed. 4 L of hexane was added, and the salt was removed by a labdori filter to obtain a filtrate. The resulting filtrate was added back to the reactor, and the hexane was removed at 70°C to obtain a yellow solution. 1 The yellow solution obtained by H-NMR identification is methyl(6-tert-butoxyhexyl)(tetramethylCpH)tert-butylaminosilane.

[0245] TiCl3(THF)3 (10 mmol) was rapidly added at -78°C to the dilithium salt of a ligand synthesized from n-BuLi and the synthesized ligand dimethyl(tetramethylCpH)tert-butylaminosilane in a THF solution. The reaction solution was stirred for 12 hours while being slowly heated from -78°C to room temperature. After stirring for 12 hours, an equivalent of PbCl2 (10 mmol) was added to the reaction solution at room temperature, followed by stirring for another 12 hours. After stirring for 12 hours, a deep black solution with a blue tint was obtained. THF was removed from the resulting reaction solution, and hexane was added to filter the product. Hexane was removed from the resulting filtrate, and then... 1 H-NMR identified the product as the target compound (tBu-O-(CH2)6)(CH3)Si(C5(CH3)4)(tBu-N)TiCl2([methyl(6-tert-butoxyhexyl)silyl(η5-tetramethylCp)(tert-butylamino)]TiCl2).

[0246] 1H-NMR (300 MHz, CDCl3): δ 3.3 (s, 4H), 2.2 (s, 6H), 2.1 (s, 6H), 1.8~ 0.8 (m), 1.4 (s, 9H), 1.2 (s, 9H), 0.7 (s, 3H).

[0247] <Preparation of Supported Catalysts> Catalyst Preparation Example 1: Preparation of Hybrid Supported Metallocene Catalysts 5.0 kg of toluene solution was added to a 20 L stainless steel (SUS) high-pressure reactor, and the reactor temperature was maintained at 40 °C. 1000 g of silica (Grace Davison, SYLOPOL 948), which had been dehydrated under vacuum at 600 °C for 12 hours, was added to the reactor and dispersed thoroughly. Then, 80 g of the metallocene compound (2) prepared in Synthesis Example 2 was dissolved in toluene and added to the reactor. The reaction was then carried out by stirring at 40 °C and 200 rpm for 2 hours. Afterward, stirring was stopped, the mixture was allowed to stand for 30 minutes, and then the reaction solution was decanted.

[0248] 2.5 kg of toluene was added to a reaction vessel, followed by 9.4 kg of a 10 wt% methylaluminoxane (MAO) / toluene solution. The mixture was then stirred at 40 °C and 200 rpm for 12 hours. After the reaction was complete, stirring was stopped, and the mixture was allowed to stand for 30 minutes before decanting. 3.0 kg of toluene was then added and stirred for 10 minutes. Stirring was then stopped, and the mixture was allowed to stand for 30 minutes before decanting.

[0249] 3.0 kg of toluene was added to the reactor, followed by 314 mL of a 29.2 wt% solution of metallocene compound (3) / toluene prepared in Synthesis Example 3. The reaction was carried out by stirring at 40 °C and 200 rpm for 2 hours. At this point, the molar ratio of metallocene compound (2) to metallocene compound (3) was 1:5 (the ratio of the number of moles of metallocene compound (2) to the number of moles of metallocene compound (3)). After the reactor temperature was lowered to room temperature, stirring was stopped, and the mixture was allowed to stand for 30 minutes before the reaction solution was decanted.

[0250] (2) (3) Add 2.0 kg of toluene to the reaction vessel and stir for 10 minutes. Then stop stirring, let stand for 30 minutes, and then decant the reaction solution.

[0251] 3.0 kg of hexane was added to the reactor, and the hexane slurry was transferred to a filter dryer to filter the hexane solution. The resulting filtrate was dried under reduced pressure at 40 °C for 4 hours to prepare 910 g of SiO2 hybrid supported catalyst.

[0252] Catalyst Preparation Example 2 Add 3.0 kg of toluene solution to a 20 L stainless steel (SUS) high-pressure reactor and maintain the reactor temperature at 40°C. Add 500 g of silica (Grace Davison, SP2212) that has been dehydrated under vacuum at 600°C for 12 hours to the reactor and disperse it thoroughly. Then add 2.78 kg of a 10 wt% methylaluminoxane (MAO) / toluene solution and stir at 80°C and 200 rpm for at least 15 hours.

[0253] After the reactor temperature was lowered to 40°C, 60g of the first metallocene compound (2) / toluene solution (7.8wt% toluene solution) prepared in Synthesis Example 2 was added to the reactor and stirred at 200 rpm for 1 hour. Subsequently, 230g of the second metallocene compound (3) / toluene solution (7.8wt% toluene solution) prepared in Synthesis Example 3 was added to the reactor and stirred at 200 rpm for 1 hour. At this time, the molar ratio of the first metallocene compound (2) to the second metallocene compound (3) was 1:2.5 (the ratio of the number of moles of the first metallocene compound (2) to the number of moles of the second metallocene compound (3).

[0254] (2) (3) Next, 70g of the co-catalyst (aniline tetra(pentafluorophenyl)borate) was diluted in toluene and added to the reactor. The mixture was then stirred at 200 rpm for at least 15 hours. After the reactor temperature was lowered to room temperature, stirring was stopped, and the mixture was allowed to stand for 30 minutes before the reaction solution was decanted.

[0255] The obtained toluene slurry was transferred to a filter dryer for filtration. 3.0 kg of toluene was added and stirred for 10 minutes, then stirring was stopped and the mixture was filtered. 3.0 kg of hexane was added to the reactor and stirred for 10 minutes, then stirring was stopped and the mixture was filtered. The resulting product was dried under reduced pressure at 50 °C for 4 hours to prepare 500 g of SiO2 supported catalyst.

[0256] Preparation of ethylene-α-olefin copolymers Preparation Example 1: Preparation of Ethylene / 1-Octene Copolymer (PE-a) A 1.5L continuous reaction vessel was preheated to 120°C, and hexane solvent and 1-octene were introduced at a rate of 5 kg / h. Triisobutylaluminum (Tibal, 0.045 mmol / min), the metallocene compound (1) obtained in Synthesis Example 1, and dimethylaniline tetra(pentafluorophenyl)borate cocatalyst (2.6 μmol / min) were simultaneously introduced into the reaction vessel. Subsequently, ethylene (0.87 kg / h) and hydrogen (10 cc / min) were introduced into the reaction vessel, and the copolymerization reaction was carried out in a continuous process at 160.0°C for more than 60 minutes under a pressure of 89 bar to obtain the ethylene / 1-octene copolymer (PE-a).

[0257] Preparation Example 2: Preparation of Ethylene / 1-Hexene Copolymer (PE-b) Slurry polymerization was carried out in the presence of the hybrid supported catalyst prepared in Catalyst Preparation Example 1 to obtain ethylene / 1-hexene copolymer (PE-b).

[0258] At this point, the polymerization reactor was a continuous polymerization reactor using an isobutane (i-C4) slurry loop process, with a reactor volume of 140 L and a flow rate of approximately 7 m / s. Ethylene, hydrogen, and the comonomer 1-hexene required for polymerization were continuously introduced, and their respective flow rates were adjusted according to the target product. At this point, the ethylene input rate was 31.1 kg / hr, the 1-hexene input rate was adjusted to 2.5 wt% based on ethylene, and the hydrogen input rate was adjusted to 56 ppm based on ethylene. Furthermore, the concentrations of all gases and the comonomer 1-hexene in Preparation Example 1 were confirmed by online gas chromatography. The supported catalyst was prepared and introduced in the form of a 4 wt% isobutane slurry, the reactor pressure was maintained at approximately 40 bar, and the polymerization temperature was approximately 80 °C.

[0259] Preparation Examples 3 and 4: Preparation of ethylene / 1-hexene copolymers (PE-c and PE-d) The hybrid supported catalyst prepared in Example 2 was used to polymerize ethylene / 1-hexene copolymers (PE-c and PE-d) in a single loop slurry reactor under the conditions shown in Table 1 below.

[0260] Table 1

[0261] In Table 1, the units for comonomer input (wt%) and hydrogen input (ppm) are based on the total weight of ethylene input.

[0262] <Preparation of Polyethylene Resin Composition> Comparative Example 1 30% by weight of the ethylene / 1-octene copolymer (PE-a) prepared in Preparation Example 1 and 70% by weight of the ethylene / 1-hexene copolymer (PE-b) prepared in Preparation Example 2 were mixed as described in Table 2, and then extruded and granulated at 220°C with a hopper speed of 18 rpm and a screw speed of 350 rpm using a twin-screw extruder (extruder: SMPLATEK TEK30MHS, length-to-diameter ratio: 40, die diameter: 4 mm, extrusion conditions: hopper speed 18 rpm, screw speed 350 rpm, 220°C) to prepare a polyethylene resin composition.

[0263] Comparative Examples 2 and 3 Except for the polyethylene prepared in Preparation Examples 3 and 4, each polyethylene resin composition was prepared in the same manner as in Comparative Example 1.

[0264] Examples 1 to 4 The polyethylene resin compositions of Examples 1 to 4 were prepared by using the polyethylene prepared in Examples 1, 3 and 4 according to the composition described in Table 3 below.

[0265] Specifically, each polyethylene resin composition was prepared by extrusion granulation at 220°C using a twin-screw extruder (extruder: SMPLATEK TEK30MHS, length-to-diameter ratio: 40, die diameter: 4 mm, extrusion conditions: hopper speed 18 rpm, screw speed 350 rpm, 220°C) at a hopper speed of 18 rpm and a screw speed of 350 rpm.

[0266] Table 2

[0267] Table 3

[0268] In Tables 2 and 3, the unit "wt%" is based on the total weight of the polyethylene resin composition.

[0269] Experimental Example 1 The physical properties of the polyethylene resin compositions prepared in the examples and comparative examples were measured using the following methods, and the results are shown in the table below. Figures 1 to 3 middle.

[0270] (1) Density Density (g / cm³) 3 Measurements were performed in accordance with the American Society for Testing and Materials (ASTM) standard D 1505.

[0271] (2) Melt index Melt Flow Index (MI) 2.16 )Measured according to ASTM D1238 (condition E, 190°C, 2.16 kg) at 190°C and 2.16 kg load (measuring equipment: Gottfert MI-4) and expressed as the weight (g) of polymer after 10 minutes of melting.

[0272] (3) Melt Flow Rate Ratio (MFRR, MI) 21.6 / MI 2.16 ) The molecular weight (MI) of the polyethylene resin composition was determined according to ASTM D1238 standard. 2.16 (190℃, under a load of 2.16kg) and MI 21.6 (190℃, under a load of 21.6kg), and through MI 21.6 value divided by MI 2.16 The value is used to calculate the melt flow rate ratio (MFRR). MFRR is commonly used as a value to indicate the shear thinning effect.

[0273] (4) Weight-average molecular weight (Mw) and molecular weight distribution (PDI) For the polyethylene resin compositions according to the examples and comparative examples, their weight-average molecular weight (Mw, g / mol) and number-average molecular weight (Mn, g / mol) were determined by gel permeation chromatography (GPC), and the molecular weight distribution (Mw / Mn, PDI, polydispersity index) was calculated by dividing the weight-average molecular weight determined above by the number-average molecular weight.

[0274] Specifically, a Waters PL-GPC 220 instrument was used as the gel permeation chromatography (GPC) instrument, employing a Polymer Laboratories PLgel MIX-B 300 mm column. The test temperature was 160 °C, 1,2,4-trichlorobenzene was used as the solvent, and the flow rate was 1 mL / min. Each of the ethylene-α-olefin copolymer samples prepared above was pretreated by dissolving it in 1,2,4-trichlorobenzene containing 0.0125% BHT at 160 °C for 3 hours using the GPC analyzer (PL-GP220), and samples were prepared at a concentration of 32 mg / 10 mL, then injected in 200 μL volumes. Mw and Mn values ​​were obtained using a calibration curve formed using polystyrene standards. Nine polystyrene standards were used, with weight-average molecular weights of 2000 g / mol, 10000 g / mol, 30000 g / mol, 70000 g / mol, 200000 g / mol, 700000 g / mol, 2000000 g / mol, 4000000 g / mol, and 10000000 g / mol.

[0275] Figure 1 The molecular weight distribution curves of the polyethylene resin compositions of Examples 1 and 2 and Comparative Example 2 obtained by gel permeation chromatography analysis are shown (x-axis: logarithm of weight-average molecular weight (Mw) (g / mol) (logMw), y-axis: molecular weight distribution relative to the logarithm (dW / dlogMw)).

[0276] (5) Bimodal Triangle Region (BMTA) For the polyethylene compositions of Examples 1 to 3 and Comparative Examples 1 to 4, the bimodal triangular region (BMTA) was measured using the following method.

[0277] Specifically, the weight-average molecular weight (Mw, g / mol) was measured using gel permeation chromatography (GPC, manufactured by Water) as described above, in accordance with the American Society for Testing and Materials (ASTM) D 6474 standard. The BMTA (bimodal triangular region) was then measured on a logarithmic plot of the weight-average molecular weight (Mw) of polyethylene, i.e., on a GPC curve with logMW on the x-axis and dw / dlogMw on the y-axis.

[0278] Here, BMTA (Bimodal Triangle Region) corresponds to the triangular region formed by connecting three coordinates on the GPC curve, where these three coordinates are defined as: the maximum peak in the low molecular weight fraction where the maximum peak intensity logMw is less than 5.0 (Peak...). low The maximum intensity coordinates (X-axis: a, Y-axis: d); the maximum peak in high molecular weight fractions with a peak intensity logMw of 5.0 or higher. high The maximum intensity coordinates (X-axis: b, Y-axis: e) of Peak; and the coordinates containing Peak low Low molecular weight fractions and those containing Peak high The coordinates of the intersection point of the high molecular weight fractions (X-axis: c, Y-axis: f). In other words, the area of ​​the BMTA (bimodal triangle region), i.e., the area connecting the low molecular weight fraction peaks (Peak). low The maximum intensity coordinates (X-axis: a, Y-axis: d) and the high molecular weight fraction peak (Peak) high The area of ​​the triangle formed by the maximum intensity coordinates (X-axis: b, Y-axis: e) and the coordinates of the intersection of these two coordinates (X-axis: c, Y-axis: f) is determined by the following formula 1.

[0279] [Formula 1]

[0280] In Formula 1, ae represents the product of the maximum intensity X-axis coordinate value of the low molecular weight fraction and the maximum intensity Y-axis coordinate value of the high molecular weight fraction, bf represents the product of the maximum intensity X-axis coordinate value of the high molecular weight fraction and the Y-axis coordinate value of the intersection point, cd represents the product of the X-axis coordinate value of the intersection point and the maximum intensity Y-axis coordinate value of the low molecular weight fraction, db represents the product of the maximum intensity Y-axis coordinate value of the low molecular weight fraction and the maximum intensity X-axis coordinate value of the high molecular weight fraction, ec represents the product of the maximum intensity Y-axis coordinate value of the high molecular weight fraction and the X-axis coordinate value of the intersection point, fa represents the product of the Y-axis coordinate value of the intersection point and the maximum intensity X-axis coordinate value of the low molecular weight fraction.

[0281] The detailed method is as follows.

[0282] - Peak deconvolution is performed on the Mw curve obtained by GPC analysis (Agilent PL-GPC 220); : Curve fitting is performed using a Gaussian probability function; : The peaks are separated into a low molecular weight fraction (the logMw at the peak maximum intensity is 5.0 or less) and a high molecular weight fraction (the logMw at the peak maximum intensity is more than 5.0); : Select the peak with the largest area among the low molecular weight fractions and the peak with the largest area among the high molecular weight fractions; - The region is determined from a triangle obtained by drawing lines between the points respectively corresponding to the maximum intensity of the selected low molecular weight fraction, the maximum intensity of the selected high molecular weight fraction, and the intersection point of the respective curves, and this region is defined as BMTA.

[0283] - When the maximum intensity coordinate of the low molecular weight fraction is defined as (a, d), the maximum intensity coordinate of the high molecular weight fraction is defined as (b, e), and the coordinate of the intersection point is defined as (c, f), the calculation formula of BMTA is the above-mentioned Formula 1.

[0284] Here, when the low molecular weight fraction and the high molecular weight fraction are not separated on the GPC curve of the polyethylene composition, or when the logMw value of the intersection point is not between the logMw values of the maximum intensity of the low molecular weight fraction and the high molecular weight fraction (c>a, b or c<a, b), BMTA is defined as 0.

[0285] The following Table 2 shows the BMTA values measured in this way. A larger BMTA value indicates a higher degree of bimodal peak separation on the GPC curve, which means a larger low molecular weight region, and accordingly indicates excellent processability.

[0286] (6) Complex viscosity (Pa·S) Using an ARES-G2 rotational rheometer (manufactured by TA) at 230 The complex viscosity (Pa·s) of the polyethylene resin composition was measured at an angular frequency of C and 500 rad / s.

[0287] Furthermore, based on the experimental results of the polyethylene resin compositions in Examples 1 and 2 and Comparative Example 2, Figure 2 The curves showing the change of complex viscosity with frequency are displayed (x-axis: logarithm of frequency (Log(frequency)), y-axis: logarithm of complex viscosity (Log(complex viscosity))).

[0288] (7) Shear viscosity (Pa·S) Using a capillary rheometer at 230 Shear viscosity was measured at C and a shear rate of 1 / 1000 second.

[0289] Specifically, using the Gottfert-manufactured RHEO-TESTER 2000 equipment, with capillary die dimensions (die length (L) = 10 mm, die diameter (D) = 2 mm, [L / D] = 10 / 2) and a temperature of 230°C... The shear viscosity (Pas) was measured at C and a shear rate of 1 / 1000 second.

[0290] (8) Shear rate M.F起始 (MF) 起始 (1 / s) Shear rate M.F起始 It refers to the shear rate (1 / s) at which melt fracture occurs.

[0291] According to ASTM D 3835, the shear viscosity (Pa·s) of a polyethylene resin composition is measured using a capillary rheometer during wire extrusion while the shear rate is varied.

[0292] The results yielded a curve showing the change in shear viscosity as a function of shear rate. The point where the slope of the shear rate / shear viscosity curve changes sharply due to increased shear viscosity instability was defined as the initiation point of melt fracture, and the shear rate at this point was determined as the shear rate. M.F起始 or MF 起始 .

[0293] Specifically, the RHEO-TESTER 2000 device manufactured by Gottfert was used to change the shear rate to 10. 2.0 10 2.2 10 2.4 10 2.6 10 2.8 10 2.9 10 2.95and 10 2.30 s -1 Simultaneously, the surface of the extruded polyethylene resin composition filament is visually observed. The shear viscosity at the point where the surface unevenness begins to be measured is measured. At this time, the orifice shape is circular, the orifice length is 10 mm, the diameter is 2 mm, the run-in angle is 180°, and the measurement temperature is 230°C.

[0294] (9) MF 起始 Stress (Pa) Used at (8) shear rate M.F起始 (MF) 起始 The partial measurements included the shear viscosity (Pa·s) at the starting point of non-uniformity on the wire surface (i.e., the point where melt fracture occurs) and the shear rate (shear rate) at that moment. M.F起始 MF is obtained according to the following formula 2 (1 / s). 起始 Stress (Pa).

[0295] [Formula 2] MF 起始 Stress (Pa) = Shear viscosity at the point where melt fracture occurs (Pa·s) × Shear rate at the point where melt fracture occurs (shear rate) M.F起始 (1 / s).

[0296] Furthermore, using a capillary rheometer, the changes in shear stress of the polyethylene resin compositions of Examples 1 and 2, and Comparative Example 2, were measured during wire extrusion while varying the shear rate. At 100 s... -1 up to 1000s -1 Within the shear rate range, wire samples were taken at eight points and the melt fracture was visually inspected. Results showed... Figure 3 middle.

[0297] Table 4

[0298] Table 5

[0299] Experimental results confirm that melt fracture can only be improved when the molecular weight distribution is broadened, the viscosity is low, and a single-peak shape is maintained; however, when the molecular weight distribution is bimodal, the effect of improving melt fracture may not be achieved. Furthermore, in Examples 1 to 4, which showed improved melt fracture, the formation of contaminants on the film surface during high-speed production can be minimized, thus promising the ability to prepare films with excellent surface properties.

Claims

1. A polyethylene resin composition comprising one or more polyethylenes and satisfying the following requirements (a1) to (a4): (a1) Melt flow rate ratio (MI) 21.6 / MI 2.16 (ASTM D1238, 190℃): 60 to 120; (a2) Density (ASTM D1505): 0.920 g / cm³ 3 Up to 0.950 g / cm 3 ; (a3) Molecular weight distribution: 5.50 to 15.00; (a4) When a molecular weight distribution curve is plotted using the logarithm of the weight-average molecular weight (Mw) (g / mol) obtained by gel permeation chromatography as the x-axis and the molecular weight distribution (dW / dlogMw) relative to the logarithm as the y-axis, the molecular weight distribution type is: single peak.

2. The polyethylene resin composition according to claim 1, wherein, The weight-average molecular weight of the polyethylene resin composition is from 110,000 g / mol to 130,000 g / mol.

3. The polyethylene resin composition according to claim 1, wherein, In 230 The complex viscosity of the polyethylene resin composition was measured using a rotational rheometer at C and 500 rad / s, and was below 400 Pa•s.

4. The polyethylene resin composition according to claim 1, wherein, In 230 C and 1000s -1 Under the conditions measured using a capillary rheometer, the shear viscosity of the polyethylene resin composition is below 300 Pa•s.

5. The polyethylene resin composition according to claim 1, wherein, In 230 C. Using a capillary rheometer, the shear rate of the polyethylene resin composition at the onset of melt fracture was measured to be 1000 s⁻¹. -1 above.

6. The polyethylene resin composition according to claim 1, wherein, The stress of the polyethylene resin composition at the onset of melt fracture was measured using a capillary rheometer at 230°C and was above 265,000 Pa.

7. The polyethylene resin composition according to claim 1, wherein, The bimodal triangular region (BMTA) of the polyethylene resin composition was determined to be 0.05 to 0.15 by gel permeation chromatography.

8. The polyethylene resin composition according to claim 1, wherein, The melt index (MI) of the polyethylene resin composition 2.16 ASTM D1238, 190 C, 2.16kg) ranged from 0.10g / 10min to 2.00g / 10min.

9. The polyethylene resin composition according to claim 1, wherein, The polyethylene resin composition comprises: (a) Density is 0.870 g / cm³ 3 Up to 0.920 g / cm 3 The first ethylene-α-olefin copolymer with a number-average molecular weight Mn of 20,000 g / mol or higher, and (b) Density is 0.945 g / cm³ 3 Up to 0.960 g / cm 3 A second ethylene-α-olefin copolymer with a number-average molecular weight Mn of 10,000 g / mol or more and less than 20,000 g / mol; The first ethylene-α-olefin copolymer and the second ethylene-α-olefin copolymer are different from each other.

10. The polyethylene resin composition according to claim 9, wherein, Based on the total weight of the polyethylene resin composition, the content of the first ethylene-α-olefin copolymer is from 10% to 40% by weight, and the content of the second ethylene-α-olefin copolymer is from 60% to 90% by weight.

11. The polyethylene resin composition according to claim 9, wherein, The melt index (MI) of the first ethylene-α-olefin copolymer 2.16 (ASTM D1238, 190℃, 2.16kg load) 3.0g / 10min to 10.0g / 10min, weight average molecular weight ≥60,000g / mol and <95,000g / mol, molecular weight distribution ≥2.0 and <3.

5.

12. The polyethylene resin composition according to claim 9, wherein, The first ethylene-α-olefin copolymer is a copolymer of ethylene and 1-octene.

13. The polyethylene resin composition according to claim 9, wherein, The melt index (MI) of the second ethylene-α-olefin copolymer 2.16 ASTM D1238, 190 C (at a 2.16 kg load) ranged from 0.10 g / 10 min to 2.00 g / 10 min, with a weight-average molecular weight of 100,000 g / mol to 200,000 g / mol and a molecular weight distribution of 7.0 to 20.

0.

14. The polyethylene resin composition according to claim 9, wherein, The second ethylene-α-olefin copolymer is a copolymer of ethylene and 1-hexene.

15. A biaxially stretched film comprising the polyethylene resin composition according to claim 1.

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