WO2025211711A1 - Polyethylene resin composition and biaxially stretched film comprising same - Google Patents

Abstract

Provided are a polyethylene resin composition and a biaxially stretched film comprising same, wherein the polyethylene resin composition has reduced melt fracture and thus can prevent surface defects during the production of the biaxially stretched film.

Description

Polyethylene resin composition and biaxially oriented film comprising the same

Cross-citation with related application(s)

This application claims the benefit of priority to Korean Patent Application No. 10-2024-0044703, filed April 2, 2024, and Korean Patent Application No. 10-2025-0041093, filed March 31, 2025, the entire contents of which are incorporated herein by reference.

The present invention is capable of preventing surface defects during the production of a biaxially stretched film by improving melt fracture. The present invention relates to a polyethylene resin composition and a biaxially oriented film comprising the same.

Thin film products made from linear low-density polyethylene (LLDPE) or high-density polyethylene (HDPE) are widely used in packaging applications such as merchandise bags, grocery bags, food and specialty packaging, and industrial liners. Shrink film is primarily used in these applications, as it maintains the shape of the product while packaging, protecting it from touch during display.

In particular, among these shrink films, biaxially oriented polymer films are widely used for packaging purposes due to their excellent mechanical properties, productivity, and printability. Commercially available packaging films typically use biaxially oriented polypropylene (BOPP), biaxially oriented polyethylene terephthalate (BOPET), or biaxially oriented polyamide (BOPA) for the print layer, and LLDPE film for the sealing layer. These composite material forms are non-recyclable, and the demand for single-material products is increasing due to the expansion of packaging material recycling regulations. Therefore, research and development is being conducted to manufacture single-material packaging films by replacing the print layer film with biaxially oriented polyethylene (BOPE) film.

However, commercial polyethylene (PE) resins lack sufficient stretching stability, and phenomena such as fracture and melting occur during stretching, making biaxial stretching difficult to apply. To ensure stretching stability, polyethylene resin compositions containing resins with low density and high melt index are being developed. However, such compositions exhibit low rigidity, shrinkage, and impact resistance, making them unsuitable as PE resins for biaxially oriented films.

Accordingly, research and development of a PE resin that has a molecular structure advantageous for stretching and exhibits excellent stretching stability during the production of a biaxially stretched film while improving the surface properties of the film is necessary.

The present invention is capable of preventing the occurrence of surface defects during the production of a biaxially stretched film by improving melt breakage. A polyethylene resin composition and a biaxially oriented film comprising the same are provided.

One embodiment of the present invention provides a polyethylene resin composition comprising at least one type of polyethylene and satisfying the following conditions (a1) to (a4):

(a1) Melt flow index (MI _21.6 /MI _2.16 , ASTM D1238, 190℃): 60 to 120

(a2) Density (ASTM D1505): 0.920 to 0.950 g/cm ³

(a3) Molecular weight distribution: 5.50 to 15.00

(a4) When a molecular weight distribution curve is drawn using the logarithm value (logMw) of the weight average molecular weight (Mw) (g/mol) as the x-axis and the molecular weight distribution (dW/dlogMw) for the logarithm value as the y-axis through gel permeation chromatography analysis, the molecular weight distribution shape is: unimodal.

In addition, another embodiment of the invention provides a biaxially oriented film comprising the polyethylene resin composition of the above embodiment.

Hereinafter, a polyethylene resin composition and a biaxially stretched film according to embodiments of the invention will be described in detail.

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

Singular expressions include plural expressions unless the context clearly indicates otherwise.

In this specification, the terms “comprise,” “include,” or “have” are intended to describe a feature, number, step, component, or combination thereof implemented, but do not exclude the possibility of one or more other features, numbers, steps, components, combinations, or additions thereof.

In addition, the terms "about," "substantially," and the like used throughout this specification are used in a meaning that is at or close to the numerical value when manufacturing and material tolerances inherent to the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosure in which exact or absolute values are mentioned to aid understanding of the present invention.

Additionally, in this specification, (co)polymer means both a homopolymer and a copolymer.

Additionally, unless otherwise defined herein, “copolymerization” may mean block copolymerization, random copolymerization, graft copolymerization, or alternating copolymerization, and “copolymer” may mean block copolymer, random copolymer, graft copolymer, or alternating copolymer.

In addition, in this specification, "part by weight" means a relative concept that expresses the weight of a substance as a ratio based on the weight of the remaining substance. For example, in a mixture containing 50 g of substance A, 20 g of substance B, and 30 g of substance C, the amounts of substance B and substance C are 40 parts by weight and 60 parts by weight, respectively, based on 100 parts by weight of substance A.

Meanwhile, "% by weight" refers to an absolute concept that expresses the weight of a certain substance as a percentage of the total weight. In the mixture in the example above, the contents of substance A, substance B, and substance C are 50% by weight, 20% by weight, and 30% by weight, respectively, out of 100% of the total weight of the mixture.

The present invention is susceptible to various modifications and takes various forms. Specific examples are illustrated and described in detail below. However, this does not limit the invention to a specific disclosed form, but rather encompasses all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

(polyethylene resin composition)

The present invention relates to a polyethylene resin composition having improved melt fracture properties, particularly shark skin melt fracture properties.

Melt fracture, or melt fracture, refers to a phenomenon in which the surface of a polyethylene resin composition becomes unsmooth when the processing speed increases during extrusion processing. Specifically, as the processing speed increases, shear stress increases. When this shear stress exceeds a critical value, the surface contact between the polymer melt and the processing equipment, such as the die, deteriorates, resulting in cohesion failure. This phenomenon causes defects on the product surface.

The inventors of the present invention confirmed that melt fracture occurs when the viscosity of the resin composition is high in the processing area that can represent the shear stress when the processing line speed increases, and improved the melt fracture characteristics, particularly the shark skin melt fracture characteristics, by controlling the molecular structure within the resin composition.

Specifically, the polyethylene resin composition according to the present invention comprises at least one type of polyethylene and satisfies the following conditions (a1) to (a4):

(a1) Melt flow index (MI _21.6 /MI _2.16 , ASTM D1238, 190℃): 60 to 120

(a2) Density (ASTM D1505): 0.920 to 0.950 g/cm ³

(a3) Molecular weight distribution: 5.50 to 15.00

(a4) When a molecular weight distribution curve is drawn using the logarithm value (logMw) of the weight average molecular weight (Mw) (g/mol) as the x-axis and the molecular weight distribution (dW/dlogMw) for the logarithm value as the y-axis through gel permeation chromatography analysis, the molecular weight distribution shape is: unimodal.

Specifically, the polyethylene resin composition according to the present invention exhibits a melt flow rate (MFRR, MI _21.6 / MI _2.16 ) of 60 to 120. If the MFRR is less than 60, the physical properties, particularly the stiffness in the MD direction, may deteriorate during the production of a stretched film, and if the MFRR exceeds 120, the toughness and transparency of the stretched film may deteriorate. More specifically, the MFRR of the polyethylene resin composition may 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 120 or less, or 100 or less, or 95 or less, or 90 or less, or 89.5 or less, or 89 or less.

In the present invention, the MFRR of the polyethylene resin composition is calculated by measuring the melt index (MI _21.6 ) at a temperature of 190°C and under a load of 21.6 kg and the melt index (MI _2.16 ) at a temperature of 190°C and under a load of 2.16 kg according to ASTM D1238, and then dividing the measured MI _21.6 by MI _2.16 .

In addition, the polyethylene resin composition has a density of 0.920 to 0.950 g/cm ³ along with the above-described melting characteristics. If the density is less than 0.920 g/cm ³ , the physical properties, particularly the stiffness in the TD direction, may deteriorate during the production of a stretched film, and if the density exceeds 0.950 g/cm ³ , the film processability and stretchability may deteriorate due to the excessively high density. More specifically, the density of the polyethylene resin composition may be 0.920 g/cm ³ or more, or 0.930 g/cm ³ or more, or 0.932 g/cm ³ or more, or 0.935 g/cm ³ or more, and 0.950 g/cm ³ or less, or 0.945 g/cm ³ or less, or 0.940 g/cm ³ or less.

In the present invention, the density (g/cm ³ ) of the polyethylene resin composition can be measured according to the American Society for Testing and Materials standard ASTM D 1505. The specific measurement method is as described in the following test examples.

Meanwhile, if the viscosity is low in the processing region, melt breakage can be suppressed. The viscosity in the processing region can be lowered by introducing long chain branching (LCB) into the polymer or by broadening the molecular weight distribution (PDI) of the resin composition to a certain level or more. Typically, the PDI is broadened by controlling the polymerization method or by using a method of mixing polymers. In the present invention, the resin composition has a wide PDI by mixing two or more polymers. Specifically, the polyethylene resin composition according to the present invention has a molecular weight distribution (PDI) of 5.50 to 15.00. If the PDI is less than 5.50, the viscosity in the processing region increases significantly due to an excessively narrow molecular weight distribution, and if the molecular weight distribution exceeds 15.00, the viscosity in the processing region decreases significantly, which may result in deterioration of film processability and stretchability. 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 15.00 or less, or 10.00 or less, or 7.00 or less, or 6.70 or less, or 6.65 or less.

Meanwhile, in the present 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), and the weight average molecular weight and number average molecular weight can be measured through gel permeation chromatography (GPC) analysis, and each is a conversion value for standard polystyrene. The specific measurement method and conditions are as described in the experimental examples below.

In addition, the polyethylene resin composition according to the present invention has a wide molecular weight distribution as described above, and when a molecular weight distribution curve is drawn with the logarithm value (log Mw) of the weight average molecular weight (Mw) (g/mol) from the GPC analysis results as the x-axis and the molecular weight distribution (dW/dlogMw) for the logarithm value as the y-axis, the molecular weight distribution curve exhibits a unimodal shape.

In conventional polyethylene resin compositions, the selective increase in the distribution (or content) of low-molecular-weight and high-molecular-weight polymers enhances the molecular structure, which is advantageous for biaxial stretching, while improving physical properties. Consequently, the molecular weight distribution curve exhibits a bimodal shape during GPC analysis.

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

Bimodal polyethylene resin compositions are known to exhibit different melt fracture tendencies from unimodal polyethylene resin compositions due to differences in molecular structure according to the ratio of high and low molecular weights (J Rheol., 57, 393 (2013)), and as the low molecular weight increases, processability improves, which is advantageous in terms of fracture tendencies. In addition, even if the same level of low molecular weight is contained, the unimodal molecular weight distribution delays the fracture tendency more than the bimodal molecular weight distribution due to the good miscibility of the low and high molecular weights.

The polyethylene resin composition according to the present invention has a unimodal molecular weight distribution with a wide PDI, so that melt fracture does not occur even under high shear stress.

Meanwhile, in the present invention, the molecular weight distribution curve of the polyethylene resin composition is drawn by performing gel permeation chromatography analysis as described above, and then using the logarithm value (logMw) of the weight average molecular weight (Mw) (g/mol) as the x-axis and the molecular weight distribution (dW/dlog Mw) for the logarithm value as the y-axis. The specific analysis method is as described in the following test examples.

In addition, the polyethylene resin composition may have a weight average molecular weight (Mw) of 110,000 to 130,000 g/mol in addition to the above-described molecular weight distribution characteristics.

The Mw of the polyethylene resin composition affects the stretchability and physical properties. When the Mw is within the above range, excellent stretchability is exhibited during film production, and the physical properties of the produced film, particularly Stiffness, can be improved. More specifically, the Mw of the polyethylene resin composition may 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 130,000 g/mol or less, or 125,000 g/mol or less, or 121,000 g/mol or less, or 120,900 g/mol or less.

In addition, the polyethylene resin composition may have a complex viscosity of 400 Pa·s or less when measured under conditions of 230°C and 500 rad/s using a rotational rheometer. More specifically, the polyethylene resin composition has a complex viscosity measured under the above conditions of 400 Pa·s or less, or 350 Pa·s or less, or 345 Pa·s or less, and 300 Pa·s or more, or 330 Pa·s or more, or 340 Pa·s or more, or 344 Pa·s or more.

In addition, the polyethylene resin composition may have a shear viscosity of 300 Pa·s or less as measured under conditions of 230°C and 1000 s ^-1 using a capillary rheometer. More specifically, the polyethylene resin composition may have a shear viscosity of 300 Pa·s or less, or 295 Pa·s or less, or 293 Pa·s or less, and 200 Pa·s or more, or 250 Pa·s or more, or 270 Pa·s or more, or 272 Pa·s or more, or 285 Pa·s or more, or 289 Pa·s or more as measured under the above conditions.

The complex viscosity of a polyethylene resin composition refers to the viscosity when deformation is in the form of vibration, and the shear viscosity refers to the viscosity when deformation is in one direction. The resin composition of the present invention can exhibit excellent film stretchability by having the complex viscosity and/or shear viscosity within the above-described range.

A polyethylene resin composition satisfying the above-mentioned property requirements exhibits improved melt fracture characteristics in which the melt fracture on-set shear rate is delayed and melt fracture does not occur even at high shear stress.

Specifically, when the shear viscosity of the polyethylene resin composition is measured by changing the shear rate at 230°C using a capillary rheometer, melt fracture on-set occurs at a shear rate of 1000 s ^-1 or higher. The shear rate at which melt fracture occurs is defined as Shear rate _{onset of MF} , and the Shear rate _onset of MF of the polyethylene resin composition according to the present invention is 1000 s ^-1 or higher. Since the higher the Shear rate _{onset of MF} value, the better, the upper limit thereof is not particularly limited, and for example, it may be 100,000 s ^-1 or lower, or 10,000 s ^-1 or lower.

In addition, the polyethylene resin composition has a melt fracture on-set stress (MF _{on_set} Stress) of 265,000 Pa or more when measured at 230°C using a capillary rheometer. Since a higher MF _{on_set} Stress value is better, the upper limit thereof is not particularly limited, and for example, it may be 1,000,000 Pa or less, or 500,000 Pa or less.

Meanwhile, in the present invention, the shear rate at the time of melt fracture of the polyethylene resin composition and the stress at the time of melt fracture can be measured using a capillary rheometer, and the specific measurement method and conditions are as described in Test Example 1 below.

In addition, the polyethylene resin composition according to the present invention may have a Bimodal Triangula Area (BMTA) of 0.05 to 0.15 derived from GPC analysis.

The BMTA region is defined by the maximum intensity coordinates (X-axis: a, Y-axis: d) of the peak (Peak _low ) with the widest area among the low-molecular fractions having a log Mw of less than 5.0 of the peak maximum intensity in the curve graph of GPC measured according to ASTM D 6474, and the maximum intensity coordinates (X-axis: b, Y-axis: e) of the peak (Peak _high ) with the widest area among the high-molecular fractions having a log Mw of 5.0 or more of the peak maximum intensity, and also by defining the coordinates (X-axis: c, Y-axis: f) of the intersection point where the low-molecular fraction including the Peak _low and the high-molecular fraction including the Peak _high intersect, and then corresponding to a triangular region connecting these three coordinates. That is, the area of the BMTA region, which is the area of the triangle connecting the maximum intensity coordinates of the above-described Peak _low (X-axis: a, Y-axis: d), the maximum intensity coordinates of the Peak _high (X-axis: b, Y-axis: e), and the intersection coordinates thereof (X-axis: c, Y-axis: f), can be measured by a method as in the following mathematical expression 1.

[Mathematical Formula 1]

In the above mathematical formula 1

ae represents the product of the maximum intensity X-axis coordinate value of the low-molecular fraction and the maximum intensity Y-axis coordinate value of the high-molecular fraction,

bf is the product of the maximum intensity X-axis coordinate value of the polymer 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 fraction,

db represents the product of the maximum intensity Y-axis coordinate value of the low-molecular fraction and the maximum intensity X-axis coordinate value of the high-molecular fraction.

ec represents the product of the maximum intensity Y-axis coordinate value of the polymer 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 X-axis coordinate value of the maximum intensity of the low-molecular fraction.

The larger the BMTA value, the higher the degree of binary separation between the low-molecular fraction and the high-molecular fraction in the GPC curve, meaning that there is a large low-molecular region, and thus exhibits excellent processability. The polyethylene composition according to the present invention may specifically have a BMTA of 0.06 or more, or 0.07 or more, or 0.08 or more, or 0.09 or more. However, since an excessively large BMTA value makes it difficult to form a crystalline framework during the production of a biaxially oriented film, resulting in poor mechanical properties, the BMTA may preferably be 0.3 or less, or 0.25 or less, or 0.2 or less, 0.15 or less, or 0.12 or less.

Meanwhile, in the present invention, BMTA can be measured by measuring the weight average molecular weight (Mw, g/mol) using gel permeation chromatography according to the American Society for Testing and Materials standard ASTM D 6474, and measuring the area of the BMTA region in a logarithmic graph for the weight average molecular weight (Mw) of the polyethylene resin composition thus measured, i.e., a GPC curve graph in which the x-axis is log M _W and the y-axis is dw/dlogMw. The method for measuring BMTA is as described in the test examples described below.

Meanwhile, the melt index (MI _2.16 ) of polyethylene resin compositions affects film processability and stretchability. If the melt index of the polyethylene resin composition is excessively low, film processability and stretchability may deteriorate due to the excessively low melt index. On the other hand, if the melt index is excessively high, processability may deteriorate, and the physical properties of the produced stretched film may also deteriorate.

The polyethylene resin composition according to the present invention exhibits a melt index (MI _2.16 ) of 0.10 to 2.00 g/10 min. Accordingly, it exhibits excellent film processability and stretchability, and the physical properties of the stretched film produced can also be improved. In particular, by simultaneously satisfying the density conditions described below, it can exhibit better biaxial stretchability. More specifically, the melt index of the polyethylene resin composition according to the present invention may 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 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.

Meanwhile, in the present invention, the melt index (MI _2.16 ) of the polyethylene resin composition can be measured under a load of 2.16 kg at 190°C according to the American Society for Testing and Materials standard ASTM D1238 (condition E). The specific measurement method is as described in the following test examples.

The above polyethylene resin composition comprises at least one ethylene-alpha olefin copolymer, and more specifically, at least one ethylene-alpha olefin copolymer.

Specifically, the polyethylene resin composition,

(a) a first ethylene-alphaolefin copolymer having a density of 0.870 g/cm ³ to 0.920 g/cm ³ and a number average molecular weight Mn of 20,000 g/mol or more, and

(b) a second ethylene-alphaolefin copolymer having a density of 0.945 g/cm ³ to 0.960 g/cm ³ and a number average molecular weight Mn of 10,000 g/mol or more and less than 20,000 g/mol;

The first ethylene-alpha olefin copolymer and the second ethylene-alpha olefin copolymer are different from each other.

In addition, by combining the first and second ethylene-alphaolefin copolymers in appropriate amounts, the polyethylene resin composition according to the present invention can satisfy the above-described excellent overall physical properties.

Specifically, the polyethylene resin composition according to the present invention may contain 10 to 40 wt% of the first ethylene-alpha olefin copolymer and 60 to 90 wt% of the second ethylene-alpha olefin copolymer based on the total weight of the composition.

More specifically, the first ethylene-alpha olefin copolymer may be included in an amount of 10 wt% or more, or 15 wt% or more, or 17 wt% or more, and 40 wt% or less, or 35 wt% or less, or 30 wt% or less, or 20 wt% or less, based on the total weight of the polyethylene resin composition.

In addition, the second ethylene-alpha olefin copolymer may be included in an amount of 60 wt% or more, or 65 wt% or more, or 70 wt% or more, or 80 wt% or more, and 90 wt% or less, or 85 wt% or less, or 83 wt% or less, based on the total weight of the polyethylene resin composition.

In addition, in the polyethylene resin composition, the first and second ethylene-alphaolefin copolymers are each a copolymer of ethylene and an alphaolefin having 3 to 20 carbon atoms, and more specifically, may be a copolymer of ethylene and 1-butene, 1-hexene, or 1-octene. In this case, the alphaolefins contained in the first and second ethylene-alphaolefin copolymers are different from each other.

More specifically, the first ethylene-alphaolefin copolymer may be an ethylene/1-octene copolymer, and the second ethylene-alphaolefin copolymer may be an ethylene/1-hexene copolymer.

(a) first ethylene-alphaolefin copolymer

First, in the polyethylene composition according to the present invention, the first ethylene-alphaolefin copolymer has excellent flowability, excellent stretching stability, and high shrinkage resistance, which can provide characteristics suitable for manufacturing a biaxially oriented film.

Specifically, the first ethylene-alphaolefin copolymer has a density of 0.870 g/cm ³ to 0.920 g/cm ³ and a number average molecular weight Mn of 20,000 g/mol or more.

More specifically, the first ethylene-alphaolefin copolymer may have a density of 0.880 g/cm ³ or more, or 0.890 g/cm ³ or more, or 0.895 g/cm ³ or more, or 0.900 g/cm ³ or more, and 0.915 g/cm ³ or less, or 0.910 g/cm ³ or less, or 0.905 g/cm ³ or less.

In addition, the number average molecular weight Mn of the first ethylene-alpha olefin copolymer may be more specifically 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 34,000 g/mol or less, or 33,000 g/mol or less, or 32,000 g/mol or less.

In addition, the first ethylene-alpha olefin copolymer may satisfy the above-described density and number-average molecular weight conditions, and additionally have a melt index (MI _2.16 , ASTM D1238, 190°C, 2.16 kg load) 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.

More specifically, the first ethylene-alpha olefin copolymer may have a melt index (MI _2.16 , ASTM D1238, 190° C., 2.16 kg load) of 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 9.0 g/10 min or less, or 8.0 g/10 min or less, or 7.0 g/10 min or less.

In addition, the weight average molecular weight Mw of the first ethylene-alpha olefin copolymer may be more specifically 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 90,000 g/mol or less, or 80,000 g/mol or less, or 70,000 g/mol or less.

In addition, the molecular weight distribution Mw/Mn of the first ethylene-alphaolefin copolymer may be, more specifically, 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 3.2 or less, or 3.0 or less, or 2.8 or less, or 2.5 or less.

The above first ethylene-alpha olefin copolymer may have at least one of the above-described properties, and may have all of the above-described properties to exhibit excellent mechanical strength.

Here, the method for measuring each property of the first ethylene-alphaolefin copolymer is the same as that described above for the polyethylene composition, and thus a detailed description thereof is omitted.

Meanwhile, the first ethylene-alpha-olefin copolymer comprises at least one alpha-olefin selected from the group consisting of ethylene, 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.

Additionally, the first ethylene-alphaolefin copolymer may be a copolymer of ethylene and 1-octene.

The above first ethylene-alpha-olefin copolymer, if it is the above-described copolymer, can more easily realize the above-described physical properties. However, the type of the above-described first ethylene-alpha-olefin copolymer is not limited to the above-described type, and various types known in the technical field to which the present invention pertains can be provided as long as they can exhibit the above-described physical properties.

Meanwhile, the first ethylene-alpha olefin copolymer having the above-described physical properties may be manufactured in the presence of a metallocene catalyst.

Specifically, the first ethylene-alphaolefin copolymer can be produced by copolymerizing ethylene and a comonomer in the presence of a catalyst composition including a first metallocene compound represented by the following chemical formula 1.

[Chemical Formula 1]

In the above chemical formula 1,

M ¹ is a group 4 transition metal;

X ¹ and X ² are the same or different, and are each independently a halogen, a nitro group, an amido group, a phosphine group, a phosphide group, a hydrocarbyl group having 1 to 30 carbon atoms, a hydrocarbyloxy group having 1 to 30 carbon atoms, a hydrocarbyloxyhydrocarbyl group having 2 to 30 carbon atoms, -SiH ₃ , a hydrocarbyl(oxy)silyl group having 1 to 30 carbon atoms, a sulfonate group having 1 to 30 carbon atoms, or a sulfone group having 1 to 30 carbon atoms;

Z is -O-, -S-, -NR _a -, or -PR _a -,

R _a is any one of hydrogen, a hydrocarbyl group having 1 to 20 carbon atoms, a hydrocarbyl(oxy)silyl group having 1 to 20 carbon atoms, and a silylhydrocarbyl group having 1 to 20 carbon atoms;

T is or And,

T ¹ is C, Si, Ge, Sn or Pb,

Q ¹ and Q ² are the same or different, and each independently represent hydrogen, a hydrocarbyl group having 1 to 30 carbon atoms, a hydrocarbyloxy group having 1 to 30 carbon atoms, a hydrocarbyloxyhydrocarbyl group having 2 to 30 carbon atoms, -SiH ₃ , a hydrocarbyl(oxy)silyl group having 1 to 30 carbon atoms, a hydrocarbyl group having 1 to 30 carbon atoms substituted with halogen, and -NR _b R _c ,

R _b and R _c are each independently hydrogen and a hydrocarbyl group having 1 to 30 carbon atoms, or are connected to each other to form an aliphatic or aromatic ring;

C ¹ is any one of the ligands represented by the following chemical formulas 1a to 1d,

[Chemical Formula 1a]

[Chemical Formula 1b]

[Chemical Formula 1c]

[Chemical Formula 1d]

In the above chemical formulas 1a to 1d,

Y is O or S,

R ¹ to R ⁶ are the same or different, and each independently represent hydrogen, a hydrocarbyl group having 1 to 30 carbon atoms, or a hydrocarbyloxy group having 1 to 30 carbon atoms.

Unless otherwise specified in this specification, the following terms may be defined as follows:

A hydrocarbyl group is a monovalent functional group in which a hydrogen atom is removed from a hydrocarbon, and may include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an aralkyl group, an aralkenyl group, an aralkynyl group, an alkylaryl group, an alkenylaryl group, and an alkynylaryl group. In addition, a hydrocarbyl group having 1 to 30 carbon atoms may be a hydrocarbyl group having 1 to 20 carbon atoms or 1 to 10 carbon atoms. For example, the hydrocarbyl group may be a straight-chain, branched-chain, or cyclic alkyl. More specifically, the hydrocarbyl group having 1 to 30 carbon atoms may be a straight-chain, branched-chain or cyclic alkyl group such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, cyclohexyl, or the like; or an aryl group such as phenyl, biphenyl, naphthyl, anthracenyl, phenanthrenyl, or fluorenyl. In addition, it may be an alkylaryl such as methylphenyl, ethylphenyl, methylbiphenyl, or methylnaphthyl, or an arylalkyl such as phenylmethyl, phenylethyl, biphenylmethyl, or naphthylmethyl. In addition, it may be an alkenyl such as allyl, allyl, ethenyl, propenyl, butenyl, or pentenyl.

A hydrocarbyloxy group is a functional group in which a hydrocarbyl group is bonded to oxygen. Specifically, the hydrocarbyloxy group having 1 to 30 carbon atoms may be a hydrocarbyloxy group having 1 to 20 carbon atoms or 1 to 10 carbon atoms. For example, the hydrocarbyloxy group may be a straight-chain, branched-chain, or cyclic alkyl. More specifically, the hydrocarbyloxy group having 1 to 30 carbon atoms may be a straight-chain, branched-chain, or cyclic alkoxy group such as a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, an iso-butoxy group, a tert-butoxy group, an n-pentoxy group, an n-heptoxy group, an n-heptoxy group, or a cycloheptoxy group; or an aryloxy group such as a phenoxy group or a naphthalenoxy group.

A hydrocarbyloxyhydrocarbyl group is a functional group in which at least one hydrogen atom of a hydrocarbyl group is replaced by at least one hydrocarbyloxy group. Specifically, the hydrocarbyloxyhydrocarbyl group having 2 to 30 carbon atoms may be a hydrocarbyloxyhydrocarbyl group having 2 to 20 carbon atoms or a hydrocarbyloxyhydrocarbyl group having 2 to 15 carbon atoms. For example, the hydrocarbyloxyhydrocarbyl group may be a straight-chain, branched-chain or cyclic alkyl. More specifically, the hydrocarbyloxyhydrocarbyl group having 2 to 30 carbon atoms may be an alkoxyalkyl group such as a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, an iso-propoxymethyl group, an iso-propoxyethyl group, an iso-propoxyhexyl group, a tert-butoxymethyl group, a tert-butoxyethyl group, or a tert-butoxyhexyl group; Or it may be an aryloxyalkyl group such as a phenoxyhexyl group.

A hydrocarbyl(oxy)silyl group is a functional group in which 1 to 3 hydrogen atoms of -SiH ₃ are replaced by 1 to 3 hydrocarbyl groups or hydrocarbyloxy groups. Specifically, the hydrocarbyl(oxy)silyl group having 1 to 30 carbon atoms may be a hydrocarbyl(oxy)silyl group having 1 to 20 carbon atoms, 1 to 15 carbon atoms, 1 to 10 carbon atoms, or 1 to 5 carbon atoms. More specifically, the hydrocarbyl(oxy)silyl group having 1 to 30 carbon atoms may be an alkylsilyl group such as a methylsilyl group, a dimethylsilyl group, a trimethylsilyl group, a dimethylethylsilyl group, a diethylmethylsilyl group, or a dimethylpropylsilyl group; an alkoxysilyl group such as a methoxysilyl group, a dimethoxysilyl group, a trimethoxysilyl group, or a dimethoxyethoxysilyl group; It may be an alkoxyalkylsilyl group such as a methoxydimethylsilyl group, a diethoxymethylsilyl group, or a dimethoxypropylsilyl group.

A silylhydrocarbyl group having 1 to 20 carbon atoms is a functional group in which at least one hydrogen atom of the hydrocarbyl group is replaced with a silyl group. The silyl group may be -SiH ₃ or a hydrocarbyl(oxy)silyl group. Specifically, the silylhydrocarbyl group having 1 to 20 carbon atoms may be a silylhydrocarbyl group having 1 to 15 carbon atoms or 1 to 10 carbon atoms. More specifically, the silylhydrocarbyl group having 1 to 20 carbon atoms may be a silylalkyl group such as -CH ₂ -SiH ₃ ; an alkylsilylalkyl group such as a methylsilylmethyl group, a methylsilylethyl group, a dimethylsilylmethyl group, a trimethylsilylmethyl group, a dimethylethylsilylmethyl group, a diethylmethylsilylmethyl group, or a dimethylpropylsilylmethyl group; or an alkoxysilylalkyl group such as a dimethylethoxysilylpropyl group.

The halogen can be fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).

The sulfonate group has a structure of -O-SO ₂ -R _d , where R _d can be a hydrocarbyl group having 1 to 30 carbon atoms. Specifically, the sulfonate group having 1 to 30 carbon atoms can be a methanesulfonate group or a phenylsulfonate group.

A sulfone group having 1 to 30 carbon atoms has a structure of -R ^e' -SO ₂ -R ^e" , where R ^e' and R ^e" are the same or different and can each independently be any one of a hydrocarbyl group having 1 to 30 carbon atoms. Specifically, the sulfone group having 1 to 30 carbon atoms can be a methylsulfonylmethyl group, a methylsulfonylpropyl group, a methylsulfonylbutyl group, or a phenylsulfonylpropyl group.

In the present specification, when two adjacent substituents are connected to each other to form an aliphatic or aromatic ring, it means that the atom(s) of the two substituents and the atom(s) to which the two substituents are bonded are connected to each other to form a ring. Specifically, an example in which R _b and R _c or R _b' and _{R c '} of -NR _{b R c} or -NR b' R c' are connected to each other to form an aliphatic ring includes a piperidinyl group, and an example in which R _b and R _c or R _b' and R c _' of -NR _{b R c or} -NR b' R c _' are connected to each other to form an aromatic ring includes a pyrrolyl group, etc.

And, the group 4 transition metal may be titanium (Ti), zirconium (Zr), hafnium (Hf), or rutherfordium (Rf), specifically titanium (Ti), zirconium (Zr), or hafnium (Hf), more specifically zirconium (Zr), or hafnium (Hf), but is not limited thereto.

Additionally, the group 13 element may be boron (B), aluminum (Al), gallium (Ga), indium (In), or thallium (Tl), specifically, but not limited to, boron (B) or aluminum (Al).

The above-described substituents may be optionally substituted with one or more substituents selected from the group consisting of a hydroxy group; a halogen; a hydrocarbyl group; a hydrocarbyloxy group; a hydrocarbyl group or hydrocarbyloxy group containing at least one heteroatom from groups 14 to 16; a silyl group; a hydrocarbyl(oxy)silyl group; a phosphine group; a phosphide group; a sulfonate group; and a sulfone group, within a range that exhibits the same or similar effect as the desired effect.

In this specification, means a bond that connects to another substituent.

Specifically, in the above chemical formula 1, Z is -NR _a -, and the R _a may be a hydrocarbyl group having 1 to 10 carbon atoms, and specifically, the R _a may be a straight-chain or branched alkyl group having 1 to 6 carbon atoms, and more specifically, may be a tert-butyl group.

And, in the above chemical formula 1, T is , T ¹ is carbon (C) or silicon (Si), and Q ¹ and Q ² can each independently be hydrogen, a hydrocarbyl group having 1 to 30 carbon atoms, or a hydrocarbyloxy group having 1 to 30 carbon atoms. Specifically, Q ¹ and Q ² can each be a hydrocarbyl group having 1 to 10 carbon atoms, or a hydrocarbyloxyhydrocarbyl group having 2 to 12 carbon atoms. More specifically, Q ¹ and Q ² can each be an alkyl group having 1 to 6 carbon atoms, or an alkoxy-substituted alkyl group having 1 to 6 carbon atoms. For example, Q ¹ and Q ² can each independently be hydrogen, methyl, ethyl, or tert-butoxy-substituted hexyl. More specifically, T ¹ is silicon (Si), and Q ¹ and Q ² can both be methyl, or one of Q ¹ and Q ² can be methyl and the other can be tert-butoxy substituted hexyl.

Specifically, the metallocene compound represented by the above chemical formula 1 may be represented by any one of the following chemical formulas 1-1 to 1-4.

[Chemical Formula 1-1]

[Chemical Formula 1-2]

[Chemical Formula 1-3]

[Chemical Formula 1-4]

In the above 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 are as defined in the above chemical formula 1.

And, in the above chemical formula 1, R ¹ to R ⁴ may each be hydrogen or a hydrocarbyl group having 1 to 10 carbon atoms, and R ⁵ and R ⁶ may each be a hydrocarbyl group having 1 to 10 carbon atoms. Specifically, R ¹ to R ⁴ may each be hydrogen or an alkyl group having 1 to 10 carbon atoms, and R ⁵ and R ⁶ may each be an alkyl group having 1 to 10 carbon atoms. More specifically, R ¹ to R ⁴ may each be hydrogen or methyl, and R ⁵ and R ⁶ may be methyl.

And, in the above chemical formula 1, M ¹ may be titanium (Ti), zirconium (Zr), or hafnium (Hf), and preferably titanium (Ti).

And, in the above chemical formula 1, X ¹ and X ² may each be a halogen or an alkyl group having 1 to 10 carbon atoms or an alkyl group having 1 to 6 carbon atoms, and specifically, may be chlorine or methyl.

And, in the above chemical formula 1, the second metallocene compound may be represented by one of the following structural formulas.

Metallocene compounds represented by the above structural formulas can be synthesized by applying known reactions, and more detailed synthesis methods can be referred to the examples and synthesis examples described below.

As described above, the transition metal compound represented by Chemical Formula 1 used in the present invention controls the degree of introduction of alpha-olefin monomers in the copolymerization process due to the structural characteristics of the catalyst, exhibits the density as described above, and as a result, secures excellent flowability and elongation processability.

In the present invention, the polymerization reaction can be carried out by continuously introducing hydrogen in the presence of a catalyst composition including at least one transition metal compound represented by Chemical Formula 1 to continuously polymerize ethylene and alpha-olefin monomers, and specifically, it can be carried out while introducing hydrogen at a rate of 5 to 100 cc/min.

The hydrogen gas suppresses the rapid reaction of the transition metal compound in the early stage of polymerization and terminates the polymerization reaction. Accordingly, by controlling the use and amount of hydrogen gas, an ethylene/alpha-olefin copolymer with a narrow molecular weight distribution can be effectively produced.

For example, the hydrogen may be introduced at 5 cc/min or more, or 7 cc/min or more, or 10 cc/min or more, or 15 cc/min or more, or 19 cc/min or more, and may be introduced at 100 cc/min or less, or 50 cc/min or less, or 45 cc/min or less, or 35 cc/min or less, or 29 cc/min or less. When introduced under the above conditions, the produced ethylene/alpha-olefin copolymer may exhibit the above-described physical properties.

If the hydrogen gas content is less than 5 cc/min, the polymerization reaction may not be completed uniformly, making it difficult to produce an ethylene/alpha-olefin copolymer with desired properties. If it is more than 100 cc/min, there is a concern that the termination reaction may occur too quickly, resulting in the production of an ethylene/alpha-olefin copolymer with very low molecular weight.

In addition, the polymerization reaction can be carried out at 100°C to 200°C, and by controlling the polymerization temperature together with the above-mentioned hydrogen input amount, the crystallinity distribution and molecular weight distribution within the ethylene/alpha-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 thereto.

In the present invention, a cocatalyst may be additionally used in the catalyst composition to activate the transition metal compound of the above chemical formula 1. The cocatalyst is an organometallic compound containing a Group 13 metal, and specifically may include at least one selected from the following chemical formulas 2 to 4.

[Chemical Formula 2]

R ₈ -[Al(R ₇ )-O] _n -R ₉

In the above chemical formula 2,

R ₇ , R ₈ and R ₉ are each independently hydrogen, halogen, a C _1-20 hydrocarbyl group, or a C _1-20 hydrocarbyl group substituted with a halogen,

n is an integer greater than or equal to 2,

[Chemical Formula 3]

D(R ₁₀ ) ₃

In the above chemical formula 3,

D is aluminum or boron,

R ₁₀ is each independently a halogen, a C _1-20 hydrocarbyl group, a C _1-20 hydrocarbyloxy group, or a C _1-20 hydrocarbyl group substituted with a halogen,

[Chemical Formula 4]

[LH] ⁺ [W(A) ₄ ] ^- or [L] ⁺ [W(A) ₄ ] ^-

In the above chemical formula 4,

L is a neutral or cationic Lewis base,

H is a hydrogen atom,

W is a group 13 element,

A is independently any one of a C _1-20 hydrocarbyl group; a C _1-20 hydrocarbyloxy group; and substituents in which at least one hydrogen atom of these substituents is substituted with at least one substituent selected from the group consisting of a halogen, a C _1-20 hydrocarbyloxy group, and a C _1-20 hydrocarbyl(oxy)silyl group.

Specifically, in the above chemical formula 4, [LH] ⁺ is Bronsted acid.

For example, the above [LH] ⁺ is trimethylammonium; triethylammonium; tripropylammonium; tributylammonium; diethylammonium; trimethylphosphonium; or triphenylphosphonium, and the above [L] ⁺ is N,N-diethylanilinium; or triphenylcarbonium.

Additionally, in the above chemical formula 4, W may be B ³⁺ or Al ³⁺ .

The compound represented by the above chemical formula 2 can act as an alkylating agent and an activator, the compound represented by the above chemical formula 3 can act as an alkylating agent, and the compound represented by the above chemical formula 4 can act as an activator.

More specifically, the compound of the above chemical formula 2 may be an alkylaluminoxane compound in which repeating units are bonded in a linear, circular or network shape, and specific examples thereof include methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane or tert-butylaluminoxane. Non-limiting examples of the compound represented by the above chemical formula 2 include methylaluminoxane, ethylaluminoxane, isobutylaluminoxane or tert-butylaluminoxane.

And, non-limiting examples of compounds represented by chemical formula 3 include trimethylaluminum, triethylaluminum, triisobutylaluminum, tripropylaluminum, tributylaluminum, dimethylchloroaluminum, triisopropylaluminum, tri-sec-butylaluminum, tricyclopentylaluminum, tripentylaluminum, triisopentylaluminum, trihexylaluminum, trioctylaluminum, ethyldimethylaluminum, methyldiethylaluminum, triphenylaluminum, tri-p-tolylaluminum, dimethylaluminum methoxide, or dimethylaluminum ethoxide.

In addition, non-limiting examples of the compound represented by the above chemical formula 4 include trimethylammonium tetrakis(pentafluorophenyl)borate, triethylammonium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium n-butyltris(pentafluorophenyl)borate, N,N-dimethylanilinium benzyltris(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(4-(t-butyldimethylsilyl)-2,3,5,6-tetrafluorophenyl)borate, N,N-dimethylanilinium tetrakis(4-(triisopropylsilyl)-2,3,5,6-tetrafluorophenyl)borate, N,N-dimethylanilinium pentafluorophenoxytris(pentafluorophenyl)borate, Examples thereof include N,N-dimethyl-2,4,6-trimethylanilinium tetrakis(pentafluorophenyl)borate, anilinium tetrakis(pentafluorophenyl)borate, trimethylammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate, N,N-dimethylanilinium tetrakis(2,3,4,6-tetrafluorophenyl)borate, hexadecyldimethylammonium tetrakis(pentafluorophenyl)borate, N-methyl-N-dodecylanilinium tetrakis(pentafluorophenyl)borate, or methyldi(dodecyl)ammonium tetrakis(pentafluorophenyl)borate.

Among the above compounds, the cocatalyst may be, more specifically, an alkylaluminoxane cocatalyst such as methylaluminoxane.

The amount of the above cocatalyst used can be appropriately adjusted depending on the properties or effects of the desired hybrid supported metallocene catalyst.

The above cocatalyst may be used in an appropriate amount so that the activation of the transition metal compound of the above chemical formula 1 may proceed sufficiently. The amount of the cocatalyst used may be appropriately adjusted depending on the properties or effects of the desired hybrid supported metallocene catalyst.

In the present invention, the transition metal compound of the above chemical formula 1 can be used in a form supported on a carrier.

When the transition metal compound of the above chemical formula 1 is supported on a carrier, the weight ratio of the transition metal compound and the carrier may be 1:10 to 1:1000, more specifically, 1:10 to 1:500. When the carrier and the transition metal compound are included in the weight ratio within the above range, an optimal shape can be exhibited. In addition, when the cocatalyst is supported on the carrier together, the weight ratio of the cocatalyst to the carrier may be 1:1 to 1:100, more specifically, 1:1 to 1:50. When the cocatalyst and the carrier are included in the above weight ratio, the catalytic activity can be improved and the microstructure of the polymer to be produced can be optimized.

Meanwhile, silica, alumina, magnesia, or a mixture thereof may be used as the carrier, or these materials may be dried at high temperature to remove moisture from the surface, thereby allowing the material to be used in a state in which it contains highly reactive hydroxyl groups or siloxane groups on the surface. In addition, the carriers dried at high temperature may further contain oxides, carbonates, sulfates, or nitrates such as Na ₂ O, K ₂ CO ₃ , BaSO ₄ , and Mg(NO ₃ ) ₂ .

The drying temperature of the carrier is preferably 200°C to 800°C, more preferably 300°C to 600°C, and most preferably 300°C to 400°C. If the drying temperature of the carrier is less than 200°C, the moisture content is too high, causing the moisture on the surface to react with the cocatalyst. If the drying temperature is more than 800°C, the pores on the surface of the carrier merge, reducing the surface area. In addition, many hydroxyl groups on the surface disappear, leaving only siloxane groups, reducing the reaction sites with the cocatalyst, which is not preferable.

In addition, the amount of hydroxyl groups on the surface of the carrier is preferably 0.1 mmol/g to 10 mmol/g, and more preferably 0.5 mmol/g to 5 mmol/g. The amount of hydroxyl groups on the surface of the carrier can be controlled by the manufacturing method and conditions of the carrier or drying conditions, such as temperature, time, vacuum or spray drying.

Additionally, during the polymerization reaction, an organic aluminum compound is further added to remove moisture within the reactor, so that the polymerization reaction can proceed in its presence. Specific examples of such organoaluminum compounds include trialkylaluminum, dialkylaluminum halides, alkylaluminum dihalides, aluminum dialkyl hydrides, or alkylaluminum sesquihalides, and more specific examples thereof include Al(C ₂ H ₅ ) ₃ , Al(C 2 H 5 ) 2 H, Al(C ₃ H ₇ ) ₃ , Al(C ₃ H ₇ ) ₂ H, Al(iC ₄ H ₉ ) ₂ H, Al(C ₈ H ₁₇ ) ₃ , Al(C ₁₂ H ₂₅ ) ₃ , Al(C ₂ H ₅ )(C ₁₂ H ₂₅ ) ₂ , Al(iC ₄ H ₉ )(C ₁₂ H ₂₅ ) ₂ , Al(iC _{4 H 9 ) 2 H , Al (} iC ₄ H ₉ ) ₃ , (C ₂ H ₅ ) ₂ AlCl, (iC ₃ H ₉ ) ₂ AlCl or (C ₂ H ₅ ) _{3 Al2} Cl ₃ . These organic aluminum compounds can be continuously fed into the reactor, and can be fed at a ratio of about 0.1 to 10 moles per 1 kg of the reaction medium fed into the reactor to ensure proper moisture removal.

Additionally, the polymerization pressure may be from about 1 Kgf/cm ² to about 100 Kgf/cm ² , preferably from about 1 Kgf/cm ² to about 50 Kgf/cm ² , more preferably from about 5 Kgf/cm ² to about 30 Kgf/cm ² .

In addition, when a transition metal compound is used in a form supported on a carrier, the transition metal compound may be dissolved or diluted and then introduced into an aliphatic hydrocarbon solvent having 5 to 12 carbon atoms, such as pentane, hexane, heptane, nonane, decane, and isomers thereof, an aromatic hydrocarbon solvent such as toluene and benzene, a hydrocarbon solvent substituted with a chlorine atom such as dichloromethane and chlorobenzene, etc. It is preferable to use the solvent used here after removing a small amount of water or air, etc. that act as catalyst poisons, by treating it with a small amount of alkyl aluminum, and it is also possible to carry out the process using an additional cocatalyst.

In this way, the first ethylene-alpha-olefin copolymer can be produced by copolymerizing ethylene and alpha-olefin using the metallocene catalyst described above.

By the above-described manufacturing method, a first ethylene-alpha olefin copolymer having the above-described physical properties can be manufactured.

(b) second ethylene-alphaolefin copolymer

The polyethylene resin composition according to the present invention can control the balance between mechanical properties and stretchability characteristics by blending the first ethylene-alpha-olefin copolymer described above with a second ethylene-alpha-olefin copolymer having excellent flowability and superior stretching stability and shrinkage resistance, thereby maintaining mechanical properties, productivity, and stretching stability equivalent to or superior to those of the prior art, and imparting characteristics suitable for manufacturing a biaxially oriented film having high shrinkage resistance, printability, and excellent transparency.

Specifically, the second ethylene-alphaolefin copolymer may be a high density polyethylene (HDPE) having a density of 0.945 g/cm ³ to 0.960 g/cm ³ as measured according to ISO 1183-2 at 23°C. More specifically, the density of the second ethylene-alphaolefin copolymer may be 0.945 g/cm ³ or more, or 0.946 g/cm ³ or more, and 0.960 g/cm ³ or less, or 0.958 g/cm ³ or less, or 0.956 g/cm ³ or less, or 0.955 g/cm ³ or less, or 0.952 g/cm ³ or less, or 0.948 g/cm ³ or less.

In addition, the number average molecular weight Mn of the second ethylene-alphaolefin copolymer may 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-alphaolefin copolymer may be 10,000 g/mol or more, or 11,000 g/mol or more, or 11,500 g/mol or more, or 11,600 g/mol or more, and 20,000 g/mol or less, or less than 20,000 g/mol or 18,000 g/mol or less, or 15,000 g/mol or less, or 14,500 g/mol or less, or 14,100 g/mol or less.

In addition, the second ethylene-alpha olefin copolymer may have a melt index (MI _2.16 ) of 0.10 g/10 min to 2.00 g/10 min measured at 190° C. under a load of 2.16 kg according to ASTM D1238, a weight average molecular weight Mw of 100,000 to 200,000 g/mol, and a molecular weight distribution Mw/Mn of 7.0 to 20.0.

More specifically, the melt index (MI _2.16 ) of the second ethylene-alphaolefin copolymer may be 0.10 g/10 min or more, or 0.20 g/10 min or more, or 0.30 g/10 min or more, or 0.35 g/10 min or more, or 0.36 g/10 min or more, and 2.00 g/10 min or less, or 1.50 g/10 min or less, or 1.00 g/10 min or less, or 0.50 g/10 min or less, or 0.40 g/10 min or less, or 0.39 g/10 min or less.

This means that the second ethylene-alpha-olefin copolymer has a high weight average molecular weight and a high content of high molecular weight components, thereby exhibiting excellent mechanical properties such as high tensile strength. Since the second ethylene-alpha-olefin copolymer has a low melting index as described above, the polyethylene resin composition of the present invention including it can satisfy excellent processability and crack resistance when manufactured for pipe use.

In addition, the weight average molecular weight Mw of the second ethylene-alpha olefin copolymer may be more specifically 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 200,000 g/mol or less, or 180,000 g/mol or less, or 170,000 g/mol or less, or 165,000 g/mol or less, or 161,000 g/mol or less.

In addition, the molecular weight distribution of the second ethylene-alpha olefin copolymer may be 7.0 or more, or 10.0 or more, or 11.0 or more, or 11.4 or more, and 20.0 or less, or 18.0 or less, or 15.0 or less, or 13.0 or less, or 12.9 or less.

Since the second ethylene-alpha olefin copolymer of the present invention has a relatively high molecular weight and narrow molecular weight distribution compared to the low melting index as described above, it can satisfy both excellent mechanical properties and tensile strength characteristics.

Meanwhile, in the present invention, the number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution of the second ethylene-alpha olefin copolymer were measured using gel permeation chromatography (GPC) to determine the weight average molecular weight (Mw) and number average molecular weight (Mn) of polyethylene, respectively, and the ratio of the weight average molecular weight to the number average molecular weight (Mw/Mn) was calculated as the molecular weight distribution.

Specifically, polyethylene samples were evaluated using a Waters PL-GPC220 instrument using a Polymer Laboratories PLgel MIX-B 300 mm column. The evaluation temperature was 160°C, 1,2,4-trichlorobenzene was used as the solvent, and the flow rate was measured at a rate of 1 mL/min. The sample was prepared at a concentration of 10 mg/10 mL and then supplied in an amount of 200 μL. The values of Mw and Mn were measured using a calibration curve formed using polystyrene standards. The molecular weights of the polystyrene standards were 9 types: 2,000 / 10,000 / 30,000 / 70,000 / 200,000 / 700,000 / 2,000,000 / 4,000,000 / 10,000,000.

In addition, the second ethylene-alpha-olefin copolymer may include at least one alpha-olefin selected from the group consisting of ethylene, 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.

More specifically, the second ethylene-alphaolefin copolymer may be a copolymer of ethylene and 1-hexene.

The second ethylene-alphaolefin copolymer as described above can be produced by copolymerizing ethylene and an alphaolefin comonomer in the presence of a catalyst composition including, but not limited to, a first metallocene compound represented by the following chemical formula 5 and a second metallocene compound represented by the following chemical formula 6, while introducing hydrogen gas in an amount of 150 to 200 ppm based on the total weight of ethylene. At this time, the alphaolefin comonomer can be introduced in an amount of 1 to 3 wt% based on the total weight of ethylene.

[Chemical Formula 5]

(Cp ¹ R ^a ) _m (Cp ² R ^b )M ² Z ² _3-m

In the above chemical formula 5,

M ² is a group 4 transition metal;

Cp ¹ and Cp ² are each cyclopentadienyl, which is substituted or unsubstituted with a C _1-20 hydrocarbon;

R ^a and R ^b are the same or different and are each independently hydrogen, C _1-20 alkyl, C _1-20 alkoxy, C _2-20 alkoxyalkyl, C _6-20 aryl, C _6-20 aryloxy, C _2-20 alkenyl, C _7-40 alkylaryl, C _7-40 arylalkyl, C _8-40 arylalkenyl, C _2-20 alkynyl, or a substituted or unsubstituted C _2-20 heteroaryl containing one or more heteroatoms selected from the group consisting of N, O and S, provided that at least one of R ^a and R ^b is not hydrogen;

Z ² is each independently halogen, C _1-20 alkyl, C _2-20 alkenyl, C _7-40 alkylaryl, C _7-40 arylalkyl, C _6-20 aryl, substituted or unsubstituted C _1-20 alkylidene, substituted or unsubstituted amino group, C _2-20 alkylalkoxy, or C _7-40 arylalkoxy;

m is 1 or 0;

[Chemical Formula 2]

In the above chemical formula 6,

M ³ is a group 4 transition metal,

T ² is carbon, silicon or germanium,

X ³ and X ⁴ are the same or different, and each independently represents halogen or C _1-20 alkyl,

R ¹¹ to R ¹⁴ are the same or different from each other, and are each independently hydrogen, C _1-20 alkyl, C _2-20 alkenyl, C _6-20 aryl, C _7-20 alkylaryl, C _7-20 arylalkyl, or R ¹¹ to R ¹⁴ Two or more adjacent rings are connected to each other to form a substituted or unsubstituted aliphatic ring, an aromatic ring, or a heteroaromatic ring including at least one selected from the group consisting of N, O, and S,

Q ³ and Q ⁴ are the same or different and are each independently C _1-20 alkyl, C _2-20 alkenyl, C _6-30 aryl, or C _2-20 alkoxy alkyl,

R ¹⁵ is C _1-20 alkyl, C _2-20 alkenyl, or C _6-30 aryl.

Meanwhile, in this specification, unless otherwise specifically limited, the following terms may be defined as follows:

The halogen can be fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).

The C _1-20 alkyl group may be a straight-chain, branched-chain or cyclic alkyl group. Specifically, the C _1-20 alkyl group may be a C _1-15 straight-chain alkyl group; a C _1-10 straight-chain alkyl group; a C _1-5 straight-chain alkyl group; a C _3-20 branched-chain or cyclic alkyl group; a C _3-15 branched-chain or cyclic alkyl group; or a C _3-10 branched-chain or cyclic alkyl group. More specifically, the C _1-20 alkyl group may be a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a tert-butyl group, an n-pentyl group, an iso-pentyl group, a neo-pentyl group or a cyclohexyl group.

The C _2-20 alkenyl group may be a straight-chain, branched-chain or cyclic alkenyl group. Specifically, the C _2-20 alkenyl group may be a C _2-20 straight-chain alkenyl group, a C _2-10 straight-chain alkenyl group, a C _2-5 straight-chain alkenyl group, a C _3-20 branched-chain alkenyl group, a C _3-15 branched-chain alkenyl group, a C _3-10 branched-chain alkenyl group, a C _5-20 cyclic alkenyl group or a C _5-10 cyclic alkenyl group. More specifically, the C _2-20 alkenyl group may be an ethenyl group, a propenyl group, a butenyl group, a pentenyl group or a cyclohexenyl group.

C _6-20 aryl refers to a monocyclic, bicyclic, or tricyclic aromatic hydrocarbon, and includes aryl having a single ring or condensed ring. Specifically, C _6-20 aryl can be a phenyl group, a biphenyl group, a naphthyl group, anthracenyl group, a phenanthrenyl group, or a fluorenyl group.

C _7-40 alkylaryl may refer to a substituent in which one or more hydrogens of aryl are replaced by alkyl. Specifically, C _7-40 alkylaryl may be methylphenyl, ethylphenyl, n-propylphenyl, iso-propylphenyl, n-butylphenyl, iso-butylphenyl, tert-butylphenyl, or cyclohexylphenyl.

C _7-40 arylalkyl may refer to a substituent in which one or more hydrogens of alkyl are replaced by aryl. Specifically, C _7-40 arylalkyl may be a benzyl group, phenylpropyl, or phenylhexyl.

Examples of C _6-20 aryloxy include, but are not limited to, phenoxy, biphenoxy, and naphthoxy.

The above C _1-20 alkoxy group includes, but is not limited to, a methoxy group, an ethoxy group, a phenyloxy group, and a cyclohexyloxy group.

The above C _2-20 alkoxyalkyl group is a functional group in which at least one hydrogen of the above-described alkyl group is replaced with an alkoxy group, and specifically, examples thereof include alkoxyalkyl groups such as a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, an iso-propoxymethyl group, an iso-propoxyethyl group, an iso-propoxyhexyl group, a tert-butoxymethyl group, a tert-butoxyethyl group, and a tert-butoxyhexyl group, but are not limited thereto.

The above C _1-20 alkylsilyl group or C _1-20 alkoxysilyl group is a functional group in which 1 to 3 hydrogen atoms of -SiH ₃ are substituted with 1 to 3 of the above-described alkyl groups or alkoxy groups, and specifically, examples thereof include, but are not limited to, alkylsilyl groups such as methylsilyl group, dimethylsilyl group, trimethylsilyl group, dimethylethylsilyl group, diethylmethylsilyl group, or dimethylpropylsilyl group; alkoxysilyl groups such as methoxysilyl group, dimethoxysilyl group, trimethoxysilyl group, or dimethoxyethoxysilyl group; and alkoxyalkylsilyl groups such as methoxydimethylsilyl group, diethoxymethylsilyl group, or dimethoxypropylsilyl group.

The above C _1-20 silylalkyl group is a functional group in which one or more hydrogens of the alkyl group described above are replaced with a silyl group, and specifically, examples thereof include, but are not limited to, -CH ₂ -SiH ₃ , a methylsilylmethyl group, or a dimethylethoxysilylpropyl group.

The above sulfonate group may have a structure of -O-SO ₂ -R', where R' may be a C _1-20 alkyl group. Specifically, the C _1-20 sulfonate group may include, but is not limited to, a methanesulfonate group or a phenylsulfonate group.

The above heteroaryl is a C _2-20 heteroaryl containing at least one of N, O, and S as a heteroatom, and includes a monocyclic or condensed ring heteroaryl. Specific examples include xanthene, thioxanthen, thiophene group, furan group, pyrrole group, imidazole group, thiazole group, oxazole group, oxadiazole group, triazole group, pyridyl group, bipyridyl group, pyrimidyl group, triazine group, acridyl group, pyridazine group, pyrazinyl group, quinolinyl group, quinazoline group, quinoxalinyl group, phthalazinyl group, pyrido pyrimidinyl group, pyrido pyrazinyl group, pyrazino pyrazinyl group, isoquinoline group, indole group, carbazole group, benzoxazole group, benzimidazole group, benzothiazole group, benzocarbazole group, benzothiophene group, dibenzothiophene group, benzofuranyl group, phenanthroline group, Examples thereof include, but are not limited to, isoxazolyl group, thiadiazolyl group, phenothiazinyl group, and dibenzofuranyl group.

The above-described substituents may be optionally substituted with one or more substituents selected from the group consisting of a hydroxy group; a halogen; an alkyl group or alkenyl group, an aryl group, an alkoxy group; an alkyl group or alkenyl group, an aryl group, an alkoxy group containing one or more heteroatoms of Groups 14 to 16; a silyl group; an alkylsilyl group or an alkoxysilyl group; a phosphine group; a phosphide group; a sulfonate group; and a sulfone group, within a range that exhibits the same or similar effect as the desired effect.

In addition, when two adjacent substituents are connected to each other to form an aliphatic or aromatic ring, it means that the atom(s) of the two substituents and the atom(s) to which the two substituents are bonded are connected to each other to form a ring. Specifically, an example in which R ₉ and R ₁₀ of -NR ₉ R ₁₀ are connected to each other to form an aliphatic ring includes a piperidinyl group, and an example in which R ₉ and R ₁₀ of -NR ₉ R ₁₀ are connected to each other to form an aromatic ring includes a pyrrolyl group, etc.

In the above catalyst composition, the first metallocene compound represented by the chemical formula 5 is a non-crosslinked compound containing ligands of Cp ¹ and Cp ² , and is advantageous in producing a low molecular weight copolymer having a low SCB (short chain branch) content.

Specifically, in the above chemical formula 5, the ligands of Cp ¹ and Cp ² may be the same or different, and each may be cyclopentadienyl, and may be substituted with 1 or more, or 1 to 3, C _1-10 alkyl. In this way, the ligands of Cp ¹ and Cp ² may exhibit high polymerization activity by having an unshared electron pair that can act as a Lewis base, and in particular, since the ligands of Cp ¹ and Cp ² are cyclopentadienyl with relatively low steric hindrance, they exhibit high polymerization activity and low hydrogen reactivity, so that low molecular weight polyethylene can be polymerized with high activity.

In addition, the ligands of Cp ¹ and Cp ² can easily control the chemical structure, molecular weight, molecular weight distribution, mechanical properties, transparency, etc. of the polyethylene produced by controlling the degree of steric hindrance effect depending on the type of substituted functional group, for example. Specifically, the ligands of Cp ¹ and Cp ² are each substituted with R ^a and R ^b , wherein R ^a and R ^b are the same as or different from each other, and each independently may be hydrogen, C _1-20 alkyl, C _2-20 alkoxyalkyl, C _7-40 arylalkyl, or a substituted or unsubstituted C _2-12 heteroaryl containing one or more heteroatoms selected from the group consisting of N, O, and S, and more specifically, may be C _1-10 alkyl, C _2-10 alkoxyalkyl, C _7-20 arylalkyl, or a substituted or unsubstituted C _4-12 heteroaryl containing one or more heteroatoms selected from the group consisting of N, O, and S.

In addition, M ² Z ² _3-m exists between the ligands of Cp ¹ and Cp ² , and M ² Z ² _3-m can affect the storage stability of the metal complex. In order to more effectively secure this effect, Z ¹ can each independently be a halogen or C _1-20 alkyl, and more specifically, can each independently be F, Cl, Br, or I. In addition, M ² can be Ti, Zr, or Hf; or Zr, or Hf; or Zr.

Among the above first metallocene compounds, in the above chemical formula 5, Cp ¹ and Cp ² are each an unsubstituted or substituted cyclopentadienyl group, R ^a and R ^b are each independently hydrogen, C _1-10 alkyl, C _2-10 alkoxyalkyl, or C _7-20 arylalkyl, and at least one of R ^a and R ^b is an alkoxyalkyl such as a t-butoxyhexyl group, more specifically, a substituent of -(CH ₂ ) _p -OR ^c (wherein R ^c is a straight or branched alkyl group having 1 to 6 carbon atoms, and p is an integer of 2 to 4). In this case, when producing polyethylene using a comonomer, it may exhibit a lower conversion rate for the comonomer compared to other Cp-based catalysts that do not include the substituent, so that low-molecular-weight polyethylene with controlled copolymerization degree or comonomer distribution may be produced. In addition, when the first metallocene compound having the above structure is supported on a carrier, the -(CH ₂ ) _p -OR ^c group among the substituents can form a covalent bond through close interaction with the silanol group on the silica surface used as the carrier, thereby enabling stable supported polymerization.

The first metallocene compound represented by the above chemical formula 5 may be, for example, a compound represented by one of the structural formulas below, but is not limited thereto.

.

The first metallocene compound represented by the above chemical formula 5 can be synthesized by applying known reactions, and a more detailed synthesis method can be found in the examples.

Meanwhile, in one embodiment of the invention, the second metallocene compound represented by the above chemical formula 6 includes an aromatic ring compound including cyclopentadienyl or a derivative thereof and a nitrogen atom, and has a structure in which the aromatic ring compound and the nitrogen atom are bridged by a bridging group T ² Q ³ Q ^4. The second metallocene compound having this specific structure can be applied to a polymerization reaction of polyethylene to exhibit high activity and copolymerizability, and can provide an olefin copolymer having a high molecular weight.

In particular, the second metallocene compound represented by the above chemical formula 6 has a well-known structure of a constrained geometry catalyst (CGC), thereby facilitating the introduction of a comonomer, and furthermore, the distribution of the comonomer is controlled by the electronic and steric properties of the ligand. From these properties, the average ethylene sequence length (ASL) is controlled, thereby increasing the medium-molecular region in the molecular weight distribution, thereby expanding the tie molecule fraction ratio and increasing the entanglement of polymer chains, thereby facilitating the production of a polyethylene resin exhibiting excellent pipe pressure characteristics along with long-term stability and processability.

As M ³ of the metallocene compound represented by the above chemical formula 6, a Group 4 transition metal may be used, and preferably, it may be titanium (Ti), zirconium (Zr), or hafnium (Hf).

Preferably, in the above chemical formula 6, T ² may be silicon.

Preferably, in the above chemical formula 6, X ³ and X ⁴ can each independently be methyl or chlorine (Cl).

Preferably, in the above chemical formula 6, R ¹¹ to R ¹⁴ are the same or different, and can each independently be methyl or phenyl.

Preferably, in the above chemical formula 6, two or more adjacent ones of R ¹¹ to R ¹⁴ may be connected to each other to form a substituted or unsubstituted aliphatic ring, an aromatic ring, or a heteroaromatic ring including at least one selected from the group consisting of N, O, and S. For example, in the above chemical formula 6, R ¹¹ to R ¹⁴ When two or more adjacent groups are connected to each other to form an aliphatic ring, an aromatic ring, or a heteroaromatic ring, a cyclopentadiene-fused indenyl group, a fluorenyl group, a benzothiophene group, or a dibenzothiophene group can be formed. In addition, the indenyl group, the fluorenyl group, the benzothiophene group, or the dibenzothiophene group can be substituted with one or more substituents.

Preferably, in the above chemical formula 6, R ¹⁵ to R ¹⁶ are the same or different, and can each independently be methyl, ethyl, phenyl, propyl, hexyl, or tert-butoxyhexyl.

Preferably, in the above formula 6, R ¹⁷ can be methyl, ethyl, n-propyl, iso-propyl, n-butyl, or tert-butyl.

As a second metallocene compound capable of providing a polyethylene resin having both excellent long-term stability and processability along with pipe pressure characteristics through a further increased medium-molecular area, the metallocene compound of the above chemical formula 6 may be any one selected from the group consisting of the following compounds, but the present invention is not limited thereto:

.

The second metallocene compound represented by the above chemical formula 6 can be synthesized by applying known reactions. Specifically, it can be synthesized by connecting a nitrogen compound and a cyclopentadiene derivative with a bridge compound to prepare a ligand compound, and then introducing a metal precursor compound to perform metallation, but is not limited thereto. For more detailed synthetic methods, refer to the examples.

The second metallocene compound of the above chemical formula 6 has excellent activity and can polymerize high molecular weight polyethylene resin. In particular, when used by being supported on a carrier, it exhibits high polymerization activity, enabling the production of ultra-high molecular weight polyethylene resin.

In addition, even when conducting a polymerization reaction including hydrogen to produce a polyethylene resin having both a high molecular weight and a broad molecular weight distribution, the second metallocene compound of chemical formula 6 according to the present invention exhibits low hydrogen reactivity, so that polymerization of an ultra-high molecular weight polyethylene resin is still possible with high activity. Therefore, even when used in combination with a catalyst having different characteristics, a polyethylene resin satisfying the characteristics of a high molecular weight can be produced without a decrease in activity, so that a polyethylene resin including a high molecular weight polyethylene resin and having a broad molecular weight distribution can be easily produced.

As described above, in the catalyst composition, the first metallocene compound represented by the chemical formula 5 mainly contributes to forming a low-molecular-weight copolymer having a low SCB content, and the second metallocene compound represented by the chemical formula 6 mainly contributes to forming a high-molecular-weight copolymer having a high SCB content. More specifically, the catalyst composition exhibits high copolymerizability toward a comonomer in a high-molecular-weight region copolymer due to the second metallocene compound, and exhibits low copolymerizability toward a comonomer in a low-molecular-weight region copolymer due to the first metallocene compound. As a result, a polyethylene resin having excellent mechanical properties as well as a bimodal molecular weight distribution and thus excellent heat resistance can be produced.

In particular, the above-described properties can be achieved by controlling the content ratio of the first and second metallocene compounds in the catalyst composition of the present invention, and the resulting improvement effect can be further enhanced. Specifically, by including the second metallocene compound in the catalyst composition at a higher content than the first metallocene compound, the intramolecular medium-molecular region can be increased, thereby expanding the tie molecule fraction ratio, increasing the entanglement of polymer chains, and optimizing the ratio of high-molecular-weight regions to low-molecular-weight regions.

Specifically, the first and second metallocene compounds should be included in a molar ratio of 1:1 to 1:8. Preferably, the first and second metallocene compounds may be included 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 metallocene compound and the second metallocene compound are in the molar ratio as described above, the polyethylene resin manufactured using the same can control the balance between mechanical properties and stretchability, thereby maintaining mechanical properties, productivity, and stretchability equivalent to or superior to those of the prior art, and can improve high shrinkage resistance, printability, and transparency.

Meanwhile, the first and second metallocene compounds have the structural characteristics described above and can be stably supported on the carrier.

In this case, the first and second metallocene compounds are used in a supported state on the carrier. When used in the supported catalyst state, the resulting polymer has excellent particle shape and bulk density, and can be suitably used in conventional slurry polymerization, bulk polymerization, and gas phase polymerization processes.

Specific examples of the above carrier include silica, alumina, magnesia, silica-alumina, silica-magnesia, etc., and these may further include oxides, carbonates, sulfates, and nitrates, such as Na ₂ O, K ₂ CO ₃ , BaSO ₄ , and Mg(NO ₃ ) ₂ . Among these, when a silica carrier is used, the transition metal compound is supported by chemically bonding with reactive functional groups, such as siloxane groups, existing on the surface of the silica carrier, so that almost no catalyst is liberated from the surface of the carrier during the propylene polymerization process, and as a result, fouling, in which the reactor wall or polymer particles stick together, can be minimized when manufacturing polypropylene by slurry or gas phase polymerization.

Additionally, the carrier may be surface-modified through a calcination or drying process to enhance the loading efficiency and minimize leaching and fouling. Through the surface modification step described above, moisture on the carrier surface that inhibits reaction with the loading components is removed, and instead, the content of reactive functional groups capable of chemical bonding with the loading components, such as hydroxyl groups and siloxane groups, can be increased.

Specifically, the calcination or drying process for the carrier may be performed at a temperature ranging from a temperature at which moisture disappears from the surface of the carrier to a temperature below which reactive functional groups, particularly hydroxyl groups (OH groups), present on the surface completely disappear. Specifically, the temperature may be 150 to 600°C, or 200 to 500°C. If the temperature during calcination or drying of the carrier is lower than 150°C, the moisture removal efficiency is low, and as a result, there is a concern that moisture remaining in the carrier may react with the cocatalyst, thereby reducing the support efficiency. On the other hand, if the drying or calcination temperature is excessively high, exceeding 600°C, the pores present on the surface of the carrier may merge, reducing the specific surface area, and also many reactive functional groups, such as hydroxyl groups or silanol groups, present on the surface may disappear, leaving only siloxane groups, which may reduce the reaction sites with the cocatalyst.

When the above-mentioned first and second metallocene compounds are supported on a carrier, for example, when the carrier is silica, the first and second metallocene compounds may be supported in a total amount of 40 μmol or more, or 80 μmol or more, and 240 μmol or less, or 160 μmol or less, based on 1 g of silica. When supported in the above-mentioned content range, it may exhibit appropriate supported catalytic activity, which may be advantageous in terms of maintaining the activity of the catalyst and economic efficiency.

Additionally, the catalyst composition may further include a cocatalyst to enhance high activity and process stability. The cocatalyst is as described above.

In addition, the amount of the cocatalyst used can be appropriately adjusted depending on the properties or effects of the desired catalyst and resin composition. For example, when silica is used as the carrier, the cocatalyst can be supported in an amount of 8 mmol or more, or 10 mmol or more, and 25 mmol or less, or 20 mmol or less, based on the weight of the carrier, for example, 1 g of silica.

In addition, the above-described catalyst composition may be used for polymerization as is, or may be used in a prepolymerized state through contact with an ethylene monomer prior to use in the polymerization reaction. In this case, the manufacturing method according to one embodiment of the invention may further include a step of prepolymerizing (or prepolymerizing) the catalyst composition by contacting it with an ethylene monomer prior to producing polyethylene through a polymerization reaction.

In addition, the above catalyst composition can be dissolved or diluted in an aliphatic hydrocarbon solvent having 5 to 12 carbon atoms, such as pentane, hexane, heptane, nonane, decane, and isomers thereof, an aromatic hydrocarbon solvent such as toluene and benzene, a hydrocarbon solvent substituted with a chlorine atom such as dichloromethane and chlorobenzene, and then introduced into the polymerization reaction described below. It is preferable to use the solvent used here after removing a small amount of water or air, which act as catalyst poisons, by treating it with a small amount of alkyl aluminum, and it is also possible to carry out the reaction using an additional cocatalyst.

Meanwhile, the polymerization process can be carried out by contacting ethylene and a comonomer in the presence of the above-described catalyst composition. In particular, the polymerization reaction can be carried out in a single polymerization reactor.

Typically, conventional bimodal polymerization reactions utilize two or more reactors, depending on the number of catalysts, and perform polymerization reactions by injecting respective catalysts into each of the two or more reactors, thereby producing polymers with different molecular weights and then mixing them. However, this method has a problem of reduced uniformity due to the different molecular weights. In response to this, the present invention hybridizes two types of catalysts onto a single carrier and performs a monomodal polymerization reaction in a single reactor, thereby simultaneously polymerizing low-molecular-weight and high-molecular-weight polymers, resulting in the production of polymers with excellent uniformity.

And, the polymerization temperature may be 25°C to 500°C, preferably 25°C to 200°C, and more preferably 50°C to 150°C. In addition, the polymerization pressure may be 1 kgf/㎠ to 100 kgf/㎠, and preferably 1 kgf/㎠ to 50 kgf/㎠.

And, during the polymerization process, the amount of alpha-olefin comonomer added may be 1 to 3 wt% based on the total weight of ethylene.

The amount of alpha-olefin comonomer input, together with the catalyst structure and the amount of hydrogen gas input, affects the molecular weight and molecular structure of the second ethylene alpha-olefin copolymer to be finally manufactured. In the present invention, when the alpha-olefin comonomer is input in the above-mentioned input range, the second ethylene alpha-olefin copolymer having a high molecular weight and a broad molecular weight distribution can be easily produced. More specifically, the alpha-olefin comonomer may be 1 wt% or more, or 1.2 wt% or more, or 1.5 wt% or more, or 1.6 wt% or more, and 3 wt% or less, or 2.5 wt% or less, or 2 wt% or less, or 1.8 wt% or less based on the total weight of ethylene.

In addition, the polymerization reaction can be carried out by continuously polymerizing ethylene and alpha-olefin monomers by continuously adding hydrogen in the presence of a catalyst composition.

The hydrogen gas suppresses the rapid reaction of the transition metal compound in the early stage of polymerization and terminates the polymerization reaction. Accordingly, by controlling the use and amount of hydrogen gas, an ethylene/alpha-olefin copolymer with a controlled molecular weight distribution can be effectively produced.

Specifically, in the present invention, the amount of hydrogen gas input may be 150 to 200 ppm based on the total weight of ethylene. When input in the above content range, a second ethylene alpha olefin copolymer having a high molecular weight and a wide molecular weight distribution can be easily realized. More specifically, the amount of hydrogen gas input may be 150 ppm or more, or 155 ppm or more, or 160 ppm or more, and 200 ppm or less, or 180 ppm or less, or 170 ppm or less, or 165 ppm or less based on the total weight of ethylene.

By the above-described manufacturing method, a second ethylene-alpha olefin copolymer having the above-described physical properties can be manufactured.

(biaxially oriented film)

The polyethylene resin composition having the above-described physical properties has improved melt breakage, enabling the production of a biaxially oriented film having excellent surface properties. Accordingly, according to the present invention, a biaxially oriented film comprising the polyethylene resin composition is provided.

The above biaxially oriented film can be manufactured by a conventional film manufacturing method, except that the above polyethylene resin composition is used.

For example, a biaxially oriented film according to the present invention can be manufactured into a 0.75 mm thick polyethylene resin composition sheet using a Bruckner lab extruder line (L/D ratio: 42, Screw diameter: 25 mm, Melt/T-Die temperature: 220°C). Thereafter, a polyethylene biaxially oriented film can be manufactured by performing biaxial stretching on a polyethylene resin composition sheet having a width x length of 90 mm x 90 mm using a KARO 5.0 device. Specific film manufacturing methods and conditions are as described in the test examples described below.

In addition, the biaxially oriented film according to the present invention may further comprise additives well known in the art in addition to the polyethylene resin composition described above. Specifically, such additives include solvents, heat stabilizers, antioxidants, UV absorbers, light stabilizers, metal deactivators, fillers, reinforcing agents, plasticizers, lubricants, emulsifiers, pigments, optical bleaching agents, flame retardants, antistatic agents, foaming agents, and the like. The types of the additives are not particularly limited, and general additives known in the art can be used.

A polyethylene biaxially oriented film according to one embodiment of the present invention manufactured by the above method exhibits excellent surface properties.

The polyethylene resin composition according to the present invention has improved melt fracture, thereby preventing the occurrence of surface defects during the production of a biaxially oriented film. Accordingly, a biaxially oriented film having excellent surface properties can be produced using the polyethylene resin composition.

Figure 1 is a molecular weight distribution graph obtained through gel permeation chromatography analysis of the polyethylene resin compositions of Examples 1 and 2 and Comparative Example 2.

Figure 2 is a graph showing the ARES analysis results for the polyethylene resin compositions of Examples 1 and 2 and Comparative Example 2.

Figure 3 is a graph showing the results of observing the melt fracture initiation temperature for the polyethylene resin compositions of Examples 1 and 2 and Comparative Example 2.

Hereinafter, embodiments of the present invention will be described in more detail in the following examples. However, the following examples are merely illustrative of embodiments of the present invention, and the content of the present invention is not limited by the following examples.

<Preparation of metallocene compounds>

Synthesis Example 1

(1)

(1) Preparation of ligand compound

1-Benzothiophene 4.0 g (30 mmol) was dissolved in THF to prepare a 1-benzothiophene solution. Then, 14 mL (36 mmol, 2.5 M in hexane) of n-BuLi solution and 1.3 g (15 mmol) of CuCN were added to the 1-benzothiophene solution. Subsequently, 3.6 g (30 mmol) of tigloyl chloride was slowly added to the solution at -80 °C, and the resulting solution was stirred at room temperature for about 10 hours. Afterwards, 10% HCl was poured into the solution to quench the reaction, and the organic layer was separated with dichloromethane to obtain (2E)-1-(1-benzothien-2-yl)-2-methyl-2-buten-1-one as a beige solid.

¹ H NMR (CDCl ₃ ): 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)

5.0 g (22 mmol) of (2E)-1-(1-benzothien-2-yl)-2-methyl-2-buten-1-one prepared above was dissolved in 5 mL of chlorobenzene, and 34 mL of sulfuric acid was slowly added to the solution while stirring vigorously. Then, the solution was stirred at room temperature for about 1 hour. Afterwards, ice water was poured into the solution, and the organic layer was separated with ether solvent to obtain 4.5 g (91% yield) of 1,2-dimethyl-1,2-dihydro-3H-benzo[b]cyclopenta[d]thiophene-3-one as a yellow solid.

¹ H NMR (CDCl ₃ ): 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)

To a solution of 2.0 g (9.2 mmol) of 1,2-dimethyl-1,2-dihydro-3H-benzo[b]cyclopenta[d]thiophene-3-one in a mixed solvent of 20 mL of THF and 10 mL of methanol, 570 mg (15 mmol) of NaBH ₄ was added at 0°C. The solution was stirred at room temperature for about 2 hours. Thereafter, HCl was added to the solution to adjust the pH to 1, and the organic layer was separated with an ether solvent to obtain an alcohol intermediate.

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

^1H NMR(CDCl ₃ ): 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)

4.65 g (15.88 mmol) of the compound prepared above was weighed and added to a 100 mL Schlenk flask, and 80 mL of THF was added thereto. tBuNH ₂ (4 eq, 6.68 mL) was added at room temperature, and the mixture was reacted at room temperature for 3 days. After the reaction, THF was removed and the residue was filtered with hexane. After drying the solvent, 4.50 g (86%) of N-tert-butyl-1-(1,2-dimethyl-3H-benzo[b]cyclopenta[d]thiophen-3-yl)-1,1-dimethylsilanamine was obtained as a yellow liquid in a yield of 4.50 g (86%).

¹ H-NMR (500 MHz, CDCl ₃ ): 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).

(2) Preparation of metallocene compound (1)

The above ligand compound (1.06 g, 3.22 mmol/1.0 eq) and MTBE 16.0 mL (0.2 M) were placed in a 50 mL Schlenk flask and stirred first. n-BuLi (2.64 mL, 6.60 mmol/2.05 eq, 2.5 M in THF) was added at -40 °C and reacted overnight at room temperature. After that, MeMgBr (2.68 mL, 8.05 mmol/2.5 eq, 3.0 M in diethyl ether) was slowly added dropwise at -40 °C, followed by TiCl ₄ (2.68 mL, 3.22 mmol/1.0 eq, 1.0 M in toluene) and reacted overnight at room temperature. The reaction mixture was then filtered through Celite using hexane. After drying the solvent, a brown solid was obtained in a yield of 1.07 g (82%).

¹ H-NMR (500 MHz, CDCl ₃ ): 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).

Synthesis Example 2

(2)

t-butyl-O-(CH ₂ ) ₆ -Cl was prepared using 6-chlorohexanol according to the method described in the literature (Tetrahedron Lett. 2951(1988)), and then Na(C ₅ H ₅ ) [NaCp] was reacted to obtain t-butyl-O-(CH ₂ ) ₆ -C ₅ H ₅ (yield 60%, bp 80 ^o C/0.1 mmHg).

Also, t-butyl-O-(CH ₂ ) ₆ -C ₅ H ₅ was dissolved in tetrahydrofuran (THF) at -78 ^o C, n-BuLi was slowly added, the mixture was warmed to room temperature, and reacted for 8 hours. The above-mentioned solution was again added slowly to a suspension solution of ZrCl ₄ (THF) ₂ (170 g, 4.50 mmol) / THF (30 mL) at -78 ^o C, and the synthesized lithium salt solution was reacted for another 6 hours at room temperature. All volatile substances were removed by vacuum drying, and the obtained oily liquid substance was filtered by adding hexane. After the filter solution was vacuum dried, hexane was added to induce a precipitate at a low temperature (-20 ^o C). The obtained precipitate was filtered at low temperature to obtain the compound [t-butyl-O-(CH ₂ ) ₆ -C ₅ H ₄ ] ₂ ZrCl ₂ in the form of a white solid (yield 92%).

¹ H-NMR (300 MHz, CDCl ₃ ): 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).

¹³ C-NMR (CDCl ₃ ): δ 135.09, 116.66, 112.28, 72.42, 61.52, 30.66, 30.31, 30.14, 29.18, 27.58, 26.00.

Synthesis Example 3

(3)

At room temperature, 50 g of Mg(s) was added to a 10 L reactor, followed by 300 mL of THF. Approximately 0.5 g of I2 was added, and the reactor temperature was maintained at 50°C. After the reactor temperature stabilized, 250 g of 6-t-butoxyhexyl chloride was added to the reactor at a rate of 5 mL/min using a feeding pump. As 6-t-butoxyhexyl chloride was added, the reactor temperature was observed to rise by approximately 4 to 5°C. The mixture was stirred for 12 hours while continuously adding 6-t-butoxyhexyl chloride. After 12 hours of reaction, a black reaction solution was obtained. 2 mL of the resulting black solution was taken, water was added, and an organic layer was obtained, and 6-t-butoxyhexane was confirmed through ¹ H-NMR. It was found that the Grignard reaction proceeded well from the above 6-t-butoxyhexane. Thus, 6-t-butoxyhexyl magnesium chloride was synthesized.

After adding 500 g of MeSiCl ₃ and 1 L of THF to the reactor, the reactor temperature was cooled to -20 °C. 560 g of the synthesized 6-t-butoxyhexyl magnesium chloride was added to the reactor at a rate of 5 mL/min using a feeding pump. After the feeding of the Grignard reagent was completed, the reactor temperature was slowly raised to room temperature and stirred for 12 hours. After 12 hours of reaction, it was confirmed that a white MgCl ₂ salt was produced. 4 L of hexane was added, and the salt was removed through a labdori to obtain a filter solution. The obtained filter solution was added to the reactor, and hexane was removed at 70 °C to obtain a pale yellow liquid. The obtained liquid was confirmed to be the desired methyl(6-t-butoxy hexyl)dichlorosilane compound through ¹ H-NMR.

¹ H-NMR (300 MHz, CDCl ₃ ): 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).

1.2 mol (150 g) of tetramethylcyclopentadiene and 2.4 L of THF were added to the reactor, and the reactor temperature was cooled to -20 ℃. 480 mL of n-BuLi was added to the reactor at a rate of 5 mL/min using a feeding pump. After adding n-BuLi, the reactor temperature was slowly raised to room temperature and stirred for 12 hours. After 12 hours of reaction, an equivalent amount of methyl(6-t-butoxy hexyl)dichlorosilane (326 g, 350 mL) was rapidly added to the reactor. The reactor temperature was slowly raised to room temperature and stirred for 12 hours. After cooling the reactor temperature to 0 ℃ again, 2 equivalents of t-BuNH ₂ were added. The reactor temperature was slowly raised to room temperature and stirred for 12 hours. After 12 hours of reaction, THF was removed, and 4 L of hexane was added to obtain a filter solution with salt removed through a labdori. The filter solution was added back to the reactor, and hexane was removed at 70°C to obtain a yellow solution. The obtained yellow solution was confirmed to be a compound called methyl(6-t-butoxyhexyl)(tetramethylCpH)t-butylaminosilane through ¹ H-NMR.

TiCl ₃ (THF) ₃ (10 mmol) was rapidly added to the dilithium salt of the ligand synthesized from n-BuLi and the ligand dimethyl(tetramethylCpH) t-butylaminosilane in THF solution at -78 °C. The reaction solution was stirred for 12 hours while slowly warming from -78 °C to room temperature. After stirring for 12 hours, an equivalent amount of PbCl ₂ (10 mmol) was added to the reaction solution at room temperature and stirred for 12 hours. After stirring for 12 hours, a dark black solution with a bluish tinge was obtained. After removing THF from the resulting reaction solution, hexane was added, and the product was filtered. After removing hexane from the obtained filter solution, it was confirmed from ¹ H-NMR that the desired ([methyl(6-t-buthoxyhexyl)silyl(η5-tetramethylCp)(t-Butylamido)]TiCl ₂ ) was (tBu-O-(CH ₂ ) ₆ )(CH ₃ )Si(C ₅ (CH ₃ ) ₄ )(tBu-N)TiCl ₂ .

¹ H-NMR (300 MHz, CDCl ₃ ): δ 3.3 (s, 4H), 2.2 (s, 6H), 2.1 (s, 6H), 1.8 to 0.8 (m), 1.4 (s, 9H), 1.2 (s, 9H), 0.7 (s, 3H).

<Manufacture of supported catalysts>

Catalyst Preparation Example 1: Preparation of a Hybrid Supported Metallocene Catalyst

5.0 kg of toluene solution was placed in a 20 L sus high-pressure reactor, and the reactor temperature was maintained at 40°C. 1000 g of silica (SYLOPOL 948, manufactured by Grace Davison) dehydrated by applying vacuum at 600°C for 12 hours was placed in the reactor, and after sufficiently dispersing the silica, 80 g of the metallocene compound (2) prepared in Synthesis Example 2 above was dissolved in toluene and placed in the reactor, and the mixture was stirred at 40°C for 2 hours at 200 rpm for reaction. Afterwards, stirring was stopped, and the reaction solution was allowed to settle for 30 minutes, and then decantated.

2.5 kg of toluene was charged into the reactor, and 9.4 kg of a 10 wt% methylaluminoxane (MAO)/toluene solution was added, followed by stirring at 200 rpm at 40°C for 12 hours. After the reaction, stirring was stopped, the reaction solution was allowed to settle for 30 minutes, and then decanted. 3.0 kg of toluene was added, stirred for 10 minutes, stopped, and the reaction solution was allowed to settle for 30 minutes, and then decanted.

3.0 kg of toluene was charged into the reactor, and 314 mL of the metallocene compound (3)/toluene solution prepared in Synthesis Example 3 at 29.2 wt% was charged into the reactor, and the mixture was stirred at 200 rpm for 2 hours at 40°C for reaction. At this time, the molar ratio of the metallocene compound (2) and the metallocene compound (3) was 1:5 (number of moles of the first metallocene compound (2): number of moles of the second metallocene compound (3)). After the reactor temperature was lowered to room temperature, stirring was stopped, and the mixture was allowed to settle for 30 minutes, and then the reaction solution was decantated.

(2) (3)

2.0 kg of toluene was added to the reactor and stirred for 10 minutes. After stopping the stirring and allowing it to settle for 30 minutes, the reaction solution was decanted.

3.0 kg of hexane was added to the reactor, the hexane slurry was transferred to a filter dryer, and the hexane solution was filtered. The hexane solution was dried under reduced pressure at 40°C for 4 hours to produce a 910 g-SiO ₂ hybrid supported catalyst.

Catalyst Preparation Example 2

3.0 kg of toluene solution was placed in a 20 L stainless steel (sus) high-pressure reactor, and the reactor temperature was maintained at 40°C. 500 g of silica (Grace Davison, SP2212), dehydrated by applying vacuum at 600°C for 12 hours, was placed in the reactor, and after sufficient dispersion, 2.78 kg of a 10 wt% methylaluminoxane (MAO)/toluene solution was placed, and the mixture was stirred at 80°C and 200 rpm for more than 15 hours.

After lowering the reactor temperature to 40 ℃, 60 g of the first metallocene compound (2)/toluene solution (7.8 wt% in toluene) prepared in Synthesis Example 2 was added to the reactor and stirred at 200 rpm for 1 hour. Next, 230 g of the second metallocene compound (3)/toluene solution (7.8 wt% in toluene) 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) and the second metallocene compound (3) was 1:2.5 (number of moles of the first metallocene compound (2): number of moles of the second metallocene compound (3)).

(2) (3)

Next, 70 g of a cocatalyst (anilinium tetrakis(pentafluorophenyl)borate) diluted in toluene was added to the reactor and stirred at 200 rpm for more than 15 hours. After lowering the reactor temperature to room temperature, stirring was stopped, and the reaction solution was allowed to settle for 30 minutes, after which it was decanted.

The resulting toluene slurry was transferred to a filter dryer and filtered. 3.0 kg of toluene was added and stirred for 10 minutes, then stirring was stopped and filtered. 3.0 kg of hexane was added to the reactor and stirred for 10 minutes, then stirring was stopped and filtered. The resulting catalyst was dried under reduced pressure at 50°C for 4 hours to produce a 500 g-SiO ₂ supported catalyst.

<Manufacture of ethylene-alphaolefin copolymer>

Manufacturing Example 1: Manufacturing of ethylene/1-octene copolymer (PE-a)

A 1.5 L continuous process reactor was preheated to 120°C while introducing 5 kg/h of hexane solvent and 0.31 kg/h of 1-octene. Triisobutylaluminum (Tibal, 0.045 mmol/min), the metallocene compound (1) obtained in Synthesis Example 1, and dimethylanilinium tetrakis(pentafluorophenyl)borate cocatalyst (2.6 μmol/min) were simultaneously introduced into the reactor. Subsequently, ethylene (0.87 kg/h) and hydrogen gas (10 cc/min) were introduced into the reactor, and the copolymerization reaction was carried out by maintaining the temperature at 160.0°C for more than 60 minutes in a continuous process at a pressure of 89 bar, thereby obtaining an ethylene/1-octene copolymer (PE-a).

Manufacturing Example 2: Manufacturing of ethylene/1-hexene copolymer (PE-b)

An ethylene/1-hexene copolymer (PE-b) was subjected to slurry polymerization in the presence of the hybrid supported catalyst prepared in the above catalyst preparation example 1.

At this time, the polymerization reactor was a continuous polymerizer of isobutane (i-C4) slurry loop process, with a reactor volume of 140 L and a reaction flow rate of approximately 7 m/s. The gases (ethylene, hydrogen) required for polymerization and the comonomer 1-hexene were continuously fed continuously and the individual flow rates were adjusted to suit the target product. At this time, the ethylene feed amount was 31.1 kg/hr, the 1-hexene input amount was adjusted to 2.5 wt% relative to ethylene, and the hydrogen input amount was adjusted to 56 ppm relative to ethylene. In addition, the concentrations of all gases and the comonomer 1-hexene of Manufacturing Example 1 were confirmed by an on-line gas chromatograph. The supported catalyst was prepared as an isobutane slurry with a concentration of 4 wt% and introduced, the reactor pressure was maintained at approximately 40 bar, and the polymerization temperature was performed at approximately 80°C.

Manufacturing Examples 3 and 4: Manufacturing of ethylene/1-hexene copolymers (PE-c and PE-d)

Using the hybrid supported catalyst manufactured in the above catalyst manufacturing example 2, ethylene/1-hexene copolymers (PE-c and PE-d) were each polymerized in a loop-type slurry reactor according to the conditions in Table 1 below.

Manufacturing Example 1 Manufacturing Example 2 Manufacturing Example 3 Manufacturing Example 4 Type of polymer PE-a PE-b PE-c PE-d Catalyst type Synthesis Example 1 Catalyst Preparation Example 1 Catalyst Preparation Example 2 Catalyst Preparation Example 2 Ethylene supply (kg/hr) 0.87 31.1 33.0 33.0 Type of comonomer 1-octene (1-C8) 1-hexene (1-C6) 1-hexene (1-C6) 1-hexene (1-C6) Monomer input amount 0.31 kg/h 2.5 wt% 1.6 wt% 1.8 wt% Hydrogen input amount 10 cc/min 56 ppm 165 ppm 160 ppm Polymerization temperature (℃) 160.0 80.0 93.0 93.0 Catalytic activity (kgPE/g Cat.hr) 5 5 5.5 6.0 MI _2.16 (g/10min) 6.0 0.6 0.39 0.36 Density (g/cm ³ ) 0.900 0.941 0.948 0.946 Mn(g/mol) 30,000 28,000 11,600 14,100 Mw(g/mol) 68,000 114,000 149,200 160,920 Mw/Mn 2.3 4.1 12.9 11.4

In the above Table 1, the unit of monomer input “wt%” and the unit of hydrogen input “ppm” are each based on the total weight of ethylene input.

<Manufacture of polyethylene resin composition>

Comparative Example 1

As described in Table 2 below, 30 wt% of the ethylene/1-octene copolymer (PE-a) manufactured in Manufacturing Example 1 and 70 wt% of the ethylene/1-hexene copolymer (PE-b) manufactured in Manufacturing Example 2 were mixed, and then, using a Twin extruder device, the mixture was extruded and granulated under the conditions of 18 rpm for the hopper, 350 rpm for the screw, and 220°C (extruder: SMPLATEK TEK30MHS, L/D ratio: 40, die diameter: 4 mm, extrusion conditions: 18 rpm for the hopper, 350 rpm for the screw, and 220°C), thereby manufacturing a polyethylene resin composition.

Comparative examples 2 and 3

A polyethylene resin composition was manufactured using the same method as in Comparative Example 1, except that the polyethylene manufactured in Manufacturing Examples 3 and 4 was used.

Examples 1 to 4

The polyethylene manufactured in Manufacturing Examples 1, 3, and 4 was used in the compositions described in Table 3 below to manufacture the polyethylene resin compositions of Examples 1 to 4, respectively.

Specifically, a polyethylene resin composition was manufactured by extruding and granulating using Twin extruder equipment at 18 rpm of the hopper, 350 rpm of the screw, and 220°C (extruder: SMPLATEK TEK30MHS, L/D ratio: 40, die diameter: 4 mm, extrusion conditions: 18 rpm of the hopper, 350 rpm of the screw, and 220°C).

Comparative Example 1 Comparative Example 2 Comparative Example 3 furtherance PE-a(30wt%)+ PE-b(70wt%) PE-c PE-d

Example 1 Example 2 Example 3 Example 4 furtherance PE-a(28wt%)+
PE-c (72 wt%) PE-a(17wt%)
+ PE-c(83wt%) PE-a(30wt%)
+ PE-d(70wt%) PE-a(20wt%)
+ PE-d(80wt%)

In Tables 2 and 3 above, the unit “wt%” is based on the total weight of the polyethylene resin composition.

Test Example 1

The physical properties of the polyethylene resin compositions manufactured in the above examples and comparative examples were measured by the following methods, and the results are shown in the following table and Figures 1 to 3.

(1) Density

Density (g/cm ³ ) was measured according to the American Society for Testing and Materials standard ASTM D 1505.

(2) Melting index

The melt index (MI _2.16 ) was measured at 190 ℃ with a load of 2.16 kg according to the American Society for Testing and Materials standard ASTM D1238 (condition E, 190 ℃, 2.16 kg) (measuring equipment: Gottfert MI-4), and expressed as the weight (g) of the polymer melted for 10 minutes.

(3) Melt flow rate ratio (MFRR, MI _21.6 /MI _2.16 )

According to ASTM D1238, the MI _2.16 (190℃, 2.16 kg load condition) and MI _21.6 (190℃, 21.6 kg load condition) of the polyethylene resin composition were measured, and the Melt Flow Rate Ratio (MFRR) was calculated by dividing the value of MI _21.6 by MI _2.16 . MFRR is generally used as a value indicating the shear thinning effect.

(4) Weight average molecular weight (Mw) and molecular weight distribution (PDI)

For the polyethylene resin compositions according to the above examples and comparative examples, the weight average molecular weight (Mw, g/mol) and number average molecular weight (Mn, g/mol) were measured through gel permeation chromatography (GPC) analysis, and the molecular weight distribution (Mw/Mn, PDI, polydispersity index) was obtained by dividing the weight average molecular weight measured above by the number average molecular weight.

Specifically, a Waters PL-GPC220 gel permeation chromatography (GPC) device and a Polymer Laboratories PLgel MIX-B 300 mm column were used. The measurement temperature was 160°C, 1,2,4-trichlorobenzene was used as the solvent, and the flow rate was 1 mL/min. Each sample of the ethylene-alpha-olefin copolymer prepared above was pretreated by dissolving in 1,2,4-trichlorobenzene containing 0.0125% BHT at 160°C for 3 hours using a GPC analysis device (PL-GP220), and then preparing a concentration of 32 mg/10 mL, and then supplying it in an amount of 200 μL. The values of Mw and Mn were derived using a calibration curve formed using polystyrene standard specimens. The weight average molecular weights of the polystyrene standard specimens were 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, which were 9 types.

The molecular weight distribution graphs of the polyethylene resin compositions of Examples 1 and 2 and Comparative Example 2 obtained from the gel permeation chromatography analysis results (x-axis: logarithm value (logMw) of the weight average molecular weight (Mw) (g/mol), y-axis: molecular weight distribution for the logarithm value (dW/dlogMw)) are shown in Figure 1.

(5) Bimodality triangular area (BMTA)

Bimodality triangular area (BMTA) was measured for the polyethylene compositions of Examples 1 to 3 and Comparative Examples 1 to 4 using the following method.

Specifically, using gel permeation chromatography (GPC, manufactured by Water) as described above, the weight average molecular weight (Mw, g/mol) was measured in accordance with the American Society for Testing and Materials standard ASTM D 6474, and the area of the BMTA (Bimodality triangular area) region was measured in a logarithmic graph for the weight average molecular weight (Mw) of polyethylene measured in this way, i.e., a GPC curve graph in which the x-axis is log MW and the y-axis is dw/dlogMw.

Here, the BMTA (Bimodality triangular area) area is defined as the maximum intensity coordinate (X-axis: a, Y-axis: d) of the peak (Peak _low ) with the widest area among the low-molecular fractions having a log Mw of less than 5.0 of the peak maximum intensity in the GPC curve graph, and the maximum intensity coordinate (X-axis: b, Y-axis: e) of the peak (Peak _high ) with the widest area among the high-molecular fractions having a log Mw of 5.0 or more of the peak maximum intensity, and the coordinate (X-axis: c, Y-axis: f) of the intersection point where the low-molecular fraction including the peak (Peak _low ) and the high-molecular fraction including the peak (Peak _high ) intersect, and corresponds to a triangular area connecting these three coordinates. That is, the area of the BMTA ( _{Bimodality triangular} area) region, which is the area of a triangle connecting the maximum intensity coordinates (X-axis: a, Y-axis: d) of the above-described low-molecular fraction peak (Peak _low ), the maximum intensity coordinates (X-axis: b, Y-axis: e) of the above-described high-molecular fraction peak (Peak high), and the intersection coordinates (X-axis: c, Y-axis: f), was measured using the following method of mathematical expression 1.

[Mathematical Formula 1]

In the above mathematical formula 1

ae represents the product of the maximum intensity X-axis coordinate value of the low-molecular fraction and the maximum intensity Y-axis coordinate value of the high-molecular fraction,

bf is the product of the maximum intensity X-axis coordinate value of the polymer 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 fraction,

db represents the product of the maximum intensity Y-axis coordinate value of the low-molecular fraction and the maximum intensity X-axis coordinate value of the high-molecular fraction.

ec represents the product of the maximum intensity Y-axis coordinate value of the polymer 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 X-axis coordinate value of the maximum intensity of the low-molecular fraction.

The specific method is as follows.

- Peak deconvolution was performed from the Mw curve obtained through GPC analysis (Agilent PL-GPC 220).

: Curve fitting using Gaussian probability function

: Peak separation into low molecular weight fraction (log Mw 5.0 or less of peak maximum intensity) and high molecular weight fraction (log Mw 5.0 or more of peak maximum intensity)

: Selection of the peak with the largest area among the low-molecular fractions and the peak with the largest area among the high-molecular fractions

- The area is calculated from the triangle derived by drawing a line connecting the point corresponding to the maximum intensity of each of the selected low-molecular fractions and high-molecular fractions and the point corresponding to the intersection of each curve, and this is defined as BMTA.

- If the maximum intensity coordinates of the above low molecular fraction are defined as (a, d), the maximum intensity coordinates of the high molecular fraction as (b, e), and the coordinates of the intersection point as (c, f), the calculation formula of BMTA is as shown in the mathematical formula 1 described above.

Here, if the low molecular weight fraction and high molecular weight fraction are not separated in the GPC curve graph of the polyethylene composition, or the log Mw value of the intersection point is not between the log Mw values of the maximum intensities of the low molecular weight fraction and the high molecular weight fraction (c > a, b or c < a, b), BMTA is defined as 0.

The BMTA values measured in this way are shown in Table 2 below. When the BMTA is high, the degree of binary separation of the GPC curve is high, which means that there is a large low-molecular-weight region, and accordingly, it can be seen that the processability is excellent.

(6) Complex viscosity (Pa·S)

The complex viscosity (Pa·s) of a polyethylene resin composition was measured under conditions of 230°C and an angular frequency of 500 rad/s using a rotational rheometer, ARES-G2 (manufactured by TA).

In addition, based on the experimental results for the polyethylene resin compositions of Examples 1 and 2 and Comparative Example 2, a graph showing the change in complex viscosity according to frequency (x-axis: logarithm of frequency (Log(Frequency)), y-axis: logarithm of complex viscosity (Log(complex viscosity))) is shown in Fig. 2.

(7) Shear viscosity (Pa·S)

Shear viscosity was measured using a capillary rheometer at 230°C and a shear rate of 1/1000 sec.

Specifically, using RHEO-TESTER 2000 equipment manufactured by Gottfert, shear viscosity (Pa·s) was measured at a capillary die specification (die length (L) = 10 mm, die diameter (D) = 2 mm, [L/D] = 10/2), a temperature of 230°C, and a shear rate of 1/1000 sec.

(8) Shear rate _{onset of MF} (MF _{on_set} )(1/s)

Shear rate _{onset of MF} is the shear rate (1/s) at which melt fracture occurs.

According to ASTM D 3835, the shear viscosity (Pa·s) of the polyethylene resin composition was measured during strand extrusion at varying shear rates using a capillary rheometer.

From the results, after obtaining a graph of the change in shear viscosity according to the shear rate, the point where the instability of the shear viscosity increases and the slope changes abruptly in the shear rate/shear viscosity curve is defined as the point at which melt fracture occurs (onset of melt fracture), and the shear rate at this time is defined as the shear rate at the point at which melt fracture occurs (shear rate _{onset of MF} or MF _{on_set} ). did.

Specifically, the surface of the extruded polyethylene resin composition strand was visually observed while changing the shear rate to 10 ^2.0 , 10 ^2.2 , 10 ^2.4 , 10 ^2.6 , 10 ^2.8 , 10 ^2.9 , 10 ^2.95 , and 10 ^2.30 s ^-1 using RHEO-TESTER 2000 equipment from Gottfert. The shear viscosity at the starting point where the uneven phenomenon of the strand surface occurred was measured. At this time, the shape of the orifice was a round hole type, the hole length was 10 mm, the diameter was 2 mm, the run-in angle was 180˚, and the measurement temperature was 230℃.

(9) MF _{on_set} Stress (Pa)

The shear viscosity (Pa·s) at the starting point of the uneven phenomenon of the strand surface, i.e., the point at which melt fracture occurs, measured at the above (8) Shear rate _{onset of MF} (MF _{on_set} ), and the shear rate (shear rate _{onset of MF} ) (1/s) at that time were used to obtain the MF _{on_set} Stress (Pa) according to the following mathematical equation 2.

[Equation 2]

MF _{on_set} Stress (Pa) = Shear viscosity at the point where melt fracture occurs (Pa·s) x Shear rate at the point where melt fracture occurs (shear rate _{onset of MF} ) (1/s)

In addition, using a capillary rheometer, the change in shear stress during strand extrusion was measured while changing the shear rate for the polyethylene resin compositions of Examples 1 and 2 and Comparative Example 2, and melt fracture was visually confirmed by taking strands at 8 points in the range of shear rates of 100 to 1000 s ^-1 . The results are shown in Fig. 3.

Unit Example 1 Example 2 Example 3 Example 4 MI _{(2.16 kg)} g/10min 0.61 0.53 0.7 0.5 MFRR _(21.6/2.16) - 81 89 79 88 Density g/cm ³ 0.936 0.940 0.935 0.940 Shape of molecular weight distribution curve - Unimodal Unimodal Unimodal Unimodal BMTA - 0.09 0.10 0.09 0.10 Mw g/mol 114,500 120,900 110,500 117,300 PDI - 5.65 6.64 5.54 6.43 Complex viscosity
@230℃ Pa·s 330 344 332 345 Shear viscosity @230℃ Pa·s 272 289 283 293 MF _{on_set} @230℃ 1/s 1,000 or more 1,000 or more 1,000 or more 1,000 or more MF _{on_set} Stress
@230℃ Pa More than 265,000 More than 265,000 More than 265,000 More than 265,000

Unit Comparative Example 1 Comparative Example 2 Comparative Example 3 MI _{(2.16 kg)} g/10min 1.13 0.39 0.36 MFRR _(21.6/2.16) - 37 99 96 Density g/cm ³ 0.931 0.948 0.946 Shape of molecular weight distribution curve - Unimodal Bimodal Bimodal BMTA - 0.01 0.20 0.19 Mw g/mol 108,400 149,290 160,920 PDI (Mn/Mw) - 3.85 12.85 11.37 Complex viscosity @230℃ Pa·s 480 343 348 Shear viscosity @230℃ Pa·s 374 251 260 MF _{on_set} @230℃ 1/s 398 891 891 MF _{on_set} Stress @230℃ Pa 245,667 245,375 253,337

The experimental results confirmed that Melt Fracture is improved only when the molecular weight distribution is wide, the viscosity is low, and the unimodal form is maintained, and the Melt Fracture improvement effect cannot be achieved when the form is bimodal. In addition, it can be expected that in the case of Examples 1 to 4 where Melt Fracture is improved, the occurrence of stains on the film surface can be minimized during high-speed production, and thus a film with excellent surface properties can be manufactured.

Claims (15)

Contains one or more types of polyethylene, A polyethylene resin composition satisfying the conditions (a1) to (a4) below: (a1) Melt flow index (MI _21.6 /MI _2.16 , ASTM D1238, 190℃): 60 to 120 (a2) Density (ASTM D1505): 0.920 to 0.950 g/cm ³ (a3) Molecular weight distribution: 5.50 to 15.00 (a4) When a molecular weight distribution curve is drawn using the logarithm value (logMw) of the weight average molecular weight (Mw) (g/mol) as the x-axis and the molecular weight distribution (dW/dlogMw) for the logarithm value as the y-axis through gel permeation chromatography analysis, the molecular weight distribution shape is: unimodal. In the first paragraph, The above polyethylene resin composition is a polyethylene resin composition having a weight average molecular weight of 110,000 to 130,000 g/mol. In the first paragraph, The above polyethylene resin composition is a polyethylene resin composition having a composite viscosity of 400 Pa·s or less, measured under conditions of 230°C and 500 rad/s using a rotational rheometer. In the first paragraph, The above polyethylene resin composition is a polyethylene resin composition having a shear viscosity of 300 Pa·s or less, measured under conditions of 230°C and 1000 s ^-1 using a capillary rheometer. In the first paragraph, The polyethylene resin composition has a shear rate of 1000 s ^-1 or more at the time of occurrence of melt fracture as measured at 230°C using a capillary rheometer. In the first paragraph, The polyethylene resin composition has a stress of 265,000 Pa or more at the time of melt fracture when measured at 230°C using a capillary rheometer. In the first paragraph, The above polyethylene resin composition is a polyethylene resin composition having a Bimodal Triangula Area (BMTA) of 0.05 to 0.15 as derived from gel permeation chromatography analysis. In the first paragraph, The above polyethylene resin composition is a polyethylene resin composition having a melting index (MI _2.16 , ASTM D1238, 190°C, 2.16kg) of 0.10 to 2.00 g/10 min. In the first paragraph, The above polyethylene resin composition, (a) a first ethylene-alphaolefin copolymer having a density of 0.870 g/cm ³ to 0.920 g/cm ³ and a number average molecular weight Mn of 20,000 g/mol or more, and (b) a second ethylene-alphaolefin copolymer having a density of 0.945 g/cm ³ to 0.960 g/cm ³ and a number average molecular weight Mn of 10,000 g/mol or more and less than 20,000 g/mol; The first ethylene-alpha olefin copolymer and the second ethylene-alpha olefin copolymer are different from each other, Polyethylene resin composition. In paragraph 9, With respect to the total weight of the polyethylene resin composition, the first ethylene-alpha olefin copolymer is included in an amount of 10 to 40 wt%, and the second ethylene-alpha olefin copolymer is included in an amount of 60 to 90 wt%. Polyethylene resin composition. In paragraph 9, The above first ethylene-alphaolefin copolymer is, The melting index (MI _2.16 , ASTM D1238, 190 ℃, 2.16 kg load) is 3.0 g/10 min to 10.0 g/10 min, The weight average molecular weight is 60,000 g/mol or more and less than 95,000 g/mol, The molecular weight distribution is 2.0 or more and less than 3.5, Polyethylene resin composition. In paragraph 9, The above first ethylene-alphaolefin copolymer is a copolymer of ethylene and 1-octene, Polyethylene resin composition. In paragraph 9, The above second ethylene-alpha olefin copolymer is, The melting index (MI _2.16 , ASTM D1238, 190 ℃, 2.16 kg load) is 0.10 g/10 min to 2.00 g/10 min, The weight average molecular weight is 100,000 to 200,000 g/mol, With a molecular weight distribution of 7.0 to 20.0, Polyethylene resin composition. In paragraph 9, The above second ethylene-alphaolefin copolymer is a copolymer of ethylene and 1-hexene. Polyethylene resin composition. A biaxially oriented film comprising the polyethylene resin composition of claim 1.