Polyethylene resin composition for biaxially oriented film

Abstract

A polyethylene resin composition for a biaxially oriented film is disclosed which can be formed by a biaxial stretching machine, exhibits excellent stretching properties, enables biaxial stretching in a wider temperature range, and is excellent in thickness smoothness and transparency. The present invention provides a polyethylene resin composition for a biaxially oriented film in which the molecular weight fractionated at a temperature of 35°C or lower by a-TREF (Analytical Temperature rising elution fractionation) analysis is 5 to 20% by weight, and the molecular weight fractionated at a temperature of 94°C or higher is 5 to 20% by weight.

Description

Technical Field

[0001] The present invention relates to a polyethylene resin product, and more particularly to a polyethylene resin product for a biaxially oriented film.

Background Art

[0002] In the plastic-related industries, the market environment is rapidly changing due to the emergence of new issues such as the marine plastic problem. Container packaging materials with high usage are no exception. Not only in the production of packaging materials, but also in processed foods / beverages and the distribution field, there is a demand for measures to address environmental problems such as plastic waste and greenhouse gas reduction.

[0003] In particular, container packaging-related companies recognize the need to focus on the development of materials that can reduce the environmental burden. Worldwide, the development and use of single-material (Uni material) related products and bioplastics that contribute to the reduction of carbon dioxide (CO 2 ) are becoming active on the premise of recycling.

[0004] Worldwide, polyethylene (PE)-based materials are the mainstream of single-materialization. This is because in the design process of multilayer films, the sealant layer is considered first in view of the contents, uses, etc. Among them, the ratio of polyethylene adopted in the sealant layer is relatively high, and as a result, when the entire product is made into a single material, the surface material also tends to be polyethylene-based.

[0005] In the United States, a recycling system for polyethylene products has been established, and the supply of polyethylene-based materials is expected to be the mainstay. Mitsui Chemicals, which includes raw material resin and film production companies under its umbrella, is focusing on single-materialization of polyethylene-based materials under the goal of replacing the nylon / polyethylene composition. In addition, Dow Chemical is changing the pouch material used for film applications (such as dried fruits, frozen foods, and pet feeds) with excessive functions from PET / PE-based to PE Uni (single product) materials.

[0006] On the other hand, in the case of biaxially oriented films, if the layers conventionally used in BOPA (biaxially oriented polyamide) or BOPET (biaxially oriented polyethylene terephthalate) are replaced with BOPE (biaxially oriented polyethylene) to form a single material, it can conform to such development trends. However, no case has been presented so far where polyethylene that can be formed by a biaxial stretching machine exhibits satisfactory stretching properties.

[0007] Patent Document 1 discloses a polyethylene-based stretched film that is excellent in Elmendorf tear strength and can be stretched uniformly. However, it is difficult to obtain satisfactory strength properties when biaxially stretching with the actually presented composition.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention aims to provide a polyethylene resin composition for biaxially oriented films that can be formed by a biaxial stretching machine, exhibits excellent stretching properties, enables biaxial stretching in a wider temperature range, and is excellent in thickness smoothness and transparency.

Means for Solving the Problems

[0010] In order to solve the above problems, the present invention provides a polyethylene resin composition for biaxially oriented films in which the molecular weight fractionated at a temperature of 35°C or lower is 5 to 20% by weight and the molecular weight fractionated at a temperature of 94°C or higher is 5 to 20% by weight as determined by a-TREF (Analytical Temperature rising elution fractionation) analysis.

[0011] Further, the resin composition comprises 1 to 30% by weight of a copolymer of ethylene and an olefin having 4 to 10 carbon atoms with a density of 0.860 to 0.910 g / cm 3 , 60 to 98% by weight of a copolymer of ethylene and an olefin having 4 to 10 carbon atoms with a density of 0.925 g / cm 3 or more and less than 0.940 g / cm 3 , and 1 to 10% by weight of a copolymer of ethylene and an olefin having 4 to 10 carbon atoms with a density of 0.940 to 0.970 g / cm 3 , and provides a polyethylene resin composition for a biaxially oriented film.

[0012] Further, the resin composition is characterized in that the molecular weight fractionated at a temperature of 35°C or lower by a-TREF analysis is 5 to 20% by weight, and the molecular weight fractionated at a temperature of 94°C or higher is 5 to 20% by weight, and provides a polyethylene resin composition for a biaxially oriented film.

[0013] Further, the (A) copolymer has a melt index (190°C, 2.16 kg load) of 0.2 to 6 g / 10 min, the (B) copolymer has a melt index (190°C, 2.16 kg load) of 1 to 3.5 g / 10 min, and the (C) copolymer has a melt index (190°C, 2.16 kg load) of 0.2 to 2.5 g / 10 min, and provides a polyethylene resin composition for a biaxially oriented film.

[0014] Further, the (A) copolymer has a glass transition temperature (Tg) of -50 to -45°C, the (B) copolymer has a melting point temperature (Tm) of 120 to 135°C and a crystallization temperature (Tc) of 110 to 115°C, and the (C) copolymer has a melting point temperature (Tm) of 130 to 140°C and a crystallization temperature (Tc) of 115 to 125°C, and provides a polyethylene resin composition for a biaxially oriented film.

[0015] Further, the resin composition has a melt index (at 190°C and a load of 2.16 kg) of 1 to 3 g / 10 min and a density of 0.920 to 0.940 g / cm 3 There is provided a polyethylene resin composition for a biaxially oriented film, which is characterized in that it is as described above.

[0016] Further, the resin composition has a tensile strength in the longitudinal direction and the transverse direction measured under the following conditions of 700 kgf / cm 2 or more, an elongation thickness deviation of 15% or less, and a haze degree of 10% or less. There is provided a polyethylene resin composition for a biaxially oriented film, which is characterized in that it is as described above.

[0017] [Measurement method] Using the resin composition, a biaxially stretched film with a film thickness of 20 μm and a film width of 8 m is manufactured under the conditions of a molding speed of 400 m / min, a longitudinal direction (MD) draw ratio of 5 times and a draw temperature of 112 to 128°C, a transverse direction draw ratio of 9 times and a draw temperature of 108 to 116°C. For a specimen of the biaxially stretched film, a tensile strength is measured using a tensile testing machine (model name: Instron, 4466) according to the provisions of ASTM D882 under the conditions of a load cell of 100 N and a test speed of 500 mm / min. The manufactured film is cut into a length of 1 m, and the thickness is measured at any of the 8 divided points to obtain a thickness contrast deviation before stretching, and the average of these is measured as the elongation thickness deviation. For the specimen, the haze of the stretched film is measured using a Haze meter (model name: Nippon Denshoku, NDH5000) according to the provisions of ASTM D1003.

Advantages of the invention

[0018] According to the present invention, there is provided a polyethylene resin composition in which three kinds of copolymers of ethylene and olefins having 4 to 10 carbon atoms with different densities within a certain range are mixed, and further having fractionation characteristics by a specific a-TREF analysis using CFC. The polyethylene resin composition can be molded by a biaxial stretching machine, exhibits excellent stretching characteristics, enables biaxial stretching in a wider temperature range, and provides a polyethylene resin composition for a biaxially oriented film having excellent thickness smoothness and transparency.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0020] Hereinafter, the present invention will be described in detail through preferred embodiments. Before that, the terms and words used in this specification and the claims should not be construed in a conventional or dictionary sense only. Based on the principle that the inventor can appropriately define the concept of the terms in order to explain his invention in the best way, it should be construed in a meaning and concept that conforms to the technical idea of the present invention. Therefore, the configuration of the embodiments described in this specification is only the most preferred embodiment of the present invention and does not represent all of the technical ideas of the present invention. Therefore, it should be understood that there may be various equivalents and modifications that can replace them at the time of this application.

[0021] When the present inventors replaced the layers conventionally used in BOPA and BOPET with BOPE to make a single material, in a situation where no composition showing satisfactory stretching properties has been presented so far, they have fractionation properties by a specific a-TREF analysis using CFC (Cross-Fractionation Chromatography), and further, in the case of a polyethylene resin composition in which three kinds of copolymers of ethylene and olefins having 4 to 10 carbon atoms with different densities in a certain range are mixed, it can be formed by a biaxial stretching machine and shows excellent stretching properties, and it was confirmed that biaxial stretching is possible in a wider temperature range and it is excellent in thickness smoothness and transparency, and thus the present invention was achieved.

[0022] Therefore, the present invention discloses a polyethylene resin composition for a biaxially oriented film in which the molecular weight fractionated at a temperature of 35°C or lower by a-TREF analysis is 5 to 20% by weight, and the molecular weight fractionated at a temperature of 94°C or higher is 5 to 20% by weight. The resin composition of the present invention comprises (A) 1 to 30% by weight of a copolymer of ethylene and an olefin having 4 to 10 carbon atoms, with a density of 0.860 to 0.910 g / cm 3 and (B) 60 to 98% by weight of a copolymer of ethylene and an olefin having 4 to 10 carbon atoms, with a density of 0.925 g / cm 3 or more and less than 0.940 g / cm 3 and (C) 1 to 10% by weight of a copolymer of ethylene and an olefin having 4 to 10 carbon atoms, with a density of 0.940 g / cm 3 to 0.970 g / cm 3 It is preferably included.

[0023] In the present invention, the (A) copolymer is a very low density polyethylene, with a density of 0.860 to 0.910 g / cm 3 and preferably 0.870 to 0.910 g / cm 3 It can be. If the density deviates from the above range, biaxial stretching molding is difficult.

[0024] Also, the (A) copolymer preferably has a glass transition temperature of -40°C or lower, and more preferably -50 to -40°C. In this case, it is possible to prevent a decrease in the physical properties of the final film when used in a low-temperature environment.

[0025] Further, the (A) copolymer is preferably one produced using a metallocene catalyst, and a copolymer of ethylene and an α-olefin such as 1-butene, 1-hexene, 1-octene, etc. can be used. Preferably, a copolymer of ethylene and an α-olefin having 6 to 8 carbon atoms can be used, and more preferably, a copolymer of ethylene and 1-hexene or 1-octene can be used. Also, the melt index (at 190°C, 2.16 kg load) can be 0.2 to 6 g / 10 min, and preferably can be 0.5 to 2 g / 10 min. If a copolymer produced using a Ziegler-Natta catalyst is applied, or a copolymer produced using an α-olefin other than those having 4 to 10 carbon atoms as a comonomer copolymerized with ethylene is applied, or if the melt index deviates from the above range, biaxial stretching molding may be difficult. The polymerization method of the (A) copolymer is not particularly limited, and it can be produced by any method such as a gas phase method, a solution method, a slurry method, etc.

[0026] The (A) copolymer is contained in the entire resin composition in an amount of 1 to 30% by weight, and preferably can be contained in an amount of 10 to 30% by weight. If the content of the (A) copolymer deviates from the above range, biaxial stretching molding is also difficult. If it exceeds 30% by weight, the mechanical properties will decrease due to a large amount of low-crystalline molecules, and the ultimate tensile strength will decrease.

[0027] In the present invention, the (B) copolymer is linear low-density polyethylene, and the density is 0.925 to 0.940 g / cm 3 and preferably can be 0.925 to 0.935 g / cm 3 If the density deviates from the above range, biaxial stretching molding is difficult.

[0028] Further, the (B) copolymer is preferably manufactured using a Ziegler-Natta catalyst so as to ensure a range where film formation is possible, and a copolymer of ethylene and an α-olefin such as 1-butene, 1-hexene, 1-octene, etc. can be used. Preferably, a copolymer of ethylene and 1-butene, 1-hexene, or 1-octene can be used. The melt index (at 190 °C, 2.16 kg load) can be 1 to 3.5 g / 10 min, and preferably can be 2 to 3 g / 10 min. If a copolymer manufactured using a metallocene catalyst is provided, or a copolymer manufactured using an α-olefin other than α-olefins having 4 to 10 carbon atoms as a comonomer copolymerized with ethylene is applied, or if the melt index deviates from the above range, biaxial stretching molding may be difficult. The polymerization method of the (B) copolymer is not particularly limited, and it can be manufactured by any method such as a gas phase method, a solution method, a slurry method, etc.

[0029] Further, in order for the final film of the (B) copolymer to be biaxially stretchable in a wider temperature range, the melting point temperature is preferably 120 to 130 °C and the crystallization temperature is preferably 110 to 115 °C, whereby biaxial stretching can be made possible in a wide temperature range of the stretching process temperature of 108 to 128 °C.

[0030] The (B) copolymer is contained in the above resin composition in a content of 60 to 98% by weight, and preferably can be contained in a content of 65 to 80% by weight. If the content of the (B) copolymer deviates from the above range, biaxial stretching is also difficult, and if it is less than 60% by weight, the tensile strength of the film significantly decreases.

[0031] In the present invention, the (C) copolymer is high-density polyethylene mixed for improving the tensile strength of the final film, as well as the stretch processability and the hue, and the density is 0.940 to 0.970 g / cm 3 and preferably can be 0.950 to 0.960 g / cm 3 If the density deviates from the above range, biaxial stretching molding is difficult.

[0032] In addition, as the (C) copolymer, a copolymer of styrene and an α-olefin such as 1-butene, 1-hexene, or 1-octene can be used. Preferably, a copolymer of ethylene and 1-butene or 1-hexene can be used. The melt index (at 190°C and a load of 2.16 kg) can be 0.2 to 2.5 g / 10 min, and preferably can be 0.2 to 1 g / 10 min. If a copolymer produced using an α-olefin other than those having 4 to 10 carbon atoms as the comonomer copolymerized with ethylene is applied, or if the melt index deviates from the above range, biaxial stretching may be difficult. The polymerization method of the (C) copolymer is not particularly limited, and it can be produced by any method such as a gas phase method, a solution method, or a slurry method.

[0033] In addition, the (C) copolymer preferably has a melting point temperature of 130°C or higher, more preferably can be 130 to 140°C, and the crystallization temperature can be 115 to 125°C in order to maintain the rigidity of the film in the stretching process, further improve the formability, and maximize the mechanical properties of the final biaxially stretched film.

[0034] The (C) copolymer is contained in the total resin composition at a content of 1 to 10% by weight, and preferably can be contained at a content of 3 to 10% by weight. If the content of the (C) copolymer exceeds 10% by weight, stretching in the stretching process becomes impossible due to a large number of crystalline molecules, and breakage may occur.

[0035] By mixing the (A) copolymer, (B) copolymer, and (C) copolymer as described above, the melt index (at 190°C and a load of 2.16 kg) of the final resin composition can be 1 to 3 g / 10 min, preferably 1.5 to 2.5 g / 10 min, and the density can be 0.900 to 0.940 g / cm 3 preferably 0.925 to 0.935 g / cm 3 and can be.

[0036] In the present invention, when the polyethylene resin composition of the above composition is formed into a biaxially oriented film, when it has certain fractionation characteristics by a-TREF analysis using CFC (Cross Fractionation Chromatography), it exhibits smooth moldability while achieving satisfactory strength characteristics, and it has been confirmed that biaxial stretching is possible in a wider temperature range and the thickness smoothness and transparency are improved. Specifically, as described above, in the resin composition according to the present invention, the molecular weight fractionated at a temperature of 35°C or lower by a-TREF analysis is 5 to 20% by weight, and the molecular weight fractionated at a temperature of 94°C or higher is 5 to 20% by weight. Preferably, the molecular weight fractionated at a temperature of 35°C or lower may be 10 to 20% by weight, and the molecular weight fractionated at a temperature of 94°C or higher may be 5 to 15% by weight.

[0037] In the present invention, the temperature-molecular weight curve by a-TREF analysis is a temperature rising elution fractionation method, and is based on the Flory Huggins statistical thermodynamics formula (see the following Mathematical Formula 1) that expresses the phenomenon of the melting point decreasing due to a diluent.

Equation

[0038] A solvent or comonomer can be said to be a diluent for the polymer, and the crystallization temperature of the polyolefin decreases as the concentration of the diluent increases. In the TREF experiment, it is necessary to dissolve the sample and inject it into the column at a high temperature, and then gradually lower the temperature to induce crystallization of the sample. When the temperature is lowered and the polymer precipitates in the column, the temperature of the column is gradually increased during the temperature rising process while analyzing the sample in which the polymer precipitated in the column is eluted by temperature, and the molecular weight eluted at each temperature is classified (see Figure 1).

[0039] Since the polyethylene resin composition for biaxially oriented films according to the present invention is applied in various applications, general polyethylene additives can be added. For example, antioxidants, heat and light stabilizers, antistatic agents, lubricants, antiblocking agents, preservatives, processing aids, slip agents, antiadhesive agents, pigments, flame retardants, foaming agents, etc. can be added in appropriate amounts and used.

[0040] The polyethylene resin composition for biaxially oriented films according to the present invention can be produced by mixing and extruding the above components by a conventional method known in the art. For example, the above components can be charged into a biaxial extruder and melt-kneaded to produce a polyethylene resin composition for biaxially oriented films.

[0041] The polyethylene resin composition for biaxially oriented films according to the present invention as described above is capable of biaxial stretching and exhibits excellent stretching properties. Specifically, the tensile strengths in the longitudinal and transverse directions measured under the following conditions are 700 kgf / cm 2 In the case of the tensile strength in the transverse direction, it can be preferably 950 kgf / cm 2 or more, the stretching thickness deviation can be 15% or less, preferably 10% or less, and the haze degree can be 10% or less, preferably 8% or less.

[0042] [Measurement method] Using the above resin composition, a biaxially stretched film with a film thickness of 20 μm and a film width of 8 m is produced under the conditions of a forming speed of 400 m / min, a longitudinal (MD) stretching ratio of 5 times and a stretching temperature of 112 to 128°C, and a transverse stretching ratio of 9 times and a stretching temperature of 108 to 116°C. For a specimen of the biaxially stretched film, a tensile strength is measured using a tensile testing machine (model name: Instron, 4466) according to the provisions of ASTM D882 under the conditions of a load cell of 100 N and a test speed of 500 mm / min. The produced film is cut into a length of 1 m and the thickness is measured at any of the 8 divided points to obtain the thickness contrast deviation before stretching, and the average of these is measured as the stretching thickness deviation. For the above specimen, the haze of the stretched film is measured using a Haze meter (model name: Nippon Denshoku, NDH5000) according to the provisions of ASTM D1003.

Example

[0043] Hereinafter, the present invention will be described in more detail through specific examples and comparative examples. In the examples and comparative examples, density, melt index, and CFC analysis were measured by the following methods.

[0044] [Measurement Method] (1) Density Measured according to ASTM D1505. (2) Melt Index (MI, Melt Index) Measured according to ASTM D1238 under the conditions of 190 °C and a load of 2.16 kg. (3) a-TREF analysis using CFC (Cross Fractionation Chromatography) The CFC analysis was performed on a CFC instrument from Polymer Char located in Valencia, Spain. The instrument includes a TREF column in the first dimension, a GPC column set in the second dimension, and an infrared detector (IR4 from Polymer Char) downstream of the GPC column set. The sample to be analyzed was stirred at 150 °C for 80 minutes and dissolved in 1,2,3-trichlorobenzene at a concentration of about 2.5 mg / ml. The solution was loaded into the center of the TREF column, stabilized at 100 °C for 45 minutes, and then gradually cooled to 35 °C (0.5 °C / min) to crystallize the polymer. Next, after maintaining the low temperature for 10 minutes, the soluble fraction was injected into the GPC column. All GPC analyses were performed using the solvent 1,2,4-trichlorobenzene at a flow rate of 1 ml / min, a column temperature of 140 °C or lower, and in the "superimposed GPC injection" mode. (4) Thermal properties Using a differential scanning calorimeter (trade name DSC, manufactured by Perkin-Elmer Co.), 10 mg of the specimen was preliminarily melted at 220 °C for 5 minutes under a nitrogen gas atmosphere, and then the temperature was lowered to -100 °C at a cooling rate of 5 °C / min. Next, the temperature was raised to 200 °C at a heating rate of 10 °C / min, and the glass transition temperature (Tg), melting point temperature (Tm), and crystallization temperature (Tc) were confirmed while cooling at the same cooling rate as the heating rate.

[0045] <Examples and Comparative Examples> Prepare the compositions as shown in Tables 1 and 2. In the case of the copolymer mixture compositions (Examples 1 to 5, Comparative Examples 2, 3, 5, and 6), the copolymers of the corresponding combinations are put into a twin-screw extruder and melt-kneaded under the conditions of 180 to 220 °C to produce a pelletized polyethylene resin composition. In the cases of Comparative Examples 1 and 4, they were prepared separately without a mixing process. The temperature-elution fractionation curves analyzed by temperature-rising elution fractionation using TREF for the compositions produced in Example 1 and Comparative Example 1 are shown in Figures 2 and 3, respectively.

[0046] <Experimental Example> Using the resin composition, a biaxially stretched film with a film thickness of 20 μm and a film width of 8 m was produced under the conditions of a forming speed of 400 m / min, a longitudinal (MD) draw ratio of 5 times and a draw temperature of 112 to 128 °C, a transverse draw ratio of 9 times and a draw temperature of 108 to 116 °C. For a specimen of the biaxially stretched film, the tensile strength was measured using a tensile testing machine (model name: Instron, 4466) under the conditions of a load cell of 100 N and a test speed of 500 mm / min in accordance with the provisions of ASTM D882. The manufactured film was cut into a length of 1 m and the thickness was measured at any of the 8 divided points to obtain the thickness contrast deviation before stretching, and the average was taken to measure the stretched thickness deviation. For the specimen, the haze of the stretched film was measured using a Haze meter (model name: Nippon Denshoku, NDH5000) in accordance with the provisions of ASTM D1003, and the results are shown in Table 1 below. The stretched thickness deviation is an index indicating the stretch processability, and is indicated as "◎" when the thickness deviation is 10% or less, "〇" when it is 15% or less, "△" when it exceeds 15%, and "×" when it breaks.

[0047]

Table 1

[0048]

Table 2

[0049] Referring to Table 1, in the case of a film produced from a resin composition in which (A) ultra-low density polyethylene, (B) linear low density polyethylene, and (C) high density polyethylene having a certain range of melt index and density, further having a certain range of glass transition temperature, melting point temperature, or crystallization temperature, and being produced using a specific comonomer, and showing a TREF weight fraction within a certain range (Examples 1 to 5), it can be confirmed that biaxial stretching is possible in a wider temperature range and the film is excellent in thickness smoothness and hue characteristics.

[0050] On the other hand, referring to Table 2, in the case of (B) linear low density polyethylene alone (Comparative Examples 1 and 4), there are problems such as breakage occurring during stretching or the thickness deviation exceeding 15%, and it can be seen that the biaxial stretching characteristics are low, deviating from the target TREF weight fraction.

[0051] Also, when (C) high density polyethylene is not mixed (Comparative Example 2) or when (A) ultra-low density polyethylene is not mixed (Comparative Example 3), there are also problems such as breakage occurring during stretching or the thickness deviation exceeding 15%, and it can be seen that the biaxial stretching characteristics are low, deviating from the target TREF weight fraction.

[0052] Moreover, even when all of the comonomers (A) to (C) are mixed, if the content of (C) high density polyethylene is excessive (Comparative Example 5), stretching is impossible in the stretching process due to a large amount of crystalline molecules and breakage occurs. If the content of (A) ultra-low density polyethylene is excessive (Comparative Example 6), the mechanical properties deteriorate due to a large amount of low-crystalline molecules and the ultimate tensile strength decreases, and it was confirmed that it is difficult to apply to actual products.

[0053] So far, the preferred embodiments of the present invention have been described in detail. The description of the present invention is for illustrative purposes, and those having ordinary knowledge in the technical field to which the present invention pertains should be able to understand that it can be easily deformed into other specific forms without changing the technical idea and essential features of the present invention.

[0054] Therefore, the scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning, scope, and equivalents concept of the claims should be construed as being included within the scope of the present invention.

Claims

1. A polyethylene resin composition for a biaxially oriented film, wherein the molecular weight fractionated at a temperature of 35°C or lower is 5 to 20% by weight and the molecular weight fractionated at a temperature of 94°C or higher is 5 to 20% by weight by a-TREF (Analytical Temperature rising elution fractionation) analysis.

2. The resin composition contains (A) 1 to 30% by weight of a copolymer of ethylene and an olefin having 4 to 10 carbon atoms, with a density of 0.860 to 0.910 g / cm ３ and, (B) A copolymer of ethylene and an olefin having 4 to 10 carbon atoms, with a density of 0.925 g / cm ３ or more and less than 0.940 g / cm ３ 60 to 98% by weight, and (C) 0.940 to 0.970 g / cm in density ３ 1 to 10% by weight of a copolymer of ethylene and an olefin having 4 to 10 carbon atoms, The polyethylene resin composition for a biaxially oriented film according to Claim 1, characterized by containing

3. The polyethylene resin composition for a biaxially oriented film according to Claim 2, wherein the (A) copolymer has a melt index (at 190°C, 2.16 kg load) of 0.2 to 6 g / 10 min, the (B) copolymer has a melt index (at 190°C, 2.16 kg load) of 1 to 3.5 g / 10 min, and the (C) copolymer has a melt index (at 190°C, 2.16 kg load) of 0.2 to 2.5 g / 10 min.

4. The polyethylene resin composition for a biaxially oriented film according to Claim 3, wherein the (A) copolymer has a glass transition temperature (Tg) of -50 to -45°C, the (B) copolymer has a melting point temperature (Tm) of 120 to 135°C and a crystallization temperature (Tc) of 110 to 115°C, and the (C) copolymer has a melting point temperature (Tm) of 130 to 140°C and a crystallization temperature (Tc) of 115 to 125°C.

5. The resin composition has a melt index (at 190 °C and a load of 2.16 kg) of 1 to 3 g / 10 min and a density of 0.920 to 0.940 g / cm ３ The polyethylene resin composition for a biaxially oriented film according to claim 1, characterized in that it is as described above.

6. The longitudinal and transverse tensile strengths of the resin composition measured under the following conditions are each 700 kgf / cm ２ or more, the stretching thickness deviation is 15% or less, and the haze is 10% or less. The polyethylene resin composition for a biaxially oriented film according to claim 1, characterized in that: [Measurement method] Using the resin composition, a biaxially stretched film with a film thickness of 20 μm and a film width of 8 m is manufactured under the conditions of a forming speed of 400 m / min, a longitudinal (MD) stretching ratio of 5 times and a stretching temperature of 112 to 128°C, and a transverse stretching ratio of 9 times and a stretching temperature of 108 to 116°C. For a specimen of the biaxially stretched film, a tensile strength is measured using a tensile testing machine (model name: Instron, 4466) under the conditions of a load cell of 100 N and a test speed of 500 mm / min in accordance with the provisions of ASTM D882. The manufactured film is cut into a length of 1 m and the thickness is measured at any of the 8 divided points to obtain the thickness contrast deviation before stretching, and the average is taken to measure the stretching thickness deviation. For the specimen, the haze of the stretched film is measured using a Haze meter (model name: Nippon Denshoku, NDH5000) in accordance with the provisions of ASTM D1003.

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