Biaxially oriented polyethylene film and laminate

Abstract

Provided is a biaxially oriented polyethylene film which has excellent processing adequacy. Specifically provided is a biaxially oriented polyethylene film which is formed of a polyethylene resin composition that contains 55 mass% or more of a polyethylene resin having a density of 0.945 g / cm3 to 0.965 g / cm3 inclusive and has a weight average molecular weight of 10,000 to 600,000 inclusive. This biaxially oriented polyethylene film satisfies the requirements (1) to (4) described below.　(1) The tensile strength at break at 23°C in the longitudinal direction is 80 MPa to 250 MPa inclusive.　(2) The tensile strength at break at 23°C in the width direction is 250 MPa to 400 MPa inclusive.　(3) The thermal shrinkage at 120°C in the longitudinal direction is 0.0% to 10.0% inclusive.　(4) The thermal shrinkage at 120°C in the width direction is -2.0% to 20.0% inclusive.

Description

Biaxially oriented polyethylene film and laminate

[0001] The present invention relates to biaxially oriented polyethylene films.

[0002] Because of its excellent heat-sealing properties, unstretched polyethylene film has traditionally been used as a sealant film for packaging bags, while biaxially oriented polypropylene film or biaxially oriented polyester film, which have high heat resistance and rigidity, have been used as the base material.

[0003] In recent years, mono-materialization has been proposed, which makes packaging materials easier to recycle by producing them from a single material. Regarding polyethylene, attempts have been made to laminate a stretched polyethylene film as a base material to a non-stretched polyethylene sealant film, but a polyethylene film with sufficient bag processability has yet to be produced (e.g., Patent Documents 1 and 2). Patent Document 3 discloses a biaxially stretched polyethylene film with excellent properties such as rigidity, toughness, and heat resistance. However, the raw material is ultra-high molecular weight polyethylene, and the film production method involves obtaining a gel-like sheet from a polyethylene resin solution obtained by melt-kneading liquid paraffin at high temperature and then biaxially stretching it, which is significantly less efficient than the conventional method of obtaining a sheet from a heated, molten resin and then biaxially stretching it.

[0004] JP-T-2023-505965 A JP-A-2023-19592 WO 2023 / 047997

[0005] An object of the present invention is to provide a biaxially oriented polyethylene film that has excellent heat resistance and mechanical properties, can be produced by a highly productive method, and has processability.

[0006] That is, the present invention includes the following inventions: [1] A granular material having a density of 0.945 g / cm ３ Above, 0.965g / cm ３

[0013] A biaxially oriented polyethylene film comprising a polyethylene resin composition containing 55% by mass or more of the following polyethylene resin and having a weight-average molecular weight of 10,000 or more and 600,000 or less, satisfying the following (1) to (4): (1) The tensile break strength in the longitudinal direction at 23°C is 80 MPa or more and 250 MPa or less. (2) The tensile break strength in the width direction at 23°C is 250 MPa or more and 400 MPa or less. (3) The heat shrinkage rate in the longitudinal direction at 120°C is 0.0% or more and 10.0% or less. (4) The heat shrinkage rate in the width direction at 120°C is -2.0% or more and 20.0% or less. [2] The biaxially oriented polyethylene film according to [1] above, which satisfies the following (5) and (6): (5) The stress at 5% elongation (F5) in the longitudinal direction at 23°C is 25 MPa or more and 70 MPa or less. (6) The stress at 5% elongation in the width direction (F5) at 23°C is 80 MPa or more and 150 MPa or less. [3] The biaxially oriented polyethylene film according to [1] or [2] above, wherein the haze of the biaxially oriented polyethylene film is 10% or less. [4] A laminate comprising a sealant film laminated on at least one side of the biaxially oriented polyethylene film according to any one of [1] to [3] above. [5] The laminate according to [4], wherein the sealant film is the polyethylene film containing 70% by mass or more of polyethylene resin.

[0007] The biaxially oriented polyethylene film of the present invention has excellent processability and can be used, for example, as a base film for packaging bags. It can also be used favorably for industrial applications such as release films that require release processability. In addition, it is possible to omit the steps of mixing liquid paraffin and forming a gel sheet, thereby improving productivity.

[0008] (1) Polyethylene Resin Composition (1-1) Polyethylene Resin The polyethylene resin used in the present invention is a polyethylene homopolymer or a polyethylene copolymer in which the copolymerization amount of an α-olefin component other than ethylene is 5 mol% or less. The copolymerization amount of the α-olefin component other than ethylene is preferably 1 mol% or less, more preferably 0.5 mol% or less, and particularly preferably 0.3 mol% or less, when the total amount of all α-olefin components is taken as 100 mol%. A copolymerization amount of 5 mol% or less tends to improve crystallinity, making it easier to obtain a film with excellent heat resistance. Examples of α-olefin components include propylene, 1-butene, 1-pentene, 3-methyl-1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 5-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, and 1-eicosene. As the polyethylene resin used in the present invention, biomass-derived polyethylene may be used instead of polyethylene obtained from fossil fuels. Biomass-derived polyethylene is a carbon-neutral material, which is preferable in terms of reducing environmental impact. The polyethylene resin composition of the present invention may contain two or more of the above-mentioned polyethylene resins. Various suitable physical properties of the polyethylene resin composition constituting the biaxially oriented ethylene film of the present invention are described below. When two or more different polyethylene polymers are used, the physical property values ​​are the mass average values ​​of the physical properties of each polyethylene polymer. (1-2) Molecular Weight: The biaxially oriented polyethylene film of the present invention is composed of a polyethylene resin composition having a weight-average molecular weight (Mw) of 10,000 or more and 600,000 or less. The weight-average molecular weight (Mw) is preferably 30,000 or more and 400,000 or less, more preferably 40,000 or more and 300,000 or less, and even more preferably 50,000 or more and 200,000 or less. The polyethylene resin composition may be a polyethylene having the properties in the above ranges, or a mixture of two or more polyethylenes so that the weighted average molecular weight falls within the above range. When the weight average molecular weight (Mw) is 10,000 or more, sufficient film tensile strength at break is likely to be obtained.If the molecular weight is 600,000 or less, the load on the extruder is reduced, and the load on the machine during stretching is also reduced. The weight average molecular weight (Mw) is calculated by the molecular weight (M) at each elution position of the GPC curve obtained via a molecular weight calibration curve. ｉ ) number of molecules (N ｉ ) is defined by the following formula: Weight average molecular weight: Mw = Σ(N ｉ ・M ｉ ２ ) / Σ(N ｉ ・M ｉ )

[0009] When the polyethylene resin composition contains a large amount of ultra-high molecular weight polyethylene, it becomes necessary to mix liquid paraffin to form a gel-like sheet and then stretch it. Therefore, the polyethylene resin having a weight-average molecular weight (Mw) of 500,000 or more is preferably contained in an amount of 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 1% by mass or less, based on the entire polyethylene resin composition.

[0010] The ratio (Mw / Mn) of the number average molecular weight (Mn) to the weight number average molecular weight (Mw) of the polyethylene resin composition used in the present invention is preferably 3.0 or more and 15 or less, more preferably 4.0 or more and 12 or less, and even more preferably 5.0 or more and 10 or less. When Mw / Mn is 3.0 or more, biaxial stretching is easily performed. In view of ease of raw material availability, Mw / Mn is preferably 15 or less.

[0011] (1-3) Melt Flow Rate (MFR) The melt flow rate (MFR) of the polyethylene resin composition used in the present invention is preferably 1.0 g / 10 min to 30 g / 10 min. It is more preferably 1.1 g / 10 min to 25 g / 10 min, even more preferably 1.2 g / 10 min to 23 g / 10 min, even more preferably 1.3 g / 10 min to 20 g / 10 min, particularly preferably 1.3 g / 10 min to 15 g / 10 min, particularly more preferably 1.3 g / 10 min to 10 g / 10 min, and most preferably 1.4 g / 10 min to 5.0 g / 10 min. When the melt flow rate MFR is 1.0 g / 10 min or more, an unstretched sheet is easily obtained in the extrusion process. When it is 30 g / 10 min or less, sufficient film tensile strength at break is easily obtained. Furthermore, the polyethylene resin having an MFR of less than 0.1 g / 10 min is preferably less than 25% by mass, more preferably 20% by mass or less, even more preferably 10% by mass or less, particularly preferably 5% by mass or less, and most preferably 1% by mass or less, based on the total polyethylene resin composition. When two or more polyethylene resins are blended, it is preferable to use polyethylene resins having similar melt flow rates (MFR). Specifically, the difference between the largest and smallest MFRs of the two or more polyethylene resins is preferably 2.0 g / 10 min or less, more preferably 1.0 g / 10 min or less, and even more preferably 0.5 g / 10 min or less.

[0012] (1-4) Density The polyethylene resin used in the present invention is high-density polyethylene (HDPE: density 0.945 to 0.965 g / cm ３ ), medium density polyethylene (MDPE: density 0.926 to 0.944 g / cm ３ ), low-density polyethylene (LDPE: density 0.910 to 0.925 g / cm ３ The polyethylene resin composition of the present invention may contain high density polyethylene (HDPE: density of 0.945 to 0.965 g / cm 3 ) in order to improve strength, rigidity, and heat resistance. ３) is blended. The blending amount of high-density polyethylene (HDPE) is preferably 55% by mass to 100% by mass, more preferably 60% by mass to 95% by mass, and even more preferably 70% by mass to 90% by mass, based on the total polyethylene resin composition. As long as the blending amount of high-density polyethylene (HDPE) is within the above range, the polyethylene composition of the present invention can blend two or more types of polyethylene resins, and two or more types of high-density polyethylene (HDPE) may be blended, or at least one selected from the group consisting of medium-density polyethylene (MDPE) and low-density polyethylene (LDPE) may be blended in addition to the high-density polyethylene.

[0013] (1-5) Components Other than Polyethylene Resin The polyethylene resin composition of the present invention contains polyethylene resin as a primary component. However, as long as the effects of the present invention are not impaired, additives such as resins other than polyethylene resin, known plasticizers, antioxidants, UV absorbers, nucleating agents, adhesives, anti-fogging agents, flame retardants, inorganic or organic fillers, etc. may be added. However, these additives are preferably added in small amounts, and the content of components other than polyethylene resin in the polyethylene resin composition is less than 30% by mass, preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less. A content of 5% by mass or less can prevent contamination of the manufacturing process due to volatilization of additives. Furthermore, deterioration of the adhesiveness and printability of the film surface can be prevented. Examples of resins other than polyethylene resin include polyolefin resins other than polyethylene resin and various elastomers. These can be sequentially polymerized using a multi-stage reactor, blended with polyethylene resin using a Henschel mixer, master pellets prepared in advance using a melt kneader diluted with polyethylene resin to a predetermined concentration, or the entire amount can be melt kneaded in advance. The biaxially oriented polyethylene film of the present invention can be made suitable as a packaging material for vegetables, fruits, flowers, and other fresh produce by incorporating an anti-fogging agent such as a fatty acid ester of a polyhydric alcohol, an amine of a higher fatty acid, an amide of a higher fatty acid, or an ethylene oxide adduct of an amine or an amide of a higher fatty acid in an amount ranging from 0.2 to 5.0% by mass. If the amount of the anti-fogging agent is 5.0% by mass or less, process contamination during production can be suppressed.

[0014] (2) Film-forming method for biaxially oriented polyethylene film The biaxially oriented polyethylene film of the present invention is preferably obtained by preparing an unstretched sheet made of a polyethylene resin composition containing a polyethylene resin as a main component, and then biaxially stretching the sheet. Regarding biaxial stretching, it is preferable to stretch the sheet in the longitudinal direction and then in the width direction, but it may also be stretched in the width direction and then in the longitudinal direction. Examples of biaxial stretching methods include inflation simultaneous biaxial stretching, tenter simultaneous biaxial stretching, tenter sequential biaxial stretching, and tube stretching, with tenter sequential biaxial stretching being preferred from the viewpoint of thickness uniformity.

[0015] The method for producing the biaxially oriented polyethylene film of the present invention will be described below. Hereinafter, a method for producing a single-layer biaxially oriented polyethylene film using a tenter sequential biaxial stretching method will be described, but the method is not limited to the following production method.

[0016] First, a polyethylene resin composition is heated and melted in a single-screw or twin-screw extruder, extruded through a T-die into a sheet, and then cooled and solidified by contacting it with a cooling roll to obtain an unstretched sheet. Next, this unstretched sheet is stretched in the longitudinal direction between two pairs of heated stretching rolls by increasing the rotation speed of the rear stretching roll to obtain a uniaxially stretched film. Subsequently, the uniaxially stretched film is heated in a preheating step, stretched in the width direction while gripping the film edges in a tenter-type stretching machine, heat-treated, and finally cooled to obtain a biaxially oriented polyethylene film. If necessary, at least one side of the biaxially oriented polyethylene film can be surface-treated, and then wound on a winder to obtain a film roll. Below, the extrusion step, longitudinal stretching step, preheating step, width stretching step, heat-treatment step, and cooling step will be described in this order.

[0017] <Extrusion Process> First, a polyethylene resin composition primarily composed of polyethylene resin is heated and melted in a single-screw or twin-screw extruder, and the molten polyethylene resin composition is extruded from a T-die in the form of a sheet. The molten polyethylene resin composition is then brought into close contact with a metal cooling roll using a contacting device such as an air knife, and then cooled and solidified to obtain an unstretched sheet. The temperature at which the composition is heated and melted in the extruder is preferably 180°C to 330°C, more preferably 200°C to 310°C, even more preferably 210°C to 300°C, particularly preferably 220°C to 290°C, and most preferably 230°C to 280°C. The resulting unstretched sheet may then be placed in a water bath. The temperature of the cooling roll, or the cooling roll and water bath, is preferably 80°C or less, more preferably 70°C or less, even more preferably 60°C or less, particularly preferably 50°C or less, and most preferably 40°C or less. A temperature of 80°C or less provides a uniform, flat sheet before stretching. A temperature of 10°C or more is preferred because it suppresses condensation on the apparatus. From the viewpoint of cooling efficiency, the thickness of the unstretched sheet before stretching is preferably 3500 μm or less, more preferably 3000 μm or less. The thickness of the unstretched sheet may be appropriately adjusted depending on the thickness of the film after sequential biaxial stretching. The thickness of the unstretched sheet can be controlled by the extrusion speed of the polyethylene resin composition, the lip width of the T-die, etc.

[0018] <Longitudinal Stretching Step> The longitudinal stretching temperature is preferably 120°C to 130°C, more preferably 121°C to 130°C, even more preferably 122°C to 130°C, particularly preferably 122°C to 129°C, and most preferably 122°C to 128°C. A temperature of 120°C or higher facilitates subsequent widthwise stretching, reduces thickness unevenness, and reduces heat shrinkage. Furthermore, a temperature of 130°C or lower facilitates increased strength and minimizes deterioration in quality due to adhesion to the stretching rolls, which makes stretching difficult, or increased surface roughness. The longitudinal stretching ratio is preferably 3.5 to 5.8 times, more preferably 3.7 to 5.5 times, even more preferably 4.0 to 5.3 times, particularly preferably 4.2 to 5.1 times, and most preferably 4.4 to 5.0 times. When the stretching ratio is 3.5 times or more, it is easy to increase the strength and reduce thickness unevenness. Furthermore, when the stretching ratio is 5.8 times or less, it is easy to perform width direction stretching in the width direction stretching step, and it is easy to improve productivity. In other words, when the stretching temperature and stretching ratio are within the above ranges, it is possible to improve the film strength and keep the thermal shrinkage rate low. Although the longitudinal stretching may be performed in two or more stages using three or more pairs of stretching rolls, it is preferable to perform stretching in one stage using two pairs of stretching rolls. When stretching in multiple stages, it is preferable that the highest stretching temperature is within the above range.

[0019] <Preheating Step> It is preferable to heat the uniaxially stretched film after longitudinal stretching in a preheating step to sufficiently soften the polyethylene resin composition before the widthwise stretching step. The heating temperature in the preheating step is preferably 125°C to 145°C, more preferably 132°C to 142°C, and even more preferably 133°C to 140°C. By setting the heating temperature in the preheating step to 130°C or higher, softening proceeds and widthwise stretching becomes easier. Furthermore, by setting the heating temperature in the preheating step to 145°C or lower, orientation proceeds during widthwise stretching, making it easier to develop rigidity. Note that when the preheating step consists of multiple zones, the temperature of the hottest zone among them is taken as the preheating temperature.

[0020] <Width Direction Stretching Step> The width direction stretching temperature is preferably 120°C or higher and lower than the heating temperature in the preheating step. A temperature of 120°C or higher tends to reduce the thermal shrinkage of the resulting film. Furthermore, a temperature of 120°C to 140°C is more preferable, 120°C to 135°C is even more preferable, 120°C to 130°C is particularly preferable, and 120°C to 128°C is most preferable. A temperature of 140°C or lower tends to reduce stretching unevenness. In the width direction stretching step, a width direction stretching step (hereinafter sometimes referred to as the early stretching step) in the above temperature range is preferably followed by a later stretching step in which stretching is performed at a lower temperature. The provision of the later stretching step tends to increase film strength. The width direction stretch ratio is preferably 8.5 to 15 times, more preferably 8.5 to 14 times, even more preferably 8.5 to 13 times, particularly preferably 8.5 to 12 times, and most preferably 8.5 to 11 times. If the stretching ratio is 8.5 times or more, the film strength is easily increased and thickness unevenness is easily reduced. Furthermore, if the stretching ratio is 15 times or less, the heat shrinkage rate is easily reduced and the film is less likely to break during stretching. In other words, by keeping the stretching temperature and stretching ratio within the above ranges, the film strength can be improved and the heat shrinkage rate can be kept low. When a later stretching step is added, it is preferable to keep the total stretching ratio within the above range.

[0021] <Heat Treatment Step> Heat treatment is carried out after the width direction stretching step is completed. Specific means for heat treatment include a method of providing a zone with a higher temperature than the stretching zone after the width direction stretching is completed, a method of increasing the zone temperature in the latter half of stretching and passing the film through a zone of the same temperature after the stretching is completed, etc. Heating means include a method of blowing hot air or a method of heating with an infrared heater, but are not particularly limited as long as the method is capable of increasing the temperature of the film from that at the end of the width direction stretching step.

[0022] The heat treatment step is preferably carried out immediately after the width direction stretching step is completed (i.e., immediately after the width direction stretching reaches the final stretch ratio). The temperature in the heat treatment step is preferably equal to or higher than the temperature at the end of the width direction stretching step, specifically, preferably 120°C or higher. The upper limit is not particularly limited, and is, for example, 150°C or lower.

[0023] It is preferable to relax the film during heat treatment. The lower limit of the relaxation rate is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, particularly preferably 4% or more, and most preferably 5% or more. If it is 1% or more, the thermal shrinkage rate tends to decrease. The upper limit of the relaxation rate is preferably 10% or less, more preferably 9% or less, even more preferably 8% or less, and particularly preferably 7% or less. If it is 10% or less, thickness unevenness tends to be reduced.

[0024] (Surface Treatment Step) In the biaxially oriented polyethylene film of the present invention, it is preferable to surface treat at least one surface to improve the surface adhesiveness and wettability. Examples of surface treatments include corona discharge treatment and flame treatment. The wetting tension of the surface-treated film is preferably 35 mN / m or more, more preferably 36 mN / m or more, particularly preferably 37 mN / m or more, and most preferably 38 mN / m or more.

[0025] Although the manufacturing method for the biaxially oriented polyethylene film of the present invention when it is a single layer has been described above, the biaxially oriented polyethylene film of the present invention may have a layer having another function (hereinafter referred to as a functional layer) laminated on at least one side. The functional layer may be laminated on only one side or on both sides. When the functional layer contains a resin, the resin may be the polyethylene resin constituting the biaxially oriented polyethylene film, or a resin other than the polyethylene resin constituting the biaxially oriented polyethylene film. The number of functional layers may be one, two, or three or more per side, but from the viewpoint of ease of manufacturing, one or two layers is preferred. The lamination method is not particularly limited, and, for example, coextrusion using a feed block method or a multi-manifold method is preferred. As long as the effects of the present invention are not impaired, a resin layer having heat sealability can be laminated as a functional layer to improve the processability of the biaxially oriented polyethylene film. In addition, one or both sides of the film can be subjected to corona treatment to impart printability.

[0026] The biaxially oriented polyethylene film of the present invention can be wound into a roll to form a film roll having a width of about 2,000 to 12,000 mm and a length of about 1,000 to 50,000 m, making it possible to obtain a long film roll. It can also be slit according to the intended use to form a slit roll having a width of about 300 to 2,000 mm and a length of about 500 to 5,000 m.

[0027] (3) Physical Properties of Biaxially Oriented Polyethylene Film <Thickness> The thickness of the biaxially oriented polyethylene film of the present invention may be appropriately set depending on the application and is not particularly limited, but is preferably 2 to 100 μm, more preferably 3 to 80 μm, even more preferably 4 to 60 μm, particularly preferably 8 to 50 μm, and most preferably 10 to 40 μm. A thickness of 2 μm or more makes it easier to obtain rigidity in the film, and as a result, makes it easier to obtain film strength. Furthermore, a thickness of 100 μm or more tends to cause crystallization of the unstretched sheet during the extrusion process, making biaxial stretching difficult.

[0028] <Haze> The upper limit of the haze of the biaxially oriented polyethylene film of the present invention is preferably 10%, more preferably 9.0%, even more preferably 8.0%, and particularly preferably 7.0%. If it is 10.0% or less, when used as a base film for packaging bags, the contents look good and a beautiful appearance can be obtained when printed. The lower limit of the haze is preferably 0.0%. Since antiblocking agents and lubricants are added for workability and ease of production, a practical lower limit of the haze is preferably 0.5%.

[0029] <Tensile Breaking Strength> The lower limit of the tensile breaking strength in the longitudinal direction of the biaxially oriented polyethylene film of the present invention at 23°C is 80 MPa, preferably 85 MPa, more preferably 90 MPa, and even more preferably 95 MPa. At 80 MPa or more, the film has excellent handleability when used as a base film for packaging bags, is easily prevented from breaking, and printing pitch deviation can be kept low. The upper limit is 250 MPa or less, and if it is 250 MPa or less, practical production is easy. The lower limit of the tensile breaking strength in the width direction of the biaxially oriented polyethylene film of the present invention at 23°C is 250 MPa, preferably 253 MPa, and more preferably 255 MPa. At 250 MPa or more, the film is easily prevented from breaking when used as a base film for packaging bags, and printing pitch deviation can be kept low. The upper limit is 400 MPa or less, and if it is 400 MPa or less, practical production is easy. The tensile strength at break in each direction can be kept within the above range by adjusting the amount of high-density polyethylene in the raw material, the temperature, stretch ratio, relaxation rate, etc. in each film-forming step within the above ranges.

[0030] <Tensile Breaking Elongation> The lower limit of the tensile breaking elongation in the longitudinal direction of the biaxially oriented polyethylene film of the present invention at 23°C is preferably 100%, more preferably 150%, even more preferably 165%, even more preferably 170%, particularly preferably 180%, and most preferably 190%. If it is 100% or more, breakage is likely to be suppressed when used as a base film for packaging bags. The upper limit of the tensile breaking elongation in the longitudinal direction at 23°C is preferably 500%. 500% is sufficient. The lower limit of the tensile breaking elongation in the width direction of the biaxially oriented polyethylene film of the present invention at 23°C is preferably 20%, more preferably 30%, even more preferably 35%, and particularly preferably 38%. If it is 20% or more, breakage is likely to be suppressed when used as a base film for packaging bags. The upper limit of the tensile breaking elongation in the width direction at 23°C is preferably 200%. 200% is sufficient, and printing pitch deviation can also be suppressed low. The tensile elongation at break can be adjusted within the above range by adjusting the amount of high density polyethylene in the raw material, the temperature, stretching ratio, relaxation rate, etc. in each film-forming step within the above ranges.

[0031] <Stress at 5% Elongation (F5)> The stress at 5% elongation (F5) in the longitudinal direction of the biaxially oriented polyethylene film of the present invention at 23°C is preferably 25 MPa or more, more preferably 30 MPa or more, even more preferably 35 MPa or more, and particularly preferably 37 MPa or more. At 25 MPa or more, the film has high rigidity, making it easier to maintain the shape of the bag when made into a packaging bag, less likely to deform the film during processing such as printing, and print pitch deviation can be kept low. The upper limit is preferably 70 MPa, and a stress of 70 MPa or less facilitates practical production. The F5 in the longitudinal direction can be kept within the above range by adjusting the amount of high-density polyethylene in the raw material, the temperature, stretch ratio, relaxation rate, etc. in each film-forming step within the above ranges.

[0032] The stress at 5% elongation (F5) in the width direction of the biaxially oriented polyethylene film of the present invention at 23°C is preferably 80 MPa or more, more preferably 85 MPa or more, even more preferably 90 MPa or more, and particularly preferably 100 MPa or more. At 80 MPa or more, the film has high rigidity, making it easier to maintain the shape of the bag when made into a packaging bag, less likely to deform the film during processing such as printing, and print pitch deviation can be kept low. The upper limit is preferably 150 MPa or less, and a value of 150 MPa or less facilitates practical production. The F5 in the width direction can be kept within the above range by adjusting the amount of high-density polyethylene in the raw material, the temperature, stretch ratio, relaxation rate, etc. in each film-forming step within the above ranges.

[0033] <Heat shrinkage at 80°C> The heat shrinkage in the longitudinal direction of the biaxially oriented polyethylene film of the present invention at 80°C is preferably 1.0% or less, more preferably 0.8% or less, even more preferably 0.6% or less, particularly preferably 0.5% or less, and most preferably 0.4% or less. If it is 1.0% or less, printing pitch deviation during printing processing is significantly less likely to occur. A lower heat shrinkage in the longitudinal direction at 80°C is preferred, and the lower limit is not particularly limited, but is, for example, 0.0% or more. The heat shrinkage in the longitudinal direction at 80°C can be kept within the above range by adjusting the amount of high-density polyethylene in the raw material, the temperature in each film-forming step, the stretch ratio, the relaxation rate, etc., within the above ranges.

[0034] The heat shrinkage rate in the width direction of the biaxially oriented polyethylene film of the present invention at 80°C is preferably 2.0% or less, more preferably 1.8% or less, even more preferably 1.7% or less, particularly preferably 1.6% or less, and most preferably 1.0% or less. When it is 2.0% or less, wrinkles are less likely to occur during heat sealing. The lower limit of the heat shrinkage rate in the width direction at 80°C is not particularly limited, but is, for example, -0.2%. The heat shrinkage rate in the width direction at 80°C can be kept within the above range by adjusting the amount of high-density polyethylene in the raw material, the temperature in each film-forming step, the stretch ratio, the relaxation rate, etc., within the above ranges.

[0035] <Heat shrinkage at 90°C> The heat shrinkage in the longitudinal direction of the biaxially oriented polyethylene film of the present invention at 90°C is preferably 1.8% or less, more preferably 1.6% or less, even more preferably 1.4% or less, particularly preferably 1.3% or less, and most preferably 1.1% or less. If it is 1.8% or less, printing pitch deviation during printing processing is significantly less likely to occur. A lower heat shrinkage in the longitudinal direction at 90°C is preferred, and the lower limit is not particularly limited, but is, for example, 0.0% or more. The heat shrinkage in the longitudinal direction at 90°C can be kept within the above range by adjusting the amount of high-density polyethylene in the raw material, the temperature in each film-forming step, the stretch ratio, the relaxation rate, etc., within the above ranges.

[0036] The heat shrinkage rate in the width direction of the biaxially oriented polyethylene film of the present invention at 90°C is preferably 5.0% or less, more preferably 4.5% or less, even more preferably 4.0% or less, particularly preferably 3.8% or less, and most preferably 3.5% or less. When it is 5.0% or less, wrinkles are less likely to occur during heat sealing. The lower limit of the heat shrinkage rate in the width direction at 90°C is not particularly limited, but is, for example, -0.2%. The heat shrinkage rate in the width direction at 90°C can be kept within the above range by adjusting the amount of high-density polyethylene in the raw material, the temperature in each film-forming step, the draw ratio, the relaxation rate, and the like within the above ranges.

[0037] <Heat shrinkage at 100°C> The heat shrinkage at 100°C in the longitudinal direction of the biaxially oriented polyethylene film of the present invention is preferably 3.0% or less, more preferably 2.5% or less, even more preferably 2.0% or less, particularly preferably 1.7% or less, and most preferably 1.5% or less. If it is 3.0% or less, printing pitch deviation during printing processing is significantly less likely to occur. A lower heat shrinkage at 100°C in the longitudinal direction is preferred, and although there is no particular lower limit, in consideration of technical difficulties, it is, for example, 0.1% or more, preferably 0.3% or more. The heat shrinkage at 100°C in the longitudinal direction can be kept within the above range by adjusting the amount of high-density polyethylene in the raw material, the temperature in each film-forming step, the stretch ratio, the relaxation rate, and the like within the above ranges.

[0038] The heat shrinkage percentage in the width direction of the biaxially oriented polyethylene film of the present invention at 100°C is preferably 7.5% or less, more preferably 6.0% or less, even more preferably 4.5% or less, and particularly preferably 3.5% or less. When it is 7.5% or less, wrinkles are less likely to occur during heat sealing. The lower limit of the heat shrinkage percentage in the width direction at 100°C is not particularly limited, but is, for example, -0.2%. The heat shrinkage percentage in the width direction at 100°C can be kept within the above range by adjusting the amount of high-density polyethylene in the raw material, the temperature in each film-forming step, the draw ratio, the relaxation rate, and the like within the above ranges.

[0039] <Heat Shrinkage at 110°C> The heat shrinkage at 110°C in the longitudinal direction of the biaxially oriented polyethylene film of the present invention is preferably 7.5% or less, more preferably 6.0% or less, even more preferably 5.0% or less, particularly preferably 4.0% or less, and most preferably 3.5% or less. When it is 7.5% or less, printing pitch deviation during printing is less likely to occur. A lower heat shrinkage at 110°C in the longitudinal direction is preferred. Although the lower limit is not particularly limited, considering technical difficulties, it is, for example, 0.1% or more, preferably 0.3% or more. The heat shrinkage at 110°C in the longitudinal direction can be kept within the above range by adjusting the amount of high-density polyethylene in the raw material, the temperature in each film-forming step, the stretch ratio, the relaxation rate, and the like within the above ranges. The heat shrinkage at 110°C in the width direction of the biaxially oriented polyethylene film of the present invention is preferably 18% or less, more preferably 16% or less, even more preferably 14% or less, particularly preferably 13% or less, and most preferably 12% or less. When the shrinkage is 18% or less, wrinkles are less likely to occur during heat sealing. The lower limit of the heat shrinkage in the width direction at 110°C is not particularly limited, but is, for example, -0.2%. The heat shrinkage in the width direction at 110°C can be kept within the above range by adjusting the amount of high-density polyethylene in the raw material, the temperature in each film-forming step, the stretch ratio, the relaxation rate, and the like within the above ranges.

[0040] <Heat Shrinkage at 120°C> The heat shrinkage in the longitudinal direction of the biaxially oriented polyethylene film of the present invention at 120°C is 10.0% or less, preferably 8.0% or less, more preferably 7.0% or less, even more preferably 6.0% or less, and particularly preferably 5.0% or less. If it is 10.0% or less, wrinkles are likely to occur during sealing, and printing pitch deviation is less likely to occur during printing processing. A lower heat shrinkage in the longitudinal direction at 120°C is preferred, and although there is no particular lower limit, it is 0.0% or more, preferably 0.5% or more, in consideration of technical difficulties. The heat shrinkage in the longitudinal direction at 120°C can be kept within the above range by adjusting the amount of high-density polyethylene in the raw material, the temperature in each film-forming step, the stretch ratio, the relaxation rate, and the like within the above ranges.

[0041] The heat shrinkage rate in the width direction of the biaxially oriented polyethylene film of the present invention at 120°C is 20.0% or less, preferably 17.0% or less, and more preferably 15.0% or less. When it is 20.0% or less, wrinkles are less likely to occur during heat sealing. The lower limit of the heat shrinkage rate in the width direction at 120°C is -2.0% or more. The heat shrinkage rate in the width direction at 120°C can be kept within the above range by adjusting the amount of high-density polyethylene in the raw material, the temperature in each film-forming step, the stretch ratio, the relaxation rate, and the like within the above ranges.

[0042] If the heat shrinkage rate in the longitudinal direction at 120°C is 10.0% or less and the heat shrinkage rate in the width direction at 120°C is 20.0% or less, wrinkles are less likely to occur during heat sealing. In particular, if the heat shrinkage rate in the longitudinal direction at 120°C is 8.0% or less and the heat shrinkage rate in the width direction is 15.0% or less, distortion when the zipper portion is fused to the opening is small, which is more preferable.

[0043] The sum of the heat shrinkage rate at 120°C in the longitudinal direction and the heat shrinkage rate at 120°C in the width direction is preferably 40.0% or less, more preferably 35.0% or less, and even more preferably 30.0% or less. When the sum is 40.0% or less, wrinkles are less likely to occur during heat sealing.

[0044] (4) Laminate The biaxially oriented polyethylene film of the present invention can be used as a packaging bag by laminating it with a sealant film and heat-sealing the laminate. When the biaxially oriented polyethylene film of the present invention is used, the bag shape is easily maintained when the laminate is made into a packaging bag from the sealant film, deformation of the film is unlikely to occur during processing such as heat-sealing at high temperatures, and printing pitch deviation is unlikely to occur during printing processing, making it suitable for packaging.

[0045] To form a bag for packaging food, the contents are filled into a pre-made bag, and the film is heated to melt and fuse to seal it. This process is often used when making a bag while filling it with food. Typically, a sealant film made of a polyolefin resin such as polyethylene resin is laminated onto a base film (the biaxially oriented polyethylene film of the present invention), and the sealant film surfaces are fused together. The sealant film is preferably a polyethylene film containing 70% by mass or more of polyethylene resin, and more preferably an unstretched polyethylene film containing 70% by mass or more of polyethylene resin. The heating method involves applying pressure from a heating plate from the base film side to hold down the film and seal it, with a seal width of approximately 10 mm being common. Since the base film is also heated during this process, the expansion and contraction that occurs during this process can cause wrinkles. Fewer wrinkles are desirable for bag durability and to increase consumer interest. A higher sealing temperature is required to increase the bag-making processing speed, and small dimensional change at high temperatures is preferred. Furthermore, if a zipper is fused to the opening of the bag, even higher sealing temperatures are required.

[0046] Printing on the biaxially oriented polyethylene film of the present invention can be carried out by relief printing, lithographic printing, intaglio printing, stencil printing, transfer printing or the like, depending on the application.

[0047] In addition, a non-oriented sheet, uniaxially oriented film, or biaxially oriented film made of low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, polyethylene, or polyester can be laminated as a sealant film to the biaxially oriented polyethylene film of the present invention to form a laminate having heat-sealability.

[0048] When it is desired to improve gas barrier properties or heat resistance, an intermediate layer of aluminum foil, a non-stretched sheet, a uniaxially stretched film, or a biaxially stretched film can be provided between the biaxially oriented polyethylene film of the present invention and the sealant film. The raw materials constituting the non-stretched sheet, the uniaxially stretched film, and the biaxially stretched film are not particularly limited, and examples thereof include polyvinylidene chloride, nylon, an ethylene-vinyl alcohol copolymer, and polyvinyl alcohol. Furthermore, an adhesive applied by dry lamination or hot melt lamination can be used to attach the sealant film.

[0049] In order to improve the gas barrier properties, inorganic oxides such as aluminum, silica, and alumina can be vapor-deposited onto the biaxially oriented polyethylene film, the intermediate layer, or the sealant film. Vacuum deposition, sputtering, ion plating, and other known methods can be used as the vapor deposition method.

[0050] When used as a base film for packaging bags, it is often made of a laminated film consisting of a printed base film and a sealant film. Examples include three-sided bags, standing bags, and gusset bags, and they can be manufactured using known bag-making machines. It is believed that print pitch deviation occurs because the film base expands and contracts due to the tension and heat applied to the film during the printing process. Eliminating defective products due to print pitch deviation is important in terms of efficient resource utilization and also for increasing purchasing desire.

[0051] This application claims the benefit of priority based on Japanese Patent Application No. 2024-131175 filed on August 7, 2024, Japanese Patent Application No. 2024-131176 filed on August 7, 2024, Japanese Patent Application No. 2025-078092 filed on May 8, 2025, and Japanese Patent Application No. 2025-078093 filed on May 8, 2025. Japanese Patent Application No. 2024-131175 filed on August 7, 2024, Japanese Patent Application No. 2024-131176 filed on August 7, 2024, Japanese Patent Application No. 2025-078092 filed on May 8, 2025, and Japanese Patent Application No. 2025-078093 filed on May 8, 2025 The entire contents of the specification are incorporated by reference into this application.

[0052] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples. The evaluation methods used in each example and comparative example are as follows.

[0053] (1) Melt Flow Rate The melt flow rate (MFR) was measured in accordance with JIS K7210 at a temperature of 190°C and a load of 2.16 kgf.

[0054] (2) Weight-average molecular weight (Mw) Using gel permeation chromatography (GPC), a quintic approximation curve was created using monodisperse polystyrene, and the molecular weight was calculated as polyethylene equivalent molecular weight using the Q-factor. The GPC measurement conditions were as follows: Apparatus: HLC-8321GPC / HT (manufactured by Tosoh Corporation); Solvent: 1,2,4-trichlorobenzene + dibutylhydroxytoluene (0.05%); Column: TSKgel Guard Column H ＨＲ (30) HT (7.5mm I.D. x 7.5cm) x 1 + TSKgel GMH ＨＲ-H(20)HT (7.8 mm I.D. x 30 cm) x 3; Flow rate: 1.0 mL / min; Detection conditions: polarity = (-); Injection volume: 0.3 mL; System temperature: 40°C; Sample concentration: 1 mg / mL (The sample was dissolved in a trichlorobenzene solvent containing 0.1% by mass of dibutylhydroxytoluene by shaking at 140°C for 1 hour, and then heated and filtered using a sintered filter with a pore size of 0.5 μm.); Detector: RI; Measurement temperature: 140°C

[0055] The weight average molecular weight (Mw) was calculated by calculating the molecular weight (M) at each elution position of the GPC curve obtained through the molecular weight calibration curve. ｉ ) number of molecules (N ｉ ) is defined by the following formula: Weight average molecular weight: Mw = Σ(N ｉ ・M ｉ ２ ) / Σ(N ｉ ・M ｉ ) When the baseline was unclear, the baseline was set in the range up to the lowest point of the high molecular weight base of the elution peak on the high molecular weight side closest to the elution peak of the standard substance.

[0056] (3) Film Thickness The film thickness was measured using a Millitron 1202D manufactured by Seiko EM Corporation.

[0057] (4) Haze: Measured at 23° C. in accordance with JIS K7105 using an NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0058] (5) Tensile Breaking Strength, Tensile Breaking Elongation, and Stress at 5% Elongation (F5) Various physical properties were measured at 23°C during tensile testing in the longitudinal and transverse directions of the film in accordance with JIS K7127. A film was cut so that the measurement direction was 200 mm and the direction perpendicular thereto was 15 mm, and the film was set in a tensile testing machine (Instron 5965, a dual-column tabletop testing machine manufactured by Instron Japan Co., Ltd.) with a chuck width of 100 mm. The tensile test was performed at a tensile speed of 200 mm / min. From the obtained strain-stress curve, the stress at 5% elongation was designated as F5. The tensile breaking strength and tensile breaking elongation were defined as the strength and elongation, respectively, at the time the sample broke.

[0059] (6) Heat Shrinkage Rate The heat shrinkage rates of the film in the longitudinal and transverse directions at 120°C were measured in accordance with JIS Z1712 by the following method. A film was cut so that the measurement direction was 200 mm and the direction perpendicular thereto was 20 mm, and the film was hung in a hot air oven at 120°C and heated for 5 minutes. The length after heating was measured, and the heat shrinkage rate at 120°C was calculated as the ratio of the shrunken length to the original length. In addition, the heat shrinkage rates at temperatures of 80°C, 90°C, 100°C, and 110°C were calculated by the same method as for the heat shrinkage rate at 120°C, except that the film was hung in a hot air oven controlled at each temperature.

[0060] (7) Wrinkles at the sealed portion Wrinkles at the sealed portion were measured by the following procedure. Procedure 1) Preparation of a laminate of a biaxially oriented polyethylene film and a non-oriented polyethylene film This was carried out using a continuous dry laminator as follows. An adhesive was applied to the corona-treated surface of the biaxially oriented polyethylene film obtained in the Examples and Comparative Examples in an amount of 2.8 g / m2 when dried. ２After gravure coating to obtain a film thickness of 100 mm, the film was introduced into a drying zone and dried at 80°C for 5 seconds. The film was then laminated with a sealant film between rolls located downstream (roll pressure: 0.2 MPa, roll temperature: 50°C). The resulting laminate film was then aged at 40°C for 3 days in a rolled-up state. The adhesive used was a urethane adhesive obtained by mixing 28.9% by mass of a base agent (TM569, manufactured by Toyo-Morton Co., Ltd.), 4.00% by mass of a curing agent (CAT10L, manufactured by Toyo-Morton Co., Ltd.), and 67.1% by mass of ethyl acetate. The sealant film used was a non-oriented polyethylene film (Rix (registered trademark) L4103, thickness 40 μm) manufactured by Toyobo Co., Ltd. Step 2) The aged laminate film obtained in Step 1 above was heat-sealed with a heat sealer to form a 130 mm x 180 mm three-sided sealed bag, thereby producing a three-sided sealed bag. The heat sealing conditions were a pressure of 0.2 MPa for 1 second, a seal bar width of 10 mm, and a heat sealing temperature of 120°C. The appearance of wrinkles in the heat-sealed portion was visually evaluated. A: No wrinkles were observed in the heat-sealed portion in either the width or length direction of the film. B: Wrinkles were observed in the heat-sealed portion in only one of the width or length directions of the film. C: Wrinkles were observed in the heat-sealed portion in both the width and length directions of the film.

[0061] (8) Printing Pitch Misalignment A 400 mm wide, 150 m long roll of biaxially oriented polyethylene film was placed in a multicolor printing press (Azumaya Iron Works' "Three-Color Gravure Printing Press PAS-247"), and two-color printing (red and black) was performed on the corona-treated side of the film. Two-color (red and black) register mark designs were printed at a 50 cm pitch. The first register marks were prepared so that the red and black colors overlapped, and the amount of misalignment between the red and black register marks after 60 m of printing was measured. The printability was evaluated based on this amount of misalignment (pitch misalignment) as follows: A: The printing pitch misalignment was within 0.5 mm, and there was no practical problem. B: The printing pitch misalignment was about 1.0 mm, but the printing press adjustment was sufficient to pass. C: The printing pitch misalignment was 1.0 mm or more, and it was difficult to adjust the printing press.

[0062] (Materials Used) The polyethylene resins constituting each layer used in the following Examples and Comparative Examples are as follows: [PE-1]: High-density polyethylene (XUS 59910.18, manufactured by The Dow Chemical Company; weight average molecular weight: 100,000, density: 0.955 g / cm ３ , MFR (190°C / 2.16 kg): 1.5 g / 10 min. [PE-2]: Linear medium-density polyethylene (Innate™ TF80 manufactured by The Dow Chemical Company: weight average molecular weight: 90,000, density: 0.926 g / cm ３ , MFR (190°C / 2.16kg); 1.7g / 10min).

[0063] Example 1 A polyethylene resin composition containing 75% by mass of high-density polyethylene resin PE-1 and 25% by mass of linear medium-density polyethylene resin PE-2 was used as the raw material. The polyethylene resin composition was heated and melted at 250°C in an extruder, extruded through a T-die at 250°C into a sheet, and solidified by contact with a cooling roll at 30°C to obtain a sheet. The sheet was then stretched 4.7 times in the longitudinal direction at 125°C using two pairs of rolls. The ends were then clamped with clips, introduced into a hot air oven, preheated to 135°C, and stretched 10.0 times in the width direction at 125°C. The sheet was then heat-treated at 125°C and relaxed to a relaxation rate of 6.0% in the width direction. Finally, it was cooled to room temperature. The thickness of the resulting film was 25 μm. Because the weight-average molecular weight of the film of Example 1 was low, it was not necessary to blend liquid paraffin to form a gel-like sheet before stretching. Table 1 shows the film production conditions, and Table 1 shows the film properties. As shown in Table 1, a biaxially oriented polyethylene film having excellent tensile strength at break and thermal dimensional stability was obtained. In addition, the film was suitable for use in packaging bags when laminated with a polyethylene sealant film.

[0064] (Examples 2 to 5) In Examples 2 to 5, the films were produced in the same manner as in Example 1, except that the film production conditions were changed to those shown in Table 1. Table 1 shows the film production conditions and film properties. As shown in Table 1, in Examples 2 to 5, biaxially oriented polyethylene films excellent in tensile strength at break and thermal dimensional stability were obtained. Furthermore, by laminating with a polyethylene sealant film, these films were suitable for use in packaging bags. Because the weight-average molecular weight of the films in Examples 2 to 5 of the present application was small, there was no need to mix liquid paraffin to form a gel-like sheet and then stretch it.

[0065] (Comparative Examples 1 to 6) In Comparative Examples 1 to 6, the films were produced in the same manner as in Example 1, except that the film production conditions were changed to those shown in Table 2. The film production conditions and film properties are shown in Table 2. Note that Comparative Example 1 was given a rating of B because it had poor film-forming properties as described below, and the comparative examples other than the examples and Comparative Example 1 were given a rating of A because they had excellent film-forming properties.

[0066] In Comparative Example 1, film production was performed under the same stretching conditions as in Example 1 without blending high-density polyethylene resin. Uneven stretching occurred, and no biaxially oriented polyethylene film was obtained. In Comparative Example 2, a biaxially oriented polyethylene film was obtained by lowering the longitudinal and widthwise stretching temperatures during the stretching process in Comparative Example 1. The resulting film had large heat shrinkage rates in the longitudinal and width directions at 120°C, and low breaking strength and stress at 5% elongation (F5) in the width direction. There was significant printing pitch deviation during printing on the film, and wrinkles occurred in the seals of three-sided sealed bags produced by laminating a sealant. In Comparative Example 3, film production was performed under the same film production conditions as in Comparative Example 2, but with 30% by mass of high-density polyethylene resin blended. The resulting biaxially oriented polyethylene film had a large heat shrinkage rate at 120°C, wrinkles occurred in the seals of the packaging bags, and there was also significant pitch deviation during printing. In Comparative Example 4, the temperature during the stretching process of film production was lowered using the same raw material composition as in Example 1. The obtained film had a large heat shrinkage at 120°C, and wrinkles occurred in the sealed portion of the packaging bag. In Comparative Example 5, the same raw material composition as in Example 1 was used, but the stretch ratio in the width direction was reduced. The obtained biaxially oriented polyethylene film had significantly low breaking strength in the width direction and stress at 5% elongation (F5), lacked firmness, and poor slitting workability. In addition, there was a large print pitch deviation during printing. In Comparative Example 6, the same raw material composition as in Example 1 was used, but the stretch ratio in the longitudinal direction was increased and the stretch ratio in the width direction was reduced. The obtained biaxially oriented polyethylene film had a large heat shrinkage at 120°C in the longitudinal direction, and wrinkles occurred in the sealed portion of the packaging bag. In addition, there was a slightly large print pitch deviation during printing.

[0067]

[0068]

[0069] The biaxially oriented polyethylene film of the present invention has high rigidity and good dimensional stability at high temperatures, making it suitable as a base material for packaging bags. Furthermore, when laminated with a non-oriented polyethylene sealant film, the laminate is made of a single material, which has the advantage of being easily recycled. The biaxially oriented polyethylene film of the present invention can also be used for industrial purposes such as release films, adhesive labels, adhesive tapes, and cover films.

Claims

1. Density is 0.945 g / cm ３ Above, 0.965g / cm ３ A biaxially oriented polyethylene film comprising a polyethylene resin composition containing 55% by mass or more of the following polyethylene resin and having a weight-average molecular weight of 10,000 or more and 600,000 or less, satisfying the following requirements (1) to (4): (1) The tensile break strength in the longitudinal direction at 23°C is 80 MPa or more and 250 MPa or less. (2) The tensile break strength in the width direction at 23°C is 250 MPa or more and 400 MPa or less. (3) The heat shrinkage rate in the longitudinal direction at 120°C is 0.0% or more and 10.0% or less. (4) The heat shrinkage rate in the width direction at 120°C is -2.0% or more and 20.0% or less.

2. The biaxially oriented polyethylene film according to claim 1, which satisfies the following (5) and (6): (5) The stress at 5% elongation (F5) in the longitudinal direction at 23°C is 25 MPa or more and 70 MPa or less, and (6) The stress at 5% elongation (F5) in the transverse direction at 23°C is 80 MPa or more and 150 MPa or less.

3. The biaxially oriented polyethylene film according to claim 1 or 2, wherein the haze of the biaxially oriented polyethylene film is 10% or less.

4. A laminate in which a sealant film is laminated on at least one side of the biaxially oriented polyethylene film according to claim 1 or 2.

5. The laminate according to claim 4, wherein the sealant film is a polyethylene film containing 70% by mass or more of polyethylene resin.

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