Packaging film

Abstract

To provide a package in which heat-fusion is suppressed in the outermost layer.SOLUTION: A package 10 is constituted by a packaging film. In the package, the outermost layer is a polyethylene resin layer, and the polyethylene resin layer is uniaxially or biaxially extended.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a package. [Background technology]

[0002] For example, packaging bags, such as pouches used as packaging materials for food products; toiletries; medicines; car supplies such as vehicle oil, washer fluid, and cooling water; industrial lubricants; and heat transfer media such as oil and water, are composed of a packaging material consisting of a heat seal layer and a base layer.

[0003] An example of a technology relating to a packaging bag consisting of a heat seal layer and a base material layer is described in Patent Document 1 (JP 2018-154133 A).

[0004] Patent Document 1 describes a packaging bag made of a laminated film obtained by laminating a base film and a sealant film having a single layer structure made of a polyethylene resin composition or a multilayer structure including at least one layer made of the polyethylene resin composition. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-154133 A Summary of the Invention [Problem to be solved by the invention]

[0006] Due to the recent increase in environmental awareness, packaging films are required to be easily recyclable. From the viewpoint of facilitating recycling of packaging films, for example, it is conceivable to construct the packaging films from as single a material (mono-material) as possible. According to the investigations of the present inventors, from the viewpoint of achieving mono-materialization, it has become clear that a package made of a packaging film having a polyethylene-based resin layer as a base layer has the following problems. First, as shown in Figures 2 and 3, when producing a package 1 using a packaging film having a polyethylene-based resin layer 4 as a base layer, there is a process of heat-sealing the heat-seal layers 2 to each other. At this time, for example, at the bottom 3 of the package 1, the polyethylene-based resin layers 4, which are the outermost layers, come into contact with each other. According to the study by the present inventors, it has become clear that in the process of heat-sealing the heat-seal layers 2 to each other, the polyethylene-based resin layers 4, which are the outermost layers, are heat-sealed to each other. It has also become clear that the polyethylene-based resin layers are fused to the heat seal bar that is heated for heat sealing. As described above, the present inventors have found that in a package having an outermost layer made of a polyethylene-based resin, heat fusion of the outermost layer may occur during the manufacturing process.

[0007] The present invention has been made in view of the above circumstances, and provides a package in which heat fusion of the outermost layer is suppressed. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to achieve the above object, and as a result have found that in a package having an outermost layer made of a polyethylene-based resin, a package in which thermal fusion of the outermost layer is suppressed can be realized by uniaxially or biaxially stretching the polyethylene-based resin layer, thereby completing the present invention.

[0009] That is, according to the present invention, there is provided a package as shown below.

[0010] [1] A packaging body made of a packaging film, The outermost layer is a polyethylene resin layer, The packaging material wherein the polyethylene resin layer is uniaxially or biaxially stretched. [2] In the packaging body according to the above [1], The polyethylene resin layer constituting the package has a melting point of 100°C or higher and 150°C or lower. [3] In the packaging body according to the above [1] or [2], The package has a heat seal layer as the innermost layer of the package. [4] In the packaging body according to any one of the above [1] to [3], The package, wherein the heat seal layer comprises a polyethylene-based resin. [5] In the packaging body according to the above [4], The packaging body, wherein the polyethylene resin constituting the heat seal layer has a melting point of 90°C or higher and 140°C or lower. [6] In the packaging body according to the above [5], A packaging body in which 90% by mass or more of the packaging body is a polyethylene-based resin, when the entire packaging body is taken as 100% by mass. Effect of the Invention

[0011] According to the present invention, it is possible to provide a package in which heat fusion of the outermost layer is suppressed. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing an example of a structure of a packaging body according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a front view showing a schematic example of a structure of a conventional packaging body. [Diagram 3] 3 is a cross-sectional view of the packaging body shown in FIG. 2 along the line XX'. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the drawings are schematic diagrams and do not correspond to the actual dimensional ratio. In addition, unless otherwise specified, the numerical range "A to B" indicates A or more and B or less.

[0014] <Package> FIG. 1 is a perspective view showing a schematic example of the structure of a packaging body 10 according to an embodiment of the present invention. The packaging body 10 in this embodiment is a packaging body made of a packaging film, the outermost layer of which is a polyethylene-based resin layer, and this polyethylene-based resin layer is uniaxially or biaxially stretched. This makes it possible to suppress heat fusion between the outermost polyethylene-based resin layers in the process of heat-sealing the heat-seal layers in a package having an outermost layer of a uniaxially or biaxially oriented polyethylene-based resin layer, and also to suppress the outermost polyethylene-based resin layer from fusing to a heat seal bar in the heat-sealing process.

[0015] In this embodiment, the package refers to a packaging bag itself or a bag containing an article, which is used for the purpose of containing an article such as food, medicine, health care products, daily necessities, industrial products, car products such as vehicle oil, washer fluid, and cooling water, industrial lubricant, and heat transfer medium such as oil and water. Examples of the packaging form of the package according to this embodiment include a three-sided bag, a four-sided bag, a pillow bag, a two-sided bag, a stick bag, a gusset bag, a pouch, and the like, which have a heat seal part formed by heat fusion on all or part of the periphery. In addition, an oxygen absorber or the like may be placed inside the package in addition to the article.

[0016] The package 10 according to the present embodiment usually has a heat seal layer in the innermost layer (the outermost layer on the inner side of the package). This allows the package 10 according to the present embodiment to be produced by heat-sealing the heat seal layers of the packaging film together.

[0017] From the viewpoint of improving recyclability, when the entire packaging body 10 of this embodiment is taken as 100% by mass, it is preferable that 90% by mass or more of the packaging body be polyethylene-based resin, more preferably 95% by mass or more of the packaging body be polyethylene-based resin, even more preferably 98% by mass or more of the packaging body be polyethylene-based resin, and even more preferably 99% by mass or more of the packaging body be polyethylene-based resin. As a result, the packaging body is made up of almost a single material (mono-material), which reduces the work of separating the materials that make up the packaging body 10, and makes it possible to improve the recyclability of the packaging body 10.

[0018] <Packaging film> As the packaging film according to the present embodiment, for example, a film including a polyethylene-based resin layer containing a polyethylene-based resin and a heat seal layer provided on at least one surface of the polyethylene-based resin layer can be used. Here, the polyethylene-based resin layer may be a single layer or two or more layers.

[0019] The thickness of the packaging film according to the present embodiment is not particularly limited and can be set arbitrarily depending on the desired purpose such as water vapor barrier property, cost, mechanical strength, transparency, recyclability, appearance, formability, lightweight, etc. The thickness is usually 10 μm or more and 220 μm or less, preferably 15 μm or more and 190 μm or less, and more preferably 20 μm or more and 175 μm or less. When the thickness of the packaging film according to the present embodiment is within the above range, the balance of mechanical properties, handleability, appearance, formability, lightweight property, and the like is excellent.

[0020] Each layer constituting the packaging film according to this embodiment will be described below.

[0021] [Polyethylene resin layer] The polyethylene-based resin layer (also referred to as a base layer) according to this embodiment is formed, for example, by uniaxially or biaxially stretching a film composed of a resin composition containing a polyethylene-based resin.

[0022] The thickness of the polyethylene-based resin layer according to this embodiment is not particularly limited as it can be set arbitrarily depending on the desired objectives, such as water vapor barrier properties, cost, mechanical strength, transparency, recyclability, appearance, moldability, and light weight, but is usually from 0.5 μm to 100 μm, preferably from 1.0 μm to 75 μm, and more preferably from 1.5 μm to 50 μm. When the thickness of the polyethylene resin layer is within the above range, the balance of mechanical properties, handling properties, appearance, moldability, lightweight properties, and the like is excellent.

[0023] The polyethylene-based resin layer according to this embodiment is sufficient as long as it includes at least an outermost layer that is uniaxially or biaxially oriented, and may be a single layer consisting of only the outermost layer, or may be a configuration in which multiple layers composed of a resin composition containing a polyethylene-based resin are laminated. In the case where a plurality of layers made of a resin composition containing a polyethylene resin are laminated, examples of layers other than the layer (also called the outermost layer) located on the outer surface of the package include a core layer, a laminate layer, and the like. From the viewpoint of the formability of the film and web handling during winding, it is preferable to provide a core layer or a laminate layer. The core layer is a layer located between the outermost layer and the laminate layer in the polyethylene resin layer, and the laminate layer is a layer located on the surface opposite to the outermost layer in the polyethylene resin layer. The polyethylene resin layer may be composed of only the outermost layer and the laminate layer. In addition, in the polyethylene resin layer, at least the outermost layer is uniaxially or biaxially stretched, and the core layer and the laminate layer may or may not be stretched. The thickness of the outermost layer is, for example, 0.05 μm to 10 μm, specifically 1.0 μm to 6 μm. The thickness of the core layer is, for example, 0.4 μm to 49.9 μm, specifically 1 μm to 48 μm. The thickness of the laminate layer is, for example, 0.05 μm to 10 μm, specifically 1.0 μm to 6 μm. Furthermore, examples of methods for laminating multiple layers composed of a resin composition containing a polyethylene-based resin include a dry lamination method; an extrusion lamination method; a heat fusion method such as a method of extruding a resin and laminating the extruded resin on a surface layer; and a method of combining the dry lamination method, the extrusion lamination method, and the heat fusion method.

[0024] (Polyethylene resin composition) The polyethylene resin composition according to the present embodiment contains a polyethylene resin. The content of the polyethylene resin contained in the polyethylene resin composition according to the present embodiment (i.e., the polyethylene resin layer) is preferably 90% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 100% by mass or less, still more preferably 98% by mass or more and 100% by mass or less, and particularly preferably 99% by mass or more and 100% by mass or less, when the entire polyethylene resin composition is taken as 100% by mass. This makes it possible to achieve a better balance between water vapor barrier properties, cost, mechanical strength, transparency, recyclability, appearance, moldability, light weight, and the like.

[0025] (Polyethylene resin) Examples of the polyethylene resin constituting the polyethylene resin layer according to the present embodiment include one or more polyethylene resins such as high density polyethylene, medium density polyethylene, low density polyethylene, linear polyethylene, ultra-high molecular weight polyethylene, etc. Among these, one or more of high density polyethylene, medium density polyethylene, low density polyethylene, and linear polyethylene are preferred, and it is more preferred to have linear polyethylene alone or linear polyethylene at 20 mass% or more and at least one of high density polyethylene, medium density polyethylene, and low density polyethylene. From the viewpoint of suppressing whitening and increasing the transparency of the package, it is preferable to combine two or more polyethylene resins. Whitening is caused by the crystallization of polyethylene. By using two or more polyethylene resins in combination, the polyethylene resin layer tends to become amorphous, so crystallization may be suppressed and whitening may be suppressed. Considerations for combining two or more polyethylene resins include MFR, density, melting point, etc. Specifically, when two or more polyethylene resins are combined, it is preferable that they fall under at least one of the following (i) to (iii) (methods for measuring MFR and density will be described later). (i) Two polyethylene resins with MFRs differing by 0.5 g / 10 min or more are used in combination. In this case, it is preferable that the mass ratio of the two resins is the same or that the resin with the smaller MFR is used more. (ii) Density is 10 kg / m 3 The above different polyethylene resins are combined. In this case, it is preferable that the mass ratio of the two resins is the same or that the resin with the lower density is used more. (iii) Combining polyethylene resins whose melting points differ by 1° C. or more In this case, it is preferable that the mass ratio of the two types of resins is the same, or that the resin with the lower melting point is used more. When the polyethylene resin layer has a multi-layer structure as described above (for example, a three-layer structure of an outermost layer, a core layer, and a laminate layer), only one layer may contain two or more polyethylene resins, or two or more layers may each contain two or more polyester resins. Of course, each layer in the polyethylene resin layer may be composed of only one polyethylene resin.

[0026] From the viewpoint of achieving a better balance of heat resistance, transparency, mechanical properties, rigidity, fluidity, moldability, and the like, the melting point of the polyethylene resin is preferably 100°C or higher, more preferably 120°C or higher, even more preferably 125°C or higher, and preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 135°C or lower. When the melting point of the polyethylene resin is equal to or higher than the above lower limit, it is possible to further suppress heat fusion between the polyethylene resin layers that are the outermost layers in the packaging body 10. When the melting point of the polyethylene resin is equal to or lower than the above upper limit, it is possible to improve the interlayer strength, fluidity, and moldability.

[0027] The density of the polyethylene resin is preferably 920 kg / m from the viewpoint of achieving a better balance of heat resistance, transparency, mechanical properties, rigidity, fluidity, moldability, and the like. 3 More preferably, 923 kg / m 3 More preferably, 925 kg / m 3 or more, and preferably 970 kg / m 3 Less than or equal to 965 kg / m 3 Less than 960 kg / m, more preferably 960 kg / m 3 Less than 950 kg / m 3 Here, in this embodiment, the density of the polyethylene resin can be measured in accordance with JIS K 7112 (1999). When the density of the polyethylene resin is equal to or greater than the above lower limit, it is possible to further suppress heat fusion between the polyethylene resin layers that are the outermost layers in the package 10. When the density of the polyethylene resin is equal to or less than the above upper limit, it is possible to improve the interlayer strength, fluidity, and moldability.

[0028] The melt flow rate (MFR) of the polyethylene resin, measured in accordance with ASTM D1238 under conditions of 190°C and a load of 2.16 kg, is preferably 0.5 g / 10 min or more, more preferably 1 g / 10 min or more, and even more preferably 2 g / 10 min or more, from the viewpoint of fluidity and moldability, and is preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, and even more preferably 10 g / 10 min or less, from the viewpoint of further stabilizing moldability.

[0029] The method for producing the polyethylene resin is not particularly limited, and the polyethylene resin can be produced by a known method. In addition, commercially available polyethylene may be used.

[0030] (Other Ingredients) To the polyethylene resin composition according to the present embodiment, various additives such as a tackifier, a heat stabilizer, a weather stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, a slip agent, a nucleating agent, an antiblocking agent, an antistatic agent, an antifogging agent, a pigment, a dye, and an inorganic or organic filler may be added as necessary within a range that does not impair the object of the present embodiment.

[0031] (Method for preparing polyethylene resin composition) The polyethylene resin composition according to the present embodiment can be prepared, for example, by mixing or melt-kneading the respective components using a method / apparatus such as a dry blend, a tumbler mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, or a heated roll.

[0032] [Heat seal layer] In order to provide the packaging film according to the present embodiment with heat sealability, it is preferable that the packaging film according to the present embodiment has a heat seal layer on at least a part of one surface of the polyethylene-based resin layer. The heat seal layer may be provided only at the site to be heat-sealed in the packaging film according to the present embodiment, or may be provided on the entire one surface of the polyethylene-based resin layer.

[0033] In the packaging film according to this embodiment, the thickness of the heat seal layer is preferably 0.1 μm or more and 200 μm or less, more preferably 0.2 μm or more and 170 μm or less, further preferably 0.5 μm or more and 150 μm or less, and particularly preferably 1 μm or more and 120 μm or less. When the thickness of the heat seal layer is equal to or more than the above lower limit, the heat sealability of the packaging film can be improved. Furthermore, by setting the thickness of the heat seal layer to the above upper limit or less, fusion of the outermost layer during heat sealing can be particularly suppressed. Generally, the thicker the heat seal layer, the higher the temperature at which sealing is required.

[0034] In the packaging film according to the present embodiment, the heat seal layer provided on one side is preferably a single layer, which can simplify the manufacturing process of the packaging film, i.e., the manufacturing process of the package 10 according to the present embodiment.

[0035] The heat seal layer may be formed by stretching simultaneously with the film before stretching of the polyethylene resin layer. This allows the packaging film to be produced using a laminated film produced by a molding method such as co-extrusion, i.e., by one molding. This allows the manufacturing process of the packaging film, i.e., the manufacturing process of the packaging body 10 according to this embodiment, to be simplified. Therefore, the heat seal layer may be uniaxially or biaxially stretched.

[0036] (Polyolefin) The heat seal layer according to the present embodiment is, for example, made of a polyolefin-based resin composition containing polyolefin. Examples of the polyolefin constituting the heat seal layer include homopolymers or copolymers of α-olefins such as ethylene, propylene, butene-1, hexene-1, 4-methyl-pentene-1, octene-1, etc.; polyethylene-based resins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear polyethylene, and ultra-high molecular weight polyethylene; polypropylene; propylene-α-olefin random copolymers; ethylene-vinyl acetate copolymers (EVA); ionomer resins, etc. Among these, a polyethylene-based resin is preferred as the polyolefin constituting the heat seal layer from the viewpoint of improving recyclability and from the viewpoint of an excellent balance of adhesiveness with the polyethylene-based resin layer, heat sealability, etc. This makes it easier to separate the materials constituting the package 10 because the package is composed of almost a single material (monomaterial), and the recyclability of the package 10 can be improved.

[0037] (Polyethylene resin) Examples of the polyethylene resin constituting the heat seal layer according to the present embodiment include high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, and ultra-high molecular weight polyethylene. Among these, low density polyethylene and linear low density polyethylene are preferred, and linear low density polyethylene is more preferred. One type of polyethylene may be used, or two or more types may be used in combination.

[0038] The melting point of the polyethylene resin is preferably 90° C. or higher, more preferably 95° C. or higher, and preferably 140° C. or lower, more preferably 120° C. or lower. When the melting point of the polyethylene resin is equal to or higher than the lower limit, the stickiness of the surface of the heat seal layer can be suppressed, and the blocking resistance of the packaging film can be improved. In addition, when the melting point of the polyethylene resin is equal to or lower than the above upper limit, the heat sealability of the packaging film can be improved.

[0039] The melt flow rate (MFR) of the polyethylene resin, measured in accordance with ASTM D1238 under conditions of 190°C and a load of 2.16 kg, is preferably 0.5 g / 10 min or more, more preferably 1 g / 10 min or more, and even more preferably 2 g / 10 min or more, from the viewpoint of fluidity and moldability, and is preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, and even more preferably 10 g / 10 min or less, from the viewpoint of further stabilizing moldability.

[0040] The method for producing the polyethylene resin is not particularly limited, and the polyethylene resin can be produced by a known method. In addition, commercially available polyethylene may be used.

[0041] The content of the polyolefin resin in the polyolefin resin composition according to the present embodiment (i.e., in the heat seal layer) is preferably 90% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 100% by mass or less, further preferably 98% by mass or more and 100% by mass or less, and particularly preferably 99% by mass or more and 100% by mass or less, when the entire polyolefin resin composition is taken as 100% by mass. This makes it possible to achieve a better balance between recyclability, adhesion to the polyethylene resin layer, heat sealability, etc.

[0042] (Other Ingredients) If necessary, various additives such as heat stabilizers, weather stabilizers, antioxidants, UV absorbers, lubricants, slipping agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, and inorganic or organic fillers may be added to the polyolefin resin composition constituting the heat seal layer according to the present embodiment, within a range that does not impair the object of the present embodiment. On the other hand, from the viewpoint of mono-materialization, it is preferable that the polyolefin resin composition does not substantially contain these various additives.

[0043] (Method for preparing polyolefin-based resin composition) The polyolefin resin composition according to the present embodiment can be prepared by mixing or melt-kneading the components using a dry blend, a tumbler mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, a heat roll, or the like.

[0044] <Manufacturing method of packaging film> The packaging film according to the present embodiment can be obtained, for example, by uniaxially or biaxially stretching a laminated film obtained by co-extrusion molding the above-mentioned polyethylene-based resin composition for forming the polyethylene-based resin layer and the above-mentioned polyolefin-based resin composition for forming the heat seal layer into a film shape, using a known stretching film production method. The molding device and molding conditions are not particularly limited, and conventionally known molding devices and molding conditions can be used. As the molding device, a multi-layer T-die extruder or a multi-layer inflation molding machine can be used. As the biaxial stretching conditions, for example, known stretched film manufacturing conditions can be used. The production conditions for the stretched film are not particularly limited, but examples thereof include the following conditions. Extrusion temperature setting: 190-250℃, Processing speed: 20-60m / min Longitudinal stretching temperature: 100 to 130°C Longitudinal stretch ratio: 3.5 to 7.5 times Lateral stretching temperature: 100~150℃ Lateral stretching ratio: 4~12 times The packaging film according to the present embodiment can also be obtained by dry lamination in which the uniaxially or biaxially oriented outermost layer or the polyethylene-based resin layer including the outermost layer and the heat seal layer are separately molded and then laminated with an adhesive, etc. Furthermore, the packaging film according to the present embodiment can also be obtained by molding the resin of the heat seal layer on the uniaxially or biaxially oriented polyethylene-based resin layer by extrusion lamination molding, etc.

[0045] Although the embodiments of the present invention have been described above with reference to the drawings, these are merely examples of the present invention, and various configurations other than those described above can also be adopted. EXAMPLES

[0046] The present embodiment will be described in detail below with reference to examples and comparative examples, but the present embodiment is not limited to the descriptions of these examples.

[0047] 1. Raw materials The raw materials used in the examples and comparative examples are shown below. (1) Polyethylene resin PE1: Polyethylene (MFR: 0.8g / 10min, density: 926kg / m 3 , melting point: 124℃) PE2: Polyethylene (MFR: 2.8g / 10min, density: 942kg / m 3 , melting point: 129℃) PE3: Polyethylene (MFR: 1.8g / 10min, density: 927kg / m 3 , melting point: 127℃) PE4: Polyethylene (MFR: 3.8g / 10min, density: 918kg / m 3 , melting point: 116℃) PE5: Polyethylene (MFR: 1.1g / 10min, density: 950kg / m 3 , melting point: 132℃)

[0048] 2. Measurement and Evaluation Methods (1) MFR of polyethylene resin Measured in accordance with ASTM D1238 at 190°C and a load of 2.16 kg.

[0049] (2) Melting point of polyethylene resin The melting point was determined as the temperature of the maximum melting peak in the DSC curve of the polyethylene resin obtained using a differential scanning calorimeter (DSC). Specifically, the following 1st and 2nd runs were performed, and the temperature of the maximum melting peak in the DSC curve of the 2nd run was determined as the melting point. 1st run: Heat to 200°C at 10°C / min, hold for 10 minutes, cool to -50°C at 10°C / min 2nd run: After the 1st run, continue to increase the temperature to 200°C at 10°C / min.

[0050] (3) Density of polyethylene resin The density of the polyethylene resin was measured in accordance with JIS K 7112 (1999).

[0051] (4) Evaluation of heat fusion The outermost layers of two packaging films cut to a width of 15 mm were heat-sealed together at 130°C, a pressure of 2.0 kgf, and a sealing time of 1 second to obtain a laminated film. The two packaging films were then peeled off at a width of 15 mm, 180° peeling, and a peeling speed of 300 mm / min, and the peel strength at this time was recorded as the heat seal strength. Next, the heat-sealing property of the packaging film was evaluated according to the following criteria. ◎(Very Good): Heat seal strength is less than 2.0N / 15mm Good: Heat seal strength is 2.0N / 15mm or more and less than 5.0N / 15mm △(Bad): Heat seal strength is 5.0N / 15mm or more and less than 10.0N / 15mm ×(Very Bad): Heat seal strength is 10.0N / 15mm or more

[0052] (5) Presence or absence of whitening (transparency) The packaging film was visually observed and judged according to the following criteria. Good: Sufficiently transparent, no problems with visibility of packaged items when used as a packaging film × (Bad): Matte finish, problems with visibility of packaged items when used as a packaging film

[0053] [Examples 1 to 13] Each layer was co-extruded and stretched to produce a packaging film with the layer structure shown in Table 1. The heat-sealing properties were evaluated using the following molding machines. Multi-layer extrusion molding machine: 260mm wide multi-layer T-die extrusion molding machine (L / D=27, manufactured by Screw Seiki Co., Ltd.) The stretch ratios were as follows: Examples 1, 2, and 4: Biaxial stretching of 4.0 to 7.5 times vertically and 7.5 to 14 times horizontally Example 3: Uniaxial stretching 8 to 14 times laterally

[0054] [Comparative Example 1] Packaging films were produced by co-extrusion molding each layer in the layer structure shown in Table 1 (no stretching treatment was carried out in Comparative Example 1). Then, the heat sealability was evaluated. The molding machines used are as follows. Multilayer extrusion machine: Multilayer T-die extrusion machine (L / D=30)

[0055] [Table 1]

[0056] This application claims priority based on Japanese Patent Application No. 2019-171374, filed on September 20, 2019, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0057] 1 package 2 Heat seal layer 3 bottom 4 Polyethylene resin layer 10 Packaging

Claims

1. A packaging film used to make a packaging bag used for the purpose of containing an article, The packaging film comprises an outermost layer that constitutes the outer surface of the packaging bag and a heat-seal layer that constitutes the innermost layer of the packaging bag. The outermost layer is a polyethylene resin layer, The polyethylene resin layer is biaxially stretched, The polyethylene resin constituting the polyethylene resin layer is a combination of two or more types of polyethylene resins. A packaging film in which the polyethylene resin constituting the polyethylene resin layer falls under at least one of the following (ii) to (iii). (ii) Combine polyethylene resins with densities differing by 10 kg / m³ or more. In this case, the ratio of the two resins should be the same by mass, or the resin with the lower density should be used in greater proportion. (iii) Combine polyethylene resins with melting points that differ by 1°C or more. In this case, the ratio of the two resins should be the same by mass, or the resin with the lower melting point should be used in greater proportion.

2. In the packaging film according to Claim 1, A packaging film in which the polyethylene resin constituting the polyethylene resin layer has a melting point of 100°C or higher and 150°C or lower.

3. In the packaging film according to claim 1 or 2, The heat-seal layer is a packaging film containing a polyethylene resin.

4. In the packaging film according to claim 3, A packaging film in which the polyethylene resin constituting the heat seal layer has a melting point of 90°C or higher and 140°C or lower.

5. In the packaging film according to claim 4, A packaging film in which, when the entirety of the packaging film is considered as 100% by mass, 90% or more by mass of the packaging film is polyethylene resin.

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