Polyethylene film, laminates and packaging bags

Abstract

The present invention provides polyethylene films with excellent heat-sealing properties, even when containing mechanically recycled polyethylene, as well as laminates and packaging bags using the same. [Solution] The polyethylene film 4 of the present disclosure comprises a first layer 1 and a second layer 2, wherein the first layer 1 constitutes one surface of the polyethylene film 4, and the first layer 1 contains at least one selected from the group consisting of virgin polyethylene and mechanically recycled polyethylene, and the second layer 2 contains mechanically recycled polyethylene and a resin impurity which is a resin other than polyethylene, wherein the resin impurity is at least one selected from the group consisting of polypropylene, polyurethane, polyamide, polyester, ethylene-vinyl alcohol copolymer, acid-modified polyolefin, polystyrene, polyvinyl alcohol and acrylic resin, and the content ratio of the resin impurity is 1.5% by mass or less with respect to the total amount of the polyethylene film 4.

Description

[Technical Field]

[0001] This disclosure relates to polyethylene films, laminates, and packaging bags. [Background technology]

[0002] In the manufacture of packaging materials for filling products such as pharmaceuticals, cosmetics, and food, plastics derived from fossil fuels are primarily used due to their ease of molding and cost-effectiveness. These plastic materials are produced from petroleum, a fossil resource. Commonly used plastic materials for packaging containers include polyester, polyolefins, and polyamides. In particular, polyolefins such as polyethylene are molded into films, sheets, bottles, etc., and are used in a wide variety of applications, including packaging materials, and are widely used worldwide.

[0003] Therefore, efforts are being made to reduce the use of fossil fuels and lessen the environmental burden by recycling (reusing) polyethylene that has been used once as a resin product. For example, Patent Document 1 describes a sealant film having an intermediate layer containing recycled polyethylene between a first virgin polyethylene layer and a second virgin polyethylene layer. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2022 / 124229 [Overview of the project] [Problems that the invention aims to solve]

[0005] There are several types of recycling, including mechanical recycling, chemical recycling, and thermal recycling. Mechanical recycling involves crushing, air separation, washing, and gravity separation of collected waste plastics before re-pelletizing them. Chemical recycling involves decomposing collected waste plastics to the molecular level using heat and pressure, then repolymerizing them for re-pelletization, gasification, liquefaction, use as a reducing agent in blast furnaces, or as a chemical raw material for coke ovens. Thermal recycling involves recovering and utilizing the thermal energy generated during the incineration of waste. Chemical recycling yields high-purity resins, but it also consumes a large amount of energy and is costly. Thermal recycling, on the other hand, is a technology that converts used resin products into other forms of energy, not a method of reusing the resin itself. Therefore, the use of mechanically recycled resins, which are inexpensive and have a low environmental impact, is currently desirable. However, mechanically recycled polyethylene may contain impurities originating from the raw packaging materials. As a result, when mechanically recycled polyethylene is used as the heat-seal layer of packaging materials, the heat-sealing properties may be impaired.

[0006] Therefore, an object of this disclosure is to provide a polyethylene film that has excellent heat-sealing properties, even if it contains mechanically recycled polyethylene. Another object of this disclosure is to provide laminates and packaging bags using the polyethylene film. [Means for solving the problem]

[0007] This disclosure is resolved by the following embodiments. <1> A polyethylene film comprising a first layer and a second layer, The first layer constitutes one side of the polyethylene film, The first layer comprises at least one selected from the group consisting of virgin polyethylene and mechanically recycled polyethylene. The second layer comprises mechanically recycled polyethylene and resin impurities, which are resins other than polyethylene. The resin impurity is at least one selected from the group consisting of polypropylene, polyurethane, polyamide, polyester, ethylene-vinyl alcohol copolymer, acid-modified polyolefin, polystyrene, polyvinyl alcohol, and acrylic resin. A polyethylene film in which the content of the aforementioned resin impurities is 1.5% by mass or less relative to the total amount of the polyethylene film. <2> The second layer further contains virgin polyethylene. <1> The polyethylene film described above. <3> The proportion of mechanically recycled polyethylene in the first layer is smaller than the proportion of mechanically recycled polyethylene in the second layer. <1> or <2> The polyethylene film described above. <4> The above first layer, the above second layer, and the third layer are provided in this order. The third layer comprises at least one selected from the group consisting of virgin polyethylene and mechanically recycled polyethylene. <1> ~ <3> Polyethylene film as described in one of the following. <5> The content of the aforementioned resin impurities is 0.01% by mass or more relative to the total amount of the polyethylene film. <1> ~ <4> Polyethylene film as described in one of the following. <6> The antioxidant further contains at least one selected from the group consisting of phenolic antioxidants and phosphorus-based antioxidants. <1> ~ <5> Polyethylene film as described in one of the following. <7> The content ratio of the antioxidant is 50 ppm or more and 500 ppm or less relative to the total amount of the polyethylene film. <6> The polyethylene film described above. <8> The polyethylene film according to any one of <1> to <7>, wherein the content ratio of recycled polyethylene is 1% by mass or more and 50% by mass or less based on the total amount of the polyethylene film. <9> The polyethylene film according to any one of <1> to <8>, which is a sealant film. <10> A laminate having a base film and the polyethylene film according to any one of <1> to <9>. <11> The laminate according to <10>, wherein the content ratio of polyethylene is 80% by mass or more based on the whole laminate. <12> A packaging bag comprising the laminate according to <10> or <11>.

Advantages of the Invention

[0008] The present disclosure can provide a polyethylene film excellent in heat sealability even if it contains mechanically recycled polyethylene. Further, the present disclosure can provide a laminate and a packaging bag using the polyethylene film.

Brief Description of the Drawings

[0009] [Figure 1] It is a schematic cross-sectional view showing an embodiment of the polyethylene film according to the present disclosure. [Figure 2] It is a schematic cross-sectional view showing an embodiment of the polyethylene film according to the present disclosure. [Figure 3] It is a schematic cross-sectional view showing an embodiment of the laminate according to the present disclosure. [Figure 4] It is a schematic cross-sectional view showing an embodiment of the laminate according to the present disclosure. [Figure 5] It is a front view showing an embodiment of the packaging bag according to the present disclosure. [Figure 6] It is a front view showing an embodiment of the packaging bag according to the present disclosure. [Figure 7]This is a front view showing one embodiment of the packaging bag according to the present disclosure. [Figure 8] This is a front view showing one embodiment of the packaging bag according to the present disclosure. [Figure 9] This is a schematic diagram illustrating a method for measuring heat seal strength. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure will be described in detail below with reference to the drawings. However, the disclosure is not limited to the embodiments described below. Furthermore, the components in the embodiments described below include those that are readily conceivable to those skilled in the art, and those that are substantially the same. Moreover, the components disclosed in the embodiments described below can be combined as appropriate.

[0011] [Polyethylene film] The polyethylene film according to this disclosure comprises a first layer and a second layer. The polyethylene film is preferably an unstretched film. An unstretched film means a film that has not undergone intentional stretching treatment (a film whose molecules have not been oriented by stretching). Details of the stretching treatment will be described later. Cases in which the film is inevitably stretched during extrusion molding or film winding are also included in the definition of an unstretched film.

[0012] The polyethylene film 4 shown in Figure 1 comprises a first layer 1 and a second layer 2. The first layer 1 constitutes one surface of the polyethylene film 4. The second layer 2 constitutes the other surface of the polyethylene film 4. The first layer 1 and the second layer 2 are in contact with each other. The polyethylene film 4 shown in Figure 2 comprises a first layer 1, a second layer 2, and a third layer 3 in that order. The first layer 1 constitutes one side of the polyethylene film 4. The third layer 3 constitutes the other side of the polyethylene film 4. The first layer 1 and the second layer 2 are in contact, and the second layer 2 and the third layer 3 are in contact. In other words, the polyethylene film 4 shown in Figure 2 is the polyethylene film 4 shown in Figure 1, further comprising a third layer 3.

[0013] The polyethylene film is preferably an unstretched resin film, and more preferably an unstretched co-extruded resin film manufactured by a co-extrusion T-die-casting method, where each layer constituting the resin film is a co-extruded resin layer. The polyethylene film 4 shown in Figure 1 is, for example, a two-layer co-extruded resin film. The polyethylene film 4 shown in Figure 2 is, for example, a three-layer co-extruded resin film. Multilayer co-extrusion allows for the production of thin layers constituting the polyethylene film. In one embodiment, the resin film is an unstretched resin film obtained by manufacturing a material constituting the first layer and a material constituting the second layer by a co-extrusion T-die-casting method. In one embodiment, the resin film is an unstretched resin film obtained by manufacturing a material constituting the first layer, a material constituting the second layer, and a material constituting the third layer by a co-extrusion T-die-casting method. Such polyethylene films have excellent heat-sealability, for example.

[0014] An embodiment of co-extrusion T-die casting is described below. Materials for forming each layer are supplied to each extruder, a fixed amount is extruded by the gear pump of the extruder, and supplied to a multi-manifold die, and a polyethylene film is obtained by co-extrusion casting. For example, in each extruder, the temperature of the screw that extrudes the material constituting the first layer is set to 230°C or more and 240°C or less, and the temperature of the screw that extrudes the material constituting the second layer is set to 230°C or more and 240°C or less. When manufacturing a polyethylene film further comprising a third layer, the temperature of the screw that extrudes the material constituting the third layer is set to 240°C or more and 260°C or less.

[0015] The thickness of the polyethylene film is preferably 10 μm to 160 μm, more preferably 20 μm to 150 μm, and even more preferably 30 μm to 130 μm. The thickness of the polyethylene film can be set appropriately depending on the application. For example, when used as a sealant film for stick pouches, the thickness of the polyethylene film is preferably 10 μm to 60 μm, and more preferably 20 μm to 40 μm. When used as a sealant film for refill pouches, the thickness of the polyethylene film is preferably 80 μm to 160 μm, and more preferably 100 μm to 130 μm. In this specification, the thickness of the polyethylene film and each layer is the average value of 10 thicknesses measured based on scanning electron microscope (SEM) images obtained by observing a cross-section perpendicular to the film surface.

[0016] [Second layer] The second layer contains mechanically recycled polyethylene. In addition to mechanically recycled polyethylene, the second layer may further contain at least one selected from the group consisting of chemically recycled polyethylene and virgin polyethylene. Let's explain the components contained in the second layer.

[0017] [Mechanically recycled polyethylene] Recycled polyethylene is polyethylene obtained by recycling resin products containing polyethylene, and includes mechanically recycled polyethylene and chemically recycled polyethylene. Mechanical recycling generally involves collecting used resin products, crushing, washing, and separating foreign matter to remove surface dirt and foreign matter, then drying them under high temperature and reduced pressure for a certain period to disperse contaminants remaining inside the resin product for decontamination, further removing internal dirt, and returning the product to resin. In this specification, polyethylene obtained by mechanical recycling is referred to as mechanically recycled polyethylene. On the other hand, chemical recycling generally involves collecting used resin products, crushing, washing, separating foreign matter, etc., to remove dirt and foreign matter from the surface of the resin products, then forming them into flakes or pellets, decomposing them to the monomer level through depolymerization, etc., and then repolymerizing the decomposed products back into resin. In this specification, polyethylene obtained by chemical recycling is referred to as chemically recycled polyethylene.

[0018] The second layer contains mechanically recycled polyethylene as recycled polyethylene. In addition, the second layer may further contain chemically recycled polyethylene. That is, the second layer may contain both mechanically recycled polyethylene and chemically recycled polyethylene. However, from the viewpoint of reducing manufacturing costs, it is preferable that the second layer contains only mechanically recycled polyethylene (and not chemically recycled polyethylene).

[0019] Mechanically recycled polyethylene typically contains various impurities in addition to polyethylene. Therefore, conventionally, using mechanically recycled polyethylene as a raw material for film sometimes resulted in the film's transparency and appearance being compromised due to the inclusion of these impurities. Even if the second layer of the polyethylene film according to this disclosure contains mechanically recycled polyethylene, the proportion of foreign matter and the haze value remain below a certain level, as described later, resulting in excellent transparency and appearance. In other words, the disadvantages of using mechanically recycled polyethylene can be overcome.

[0020] [Virgin Polyethylene] Virgin polyethylene is polyethylene that has not been recycled. The second layer may also contain virgin polyethylene in addition to mechanically recycled polyethylene. This makes it easier to improve the transparency of the polyethylene film while reducing the environmental impact.

[0021] In the second layer, the recycled polyethylene content is preferably 1% by mass or more and 85% by mass or less, and more preferably 5% by mass or more and 50% by mass or less. If the recycled polyethylene contained in the second layer is only mechanically recycled polyethylene, the recycled polyethylene content refers to the content of mechanically recycled polyethylene. If the recycled polyethylene contained in the second layer is both mechanically recycled polyethylene and chemically recycled polyethylene, the recycled polyethylene content refers to the total content of mechanically recycled polyethylene and chemically recycled polyethylene. Furthermore, in the second layer, the content of virgin polyethylene is preferably 15% by mass or more and 99% by mass or less, and more preferably 50% by mass or more and 95% by mass or less. If the proportion of recycled polyethylene and virgin polyethylene is within the above range, it becomes easier to improve the transparency of polyethylene film while reducing the environmental impact.

[0022] The type of polyethylene used in mechanically recycled polyethylene, chemically recycled polyethylene, and virgin polyethylene can be appropriately selected from high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and ultra-low-density polyethylene, depending on differences in density and branching.

[0023] The density of high-density polyethylene is preferably 0.945 g / cm³. 3 It is extremely high. The upper limit of density for high-density polyethylene is, for example, 0.965 g / cm³. 3 That is the case. The density of medium-density polyethylene is preferably 0.925 g / cm³. 3 Super 0.945g / cm 3 The following applies: The density of low-density polyethylene is preferably 0.900 g / cm³. 3 Super 0.925g / cm 3 The following applies: The density of linear low-density polyethylene is preferably from 0.900 g / cm 3 to less than 0.925 g / cm 3 as follows. The density of ultra-low density polyethylene is preferably 0.900 g / cm 3 or less. The lower limit of the density of ultra-low density polyethylene is, for example, 0.860 g / cm 3 or the like. The density of polyethylene is measured in accordance with JIS K7112;1999, Method D (density gradient column method, 23°C).

[0024] From the viewpoints of film-forming property and processability, the melt flow rate (MFR) of polyethylene is preferably 0.1 g / 10 min or more, more preferably 0.2 g / 10 min or more, still more preferably 0.3 g / 10 min or more, and particularly preferably 0.5 g / 10 min or more. From the viewpoints of film-forming property and processability, the MFR of polyethylene is preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, still more preferably 10 g / 10 min or less, and particularly preferably 5 g / 10 min or less. In this specification, the MFR of polyethylene is measured by Method A under the conditions of a temperature of 190°C and a load of 2.16 kg in accordance with JIS K7210-1:2014.

[0025] [Resin impurities] The second layer contains a resin other than polyethylene as long as the characteristics of the polyethylene film according to the present disclosure are not impaired. In this specification, a resin other than polyethylene among the resins contained in the polyethylene film is referred to as a "resin impurity". Specific examples of resin impurities include polypropylene, polyurethane, polyamide (e.g., nylon 6, nylon 6,6 or polymetaxylene adipamide), polyester (e.g., polyethylene terephthalate or polyethylene naphthalate), ethylene-vinyl alcohol copolymer, acid-modified polyolefin, polystyrene, polyvinyl alcohol, and acrylic resin. That is, the polyethylene film according to the present disclosure may contain at least one resin impurity selected from the group consisting of these resins. Resin impurities may be present in the first layer, which will be described later. Furthermore, resin impurities may also be present in the third layer, which will be described later.

[0026] In the polyethylene film according to this disclosure, the content of resin impurities is 1.5% by mass or less, preferably 1% by mass or less, more preferably 0.8% by mass or less, and even more preferably 0.5% by mass or less, based on the total amount of polyethylene film. Keeping the resin impurity content below a certain level improves the heat-sealability of the polyethylene film. That is, it can be suitably used as a sealant film. While a low percentage of resin impurities is preferable, a practical percentage is 0.01% by mass or more, a more practical percentage is 0.05% by mass or more, and an even more practical percentage is 0.1% by mass or more.

[0027] The types and proportions of resin impurities contained in the polyethylene film according to this disclosure are identified and measured by FT-IR (Fourier transform infrared spectroscopy). Specifically, they are identified and measured by the method described in the examples below.

[0028] The thickness of the second layer varies depending on the layer structure of the polyethylene film. When the polyethylene film consists of two layers, a first layer and a second layer, the thickness of the second layer is preferably 30% or more, more preferably 40% or more, even more preferably 50% or more, and also preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less, relative to the thickness of the polyethylene film. When the polyethylene film consists of three layers, a first layer, a second layer, and a third layer, the thickness of the second layer is preferably 10% or more, more preferably 20% or more, even more preferably 30% or more, and also preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less, relative to the thickness of the polyethylene film. A polyethylene film having a second layer with a thickness greater than or equal to the lower limit above exhibits, for example, excellent strength. A polyethylene film having a second layer with a thickness less than or equal to the upper limit above exhibits, for example, excellent processability.

[0029] [1st layer] The first layer includes at least one material selected from the group consisting of virgin polyethylene and mechanically recycled polyethylene. In addition, the first layer may further include chemically recycled polyethylene in addition to at least one material selected from the group consisting of virgin polyethylene and mechanically recycled polyethylene.

[0030] In the first layer, the content of recycled polyethylene is preferably 1% by mass or more and 85% by mass or less, and more preferably 5% by mass or more and 50% by mass or less. If the recycled polyethylene contained in the first layer is only mechanically recycled polyethylene, the recycled polyethylene content refers to the content of mechanically recycled polyethylene. If the recycled polyethylene contained in the first layer is only chemically recycled polyethylene, the recycled polyethylene content refers to the content of chemically recycled polyethylene. If the recycled polyethylene contained in the first layer is both mechanically recycled polyethylene and chemically recycled polyethylene, the recycled polyethylene content refers to the total content of mechanically recycled polyethylene and chemically recycled polyethylene. Furthermore, in the first layer, the content of virgin polyethylene is preferably 15% by mass or more and 99% by mass or less, and more preferably 50% by mass or more and 95% by mass or less. If the proportion of recycled polyethylene and virgin polyethylene is within the above range, it becomes easier to improve the transparency of polyethylene film while reducing the environmental impact.

[0031] It is preferable that the proportion of mechanically recycled polyethylene in the first layer is smaller than the proportion of mechanically recycled polyethylene in the second layer. By reducing the proportion of mechanically recycled polyethylene in the first layer, which constitutes one side of the polyethylene film, the hygiene of the polyethylene film can be improved.

[0032] The characteristics of the virgin polyethylene, mechanically recycled polyethylene, and chemically recycled polyethylene contained in the first layer are the same as those of the virgin polyethylene, mechanically recycled polyethylene, and chemically recycled polyethylene contained in the second layer, so they are omitted from this description.

[0033] The thickness of the first layer is preferably 10% or more, more preferably 15% or more, even more preferably 20% or more, also preferably 70% or less, more preferably 60% or less, even more preferably 50% or less, and even more preferably 40% or less, relative to the thickness of the polyethylene film. A polyethylene film having a first layer with a thickness equal to or greater than the lower limit above has, for example, excellent strength. A polyethylene film having a first layer with a thickness equal to or less than the upper limit above has, for example, excellent processability.

[0034] The thickness of the first layer is preferably less than or equal to the thickness of the second layer. The ratio of the thickness of the first layer to the second layer is preferably 1:8 to 1:1, and more preferably 1:5 to 1:1. A polyethylene film in which the first and second layers satisfy the above relationship is, for example, more likely to achieve a reduction in environmental impact.

[0035] [Third layer] The third layer includes, for example, at least one selected from the group consisting of virgin polyethylene and mechanically recycled polyethylene. In addition, the third layer may further include chemically recycled polyethylene in addition to at least one selected from the group consisting of virgin polyethylene and mechanically recycled polyethylene.

[0036] In the third layer, the recycled polyethylene content is preferably 1% by mass or more and 85% by mass or less, and more preferably 5% by mass or more and 50% by mass or less. If the recycled polyethylene contained in the third layer is only mechanically recycled polyethylene, the recycled polyethylene content refers to the content of mechanically recycled polyethylene. If the recycled polyethylene contained in the third layer is only chemically recycled polyethylene, the recycled polyethylene content refers to the content of chemically recycled polyethylene. If the recycled polyethylene contained in the third layer is both mechanically recycled polyethylene and chemically recycled polyethylene, the recycled polyethylene content refers to the total content of mechanically recycled polyethylene and chemically recycled polyethylene. Furthermore, in the third layer, the content of virgin polyethylene is preferably 15% by mass or more and 99% by mass or less, and more preferably 50% by mass or more and 95% by mass or less. If the proportion of recycled polyethylene and virgin polyethylene is within the above range, it becomes easier to improve the transparency of polyethylene film while reducing the environmental impact.

[0037] The proportion of mechanically recycled polyethylene in the third layer is preferably smaller than the proportion of mechanically recycled polyethylene in the second layer. By reducing the proportion of mechanically recycled polyethylene in the third layer, which constitutes the other side of the polyethylene film, the hygiene of the polyethylene film can be improved.

[0038] The characteristics of the virgin polyethylene, mechanically recycled polyethylene, and chemically recycled polyethylene contained in the third layer are the same as those of the virgin polyethylene, mechanically recycled polyethylene, and chemically recycled polyethylene contained in the second layer, so they are omitted from this description.

[0039] The thickness of the third layer is preferably 10% or more, more preferably 15% or more, even more preferably 20% or more, and also preferably 60% or less, more preferably 50% or less, and even more preferably 40% or less, relative to the thickness of the polyethylene film. A polyethylene film having a third layer with a thickness greater than or equal to the lower limit above exhibits, for example, excellent strength. A polyethylene film having a third layer with a thickness less than or equal to the upper limit above exhibits, for example, excellent processability.

[0040] The thickness of the third layer is preferably less than or equal to the thickness of the second layer. The ratio of the thickness of the third layer to the second layer is preferably 1:8 to 1:1, and more preferably 1:5 to 1:1. A polyethylene film in which the second and third layers satisfy the above relationship is, for example, more likely to achieve a reduction in environmental impact.

[0041] In the polyethylene film according to this disclosure, the polyethylene content is preferably more than 50% by mass, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more. Such a polyethylene film has excellent recyclability, for example. The polyethylene content refers to the ratio of the mass of polyethylene (mechanically recycled polyethylene, chemically recycled polyethylene, and virgin polyethylene) to the total mass of the materials constituting the polyethylene film.

[0042] The recycled polyethylene content is preferably 1% by mass or more and 85% by mass or less, and more preferably 5% by mass or more and 50% by mass or less, relative to the total amount of polyethylene film. If the recycled polyethylene contained in the polyethylene film is only mechanically recycled polyethylene, the recycled polyethylene content refers to the content of mechanically recycled polyethylene. If the recycled polyethylene contained in the polyethylene film is both mechanically recycled polyethylene and chemically recycled polyethylene, the recycled polyethylene content refers to the total content of mechanically recycled polyethylene and chemically recycled polyethylene. Furthermore, the virgin polyethylene content is preferably 15% by mass or more and 99% by mass or less, and more preferably 50% by mass or more and 95% by mass or less, based on the total amount of polyethylene film. If the proportion of recycled polyethylene and virgin polyethylene in the total amount of polyethylene film is within the above range, it becomes easier to improve the transparency of the polyethylene film while reducing the environmental impact.

[0043] [Additives] The polyethylene film according to this disclosure may contain various additives, to the extent that they do not impair the properties of the polyethylene film. Examples of additives include antioxidants, slip agents, plasticizers, ultraviolet stabilizers, color inhibitors, matting agents, deodorants, flame retardants, weather-resistant agents, antistatic agents, yarn friction reducers, mold release agents, ion exchange agents, antiblocking agents, and coloring pigments. In particular, it is preferable to contain at least one selected from the group consisting of antioxidants and slip agents. The additive may be contained in any of the first, second, and third layers. For example, one of the first, second, and third layers may contain the additive, two of the first, second, and third layers may contain the additive, or all three layers may contain the additive.

[0044] [Antioxidant] Antioxidants include phenol-based, amine-based, sulfur-based, and phosphorus-based antioxidants. Examples of phenolic antioxidants include 2,6-di-t-butyl-p-cresol (BHT), 2,2'-methylenebis(4-methyl-6-t-butylphenol), triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenylpropionate), and 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester. Examples of amine-based antioxidants include octyldiphenylamine, Nn-butyl-p-aminophenol, N,N-diisopropyl-p-phenylenediamine, n-butylamine, triethylamine, and diethylaminomethyl methacrylate. Examples of sulfur-based antioxidants include dilauryl-3,3'-thiodipropionate (DLTDP) and distearyl-3,3'-thiodipropionate (DSTDP). Examples of phosphorus-based antioxidants include triphenyl phosphite (TTP) and triisodecyl phosphite (TDP).

[0045] It is preferable that the polyethylene film contains a phenolic antioxidant as an antioxidant. This allows the phenolic antioxidant to capture radicals and stop the radical chain reaction even if radicals are generated in the polyethylene film. It is also preferable for the polyethylene film to contain a phosphorus-based antioxidant as an antioxidant. This allows the phosphorus-based antioxidant to decompose peroxides, which are the source of radical generation, thereby suppressing the generation of radicals. It is preferable that the polyethylene film contains both a phenolic antioxidant and a phosphorus-based antioxidant. The synergistic effect of the phenolic and phosphorus-based antioxidants effectively prevents oxidation of polyethylene by radicals.

[0046] In the polyethylene film, the antioxidant content in each of the first, second, and third layers is preferably 50 ppm to 500 ppm, more preferably 150 ppm to 400 ppm, and even more preferably 200 ppm to 350 ppm. Generally, when polyethylene with added antioxidants is repeatedly processed through recycling, the antioxidants are consumed, and the antioxidant content decreases. Therefore, in conventional technology, films using recycled polyethylene as the resin sometimes exhibited inferior quality compared to films using only virgin polyethylene as the resin. In the polyethylene film according to this disclosure, quality deterioration can be suppressed by further adding antioxidants to maintain the antioxidant content within a certain range. Furthermore, the proportion of foreign matter can be reduced.

[0047] [Slip agent] Examples of slip agents include amide lubricants, fatty acid esters such as glycerin fatty acid esters, hydrocarbon waxes, higher fatty acid waxes, metal soaps, hydrophilic silicones, silicone-modified (meth)acrylic resins, silicone-modified epoxy resins, silicone-modified polyethers, silicone-modified polyesters, block-type silicone (meth)acrylic copolymers, polyglycerol-modified silicones, and paraffins.

[0048] Among lubricants, amide-based lubricants are preferred. Examples of amide-based lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides.

[0049] Examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Examples of substituted amides include N-oleyl palmitate amide, N-stearyl stearate amide, N-stearyl oleate amide, N-oleyl stearate amide, and N-stearyl erucate amide. An example of a methylolamide is methylol stearate. Examples of saturated fatty acid bisamides include methylenebisstearate, ethylenebiscaprate, ethylenebislaurate, ethylenebisstearate, ethylenebishydroxystearate, ethylenebisbehenamide, hexamethylenebisstearate, hexamethylenebisbehenamide, hexamethylenehydroxystearate, N,N'-distearyladipamide, and N,N'-distearylsebacinamide. Examples of unsaturated fatty acid bisamides include ethylenebisoleamide, ethylenebiserucamide, hexamethylenebisoleamide, N,N'-dioleyladipamide, and N,N'-dioleylsebacinamide. An example of a fatty acid ester amide is stearamidoethyl stearate. Examples of aromatic bisamides include m-xylylenebisstearate, m-xylylenebishydroxystearate, and N,N'-distearyl isophthalamide.

[0050] Among slip agents, erucic acid amide is preferred. One or more types of slip agents can be used.

[0051] To improve the dispersibility of the slip agent in the polyethylene film according to this disclosure, a masterbatch containing the slip agent and polyethylene may be used. The content of the slip agent in the masterbatch is preferably 1% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 20% by mass or less, and even more preferably 3% by mass or more and 10% by mass or less. Specific examples of polyethylene can be found as described above. The preferred physical properties (density, melt flow rate, etc.) that the polyethylene satisfies are also as described above.

[0052] In the polyethylene film, the slip agent content in each of the first, second, and third layers may be, for example, 0.01% to 3% by mass, or 0.03% to 1% by mass. This improves the processability of the polyethylene film.

[0053] Next, we will describe the laminate and packaging bag using polyethylene film according to this disclosure.

[0054] [Laminated structure] A laminate can be obtained by laminating the polyethylene film according to this disclosure onto the other side of the base film (the side not composed of the first layer). That is, the laminate according to this disclosure comprises a base film and a polyethylene film. It is preferable that the first layer of polyethylene film constitutes one side of the laminate. This allows the innermost surface of the packaging bag to be made of the first layer, which has a relatively low content of mechanically recycled polyethylene, when the laminate is applied to a packaging bag, resulting in a packaging bag with superior hygiene. The base film may constitute the other surface of the laminate.

[0055] As the base film, any resin film or sheet can be used depending on the application of the laminate. For example, when applying the laminate to a refill pouch for sealing refillable shampoo or conditioner, the base film is preferably excellent in mechanical strength such as tensile strength, flexural strength, and impact strength, as well as excellent printability. For example, as the base film, polyester films such as nylon film, polyethylene terephthalate film, or polybutylene terephthalate, polyolefin films such as polypropylene film, or polyethylene film can be suitably used. These films may be unoriented films, uniaxially oriented films, or biaxially oriented films. Alternatively, synthetic paper can also be used as the base film. These may be used individually or in combination.

[0056] The base film and polyethylene film can be bonded using a solvent-based adhesive via a dry lamination method, or using a solvent-free adhesive via a non-solvent lamination method. This provides excellent adhesive strength and tear resistance. Two-component polyurethane adhesives are one example of adhesives that can be used.

[0057] Alternatively, the parts can be bonded together via an adhesive layer using an extrusion lamination method (the so-called sandwich lamination method). In this case, the adhesive layer can be made of polyolefin-based heat-adhesive resins (e.g., LDPE), as well as ethylene-methacrylic acid copolymers, ethylene-acrylic acid copolymers, ionomers, etc., individually, or resins blended with adhesion-enhancing agents such as hard resins.

[0058] An example of a laminate formed by bonding a polyethylene film and a base film via an adhesive layer is the laminate 7 shown in Figures 3 and 4. The laminate 7 shown in Figure 3 comprises a first layer 1, a second layer 2, an adhesive layer 5, and a base film 6 in that order. The laminate 7 shown in Figure 4 comprises a first layer 1, a second layer 2, a third layer 3, an adhesive layer 5, and a base film 6 in that order. The laminate 7 shown in Figures 3 and 4 is one embodiment of the laminate according to the present disclosure.

[0059] The laminate according to this disclosure may have an intermediate layer between the base film and the polyethylene film. Examples of the intermediate layer include a barrier layer, a light-shielding layer, and a strength-enhancing layer. As a barrier layer, metal foils such as aluminum foil can be used, as well as vapor-deposited films in which metals such as aluminum or inorganic oxides such as aluminum oxide or silicon oxide are vapor-deposited onto a base film such as biaxially oriented polyethylene terephthalate film, polyacrylonitrile film, ethylene-vinyl alcohol copolymer film, etc.

[0060] The base film and the intermediate layer, and the intermediate layer and the polyethylene film, can be laminated using methods such as dry lamination, extrusion lamination, or extrusion coating, similar to the bonding of the base film and the polyethylene film described above.

[0061] In either case, the adhesive strength between layers can be increased by pre-applying an anchor coating agent to the laminated surface or by performing pre-treatment such as corona treatment.

[0062] A typical example of a laminate according to this disclosure is a laminate consisting of the following layer configuration. The following laminate is a laminate produced by dry lamination or non-solvent lamination, and each layer is bonded together with an adhesive. Alternatively, the following laminate may be laminated by extrusion lamination with an adhesive layer in between. The values ​​in parentheses indicate the thickness of each layer. • Polyethylene terephthalate film (12 μm) / Polyethylene film (10-160 μm) • Biaxially oriented nylon film (15 μm) / Polyethylene film (10-160 μm) • Transparent vapor-deposited polyethylene terephthalate film (12 μm) / Polyethylene film (10-160 μm) • Polyethylene terephthalate film (12 μm) / Biaxially oriented nylon film (15 μm) / Polyethylene film (10-160 μm) • Polyethylene terephthalate film (12μm) / Transparent vapor-deposited polyethylene terephthalate film (12μm) / Polyethylene film (10~160μm) • OPP film (20μm) / Polyethylene film (10~160μm) • Stretched polyethylene film (25 μm) / Polyethylene film (10-160 μm)

[0063] From the viewpoint of providing a laminate with excellent recyclability, the polyethylene content in the laminate according to this disclosure is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, relative to the entire laminate. The upper limit for the polyethylene content in the laminate is 100% by mass, but 99% by mass or less is practical.

[0064] [Packaging bag] The packaging bag according to this disclosure comprises the laminate according to this disclosure. By using the laminate according to this disclosure, a packaging bag with reduced environmental impact can be manufactured. The packaging bag may be a refill pouch, particularly a standing pouch, that contains fluid contents such as liquids or powders that are transferred into containers such as bottles.

[0065] Examples of packaging bags include various types such as standing pouch type, side seal type, two-sided seal type, three-sided seal type, four-sided seal type, envelope seal type, gusset seal type (pillow seal type), pleated seal type, flat bottom seal type, square bottom seal type, and gusset type.

[0066] The packaging bag could be, for example, a small bag or a resealable bag. The packaging bag may be, for example, a flexible packaging bag.

[0067] The packaging bag may have an easy-open line to enhance its tear resistance. The packaging bag may have a notch that serves as a starting point for tearing.

[0068] The packaging bag may have a sealed portion where the laminated sealant films are joined together. Methods for forming a seal include heat sealing, which involves melting the sealant film of a laminate by heating or other means and fusing the sealant films together. Specifically, these include bar seals, rotary roll seals, belt seals, impulse seals, high-frequency seals, and ultrasonic seals.

[0069] Examples of contents that can be placed inside the packaging bag include liquids, solids, powders, and gels. The contents may be food or beverages or non-food items. After placing the contents inside the packaging bag, the bag can be sealed by heat-sealing the opening. Examples of food and beverages include liquid or viscous seasonings (sauces, soy sauce, dressings, cooking oils, mayonnaise, ketchup, syrups, cooking alcoholic beverages), fruit juices, spices, liquid beverages, jelly-like beverages, liquid soups, powdered soups, instant foods, and creams. Non-food items include shampoo, conditioner, rinse, hand soap, body soap, air fresheners, deodorizers, insect repellents, fabric softeners, detergents, and creams.

[0070] In one embodiment, a packaging bag according to the present disclosure can be produced by folding the laminate according to the present disclosure in half so that the base film is on the outside and the polyethylene film is on the inside, overlapping the two halves, and heat-sealing the edges. In another embodiment, a packaging bag according to the present disclosure can be produced by preparing two laminates according to the present disclosure, overlapping them so that the polyethylene films face each other, and heat-sealing the edges. The entire packaging bag may be made of the laminate according to the present disclosure, or only a part of the packaging bag may be made of the laminate according to the present disclosure.

[0071] Hereinafter, several examples of embodiments of the packaging bags according to this disclosure will be described with reference to the drawings. Figure 5 is a front view showing a packaging bag 10 according to one embodiment. Figure 5 shows the packaging bag 10 before it is filled with contents (when it does not contain contents). The packaging bag 10 is a gusset-type pouch that is configured to stand upright. The packaging bag 10 includes an upper part 11, a lower part 12, and a side part 13, and has a substantially rectangular outline in the front view. The names "upper part," "lower part," and "side part," as well as terms such as "upper" and "lower," merely represent the relative position and orientation of the packaging bag 10 and its components based on the state in which the packaging bag 10 is standing upright with the gusset part facing downwards. The orientation of the packaging bag 10 during transport and use is not limited by the names and terms used herein.

[0072] The packaging bag 10 has a storage section 17 and a sealing section 19. The storage section 17 contains the contents. The sealing section 19 includes an inner edge 19x that defines the storage section 17. The sealing section 19 is formed by joining together the sealant films of the laminate that make up the packaging bag 10. In front views such as Figure 5, the sealing section 19 is hatched.

[0073] The storage section 17 may include a spout section 20. The spout section 20 is the part through which the contents pass when the contents are removed from the packaging bag 10. The width of the spout section 20 is narrower than the width of the other parts of the storage section 17. Therefore, the user can accurately determine the direction in which the contents are dispensed from the packaging bag 10 through the spout section 20.

[0074] The packaging bag 10 may have an easy-open line 26. The easy-open line 26 can be formed in the packaging bag 10, for example, to improve the tearability of the packaging bag 10. In a plan view of the packaging bag 10, the easy-open line 26 crosses the storage section 17. In the example shown in Figure 5, the easy-open line 26 crosses the spout section 20 in a plan view. As shown in Figure 5, a notch 28 adjacent to the easy-open line 26 may be formed on the outer edge of the packaging bag 10. Instead of a notch 28, a cut may be formed on the outer edge of the packaging bag 10.

[0075] The packaging bag 10 comprises a surface film 14 that constitutes the front surface, a back film 15 that constitutes the back surface, and a bottom film 16 that constitutes the bottom 12. The bottom film 16 is folded over at the folded portion 16f and positioned between the surface film 14 and the back film 15.

[0076] Either or both of the surface film 14 and the back film 15 are composed of a laminate according to the Disclosure. The bottom film 16 may also be composed of a laminate according to the Disclosure. The laminate includes an inner surface and an outer surface. The inner surface is the surface in contact with the contents. The outer surface is the surface located opposite the inner surface. The polyethylene film is located on the inner side with respect to the stretched substrate film.

[0077] The terms "front film," "back film," and "bottom film" are merely ways of defining each film according to its positional relationship, and the method of providing the film when manufacturing the packaging bag 10 is not limited by these terms. For example, the packaging bag 10 may be manufactured using a single film in which the front film 14, back film 15, and bottom film 16 are connected; it may be manufactured using a total of two films: a single film in which the front film 14 and bottom film 16 are connected and a single back film 15; or it may be manufactured using a total of three films: a single front film 14, a single back film 15, and a single bottom film 16.

[0078] As shown in Figure 5, the seal portion 19 includes a lower seal portion 12a, a side seal portion 13a, and a spout seal portion 20a. The lower seal portion 12a extends to the lower part 12. The side seal portion 13a extends along a pair of side portions 13. The spout seal portion 20a defines the spout portion 20. The distance between the inner edges of the spout seal portion 20a is smaller than the distance between the inner edges of the pair of side seal portions 13a. When the spout portion 20 is formed in a corner between the upper part 11 and the side portion 13 of the packaging bag 10, the spout seal portion 20a is connected to the side seal portion 13a.

[0079] In the packaging bag 10 when it does not contain any contents, the top 11 of the packaging bag 10 is an opening 11b, as shown in Figure 5. After the contents are placed in the packaging bag 10 through the opening 11b, the sealant film of the surface film 14 and the sealant film of the back film 15 are joined at the top 11, thereby forming an upper seal portion at the opening 11b. This seals the contents portion 17 from the outside of the packaging bag 10.

[0080] The side seal portion 13a, the spout seal portion 20a, and the upper seal portion are formed by joining the sealant film of the surface film 14 and the sealant film of the back film 15. The lower seal portion 12a includes the portion where the sealant film of the surface film 14 and the sealant film of the lower film 16 are joined, and the portion where the sealant film of the back film 15 and the sealant film of the lower film 16 are joined. As shown by the dotted line in Figure 5, a notch 13c may be formed in a part of the lower film 16. At the location of the notch 13c, the sealant film of the surface film 14 and the sealant film of the back film 15 may be joined.

[0081] Next, the layer structure of the lower film 16 will be described. The layer configuration of the lower film 16 is arbitrary, as long as it has an inner surface that can be bonded to the sealant film of the surface film 14 and the sealant film of the back film 15. For example, the laminate according to this disclosure may be used as the lower film 16, similar to the surface film 14 and the back film 15. Alternatively, a film with a different configuration from the laminate according to this disclosure may be used as the lower film 16.

[0082] The packaging bag 10 can be manufactured, for example, as follows: Prepare the laminate according to this disclosure. Cut the laminate in half to make two pieces, one of which will be the surface film 14 and the other the back film 15. Next, insert the folded lower film 16 between the surface film 14 and the back film 15. Then, heat seal the sealant films of each film together to form seal portions such as the lower seal portion 12a, the side seal portion 13a, and the spout seal portion 20a. Cut the films joined together by heat sealing into an appropriate shape. This will give you the packaging bag 10 shown in Figure 5.

[0083] Next, the contents are filled into the storage section 17 of the packaging bag 10. Then, the top section 11 is heat-sealed to form the top seal. In this way, a packaging bag 10 containing and sealed with contents is obtained.

[0084] In the above description of the embodiments, an example was shown in which the packaging bag 10 is a gusset-type pouch, but the specific configuration of the packaging bag 10 is not particularly limited.

[0085] For example, the packaging bag 10 does not have to have a lower film 16, as shown in Figures 6 and 7. In Figures 6 and 7, the lower seal portion 12a and the side seal portion 13a of the packaging bag 10 are formed by joining the sealant films of the laminated surface film 14 and back film 15, respectively. After the contents are placed in the packaging bag 10, the packaging bag 10 is sealed by joining the sealant film of the surface film 14 and the sealant film of the back film 15 at the opening 11b of the upper part 11. The packaging bag 10 shown in Figures 6 and 7 may have an easy-open line 26.

[0086] As shown in Figure 8, the packaging bag 10 may be a pillow pouch. The packaging bag 10 includes a gusset portion 18 formed by overlapping the edges of the laminates that make up the surface film 14 and the back film 15. The gusset portion 18 includes a gusset seal portion 18a where the sealant films of the laminates are joined together. The packaging bag 10 shown in Figure 8 may have an easy-open line 26. As shown in Figure 8, a notch 28 or an incision (not shown) may be formed on the outer edge of the gusset portion. [Examples]

[0087] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to the following examples.

[0088] The various raw materials used in the polyethylene films of Examples 1 to 16 and Comparative Examples 1 to 12 are as follows: Mechanical recycled polyethylene A Low-density polyethylene, product name: LCY02, manufactured by APK, density: 0.920~0.924 g / cm³ 3 Melt flow rate: 1.8~2.3g / 10 minutes Mechanical recycled polyethylene B Low-density polyethylene, repelled from manufacturing process losses such as selvage loss during film formation; density: 0.920~0.924 g / cm³ 3 Melt flow rate: 1.8~2.3g / 10 minutes Virgin polyethylene A Low-density polyethylene, product name: F224N, manufactured by Ube Maruzen Polyethylene Co., Ltd., density: 0.924 g / cm³ 3 Meltflow rate: 2.0g / 10 minutes Virgin polyethylene B Low-density polyethylene, product name: Sumikasen G201-F, manufactured by Sumitomo Chemical Co., Ltd., density: 0.919 g / cm³ 3 Meltflow rate: 2.0g / 10 minutes Virgin polyethylene C Linear low-density polyethylene, product name: Ultzex ​​2010L, manufactured by Prime Polymer Co., Ltd., density: 0.922 g / cm³ 3 Meltflow rate: 2.2g / 10 minutes Virgin Polyethylene D Linear low-density polyethylene, product name: Evolu SP2040F, manufactured by Prime Polymer Co., Ltd., density: 0.918 g / cm³ 3 Melt flow rate: 3.8g / 10 minutes • Slip agent-containing masterbatch A Virgin low-density polyethylene containing 2.0% by mass of erucamide, product name: M425, manufactured by Ube Maruzen Polyethylene Co., Ltd., density: 0.921 g / cm³ 3 Melt flow rate: 5.4g / 10 minutes • Slip agent-containing masterbatch B Virgin low-density polyethylene containing 4.0% by mass of erucic acid amide, product name: Sumikasen EMB-10, manufactured by Sumitomo Chemical Co., Ltd., density: 0.910 g / cm³ 3 Melt flow rate: 4.7g / 10 minutes • Antioxidant 2,6-di-t-butyl-p-cresol (BHT), a phenolic antioxidant, and triphenyl phosphite (TTP), a phosphorus-based antioxidant. Trade name: EAG-5. Manufactured by Prime Polymer Co., Ltd. Density: 0.920 g / cm³ 3 Melt flow rate: 4.9g / 10 minutes

[0089] [Example 1] A resin composition for forming the first layer was obtained by blending 97% by mass of virgin polyethylene A, 2% by mass of a slip agent-containing masterbatch A, and 1% by mass of an antioxidant, and then melt-kneading the mixture. A resin composition for forming the second layer was obtained by blending 50% by mass of mechanically recycled polyethylene A, 49% by mass of virgin polyethylene A, and 1% by mass of an antioxidant, and then melt-kneading the mixture. The polyethylene film of Example 1 was obtained by co-extruding the resin composition for forming the first layer and the resin composition for forming the second layer into a film using a T-die, such that the thickness of both the first and second layers was 15 μm.

[0090] [Examples 2 and 7 and Comparative Examples 1-5] Polyethylene films of Examples 2 and 7 and Comparative Examples 1 to 5 were obtained in the same manner as in Example 1, except that the formulations of the resin composition for forming the first layer and the resin composition for forming the second layer were changed as shown in Table 1.

[0091] [Examples 3-6 and 8, and Comparative Example 6] The polyethylene films of Examples 3-6 and 8 and Comparative Example 6 were obtained in the same manner as in Example 1, except that the formulations of the resin composition for forming the first layer and the resin composition for forming the second layer were changed as shown in Table 1, and the first and second layers were co-extruded so that both layers had a thickness of 60 μm.

[0092] [Example 9] A resin composition for forming the first layer was obtained by blending 97% by mass of virgin polyethylene A, 2% by mass of a slip agent-containing masterbatch A, and 1% by mass of an antioxidant, and then melt-kneading the mixture. A resin composition for forming the second layer was obtained by blending 50% by mass of mechanically recycled polyethylene A, 49% by mass of virgin polyethylene A, and 1% by mass of an antioxidant, and then melt-kneading the mixture. A resin composition for forming the third layer was obtained by blending 99% by mass of virgin polyethylene A and 1% by mass of an antioxidant, and then melt-kneading the mixture. The polyethylene film of Example 9 was obtained by co-extruding the resin composition for forming the first layer, the resin composition for forming the second layer, and the resin composition for forming the third layer into a film using a T-die, such that the first layer had a thickness of 7.5 μm, the second layer had a thickness of 15 μm, and the third layer had a thickness of 7.5 μm.

[0093] [Examples 10 and 15 and Comparative Examples 7-11] Polyethylene films for Examples 10 and 15 and Comparative Examples 7 to 11 were obtained in the same manner as in Example 9, except that the formulations of the resin composition for forming the first layer, the resin composition for forming the second layer, and the resin composition for forming the third layer were changed as shown in Tables 2 and 3.

[0094] [Examples 11-14 and 16, and Comparative Example 12] The polyethylene films of Examples 11-14 and 16 and Comparative Example 12 were obtained in the same manner as in Example 9, except that the formulations of the resin composition for forming the first layer, the resin composition for forming the second layer, and the resin composition for forming the third layer were changed as shown in Tables 2 and 3, and the films were co-extruded so that the thickness of the first layer was 30 μm, the thickness of the second layer was 60 μm, and the thickness of the third layer was 30 μm.

[0095] [Identification and quantification of resin impurities] For the polyethylene films of Examples 1 to 16 and Comparative Examples 1 to 12, the FT-IR (Fourier Transform Infrared Spectroscopy) spectra were measured using an FT-IR detector under the following measurement conditions. (Measurement conditions) • Equipment: Nicolet 6700 (manufactured by Thermo Fisher Scientific Co., Ltd.) ·Resolution: 4cm -1 • Total number of times: 64 ·Measurement method: transmission method • Wire grid polarizer: KRS-5 Wave number 2915cm -1 A peak originating from polyethylene was observed in the vicinity. Additionally, a wavenumber of 3300~cm was detected. -1 We checked whether or not peaks originating from resin impurities appeared in the vicinity. When peaks originating from resin impurities appeared, the type of resin impurity was identified by comparing the measurement results with a database. The percentage of resin impurities was also determined from the peak area. The results are shown in Tables 1-3. In Tables 1 and 3, "-" indicates that no resin impurities were detected during the measurement. If two or more types of resin impurities are detected, the resin impurity content is the sum of the content of each resin impurity.

[0096] [Measurement of heat seal strength] The heat seal strength of the polyethylene films of Examples 1 to 16 and Comparative Examples 1 to 12 was measured in accordance with JIS Z 1707:2019. Specifically, a laminate was first fabricated by dry lamination, using a urethane-based adhesive (RU-77T / H-7, manufactured by Rock Paint Co., Ltd.) to bond a 12 μm thick biaxially oriented polyethylene terephthalate film (E5100, manufactured by Toyobo Co., Ltd.) to each polyethylene film. Next, the two laminated polyethylene films are subjected to a pressure of 1 kgf / cm². 2 Under a load, the material was heat-sealed at 160°C for 1 second to form a seal. A section including the seal was cut out to a width of 15 mm and a length of 100 mm to prepare a test piece 60 for measuring the heat seal strength. As shown in Figure 9, the unsealed portions of the test piece 60 were each gripped with a gripper 61 of a Tensilon universal material testing machine (RTC-1530, manufactured by Orientec Co., Ltd.). The length of the seal portion 62 was set to 15 mm. Next, the grippers 61 were each pulled at a speed of 300 mm / min in opposite directions perpendicular to the surface direction of the seal portion 62 of the test piece 60, and the maximum value of the tensile stress was measured. Measurements were performed on five test pieces, and the average of the maximum values ​​of the tensile stress was defined as the heat seal strength. The distance S2 between the grippers 61 at the start of pulling was set to 50 mm. The results are shown in Tables 1-3.

[0097] [Quantitative determination of antioxidants] The polyethylene films of Examples 1-16 and Comparative Examples 1-12 were each dissolved in chloroform. The resin was reprecipitated using methanol as a poor solvent. The filtrate was collected and the solvent was removed by vacuum distillation. The concentrate was dissolved in a small amount of chloroform and acetonitrile, and the total volume was made up to 50 mL. The obtained solution was subjected to quantitative analysis by ultrafast high-resolution liquid chromatography (UPLC) under the following measurement conditions to determine the antioxidant content. The results are shown in Tables 1-3. (Measurement conditions) • Equipment: UPLC ACQUITY (manufactured by Waters Japan Co., Ltd.) • Column: BEH C18 (particle size: 1.7 μm, column size: 2.1 × 50 mm) • Solvent: Mixed solvent of acetonitrile and distilled water (gradient mode) ·Flow rate: 0.2mL / min Column temperature: 40°C • Detector: PDA (Photodiode Array) • Measurement wavelength range: 190~500nm • Sample injection volume: 1 μL

[0098] [Gel evaluation] For the polyethylene films of Examples 1-16 and Comparative Examples 1-12, the number of unmelted gel particles present in a 1 mm width and 10 mm length was counted using a transmission optical microscope (product name: DSX1000, manufactured by Olympus Corporation), and the number of unmelted gel particles was counted per 1 m 2 The gel generation rate per unit was calculated and evaluated. The evaluation criteria were as follows. The results are shown in Tables 1-3. (Evaluation Criteria) A: Gel generation rate is 0 units / m 2 More than 0.031 pieces / m 2 less than B: Gel generation rate is 0.031 particles / m 2 More than 0.038 pieces / m 2 less than C: Gel generation rate is 0.038 particles / m 2 That's all.

[0099] [Odor evaluation] The polyethylene films from Examples 1-16 and Comparative Examples 1-12 were each cut to 10cm x 10cm and packaged in aluminum bags. After being stored in a 40°C oven for one week, the odor inside the aluminum bags was checked. The evaluation criteria were as follows. The results are shown in Tables 1-3. (Evaluation Criteria) A: It has a faint polyethylene smell. B: It has a strong polyethylene smell. C: It has a very strong polyethylene smell.

[0100] [Table 1]

[0101] [Table 2]

[0102] [Table 3]

[0103] As is clear from Tables 1-3 above, the polyethylene films of Examples 1, 2, 7, 9, 10, and 15, and Comparative Examples 3-5 and 9-11, all have a thickness of 30 μm and contain mechanically recycled polyethylene. However, the polyethylene films of Examples 1, 2, 7, 9, 10, and 15, which have a resin impurity content of 1.5% by mass or less, have greater heat seal strength and superior heat sealability than the polyethylene films of Comparative Examples 3-5 and 9-11, which have a resin impurity content of more than 1.5% by mass. The heat seal strength of the polyethylene films of Examples 1, 2, 7, 9, 10, and 15 is equivalent to that of the polyethylene films of Comparative Examples 1, 2, 7, and 8, which have the same thickness but do not contain mechanically recycled polyethylene. This shows that the polyethylene films of Examples 1, 2, 7, 9, 10, and 15 have superior heat sealability even though they contain mechanically recycled polyethylene. Furthermore, the heat seal strength of the polyethylene films of Examples 3-6, 8, 11-14, and 16, which have a thickness of 120 μm, is equivalent to that of the polyethylene films of Comparative Examples 6 and 12, which have the same thickness but do not contain mechanically recycled polyethylene. This indicates that the polyethylene films of Examples 3-6, 8, 11-14, and 16 have excellent heat sealability even when they contain mechanically recycled polyethylene. [Explanation of symbols]

[0104] 1 1st layer 2 2nd layer 3 3rd layer 4. Polyethylene film 5 Adhesive layer 6. Base film 7 Laminate 10 packaging bags 11 Top 11b opening 12 Lower part 12a Lower seal section 13 Side 13a Side seal portion 13c Notch 14 Surface film 15 Backside film 16 Lower film 16f Turning point 17. Detention Unit 18 Gassho section 18a Joint seal section 19. Seal part 19x inner edge 20 Spout part 20a Dispensing outlet seal 26 Easy-open line 27 Notches 28 Notches 60 test specimens 61. Gripping tools 62 Seal part S2 Distance between gripping devices

Claims

1. A polyethylene film comprising a first layer and a second layer, The first layer constitutes one side of the polyethylene film, The first layer comprises at least one selected from the group consisting of virgin polyethylene and mechanically recycled polyethylene. The second layer comprises mechanically recycled polyethylene and resin impurities which are resins other than polyethylene. The resin impurity is at least one selected from the group consisting of polypropylene, polyurethane, polyamide, polyester, ethylene-vinyl alcohol copolymer, acid-modified polyolefin, polystyrene, polyvinyl alcohol, and acrylic resin. A polyethylene film in which the content of the aforementioned resin impurities is 1.5% by mass or less relative to the total amount of the polyethylene film.

2. The polyethylene film according to claim 1, wherein the second layer further comprises virgin polyethylene.

3. The polyethylene film according to claim 1 or 2, wherein the content of mechanically recycled polyethylene in the first layer is smaller than the content of mechanically recycled polyethylene in the second layer.

4. The above-mentioned first layer, the above-mentioned second layer, and the third layer are provided in this order. The polyethylene film according to claim 1 or 2, wherein the third layer comprises at least one selected from the group consisting of virgin polyethylene and mechanically recycled polyethylene.

5. The polyethylene film according to claim 1 or 2, wherein the content of the resin impurities is 0.01% by mass or more with respect to the total amount of the polyethylene film.

6. The polyethylene film according to claim 1 or 2, further containing at least one selected from the group consisting of phenolic antioxidants and phosphorus-based antioxidants as an antioxidant.

7. The polyethylene film according to claim 6, wherein the content ratio of the antioxidant is 50 ppm or more and 500 ppm or less with respect to the total amount of the polyethylene film.

8. The polyethylene film according to claim 1 or 2, wherein the recycled polyethylene content is 1% by mass or more and 50% by mass or less of the total amount of the polyethylene film.

9. A polyethylene film according to claim 1 or 2, which is a sealant film.

10. A laminate comprising a base film and the polyethylene film described in claim 1 or 2.

11. The laminate according to claim 10, wherein the polyethylene content is 80% by mass or more of the entire laminate.

12. A packaging bag comprising the laminate described in claim 10.

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