Polyethylene film, laminate and packaging bag

Abstract

To provide a polyethylene film which is excellent in heat sealability while containing mechanically recycled polyethylene, and a laminate and a packaging bag using the same.SOLUTION: A polyethylene film 1 of a single layer contains mechanically recycled polyethylene, and a resin impurity as a resin other than polyethylene, wherein the resin impurity is at least one selected from the group consisting of polypropylene, polyurethane, polyamide, polyester, an ethylene-vinyl alcohol copolymer, acid-modified polyolefin, polystyrene, polyvinyl alcohol and an acrylic resin, and a content of the resin impurity is 1.5 mass% or less with respect to the total amount of the polyethylene film.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In the manufacture of packaging materials for filling products such as medicines, cosmetics, and food, plastics, which are materials derived from fossil fuels, are mainly used from the viewpoints of ease of molding, cost, etc., and these plastic materials are produced from petroleum, a fossil resource. Plastic materials that are commonly used as materials for packaging containers include polyesters, polyolefins, polyamides, etc. In particular, polyolefins such as polyethylene are molded into films, sheets, bottles, etc., and are used in various applications such as packaging materials, and are used in large quantities around the world.

[0003] Therefore, efforts are being made to reduce the amount of fossil fuels used and to alleviate the environmental burden by recycling (reusing) polyethylene that has once been used 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 Summary of the Invention [Problem to be solved by the invention]

[0005] There are various types of recycling, including mechanical recycling, chemical recycling, and thermal recycling. Mechanical recycling involves crushing, winnowing, washing, and gravity separating collected waste plastic before repelletizing it. Chemical recycling involves breaking down collected waste plastic down to the molecular level using heat and pressure, repolymerizing it to repelletize it, or turning it into gas, oil, blast furnace reducing agent, or coke oven chemical raw material. Thermal recycling involves recovering and utilizing the thermal energy generated during the incineration of waste. Chemical recycling produces resins with high purity, but consumes a large amount of energy and is expensive. Thermal recycling is a technology for converting used resin products into other energy sources, and is not a method for reusing resins. Therefore, the current situation is that it is desirable to use mechanically recycled resins, which are inexpensive and have a low environmental impact. However, mechanically recycled polyethylene may be contaminated with impurities derived from the packaging material, which is the raw material. Therefore, when mechanically recycled polyethylene is used as a heat seal layer for packaging materials, the heat sealability may be impaired.

[0006] Therefore, an object of the present disclosure is to provide a polyethylene film having excellent heat sealability even if it contains mechanically recycled polyethylene. Another object of the present disclosure is to provide a laminate and a packaging bag using the polyethylene film. [Means for solving the problem]

[0007] The present disclosure is solved by the following embodiments. <1> A single-layer polyethylene film containing mechanically recycled polyethylene and resin impurities that 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, wherein the content of the resin impurities is 1.5 mass% or less based on the total amount of the polyethylene film. <2> Further containing virgin polyethylene, which is polyethylene that has not been recycled; <1> The polyethylene film according to claim 1. <3> The content of the resin impurities is 0.01% by mass or more based on the total amount of the polyethylene film. <1> or <2> The polyethylene film according to claim 1. <4> The antioxidant further contains at least one selected from the group consisting of phenol-based antioxidants and phosphorus-based antioxidants. <1> ~ <3> 13. The polyethylene film according to claim 12 . <5> The content of the antioxidant is 50 ppm or more and 500 ppm or less based on the total amount of the polyethylene film. <4> The polyethylene film according to claim 1. <6> The content of recycled polyethylene is 1% by mass or more and 50% by mass or less based on the total amount of the polyethylene film. <1> ~ <5> 13. The polyethylene film according to claim 12 . <7> It is a sealant film. <1> ~ <6> 13. The polyethylene film according to claim 12 . <8> A base film; <1> ~ <7> and a polyethylene film according to any one of the above. <9> The polyethylene content is 90% by mass or more based on the entire laminate. <8> The laminate according to claim 1. <10> <8> or <9> A packaging bag comprising the laminate according to claim 1. <11> Accommodates non-food and beverage items; <10> The packaging bag described in. Effect of the Invention

[0008] The present disclosure can provide a polyethylene film having excellent heat sealability even when it contains mechanically recycled polyethylene. The present disclosure also provides a laminate and a packaging bag using the polyethylene film. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one embodiment of a polyethylene film according to the present disclosure. [Diagram 2] 1 is a schematic cross-sectional view showing one embodiment of a laminate according to the present disclosure. [Diagram 3] 1 is a front view showing one embodiment of a packaging bag according to the present disclosure. [Figure 4] 1 is a front view showing one embodiment of a packaging bag according to the present disclosure. [Diagram 5] 1 is a front view showing one embodiment of a packaging bag according to the present disclosure. [Figure 6] 1 is a front view showing one embodiment of a packaging bag according to the present disclosure. [Figure 7] FIG. 2 is a schematic diagram showing a method for measuring heat seal strength. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the following embodiments. In addition, the components in the following embodiments include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the components disclosed in the following embodiments can be appropriately combined.

[0011] [Polyethylene film] A polyethylene film according to the present disclosure will be described. The polyethylene film according to the present disclosure contains mechanically recycled polyethylene. FIG. 1 is a schematic cross-sectional view showing one embodiment of the polyethylene film according to the present disclosure. As shown in FIG. 1, the polyethylene film 1 is composed of a single layer of polyethylene film. The polyethylene film according to the present disclosure may further contain, in addition to the mechanically recycled polyethylene, at least one selected from the group consisting of chemically recycled polyethylene and virgin polyethylene. The components contained in the polyethylene film according to the present disclosure will be described.

[0012] [Mechanically recycled polyethylene] Recycled polyethylene is polyethylene obtained by recycling resin products containing polyethylene, and examples of recycled polyethylene include mechanically recycled polyethylene and chemically recycled polyethylene. Mechanical recycling is generally a method in which used resin products are collected, crushed, washed, and separated for foreign matter to remove dirt and foreign matter from the surface of the resin product, and then the resin product is dried for a certain period of time under high temperature and reduced pressure to diffuse and decontaminate contaminants remaining inside the resin product, further removing internal dirt, and then returned to resin. In this specification, polyethylene obtained by mechanical recycling is called mechanically recycled polyethylene. On the other hand, chemical recycling is a method in which used resin products are generally collected, crushed, washed, separated for foreign matter, etc. to remove dirt and foreign matter from the surface of the resin product, then formed into flakes or pellets, decomposed to the monomer level by depolymerization or the like, and the decomposed material is polymerized again to return it to resin. In this specification, polyethylene obtained by chemical recycling is referred to as chemically recycled polyethylene.

[0013] The polyethylene film according to the present disclosure contains mechanically recycled polyethylene as the recycled polyethylene. In addition to this, the polyethylene film according to the present disclosure may further contain chemically recycled polyethylene. That is, the polyethylene film according to the present disclosure may contain both mechanically recycled polyethylene and chemically recycled polyethylene. However, from the viewpoint of reducing production costs, it is preferable that the recycled polyethylene contained in the polyethylene film according to the present disclosure is only mechanically recycled polyethylene (no chemically recycled polyethylene).

[0014] Mechanically recycled polyethylene generally contains various impurities other than polyethylene. Therefore, when mechanically recycled polyethylene was used as a raw material for film, the transparency and appearance of the film were often impaired due to the inclusion of impurities. The polyethylene film according to the present disclosure, even if it contains mechanically recycled polyethylene, has excellent transparency and appearance because the content of foreign matter and the haze value are below a certain level as described below. In other words, the disadvantages of using mechanically recycled polyethylene can be overcome.

[0015] [Virgin polyethylene] Virgin polyethylene is polyethylene that has not been recycled. The polyethylene film according to the present disclosure further contains virgin polyethylene in addition to mechanically recycled polyethylene, which makes it easier to improve the transparency of the polyethylene film while reducing the environmental impact.

[0016] In the polyethylene film according to the present disclosure, the content of recycled polyethylene is preferably from 1% by mass to 85% by mass, and more preferably from 5% by mass to 50% by mass, based on the total amount of the polyethylene film. Furthermore, in the polyethylene film according to the present disclosure, the content of virgin polyethylene is preferably from 15% by mass to 99% by mass, and more preferably from 50% by mass to 95% by mass. When the recycled polyethylene content and the virgin polyethylene content are within the above ranges, the transparency of the polyethylene film can be easily improved while reducing the environmental impact.

[0017] The type of polyethylene 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 very low density polyethylene, etc., depending on differences in density and branching.

[0018] The density of the high density polyethylene is preferably 0.945 g / cm 3 The upper limit of the density of high density polyethylene is, for example, 0.965 g / cm 3 It is. The density of the medium density polyethylene is preferably 0.925 g / cm 3 Super 0.945g / cm 3 The following is the result. The density of the low density polyethylene is preferably 0.900 g / cm 3 Super 0.925g / cm 3 The following is the result. The density of the linear low density polyethylene is preferably 0.900 g / cm 3 Super 0.925g / cm 3 The following is the result. The density of the very low density polyethylene is preferably 0.900 g / cm 3 The lower limit of the density of the very low density polyethylene is, for example, 0.860 g / cm 3 It is. The density of polyethylene is measured in accordance with JIS K7112;1999, Method D (density gradient tube method, 23°C).

[0019] From the viewpoint of film-forming and processability, the melt flow rate (MFR) of the polyethylene is preferably 0.1 g / 10 min or more, more preferably 0.2 g / 10 min or more, even more preferably 0.3 g / 10 min or more, and particularly preferably 0.5 g / 10 min or more. From the viewpoint of film-forming and processability, the MFR of the polyethylene is preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, even more preferably 10 g / 10 min or less, and particularly preferably 5 g / 10 min or less. In this specification, the MFR of the polyethylene is measured by the A method in accordance with JIS K7210-1:2014 under the conditions of a temperature of 190 ° C. and a load of 2.16 kg.

[0020] [Resin impurities] The polyethylene film according to the present disclosure may contain resins other than polyethylene to the extent that the properties are not impaired. In this specification, among the resins contained in the polyethylene film, resins other than polyethylene are referred to as "resin impurities". 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 type of resin impurity selected from the group consisting of these resins.

[0021] In the polyethylene film according to the present 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 the polyethylene film. By keeping the content of resin impurities below a certain level, the heat sealability of the polyethylene film is improved. In other words, the polyethylene film can be suitably used as a sealant film. The lower the content of resin impurities, the more preferable, but it is practical to have a content of 0.01 mass % or more, more practical to have a content of 0.05 mass % or more, and even more practical to have a content of 0.1 mass % or more.

[0022] The type and content of resin impurities contained in the polyethylene film according to the present 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.

[0023] [Additives] The polyethylene film according to the present disclosure may contain various additives within a range that does not impair the properties. Examples of additives include antioxidants, slip agents, plasticizers, UV stabilizers, color inhibitors, matting agents, deodorants, flame retardants, weather resistance agents, antistatic agents, thread friction reducers, release agents, ion exchange agents, antiblocking agents, and color pigments. Among these, it is preferable to contain at least one selected from the group consisting of antioxidants and slip agents.

[0024] [Antioxidants] The 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 the amine-based antioxidant include octyldiphenylamine, Nn-butyl-p-aminophenol, N,N-diisopropyl-p-phenylenediamine, n-butylamine, triethylamine, and diethylaminomethyl methacrylate. Examples of the 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).

[0025] The polyethylene film according to the present disclosure preferably contains a phenol-based antioxidant as the antioxidant, so that even if radicals are generated in the polyethylene film, the phenol-based antioxidant can capture the radicals and stop the radical chain reaction. The polyethylene film according to the present disclosure also preferably contains a phosphorus-based antioxidant as the antioxidant, which decomposes peroxides, which are a source of radical generation, thereby suppressing the generation of radicals. The polyethylene film according to the present disclosure preferably contains both a phenol-based antioxidant and a phosphorus-based antioxidant. The synergistic effect of the phenol-based antioxidant and the phosphorus-based antioxidant can effectively prevent oxidation of polyethylene caused by radicals.

[0026] In the polyethylene film according to the present disclosure, the content of the antioxidant is preferably 50 ppm or more and 500 ppm or less, more preferably 150 ppm or more and 400 ppm or less, and even more preferably 200 ppm or more and 350 ppm or less. In general, when polyethylene containing an antioxidant is repeatedly processed by recycling or the like, the antioxidant is consumed and the antioxidant content decreases. Therefore, in the prior art, a film using recycled polyethylene as a resin may have deteriorated in quality compared to a film using only virgin polyethylene as a resin. In the polyethylene film according to the present disclosure, deterioration of quality can be suppressed by setting the antioxidant content within a certain range by further adding an antioxidant or the like. Furthermore, the proportion of foreign matter present, which will be described later, can be reduced.

[0027] [Slip agent] Examples of slip agents include amide-based 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.

[0028] Among the slip agents, amide-based lubricants are preferred, and examples of the amide-based lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylol amides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides.

[0029] Saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Unsaturated fatty acid amides include oleamide and erucamide. Substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide. Methylol amides include methylol stearic acid amide. Examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipic acid amide, and N,N'-distearyl sebacic acid amide. Examples of the unsaturated fatty acid bisamide include ethylene bisoleamide, ethylene biserucamide, hexamethylene bisoleamide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacamide. The fatty acid ester amides include stearamidoethyl stearate. Examples of the aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, and N,N'-distearylisophthalic acid amide.

[0030] Among the slip agents, erucamide is preferred. The slip agents may be used alone or in combination.

[0031] In order to improve the dispersibility of the slip agent in the polyethylene film according to the present 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 include those mentioned above. The preferred physical properties (density, melt flow rate, etc.) that the polyethylene satisfies are also as described above.

[0032] In the polyethylene film according to the present disclosure, the content of the slip agent may be, for example, from 0.01% by mass to 3% by mass, or from 0.03% by mass to 1% by mass, which can improve the processability of the polyethylene film.

[0033] [Manufacturing method of polyethylene film] The method for producing the polyethylene film according to the present disclosure is not particularly limited, and a conventionally known method for producing a polyethylene film made only of virgin polyethylene can be applied. For example, the polyethylene film according to the present disclosure can be produced by melting mechanically recycled polyethylene and, if necessary, chemically recycled polyethylene, virgin polyethylene, and additives, and forming the melt into a film by a melt extrusion molding method such as inflation molding or T-die molding.

[0034] The thickness of the polyethylene film according to the present disclosure is preferably 10 μm or more and 160 μm or less, more preferably 20 μm or more and 150 μm or less, and even more preferably 30 μm or more and 130 μm or less. The thickness of the polyethylene film according to the present disclosure can be appropriately set depending on the application. For example, when used as a sealant film for a stick pouch, the thickness of the polyethylene film is preferably 10 μm or more and 60 μm or less, more preferably 20 μm or more and 40 μm or less. When used as a sealant film for a refill pouch, the thickness of the polyethylene film is preferably 80 μm or more and 160 μm or less, more preferably 100 μm or more and 130 μm or less.

[0035] Next, a laminate and a packaging bag using the polyethylene film according to the present disclosure will be described.

[0036] [Laminate] A laminate can be obtained by laminating the polyethylene film according to the present disclosure on one side of a base film. That is, the laminate according to the present disclosure has a base film and a polyethylene film.

[0037] As the base film, any resin film or sheet can be used depending on the application of the laminate. For example, when the laminate is applied to a refill pouch for sealing and packaging refillable shampoo or rinse, the base film is preferably excellent in mechanical strength such as tensile strength, flexural strength, and impact strength, as well as printability. For example, nylon films, polyester films such as polyethylene terephthalate films or polybutylene terephthalate, and polyolefin films such as polypropylene films or polyethylene films can be suitably used as the base film. These films may be unstretched films, uniaxially stretched films, or biaxially stretched films. Alternatively, synthetic paper or the like can be used as the base film. These may be used alone or in combination.

[0038] The substrate film and the polyethylene film can be bonded together by dry lamination using a solvent-based adhesive, or by non-solvent lamination using a solvent-free adhesive. This provides excellent adhesive strength and tearability. The adhesive used can be a two-component curing polyurethane adhesive.

[0039] They can also be laminated via an adhesive layer by extrusion lamination (so-called sandwich lamination). In this case, the adhesive layer can be made of a polyolefin-based heat-adhesive resin (e.g., LDPE), as well as a simple substance such as an ethylene-methacrylic acid copolymer, an ethylene-acrylic acid copolymer, or an ionomer, or a resin obtained by blending these with an adhesion improver such as a hard resin.

[0040] An example of a laminate in which a polyethylene film and a base film are bonded together via an adhesive layer is laminate 5 shown in Fig. 4. Laminate 5 includes, in this order, a base film 8, an adhesive layer 6, and a polyethylene film 1. Laminate 5 shown in Fig. 4 is one embodiment of a laminate according to the present disclosure.

[0041] The laminate according to the present disclosure may have an intermediate layer between the substrate film and the polyethylene film. Examples of the intermediate layer include a barrier layer, a light-shielding layer, and a strength-improving layer. As the barrier layer, in addition to metal foils such as aluminum foil, vapor-deposited films in which metals such as aluminum or inorganic oxides such as aluminum oxide or silicon oxide are vapor-deposited on a base film such as a biaxially oriented polyethylene terephthalate film, polyacrylonitrile films, ethylene-vinyl alcohol copolymer films, etc. can be used.

[0042] The base film and the intermediate layer, and the intermediate layer and the polyethylene film can be laminated by a dry lamination method, an extrusion lamination method, an extrusion coating method or the like, in the same manner as in the adhesion between the base film and the polyethylene film described above.

[0043] In either case, the adhesive strength between the layers can be increased by applying an anchor coating agent to the lamination surfaces beforehand or by subjecting them to a pretreatment such as a corona treatment.

[0044] Specific examples of laminates according to the present disclosure include laminates having the following layer configurations. The following laminates are laminates produced by a dry lamination method or a non-solvent lamination method, and each layer is bonded together with an adhesive. Alternatively, the following laminates may be laminated by extrusion lamination, with each layer interposed between an adhesive layer. The values ​​in parentheses indicate the thickness of each layer. ·Polyethylene terephthalate film (12μm) / Polyethylene film (10~160μm) Biaxially oriented nylon film (15μm) / Polyethylene film (10~160μm) ·Transparent vapor-deposited polyethylene terephthalate film (12μm) / polyethylene film (10~160μm) ·Polyethylene terephthalate film (12μm) / Biaxially oriented nylon film (15μm) / Polyethylene film (10~160μm) ·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 (25μm) / Polyethylene film (10~160μm)

[0045] From the viewpoint of obtaining a laminate having excellent recyclability, the polyethylene content in the laminate according to the present disclosure is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more, based on the total mass of the laminate. The upper limit of the polyethylene content in the laminate is 100% by mass, but 99.9% by mass or less is practical.

[0046] [Packaging bag] The packaging bag according to the present disclosure includes the laminate according to the present disclosure. By using the laminate according to the present 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 a fluid content such as a liquid or powder and is refilled into a container such as a bottle.

[0047] Examples of packaging bags include packaging bags of 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, palm seal type (pillow seal type), pleated seal type, flat bottom seal type, square bottom seal type, and gusset type.

[0048] The packaging bag may be, for example, a small bag or a zipper bag. The packaging bag may be, for example, a flexible packaging bag.

[0049] The packaging bag may have an easy-open line to enhance the tearability of the packaging bag. The packaging bag may have a notch portion which serves as a tear starting point.

[0050] The packaging bag may have a seal portion where the sealant films of the laminate are joined together. Examples of methods for forming the sealed portion include heat sealing, in which the sealant film of the laminate is melted by heating or the like to fuse the sealant films together. Specific examples of the method include bar sealing, rotary roll sealing, belt sealing, impulse sealing, high frequency sealing, and ultrasonic sealing.

[0051] The contents to be contained in the packaging bag include, for example, liquids, solids, powders, and gels. The contents may be food or beverages or non-food or beverages. After the contents are contained in the packaging bag, the opening of the packaging bag can be heat-sealed to seal the packaging bag. Examples of food and beverage products include liquid or viscous condiments (sauces, soy sauce, dressings, edible oils, mayonnaise, ketchup, syrups, cooking alcoholic beverages), fruit juices, spices, liquid beverages, jelly-like beverages, liquid soups, powdered soups, instant foods, and creams. Examples of non-food and beverage products include shampoos, rinses, conditioners, hand soaps, body soaps, air fresheners, deodorants, insect repellents, fabric softeners, detergents, and creams. However, from the viewpoint of preventing foreign matter in the polyethylene film from being mixed into food or drink, it is preferable that the contents are not food or drink.

[0052] In one embodiment, the laminate according to the present disclosure is folded in half so that the base film is on the outside and the polyethylene film is on the inside, and the ends and the like are heat-sealed to produce a packaging bag according to the present disclosure. In another embodiment, two laminates according to the present disclosure are prepared, and the polyethylene films are placed opposite each other, and the ends and the like are heat-sealed to produce a packaging bag according to the present disclosure. 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.

[0053] Hereinafter, several examples of embodiments of the packaging bag according to the present disclosure will be described with reference to the drawings. FIG. 3 is a front view showing a packaging bag 10 of one embodiment. FIG. 3 shows the packaging bag 10 in a state before it is filled with contents (a state in which no contents are contained). The packaging bag 10 is a gusset-type pouch configured to be self-supporting. The packaging bag 10 includes an upper portion 11, a lower portion 12, and a side portion 13, and has a substantially rectangular outline in a front view. The names "upper portion", "lower portion", "side portion", and the like, as well as the terms "above" and "below" are merely relative expressions of the positions and directions of the packaging bag 10 and its components based on a state in which the packaging bag 10 stands on its own with the gusset portion facing down. The position of the packaging bag 10 during transportation or use is not limited by the names and terms used in this specification.

[0054] The packaging bag 10 has a storage section 17 and a sealed section 19. The storage section 17 stores the contents. The sealed section 19 includes an inner edge 19x that defines the storage section 17. The sealed section 19 is formed by joining the sealant films of the laminate that constitutes the packaging bag 10. In front views such as FIG. 3, the sealed section 19 is hatched.

[0055] The storage section 17 may include a pouring outlet section 20. The pouring outlet section 20 is a section through which the contents pass when the contents are removed from the packaging bag 10. The width of the pouring outlet section 20 is narrower than the width of other parts of the storage section 17. This allows the user to accurately determine the pouring direction of the contents poured out of the packaging bag 10 through the pouring outlet section 20.

[0056] 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 increase the tearability of the packaging bag 10. The easy-open line 26 crosses the storage section 17 in a plan view of the packaging bag 10. In the example shown in Fig. 3, the easy-open line 26 crosses the spout section 20 in a plan view. As shown in Fig. 3, a notch 28 adjacent to the easy-open line 26 may be formed in the outer edge of the packaging bag 10. Instead of the notch 28, a slit may be formed in the outer edge of the packaging bag 10.

[0057] The packaging bag 10 includes a surface film 14 that constitutes the surface, a back film 15 that constitutes the back surface, and a lower film 16 that constitutes the lower portion 12. The lower film 16 is disposed between the surface film 14 and the back film 15 in a state where it is folded back at a folding portion 16f.

[0058] Either or both of the front film 14 and the back film 15 are composed of a laminate according to the present disclosure. The bottom film 16 may also be composed of a laminate according to the present disclosure. The laminate includes an inner surface and an outer surface. The inner surface is the surface that contacts the contents. The outer surface is the surface located opposite the inner surface. The polyethylene film is located on the inner surface side relative to the stretched substrate film.

[0059] The terms "front film," "back film," and "lower film" are merely used to divide each film according to its positional relationship, and the above-mentioned terms do not limit the method of providing the films when manufacturing the packaging bag 10. For example, the packaging bag 10 may be manufactured using one film in which the front film 14, the back film 15, and the lower film 16 are continuously arranged, or may be manufactured using a total of two films, one film in which the front film 14 and the lower film 16 are continuously arranged and one back film 15, or may be manufactured using a total of three films, one front film 14, one back film 15, and one lower film 16.

[0060] As shown in FIG. 3, the seal portion 19 includes a bottom seal portion 12a, a side seal portion 13a, and a spout seal portion 20a. The bottom seal portion 12a extends to the bottom portion 12. The side seal portion 13a extends along a pair of side portions 13. The spout seal portion 20a defines a 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 at a corner between the top portion 11 and the side portions 13 of the packaging bag 10, the spout seal portion 20a is connected to the side seal portion 13a.

[0061] In the packaging bag 10 in a state where no contents are contained therein, the upper portion 11 of the packaging bag 10 is an opening portion 11b, as shown in Fig. 3. After the contents are contained in the packaging bag 10 through the opening portion 11b, the sealant film of the front film 14 and the sealant film of the back film 15 are joined at the upper portion 11 to form an upper seal portion at the opening portion 11b. This causes the containing portion 17 to be sealed from the outside of the packaging bag 10.

[0062] The side seal portion 13a, the spout seal portion 20a, and the upper seal portion are formed by joining the sealant film of the front film 14 and the sealant film of the back film 15. The lower seal portion 12a includes a portion where the sealant film of the front film 14 and the sealant film of the lower film 16 are joined, and a 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 3, a notch 13c may be formed in a part of the lower film 16. At the position of the notch 13c, the sealant film of the front film 14 and the sealant film of the back film 15 may be joined.

[0063] 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 front film 14 and the sealant film of the back film 15. For example, a laminate according to the present disclosure may be used as the lower film 16, similar to the front film 14 and the back film 15. A film having a different configuration from the laminate according to the present disclosure may be used as the lower film 16.

[0064] The packaging bag 10 can be produced, for example, as follows. A laminate according to the present disclosure is prepared. The laminate is cut into two pieces, one of which is the front film 14 and the other is the back film 15. Next, the folded-over lower film 16 is inserted between the front film 14 and the back film 15. Next, the sealant films of each film are heat-sealed to each other to form seals such as the bottom seal portion 12a, the side seal portion 13a, and the spout seal portion 20a. The films joined together by heat sealing are cut into an appropriate shape. This results in the packaging bag 10 shown in FIG. 3.

[0065] Next, the contents are filled into the storage section 17 of the packaging bag 10. After that, the upper section 11 is heat-sealed to form the upper seal section. In this manner, the packaging bag 10 in which the contents are stored and sealed is obtained.

[0066] In the above description of the embodiment, an example has been given in which the packaging bag 10 is a gusset-type pouch, but the specific configuration of the packaging bag 10 is not particularly limited.

[0067] For example, the packaging bag 10 may not have a lower film 16, as shown in Figures 4 and 5. In Figures 4 and 5, 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 front film 14 and the back film 15, which are respectively made of a laminate. After the contents are placed in the packaging bag 10, the sealant film of the front film 14 and the sealant film of the back film 15 are joined at the opening 11b of the upper portion 11, thereby sealing the packaging bag 10. The packaging bag 10 shown in Figures 4 and 5 may have an easy-open line 26.

[0068] As shown in Fig. 6, the packaging bag 10 may be a pillow pouch. The packaging bag 10 includes a seam 18 formed by overlapping the ends of a laminate that constitutes the front film 14 and the back film 15. The seam 18 includes a seam seal portion 18a in which the sealant films of the laminate are joined together. The packaging bag 10 shown in Fig. 6 may have an easy-open line 26. As shown in Fig. 6, a notch 28 or a notch (not shown) may be formed on the outer edge of the seam. EXAMPLES

[0069] The present disclosure will be described more specifically below with reference to examples, but the present disclosure is not limited to the following examples.

[0070] The various raw materials used in the polyethylene films of the following Examples 1 to 6 and Comparative Examples 1 to 6 are as follows. Mechanically recycled polyethylene A Low density polyethylene, product name: LCY02, manufactured by APK, density: 0.920-0.924g / cm 3 , Melt flow rate: 1.8~2.3g / 10min Mechanically recycled polyethylene B Low density polyethylene, recycled from waste materials during the manufacturing process such as waste from the edges of the film during film production, density: 0.920-0.924g / cm 3 , Melt flow rate: 1.8~2.3g / 10min · Virgin Polyethylene A Low density polyethylene, product name: F224N, manufactured by Ube Maruzen Polyethylene Co., Ltd., density: 0.924 g / cm 3 , Melt flow rate: 2.0g / 10min Virgin polyethylene B Low density polyethylene, product name: Sumikasen G201-F, manufactured by Sumitomo Chemical Co., Ltd., density: 0.919 g / cm 3 , Melt flow rate: 2.0g / 10min Virgin Polyethylene C Linear low-density polyethylene, product name: Ultzex ​​2010L, manufactured by Prime Polymer Co., Ltd., density: 0.922 g / cm3 , Melt flow rate: 2.2g / 10min Virgin polyethylene D Linear low-density polyethylene, product name: Evolue SP2040F, manufactured by Prime Polymer Co., Ltd., density: 0.918 g / cm 3 , Melt flow rate: 3.8g / 10min · Slip agent-containing masterbatch A Virgin low-density polyethylene containing 2.0% by mass of erucic acid amide, product name: M425, manufactured by Ube Maruzen Polyethylene Co., Ltd., density: 0.921 g / cm 3 , Melt flow rate: 5.4g / 10min · 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 / cm 3 , Melt flow rate: 4.7g / 10min Antioxidants 2,6-di-t-butyl-p-cresol (BHT), a phenol-based antioxidant, and triphenyl phosphite (TTP), a phosphorus-based antioxidant, product name: EAG-5, manufactured by Prime Polymer Co., Ltd., density: 0.920 g / cm 3 , Melt flow rate: 4.9g / 10min

[0071] [Example 1] 49% by mass of mechanically recycled polyethylene A, 48% by mass of virgin polyethylene A, 2% by mass of slip agent-containing master batch A, and 1% by mass of an antioxidant were blended and melt-kneaded to obtain a resin composition. The obtained resin composition was formed into a film by a top-blowing air-cooled inflation film formation method under the following film formation conditions to obtain the polyethylene film of Example 1. (Film forming conditions) Screw temperature: 160℃ Cylinder temperature: 160℃ Die temperature: 170℃ Screw speed: 25 rpm -Retraction speed: 60m / min Resin pressure: 24.2MPa ·Discharge amount: 190kg / h Film width: 900mm Film thickness: 30μm

[0072] [Example 2] A polyethylene film of Example 2 was obtained in the same manner as in Example 1, except that the formulation of the resin composition was changed as shown in Table 1.

[0073] [Example 3] A polyethylene film of Example 3 was obtained in the same manner as in Example 1, except that the formulation of the resin composition was changed as shown in Table 1 and the film-forming conditions were changed as shown below. (Film forming conditions) Screw temperature: 160℃ Cylinder temperature: 160℃ Die temperature: 165℃ Screw speed: 25 rpm -Retraction speed: 20m / min Resin pressure: 28.2MPa ·Discharge amount: 240kg / h Film width: 1000mm Film thickness: 120μm

[0074] [Examples 4 to 6] The polyethylene films of Examples 4 to 6 were obtained in the same manner as in Example 3, except that the formulation of the resin composition was changed as shown in Table 1.

[0075] [Comparative Examples 1 to 5] Polyethylene films of Comparative Examples 1 to 5 were obtained in the same manner as in Example 1, except that the formulation of the resin composition was changed as shown in Table 1.

[0076] [Comparative Example 6] A polyethylene film of Comparative Example 6 was obtained in the same manner as in Example 3, except that the formulation of the resin composition was changed as shown in Table 1.

[0077] [Identification and quantification of resin impurities] For the polyethylene films of Examples 1 to 6 and Comparative Examples 1 to 6, FT-IR spectra were measured using an FT-IR (Fourier transform infrared spectroscopy) measuring device under the following measurement conditions. (Measurement conditions) Apparatus: Nicolet 6700 (Thermo Fisher Scientific) ·Resolution: 4cm -1 Number of times accumulated: 64 ·Measurement method: transmission method Wire grid polarizer: KRS-5 Wave number 2915cm -1 A peak due to polyethylene was confirmed around wavenumber 3300-cm. -1 It was confirmed whether a peak due to resin impurities appeared in the vicinity. When a peak due to resin impurities appeared, the type of resin impurity was identified by comparing the measurement results with a database. The content of the resin impurity was also calculated from the peak area. The results are shown in Table 1. In Table 1, "-" indicates that no resin impurities were detected by the measurement. When two or more types of resin impurities were detected, the content of the resin impurities is the sum of the contents of each resin impurity.

[0078] [Heat seal strength measurement] For the polyethylene films of Examples 1 to 6 and Comparative Examples 1 to 6, the heat seal strength was measured in accordance with JIS Z 1707:2019. Specifically, first, a 12 μm-thick biaxially oriented polyethylene terephthalate film (E5100, manufactured by Toyobo Co., Ltd.) was used to bond each polyethylene film to a laminate by dry lamination using a urethane-based adhesive (RU-77T / H-7, manufactured by Rock Paint Co., Ltd.). Next, the two laminated polyethylene films were pressed together with a pressure of 1 kgf / cm 2The specimen was heat-sealed at 160°C for 1 second under a load of 0.05 mm to form a sealed portion. The portion including the sealed portion was cut out to a width of 15 mm and a length of 100 mm to prepare a test piece 60 for measuring heat seal strength. As shown in FIG. 7, the unsealed portion of the test piece 60 was held by a gripper 61 of a Tensilon universal material testing machine (RTC-1530, manufactured by Orientec Co., Ltd.). The length of the sealed portion 62 was set to 15 mm. Next, the grippers 61 were pulled at a speed of 300 mm / min in opposite directions perpendicular to the surface direction of the sealed 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 value of the maximum value of the tensile stress was taken as the heat seal strength. The interval S2 between the grippers 61 at the start of pulling was set to 50 mm. The results are shown in Table 1.

[0079] [Quantitative analysis of antioxidants] The polyethylene films of Examples 1 to 6 and Comparative Examples 1 to 6 were each dissolved in chloroform. Methanol was used as a poor solvent to reprecipitate the resin. The filtrate was collected, and the solvent was distilled off under reduced pressure. The concentrate was dissolved in a small amount of chloroform and acetonitrile, and the total volume was adjusted to 50 mL. The obtained solution was quantitatively analyzed by ultra-performance high-resolution liquid chromatography (UPLC) under the following measurement conditions to measure the antioxidant content. The results are shown in Table 1. (Measurement conditions) Equipment: UPLC ACQUITY (manufactured by Nihon Waters, Inc.) Column: BEH C18 (particle size: 1.7 μm, column size: 2.1 × 50 mm) Solvent: Acetonitrile and distilled water (gradient mode) ·Flow rate: 0.2mL / min Column temperature: 40℃ Detector: PDA (photodiode array) Measurement wavelength range: 190~500nm Sample injection volume: 1μL

[0080] [Gel evaluation] For the polyethylene films of Examples 1 to 6 and Comparative Examples 1 to 6, the number of unmelted gels present within a width of 1 mm and a length of 10 mm was counted using a transmission optical microscope (product name: DSX1000, manufactured by Olympus Corporation). 2 The rate of gel formation per unit area was calculated and evaluated. The evaluation criteria were as follows. The results are shown in Table 1. (Evaluation Criteria) A: Gel occurrence rate is 0 particles / m 2 More than 0.031 pieces / m 2 less than B: Gel occurrence rate is 0.031 particles / m 2 More than 0.038 pieces / m 2 less than C: Gel occurrence rate is 0.038 particles / m 2 End

[0081] [Odor evaluation] The polyethylene films of Examples 1 to 6 and Comparative Examples 1 to 6 were each cut into a size of 10 cm x 10 cm and packed in an aluminum bag. After storing in an oven at 40°C for one week, the odor inside the aluminum bag was confirmed. The evaluation criteria were as follows. The results are shown in Table 1. (Evaluation Criteria) A: It has a faint polyethylene smell. B: There is a strong polyethylene smell. C: There is a very strong polyethylene smell.

[0082] [Table 1]

[0083] As is clear from Table 1 above, the polyethylene films of Examples 1 and 2 and Comparative Examples 3 to 5 all have a thickness of 30 μm and contain mechanically recycled polyethylene, but the polyethylene films of Examples 1 and 2, which have a resin impurity content of 1.5 mass% or less, have a higher heat seal strength and are excellent in heat sealability than the polyethylene films of Comparative Examples 3 to 5, which have a resin impurity content of more than 1.5 mass%. The heat seal strength of the polyethylene films of Examples 1 and 2 is equivalent to that of the polyethylene films of Comparative Examples 1 and 2, which have the same thickness and do not contain mechanically recycled polyethylene, and it is understood that the polyethylene films of Examples 1 and 2 have excellent heat sealability even though they contain mechanically recycled polyethylene. In addition, the heat seal strength of the polyethylene films of Examples 3 to 6, which have a thickness of 120 μm, is equivalent to that of the polyethylene film of Comparative Example 6, which has the same thickness and does not contain mechanically recycled polyethylene, and it is understood that the polyethylene films of Examples 3 to 6 have excellent heat sealability even though they contain mechanically recycled polyethylene. [Explanation of symbols]

[0084] 1 Polyethylene film 5. Laminate 6 Adhesive layer 8. Base Film 10 packaging bags 11 Top 11b opening 12 Lower 12a Lower seal part 13 Side 13a Side seal 13c Notch 14 Surface film 15 Back film 16 Lower Film 16f Folded part 17 Storage unit 18 Gassho section 18a Joint seal part 19 Seal part 19x inner edge 20 Spout part 20a Spout seal part 26 Easy-open line 27 Cutout 28 Cutout 60 Test Pieces 61 Grasping Tool 62 Seal part S2 Distance between grips

Claims

1. A single-layer polyethylene film containing mechanically recycled polyethylene and resin impurities that 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; The content of the resin impurities is 1.5 mass% or less based on the total amount of the polyethylene film.

2. 10. The polyethylene film of claim 1, further comprising virgin polyethylene, which is non-recycled polyethylene.

3. The polyethylene film according to claim 1 or 2, wherein the content of the resin impurities is 0.01 mass% or more based on the total amount of the polyethylene film.

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

5. The polyethylene film according to claim 4 , wherein the content of the antioxidant is 50 ppm or more and 500 ppm or less based on the total amount of the polyethylene film.

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

7. The polyethylene film according to claim 1 or 2, which is a sealant film.

8. A laminate comprising a substrate film and the polyethylene film according to claim 1 or 2.

9. The laminate according to claim 8 , wherein the polyethylene content is 90% by mass or more based on the total mass of the laminate.

10. A packaging bag comprising the laminate according to claim 8.

11. The packaging bag according to claim 10, which contains a non-food or beverage product.

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