Laminate, and packaging material and packaging bag using the same

Abstract

To provide a laminate for packaging which has a small environmental load, is excellent in recycling suitability, and is excellent in barrier properties while having sufficient strength and heat resistance, and to provide a packaging material and a packaging bag.SOLUTION: A laminate comprising a base film, a first adhesive layer, an intermediate film, a second adhesive layer, and a heat seal film laminated in this order, and a protective layer further laminated on an outermost surface side of the base film, wherein the protective layer is made of a thermosetting resin, the base film is a stretched polyethylene film, the intermediate film and the heat seal film are non-stretched polyethylene films, a vapor deposition film is provided on one surface of the intermediate film, and a proportion of polyethylene in the laminate is 90% by weight or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate for packaging, and a packaging material and a packaging bag using the same. In particular, the present invention relates to a laminate with excellent material recyclability and a small environmental impact, and a packaging material and a packaging bag using the same. [Background technology]

[0002] Packaging bags are made from a variety of materials, depending on the nature of the contents to be packaged, the amount of contents, post-processing to protect the contents from deterioration, the form in which the packaging bag is transported, the method of opening the packaging bag, and the method of disposal.

[0003] For example, in packaging bags for flexible packages using laminated films, biaxially oriented films such as polypropylene and polyester are used to provide the mechanical strength of the packaging bag, and polyethylene, polypropylene, ethylene-vinyl acetate copolymer, etc. are used as heat-sealing materials to seal the contents as the packaging bag. Also, aluminum foil and ethylene-vinyl alcohol copolymer are laminated to prevent deterioration of the contents.

[0004] The above-mentioned laminates of various functionally separated materials are designed with an emphasis on each process, from packaging the contents to transportation, storage, and opening. However, with the recent increase in awareness of environmental issues, emphasis has been placed on resource conservation and recyclability of various products, and similar functions are being demanded of laminates used in packaging bags. Generally, packaging materials containing 90% or more of the main resin are considered to be highly recyclable, but many conventional packaging materials are composed of multiple resin materials and, in some cases, paper and metal materials, and do not meet this standard, so they are not currently recycled.

[0005] For example, in order to reduce the environmental impact, a packaging bag made of a laminate in which various plastics are replaced with plant-based ones instead of petroleum-based ones has been proposed (Patent Document 1). This reduces the amount of petroleum resources used and carbon dioxide emissions. However, a laminate made up of various materials must be separated and sorted in order to reuse the materials. This involves the problem of consuming energy, as the materials must be separated using various thermal, chemical, and mechanical processes, and then sorted using physical processes based on specific gravity or spectroscopic methods that differ for each material.

[0006] Therefore, Patent Document 2 describes a laminate having a substrate, an adhesive layer, and a heat-sealing layer, in which the substrate and heat-sealing layer are made of polyethylene. Using the same material for the substrate and heat-sealing layer makes it easier to meet the recyclability standards. However, when the laminate described in Patent Document 2 is used in a packaging bag, the bag-making process involves a step of joining the sealant layers of the laminate together and then clamping the laminate between a high-temperature jig and applying pressure from the outer surface of the substrate layer to a high-temperature jig to heat-seal the laminate. The jig of the heat-sealing machine is heated to a high temperature, and the outer surface of the substrate layer that directly contacts the jig is exposed to high temperatures, which can cause problems such as the substrate layer being affected by heat and adhering to the jig. As a result, there are issues such as a narrow range of appropriate bag-making temperatures, poor productivity, and insufficient packaging bag strength.

[0007] Furthermore, Patent Document 3 proposes a packaging bag that has excellent blocking resistance and ease of opening by providing a resin coating layer on the outer surface of a polyethylene substrate layer. However, this document proposes a simplified layer structure from the perspective of ease of recycling, and uses a single-layer structure in which a sealant layer is provided on a substrate layer, or a structure in which substrates are bonded together, so it is limited to light packaging applications and is difficult to apply due to insufficient strength to packaging bags containing liquids that require sufficient sealing properties. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6699779 [Patent Document 2] Japanese Patent Publication No. 2020-55157 [Patent Document 3] Japanese Patent Publication No. 2020-196791 Summary of the Invention [Problem to be solved by the invention]

[0009] The problem to be solved by the present invention is to provide a packaging laminate, a packaging material, and a packaging bag that have a small environmental impact, excellent recyclability, and excellent barrier properties while having sufficient strength and heat resistance. [Means for solving the problem]

[0010] In order to solve the above problem, the invention of claim 1 of the present invention is a laminate comprising a base film, a first adhesive layer, an intermediate film, a second adhesive layer, and a heat seal film laminated in this order, with a protective layer further laminated on the outermost side of the base film, wherein the protective layer is made of a thermosetting resin, the base film is a stretched polyethylene film, the intermediate film and the heat seal film are unstretched polyethylene films, one side of the intermediate film is provided with a vapor-deposited film, and the proportion of polyethylene in the laminate is 90% by weight or more.

[0011] The invention of claim 2 of the present invention is the laminate described in claim 1, characterized in that the thermosetting resin is a cured product of one or more resin compositions consisting of urethane, polyester, polyamide, acrylic, and epoxy.

[0012] A third aspect of the present invention is the laminate according to the first or second aspect, wherein the vapor-deposited film is a barrier film made of a metal oxide.

[0013] A fourth aspect of the present invention is the laminate according to any one of the first to third aspects, characterized in that the base film and the intermediate film are made of high-density polyethylene or medium-density polyethylene.

[0014] A fifth aspect of the present invention is the laminate according to any one of the first to fourth aspects, wherein the heat seal film contains low-density polyethylene.

[0015] A sixth aspect of the present invention is a packaging material comprising the laminate according to any one of the first to fifth aspects.

[0016] A seventh aspect of the present invention is a packaging bag characterized by using the laminate according to any one of the first to fifth aspects, wherein the thickness of the heat seal film is 20 μm or more and 150 μm or less. [Effects of the Invention]

[0017] By providing the laminate of the present invention, packaging bags can be produced with high productivity, which are easy to recycle and have strength, heat resistance and barrier properties. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view illustrating an embodiment of a laminate of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail.

[0020] 1 is a cross-sectional schematic diagram of a laminate 1 according to the present invention. The laminate 1 comprises a base film 10, a first adhesive layer 40, an intermediate film 20, a second adhesive layer 50, and a heat seal film 30. The base film 10 is provided with a protective layer 11 on the outermost surface thereof, and the intermediate film 20 is provided with a vapor-deposited film 14 on one surface thereof.

[0021] The base film 10 is a stretched film made of polyethylene, and is the portion that becomes the outer surface when a packaging material is formed using the laminate 1. The base film 10 may be a uniaxially stretched film or a biaxially stretched film. Here, high-density polyethylene (density 0.94 g / cm 3 or more), medium density polyethylene (density 0.925 to 0.945 g / cm 3 ) can be used. These materials may be petroleum-derived, plant-derived, or a mixture thereof. The film can be produced by known methods such as a casting method or an inflation method, and the surface of the film can be subjected to a dry surface treatment such as a corona treatment or an atmospheric pressure plasma treatment to enhance adhesion. A multilayer stretched polyethylene film obtained by co-extrusion of polyethylenes with different densities can also be used as the base film 10. The thickness of the base film 10 is preferably 10 μm or more and 50 μm or less, and more preferably 12 μm or more and 35 μm or less. By making the thickness of the base film 10 10 μm or more, the strength of the laminate 1 can be improved. By making the thickness of the base film 10 50 μm or less, the processability of the laminate 1 can be improved.

[0022] The protective layer 11 provided on the outermost surface of the base film 10 can be formed from a coating agent that produces a cured product of one or more resin compositions made from urethane, polyester, polyamide, acrylic, and epoxy. The thickness of the protective layer 11 is 0.3 to 4.0 μm.

[0023] The printed layer 12 can be formed on the outer surface 10a of the base film 10, which is the side on which the protective layer 11 is formed, or on the inner surface 10b, which is the side on which the intermediate film 20 is laminated. The method for forming the image is not particularly limited, and it can be formed by ordinary gravure printing, flexographic printing, or the like, using an appropriate ink. While solvent-based inks and water-based inks are available, water-based inks are preferred from an environmental perspective. Furthermore, the outer surface 10a or inner surface 10b of the base film 10 may be subjected to a surface treatment such as corona treatment or plasma treatment to improve the adhesion of the printed layer 12.

[0024] The base film 10 is a stretched film and has excellent transparency, allowing the display on the printing layer 12 provided on the inner surface 10b to be easily viewed. The transparency that allows easy viewing is 20% or less in terms of haze value measured in accordance with JIS K 7105, and is even better when it is 10% or less.

[0025] Furthermore, in consideration of better recyclability, placing the printed layer 12 on the outside of the base film 10 makes deinking easier and prevents the ink on the printed layer 12 from being mixed in as foreign matter with the recycled polyethylene resin during the recycling process.

[0026] The intermediate film 20 is an unstretched film made of polyethylene. From the viewpoints of strength and heat resistance, high-density polyethylene and medium-density polyethylene are preferred as the polyethylene contained in the intermediate film 20. Like the base film 10, the intermediate film 20 may be a multilayer film.

[0027] The thickness of the intermediate film 20 is preferably 9 μm or more and 50 μm or less, and more preferably 12 μm or more and 30 μm or less. By making the thickness of the intermediate film 20 9 μm or more, the strength and heat resistance of the laminate can be improved. By making the thickness of the intermediate film 20 50 μm or less, the processability of the laminate can be improved.

[0028] The intermediate film 20 can be produced by forming polyethylene into a film using a T-die method, an inflation method, or the like. When producing the intermediate film 20 using the T-die method, the melt flow rate (MFR) of the polyethylene is preferably 3 g / 10 min or more and 20 g / 10 min or less. By setting the MFR to 3 g / 10 min or more, the processability of the laminate can be improved. Furthermore, by setting the MFR to 20 g / 10 min or less, the produced substrate can be prevented from breaking.

[0029] When the intermediate film 20 is produced by the inflation method, the MFR of the polyethylene is preferably 0.5 g / 10 min or more and 5 g / 10 min or less. By setting the MFR to 0.5 g / 10 min or more, the processability of the laminate can be improved. Furthermore, by setting the MFR to 5 g / 10 min or less, the film formability can be improved.

[0030] The unstretched film to be the intermediate film 20 may be produced by the method described above, or may be a commercially available film.

[0031] A vapor-deposited film 14 is formed on one surface of the intermediate film 20. In this embodiment, the vapor-deposited film 14 is formed on the surface facing the second adhesive layer 50, but it may be formed on the opposite surface. The vapor-deposited film 14 imparts oxygen barrier properties and water vapor barrier properties to the laminate 1.

[0032] Examples of the composition of the vapor-deposited film 14 include vapor-deposited films made of metal oxides such as aluminum oxide, silicon oxide, magnesium oxide, and tin oxide. From the viewpoints of transparency and barrier properties, the metal oxide may be selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide. Furthermore, from the viewpoint of cost, it is selected from aluminum oxide and silicon oxide. Furthermore, from the viewpoint of excellent tensile elongation during processing, it is more preferable to use a layer made of silicon oxide. By using a metal oxide as the barrier film for the vapor-deposited film 14, high barrier properties can be obtained with an extremely thin layer that does not affect the recyclability of the laminate 1.

[0033] A vapor-deposited film made of a metal oxide has transparency, and therefore has the advantage that, compared to a vapor-deposited film made of a metal, it is less likely to cause a user who holds a packaging material made of a laminate to mistakenly believe that a metal foil is used.

[0034] The thickness of the vapor-deposited film made of aluminum oxide is preferably 5 nm or more and 30 nm or less. A film thickness of 5 nm or more can provide sufficient gas barrier properties. Furthermore, a film thickness of 30 nm or less can prevent cracks from occurring due to deformation caused by internal stress in the thin film, thereby preventing a decrease in gas barrier properties. Note that a film thickness exceeding 30 nm is undesirable from an economic standpoint, as it increases costs due to an increase in the amount of material used and a longer film formation time. From the same viewpoint as above, the film thickness of the vapor-deposited film is more preferably 7 nm or more and 15 nm or less.

[0035] The thickness of the vapor-deposited film made of silicon oxide is preferably 10 nm or more and 50 nm or less. A film thickness of 10 nm or more can provide sufficient gas barrier properties. Furthermore, a film thickness of 50 nm or less can prevent cracks from occurring due to deformation caused by internal stress in the thin film, thereby preventing a decrease in gas barrier properties. Note that a film thickness exceeding 50 nm is undesirable from an economic standpoint, as it increases costs due to an increase in the amount of material used and a longer film formation time. From the same viewpoint as above, the film thickness of the vapor-deposited film is more preferably 20 nm or more and 40 nm or less.

[0036] The vapor deposition film 14 can be formed by, for example, vacuum film formation. Vacuum film formation can use physical vapor deposition or chemical vapor deposition. Physical vapor deposition methods include, but are not limited to, vacuum deposition, sputtering, and ion plating. Chemical vapor deposition methods include, but are not limited to, thermal CVD, plasma CVD, and photo CVD.

[0037] In the vacuum film formation, resistance heating vacuum evaporation, EB (Electron Beam) heating vacuum evaporation, induction heating vacuum evaporation, sputtering, reactive sputtering, dual magnetron sputtering, plasma enhanced chemical vapor deposition (PECVD), and the like are particularly preferably used. However, in terms of productivity, vacuum evaporation is currently the most superior. As a heating means for vacuum evaporation, it is preferable to use any of the electron beam heating method, resistance heating method, and induction heating method.

[0038] As in this embodiment, an anchor coating layer may be formed on the surface of the intermediate film 20 on which the vapor-deposited film 14 is formed, using a known anchor coating agent. This improves the adhesion of the vapor-deposited film made of metal oxide. Examples of anchor coating agents include polyester-based polyurethane resins and polyether-based polyurethane resins. From the viewpoints of heat resistance and interlayer adhesive strength, polyester-based polyurethane resins are preferred.

[0039] Furthermore, in order to improve adhesion with the first adhesive layer 40, the second adhesive layer 50, the vapor deposition film 14, and the above-mentioned anchor coat layer, the corresponding surfaces of the intermediate film 20 may be subjected to surface treatment such as corona treatment or plasma treatment.

[0040] The heat seal film 30 is made of polyethylene and is bonded by heat fusion (heat sealing) when the laminate 1 is used to form a packaging material such as a packaging bag. From the viewpoint of heat sealing properties, the polyethylene constituting the heat seal film 30 is preferably low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or very low-density polyethylene (VLDPE). From the viewpoint of environmental impact, it is preferable to use biomass-derived polyethylene or recycled polyethylene for the heat seal film 30.

[0041] Low density polyethylene has a density of 0.900 g / cm 3 More than 0.925g / cm 3The linear low-density polyethylene may be polyethylene having a density of 0.900 g / cm. 3 More than 0.925g / cm 3 Ultra-low density polyethylene can be used with a density of 0.900 g / cm. 3 For the heat seal film 30, a copolymer of ethylene and other monomers can be used as long as the properties of the laminate 1 are not impaired.

[0042] The thickness of the heat seal film 30 can be changed as appropriate depending on the weight of the contents to be filled into the packaging material to be produced. For example, when producing a packaging bag to be filled with contents of 1 g or more and 200 g or less, the thickness of the heat seal film 30 is preferably 20 μm or more and 60 μm or less. By making the thickness 20 μm or more, it is possible to prevent the filled contents from leaking due to damage to the heat seal film 30. By making the thickness 60 μm or less, it is possible to improve the processability of the laminate 1.

[0043] As another example, when producing a standing pouch to be filled with contents of 50 g or more and 2000 g or less, the thickness of the heat seal film 30 is preferably 50 μm or more and 200 μm or less. By making the thickness 50 μm or more, it is possible to prevent the filled contents from leaking due to damage to the heat seal film 30. Furthermore, by making the thickness 200 μm or less, the processability of the laminate 1 can be improved, and a thickness of 150 μm is more preferable.

[0044] The polyethylene used for the base film 10, the intermediate film 20, and the heat seal film 30 may contain additives such as antioxidants, antistatic agents, nucleating agents, and ultraviolet absorbers.

[0045] The first adhesive layer 40 is a layer containing at least one type of adhesive and is provided between the base film 10 and the intermediate film 20 to bond them together. The second adhesive layer 50 is a layer containing at least one type of adhesive and is provided between the intermediate film 20 and the heat seal film 30 to bond them together. Any adhesive, such as a one-component curing or two-component curing urethane adhesive, can be used for the first adhesive layer 40 and the second adhesive layer 50. These adhesives may contain a layered inorganic compound to further enhance the barrier properties.

[0046] The first adhesive layer 40 and the second adhesive layer 50 can also be formed using an adhesive that can exhibit gas barrier properties after curing. In particular, forming the second adhesive layer 50 that comes into contact with the vapor-deposited film using an adhesive that exhibits gas barrier properties can further suppress deterioration of the gas barrier properties due to cracking of the vapor-deposited film 14. This can further improve the gas barrier performance of the laminate 1. Examples of such gas barrier adhesives include epoxy-based adhesives and polyester-polyurethane-based adhesives. Specific examples include "Maxieve" manufactured by Mitsubishi Gas Chemical Company, Inc. and "Paslim" manufactured by DIC Corporation.

[0047] The thickness of the first adhesive layer 40 and the second adhesive layer 50 is preferably 0.5 μm or more and 6 μm or less, more preferably 0.8 μm or more and 5 μm or less, and even more preferably 1.0 μm or more and 4.5 μm or less. By making the thickness of the first adhesive layer 40 and the second adhesive layer 50 0.5 μm or more, the adhesiveness of the first adhesive layer 40 and the second adhesive layer 50 can be improved. By making the thickness of the first adhesive layer 40 and the second adhesive layer 50 6 μm or less, the processability of the laminate 1 can be improved.

[0048] The first adhesive layer 40 and the second adhesive layer 50 can be formed by various known methods such as direct gravure roll coating, gravure roll coating, kiss coating, reverse roll coating, Fontaine method, and transfer roll coating.

[0049] In the laminate 1 of this embodiment configured as described above, the base film 10, intermediate film 20, and heat seal film 30 are made of polyethylene, so the proportion of polyethylene in the laminate 1 is 90 mass % (wt%) or more. This gives the laminate 1 high recyclability. The proportion (wt%) of polyethylene in the laminate 1 can be calculated using the following formula (1).

[0050] (mass of base film + mass of intermediate film 20 + mass of heat seal film 30) / mass of entire laminate 1 × 100 (1) A packaging bag can be formed from the laminate 1 by folding one laminate 1 with the heat seal films 30 facing each other, or by stacking two laminates 1 with the heat seal films 30 facing each other, and then joining the peripheral heat seal films 30 by heat sealing, leaving the portion filled with the contents. A standing pouch can be formed by joining the laminate 1 as described above while sandwiching the folded bottom film. It can also be used for various other packaging bags, such as pillow packaging, four-sided sealing, three-sided sealing, and gusset bags. In this way, the laminate 1 can be applied to various packaging bags.

[0051] The laminate of the present invention has a base film 10 made of a stretched high-density polyethylene film and a protective layer 11 made of a thermosetting resin on the outermost layer, which increases the heat resistance of the heat-sealed portion, enabling bag production under appropriate conditions and improving the strength and appearance required for packaging bags. Furthermore, by combining the intermediate film 20 made of a non-stretched film with a vapor-deposited film 14, the packaging bag filled with liquid will not easily break due to impact when dropped, and the strength of the packaging bag is increased.

[0052] The laminate of this embodiment will be further described using examples and comparative examples, but the present invention is not limited to the specific contents of the examples and comparative examples. (Preparation of anchor coating agent) Acrylic polyol and tolylene diisocyanate were mixed so that the number of NCO groups in the tolylene diisocyanate was equal to the number of OH groups in the acrylic polyol, and the mixture was diluted with ethyl acetate to a total solids content (total amount of acrylic polyol and tolylene diisocyanate) of 5% by mass. β-(3,4-epoxycyclohexyl)trimethoxysilane was added to the diluted mixture in an amount of 5 parts by mass per 100 parts by mass of the total amount of acrylic polyol and tolylene diisocyanate, and the mixture was mixed to prepare an anchor coating agent. (Preparation of Overcoat Agent) An overcoat agent was prepared by mixing the following liquids A, B, and C in a mass ratio of 70 / 20 / 10, respectively. Solution A: A hydrolyzed solution with a solid content of 5% by mass (SiO2 equivalent) obtained by adding 72.1 g of 0.1N hydrochloric acid to 17.9 g of tetraethoxysilane (Si(OC2H5)4) and 10 g of methanol and stirring for 30 minutes. Solution B: 5% by mass of polyvinyl alcohol in water / methanol (water:methanol mass ratio 95:5). Liquid C: A hydrolysis solution prepared by diluting 1,3,5-tris(3-trialkoxysilylpropyl) isocyanurate with a water / isopropyl alcohol mixture (water:isopropyl alcohol mass ratio 1:1) to a solids content of 5 mass%. (Preparation of intermediate film A) The anchor coating agent described above was applied by gravure coating to one side of a 25 μm-thick unstretched polyethylene film (three-layer structure: HDPE / MDPE / HDPE) that had been corona-treated on both sides, and then dried to form a 0.1 μm-thick anchor coating layer. Next, a 30 nm-thick transparent vapor-deposited film made of silicon oxide was formed on the anchor coating layer using a vacuum deposition device with electron beam heating. The O / Si ratio of the vapor-deposited film was set to 1.8 by adjusting the type of vapor-deposited material. The overcoat agent described above was applied by gravure coating to the vapor-deposited film and then dried to form a 0.3 μm-thick overcoat layer with gas barrier properties. As a result, intermediate film A was obtained, on which a vapor-deposited film made of silica was formed. (Preparation of intermediate film B) An anchor coating agent was applied to one side of the same unstretched polyethylene film as intermediate film A by gravure coating and dried to form a 0.1 μm thick anchor coating layer. Next, a 10 nm thick transparent vapor deposition film made of aluminum oxide was formed on the anchor coating layer using a vacuum deposition device with electron beam heating. The O / Al ratio of the vapor deposition film was set to 1.5 by adjusting the type of vapor deposition material. An overcoat agent was then applied to the vapor deposition film by gravure coating and dried to form a 0.3 μm thick overcoat layer with gas barrier properties. As a result of the above, intermediate film B was obtained, on which a vapor deposition film made of alumina was formed. (Preparation of intermediate film C) An anchor coating agent was applied by gravure coating to a 25 μm-thick biaxially oriented polyethylene film (three-layer structure of HDPE / MDPE / HDPE) that had been corona-treated on both sides, and dried to form a 0.1 μm-thick anchor coating layer. Next, a 30 nm-thick transparent vapor-deposited film made of silicon oxide was formed using a vacuum deposition device with electron beam heating. The O / Si ratio of the vapor-deposited film was set to 1.8 by adjusting the type of vapor-deposited material. The above-mentioned overcoat agent was applied by gravure coating on top of the vapor-deposited film and dried to form a 0.3 μm-thick overcoat layer with gas barrier properties. As a result, intermediate film C was obtained, on which a vapor-deposited film made of silica was formed. (Coating solution for forming protective layer) An organic solvent-based coating solution containing polyamideimide (Viromax HR-15ET) manufactured by Toyobo Co., Ltd. was used as the coating solution for forming the protective layer, with the non-volatile component concentration adjusted to 5% by mass. Example 1 A 25 μm-thick biaxially oriented polyethylene film (three-layer structure: HDPE / MDPE / HDPE) with corona treatment on both sides was prepared as the base film. The coating solution for forming the protective layer described above was applied to the corona-treated outer surface of the base film by gravure coating and dried to form a 0.5 μm-thick protective layer. Furthermore, an image was formed on the corona-treated inner surface of the base film by flexographic printing using water-based flexographic ink.

[0053] Next, the ink layer-formed surface of the base film was bonded to the corona-treated surface of intermediate film A, on which no vapor-deposited film was formed, by a non-sol lamination method using a two-component curing urethane adhesive. This adhesive layer was designated as the first adhesive layer.

[0054] Furthermore, a 40 μm thick unstretched polyethylene film (single layer of LLDPE) was prepared as a heat seal film, and a two-component curing urethane adhesive was used as a second adhesive layer, and the surface of intermediate film A facing the vapor-deposited film was bonded to the heat seal film by a non-sol lamination method. In this way, a laminate according to Example 1 was obtained. Example 2 A laminate according to Example 2 was obtained in the same manner as in Example 1, except that Intermediate Film B was used instead of Intermediate Film A. (Comparative Example 1) A laminate according to Comparative Example 1 was obtained in the same manner as in Example 1, except that no protective layer was formed and intermediate film C was used instead of intermediate film A. (Comparative Example 2) A laminate for Comparative Example 2 was obtained using the same procedure as in Example 1, except that a 25 μm thick unstretched polyethylene film (three-layer structure of HDPE / MDPE / HDPE) with one side corona-treated was used as the base film, no protective layer was formed, and intermediate film C was used instead of intermediate film A.

[0055] The laminates according to the examples and comparative examples were evaluated as follows. (Recyclability) The wt% of polyethylene in the laminate of each example was calculated based on the above formula (1), and the evaluation was based on the following two levels. 〇 (good): Contains 90wt% or more polyethylene. × (bad): The polyethylene content is less than 90 wt%. (Evaluation of heat sealability) Each laminate was cut into a 10 cm square, folded in half with the heat seal film facing inward, and heat sealed using a heat seal tester at a temperature of 140°C, a pressure of 0.1 MPa, and a time of 1 second. The heat-sealed portions of the obtained samples were visually observed and subjected to a sensory evaluation. The evaluation was based on the following two levels: ◯ (good): There are no wrinkles on the surface of the packaging material, and no melting or adhesion to the seal bar is observed. × (bad): Wrinkles appear on the surface of the packaging material, and melting and adhesion to the seal bar is observed. (Puncture strength) The puncture strength was measured in accordance with JIS Z 1707: 2019. The laminate according to each example was held flat under tension, and a hemispherical needle with a diameter of 1.0 mm and a tip radius of 0.5 mm was pressed against it from the substrate side at a rate of 50 mm / min, and the force (Newton: N) at the time of puncture was measured. (shock resistance) Using the laminate according to each example, ten 100 mm x 150 mm packaging bags with heat-sealed edges were produced. These packaging bags were filled with 200 g of distilled water, heat-sealed, and stored at 5°C for one day. After storage, each packaging bag was dropped 50 times from a height of 1.5 m, and the number of packaging bags that broke was recorded. (Oxygen Transmission Rate: OTR) Measurement was carried out using the Mocon method under conditions of 30° and 70% RH (relative humidity). (Water vapor transmission rate: WVTR) Measurement was carried out using the Mocon method under conditions of 40° and 90% RH.

[0056] The evaluation results are shown in Table 1.

[0057] As shown in Table 1, all of the Examples and Comparative Examples had high recyclability, but the laminates of Comparative Examples 1 and 2, which did not have a protective layer, had poor heat sealability, and the laminates of Comparative Examples 1 and 2, in which the intermediate film was made of a stretched polyethylene film, did not have sufficient impact resistance.

[0058] [Table 1] [Explanation of symbols]

[0059] 1. Laminate 10. Base film 10a: Outer surface of base film 10b: Inner surface of base film 11...Protective layer 14 Vapor-deposited film 20 Intermediate film 30 Heat seal film 40 First adhesive layer 50...Second adhesive layer

Claims

[Claim 1] A laminate comprising a base film, a first adhesive layer, an intermediate film, a second adhesive layer, and a heat seal film laminated in this order, with a protective layer further laminated on the outermost surface side of the base film, wherein the protective layer is made of a thermosetting resin, the base film is an oriented polyethylene film, the intermediate film and the heat seal film are unoriented polyethylene films, one side of the intermediate film is provided with a vapor-deposited film, and the proportion of polyethylene in the laminate is 90% by weight or more.

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