Laminated film, paper container, and paper container with lid

Abstract

To provide a laminated film, a paper container, and a paper container with a lid, which can improve practicality and recyclability.SOLUTION: A laminated film 10 comprises a base material layer 11 and a sealant layer 12 laminated on the base layer 11. The base material layer 11 is an unstretched polyethylene terephthalate film. The sealant layer 12 contains an ethylene-methacrylic acid copolymer. In the ethylene-methacrylic acid copolymer, a content of methacrylic acid is 5 mass% less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a laminate film, a paper container, and a paper container with a lid. [Background technology]

[0002] Pulp-molded containers made from pulp materials such as reeds or sugar cane have been known (see, for example, Patent Document 1). Patent Document 1 discloses a pulp-molded container provided with a window through which the inside can be viewed.

[0003] Such pulp-molded containers may have lower water resistance and oil resistance than plastic containers, so when storing food or the like in a pulp-molded container, it is common to laminate a polypropylene (PP) film onto the inner surface of the pulp-molded container or to add an oil-proofing agent or water-proofing agent to the pulp material used as the raw material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-144612 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a food contained in a film-laminated pulp-molded container is heated in a microwave oven, the film itself is required to have a heat resistance sufficient to withstand heating in a microwave oven. Also, when a film having high heat resistance is laminated on a pulp-molded container, it may be difficult to select an appropriate adhesive resin capable of adhering the film to the inner surface of the pulp-molded container.

[0006] Furthermore, in the case of pulp molded containers, recycling of pulp molded containers is being promoted for the purpose of reducing the environmental load. However, when an oil-proofing agent or a water-proofing agent is added to the raw pulp material, there is a possibility that the pulp molded container cannot be recycled after use.

[0007] The present disclosure has been made in consideration of these points, and aims to provide a laminated film, a paper container, and a paper container with a lid that can improve practicality and recyclability. [Means for solving the problem]

[0008] The embodiments of the present disclosure relate to the following [1] to [7].

[0009] [1] A base layer; A sealant layer is laminated on the base layer, The substrate layer is an unstretched polyethylene terephthalate film, the sealant layer comprises an ethylene-methacrylic acid copolymer; The laminated film, wherein the ethylene-methacrylic acid copolymer has a methacrylic acid content of 5 mass % or less.

[0010] [2] The laminated film according to [1], wherein the ethylene-methacrylic acid copolymer has a methacrylic acid content of 1 mass % or more.

[0011] [3] The laminated film according to [1] or [2], wherein the peel strength between the base layer and the sealant layer is 3.0 N / 15 mm or more.

[0012] [4] The laminate film according to any one of [1] to [3], wherein the thickness of the sealant layer is 10 μm or more and 50 μm or less.

[0013] [5] A porous paper container body; A paper container comprising a laminate film according to any one of [1] to [4] laminated on the surface of the container body.

[0014] [6] The paper container according to [5], wherein the peel strength between the laminate film and the container body is 0.5 N / 15 mm or more and less than 3.0 N / 15 mm.

[0015] [7] [5] or [6], and A paper container with a lid, comprising a lid that seals the paper container. Effect of the Invention

[0016] According to the present disclosure, the practicality and recyclability of paper containers and paper containers with lids can be improved. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view showing a laminated film according to the present embodiment. [Diagram 2] 2(a)-(b) are diagrams illustrating a method for measuring the peel strength between the base layer and the sealant layer of the laminated film according to the present embodiment. [Diagram 3] FIG. 3 is a perspective view showing a paper container according to the present embodiment. [Figure 4] FIG. 4 is a cross-sectional view (cross-sectional view taken along line IV-IV in FIG. 3) showing the paper container according to this embodiment. [Diagram 5] FIG. 5 is a perspective view showing another example of the paper container according to the present embodiment. [Figure 6] FIG. 6 is a perspective view showing another example of the paper container according to the present embodiment. [Figure 7] FIG. 7 is a perspective view showing another example of a paper container according to the present embodiment. [Figure 8] FIG. 8 is a cross-sectional view showing a paper container with a lid according to this embodiment. [Figure 9] FIG. 9 is a cross-sectional view showing a method for manufacturing a container body according to this embodiment. [Figure 10] FIG. 10 is a cross-sectional view showing a method for manufacturing a container body according to this embodiment. [Figure 11] FIG. 11 is a cross-sectional view showing a method for manufacturing a paper container according to this embodiment. [Figure 12] FIG. 12 is a cross-sectional view showing a method for manufacturing a paper container according to this embodiment. [Figure 13] FIG. 13 is a cross-sectional view showing a method for manufacturing a paper container according to this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, the present embodiment will be described with reference to the drawings. FIGS. 1 to 13 are diagrams showing the present embodiment. Each of the following diagrams is a schematic diagram. Therefore, the size and shape of each part are appropriately exaggerated to facilitate understanding. In addition, the present invention can be modified appropriately within the scope of the technical concept. In each of the following diagrams, the same parts are given the same reference numerals, and some detailed explanations may be omitted. In addition, the numerical values ​​such as the dimensions of each member and the material names described in this specification are examples of the embodiment, and are not limited thereto, and can be appropriately selected and used. In this specification, terms that specify shapes and geometric conditions, such as parallel, orthogonal, and vertical, are interpreted to include substantially the same state in addition to their strict meanings.

[0019] In this specification, "top" and "bottom" refer to the top and bottom, respectively, of the paper container when it is held upright (FIG. 4). In this specification, "surface" refers to the surface facing the contents or the surface facing upward when the paper container is held upright.

[0020] (Laminated film) As shown in FIG. 1, the laminated film 10 according to the present embodiment includes a base layer 11 and a sealant layer 12 laminated on the base layer 11. The sealant layer 12 is laminated directly on the base layer 11. In other words, the base layer 11 and the sealant layer 12 are in contact with each other. The base layer 11 and the sealant layer 12 are arranged in order from the outer surface 10a to the inner surface 10b. Here, the outer surface 10a is the surface that comes into contact with the contents in the paper container 20 described later. The inner surface 10b is the surface that is arranged to face the container body 30 when the paper container 20 described later is produced.

[0021] Among these, the base layer 11 is, for example, a layer that supports the sealant layer 12 and enhances the strength of the entire laminated film 10. In this embodiment, the base layer 11 is a layer that constitutes the outer surface 10a of the laminated film 10. In this embodiment, the base layer 11 is an unstretched polyethylene terephthalate film. Unstretched polyethylene terephthalate is resistant to moisture and oil and has excellent heat resistance. Therefore, food contained in the paper container 20 described later can be heated using a microwave oven. In addition, unstretched polyethylene terephthalate has excellent adhesion and conformability to the surface of the container body 30, which is a pulp molded container described later, and therefore can improve the moldability of the paper container 20. In the following description, polyethylene terephthalate is also simply referred to as PET.

[0022] In this embodiment, the polyethylene terephthalate is crystalline polyethylene terephthalate (C-PET). This crystalline PET is a material in which the heat resistance is increased to 220°C by crystallizing PET resin. Therefore, the laminated film 10 according to this embodiment can be used for a container that is heated in a microwave oven or an oven. Crystalline PET is produced by gradually lowering the temperature of PET resin in a molten state. In addition, a crystal nucleating agent may be added to the polyethylene terephthalate so that heat resistance is imparted by crystallization during the process of forming the paper container 20 described later. Examples of the crystal nucleating agent include metal benzoates.

[0023] In the present embodiment, the thickness of the base layer 11 may be 15 μm or more and 40 μm or less, and may be 25 μm or less, for example. When the thickness of the base layer 11 is 15 μm or more, the heat resistance and strength of the laminated film 10 can be improved. Furthermore, when the thickness of the base layer 11 is 40 μm or less, the laminated film 10 can be prevented from becoming too thick. Therefore, the formability of the laminated film 10 can be improved. The base layer 11 may be composed of multiple layers. In this case, the thickness of the base layer 11 is the total thickness of the multiple layers.

[0024] The sealant layer 12 is a layer for bonding the laminated film 10 to the container body 30 described later. In this embodiment, the sealant layer 12 is a layer constituting the inner surface 10b of the laminated film 10. This sealant layer 12 is a layer configured to have adhesiveness to the container body 30 even when the food contained in the paper container 20 described later is heated using a microwave oven. In this embodiment, the sealant layer 12 contains ethylene-methacrylic acid copolymer (hereinafter, also simply referred to as EMAA). In addition, the methacrylic acid content in the ethylene-methacrylic acid copolymer is 5 mass% or less. Such EMAA can exert a desired adhesive force to the surface of the container body 30, which is an unstretched PET film and a pulp molded container described later, and has excellent heat resistance. Therefore, the moldability of the paper container 20 can be improved, and the food contained in the paper container 20 can be heated using a microwave oven. Furthermore, since the sealant layer 12 contains EMAA with a methacrylic acid content of 5% by mass or less, the adhesive strength between the laminated film 10 and the container body 30 can be prevented from becoming too high. That is, since the sealant layer 12 contains EMAA with a methacrylic acid content of 5% by mass or less, the adhesive strength between the laminated film 10 and the container body 30 can be made to a desired strength without adding an oil-proofing agent or a water-proofing agent to the raw material of the pulp molded container. Therefore, when recycling the container body 30, which is a pulp molded container, the laminated film 10 and the container body 30 can be easily separated. Furthermore, the content of methacrylic acid in the ethylene-methacrylic acid copolymer may be 4% by mass or less, 3% by mass or less, or 2% by mass or less.

[0025] In the ethylene-methacrylic acid copolymer, the content of methacrylic acid may be 1% by mass or more. This allows the adhesive strength to the unstretched PET film to be high. In addition, in the ethylene-methacrylic acid copolymer, the content of methacrylic acid may be 2% by mass or more, 3% by mass or more, or 4% by mass or more.

[0026] In this embodiment, the thickness of the sealant layer 12 may be 10 μm or more and 50 μm or less, and may be 25 μm or less, for example. When the thickness of the sealant layer 12 is 10 μm or more, the adhesiveness to the container body 30, which is a pulp molded container described later, can be improved. Also, when the thickness of the sealant layer 12 is 50 μm or less, the extensibility to the container body 30, which is a pulp molded container, can be improved.

[0027] In such a laminated film 10, the peel strength between the base layer 11 and the sealant layer 12 may be 3.0 N / 15 mm or more. The peel strength between the base layer 11 and the sealant layer 12 is measured in accordance with JIS K 6854-3:1999. At this time, as shown in FIG. 2(a), a rectangular specimen Sa is cut out of the laminated film 10 with a width (W) of 15 mm and a length (L1) of 60 mm. Next, the peel strength between the base layer 11 and the sealant layer 12 is measured for these test specimens Sa using a tensile tester (Tensilon universal material testing machine RTC-1310, manufactured by A&D Co., Ltd.). In measuring the peel strength, first, a part of the base layer 11 is peeled off from the sealant layer 12 as shown in FIG. 2(b). The length (L2) of the peeled part along the longitudinal direction (the left-right direction in FIG. 2(b)) is about 2 cm. Next, the already peeled portions of the test piece Sa are gripped by a pair of grippers of a measuring device, and the grippers are moved in opposite directions to pull the test piece Sa. The pulling speed of the test piece Sa is 50 mm / min. The average value of the obtained tensile strengths is regarded as the peel strength between the base layer 11 and the sealant layer 12.

[0028] By setting the peel strength between the base material layer 11 and the sealant layer 12 to 3.0 N / 15 mm or more, it is possible to prevent the base material layer 11 from unintentionally peeling off from the sealant layer 12 when removing the lid material 50 from the paper container 20 of the lid-attached paper container 1 described below. There need not be any upper limit to the peel strength between the base material layer 11 and the sealant layer 12.

[0029] Moreover, such a laminated film 10 may be produced by laminating the sealant layer 12 on the base layer 11 by extrusion lamination. At this time, the surface of the base layer 11 on which the sealant layer 12 is laminated (the inner surface 10b side of the laminated film 10) may be subjected to a corona treatment.

[0030] (Paper containers) Next, a paper container 20 according to the present embodiment will be described. As shown in Fig. 3 and Fig. 4, the paper container 20 includes a container body 30 made of porous paper and the above-mentioned laminated film 10 laminated on the surface of the container body 30. In the paper container 20, the above-mentioned laminated film 10 plays a role in protecting the container body 30. In addition, the laminated film 10 covers the entire surface of the container body 30. This prevents the contents filled in the paper container 20 from leaking out of the paper container 20. The laminated film 10 is adhered to the container body 30 by, for example, heat sealing (thermal welding).

[0031] (Container body) The container body 30 has a bottom 31, a side portion 33 connected to the bottom 31, and a flange portion 35 connected to the side portion 33. The bottom portion 31, the side portion 33, and the flange portion 35 are integrally molded. The bottom portion 31 and the side portion 33 form a storage space Sp in which the contents are stored. In the illustrated example, a single storage space Sp is formed. The depth of the storage space Sp is not particularly limited, and may be, for example, 1 cm or more and 10 cm or less, or 2 cm or more and 10 cm or less.

[0032] The bottom 31 of the container body 30 has a generally rectangular shape in plan view. The bottom 31 may have a polygonal shape, such as an octagonal shape, in plan view.

[0033] The side portion 33 extends upward from the bottom portion 31. In the illustrated example, the side portion 33 is formed in an inverted quadrangular pyramid shape. However, this is not limited thereto, and the side portion 33 may be formed in a polygonal pyramid shape such as an inverted octagonal pyramid shape.

[0034] The flange portion 35 protrudes horizontally toward the side from the upper end of the side portion 33. The flange portion 35 is formed into an annular shape as a whole. In addition, since the side portion 33 is formed into an inverted quadrangular pyramid shape as described above, the flange portion 35 includes four corners.

[0035] In the examples shown in Figs. 3 and 4, an example in which a single storage space Sp is formed has been described, but the present invention is not limited thereto. For example, as shown in Fig. 5, the storage space Sp may be divided into a plurality of regions by a partition plate 37. In this case, the partition plate 37 may be integrally formed with the bottom portion 31 and the side portion 33. As described above, the base layer 11 of the laminated film 10 is an unstretched polyethylene terephthalate film. Also, as described above, the unstretched polyethylene terephthalate film has excellent conformability to the surface of the container body 30. Therefore, the laminated film 10 according to the present embodiment can be in close contact with the entire surface of the container body 30 even when the storage space Sp is divided into a plurality of regions.

[0036] 6, a tab 38 that can be cut off from the flange portion 35 may be connected to the flange portion 35. In the illustrated example, the tab 38 is connected to one of the four corners of the flange portion 35. The tab 38 is connected to the flange portion 35 via a cutting line 38a formed in a perforated shape. By connecting the tab 38 to the flange portion 35 in this manner, when recycling the container body 30, the tab 38 can be cut off from the flange portion 35 to facilitate separation of the laminated film 10 from the container body 30.

[0037] Furthermore, as shown in FIG. 7, an unsealed portion 39 (a shaded portion in FIG. 7) may be formed on the flange portion 35. Here, the unsealed portion 39 is a portion where the laminated film 10 is not sealed to the container body 30. In the illustrated example, the unsealed portion 39 is formed at one of the four corners of the flange portion 35. The unsealed portion 39 is also formed so as to reach the outer edge of the flange portion 35. In this way, the unsealed portion 39 is formed on the flange portion 35, so that the user can easily pick up the laminated film 10 at the unsealed portion 39. Therefore, when recycling the container body 30, the laminated film 10 located on the unsealed portion 39 can be used as a trigger to easily separate the laminated film 10 from the container body 30.

[0038] As described above, the container body 30 is a porous paper container. The container body 30 may be a pulp-molded container. The pulp-molded container is a container obtained from a raw material such as a slurry of wood pulp fibers, such as recycled paper pulp or virgin pulp, or non-wood fibers, such as reed, straw, or hemp. By using the container body 30 as a pulp-molded container, the weight of the paper container 20 can be reduced. In addition, the pulp-molded container is easy to dispose of and can be reused. Therefore, by using the container body 30 as a pulp-molded container, the recyclability of the container body 30 can be improved.

[0039] When producing a pulp molded container, for example, first, the above-mentioned raw materials are poured into a mesh-shaped mold (female mold) having a predetermined inner surface shape, and the raw materials are laminated on the inner surface of the mold by sucking the raw materials from the outside of the mold. Next, the obtained laminate of raw materials is dehydrated, dried, and molded by natural drying or hot air drying, and hot pressing using a male mold, etc. In this way, a pulp molded container is obtained. Note that the above-mentioned manufacturing method of a pulp molded container is an example of a manufacturing method of a pulp molded container, and the pulp molded container may be produced by other molding methods.

[0040] In addition, since the container body 30 is porous, air can pass through from the inner surface to the outer surface of the container body 30. Therefore, the laminated film 10 is configured to be pressed against the container body 30 by sucking air through suction holes 61 of a cavity side mold 60 described later.

[0041] In a paper container 20 including such a container body 30, the peel strength between the laminate film 10 and the container body 30 may be 0.5 N / 15 mm or more and less than 3.0 N / 15 mm. The peel strength between the laminate film 10 and the container body 30 is measured in accordance with JIS K 6854-3:1999 by the same method as the peel strength between the base layer 11 and the sealant layer 12 described above.

[0042] By having a peel strength between the laminated film 10 and the container body 30 of 0.5 N / 15 mm or more, it is possible to prevent the laminated film 10 from unintentionally peeling off from the container body 30. In particular, it is possible to prevent the laminated film 10 from unintentionally peeling off from the container body 30 when removing the lid material 50 from the paper container 20 of the lid-attached paper container 1. In addition, by having a peel strength between the laminated film 10 and the container body 30 of less than 3.0 N / 15 mm, it is possible to prevent the laminated film 10 from becoming difficult to peel off from the container body 30 when recycling the container body 30. Therefore, it is possible to easily separate the container body 30 and the laminated film 10 when recycling the container body 30.

[0043] Furthermore, the peel strength between the laminate film 10 and the container body 30 may be smaller than the peel strength between the base material layer 11 and the sealant layer 12. This allows the laminate film 10 to be peeled off from the container body 30 without peeling off the laminate film 10 when recycling the container body 30. This allows the container body 30 and the laminate film 10 to be more easily separated when recycling the container body 30.

[0044] A heat seal agent may be applied to the surface of the container body 30. In this case, the adhesive strength between the container body 30 and the laminated film 10 can be easily adjusted. The heat seal agent may be ink. The heat seal agent may contain ethylene-vinyl acetate copolymer (EVA), ionomer, polyethylene (PE) or polypropylene (PP). The heat seal agent may contain vinyl, acrylic, polyamide, polyester, polyether, polyurethane, epoxy, chlorinated EVA, chlorinated PP, vinyl chloride acetate, polyol, polyethyleneimine, starch, nitrocellulose, rubber resin, etc. Furthermore, the heat seal agent may be applied to the container body 30 by gravure printing, flexographic printing, offset printing, etc.

[0045] (Paper container with lid) Next, the paper container with a lid 1 according to this embodiment will be described. As shown in Figure 8, the paper container with a lid 1 according to this embodiment comprises the paper container 20 described above and a lid 50 that seals the paper container 20.

[0046] (lid material) The lid material 50 is sealed over the entire periphery of the area of ​​the laminate film 10 of the paper container 20 that corresponds to the flange portion 35 .

[0047] Such a lid material 50 may be made, for example, from a laminate having the following layer structure. (1) PET / seal layer (2) Oriented nylon (ONY) / sealing layer (3) PET / oriented nylon (ONY) / sealing layer (4) PET / polyethylene (PE) / sealing layer (5) K-coated oriented nylon (KONY) / polyethylene (PE) / seal layer (6) Paper / seal layer The laminate constituting the lid material 50 may be, for example, a laminate in which a gas barrier material such as ethylene-vinyl alcohol copolymer (EVOH) is laminated in the middle layer. In this case, the lid material 50 may be made of a laminate having a layer structure such as PET / polyethylene (PE) / ethylene-vinyl alcohol copolymer (EVOH) / polyethylene (PE) / sealing layer.

[0048] The lid material 50 may be made, for example, from a laminate having the following layer structure. (Outside) Polyethylene terephthalate film with transparent vapor deposition layer (12 μm) / Nylon film (15 μm) / Polyethylene film (40 μm) (Inside)

[0049] It is preferable to use a resin material that can exhibit so-called easy peel properties for the laminate constituting the lid material 50. Each of the above layers is formed according to a conventional method, such as a dry lamination method, an extrusion lamination method, an extrusion coating method, or another coating method.

[0050] In the paper container 1 with a lid material having such a configuration, first, the contents are filled into the paper container 20. Next, the lid material 50 is sealed to the area of ​​the laminated film 10 of the paper container 20 corresponding to the flange portion 35. In this way, the paper container 1 with a lid material filled with the contents is obtained. The paper container 1 with a lid material may be a container for a microwave oven. That is, the paper container 1 with a lid material may be a container for heating in a microwave oven. Such a paper container 1 with a lid material may be a container for chilled or frozen foods, or may be used as a take-out container. The contents may be food such as rice, side dishes, meat, dairy products, etc.

[0051] Next, the operation of the present embodiment having such a configuration will be described. Here, a manufacturing method of the laminated film 10, a manufacturing method of the paper container 20, and a manufacturing method of the paper container 1 with a lid material will be described with reference to Figs. 9 to 13.

[0052] (Laminated Film Manufacturing Method) First, the base layer 11 is prepared. At this time, an unstretched polyethylene terephthalate film is prepared as the base layer 11. The polyethylene terephthalate of the unstretched polyethylene terephthalate film may be crystalline polyethylene terephthalate (C-PET).

[0053] Next, the sealant layer 12 is laminated on the base layer 11 by extrusion lamination. At this time, an ethylene-methacrylic acid copolymer having a methacrylic acid content of 5 mass% or less is used as the sealant layer 12. When laminating the sealant layer 12 on the base layer 11, the sealant layer 12 may be extruded onto the base layer 11 at a temperature of, for example, 280°C or more and 320°C or less.

[0054] In this manner, a laminated film 10 including the base layer 11 and the sealant layer 12 laminated on the base layer 11 is obtained.

[0055] (Manufacturing method of container body) Next, a method for manufacturing the container body 30 will be described.

[0056] First, a slurry SL (see FIG. 9) of fibers such as wood pulp fibers, for example, recycled paper pulp or virgin pulp, or non-wood fibers, for example, reed, straw or hemp, is prepared.

[0057] 9, the slurry SL is poured into a mesh-shaped first mold 71 (female mold). The inner surface of this first mold 71 has a shape corresponding to the outer surface of the container body 30. The slurry SL is then layered on the inner surface of the first mold 71 by sucking the slurry SL from the outside of the first mold 71 through suction holes (not shown) formed in the first mold 71. Thereafter, the slurry SL is dried. The slurry SL may be dried by natural drying or hot air drying.

[0058] Next, as shown in FIG. 10, the slurry SL is subjected to hot press molding using a second mold 72 (male mold).

[0059] In this manner, a pulp molded container as the container body 30 is obtained.

[0060] (Method of manufacturing paper containers and paper containers with lids) Next, a method for manufacturing the paper container 20 will be described.

[0061] 11, the container body 30 is attached to a cavity side mold 60. This cavity side mold 60 has a suction hole 61 formed therein, and the container body 30 is attached to the cavity side mold 60 by sucking air through the suction hole 61.

[0062] Next, the container body 30 and the laminated film 10 (film 10c described later) are subjected to vacuum forming, so that the laminated film 10 is laminated on the surface of the container body 30. At this time, first, as shown in FIG. 12, the film 10c constituting the laminated film 10 is placed above the container body 30. Next, the film 10c is heated by the hot plate 62. Then, after the film 10c is heated by the hot plate 62 to about 100°C or more and 150°C or less, air is sucked through the suction hole 61. As described above, the container body 30 is a porous paper container. Therefore, as shown in FIG. 13, the film 10c is sucked into the container body 30 by sucking air through the suction hole 61. As a result, the film 10c is in close contact with the container body 30. Here, the base layer 11 of the laminated film 10 (film 10c) is an unstretched polyethylene terephthalate film. In addition, the unstretched polyethylene terephthalate film has excellent conformability to the surface of the container body 30. Therefore, when the laminate film 10 is laminated on the surface of the container body 30, the laminate film 10 can deform to conform to the uneven shape of the surface of the container body 30. Therefore, the laminate film 10 can be adhered to the entire surface of the container body 30, improving the formability of the paper container 20.

[0063] Thereafter, the film 10c is cut into a desired shape by a cutting mechanism (not shown), thereby obtaining the laminated film 10 laminated on the container body 30. In this manner, the paper container 20 is obtained.

[0064] In parallel with the production of the paper container 20, the lid material 50 is prepared. At this time, a predetermined laminate is produced by a dry lamination method or the like. Then, the laminate is punched into a predetermined shape with a blade or the like to produce the lid material 50.

[0065] Next, the paper container 20 is filled with the contents, and the paper container 20 is sealed with the lid 50. At this time, the paper container 20 is first filled with the contents (not shown). Next, the lid 50 is placed on the laminated film 10 at a position corresponding to the flange portion 35.

[0066] Next, the lid material 50 is sealed to the laminated film 10 by a sealing hot plate (not shown) or the like. At this time, the air inside the paper container 20 may be replaced by, for example, nitrogen gas or the like.

[0067] In this way, a paper container with lid 1 is obtained, which comprises the paper container 20 and the lid 50 that seals the paper container 20.

[0068] Here, when eating the contents contained in the paper container with lid 1, the user may heat the paper container with lid 1, for example, by placing it in a microwave oven. In this embodiment, the base layer 11 of the laminated film 10 is an unstretched polyethylene terephthalate (PET) film. This unstretched PET has excellent heat resistance. Therefore, even when the food contained in the paper container with lid 1 is heated using a microwave oven, the occurrence of defects such as holes in the laminated film 10 can be suppressed. In addition, even when the food contained in the paper container with lid 1 is heated using a microwave oven, the occurrence of unintentional peeling of a part of the laminated film 10 from the container body 30 can be suppressed.

[0069] Next, the paper container 1 with lid material that has now been heated is removed from the microwave oven. Thereafter, the lid material 50 is removed from the paper container 20, allowing the user to eat the contents.

[0070] In addition, after the user consumes the contents, the container body 30 and the laminated film 10 of the paper container 20 may be separated and discarded, so that the container body 30 can be recycled. At this time, the user first peels off the laminated film 10 from the container body 30. In this embodiment, the sealant layer 12 of the laminated film 10 contains EMAA, which has a methacrylic acid content of 5% by mass or less. This makes it possible to prevent the adhesive strength between the laminated film 10 and the container body 30 from becoming too high, and the laminated film 10 and the container body 30 can be easily separated. In this way, the laminated film 10 is removed from the paper container 20, and the container body 30 and the laminated film 10 of the paper container 20 are separated and discarded. This allows the container body 30 to be recycled.

[0071] As described above, according to this embodiment, the base layer 11 of the laminated film 10 is an unstretched polyethylene terephthalate (PET) film. This unstretched PET has excellent heat resistance. Therefore, the food contained in the paper container 20 can be heated using a microwave oven. In addition, the unstretched PET has excellent adhesion and conformability to the surface of the container body 30, which is a pulp molded container, and therefore the formability of the paper container 20 can be improved.

[0072] According to the present embodiment, the sealant layer 12 of the laminated film 10 contains ethylene-methacrylic acid copolymer (EMAA). The methacrylic acid content in EMAA is 5% by mass or less. Such EMAA can exert a desired adhesive force on the surface of the container body 30, which is an unstretched PET and a pulp molded container, and has excellent heat resistance. This improves the moldability of the paper container 20, and allows the food contained in the paper container 20 to be heated using a microwave oven. Furthermore, since the sealant layer 12 contains EMAA with a methacrylic acid content of 5% by mass or less, it is possible to prevent the adhesive strength between the laminated film 10 and the container body 30 from becoming too high. That is, since the sealant layer 12 contains EMAA with a methacrylic acid content of 5% by mass or less, it is possible to achieve a desired adhesive strength between the laminated film 10 and the container body 30 without adding an oil-proofing agent or a water-proofing agent to the raw material of the pulp molded container. Therefore, when recycling the container body 30, which is a pulp-molded container, the laminated film 10 can be easily separated from the container body 30. It will be explained by examples described later that the practicality and recyclability of the paper container 20 can be improved by using the laminated film 10 according to this embodiment. EXAMPLES

[0073] Next, a specific example of the above embodiment will be described.

[0074] (Example) First, the laminated film shown in Figure 1 was produced. In this case, an unstretched polyethylene terephthalate film (C-PET, manufactured by Shin-Etsu Finetech Co., Ltd., thickness 25 μm) was prepared as the base layer of the laminated film. In addition, an ethylene-methacrylic acid copolymer (Nucrel (registered trademark), AN-4233C (methacrylic acid content: 1.3%) manufactured by Dow Mitsui Polychemicals) was prepared as the resin for the sealant layer.

[0075] Next, the surface of the unstretched PET that was to be the base layer described above, on which the sealant layer was to be laminated, was subjected to a corona treatment. Next, EMAA was extruded onto the corona-treated surface as a sealant layer, and the sealant layer was laminated on the base layer. The thickness of the sealant layer was set to 25 μm.

[0076] In addition, a paper container shown in Figures 3 and 4 was produced. At this time, a container body was first prepared. The container body was produced by the method shown in Figures 9 and 10.

[0077] Next, a laminate film was laminated on the surface of the container body to produce a paper container. When laminating the laminate film on the container body, the laminate film (film) was heated to 150°C.

[0078] (Comparative Example) A laminated film and a paper container were produced in the same manner as in the Examples, except that an ethylene-methacrylic acid copolymer (Nucrel (registered trademark) AN0908C (methacrylic acid content: 9.0%) manufactured by Dow Mitsui Polychemicals) was used as the resin for the sealant layer.

[0079] (1) Peel strength evaluation test for laminated film The obtained laminated film was used to carry out a peel strength evaluation test between the base layer and the sealant layer. The peel strength between the base layer and the sealant layer was measured in accordance with JIS K 6854-3:1999. At this time, the laminated film was cut into a rectangular shape with a width (W) of 15 mm and a length (L1) of 60 mm to be used as a test piece. At this time, three test pieces (test pieces S1 to S3) were prepared.

[0080] Next, the peel strength between the base layer and the sealant layer of these test pieces was measured using a tensile tester (Tensilon universal material testing machine RTC-1310, manufactured by A&D Co., Ltd.). In measuring the peel strength, first, a part of the base layer was peeled off from the sealant layer. The length (L2) of the peeled part along the longitudinal direction was set to 2 cm. Next, the already peeled parts of the test pieces were held by a pair of grippers of the measuring device, and the test pieces were pulled by moving the grippers in opposite directions. The pulling speed for pulling the test pieces was set to 50 mm / min. The average value of the obtained tensile strength was taken as the peel strength between the base layer and the sealant layer.

[0081] (2) Peel strength evaluation test for paper containers Using the obtained paper container, a peel strength evaluation test between the laminated film and the container body was performed. The peel strength between the laminated film and the container body was measured in accordance with JIS K 6854-3:1999. In this case, three test pieces (test pieces S4 to S6) were prepared in the same manner as in the case of measuring the peel strength between the base layer and the sealant layer, and the peel strength between the laminated film and the container body was measured.

[0082] (3) Heat resistance evaluation test A heat resistance evaluation test was also conducted using the obtained paper container. First, chicken meat (150 g) was placed in the paper container. Next, the chicken meat in the paper container was heated using a microwave oven. The microwave oven output was 600 W, and the heating time was 15 minutes. Then, the appearance of the paper container after heating was evaluated.

[0083] The results are shown in Table 1. Table 2 shows the results of the peel strength evaluation test for the laminated film, Table 3 shows the results of the peel strength evaluation test for the paper container, and Table 4 shows the results of the heat resistance evaluation test.

[0084] [Table 1]

[0085] [Table 2]

[0086] [Table 3]

[0087] [Table 4]

[0088] In Table 4 above, "Fair" means that the laminate film and container body had no appearance defects such as holes in the paper container after heating, and the laminate film had not peeled off from the container body. "Fail" means that the laminate film or container body had an appearance defect such as holes in the paper container after heating, or part of the laminate film had peeled off from the container body.

[0089] As a result, as shown in Table 2, in the peel strength evaluation test of the laminated film, the average peel strength between the base layer and the sealant layer in the laminated film according to the comparative example was 0.11 N / 15 mm. In contrast, the average peel strength between the base layer and the sealant layer in the laminated film according to the example was 4.23 N / 15 mm. In this way, the laminated film according to the present embodiment was able to increase the peel strength between the base layer and the sealant layer. Therefore, it was found that the laminated film according to the present embodiment can suppress the base layer from being unintentionally peeled off from the sealant layer when removing the lid from the paper container of the lid-attached paper container. As a result, it was found that the laminated film according to the present embodiment can improve practicality.

[0090] Also, as shown in Table 3, in the peel strength evaluation test of the paper container, the average peel strength between the laminated film and the container body in the paper container according to the comparative example was 2.32 N / 15 mm. In contrast, the average peel strength between the laminated film and the container body in the paper container according to the embodiment was 0.95 N / 15 mm. In this way, in the paper container according to the present embodiment, the peel strength between the laminated film and the container body can be prevented from becoming too large, and the peel strength can be made to a desired value. Therefore, it was found that the paper container according to the present embodiment can prevent the laminated film from being unintentionally peeled off from the container body, and that the container body and the laminated film can be easily separated when recycling the container body. As a result, it was found that the paper container according to the present embodiment can improve practicality and recyclability.

[0091] Furthermore, as shown in Table 4, in the paper container according to the comparative example, when food contained in the paper container was heated using a microwave oven, a part of the laminate film peeled off from the container body in the paper container after heating. In contrast, in the paper container according to the example, when food contained in the paper container was heated using a microwave oven, there were no appearance defects such as holes in the laminate film and container body, and the laminate film did not peel off from the container body. Therefore, it was found that the laminate film according to this embodiment can improve the heat resistance of the paper container. As a result, it was found that the paper container according to this embodiment can improve practicality.

[0092] The present disclosure is not limited to the above-mentioned embodiment and each modification, and the components can be modified and embodied in the implementation stage without departing from the gist of the present disclosure. In addition, various inventions can be formed by appropriate combinations of multiple components disclosed in the above-mentioned embodiment and each modification. Some components may be deleted from all the components shown in the embodiment and each modification. [Explanation of symbols]

[0093] 1 Paper container with lid 10 Laminated film 11 Base material layer 12 Sealant layer 20 Paper containers 30 Container body 50 Lid material

Claims

1. A base layer; A sealant layer is laminated on the base layer, The substrate layer is an unstretched polyethylene terephthalate film, the sealant layer comprises an ethylene-methacrylic acid copolymer; The laminated film, wherein the ethylene-methacrylic acid copolymer has a methacrylic acid content of 5% by mass or less.

2. The laminated film according to claim 1, wherein the ethylene-methacrylic acid copolymer has a methacrylic acid content of 1% by mass or more.

3. The laminated film according to claim 1 , wherein the peel strength between the base layer and the sealant layer is 3.0 N / 15 mm or more.

4. The laminated film according to claim 1 , wherein the sealant layer has a thickness of 10 μm or more and 50 μm or less.

5. A porous paper container body; A paper container comprising the laminate film according to claim 1 laminated on a surface of the container body.

6. The paper container according to claim 5 , wherein a peel strength between the laminated film and the container body is 0.5 N / 15 mm or more and less than 3.0 N / 15 mm.

7. The paper container according to claim 5 , A paper container with a lid, comprising a lid that seals the paper container.

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