Paper resin composite container and manufacturing method of paper resin composite container

Abstract

To provide a paper resin composite container capable of achieving both a barrier property and form stability as a container, and to provide a manufacturing method of paper resin composite container.SOLUTION: A paper resin composite container includes: a three-dimensional blank in which a side panel is folded with respect to a bottom panel in a blank for container containing the bottom panel and at least one side panel continued to a peripheral edge part of the bottom panel; and a resin skeleton part which extends along the bottom surface or the side surface so as to cover the bottom panel and an end surface of the side panel, and integrated with the three-dimensional blank. The bottom panel and the side panel are formed integrally and in a planar manner. The blank for container includes a paper layer, a heat-welding layer and a barrier layer. The resin skeleton part includes a core layer having a barrier property, and a skin layer covering the core layer and having a heat-welding property.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a paper-resin composite container and a method for manufacturing the paper-resin composite container. [Background technology]

[0002] A known technology for paper-resin composite containers involves inserting a blank plate made of a laminated sheet of at least paper and plastic film into a mold and integrating the resin and the blank plate by injection molding, as described in Patent Document 1. In one example described in Patent Document 1, a tapered round composite container is manufactured using a blank plate made of a circular bottom plate and a fan-shaped body plate connected to the bottom plate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-207880 Summary of the Invention [Problem to be solved by the invention]

[0004] In a composite container in which a resin and a blank plate are integrated by injection molding as in the conventional technology described above, if the portion formed by injection molding is referred to as the resin skeleton, the resin skeleton is required to have barrier properties to insulate the articles contained in the container from the outside and heat-weldability to be properly bonded to the blank plate. However, using a resin with barrier properties reduces the bondability with the blank plate, resulting in a decrease in the dimensional stability of the container. On the other hand, there is a problem in that the barrier properties are reduced when trying to ensure the bondability with the blank plate.

[0005] An object of the present disclosure is to provide a paper-resin composite container that can achieve both barrier properties and stability of the container's shape, and a method for manufacturing the paper-resin composite container. [Means for solving the problem]

[0006] [1] A paper-resin composite container according to one embodiment of the present disclosure comprises a container blank including a bottom panel corresponding to the bottom surface of the container and at least one side panel corresponding to the side surface of the container and connected to the peripheral portion of the bottom panel, the side panel being folded relative to the bottom panel to form a three-dimensional blank; and a resin skeleton portion integrated into the three-dimensional blank, extending along the bottom surface or the side surface so as to cover the end surfaces of the bottom panel and the side panel, wherein the bottom panel and the side panel are integrally molded into a planar shape, the container blank having a paper layer, a heat-sealable layer having heat-sealable properties, and a barrier layer, and the resin skeleton portion having a core layer having barrier properties and a skin layer covering the core layer and having heat-sealable properties.

[0007] The paper-resin composite container described in [1] has a three-dimensional blank and a resin skeleton integrated with the three-dimensional blank. The three-dimensional blank is formed by folding a container blank, and thus has a paper layer, a heat-sealed layer, and a barrier layer, just like the container blank. The resin skeleton has a core layer with barrier properties and a skin layer with heat-sealed properties. The core layer is covered with a skin layer, and the skin layer contacts the end face of the three-dimensional blank (container blank). Because the three-dimensional blank has a heat-sealed layer as described above, the skin layer (resin skeleton) and the three-dimensional blank can be integrated by heat welding. Therefore, the stability of the container shape can be ensured. The three-dimensional blank has a barrier layer, and the core layer of the resin skeleton has barrier properties. Therefore, the paper-resin composite container can also ensure barrier properties. In other words, the paper-resin composite container described in [1] above can achieve both barrier properties and stability of the container shape.

[0008] [2] The container blank has a plurality of the side panels, and in the three-dimensional blank, gaps are formed between adjacent side panels along the peripheral portion of the plurality of side panels bent relative to the bottom panel, and the resin skeleton portion may have side column portions that fill the gaps and join the adjacent side panels.

[0009] [3] The skin layer may be formed of a resin having a flexural modulus of less than 2000 MPa, and the skin layer may occupy 60% or more in a cross section perpendicular to the extending direction of the resin skeleton.

[0010] In the paper-resin composite container described in [3] above, the resin skeleton is easily bent, so even if the paper-resin composite container is dropped during distribution, handling by consumers, etc., the resin skeleton is not likely to break. Therefore, the paper-resin composite container is not likely to break.

[0011] [4] A method for manufacturing a paper-resin composite container according to another aspect of the present disclosure includes the steps of: forming a three-dimensional blank by bending a container blank, the container blank including a bottom panel corresponding to the bottom surface of the container and at least one side panel corresponding to the side surface of the container and connected to the peripheral edge of the bottom panel, relative to the bottom panel; and forming a resin skeleton portion that extends along the bottom surface or the side surface so as to cover the end surfaces of the bottom panel and the side panel and is integrated into the three-dimensional blank, the resin skeleton portion having a core layer with barrier properties and a skin layer covering the core layer and with heat-weldability; and forming the resin skeleton portion by injecting a resin for the skin layer into a mold, and then injecting a resin for the core layer into the mold to form the resin skeleton portion.

[0012] The manufacturing method described in [4] above can suitably manufacture the paper-resin composite container described in [1] above. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a paper-resin composite container that can achieve both barrier properties and stability of the container shape, and a method for manufacturing a paper-resin composite container. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view of a paper-resin composite container according to one embodiment. [Figure 2] FIG. 2 is a plan view of an example of a container blank for forming the paper-resin composite container shown in FIG. [Figure 3] FIG. 3 is a perspective view of a three-dimensional blank formed from the container blank shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view showing an example of the layer structure of the container blank shown in FIG. [Figure 5] 5 is a cross-sectional view taken along line VV of the resin skeleton of the paper-resin composite container shown in FIG. [Figure 6] FIG. 6 is a diagram showing another example of the cross-sectional structure of the resin skeleton of the paper-resin composite container shown in FIG. [Figure 7] FIG. 7 is a diagram illustrating a test piece for evaluating the weldability of the container (paper-resin composite container) produced in the experimental example. [Figure 8] FIG. 8 is a table showing the evaluation results of the containers (paper-resin composite containers) produced in Experimental Examples 1 to 7. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail, with reference to the drawings as needed, but the present disclosure is not limited to the following embodiments. In the drawings, the same or corresponding parts are designated by the same reference numerals, and duplicate explanations will be omitted as appropriate.

[0016] A paper resin composite container 1 and a container blank 10 according to one embodiment will be described with reference to Figures 1, 2, 3, and 4. Figure 1 is a perspective view of a paper resin composite container according to one embodiment. Figure 2 is a plan view of an example of a container blank for forming the paper resin composite container shown in Figure 1. Figure 3 is a perspective view of a three-dimensional blank formed from the container blank shown in Figure 2. Figure 4 is a cross-sectional view showing an example of the layer structure of the container blank shown in Figure 2.

[0017] As shown in FIG. 1, the paper-resin composite container 1 is a container for storing some kind of item in an internal space S. The paper-resin composite container 1 has, for example, a circular bottom surface 5 and, for example, a cylindrical side surface 6 rising from the bottom surface 5. The paper-resin composite container 1 is a composite container formed by integrating a three-dimensional blank 20 (see FIG. 3), which is a three-dimensional version of a container blank 10 (see FIG. 2), with a resin skeleton 30 by injection molding. Because the container blank 10 contains a predetermined amount of paper layers, the paper-resin composite container 1 uses a small amount of resin compared to its size (volume), thereby reducing the environmental impact. Hereinafter, the "paper-resin composite container 1" will be simply referred to as the "container 1."

[0018] The product contained in the container 1 may be a food product, or a non-food product such as cream or cosmetics. The product contained in the container 1 may be a liquid, solid, granular, or powder, or a mixture containing one or more of these. If the product is a food product and a liquid, it may be, for example, a beverage such as water, tea, juice, a lactic acid bacteria drink, or alcoholic beverage. The container 1 can also contain products that change from a solid to a liquid depending on the external temperature (e.g., ice cream). The airtightness, liquidtightness, and barrier properties required of the container 1 vary depending on the product (contents) to be contained, so the layer structure of the three-dimensional blank 20 (container blank 10) can be changed and adjusted as appropriate.

[0019] The container 1 is open at the top (opposite the bottom surface 5). An upper annular portion 33, which is part of the resin skeleton 30, is formed above the side surface 6, and a flange portion 36 and a threaded portion 37, for example, are formed on the outer surface of the upper annular portion 33. Both the flange portion 36 and the threaded portion 37 protrude outward from the cylindrical surface of the upper annular portion 33. The flange portion 36 is formed around the entire circumference (over the entire circumferential direction) at the lower end of the upper annular portion 33. The threaded portion 37 is formed, for example, over a portion of the circumferential direction in an area above the flange portion 36, and forms a multi-threaded threaded portion. The threaded portion 37 may be formed around the entire circumference. For example, a lid member (not shown) molded separately from the container 1 is attached to the upper annular portion 33. If the threaded portion 37 is provided, the lid member has a threaded portion on its inner surface that screws into the threaded portion 37.

[0020] The configuration of the upper part of container 1 can be changed as desired, and at least one of flange portion 36 and threaded portion 37 may be omitted. Threaded portion 37 may be omitted, and a lid member may be attached to the upper end surface of upper annular portion 33 by sealing (adhesion) or the like. When food (including beverages) is stored in container 1, the lid member may be a member that cannot be attached to container 1 after opening and that is discarded when the food is consumed.

[0021] The container 1 has a bottom surface 5 that is circular, elliptical, or has another shape including a curved peripheral portion. The container 1 is typically cylindrical or inverted truncated cone shape. An inverted truncated cone shape means that the container 1 has a tapered side surface 6 whose diameter increases upward (away from the bottom surface 5). The container 1 may also have a truncated cone shape. Even if the bottom surface 5 is not circular, the side surface 6 may have a constant diameter or may have a tapered shape with a varying diameter. Even if the bottom surface 5 includes a curved peripheral portion, the container blank 10 allows each panel of the three-dimensional blank 20 to be suitably positioned, thereby achieving a container 1 with the desired strength.

[0022] As shown in Figure 2, the container blank 10 is formed into a flat shape and includes at least a paper layer, a barrier layer, and a heat-sealed layer. The layer structure of the container blank 10 is, for example, uniform throughout. The container blank 10 is manufactured by punching a sheet having a laminated structure (described later) into an appropriate shape. Therefore, the layer structure is exposed on the end surfaces around the entire periphery of the container blank 10 (there is no layer extending in the thickness direction that covers the end surfaces).

[0023] The container blank 10 includes a bottom panel 11 corresponding to the bottom surface 5 of the container 1 and two side panels 12 corresponding to the side surfaces 6 of the container 1. The bottom panel 11 and the two side panels 12 are integrally formed into a flat shape. The bottom panel 11 is, for example, a circular plate-like portion. The side panels 12 are, for example, rectangular plate-like portions. A folding line may be provided at each boundary 16 between the bottom panel 11 and the two side panels 12. In FIG. 2, the boundary 16 is shown with a dashed line to have a constant width in order to distinguish it from the incision 15 described below, but the boundary 16 may be substantially linear.

[0024] The two side panels 12A, 12B are connected to opposite peripheral edges (positions 180 degrees apart) of the bottom panel 11. The two side panels 12A, 12B have, for example, the same size and shape. The two side panels 12A, 12B are formed symmetrically with respect to an imaginary plane (a plane perpendicular to the bottom panel 11) that passes through the center of the bottom panel 11 and is equidistant from the two boundaries 16. Each of the two side panels 12A, 12B includes a bottom edge 12f that is slightly shorter than half the perimeter of the bottom panel 11 (a length equivalent to half the circumference). When the container 1 is cylindrical, each of the two side panels 12A, 12B includes a top edge 12e that is equal in length to the bottom edge 12f. The top edge 12e is parallel to the bottom edge 12f. The side edge 12g of the side panel 12 has an appropriate length depending on the height of the container 1. The top and bottom edges 12e, 12f of the side panels 12A, 12B may be curved.

[0025] As shown in FIG. 2, linear incisions 15 may be formed along each boundary 16 of the bottom panel 11 and the two side panels 12. The incisions 15 do not reach both ends of the boundary 16 (both ends of the folding line L), but are formed only near the center of the boundary. That is, the incisions 15 are shorter than the boundary 16. The incisions 15 may be formed to penetrate the entire layer structure of the container blank 10 (the entire thickness direction), or may be formed only in a portion of the inner or outer surface of the container blank 10 in the thickness direction (not penetrating). When the incisions 15 (penetrating portions) are provided, the container blank 10 can be easily formed into a three-dimensional shape.

[0026] The side panel 12 of the container blank 10 corresponds to the side portion 22 of the side surface 6 of the container 1 shown in FIG. 1. The side surface portion 22 extends over a predetermined range less than 360 degrees. The two side surface panels 12A and 12B correspond to the side surface portions 22A and 22B of the side surface 6 of the container 1, respectively.

[0027] The container blank 10 has a paper layer, a heat-sealing layer, and a barrier layer. In one embodiment, the container blank 10 is a sheet-like body in which a barrier layer and a paper layer are laminated on a heat-sealing layer. In the container blank 10, the content of the paper layer is, for example, 50% by weight or more, or may be 60% by weight or more, or 70% by weight or more. A higher content of the paper layer in the container blank 10 is advantageous from the viewpoint of reducing environmental impact. The heat-sealing layer is a layer for joining the container blank 10 to the resin skeleton 30. The barrier layer is a layer that barriers at least gas (e.g., oxygen). The barrier layer may also barrier moisture.

[0028] An example of the layer configuration (laminate structure) of the container blank 10 will be described with reference to Fig. 4. As shown in Fig. 4, the container blank 10 of this embodiment includes, for example, a protective layer 51, an ink layer 52, an outer sealant layer 54, a paper layer 55, an adhesive layer 53, a stretched film layer 561, a vapor deposition layer 562, and an inner sealant layer 57 in this order from the outer layer (outer surface side) to the inner layer (inner surface side).

[0029] The protective layer 51 is a layer that protects the ink layer 52 and the paper layer 55. The protective layer 51 may have heat-welding properties. The protective layer 51 is formed of a thermoplastic resin, OP varnish, or the like. When the protective layer 51 is a thermoplastic resin having thermoplastic properties, examples of the thermoplastic resin that forms the protective layer 51 include polyethylene-based resin, polypropylene-based resin, and polyester-based resin. The protective layer 51 is formed by film attachment, extrusion processing, coating, or the like.

[0030] Known ink materials can be used for the ink layer 52. Whether or not to use the ink layer 52 is determined depending on the appearance.

[0031] The paper layer 55 is a structural layer that imparts strength to the container blank 10 (three-dimensional blank 20). There are no limitations on the type of paper used for the paper layer 55. Considering printability, it is desirable to use double-gloss paper for the paper layer 55. Waterproof paper or oil-resistant paper may be used as needed. The basis weight of the paper layer 55 is not limited. The thickness of the paper layer 55 is, for example, within a range of 200 to 1000 μm. When the thickness of the paper layer 55 is 200 μm or greater, it is possible to reduce the occurrence of burrs due to local variations in paper thickness, and rigidity is easily achieved, making it easier to ensure container strength against drops, vibrations, and the like. From a similar perspective, the thickness of the paper layer 55 may be 250 μm or greater. When the thickness of the paper layer 55 is 1000 μm or less, it is possible to reduce the repulsion of the side surface portion 22 (side panel portion) during three-dimensional formation, making it easier to ensure the roundness of the container.

[0032] The adhesive layer 53 is a layer for bonding the paper layer 55 and the stretched film layer 561 (or the barrier layer 56 described later). The adhesive layer 53 can be formed, for example, as an extruded resin layer. The adhesive layer 53 is formed, for example, from low-density polyethylene (LDPE) or the like.

[0033] The stretched film layer 561 is a layer for preventing tearing, rupture, and the like. The stretched film layer 561 is preferably disposed closer to the inner surface of the container 1 than the paper layer 55. The stretched film layer 561 may be made of any material as long as it is a stretched base material, such as polyethylene terephthalate (PET), nylon (Ny), or polypropylene (PP). The tensile strength of the stretched film layer 561 is preferably 100 MPa or more, and more preferably 200 MPa or more. A tensile strength of 100 MPa or more makes it less likely for breakage to occur at the seams. There is no limit to whether the stretched film layer 561 is uniaxially stretched or biaxially stretched.

[0034] The stretched film layer 561 may be subjected to a surface treatment. By performing the surface treatment, adhesion to other layers (such as a vapor deposition layer or an anchor coat layer) can be improved when laminating the other layers. Examples of the surface treatment that may be used include (1) physical treatments such as corona treatment, plasma treatment, and flame treatment, and (2) chemical treatments such as chemical treatments using acids, alkalis, etc.

[0035] The vapor deposition layer 562 is a layer formed on at least one surface of the stretched film layer 561 in order to impart gas barrier properties to the container blank 10. In the embodiment shown in Fig. 4, the vapor deposition layer 562 is formed on the surface of the stretched film layer 561 opposite the paper layer 55, but it may be formed on the surface of the stretched film layer 561 facing the paper layer 55, or may be formed on both surfaces.

[0036] The deposition layer 562 is a layer formed by depositing a deposition material on the stretched film layer 561. The deposition material used for the deposition layer may be appropriately selected from inorganic materials that constitute known gas barrier deposition films. Examples include metals such as Si, Al, Zn, Sn, Fe, and Mn, and inorganic compounds containing one or more of these metals. Examples of the inorganic compounds include oxides, nitrides, carbides, and fluorides. Among these, at least one selected from metals and metal oxides is preferred. Specifically, silicon oxides (SiO ) such as silicon monoxide and silicon dioxide are preferred. x), aluminum oxide, magnesium oxide, tin oxide, etc.

[0037] In this embodiment, the stretched film layer 561 on which the vapor deposition layer 562 is formed functions as the barrier layer 56 in the container blank 10.

[0038] However, instead of the stretched film layer 561 on which the vapor deposition layer 562 is formed, a stretched film layer on which a barrier coat is applied may be used as the barrier layer, or a barrier layer formed of a barrier resin such as ethylene vinyl alcohol copolymer resin (EVOH) may be provided on the stretched film layer 561. Alternatively, a metal foil (e.g., aluminum foil) may be provided as the barrier layer on the stretched film layer 561. In the stretched film layer 561 on which the vapor deposition layer 562 is formed or the stretched film layer 561 on which the barrier coat is applied, the vapor deposition layer or the barrier coat itself may also be referred to as the barrier layer.

[0039] In this embodiment, the outer sealant layer 54 and the inner sealant layer 57 are heat-sealable layers having heat-sealing properties. The outer sealant layer 54 and the inner sealant layer 57 are layers for heat-sealing the resin skeleton 30 and the three-dimensional blank 20 (or the container blank 10). The resins forming the outer sealant layer 54 and the inner sealant layer 57 may be the same or different. Examples of resins forming the outer sealant layer 54 and the inner sealant layer 57 include LDPE and linear low-density polyethylene (LLDPE). The outer sealant layer 54 and the inner sealant layer 57 are formed by film application, extrusion processing, coating, etc.

[0040] When the container blank 10 has a protective layer 51 as the outermost layer, and when the resin forming the protective layer 51 is a varnish or the like that is not heat-weldable to the resin skeleton 30, as shown in Figure 4, an outer sealant layer 54 can be provided on the outside of the paper layer 55, and the ink layer 52 can be refrained from being applied to the welded portion with the resin skeleton 30 (the portion connecting to the resin skeleton 30 is not printed), thereby better ensuring heat-weldability (sealability) with the resin skeleton 30.

[0041] If the material forming the outermost layer of the container blank 10 (protective layer 51 in the example shown in Figure 4) has the ability to be thermally welded to the resin skeleton 30, the container blank 10 does not need to have an outer sealant layer 54.

[0042] The three-dimensional blank 20 shown in Figure 3 is formed by folding the two side panels 12A, 12B (at least one side panel 12) of the container blank 10 shown in Figure 2 relative to the bottom panel 11 at the boundary 16 with the bottom panel 11. As mentioned above, the bottom edges 12f of the two side panels 12A, 12B are slightly shorter than half the perimeter of the bottom panel 11 (a length equivalent to half the circumference). Therefore, in the three-dimensional blank 20, a gap 23 is formed between the two side panels 12A, 12B in the direction along the peripheral edge of the bottom panel 11 (the circumferential direction in Figure 3).

[0043] The bottom panel 11 and the side panel 12 (side panel 12A and side panel 12B) of the three-dimensional blank 20 correspond to the bottom surface 5 and the side portion 22 (side portion 22A and side portion 22B) of the container 1. The top side edge portion 12e of the side panel 12 corresponds to the upper end surface 22e of the side portion 22, and the side edge portion 12g of the side panel 12 corresponds to the side end surface 22g of the side portion 22.

[0044] 1 and 2, a container 1 manufactured from the above-mentioned container blank 10 will be described. The container 1 is formed by integrating a resin skeleton 30 with the three-dimensional blank 20 shown in Fig. 3. In the container 1, the end faces of the bottom panel 11 and the side panels 12 are covered with the resin skeleton 30.

[0045] 1, the resin skeleton 30 extends along the bottom surface 5 and side surface 6 of the container 1. The resin skeleton 30 includes a circular lower annular portion 31 formed along the boundary (ridge) between the bottom surface 5 and the side surface 6, the above-mentioned upper annular portion 33, and two side surface pillar portions 32 that connect the lower annular portion 31 and the upper annular portion 33.

[0046] The upper end surface 22e of the side surface portion 22 is covered by at least one of the upper annular portion 33 and the flange portion 36. That is, the upper end surface 22e is contained within the resin skeleton portion 30 without being exposed to the outside or protruding from the resin skeleton portion 30. A portion of the front surface 22c and a portion of the back surface 22d of the side surface portion 22 are covered by at least one of the upper annular portion 33 and the flange portion 36, but most of the front surface 22c and most of the back surface 22d are exposed and not covered by the resin skeleton portion 30.

[0047] The side end faces 22g of the side surface portion 22 corresponding to the side edge portions 12g of the side panel 12 are covered by two side surface pillar portions 32. The side surface pillar portions 32 close the gap 23 between the side surface panel 12A (side surface portion 22A) and the side surface panel 12B (side surface portion 22B).

[0048] The peripheral end surface of the bottom portion 21 corresponding to the peripheral edge portion 11e of the bottom panel 11, the lower end surface of the side portion 22 corresponding to the bottom side edge portion 12f of the side panel 12, and the notch 15 are covered by the lower annular portion 31. As a result, the entire end surface of the three-dimensional blank 20 is covered by the three-dimensional blank 20.

[0049] In this way, the resin skeleton portion 30 covers the end faces of the three-dimensional blank 20 and also plays a role in forming the skeleton of the container 1, the portion that ensures strength, or the portion that is required for functionality (and also requires strength) such as the screw portion 37.

[0050] The resin skeleton 30 covers the end faces of the three-dimensional blank 20. The layer structure of the container blank 10 is exposed at the end faces of the three-dimensional blank 20. Therefore, the resin skeleton 30 contacts the outer sealant layer 54 and the inner sealant layer 57 and is heat-welded thereto. For example, the lower annular portion 31 is formed along the boundary (ridge) between the bottom surface 5 and the side surface 6 and contacts the inner surface of the three-dimensional blank 20. The inner surface of the three-dimensional blank 20 corresponds to the surface of the inner sealant layer 57. Therefore, the lower annular portion 31 is also heat-welded to the three-dimensional blank 20. In this way, the three-dimensional blank 20 and the resin skeleton 30 are integrated by being heat-welded.

[0051] Fig. 5 is a cross-sectional view of the resin skeleton 30 taken along line VV shown in Fig. 1. Specifically, Fig. 5 is a cross-sectional view perpendicular to the extension direction of the side column portion 32. Fig. 5 also illustrates the side portion 22A (side panel 12A) and the side portion 22B (side panel 12B).

[0052] 5, the resin skeleton 30 has a core layer 301 located inside the resin skeleton 30 and a skin layer 302 covering the core layer 301. In other words, the resin skeleton 30 has a multi-layer structure. The resins forming the core layer 301 and the skin layer 302 are referred to as a core resin and a skin resin.

[0053] The core layer 301 has barrier properties. The core resin (resin for the core layer 301) is not limited as long as it is an injection-moldable resin and has barrier properties. Examples of the core resin include barrier resins such as EVOH, polyvinylidene chloride (PVDC), and barrier nylon (e.g., nylon MXD6 (trade name: MX nylon)). The core resin may be a thermoplastic resin to which a labyrinth effect is imparted by adding a layered mineral or the like. In this case, montmorillonite, mica, or the like is used as the layered mineral, and the base thermoplastic resin is preferably of the same type as the resin forming the skin layer 302, which is effective from the standpoint of adhesion to the skin layer 302.

[0054] As shown in Fig. 5, the skin layer 302 is in contact with and joined to the side end surfaces 22g of the side portion 22A (side panel 12A) and the side portion 22B (side panel 12B). The skin layer 302 is formed of a thermoplastic resin that can be heat-sealed to at least the inner sealant layer 57 of the container blank 10. The skin resin that forms the skin layer 302 is preferably a resin that can be welded to the container blank 10 (at least the inner sealant layer 57) with a strength of 5N / 15mm width or more in order to maintain sufficient physical strength against vibrations, drops, etc. that occur during distribution or when the container 1 is handled by a consumer.

[0055] The skin resin and the resin forming the inner sealant layer 57 may be the same type of resin. The resin forming the outer sealant layer 54 or the heat-weldable protective layer 51 of the container blank 10 may also be the same type of resin as the skin resin. Of the multiple layers of the container blank 10, the resin forming the layer that is heat-welded to the skin resin (the inner sealant layer 57, the outer sealant layer 54, etc.) is not limited as long as the welding strength between the skin layer 302 and the container blank 10 is 5 N / 15 mm or more, and may be a resin of a different type from the skin resin.

[0056] Examples of skin resins include polyolefin resins, polyester resins, and acrylic resins. An adhesive resin may be added to the skin resin to improve adhesion to the core layer 301. When an adhesive resin is added to the skin layer 302, if the resin components in the skin layer 302 other than the adhesive resin are referred to as the base resin, the adhesive resin used is a resin that can adhere to both the base resin and the core resin. Examples of adhesive resins include ethylene-methacrylic acid copolymer resin (EMAA), ethylene-methyl methacrylate copolymer resin (EMMA), and maleic anhydride-modified polyolefin resin.

[0057] The resin skeleton 30 may have an adhesive resin layer formed of the adhesive resin between the skin layer 302 and the core layer 301. In this case, the skin layer 302 is formed of the base resin.

[0058] The resin skeleton 30 may satisfy the following conditions a and b. (Condition a) The resin forming the skin layer 302 has a flexural modulus of elasticity of less than 2000 MPa. (condition b) The occupancy rate of the skin layer 302 in a cross section perpendicular to the extending direction of the resin skeleton 30 is 60% or more.

[0059] As shown in Fig. 5, in a cross section perpendicular to the extending direction of the resin skeleton 30, the shape of the core layer 301 is rectangular with the short side direction being the thickness direction of the side surface portion 22 of the container 1, and the thickness of the skin layer 302 may be thicker than the thickness of the core layer 301. The extending direction of the resin skeleton 30 may be the extending direction of each of the lower circular ring portion 31, the upper circular ring portion 33, and the side column portion 32. The extending direction of the lower circular ring portion 31 and the upper circular ring portion 33 means the circumferential direction. In other words, the extending direction of the resin skeleton 30 corresponds to the direction in which resin flows when the resin skeleton 30 is formed by injection molding.

[0060] Resins used in the core layer 301 tend to have a relatively high flexural modulus. On the other hand, even if the core layer 301 is thin, it is possible to ensure barrier properties. Therefore, as shown in FIG. 5, by employing a thin core layer 301 and increasing the thickness of the skin layer 302, it is possible to increase the flexibility of the resin skeleton 30 while also ensuring barrier properties. Because the resin skeleton 30 is flexible, even if the container 1 is dropped or deformed during distribution or when handled by a consumer, the resin skeleton 30 is less likely to be damaged (for example, broken or cracked).

[0061] From the viewpoint of improving flexibility while ensuring barrier properties, the core layer 301 may be formed in an X-shape as shown in FIG.

[0062] Next, an example of a method for manufacturing the container 1 will be described.

[0063] When manufacturing a container 1, a planar container blank 10 is folded to form a three-dimensional blank 20 (three-dimensional blank forming process). Specifically, multiple container blanks 10 are stacked and stored in a predetermined location. Meanwhile, a mold consisting of a female mold and a male mold arranged opposite each other is prepared in an injection molding machine. The outer shapes of these molds and the container blank 10 are designed to correspond in advance. The container blanks 10 are picked up one by one by a gripping device having a gripping mechanism such as a suction mechanism, and the container blank 10 is attached to a dummy core having the same outer shape and size as the male mold. At this time, the inner side of the container blank 10 abuts against the surface of the dummy core. The side panel 12 is folded relative to the bottom panel 11 to form the three-dimensional blank 20. The three-dimensional blank 20 formed in this manner is held on the dummy core.

[0064] After the three-dimensional blank forming process, a resin skeleton 30 integrated with the three-dimensional blank 20 is formed by a multilayer injection molding method (resin skeleton forming process). Specifically, a dummy core holding the three-dimensional blank 20 is inserted into a female mold, and the holding by the dummy core is released. The dummy core is removed, and the three-dimensional blank 20 is set in the female mold. At this time, the outer surface of the three-dimensional blank 20 abuts against the surface of the female mold. Each panel of the three-dimensional blank 20 is set in a predetermined position relative to the surface of the female mold. In this state, a male mold is inserted into the female mold. The clearance between the female mold and the male mold is narrowed, and the three-dimensional blank 20 is pressed down. All end faces of the three-dimensional blank 20 face each other within the clearance and do not abut against the surface of either the female mold or the male mold.

[0065] Next, the skin resin is first injected through one or more gates formed in the mold, and then the hot runner valve of the injection molding machine is switched to inject the core resin. The resin material is filled, and injection molding is performed. As the skin resin gradually cools and solidifies from the surface that contacts the mold, the core resin, which is filled later at high pressure, flows inside the skin layer 302, which still retains fluidity, and as shown in Figure 5, a resin skeleton 30 is formed that has a core layer 301 inside the skin layer 302 and is integrated with the three-dimensional blank 20. As a result, a container 1 (a paper-resin composite container) is manufactured.

[0066] An injection molding apparatus including a mold for carrying out the multilayer injection molding method can be designed as appropriate within the scope of known technology. The gate position may be set at an appropriate location on the lower annular portion 31 or the side pillar portion 32 of the container 1. An opening or the like may be formed in one of the panels of the container blank 10, and the gate may be provided in that opening.

[0067] According to the container 1 of this embodiment, the resin skeleton 30 has a core layer 301 with barrier properties and a skin layer 302 with thermal welding properties. Since the resin skeleton 30 has the core layer 301, the resin skeleton 30 has barrier properties. The core layer 301 is covered with the skin layer 302, which contacts at least the end surface of the three-dimensional blank 20 (container blank 10). Because the three-dimensional blank 20 is formed by folding the container blank 10, the layer structure of the three-dimensional blank 20 is the same as that of the container blank 10, and thermal welding layers (such as the inner sealant layer 57 and outer sealant layer 54) are exposed at the end surfaces of the three-dimensional blank 20. Because the skin layer 302 is formed from a resin with thermal welding properties, the resin skeleton 30 can be integrated with the three-dimensional blank 20 by thermal welding to the three-dimensional blank 20.

[0068] For example, it is conceivable to use a resin having barrier properties (hereinafter referred to as "barrier resin") as the resin forming the resin skeleton. However, since the melting point of barrier resins tends to be high, their thermal welding (or heat sealing) properties are poor, making them difficult to form into containers. In addition, the joint between the resin skeleton and the three-dimensional blank 20 is prone to peeling, reducing the stability of the container shape. Even if the resin can be formed into a container, the airtightness of the joint between the resin skeleton and the three-dimensional blank 20 will be reduced. As a method for solving these problems, it is conceivable to use a resin formed by blending a barrier resin with a resin similar to a sealant as the resin forming the resin skeleton. However, since the barrier resin is diluted by the resin blended with it, the barrier properties of the resin skeleton will be significantly reduced.

[0069] In contrast, the resin skeleton 30 of the container 1 has a core layer 301 and a skin layer 302, and thus the resin skeleton 30 has both barrier properties and the ability to be thermally welded to the three-dimensional blank 20. Therefore, the resin skeleton 30 and the three-dimensional blank 20 can be tightly attached and firmly joined, ensuring the barrier properties of the resin skeleton 30 itself and the joint between the resin skeleton 30 and the three-dimensional blank 20, while also stabilizing the shape of the container 1. Therefore, the container 1 can ensure both barrier properties and shape stability.

[0070] When the resin skeleton 30 satisfies the above-mentioned condition a, i.e., when the resin forming the skin layer 302 has a flexural modulus of less than 2000 MPa, the resin is easier to form into a container and is not too hard, so it is resistant to deformation during distribution and handling by consumers (deformation due to impact due to dropping, etc.). The barrier resin forming the core layer 301 usually has a higher flexural modulus than the skin resin. When the resin skeleton 30 satisfies the above-mentioned condition b, i.e., when the skin layer 302 occupies 60% or more of the area of ​​the cross section perpendicular to the extension direction of the resin skeleton 30, the resin skeleton 30 is less susceptible to the flexural modulus of the core layer 301 and is therefore resistant to deformation during distribution and handling by consumers (deformation due to impact due to dropping, etc.). Therefore, when the resin skeleton 30 satisfies conditions a and b, it is resistant to deformation during distribution and handling by consumers, and the container 1 is less likely to break. For example, when the resin skeleton 30 satisfies the conditions a and b, the container 1 is less likely to break even if dropped during distribution or handling by consumers, and the stability of the shape of the container 1 is further improved.

[0071] Next, an experimental example will be described.

[0072] In the experimental example, a container blank was prepared as shown in FIG. 2, and a container having the shape shown below was manufactured. Diameter of the container base: 54.8mm Container height: 40.0mm Diameter of the opening on the top of the container: 58.0 mm Full capacity of the container: 100ml

[0073] The container blank thus produced had a bottom panel and two side panels corresponding to the bottom panel 11 and two side panels 12A, 12B shown in FIG.

[0074] The length of the boundary between the bottom panel and the side panel of the container blank (corresponding to boundary 16 shown in Figure 2) was 17.74 mm. The width of the two side panels of the container blank was such that when the container blank was formed into a three-dimensional blank, the gap between the two side panels (corresponding to gap 23 shown in Figure 3) was 0.7 mm.

[0075] PP-based blanks, PE-based blanks, and EVOH-based blanks were prepared as container blanks.

[0076] (PP blanks) An interior film was produced by bonding a transparent vapor-deposited PET film (GL-ARH-F manufactured by TOPPAN Corporation, thickness: 12 μm) corresponding to the barrier layer 56 (stretched film layer 561 with vapor-deposited layer 562 formed on one surface) shown in FIG. 4 with a CPP film (FHK-2 manufactured by Futamura Corporation, thickness: 30 μm) corresponding to the inner sealant layer 57 shown in FIG. 4 using a two-component curing urethane-based dry laminating adhesive. Takelac A626 / A50 manufactured by Mitsui Chemicals, Inc. was used as the two-component curing dry laminating adhesive. The amount of adhesive applied was 2.5 g / m. 2 It was.

[0077] Card paper (OK Frace manufactured by Oji Paper Co., Ltd., basis weight: 310 g / m) corresponding to the paper layer 55 shown in FIG. 2 ) and the transparent vapor-deposited PET film of the interior film were extruded with LDPE (L1850K manufactured by Asahi Kasei Corporation) by extruder lamination to form a first LDPE layer (thickness: 20 μm) corresponding to adhesive layer 53 shown in Figure 4, thereby bonding the card paper and the interior film.

[0078] Furthermore, PP (Novatec FB3B manufactured by Japan Polychem Corporation) was extruded by extruder lamination onto the surface of the cardboard opposite the interior film to form a PP layer (thickness: 20 μm) corresponding to the outer sealant layer 54 shown in FIG. 4. A print pattern corresponding to the ink layer 52 shown in FIG. 4 was printed by UV offset printing on the surface of the PP layer formed by extrusion (the surface opposite the cardboard), and the resulting pattern was cut into the shape shown in FIG. 2 to produce a PP blank. The PP blank had a layer structure shown in FIG. 4 that did not have the protective layer 51.

[0079] (PE blanks) An interior film was produced in the same manner as in Experimental Example 1, in which a transparent vapor-deposited PET film (GL-ARH-F, thickness: 12 μm, manufactured by Toppan Corporation) and an LDPE film were bonded together with an adhesive, except that an LDPE film (SE620A, manufactured by Tamapoly Corporation, thickness: 30 μm) was used instead of the CPP film in Experimental Example 1 as the film corresponding to the inner sealant layer 57 shown in Figure 4. The two-component curing dry laminating adhesive used and the amount applied were the same as in the case of the PP blanks.

[0080] The interior film prepared as described above and the cardboard used in Experimental Example 1 were bonded together in the same manner as in Experimental Example 1.

[0081] LDPE (L1850K manufactured by Asahi Kasei Corporation) was extruded by extruder lamination onto the surface of the cardboard opposite the interior film to form a second LDPE layer (thickness: 20 μm) corresponding to the outer sealant layer 54 shown in FIG. 4. A print pattern corresponding to the ink layer 52 shown in FIG. 4 was printed by UV offset printing on the surface of the second LDPE layer formed by extrusion (the surface opposite the cardboard), and the resulting pattern was punched into the shape shown in FIG. 2 to produce a PE blank. The container blank had a layer structure shown in FIG. 4 but did not have the protective layer 51.

[0082] (EVOH blanks) An interior film was produced in the same manner as in Experimental Example 1, in which a transparent vapor-deposited PET film (GL-ARH-F, thickness: 12 μm, manufactured by TOPPAN Corporation) and an EVOH film were bonded together with an adhesive, except that an EVOH film (EF-E, manufactured by Kuraray Co., Ltd., thickness: 25 μm) was used instead of the CPP film in Experimental Example 1 as the film corresponding to the inner sealant layer 57 shown in Figure 4. The two-component curing dry laminating adhesive used and the amount applied were the same as in the case of the PP blanks.

[0083] The interior film prepared as described above and the cardboard used in Experimental Example 1 were bonded together in the same manner as in Experimental Example 1.

[0084] LDPE (L1850K manufactured by Asahi Kasei Corporation) was extruded by extruder lamination onto the surface of the cardboard opposite the interior film, and an EVOH film (EF-E manufactured by Kuraray Co., Ltd., thickness: 25 μm) corresponding to the outer sealant layer 54 shown in FIG. 4 was laminated. A print pattern corresponding to the ink layer 52 shown in FIG. 4 was printed by UV offset printing on the surface of the EVOH film (the side opposite the cardboard), and the film was punched into the shape shown in FIG. 2 to produce an EVOH blank. The EVOH blank had a layer structure shown in FIG. 4 but did not have the protective layer 51.

[0085] (Experimental Example 1) In Experimental Example 1, a PP blank was bent to form a three-dimensional blank (corresponding to the three-dimensional blank 20 shown in Fig. 3), and then the three-dimensional blank was injection molded to form a resin skeleton (corresponding to the resin skeleton 30 shown in Fig. 1). In this way, a container was obtained that had a three-dimensional blank and a resin skeleton integrated with the three-dimensional blank.

[0086] In Experimental Example 1, a resin skeleton was formed by multilayer injection molding. The resin skeleton had a core layer and a skin layer corresponding to the core layer 301 and the skin layer 302 shown in FIG. 5. The core resin was EVOH (Soarnol DC manufactured by Mitsubishi Chemical Corporation). The skin resin was PP (BC03C manufactured by Japan Polychem Corporation, flexural modulus: 1800 MPa). In Experimental Example 1, the occupancy rate (area rate) of the skin layer in a cross section perpendicular to the extension direction of the resin skeleton (specifically, a cross section perpendicular to the extension direction of the side column portion) was 70%.

[0087] The manufactured containers were evaluated in terms of the following points. (Weldability) The fracture strength (peel strength) of the joint between the side panel (side portion) and the resin skeleton was measured in accordance with "JIS K7161 Plastics - Determination of Tensile Properties." Specifically, the portion where the side panels (side portions) were joined by the resin skeleton (the portion of the side column) was cut to a width of 15 mm to prepare test piece 40 shown in Figure 7. Test piece 40 had a side column 41 (resin skeleton) between side panel 42A and side panel 42B. Side panel 42A and side panel 42B correspond to side panel 12A and side panel 12B (see Figure 3), and side column 41 corresponds to side column 32 (see Figure 1). The test piece 40 was set in a tensile testing machine, and the side panels 42A and 42B were pulled in the directions of arrows α1 and α2 at a crosshead speed of 300 mm / min, and the breaking strength of the joints between the side panels 42A and 42B and the side column portion 41 (resin skeleton portion) was measured.

[0088] The breaking strength (tensile strength) measured as above was 10 N / 15 mm.

[0089] (barrier properties) The oxygen permeability of the manufactured container was measured as a barrier property using an oxygen barrier measuring instrument for packaging, OX-TRAN 2 / 22, manufactured by MOCON Co. The measurement conditions were as follows: Temperature: 40℃ Humidity: 75%RH

[0090] The oxygen permeability (barrier property) measured as above was 0.03 cc / (pkg·day).

[0091] (Drop impact) The manufactured container was filled with 100 ml of 4°C cold water and then closed with a lid. A drop impact test was conducted on the container filled with cold water in this way in accordance with JIS Z200:2013. Specifically, the container filled with cold water was dropped upright from a height of 1 m, and the number of times it took for the water inside the container to leak was determined. Drops were not conducted more than six times.

[0092] In the drop impact test, no water leakage occurred from the container.

[0093] (Experimental Example 2) In Experimental Example 2, a PE blank was bent to form a three-dimensional blank (corresponding to the three-dimensional blank 20 shown in Fig. 3), and then the three-dimensional blank was injection molded to form a resin skeleton (the resin skeleton 30 shown in Fig. 1). In this way, a container having a three-dimensional blank and a resin skeleton integrated with the three-dimensional blank was obtained.

[0094] In Experimental Example 2, a resin skeleton was formed by multilayer injection molding. The resin skeleton had a core layer and a skin layer corresponding to core layer 301 and skin layer 302 shown in FIG. 5. The core resin was EVOH (Soarnol DC manufactured by Mitsubishi Chemical Corporation). The skin resin was PE (Suntec M7620 manufactured by Asahi Kasei Corporation, flexural modulus: 2050 MPa). In Experimental Example 2, the occupancy rate (area rate) of the skin layer in a cross section perpendicular to the extension direction of the resin skeleton (specifically, a cross section perpendicular to the extension direction of the side column portion) was 65%.

[0095] The manufactured containers were evaluated in terms of "weldability," "barrier properties," and "drop impact" in the same manner as in Experimental Example 1. The evaluation methods were the same as in Experimental Example 1.

[0096] The breaking strength (tensile strength), measured as an index for evaluating weldability, was 10 N / 15 mm. The oxygen permeability, measured as an index for evaluating barrier properties, was 0.03 cc / (pkg·day). In a drop impact test, no water leakage occurred from the container.

[0097] (Experimental Example 3) In Experimental Example 3, a PP blank was bent to form a three-dimensional blank (corresponding to the three-dimensional blank 20 shown in Fig. 3), and then the three-dimensional blank was injection molded to form a resin skeleton (the resin skeleton 30 shown in Fig. 1). In this way, a container having a three-dimensional blank and a resin skeleton integrated with the three-dimensional blank was obtained.

[0098] In Experimental Example 3, a resin skeleton was formed by multilayer injection molding. The resin skeleton had a core layer and a skin layer corresponding to the core layer 301 and the skin layer 302 shown in FIG. 5. The core resin was EVOH (Soarnol DC, manufactured by Mitsubishi Chemical Corporation). The skin resin was PE (MA3H, manufactured by Japan Polychem Corporation, flexural modulus: 2,050 MPa). In Experimental Example 3, the occupancy rate of the skin layer in a cross section perpendicular to the extension direction of the resin skeleton (specifically, a cross section perpendicular to the extension direction of the side column portion) was 70%.

[0099] The manufactured containers were evaluated in terms of "weldability," "barrier properties," and "drop impact" in the same manner as in Experimental Example 1. The evaluation methods were the same as in Experimental Example 1.

[0100] The breaking strength (tensile strength), measured as an index for evaluating weldability, was 6 N / 15 mm. The oxygen permeability, measured as an index for evaluating barrier properties, was 0.03 cc / (pkg·day). In a drop impact test, water leaked from the container after the second drop.

[0101] (Experimental Example 4) In Experimental Example 4, a 3D blank (corresponding to the 3D blank 20 shown in FIG. 3) was formed by bending a PP blank, and then a resin skeleton was formed by injection molding the 3D blank. This resulted in a container having a 3D blank and a resin skeleton integrated with the 3D blank. The external shape of the resin skeleton formed in Experimental Example 4 was the same as in Experimental Example 1.

[0102] In Experimental Example 4, the resin skeleton was formed using only one resin. Therefore, the resin skeleton did not have two layers corresponding to the core layer 301 and the skin layer 302 shown in Fig. 5. In other words, the resin skeleton in Experimental Example 4 had a single-layer structure.

[0103] In the following, for the sake of convenience, in the case of a resin skeleton having a single-layer structure as in Experimental Example 4, the resin forming the resin skeleton will also be referred to as the "skin resin," and the injection molding method used when forming the resin skeleton using only the skin resin will be referred to as the "general injection molding method." In Experimental Example 4, the resin skeleton was formed by the general injection molding method.

[0104] In Experimental Example 4, the resin forming the resin skeleton (skin resin) was the same as in Experimental Example 1, PP (BC03C manufactured by Japan Polychem Corporation, flexural modulus: 1800 MPa).

[0105] The manufactured containers were evaluated in terms of "weldability," "barrier properties," and "drop impact" in the same manner as in Experimental Example 1. The evaluation methods were the same as in Experimental Example 1.

[0106] The breaking strength (tensile strength), measured as an evaluation index for weldability, was 6N / 15mm. In the evaluation of barrier properties, the oxygen permeability was far beyond the measurable range, making it impossible to measure. In the drop impact test, no water leakage occurred from the container.

[0107] (Experimental Example 5) In Experimental Example 5, a 3D blank (corresponding to the 3D blank 20 shown in FIG. 3) was formed by bending a PE blank, and then a resin skeleton was formed by injection molding the 3D blank. This resulted in a container having a 3D blank and a resin skeleton integrated with the 3D blank. The external shape of the resin skeleton formed in Experimental Example 5 was the same as in Experimental Example 1.

[0108] In Experimental Example 5, a resin skeleton was formed by a general injection molding method, as in Experimental Example 4. Therefore, the resin skeleton in Experimental Example 5 also had a single-layer structure. The skin resin used to form the resin skeleton was a blend resin obtained by blending EVOH (Soarnol DC manufactured by Mitsubishi Chemical Corporation) and PP (BC03C manufactured by Japan Polychem Corporation) in a ratio of 7:3. The flexural modulus of the skin resin used to form the resin skeleton was 1800 MPa.

[0109] The manufactured containers were evaluated in terms of "weldability," "barrier properties," and "drop impact" in the same manner as in Experimental Example 1. The evaluation methods were the same as in Experimental Example 1.

[0110] The breaking strength (tensile strength), measured as an index for evaluating weldability, was 1 N / 15 mm. The oxygen permeability, measured as an index for evaluating barrier properties, was 5 cc / (pkg·day). In a drop impact test, water leaked from the container after the first drop.

[0111] (Experimental Example 6) In Experimental Example 6, a 3D blank (corresponding to the 3D blank 20 shown in FIG. 3) was formed by bending a PP blank, and then a resin skeleton was formed by injection molding the 3D blank. This resulted in a container having a 3D blank and a resin skeleton integrated with the 3D blank. The external shape of the resin skeleton formed in Experimental Example 6 was the same as in Experimental Example 1.

[0112] In Experimental Example 6, a resin skeleton was formed by a general injection molding method, as in Experimental Example 4. Therefore, the resin skeleton in Experimental Example 6 also had a single-layer structure. The skin resin used to form the resin skeleton was the same PP (BC03C manufactured by Japan Polychem Corporation, flexural modulus: 1800 MPa) as in Experimental Example 1.

[0113] The manufactured containers were evaluated in terms of "weldability," "barrier properties," and "drop impact" in the same manner as in Experimental Example 1. The evaluation methods were the same as in Experimental Example 1.

[0114] The breaking strength (tensile strength), measured as an evaluation index for weldability, was 10 N / 15 mm. In the evaluation of barrier properties, the oxygen permeability was far beyond the measurable range, making it impossible to measure. In the drop impact test, water leaked from the container after the third drop.

[0115] (Experimental Example 7) In Experimental Example 7, a three-dimensional blank (corresponding to the three-dimensional blank 20 shown in FIG. 3) was formed by bending an EVOH-based blank, and then a resin skeleton was formed by injection molding the three-dimensional blank. This resulted in a container having a three-dimensional blank and a resin skeleton integrated with the three-dimensional blank. The external shape of the resin skeleton formed in Experimental Example 7 was the same as in Experimental Example 1.

[0116] In Experimental Example 7, a resin skeleton was formed by a general injection molding method, as in Experimental Example 4. Therefore, the resin skeleton in Experimental Example 7 also had a single-layer structure. The skin resin used to form the resin skeleton was EVOH (Soarnol DC manufactured by Mitsubishi Chemical Corporation, flexural modulus: 4350 MPa).

[0117] The manufactured containers were evaluated in terms of "weldability," "barrier properties," and "drop impact" in the same manner as in Experimental Example 1. The evaluation methods were the same as in Experimental Example 1.

[0118] The breaking strength (tensile strength), measured as an index for evaluating weldability, was 2 N / 15 mm. The oxygen permeability, measured as an index for evaluating barrier properties, was 0.01 cc / (pkg·day). In a drop impact test, water leaked from the container after the first drop.

[0119] (Evaluation results) The results of "weldability," "barrier properties," and "drop impact" in Experimental Examples 1 to 7 were evaluated from the following perspectives.

[0120] (Weldability) Rating A: The breaking strength (tensile strength) is 5N / 15mm or more. Rating B: The breaking strength (tensile strength) is less than 5N / 15mm.

[0121] (barrier properties) Rating A + : Oxygen permeability is 0.01cc / (pkg·day) or less. Grade A: Oxygen permeability is greater than 0.01 cc / (pkg·day) and less than 0.1 cc / (pkg·day). Rating B: Oxygen permeability is 0.1 cc / (pkg·day) or more and 5 cc / (pkg·day) or less. Rating B ― : Oxygen permeability could not be measured.

[0122] (Drop impact) Evaluation A: No water leakage occurred from the container during the drop impact test. Rating B: Water leaked from the container during the drop impact test.

[0123] FIG. 8 is a chart showing the evaluation results of Experimental Examples 1 to 7. In the figure, "flexural modulus" refers to the flexural modulus of the skin resin, and "occupancy" refers to the occupancy (area ratio) of the skin layer in a cross section perpendicular to the extension direction of the resin skeleton (specifically, a cross section perpendicular to the extension direction of the side column section). The occupancy in a resin skeleton with a single layer structure is described as 100%. "Multilayer" and "general" in FIG. 8 refer to the multilayer injection molding and general injection molding described above, and "blend resin" in FIG. 8 refers to the blend resin of the aforementioned EVOH (Soarnol DC manufactured by Mitsubishi Chemical Corporation) and PP (BC03C manufactured by Japan Polychem Corporation).

[0124] As shown in FIG. 8, in Experimental Examples 4, 5, 6, and 7, which have a single-layer resin skeleton, both the weldability and the barrier property were rated B or B. - In contrast, in Experimental Examples 1, 2, and 3 in which the resin skeleton had a core layer and a skin layer corresponding to core layer 301 and skin layer 302 shown in Fig. 5, both the weldability and the barrier property were evaluated as A. In other words, it was found that by having a resin skeleton with a core layer having barrier properties and a skin layer having thermal weldability, it is possible to ensure both the weldability and the barrier property.

[0125] Furthermore, it can be seen that in Experimental Examples 1 and 2, which satisfy the conditions that the flexural modulus of the skin resin is less than 2000 MPa (condition a) (and the occupancy rate of the skin layer is 60% or more (condition b)), the drop impact resistance is improved. In other words, when conditions a and b are satisfied, the container is less likely to break even when dropped.

[0126] Although the embodiments and experimental examples of the present invention have been described above, the present invention is not limited to the above-described embodiments and experimental examples, and is intended to include the scope indicated by the claims, as well as all modifications within the meaning and scope equivalent to the claims.

[0127] The number of side panels provided in a container blank is not limited to two and may be one. For example, one of the two illustrated side panels 12A, 12B may be omitted. In that case, the container blank has only one side panel. The one side panel includes a bottom edge portion that is slightly shorter than the entire circumference of the bottom panel. The number of side panels provided in a container blank may be three or more.

[0128] The layer structure of the container planks is not limited as long as it has a paper layer, a heat-sealing layer for heat-sealing to the resin skeleton, and a barrier layer for ensuring barrier properties. [Explanation of symbols]

[0129] 1...container (paper-resin composite container), 11...bottom panel, 5...bottom, 6...side, 10...container blank, 11e...periphery, 12, 12A, 12B...side panels, 20...three-dimensional blank, 23...gap, 30...resin skeleton, 32...side column, 55...paper layer, 56...barrier layer, 57...inner sealant layer (thermal weld layer), 301...core layer, 302...skin layer

Claims

1. a container blank including a bottom panel corresponding to the bottom surface of the container and at least one side panel corresponding to a side surface of the container and connected to a peripheral edge of the bottom panel, the side panel being folded relative to the bottom panel; a resin skeleton portion that extends along the bottom surface or the side surface so as to cover the end surfaces of the bottom panel and the side panel and is integrated with the three-dimensional blank; Equipped with the bottom panel and the side panels are integrally molded and planar; The container blank is A paper layer; a thermal welding layer having thermal welding properties; A barrier layer; and The resin skeleton is a core layer having barrier properties; a skin layer covering the core layer and having thermal weldability; having Paper-resin composite container.

2. The container blank has a plurality of the side panels, In the three-dimensional blank, a gap is formed between adjacent side panels along the peripheral edge of the plurality of side panels folded relative to the bottom panel, The resin skeleton has side pillar portions that close the gaps and join the adjacent side panels. The paper-resin composite container according to claim 1.

3. the skin layer is formed of a resin having a flexural modulus of less than 2000 MPa, In a cross section perpendicular to the extending direction of the resin skeleton, the occupancy rate of the skin layer is 60% or more. The paper-resin composite container according to claim 1 or 2.

4. a step of forming a three-dimensional blank by folding a bottom panel corresponding to the bottom surface of the container and at least one side panel corresponding to a side surface of the container and connected to a peripheral edge of the bottom panel relative to the bottom panel; forming a resin skeleton portion that extends along the bottom surface or the side surfaces so as to cover the end surfaces of the bottom panel and the side panels and is integrated with the three-dimensional blank; Equipped with The resin skeleton is a core layer having barrier properties; a skin layer covering the core layer and having thermal weldability; and In the step of forming the resin skeleton, the resin skeleton is formed by injecting a resin for the skin layer into a mold, and then injecting a resin for the core layer into the mold. A method for manufacturing a paper-resin composite container.

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