Filling paper food containers

Abstract

In order to obtain a paper container for filled food that can prevent leakage of the content liquid, the container material comprises the following layers from the outer surface side to the inner surface side: a thermoplastic resin layer (A layer) mainly composed of polyethylene resin, a paper base material layer (B layer), a thermoplastic resin layer (C layer) mainly composed of polyethylene resin, a barrier layer (D layer), an adhesive layer (E layer) mainly composed of ethylene-methacrylic acid copolymer resin, a thermoplastic resin layer (I layer) mainly composed of polyethylene resin, a thermoplastic resin layer (F layer) mainly composed of polyethylene resin, a thermoplastic resin layer (G layer) obtained by mixing polyethylene resin and polypropylene resin, and a thermoplastic resin layer (H layer) obtained by adding a compounding agent selected from polyols or their derivatives and polyoxyethylene derivatives to a polyolefin-based resin; the adhesive layer (E layer) mainly composed of ethylene-methacrylic acid copolymer resin and the thermoplastic resin layer (I layer) mainly composed of polyethylene resin are formed into a laminated state by co-extruding the raw materials with each other.

Description

Technical Field

[0001] The present invention relates to a paper container for filling food used for preparing container-packed food, which is obtained by filling food materials such as tofu in the container, sealing the container, and heating and curing the container. Background Art

[0002] There are foods such as tofu, mizuyokan, and pudding, which are prepared by filling their materials in a container, sealing it, and heating and curing it (hereinafter referred to as filled foods).

[0003] For example, when the filled food is tofu, the filled tofu is prepared by filling a container with tofu material to which soy milk and a coagulant are added and sealing the container, and heating the container filled with the tofu material at 60 to 100 degrees (see, for example, Patent Document 1).

[0004] As containers used for filled foods such as filled tofu, metal containers, synthetic resin containers, and paper containers are known, and paper containers have become popular because they are easy to discard after use and have recycling characteristics. As paper containers for sealing and containing food, there are paper containers formed of a paper container material having the following layers from the outer surface side to the inner surface side: a thermoplastic resin layer with polyethylene resin as the main component, a paper base material layer, a thermoplastic resin layer with polyethylene resin as the main component, and a thermoplastic resin layer with polyethylene resin as the main component in the innermost layer via a barrier layer (for example, see Patent Document 2).

[0005] However, when a paper container formed from the paper container material described in Patent Document 2 is used as a container for filling food, the food solidified in the container and the thermoplastic resin layer composed mainly of polyethylene resin, which forms the inner surface of the container, are poorly separable, and there is a risk that the food may adhere to the inner surface of the container and become difficult to remove or may be partially damaged when being taken out.

[0006] As a technique for improving the separability of the inner surface of a container from solidified food in the container, a polyolefin resin composition has been proposed in which a compounding agent selected from a polyol or its derivative and a polyoxyethylene derivative is added to a polyolefin resin (see, for example, Patent Document 3).

[0007] If the technology described in Patent Document 3 is applied to the innermost layer of the paper container material described in Patent Document 2, the separation property between the inner surface of the paper container and the food is improved, and the food can be easily taken out of the paper container.

[0008] As an example of applying the technology described in Patent Document 3 to the innermost layer of the paper container material described in Patent Document 2, consider laminating a polyethylene resin film to which a compounding agent selected from a polyol or its derivatives and a polyoxyethylene derivative is added as the innermost layer on a thermoplastic resin layer having a polyethylene resin as the main component constituting the innermost layer of the above-mentioned paper container material.

[0009] However, if a paper container formed from the paper container material obtained in this way is used as a container filled with food, peeling sometimes occurs between the innermost polyethylene resin layer to which a compounding agent is added and the thermoplastic resin layer located inside it with the polyethylene resin as the main component, resulting in leakage of the content liquid.

[0010] As a technology to solve such a problem, Figure 2 As shown, a filled food paper container is proposed, which is formed by a container material having the following layers from the outer surface side to the inner surface side: a thermoplastic resin layer (A layer) composed mainly of polyethylene resin, a paper base material layer (B layer), a thermoplastic resin layer (C layer) composed mainly of polyethylene resin, a barrier layer (D layer), an adhesive layer (E layer) composed mainly of ethylene-methacrylic acid copolymer resin, a thermoplastic resin layer (F layer) composed mainly of polyethylene resin, a thermoplastic resin layer (G layer) composed of a mixture of polyethylene resin and polypropylene resin, and a thermoplastic resin layer (H layer) composed of a polyolefin resin to which a compounding agent selected from polyols or their derivatives and polyoxyethylene derivatives is added (for example, refer to Patent Document 4).

[0011] According to the paper container for filling food described in Patent Document 4, since a laminated structure is formed in which a thermoplastic resin layer (G layer) formed by mixing polyethylene resin and polypropylene resin is sandwiched between the inner side of the thermoplastic resin layer (H layer) and the thermoplastic resin layer (F layer) whose main component is polyethylene resin, during the preparation process of filling the material of food such as tofu in the container, sealing it and heat-curing it, the dissolution of the compounding agent from the innermost layer, i.e., the thermoplastic resin layer (H layer), is suppressed by the above-mentioned thermoplastic resin layer (G layer), and the migration of the compounding agent to the thermoplastic resin layer (F layer) can be prevented, thereby preventing the thermoplastic resin layer (H layer) from peeling off from the above-mentioned thermoplastic resin layer (F layer), thereby obtaining a paper container for filling food in which the content liquid will not leak.

[0012] Prior art literature

[0013] Patent Literature

[0014] Patent Document 1: Japanese Patent Application Publication No. 2014-187975,

[0015] Patent Document 2: Japanese Patent Application Publication No. 2004-17984,

[0016] Patent Document 3: Japanese Patent Application Laid-Open No. 7-62163,

[0017] Patent document 4: Japanese Patent Application Publication No. 2017-24762. Summary of the invention

[0018] Problems to be solved by the invention

[0019] In the container material for filling paper containers for food described in Patent Document 4, a thermoplastic resin layer (F layer) composed mainly of polyethylene resin is laminated on an adhesive layer (E layer) composed mainly of ethylene-methacrylic acid copolymer resin laminated on a barrier layer (D layer). However, since the adhesive layer (E layer) and the thermoplastic resin layer (F layer) contain different resins, such as ethylene-methacrylic acid copolymer resin and polyethylene resin, as main components, it cannot be said that the adhesion between the two is high.

[0020] The bonding strength between the adhesive layer (E layer) and the thermoplastic resin layer (F layer) is a necessary condition for maintaining the performance of the paper container for filled food. However, since the adhesion between ethylene-methacrylic acid copolymer resin and polyethylene resin is not high, the bonding strength between the adhesive layer (E layer) and the thermoplastic resin layer (F layer) will be reduced due to long-term storage of the paper container for filled food or, for example, heat treatment in the preparation process when the filled food is tofu, there is a problem that peeling occurs between the adhesive layer (E layer) and the thermoplastic resin layer (F layer), which may cause leakage of the content liquid.

[0021] An object of the present invention is to provide a paper container for filling food, which can improve the initial bonding strength between laminated layers and prevent leakage of content liquid due to delamination between the layers.

[0022] Means of solving problems

[0023] In order to achieve the above-mentioned object, the invention described in claim 1 is characterized in that it is composed of a container material having the following layers from the outer surface side to the inner surface side: a thermoplastic resin layer (A layer) mainly composed of polyethylene resin, a paper base material layer (B layer), a thermoplastic resin layer (C layer) mainly composed of polyethylene resin, a barrier layer (D layer), an adhesive layer (E layer) mainly composed of ethylene-methacrylic acid copolymer resin, a thermoplastic resin layer (I layer) mainly composed of polyethylene resin, a thermoplastic resin layer (F layer) mainly composed of polyethylene resin, a thermoplastic resin layer (G layer) of a mixture of polyethylene resin and polypropylene resin, and a thermoplastic resin layer (H layer) in which a compounding agent selected from polyols or derivatives thereof and polyoxyethylene derivatives are added to a polyolefin-based resin; the adhesive layer (E layer) mainly composed of ethylene-methacrylic acid copolymer resin and the thermoplastic resin layer (I layer) mainly composed of polyethylene resin are formed into a laminated state by co-extruding the raw materials with each other.

[0024] According to the invention described in claim 1, since the adhesive layer (E layer) mainly composed of ethylene-methacrylic acid copolymer resin and the thermoplastic resin layer (I layer) mainly composed of polyethylene resin are formed into a laminated state by co-extruding the raw materials with each other, the raw materials of the adhesive layer (E layer) mainly composed of ethylene-methacrylic acid copolymer resin and the thermoplastic resin layer (I layer) mainly composed of polyethylene resin are in contact with each other during co-extrusion and are in a state of mixing on the contact surface sides, the adhesive layer (E layer) and the thermoplastic resin layer (I layer) have a laminated structure without the possibility of peeling. Furthermore, since the thermoplastic resin layer (F layer) is laminated on the thermoplastic resin layer (I layer) laminated on the adhesive layer (E layer), since the thermoplastic resin layer (I layer) and the thermoplastic resin layer (F layer) are made of the same resin, a high bonding strength is obtained between the thermoplastic resin layer (I layer) and the thermoplastic resin layer (F layer). Therefore, there is no problem of peeling between the adhesive layer (E layer) and the thermoplastic resin layer (F layer) as in the paper container for filled food described in Patent Document 4, and the occurrence of situations such as leakage of the content liquid due to interlayer peeling can be prevented.

[0025] The invention described in claim 2 is characterized in that the co-extrusion of the adhesive layer (E layer) mainly composed of ethylene-methacrylic acid copolymer resin and the thermoplastic resin layer (I layer) mainly composed of polyethylene resin described in claim 1 is carried out by a T-die method.

[0026] According to the invention described in claim 2, since the co-extrusion of the adhesive layer (E layer) mainly composed of ethylene-methacrylic acid copolymer resin and the thermoplastic resin layer (I layer) mainly composed of polyethylene resin described in claim 1 utilizes the T-die method, the raw materials of the adhesive layer (E layer) mainly composed of ethylene-methacrylic acid copolymer resin and the thermoplastic resin layer (I layer) mainly composed of polyethylene resin are in contact with each other in the T-die during co-extrusion, thereby increasing the mixing range of the two, and the adhesive layer (E layer) and the thermoplastic resin layer (I layer) become a laminated structure with less risk of peeling, which can more reliably prevent the occurrence of situations such as leakage of content liquid due to interlayer peeling.

[0027] Effects of the Invention

[0028] According to the paper container for filled food of the present invention, it is possible to prevent leakage of the content liquid due to delamination between layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] [ Figure 1 ] An explanatory diagram showing an example of a layered structure of a container material for molding a paper container for filling food according to the present invention.

[0030] [ Figure 2 ] An explanatory diagram showing the layered structure of container materials for molding conventional paper containers for filling food. DETAILED DESCRIPTION

[0031] Hereinafter, an example of an embodiment of a filled food paper container according to the present invention will be described in detail with reference to the drawings.

[0032] Figure 1 This is an explanatory diagram showing an example of a layered structure of a container material forming the filled food paper container according to the present invention.

[0033] The filled food paper container of this example is composed of a container material having the following layers from the outer surface side to the inner surface side: a thermoplastic resin layer (A layer) mainly composed of polyethylene resin, a paper base material layer (B layer), a thermoplastic resin layer (C layer) mainly composed of polyethylene resin, a barrier layer (D layer), an adhesive layer (E layer) mainly composed of ethylene-methacrylic acid copolymer resin, a thermoplastic resin layer (I layer) mainly composed of polyethylene resin, a thermoplastic resin layer (F layer) mainly composed of polyethylene resin, a thermoplastic resin layer (G layer) obtained by mixing polyethylene resin and polypropylene resin, and a thermoplastic resin layer (H layer) obtained by adding a compounding agent selected from polyols or their derivatives and polyoxyethylene derivatives to a polyolefin-based resin; and the container material is formed by co-extruding the above-mentioned adhesive layer (E layer) mainly composed of ethylene-methacrylic acid copolymer resin and the above-mentioned thermoplastic resin layer (I layer) mainly composed of polyethylene resin into a stacked state.

[0034] The laminated structure of the above-mentioned container material, including a thermoplastic resin layer (A layer) with polyethylene resin as the main component, a paper base material layer (B layer), a thermoplastic resin layer (C layer) with polyethylene resin as the main component, a barrier layer (D layer), an adhesive layer (E layer) with ethylene-methacrylic acid copolymer resin as the main component, a thermoplastic resin layer (F layer) with polyethylene resin as the main component, a thermoplastic resin layer (G layer) formed by mixing polyethylene resin and polypropylene resin, and a thermoplastic resin layer (H layer) with a compounding agent selected from polyols or their derivatives and polyoxyethylene derivatives added to a polyolefin-based resin, is no different from the container material used as a conventional paper container for filling food described in Patent Document 4.

[0035] In this example, the thermoplastic resin layer (C layer) is composed of linear low-density polyethylene resin (LLDPE), and the thermoplastic resin layer (F layer) is composed of high-pressure low-density polyethylene resin (LDPE). In addition, aluminum foil is used as the barrier layer (D layer).

[0036] In the container material for forming the filled food paper container according to the present invention, a thermoplastic resin layer (layer I) mainly composed of polyethylene resin is laminated between the adhesive layer (layer E) and the thermoplastic resin layer (layer F) of the laminated structure laminated as described above.

[0037] An example of preparation of a container material having such a laminated structure will be described.

[0038] First, the thermoplastic resin layer (layer A) is laminated on the outer surface of the paper base layer (layer B).

[0039] Next, a thermoplastic resin layer (layer C) mainly composed of polyethylene resin is laminated on the inner surface of the paper base layer (layer B), and a barrier layer (layer D) is laminated on the thermoplastic resin layer (layer C).

[0040] Next, the adhesive layer (E layer) and the thermoplastic resin layer (I layer) are sequentially laminated on the barrier layer (D layer). When laminating the adhesive layer (E layer) and the thermoplastic resin layer (I layer), the raw materials of the adhesive layer (E layer) and the thermoplastic resin layer (I layer) are laminated on the barrier layer (D layer) by coextrusion. In this example, the coextrusion of the raw materials of the adhesive layer (E layer) and the thermoplastic resin layer (I layer) is coextrusion using a T-die method.

[0041] Next, a thermoplastic resin layer (F layer), a thermoplastic resin layer (G layer), and a thermoplastic resin layer (H layer) are laminated in this order on the thermoplastic resin layer (I layer).

[0042] When stacking the thermoplastic resin layer (F layer), the thermoplastic resin layer (G layer), and the thermoplastic resin layer (H layer), the three-layer film of the thermoplastic resin layer (F layer), the thermoplastic resin layer (G layer), and the thermoplastic resin layer (H layer) may be laminated and stacked on the thermoplastic resin layer (I layer), or the raw materials of the thermoplastic resin layer (F layer), the thermoplastic resin layer (G layer), and the thermoplastic resin layer (H layer) may be laminated with each other by co-extrusion and stacked on the thermoplastic resin layer (I layer).

[0043] It should be noted that, in this embodiment, the thermoplastic resin layer (A layer) is first laminated on the outer surface of the paper base layer (B layer), but the thermoplastic resin layer (C layer), barrier layer (D layer), adhesive layer (E layer), thermoplastic resin layer (I layer), thermoplastic resin layer (F layer), thermoplastic resin layer (G layer), and thermoplastic resin layer (H layer) may be laminated on the inner surface of the paper base layer (B layer), and finally the thermoplastic resin layer (A layer) may be laminated on the outer surface of the paper base layer (B layer).

[0044] In the filled food paper container molded from the container material having a laminated structure prepared in this manner, the adhesive layer (E layer) and the thermoplastic resin layer (I layer) are formed into a laminated state by co-extruding the raw materials with each other. Therefore, the raw materials are in contact with each other. Even if the adhesive layer (E layer) and the thermoplastic resin layer (I layer) have different resins as main components, they are mixed on the contact surface side, so that the adhesive layer (E layer) and the above-mentioned thermoplastic resin layer (I layer) have a laminated structure without the risk of peeling.

[0045] Moreover, since the thermoplastic resin layer (F layer) is laminated on the thermoplastic resin layer (I layer) laminated on the adhesive layer (E layer), since the above-mentioned thermoplastic resin layer (F layer) and the thermoplastic resin layer (I layer) are the same resin, high bonding strength is obtained between the thermoplastic resin layer (I layer) laminated on the adhesive layer (E layer).

[0046] In this example, since the co-extrusion of the raw materials of the adhesive layer (E layer) and the thermoplastic resin layer (I layer) is carried out by co-extrusion using a T-die method, the raw materials of the adhesive layer (E layer) and the thermoplastic resin layer (I layer) are contacted and mixed with each other in the T-die, thereby increasing the mixing range of the two, and the adhesive layer (E layer) and the thermoplastic resin layer (I layer) become a laminated structure with less risk of peeling.

Claims

1. A paper container for filling food, characterized in that: A container material having the following layers from the outer surface side to the inner surface side: a thermoplastic resin layer (A layer) mainly composed of polyethylene resin, a paper base material layer (B layer), a thermoplastic resin layer (C layer) mainly composed of polyethylene resin, a barrier layer (D layer), an adhesive layer (E layer) mainly composed of ethylene-methacrylic acid copolymer resin, a thermoplastic resin layer (I layer) mainly composed of polyethylene resin, a thermoplastic resin layer (F layer) mainly composed of polyethylene resin, a thermoplastic resin layer (G layer) of a mixture of polyethylene resin and polypropylene resin, and a thermoplastic resin layer (H layer) of a polyolefin resin to which a compounding agent selected from polyols or derivatives thereof and polyoxyethylene derivatives is added; The adhesive layer (E layer) mainly composed of ethylene-methacrylic acid copolymer resin and the thermoplastic resin layer (I layer) mainly composed of polyethylene resin are formed into a laminated state by co-extruding the raw materials. The thermoplastic resin layer (layer I) containing polyethylene resin as a main component and the thermoplastic resin layer (layer F) containing polyethylene resin as a main component are made of the same resin.

2. The paper container for filling food according to claim 1, characterized in that: The co-extrusion of the adhesive layer (E layer) mainly composed of the ethylene-methacrylic acid copolymer resin and the thermoplastic resin layer (I layer) mainly composed of the polyethylene resin is carried out by a T-die method.

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