Container lid material and package

Abstract

To provide a container lid material which is unlikely to peel off from an opening edge part of the container and cause leakage of a content even when internal pressure of a package changes.SOLUTION: A container lid material 3 comprises a laminated body 30 including an aluminum foil layer 31 and a heat sealing layer 32 composed of two or more resin layers 321 and 322 including the hot melt resin layer 321 which is the innermost layer of the container lid material. The hot melt resin layer 321 comprises 10 to 30 mass% of an ethylene-vinyl acetate copolymer, 25 to 55 mass% of a wax having a melting point of 55 to 115°C, and 15 to 30 mass% of a tackifier having a softening point of 120 to 160°C.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a lid material for a container used for hermetically packaging contents by heat-sealing the opening edge of a container filled with beverages, foods, etc. as contents, and a package formed by using the lid material together with a container to hermetically package the contents of beverages, foods, etc.

Background Art

[0002] For example, as containers for filling and packaging beverages such as soft drinks, milk drinks, vegetable juices, smoothies, soups, etc. and semi-solid foods such as jelly, pudding, yogurt, etc., cups and pouches made of thermoplastic resins are generally used. In particular, since cups also have a function as tableware, they are used in many food containers. In the case of a food container made of a cup, after filling the contents, sealing is performed by heat-sealing a lid material to the opening edge of the container. As the heat-sealing layer constituting the innermost layer of the lid material, a thermally adhesive resin having relatively high sealability is used to prevent leakage of the contents from the seal portion. As such a thermally adhesive resin, hot melt adhesives are often used because of their price and ease of handling, and various proposals have been made for hot melt adhesives. For example, in Patent Document 1 below, an olefin-based polymer (A) having a melt flow rate in the range of 1 to 50 g / 10 minutes at 230°C and 21.18 N: 5 to 45% by mass, a wax (B) having a melting point of 70°C or higher and 150°C or lower and a needle penetration of 0.2 to 9 when a load of 100 g is applied at 25°C for 5 seconds: 5 to 30% by mass, and a wax (C) having a melting point of 40°C or higher and lower than 70°C and a Saybolt universal viscosity at 100°C of 0.5 to 8 seconds: 35 to 75% by mass (however, the total of (A) to (C) is 100% by mass), the difference between the melting point of the wax (B) and the melting point of the wax (C) is 20°C or higher, and the total of the wax (B) and the wax (C) is 55 to 95% by mass, a hot-melt composition is disclosed.

Prior Art Documents

Patent Documents

[0003] Patent Document 1 Japanese Patent Application Laid-Open No. 2016-175957 Summary of the Invention Problems to be Solved by the Invention

[0004] By the way, packages containing food or beverages are generally stored at low temperatures such as in a refrigerator, so it is natural that sealing performance at low temperatures is required. However, there are cases where heating and processing are performed after filling and sealing the contents at room temperature, or where the contents are fermented foods. In such cases, inside the sealed package, the internal pressure changes due to temperature changes or the generation of gas from fermented foods, which causes seal recession, that is, peeling of the seal part, and ultimately the contents may leak. However, in the case of conventional lid materials for containers, it has been difficult to reliably prevent seal recession due to changes in the internal pressure of the package.

[0005] This invention has been made in view of the above problems, and an object thereof is to provide a lid material for a container that can reliably prevent seal recession due to changes in the internal pressure of the package. Means for Solving the Problems

[0006] In order to achieve the above object, this invention comprises the following aspects.

[0007] 1) A lid material for a container that is heat-sealed to the opening edge of the container so as to cover the opening of the container filled with contents, which is composed of a laminate including an aluminum foil layer and a heat-sealing layer composed of two or more resin layers including a hot-melt resin layer that becomes the innermost layer of the lid material for the container, wherein the hot-melt resin layer At least one polyolefin resin: 5 to 50% by mass, Ethylene vinyl acetate copolymer: 10 to 30% by mass, wax with a melting point of 55 to 115 °C: 25 to 55% by mass, tackifier with a softening point of 120 to 160 °C: containing 15 to 30% by mass and the melting point of the hot melt resin layer is 68 to 85°C , a lid material for a container.

[0008] 2) the melting point of the wax is 65 to 115°C , the lid material for a container of 1) above.

[0009] 3) The reinforcing resin layer interposed between the aluminum foil layer and the heat-sealing layer in the laminate and provided, the lid material for a container of 1) or 2) above.

[0010] 4) the reinforcing resin layer is composed of a single-layer or multi-layer film made of a polyester resin and has a thickness of 5 to 20 μm, and is laminated via an adhesive layer on the surface of the aluminum foil layer on the heat-sealing layer side, the lid material for a container of 3).

[0011] 5 ) The two or more resin layers constituting the heat-sealing layer include an adhesive interposed layer made of a polyolefin resin, the above 1) to 4 ) Any one of the lid materials for a container.

[0012] 6) The lid material for a container of 5), wherein the adhesive intervening layer has a thickness of 10 to 40 μm.

[0013] 7 ) A container filled with contents and any one of the lid materials for a container of 1) to 6 ) heat-sealed to the opening edge of the container so as to cover the opening of the container, a package.

[0014] 8 ) The lid material for a container has a flat top wall portion whose peripheral portion is heat-sealed to the upper surface of the opening edge of the container, and a skirt portion extending downward from the peripheral portion of the top wall portion and a part of whose height is heat-sealed to the outer surface of the opening edge of the container, the above 7 ) package.

[0015] Here, the melting point of the wax and the melting point of the hot melt resin layer refer to those measured by a differential scanning calorimeter (DSC) under the condition of 10 °C / min. The softening point of the tackifier is measured in accordance with the provisions of JIS K6863 (1994).

Advantages of the Invention

[0016] According to the lid material for containers of 1) above, since a material having the above composition is used as the hot-melt resin layer, even when the internal pressure of the package formed by heat-sealing the lid material to the opening edge of the container filled with the contents changes due to deformation of the container or the like immediately after heat-sealing, seal recession is unlikely to occur. Moreover, according to the lid material for a container of 1), since the melting point of the hot melt resin layer is 68 to 85°C, the sealing property is good even at a low sealing temperature, and even when the internal pressure of the package increases due to deformation of the container immediately after heat sealing, seal regression is less likely to occur.

[0017] The above 3) or 4 According to the lid material for containers, since the strength is improved by the presence of the reinforcing resin layer of even when the internal pressure or external pressure of the package changes, it is difficult for the lid material to break and the contents to leak.

[0018] The above 5) or 6 According to the lid material for containers, since the heat-sealing layer includes an adhesive intervening layer made of a polyolefin resin, the sealing property with containers made of resins such as polystyrene resin generally used, or containers formed by molding a laminate of paper, aluminum foil and a resin layer is improved. Therefore, even when the internal pressure of the package increases, seal recession is unlikely to occur.

[0019] The above 7 According to the package of ) above, even when the internal pressure thereof changes due to deformation of the container or the like immediately after heat-sealing, seal recession is unlikely to occur in the lid material for containers. Therefore, leakage of the contents due to seal recession can be reliably prevented.

[0020] The above 8 According to the package of ), a part of the melted resin of the heat-sealing layer of the lid main body portion in the lid material for containers wraps around the outer surface of the opening edge of the container, and thereby a part of the height of the skirt portion is also heat-sealed to the opening edge of the container, increasing the seal area. Therefore, even when seal recession occurs, the sealing property is maintained.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.

[0023] FIG. 1 shows the layer structure of a laminate (sheet) (30) that constitutes a lid material (3) for a container according to the present invention. The illustrated laminate (30) includes an aluminum foil layer (31), a heat-sealing layer (32), a reinforcing resin layer (33) interposed between the aluminum foil layer (31) and the heat-sealing layer (32), and a protective resin layer (34) laminated on the surface of the aluminum foil layer (31) opposite to the heat-sealing layer (32).

[0024] The aluminum foil layer (31) functions as a barrier layer that imparts barrier properties against gas, moisture, light, etc. to the lid material (3). As the aluminum foil constituting the aluminum foil layer (31), soft materials (O materials) such as A1N30, A8021, and A8079 defined in JIS H4160 (2006) are preferably used in consideration of workability and versatility. Considering formability, pinhole generation rate, etc., the thickness of the aluminum foil layer (31) is preferably about 5 to 40 μm. It is preferable that a base layer (not shown) made of a chemical conversion coating film is formed on both surfaces of the aluminum foil layer (31). With such a base layer, the adhesiveness between the aluminum foil layer (31), the reinforcing resin layer (33), and the protective resin layer (34) is improved, and the corrosion resistance of the aluminum foil layer (31) is also improved. Specifically, for example, on the surface of the degreased aluminum foil layer (31), 1) An aqueous solution of a mixture containing phosphoric acid, chromic acid, and at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides 2) An aqueous solution of a mixture containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, and at least one compound selected from the group consisting of chromic acid and chromium(III) salts 3) An aqueous solution of a mixture containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, at least one compound selected from the group consisting of chromic acid and chromium(III) salts, and at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides By applying any of the aqueous solutions of 1) to 3) above and then drying, a chemical conversion treatment is performed to form a film. The film formed on the surface of the aluminum foil layer (31) by the chemical conversion treatment, that is, the base layer, preferably has a chromium adhesion amount (per side) of 0.1 mg / m 2 ~50 mg / m 2 and particularly preferably 2 mg / m 2 ~20 mg / m 2

[0025] ​The heat-sealing layer (32) is for heat-sealing the lid material (3) for the container to the opening edge (21) of the container (2). In this embodiment, the heat-sealing layer (32) consists of two resin layers (321) and (322). One of them is a hot-melt resin layer (321) that constitutes the innermost layer of the lid material (3) for the container, and the other is an adhesive intervening layer (322) made of a polyolefin resin.

[0026] As the hot-melt resin layer (321), those containing at least one polyolefin resin: 5 to 50% by mass, ethylene-vinyl acetate copolymer (EVA): 10 to 30% by mass, wax with a melting point of 55 to 115°C: 25 to 55% by mass, and tackifier with a softening point of 120 to 160°C: 15 to 30% by mass are used. By using the hot-melt resin layer (321) having such a composition, as will be described later, even when the internal pressure of the package (1) obtained by using the lid material (3) for the container together with the container (2) changes, the effect that seal recession is unlikely to occur can be obtained. Examples of the polyolefin resin include homopolymers such as polyethylene, polypropylene, polybutene, and polyisobutylene, and copolymers of ethylene with olefins such as propylene and 1-butene. Examples of the wax include paraffin wax, montan wax, ethylene wax, propylene wax, and modified wax obtained by grafting styrene onto a polyethylene-polypropylene copolymer. Examples of the tackifier (tackifier) include rosins such as rosin and disproportionated rosin, esters of rosins with polyhydric alcohols such as glycol, glycerin, and pentaerythritol, terpenes, and hydrocarbon resins having monomers such as styrene. Also, the hot-melt resin layer (321) preferably has a melting point of 70 to 85°C, whereby, for example, even when the internal pressure of the package (1) increases due to deformation of the container immediately after heat-sealing, seal recession is less likely to occur. The hot-melt resin layer (321) is, for example, the hot-melt resin having the above composition prepared using a gravure roll, preferably at 12 to 16 g / m 2It is formed by coating the surface of the adhesive intermediate layer (322) with a basis weight and then drying and curing.

[0027] The adhesive intermediate layer (322) is a layer laminated as a base for equalizing the layer thickness of the hot melt resin layer (321). Further, in order to also have a function as an adhesive layer during heat sealing, it is preferably composed of a resin having a melting point close to that of the hot melt resin layer (321), for example, a polyolefin resin such as a polyethylene resin (PE) or its compound. The thickness of the adhesive intermediate layer (322) is preferably 10 to 40 μm in order to equalize the layer thickness of the hot melt resin layer (321).

[0028] Note that the heat-sealing layer (32) may be composed of three or more resin layers, for example, by laminating a resin layer containing hydrophobic particles or the like further outside the hot melt resin layer (321).

[0029] The reinforcing resin layer (33) is interposed between the aluminum foil layer (31) and the heat-sealing layer (32) to enhance the strength of the container lid material (3), particularly the strength against changes in the internal and external pressures of the package (1). The reinforcing resin layer (33) is composed of, for example, a single-layer or multi-layer film made of a polyester resin such as polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), or polyethylene naphthalate resin (PEN), and is dry-laminated to the surface of the aluminum foil layer (31) via an adhesive layer (not shown) made of a urethane resin-based adhesive or the like. The thickness of the reinforcing resin layer (33) is preferably 5 to 20 μm in consideration of the strength and the dead-hold property for maintaining the shape of the skirt portion (3b).

[0030] The protective resin layer (34) constitutes the outermost layer of the container lid material (3) and bears the function of decorating and protecting the lid material (3). The protective resin layer (34) is preferably a single-layer or multi-layer film made of, for example, polyester resin films such as polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polyethylene naphthalate resin (PEN), polyamide resin films such as 6 nylon (PA6), 6,6 nylon (PA66), stretched polyolefin resin films such as biaxially stretched polypropylene resin film (OPP), or a coating film made of thermosetting resins such as nitrocellulose and epoxy resin. Considering the dead-hold property and the corrosion resistance of the aluminum foil layer (31), the thickness of the protective resin layer (34) is preferably 2 to 25 μm. Although not shown, a printing layer may be entirely or partially interposed between the protective resin layer (34) and the aluminum foil layer (31).

[0031] Figure 2 shows a lid material (3) for a container formed from the above laminate (30). The lid material (3) for a container includes a flat top wall portion (3a) having a shape and size capable of covering the upper opening of the container (2), and a skirt portion (3b) extending downward from the peripheral portion of the top wall portion (3a). In the illustrated lid material (3) for a container, the top wall portion (3a) is formed in a disc shape. The skirt portion (3b) is provided in a hanging manner so as to cover the outer surface of the opening edge portion (21) of the container (2). This lid material (3) for a container can be formed by cutting the above laminate (30) into a predetermined shape and size and then performing press molding. A number of longitudinal pleats (3c) are formed at intervals in the circumferential direction on the skirt portion (3b).

[0032] Figure 3 shows a package (1) formed by hermetically packaging a content (C) such as a beverage or food using the container (2) and the above lid material (3) for a container. The container (2) is in a cup shape with an upper opening, and is made of, for example, a thermoplastic resin molded product such as polystyrene resin. Note that the shape and material of the container (2) are not limited to the above. The package (1) is formed by heat-sealing a container lid material (3) to the opening edge (21) of a container (2) filled with contents (C). More specifically, the hot-melt resin layer (321) at the peripheral portion of the top wall portion (3a) of the container lid material (3) is heat-sealed to the upper surface of the opening edge (21) of the container (2), and the hot-melt resin layer (321) at the upper end side portion of the skirt portion (3b) of the container lid material (3) is heat-sealed to the outer surface of the opening edge (21) of the container (2). As the heat-sealing method, in addition to heat-welding the hot-melt resin layer (321) of the container lid material (3) and the opening edge (21) of the container (2) with a hot plate or the like, ultrasonic welding or high-frequency welding may also be used.

Example

[0033] Next, specific embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0034] [Production of laminate] A polyethylene terephthalate resin film (PET) with a thickness of 9 μm as a reinforcing resin layer was dry-laminated via a urethane resin adhesive (layer thickness: 2 μm) on one side of an aluminum foil with a thickness of 25 μm made of A1N30-O defined in JIS H4160 (2006). Next, polyethylene resin (PE) was heat-laminated by an extruder on the surface of the polyethylene terephthalate resin film (PET) to a layer thickness of 20 μm as an adhesive intervening layer. Then, the amounts (mass %) of polyolefin resin, the amounts (mass %) of ethylene vinyl acetate copolymer (EVA), the melting point and amounts (mass %) of wax, the softening point and amounts (mass %) of tackifier, and hot-melt resins having melting points as shown in the columns of Examples 1 to 4 and Comparative Examples 1 to 8 in Table 1 below were prepared, and each hot-melt resin was applied to the surface of the polyethylene resin layer (PE) at a basis weight of 14 g / m 2 with a gravure roll. Finally, nitrocellulose was applied as a protective resin layer to the other surface of the aluminum foil so that the layer thickness was 5 μm. Thus, the laminates of Examples 1 to 4 and Comparative Examples 1 to 8 were produced. Also, a laminate was produced in the same manner as in Example 4 except that the polyethylene resin layer (PE) was not formed, and this was designated as Comparative Example 9.

[0035]

Table 1

[0036] [Creep Test] In order to verify the influence of the change in the internal pressure in the sealed package on the seal portion between the container and the lid material, the deformation that occurs over time when a constant stress is applied to the seal portion was confirmed by the following creep test. Referring to FIG. 4, first, each of the laminates of Examples 1 to 4 and Comparative Examples 1 to 9 was cut into strips having a width of 15 mm and a length of 50 mm to prepare a lid material side test specimen (A). Also, as a container side test specimen (B), a polystyrene resin sheet having a thickness of 1 mm cut into strips having a width of 15 mm and a length of 50 mm was prepared. Then, the lid material side test specimen (A) and the container side test specimen (B) were arranged in series such that one end portion (A1) (B1) of each of them overlapped by 10 mm, and the overlapping one end portions (A1) (B1) of both test specimens (A) (B) were heat-sealed using a hot plate under the conditions of a seal temperature of 140 ° C., a seal pressure of 0.3 MPa, and a seal time of 1 second. Next, after the other end portion of the container side test specimen (B) was held and fixed by a chuck (D), a load (P) of 45 gf was applied to the other end portion of the lid material side test specimen (A) in an environment at 45 ° C., and the time until the seal portions (A1) (B1) of both test specimens (A) (B) were peeled off was measured. The maximum measurement time was set to 60 minutes. The results are as shown in the column of the creep test results in Table 1 above, where “◎” indicates those that did not peel off in 60 minutes, “○” indicates those that did not peel off for 50 minutes or more and less than 60 minutes, and “×” indicates those that peeled off in less than 50 minutes. As is clear from the results in Table 1, in Examples 1 to 4, the time until peeling is sufficiently long, indicating that the amount of deformation of the seal portion is small. Therefore, according to the package using the lid material composed of the laminate of Examples 1 to 4, it is considered that seal recession hardly occurs even with a change in internal pressure, and thus leakage of the contents from the seal portion hardly occurs.

Industrial Applicability

[0037] The present invention can be suitably used as a lid material for a container used for heat-sealing an opening edge portion of a container filled with a beverage, food, or the like as a content to hermetically package the content, and as a package obtained by hermetically packaging the content such as a beverage or food using the lid material.

Explanation of Signs

[0038] (1): Package (2): Container (21): Opening edge portion (3): Lid material for a container (3a): Top wall portion (3b): Skirt portion (30): Laminate (31): Aluminum foil layer (32): Heat-sealing layer (321): Hot melt resin layer (322): Adhesion intervening layer (33): Reinforcing resin layer (34): Protective resin layer (C): Content

Claims

1. A container lid that is heat sealed to an opening edge portion of a container filled with a content so as to cover the opening of the container, The container lid material is made of a laminate including an aluminum foil layer and a heat sealing layer composed of two or more resin layers including a hot melt resin layer which is the innermost layer of the container lid material, The hot melt resin layer contains 23 to 50% by mass of at least one polyolefin resin, 10 to 30% by mass of an ethylene-vinyl acetate copolymer, 25 to 50% by mass of a wax having a melting point of 65 to 115°C, and 15 to 30% by mass of a tackifier having a softening point of 120 to 160°C, The container lid material, wherein the hot melt resin layer has a melting point of 68 to 85°C.

2. The container lid material according to claim 1, wherein the hot melt resin layer has a basis weight of 12 to 16 g / m 2 .

3. 3. The container lid material according to claim 1, wherein the laminate further comprises a reinforced resin layer interposed between the aluminum foil layer and the heat sealing layer.

4. The reinforced resin layer is composed of a single layer or multilayer film made of polyester resin and has a thickness of 5 to 20 μm, and is laminated on the surface of the aluminum foil layer facing the heat sealing layer via an adhesive layer. The container lid material according to claim 3.

5. The container lid material according to any one of claims 1 to 4, wherein the two or more resin layers constituting the heat sealing layer include an adhesive intervening layer made of a polyolefin resin.

6. 6. The container lid material according to claim 5, wherein the adhesive intervening layer has a thickness of 10 to 40 μm.

7. A packaging body comprising a container filled with contents and a container lid material according to any one of claims 1 to 6 that is heat sealed to an opening edge portion of the container so as to cover the opening of the container.

8. 8. The package of claim 7, wherein the container lid comprises a flat top wall portion whose peripheral edge is heat sealed to the upper surface of the opening edge of the container, and a skirt portion extending downward from the peripheral edge of the top wall portion and having a portion of its height heat sealed to the outer surface of the opening edge of the container.

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