Packaging materials

Abstract

To provide a packaging material capable of being packaged into a pillow type with stable seal strength.SOLUTION: A packaging material is constituted of a laminated body with a base material and a seal layer laminated on the base material. The packaging material can be packaged into a pillow type with lateral seal parts provided at an upper end and a lower end and a vertical seal part connecting the lateral seal parts with each other. In forming the lateral seal parts and the vertical seal part at a seal temperature 140-160°C, a seal strength is 2-10 N / 15 mm and an intensity ratio which is a ratio of the maximum intensity to the minimum intensity in the temperature range is 1.5 or less.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to packaging materials. [Background technology]

[0002] From the perspective of convenience, it is common to heat and cook fresh foods such as prepared foods and vegetables packaged in packaging materials in a microwave oven while they are still unopened. Packaging materials that can be formed into a pillow shape are used for this purpose. An example of such a packaging material is disclosed in, for example, Japanese Patent Application Laid-Open No. 2019-1495 (Patent Document 1). The packaging material of Patent Document 1 is composed of a laminate having a base material (layer 8 based on a plastic film) and a seal layer (heat seal layer 9) laminated thereon. The seal layers can be heat-sealed to form a pillow-shaped bag with horizontal seal portions (top and bottom seal portions 2) at the top and bottom ends and a vertical seal portion (back seal portion 3) connecting the horizontal seal portions.

[0003] The packaging material of Patent Document 1 has a seal strength that meets specified conditions in an 80°C environment, and therefore it is possible to release steam by opening the seal near the intersection of the horizontal and vertical seals without providing a laminate strength adjustment layer.

[0004] However, packaging conditions (particularly conditions related to sealing temperature) when making bags using a laminate having a base material and a sealing layer laminated thereon are likely to vary to some extent depending on the main body of packaging. Patent Document 1 does not take this into consideration at all, and as a result, there is a possibility that the seal strength will also vary. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-1495 Summary of the Invention [Problem to be solved by the invention]

[0006] It is desirable to develop a packaging material that can be made into pillow-shaped bags with stable seal strength. [Means for solving the problem]

[0007] The packaging material according to the present invention comprises: A packaging material comprising a laminate having a substrate and a seal layer laminated on the substrate, The bag can be made into a pillow-shaped bag having horizontal seal portions at the upper and lower ends and vertical seal portions connecting the horizontal seal portions, When the horizontal seal portion and the vertical seal portion are formed at a sealing temperature of 140 to 160°C, the seal strength is 2 to 10 N / 15 mm, and the strength ratio, which is the ratio of the maximum strength to the minimum strength in that temperature range, is 1.5 or less.

[0008] According to this configuration, when pillow-shaped bags are made at a sealing temperature of 140 to 160°C, the strength ratio (= ratio of maximum strength to minimum strength) in that temperature range is 1.5 or less, minimizing variations in seal strength. This allows for stable seal strength to be achieved regardless of the sealing temperature conditions for the packaging body. Furthermore, when pillow-shaped bags are made, the seal strength of the horizontal and vertical seals is 2 to 10 N / 15 mm, ensuring a constant seal strength while allowing for easy opening and steam release when heated, for example, in a microwave oven. This makes it possible to provide a packaging material that can be made into pillow-shaped bags with stable seal strength and that allows for appropriate steam release as needed.

[0009] Preferred embodiments of the present invention will be described below, but the scope of the present invention is not limited to the preferred embodiments described below.

[0010] In one embodiment, The internal pressure when either the horizontal seal portion or the vertical seal portion is peeled off first due to an increase in internal pressure is preferably 14 to 18 MPa.

[0011] With this configuration, neither the horizontal nor the vertical seals will peel off when the internal pressure is below 14 MPa, preventing either the horizontal or the vertical seals from peeling off during transport, etc. Also, when the internal pressure is 18 MPa or less, either the horizontal or the vertical seals will peel off and open, preventing the internal pressure from rising too high and causing the bag to burst.

[0012] In one embodiment, It is preferable that the horizontal seal portion and the vertical seal portion are configured as easy-peel seal portions of a cohesive peeling type.

[0013] With this configuration, when a force is applied to peel the horizontal and vertical seals, the force is dispersed and the package can be opened smoothly, thereby ensuring a certain level of seal strength and preventing rupture.

[0014] In one embodiment, It is preferable that the seal strength of the vertical seal portion is smaller than the seal strength of the horizontal seal portion.

[0015] With this configuration, for example, when the internal pressure increases during heating in a microwave oven or the like, the vertical seal portion can be opened first.

[0016] In one embodiment, It is preferable that the vertical seal portion is formed by butt-seaming.

[0017] According to this configuration, for example, when the internal pressure increases during heating in a microwave oven or the like, the vertical seal portion can be easily opened.

[0018] Further features and advantages of the present invention will become more apparent from the following description of exemplary and non-limiting embodiments, which is given with reference to the drawings. [Brief explanation of the drawings]

[0019] [Figure 1] Cross-sectional view of a packaging material according to an embodiment [Figure 2] Schematic diagram of pillow packaging [Figure 3] III-III cross section in Figure 2 [Figure 4] Graph showing the relationship between sealing temperature and seal strength DETAILED DESCRIPTION OF THE INVENTION

[0020] An embodiment of the packaging material will be described with reference to the drawings. As shown in Fig. 1, the packaging material 1 of this embodiment is composed of a laminate having a base material 2 and a seal layer 3 laminated on the base material 2.

[0021] The substrate 2 includes a polymer film having a certain strength. The constituent material of the substrate 2 is not particularly limited, but examples thereof include polyolefin, polyester, polyamide, and polyimide. Examples of polyolefin include polyethylene and polypropylene. Examples of polyester include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Examples of polyamide include nylon-6 and nylon-66. Among these, polypropylene is preferably used from the viewpoints of cost, appearance, and the like.

[0022] The substrate 2 may be stretched or unstretched. When the substrate 2 is stretched, it may be uniaxially stretched or biaxially stretched. Preferably, the substrate 2 contains biaxially stretched polypropylene.

[0023] The substrate 2 may be a single-layer film or a laminated film having multiple layers. When the substrate 2 is a laminated film, the substrate 2 may have other functional layers such as a printed layer, a gas barrier layer, an adhesive layer, etc. in addition to at least one substrate layer made of the various materials described above. As an example, the substrate 2 may be a laminated film in which a first substrate layer, a printed layer, an adhesive layer, and a second substrate layer are laminated in this order.

[0024] The thickness of the substrate 2 is not particularly limited, but can be, for example, 10 μm to 60 μm. The thickness of the substrate 2 is preferably 15 μm to 55 μm, more preferably 20 μm to 50 μm, and particularly preferably 20 μm to 25 μm.

[0025] The sealing layer 3 is made of an easy-peel sealant. Examples of easy-peel sealants that can be used to make up the sealing layer 3 include an interface peeling type that is a mixture of resins with different compositions, a cohesive peeling type that peels off with cohesive failure when opened, and an interlayer peeling type that peels off between the sealing layer and the peel layer when opened. Among these, a cohesive peeling type easy-peel sealant can be preferably used. By making the sealing layer 3 out of an easy-peel sealant, the sealing layer 3 can be made easily peelable.

[0026] The constituent material of the sealing layer 3 is not particularly limited, but examples thereof include polypropylene, polyethylene, ethylene-vinyl acetate copolymer resin (EVA), ethylene-methyl acrylate copolymer resin (EMA), ethylene-methyl methacrylate copolymer resin (EMMA), polystyrene, acrylic acid ester, vinyl acetate, polyethylene terephthalate, etc. One of these may be used alone, or two or more may be used in combination.

[0027] The thickness of the sealing layer 3 is not particularly limited, but can be, for example, 0.5 μm to 5 μm. Sealing layer 3 The thickness is preferably 1 μm to 4.5 μm, and more preferably 1.5 μm to 4 μm.

[0028] The packaging material 1 can be folded so that the base material 2 faces outward and the seal layer 3 faces inward, and the seal layers 3 are heat-sealed together to form a bag. In this embodiment, the packaging material 1 can be formed into a pillow-shaped bag (a pillow package 10 can be formed). As shown in FIG. 2, the pillow package 10 has horizontal seal portions 12 at the top and bottom, and a vertical seal portion 14 connecting the horizontal seal portions 12. The horizontal seal portions 12 are formed by simple lamination. The vertical seal portion 14 is formed by back-seaming (see also FIG. 3). A notch (e.g., an I-notch, a U-notch, a V-notch, etc.) may be formed in the outer edge of at least one of the horizontal seal portions 12 and the vertical seal portion 14 to serve as a starting point for tearing.

[0029] The horizontal seal portion 12 and the vertical seal portion 14 are composed of easy-peel seal portions formed by bonding together seal layers 3. As described above, it is preferable to use a cohesive peeling type easy-peel sealant as the seal layer 3, and it is preferable that the horizontal seal portion 12 and the vertical seal portion 14 are composed of cohesive peeling type easy-peel seal portions. By constructing the horizontal seal portion 12 and the vertical seal portion 14 with cohesive peeling type easy-peel seal portions, the peeled portion becomes white and visible after opening. Therefore, since the horizontal seal portion 12 and the vertical seal portion 14 remain transparent, it is possible to guarantee that the package is unopened.

[0030] The horizontal seals 12 and the vertical seals 14 can be formed, for example, by heat sealing. The sealing temperature when forming the horizontal seals 12 and the vertical seals 14 is not particularly limited, but can be, for example, 140°C to 160°C.

[0031] In the pillow package 10 of this embodiment, when the horizontal seals 12 and vertical seals 14 are formed at a sealing temperature of 140°C to 160°C, the seal strength of the horizontal seals 12 and vertical seals 14 is 2N / 15mm to 10N / 15mm. A seal strength of 2N / 15mm or greater prevents the pillow package 10 from being unintentionally opened during transportation. A seal strength of 10N / 15mm or less prevents the pillow package 10 from bursting due to steam when the internal pressure increases to a certain level. The seal strength of the horizontal seals 12 and vertical seals 14 is preferably 2.5N / 15mm or greater, and more preferably 3N / 15mm or greater. The seal strength of the horizontal seals 12 and vertical seals 14 is preferably 9N / 15mm or less, and more preferably 8N / 15mm or less.

[0032] When the horizontal seals 12 and vertical seals 14 are formed at a sealing temperature of 140°C to 160°C, the ratio (strength ratio) of the maximum seal strength (maximum strength) to the minimum seal strength (minimum strength) within that temperature range is 1.5 or less. Here, the strength ratio is 1.5 or less for each of the horizontal seals 12 and the vertical seals 14. By keeping the strength ratio 1.5 or less, it is possible to minimize variations in seal strength. This allows for stable seal strength to be achieved regardless of the sealing temperature conditions associated with the packaged object.

[0033] Although there are no particular limitations on the relationship between the seal strength of horizontal seal portion 12 and that of vertical seal portion 14, it is preferable that the seal strength of vertical seal portion 14 be smaller than the seal strength of horizontal seal portion 12. In this way, once the internal pressure of pillow package 10 has risen to a certain level, vertical seal portion 14 can be preferentially vaporized.

[0034] The internal pressure at which either the horizontal seal 12 or the vertical seal 14 (or the vertical seal 14 if the vertical seal 14 has a lower seal strength) peels first due to an increase in internal pressure is not particularly limited, but can be set to 14 to 18 MPa. If the internal pressure is less than 14 MPa, neither the horizontal seal 12 nor the vertical seal 14 will peel, preventing the package from being unintentionally opened during transport. Furthermore, if the internal pressure is 18 MPa or less, either the horizontal seal 12 or the vertical seal 14 will peel and open, preventing the pillow package 10 from bursting due to an excessive increase in internal pressure.

[0035] The pillow packaging 10 of this embodiment can be used to package food 20, as shown in FIG. 3 . Examples of food 20 include cooked foods and fresh foods. Examples of cooked foods include gyoza (dumplings), shumai (steamed dumplings), spring rolls, fried rice, hamburger steak, croquettes, pork cutlets, fried chicken, oden, and boiled beans. Examples of fresh foods include cut vegetables such as cabbage, broccoli, cauliflower, asparagus, corn, carrots, bean sprouts, onions, potatoes, pumpkins, sweet potatoes, bell peppers, and paprika, and cut fruits such as apples, melons, pineapples, mangoes, and watermelons. Among these, the pillow packaging 10 can be suitably used to package cooked foods that may be heated in a microwave oven before eating as food 20. Alternatively, the pillow packaging body 10 can be suitably used to package raw vegetables as food 20, such as cabbage, carrots, bean sprouts, corn, paprika, etc., which may be heated in a microwave oven and eaten as hot vegetables.

[0036] A pillow package 10 was produced using the packaging material 1 of this embodiment to package cut vegetables including corn and peppers as food 20. This pillow package 10 was placed in a microwave oven and heated at 600W for 4 minutes. When the process was observed, steam gradually generated inside and the pillow package 10 expanded. Continuing observation revealed that the vertical seal 14 eventually peeled off and steamed before the pillow package 10 burst. The vertical seal 14 peeled gently by cohesive peeling, and no phenomenon such as a forceful eruption of steam was observed during steaming.

[0037] Additionally, the sealing temperature during bag production of pillow package 10 was changed in 10°C increments within the range of 110°C to 170°C, and the seal strength of each of the pair of upper and lower horizontal seals 12 and the vertical seal 14 connecting them was measured. The seal strength measurements were performed using an A&D universal material testing machine (model number: TENSILON RTG-1310). The results are shown in Figure 4.

[0038] As shown in Figure 4, in the sealing temperature range of 140°C or less, there was a large variation in seal strength for both horizontal seal portion 12 and vertical seal portion 14 (strength ratio of approximately 3 to 11). In contrast, in the sealing temperature range of 140°C to 160°C, there was a small variation in seal strength for both horizontal seal portion 12 and vertical seal portion 14 (strength ratio of approximately 1.03 to 1.13), confirming that a stable seal strength can be achieved in this temperature range.

[0039] Furthermore, with regard to the vertical seal portion 14, it was confirmed that the variation in seal strength was small over a wider temperature range of 130°C to 170°C (strength ratio of approximately 1.18), and that stable seal strength could be achieved over a wider temperature range.

[0040] The packaging material 1 and the pillow package 10 using the same have been described in detail above by showing specific embodiments, but the present invention is not limited thereto. The embodiments disclosed in this specification are illustrative in all respects and can be modified as appropriate within the scope of the present disclosure. [Explanation of symbols]

[0041] 1 Packaging materials 2 Base material 3 Sealing Layer 10 Pillow packaging 12 Horizontal seal section 14 Vertical seal 20 Food

Claims

[Claim 1] A packaging material comprising a laminate having a substrate having a thickness of 20 to 50 μm and a single-layer seal layer having a thickness of 1.5 μm to 4 μm laminated on the substrate, The bag can be made into a pillow-shaped bag having horizontal seal portions at the upper and lower ends and a vertical seal portion formed by joining the horizontal seal portions together, the seal strength when the horizontal seal portion and the vertical seal portion are formed at a sealing temperature of 140 to 160°C is 2 to 8 N / 15 mm, and the strength ratio, which is the ratio of the maximum strength to the minimum strength in that temperature range, is 1.5 or less; The single-layer seal layer is made of a cohesive peelable easy-peel sealant, and the horizontal seal portion and the vertical seal portion are made of a cohesive peelable easy-peel seal portion, the seal strength of the vertical seal portion is smaller than the seal strength of the horizontal seal portion; Packaging material used in pillow packaging for heating packaged raw vegetables in a microwave oven.

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