bag

Abstract

To provide a bag with the steam vent structure and a peeling property.SOLUTION: A laminated body for composing a steam vent bag at least consists of a first stretched plastic film, a second stretched plastic film, and a sealant layer laminated from the outer surface to the inner surface. The first stretched plastic film has either polyester or polyamide as the major component. When the first stretched plastic film has polyester as the major component, the second stretched plastic film has either polyester or polyamide as the major component. When the first stretched plastic film has polyamide as the major component, the second stretched plastic film has polyester as the major component. When the width direction of the bag becomes the first direction and the direction crossing the first direction at right angles becomes the second direction, the tensile strength of the second stretched plastic film in the first direction is bigger than that of the second stretched plastic film in the second direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a bag constructed from a laminate including an oriented plastic film. [Background technology]

[0002] Conventionally, there are many bags on the market that are filled and sealed with cooked or semi-cooked liquid, viscous material, or a mixture of liquid and solid, made of plastic laminates. In the bag, the non-sealed portion where the laminates are not joined constitutes the storage portion in which the contents are stored. Also, the sealed portion where the laminates are joined seals the storage portion. The contents are, for example, cooked foods such as curry, stew, soup, etc. The contents are heated in a microwave oven or the like while contained in the bag.

[0003] However, when the contents stored in a sealed bag are heated using a microwave oven, the moisture contained in the contents evaporates as the bag is heated, and the pressure in the storage section increases. If the pressure in the storage section of the bag increases, the bag may burst, causing the contents to scatter and soil the inside of the microwave oven. In consideration of such a problem, for example, Patent Document 1 proposes providing a mechanism for automatically connecting the storage section to the outside when the pressure in the storage section increases, and releasing the steam in the storage section to the outside. Patent Document 1 also proposes using, as a laminate constituting the bag, a stretched polyethylene terephthalate film, a silica-deposited stretched polyethylene terephthalate film, an alumina-deposited stretched polyethylene terephthalate film, a stretched nylon film, a stretched polypropylene film, or a polypropylene / ethylene-vinyl alcohol copolymer co-extruded co-stretched film, or a composite film in which two or more of these films are laminated, in order to give the bag resistance to heat. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-120550 A Summary of the Invention [Problem to be solved by the invention]

[0005] When removing the contents from the storage section, the consumer tears the bag to open it. For consumer convenience, it is preferable that the laminate of the bag is configured so that the bag can be opened by tearing it with the hands or the like.

[0006] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a bag that is equipped with a steam vent mechanism and has tearability. [Means for solving the problem]

[0007] The present invention is a bag having a steam venting mechanism, wherein the laminate constituting the bag comprises, in order from the outer surface side to the inner surface side, at least a first stretched plastic film, a second stretched plastic film, and a sealant layer, wherein the first stretched plastic film contains polyester or polyamide as a main component, and when the first stretched plastic film contains polyester as a main component, the second stretched plastic film contains polyester or polyamide as a main component, and when the first stretched plastic film contains polyamide as a main component, the second stretched plastic film contains polyester as a main component, and when the width direction of the bag is a first direction and a direction perpendicular to the first direction is a second direction, the tensile strength of the second stretched plastic film in the first direction is greater than the tensile strength of the second stretched plastic film in the second direction.

[0008] In the bag according to the present invention, the tensile strength of the second stretched plastic film in the first direction may be at least 1.05 times the tensile strength of the second stretched plastic film in the second direction.

[0009] In the bag according to the present invention, both the first stretched plastic film and the second stretched plastic film may contain polyester as a main component.

[0010] In the bag according to the present invention, the first stretched plastic film may contain polyamide as a main component, and the second stretched plastic film may contain polyester as a main component.

[0011] In the bag according to the present invention, the first stretched plastic film may contain polyester as a main component, and the second stretched plastic film may contain polyamide as a main component. Effect of the Invention

[0012] According to the present invention, a bag having a steam vent mechanism and tearability can be provided. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a front view showing a bag according to the embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view showing the bag shown in FIG. 1 as viewed along line II-II. [Diagram 3] FIG. 2 is a cross-sectional view showing an example of a layer structure of a laminate constituting a bag. [Figure 4] FIG. 2 is a cross-sectional view showing an example of a layer structure of a first stretched plastic film. [Diagram 5] 4 is a cross-sectional view showing an example of heat transfer from the inner surface side to the outer surface side of the laminate. FIG. [Figure 6] FIG. 1 is a diagram showing an example of a method for measuring piercing strength. [Figure 7] FIG. 2 is a plan view showing a test piece for evaluating impact strength. [Figure 8] FIG. 8 is a cross-sectional view of the test piece shown in FIG. [Figure 9] FIG. 2 is a diagram showing an example of a method for measuring impact strength. [Figure 10]FIG. 2 is a plan view showing a test piece for evaluating tearability. [Figure 11] FIG. 1 is a diagram showing the evaluation results of Examples 1 to 4 and Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] An embodiment of the present invention will be described with reference to Figures 1 to 5. In the drawings attached to this specification, the scale and aspect ratios have been appropriately changed and exaggerated from those of the actual objects for the convenience of illustration and understanding.

[0015] In addition, terms used in this specification that specify shapes, geometric conditions, and the degree thereof, such as "parallel," "orthogonal," and "same," as well as values ​​of length and angle, are not to be bound by strict meanings, but are to be interpreted to include a range within which similar functions can be expected.

[0016] Fig. 1 is a front view showing bag 10 according to the present embodiment. Bag 10 has a storage section 17 for storing contents. Note that Fig. 1 shows bag 10 in a state before the contents are stored in it. Bag 10 according to the present embodiment is configured so that it can be suitably used as a microwave pouch in which the contents are heated in a microwave oven.

[0017] 1, bag 10 according to the present embodiment includes a steam release mechanism 20 for releasing steam generated when the contents contained in bag 10 are heated to the outside. Steam release mechanism 20 is configured to communicate between the inside and outside of bag 10 to release steam when the steam pressure reaches or exceeds a predetermined value, and to prevent steam from escaping from places other than steam release mechanism 20. The configuration of bag 10 will be described below.

[0018] bag In this embodiment, the bag 10 is a gusset-type bag configured to be self-supporting. The bag 10 includes an upper portion 11, a lower portion 12, and a pair of side portions 13, and has a generally rectangular outline in a front view. The names "upper portion", "lower portion", and "side portion", as well as the terms "upper" and "lower" merely indicate the relative positions and directions of the bag 10 and its components based on a state in which the bag 10 stands on its own with the gusset portion facing down. The position of the bag 10 during transportation or use is not limited by the names and terms used in this specification.

[0019] In this embodiment, the width direction of bag 10 is also referred to as first direction D1. The pair of side portions 13 described above face each other in first direction D1. The direction perpendicular to first direction D1 is also referred to as second direction D2. It is assumed that bag 10 of this embodiment will be used in such a way that the consumer opens bag 10 by tearing bag 10 along first direction D1 after the contents of bag 10 are heated in a microwave oven.

[0020] 1, the bag 10 includes a surface film 14 that forms the surface, a back film 15 that forms the back surface, and a lower film 16 that forms the lower portion 12. The lower film 16 is disposed between the surface film 14 and the back film 15 in a state where it is folded back at a fold-back portion 16f.

[0021] The above-mentioned terms "front film," "back film," and "lower film" merely divide each film according to its positional relationship, and the above-mentioned terms do not limit the method of providing the films when manufacturing the bag 10. For example, the bag 10 may be manufactured using one film in which the front film 14, the back film 15, and the lower film 16 are arranged in series, or may be manufactured using a total of two films, one film in which the front film 14 and the lower film 16 are arranged in series and one back film 15, or may be manufactured using a total of three films, one front film 14, one back film 15, and one lower film 16.

[0022] The inner surfaces of the front film 14, the back film 15 and the lower film 16 are joined together by sealed portions. In a plan view of the bag 10 such as Fig. 1, the sealed portions are hatched.

[0023] As shown in Fig. 1, the seal portion has an outer edge seal portion that extends along the outer edge of bag 10, and a steam release seal portion 20a that constitutes steam release mechanism 20. The outer edge seal portion includes a lower seal portion 12a that extends to lower portion 12, and a pair of side seal portions 13a that extend along a pair of side portions 13. Note that, in bag 10 before the contents are contained therein, upper portion 11 of bag 10 forms an opening 11b, as shown in Fig. 1. After the contents are contained in bag 10, the inner surface of front film 14 and the inner surface of back film 15 are joined at upper portion 11 to form an upper seal portion and seal bag 10.

[0024] The side seal portion 13a, the steam release seal portion 20a, and the upper seal portion are seal portions formed by joining the inner surface of the front film 14 and the inner surface of the back film 15. On the other hand, the lower seal portion 12a includes a seal portion formed by joining the inner surface of the front film 14 and the inner surface of the lower film 16, and a seal portion formed by joining the inner surface of the back film 15 and the inner surface of the lower film 16.

[0025] There is no particular limitation on the method for forming the sealed portion, so long as the opposing films can be joined together to seal the bag 10. For example, the sealed portion may be formed by melting the inner surfaces of the films by heating or the like to weld the inner surfaces together, i.e., by heat sealing. Alternatively, the sealed portion may be formed by bonding the inner surfaces of the opposing films together using an adhesive or the like.

[0026] Steam release mechanism The following describes the configuration of the steam release mechanism 20. Figure 2 is a cross-sectional view showing the steam release mechanism 20 of the bag 10 shown in Figure 1, taken along line II-II.

[0027] The steam release seal portion 20a of the steam release mechanism 20 has a shape that is easily peeled off as the pressure of the storage portion 17 increases. For example, the steam release seal portion 20a has a shape that protrudes from the side seal portion 13a toward the inside of the bag 10. This makes it possible to make the force applied to the steam release seal portion 20a larger than the force applied to the side seal portion 13a when the pressure of the storage portion 17 increases. In addition, the width of the steam release seal portion 20a is smaller than the width of the side seal portion 13a. In addition, as shown in Figures 1 and 2, a non-sealed portion 20b is formed between the steam release seal portion 20a and the outer edge of the side portion 13. This makes it easier for the steam release seal portion 20a to communicate with the storage portion 17 and the outside due to peeling of the seal portion compared to the side seal portion 13a. In addition, as long as it is possible to establish communication between the storage section 17 and the outside of the bag 10 when the pressure in the storage section 17 increases, the configuration and arrangement of the steam release mechanism 20 are not limited to the examples shown in Figures 1 and 2.

[0028] Easy-to-open means The front film 14 and the back film 15 may be provided with easy-open means 25 for tearing the front film 14 and the back film 15 along the first direction D1 to open the bag 10. For example, as shown in Fig. 1, the easy-open means 25 may include a notch 26 that serves as a starting point for tearing and is formed in the side seal portion 13a of the bag 10. In addition, a half-cut line formed by laser processing, a cutter, or the like may be provided as the easy-open means 25 in a portion that serves as a path for tearing the bag 10.

[0029] Although not shown, the easy-open means 25 may include a group of cuts or scars formed in the area where the seal portion is formed in the front film 14 and the back film 15. The group of scars may include, for example, a plurality of through holes formed so as to penetrate the front film 14 and / or the back film 15. Alternatively, the group of scars may include a plurality of holes formed on the outer surface of the front film 14 and / or the back film 15 so as not to penetrate the front film 14 and / or the back film 15.

[0030] 1, the easy-open means 25 is located closer to the upper portion 11 than the steam release mechanism 20. However, the present invention is not limited to this, and although not shown, the easy-open means 25 may be located closer to the lower portion 12 than the steam release mechanism 20.

[0031] Layer structure of front and back films Next, a description will be given of the layer structure of the front film 14 and the back film 15. Fig. 3 is a cross-sectional view showing an example of the layer structure of a laminate 30 constituting the front film 14 and the back film 15.

[0032] 3, the laminate 30 includes at least a first stretched plastic film 40, a first adhesive layer 45, a second stretched plastic film 50, a second adhesive layer 55, and a sealant layer 70, in this order. The first stretched plastic film 40 is located on the outer surface 30y side, and the sealant layer 70 is located on the inner surface 30x side opposite the outer surface 30y. The inner surface 30x is the surface located on the storage section 17 side.

[0033] Each layer of the laminate 30 will now be described in detail.

[0034] (First oriented plastic film) The first stretched plastic film 40 is a plastic film stretched in a predetermined direction. The first stretched plastic film 40 functions as a base layer for imparting a predetermined strength to the laminate 30. The first stretched plastic film 40 may be a uniaxially stretched film stretched in one predetermined direction, or a biaxially stretched film stretched in two predetermined directions. The stretching direction of the first stretched plastic film 40 is not particularly limited. For example, the first stretched plastic film 40 may be stretched in the direction in which the side portion 13 extends, or may be stretched in a direction perpendicular to the direction in which the side portion 13 extends. The stretching ratio of the first stretched plastic film 40 is, for example, 1.05 times or more.

[0035] The first stretched plastic film 40 contains, for example, polyester as a main component. For example, the first stretched plastic film 40 contains 51 mass % or more of polyester. Examples of polyester include polyethylene terephthalate (hereinafter also referred to as PET) and polybutylene terephthalate (hereinafter also referred to as PBT). Note that the 51 mass % or more of polyester in the first stretched plastic film 40 may be composed of one type of polyester or may be composed of two or more types of polyester.

[0036] When the first stretched plastic film 40 contains polyester as a main component, the thickness of the first stretched plastic film 40 is preferably 9 μm or more, more preferably 12 μm or more. When the first stretched plastic film 40 contains polyester as a main component, the thickness of the first stretched plastic film 40 is preferably 25 μm or less, more preferably 20 μm or less. By making the thickness of the first stretched plastic film 40 9 μm or more, the first stretched plastic film 40 has sufficient strength. By making the thickness of the first stretched plastic film 40 25 μm or less, the first stretched plastic film 40 exhibits excellent formability. Therefore, the process of processing the laminate 30 to manufacture the bag 10 can be carried out efficiently.

[0037] When the first stretched plastic film 40 contains polyester as a main component, the thermal conductivity of the material constituting the first stretched plastic film 40 is preferably 0.05 W / m·K or more, and more preferably 0.1 W / m·K or more. The thermal conductivity of PET is, for example, 0.14 W / m·K. The thermal conductivity of PBT is higher than that of PET, and is, for example, 0.25 W / m·K. When the thermal conductivity of the material constituting the first stretched plastic film 40 is a predetermined value or more, the heat resistance of the laminate 30 can be improved.

[0038] Furthermore, when the first stretched plastic film 40 contains polyester as a main component, the melting point of the first stretched plastic film 40 is preferably 200° C. or higher, and more preferably 220° C. or higher. By making the melting point of the first stretched plastic film 40 220° C. or higher, it is possible to prevent holes from being formed in the first stretched plastic film 40 and to prevent wrinkles from being formed in the first stretched plastic film 40 when the contents contained in the bag 10 produced using the laminate 30 are heated.

[0039] The first stretched plastic film 40 may contain polyamide as a main component. For example, the first stretched plastic film 40 contains 51% by mass or more of polyamide. Examples of polyamide-based materials include aliphatic polyamides and aromatic polyamides. Examples of aliphatic polyamides include nylons such as nylon-6, nylon-6,6, and copolymers of nylon 6 and nylon 6,6, and examples of aromatic polyamides include polymetaxylene adipamide (MXD6). When the first stretched plastic film 40 contains polyamide as a main component, the puncture strength of the laminate 30 including the first stretched plastic film 40 can be increased.

[0040] When the first stretched plastic film 40 contains polyamide as a main component, the thickness of the first stretched plastic film 40 is preferably 12 μm or more, more preferably 15 μm or more. When the first stretched plastic film 40 contains polyamide as a main component, the thickness of the first stretched plastic film 40 is preferably 25 μm or less, more preferably 20 μm or less. When the first stretched plastic film 40 contains polyamide as a main component, the thermal conductivity of the first stretched plastic film 40 is preferably 0.25 W / m·K or more, more preferably 0.3 W / m·K or more. The thermal conductivity of nylon is, for example, 0.35 W / m·K. When the first stretched plastic film 40 contains polyamide as a main component, the stretch ratio of the first stretched plastic film 40 is, for example, 1.05 times or more.

[0041] The first stretched plastic film 40 may be composed of a single layer or may be composed of multiple layers. When the first stretched plastic film 40 includes multiple layers, the first stretched plastic film 40 is, for example, a co-extruded film produced by co-extrusion. The first stretched plastic film 40 produced by co-extrusion includes, for example, a first layer 41 made of polyester such as PET, a second layer 42 made of polyamide such as nylon, and a third layer 43 made of polyester such as PET, which are laminated in this order, as shown in FIG. 4. In addition, when the mass of the second layer 42 made of polyamide such as nylon is 51% or more of the mass of the entire first stretched plastic film 40, it can be said that the main component of the first stretched plastic film 40 produced by co-extrusion is polyamide.

[0042] (First adhesive layer) The first adhesive layer 45 contains an adhesive for bonding the first stretched plastic film 40 and the second stretched plastic film 50 by a dry lamination method. The adhesive constituting the first adhesive layer 45 is produced from an adhesive composition produced by mixing a first composition containing a base agent and a solvent with a second composition containing a curing agent and a solvent. Specifically, the adhesive contains a cured product produced by reaction of the base agent and the solvent in the adhesive composition.

[0043] Examples of adhesives include polyurethane. Polyurethane is a cured product produced by reacting a polyol as a base agent with an isocyanate compound as a curing agent. Examples of polyurethane include polyether polyurethane and polyester polyurethane. Polyether polyurethane is a cured product produced by reacting a polyether polyol as a base agent with an isocyanate compound as a curing agent. Polyester polyurethane is a cured product produced by reacting a polyester polyol as a base agent with an isocyanate compound as a curing agent.

[0044] As the isocyanate compound, aromatic isocyanate compounds such as tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), etc., aliphatic isocyanate compounds such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), etc., or adducts or oligomers of the above-mentioned various isocyanate compounds can be used.

[0045] The material constituting the first adhesive layer 45 preferably has a higher thermal conductivity than the materials constituting the first stretched plastic film 40, the second stretched plastic film 50, and the sealant layer 70. For example, the thermal conductivity of the material constituting the first adhesive layer 45 is preferably 1.0 W / m·K or more, more preferably 3.0 W / m·K or more. The thermal conductivity of polyurethane is in the range of 3.0 W / m·K to 5.0 W / m·K, for example, 5.0 W / m·K. Since the material constituting the first adhesive layer 45 has a high thermal conductivity, when the bag 10 made using the laminate 30 is heated, the heat generated in the storage section 17 is easily diffused in the surface direction of the laminate 30 while being transferred from the inner surface 30x side to the outer surface 30y side of the laminate 30. This can increase the heat dissipation of the laminate 30, thereby suppressing the temperature rise of the laminate 30. This can suppress damage to the laminate 30 caused by heat when the bag 10 is heated. That is, the heat resistance of the laminate 30 can be improved.

[0046] The thickness of the first adhesive layer 45 is preferably 2 μm or more, and more preferably 3 μm or more. The thickness of the first adhesive layer 45 is preferably 6 μm or less, and more preferably 5 μm or less. By making the thickness of the first adhesive layer 45 3 μm or more, heat diffusion in the surface direction of the laminate 30 becomes easier to occur.

[0047] (Second oriented plastic film) The second stretched plastic film 50 is a plastic film stretched in a predetermined direction, similar to the first stretched plastic film 40. The second stretched plastic film 50 also functions as a base layer for imparting a predetermined strength to the laminate 30, similar to the first stretched plastic film 40. The stretching direction of the second stretched plastic film 50 is not particularly limited, similar to the first stretched plastic film 40.

[0048] In addition, the second stretched plastic film 50 also functions as a base layer for imparting tearability to the laminate 30, as described below.

[0049] 3, the second stretched plastic film 50 is adjacent to the sealant layer 70 via the second adhesive layer 55. The sealant layer 70 has a smaller tensile modulus of elasticity than stretched plastic films such as the first stretched plastic film 40 and the second stretched plastic film 50, and is therefore more likely to stretch. For this reason, when a consumer tears open the bag 10, if the sealant layer 70 peels off from the second stretched plastic film 50, the force applied to the bag 10 by the consumer mainly acts as a force to stretch the sealant layer 70 peeled off from the second stretched plastic film 50, making it difficult to tear the bag 10.

[0050] In consideration of such problems, in the present embodiment, the second stretched plastic film 50 is configured to have tearability in the first direction D1. This makes it easier for the force applied to the bag 10 by the consumer to act as a force that tears the laminate 30 including the second stretched plastic film 50. This makes it possible to suppress stretching of the sealant layer 70 when the consumer tears the bag 10 to open it.

[0051] The mechanical properties of the second stretched plastic film 50 for imparting tearability in the first direction D1 to the laminate 30 will be described. In this embodiment, the tensile strength of the second stretched plastic film 50 in the first direction D1 is greater than the tensile strength of the second stretched plastic film 50 in the second direction D2. The tensile strength can be measured in accordance with JIS K 7127. As a measuring device, a thermostatic bath-equipped tensile tester RTC-1310A manufactured by Orientec Co., Ltd. can be used. Unless otherwise specified, the tensile strength is measured at 25°C. In the bag 10 shown in FIG. 1, the first direction D1 corresponds to the machine direction (MD) of the second stretched plastic film 50. The second direction D2 corresponds to the perpendicular direction (TD) of the second stretched plastic film 50.

[0052] In the second stretched plastic film 50, the tensile strength of the second stretched plastic film 50 in the first direction D1 is preferably 1.05 times or more, more preferably 1.10 times or more, and even more preferably 1.2 times or more, the tensile strength of the second stretched plastic film 50 in the second direction D2. The tensile strength of the second stretched plastic film 50 in the first direction D1 is, for example, 200 MPa or more and 300 MPa or less.

[0053] Next, the material constituting the second stretched plastic film 50 will be described. The second stretched plastic film 50 contains polyester or polyamide as a main component. In order to provide the laminate 30 with heat resistance, it is preferable that at least one of the first stretched plastic film 40 and the second stretched plastic film 50 contains polyester as a main component. Therefore, when the first stretched plastic film 40 contains polyamide as a main component, the second stretched plastic film 50 contains polyester as a main component. When the first stretched plastic film 40 contains polyester as a main component, the second stretched plastic film 50 may contain polyester as a main component or may contain polyamide as a main component.

[0054] When the second stretched plastic film 50 contains polyester as a main component, for example, when it contains 51 mass % or more of polyester, examples of the polyester include PET, PBT, etc., as in the case of the first stretched plastic film 40. The thickness of the second stretched plastic film 50 is preferably 9 μm or more, more preferably 12 μm or more. Furthermore, when the second stretched plastic film 50 contains polyester as a main component, the thickness of the second stretched plastic film 50 is preferably 25 μm or less, more preferably 20 μm or less. When the second stretched plastic film 50 contains polyester as a main component, the thermal conductivity, melting point, etc. of the second stretched plastic film 50 are the same as those of the first stretched plastic film 40 containing polyester as a main component.

[0055] When the second stretched plastic film 50 contains polyamide as a main component, for example, when it contains 51 mass % or more of polyamide, examples of the polyamide include aliphatic polyamide or aromatic polyamide, as in the case of the first stretched plastic film 40. The thickness of the second stretched plastic film 50 is preferably 12 μm or more, more preferably 15 μm or more. In addition, when the second stretched plastic film 50 contains polyamide as a main component, the thickness of the second stretched plastic film 50 is preferably 25 μm or less, more preferably 20 μm or less. When the second stretched plastic film 50 contains polyamide as a main component, the thermal conductivity, melting point, etc. of the second stretched plastic film 50 are the same as those of the first stretched plastic film 40 containing polyamide as a main component.

[0056] (Second adhesive layer) The second adhesive layer 55 contains an adhesive for bonding the second stretched plastic film 50 and the sealant layer 70 by a dry lamination method. An example of the adhesive for the second adhesive layer 55 is polyurethane, as in the case of the first adhesive layer 45. In addition to the configurations, materials, and characteristics described below, the second adhesive layer 55 can adopt the same configurations, materials, and characteristics as the first adhesive layer 45.

[0057] The material constituting the second adhesive layer 55, like the first adhesive layer 45, preferably has a higher thermal conductivity than the materials constituting the first stretched plastic film 40, the second stretched plastic film 50, and the sealant layer 70. For example, the thermal conductivity of the material constituting the second adhesive layer 55 is preferably 1 W / m·K or more, and more preferably 3 W / m·K or more.

[0058] The thickness of the second adhesive layer 55 is preferably 2 μm or more, and more preferably 3 μm or more. The thickness of the second adhesive layer 55 is preferably 6 μm or less, and more preferably 5 μm or less.

[0059] Incidentally, as the isocyanate compound constituting the curing agent of the adhesive, there are aromatic isocyanate compounds and aliphatic isocyanate compounds, as described above. Among these, aromatic isocyanate compounds leach out components that cannot be used for food applications under high temperature environments such as heat sterilization. Incidentally, the second adhesive layer 55 is in contact with the sealant layer 70. Therefore, when the second adhesive layer 55 contains an aromatic isocyanate compound, the components leach out from the aromatic isocyanate compound may adhere to the contents contained in the container 17 in contact with the sealant layer 70.

[0060] Considering these problems, a cured product produced by reacting a polyol as a base agent with an aliphatic isocyanate compound as a curing agent is preferably used as the adhesive constituting the second adhesive layer 55. This makes it possible to prevent components that cannot be used for food applications, which are caused by the second adhesive layer 55, from adhering to the contents.

[0061] (Relationship) Next, a description will be given of the relationship that holds between the stretched plastic films 40, 50 and the adhesive layers 45, 55. In the laminate 30, the following relationship preferably holds. A1+A2 <B1+B2 A1 is the product of the thickness and thermal conductivity of the first stretched plastic film 40. A2 is the product of the thickness and thermal conductivity of the second stretched plastic film 50. B1 is the product of the thickness and thermal conductivity of the first adhesive layer 45. B2 is the product of the thickness and thermal conductivity of the second adhesive layer 55.

[0062] The above relational expression means that the adhesive layers 45, 55 have higher thermal conductivity in the plane direction of the laminate 30 than the stretched plastic films 40, 50. This makes it possible to prevent the laminate 30 from being damaged by heat when the contents contained in the bag 10 are heated. Examples of damage caused to the laminate 30 by heat include holes being made in the laminate 30 and wrinkles being formed in the laminate 30.

[0063] The reason why damage caused by heat can be suppressed by satisfying the above-mentioned relational expressions will be considered. Note that the reason for such an action is not limited to the following consideration, and other considerations may also be adopted.

[0064] 5 is a diagram showing contents 18 adhering to inner surface 30x of laminate 30 constituting bag 10. Adhesion of contents 18 to inner surface 30x can occur, for example, when contents 18 contained in bag 10 are heated using a microwave oven, and part of contents 18 splashes and reaches inner surface 30x. If contents 18 adhering to inner surface 30x is further heated, the temperature of laminate 30 in contact with contents 18 also rises, and it is considered that holes will be formed in laminate 30 or wrinkles will be formed in laminate 30.

[0065] Here, in this embodiment, the laminate 30 is configured so that the above-mentioned relational expression is established. The laminate 30 also includes two or more stretched plastic films 40, 50 and adhesive layers 45, 55. Therefore, as shown in FIG. 5, while the heat generated in the contents 18 is transferred from the inner surface 30x side to the outer surface 30y side of the laminate 30, the heat is easily diffused in the surface direction of the laminate 30, particularly in the adhesive layers 45, 55. This makes it easier to release heat to the outside of the bag 10, so that the temperature rise in the part of the laminate 30 to which the contents 18 are attached can be suppressed. This makes it possible to suppress damage to the laminate 30 due to heat. In other words, the heat resistance of the laminate 30 can be improved.

[0066] B1+B2 is preferably 3.5 times or more, more preferably 4.0 times or more, and even more preferably 4.5 times or more, of A1+A2.

[0067] (Sealant layer) Next, the sealant layer 70 will be described. As a material for forming the sealant layer 70, one or more resins selected from polyethylene such as low-density polyethylene and linear low-density polyethylene, and polypropylene can be used. The sealant layer 70 may be a single layer or a multilayer. The sealant layer 70 is preferably made of an unstretched film. The term "unstretched" includes not only a film that is not stretched at all, but also a film that is slightly stretched due to the tension applied during film formation.

[0068] The bag 10 formed from the laminate 30 is subjected to a sterilization treatment such as boiling or retort treatment at high temperatures. Therefore, the sealant layer 70 used has heat resistance that can withstand such high temperature treatments.

[0069] The melting point of the material constituting the sealant layer 70 is preferably 150° C. or higher, and more preferably 160° C. or higher. By increasing the melting point of the sealant layer 70, it becomes possible to perform the retort treatment of the bag 10 at a high temperature, and therefore the time required for the retort treatment can be shortened. The melting point of the material constituting the sealant layer 70 is lower than the melting point of the resin constituting the stretched plastic films 40, 50, and 60.

[0070] From the viewpoint of retort processing, a material mainly composed of propylene can be used as a material constituting the sealant layer 70. Here, a material "mainly composed" of propylene means a material having a propylene content of 90% by mass or more. Specific examples of a material mainly composed of propylene include propylene-ethylene block copolymer, propylene-ethylene random copolymer, polypropylene such as homopolypropylene, and a mixture of polypropylene and polyethylene. Here, "propylene-ethylene block copolymer" means a material having a structural formula shown in the following formula (I). Also, "propylene-ethylene random copolymer" means a material having a structural formula shown in the following formula (II). Also, "homopolypropylene" means a material having a structural formula shown in the following formula (III).

[0071] [ka]

[0072] [ka]

[0073] [ka]

[0074] When a mixture of polypropylene and polyethylene is used as the propylene-based material, the material may have an island-in-a-sea structure, where the polyethylene is discontinuously dispersed within a continuous region of polypropylene.

[0075] From the viewpoint of boiling treatment, examples of the material constituting the sealant layer 70 include polyethylene, polypropylene, and combinations thereof. Examples of polyethylene include medium density polyethylene, linear low density polyethylene, and combinations thereof. For example, it is also possible to use the materials listed as the material constituting the sealant layer 70 from the viewpoint of the above-mentioned retort treatment. The material constituting the sealant layer 70 has a melting point of, for example, 100°C or higher, more preferably 105°C or higher, and even more preferably 110°C or higher. When polyethylene is used as the material constituting the sealant layer 70, the melting point of 100°C or higher is, for example, when the density of polyethylene is 0.920 g / cm. 3 This can be realized in the above cases. Specific examples of the sealant film for constituting the sealant layer 70 having a melting point of 100°C or more include TUX-HC manufactured by Mitsui Chemicals Tohcello, L6101 manufactured by Toyobo, and LS700C manufactured by Idemitsu Unitech. Specific examples of the sealant film for constituting the sealant layer 70 having a melting point of 105°C or more include NB-1 manufactured by Tamapoly. Specific examples of the sealant film for constituting the sealant layer 70 having a melting point of 110°C or more include LS760C manufactured by Idemitsu Unitech and TUX-HZ manufactured by Mitsui Chemicals Tohcello.

[0076] Preferably, the sealant layer 70 is a single-layer film containing a propylene-ethylene block copolymer. For example, the sealant film containing the sealant layer 70 is a single-layer unstretched film containing a propylene-ethylene block copolymer as a main component. By using a propylene-ethylene block copolymer, the impact resistance of the sealant film can be increased, and thus the bag 10 can be prevented from breaking due to an impact when dropped. In addition, the puncture resistance of the laminate 30 can be increased.

[0077] Furthermore, by using a propylene-ethylene block copolymer, the strength of the seal portion formed by the sealant layer 70 at high temperatures, for example, 100° C. or higher (hereinafter also referred to as hot seal strength) becomes extremely small compared to the seal strength at low temperatures, for example, room temperature. For example, the hot seal strength at 100° C. is one third or less, preferably one quarter or less, of the seal strength at 25° C. (hereinafter also referred to as room temperature seal strength). For example, the hot seal strength at 100° C. in a width of 15 mm is 30 N or less, preferably 25 N or less, more preferably 20 N or less, and even more preferably 15 N or less. Furthermore, the room temperature seal strength at 25° C. in a width of 15 mm is 23 N or more, preferably 40 N or more, more preferably 50 N or more, and even more preferably 60 N or more. Due to the low hot seal strength, when the bag 10 is heated using a microwave oven, the steam release seal portion 20a is easily peeled off, and the steam in the storage portion 17 is easily released to the outside of the bag 10. This makes it possible to prevent the internal pressure of the storage section 17 from becoming excessive, thereby making it possible to prevent damage to the laminate 30 during heating. The seal strength can be measured in accordance with JIS Z1707 7.5. As a measuring device, for example, a thermostatic chamber equipped tensile tester RTC-1310A manufactured by Orientec Co., Ltd. can be used.

[0078] A propylene-ethylene block copolymer, for example, contains a sea component made of polypropylene and an island component made of an ethylene-propylene copolymer rubber component. The sea component can contribute to improving the blocking resistance, heat resistance, rigidity, seal strength, etc. of the propylene-ethylene block copolymer. The island component can also contribute to improving the impact resistance of the propylene-ethylene block copolymer. Therefore, by adjusting the ratio of the sea component and the island component, the mechanical properties of the sealant film containing the propylene-ethylene block copolymer can be adjusted.

[0079] In the propylene-ethylene block copolymer, the mass ratio of the sea part made of polypropylene is higher than the mass ratio of the island part made of the ethylene-propylene copolymer rubber component. For example, in the propylene-ethylene block copolymer, the mass ratio of the sea part made of polypropylene is at least 51 mass%, preferably 60 mass% or more, and more preferably 70 mass% or more.

[0080] The single-layer sealant film may further contain a second thermoplastic resin in addition to the first thermoplastic resin consisting of a propylene-ethylene block copolymer. Examples of the second thermoplastic resin include α-olefin copolymer and polyethylene. The α-olefin copolymer is, for example, linear low-density polyethylene. Examples of polyethylene include low-density polyethylene, medium-density polyethylene, and high-density polyethylene. The second thermoplastic resin may contribute to increasing the impact resistance of the sealant film.

[0081] Low density polyethylene has a density of 0.910g / cm 3 Above 0.925g / cm 3 Medium density polyethylene has a density of 0.926 g / cm 3 Above 0.940g / cm 3 The following polyethylene: High density polyethylene has a density of 0.941 g / cm 3 Above 0.965g / cm 3The following polyethylenes are available. Low density polyethylene is obtained by polymerizing ethylene at a high pressure, for example, from 1000 atm to less than 2000 atm. Medium density polyethylene and high density polyethylene are obtained by polymerizing ethylene at a medium or low pressure, for example, from 1 atm to less than 1000 atm.

[0082] The medium-density polyethylene and high-density polyethylene may partially contain a copolymer of ethylene and an α-olefin. Even when ethylene is polymerized at medium or low pressure, if a copolymer of ethylene and an α-olefin is contained, a medium-density or low-density polyethylene can be produced. Such polyethylene is called the above-mentioned linear low-density polyethylene. Linear low-density polyethylene is obtained by copolymerizing an α-olefin with a linear polymer obtained by polymerizing ethylene at medium or low pressure to introduce short-chain branches. Examples of α-olefins include 1-butene (C4), 1-hexene (C6), 4-methylpentene (C6), and 1-octene (C8). The density of linear low-density polyethylene is, for example, 0.915 g / cm. 3 Above 0.945g / cm 3 The following is the result.

[0083] The α-olefin copolymer constituting the second thermoplastic resin of the propylene-ethylene block copolymer is not limited to the linear low-density polyethylene described above. The α-olefin copolymer means a material having the structural formula shown in the following formula (IV).

[0084] [ka] Both R1 and R2 are H (hydrogen atom) or alkyl groups such as CH3 and C2H5. In addition, both j and k are integers of 1 or more. In addition, j is greater than k. That is, in the α-olefin copolymer shown in formula (IV), the structure on the left side including R1 is the base. R1 is, for example, H, and R2 is, for example, C2H5.

[0085] In the sealant film, the mass ratio of the first thermoplastic resin consisting of a propylene-ethylene block copolymer is higher than the mass ratio of the second thermoplastic resin containing at least an α-olefin copolymer or polyethylene. For example, in a single-layer sealant film, the mass ratio of the first thermoplastic resin consisting of a propylene-ethylene block copolymer is at least 51 mass%, preferably 60 mass% or more, and more preferably 70 mass% or more.

[0086] As described above, the second thermoplastic resin can contribute to increasing the impact resistance of the sealant film. Therefore, by adjusting the mass ratio of the second thermoplastic resin containing at least an α-olefin copolymer or polyethylene in the single-layer sealant film, the mechanical properties of the sealant film can be adjusted.

[0087] The sealant layer 70 may further contain a thermoplastic elastomer. By using a thermoplastic elastomer, the impact resistance and puncture resistance of the sealant layer 70 can be further improved.

[0088] The thermoplastic elastomer is, for example, a hydrogenated styrene-based thermoplastic elastomer. The hydrogenated styrene-based thermoplastic elastomer has a structure consisting of a polymer block A mainly made of at least one vinyl aromatic compound and a polymer block B mainly made of at least one hydrogenated conjugated diene compound. The thermoplastic elastomer may also be an ethylene-α-olefin elastomer. The ethylene-α-olefin elastomer is a low-crystalline or amorphous copolymer elastomer, and is a random copolymer of 50 to 90 mass% of ethylene as a main component and an α-olefin as a copolymerization monomer.

[0089] The content of the propylene-ethylene block copolymer in the sealant layer 70 is, for example, 80% by mass or more, and preferably 90% by mass or more.

[0090] Propylene-ethylene block copolymers can be produced by polymerizing the raw materials propylene and ethylene using a catalyst, such as a Ziegler-Natta catalyst or a metallocene catalyst.

[0091] The thickness of the sealant layer 70 is preferably 30 μm or more, and more preferably 40 μm or more. The thickness of the sealant layer 70 is preferably 100 μm or less, and more preferably 80 μm or less.

[0092] The following describes the favorable mechanical properties of a single-layer sealant film containing a propylene-ethylene block copolymer. The tensile elongation of the sealant film in the machine direction (MD) at 25°C is preferably 600% or more and 1300% or less. The product of the tensile elongation (%) of the sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably 35000 or more and 80000 or less. The tensile elongation of the sealant film in the transverse direction (TD) at 25°C is preferably 700% or more and 1400% or less. The product of the tensile elongation (%) of the sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably 40000 or more and 85000 or less. The tensile modulus of the sealant film in the machine direction (MD) at 25°C is preferably 400 MPa or more and 1100 MPa or less. The product of the tensile modulus of the sealant film in the machine direction (MD) (MPa) and the thickness (μm) of the sealant film is preferably 30000 or more and 55000 or less. The tensile modulus of the sealant film in the transverse direction (TD) at 25°C is preferably 250 MPa or more and 900 MPa or less. The product of the tensile modulus of the sealant film in the transverse direction (TD) (MPa) and the thickness (μm) of the sealant film is preferably 20000 or more and 45000 or more.

[0093] The tensile modulus and tensile elongation can be measured in accordance with JIS K7127. A thermostatic bath-equipped tensile tester RTC-1310A manufactured by Orientec Co., Ltd. can be used as a measuring device. In the bag 10 shown in FIG. 1, the direction in which the upper portion 11 and the lower portion 12 extend is the flow direction of the film constituting the bag 10, such as a sealant film, and the direction in which the side portion 13 extends is the vertical direction of the film constituting the bag 10, such as a sealant film. Although not shown, the bag 10 may be configured so that the direction in which the upper portion 11 and the lower portion 12 extend is the vertical direction of the film, and the direction in which the side portion 13 extends is the flow direction of the film.

[0094] There are two main types of single-layer sealant films containing propylene-ethylene block copolymers. The first type is a type having high tensile elongation and impact resistance, such as ZK500 described later. The first type of sealant film preferably further has a property of low hot seal strength. This can prevent the internal pressure of the storage section 17 from becoming excessive when the bag 10 is heated, and can prevent damage to the laminate 30. The second type is a type having a high tensile modulus, such as ZK207 described later. By using the second type of sealant film, it is possible to improve the tearability when a consumer opens the bag 10 by tearing the bag 10 along the first direction D1.

[0095] The product of the tensile elongation (%) of the first type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably 45,000 or more, more preferably 50,000 or more, and may be 55,000 or more, or 60,000 or more. The product of the tensile elongation (%) of the first type sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably 53,000 or more, more preferably 60,000 or more. The high tensile elongation of the sealant film can prevent the bag 10 from breaking due to impact when dropped, etc. Moreover, the product of the tensile modulus (MPa) of the first type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably not more than 38000, more preferably not more than 35000. Moreover, the product of the tensile modulus (MPa) of the first type sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably not more than 30000, more preferably not more than 25000.

[0096] The product of the tensile modulus (MPa) of the second type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably 35,000 or more, more preferably 38,000 or more, and even more preferably 45,000 or more. The product of the tensile modulus (MPa) of the second type sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably 25,000 or more, more preferably 30,000 or more, and even more preferably 35,000 or more, and may be 38,000 or more. When the sealant film has a high tensile modulus, the tearability when opening the bag 10 can be improved. Moreover, the product of the tensile elongation (%) of the second type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably not more than 55000, more preferably not more than 50000. Moreover, the product of the tensile elongation (%) of the second type sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably not more than 60000, more preferably not more than 55000.

[0097] (Other layers) The laminate 30 may include additional layers not shown in Figure 3. Examples of additional layers are described below.

[0098] The laminate 30 may further include a printed layer. The printed layer is a layer provided on the laminate 30 to indicate product information or impart an aesthetic feel to the bag 10, and is printed, for example, on the first stretched plastic film 40. The printed layer expresses letters, numbers, symbols, figures, pictures, etc. As a material for forming the printed layer, ink for gravure printing or ink for flexographic printing can be used. A specific example of an ink for gravure printing is Finart manufactured by DIC Graphics Corporation.

[0099] The laminate 30 may further include a transparent gas barrier layer. The transparent gas barrier layer is formed on the surface of the stretched plastic film 40, 50, 60, etc., and includes at least a transparent vapor deposition layer made of a transparent inorganic material. The transparent gas barrier layer may further include a transparent gas barrier coating film formed on the surface of the transparent vapor deposition layer, and includes a transparent gas barrier coating film.

[0100] The transparent deposition layer functions as a layer having a gas barrier function that prevents the permeation of oxygen gas and water vapor. Two or more transparent deposition layers may be provided. When two or more transparent deposition layers are provided, each may have the same composition or different compositions. Examples of the method for forming the transparent deposition layer include physical vapor deposition methods (PVD methods) such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition methods (CVD methods) such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition. Specifically, a deposition layer can be formed on a film-forming roller using a roller-type deposition film-forming device. Examples of inorganic materials constituting the transparent deposition layer include aluminum oxide (aluminum oxide) and silicon oxide. The thickness of the transparent deposition layer is preferably 40 Å or more and 130 Å or less, more preferably 50 Å or more and 120 Å or less.

[0101] The transparent gas barrier coating film is a layer that functions as a layer that suppresses the transmission of oxygen gas, water vapor, etc. 1 n M(OR 2 ) m (In the formula, R 1 , R 2 represents an organic group having 1 to 8 carbon atoms, M represents a metal atom, n represents an integer of 0 or more, m represents an integer of 1 or more, and n+m represents the atomic valence of M. The transparent gas barrier composition contains at least one alkoxide represented by the formula (I) and the above-mentioned polyvinyl alcohol resin and / or ethylene-vinyl alcohol copolymer, and is further polycondensed by a sol-gel method in the presence of a sol-gel catalyst, an acid, water, and an organic solvent.

[0102] Layer composition of the lower film Next, the layer structure of the lower film 16 will be described.

[0103] The layer configuration of the lower film 16 is arbitrary so long as it has an inner surface that can be joined to the inner surfaces of the front film 14 and the back film 15. For example, the above-mentioned laminate 30 may be used as the lower film 16, similarly to the front film 14 and the back film 15. Alternatively, a film whose inner surface is formed of a sealant layer and has a different configuration from the laminate 30 may be used as the lower film 16.

[0104] Manufacturing method of laminate Next, an example of a method for producing the laminate 30 will be described.

[0105] First, the above-mentioned first stretched plastic film 40 and second stretched plastic film 50 are prepared. Next, the first stretched plastic film 40 and the second stretched plastic film 50 are laminated via the first adhesive layer 45 by a dry lamination method. After that, the laminate including the first stretched plastic film 40 and the second stretched plastic film 50 and a sealant film for constituting the sealant layer 70 are laminated via the second adhesive layer 55 by a dry lamination method. In this way, the laminate 30 including the first stretched plastic film 40, the second stretched plastic film 50, and the sealant layer 70 can be obtained.

[0106] Alternatively, the laminate 30 may be produced by first laminating the second stretched plastic film 50 and the sealant film via the second adhesive layer 55 using a dry lamination method, and then laminating the first stretched plastic film 40 and a laminate including the second stretched plastic film 50 and the sealant film via the first adhesive layer 45 using a dry lamination method.

[0107] In the dry lamination method, first, an adhesive composition is applied to one of the two films to be laminated. Then, the applied adhesive composition is dried to volatilize the solvent. Then, the two films are laminated via the dried adhesive composition. Then, the two laminated films are wound up and aged, for example, in an environment of 20°C or higher for 24 hours or more.

[0108] Bag manufacturing method Next, a method for manufacturing the bag 10 using the laminate 30 described above will be described. First, the surface film 14 and the back film 15 made of the laminate 30 are prepared. Also, the lower film 16 in a folded state is inserted between the surface film 14 and the back film 15. Next, the inner surfaces of the films are heat-sealed to form seals such as the lower seal portion 12a and the side seal portion 13a. Also, the films joined to each other by heat sealing are cut into an appropriate shape to obtain the bag 10 shown in FIG. 1. Next, the contents 18 are filled into the bag 10 through the opening 11b of the upper portion 11. The contents 18 are, for example, cooked foods containing moisture such as curry, stew, soup, etc. Also, the contents 18 may have materials containing a lot of oil, such as meat, fish, and seasonings for them. Also, other than food, things that can be heated by hot water or the like can be contained in the bag 10 as contents. Then, the upper portion 11 is heat-sealed to form the upper seal portion. In this manner, the bag 10 containing and sealed with the contents 18 can be obtained.

[0109] How to heat the contents Next, an example of a method for heating the contents 18 contained in the bag 10 will be described.

[0110] First, bag 10 is placed in a microwave oven with bottom 12 facing down and the bag 10 standing upright. Next, the contents are heated using the microwave oven. This causes the temperature of contents 18 to rise, and as a result, the moisture contained in contents 18 evaporates, increasing the pressure in storage section 17.

[0111] When the pressure in the storage section 17 increases, the front film 14 and the back film 15 bulge outward due to the force received from the storage section 17. Here, in this embodiment, the laminate 30 constituting the front film 14 and the back film 15 includes two stretched plastic films 40, 50. Therefore, the rigidity of the laminate 30 is increased, and as a result, the front film 14 and the back film 15 can be prevented from stretching when they receive a force. This allows the force generated due to the pressure generated in the storage section 17 to be mainly used as a force for peeling off the steam release seal portion 20a, rather than a force for stretching the front film 14 and the back film 15. Therefore, the force applied to the steam release seal portion 20a can be increased. This makes it easier for the steam release seal portion 20a to peel off when heated, and allows the steam in the storage section 17 to escape to the outside via the steam release mechanism 20.

[0112] Moreover, according to the present embodiment, as described above, the laminate 30 has heat resistance, which can prevent holes from being formed in the laminate 30 or wrinkles from being formed in the laminate 30 during heating.

[0113] Furthermore, according to this embodiment, when the above-mentioned first type sealant film having high tensile elongation and impact resistance is used, the impact strength of the laminate 30 can be increased. This can increase the impact resistance of the bag 10 formed by the laminate 30. For example, it is possible to prevent the bag 10 from breaking due to the impact when dropped. The impact strength of the laminate 30 is preferably 500 kJ / m or more, and more preferably 600 kJ / m or more.

[0114] Furthermore, according to this embodiment, as described above, the laminate 30 includes at least two stretched plastic films 40, 50. This makes it possible to impart puncture resistance to the laminate 30 and the bag 10 formed by the laminate 30. The puncture strength of the laminate 30 is preferably 14 N or more, more preferably 16 N or more, even more preferably 17 N or more, and particularly preferably 18 N or more.

[0115] How to open the bag After heating the contents, the consumer opens the bag 10 by tearing the bag 10 along the first direction D1. In this embodiment, as described above, the second stretched plastic film 50 adjacent to the sealant layer 70 has tearability in the first direction D1. This makes it possible to prevent the sealant layer 70 from stretching when the consumer tears the bag 10 to open it. This allows the consumer to easily tear the bag 10. Note that, in order to improve the tearability of the bag 10, it is preferable to use the above-mentioned second type of sealant film having a high tensile modulus.

[0116] It should be noted that various modifications can be made to the above-described embodiment. Below, the modified examples will be described with reference to the drawings as necessary. In the following description and the drawings used in the following description, the same reference numerals as those used for the corresponding parts in the above-described embodiment will be used for parts that can be configured in the same manner as in the above-described embodiment, and duplicated descriptions will be omitted. Also, if it is clear that the effects obtained in the above-described embodiment can also be obtained in the modified examples, the description may be omitted.

[0117] (Variations in the bag) In the above-described embodiment, an example has been shown in which bag 10 is a gusset-type bag, but there is no particular limitation on the specific configuration of bag 10. For example, bag 10 may be a so-called four-sided sealed bag formed by joining the inner surfaces of front film 14 and back film 15 made of laminate 30 at upper portion 11, lower portion 12, and side portion 13.

[0118] In addition, in the above-described embodiment, an example has been shown in which content 18 contained in bag 10 is heated using a microwave oven, but this is not limiting. For example, content 18 contained in bag 10 may be heated by boiling in hot water. In this case, bag 10 does not need to be equipped with steam release mechanism 20 described above. EXAMPLES

[0119] Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the description of the following examples as long as it does not depart from the gist of the present invention.

[0120] The laminate 30 of the present invention was evaluated for puncture strength, impact strength, and tear property in accordance with Examples 1 to 4 and Comparative Example 1.

[0121] Example 1 A stretched PET film having a thickness of 16 μm was prepared as the first stretched plastic film 40. A stretched PET film having a thickness of 12 μm and tearability in the machine direction (MD) was prepared as the second stretched plastic film 50. In the following description, the stretched PET film having tearability in the machine direction (MD) is also referred to as straight cut PET. As the straight cut PET, Emblet (registered trademark) PC manufactured by Unitika Co., Ltd. was used. In addition, an unstretched polypropylene film ZK500 manufactured by Toray Advanced Film Co., Ltd. was prepared as a film for constituting the sealant layer 70. ZK500 contains the above-mentioned propylene-ethylene block copolymer and elastomer. The thickness of the sealant layer 70 was 60 μm.

[0122] Compared to typical stretched PET films, EMBLET® PC has high tear resistance in the machine direction (MD). The tensile strength of EMBLET® PC in the machine direction (MD) is 200 MPa, and the tensile strength of EMBLET® PC in the transverse direction (TD) is 180 MPa.

[0123] ZK500 has a higher tensile elongation than a general unstretched polypropylene film. Specifically, the tensile elongation of ZK500 in the machine direction (MD) is 1180% when the thickness is 50 μm, and 1100% when the thickness is 60 μm. The tensile elongation of ZK500 in the transverse direction (TD) is 1240% when the thickness is 50 μm, and 1150% when the thickness is 60 μm. Therefore, the product of the tensile elongation (%) and thickness (μm) of ZK500 in the machine direction is 59000 when the thickness is 50 μm, and 66000 when the thickness is 60 μm. The product of the tensile elongation (%) and thickness (μm) of ZK500 in the transverse direction is 62000 when the thickness is 50 μm, and 69000 when the thickness is 60 μm.

[0124] In addition, ZK500 has a lower tensile modulus than a general unstretched polypropylene film. Specifically, the tensile modulus of ZK500 in the machine direction (MD) is 640 MPa when the thickness is 50 μm, and 550 MPa when the thickness is 60 μm. In addition, the tensile modulus of ZK500 in the perpendicular direction (TD) is 480 MPa when the thickness is 50 μm, and 400 MPa when the thickness is 60 μm. Therefore, the product of the tensile modulus (MPa) and thickness (μm) of ZK500 in the machine direction is 32000 when the thickness is 50 μm, and 33000 when the thickness is 60 μm. In addition, the product of the tensile modulus (MPa) and thickness (μm) of ZK500 in the perpendicular direction is 24000 when the thickness is 50 μm, and 35000 when the thickness is 60 μm.

[0125] Next, the first stretched plastic film 40, the second stretched plastic film 50, and the sealant layer 70 were laminated by dry lamination to produce the laminate 30. A two-component polyurethane adhesive (main agent: RU-40, hardener: H-4) manufactured by Rock Paint Co., Ltd. was used as the first adhesive layer 45 and the second adhesive layer 55. The main agent RU-40 is polyester polyol. The thickness of the first adhesive layer 45 and the second adhesive layer 55 was 3.5 μm.

[0126] [Evaluation of puncture resistance] Next, the puncture strength of the laminate 30 was measured in accordance with JIS Z1707 7.4. A Tensilon universal material testing machine RTC-1310 manufactured by A&D was used as the measuring device. Specifically, as shown in FIG. 6, a semicircular needle 90 having a diameter of 1.0 mm and a tip radius of 0.5 mm was pierced from the outer surface 30y side of the test piece of the laminate 30 in a fixed state at a speed of 50 mm / min (50 mm per minute), and the maximum value of the stress until the needle 90 penetrated the laminate 30 was measured. The maximum value of the stress was measured for five or more test pieces, and the average value was taken as the puncture strength of the laminate 30. The environment during the measurement was a temperature of 23°C and a relative humidity of 50%. As a result, the puncture strength was 16.7 N.

[0127] [Evaluation of impact resistance] Next, two laminates 30 were stacked and heated at 190° C. for one second to heat-seal the inner surfaces 30x of the laminates 30. Next, the two heat-sealed laminates 30 were cut into a width of 15 mm to prepare a test piece 100. FIG. 7 is a plan view showing the test piece 100, and FIG. 8 is a cross-sectional view of the test piece 100 in FIG. 7. The test piece 100 has a width W3 of 15 mm and a length W4 of 50 mm, and a sealed portion 101 is formed over a length W5 of 10 mm from one end, and no sealed portion is formed over a length of 40 mm from the other end. Next, as shown in FIG. 9, the unsealed portion of one laminate 30 and the unsealed portion of the other laminate 30 were arranged in a direction perpendicular to the surface direction of the seal portion 101 so as to be inverse to each other, i.e., in a T-shape, and then the end of the unsealed portion of one laminate 30 and the end of the unsealed portion of the other laminate 30 were fixed to jigs 102 and 103, respectively. At this time, the distance T between the jigs 102 and 103 in the direction perpendicular to the surface direction of the seal portion 101 was set to 40 mm. Next, the one jig 102 was struck with a hammer 104 from the surface of the one laminate 30 on the first stretched plastic film 40 side, to measure the impact strength when the one laminate 30 and the other laminate 30 were separated. The evaluation was performed using a digital impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd. as a measuring instrument. A hammer of 2 J was used as a hammer for applying an impact to the test piece 100. As a result, the impact strength was 675 kJ / m.

[0128] [Evaluation of tearability] Next, the two laminates 30 joined via the sealant layer 70 were cut out to have a width W1 of 15 mm and a length W2 of 100 mm as shown in FIG. 10 to prepare a test piece 110. The width W1 of the test piece 110 was parallel to the second direction D2 shown in FIG. 1. The length W2 of the test piece 110 was parallel to the machine direction (MD) when the second stretched plastic film 50 was formed, and was also parallel to the first direction D1 shown in FIG. 1. Next, as shown in FIG. 10, a slit 28 was formed in the center of the width W1 of the test piece 110. Next, the test piece 110 was torn by hand in the direction of the length W2 starting from the slit 28. As a result, the sealant layer 70 of the laminate 30 was not stretched in the middle, and the test piece 110 could be torn in the direction of the length W2.

[0129] Example 2 The laminate 30 was produced in the same manner as in Example 1, except that a stretched plastic film containing polyamide as a main component and having a thickness of 15 μm was used as the first stretched plastic film 40. Specifically, the first stretched plastic film 40 used was a co-extruded film produced by co-extrusion, including a first layer 41 made of PET having a thickness of 2 μm, a second layer 42 made of nylon-6 having a thickness of 11 μm, and a third layer 43 made of PET having a thickness of 2 μm.

[0130] Subsequently, the puncture strength and impact strength of the laminate 30 were measured in the same manner as in Example 1. As a result, the puncture strength was 15 N and the impact strength was 642 kJ / m.

[0131] Subsequently, the tearability of the laminate 30 was evaluated in the same manner as in Example 1. As a result, the sealant layer 70 of the laminate 30 was not stretched during the tearing process, and the test piece 110 could be torn in the direction of the length W2.

[0132] Example 3 A laminate 30 was produced in the same manner as in Example 1, except that a stretched PET film having a thickness of 12 μm was used as the first stretched plastic film 40, and a stretched plastic film containing polyamide, specifically nylon, as a main component, having a thickness of 15 μm, and having tearability in the machine direction (MD) was used as the second stretched plastic film 50. In the following description, the stretched nylon film having tearability in the machine direction (MD) is also referred to as straight cut nylon. Bonyl CL manufactured by Kojin Film & Chemicals Co., Ltd. was used as the straight cut nylon.

[0133] Bonyl CL has higher tear resistance in the machine direction (MD) than general oriented nylon films. The tensile strength of Bonyl CL in the machine direction (MD) is 269 MPa, and the tensile strength of Bonyl CL in the transverse direction (TD) is 255 MPa.

[0134] Subsequently, the puncture strength and impact strength of the laminate 30 were measured in the same manner as in Example 1. As a result, the puncture strength was 17 N and the impact strength was 1531 kJ / m.

[0135] Subsequently, the tearability of the laminate 30 was evaluated in the same manner as in Example 1. As a result, the sealant layer 70 of the laminate 30 was not stretched during the tearing process, and the test piece 110 could be torn in the direction of the length W2.

[0136] Example 4 The laminate 30 was produced in the same manner as in Example 1, except that an unstretched polypropylene film ZK207 manufactured by Toray Advanced Film Co., Ltd. was used as the sealant film for constituting the sealant layer 70. The thickness of the unstretched polypropylene film ZK207 was 70 μm.

[0137] ZK207 has a higher tensile modulus than ZK500. Specifically, the tensile modulus of ZK207 in the machine direction (MD) is 780 MPa when the thickness is 50 μm, and 680 MPa when the thickness is 60 μm. The tensile modulus of ZK207 in the transverse direction (TD) is 630 MPa when the thickness is 50 μm, and 560 MPa when the thickness is 60 μm. Therefore, the product of the tensile modulus (MPa) and thickness (μm) of ZK207 in the machine direction is 39000 when the thickness is 50 μm, and 40800 when the thickness is 60 μm. The product of the tensile modulus (MPa) and thickness (μm) of ZK207 in the transverse direction is 31500 when the thickness is 50 μm, and 33600 when the thickness is 60 μm. By using ZK207, the tearability of the laminate 30 and the bag 10 including the laminate 30 can be improved.

[0138] In addition, ZK207 has a lower tensile elongation than ZK500. Specifically, the tensile elongation of ZK207 in the machine direction (MD) is 790% when the thickness is 50 μm, and 730% when the thickness is 60 μm. In addition, the tensile elongation of ZK207 in the transverse direction (TD) is 1020% when the thickness is 50 μm, and 870% when the thickness is 60 μm. Therefore, the product of the tensile elongation (%) and the thickness (μm) of ZK207 in the machine direction is 39500 when the thickness is 50 μm, and 43800 when the thickness is 60 μm. In addition, the product of the tensile elongation (%) and the thickness (μm) of ZK207 in the transverse direction is 51000 when the thickness is 50 μm, and 52200 when the thickness is 60 μm.

[0139] Subsequently, the puncture strength and impact strength of the laminate 30 were measured in the same manner as in Example 1. As a result, the puncture strength was 16.5 N and the impact strength was 463 kJ / m.

[0140] Next, the tearability of the laminate 30 was evaluated in the same manner as in Example 1. As a result, the test piece 110 could be torn in the direction of length W2 without the sealant layer 70 of the laminate 30 stretching during the tearing process. In addition, the positional deviation in the direction of width W1 between the two laminates 30 at the torn portion was 5 mm or less.

[0141] Comparative Example 1 The laminate 30 was produced in the same manner as in Example 1, except that a stretched PET film having a thickness of 12 μm was used as the first stretched plastic film 40, and a stretched PET film having no tearability in the machine direction (MD) was used as the second stretched plastic film 50. Specifically, a stretched PET film having the same tensile strength in the machine direction (MD) and the same tensile strength in the perpendicular direction (TD) and having a thickness of 12 μm was used as the second stretched plastic film 50.

[0142] Subsequently, the puncture strength and impact strength of the laminate 30 were measured in the same manner as in Example 1. As a result, the puncture strength was 13.7 N and the impact strength was 1109 kJ / m.

[0143] Next, the tearability of the laminate 30 was evaluated in the same manner as in Example 1. As a result, the sealant layer 70 of the laminate 30 stretched during the process, and the test piece 110 could not be torn in the direction of the length W2.

[0144] The layer structures and evaluation results of the laminates of Examples 1 to 4 and Comparative Example 1 are shown together in Fig. 11. In Fig. 11, in the column "Layer structure", the components of the laminate are listed in order from the outer surface side to the top.

[0145] As can be seen from the comparison between Examples 1 to 4 and Comparative Example 1, by using a stretched plastic film having tearability in the machine direction (MD) as the second stretched plastic film 50 adjacent to the sealant layer 70, it was possible to suppress the sealant layer 70 from stretching when the laminate 30 was torn. Regarding the tearability, in Examples 1 to 3, the test piece 110 could be torn smoothly over the entire area in the direction of length W2, so the evaluation result was "good". In Example 4, the test piece 110 could be torn smoothly over the entire area in the direction of length W2, and the positional deviation amount in the direction of width W1 of the two laminates 30 constituting the test piece 110 was 5 mm or less, so the evaluation result was "great". On the other hand, in Comparative Example 1, the sealant layer 70 of the laminate 30 stretched midway, and therefore the test piece 110 could not be torn smoothly over the entire area in the direction of length W2, so the evaluation result was "bad". [Explanation of symbols]

[0146] 10 bags 11 Top 12 Lower 12a Lower seal part 13 Side 13a Side seal 14 Surface film 15 Back film 16 Lower Film 17 Storage unit 18 Contents 20 Steam release mechanism 20a Steam release seal 25 Easy-to-open means 26 Notches 30 Laminate 40 First oriented plastic film 45 First adhesive layer 50 Second oriented plastic film 55 Second adhesive layer 70 Sealant Layer

Claims

1. A bag having a steam venting mechanism, A laminate; A seal portion in which inner surfaces of the laminate are joined together, The laminate comprises, from the outer surface side to the inner surface side, at least a first stretched plastic film, a second stretched plastic film, and a sealant layer (excluding the sealant layer made of a polypropylene-based film containing a hydrogenated styrene-based thermoplastic elastomer), in this order; The first stretched plastic film contains polyester as a main component, The second stretched plastic film contains polyamide as a main component, When the machine direction of the second stretched plastic film is defined as a first direction and a direction perpendicular to the first direction is defined as a second direction, the tensile strength of the second stretched plastic film in the first direction is 1.05 times or more of the tensile strength of the second stretched plastic film in the second direction, The tensile strength of the second stretched plastic film in the first direction is 200 MPa or more and 300 MPa or less, the sealant layer is an unstretched film containing a first thermoplastic resin and a second thermoplastic resin, the first thermoplastic resin is a propylene-ethylene block copolymer; The second thermoplastic resin contains at least an α-olefin copolymer or polyethylene, The mass ratio of the first thermoplastic resin is higher than the mass ratio of the second thermoplastic resin, The room temperature seal strength of the seal portion at 25°C in a width of 15 mm is 40 N or more, The bag has a hot seal strength of 15 N or less at 100° C. over a width of 15 mm.

2. The bag of claim 1 , wherein the width direction of the bag is the first direction.

Images