bag

Abstract

This prevents damage to the laminated structure that makes up the bag. [Solution] The bag having a storage compartment comprises a laminate including a sealant film consisting of a single layer located on the inner surface of the bag, and at least one plastic film located on the outer surface side of the sealant film, and a sealing portion that joins the inner surfaces of a pair of laminates together. The product of the tensile elongation (%) of the sealant film in the flow direction and the thickness (μm) of the sealant film is 45,000 or more. The sealing portion has an outer edge sealing portion located on the outer edge of the bag, and a vapor vent sealing portion located on the center point side of the storage compartment than the outer edge sealing portion, which peels off when the pressure in the storage compartment increases. The sealing strength of the sealing portion at 100°C is 15N or less.

Description

[Technical Field]

[0001] The present invention relates to a bag having a steam-venting seal portion that peels off due to an increase in internal pressure. [Background technology]

[0002] Conventionally, many products on the market consist of pre-cooked or semi-cooked liquids, viscous substances, or mixtures of liquids and solids, sealed in bags made of laminated plastic. In these bags, the non-sealed sections, where the laminated layers are not joined, constitute the storage area where the contents are contained. The sealed sections, where the laminated layers are joined, seal the storage area. The contents are, for example, pre-cooked foods such as curry, stew, and soup. The contents are heated in the bag using a microwave oven or similar device.

[0003] Incidentally, when contents contained in a sealed bag are heated using a microwave oven, the water contained in the contents evaporates as heating occurs, increasing the pressure inside the bag. When the pressure inside the bag increases, there is a risk that the bag may burst, scattering the contents and contaminating the inside of the microwave oven. Considering this problem, for example, Patent Document 1 proposes a mechanism that automatically connects the contents inside the bag to the outside when the pressure inside the bag increases, thereby releasing the steam inside the bag to the outside. The mechanism includes a steam-releasing seal that peels off as the pressure inside the bag increases. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-120550 [Overview of the project] [Problems that the invention aims to solve]

[0005] Through diligent research by the inventors of this case, it was discovered that in conventional bags, the pressure and temperature inside the storage area become too high when the steam vent seal peels off, which can cause damage such as holes or wrinkles in the laminated material that makes up the bag.

[0006] The present invention aims to provide a bag that can effectively solve these problems. [Means for solving the problem]

[0007] The present invention relates to a bag having a storage compartment, comprising a laminate including a sealant film located on the inner surface of the bag and consisting of a single layer, and at least one plastic film located on the outer surface side of the sealant film, and a sealing portion that joins the inner surfaces of a pair of the laminates, wherein the product of the tensile elongation (%) of the sealant film in the flow direction and the thickness (μm) of the sealant film is 45000 or more, the sealing portion comprises an outer edge sealing portion located on the outer edge of the bag and a vapor-venting sealing portion located on the center point side of the storage compartment from the outer edge sealing portion and peeling off due to an increase in pressure in the storage compartment, the bag further comprises an unsealed portion isolated from the storage compartment by the vapor-venting sealing portion, the unsealed portion extends from a position on the center point side of the storage compartment from the outer edge sealing portion to the outer edge of the bag, the sealing strength of the sealing portion at 100°C is 15N or less, and the peeling pressure of the vapor-venting sealing portion is 130kPa or less.

[0008] In the bag according to the present invention, the sealing strength of the sealed portion at 100°C may be 10N or less.

[0009] In the bag according to the present invention, the peeling pressure of the steam vent seal portion may be 120 kPa or less.

[0010] In the bag according to the present invention, the sealant film may contain a propylene-ethylene block copolymer as its main component.

[0011] In the bag according to the present invention, the sealant film may contain an α-olefin copolymer or polyethylene.

Advantages of the Invention

[0012] According to the present invention, it is possible to suppress damage such as holes and wrinkles in the laminate constituting the bag.

Brief Description of the Drawings

[0013] [Figure 1] It is a front view showing the bag in the embodiment of the present invention. [Figure 2] It is a cross-sectional view showing the case where the bag shown in FIG. 1 is viewed along the line II-II. [Figure 3] It is a cross-sectional view showing an example of the layer structure of the laminate constituting the bag. [Figure 4] It is a front view showing the bag in a state where the upper part is sealed. [Figure 5] It is a cross-sectional view showing a test piece for measuring the seal strength. [Figure 6] It is a diagram showing an example of a method for measuring the seal strength. [Figure 7] It is a diagram showing the change in tensile stress with respect to the distance between a pair of gripping tools for pulling the test piece to measure the seal strength. [Figure 8] It is a diagram showing an example of a method for measuring the pressure in the storage part. [Figure 9] It is a front view showing a modified example of the bag. [Figure 10] It is a front view showing a modified example of the bag. [Figure 11] It is a front view showing a modified example of the bag. [Figure 12] It is a table showing the evaluation results of the relationship between the seal temperature and the seal strength. [Figure 13] It is a graph showing the evaluation results of the relationship between the seal temperature and the seal strength. [Figure 14] It is a table showing the evaluation results of the examples and comparative examples.

Embodiments for Carrying Out the Invention

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

[0015] Furthermore, terms used in this specification to specify shapes, geometric conditions, and their degrees, such as "parallel," "orthogonal," and "identical," as well as values ​​for length and angle, shall not be strictly interpreted, but shall be interpreted to include a range that allows for the expectation of similar functionality.

[0016] Figure 1 is a front view showing the bag 10 according to this embodiment. The bag 10 includes a storage section 17 for containing contents. Note that Figure 1 shows the bag 10 before contents are placed inside. The bag 10 according to this embodiment is configured to be suitably used as a microwave pouch in which the contents are heated by a microwave oven.

[0017] As shown in Figure 1, the bag 10 according to this embodiment is equipped with a steam release mechanism 20 for releasing steam generated when the contents of the bag 10 are heated. The steam release mechanism 20 is configured to release steam by connecting the inside and outside of the bag 10 when the steam pressure exceeds a predetermined value, and to suppress steam from escaping from locations other than the steam release mechanism 20. The configuration of the 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 part 11, a lower part 12, and a pair of side parts 13, and has a substantially rectangular outline in the front view. The names such as "upper part," "lower part," and "side parts," as well as terms such as "upper" and "lower," merely describe the relative position and orientation of the bag 10 and its components based on the state in which the bag 10 is self-supporting with the gusset part facing downwards. The orientation of the bag 10 during transport or use is not limited by the names and terms used herein.

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

[0020] As shown in Figure 1, the bag 10 comprises a surface film 14 that constitutes the surface, a back film 15 that constitutes the back surface, and a bottom film 16 that constitutes the bottom 12. The bottom film 16 is folded over at the folded portion 16f and is positioned between the surface film 14 and the back film 15.

[0021] It should be noted that the terms "front film," "back film," and "bottom film" mentioned above are merely ways of dividing the films according to their positional relationship, and the method of providing the films when manufacturing the bag 10 is not limited by these terms. For example, the bag 10 may be manufactured using a single film in which the front film 14, back film 15, and bottom film 16 are connected; it may be manufactured using a total of two films: a single film in which the front film 14 and bottom film 16 are connected and a single back film 15; or it may be manufactured using a total of three films: a single front film 14, a single back film 15, and a single bottom film 16.

[0022] The surface film 14, the back film 15, and the bottom film 16 are joined together on their inner surfaces by a sealing portion. In the plan view of the bag 10, such as in Figure 1, hatching is applied to the sealing portion.

[0023] As shown in Figure 1, the seal portion has an outer edge seal portion extending along the outer edge of the bag 10 and a steam vent seal portion 20a that constitutes the steam vent mechanism 20. The outer edge seal portion includes a lower seal portion 12a that extends to the lower part 12 and a pair of side seal portions 13a that extend along the pair of side portions 13. In the bag 10 before contents are placed inside, as shown in Figure 1, the upper part 11 of the bag 10 is an opening 11b. After contents are placed inside the bag 10, the upper seal portion is formed and the bag 10 is sealed by joining the inner surface of the surface film 14 and the inner surface of the back film 15 at the upper part 11.

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

[0025] The method for forming the seal is not particularly limited, as long as the opposing films can be joined together to seal the bag 10. For example, the seal may be formed by melting the inner surfaces of the films by heating and welding the inner surfaces together, i.e., by heat sealing. Alternatively, the seal may be formed by bonding the inner surfaces of the opposing films together using an adhesive or the like.

[0026] Steam venting mechanism The configuration of the steam venting mechanism 20 will be described below. Figure 2 is a cross-sectional view of the steam venting mechanism 20 of the bag 10 shown in Figure 1, viewed along line II-II.

[0027] The steam venting seal portion 20a of the steam venting mechanism 20 has a shape that makes it easily peeled off as the pressure in the containment portion 17 increases. For example, the steam venting seal portion 20a has a shape that protrudes inward from the side seal portion 13a towards the inside of the bag 10. This makes it possible to make the force applied to the steam venting seal portion 20a greater than the force applied to the side seal portion 13a when the pressure in the containment portion 17 increases. In addition, the width of the steam venting seal portion 20a is smaller than the width of the side seal portion 13a. Furthermore, as shown in Figures 1 and 2, an unsealed portion 20b is formed between the steam venting seal portion 20a and the outer edge of the side portion 13, which is isolated from the containment portion 17 by the steam venting seal portion 20a.

[0028] When the contents of bag 10 are heated, the water contained in the contents evaporates and the pressure in the containment section 17 increases, causing bag 10 to expand around the center point C of the containment section 17. In this case, a force is applied to the sealing parts, such as the side sealing section 13a and the steam vent sealing section 20a, in the direction from the center point C toward the sealing section. The force applied to each position of the sealing section increases as the distance from the center point C decreases. The aforementioned steam vent sealing section 20a protrudes from the side sealing section 13a toward the containment section 17, and therefore the force applied to the steam vent sealing section 20a is greater than the force applied to the side sealing section 13a. Consequently, communication between the containment section 17 and the outside due to the peeling of the sealing section can be more easily created at the steam vent sealing section 20a compared to the side sealing section 13a.

[0029] In the examples shown in Figures 1 and 2, the unsealed portion 20b of the steam venting mechanism 20 extends to the side edge of the bag 10. Therefore, the portion of the side edge of the bag 10 that overlaps with the unsealed portion 20b is open. In this case, steam that flows from the containment portion 17 to the unsealed portion 20b through the peeled portion of the steam venting seal portion 20a can smoothly escape to the outside of the bag 10 through the opening in the side edge of the bag 10. In the following description, a bag of the type in which the unsealed portion 20b of the steam venting mechanism 20 extends to the outer edge such as the side edge of the bag 10, as shown in Figures 1 and 2 and Figure 4 described later, will also be referred to as a Type 1 bag.

[0030] Incidentally, when heating the contents of bag 10 using a microwave oven or similar device, some of the contents may splatter and reach the inner surface of the laminate that makes up bag 10. If the contents that adhere to the inner surface of the laminate contain moisture, the contents that adhere to the inner surface of the laminate will be further heated by the microwave oven. In this case, the temperature of the laminate in contact with the contents will also rise, which could cause holes to form in the laminate or wrinkles to form in the laminate.

[0031] Considering these issues, in this embodiment, the seal portion of the bag 10 is configured such that the seal strength of the seal portion when heated to a high temperature is at an appropriately low value. For example, the seal portion of the bag 10 is configured such that the seal strength (hereinafter also referred to as the hot seal strength) of the seal portion of the bag 10 at 100°C is 15N or less. In this case, when the contents of the bag 10 are heated using a microwave oven or the like, the steam vent seal portion 20a of the seal portion becomes easier to peel off based on the force received from the pressure of the steam generated in the containment portion 17. That is, the steam vent seal portion 20a peels off at a lower pressure. As a result, the steam vent seal portion 20a can be peeled off and the steam in the containment portion 17 can be released to the outside before the temperature of the contents adhering to the inner surface of the bag 10 becomes excessively high, thereby lowering the pressure and temperature of the containment portion 17. This makes it possible to suppress damage such as holes and wrinkles from occurring in the laminate of the bag 10. In the following description, the pressure in the containment section 17 when the steam vent seal section 20a peels off and the containment section 17 communicates with the outside of the bag 10 will also be referred to as the peeling pressure.

[0032] Factors determining the hot seal strength of the sealed portion include the mechanical properties and thickness of the sealant film located on the inner surface of the laminate, as described later. Furthermore, when a sealed portion such as the steam vent seal portion 20a is formed by heat sealing, the seal strength of the sealed portion of the bag 10 may change depending on the heat sealing conditions, such as temperature. Also, the seal strength of the sealed portion of the bag 10 may change due to sterilization treatments such as boiling or retorting. In this embodiment, by appropriately adjusting and considering these factors, a sealed portion having a hot seal strength of 15N or less is formed. Note that when the bag 10 is subjected to treatments such as boiling or retorting, unless otherwise specified, the seal strength of the sealed portion of the bag 10 refers to the seal strength of the sealed portion of the bag 10 after the treatment has been performed.

[0033] Retort processing is a process in which the contents are filled into bag 10, the bag 10 is sealed, and then the bag 10 is heated under pressure using steam or hot water. The temperature for retort processing is, for example, 120°C or higher. Boiling processing is a process in which the contents are filled into bag 10, the bag 10 is sealed, and then the bag 10 is heated in a water bath under atmospheric pressure. The temperature for boiling processing is, for example, 90°C or higher and 100°C or lower.

[0034] Furthermore, factors determining the peeling pressure of the steam vent seal portion 20a include the shape, dimensions, and hot seal strength of the steam vent seal portion 20a. The peeling pressure of the steam vent seal portion 20a is preferably 130 kPa or less, and more preferably 120 kPa or less.

[0035] Furthermore, if the peeling pressure of the steam vent seal portion 20a is too low, the steam vent seal portion 20a may peel off before the contents are sufficiently heated and pressurized, causing a decrease in the pressure and temperature of the containment portion 17. Considering this point, the peeling pressure of the steam vent seal portion 20a is preferably 105 kPa or higher, and more preferably 110 kPa or higher.

[0036] Layer structure of surface film and back film Next, the layer structure of the surface film 14 and the back film 15 will be described. Figure 3 is a cross-sectional view showing an example of the layer structure of the laminate 30 that makes up the surface film 14 and the back film 15.

[0037] As shown in Figure 3, the laminate 30 comprises at least a first plastic film 40, a first adhesive layer 45, a second plastic film 50, a second adhesive layer 55, and a sealant film 70 in this order. The first plastic film 40 is located on the outer surface 30y side, and the sealant film 70 is located on the inner surface 30x side opposite the outer surface 30y. The inner surface 30x is the surface located on the side of the housing 17.

[0038] The following describes each layer of the laminate 30 in detail.

[0039] (First plastic film) The first plastic film 40 is, for example, a stretched plastic film that is stretched in a predetermined direction. The first plastic film 40 functions as a base layer for giving the laminate 30 a predetermined strength. The first plastic film 40 may be a uniaxially oriented film stretched in a predetermined one direction, or a biaxially oriented film stretched in two predetermined directions. The stretching direction of the first plastic film 40 is not particularly limited. For example, the first plastic film 40 may be stretched in the direction in which the side portion 13 extends, or it may be stretched in a direction perpendicular to the direction in which the side portion 13 extends. The stretching ratio of the first plastic film 40 is, for example, 1.05 times or more.

[0040] The first plastic film 40 contains, for example, polyester as its main component. For example, the first plastic film 40 contains 51% by 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). The 51% by mass or more of polyester in the first plastic film 40 may be composed of one type of polyester or of two or more types of polyester.

[0041] When the first plastic film 40 contains polyester as its main component, the thickness of the first plastic film 40 is preferably 9 μm or more, and more preferably 12 μm or more. Also, when the first plastic film 40 contains polyester as its main component, the thickness of the first plastic film 40 is preferably 25 μm or less, and more preferably 20 μm or less. By making the thickness of the first plastic film 40 9 μm or more, the first plastic film 40 will have sufficient strength. Also, by making the thickness of the first plastic film 40 25 μm or less, the first plastic film 40 will exhibit excellent moldability. Therefore, the process of processing the laminate 30 to manufacture the bag 10 can be carried out efficiently.

[0042] The first plastic film 40 may contain polyamide as its main component. For example, the first plastic film 40 contains 51% by mass or more of polyamide. Examples of polyamides include aliphatic polyamides and aromatic polyamides. Examples of aliphatic polyamides include nylon such as nylon-6, nylon-6,6, and copolymers of nylon-6 and nylon-6,6, while examples of aromatic polyamides include polymetaxylene adipamide (MXD6). By containing polyamide as the main component of the first plastic film 40, the puncture strength of the laminate 30 comprising the first plastic film 40 can be increased.

[0043] When the first plastic film 40 contains polyamide as its main component, the thickness of the first plastic film 40 is preferably 12 μm or more, and more preferably 15 μm or more. Also, when the first plastic film 40 contains polyamide as its main component, the thickness of the first plastic film 40 is preferably 25 μm or less, and more preferably 20 μm or less.

[0044] The first plastic film 40 may consist of a single layer or multiple layers. If the first plastic film 40 includes multiple layers, the first plastic film 40 is, for example, a co-extruded film produced by co-extrusion. The first plastic film 40 produced by co-extrusion includes, for example, a first layer made of polyester such as PET, a second layer made of polyamide such as nylon, and a third layer made of polyester such as PET, which are laminated in order. If the mass of the second layer made of polyamide such as nylon is 51% or more of the total mass of the first plastic film 40, then the main component of the first plastic film 40 produced by co-extrusion can be said to be polyamide.

[0045] (First adhesive layer) The first adhesive layer 45 contains an adhesive for bonding the first plastic film 40 and the second plastic film 50 by a dry lamination method. The adhesive constituting the first adhesive layer 45 is produced from an adhesive composition made by mixing a first composition containing a main agent and a solvent with a second composition containing a curing agent and a solvent. Specifically, the adhesive includes a cured product produced by the reaction of the main agent and the solvent in the adhesive composition.

[0046] Examples of adhesives include polyurethane. Polyurethane is a cured product produced by the reaction of a polyol as the main component with an isocyanate compound as the curing agent. Examples of polyurethane include polyether polyurethane and polyester polyurethane. Polyether polyurethane is a cured product produced by the reaction of a polyether polyol as the main component with an isocyanate compound as the curing agent. Polyester polyurethane is a cured product produced by the reaction of a polyester polyol as the main component with an isocyanate compound as the curing agent.

[0047] As isocyanate compounds, aromatic isocyanate compounds such as tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), and xylylene diisocyanate (XDI), aliphatic isocyanate compounds such as hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), or adducts or polymers of the above isocyanate compounds can be used.

[0048] The thickness of the first adhesive layer 45 is preferably 2 μm or more, and more preferably 3 μm or more. Furthermore, the thickness of the first adhesive layer 45 is preferably 6 μm or less, and more preferably 5 μm or less.

[0049] (Second plastic film) The second plastic film 50 is, for example, a plastic film stretched in a predetermined direction, similar to the first plastic film 40. The second plastic film 50, like the first plastic film 40, functions as a base layer for providing the laminate 30 with a predetermined strength. The stretching direction of the second plastic film 50 is not particularly limited, similar to the case of the first plastic film 40.

[0050] The second plastic film 50, like the first plastic film 40, mainly contains polyester or polyamide. In order to provide heat resistance to the laminate 30, it is preferable that at least one of the first plastic film 40 and the second plastic film 50 mainly contains polyester. Therefore, if the first plastic film 40 mainly contains polyamide, the second plastic film 50 mainly contains polyester. If the first plastic film 40 mainly contains polyester, the second plastic film 50 may mainly contain polyester or mainly contain polyamide.

[0051] When the second plastic film 50 contains polyester as its main component, for example, when it contains 51% by mass or more of polyester, examples of polyester include PET, PBT, etc., as in the case of the first plastic film 40. The thickness of the second plastic film 50 is preferably 9 μm or more, and more preferably 12 μm or more. Furthermore, when the second plastic film 50 contains polyester as its main component, the thickness of the second plastic film 50 is preferably 25 μm or less, and more preferably 20 μm or less. When the second plastic film 50 contains polyester as its main component, the thermal conductivity, melting point, etc., of the second plastic film 50 are the same as in the case of the first plastic film 40 which contains polyester as its main component.

[0052] When the second plastic film 50 contains polyamide as its main component, for example, when it contains 51% by mass or more of polyamide, examples of polyamide include aliphatic polyamide or aromatic polyamide, as in the case of the first plastic film 40. The thickness of the second plastic film 50 is preferably 12 μm or more, and more preferably 15 μm or more. Furthermore, if the second plastic film 50 contains polyamide as the main component, the thickness of the second plastic film 50 is preferably 25 μm or less, and more preferably 20 μm or less.

[0053] (Second adhesive layer) The second adhesive layer 55 contains an adhesive for bonding the second plastic film 50 and the sealant film 70 by a dry lamination method. An example of the adhesive for the second adhesive layer 55 is polyurethane, similar to that used for the first adhesive layer 45. In addition to the configuration, materials, and properties described below, the same configuration, materials, and properties as those of the first adhesive layer 45 can be adopted for the second adhesive layer 55.

[0054] The thickness of the second adhesive layer 55 is preferably 2 μm or more, and more preferably 3 μm or more. Furthermore, the thickness of the second adhesive layer 55 is preferably 6 μm or less, and more preferably 5 μm or less.

[0055] Incidentally, as mentioned above, the isocyanate compounds that constitute the curing agent of the adhesive include aromatic isocyanate compounds and aliphatic isocyanate compounds. Of these, aromatic isocyanate compounds may leach components that are unsuitable for food use under high-temperature environments such as heat sterilization. Furthermore, the second adhesive layer 55 is in contact with the sealant film 70. Therefore, if the second adhesive layer 55 contains an aromatic isocyanate compound, components leached from the aromatic isocyanate compound may adhere to the contents contained in the containment section 17 that is in contact with the sealant film 70.

[0056] In consideration of these issues, preferably, the adhesive constituting the second adhesive layer 55 is a cured product produced by the reaction of a polyol as the main component and an aliphatic isocyanate compound as the curing agent. This prevents components unsuitable for food use due to the second adhesive layer 55 from adhering to the contents.

[0057] (Sealant film) Next, the sealant film 70 will be described. The material constituting the sealant film 70 can be one or more resins selected from polyethylene such as low-density polyethylene and linear low-density polyethylene, and polypropylene. The sealant film 70 may be a single layer or a multi-layer film. Furthermore, the sealant film 70 preferably consists of an unstretched film. Note that "unstretched" is a concept that includes not only films that are not stretched at all, but also films that are slightly stretched due to the tension applied during film formation.

[0058] The bag 10, which is composed of a laminate 30, is subjected to sterilization treatments such as boiling or retorting at high temperatures. Therefore, the sealant film 70 used has heat resistance that can withstand these high-temperature treatments.

[0059] The melting point of the material constituting the sealant film 70 is preferably 150°C or higher, and more preferably 160°C or higher. By increasing the melting point of the sealant film 70, it becomes possible to perform retort processing of the bag 10 at a high temperature, and thus the time required for retort processing can be shortened. Note that the melting point of the material constituting the sealant film 70 is lower than the melting point of the resin constituting the plastic films 40 and 50.

[0060] From the perspective of retort processing, a material mainly composed of propylene can be used as the material constituting the sealant film 70. Here, "material mainly composed of propylene" means a material in which the propylene content is 90% by mass or more. Specifically, examples of materials mainly composed of propylene include polypropylene such as propylene-ethylene block copolymer, propylene-ethylene random copolymer, homopolypropylene, or a mixture of polypropylene and polyethylene. Here, "propylene-ethylene block copolymer" means a material having the structural formula shown in formula (I) below. Also, "propylene-ethylene random copolymer" means a material having the structural formula shown in formula (II) below. Also, "homopolypropylene" means a material having the structural formula shown in formula (III) below.

[0061] [ka]

[0062] [ka]

[0063] [ka]

[0064] When a mixture of polypropylene and polyethylene is used as a material with propylene as the main component, the material may have a sea-island structure. Here, "sea-island structure" refers to a structure in which polyethylene is discontinuously dispersed within a continuous region of polypropylene.

[0065] From the perspective of boiling treatment, examples of materials constituting the sealant film 70 include polyethylene, polypropylene, or combinations thereof. Examples of polyethylene include medium-density polyethylene, linear low-density polyethylene, or combinations thereof. For example, it is also possible to use the materials listed above as materials constituting the sealant film 70 from the perspective of retort treatment. The materials constituting the sealant film 70 have 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 film 70, a melting point of 100°C or higher is, for example, when the density of polyethylene is 0.920 g / cm³. 3 This can be achieved if the above conditions are met. Specific examples of sealant films 70 having a melting point of 100°C or higher include TUX-HC manufactured by Mitsui Chemicals Tohcello, L6101 manufactured by Toyobo, and LS700C manufactured by Idemitsu Unitech. Specific examples of sealant films 70 having a melting point of 105°C or higher include NB-1 manufactured by Tamapoly. Specific examples of sealant films 70 having a melting point of 110°C or higher include LS760C manufactured by Idemitsu Unitech and TUX-HZ manufactured by Mitsui Chemicals Tohcello.

[0066] Preferably, the sealant film 70 is a single-layer film containing a propylene-ethylene block copolymer. For example, the sealant film 70 is a single-layer unstretched film mainly composed of a propylene-ethylene block copolymer. By using a propylene-ethylene block copolymer, the impact resistance of the sealant film 70 can be increased, thereby preventing the bag 10 from tearing due to impact during a fall. In addition, the puncture resistance of the laminate 30 can be increased.

[0067] Furthermore, by using a propylene-ethylene block copolymer, the strength of the seal portion formed by the sealant film 70 at high temperatures, for example 100°C, i.e., the hot seal strength mentioned above, becomes extremely small compared to the seal strength at low temperatures, for example 25°C (hereinafter also referred to as room temperature seal strength). Due to the low hot seal strength, when the bag 10 is heated using a microwave oven, the steam vent seal portion 20a is more likely to peel off, and steam from the containment portion 17 can easily escape to the outside of the bag 10. As a result, it is possible to suppress the internal pressure of the containment portion 17 from becoming excessive, thereby suppressing damage to the laminate 30 during heating.

[0068] The hot seal strength of the sealed portion of bag 10 at 100°C over a width of 15 mm is preferably 15 N or less, more preferably 11 N or less, and even more preferably 10 N or less. Alternatively, the hot seal strength of the sealed portion of bag 10 may be 9 N or less or 8 N or less. However, if the hot seal strength is too low, the steam vent seal portion 20a may peel off before the contents are sufficiently heated and pressurized, causing a decrease in the pressure and temperature of the containment portion 17. Considering this point, the hot seal strength of the sealed portion of bag 10 is preferably 4 N or more, and more preferably 5 N or more.

[0069] Furthermore, the room temperature seal strength of the sealed portion of the bag 10 at 25°C over a 15 mm width is preferably 65 N or less, more preferably 60 N or less, and even more preferably 55 N or less. Also, the room temperature seal strength of the sealed portion of the bag 10 at 25°C over a 15 mm width is preferably 35 N or more, more preferably 40 N or more, and may be 45 N or more or 50 N or more. By forming the sealed portion such that the room temperature seal strength is above a predetermined value, it is possible to suppress the peeling of the sealed portion of the bag 10 due to forces that the bag 10 receives during transport, etc.

[0070] The propylene-ethylene block copolymer includes, for example, a marine component made of polypropylene and an island component made of ethylene-propylene copolymer rubber. The marine component can contribute to improving the blocking resistance, heat resistance, rigidity, and seal strength of the propylene-ethylene block copolymer. The island component can also contribute to improving the impact resistance of the propylene-ethylene block copolymer. Therefore, the mechanical properties of the sealant film 70 containing the propylene-ethylene block copolymer can be adjusted by adjusting the ratio of the marine component to the island component.

[0071] In a propylene-ethylene block copolymer, the mass ratio of the polypropylene component (sea component) is higher than the mass ratio of the ethylene-propylene copolymer rubber component (island component). For example, in a propylene-ethylene block copolymer, the mass ratio of the polypropylene component is at least 51% by mass, preferably 60% by mass or more, and more preferably 70% by mass or more.

[0072] The single-layer sealant film 70 may further contain a second thermoplastic resin in addition to a first thermoplastic resin consisting of a propylene-ethylene block copolymer. Examples of the second thermoplastic resin include α-olefin copolymers and polyethylene. An example of an α-olefin copolymer is 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 improving the impact resistance of the sealant film 70.

[0073] Low-density polyethylene has a density of 0.910 g / cm³. 3 The above and 0.925 g / cm³ 3 The following polyethylenes are used. Medium-density polyethylene has a density of 0.926 g / cm³. 3 The above and 0.940 g / cm³ 3 The following polyethylenes are used. High-density polyethylene has a density of 0.941 g / cm³. 3 The above and 0.965 g / cm³3 The following is polyethylene. Low-density polyethylene can be obtained, for example, by polymerizing ethylene at a high pressure of 1000 atmospheres or more and less than 2000 atmospheres. Medium-density polyethylene and high-density polyethylene can be obtained, for example, by polymerizing ethylene at a medium or low pressure of 1 atmosphere or more and less than 1000 atmospheres.

[0074] Note that medium-density polyethylene and high-density polyethylene may partially contain a copolymer of ethylene and an α-olefin. Also, even when ethylene is polymerized at a medium or low pressure, when a copolymer of ethylene and an α-olefin is included, medium-density or low-density polyethylene can be produced. Such polyethylene is referred to as 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 a medium or low pressure to introduce short-chain branches. Examples of α-olefins include 1-butene (C4), 1-hexene (C6), 4-methylpentene (C6), 1-octene (C8), and the like. The density of linear low-density polyethylene is, for example, 0.915 g / cm 3 or more and 0.945 g / cm 3 or less.

[0075] Note that the α-olefin copolymer constituting the second thermoplastic resin of the propylene-ethylene block copolymer is not limited to the above-mentioned linear low-density polyethylene. The α-olefin copolymer means a material having a structural formula shown in the following formula (IV).

[0076]

Chemical formula

[0077] In the sealant film 70, the mass ratio of the first thermoplastic resin made of propylene-ethylene block copolymer is higher than the mass ratio of the second thermoplastic resin containing at least α-olefin copolymer or polyethylene. For example, in a single layer sealant film 70, the mass ratio of the first thermoplastic resin made of propylene-ethylene block copolymer is at least 51% by mass, preferably 60% by mass or more, and more preferably 70% by mass or more.

[0078] As described above, the second thermoplastic resin can contribute to improving the impact resistance of the sealant film 70. Therefore, the mechanical properties of the sealant film 70 can be adjusted by adjusting the mass ratio of the second thermoplastic resin, which contains at least an α-olefin copolymer or polyethylene, in the single-layer sealant film 70.

[0079] Furthermore, the sealant film 70 may further contain a thermoplastic elastomer. By using a thermoplastic elastomer, the impact resistance and puncture resistance of the sealant film 70 can be further enhanced.

[0080] Thermoplastic elastomers are, for example, hydrogenated styrene-based thermoplastic elastomers. Hydrogenated styrene-based thermoplastic elastomers have a structure consisting of polymer block A mainly composed of at least one vinyl aromatic compound and polymer block B mainly composed of at least one hydrogenated conjugated diene compound. Alternatively, thermoplastic elastomers may also be ethylene-α-olefin elastomers. Ethylene-α-olefin elastomers are low-crystallinity or amorphous copolymer elastomers, and are random copolymers of 50-90% by mass of ethylene as the main component and α-olefin as the copolymer monomer.

[0081] The content of propylene-ethylene block copolymer in the sealant film 70 is, for example, 80% by mass or more, and preferably 90% by mass or more.

[0082] One method for producing propylene-ethylene block copolymers involves polymerizing the raw materials, such as propylene and ethylene, using a catalyst. Suitable catalysts include Ziegler-Natta type catalysts and metallocene catalysts.

[0083] The thickness of the sealant film 70 is preferably 30 μm or more, and more preferably 40 μm or more. Furthermore, the thickness of the sealant film 70 is preferably 100 μm or less, and more preferably 80 μm or less.

[0084] The preferred mechanical properties of a single-layer sealant film 70 containing a propylene-ethylene block copolymer are described below. The tensile elongation of the sealant film 70 in the flow direction (MD) at 25°C is preferably 800% or more, more preferably 900% or more, and may be 1000% or more, or 1100% or more. Furthermore, the product of the tensile elongation (%) of the sealant film 70 in the flow direction (MD) and the thickness (μm) of the sealant film 70 is preferably 45000 or more, more preferably 50000 or more, 55000 or more, or 60000 or more. Furthermore, the tensile elongation of the sealant film 70 in the vertical direction (TD) at 25°C is preferably 1050% or more, and more preferably 1100% or less. Furthermore, the product of the tensile elongation (%) of the sealant film 70 in the vertical direction (TD) and the thickness (μm) of the sealant film 70 is preferably 53000 or more, and more preferably 60000 or more. The sealant film 70 has high tensile elongation, which helps to prevent the bag 10 from tearing due to impacts such as dropping.

[0085] Furthermore, the tensile modulus of the sealant film 70 in the flow direction (MD) at 25°C is preferably 670 MPa or less, and more preferably 650 MPa or less. Also, the product of the tensile modulus of the sealant film 70 in the flow direction (MD) (MPa) and the thickness of the sealant film 70 (μm) is preferably 38000 or less, and more preferably 35000 or less. Furthermore, the tensile modulus of the sealant film 70 in the vertical direction (TD) at 25°C is preferably 550 MPa or less, and more preferably 500 MPa or less. Also, the product of the tensile modulus of the sealant film 70 in the vertical direction (TD) (MPa) and the thickness of the sealant film 70 (μm) is preferably 30000 or less, and more preferably 25000 or less.

[0086] The tensile modulus and tensile elongation can be measured in accordance with JIS K7127. A tensile testing machine with a constant temperature chamber, model RTC-1310A, manufactured by Orientec Co., Ltd., can be used as the measuring instrument. In the bag 10 shown in Figure 1, the direction in which the upper part 11 and lower part 12 extend is the flow direction of the film constituting the bag 10, such as the sealant film 70, and the direction in which the side part 13 extends is the perpendicular direction of the film constituting the bag 10, such as the sealant film 70. Although not shown, the bag 10 may be constructed such that the direction in which the upper part 11 and lower part 12 extend is the perpendicular direction of the film, and the direction in which the side part 13 extends is the flow direction of the film.

[0087] (Other layers) The laminate 30 may further comprise layers not shown in Figure 3. Examples of these additional layers are described below.

[0088] The laminate 30 may further include a printed layer. The printed layer is a layer provided on the laminate 30 to display product information or add aesthetic appeal to the bag 10, and is printed on, for example, the first plastic film 40. The printed layer can represent letters, numbers, symbols, figures, pictures, etc. Gravure printing inks or flexographic printing inks can be used as materials for the printed layer. A specific example of a gravure printing ink is Finart manufactured by DIC Graphics Corporation.

[0089] Furthermore, the laminate 30 may further comprise a transparent gas barrier layer. The transparent gas barrier layer is formed on the surface of the plastic films 40, 50, and includes at least a transparent vapor-deposited layer made of a transparent inorganic material. The transparent gas barrier layer may further comprise a transparent gas barrier coating film formed on the surface of the transparent vapor-deposited layer.

[0090] The transparent vapor-deposited layer functions as a gas barrier layer that prevents the permeation of oxygen gas and water vapor. Two or more transparent vapor-deposited layers may be provided. If there are two or more transparent vapor-deposited layers, each may have the same composition or different compositions. Examples of methods for forming the transparent vapor-deposited layer include physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, or chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition, thermochemical vapor deposition, and photochemical vapor deposition. Specifically, the vapor-deposited layer can be formed on a deposition roller using a roller-type vapor deposition apparatus. Examples of inorganic materials constituting the transparent vapor-deposited layer include aluminum oxide and silicon oxide. The thickness of the transparent vapor-deposited layer is preferably 40 Å or more and 130 Å or less, more preferably 50 Å or more and 120 Å or less.

[0091] The transparent gas barrier coating film is a layer that functions as a layer that suppresses the permeation of oxygen gas and water vapor. The transparent gas barrier coating film 37 is of general formula R 1 n M(OR 2 ) m (However, in the formula, R 1 , R 2 The transparent gas barrier composition is obtained by polycondensing a polyvinyl alcohol resin and / or ethylene-vinyl alcohol copolymer as described above, in the presence of a sol-gel catalyst, acid, water, and an organic solvent. (where 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 valence of M.)

[0092] Furthermore, the layer configuration of the laminate 30 is not limited to those described above, as long as the hot seal strength can be kept below 15N. For example, the laminate 30 may consist of only one plastic film.

[0093] Layer structure of the lower film Next, the layer structure of the lower film 16 will be described.

[0094] The layer configuration of the lower film 16 is arbitrary, as long as it has an inner surface that can be bonded to the inner surface of the surface film 14 and the inner surface of the back film 15. For example, the laminate 30 described above may be used as the lower film 16, similar to the surface film 14 and the back film 15. Alternatively, a film whose inner surface is composed of a sealant layer and has a different configuration from the laminate 30 may be used as the lower film 16.

[0095] Manufacturing method of laminates Next, an example of a method for manufacturing the laminate 30 will be described.

[0096] First, the first stretched plastic film 40 and the second stretched plastic film 50 described above are prepared. Next, the first stretched plastic film 40 and the second stretched plastic film 50 are laminated together via a first adhesive layer 45 using a dry lamination method. Subsequently, the laminate containing the first stretched plastic film 40 and the second stretched plastic film 50 and the sealant film 70 are laminated together via a second adhesive layer 55 using a dry lamination method. This makes it possible to obtain a laminate 30 comprising the first stretched plastic film 40, the second stretched plastic film 50 and the sealant film 70.

[0097] Alternatively, the laminate 30 may be manufactured by first laminating the second stretched plastic film 50 and the sealant film 70 via a second adhesive layer 55 using a dry lamination method, and then laminating the first stretched plastic film 40 and the laminate containing the second stretched plastic film 50 and the sealant film 70 via a first adhesive layer 45 using a dry lamination method.

[0098] 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 evaporate the solvent. Subsequently, the two films are laminated via the dried adhesive composition. Then, the two laminated films are wound up and aged for 24 hours or more in an environment of, for example, 20°C or higher.

[0099] Bag manufacturing method Next, a method for manufacturing a bag 10 using the laminate 30 described above will be explained. First, a surface film 14 and a back film 15 made of the laminate 30 are prepared. A folded lower film 16 is then inserted between the surface film 14 and the back film 15. Subsequently, the inner surfaces of each film are heat-sealed to form seals such as a lower seal portion 12a, a side seal portion 13a, and a steam vent seal portion 20a. The conditions for the heat sealing process are set according to the material of the sealant film 70 so that the hot seal strength of the seal portion is 15N or less.

[0100] Next, the films joined together by heat sealing are cut into an appropriate shape to obtain the bag 10 shown in Figure 1. Then, the contents 18 are filled into the bag 10 through the opening 11b at the top 11. The contents 18 are, for example, cooked foods containing moisture, such as curry, stew, or soup. The contents 18 may also contain materials with a high oil content, such as meat, fish, and seasonings for them. In addition to food, items that can be heated by methods such as boiling can also be placed in the bag 10 as contents. After that, the top 11 is heat-sealed to form the top seal. In this way, a sealed bag 10 containing the contents 18 can be obtained, as shown in Figure 4. After that, sterilization treatments such as boiling or retorting are performed on the bag 10 containing the contents 18 as necessary.

[0101] In Figure 4, the symbol H1 represents the distance in the second direction D2 from the upper seal portion 11a to the center point C of the containment portion 17. The symbol H2 represents the shortest distance from the steam vent seal portion 20a to the center point C of the containment portion 17. In a Type 1 bag as shown in Figure 4, the ratio of distance H2 to distance H1 is, for example, 1.05 or more and 4.0 or less. By setting the distance H2 in this way, it is possible to suppress the upper seal portion 11a from peeling off before the steam vent seal portion 20a when the bag 10 is heated. The center point C of the containment portion 17 is defined as the midpoint of the line segment connecting the midpoint Y1 of the inner edge of the upper seal portion 11a and the midpoint Y2 of the inner edge of the lower seal portion 12a.

[0102] Method for measuring seal strength Next, a method for measuring the seal strength of the sealed portion of bag 10 will be described. The seal strength can be measured in accordance with JIS Z1707 7.5. As a measuring instrument, for example, a tensile testing machine with a constant temperature chamber, model RTC-1310A, manufactured by Orientec Co., Ltd., can be used.

[0103] First, a test specimen 90 is prepared to measure the seal strength of the sealed portion. For example, as shown by the dashed-dotted frame labeled V in Figure 4, a portion of the bag 10 including the side seal portion 13a is cut out from the surface film 14 and back film 15 to obtain a test specimen 90 extending along the first direction D1. The width W of the test specimen 90 in the second direction D2 perpendicular to the first direction D1 is 15 mm.

[0104] Figure 5 is a cross-sectional view showing the test specimen 90. The test specimen 90 includes a sealed portion 95, such as a side sealed portion, where the sealant film 70 of the surface film 14 and the sealant film 70 of the back film 15 are joined, and a non-sealed portion 96, where the sealant film 70 of the surface film 14 and the sealant film 70 of the back film 15 are not joined.

[0105] Figure 6 shows the process of measuring the seal strength using a test specimen 90. First, the surface film 14 and the back film 15 are gripped at the non-sealed portion 96 by the grips 91 and 92 of the measuring instrument, respectively. Then, the grips 91 and 92 are pulled at a speed of 300 mm / min in opposite directions perpendicular to the surface direction of the seal portion 95 of the test specimen 90, and the maximum value of the tensile stress (see Figure 7) is measured. Figure 7 shows the change in tensile stress with respect to the gap S.

[0106] For multiple test specimens 90, the maximum tensile stress can be measured, and the average value can be used as the seal strength. The distance S between the grips 91 and 92 at the start of tensioning is, for example, 20 mm, and the distance S between the grips 91 and 92 at the end of tensioning is, for example, 40 mm. When measuring the hot seal strength as described above, the measurement environment is, for example, a temperature of 100°C and a relative humidity of 50%. When measuring the room temperature seal strength as described above, the measurement environment is, for example, a temperature of 25°C and a relative humidity of 50%.

[0107] Method for measuring separation pressure Next, with reference to Figure 8, a method for measuring the peeling pressure of the steam vent seal portion 20a will be described. Figure 8 is a longitudinal cross-sectional view showing a bag 10 in which a sensor 81 for measuring the peeling pressure is provided in the housing portion 17.

[0108] First, prepare a bag 10 with a portion open, as shown in Figure 1 above. Next, install a pressure-measuring data logger sensor 81 inside the bag 10. For example, attach the sensor 81 to the inner surface of the bag 10. Then, fill the storage compartment 17 of the bag 10 with a predetermined amount of water, for example, 100 ml of water. After that, seal the bag 10 by forming a seal at the opening. As a data logger, for example, a PicoVACQ PT manufactured by TMI-ORION can be used. The PicoVACQ PT can measure temperature in addition to pressure.

[0109] Next, the water in the bag 10 is heated using a microwave oven or similar device while measuring the pressure in the storage section 17 at predetermined time intervals using the sensor 81. Any microwave oven with an output in the range of 500W to 1500W can be used. The time interval is, for example, 0.1 seconds or more and 10 seconds or less, for example, 1.0 second.

[0110] As water evaporates and the pressure in the containment section 17 increases, the steam vent seal section 20a begins to peel off. When the peeling of the steam vent seal section 20a progresses to the outer edge of the bag 10 and the containment section 17 communicates with the unsealed section 20b and the outside of the bag 10, the pressure in the containment section 17, as measured by the sensor 81, drops sharply. The pressure in the containment section 17 measured just before the pressure begins to drop sharply is recorded as the peeling pressure of the steam vent seal section 20a. The temperature of the containment section 17 just before the pressure begins to drop sharply is, for example, 80°C or higher and 120°C or lower.

[0111] Heating method for contents Next, an example of a method for heating the contents 18 contained in bag 10 will be described.

[0112] First, the bag 10 is placed inside the microwave oven with its bottom 12 facing downwards, allowing it to stand upright. Next, the contents are heated using the microwave oven. This raises the temperature of the contents 18, causing the moisture in the contents 18 to evaporate and increasing the pressure in the storage compartment 17.

[0113] When the pressure in the storage section 17 increases, the surface film 14 and the back film 15 bulge outward due to the force acting from the storage section 17. In this embodiment, the seal section is configured such that the hot seal strength is 15N or less. Therefore, the steam vent seal section 20a can be peeled off before the temperature of the contents 18 stored in the bag 10 becomes excessively high or the pressure of the contents 18 becomes excessively high. Consequently, it is possible to suppress the formation of holes or wrinkles in the laminate 30 of the bag 10 during heating.

[0114] It is possible to make various modifications to the embodiments described above. The following descriptions of modifications will be made with reference to the drawings as needed. In the following descriptions and the drawings used therein, parts that can be configured similarly to the embodiments described above will be given the same reference numerals as those used for the corresponding parts in the embodiments described above, and redundant explanations will be omitted. Furthermore, if it is clear that the effects and advantages obtained in the embodiments described above can also be obtained in the modifications, the explanation may be omitted.

[0115] (First variation of the bag) In the steam venting mechanism 20 of the above embodiment, an example was shown in which the unsealed portion 20b, which is isolated from the containment portion 17 by the steam venting seal portion 20a, extends to the outer edge of the bag 10. However, it is not limited to this, and as shown in Figure 9, the unsealed portion 20b may be surrounded by the steam venting seal portion 20a and the side seal portion 13a. In this case, the unsealed portion 20b has a through hole 20c that penetrates at least one of the surface film 14 or the back film 15. In this case, steam that flows from the containment portion 17 to the unsealed portion 20b through the peeled portion of the steam venting seal portion 20a escapes to the outside of the bag 10 through the through hole 20c. In the following description, a bag of the type in which the unsealed portion 20b of the steam venting mechanism 20 is surrounded by the steam venting seal portion 20a and the side seal portion 13a, as shown in Figure 9, will also be referred to as a Type 2 bag.

[0116] In the bag 10 shown in Figure 9, the non-seal portion 20b is located closer to the storage portion 17 than the side seal portion 13a. Therefore, when the width of the non-seal portion 20b in the first direction D1 is the same, the distance H2 from the steam vent seal portion 20a to the center point C in the Type 2 bag 10 of this modified example is shorter than the distance H2 from the steam vent seal portion 20a to the center point C in the Type 1 bag 10 shown in Figures 1 and 4. Therefore, when heating the contents of the bag 10 using a microwave oven or the like, force is more easily applied to the steam vent seal portion 20a, and the peeling pressure of the steam vent seal portion 20a tends to be lower. In the Type 2 bag as shown in Figure 9, the ratio of distance H2 to distance H1 is, for example, 1.05 or more and 5.0 or less.

[0117] In this modified example, the seal portion is configured such that the hot seal strength is 15N or less. Therefore, the steam vent seal portion 20a can be peeled off before the temperature of the contents 18 contained in the bag 10 becomes excessively high or the pressure of the contents 18 becomes excessively high. Consequently, it is possible to suppress the formation of holes or wrinkles in the laminate 30 of the bag 10 during heating.

[0118] (A second variation of the bag) In the above-described embodiment and the first modified example of the steam venting mechanism 20, an example was shown in which the steam venting seal portion 20a is connected to the side seal portion 13a. However, it is not limited to this, and as shown in Figure 10, the steam venting seal portion 20a may be spaced apart from the side seal portion 13a. In this case, a through hole 20c is formed in the unsealed portion 20b surrounded by the steam venting seal portion 20a, penetrating at least one of the surface film 14 or the back film 15. Similar to the first modified example, steam that flows from the containment portion 17 to the unsealed portion 20b through the peeled portion of the steam venting seal portion 20a escapes to the outside of the bag 10 through the through hole 20c. In the following description, a bag of the type in which the steam venting seal portion 20a of the steam venting mechanism 20 is spaced apart from the side seal portion 13a, as shown in Figure 10, will also be referred to as a Type 3 bag.

[0119] In the bag 10 shown in Figure 10, the non-seal portion 20b is spaced apart from the side seal portion 13a. Therefore, when the width of the non-seal portion 20b in the first direction D1 is the same, the distance H2 from the steam vent seal portion 20a to the center point C in the Type 3 bag 10 of this modified example is shorter than the distance H2 from the steam vent seal portion 20a to the center point C in the Type 2 bag 10 shown in Figure 9. Therefore, when heating the contents of the bag 10 using a microwave oven or the like, more force is more easily applied to the steam vent seal portion 20a, and the peeling pressure of the steam vent seal portion 20a tends to be lower. In the Type 3 bag as shown in Figure 10, the ratio of distance H2 to distance H1 is, for example, 1.05 or more and 6.0 or less.

[0120] In this modified example, the seal portion is configured such that the hot seal strength is 15N or less. Therefore, the steam vent seal portion 20a can be peeled off before the temperature of the contents 18 contained in the bag 10 becomes excessively high or the pressure of the contents 18 becomes excessively high. Consequently, it is possible to suppress the formation of holes or wrinkles in the laminate 30 of the bag 10 during heating.

[0121] Furthermore, if the distance H2 from the steam vent seal portion 20a to the center point C becomes shorter, force is more easily applied to the steam vent seal portion 20a even when the contents of the bag 10 are not being heated using a microwave oven or the like. For example, when transporting the bags 10 in a stacked state, force is more easily applied to the steam vent seal portion 20a, making unintended peeling of the steam vent seal portion 20a more likely. In other words, the shorter the distance H2 from the steam vent seal portion 20a to the center point C, the lower the load-bearing capacity of the bag 10. Therefore, in terms of the load-bearing capacity of the bag 10, the type 2 bag 10 is preferable to the type 3 bag 10, and the type 1 bag 10 is even more preferable.

[0122] (Third variation of the bag) Figure 11 is a front view showing a modified example of the bag 10. As shown in Figure 11, the surface film 14 may include a gusset portion 14a where the inner surfaces of the surface films 14 are partially overlapped. The gusset portion 14a can be formed, for example, by folding a single surface film 14 at a folded portion 14f to form pleats. Alternatively, the gusset portion 14a may be formed by overlapping parts of two surface films 14.

[0123] The gable portion 14a has a gable seal portion 14b that extends from one side seal portion 13a to the other side seal portion 13a. In this case, the steam venting mechanism 20 has, for example, a steam venting seal portion 20a that protrudes from the gable seal portion 14b toward the housing portion 17, an unsealed portion 20b surrounded by the steam venting seal portion 20a and the gable seal portion 14b, and a through hole 20c formed in the surface film 14 in the unsealed portion 20b.

[0124] In this modified example as well, when the pressure in the containment section 17 increases, the steam vent seal section 20a peels off, allowing the containment section 17 and the unsealed section 20b to communicate. Steam that flows from the containment section 17 to the unsealed section 20b through the peeled portion of the steam vent seal section 20a escapes to the outside of the bag 10 through the through-hole 20c. In the following description, a bag of the type in which the steam vent mechanism 20 is provided in the gable section 14a, as shown in Figure 11, will also be referred to as a Type 4 bag. In a Type 4 bag as shown in Figure 11, the ratio of distance H2 to distance H1 is, for example, 1.10 or more and 6.0 or less.

[0125] In this modified example, the seal portion is configured such that the hot seal strength is 15N or less. Therefore, the steam vent seal portion 20a can be peeled off before the temperature of the contents 18 contained in the bag 10 becomes excessively high or the pressure of the contents 18 becomes excessively high. Consequently, it is possible to suppress the formation of holes or wrinkles in the laminate 30 of the bag 10 during heating.

[0126] (Other aspects) Another aspect of the present invention is a bag having a storage compartment, comprising a laminate including a sealant film consisting of a single layer located on the inner surface of the bag and at least one plastic film located on the outer surface side of the sealant film, and a sealing portion that joins the inner surfaces of a pair of the laminates, wherein the product of the tensile elongation (%) of the sealant film in the flow direction and the thickness (μm) of the sealant film is 45,000 or more, and the sealing portion comprises an outer edge sealing portion located on the outer edge of the bag and a vapor vent sealing portion located on the center point side of the storage compartment than the outer edge sealing portion and peeling off due to an increase in pressure in the storage compartment, and the sealing strength of the sealing portion at 100°C is 15N or less.

[0127] In another embodiment of the present invention, the peeling pressure of the steam vent seal portion may be 130 kPa or less.

[0128] In another embodiment of the present invention, the seal strength of the seal portion at 100°C may be 10N or less.

[0129] In a bag according to another aspect of the present invention, the peeling pressure of the steam vent seal portion may be 120 kPa or less.

[0130] In a bag according to another aspect of the present invention, the sealant film may contain a propylene-ethylene block copolymer as the main component and an α-olefin copolymer.

[0131] A bag according to another aspect of the present invention further comprises an unsealed portion isolated from the containment portion by the steam venting seal portion, The unsealed portion may extend from a position closer to the center point of the storage portion than the outer edge sealed portion to the outer edge of the bag. [Examples]

[0132] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention.

[0133] (Example A1) As the first plastic film 40, a stretched PET film with a thickness of 12 μm was prepared. As the second plastic film 50, a stretched nylon film with a thickness of 15 μm was prepared. As the sealant film 70, an unstretched polypropylene film ZK500 manufactured by Toray Film Processing Co., Ltd. was prepared. ZK500 contains the aforementioned propylene-ethylene block copolymer and elastomer. The thickness of the sealant film 70 was 60 μm.

[0134] ZK500 has a higher tensile elongation compared to general unoriented polypropylene films. Specifically, the tensile elongation of ZK500 in the flow direction (MD) is 1180% when the thickness is 50 μm and 1100% when the thickness is 60 μm. In the perpendicular direction (TD), the tensile elongation of ZK500 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 flow direction is 59000 when the thickness is 50 μm and 66000 when the thickness is 60 μm. In the perpendicular direction, the product of the tensile elongation (%) and thickness (μm) of ZK500 is 62000 when the thickness is 50 μm and 69000 when the thickness is 60 μm.

[0135] Furthermore, ZK500 has a lower tensile modulus compared to general unoriented polypropylene films. Specifically, the tensile modulus of ZK500 in the flow direction (MD) is 640 MPa when the thickness is 50 μm and 550 MPa when the thickness is 60 μm. 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 flow direction is 32,000 when the thickness is 50 μm and 33,000 when the thickness is 60 μm. The product of the tensile modulus (MPa) and thickness (μm) of ZK500 in the perpendicular direction is 24,000 when the thickness is 50 μm and 35,000 when the thickness is 60 μm.

[0136] Next, a laminate 30 was fabricated by laminating the first plastic film 40, the second plastic film 50, and the sealant film 70 using the dry lamination method. For the first adhesive layer 45 and the second adhesive layer 55, a two-component polyurethane adhesive (main component: RU-40, curing agent: H-4) manufactured by Rock Paint Co., Ltd. was used. The main component RU-40 is a polyester polyol. The thickness of the first adhesive layer 45 and the second adhesive layer 55 was 3.5 μm.

[0137] Next, the inner surfaces 30x of the two laminated bodies 30 were partially heat-sealed to form a sealed area. The temperature during the heat-sealing process (hereinafter also referred to as the sealing temperature) was 170°C. Subsequently, the portion of the two laminated bodies 30 including the sealed area was cut out to prepare the test piece 90 described above for measuring the seal strength. After that, the room-temperature seal strength of the laminated bodies 30 was measured in accordance with JIS 1707 7.5, under conditions of 25°C and 50% relative humidity. The measuring instrument used was the RTC-1310A tensile testing machine with a constant temperature chamber manufactured by Orientec Co., Ltd.

[0138] In this embodiment, no heat simulating retort treatment or boiling treatment was applied to the test specimen 90 before measuring the seal strength. In the following description, the state of the laminate 30 and test specimen 90 before heat simulating retort treatment or boiling treatment is applied will also be referred to as the state before retort treatment.

[0139] Furthermore, 90 test specimens prepared at different sealing temperatures were created, and their room-temperature seal strength was measured. Here, 90 test specimens were prepared with different sealing temperatures ranging from 175°C to 220°C in 5°C increments. The results are shown in the "Room-Temperature Seal Strength (Before Retort Treatment)" row in Figure 12. Figure 13 shows a graph obtained by plotting the seal strength against the sealing temperature.

[0140] (Example A2) Except for preparing the test specimen 90 using a laminate 30 that had been subjected to heat simulating retort processing, the room-temperature seal strength of the test specimen 90 was measured in the same manner as in Example A1. The results are shown in the row "Room-temperature seal strength (after retort processing)" in Figure 12. Figure 13 shows a graph obtained by plotting the seal strength against the seal temperature.

[0141] The following treatments were applied to the laminate 30 that constitutes the test specimen 90. ·Heating temperature: 121℃ • Heating time: 40 minutes • Pressure: 0.2 MPa

[0142] (Example A3) The hot seal strength of each test piece 90 was measured in the same manner as in Example A1, except that the seal strength was measured in an environment with a temperature of 100°C and a relative humidity of 50%. The results are shown in the row "Hot seal strength (before retort treatment)" in Figure 12. Figure 13 shows a graph obtained by plotting the seal strength against the seal temperature.

[0143] (Example A4) Except for preparing the test specimen 90 using a laminate 30 that had been subjected to heat simulating retort processing, the hot seal strength of the test specimen 90 was measured in the same manner as in Example A2. The results are shown in the row "Hot seal strength (after retort processing)" in Figure 12. Figure 13 shows a graph obtained by plotting the seal strength against the seal temperature.

[0144] As shown in Figures 12 and 13, there was a tendency for the room-temperature seal strength to increase as the sealing temperature increased. In particular, when the room-temperature seal strength after retort processing was less than 40 N, the dependence of the room-temperature seal strength on the sealing temperature was large. Therefore, it can be said that it is preferable for the room-temperature seal strength after retort processing to be 40 N or higher. This can suppress variations in room-temperature seal strength after retort processing caused by variations in sealing temperature.

[0145] The hot seal strength also tended to increase with increasing seal temperature, or it showed less dependence on seal temperature compared to the room temperature seal strength.

[0146] As shown in Figures 12 and 13, the room-temperature seal strength of the test specimen 90 after retort treatment tended to be lower than that of the test specimen 90 before retort treatment. The difference between the room-temperature seal strength of the test specimen 90 after retort treatment and the room-temperature seal strength of the test specimen 90 before retort treatment was in the range of 4N to 10N. On the other hand, the difference between the hot seal strength of the test specimen 90 after retort treatment and the hot seal strength of the test specimen 90 before retort treatment was smaller than that of the room-temperature seal strength, being 2N or less.

[0147] (Example B1) As the first plastic film 40, a stretched PET film with a thickness of 12 μm was prepared. As the second plastic film 50, a stretched nylon film with a thickness of 15 μm was prepared. As the sealant film 70, an unstretched polypropylene film ZK500 manufactured by Toray Film Processing Co., Ltd. was prepared. ZK500 contains the aforementioned propylene-ethylene block copolymer and elastomer. The thickness of the sealant film 70 was 60 μm.

[0148] Next, a laminate 30 was fabricated by laminating the first plastic film 40, the second plastic film 50, and the sealant film 70 using the dry lamination method. For the first adhesive layer 45 and the second adhesive layer 55, a two-component polyurethane adhesive (main component: RU-40, curing agent: H-4) manufactured by Rock Paint Co., Ltd. was used. The main component RU-40 is a polyester polyol. The thickness of the first adhesive layer 45 and the second adhesive layer 55 was 3.5 μm.

[0149] [Evaluation of seal strength] Next, the inner surfaces 30x of the two laminated bodies 30 were heat-sealed at the first sealing temperature to form a sealed portion. Subsequently, the portion of the two laminated bodies 30 including the sealed portion was cut out to prepare a test piece 90 for measuring the seal strength. Here, multiple test pieces 90 were prepared, both before retort treatment as in Example A1 described above, and after retort treatment as in Example A2 described above. Next, the room temperature seal strength and hot seal strength were measured using the test piece 90 before retort treatment. As a result, the room temperature seal strength and hot seal strength were 62 N and 9.2 N, respectively. Furthermore, the room temperature seal strength and hot seal strength were measured using the test piece 90 after retort treatment. As a result, the room temperature seal strength and hot seal strength were 58 N and 8.5 N, respectively.

[0150] [Evaluation of peeling pressure] Next, a bag 10 equipped with a type 1 steam venting mechanism 20, as shown in Figures 1 and 4, was fabricated using the laminate 30. The height S1 of the bag 10 was 145 mm, and the width S2 was 140 mm. The height S3 of the folded lower film 16, i.e., the height from the bottom end of the bag 10 to the folded portion 16f, was 40 mm. In the following description, the bag 10 with a height S1 of 145 mm, a width S2 of 140 mm, and a height S3 of 40 mm will also be referred to as the S-size bag 10. Next, 100 ml of water was filled into the bag 10, and the sensor 81 of the data logger was placed inside the bag 10. The upper part 11 of the bag 10 was then heat-sealed to form the upper seal portion 11a.

[0151] Next, while measuring the pressure in the containment section 17 every second using the sensor 81, the water inside the bag 10 was heated using a 500W microwave oven. A Panasonic NE-MS261 microwave oven was used as the 500W microwave oven. As the pressure in the containment section 17 increased and the peeling of the steam vent seal section 20a reached the outer edge of the bag 10, steam from the containment section 17 began to be discharged to the outside of the bag 10, and the pressure in the containment section 17 dropped sharply. The peeling pressure, which is the pressure in the containment section 17 just before the pressure began to drop sharply, was 116.1 kPa.

[0152] [Evaluation of heat resistance] Similar to the evaluation of peel pressure, an S-sized bag 10 was fabricated using the laminate 30. Next, 100g of oil-rich contents were filled into the S-sized bag 10, and the top 11 was heat-sealed to form the top seal portion 11a.

[0153] Subsequently, the bag 10 containing the contents was heated for 2 minutes using a 500W microwave oven to check whether or not damage occurred to the laminated material 30 that makes up the bag 10. As a result, no holes or wrinkles were formed in the laminated material 30 of the bag 10 after heating.

[0154] (Example B2) A Type 1 bag 10 was fabricated using the same laminate 30 as in Example B1. The height S1 of the bag 10 was 145 mm, the width S2 was 150 mm, and the height S3 of the folded lower film 16 was 43 mm. In the following description, a bag 10 with a height S1 of 145 mm, a width S2 of 150 mm, and a height S3 of 43 mm will also be referred to as a size M bag 10.

[0155] Next, as in Example B1, 100 ml of water was filled into the bag 10, and the top 11 was heat-sealed to form the top seal. Then, as in Example B1, the water inside the bag 10 was heated using a 500W microwave oven while measuring the pressure in the containment section 17 using the sensor 81, and the peeling pressure was measured. As a result, the peeling pressure was 113.5 kPa.

[0156] Furthermore, similar to Example B1, 100g of oil-rich contents were filled into a medium-sized bag 10, and the top 11 was heat-sealed to form the top seal portion 11a. Then, the bag 10 containing the contents was heated for 2 minutes using a 500W microwave oven to check whether or not damage occurred to the laminate 30 that makes up the bag 10. As a result, no holes or wrinkles were formed in the laminate 30 of the bag 10 after heating.

[0157] (Example B3) The seal strength was measured using a test specimen 90 prepared by heat-sealing the same laminate 30 as in Example B1 at a second seal temperature lower than the first seal temperature described above. Before retort treatment, the room temperature seal strength and hot seal strength of the test specimen 90 were 55 N and 7.6 N, respectively. After retort treatment, the room temperature seal strength and hot seal strength of the test specimen 90 were 50 N and 7.2 N, respectively.

[0158] Furthermore, a Type 1 bag 10 of size S was prepared in the same manner as in Example B1, except that the sealing temperature was set to the second sealing temperature described above. Then, as in Example B1, the water inside the bag 10 was heated using a 500W microwave oven while measuring the pressure in the containment section 17 using a sensor 81, and the peeling pressure was measured. As a result, the peeling pressure was 110kPa.

[0159] Furthermore, except that the sealing temperature was the second sealing temperature described above, 100g of oil-rich contents were filled into a Type 1 bag 10 of size S, and the top 11 was heat-sealed to form the top seal portion 11a, in the same manner as in Example B1. Then, the bag 10 containing the contents was heated for 2 minutes using a microwave oven with a power output of 500W to check whether or not damage occurred to the laminate 30 that makes up the bag 10. As a result, no holes or wrinkles were formed in the laminate 30 of the bag 10 after heating.

[0160] (Example B4) A Type 1 bag 10 of size M was prepared in the same manner as in Example B2, except that the heat sealing temperature was set to the second sealing temperature, as in Example B3. Then, as in Example B1, the water inside the bag 10 was heated using a 500W microwave oven while measuring the pressure in the storage compartment 17 using a sensor 81, and the peel pressure was measured. As a result, the peel pressure was 110.5 kPa.

[0161] Furthermore, in the same manner as in Example B2, except that the heat sealing temperature was set to the second sealing temperature, as in Example B3, 100g of oil-rich contents were filled into a medium-sized bag 10, and the top 11 was heat-sealed to form the top seal portion 11a. Then, the bag 10 containing the contents was heated for 2 minutes using a 500W microwave oven to check whether or not damage occurred to the laminate 30 constituting the bag 10. As a result, no holes or wrinkles were formed in the laminate 30 of the bag 10 after heating.

[0162] (Example B5) A Type 1 bag 10 of the same S size as in Example B3 was fabricated by heat-sealing the same laminate 30 as in Example B3 at the second sealing temperature described above. Subsequently, while measuring the pressure in the containment section 17 using a sensor 81, the water inside the bag 10 was heated using a 1600W microwave oven, and the peel pressure was measured. A Panasonic NE-1801 microwave oven was used as the 1600W microwave oven. As a result, the peel pressure was 117kPa.

[0163] Furthermore, by heat-sealing the same laminate 30 as in Example B3 at the second sealing temperature described above, a Type 1 bag 10 of size S, similar to that in Example B3, was produced. Next, 100g of the contents containing a high amount of oil was filled into the inside of a Type 1 bag 10 of size S, and the top 11 was heat-sealed to form the top seal portion 11a. Then, the water inside the bag 10 was heated for 40 seconds using a microwave oven with an output of 1600W to check whether or not damage occurred to the laminated material 30 that makes up the bag 10. As a result, no holes or wrinkles were formed in the laminated material 30 of the bag 10 after heating.

[0164] (Example B6) A Type 1 bag 10 of size M, similar to that in Example B4, was fabricated by heat-sealing the same laminate 30 as in Example B4 at a second sealing temperature. Subsequently, while measuring the pressure in the containment section 17 using a sensor 81, the water inside the bag 10 was heated using a 1600W microwave oven, similar to that in Example B5, and the peel pressure was measured. As a result, the peel pressure was 117.9 kPa.

[0165] Furthermore, by heat-sealing the same laminate 30 as in Example B4 at the second sealing temperature described above, a Type 1 bag 10 of size M, similar to that in Example B4, was produced. Next, 100g of the contents containing a high amount of oil was filled into a medium-sized Type 1 bag 10, and the top 11 was heat-sealed to form the top seal portion 11a. Then, the water inside the bag 10 was heated for 40 seconds using a 1600W microwave oven to check whether or not damage occurred to the laminated material 30 that makes up the bag 10. As a result, no holes or wrinkles were formed in the laminated material 30 of the bag 10 after heating.

[0166] (Example B7) As the first plastic film 40, a stretched PET film with a thickness of 12 μm was prepared. Also, as the second plastic film 50, a stretched PET film with a thickness of 12 μm was prepared. Furthermore, as the sealant film 70, an unstretched polypropylene film ZK500 manufactured by Toray Film Processing Co., Ltd. was prepared. The thickness of the sealant film 70 was 60 μm.

[0167] Next, using a test specimen 90 prepared by partially heat-sealing the inner surfaces 30x of two laminated bodies 30, the seal strength between the laminated bodies 30 was measured in the same manner as in Example B1. Before retort treatment, the room temperature seal strength and hot seal strength of the test specimen 90 were 55 N and 7.6 N, respectively. After retort treatment, the room temperature seal strength and hot seal strength of the test specimen 90 were 50 N and 7.2 N, respectively.

[0168] Furthermore, a Type 1 bag 10 of size M was prepared in the same manner as in Example B1. Then, in the same manner as in Example B5, the water inside the bag 10 was heated using a 1600W microwave oven while measuring the pressure in the containment section 17 using a sensor 81, and the peeling pressure was measured. As a result, the peeling pressure was 114.8 kPa.

[0169] Furthermore, similar to the evaluation of peel pressure, a medium-sized bag 10 was fabricated using the laminate 30. Next, 100g of contents containing a high amount of oil was filled into the bag 10, and the top 11 was heat-sealed to form the top seal portion 11a. Then, the bag 10 containing the contents was heated for 40 seconds using a microwave oven with an output of 1600W to check whether or not damage occurred to the laminate 30 constituting the bag 10. As a result, no holes or wrinkles were formed in the laminate 30 of the bag 10 after heating.

[0170] (Example B8) The seal strength was measured using a test specimen 90 prepared by heat-sealing the same laminate 30 as in Example B1 at a third seal temperature higher than the first seal temperature described above. Before retort treatment, the room temperature seal strength and hot seal strength of the test specimen 90 were 65 N and 11.5 N, respectively. After retort treatment, the room temperature seal strength and hot seal strength of the test specimen 90 were 60 N and 10.8 N, respectively.

[0171] Furthermore, a Type 1 bag 10 of size S was prepared in the same manner as in Example B1, except that the sealing temperature was set to the third sealing temperature described above. Then, as in Example B1, the water inside the bag 10 was heated using a 500W microwave oven while measuring the pressure in the containment section 17 using a sensor 81, and the peeling pressure was measured. As a result, the peeling pressure was 112.5 kPa.

[0172] Furthermore, except that the sealing temperature was set to the third sealing temperature described above, 100g of oil-rich contents were filled into a Type 1 bag 10 of size S, and the top 11 was heat-sealed to form the top seal portion 11a, in the same manner as in Example B1. Then, the bag 10 containing the contents was heated for 2 minutes using a microwave oven with an output of 500W to check whether or not damage occurred to the laminate 30 that makes up the bag 10. As a result, wrinkles were formed in the laminate 30 of the bag 10 after heating, but no holes were formed.

[0173] (Comparative Example B1) A stretched PET film with a thickness of 12 μm was prepared as the first plastic film 40. A stretched PET film with a thickness of 12 μm was also prepared as the second plastic film 50. Furthermore, an unstretched polypropylene film ZK207 manufactured by Toray Film Processing Co., Ltd. was prepared as the sealant film 70. The thickness of the sealant film 70 was 70 μm.

[0174] ZK207 has a lower tensile elongation compared to ZK500. Specifically, the tensile elongation of ZK207 in the flow direction (MD) is 790% when the thickness is 50 μm and 730% when the thickness is 60 μm. In the perpendicular direction (TD), the tensile elongation of ZK207 is 1020% when the thickness is 50 μm and 870% when the thickness is 60 μm. Therefore, the product of the tensile elongation (%) and thickness (μm) of ZK207 in the flow direction is 39500 when the thickness is 50 μm and 43800 when the thickness is 60 μm. In the perpendicular direction, the product of the tensile elongation (%) and thickness (μm) of ZK207 is 51000 when the thickness is 50 μm and 52200 when the thickness is 60 μm.

[0175] Furthermore, ZK207 has a higher tensile modulus than ZK500. Specifically, the tensile modulus of ZK207 in the flow direction (MD) is 780 MPa when the thickness is 50 μm and 680 MPa when the thickness is 60 μm. In the vertical direction (TD), the tensile modulus of ZK207 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 flow direction is 39000 when the thickness is 50 μm and 40800 when the thickness is 60 μm. In the vertical direction, the product of the tensile modulus (MPa) and thickness (μm) of ZK207 is 31500 when the thickness is 50 μm and 33600 when the thickness is 60 μm.

[0176] Next, using a test specimen 90 prepared by heat-sealing the inner surfaces 30x of two laminates 30, the seal strength between the laminates 30 was measured in the same manner as in Example B1. Before retort treatment, the room temperature seal strength and hot seal strength of the test specimen 90 were 65 N and 23 N, respectively. After retort treatment, the room temperature seal strength and hot seal strength of the test specimen 90 were 60 N and 23 N, respectively.

[0177] Furthermore, a Type 1 bag 10 of size S was prepared in the same manner as in Example B1. Then, in the same manner as in Example B1, the water inside the bag 10 was heated using a 500W microwave oven while measuring the pressure in the containment section 17 using a sensor 81, and the peeling pressure was measured. As a result, the peeling pressure was 130.7 kPa.

[0178] Furthermore, similar to the evaluation of peel pressure, a Type 1 bag 10 of size S was fabricated using the laminate 30. Next, 100g of contents containing a large amount of oil was filled into the inside of the size S bag 10, and the top 11 was heat-sealed to form the top seal portion 11a. Then, the bag 10 containing the contents was heated for 2 minutes using a microwave oven with an output of 500W to check whether or not damage occurred to the laminate 30 that makes up the bag 10. As a result, holes and wrinkles were formed in the laminate 30 of the bag 10 after heating.

[0179] (Comparative example B2) A Type 1 bag 10 of size M was prepared using the same laminate 30 as in Comparative Example B1. Then, as in Example B1, the water inside the bag 10 was heated using a 500W microwave oven while measuring the pressure in the containment section 17 using a sensor 81, and the peel pressure was measured. As a result, the peel pressure was 132.5 kPa.

[0180] Furthermore, similar to the evaluation of peel pressure, a medium-sized Type 1 bag 10 was fabricated using the laminate 30. Next, 100g of contents containing a high amount of oil was filled into the medium-sized bag 10, and the top 11 was heat-sealed to form the top seal portion 11a. Then, the bag 10 containing the contents was heated for 2 minutes using a 500W microwave oven to check whether or not damage occurred to the laminate 30 constituting the bag 10. As a result, holes and wrinkles were formed in the laminate 30 of the bag 10 after heating.

[0181] (Example B9) Using the same laminate 30 as in Example B1, a Type 2 bag 10 of size S was prepared. Next, as in Example B1, 100 ml of water was filled into the bag 10, and the top 11 was heat-sealed to form the top seal. Then, as in Example B1, the water inside the bag 10 was heated using a 500W microwave oven while measuring the pressure in the containment section 17 using a sensor 81, and the peel pressure was measured. As a result, the peel pressure was 110.8 kPa.

[0182] Furthermore, similar to the evaluation of peel pressure, a Type 2 bag 10 of size S was fabricated using the laminate 30. Next, 100g of contents containing a large amount of oil was filled into the bag 10, and the top 11 was heat-sealed to form the top seal portion 11a. Then, the bag 10 containing the contents was heated for 2 minutes using a 500W microwave oven to check whether or not damage occurred to the laminate 30 constituting the bag 10. As a result, no holes or wrinkles were formed in the laminate 30 of the bag 10 after heating.

[0183] (Example B10) Using the same laminate 30 as in Example B1, a Type 3 bag 10 of size S was prepared. Next, as in Example B1, 100 ml of water was filled into the bag 10, and the top 11 was heat-sealed to form the top seal. Then, as in Example B1, the water inside the bag 10 was heated using a 500W microwave oven while measuring the pressure in the containment section 17 using a sensor 81, and the peel pressure was measured. As a result, the peel pressure was 108.9 kPa.

[0184] Furthermore, similar to the evaluation of peel pressure, a Type 3 bag 10 of size S was fabricated using the laminate 30. Next, 100g of contents containing a large amount of oil was filled into the bag 10, and the top 11 was heat-sealed to form the top seal portion 11a. Then, the bag 10 containing the contents was heated for 2 minutes using a microwave oven with an output of 500W to check whether or not damage occurred to the laminate 30 constituting the bag 10. As a result, no holes or wrinkles were formed in the laminate 30 of the bag 10 after heating.

[0185] Figure 14 summarizes the layer structure, seal strength measurement results, peel pressure measurement results, and heat resistance evaluation results of the laminates for Examples B1-B10 and Comparative Examples B1-B2. In Figure 14, the "Layer Structure" column lists the components of the laminate from top to bottom, starting with the outermost layer. In addition, in the "heat resistance" column, "great" was written if no holes or wrinkles were formed in the laminate 30, "good" was written if wrinkles were formed in the laminate 30 but no holes were formed, and "bad" was written if both holes and wrinkles were formed in the laminate 30.

[0186] As can be seen from the comparison between Examples B1-B10 and Comparative Examples B1-B2, by using unstretched polypropylene film ZK500 manufactured by Toray Film Processing Co., Ltd. as the sealant film 70, the hot seal strength of the sealed portion after retort processing could be reduced to 15N or less. This made it possible to reduce the peeling pressure when the bag 10 is heated to 130kPa or less. This prevented holes from forming in the laminate 30 of the bag 10 during heating. Furthermore, by adjusting the sealing temperature so that the hot seal strength of the sealed portion after retort processing is 10N or less, the peeling pressure when the bag 10 is heated could be reduced to 120kPa or less. This prevented holes from forming in the laminate 30 of the bag 10 and prevented wrinkles from forming in the laminate 30 during heating. [Explanation of symbols]

[0187] 10 bags 11 Top 11a Upper seal section 12 Lower part 12a Lower seal section 13 Side 13a Side seal portion 14 Surface film 15 Backside film 16 Lower film 17. Detention Unit 18 Contents 20. Steam venting mechanism 20a Steam vent seal section 30-layer structure 40. First Plastic Film 45. First adhesive layer 50 Second Plastic Film 55 Second adhesive layer 70 Sealant Film 81 Sensors

Claims

[Claim 1] A bag having a storage compartment, A laminate comprising a sealant film located on the inner surface of the bag and consisting of a single layer, and at least one plastic film located on the outer surface of the sealant film, It comprises a sealing portion that joins the inner surfaces of a pair of laminates, The product of the tensile elongation (%) of the sealant film in the flow direction and the thickness (μm) of the sealant film is 45,000 or more. The sealing portion comprises an outer edge sealing portion located at the outer edge of the bag, and a steam vent sealing portion located closer to the center point of the containment portion than the outer edge sealing portion, which peels off when the pressure in the containment portion increases. The bag further comprises an unsealed portion isolated from the containment portion by the steam vent seal portion, The unsealed portion extends from a position closer to the center point of the storage portion than the outer edge sealed portion to the outer edge of the bag. The sealing strength of the seal portion at 100°C is 15N or less. A bag in which the peeling pressure of the steam vent seal portion is 130 kPa or less.

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