bag

Abstract

To suppress a laminate which constitutes a bag from having damage such as a hole and a wrinkle.SOLUTION: A bag which has a storage part comprises: a laminate including a sealant film located on an inner surface of the bag and at least one plastic film positioned more on an outer surface side than the sealant film; and a seal part joining inner surfaces of the pair of laminates together. The seal part has an outer edge seal part positioned at an outer edge of the bag, and a steam release seal part positioned more on a center point side of the storage part than the outer edge seal part, and peeling off as the pressure in the storage part rises. The steam release seal part peels off when the pressure in the storage part is 130 kPa or lower.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a bag having a vapor release seal that peels upon an increase in internal pressure. [Background technology]

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

[0003] However, when the contents stored in a sealed bag are heated in a microwave oven, the moisture in the contents evaporates as the bag is heated, causing the pressure in the storage section to increase. If the pressure in the storage section of the bag increases, the bag may burst, causing the contents to scatter and soil the microwave oven. In consideration of this problem, for example, Patent Document 1 proposes providing a mechanism for automatically connecting the storage section to the outside when the pressure in the storage section increases, thereby releasing the steam in the storage section to the outside. The mechanism includes a steam release seal that peels off when the pressure in the storage section increases. [Prior art documents] [Patent documents]

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

[0005] As a result of extensive research, the inventors of the present invention found that in conventional bags, the pressure and temperature in the storage section can become too high when the steam release seal is peeled off, which can cause damage such as holes and wrinkles in the laminate that makes up the bag.

[0006] An object of the present invention is to provide a bag that can effectively solve such problems. [Means for solving the problem]

[0007] The present invention is a bag having a storage section, comprising a laminate including a sealant film 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 section joining the inner surfaces of the pair of laminates, wherein the sealing section has an outer edge seal section located on the outer edge of the bag, and a steam release seal section located closer to the center point of the storage section than the outer edge seal section and which peels off due to an increase in pressure in the storage section, and the steam release seal section peels off when the pressure in the storage section is 130 kPa or less.

[0008] A bag according to the invention may comprise a non-sealed portion separated from the container by the steam release seal and extending to an outer edge of the bag.

[0009] In the bag according to the present invention, the sealant film may have a tensile elongation (%) of 800% or more in the machine direction, and a tensile elongation (%) of the sealant film in the perpendicular direction of the machine direction may be 1,050% or more.

[0010] In the bag according to the present invention, the product of the tensile elongation (%) of the sealant film in the machine direction and the thickness (μm) of the sealant film may be 45,000 or more, and the product of the tensile elongation (%) of the sealant film in the vertical direction and the thickness (μm) of the sealant film may be 53,000 or more.

[0011] In the bag according to the present invention, the sealant film may contain a propylene-ethylene block copolymer and an elastomer. Effect of the Invention

[0012] According to the present invention, damage such as holes and wrinkles can be prevented from occurring in the laminate that constitutes the bag. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a front view showing a bag according to the embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view showing the bag shown in FIG. 1 as viewed along line II-II. [Diagram 3] FIG. 2 is a cross-sectional view showing an example of a layer structure of a laminate constituting a bag. [Figure 4] FIG. 2 is a front view showing the bag with the top sealed. [Diagram 5] FIG. 11 is a diagram showing an example of a method for measuring the pressure in the container. [Figure 6] FIG. 13 is a front view showing a modified example of the bag. [Figure 7] FIG. 13 is a front view showing a modified example of the bag. [Figure 8] FIG. 2 is a diagram showing an example of a method for measuring seal strength. [Figure 9] FIG. 2 is a diagram showing an example of a method for measuring seal strength. [Figure 10] FIG. 13 is a graph showing the change in tensile stress with respect to the distance between a pair of grippers that pull a laminated film to measure seal strength. [Figure 11] FIG. 1 is a diagram showing the evaluation results of Examples A1 to A14 and Comparative Examples A1 to A2. [Figure 12A] 13A and 13B are diagrams illustrating another example of a method for measuring the pressure in the container. [Figure 12B] 13A and 13B are diagrams illustrating another example of a method for measuring the pressure in the container. [Figure 12C] 13A and 13B are diagrams illustrating another example of a method for measuring the pressure in the container. [Figure 12D]13A and 13B are diagrams illustrating another example of a method for measuring the pressure in the container. [Figure 13] FIG. 13 is a front view showing a modified example of the bag. [Figure 14] FIG. 2 is a front view showing a bag in the embodiment. [Figure 15] FIG. 1 is a diagram showing the evaluation results of Examples B1 to B3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

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

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

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

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

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

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

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

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

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

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

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

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

[0027] The steam release seal portion 20a of the steam release mechanism 20 has a shape that is easily peeled off as the pressure in the storage section 17 increases. For example, the steam release seal portion 20a has a shape that protrudes from the side seal portion 13a toward the inside of the bag 10. This allows the force applied to the steam release seal portion 20a to be greater than the force applied to the side seal portion 13a when the pressure in the storage section 17 increases. In addition, the width of the steam release seal portion 20a is smaller than the width of the side seal portion 13a. In addition, as shown in Figures 1 and 2, a non-sealed portion 20b that is isolated from the storage section 17 by the steam release seal portion 20a is formed between the steam release seal portion 20a and the outer edge of the side portion 13.

[0028] When the contents of bag 10 are heated, the moisture contained in the contents evaporates and the pressure in storage section 17 increases, causing bag 10 to expand around center point C of storage section 17. In this case, a force is applied to the sealed sections, such as side seal section 13a and steam release seal section 20a, in the direction from center point C toward the sealed sections. The force applied to each position of the sealed section increases as the distance from center point C decreases. The above-mentioned steam release seal section 20a protrudes from side seal section 13a toward storage section 17, and therefore the force applied to steam release seal section 20a is greater than the force applied to side seal section 13a. Therefore, compared to side seal section 13a, steam release seal section 20a can more easily cause communication between storage section 17 and the outside due to peeling of the sealed section.

[0029] 1 and 2, the non-sealed portion 20b of the steam release mechanism 20 spreads to reach the side edge of the bag 10. Therefore, the portion of the side edge of the bag 10 that overlaps with the non-sealed portion 20b is open. In this case, steam that flows from the storage section 17 into the non-sealed portion 20b through the peeled portion of the steam release 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 non-sealed portion 20b of the steam release mechanism 20 spreads to reach the outer edge, such as the side edge, of the bag 10, as shown in FIGS. 1 and 2 and FIG. 4 described later, is also referred to as a Type 1 bag.

[0030] Incidentally, when the contents of bag 10 are heated using a microwave oven or the like, some of the contents may splash and reach the inner surface of the laminate that constitutes bag 10. If the contents adhering to the inner surface of the laminate contain moisture, the contents adhering to the inner surface of the laminate are further heated by the microwave oven. In this case, the temperature of the laminate in contact with the contents also rises, which may cause holes or wrinkles to form in the laminate.

[0031] In consideration of such problems, in this embodiment, it is proposed to configure the steam release seal portion 20a so that when the contents of the bag 10 are heated using a microwave oven or the like, the steam release seal portion 20a is peeled off before the pressure of the storage portion 17 increases to 130 kPa. This makes it possible to peel off the steam release seal portion 20a and release the steam in the storage portion 17 to the outside before the temperature of the contents attached to the inner surface of the bag 10 becomes excessively high, thereby reducing the pressure and temperature of the storage portion 17. This makes it possible to prevent damage such as holes and wrinkles from occurring in the laminate of the bag 10. In the following description, the pressure in the storage portion 17 when the steam release seal portion 20a is peeled off and the storage portion 17 communicates with the outside of the bag 10 is also referred to as the peeling pressure.

[0032] Factors that determine the peel pressure of the steam release seal portion 20a include the shape and dimensions of the steam release seal portion 20a, and the mechanical properties of the sealant film (described later) located on the inner surface of the laminate. When the steam release seal portion 20a is formed by heat sealing, the peel pressure of the steam release seal portion 20a may also change depending on the conditions of the heat sealing, such as temperature. In this embodiment, these factors are appropriately adjusted to control the peel pressure of the steam release seal portion 20a to 130 kPa or less. The peel pressure of the steam release seal portion 20a is more preferably 120 kPa or less.

[0033] If the peeling pressure of the steam release seal portion 20a is too low, it is considered that the steam release seal portion 20a will peel off before the contents are sufficiently heated and pressurized, resulting in a drop in the pressure and temperature of the storage portion 17. Taking this into consideration, the peeling pressure of the steam release seal portion 20a is preferably 105 kPa or more, and more preferably 110 kPa or more.

[0034] Layer structure of front and back films Next, a description will be given of the layer structure of the front film 14 and the back film 15. Fig. 3 is a cross-sectional view showing an example of the layer structure of a laminate 30 constituting the front film 14 and the back film 15.

[0035] 3, the laminate 30 includes 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 storage section 17 side.

[0036] Each layer of the laminate 30 will now be described in detail.

[0037] (First plastic film) The first plastic film 40 is, for example, a stretched plastic film stretched in a predetermined direction. The first plastic film 40 functions as a base layer for imparting a predetermined strength to the laminate 30. The first plastic film 40 may be a uniaxially stretched film stretched in one predetermined direction, or a biaxially stretched film stretched in two predetermined directions. The stretching direction of the first 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 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.

[0038] The first plastic film 40 contains, for example, polyester as a main component. For example, the first plastic film 40 contains 51 mass % or more of polyester. Examples of polyester include polyethylene terephthalate (hereinafter also referred to as PET) and polybutylene terephthalate (hereinafter also referred to as PBT). Note that the 51 mass % or more of polyester in the first plastic film 40 may be composed of one type of polyester or may be composed of two or more types of polyester.

[0039] When the first plastic film 40 contains polyester as a main component, the thickness of the first plastic film 40 is preferably 9 μm or more, more preferably 12 μm or more. When the first plastic film 40 contains polyester as a main component, the thickness of the first plastic film 40 is preferably 25 μm or less, 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 has sufficient strength. By making the thickness of the first plastic film 40 25 μm or less, the first plastic film 40 exhibits excellent formability. Therefore, the process of manufacturing the bag 10 by processing the laminate 30 can be efficiently carried out.

[0040] The first plastic film 40 may contain polyamide as a main component. For example, the first plastic film 40 contains 51 mass % or more of polyamide. Examples of polyamide-based materials include aliphatic polyamides and aromatic polyamides. Examples of aliphatic polyamides include nylons such as nylon-6, nylon-6,6, and copolymers of nylon 6 and nylon 6,6, and examples of aromatic polyamides include polymetaxylene adipamide (MXD6). When the first plastic film 40 contains polyamide as a main component, the puncture strength of the laminate 30 including the first plastic film 40 can be increased.

[0041] When the first plastic film 40 contains polyamide as a main component, the thickness of the first plastic film 40 is preferably 12 μm or more, and more preferably 15 μm or more. When the first plastic film 40 contains polyamide as a main component, the thickness of the first plastic film 40 is preferably 25 μm or less, and more preferably 20 μm or less.

[0042] The first plastic film 40 may be composed of a single layer or may be composed of multiple layers. When 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 this order. Note that when 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, it can be said that the main component of the first plastic film 40 produced by co-extrusion is polyamide.

[0043] (First adhesive layer) The first adhesive layer 45 includes 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 produced by mixing a first composition including a base agent and a solvent with a second composition including a curing agent and a solvent. Specifically, the adhesive includes a cured product produced by reaction of the base agent and the solvent in the adhesive composition.

[0044] Examples of adhesives include polyurethane. Polyurethane is a cured product produced by reacting a polyol as a base agent with an isocyanate compound as a curing agent. Examples of polyurethane include polyether polyurethane and polyester polyurethane. Polyether polyurethane is a cured product produced by reacting a polyether polyol as a base agent with an isocyanate compound as a curing agent. Polyester polyurethane is a cured product produced by reacting a polyester polyol as a base agent with an isocyanate compound as a curing agent.

[0045] As the isocyanate compound, aromatic isocyanate compounds such as tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), etc., aliphatic isocyanate compounds such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), etc., or adducts or oligomers of the above-mentioned various isocyanate compounds can be used.

[0046] The thickness of the first adhesive layer 45 is preferably 2 μm or more, and more preferably 3 μm or more. The thickness of the first adhesive layer 45 is preferably 6 μm or less, and more preferably 5 μm or less.

[0047] (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. Like the first plastic film 40, the second plastic film 50 also functions as a base layer for imparting a predetermined strength to the laminate 30. As with the first plastic film 40, the stretching direction of the second plastic film 50 is not particularly limited.

[0048] The second plastic film 50 contains polyester or polyamide as a main component, similar to the first plastic film 40. In order to impart 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 contains polyester as a main component. Therefore, when the first plastic film 40 contains polyamide as a main component, the second plastic film 50 contains polyester as a main component. When the first plastic film 40 contains polyester as a main component, the second plastic film 50 may contain polyester as a main component or may contain polyamide as a main component.

[0049] When the second plastic film 50 contains polyester as a main component, for example, when it contains 51 mass % or more of polyester, examples of the polyester include PET, PBT, etc., as in the case of the first 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 a 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 a main component, the thermal conductivity, melting point, etc. of the second plastic film 50 are the same as those of the first plastic film 40 containing polyester as a main component.

[0050] When the second plastic film 50 contains polyamide as a main component, for example, when it contains 51 mass % or more of polyamide, examples of the polyamide include aliphatic polyamide or aromatic polyamide, as in the case of the first 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, when the second plastic film 50 contains polyamide as a main component, the thickness of the second plastic film 50 is preferably 25 μm or less, and more preferably 20 μm or less.

[0051] (Second adhesive layer) The second adhesive layer 55 includes 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, as in the case of the first adhesive layer 45. In addition to the configurations, materials, and characteristics described below, the second adhesive layer 55 can adopt the same configurations, materials, and characteristics as the first adhesive layer 45.

[0052] The thickness of the second adhesive layer 55 is preferably 2 μm or more, and more preferably 3 μm or more. The thickness of the second adhesive layer 55 is preferably 6 μm or less, and more preferably 5 μm or less.

[0053] Incidentally, as the isocyanate compound constituting the curing agent of the adhesive, there are aromatic isocyanate compounds and aliphatic isocyanate compounds, as described above. Among these, aromatic isocyanate compounds leach out components that cannot be used for food applications under high temperature environments such as heat sterilization. Incidentally, the second adhesive layer 55 is in contact with the sealant film 70. Therefore, when the second adhesive layer 55 contains an aromatic isocyanate compound, the components leach out from the aromatic isocyanate compound may adhere to the contents contained in the container 17 that is in contact with the sealant film 70.

[0054] Considering these problems, a cured product produced by reacting a polyol as a base agent with an aliphatic isocyanate compound as a curing agent is preferably used as the adhesive constituting the second adhesive layer 55. This makes it possible to prevent components that cannot be used for food applications, which are caused by the second adhesive layer 55, from adhering to the contents.

[0055] (Sealant film) Next, the sealant film 70 will be described. As a material constituting the sealant film 70, one or more resins selected from polyethylene such as low-density polyethylene and linear low-density polyethylene, and polypropylene can be used. The sealant film 70 may be a single layer or a multilayer. The sealant film 70 is preferably made of an unstretched film. The term "unstretched" includes not only a film that is not stretched at all, but also a film that is slightly stretched due to the tension applied during film formation.

[0056] The bag 10 formed from the laminate 30 is subjected to a sterilization treatment such as boiling or retort treatment at high temperatures. Therefore, the sealant film 70 used has heat resistance that can withstand such high temperature treatments.

[0057] 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 the retort treatment of the bag 10 at a high temperature, and therefore the time required for the retort treatment 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, 50.

[0058] From the viewpoint of retort processing, a material mainly composed of propylene can be used as a material constituting the sealant film 70. Here, a material "mainly composed" of propylene means a material having a propylene content of 90% by mass or more. Specific examples of a material mainly composed of propylene include propylene-ethylene block copolymer, propylene-ethylene random copolymer, polypropylene such as homopolypropylene, and a mixture of polypropylene and polyethylene. Here, "propylene-ethylene block copolymer" means a material having a structural formula shown in the following formula (I). Also, "propylene-ethylene random copolymer" means a material having a structural formula shown in the following formula (II). Also, "homopolypropylene" means a material having a structural formula shown in the following formula (III).

[0059] [ka]

[0060] [ka]

[0061] [ka]

[0062] When a mixture of polypropylene and polyethylene is used as the propylene-based material, the material may have an islands-in-a-sea structure, where the polyethylene is discontinuously dispersed within a region of continuous polypropylene.

[0063] From the viewpoint of boiling treatment, examples of the material constituting the sealant film 70 include polyethylene, polypropylene, and combinations thereof. Examples of polyethylene include medium density polyethylene, linear low density polyethylene, and combinations thereof. For example, it is also possible to use the materials listed as the material constituting the sealant film 70 from the viewpoint of the above-mentioned retort treatment. The material constituting the sealant film 70 has a melting point of, for example, 100°C or higher, more preferably 105°C or higher, and even more preferably 110°C or higher. When polyethylene is used as the material constituting the sealant film 70, the melting point of 100°C or higher is, for example, when the density of polyethylene is 0.920 g / cm. 3 This can be realized when the above conditions are satisfied. Specific examples of the sealant film 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 the sealant film 70 having a melting point of 105°C or higher include NB-1 manufactured by Tamapoly. Specific examples of the sealant film 70 having a melting point of 110°C or higher include LS760C manufactured by Idemitsu Unitech and TUX-HZ manufactured by Mitsui Chemicals Tohcello.

[0064] 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, and thus the bag 10 can be prevented from breaking due to an impact when dropped. In addition, the puncture resistance of the laminate 30 can be increased.

[0065] In addition, 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. or higher (hereinafter also referred to as hot seal strength) is extremely small compared to the seal strength at low temperatures, for example, room temperature. For example, the hot seal strength at 100° C. is less than one-fourth of the seal strength at 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 release seal portion 20a is easily peeled off, and the steam in the storage portion 17 is easily released to the outside of the bag 10. Therefore, it is possible to prevent the internal pressure of the storage portion 17 from becoming excessive, and thus it is possible to prevent damage to the laminate 30 during heating. The seal strength can be measured in accordance with JIS Z1707 7.5. As a measuring instrument, for example, a thermostatic bath equipped tensile tester RTC-1310A manufactured by Orientec Co., Ltd. can be used.

[0066] The propylene-ethylene block copolymer contains, for example, a sea component made of polypropylene and an island component made of an ethylene-propylene copolymer rubber component. The sea component can contribute to improving the blocking resistance, heat resistance, rigidity, seal strength, etc. of the propylene-ethylene block copolymer. The island component can also contribute to improving the impact resistance of the propylene-ethylene block copolymer. Therefore, by adjusting the ratio of the sea component and the island component, the mechanical properties of the sealant film 70 containing the propylene-ethylene block copolymer can be adjusted.

[0067] In the propylene-ethylene block copolymer, the mass ratio of the sea part made of polypropylene is higher than the mass ratio of the island part made of the ethylene-propylene copolymer rubber component. For example, in the propylene-ethylene block copolymer, the mass ratio of the sea part made of polypropylene is at least 51 mass%, preferably 60 mass% or more, and more preferably 70 mass% or more.

[0068] The single-layer sealant film 70 may further include a second thermoplastic resin in addition to the first thermoplastic resin made of a propylene-ethylene block copolymer. Examples of the second thermoplastic resin include an α-olefin copolymer and polyethylene. The α-olefin copolymer is, for example, linear low-density polyethylene. Examples of polyethylene include low-density polyethylene, medium-density polyethylene, and high-density polyethylene. The second thermoplastic resin may contribute to increasing the impact resistance of the sealant film 70.

[0069] Low density polyethylene has a density of 0.910g / cm 3 Above 0.925g / cm 3 Medium density polyethylene has a density of 0.926 g / cm 3 Above 0.940g / cm 3 The following polyethylene: High density polyethylene has a density of 0.941 g / cm 3 Above 0.965g / cm 3 The following polyethylenes are available. Low density polyethylene is obtained by polymerizing ethylene at a high pressure, for example, from 1000 atm to less than 2000 atm. Medium density polyethylene and high density polyethylene are obtained by polymerizing ethylene at a medium or low pressure, for example, from 1 atm to less than 1000 atm.

[0070] The medium-density polyethylene and high-density polyethylene may partially contain a copolymer of ethylene and an α-olefin. Even when ethylene is polymerized at medium or low pressure, if a copolymer of ethylene and an α-olefin is contained, a medium-density or low-density polyethylene can be produced. Such polyethylene is called the above-mentioned linear low-density polyethylene. Linear low-density polyethylene is obtained by copolymerizing an α-olefin with a linear polymer obtained by polymerizing ethylene at medium or low pressure to introduce short-chain branches. Examples of α-olefins include 1-butene (C4), 1-hexene (C6), 4-methylpentene (C6), and 1-octene (C8). The density of linear low-density polyethylene is, for example, 0.915 g / cm. 3 Above 0.945g / cm 3 The following is the result.

[0071] The α-olefin copolymer constituting the second thermoplastic resin of the propylene-ethylene block copolymer is not limited to the linear low-density polyethylene described above. The α-olefin copolymer means a material having the structural formula shown in the following formula (IV).

[0072] [ka] Both R1 and R2 are H (hydrogen atom) or alkyl groups such as CH3 and C2H5. In addition, both j and k are integers of 1 or more. In addition, j is greater than k. That is, in the α-olefin copolymer shown in formula (IV), the structure on the left side including R1 is the base. R1 is, for example, H, and R2 is, for example, C2H5.

[0073] In the sealant film 70, the mass ratio of the first thermoplastic resin made of a propylene-ethylene block copolymer is higher than the mass ratio of the second thermoplastic resin containing at least an α-olefin copolymer or polyethylene. For example, in a single-layer sealant film 70, the mass ratio of the first thermoplastic resin made of a propylene-ethylene block copolymer is at least 51 mass% or more, preferably 60 mass% or more, and more preferably 70 mass% or more.

[0074] As described above, the second thermoplastic resin can contribute to increasing the impact resistance of the sealant film 70. Therefore, by adjusting the mass ratio of the second thermoplastic resin containing at least an α-olefin copolymer or polyethylene in the single-layer sealant film 70, the mechanical properties of the sealant film 70 can be adjusted.

[0075] 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 improved.

[0076] The thermoplastic elastomer is, for example, a hydrogenated styrene-based thermoplastic elastomer. The hydrogenated styrene-based thermoplastic elastomer has a structure consisting of a polymer block A mainly made of at least one vinyl aromatic compound and a polymer block B mainly made of at least one hydrogenated conjugated diene compound. The thermoplastic elastomer may also be an ethylene-α-olefin elastomer. The ethylene-α-olefin elastomer is a low-crystalline or amorphous copolymer elastomer, and is a random copolymer of 50 to 90 mass% of ethylene as a main component and an α-olefin as a copolymerization monomer.

[0077] The content of the propylene-ethylene block copolymer in the sealant film 70 is, for example, 80% by mass or more, and preferably 90% by mass or more.

[0078] Propylene-ethylene block copolymers can be produced by polymerizing the raw materials propylene and ethylene using a catalyst, such as a Ziegler-Natta catalyst or a metallocene catalyst.

[0079] The thickness of the sealant film 70 is preferably 30 μm or more, and more preferably 40 μm or more. The thickness of the sealant film 70 is preferably 100 μm or less, and more preferably 80 μm or less.

[0080] Preferred mechanical properties of the single layer sealant film 70 containing a propylene-ethylene block copolymer are described below. The tensile elongation of the sealant film 70 in the machine direction (MD) at 25°C is preferably 600% or more and 1300% or less. The product of the tensile elongation (%) of the sealant film 70 in the machine direction (MD) and the thickness (μm) of the sealant film 70 is preferably 35000 or more and 80000 or less. The tensile elongation of the sealant film 70 in the transverse direction (TD) at 25°C is preferably 700% or more and 1400% or less. The product of the tensile elongation (%) of the sealant film 70 in the transverse direction (TD) and the thickness (μm) of the sealant film 70 is preferably 40000 or more and 85000 or less. The tensile modulus of the sealant film 70 in the machine direction (MD) at 25°C is preferably 400 MPa or more and 1100 MPa or less. The product of the tensile modulus of the sealant film 70 in the machine direction (MD) (MPa) and the thickness (μm) of the sealant film 70 is preferably 30000 or more and 55000 or less. The tensile modulus of the sealant film 70 in the transverse direction (TD) at 25°C is preferably 250 MPa or more and 900 MPa or less. The product of the tensile modulus of the sealant film 70 in the transverse direction (TD) (MPa) and the thickness (μm) of the sealant film 70 is preferably 20000 or more and 45000 or more.

[0081] The tensile modulus and tensile elongation can be measured in accordance with JIS K7127. A thermostatic bath-equipped tensile tester RTC-1310A manufactured by Orientec Co., Ltd. can be used as a measuring device. In the bag 10 shown in FIG. 1, the direction in which the upper portion 11 and the lower portion 12 extend is the flow direction of the sealant film 70, and the direction in which the side portion 13 extends is the vertical direction of the sealant film 70. Although not shown, the bag 10 may be configured so that the direction in which the upper portion 11 and the lower portion 12 extend is the vertical direction of the sealant film 70, and the direction in which the side portion 13 extends is the flow direction of the sealant film 70.

[0082] There are two main types of single-layer sealant film 70 containing a propylene-ethylene block copolymer. The first type is a type having high tensile elongation and impact resistance, such as ZK500 described later. The first type of sealant film 70 preferably further has a property of low hot seal strength. This can prevent the internal pressure of the storage section 17 from becoming excessive when the bag 10 is heated, and can prevent damage to the laminate 30. The second type is a type having a high tensile modulus, such as ZK207 described later. By using the second type of sealant film 70, it is possible to improve the tearability when a consumer opens the bag 10 by tearing the bag 10 along the first direction D1.

[0083] The product of the tensile elongation (%) of the first type sealant film 70 in the machine direction (MD) and the thickness (μm) of the sealant film 70 is preferably 45,000 or more, more preferably 50,000 or more, and may be 55,000 or more, or 60,000 or more. The product of the tensile elongation (%) of the first type sealant film 70 in the transverse direction (TD) and the thickness (μm) of the sealant film 70 is preferably 53,000 or more, more preferably 60,000 or more. The sealant film 70 has a high tensile elongation, which can prevent the bag 10 from breaking due to an impact when dropped, etc. Moreover, the product of the tensile modulus (MPa) of the first type sealant film 70 in the machine direction (MD) and the thickness (μm) of the sealant film 70 is preferably not more than 38000, more preferably not more than 35000. Moreover, the product of the tensile modulus (MPa) of the first type sealant film 70 in the perpendicular direction (TD) and the thickness (μm) of the sealant film 70 is preferably not more than 30000, more preferably not more than 25000.

[0084] The product of the tensile modulus (MPa) of the second type sealant film 70 in the machine direction (MD) and the thickness (μm) of the sealant film 70 is preferably 35,000 or more, more preferably 38,000 or more, and even more preferably 45,000 or more. The product of the tensile modulus (MPa) of the second type sealant film 70 in the perpendicular direction (TD) and the thickness (μm) of the sealant film 70 is preferably 25,000 or more, more preferably 30,000 or more, and even more preferably 35,000 or more, and may be 38,000 or more. When the sealant film 70 has a high tensile modulus, the tearability when opening the bag 10 can be improved. Moreover, the product of the tensile elongation (%) of the second type sealant film 70 in the machine direction (MD) and the thickness (μm) of the sealant film 70 is preferably not more than 55,000, and more preferably not more than 50,000. Moreover, the product of the tensile elongation (%) of the second type sealant film 70 in the transverse direction (TD) and the thickness (μm) of the sealant film 70 is preferably not more than 60,000, and more preferably not more than 55,000.

[0085] (Other layers) The laminate 30 may include additional layers not shown in Figure 3. Examples of additional layers are described below.

[0086] The laminate 30 may further include a printed layer. The printed layer is a layer provided on the laminate 30 to indicate product information or impart an aesthetic feel to the bag 10, and is printed on, for example, the first plastic film 40. The printed layer expresses letters, numbers, symbols, figures, pictures, etc. Ink for gravure printing or ink for flexographic printing can be used as a material for forming the printed layer. A specific example of an ink for gravure printing is Finart manufactured by DIC Graphics Corporation.

[0087] The laminate 30 may further include a transparent gas barrier layer. The transparent gas barrier layer is formed on the surface of the plastic films 40, 50, etc., and includes at least a transparent vapor deposition layer made of a transparent inorganic material. The transparent gas barrier layer may further include a transparent gas barrier coating film formed on the surface of the transparent vapor deposition layer, and includes a transparent gas barrier coating film.

[0088] The transparent deposition layer functions as a layer having a gas barrier function that prevents the permeation of oxygen gas and water vapor. Two or more transparent deposition layers may be provided. When two or more transparent deposition layers are provided, each may have the same composition or different compositions. Examples of the method for forming the transparent deposition layer include physical vapor deposition methods (PVD methods) such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition methods (CVD methods) such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition. Specifically, a deposition layer can be formed on a film-forming roller using a roller-type deposition film-forming device. Examples of inorganic materials constituting the transparent deposition layer include aluminum oxide (aluminum oxide) and silicon oxide. The thickness of the transparent deposition layer is preferably 40 Å or more and 130 Å or less, more preferably 50 Å or more and 120 Å or less.

[0089] The transparent gas barrier coating film is a layer that functions as a layer that suppresses the transmission of oxygen gas, water vapor, etc. 1 n M(OR 2 ) m (In the formula, R 1 , R 2 represents an organic group having 1 to 8 carbon atoms, M represents a metal atom, n represents an integer of 0 or more, m represents an integer of 1 or more, and n+m represents the atomic valence of M. The transparent gas barrier composition contains at least one alkoxide represented by the formula (I) and the above-mentioned polyvinyl alcohol resin and / or ethylene-vinyl alcohol copolymer, and is further polycondensed by a sol-gel method in the presence of a sol-gel catalyst, an acid, water, and an organic solvent.

[0090] Layer composition of the lower film Next, the layer structure of the lower film 16 will be described.

[0091] The layer configuration of the lower film 16 is arbitrary so long as it has an inner surface that can be joined to the inner surfaces of the front film 14 and the back film 15. For example, the above-mentioned laminate 30 may be used as the lower film 16, similarly to the front film 14 and the back film 15. Alternatively, a film whose inner surface is formed of a sealant layer and has a different configuration from the laminate 30 may be used as the lower film 16.

[0092] Manufacturing method of laminate Next, an example of a method for producing the laminate 30 will be described.

[0093] First, the above-mentioned first plastic film 40 and second plastic film 50 are prepared. Next, the first plastic film 40 and the second plastic film 50 are laminated together via the first adhesive layer 45 by dry lamination. After that, the laminate including the first plastic film 40 and the second plastic film 50 and the sealant film 70 are laminated together via the second adhesive layer 55 by dry lamination. In this way, the laminate 30 including the first plastic film 40, the second plastic film 50, and the sealant film 70 can be obtained.

[0094] Alternatively, the laminate 30 may be produced by first laminating the second plastic film 50 and the sealant film 70 via the second adhesive layer 55 using a dry lamination method, and then laminating the first plastic film 40 and a laminate including the second plastic film 50 and the sealant film 70 via the first adhesive layer 45 using a dry lamination method.

[0095] In the dry lamination method, first, an adhesive composition is applied to one of the two films to be laminated. Then, the applied adhesive composition is dried to volatilize the solvent. Then, the two films are laminated via the dried adhesive composition. Then, the two laminated films are wound up and aged, for example, in an environment of 20°C or higher for 24 hours or more.

[0096] How the bags are made Next, a method for manufacturing the bag 10 using the laminate 30 described above will be described. First, the surface film 14 and the back film 15 made of the laminate 30 are prepared. The lower film 16 in a folded state is inserted between the surface film 14 and the back film 15. Next, the inner surfaces of the films are heat-sealed to form seals such as the lower seal portion 12a, the side seal portion 13a, and the steam release seal portion 20a. The films joined to each other by heat sealing are cut into an appropriate shape to obtain the bag 10 shown in FIG. 1. Next, the contents 18 are filled into the bag 10 through the opening 11b of the upper portion 11. The contents 18 are, for example, cooked foods containing moisture such as curry, stew, and soup. The contents 18 may also include materials containing a lot of oil, such as meat, fish, and seasonings for them. In addition to food, any material that can be heated by boiling water or the like can be stored in the bag 10 as the contents. After that, the upper portion 11 is heat-sealed to form the upper seal portion. In this manner, bag 10 containing content 18 and sealed can be obtained as shown in Fig. 4. Thereafter, sterilization treatment such as boiling or retort treatment is carried out on bag 10 containing content 18 as necessary.

[0097] In FIG. 4, the symbol H1 indicates the distance in the second direction D2 from the upper seal portion 11a to the center point C of the storage portion 17. The symbol H2 indicates the shortest distance from the steam release seal portion 20a to the center point C of the storage portion 17. In the type 1 bag shown in FIG. 4, the ratio of the distance H1 to the distance H2 (=H1 / H2) is, for example, 1.05 or more and 4.0 or less, and more preferably 1.1 or more and 4.0 or less. By setting the distance H1 and the distance H2 in this manner, it is possible to prevent the upper seal portion 11a from peeling off before the steam release seal portion 20a when the bag 10 is heated. The center point C of the storage 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.

[0098] When the steam release seal portion 20a and other seal portions are formed by heat sealing, the conditions of the heat sealing are set according to the material of the sealant film 70 so that the peel pressure of the steam release seal portion 20a is 130 kPa or less.

[0099] How to measure peel pressure Next, a method for measuring the peeling pressure of the steam release seal portion 20a will be described. First, a method for measuring the peeling pressure of the steam release seal portion 20a will be described with reference to Fig. 5 when bag 10 in a state where upper seal portion 11a is not formed in upper portion 11 as shown in Fig. 1 above is available. Fig. 5 is a vertical cross-sectional view showing bag 10 in which sensor 81 for measuring the peeling pressure is provided in storage portion 17.

[0100] First, as shown in FIG. 1, a bag 10 is prepared in a state where the upper seal portion 11a is not formed on the upper portion 11 and the upper portion 11 has an opening 11b. Next, a sensor 81 of a data logger capable of measuring pressure is provided inside the bag 10. For example, the sensor 81 is attached to the inner surface of the bag 10. A predetermined amount of water, for example, 100 ml of water, is filled into the storage portion 17 of the bag 10. Then, a seal portion is formed at the opening of the bag 10 to seal the bag 10. For example, a PicoVACQ PT manufactured by TMI-ORION can be used as the data logger. The PicoVACQ PT can also measure temperature in addition to pressure.

[0101] Next, the water in bag 10 is heated using a microwave oven or the like while the pressure in storage section 17 is measured at predetermined time intervals using sensor 81. As the microwave oven, any microwave oven with an output in the range of 500 W to 1500 W can be used. The time interval is, for example, 0.1 seconds or more and 10 seconds or less, for example 1.0 second.

[0102] When the water evaporates and the pressure in the storage section 17 increases, the steam release seal section 20a begins to peel off. When the peeling of the steam release seal section 20a progresses to the outer edge of the bag 10 and the storage section 17 communicates with the non-sealed section 20b and the outside of the bag 10, the pressure in the storage section 17 measured by the sensor 81 suddenly drops. The pressure in the storage section 17 measured just before the pressure starts to drop suddenly is recorded as the peeling pressure of the steam release seal section 20a. The temperature of the storage section 17 just before the pressure starts to drop suddenly is, for example, 80°C or higher and 120°C or lower.

[0103] Next, a method for measuring the peel pressure of the steam release seal portion 20a using a bag 10 containing contents and with the upper portion 11 sealed as shown in FIG. 4 will be described with reference to FIGS. 12A to 12D.

[0104] First, the bag 10 is prepared in a partially open state. Specifically, first, the bag 10 is prepared in a state in which the contents are contained and the upper portion 11 is sealed as shown in FIG. 4. Next, an opening for taking out the contents is provided in either the front film 14 or the back film 15. For example, as shown in FIG. 12A, a slit penetrating the front film 14 is formed in the front film 14 to provide an opening 14c in the front film 14. The opening 14c is located below the upper seal portion 11a and above the steam release seal portion 20a. The opening 14c extends in the first direction D1 so as not to reach either the one side seal portion 13a or the other side seal portion 13a. Then, the contents contained in the bag 10 are taken out to the outside through the opening 14c. Then, the inside of the bag 10 may be washed to further remove the contents adhering to the inner surface of the bag 10.

[0105] Next, a film 14d is prepared that can be heat-sealed to the inner surface 30x of the surface film 14 in which the opening 14c is provided. The film 14d has a shape that can be introduced into the storage section 17 of the bag 10 through the opening 14c and can cover the opening 14c. The film 14d can be the same laminate as the surface film 14. For example, when the bag 10 is commercially available in a state in which the contents are stored, such a film 14d can be prepared by purchasing the bag 10 and cutting out the surface film 14 of the bag 10.

[0106] Next, as shown in FIG. 12B, the film 14d is introduced into the storage section 17 of the bag 10 through the opening 14c. At this time, the inner surface of the film 14d is made to face the inner surface 30x of the surface film 14. The film 14d is located between the inner edge 11c of the upper seal section 11a of the bag 10 and the upper edge 20d of the steam release seal section 20a in the second direction D2. The film 14d is also located between the inner edge 13d of one side seal section 13a and the inner edge 13d of the other side seal section 13a. The film 14d also covers the entire area of ​​the opening 14c. After that, the inner surface of the part of the film 14d located above the opening 14c is heat-sealed to the inner surface 30x of the surface film 14. In FIG. 12B, the seal section 14e formed by heat-sealing is hatched.

[0107] Next, as shown in FIG. 12C, a sensor 81 of a data logger capable of measuring pressure is introduced into the bag 10 through the opening 14c. For example, the sensor 81 is attached to the inner surface of the bag 10. A predetermined amount of water, for example, 100 ml of water, is filled into the storage section 17 of the bag 10 through the opening 14c. Thereafter, the inner surface of the film 14d is heat-sealed to the inner surface 30x of the surface film 14 so as to seal the bag 10 from the outside. For example, a portion of the inner surface of the film 14d that has not yet been heat-sealed to the inner surface 30x of the surface film 14 is heated and pressed. This allows the opening 14c of the bag 10 to be sealed as shown in FIG. 12D. Thereafter, as described above, the pressure of the storage section 17 is measured at predetermined time intervals using the sensor 81 while the water in the bag 10 is heated using a microwave oven or the like, thereby allowing the peeling pressure to be measured.

[0108] How to heat the contents Next, an example of a method for heating the contents 18 contained in the bag 10 will be described.

[0109] First, bag 10 is placed in a microwave oven with bag 10 standing upright with lower part 12 facing down. Next, the contents are heated using the microwave oven. This increases the temperature of contents 18, and as a result, the moisture contained in contents 18 evaporates, increasing the pressure in storage section 17.

[0110] When the pressure in the storage section 17 increases, the front film 14 and the back film 15 bulge outward due to the force they receive from the storage section 17. In this embodiment, the steam release mechanism 20 is configured so that the peeling pressure of the steam release seal section 20a is 130 kPa or less. Therefore, the steam release seal section 20a peels off before the pressure in the storage section 17 increases to 130 kPa. This makes it possible to prevent holes from being formed in the laminate 30 of the bag 10 or wrinkles from being formed in the laminate 30 when heated.

[0111] It should be noted that various modifications can be made to the above-described embodiment. Below, the modified examples will be described with reference to the drawings as necessary. In the following description and the drawings used in the following description, the same reference numerals as those used for the corresponding parts in the above-described embodiment will be used for parts that can be configured in the same manner as in the above-described embodiment, and duplicated descriptions will be omitted. Also, if it is clear that the effects obtained in the above-described embodiment can also be obtained in the modified examples, the description may be omitted.

[0112] (First variation of the bag) In the steam release mechanism 20 of the present embodiment described above, the non-sealed portion 20b, which is isolated from the storage portion 17 by the steam release seal portion 20a, is extended to the outer edge of the bag 10. However, the present invention is not limited to this, and the non-sealed portion 20b may be surrounded by the steam release seal portion 20a and the side seal portion 13a as shown in FIG. 6. In this case, the non-sealed portion 20b has a through hole 20c penetrating at least one of the front film 14 or the back film 15. In this case, steam that flows from the storage portion 17 into the non-sealed portion 20b through the peeled portion of the steam release 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 non-sealed portion 20b of the steam release mechanism 20 is surrounded by the steam release seal portion 20a and one side seal portion 13a as shown in FIG. 6 is also referred to as a type 2 bag.

[0113] In the bag 10 shown in Fig. 6, the non-sealed portion 20b is located closer to the storage portion 17 than the side seal portion 13a. For this reason, when the width of the non-sealed portion 20b in the first direction D1 is the same, the distance H2 from the steam release seal portion 20a to the center point C of the type 2 bag 10 of this modified example is shorter than the distance H2 from the steam release seal portion 20a to the center point C of the type 1 bag 10 shown in Figs. 1 and 4. For this reason, when the contents of the bag 10 are heated using a microwave oven or the like, a force is likely to be applied to the steam release seal portion 20a, and the peel pressure of the steam release seal portion 20a is likely to be low. In the type 2 bag as shown in Fig. 6, the ratio of the distance H1 to the distance H2 (=H1 / H2) is, for example, 1.05 or more and 5.0 or less.

[0114] In this modified example, the steam release mechanism 20 is also configured so that the peeling pressure of the steam release seal portion 20a is 130 kPa or less. Therefore, the steam release seal portion 20a peels off before the pressure in the storage section 17 increases to 130 kPa. This makes it possible to prevent holes from being formed in the laminate 30 of the bag 10 or wrinkles from being formed in the laminate 30 when heated.

[0115] (Second variation of the bag) In the steam release mechanism 20 of the present embodiment and the first modified example described above, the steam release seal portion 20a is connected to one of the side seal portions 13a. However, this is not limited thereto, and as shown in FIG. 7, the steam release seal portion 20a may be separated from the side seal portion 13a. In this case, the non-seal portion 20b surrounded by the steam release seal portion 20a has a through hole 20c penetrating at least one of the front film 14 or the back film 15. As in the first modified example, steam that flows from the storage portion 17 into the non-seal portion 20b through the peeled portion of the steam release 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 release seal portion 20a of the steam release mechanism 20 is separated from the side seal portion 13a as shown in FIG. 7 is also referred to as a type 3 bag.

[0116] In the bag 10 shown in Fig. 6, the non-sealed portion 20b is spaced from the side seal portion 13a. For this reason, when the width of the non-sealed portion 20b in the first direction D1 is the same, the distance H2 from the steam release seal portion 20a to the center point C of the type 3 bag 10 of this modified example is shorter than the distance H2 from the steam release seal portion 20a to the center point C of the type 2 bag 10 shown in Fig. 6. For this reason, when the contents of the bag 10 are heated using a microwave oven or the like, a force is more likely to be applied to the steam release seal portion 20a, and the peel pressure of the steam release seal portion 20a is more likely to be lower. In the type 3 bag as shown in Fig. 7, the ratio of the distance H1 to the distance H2 (=H1 / H2) is, for example, 1.05 or more and 6.0 or less.

[0117] In this modified example, the steam release mechanism 20 is also configured so that the peeling pressure of the steam release seal portion 20a is 130 kPa or less. Therefore, the steam release seal portion 20a peels off before the pressure in the storage section 17 increases to 130 kPa. This makes it possible to prevent holes from being formed in the laminate 30 of the bag 10 or wrinkles from being formed in the laminate 30 when heated.

[0118] In addition, when the distance H2 from the steam release seal portion 20a to the center point C is shortened, force is more likely to be applied to the steam release seal portion 20a even when the contents of the bag 10 are not heated using a microwave oven or the like. For example, when a plurality of bags 10 are stacked and transported, force is more likely to be applied to the steam release seal portion 20a, making it easier for the steam release seal portion 20a to peel off unintentionally. In other words, the shorter the distance H2 from the steam release 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, type 2 bags 10 are more preferable than type 3 bags 10, and type 1 bags 10 are even more preferable.

[0119] (Third variation of the bag) In the above-described embodiment, an example has been shown in which bag 10 is a gusset-type pouch having front film 14, back film 15, and bottom film 16. However, this is not limited thereto, and bag 10 may be a so-called flat pouch having front film 14 and back film 15, as shown in Fig. 13. In this case, bag 10 is heated in a microwave oven while maintaining the posture of bag 10 such that steam release seal portion 20a is positioned vertically above center point C of storage portion 17. For example, when bag 10 is sold in a state where it is stored in a paper box (not shown), bag 10 can be maintained in a predetermined posture using the box. EXAMPLES

[0120] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the description of the following examples as long as it does not depart from the gist of the present invention. Here, the seal strength of the laminate 30 constituting the bag 10 and the peel pressure of the steam release seal portion 20a of the bag 10 were evaluated.

[0121] (Example A1) A stretched PET film having a thickness of 12 μm was prepared as the first plastic film 40. A stretched nylon film having a thickness of 15 μm was prepared as the second plastic film 50. An unstretched polypropylene film ZK500 manufactured by Toray Advanced Film Co., Ltd. was prepared as the sealant film 70. ZK500 contains the above-mentioned propylene-ethylene block copolymer and elastomer. The thickness of the sealant film 70 was 60 μm.

[0122] ZK500 has a higher tensile elongation than a general unstretched polypropylene film. Specifically, the tensile elongation of ZK500 in the machine direction (MD) is 1180% when the thickness is 50 μm, and 1100% when the thickness is 60 μm. The tensile elongation of ZK500 in the transverse direction (TD) is 1240% when the thickness is 50 μm, and 1150% when the thickness is 60 μm. Therefore, the product of the tensile elongation (%) and thickness (μm) of ZK500 in the machine direction is 59000 when the thickness is 50 μm, and 66000 when the thickness is 60 μm. The product of the tensile elongation (%) and thickness (μm) of ZK500 in the transverse direction is 62000 when the thickness is 50 μm, and 69000 when the thickness is 60 μm.

[0123] In addition, ZK500 has a lower tensile modulus than a general unstretched polypropylene film. Specifically, the tensile modulus of ZK500 in the machine direction (MD) is 640 MPa when the thickness is 50 μm, and 550 MPa when the thickness is 60 μm. In addition, the tensile modulus of ZK500 in the perpendicular direction (TD) is 480 MPa when the thickness is 50 μm, and 400 MPa when the thickness is 60 μm. Therefore, the product of the tensile modulus (MPa) and thickness (μm) of ZK500 in the machine direction is 32000 when the thickness is 50 μm, and 33000 when the thickness is 60 μm. In addition, the product of the tensile modulus (MPa) and thickness (μm) of ZK500 in the perpendicular direction is 24000 when the thickness is 50 μm, and 35000 when the thickness is 60 μm.

[0124] Next, the first plastic film 40, the second plastic film 50, and the sealant film 70 were laminated by a dry lamination method to produce the laminate 30. A two-component polyurethane adhesive (base: RU-40, hardener: H-4) manufactured by Rock Paint Co., Ltd. was used as the first adhesive layer 45 and the second adhesive layer 55. The base RU-40 is a polyester polyol. The thickness of the first adhesive layer 45 and the second adhesive layer 55 was 3.5 μm.

[0125] (Seal strength evaluation) Next, the inner surfaces 30x of the two laminates 30 were partially heat-sealed together at 210°C. Thereafter, the seal strength between the laminates 30 was measured in an atmosphere of 23°C in accordance with JIS 1707 7.5. As a measuring instrument, a thermostatically-controlled tensile tester RTC-1310A manufactured by Orientec Co., Ltd. was used. Specifically, first, the two heat-sealed laminates 30 were cut out to prepare a rectangular test piece 90 having a width (short side) of 15 mm. In the test piece 90, as shown in FIG. 8, the two laminates 30 were peeled off over a length of 15 mm from one end in the long side direction. Thereafter, as shown in FIG. 9, the already peeled portions of the two laminates 30 were held by a gripper 91 and a gripper 92 of the measuring instrument, respectively. The grippers 91 and 92 were pulled at a speed of 300 mm / min in opposite directions perpendicular to the plane direction of the portion where the two laminates 30 were still joined, and the maximum tensile stress (see FIG. 10) was measured. FIG. 10 is a graph showing the change in tensile stress with respect to the distance S. The maximum tensile stress was measured for five test pieces 90, and the average value was regarded as the seal strength of the laminate 30. The distance S between the grippers 91, 92 when pulling started was 20 mm, and the distance S between the grippers 91, 92 when pulling ended was 40 mm. The environment during measurement was a temperature of 23°C and a relative humidity of 50%. As a result, the seal strength at a width of 15 mm (hereinafter also referred to as room temperature seal strength) was 65 N.

[0126] The seal strength may be measured using a test piece 90 obtained by cutting out a portion including one of the side seal portion 13a from the front film 14 and the back film 15 of the bag 10.

[0127] (Evaluation of peeling pressure) Next, a bag 10 having a type 1 steam release mechanism 20 shown in FIG. 1 and FIG. 4 was produced using the laminate 30. In the produced bag 10, the upper part 11 was not formed with the upper seal part 11a, and the upper part 11 was an opening part 11b. 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, that is, the height from the lower end of the bag 10 to the folded part 16f, was 40 mm. In the following description, the bag 10 having a height S1 of 145 mm, a width S2 of 140 mm, and a height S3 of 40 mm is also referred to as an S-size bag 10. Next, 100 ml of water was filled inside the bag 10, and a data logger sensor 81 was placed inside the bag 10, and the upper part 11 of the bag 10 was heat-sealed to form the upper seal part 11a. The distance H1 in the second direction D2 from the upper seal portion 11a to the center point C of the storage portion 17 was 67 mm. Also, the shortest distance H2 from the steam release seal portion 20a to the center point C of the storage portion 17 was 60 mm. In this case, the ratio of the distance H1 to the distance H2 (=H1 / H2) was 1.12.

[0128] Next, the water in the bag 10 was heated using a microwave oven with an output of 500 W while measuring the pressure in the storage section 17 every second using the sensor 81. The microwave oven with an output of 500 W was a Panasonic NE-MS261. When the pressure in the storage section 17 increased and the peeling of the steam release seal section 20a reached the outer edge of the bag 10, the steam in the storage section 17 started to be discharged to the outside of the bag 10, and the pressure in the storage section 17 dropped suddenly. The peeling pressure, which is the pressure in the storage section 17 just before the pressure started to drop suddenly, was 116.1 kPa. The temperature that the storage section 17 had reached just before the pressure started to drop suddenly (hereinafter also referred to as the reached temperature) was 102°C. The time from the start of heating until the pressure started to drop suddenly (hereinafter also referred to as the required time) was 145 seconds. In the bag 10 after heating, no holes or wrinkles were formed in the laminate 30.

[0129] (Example A2) A type 1 bag 10 was produced using the same laminate 30 as in Example A1. 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, the bag 10 with a height S1 of 145 mm, a width S2 of 150 mm, and a height S3 of 43 mm is also referred to as a medium-sized bag 10. Next, as in Example A1, 100 ml of water was filled into the bag 10, and the upper portion 11 was heat-sealed to form an upper seal portion. The temperature of the heat seal process was 210°C, as in Example A1. In this case, the room temperature seal temperature was 65N, as in Example A1. The distance H1 in the second direction D2 from the upper seal portion 11a to the center point C of the storage portion 17 was 68 mm. In addition, the shortest distance H2 from the steam release seal portion 20a to the center point C of the storage portion 17 was 65 mm. In this case, the ratio of the distance H1 to the distance H2 (=H1 / H2) is 1.04.

[0130] Thereafter, in the same manner as in Example A1, the water in bag 10 was heated using a microwave oven with an output of 500 W while measuring the pressure in storage section 17 using sensor 81. The peeling pressure was 113.5 kPa, the temperature reached was 100° C., and the time required was 131 seconds. Furthermore, in bag 10 after heating, no holes or wrinkles were formed in laminate 30.

[0131] (Example A3) The same laminate 30 as in Example A1 was heat-sealed at 200° C. to prepare a test piece 90, which was used to measure the seal strength between the laminates 30. As a result, the room temperature seal strength was 55 N.

[0132] Also, a type 1 bag 10 of S size was produced in the same manner as in Example A1, except that the temperature of the heat sealing process was 200°C. Thereafter, similarly to Example A1, the water in the bag 10 was heated using a microwave oven with an output of 500 W while the pressure in the storage section 17 was measured using the sensor 81. The peeling pressure was 110 kPa, the temperature reached was 102°C, and the required time was 160 seconds. Furthermore, in the bag 10 after heating, no holes or wrinkles were formed in the laminate 30.

[0133] (Example A4) A medium-sized bag 10 of type 1 was produced in the same manner as in Example A2, except that the temperature of the heat sealing process was 200°C, as in Example A3. Thereafter, as in Example A1, the water in the bag 10 was heated using a microwave oven with an output of 500 W while measuring the pressure in the storage section 17 using the sensor 81. The peeling pressure was 110.5 kPa, the temperature reached was 102°C, and the required time was 163 seconds. In addition, in the bag 10 after heating, no holes or wrinkles were formed in the laminate 30. The room temperature sealing temperature in this example was 55 N, as in Example A3.

[0134] (Example A5) The same laminate 30 as in Example A3 was heat-sealed at 200°C to produce a bag 10 of type 1 of S size similar to that in Example A3. Next, the water in the bag 10 was heated using a microwave oven with an output of 1600W while measuring the pressure in the storage section 17 using the sensor 81. The NE-1801 manufactured by Panasonic was used as the microwave oven with an output of 1600W. The peeling pressure was 117kPa, the temperature reached was 98.9°C, and the time required was 52 seconds. Furthermore, in the bag 10 after heating, no holes or wrinkles were formed in the laminate 30.

[0135] (Example A6) The same laminate 30 as in Example A4 was heat-sealed at 200°C to produce a medium-sized type 1 bag 10 similar to that in Example A4. Next, while measuring the pressure in the storage section 17 using the sensor 81, the water in the bag 10 was heated using a microwave oven with an output of 1600 W, similar to that in Example A5. The peeling pressure was 117.9 kPa, the temperature reached was 99.7, and the time required was 54 seconds. Furthermore, no holes or wrinkles were formed in the laminate 30 in the bag 10 after heating.

[0136] (Example A7) A stretched PET film having a thickness of 12 μm was prepared as the first plastic film 40. A stretched PET film having a thickness of 12 μm was prepared as the second plastic film 50. An unstretched polypropylene film ZK500 manufactured by Toray Advanced Film Co., Ltd. was prepared as the sealant film 70. The thickness of the sealant film 70 was 60 μm.

[0137] Next, the seal strength between the laminates 30 was measured in the same manner as in Example A1 using a test piece 90 prepared by partially heat-sealing the inner surfaces 30x of two laminates 30 at 200° C. As a result, the room temperature seal strength was 55 N.

[0138] Also, in the same manner as in Example A1, a type 1 bag 10 of S size was produced. The temperature of the heat sealing process was 200°C. Thereafter, in the same manner as in Example A5, the water in the bag 10 was heated using a microwave oven with an output of 1600 W while measuring the pressure in the storage section 17 using the sensor 81. The peeling pressure was 114.8 kPa, the temperature reached was 102°C, and the time required was 63 seconds. Furthermore, in the bag 10 after heating, no holes or wrinkles were formed in the laminate 30.

[0139] (Comparative Example A1) A stretched PET film having a thickness of 12 μm was prepared as the first plastic film 40. A stretched PET film having a thickness of 12 μm was prepared as the second plastic film 50. An unstretched polypropylene film ZK207 manufactured by Toray Advanced Film Co., Ltd. was prepared as the sealant film 70. The thickness of the sealant film 70 was 70 μm.

[0140] ZK207 has a lower tensile elongation than ZK500. Specifically, the tensile elongation of ZK207 in the machine direction (MD) is 790% when the thickness is 50 μm, and 730% when the thickness is 60 μm. The tensile elongation of ZK207 in the transverse direction (TD) is 1020% when the thickness is 50 μm, and 870% when the thickness is 60 μm. Therefore, the product of the tensile elongation (%) and thickness (μm) of ZK207 in the machine direction is 39500 when the thickness is 50 μm, and 43800 when the thickness is 60 μm. The product of the tensile elongation (%) and thickness (μm) of ZK207 in the transverse direction is 51000 when the thickness is 50 μm, and 52200 when the thickness is 60 μm.

[0141] In addition, ZK207 has a higher tensile modulus than ZK500. Specifically, the tensile modulus of ZK207 in the machine direction (MD) is 780 MPa when the thickness is 50 μm, and 680 MPa when the thickness is 60 μm. In addition, the tensile modulus of ZK207 in the transverse direction (TD) is 630 MPa when the thickness is 50 μm, and 560 MPa when the thickness is 60 μm. Therefore, the product of the tensile modulus of ZK207 (MPa) and the thickness (μm) in the machine direction is 39000 when the thickness is 50 μm, and 40800 when the thickness is 60 μm. In addition, the product of the tensile modulus of ZK207 (MPa) and the thickness (μm) in the transverse direction is 31500 when the thickness is 50 μm, and 33600 when the thickness is 60 μm.

[0142] Next, the seal strength between the laminates 30 was measured in the same manner as in Example A1 using a test piece 90 prepared by partially heat-sealing the inner surfaces 30x of two laminates 30 at 210° C. As a result, the room temperature seal strength was 65 N.

[0143] Also, in the same manner as in Example A1, a type 1 bag 10 of S size was produced. The temperature of the heat sealing process was 210°C. Thereafter, in the same manner as in Example A1, the water in the bag 10 was heated using a microwave oven with an output of 500 W while measuring the pressure in the storage section 17 using the sensor 81. The peeling pressure was 130.7 kPa, the temperature reached was 101°C, and the time required was 147 seconds. Furthermore, holes and wrinkles were formed in the laminate 30 of the bag 10 after heating.

[0144] (Comparative example A2) A medium-sized bag 10 of type 1 was produced using the same laminate 30 as in Comparative Example A1. The temperature for the heat sealing process was 210°C. Thereafter, as in Example A1, the water in the bag 10 was heated using a microwave oven with an output of 500 W while measuring the pressure in the storage section 17 using the sensor 81. The peeling pressure was 132.5 kPa, the temperature reached was 102°C, and the time required was 125 seconds. Furthermore, holes and wrinkles were formed in the laminate 30 in the bag 10 after heating.

[0145] (Example A8) The same laminate 30 as in Comparative Example A1 was heat-sealed at 200° C. to prepare a test piece 90, and the seal strength between the laminates 30 was measured. As a result, the room temperature seal strength was 55 N.

[0146] Also, a type 1 bag 10 of S size was produced in the same manner as in Comparative Example A1, except that the temperature of the heat sealing process was set to 200°C. Thereafter, as in Example A1, the water in the bag 10 was heated using a microwave oven with an output of 500 W while the pressure in the storage section 17 was measured using the sensor 81. The peeling pressure was 124.9 kPa, the temperature reached was 101°C, and the time required was 144 seconds. Furthermore, in the bag 10 after heating, wrinkles were formed in the laminate 30, but no holes were formed.

[0147] (Example A9) A bag 10 of type 1 of M size was produced in the same manner as in Comparative Example A2, except that the temperature of the heat sealing process was 200°C as in Example A8. Thereafter, as in Example A1, the water in the bag 10 was heated using a microwave oven with an output of 500 W while measuring the pressure of the storage section 17 using the sensor 81. The peeling pressure was 125.5 kPa, the temperature reached was 102°C, and the required time was 141 seconds. In addition, in the bag 10 after heating, wrinkles were formed in the laminate 30, but no holes were formed. The room temperature sealing temperature in this example was 55 N as in Example A8.

[0148] (Example A10) The same laminate 30 as in Example A9 was heat-sealed at 200°C to produce a medium-sized type 1 bag 10 similar to that in Example A9. Next, while measuring the pressure in the storage section 17 using the sensor 81, the water in the bag 10 was heated using a microwave oven with an output of 1600W, similar to that in Example A5. The peeling pressure was 124.8kPa, the temperature reached was 99°C, and the time required was 45 seconds. Furthermore, in the bag 10 after heating, wrinkles were formed in the laminate 30, but no holes were formed.

[0149] (Example A11) A type 2 bag 10 of S size was produced using the same laminate 30 as in Example A1. Then, as in Example A1, 100 ml of water was filled into the bag 10, and the upper part 11 was heat-sealed to form an upper sealed part. The heat-sealing temperature was 210°C, as in Example A1. In this case, the room temperature sealing temperature was 65 N, as in Example A1.

[0150] Thereafter, in the same manner as in Example A1, the water in bag 10 was heated using a microwave oven with an output of 500 W while measuring the pressure in storage section 17 using sensor 81. The peeling pressure was 110.8 kPa, the temperature reached was 101° C., and the time required was 142 seconds. Furthermore, in bag 10 after heating, no holes or wrinkles were formed in laminate 30.

[0151] (Example A12) A type 2 bag 10 of size S was produced using the same laminate 30 as in Comparative Example A1. Then, as in Comparative Example A1, 100 ml of water was filled into the bag 10, and the upper part 11 was heat-sealed to form an upper sealed part. The heat-sealing temperature was 210°C, as in Comparative Example A1. In this case, the room temperature sealing temperature was 65 N, as in Comparative Example A1.

[0152] Thereafter, in the same manner as in Example A1, the water in bag 10 was heated using a microwave oven with an output of 500 W while measuring the pressure in storage section 17 using sensor 81. The peeling pressure was 124.2 kPa, the temperature reached was 99° C., and the time required was 145 seconds. Furthermore, in bag 10 after heating, wrinkles were formed in laminate 30, but no holes were formed.

[0153] (Example A13) A type 3 bag 10 of S size was produced using the same laminate 30 as in Example A1. Then, as in Example A1, 100 ml of water was filled into the bag 10, and the upper part 11 was heat-sealed to form an upper sealed part. The heat-sealing temperature was 210°C, as in Example A1. In this case, the room temperature sealing temperature was 65 N, as in Example A1.

[0154] Thereafter, in the same manner as in Example A1, the water in bag 10 was heated using a microwave oven with an output of 500 W while measuring the pressure in storage section 17 using sensor 81. The peeling pressure was 108.9 kPa, the temperature reached was 101° C., and the required time was 130 seconds. Furthermore, in bag 10 after heating, no holes or wrinkles were formed in laminate 30.

[0155] (Example A14) A type 3 bag 10 of S size was produced using the same laminate 30 as in Comparative Example A1. Then, as in Comparative Example A1, 100 ml of water was filled into the bag 10, and the upper part 11 was heat-sealed to form an upper sealed part. The heat-sealing temperature was 210°C, as in Comparative Example A1. In this case, the room temperature sealing temperature was 65 N, as in Comparative Example A1.

[0156] Thereafter, similarly to Example A1, the water in bag 10 was heated using a microwave oven with an output of 500 W while measuring the pressure in storage section 17 using sensor 81. The peeling pressure was 122.1 kPa, the temperature reached was 102° C., and the time required was 131 seconds. Furthermore, in bag 10 after heating, wrinkles were formed in laminate 30, but no holes were formed.

[0157] The evaluation results of the examples and comparative examples are shown in Figure 11. As can be seen from a comparison between Examples A1 to A7, A11, and A13 and Comparative Examples A1 to A5, by using an unstretched polypropylene film ZK500 manufactured by Toray Advanced Film Co., Ltd. as the sealant film 70, it was possible to reduce the peel pressure when the bag 10 was heated to 120 kPa or less. This made it possible to prevent holes from being formed in the laminate 30 of the bag 10 and the laminate 30 from being wrinkled when heated.

[0158] Furthermore, as can be seen from the comparison between Example A8 and Comparative Example A1, or the comparison between Example A9 and Comparative Example A2, even when the sealant film 70 was made of the unstretched polypropylene film ZK207 manufactured by Toray Advanced Film Co., Ltd., the peel pressure when the bag 10 was heated could be reduced to 130 kPa or less by lowering the temperature of the heat sealing treatment. This made it possible to prevent holes from being made in the laminate 30 of the bag 10 when heated.

[0159] Furthermore, as can be seen from a comparison between Example A12 and Comparative Example A1, even when the sealant film 70 was made of unstretched polypropylene film ZK207 manufactured by Toray Advanced Film Co., Ltd., by adopting Type 2 shown in Fig. 6 as the type of bag, the peel pressure when the bag 10 was heated could be reduced to 130 kPa or less. This made it possible to prevent holes from being made in the laminate 30 of the bag 10 when heated.

[0160] Furthermore, as can be seen from the comparison between Example A14 and Comparative Example A1, even when the sealant film 70 was made of unstretched polypropylene film ZK207 manufactured by Toray Advanced Film Co., Ltd., the peel pressure when the bag 10 was heated could be reduced to 130 kPa or less by adopting the bag type 3 shown in Fig. 7. This made it possible to prevent holes from being made in the laminate 30 of the bag 10 when heated.

[0161] (Examples B1 to B3) As shown in Fig. 14, a number of S-size type 1 bags 10 were produced in which the position of the inner edge 11c of the top seal portion 11a in the second direction D2 was different. The laminate 30 used was the same as that in Example A1. The heat sealing temperature was 210°C, the same as in Example A1.

[0162] Changing the position of the inner edge 11c of the upper seal portion 11a changes the distance H1 in the second direction D2 from the upper seal portion 11a to the center point C of the storage portion 17, and the shortest distance H2 from the steam release seal portion 20a to the center point C of the storage portion 17. The distances H1 and H2 in Examples B1 to B3 were as follows. Example B1: H1 = 67 mm, H2 = 60 mm Example B2: H1 = 62 mm, H2 = 63 mm Example B3: H1 = 57 mm, H2 = 65 mm

[0163] Next, similarly to Example A1, the water in bag 10 was heated using a 500 W microwave oven while measuring the pressure in storage section 17 using sensor 81, and the peel pressure was measured. The results are shown in Figure 15. As shown in Figure 15, there was a tendency for the peel pressure to increase as H1 / H2 decreased. [Explanation of symbols]

[0164] 10 bags 11 Top 11a Upper seal part 12 Lower 12a Lower seal part 13 Side 13a Side seal 14 Surface film 15 Back film 16 Lower Film 17 Storage unit 18 Contents 20 Steam release mechanism 20a Steam release seal 25 Easy-to-open means 26 Notches 30 Laminate 40 No. 1 Plastic Film 45 First adhesive layer 50 Second Plastic Film 55 Second adhesive layer 70 Sealant Film 81 Sensors

Claims

1. A bag having a storage section, A laminate including a sealant film positioned on the inner surface of the bag and at least one plastic film positioned on the outer surface side of the sealant film; A seal portion that joins inner surfaces of the pair of laminates to each other, The sealing portion has an outer edge seal portion located on the outer edge of the bag, and a steam release seal portion located closer to the center point of the storage portion than the outer edge seal portion and peeled off due to an increase in pressure in the storage portion, the bag includes a non-sealed portion that is separated from the container by the steam release seal portion and that extends to an outer edge of the bag; In the non-sealed portion isolated from the storage portion by the steam release seal portion, no through-hole is formed in the laminate, The sealant film is a single-layer unstretched film containing a first thermoplastic resin and a second thermoplastic resin, the first thermoplastic resin is a propylene-ethylene block copolymer; the second thermoplastic resin comprises polyethylene; The mass ratio of the first thermoplastic resin in the sealant film is 70 mass% or more, The steam release seal portion peels off when the pressure in the storage portion is 105 kPa or more and 130 kPa or less, The tensile elongation (%) of the sealant film in the machine direction is 800% or more, The bag, wherein the tensile elongation (%) of the sealant film in the vertical direction is 1050% or more.

2. A bag having a storage section, A laminate including a sealant film positioned on the inner surface of the bag and at least one plastic film positioned on the outer surface side of the sealant film; A seal portion that joins inner surfaces of the pair of laminates to each other, The sealing portion has an outer edge seal portion located on the outer edge of the bag, and a steam release seal portion located closer to the center point of the storage portion than the outer edge seal portion and peeled off due to an increase in pressure in the storage portion, the bag includes a non-sealed portion that is separated from the container by the steam release seal portion and that extends to an outer edge of the bag; In the non-sealed portion isolated from the storage portion by the steam release seal portion, no through-hole is formed in the laminate, The sealant film is a single-layer unstretched film containing a first thermoplastic resin and a second thermoplastic resin, the first thermoplastic resin is a propylene-ethylene block copolymer; the second thermoplastic resin comprises polyethylene; The mass ratio of the first thermoplastic resin in the sealant film is 70 mass% or more, The steam release seal portion peels off when the pressure in the storage portion is 105 kPa or more and 130 kPa or less, The product of the tensile elongation (%) of the sealant film in the machine direction and the thickness (μm) of the sealant film is 45,000 or more; A bag, wherein the product of the tensile elongation (%) of the sealant film in the vertical direction and the thickness (μm) of the sealant film is 53,000 or more.

3. The product of the tensile elongation (%) of the sealant film in the machine direction and the thickness (μm) of the sealant film is 45,000 or more; The bag according to claim 1, wherein the product of the tensile elongation (%) of the sealant film in the vertical direction and the thickness (μm) of the sealant film is 53,000 or more.

4. The bag of claim 2 or 3, wherein the sealant film comprises an elastomer.

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