Packaging bags and packaging bodies

Abstract

To provide a packaging bag capable of forming a vapor vent opening as envisaged with high accuracy when heated in a microwave oven.SOLUTION: A packaging bag 100 is composed of laminates 10a, 10b including a sealant layer, one or more adhesive layers, and a base material layer, which is heated in a microwave oven. The packaging bag 100 includes a sealing part 30 formed by heat-sealing oppositely arranged sealant layers, and a container part 22 surrounded by laminates 10a, 10b and configured to accommodate a contained object. The sealing part 30 includes a vapor vent part 50 that forms a vapor vent opening when the pressure in the container part 22 is increased. The average nanoindentation hardness of at least one adhesive layer is greater than or equal to 0.95 MPa.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a packaging bag and a package.

Background Art

[0002] Packaging bags that contain and hermetically store food and the like and are heated in a microwave oven before opening are known. The microwave pouch described in Patent Document 1 has a structure for releasing steam generated when heating the contents. Specifically, a side seal portion of the microwave pouch has a protruding portion that protrudes toward the containing space. When the contents are heated and steam is generated, the seal at the protruding portion peels off. As a result, the containing portion that contains the contents communicates with the outside, and the steam is discharged from the containing portion to the outside.

[0003] It is known to use a laminate including a base material layer and a sealant layer as a film constituting such a microwave pouch. Patent Document 1 mentions polyester films, polyamide films, polypropylene films and the like as materials for the base material layer.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of Invention

Problem to be Solved by the Invention

[0005] The manner of increase in pressure and temperature of the containing portion of the package accompanying heating by a microwave oven varies depending on various factors, such as heating conditions and the type of contents. Therefore, even if the structure of the steam vent is adjusted, a steam vent may not be formed as expected. Accordingly, the present disclosure provides a packaging bag capable of forming a steam vent as expected with high accuracy when heated in a microwave oven, and a package including such a packaging bag.

Means for Solving the Problem

[0006] One aspect of the present disclosure provides a packaging bag that is heated in a microwave oven and comprises a laminate including a sealant layer, one or more adhesive layers, and a base layer, the packaging bag comprising a seal portion formed by heat sealing of the opposing sealant layers, and a storage portion surrounded by the laminate and configured to accommodate contents, wherein the seal portion includes a steam vent portion that forms a steam vent when the pressure in the storage portion rises, and the average value of the nanoindentation hardness of at least one of the adhesive layers is 0.95 MPa or higher.

[0007] In packaging bags heated in a microwave oven, tensile stress is generated in the laminate and seal portion as the pressure inside the bag increases. If the adhesive layer is soft, the layers bonded together by the adhesive layer will not be sufficiently fixed, and the tensile stress may not be applied sufficiently to the intended location but rather dispersed to other locations, or it may occur in a location different from the intended location. In contrast, the average nanoindentation hardness of the adhesive layer contained in the laminate constituting the packaging bag is 0.95 MPa or higher. Because the nanoindentation hardness of the adhesive layer is so high, the layers bonded together by the adhesive layer can be firmly fixed even when the pressure inside the bag increases. Therefore, the location where tensile stress is applied when the internal pressure of the packaging bag increases is less likely to deviate from the intended location, and the vent can be formed with high precision as intended when heated in a microwave oven.

[0008] One aspect of this disclosure is to provide a packaging body that is heated in a microwave oven, comprising the aforementioned packaging bag and contents contained in a compartment of the packaging bag.

[0009] Since the above-mentioned packaging body is equipped with the aforementioned packaging bag, the position where tensile stress is applied when the internal pressure of the packaging bag increases is less likely to deviate from the intended position, and when heated in a microwave oven, the steam vents can be formed with high precision as intended. [Effects of the Invention]

[0010] This invention provides a packaging bag that can form steam vents with high precision and as intended when heated in a microwave oven, and a package containing such a packaging bag. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram showing packaging bags and packaging materials. [Figure 2] Figure 1 shows a packaging bag and a diagram of a packaging bag used in the production of the packaging body. [Figure 3] This is a cross-sectional view along the lamination direction (thickness direction) of the laminated material provided in the packaging bag. [Figure 4] This is a cross-sectional view illustrating the method for preparing a sample for measuring nanoindentation hardness. [Figure 5] This is a cross-sectional view along the lamination direction (thickness direction) of the laminated material provided in the packaging bag. [Figure 6] This graph shows the changes in cutting depth and load when using the oblique cutting device used in the example. [Figure 7] This is the measurement curve obtained by the nanoindentation method in the example. [Modes for carrying out the invention]

[0012] Embodiments of this disclosure will be described below, with reference to the drawings as appropriate. However, the following embodiments are illustrative examples for illustrating this disclosure and are not intended to limit this disclosure to the following. In the description, the same reference numerals will be used for identical elements or elements having the same function, and redundant explanations will be omitted as appropriate. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships relative to the orientation of the reference numerals shown in the drawings. The dimensional ratios of each element are not limited to those shown.

[0013] A packaging bag according to one embodiment is a packaging bag for microwave heating, composed of one or more laminates and having a storage compartment. The packaging body according to one embodiment comprises a packaging bag and contents to be stored in the storage compartment of the packaging bag. Examples of packaging bags and packaging bodies are as follows.

[0014] The packaging 200 in Figure 1 comprises a packaging bag 100 and contents 20 contained in the storage section 22 of the packaging bag 100. The packaging bag 100 is composed of two laminated bodies 10a and 10b that form the sides and a laminated body 10c (gusset sheet) that forms the bottom. The packaging bag 100 has an upper end seal portion 31 (seal portion 30) at the upper end, side end seal portions 33 and 34 (seal portions 30) at both side ends, and lower end seal portions 35 and 36 (seal portions 30) at the lower end. The upper end seal portion 31 and the side end seal portions 33 and 34 are formed by overlapping and heat-sealing the sealant layers 15 at the ends of the laminated bodies 10a and 10b.

[0015] The lower end seal portion 35 (gusset seal portion) is formed by overlapping and heat-sealing the sealant layers 15 at the ends of laminates 10a and 10c. The lower end seal portion 36 (gusset seal portion) is formed by overlapping and heat-sealing the sealant layers 15 at the ends of laminates 10b and 10c. The structures of laminates 10a, 10b, and 10c may be as shown in Figure 3.

[0016] The sealant layers 15 of the laminates 10a, 10b, and 10c are heat-sealed at the upper end seal portion 31, the side end seal portions 33, 34, and the lower end seal portions 35, 36. That is, the parts indicated by dots in Figure 1 are the sealed portions formed by heat sealing. In parts other than these sealed portions, the laminates 10a, 10b, and 10c are not heat-sealed (unsealed portions). The laminates 10a, 10b, and 10c that constitute the packaging bag 100 form an internal space (storage portion 22) for accommodating the contents 20 when each of the sealed portions is sealed. Thus, the storage portion 22 is surrounded by the laminates 10a, 10b, and 10c.

[0017] The package 200 may be manufactured using the packaging bag 101 shown in FIG. 2. In the packaging bag 101, the upper end 31a of the laminated body 10a (10b) is not heat-sealed. Before heat-sealing the upper end 31a, the contents 20 are inserted through the opening formed by the upper end 31a, and then the upper end 31a of the laminated body 10a (10b) is heat-sealed. By forming the upper seal portion 31 in this manner, the packaging bag 100 and the package 200 in which the contents 20 are sealed in the accommodating portion 22 of the packaging bag 100 as shown in FIG. 1 can be obtained.

[0018] A pair of notches 41, 41 are provided on the side end seal portions 33, 34 of the packaging bag 100. A scheduled cutting line (not shown) may be provided so as to connect the pair of notches 41, 41. After heating the package 200 in a microwave oven, the end user can open the package 200 from one notch 41 along the scheduled cutting line and take out the heated contents 20.

[0019] The contents 20 are not particularly limited, and may contain oil and fat as well as moisture. When oil and fat are contained, local high temperature may occur. Even when the package 200 becomes high temperature after being heated in a microwave oven, the steam vent can be formed as expected with high accuracy. Therefore, the occurrence of leakage caused by interlayer delamination of the laminated bodies 10a, 10b, 10c and bag breakage can be sufficiently suppressed. Examples of the contents 20 include foods such as curry, stew, soup, boiled food, and roasted food. However, the contents 20 are not limited to these.

[0020] The side seal portion 34 includes a steam vent portion 50 configured to be capable of forming a steam vent that communicates the storage portion 22 with the outside of the packaging bag 100 when the pressure in the storage portion 22 of the packaging bag 100 increases. The steam vent portion 50 protrudes toward the center C of the packaging bag 100. When the content 20 stored in the storage portion 22 is heated by a microwave oven and steam is generated, the storage portion 22 expands. As a result of the expansion, the force applied to the upper end seal portion 31, the side end seal portions 33, 34, and the lower end seal portions 35, 36 increases as the distance from the center C decreases. For this reason, a large tensile stress is applied to the steam vent portion 50 protruding toward the center C as the content 20 is heated. Therefore, when the pressure in the storage portion 22 reaches or exceeds a predetermined value, the side seal portion 34 peels from the inner edge at the steam vent portion 50, and the storage portion 22 communicates with the outside of the packaging bag 100 (packaging body 200). In this manner, steam is discharged to the outside through the steam vent (steam discharge port) formed in the steam vent portion 50. As described above, the steam vent portion 50 has a function of forming the steam vent when the pressure in the storage portion 22 increases, thereby preventing the packaging bag 100 (packaging body 200) from breaking.

[0021] In the steam vent portion 50, a non-seal portion 53 is provided outside the side end seal portion 34. Thereby, the seal width of the side end seal portion 34 at the steam vent portion 50 is smaller than the seal width of the side end seal portion 34 at portions other than the steam vent portion 50. For this reason, when the pressure inside the storage portion 22 increases, a steam vent (steam discharge port) that communicates the storage portion 22 with the outside is smoothly formed in the steam vent portion 50. In order to sufficiently smooth the steam discharge (exhaust) from the storage portion 22 to the outside, the non-seal portion 53 may be provided with a through-hole penetrating in the lamination direction of the laminated bodies 10a and 10b.

[0022] The minimum seal width of the side end seal portion 34 in the steam vent portion 50 may be 1 to 5 mm, or it may be 2 to 4 mm. This allows for smooth steam release during heating in a microwave oven while maintaining good airtightness. The shape and position of the steam vent portion 50 are not particularly limited. In a modified example, the steam vent portion 50 may be provided in the upper end seal portion 31 or the side end seal portion 33. Regardless of the shape and position, the minimum seal width of the steam vent portion 50 may be within the above numerical range. Multiple steam vent portions 50 may be provided.

[0023] The packaging bag 100 (packaging body 200) may be subjected to retort processing, which involves heating in a hot water spray exceeding 100°C for 10 minutes or more.

[0024] The laminates 10a, 10b, and 10c may have, for example, a cross-sectional structure as shown in Figure 3. The laminate in Figure 3 has, from the outside of the packaging bag 100, a base layer 11, an ink layer 13, an adhesive layer 14, and a sealant layer 15 in that order. The surface 10B of the laminate in Figure 3 forms the containment section 22, and the surface 10A is exposed to the outside.

[0025] The base layer 11 may comprise, for example, one or both of a metal foil such as aluminum foil and a resin film. Examples of resin films include biaxially oriented polypropylene (BOPP), polyethylene terephthalate (PET), oriented polyamides such as nylon (OPA), unoriented polypropylene (CPP), linear low-density polyethylene (LLDPE), and low-density polyethylene (LDPE).

[0026] The base layer 11 (base film) may be a vapor-deposited film (transparent vapor-deposited film) in which a barrier layer (vapor-deposited layer) is formed on a resin layer such as a PET film. Examples of the barrier layer include a vapor-deposited layer of metal foil, metal (e.g., aluminum), or metal oxide (e.g., silica or alumina). The thickness of the base layer 11 may be 7 to 150 μm, 10 to 100 μm, or 12 to 80 μm. A specific example of a transparent vapor-deposited film is a transparent vapor-deposited PET film in which a transparent vapor-deposited layer is formed on a PET film. Examples of the transparent vapor-deposited layer include an alumina vapor-deposited layer and a silica vapor-deposited layer. The base layer 11 may also be a barrier nylon film.

[0027] The ink layer 13 may be printed by gravure printing or the like, and may contain, for example, a binder and a pigment. Alternatively, the ink layer 13 may be an electrostatic ink layer. In this case, a primer layer containing a resin may be provided between the substrate layer 11 and the ink layer 13. Examples of resins included in the primer layer include polyvinyl alcohol resin, cellulose resin, polyester, polyamine, polyethyleneimine resin, polyamide resin, polyurethane, polyacrylic polymer hydroxyl-containing resin, carboxyl group-containing resin, and amine-based polymer. The presence of a primer layer allows for smooth printing of the electrostatic ink composition using a digital printing press.

[0028] The adhesive layer 14 may contain a cured product obtained by curing the adhesive composition. An example of the adhesive composition is a urethane adhesive. The urethane adhesive contains a polyol and a polyisocyanate. The adhesive layer 14 may contain polyurethane obtained by curing these. It may also contain an uncured product of the adhesive composition.

[0029] Polyols, for example, have a number-average molecular weight of 400 or more and contain two or more hydroxyl groups in one molecule. Polyisocyanates contain two or more isocyanate groups in one molecule. Polyols and polyisocyanates may react as a main agent and a curing agent, respectively, to produce polyurethane. The number-average molecular weight of the polyol may be, for example, 10,000 or less.

[0030] The polyol may contain at least one selected from the group consisting of polyester polyols and polyether polyols. Of these, from the viewpoint of sufficiently increasing the adhesive strength of the adhesive layer 14 in a high-temperature environment, the polyol may contain polyester polyols or aliphatic polyester polyols.

[0031] Polyester polyols can be obtained, for example, by condensation reactions or transesterification reactions between a polyhydric alcohol and a polybasic acid, its alkyl ester, its acid anhydride, or its acid halide. Examples of polyhydric alcohols include low molecular weight diols, low molecular weight triols, and low molecular weight polyols having four or more hydroxyl groups.

[0032] Examples of low molecular weight diols include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, neopentyl glycol, 1,6-hexanediol, 2,2-diethyl-1,3-propanediol, 3,3-dimethylolheptane, and 2-ethyl-2-butyl-1,3-propanediol.

[0033] Examples of low molecular weight triols include glycerin, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2,4-dihydroxy-3-hydroxymethylpentane, 1,2,6-hexanetriol, trimethylolethane, trimethylolpropane, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2,4-dihydroxy-3-(hydroxymethyl)pentane, and 2,2-bis(hydroxymethyl)-3-butanol.

[0034] Examples of low molecular weight polyols having four or more hydroxyl groups include tetramethylolmethane, pentaerythritol, dipentaerythritol, D-sorbitol, xylitol, D-mannitol, and D-mannitol.

[0035] Examples of alkyl esters of polybasic acids include methyl esters and ethyl esters of polybasic acids. Examples of acid anhydrides include acid anhydrides derived from polybasic acids. Examples include oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, 2-alkyl (12-18 carbon atoms) succinic anhydride, tetrahydrophthalic anhydride, and trimellitic anhydride.

[0036] Examples of acid halides include those derived from the polybasic acids mentioned above. For example, oxalic acid dichloride, adipic acid dichloride, and sebatic acid dichloride are examples.

[0037] Polyether polyols may be polyalkylene oxides. For example, they may be obtained by adding an alkylene oxide such as ethylene oxide and / or propylene oxide to a low molecular weight polyol as an initiator. Specific examples include polyethylene glycol, polypropylene glycol, and polyethylene-polypropylene glycol (random or block copolymer). Another example is polytetramethylene ether glycol obtained by ring-opening polymerization of tetrahydrofuran.

[0038] Examples of polyisocyanates include polyisocyanate monomers, polyisocyanate derivatives, and isocyanate-terminated prepolymers. The adhesive composition may contain multiple types of polyisocyanates that are different from each other. The molar ratio (NCO / OH) of isocyanate groups in the polyisocyanate to the hydroxyl groups in the polyol may be 0.5 to 10, or 0.8 to 8.4. Such an adhesive composition can form a cured product that has high adhesive strength while exhibiting excellent flexibility.

[0039] Examples of polyisocyanate monomers include aliphatic polyisocyanates, aromatic polyisocyanates, aromatic aliphatic polyisocyanates, and alicyclic polyisocyanates.

[0040] Examples of aliphatic polyisocyanates include trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate), 1,5-pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 2,6-diisocyanate methyl capeate.

[0041] Examples of aromatic aliphatic polyisocyanates include xylylene diisocyanate derivatives. Examples of xylylene diisocyanate derivatives include xylylene diisocyanate (1,3-xylylene diisocyanate or 1,4-xylylene diisocyanate) (XDI), tetramethyl xylylene diisocyanate (1,3-tetramethyl xylylene diisocyanate or 1,4-tetramethyl xylylene diisocyanate) (TMXDI), ω,ω'-diisocyanate-1,4-diethylbenzene, and polyol-modified xylylene diisocyanates obtained by the reaction of xylylene diisocyanate with trimethylolpropane.

[0042] The content of xylylene diisocyanate derivative relative to the total polyisocyanate may be 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more, from the viewpoint of improving reactivity with the main component (e.g., polyol). A content of 30% by mass or more can further increase reactivity.

[0043] Examples of alicyclic polyisocyanates include 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isoholodiisocyanate) (IPDI), methylcyclohexane diisocyanate (methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate), and norbornane diisocyanate (NBDI).

[0044] Examples of polyisocyanate derivatives include polymers of the polyisocyanate monomers mentioned above, allophanate-modified derivatives, polyol-modified derivatives, polyol-modified derivatives produced by the reaction of monomers with alcohols, biuret-modified derivatives, urea-modified derivatives, oxadiazinetrione-modified derivatives, carbodiimide-modified derivatives, uretdione-modified derivatives, and uretonimine-modified derivatives.

[0045] An isocyanate-terminated prepolymer is a urethane prepolymer having at least two isocyanate groups at its molecular ends. It can be obtained by urethane-forming a polyol with at least one selected from the group consisting of polyisocyanate monomers, polyisocyanate derivatives, and isocyanate-terminated prepolymers. In this case, the molar ratio (NCO / OH) of isocyanate groups contained in the polyisocyanate to the hydroxyl groups of the polyol may be 0.5 or more, 0.6 or more, 0.8 or more, 1 or more, or 1.5 or more. The above molar ratio (NCO / OH) may also be 10 or less, 5 or less, 4 or less, or 3 or less. Examples of numerical ranges for the molar ratio (NCO / OH) include 0.5 to 10, 0.5 to 5, 0.8 to 4, and 0.6 to 3.

[0046] In the adhesive composition, the amount of polyisocyanate per 100 parts by mass of polyol may be 10 to 50 parts by mass, 15 to 35 parts by mass, or 20 to 30 parts by mass, from the viewpoint of maintaining sufficiently high peel adhesion strength in the adhesive layer.

[0047] The adhesive layer 14 may contain optional components such as additives in addition to the components described above. Examples of additives include antioxidants, ultraviolet absorbers, light stabilizers, fillers, silane coupling agents, epoxy resins, catalysts, coating properties improvers, leveling agents, nucleating agents, lubricants, mold release agents, defoamers, plasticizers, surfactants, pigments, dyes, organic fine particles, inorganic fine particles, antifungal agents, and flame retardants.

[0048] The thickness of the adhesive layer 14 may be 1 to 12 μm, or 1.5 to 8 μm. By having an adhesive layer 14 thickness greater than or equal to the lower limit, delamination between layers of the laminates 10a, 10b, and 10c can be sufficiently suppressed even when the pressure in the containment section 22 increases and it comes into contact with high-temperature steam. By having an adhesive layer 14 thickness less than or equal to the upper limit, the manufacturing cost of the packaging bag 100 can be reduced and the productivity of the packaging bag 100 can be increased.

[0049] Examples of sealant layers 15 include unoriented polypropylene film (CPP film), linear low-density polyethylene film (LLDPE film), biaxially oriented polypropylene film (OPP film), polyester film such as polybutylene terephthalate (PBT), and biaxially oriented nylon film. Using polybutylene terephthalate can further improve heat resistance. The thickness of the sealant layer 15 may be 10 to 150 μm, 20 to 100 μm, or 30 to 80 μm.

[0050] The average nanoindentation hardness of the adhesive layer 14 is 0.95 MPa or higher. Preferably, the average nanoindentation hardness is 1.2 MPa or higher, more preferably 1.5 MPa or higher, and even more preferably 1.9 MPa or higher. If the nanoindentation hardness is sufficiently high, the ink layer 13 and the sealant layer 15 bonded by the adhesive layer 14 will be fixed even more firmly, and even if the heating conditions in the microwave oven become severe, the steam vents 50 will be able to form the steam vents as intended. This will sufficiently suppress the occurrence of delamination between layers of the laminates 10a, 10b, and 10c, the occurrence of seal setback in the seal parts other than the steam vents 50 (side seal parts 33, 34, upper seal part 31, lower seal parts 35, 36), and the rupture of the packaging 200.

[0051] The average nanoindentation hardness of the adhesive layer 14 may be 4.0 MPa or less, 3.0 MPa or less, or 2.5 MPa or less. This suppresses an increase in rigidity at room temperature and allows the drop strength of the packaging bag 100 and the packaging body 200 to be maintained at a sufficiently high level.

[0052] The nanoindentation hardness of the adhesive layer 14 can be measured by exposing the adhesive layer 14 by cutting the sealant layer 15. The procedure for obtaining the exposed surface of the adhesive layer may be as described in the examples. Whether the exposed surface obtained by cutting the sealant layer 15 is the adhesive layer 14 can be easily confirmed because the nanoindentation hardness of the adhesive layer 14 is at least an order of magnitude lower than that of the sealant layer 15 and other adjacent layers such as resin film layers.

[0053] The average value of the stress relaxation degree of the adhesive layer 14, measured by the nanoindentation method, may be between 0.54 and 0.80. The stress relaxation degree is a parameter that indicates the degree to which stress changes in response to a constant strain. If the stress relaxation degree becomes too small, the adhesive layer 14 may not be able to follow the deformation of the sealant layer 15 during steaming, and triangular delamination (delamination between the adhesive layer 14 and the layer opposite the sealant layer 15) and blockage tend to occur. For this reason, the average value of the stress relaxation degree of the adhesive layer 14 may be 0.60 or higher, and may also be 0.65 or higher. The stress relaxation degree can be determined by the procedure described in the examples.

[0054] Nanoindentation hardness and stress relaxation are measured by the nanoindentation method. The nanoindentation method is a measurement method that obtains the mechanical properties of a sample by performing a quasi-static indentation test on the sample. A Hysitron TI-Premier (product name) manufactured by Bruker Japan Co., Ltd. can be used as the measuring device. A Berkovich-type diamond indenter manufactured by Bruker Japan Co., Ltd. can be used as the indenter. Details of the measurement conditions and measurement positions are as described in the examples.

[0055] The average values ​​of nanoindentation hardness and stress relaxation are determined as follows: Nanoindentation hardness is measured at 30 or more arbitrarily selected measurement locations on the exposed surface 62 (Figure 4) which has been confirmed to be the adhesive layer 14. The arithmetic mean of the measured values, excluding the maximum and minimum values, is calculated. In this way, the average value of nanoindentation hardness is obtained. Stress relaxation values ​​at 30 or more locations are obtained based on the measurement curve obtained by the nanoindentation method when measuring nanoindentation hardness. The arithmetic mean of these values ​​is the average value of stress relaxation.

[0056] The nanoindentation hardness of the adhesive layer 14 may be adjusted by changing the ratio of the main agent to the curing agent. Furthermore, when a polyol is used as the main agent, the number of terminal OH groups increases as the number-average molecular weight of the polyol increases. Therefore, increasing the amount of curing agent while maintaining a constant molar ratio (NCO / OH) can increase the nanoindentation hardness. The nanoindentation hardness of the adhesive layer 14 may also be adjusted by changing the type of curing agent. For example, comparing IPDI and XDI, IPDI can achieve higher nanoindentation hardness. This is because, regardless of whether it is unsaturated or saturated, isocyanates in which isocyanate groups are partially and directly bonded to the cyclic structure are less sterically mobile than isocyanates in which they are not directly bonded to the cyclic structure, thus forming a stronger structure. Adding a polyfunctional monomer or polymer to the curing agent can increase the nanoindentation hardness. The nanoindentation hardness of the adhesive layer 14 may also be adjusted by changing the retort processing conditions (temperature, time, etc.) of the packaging 200. Furthermore, the degree of stress relaxation in the adhesive layer 14 can be increased by reducing the number-average molecular weight of the main component.

[0057] The laminate used in the packaging bag 100 is not limited to that shown in Figure 3. As shown in Figure 5, the laminates 10a, 10b, and 10c may have multiple adhesive layers. The laminate in Figure 5 has, from the outside of the packaging bag 100, a base layer 11, an ink layer 13, a first adhesive layer 14a, a resin layer 16, a second adhesive layer 14b, and a sealant layer 15 in that order. That is, it differs from the laminate in Figure 3 in that it has two adhesive layers and a resin layer 16 between them. The configuration of the base layer 11, ink layer 13, and sealant layer 15 in the laminate in Figure 5 may be the same as that of the laminate in Figure 3.

[0058] The first adhesive layer 14a and the second adhesive layer 14b may contain the same components as the adhesive layer 14 in Figure 3 and have the same thickness. However, the first adhesive layer 14a and the second adhesive layer 14b may be the same or different in terms of composition and / or thickness. The second adhesive layer 14b is positioned closer to the housing portion 22 than the first adhesive layer 14a. It is preferable that the second adhesive layer 14b, positioned closest to the housing portion 22, has the same average nanoindentation hardness and average stress relaxation degree as the adhesive layer 14 in Figure 3. This is because, when heated in a microwave oven, the second adhesive layer 14b, positioned closer to the housing portion 22 than the first adhesive layer 14a, is exposed to higher temperatures and more easily to steam.

[0059] The average nanoindentation hardness of the second adhesive layer 14b is 0.95 MPa or higher, preferably 1.2 MPa or higher, more preferably 1.5 MPa or higher, and even more preferably 1.9 MPa or higher. This ensures that even under harsh heating conditions in a microwave oven, the steam vents in the steam vent section 50 can form as intended. The average nanoindentation hardness of the second adhesive layer 14b may also be 4.0 MPa or lower, 3.0 MPa or lower, or 2.5 MPa or lower. The average stress relaxation degree of the second adhesive layer 14b, measured by the nanoindentation method, may be between 0.54 and 0.80. This ensures that the adhesive layer 14 can adequately follow the deformation of the sealant layer 15 during steaming, allowing for smooth steaming.

[0060] The average range of nanoindentation hardness and stress relaxation of the first adhesive layer 14a may be the same as that of the second adhesive layer 14b. This allows for the formation of the steam vent in the steam vent section 50 as intended, with even greater reliability, even when the temperature inside the microwave oven becomes high.

[0061] The nanoindentation hardness and stress relaxation of the second adhesive layer 14b and the first adhesive layer 14a can be measured in the same manner as the adhesive layer 14. Specifically, when measuring the nanoindentation hardness and stress relaxation of the second adhesive layer 14b, the sealant layer 15 is cut with the cutting blade 60 of the oblique cutting device to expose the second adhesive layer 14b. Then, the nanoindentation hardness and stress relaxation are measured on the exposed surface, which is determined to be the second adhesive layer 14b based on the difference in hardness with the adjacent layer. The nanoindentation hardness of the first adhesive layer 14a is measured by cutting the sealant layer 15, the second adhesive layer 14b, and the resin layer 16 with the cutting blade 60 of the oblique cutting device to expose the first adhesive layer 14a. Then, the nanoindentation hardness and stress relaxation are measured on the exposed surface, which is determined to be the first adhesive layer 14a based on the difference in hardness with the adjacent layer. The average values ​​of the nanoindentation hardness and stress relaxation are also obtained in the same manner as the adhesive layer 14. The procedure for measuring nanoindentation hardness and stress relaxation is the same as for the adhesive layer 14.

[0062] Examples of the resin layer 16 include polyamide films such as nylon film and polyester films such as PET film. The laminate constituting the packaging bag 100 is not limited to the laminated structure shown in Figures 3 and 5, and may have any resin layer and adhesive layer. In this case, it is sufficient that the average value of the nanoindentation hardness of the adhesive layer provided closest to the containment portion 22 is within the range described above.

[0063] As shown in Figure 3, examples of laminates with a single adhesive layer include the following:

[0064] Example 1) PET film / ink layer / adhesive layer / LLDPE film (linear low-density polyethylene film) Example 2) Nylon film / Ink layer / Adhesive layer / LLDPE film Example 3) Transparent vapor-deposited PET film / ink layer / adhesive layer / CPP film (unoriented polypropylene film) Example 4) Barrier nylon film / ink layer / adhesive layer / CPP film

[0065] As shown in Figure 5, examples of laminates with two adhesive layers include the following. The laminate in Example 5 has excellent drop strength because it contains a nylon film. The laminate in Example 6 has excellent tear resistance. In addition, it has superior heat resistance compared to those with a nylon film as an intermediate layer, as in Example 5.

[0066] Example 5) Transparent vapor-deposited PET film / ink layer / first adhesive layer / nylon film / second adhesive layer / CPP film Example 6) Transparent vapor-deposited PET film / ink layer / first adhesive layer / PET film / second adhesive layer / CPP film

[0067] The laminated structure of the laminate is not limited to the examples described above. For example, it may have three or more adhesive layers. Examples of such laminated structures include the following:

[0068] Example 7) Transparent vapor-deposited PET film / ink layer / first adhesive layer / PET film / second adhesive layer / nylon film / third adhesive layer / CPP film Example 8) Transparent vapor-deposited PET film / ink layer / first adhesive layer / nylon film / second adhesive layer / PET film / third adhesive layer / CPP film Example 9) Transparent vapor-deposited PET film / ink layer / first adhesive layer / PET film / second adhesive layer / PET film / third adhesive layer / CPP film Example 10) Transparent vapor-deposited PET film / ink layer / first adhesive layer / PET film / second adhesive layer / nylon film / third adhesive layer / CPP film

[0069] As shown in Example 9, if all resin layers other than the sealant layer are PET film, the heat resistance can be further improved. On the other hand, if a nylon film is present, as in Examples 7 and 8, the drop strength can be increased. In particular, as in Example 7, if the resin layer bonded to the sealant layer (CPP film) via the third adhesive layer is nylon film, the drop strength of the packaging bag and package can be further improved. That is, the packaging bag (package) can be made less likely to break when dropped. Note that regardless of the presence or absence of nylon film, a larger number of resin layers can increase the drop strength.

[0070] In each of the above-described examples 1 to 10, the leftmost layer is the substrate layer, the rightmost layer is the sealant layer, and the layers are stacked sequentially from left to right. By ensuring that the nanoindentation hardness range of the adhesive layers near the sealant layer (second adhesive layer, third adhesive layer) is within the above-described range, the steam vents in the steam vent section 50 can be formed as intended. It is also preferable that the nanoindentation hardness range of the other adhesive layers is within the above-described range. The components and / or thicknesses of the first adhesive layer, second adhesive layer, and third adhesive layer may be the same or different from each other. In any of the examples, the ink layer may be omitted. Furthermore, if the ink layer is an electrostatic ink layer, a primer layer may be present between the substrate layer and the ink layer.

[0071] The shape of the packaging bag 100 is not particularly limited and is suitable for microwave heating as long as it has a steam vent. The packaging bag is not limited to a standing pouch and may be, for example, a two-sided bag, a three-sided bag, or a gusseted bag. For example, the laminate shown in Figure 3, Figure 5, or each of the above examples may be folded in half so that the sealant layers 15 (surface 10B) face each other, and the side ends and top ends may be heat-sealed to produce a packaging bag, or the ends of two opposing laminates may be heat-sealed to produce a packaging bag. Alternatively, three or more laminates may be used and the sealant layers 15 may be heat-sealed to form a packaging bag.

[0072] Although one embodiment of the present disclosure has been described above, the present disclosure is not limited in any way to the above embodiment.

[0073] This disclosure includes the following [1] to [8]: [1] A packaging bag that is heated in a microwave oven, comprising a laminate including a sealant layer, one or more adhesive layers, and a base layer, A seal portion formed by heat-sealing the opposing sealant layers, It comprises a storage section surrounded by the aforementioned laminate and configured to accommodate the contents, The sealing portion includes a steam vent that forms a steam passage when the pressure in the housing rises. A packaging bag in which the average value of the nanoindentation hardness of at least one of the adhesive layers is 0.95 MPa or higher. [2] The packaging bag according to [1], wherein the average value of the degree of stress relaxation of at least one of the adhesive layers, as measured by nanoindentation, is 0.54 or more and 0.80 or less. [3] The packaging bag according to [1] or [2], wherein the adhesive layer comprises a cured urethane adhesive. [4] The laminate includes a nylon film between the sealant layer and the substrate layer. The packaging bag according to [1] to [3], wherein the average value of the nanoindentation hardness of the adhesive layer that bonds the sealant layer and the nylon film is 0.95 MPa or more. [5] The packaging bag according to any one of [1] to [4], wherein the base material layer comprises an outermost resin layer and a barrier layer located closer to the adhesive layer than the resin layer. [6] The packaging bag according to [5], wherein the barrier layer comprises at least one selected from the group consisting of an alumina vapor-deposited layer and a silica vapor-deposited layer. [7] A packaging bag according to any one of [1] to [6], wherein the average value of the nanoindentation hardness after retort treatment is 0.95 MPa or higher. [8] A packaging body that is heated in a microwave oven, comprising a packaging bag according to any one of [1] to [7] above, and contents contained in the storage portion of the packaging bag. [Examples]

[0074] The contents of this disclosure will be described in more detail with reference to examples and comparative examples, but this disclosure is not limited to the following examples.

[0075] [Fabrication of laminates] (Example 1) Alumina-deposited PET film (Toppan Printing Co., Ltd., product name: GLARHF, thickness: 12 μm) was prepared as the base layer, nylon film (Unitika Ltd., product name: Emblem ONMB, thickness: 15 μm) as the resin layer, and unoriented polypropylene film (Toray Film Processing Co., Ltd., product name: ZK-207, thickness: 60 μm) as the sealant layer.

[0076] An adhesive composition (two-component curing type urethane adhesive) with a solid content concentration of 36.5% by mass was prepared by blending an aliphatic polyester polyol (manufactured by Mitsui Chemicals, Inc., trade name: Takelac A505, sometimes referred to as "(A)") as the main agent, a polyisocyanate (manufactured by Mitsui Chemicals, Inc., trade name: Takenate A20, sometimes referred to as "(B)") as the curing agent, and ethyl acetate as the solvent. The blending ratio (by mass) of each component was (A):(B)=9:1.

[0077] The adhesive composition prepared as described above was applied to the alumina-deposited surface of the alumina-deposited PET film using a dry laminating apparatus to form a first adhesive layer having a predetermined thickness.

[0078] A laminated film was prepared by bonding a nylon film (manufactured by Unitika Ltd., product name: Emblem ONMB, thickness: 15 μm) and an unoriented polypropylene film (manufactured by Toray Film Processing Co., Ltd., product name: ZK-207, thickness: 60 μm) using the above-mentioned adhesive composition. Using the above-mentioned dry laminating apparatus, the nylon film and the adhesive layer were bonded together so that the adhesive layer on the substrate layer and the nylon film of the laminated film faced each other. Subsequently, aging was performed at 40°C for 120 hours to obtain a plain laminate having a laminated structure of alumina-deposited PET film / first adhesive layer / nylon film / second adhesive layer / unoriented polypropylene film.

[0079] (Example 2, Comparative Examples 1, 2) Except for changing the types of main component and curing agent of the adhesive composition, the mixing ratio (by mass) of the main component and curing agent, and the aging conditions as shown in Table 1, a plain laminate having a laminated structure of alumina-deposited PET film / first adhesive layer / nylon film / second adhesive layer / unoriented polypropylene film was obtained in the same manner as in Example 1. The adhesive composition shown in Table 1 (two-component curing type urethane adhesive) was used for both the first and second adhesive layers.

[0080] (Example 3) An aliphatic polyester polyol with a smaller number-average molecular weight than the main component used in Example 2 was prepared. Except for using this main component and using a curing agent that had a polyfunctional monomer added to the curing agent of Example 2, the same laminate as in Example 2 was obtained in the same manner as in Example 2. The aging conditions were the same as in Example 2.

[0081] [Table 1]

[0082] In Table 1, the "Main component (A)" and "Hardening agent (B)" columns show the product names (both manufactured by Mitsui Chemicals, Inc.). Each aging test was performed in air.

[0083] [Production of packaging bags (packaging bodies)] (Example 1A) Using three laminates from Example 1, a pouch (packaging bag) with a steam vent in the side seal portion was fabricated as shown in Figure 2. Specifically, the side seal portions and bottom seal portions other than the steam vent portion were heat-sealed using the impulse method (temperature: 190°C), and then the steam vent portion was formed by heat-sealing using a mold. The heat-sealing conditions for forming the steam vent portion were performed using each of the conditions 1 to 4 in Table 2, and four packaging bags with different heat-sealing conditions were fabricated. Then, 100g of water was placed in the containment portion, and the top end was heat-sealed using the impulse method (temperature: 190°C) to form the top end seal portion. In this way, four standing pouches (packaging bags and packaging bodies) with water sealed in the containment portion were obtained as shown in Figure 1.

[0084] (Example 2A) Except for using the laminate of Example 2 instead of the laminate of Example 1, a standing pouch (packaging bag and packaging body) with water sealed in the containment section was obtained in the same manner as in Example 1A. In Example 2A, as in Example 1, the heat sealing conditions for forming the steam vent section were carried out under each of the conditions 1 to 4 in Table 2, and four standing pouches with different heat sealing conditions were produced.

[0085] (Example 3A) Except for using the laminate of Example 3 instead of the laminate of Example 1, a standing pouch (packaging bag and packaging body) with water sealed in the containment section was obtained in the same manner as in Example 1A. In Example 2A, as in Example 1, the heat sealing conditions for forming the steam vent section were carried out using each of the conditions 1 to 4 in Table 2, and four standing pouches with different heat sealing conditions were produced.

[0086] (Comparative Example 1A) Except for using the laminate of Comparative Example 1 instead of the laminate of Example 1, a standing pouch (packaging bag and packaging body) with water sealed in the containment section was obtained in the same manner as in Example 1A. In Comparative Example 1A, as in Example 1, the heat sealing conditions for forming the steam vent section were carried out under each of the conditions 1 to 4 in Table 2, and four standing pouches with different heat sealing conditions were produced.

[0087] (Comparative example 2A) A standing pouch (packaging) with water sealed in the containment section was obtained in the same manner as in Example 1A, except that the laminate of Comparative Example 2 was used instead of the laminate of Example 1. In Comparative Example 2A, as in Example 1, the heat sealing conditions for forming the steam vent section were carried out under each of the conditions 1 to 4 in Table 2, and four standing pouches with different heat sealing conditions were produced.

[0088] [Table 2]

[0089] [Steam release test] The standing pouches of Examples 1 and 2 and Comparative Example 2 were subjected to retort processing. Retort processing was carried out by heating in a 121°C hot water spray for 30 minutes. After retort processing, each package was left at room temperature for 24 hours to cool, and then a steam release test was performed by heating in a microwave oven (output: 500W) for 2 minutes. The results of the steam release test were evaluated according to the following criteria. The evaluation results are shown in Table 3.

[0090] A: As expected, a steam vent was formed in the steam vent section, and after the water boiled, the steam was quickly released through the vent. B: Although a steam vent was formed in the steam vent section as expected, the formation of the steam vent was slower than in evaluation "A" above, and steam was released all at once from the steam vent after the pressure in the containment section became higher than in A. C: The steam vent did not form as expected in the steam vent section, and delamination occurred between the layers (adhesive layer), causing a sudden release of steam.

[0091] [Table 3]

[0092] As shown in Table 3, the steam venting test evaluation for Examples 1A and 3A was "A" under all heat sealing conditions. On the other hand, in Comparative Example 2A, under condition 2, steam was ejected not from between the bonded sealant layers, but from the adhesive layer. As a result, the force of the steam ejection caused the package to rotate inside the microwave oven.

[0093] [Fabrication of laminates] (Example 1B) An ink layer was applied to the alumina-deposited surface of an alumina-deposited PET film using gravure printing. Aside from the addition of this ink layer, the laminate was prepared using the same procedure as in Example 1. Specifically, a laminate with a laminated structure of alumina-deposited PET film / first adhesive layer / nylon film / second adhesive layer / unoriented polypropylene film was obtained. This was designated as the laminate of Example 1B. The compositions of the first and second adhesive layers in Example 1B are the same as those in Example 1.

[0094] (Example 2B, Example 3B, Comparative Example 1B, Comparative Example 2B) Laminates were prepared using the same procedure as in Examples 2, 3, Comparative Example 1, and Comparative Example 2, except that the same ink layer as in Example 1B was provided. These laminates were designated as the laminates of Example 2A, Comparative Example 1A, and Comparative Example 2A, respectively. All of these laminates had a laminated structure consisting of alumina-deposited PET film / ink layer / first adhesive layer / nylon film / second adhesive layer / unoriented polypropylene film. The compositions of the first and second adhesive layers in Examples 2B, 3B, and Comparative Examples 1B, 2B were the same as the compositions of the first and second adhesive layers in Examples 2, 3, and Comparative Examples 1, 2, respectively.

[0095] [Retort processing] The laminates of Examples 1B, 2B, and 3B, and Comparative Examples 1B and 2B were subjected to retort processing. The retort processing conditions were the same as those for the standing pouches (packaging) of Examples 1, 2, and 3 and Comparative Examples 1 and 2.

[0096] [Evaluation of nanoindentation hardness of adhesive layers] Using an oblique cutting device (SAICAS®, manufactured by Daipla Wintes Co., Ltd.), the unoriented polypropylene film of each laminate in Examples 1B, 2B, and 3B, and Comparative Examples 1B and 2B, was cut to expose the second adhesive layer. Specifically, epoxy adhesive was applied to the side opposite the unoriented polypropylene film (sealant layer) of the laminate, and it was bonded to a glass plate and fixed smoothly. After the epoxy adhesive hardened, the adhesive layer was exposed using the oblique cutting device as shown in Figure 4. The oblique cutting device used was SAICAS DN-GS (product name) manufactured by Daipla Wintes Co., Ltd. After attaching the diamond cutting blade 60, which has a V-shaped tip, to the oblique cutting device, side cut lines were made at 1 mm intervals on the surface of the unoriented polypropylene film (sealant layer) of the measurement sample (laminated). Subsequently, a diamond knife with a blade width of 1 mm, a rake angle of 20 degrees, and a relief angle of 10 degrees was brought into contact with the surface of an unstretched polypropylene film (sealant layer) under a load of 0.05 N, and then oblique cutting was performed under conditions of a horizontal speed of 50 μm / s and a vertical speed of 1 μm / s.

[0097] After the cutting depth reached 55 μm, 10 mm of cutting was performed horizontally. Finish cutting was performed under the conditions of a horizontal speed of 50 μm / s, a vertical speed of 1 μm / s, and a cutting depth of 1 μm. The exposed surface after cutting was observed to confirm that the adhesive layer had been exposed. If the adhesive layer was not sufficiently exposed, additional finish cutting was performed. Figure 6 shows an example of the changes in cutting depth, horizontal load, and vertical load using an oblique cutting device.

[0098] The surface of the adhesive layer exposed by cutting was observed using an optical microscope attached to a measuring device capable of nanoindentation measurement to determine the measurement position. At the measurement position, nanoindentation measurements were performed to identify the areas where the unstretched polypropylene film remained, the areas where the second adhesive layer was exposed, and the areas where the nylon film was exposed.

[0099] A Hysitron TI-Premier (product name) manufactured by Bruker Japan Co., Ltd. was used as the measuring device. A Bruker Japan Co., Ltd. Berkovich-type diamond indenter was used as the indenter. Hardness was measured using the nanoindentation method in the following procedure. First, at room temperature (25°C), indentation was performed in displacement control mode with the indentation speed set to 100 nm / second and the test depth to 125 nm. After holding at maximum displacement for 2 seconds, the load was removed at a speed of 50 nm / second. The surface detection load was set to 1 μN, and the point where the load indicated 0 was considered the surface. Surface correction was performed using TriboScan software.

[0100] Hardness measurements were performed on the exposed surface of the adhesive layer at 30 locations (n=30) at intervals of 30 μm or more, using the nanoindentation method. The measurement locations were determined by dividing the distance between the sealant layer and the substrate layer into four equal parts, and selecting a location 1 / 4 of the way from the sealant layer. The results of the first measurement are shown in Figure 7.

[0101] The calculation method for nanoindentation hardness and stress relaxation was as follows. First, a standard sample of fused silica was tested in advance to calibrate the relationship between the contact depth and contact projected area between the indenter and the sample. Then, the contact depth hc was determined by analyzing the unloading curve in the 20-95% range for the maximum load during unloading using the Oliver-Pharr method. Specifically, the contact depth hc was determined by the following equation (1).

[0102]

number

[0103] In equation (1), ε is a constant relating to the indenter shape. For a Berkovich indenter, this constant is 0.75. The maximum load Pmax and maximum displacement hmax of the unloading curve were determined based on the graph shown in Figure 7. S is the contact stiffness. The contact stiffness S is the slope immediately after withdrawal of the approximate curve when the range from 20% to 95% of the maximum load in the unloading curve in Figure 7 is fitted with the function of equation (2) below. In equation (2), A, hf, and m represent the fitting parameters during the fitting process.

[0104]

number

[0105] Next, the contact projected area Ac was determined based on the shape of the indenter and the contact depth hc. The contact projected area Ac can be expressed as a function of the contact depth hc, as shown in equation (3) below. Equation (3) corrects for the effect of the roundness of the indenter tip using correction terms C1 to C5. C1 to C5 were calculated by measuring fused silica as a test specimen under maximum loads of 20 μN to 10 mN, and ensuring that the measured composite modulus at each maximum load condition matched the composite modulus Er: 69.6 GPa of fused silica.

[0106]

number

[0107] Next, the nanoindentation hardness H was calculated using the contact projected area Ac and the following formula (4).

number

[0108] The degree of stress relaxation was derived using the following equation (5) by determining the maximum load under load (Fmax) and the maximum load during unloading (Pmax) from the measurement curve in Figure 7 obtained by the nanoindentation method. Stress relaxation degree = (Fmax - Pmax) / Fmax (5)

[0109] Nanoindentation hardness was measured at 30 locations (n=30). The average value, standard deviation, and coefficient of variation of 28 measurements (excluding the maximum and minimum values) were calculated. The average stress relaxation degree was determined by averaging the measurements obtained based on 30 measurement curves obtained using the nanoindentation method during the nanoindentation hardness measurement. The results are shown in Table 4.

[0110] [Table 4]

[0111] As shown in Table 4, the second adhesive layer in Examples 1B, 2B, and 3B had greater hardness than the second adhesive layer in Comparative Example 2B. In Examples 1B, 2B, and 3B, where the nanoindentation hardness of the second adhesive layer is high, the unoriented polypropylene film and nylon film bonded by the second adhesive layer remain firmly fixed even when the package is heated in a microwave oven. Therefore, it is thought that tensile stress is applied to the steam vent as expected, and the steam vent can be formed as intended. On the other hand, in Comparative Example 2B, where the nanoindentation hardness of the second adhesive layer is low, it is thought that when heated in a microwave oven, the unoriented polypropylene film and nylon film bonded by the second adhesive layer move slightly due to the tensile stress, preventing tensile stress from being applied to the steam vent as expected. As a result, delamination occurs in the second adhesive layer, and steam is released.

[0112] To investigate the effects of retort processing, the second adhesive layer of each laminate from Examples 1B, 2B, and 3B (before retort processing) and Comparative Example 2B was exposed using an oblique cutting device, similar to the procedure used for the laminates after retort processing, and the nanoindentation hardness of the second adhesive layer was measured. The measurement conditions were the same as those for the laminates after retort processing. Nanoindentation hardness was measured at 30 locations (n=30), and the average value (AVE0) of 28 measurements excluding the maximum and minimum values ​​was calculated. The difference between AVE1 and AVE0 (AVE1-AVE0) was then calculated, and the rate of decrease in nanoindentation hardness associated with retort processing was determined using the following formula. The results are shown in Table 5. Nanoindentation hardness reduction rate = [(AVE1-AVE0) / AVE1]×100

[0113] [Table 5]

[0114] As shown in Table 5, it was confirmed that the nanoindentation hardness of the second adhesive layer may change due to retort processing. The smaller the decrease in nanoindentation hardness due to retort processing (if negative, the larger the absolute value), the lower the hardness of the second adhesive layer after retort processing. If the decrease in nanoindentation hardness of the second adhesive layer due to retort processing is large, the vapor vents can be formed as intended even after retort processing by ensuring that the nanoindentation hardness of the second adhesive layer is sufficiently high before retort processing. [Industrial applicability]

[0115] This invention provides a packaging bag that can form steam vents with high precision and as intended when heated in a microwave oven, and a packaging body equipped with such a packaging bag. [Explanation of Symbols]

[0116] 10a, 10b, 10c... Laminate, 10A, 10B... Surface, 11... Base layer, 13... Ink layer, 14... Adhesive layer, 14a... First adhesive layer, 14b... Second adhesive layer, 15... Sealant layer, 16... Resin layer, 20... Contents, 22... Contents section, 30... Seal section, 31... Upper end seal section, 31a... Upper end, 33... Side end seal section, 33, 34... Side end seal section, 34... Side end seal section, 35, 36... Lower end seal section, 41... Notch, 53... Non-sealed section, 60... Cutting edge, 62... Exposed surface, 100, 101... Packaging bag, 200... Packaging body.

Claims

1. A packaging bag that is heated in a microwave oven, comprising a laminate including a sealant layer, one or more adhesive layers, and a base layer, A seal portion formed by heat-sealing the opposing sealant layers, It comprises a storage section surrounded by the aforementioned laminate and configured to accommodate the contents, The sealing portion includes a steam vent that forms a steam passage when the pressure in the housing rises. A packaging bag in which the average value of the nanoindentation hardness of at least one of the adhesive layers is 0.95 MPa or higher.

2. The packaging bag according to claim 1, wherein the average value of the degree of stress relaxation of at least one of the adhesive layers, as measured by nanoindentation, is 0.54 or more and 0.80 or less.

3. The packaging bag according to claim 1, wherein the adhesive layer includes a cured product of a urethane adhesive.

4. The laminate includes a nylon film between the sealant layer and the substrate layer. The packaging bag according to claim 1, wherein the average value of the nanoindentation hardness of the adhesive layer that bonds the sealant layer and the nylon film is 0.95 MPa or more.

5. The packaging bag according to claim 1, wherein the base material layer has an outermost resin layer and a barrier layer closer to the adhesive layer than the resin layer.

6. The packaging bag according to claim 5, wherein the barrier layer comprises at least one selected from the group consisting of an alumina vapor-deposited layer and a silica vapor-deposited layer.

7. The packaging bag according to claim 1, wherein the average value of the nanoindentation hardness after retort processing is 0.95 MPa or more.

8. A package that is heated in a microwave oven, A packaging body comprising a packaging bag according to any one of claims 1 to 7, and an object contained in the storage portion of the packaging bag.

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