Pouch for microwave ovens and filled pouch for microwave ovens

Abstract

[Problem] To provide a pouch for microwave ovens which has a simple configuration and has improved drop strength, and a filled pouch for microwave ovens. [Solution] A pouch 10 for microwave ovens comprises: a heat seal layer 30 having a sea-island structure comprising a sea portion 31 made of polypropylene, first island portions 32 made of polyethylene, and second island portions 33 made of an ethylene / propylene copolymer; and a base layer 70 having a sea-island structure comprising a sea portion 71 made of poly(ethylene terephthalate) and island portions 72 made of a modified poly(butylene terephthalate). The base layer 70 has a content of the modified poly(butylene terephthalate) of 5-45 wt%.

Description

Microwave pouches and filled microwave pouches

[0001] MICROWAVE POUCH AND PACKED MICROWAVE POUCH FIELD OF THE INVENTION The present invention relates to a microwaveable pouch and a filled microwaveable pouch.

[0002] Conventionally, a microwaveable pouch has been known which is made by forming a laminated film into a bag shape and which is provided with an automatic steam release mechanism in which a steam release section is formed inside a steam release seal section (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2002-249176

[0004] In the course of research and development into such microwave pouches, the applicant has found that there is room for improvement in terms of drop strength.

[0005] SUMMARY OF THE INVENTION The present invention is intended to solve these problems and to provide a microwave pouch and a microwave pouch containing a content that have a simple structure and improved drop strength.

[0006] The microwave pouch of the present invention is made by forming a laminated film into a bag shape and is equipped with an automatic steam vent mechanism that automatically releases internal steam during microwave heating. The laminated film is made of, from the inner layer side, a heat-seal layer, an adhesive layer, and a base layer. The heat-seal layer has a sea-island structure having a sea region made of polypropylene, a first island region made of polyethylene, and a second island region made of an ethylene-propylene copolymer. The base layer has a sea-island structure having a sea region made of polyethylene terephthalate and islands made of modified polybutylene terephthalate. The base layer contains 5 to 45 wt % of modified polybutylene terephthalate, thereby solving the above-mentioned problems. In the microwave pouch, the first island region may be made of linear low-density polyethylene, and the heat-seal layer may contain 10 to 30 wt % of linear low-density polyethylene. In any of the above microwave pouches, the microwave pouch is formed into a bag shape by having an outer edge seal portion formed by heat welding the laminated film, and the heat seal layer has a tensile impact strength of 300 kJ / m at 5°C in either the width direction or the length direction of the pouch, whichever is shorter, of the inner edges of the outer edge seal portion. ２The microwave pouch may be formed as described above. In any of the microwave pouches described above, only a printed layer, or only a printed layer and a barrier layer, may be formed between the adhesive layer and the base layer. In any of the microwave pouches described above, the laminate film may not include any layer made of adhesive other than the adhesive layer, and may not include any layer made of ink other than the printed layer, and the adhesive layer may be formed from a solvent-free adhesive. In any of the microwave pouches described above, the printed layer may be formed from an ink that does not contain toluene. In any of the microwave pouches described above, the automatic steam release mechanism may be configured to peel a steam release seal portion to allow steam to escape during microwave heating, and the number of ink colors making up the printed layer may be set to two or less at the outer edge of the steam release seal portion. The content-filled microwave pouch of the present invention is a content-filled microwave pouch comprising the microwave pouch and a content filled in the microwave pouch, wherein the laminated film has a printed layer formed between the adhesive layer and the base layer, and the hue of the heat seal layer colored by the content and the hue of the ink constituting the printed layer that has the largest area in the planar direction of the pouch are the same hue or adjacent hues in the color arrangement on a hue wheel chart of 10 hues of the Munsell color system, thereby solving the above-mentioned problem.

[0007] According to the present invention, drop strength can be improved with a simple configuration.

[0008] 1 is a plan view showing a microwave pouch according to one embodiment of the present invention; 2 is a cross-sectional view of the microwave pouch; 3 is an explanatory diagram showing the structure of a heat seal layer and a base material layer; 4 is an explanatory diagram showing a hue circle chart of 10 hues of the Munsell color system; 5 is an explanatory diagram showing the results of a first test example; 6 is an explanatory diagram showing the results of a second test example;

[0009] A microwave pouch 10 according to one embodiment of the present invention will now be described with reference to the drawings.

[0010] First, as shown in Figures 1 and 2, a microwave pouch 10 is formed into a bag shape by forming an outer edge seal portion (heat seal portion) 11 for bag making, which is formed by heat-sealing the outer edge of overlapping laminated films 20, and the contents such as food are contained in the inner storage portion.

[0011] As shown in Fig. 1, microwave pouch 10 is equipped with an automatic steam release mechanism 80 that automatically releases steam within microwave pouch 10 to the outside when heated in a microwave oven. As shown in Fig. 1, automatic steam release mechanism 80 has a steam release seal portion 81 formed by heat-sealing front and back laminate films 20 (and heat seal layers 30, described below), a steam release portion 82 surrounded by steam release seal portion 81 (wherein heat seal layers 30 of front and back laminate films 20 are not heat-sealed), and hole- or slit-shaped steam release portions 83 formed in at least one of front and back laminate films 20 in steam release portion 82. When microwave heating is performed, steam release seal portion 81 peels off as the internal pressure within the storage compartment of microwave pouch 10 increases, allowing the pressure within microwave pouch 10 to be released to the outside through steam release portion 82 and steam release portion 83. Furthermore, the steam release portion 82 may be open to the side edge of the pouch and connected to the outside when the steam release seal portion 81 is peeled off to release pressure, and any structure other than that described above may be adopted for the automatic steam release mechanism 80 as long as it allows the release of steam generated during heating in a microwave oven. Furthermore, as shown in Figure 1, the steam release seal portion 81 has a seal peel start planned portion 81b, which is the portion of the outer edge 81a of the steam release seal portion 81 that is closest to the center of the containing portion and is the portion where peeling of the steam release seal portion 81 is planned to start first when heating in a microwave oven.

[0012] Next, specific embodiments of the laminated film 20 constituting the microwave pouch 10 will be described.

[0013] First, as shown in FIG. 2, each laminated film 20 is formed by laminating, from the inner layer side, a heat seal layer 30, an adhesive layer 40, a printing layer 50, a barrier layer 60, and a base layer 70 in that order.

[0014] As shown in FIG. 2, when the microwave pouch 10 is made, the heat seal layer 30 is positioned as the innermost layer facing the other laminate film 20, and is heat-sealed to the heat seal layer 30 of the other laminate film 20.

[0015] Specifically, as shown in FIG. 3( a), the heat-seal layer 30 is formed from impact polypropylene (also called impact PP, block polypropylene, impact copolymer, or high-impact polypropylene), a type of non-oriented polypropylene (CPP or cast PP film), having a sea-island structure with a sea portion 31 made of polypropylene (PP), a first island portion 32 made of polyethylene such as linear low-density polyethylene (LLDPE) or low-density polyethylene (LDPE), and a second island portion 33 made of ethylene-propylene copolymer (EPR). In this embodiment, the first island portion 32 is made of linear low-density polyethylene (LLDPE), and the heat-seal layer 30 is formed so that the content of linear low-density polyethylene (LLDPE) in the heat-seal layer 30 is 10 to 30 wt %. The heat-seal layer 30 may be formed by mixing an elastomer, such as styrene-butadiene copolymer (SBR), in addition to the above materials. Furthermore, when the above-mentioned sea-island structure is adopted, the drop strength (impact resistance) of microwave pouch 10 is improved. This is thought to be partly because voids are likely to form between sea portion 31 and island portions 32, 33, and these voids function as cushions when microwave pouch 10 is subjected to an impact, such as when microwave pouch 10 is dropped. The thickness of heat-seal layer 30 is preferably 40 μm or more, and more preferably 60 μm or more. The thickness of heat-seal layer 30 is preferably 100 μm or less, and more preferably 80 μm or less.

[0016] In addition, each heat seal layer 30 has a tensile impact strength of 300 kJ / m at 5° C. in either the pouch horizontal direction X or the pouch vertical direction Y, whichever is shorter in the distance between the inner edges of the outer edge seal portion 11 (in this embodiment, the pouch horizontal direction X). ２The outer edge seal portion 11 is formed as described above. Here, the distance L1 between the inner edges of the outer edge seal portion 11 in the pouch width direction X refers to the distance between the inner edges of the left and right side seals 11c that make up the outer edge seal portion 11 in the pouch width direction X, as shown in FIG. 1 , between the points furthest apart in the pouch width direction X (in other words, the longest distance in the pouch width direction X between the inner edges of the left and right side seals 11c). Furthermore, the distance L2 between the inner edges of the outer edge seal portion 11 in the pouch length direction Y refers to the distance between the inner edges of the top seal portion 11a and the bottom seal portion 11b that make up the outer edge seal portion 11 in the pouch length direction Y, as shown in FIG. 1 , between the points furthest apart in the pouch length direction Y (in other words, the longest distance in the pouch length direction Y between the inner edges of the top seal portion 11a and the bottom seal portion 11b). As described above, the heat seal layer 30 has a tensile impact strength of 300 kJ / m ２ To achieve the above, the blending ratio of each component constituting the heat seal layer 30, the layer thickness, and conditions such as the extrusion temperature, screw rotation speed, and screw shape when forming the heat seal layer 30 may be adjusted.

[0017] The adhesive layer 40 is made of an adhesive such as a urethane-based adhesive or an epoxy-based adhesive, and bonds the heat-seal layer 30 to the base layer 70 (having the barrier layer 60 and the printed layer 50 laminated on its inner surface) as shown in Fig. 2. Specifically, the heat-seal layer 30 and the base layer 70 are bonded by a dry lamination method (a method in which an adhesive such as a urethane-based adhesive is applied to the inner layer side of the base layer 70 having the barrier layer 60 and the printed layer 50 laminated on its inner surface, the solvent is evaporated in a drying device, and the heat-seal layer 30 and the base layer 70 are then thermocompression-bonded together). The thickness of the adhesive layer 40 (the thickness of the adhesive layer 40 in the portion where the printed layer 50 is not interposed between the heat-seal layer 30 and the barrier layer 60) is preferably 0.5 µm or more, and more preferably 1.0 µm or more. Furthermore, the thickness of the adhesive layer 40 (the thickness of the adhesive layer 40 in the portion where the printed layer 50 is not interposed between the heat seal layer 30 and the barrier layer 60) is preferably 6.0 μm or less, and more preferably 4.0 μm or less.

[0018] As shown in FIG. 2 , the printed layer 50 is a layer composed of one or more inks 50 a (one color) arranged on the inner surface side of the barrier layer 60. In the example shown in FIG. 2 , the printed layer 50 of one of the laminate films 20 (the laminate film 20 shown on the upper side of FIG. 2 ) is formed by two inks 50 a (two colors) laminated in the film thickness direction, while the printed layer 50 of the other of the laminate films 20 (the laminate film 20 shown on the lower side of FIG. 2 ) is formed by one ink 50 a (one color) laminated in the film thickness direction. As shown in the example shown in FIG. 2 , a region without the printed layer 50 (ink 50 a) may be provided between the adhesive layer 40 and the barrier layer 60, i.e., a region where the adhesive layer 40 and the barrier layer 60 are directly laminated. The thickness of each ink 50 a is preferably 1.0 μm or more, more preferably 2.0 μm or more. The thickness of each ink 50 a is preferably 10.0 μm or less, more preferably 8.0 μm or less.

[0019] With regard to this printed layer 50, from the viewpoint of preventing delamination between the heat seal layer 30 and the barrier layer 60 in the steam release seal portion 81 during heating in a microwave oven, it is preferable that the number of colors of the inks 50a constituting the printed layer 50 be set to two or less (i.e., the number of inks 50a laminated in the film thickness direction be set to two or less) at the outer edge 81a of the steam release seal portion 81 (i.e., at the position overlapping the outer edge 81a of the steam release seal portion 81 in the film thickness direction), and more preferably the number of colors be set to one or less (one color or zero colors). From the same viewpoint, when the ink 50a is disposed at the outer edge 81a of the steam release seal portion 81, it is preferable that the ink 50a (preferably of one color) be disposed at the outer edge 81a of the steam release seal portion 81 by halftone printing (i.e., the ink 50a is disposed in a discrete dot pattern)

[0020] Furthermore, from the viewpoint of avoiding the occurrence of the above-mentioned delamination while peeling off the steam vent seal portion 81 well when heated in a microwave oven, it is preferable to form the steam vent seal portion 81 so that the seal strength of the steam vent seal portion 81 at 100°C is 20 N or less, and it is more preferable to form it so that the seal strength is 15 N or less.

[0021] Furthermore, in a state where the storage section is filled with a content such as food to form a content-filled microwave pouch, heat seal layer 30 having a sea-island structure tends to be easily discolored by the content filled in the storage section of microwave pouch 10. Therefore, from the viewpoint of preventing the appearance of the pouch from being adversely affected by such discoloration of heat seal layer 30, it is preferable that, for each laminate film 20, the hue of heat seal layer 30 colored by the content and the hue of ink 50a constituting printed layer 50 and having the largest area in the planar direction of the pouch are the same hue or adjacent hues in the color arrangement of the 10-hue hue circle chart of the Munsell color system shown in Figure 4 (a chart consisting of the 10 hues: red, red-yellow, yellow, yellow-green, green, blue-green, blue, blue-purple, purple, and red-purple). The expression "the same hue" between the hue of the heat seal layer 30 and the hue of the ink 50a in the color arrangement on the hue wheel chart means, for example, that one hue belongs to the yellow hue range among the 10 hues of the Munsell color system (more specifically, when each hue is expressed by dividing it into 10, it is any one of 1Y to 10Y), and the other hue belongs to the yellow hue range among the 10 hues of the Munsell color system (more specifically, when each hue is expressed by dividing it into 10, it is any one of 1Y to 10Y). Furthermore, the expression "the hue of the heat seal layer 30 and the hue of the ink 50a are adjacent hues" in the color arrangement on the hue wheel chart means, for example, that when one hue belongs to the yellow hue range of the 10 hues of the Munsell color system (more specifically, when each hue is divided into 10 parts, it is any one of 1Y to 10Y), the other hue belongs to the reddish-yellow hue range of the 10 hues of the Munsell color system (more specifically, when each hue is divided into 10 parts, it is any one of 1YR to 10YR), or belongs to the yellow-green hue range (more specifically, when each hue is divided into 10 parts, it is any one of 1GY to 10GY).

[0022] The barrier layer 60 is a layer for imparting gas barrier properties and moisture barrier properties to the laminated film 20, and in this embodiment, it is made of aluminum oxide (alumina, Al ２ O ３The barrier layer 60 is formed by depositing an inorganic substance or inorganic oxide, such as silicon (Si), aluminum (Al), or the like, onto the substrate layer 70, and then coating the deposited layer with a coating layer to protect the deposited layer. The coating layer is formed from a compound containing at least one of a water-soluble polymer, a metal alkoxide, or a hydrolyzate thereof (specifically, containing at least one of these as a main component). The specific form of the barrier layer 60 is not limited to the above-described deposition layer and coating layer, and any material may be used as long as it can impart various barrier properties to the substrate film 30. For example, a gas barrier resin, such as a polyvinyl alcohol polymer or a polycarboxylic acid polymer, may be used as the coating layer, so that the coating layer alone serves as a barrier layer. Alternatively, a resin film, such as polyvinylidene chloride, polyacrylonitrile, or an ethylene-vinyl alcohol copolymer, may be used as the barrier layer 60 and adhered to the substrate layer 70. An anchor coating layer may be provided between the substrate layer 70 and the barrier layer 60 to improve adhesion to the substrate layer 70. The thickness of the barrier layer 60 varies depending on the form of the barrier layer 60, but when the barrier layer 60 is formed from a vapor deposition layer and a coating layer, or from a coating layer only, the thickness is preferably from 0.1 μm to 10 μm, and more preferably from 0.2 μm to 5 μm. When the barrier layer 60 is formed as a film, the thickness is preferably from 10 μm to 25 μm, and more preferably from 12 μm to 16 μm.

[0023] In this embodiment, the substrate layer 70 is formed as the outermost layer of the laminate film 20. As shown in FIG. 3( b), the substrate layer 70 has a sea-island structure with a sea portion 71 made of polyethylene terephthalate (PET) and an island portion 72 made of modified polybutylene terephthalate (modified PBT), with the modified PBT content being 5 to 45 wt %. Forming the substrate layer 70 in this manner provides the laminate film 20 with good tearability (linear tearing) and good drop strength (impact resistance). The thickness of the substrate layer 70 is preferably 10 μm or more, more preferably 12 μm or more. The thickness of the substrate layer 70 is preferably 25 μm or less, more preferably 16 μm or less.

[0024] Note that various conventionally known modified polybutylene terephthalates (modified PBTs) can be used. For example, modified PBT containing polybutylene terephthalate (PBT) and polytetramethylene glycol (PTMG), specifically polybutylene terephthalate containing 5 to 20% by mass of polytetramethylene glycol units having a molecular weight of 600 to 4000, can be used. These can be used alone or in combination of two or more. Modified PBT can be produced, for example, as follows. That is, 194 parts by mass of dimethyl terephthalate, 108 parts by mass of 1,4-butanediol, and 80 ppm of tetrabutyl titanate (mass of titanium metal relative to the theoretical production amount) are added to an ester exchange reactor, and the ester exchange reaction is carried out at 150 to 210°C for 2.5 hours. The resulting ester exchange reaction product is transferred to a polymerization vessel, and 40 ppm of tetrabutyl titanate is added, followed by the addition of 15% by mass of PTMG. The pressure is then reduced, and finally, melt polymerization is carried out at a temperature of 210 to 245°C for 2 hours under a reduced pressure of 4 hPa.

[0025] Next, the configuration for suppressing odor transfer in this embodiment will be described below.

[0026] First, in such a microwave pouch 10, the odor (flavor) of laminate film 20 may transfer to the contents. Therefore, from the viewpoint of suppressing such odor transfer, laminate film 20 does not include any layer made of adhesive other than adhesive layer 40 (i.e., laminate film 20 has only one adhesive layer 40) and does not include any layer made of ink other than printed layer 50 (i.e., laminate film 20 has only one printed layer 50). Furthermore, adhesive layer 40 is preferably formed from a solvent-free adhesive (non-solvent adhesive, adhesive that does not use organic solvents) containing a polyester resin and an isocyanate compound, and printed layer 50 is preferably formed from a toluene-free ink (non-toluene ink) made from a polyester-based urethane resin.

[0027] Here, the test carried out to confirm the effect of suppressing odor transfer will be described below with reference to FIG.

[0028] First, in this test, a pouch (test sample) was formed for each of two laminated films (Example and Comparative Example) with different layer structures, and each pouch (test sample) was filled with 180 ml of water. The filling port was then sealed by heat welding, and the pouches were retort sterilized at 127°C for 30 minutes. After that, the pouches (test samples) were left to stand for a predetermined time (approximately 24 hours) at 23°C, and each pouch (test sample) was opened and checked for odor transfer to the contents (water) by 15 panelists.

[0029] The specific test conditions are as follows:

[0030] "Layer structure of laminated film" Example: A laminated film formed by laminating, in order from the inner layer side, a CPP layer (heat seal layer), an adhesive layer, a printed layer, a barrier layer, and a PET layer (base layer). Comparative example: A laminated film formed by laminating, in order from the inner layer side, a CPP layer (heat seal layer), an adhesive layer, a PET layer (base layer), a barrier layer, an adhesive layer, a printed layer, and a PET layer (base layer). Specific embodiments of each of the above layers are as follows: CPP layer (heat seal layer): a 70 μm layer made of impact polypropylene with a sea-island structure having a sea portion 31 made of the above-mentioned PP, first island portions 32 made of PE such as LLDPE, and second island portions 33 made of EPR (and with an LLDPE content of 10 to 30 wt %). Adhesive layer: a 3 μm layer formed from a urethane-based two-component curing adhesive. Barrier layer: a 0.3 μm layer formed by vapor-depositing aluminum oxide on the inner surface of a PET layer (substrate layer) and protecting the inner surface of the aluminum oxide with an overcoat made of polyvinyl alcohol resin (PVA) and tetraethoxysilane {Si(OC2H5)4}. Printing layer: a layer formed from a non-ink made of polyester-based urethane resin. PET layer (substrate layer): a 12 μm layer with a sea-island structure having a sea portion 71 made of PET and islands 72 made of modified PBT. The thickness (μm) of the adhesive layer above refers to the thickness of the ink-free portion of the printing layer. "Configuration of Pouch (Test Sample)" For each laminated film (Example and Comparative Example), a 180 ml pouch similar to the pouch shown in FIG. 1 (a flat pouch made of two laminated films with an automatic steam release mechanism 80, etc.) was formed and used as the test sample. Ten pouches (test samples) were prepared for each Example and Comparative Example. All of the water in the ten Example pouches was transferred to one clean beaker, and all of the water in the ten Comparative Example pouches was transferred to another clean beaker. Samples were then taken from each beaker for each panelist. "Method for Evaluating Odor Transfer" A flavor test was conducted on 15 panelists using a rating system (1 point: no taste, 2 points: slight taste, 3 points: taste, 4 points: strong taste).

[0031] The experimental results shown in Figure 5 confirm that when there was one adhesive layer (in the case of the Example), odor transfer to the contents (water) was suppressed, whereas when there were two adhesive layers (in the case of the Comparative Example), the odor of the laminated film was transferred relatively strongly to the contents (water).

[0032] Next, a test conducted to confirm drop strength (impact resistance) will be described below with reference to FIG.

[0033] First, in this test, a plurality of laminate films (Examples 1 and 2, Comparative Example) were prepared, and a pouch (test sample) was formed for each laminate film (Examples 1 and 2, Comparative Example). Each pouch (test sample) containing 180 ml of water was dropped onto the floor from a height of 120 cm, and the rate (%) of breakage of each pouch (test sample) due to dropping was confirmed.

[0034] The specific test conditions are as follows:

[0035] "Laminated Film" In all of Examples 1 and 2 and the Comparative Example, a laminated film was used which was formed by laminating, from the inner layer side, a heat seal layer, an adhesive layer, and a base layer. Here, specific aspects of each of the above layers are as follows. CPP layer (heat seal layer): In Examples 1 and 2, a 70 μm layer made of impact polypropylene having a sea-island structure with a sea region 31 made of PP, first island regions 32 made of LLDPE, and second island regions 33 made of EPR (and with an LLDPE content of 10 to 30 wt %), as described above; and in Comparative Example 1, a 70 μm layer made of impact polypropylene having a sea-island structure with a sea region 31 made of PP and second island regions 33 made of EPR. Adhesive layer: A 3 μm layer formed of a urethane-based two-component curing adhesive. PET layer (substrate layer): A 12 μm layer having a sea-island structure with a sea region 71 made of PET and islands 72 made of modified PBT with a content of 5 to 45 wt %. The physical properties of the laminate films of Examples 1, 2, and the Comparative Example are as shown in FIG. 6. Here, the "tensile impact strength," "breaking strength," and "breaking elongation" are values ​​in either the pouch width direction X or the pouch length direction Y in the state of a pouch (test sample) described below, whichever direction has the shorter distance between the inner edges of the outer edge seal portion 11 (in this embodiment, the pouch width direction X). In other words, the pouch (test sample) was formed with the orientation of the laminate film (heat seal layer) for which the above values ​​were measured facing the pouch width direction X. The "tensile impact strength" was also measured in either the pouch width direction X or the pouch length direction Y, whichever direction has the longer distance between the inner edges of the outer edge seal portion 11 (in this embodiment, the pouch length direction Y). The results are shown in FIG. 6 . The "tensile impact strength" value shown in FIG. 6 is a value for the CPP layer (heat seal layer) alone, while the "breaking strength," "breaking elongation," and "puncture strength" shown in FIG. 6 are values ​​for the entire laminate film. "Measurement method" "Tensile impact strength" A CPP film was punched out with a dumbbell as specified in ASTM D 1822-S to prepare a test piece. The test piece was set in a tensile impact tester and measured in an in-base method in an environment of 5°C. The number of measurements, n = 5, was used as the average value to be measured."Breaking Strength and Breaking Elongation" The laminated film was cut into 15 mm strips and set in a tensile tester with a chuck distance of 100 mm. The length of the laminated film could be freely set within the range that allowed chucking. The laminated film was pulled at a tensile speed of 300 m / min to obtain an S-S curve. The breaking strength and breaking elongation were calculated from the obtained S-S curve. The number of measurements (n = 5) was the average value, and the measured value was the mean value. "Puncture Strength" The puncture strength was measured in accordance with JIS Z1707 (1997). The puncture speed was 50 mm / min. The number of measurements (n = 5) was the average value, and the measured value was the mean value. "Configuration of Pouch (Test Sample)" For each laminated film (Examples 1 and 2, Comparative Example), a 180 ml pouch was formed in the same configuration as the pouch shown in Figure 1 (a flat pouch made of two laminated films with an automatic steam release mechanism 80, etc.) and used as a test sample. Measurement of the rate of bag breakage due to dropping (%): A pouch (test sample) containing 180 ml of water was dropped onto the floor from a height of 120 cm to check for bag breakage (water leakage). Thirty pouches (test samples) were used for the measurement for each laminated film (Examples 1 and 2, Comparative Example).

[0036] The experimental results shown in FIG. 6 reveal that the drop strength (impact resistance) is further improved when the heat seal layer 30 has a sea-island structure having a sea portion 31 made of polypropylene, first island portions 32 made of polyethylene, and second island portions 33 made of an ethylene-propylene copolymer, and the base layer 70 has a sea-island structure having a sea portion 71 made of polyethylene terephthalate and island portions 72 made of modified polybutylene terephthalate with a content of 5 to 45 wt %.

[0037] Furthermore, from the experimental results shown in FIG. 6, it was found that in microwave pouch 10, heat seal layer 30 has a tensile impact strength of 300 kJ / m at 5° C. in either pouch width direction X or pouch length direction Y, whichever is shorter, of outer edge seal portion 11. ２ It was found that when the above-mentioned structure is used, the drop strength (impact resistance) is further improved.

[0038] In the microwave pouch 10 of the present embodiment obtained in this manner, the heat seal layer 30 has a sea-island structure having a sea portion 31 made of polypropylene, a first island portion 32 made of polyethylene, and a second island portion 33 made of an ethylene-propylene copolymer, and the base layer 70 has a sea-island structure having a sea portion 71 made of polyethylene terephthalate and islands 72 made of modified polybutylene terephthalate, and the content of modified polybutylene terephthalate in the base layer 70 is 5 to 45 wt %, thereby improving the drop strength of the microwave pouch 10.

[0039] This also makes it possible to ensure the drop strength of the microwave pouch 10 without providing a resin film made of nylon, PET, PBT, modified PBT, etc. between the heat seal layer 30 and the base layer 70 to ensure film strength, thereby making it possible to reduce the amount of film used while ensuring drop strength.

[0040] In the laminate films of Examples 1 and 2 described above, it is preferable to design the Young's modulus (MPa) of the entire laminate film to be 1000 MPa or less (for example, 940 MPa for the laminate film of Example 1, 1000 MPa for the laminate film of Example 2, etc.). This is because a lower Young's modulus makes the laminate film more susceptible to deformation and easier to absorb when an impact is applied to the laminate film. The Young's modulus (MPa) of the entire laminate film of Comparative Example 1 is 1100 MPa. Here, the above Young's modulus (MPa) is the value in the pouch (test product) state described above, in either the pouch width direction X or the pouch length direction Y, whichever has the shorter distance between the inner edges of the outer edge seal portion 11 (in this embodiment, the pouch width direction X). The Young's modulus (MPa) is a value calculated based on an S-S curve obtained by cutting a laminated film into a 15 mm strip to form a test piece, setting the test piece in a tensile tester with a chuck distance of 100 mm, and pulling the test piece (laminated film) at a pulling speed of 300 m / min. It is preferable to measure five or more times and use the average of these as the measured value.

[0041] Furthermore, in the laminate films of Examples 1 and 2 described above, it is preferable to design the loop stiffness (rigidity) of the entire laminate film to be 40 mN or less (for example, 33 mN for the laminate film of Example 1, and 39 mN for the laminate film of Example 2). This is because a lower loop stiffness (rigidity) is considered to result in a higher impact absorption capacity. The loop stiffness (rigidity) of the entire laminate film of Comparative Example 1 is 45 mN. Here, the loop stiffness (mN) is the value in the pouch (test sample) state described above, in either the pouch width direction X or the pouch length direction Y, whichever has the shorter distance between the inner edges of the outer edge seal portion 11 (in this embodiment, the pouch width direction X). The loop stiffness (mN) is a value obtained by pressing a laminated film held in a loop (hoop) shape with a load cell and measuring the stress required to deform the laminated film. Specifically, a test piece (laminated film) cut to a width of 10 mm is attached to a Loop Stiffness Tester DA manufactured by Toyo Seiki Seisaku-sho, Ltd. so that the loop length is 70 mm, and the test piece is pressed at a speed of 3.3 mm / s until the distance between the indenter at the tip of the load cell and the chuck becomes 20 mm. It is preferable to measure five or more measurements and take the average of these measurements as the measured value.

[0042] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various design modifications can be made without departing from the present invention as set forth in the claims, such as constructing a microwave pouch 10 by any combination of the configurations of the above or following embodiments and variations.

[0043] For example, the microwave pouch 10 of the present invention is not limited to the four-sided seal type described above, but can be applied to various types of pouches such as standing pouches, flat pouches, three-sided seal types, pillow types, and gusset types.

[0044] In the above-described embodiment, the laminate film 20 is described as being formed by laminating the heat seal layer 30, the adhesive layer 40, the printing layer 50, the barrier layer 60, and the base layer 70, but layers other than those described above may be provided at any location. In the above-described embodiment, the laminate film 20 is described as being formed by interposing (only) the printing layer 50 and the barrier layer 60 between the adhesive layer 40 and the base layer 70, but the laminate film 20 may be formed by interposing only the printing layer between the adhesive layer 40 and the base layer 70 without providing the barrier layer 60.

[0045] Furthermore, in the above-described embodiment, the steam release seal portion 81 is described as being formed continuously with the outer edge seal portion 11 for bag making, which is heat-sealed to the outer edge of the laminated film 20. However, the steam release seal portion 81 may be formed independently from the outer edge seal portion 11 for bag making, and the formation position of the steam release seal portion 81 may be set at any desired location.

[0046] DESCRIPTION OF SYMBOLS 10: Microwave pouch 11: Outer edge seal portion 11a: Top seal portion 11b: Bottom seal portion 11c: Side seal portion 20: Laminated film 30: Heat seal layer 31: Sea portion 32: First island portion 33: Second island portion 40: Adhesive layer 50: Printed layer 50a: Ink 60: Barrier layer 70: Base material layer 71: Sea portion 72: Island portion 51: Second coated layer 80: Automatic steam release mechanism 81: Steam release seal portion 81a: Outer edge 81b: Seal peel start portion 82: Steam release portion 83: Steam release portion X: Pouch horizontal direction Y: Pouch vertical direction

Claims

1. A microwave pouch made of laminated film formed into a bag shape and equipped with an automatic steam release mechanism that automatically releases internal steam when heated in a microwave oven, wherein the laminated film is made of, in order from the inner layer side, a heat seal layer, an adhesive layer, and a base layer, the heat seal layer has a sea-island structure having a sea part made of polypropylene, a first island part made of polyethylene, and a second island part made of an ethylene-propylene copolymer, the base layer has a sea-island structure having a sea part made of polyethylene terephthalate and islands made of modified polybutylene terephthalate, and the content of modified polybutylene terephthalate in the base layer is 5 to 45 wt %.

2. The microwave pouch according to claim 1, wherein the first island portion is made of linear low density polyethylene, and the content of linear low density polyethylene in the heat seal layer is 10 to 30 wt %.

3. The microwave pouch is formed into a bag shape by having an outer edge seal part heat-sealed by heat-sealing the laminated film, and the heat seal layer has a tensile impact strength of 300 kJ / m at 5°C in the pouch width direction or the pouch length direction, whichever is shorter, of the outer edge seal parts. ２ 2. The microwave pouch of claim 1, wherein the pouch is formed as described above.

4. The pouch for use in a microwave oven according to claim 1, characterized in that only a printed layer, or only a printed layer and a barrier layer, are interposed between the adhesive layer and the base layer.

5. A pouch for use in a microwave oven as described in claim 4, characterized in that the laminated film does not have any layers made of adhesive other than the adhesive layer, and does not have any layers made of ink other than the printed layer, and the adhesive layer is formed from a solvent-free adhesive.

6. The microwave pouch according to claim 5, wherein the printed layer is formed from an ink that does not contain toluene.

7. A microwave pouch as described in claim 2, characterized in that the automatic steam release mechanism is configured to peel off the steam release seal portion during heating in a microwave oven to allow steam to escape, and the number of ink colors constituting the printing layer at the outer edge of the steam release seal portion is set to two or less.

8. A content-filled microwave pouch comprising the microwave pouch of claim 1 and a content filled in said microwave pouch, wherein said laminated film has a printed layer formed between said adhesive layer and said base layer, and the hue of said heat seal layer colored by said content and the hue of the ink constituting said printed layer that has the largest area in the pouch plane direction are the same hue or adjacent hues in the color arrangement on a hue wheel chart of 10 hues of the Munsell color system.

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