Pouch and laminated film for packaging container

Abstract

The present invention provides a pouch and a laminated film for a packaging container which each improve drop strength with a simple configuration. Provided is a pouch (10) wherein: a heat seal layer (30) has a sea-island structure that includes a sea part (31) composed of polypropylene, a first island part (32) composed of polyethylene, and a second island part (33) composed of an ethylene-propylene copolymer; a base material layer (70) has a sea-island structure that includes a sea part (71) composed of polyethylene terephthalate and an island part (72) composed of modified polybutylene terephthalate; and the modified polybutylene terephthalate content in the base material layer (70) is 5-45 wt%.

Description

Laminated films for pouches and packaging containers

[0001] The present invention relates to a laminated film for pouches and packaging containers.

[0002] BACKGROUND ART Conventionally, a pouch formed by forming a laminated film into a bag shape has been known (see, for example, Patent Document 1).

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

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

[0005] Therefore, the present invention is intended to solve these problems, and has as its object to provide a laminated film for pouches and packaging containers that has a simple structure and improves drop strength.

[0006] The pouch of the present invention is a pouch formed by forming a laminated film into a bag shape, and the laminated film is formed by laminating, in this order from the inner layer side, a heat seal layer, an adhesive layer, and a base material layer, the heat seal layer having a sea-island structure with a sea portion made of polypropylene, a first island portion made of polyethylene, and a second island portion made of an ethylene-propylene copolymer, the base material layer having a sea-island structure with a sea portion made of polyethylene terephthalate and islands made of modified polybutylene terephthalate, and the content of modified polybutylene terephthalate in the base material layer is 5 to 45 wt %, thereby solving the above-mentioned problem. The laminated film of the present invention is a laminated film for packaging containers, the laminated film being formed by laminating, in order from the inner layer side, a heat-sealing layer, an adhesive layer, and a base layer, the heat-sealing layer having a sea-island structure with 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 having a sea-island structure with a sea part made of polyethylene terephthalate and an island part made of modified polybutylene terephthalate, the content of modified polybutylene terephthalate in the base layer being 5 to 45 wt %, thereby solving the above-mentioned problems. In the above pouch, the pouch is formed into a bag shape by having an outer edge seal part formed by heat-welding the laminated film, and the heat-sealing layer has a tensile impact strength of 300 kJ / m at 5°C in either the pouch width direction or the pouch length direction, whichever is shorter, of the outer edge seal parts. ２In any of the above pouches or laminate films, the first island portion may be made of linear low-density polyethylene, and the content of linear low-density polyethylene in the heat-seal layer may be 10 to 30 wt %. In any of the above pouches or laminate films, the proportion of the olefin resin contained in the heat-seal layer relative to the total mass of the pouch (or laminate film) may be 70 mass % or more. In any of the above pouches or laminate films, only a printed layer, or only a printed layer and a barrier layer, may be interposed between the adhesive layer and the base layer. In any of the above pouches or laminate films, 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 above pouches or laminate films, the printed layer may be formed from an ink that does not contain toluene.

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

[0008] 1 is a plan view showing a pouch according to an embodiment of the present invention; 2 is a cross-sectional view of the 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 the results of a first test example; and 5 is an explanatory diagram showing the results of a second test example.

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

[0010] First, as shown in Figures 1 and 2, the 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 a laminated film 20, and the contents such as food are contained in the inner storage portion.

[0011] Next, a specific embodiment of the laminated film 20 constituting the pouch 10 will be described.

[0012] 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.

[0013] As shown in FIG. 2 , when the pouch 10 is made, the heat seal layer 30 is positioned on the innermost layer side so as to face the other laminate film 20, and is heat-sealed to the heat seal layer 30 of the other laminate film 20.

[0014] 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), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), or high-density polyethylene (HDPE), and a second island portion 33 made of ethylene-propylene copolymer (EPR). The components may also be made from chemically recycled raw materials. 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 %. In addition to the above materials, the heat-seal layer 30 may be formed by mixing an elastomer such as styrene-butadiene copolymer (SBR). The adoption of the above-described sea-island structure improves the drop strength (impact resistance) of the pouch 10. This is thought to be partly due to the fact that voids are likely to form between the sea portion 31 and the island portions 32 and 33, and these voids function as cushions when the pouch 10 is subjected to an impact, such as when it is dropped. The thickness of the heat-seal layer 30 is preferably 40 μm or more, more preferably 60 μm or more. The thickness of the heat-seal layer 30 is preferably 100 μm or less, more preferably 80 μm or less.

[0015] The proportion of the olefin resin (such as the above-mentioned polypropylene, polyethylene, ethylene-propylene copolymer, etc.) contained in the heat seal layer 30 relative to the total mass of the pouch 10 (or laminate film 20) is preferably set to 70 mass% or more, and more preferably set to 80 mass% or more, which can improve the recyclability of the pouch 10.

[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). ２ The 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] 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.

[0020] 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 6 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.

[0021] 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.

[0022] Next, the configuration for suppressing odor transfer in this embodiment will be described below.

[0023] First, in such a pouch 10, the odor (flavor) of the laminate film 20 may transfer to the contents. Therefore, from the viewpoint of suppressing such odor transfer, the laminate film 20 does not include any layer made of adhesive other than the adhesive layer 40 (i.e., only one adhesive layer 40 is provided on the laminate film 20), and does not include any layer made of ink other than the printed layer 50 (i.e., only one printed layer 50 is provided on the laminate film 20). Furthermore, the adhesive layer 40 is preferably formed from a solvent-free adhesive (a non-solvent adhesive, an adhesive that does not use organic solvents) containing a polyester resin and an isocyanate compound, and the printed layer 50 is preferably formed from a toluene-free ink (a non-toluene ink) made of a polyester-based urethane resin.

[0024] Here, the test carried out to confirm the effect of suppressing odor transfer will be described below with reference to FIG.

[0025] 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.

[0026] The specific test conditions are as follows:

[0027] "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 in configuration to the pouch shown in Figure 1 (a flat pouch made of two sheets of laminated film) 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, and samples were 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).

[0028] The experimental results shown in Figure 4 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).

[0029] Next, a test conducted to confirm drop strength (impact resistance) will be described below with reference to FIG.

[0030] First, in this test, a plurality of laminate films (Examples 1 and 2, Comparative Examples 1 and 2) were prepared, and a pouch (test sample) was formed for each laminate film (Examples 1 and 2, Comparative Examples 1 and 2). 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.

[0031] The specific test conditions are as follows:

[0032] "Laminated film" In Examples 1 and 2 and Comparative Example 1, 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. In Comparative Example 2, a laminated film was used which was formed by laminating, from the inner layer side, a heat seal layer, an adhesive layer, a nylon 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 portion 31 made of the above-mentioned PP, a first island portion 32 made of PE such as LLDPE, and a second island portion 33 made of EPR; and in Comparative Examples 1 and 2, a 70 μm layer made of impact polypropylene having a sea-island structure with a sea portion 31 made of the above-mentioned PP and a second island portion 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 portion 71 made of the above-mentioned PET and islands 72 made of modified PBT. Nylon layer: A 15 μm layer made of NY (nylon). In Examples 1 and 2, the first island portion 32 of the CPP layer (heat seal layer) was made of LLDPE, and the LLDPE content was set to 10 to 30 wt %. In Examples 1 and 2, different CPPs were used to form the laminate films, while in Comparative Examples 1 and 2, the same CPP was used to form the laminate films. The physical properties (tensile impact strength, olefin content) of the laminate films of Examples 1, 2, and Comparative Example 1 are shown in Figure 5. Here, "tensile impact strength" refers to a value for the CPP layer (heat-seal layer) alone, and is a value in either the pouch width direction X or the pouch length direction Y in the state of a pouch (test sample) described below, where the distance between the inner edges of the outer edge seal portion 11 is shorter (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 "olefin ratio" refers to the ratio of the mass of the olefin resin to the total mass of the laminate film. Specifically, it refers to the ratio of the mass of the heat seal layer (more precisely, the olefin resin contained in the heat seal layer) to the total mass of the laminate film (in Examples 1 and 2 and Comparative Example 1, the total mass of the heat seal layer, adhesive layer, and base layer; in Comparative Example 2, the total mass of the heat seal layer, adhesive layer, nylon layer, adhesive layer, and base layer). The olefin ratio was calculated based on the specific gravity and volume of each component. "Measurement Method" "Tensile Impact Strength" The film was punched out with a dumbbell as specified in ASTM D 1822-S to prepare a test specimen. The test specimen was placed in a tensile impact tester and measured using the in-base method at 5°C. The number of measurements (n) was 5, and the average value was used as the measured value. "Aspects of the pouch (test sample)" For each laminate film (Examples 1 and 2, Comparative Examples 1 and 2), a pouch with a capacity of 180 ml was formed in the same manner as the pouch shown in Figure 1 (a flat pouch made of two sheets of laminate film), 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, and the presence or absence of bag breakage (presence or absence of water leakage) was confirmed. Thirty pouches (test samples) were used for the measurement for each laminate film (Examples 1 and 2, Comparative Examples 1 and 2).

[0033] From the experimental results shown in FIG. 5 , it can be seen that in a pouch 10 in which 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 material layer 70 has a sea-island structure having a sea portion 71 made of polyethylene terephthalate and an island portion 72 made of modified polybutylene terephthalate, the heat seal layer 30 has a tensile impact strength of 300 kJ / m at 5° C. in either the pouch transverse direction X or the pouch longitudinal direction Y, whichever is shorter, in which the distance between the inner edges of the outer edge seal portions 11 is shorter. ２ It was found that when the above-mentioned structure is used, the drop strength (impact resistance) is further improved.

[0034] In the 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 pouch 10.

[0035] This also makes it possible to ensure the drop strength of the pouch 10 without providing a film (layer) made of nylon, PET, PBT, modified PBT, or the like between the heat seal layer 30 and the base material layer 70 in order to ensure film strength. This makes it possible to ensure the olefin rate, improve recyclability, and reduce the amount of film used while ensuring the drop strength of the pouch 10 (packaging container).

[0036] In particular, with regard to the olefin ratio, the EU (European) Packaging and Packaging Waste Regulation (PPWR) requires that packaging such as pouches use 70% recyclable material by weight (mass ratio). By setting the olefin ratio to 70% or more, as in Examples 1 and 2 and Comparative Example 1 of the test shown in FIG. 5 , the PPWR requirement can be met.

[0037] 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.

[0038] 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.

[0039] 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 defined in the claims, such as constructing pouch 10 by any combination of the configurations of the above or following embodiments and modified examples.

[0040] For example, the 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.

[0041] 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.

[0042] Furthermore, in the above-described embodiment, the laminate film 20 has been described as constituting the pouch 10 as a packaging container, but the laminate film 20 may be any laminate film for a packaging container that is used to form a packaging container, and for example, the laminate film 20 may be configured as a lid material whose heat seal layer 30 is heat-sealed to a container body made of synthetic resin or the like for containing jelly, yogurt, cooked rice, or the like.

[0043] DESCRIPTION OF SYMBOLS 10 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 X Pouch horizontal direction Y Pouch vertical direction

Claims

1. A pouch made by forming a laminated film into a bag shape, wherein the laminated film is made by laminating, in order from the inner layer, a heat seal layer, an adhesive layer, and a base layer, wherein the heat seal layer has a sea-island structure with a sea part made of polypropylene, a first island part made of polyethylene, and a second island part made of an ethylene-propylene copolymer, and the base layer has a sea-island structure with 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 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 horizontal direction or the vertical direction of the pouch, whichever is shorter, between the inner edges of the outer edge seal portion. ２ 2. The pouch according to claim 1, wherein the pouch is formed as described above.

3. The 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-sealable layer is 10 to 30 wt %.

4. The pouch according to claim 1, wherein the proportion of the olefin resin contained in the heat seal layer relative to the total mass of the pouch is 70 mass % or more.

5. The pouch according to claim 1, wherein only a printed layer, or only a printed layer and a barrier layer, are interposed between the adhesive layer and the base layer.

6. The pouch according to claim 5, 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.

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

8. A laminated film for packaging containers, the laminated film being formed by laminating, in order from the inner layer side, a heat seal layer, an adhesive layer, and a base layer, the heat seal layer having a sea-island structure with 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 having a sea-island structure with a sea part made of polyethylene terephthalate and islands made of modified polybutylene terephthalate, the content of modified polybutylene terephthalate in the base layer being 5 to 45 wt%.

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