Packaging material and packaged product comprising the packaging material

Abstract

To provide a packaging material excellent in strength and hard to generate white turbidity.SOLUTION: The packaging material includes a base material, a metal foil, and a sealant layer in order from an outer surface side to an inner surface side. The packaging material constitutes the lid of a container or a bag-in-box. The substrate has only one biaxially oriented plastic film comprising polyester as the main component. The Young's moduli of the packaging material in one direction and a direction orthogonal to the one direction are 3800MPa or more.SELECTED DRAWING: Figure 13A

Description

[Technical Field]

[0001] The present invention relates to a packaging material and a packaging product comprising the packaging material. The packaging product may be a lidstock or a bag-in-box. [Background technology]

[0002] Various packaging materials have been developed and proposed for use in packaging products filled with various items such as food and beverages, pharmaceuticals, chemicals, cosmetics, hygiene products, daily necessities, etc. The packaging materials include a plastic film as a substrate. For example, Patent Document 1 discloses an example of a packaging material including a substrate containing polyethylene terephthalate and a substrate containing nylon. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-242825 Summary of the Invention [Problem to be solved by the invention]

[0004] Nylon has high strength but also has the property of easily absorbing moisture, so when a substrate contains nylon, the substrate may become cloudy due to moisture absorbed by the nylon.

[0005] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a packaging material that is excellent in strength and is less likely to become cloudy. [Means for solving the problem]

[0006] The present invention provides a packaging material comprising, in order from the outer surface side to the inner surface side, a substrate, a metal foil, and a sealant layer, The substrate has only one biaxially stretched plastic film containing polyester as a main component, The packaging material has a Young's modulus of 3800 MPa or more in one direction and in a direction perpendicular to the one direction. The packaging material may constitute a lid for a container or a bag-in-box.

[0007] The packaging material according to the present invention may have a puncture strength of 15.0 N or more.

[0008] In the packaging material according to the present invention, the packaging material may have a Young's modulus in the one direction of 4000 MPa or more.

[0009] In the packaging material according to the present invention, the biaxially stretched plastic film may have a thickness of 14 μm or more and 30 μm or less.

[0010] In the packaging material according to the present invention, the biaxially oriented plastic film may contain 90% by mass or more of polyethylene terephthalate.

[0011] In the packaging material according to the present invention, the sealant layer may contain polypropylene as a main component.

[0012] In the packaging material according to the present invention, the sealant layer may contain polyethylene having a melting point of 100°C or higher.

[0013] In the packaging material according to the present invention, the sealant layer may have a first layer mainly composed of polyethylene or polypropylene, and a second layer located on the inner side of the first layer and containing a mixed resin of polyethylene and polypropylene.

[0014] The present invention is a packaging product comprising the packaging material described above. [Effects of the Invention]

[0015] According to the present invention, a packaging material that is excellent in strength and is less likely to become cloudy can be provided. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a front view showing a bag according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an example of the layer structure of a packaging material that constitutes a bag. [Figure 3] FIG. 1 is a plan view showing an example of a loop stiffness measuring device. [Figure 4] FIG. 4 is a cross-sectional view of the loop stiffness measuring device of FIG. 3 taken along line IV-IV. [Figure 5] FIG. 10 is a diagram showing an example of a method for preparing a test piece used in a loop stiffness measuring device. [Figure 6] FIG. 10 is a diagram illustrating a process of attaching a test piece to a loop stiffness measuring instrument. [Figure 7] FIG. 10 is a diagram illustrating a step of forming a loop portion in a test piece. [Figure 8] FIG. 10 is a diagram illustrating a process of applying a load to a loop portion of a test piece. [Figure 9] FIG. 10 is a diagram illustrating a process of applying a load to a loop portion of a test piece. [Figure 10] FIG. 2 is a diagram showing an example of a layer structure of a sealant layer. [Figure 11] 10A and 10B are diagrams showing an example of a method for filling a bag with contents. [Figure 12] FIG. 10 is a front view showing a modified example of the bag. [Figure 13A] 1 is a longitudinal cross-sectional view illustrating an example of a packaged product including packaging material. [Figure 13B] FIG. 1 is a plan view illustrating an example of a packaged product including packaging material. [Figure 14] FIG. 1 is a perspective view illustrating an example of a packaged product including packaging material. [Figure 15] FIG. 10 is a diagram showing an example of a method for measuring puncture strength. [Figure 16] FIG. 10 is a diagram showing the evaluation results of the examples. [Figure 17] FIG. 10 is a diagram showing the evaluation results of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of the present invention will be described with reference to Figures 1 to 11. In the drawings accompanying this specification, the scale and aspect ratios have been appropriately changed and exaggerated from those of the actual objects for the sake of ease of illustration and understanding.

[0018] Furthermore, terms used in this specification that specify shapes, geometric conditions, and their degrees, such as "parallel," "orthogonal," and "identical," as well as values ​​of lengths and angles, are not to be construed as being bound by strict meanings, but rather as including a range within which similar functions can be expected.

[0019] Fig. 1 is a front view showing bag 10 according to the present embodiment. Bag 10 includes a storage section 17 for storing contents. Fig. 1 shows bag 10 in a state before contents are stored in it. The configuration of bag 10 will be described below.

[0020] bag In this embodiment, bag 10 is a so-called flat pouch made by joining a film on the front side of bag 10 with a film on the back side. Bag 10 includes an upper portion 11, a lower portion 12, and a pair of side portions 13, and has a generally rectangular outline in a front view. Note that names such as "upper portion," "lower portion," and "side portion," as well as terms such as "above" and "below," merely describe the relative positions and directions of bag 10 and its components with respect to a state in which the opening for filling the contents is located at the top. The position of bag 10 during transportation or use is not limited by the names and terms used in this specification.

[0021] In this embodiment, the width direction of bag 10 is also referred to as first direction D1. The pair of side portions 13 described above face each other in first direction D1. The direction perpendicular to first direction D1 is also referred to as second direction D2. Bag 10 of this embodiment is intended to be used in such a way that a consumer tears bag 10 along first direction D1 to open bag 10.

[0022] As shown in FIG. 1, the bag 10 includes a surface film 14 that forms the surface, and a back film 15 that forms the back.

[0023] The terms "surface film" and "back surface film" mentioned above merely distinguish between the films according to their positional relationships, and the terms do not limit the method of providing the films when manufacturing bag 10. For example, bag 10 may be manufactured using a single film in which surface film 14 and back surface film 15 are continuously disposed, or may be manufactured using a total of two films: one surface film 14 and one back surface film 15.

[0024] The inner surfaces of the front film 14 and the back film 15 are joined together by a seal portion. In a front view of the bag 10 such as Figure 1, the seal portion is hatched.

[0025] As shown in Figure 1, the seal portion has an outer edge seal portion that extends along the outer edge of bag 10. The outer edge seal portion includes a bottom seal portion 12a that extends along bottom portion 12, and a pair of side seal portions 13a that extend along a pair of side portions 13. Before contents are placed inside bag 10, as shown in Figure 1, top 11 of bag 10 forms opening 11b. After contents are placed inside bag 10, the inner surfaces of front film 14 and back film 15 are joined at top 11 to form the top seal portion and seal bag 10.

[0026] The bottom seal portion 12a, the side seal portion 13a, and the top seal portion are seal portions formed by joining the inner surface of the front film 14 and the inner surface of the back film 15 together.

[0027] There are no particular limitations on the method for forming the seal portion, as long as it is possible to join opposing films together and seal bag 10. For example, the seal portion may be formed by melting the inner surfaces of the films by heating or the like, welding the inner surfaces together, i.e., by heat sealing. Alternatively, the seal portion may be formed by bonding the inner surfaces of opposing films together using an adhesive or the like.

[0028] Easy-to-open means The front film 14 and the back film 15 may be provided with easy-open means 25 for tearing the front film 14 and the back film 15 along the first direction D1 to open the bag 10. For example, as shown in Fig. 1, the easy-open means 25 may include a notch 26 formed in the side seal portion 13a of the bag 10, which serves as a starting point for tearing. Alternatively, the easy-open means 25 may be a half-cut line formed by laser processing, a cutter, or the like, in a portion that serves as a path for tearing the bag 10.

[0029] Furthermore, although not shown, the easy-open means 25 may include a group of cuts or scars formed in the area where the seal portion is formed of the front film 14 and the back film 15. The group of scars may include, for example, a plurality of through holes formed so as to penetrate the front film 14 and / or the back film 15. Alternatively, the group of scars may include a plurality of holes formed on the outer surface of the front film 14 and / or the back film 15 so as not to penetrate the front film 14 and / or the back film 15.

[0030] Layer structure of surface film and back film Next, a description will be given of the layer structure of the front film 14 and the back film 15. Fig. 2 is a cross-sectional view showing an example of the layer structure of a packaging material 30 that constitutes the front film 14 and the back film 15.

[0031] As shown in FIG. 2, the packaging material 30 includes a substrate 35, a first adhesive layer 45, a metal foil 50, a second adhesive layer 55, and a sealant layer 70, in this order. The substrate 35 includes only one biaxially stretched plastic film 40. The substrate 35 is located on the outer surface 30y side, and the sealant layer 70 is located on the inner surface 30x side opposite the outer surface 30y. The inner surface 30x is the surface located on the storage section 17 side. The thickness of the packaging material 30 is, for example, 60 μm or more, and may be 70 μm or more, 80 μm or more, or 90 μm or more. The thickness of the packaging material 210 may be 130 μm or less, 120 μm or less, or 110 μm or less.

[0032] The films constituting the packaging material 30, such as the biaxially oriented plastic film 40, and the packaging material 30 have a machine direction and a perpendicular direction. When the sealant layer 70 is composed of a sealant film, the sealant layer 70 also has a machine direction and a perpendicular direction. The machine direction is the direction in which the film flows when formed, and is known as the MD (Machine Direction). The perpendicular direction is the direction perpendicular to the machine direction, and is known as the TD (Transverse Direction). In the bag 10 shown in FIG. 1, the direction in which the upper portion 11 and the lower portion 12 extend is the machine direction, and the direction in which the side portion 13 extends is the perpendicular direction.

[0033] The packaging material 30 of this embodiment is configured to have excellent puncture strength, which can prevent the bag 10 from being torn when a sharp member with a pointed tip comes into contact with the bag 10. In other words, a packaged product such as the bag 10 made of the packaging material 30 can have puncture resistance.

[0034] Each layer of packaging material 30 will now be described in detail.

[0035] (biaxially oriented plastic film) The biaxially stretched plastic film 40 is a biaxially stretched film stretched in two predetermined directions. A biaxially stretched plastic film is a plastic film that has been intentionally stretched to improve the mechanical strength of the plastic film. The stretching direction of the biaxially stretched plastic film 40 is not particularly limited. For example, the biaxially stretched plastic film 40 may be stretched in the direction in which the side portions 13 extend and in a direction perpendicular to the direction in which the side portions 13 extend. Furthermore, the stretching directions of each biaxially stretched plastic film 40 may be the same as or different from each other. The stretching ratio of each biaxially stretched plastic film 40 is, for example, 1.05 times or more.

[0036] In this embodiment, we propose using a biaxially oriented plastic film 40 that has a loop stiffness of 0.0017 N or greater in at least one direction and contains polyester as the primary component. In the following description, a biaxially oriented plastic film that has a loop stiffness of 0.0017 N or greater in at least one direction and contains polyester as the primary component is also referred to as a high-stiffness polyester film. A high-stiffness polyester film may have a loop stiffness of 0.0017 N or greater in at least one of the machine direction (MD) and the transverse direction (TD). A high-stiffness polyester film may have a loop stiffness of 0.0017 N or greater in both the machine direction (MD) and the transverse direction (TD). By including a high-stiffness polyester film in the packaging material 30, the packaging material 30 can have excellent puncture strength. In this application, the term "primary component" refers to a component that accounts for 51% by mass. The high-stiffness polyester film does not contain polyamide. The polyester is preferably a polyester primarily composed of an aromatic polyester consisting of at least one aromatic dicarboxylic acid selected from terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid and at least one aliphatic alcohol selected from ethylene glycol, 1,3-propanediol, and 1,4-butanediol. Examples of polyesters include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Examples of high-stiffness polyester films include high-stiffness PET films containing 51% by mass or more of PET as the main component, and high-stiffness PBT films containing 51% by mass or more of PBT as the main component. The thickness of the high-stiffness polyester film is preferably 5 μm or more, more preferably 7 μm or more. The thickness of the high-stiffness polyester film is preferably 25 μm or less, more preferably 20 μm or less.

[0037] Loop stiffness is a parameter that represents the stiffness of a film such as a biaxially stretched plastic film. A method for measuring loop stiffness will be described below with reference to FIGS. 3 to 9. The measurement method described below can be used not only for single-layer films such as biaxially stretched plastic films, but also for films with multiple layers such as vapor-deposited films and laminated films. A vapor-deposited film is a film that includes a single-layer film such as a biaxially stretched plastic film and a vapor-deposited layer formed on the single-layer film. A laminated film is a film that includes multiple laminated films, such as packaging material 30.

[0038] FIG. 3 is a plan view showing the test piece 80 and the loop stiffness measuring device 85, and FIG. 4 is a cross-sectional view of the test piece 80 and the loop stiffness measuring device 85 taken along line IV-IV in FIG. 3. The test piece 80 is a rectangular film having long and short sides. In the present application, the length L1 of the long side of the test piece 80 is 150 mm, and the length L2 of the short side is 15 mm. As the loop stiffness measuring device 85, for example, No. 581 Loop Stiffness Tester (registered trademark) LOOP STIFFNESS TESTER DA type manufactured by Toyo Seiki Seisakusho, Ltd. can be used. The length L1 of the long side of the test piece 80 is adjustable as long as the test piece 80 can be gripped by a pair of chucks 86, which will be described later.

[0039] The loop stiffness measuring device 85 has a pair of chuck portions 86 for gripping a pair of ends in the long side direction of the test specimen 80, and a support member 87 for supporting the chuck portions 86. The chuck portions 86 include a first chuck 861 and a second chuck 862. In the state shown in FIGS. 3 and 4 , the test specimen 80 is placed on the pair of first chucks 861, and the second chuck 862 has not yet gripped the test specimen 80 between the first chuck 861 and the second chuck 862. As will be described later, during measurement, the test specimen 80 is gripped between the first chuck 861 and the second chuck 862 of the chuck portions 86. The second chuck 862 may be connected to the first chuck 861 via a hinge mechanism.

[0040] When a film to be measured, such as a biaxially oriented plastic film, a vapor-deposited film, or a laminated film, is available in a state before being processed into a packaging product, the test piece 80 may be prepared by cutting the film to be measured. Alternatively, the test piece 80 may be prepared by cutting a packaging product made from the packaging material 30, such as a bag. FIG. 5 shows an example of a method for preparing the test piece 80 by cutting the surface film 14 or the back film 15 of the bag 10. When measuring the loop stiffness of the packaging material 30 in the machine direction, the test piece is prepared by cutting the surface film 14 or the back film 15 of the bag 10 so that the long side direction of the test piece coincides with the machine direction, as shown by reference numeral 80A in FIG. 5. When measuring the loop stiffness of the packaging material 30 in the vertical direction, the test piece is prepared by cutting the surface film 14 or the back film 15 of the bag 10 so that the long side direction of the test piece coincides with the vertical direction, as shown by reference numeral 80B in FIG. 5.

[0041] A method for measuring the loop stiffness of the test piece 80 using the loop stiffness measuring device 85 will be described. First, as shown in FIGS. 3 and 4 , the test piece 80 is placed on the first chuck 861 of a pair of chucks 86 arranged with a gap L3 therebetween. In the present application, the gap L3 is set so that the length of a loop portion 81 (described later, also referred to as the loop length) is 60 mm. The test piece 80 includes an inner surface 80x located on the first chuck 861 side and an outer surface 80y located opposite the inner surface 80x. When the test piece 80 is made of a packaging material 30, the inner surface 80x and the outer surface 80y of the test piece 80 coincide with the inner surface 30x and the outer surface 30y of the packaging material 30. When a loop portion 81 (described later) is formed in the test piece 80, the inner surface 80x is located inside the loop portion 81, and the outer surface 80y is located outside the loop portion 81. Next, as shown in FIG. 6, the second chuck 862 is placed on the test piece 80 so that the end of the test piece 80 in the long side direction is gripped between the first chuck 861 and the second chuck 862.

[0042] Next, as shown in FIG. 7 , at least one of the pair of chuck portions 86 is slid on the support member 87 in a direction that reduces the distance between the pair of chuck portions 86. This allows a loop portion 81 to be formed on the test piece 80. The test piece 80 shown in FIG. 7 has a loop portion 81, a pair of intermediate portions 82, and a pair of fixing portions 83. The pair of fixing portions 83 are portions of the test piece 80 that are gripped by the pair of chuck portions 86. The pair of intermediate portions 82 are portions of the test piece 80 that are located between the loop portion 81 and the pair of intermediate portions 82. As shown in FIG. 7 , the chuck portion 86 is slid on the support member 87 until the inner surfaces 80x of the pair of intermediate portions 82 come into contact with each other. This allows a loop portion 81 having a loop length of 60 mm to be formed. The loop length of the loop portion 81 is the length of the test piece 80 between position P1 where the surface of one second chuck 862 on the loop portion 81 side intersects with the test piece 80, and position P2 where the surface of the other second chuck 862 on the loop portion 81 side intersects with the test piece 80. If the thickness of the test piece 80 is ignored, the above-mentioned distance L3 is the value obtained by adding 2×t to the length of the loop portion 81, where t is the thickness of the second chuck 862 of the chuck portion 86.

[0043] Then, as shown in FIG. 8 , the posture of the chuck portion 86 is adjusted so that the protruding direction Y of the loop portion 81 relative to the chuck portion 86 is horizontal. For example, the posture of the chuck portion 86 supported by the support member 87 is adjusted by moving the support member 87 so that the normal direction of the support member 87 is horizontal. In the example shown in FIG. 8 , the protruding direction Y of the loop portion 81 coincides with the thickness direction of the chuck portion. Furthermore, a load cell 88 is prepared at a position a distance Z1 away from the second chuck 862 in the protruding direction Y of the loop portion 81. In this application, the distance Z1 is set to 50 mm. Next, the load cell 88 is moved toward the loop portion 81 of the test piece 80 at a speed V by a distance Z2 shown in FIG. 8 . The distance Z2 is set so that the load cell 88 contacts the loop portion 81 and then pushes the loop portion 81 toward the chuck portion 86, as shown in FIGS. 8 and 9 . In this application, the distance Z2 is set to 40 mm. In this case, the distance Z3 between the load cell 88 and the second chuck 862 of the chuck portion 86 is 10 mm when the load cell 88 is pressing the loop portion 81 toward the chuck portion 86. The speed V at which the load cell 88 is moved is 3.3 mm / sec.

[0044] Next, as shown in Fig. 9, the load cell 88 is moved a distance Z2 toward the chuck portion 86, and in a state where the load cell 88 is pressing into the loop portion 81 of the test piece 80, the value of the load applied to the load cell 88 from the loop portion 81 becomes stable, and then the value of the load is recorded. The value of the load thus obtained is used as the loop stiffness of the film constituting the test piece 80. In this application, unless otherwise specified, the environment during measurement of loop stiffness is a temperature of 23°C and a relative humidity of 50%.

[0045] By using a high-stiffness film having a loop stiffness of 0.0017 N or more in at least one direction as the biaxially stretched plastic film 40, it is possible to increase the puncture strength of the biaxially stretched plastic film 40. This makes it possible to increase the puncture strength of the packaging material 30 including the biaxially stretched plastic film 40 to, for example, 15.0 N or more, more preferably 16.0 N or more, and even more preferably 17.0 N or more.

[0046] An example of a high-stiffness film is a high-stiffness PET film containing 51% by mass or more of PET. The PET content in the high-stiffness PET film may be 80% by mass or more, 90% by mass or more, or even 95% by mass or more. The thickness of the high-stiffness film is preferably 5 μm or more, more preferably 7 μm or more. The thickness of the high-stiffness film may be 10 μm or more, or may be 14 μm or more. The thickness of the high-stiffness film is preferably 30 μm or less, and may be 25 μm or less, or may be 20 μm or less.

[0047] The preferred mechanical properties of the high stiffness polyester film will be further described. The puncture strength of the high stiffness polyester film is preferably 10 N or more, and more preferably 11 N or more.

[0048] The tensile strength of the high-stiffness polyester film in at least one direction is preferably 250 MPa or more, more preferably 280 MPa or more. For example, the tensile strength of the high-stiffness polyester film in the machine direction is preferably 250 MPa or more, more preferably 280 MPa or more. The tensile strength of the high-stiffness polyester film in the perpendicular direction is preferably 250 MPa or more, more preferably 280 MPa or more. The tensile elongation of the high stiffness polyester film in at least one direction is preferably 130% or less, more preferably 120% or less. For example, the tensile elongation of the high stiffness polyester film in the machine direction is preferably 130% or less, more preferably 120% or less. The tensile elongation of the high stiffness polyester film in the perpendicular direction is preferably 120% or less, more preferably 110% or less. Preferably, the tensile strength of the high-stiffness polyester film divided by the tensile elongation in at least one direction is 2.0 [MPa / %] or more. For example, the tensile strength of the high-stiffness polyester film divided by the tensile elongation in the transverse direction (TD) is preferably 2.0 [MPa / %] or more, more preferably 2.2 [MPa / %] or more. The tensile strength of the high-stiffness polyester film divided by the tensile elongation in the machine direction (MD) is preferably 1.8 [MPa / %] or more, more preferably 2.0 [MPa / %] or more.

[0049] The tensile strength and tensile elongation can be measured in accordance with JIS K7127. A tensile tester STA-1150 manufactured by Orientec Co., Ltd. can be used as a measuring instrument. A rectangular film cut from a high-stiffness polyester film with a width of 15 mm and a length of 150 mm can be used as a test piece. The distance between the pair of chucks holding the test piece at the start of measurement is 100 mm, and the tensile speed is 300 mm / min. The length of the test piece can be adjusted as long as the test piece can be held by the pair of chucks. Unless otherwise specified, the environment during measurement of the tensile strength and tensile elongation is a temperature of 23°C and a relative humidity of 50%. The tensile strength and tensile elongation of the packaging material 30 are measured in the same manner as for the high-stiffness polyester film, except that an Orientec RTC-1310A tensile tester is used as the measuring instrument and the distance between the pair of chucks holding the test piece is 50 mm at the start of the measurement. When measuring the tensile strength and tensile elongation of the packaging material 30, a test piece can be prepared by cutting the front film 14 or back film 15 of the bag 10 so that the long side direction of the test piece coincides with the machine direction or perpendicular to the machine direction, as in the case of measuring the loop stiffness shown in Figure 5.

[0050] The heat shrinkage of the high stiffness polyester film in at least one direction is preferably 0.7% or less, more preferably 0.5% or less. For example, the heat shrinkage of the high stiffness polyester film in the machine direction is preferably 0.7% or less, more preferably 0.5% or less. The heat shrinkage of the high stiffness polyester film in the perpendicular direction is preferably 0.7% or less, more preferably 0.5% or less. The heating temperature for measuring the heat shrinkage is 100°C, and the heating time is 40 minutes. The Young's modulus of the high-stiffness polyester film in at least one direction is preferably 4.0 GPa or more, more preferably 4.5 MPa or more. For example, the Young's modulus of the high-stiffness polyester film in the machine direction is preferably 4.0 GPa or more, more preferably 4.5 MPa or more. The Young's modulus of the high-stiffness polyester film in the perpendicular direction is preferably 4.0 GPa or more, more preferably 4.5 GPa or more.

[0051] Like tensile strength and tensile elongation, Young's modulus can be measured in accordance with JIS K7127. A tensile tester STA-1150 manufactured by Orientec Co., Ltd. can be used as a measuring instrument. A rectangular film cut from a high-stiffness polyester film with a width of 15 mm and a length of 150 mm can be used as a test piece. The distance between the pair of chucks holding the test piece at the start of measurement is 100 mm, and the tensile speed is 300 mm / min. The length of the test piece can be adjusted as long as the test piece can be held by the pair of chucks. Unless otherwise specified in this application, the environment during measurement of Young's modulus is a temperature of 23°C and a relative humidity of 50%. The Young's modulus of the packaging material 30 is measured in the same manner as for the high-stiffness polyester film, except that the measuring instrument is an Orientec RTC-1310A tensile tester, and the distance between the pair of chucks holding the test piece is 50 mm at the start of the measurement. When measuring the Young's modulus of the packaging material 30, a test piece can be prepared by cutting the front film 14 or back film 15 of the bag 10 so that the long side direction of the test piece coincides with the flow direction or the perpendicular direction, as in the case of measuring the loop stiffness shown in Figure 7.

[0052] In the manufacturing process of a high-stiffness polyester film, for example, a plastic film obtained by melting and molding a polyester is first stretched 3 to 4.5 times in both the machine direction and the perpendicular direction at 90 to 145°C in a first stretching step. This is followed by a second stretching step in which the plastic film is stretched 1.1 to 3.0 times in both the machine direction and the perpendicular direction at 100 to 145°C in a second stretching step. This is followed by heat setting at 190 to 220°C. This is followed by relaxation treatment (treatment to reduce the film width) at 100 to 190°C in both the machine direction and the perpendicular direction at approximately 0.2 to 2.5%. By adjusting the stretch ratio, stretching temperature, heat setting temperature, and relaxation treatment rate in these steps, a high-stiffness polyester film having the above-mentioned mechanical properties can be obtained.

[0053] According to this embodiment, the packaging material 30 contains a high-stiffness polyester film, which imparts excellent puncture strength to the packaging material 30 and to packaged products such as bags 10 made from the packaging material 30. This makes it possible to prevent the bag 10 from being torn when it comes into contact with a sharp object having a pointed tip. The puncture strength of the packaging material 30 is preferably 15.0 N or more, more preferably 16.0 N or more, and more preferably 17.0 N or more. A method for measuring the puncture strength will be described in the examples below.

[0054] Furthermore, according to this embodiment, the packaging material 30 contains a high-stiffness polyester film, thereby increasing the Young's modulus of the packaging material 30. The Young's modulus of the packaging material 30 in both directions is, for example, 3800 MPa or more, and may be 3900 MPa or more, 4000 MPa or more, or 4100 MPa or more. For example, the Young's modulus of the packaging material 30 in the machine direction (MD) is, for example, 3800 MPa or more, 3900 MPa or more, 4000 MPa or more, or 4100 MPa or more. The Young's modulus of the packaging material 30 in the transverse direction (TD), which is the direction perpendicular to the machine direction (MD), is, for example, 3800 MPa or more, 3900 MPa or more, 4000 MPa or more, 4100 MPa or more, 4200 MPa or more, or 4300 MPa or more. A high Young's modulus of the packaging material 30 makes the packaging material 30 less likely to stretch. This increases the processing accuracy when processing packaging material 30 in the manufacturing process of packaged products such as bags 10. Furthermore, when packaging material 30 is used to produce a gusseted bag 10 configured to be self-standing, as described below, it increases the self-standing ability of bag 10. The Young's modulus of packaging material 30 in the transverse direction (TD) may be higher than the Young's modulus of packaging material 30 in the machine direction (MD).

[0055] In this embodiment, the loop stiffness of the packaging material 30 in at least one direction is, for example, 0.090 N or more, and may be 0.100 N or more, 0.110 N or more, 0.120 N or more, or 0.130 N or more. For example, the loop stiffness of the packaging material 30 in the machine direction (MD) is, for example, 0.090 N or more, and may be 0.100 N or more, 0.110 N or more, 0.120 N or more, or 0.130 N or more. Furthermore, the loop stiffness of the packaging material 30 in the transverse direction (TD) is, for example, 0.090 N or more, and may be 0.100 N or more, 0.110 N or more, or 0.120 N or more.

[0056] On the other hand, if the loop stiffness of the packaging material 30 is too high, the packaging material 30 may be more susceptible to damage, such as tearing, when a packaged product made of the packaging material 30 is dropped. In consideration of this, the loop stiffness of the packaging material 30 in at least one direction may be less than 0.150 N or less than 0.140 N. For example, the loop stiffness of the packaging material 30 in the machine direction (MD) may be less than 0.150 N or less than 0.140 N. Furthermore, the loop stiffness of the packaging material 30 in the transverse direction (TD) may be less than 0.150 N, less than 0.140 N, or less than 0.130 N.

[0057] (First adhesive layer) The first adhesive layer 45 contains an adhesive for bonding the biaxially oriented plastic film 40 and the metal foil 50 by a dry lamination method. The adhesive constituting the first adhesive layer 45 is produced from an adhesive composition prepared by mixing a first composition containing a base agent and a solvent with a second composition containing a curing agent and a solvent. Specifically, the adhesive contains a cured product produced by reaction of the base agent and the solvent in the adhesive composition.

[0058] An example of an adhesive is polyurethane. Polyurethane is a cured product produced by reacting a polyol as a base agent with an isocyanate compound as a curing agent. Examples of polyurethane include polyether polyurethane and polyester polyurethane. Polyether polyurethane is a cured product produced by reacting a polyether polyol as a base agent with an isocyanate compound as a curing agent. Polyester polyurethane is a cured product produced by reacting a polyester polyol as a base agent with an isocyanate compound as a curing agent.

[0059] As the isocyanate compound, aromatic isocyanate compounds such as tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), and xylylene diisocyanate (XDI), aliphatic isocyanate compounds such as hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), or adducts or polymers of the above-mentioned various isocyanate compounds can be used.

[0060] The material constituting the first adhesive layer 45 preferably has a higher thermal conductivity than the materials constituting the biaxially oriented plastic film 40, the metal foil 50, and the sealant layer 70. For example, the thermal conductivity of the material constituting the first adhesive layer 45 is preferably 1.0 W / m·K or higher, more preferably 3.0 W / m·K or higher. The thermal conductivity of polyurethane is in the range of 3.0 W / m·K to 5.0 W / m·K, e.g., 5.0 W / m·K. The high thermal conductivity of the material constituting the first adhesive layer 45 facilitates heat diffusion in the planar direction of the packaging material 30 as heat generated in the storage section 17 is transferred from the inner surface 30x of the packaging material 30 to the outer surface 30y of the packaging material 30 when the bag 10 made using the packaging material 30 is heated. This improves the heat dissipation properties of the packaging material 30, thereby suppressing temperature rise in the packaging material 30. This also reduces damage to the packaging material 30 caused by heat when the bag 10 is heated. That is, the heat resistance of the packaging material 30 can be improved.

[0061] The thickness of the first adhesive layer 45 is preferably 2 μm or more, and more preferably 3 μm or more. The thickness of the first adhesive layer 45 is preferably 6 μm or less, and more preferably 5 μm or less. By making the thickness of the first adhesive layer 45 3 μm or more, heat diffusion in the surface direction of the packaging material 30 becomes easier to occur.

[0062] (metal foil) The metal foil 50 is located between the biaxially oriented plastic film 40 and the sealant layer 70. The metal foil 50 contains a metal material as a main component. By including the metal foil 50 in the packaging material 30, the packaging material 30 can be endowed with gas barrier properties that prevent the transmission of oxygen gas, water vapor, and the like, and light-blocking properties that prevent the transmission of visible light, ultraviolet light, and the like.

[0063] Aluminum can be given as an example of the metal material constituting the metal foil 50. The aluminum content in the metal foil 50 is, for example, 90% by mass or more, or may be 95% by mass or more, or may be 98% by mass or more.

[0064] The thickness of the metal foil 50 is, for example, 5 μm or more, or may be 6.5 μm or more, 8 μm or more, or 10 μm or more, or may be 20 μm or less, or may be 15 μm or less.

[0065] (Second adhesive layer) When the sealant layer 70 is made of a sealant film, the second adhesive layer 55 contains an adhesive for bonding the metal foil 50 and the sealant film by dry lamination. An example of the adhesive for the second adhesive layer 55 is polyurethane, as in the case of the first adhesive layer 45. In addition to the configuration, materials, and properties described below, the second adhesive layer 55 can also have the same configuration, materials, and properties as the first adhesive layer 45.

[0066] The material constituting the second adhesive layer 55, like the first adhesive layer 45, preferably has a higher thermal conductivity than the materials constituting the biaxially oriented plastic film 40, the metal foil 50, and the sealant film. For example, the thermal conductivity of the material constituting the second adhesive layer 55 is preferably 1 W / m·K or more, and more preferably 3 W / m·K or more.

[0067] The thickness of the second adhesive layer 55 is preferably 2 μm or more, and more preferably 3 μm or more. The thickness of the second adhesive layer 55 is preferably 6 μm or less, and more preferably 5 μm or less.

[0068] As described above, the isocyanate compounds constituting the curing agent of the adhesive include aromatic isocyanate compounds and aliphatic isocyanate compounds. Among these, aromatic isocyanate compounds leach out components that cannot be used in food applications under high-temperature conditions such as heat sterilization. The second adhesive layer 55 contacts the sealant film. Therefore, if the second adhesive layer 55 contains an aromatic isocyanate compound, components leach out from the aromatic isocyanate compound may adhere to the contents contained in the container 17, which contacts the sealant film.

[0069] In consideration of these issues, a cured product produced by the reaction of a polyol as the main agent with an aliphatic isocyanate compound as the curing agent is preferably used as the adhesive that constitutes the second adhesive layer 55. This makes it possible to prevent components that cannot be used for food applications, which originate from the second adhesive layer 55, from adhering to the contents.

[0070] (sealant layer) Next, the sealant layer 70 will be described. The material constituting the sealant layer 70 can be one or more resins selected from polyethylene, such as low-density polyethylene and linear low-density polyethylene, and polypropylene. The sealant layer 70 may be a single layer or a multilayer. The sealant layer 70 may also be composed of an unstretched sealant film. Note that the term "unstretched" refers not only to a film that is not stretched at all, but also to a film that is slightly stretched due to the tension applied during film formation.

[0071] The sealant film constituting the sealant layer 70 is, for example, a plastic film that has been stretched to an extent necessary for transportation but has not been intentionally stretched. Preferred mechanical properties of the sealant film will be further described. The Young's modulus of the sealant film in at least one direction is preferably 1000 MPa or less, for example, the Young's modulus of the sealant film in the machine direction and perpendicular direction is preferably 1000 MPa or less. The tensile elongation of the sealant film in at least one direction is preferably 300% or more, for example, the tensile elongation of the sealant film in the machine direction and the perpendicular direction is preferably 300% or more.

[0072] The Young's modulus and tensile elongation of the sealant film can be measured in accordance with JIS K7127, as in the case of high-stiffness polyester films. A tensile tester STA-1150 manufactured by Orientec Co., Ltd. can be used as the measuring instrument. A rectangular film 15 mm wide and 150 mm long cut from the film can be used as the test piece. The distance between the pair of chucks holding the test piece at the start of measurement is 100 mm, and the tensile speed is 300 mm / min.

[0073] Bags 10 made from packaging material 30 may be subjected to sterilization treatments such as boiling or retort treatment at high temperatures. The sealant layer 70 preferably has heat resistance that can withstand these high-temperature treatments. Retort treatment is a process in which the contents are filled into bag 10, the bag 10 is sealed, and then the bag 10 is heated under pressure using steam or heated hot water. The temperature for retort treatment is, for example, 120°C or higher. Boiling treatment is a process in which the contents are filled into bag 10, the bag 10 is sealed, and then the bag 10 is heated in a water bath under atmospheric pressure. The temperature for boiling treatment is, for example, 90°C or higher and 100°C or lower.

[0074] The melting point of the material that constitutes the sealant layer 70 is preferably 150°C or higher, and more preferably 160°C or higher. Increasing the melting point of the sealant layer 70 makes it possible to perform the retort treatment of the bag 10 at a high temperature, thereby shortening the time required for the retort treatment. Note that the melting point of the material that constitutes the sealant layer 70 is lower than the melting point of the resin that constitutes the biaxially oriented plastic film 40.

[0075] From the perspective of retort processing, a material primarily composed of propylene can be used to form the sealant layer 70. Here, a material "primarily composed of" propylene refers to a material with a propylene content of 90% by mass or more. Specific examples of materials primarily composed of propylene include polypropylenes such as propylene-ethylene block copolymers, propylene-ethylene random copolymers, and homopolypropylenes, as well as mixtures of polypropylene and polyethylene. Here, "propylene-ethylene block copolymers" refer to materials having the structural formula shown in formula (I) below. Furthermore, "propylene-ethylene random copolymers" refer to materials having the structural formula shown in formula (II) below. Furthermore, "homopolypropylene" refers to materials having the structural formula shown in formula (III) below.

[0076] [ka]

[0077] [ka]

[0078] [ka]

[0079] When a mixture of polypropylene and polyethylene is used as the propylene-based material, the material may have an island-in-a-sea structure, where the polyethylene is discontinuously dispersed within a continuous polypropylene region.

[0080] Considering the boiling treatment, examples of materials constituting the sealant layer 70 include polyethylene, polypropylene, and combinations thereof. Examples of polyethylene include medium-density polyethylene, linear low-density polyethylene, and combinations thereof. For example, it is also possible to use the materials listed above as materials constituting the sealant layer 70 from the viewpoint of retort treatment. The material constituting the sealant layer 70 has a melting point of, for example, 100°C or higher, more preferably 105°C or higher, more preferably 110°C or higher, and even more preferably 115°C or higher. When the sealant layer 70 contains polyethylene as a main component, a melting point of 100°C or higher is achieved, for example, when the density of polyethylene is 0.920 g / cm. 3 This can be achieved when the temperature is above 100°C. Specific examples of sealant films for forming the sealant layer 70 having a melting point of 100°C or higher include TUX-HC manufactured by Mitsui Chemicals Tohcello, L6101 manufactured by Toyobo, and LS700C manufactured by Idemitsu Unitech. Specific examples of sealant films for forming the sealant layer 70 having a melting point of 105°C or higher include NB-1 manufactured by Tamapoly. Specific examples of sealant films for forming the sealant layer 70 having a melting point of 110°C or higher include LS760C manufactured by Idemitsu Unitech and TUX-HZ manufactured by Mitsui Chemicals Tohcello. The polyethylene content in the sealant layer 70 is, for example, 70% by mass or higher, and may be 80% by mass or higher.

[0081] Preferably, the sealant layer 70 is a single-layer film containing a propylene-ethylene block copolymer. For example, the sealant layer including the sealant layer 70 is a single-layer unstretched film whose main component is a propylene-ethylene block copolymer. By using a propylene-ethylene block copolymer, the impact resistance of the sealant layer can be increased, thereby preventing the bag 10 from breaking due to an impact when dropped. Furthermore, the puncture resistance of the packaging material 30 can be increased.

[0082] A propylene-ethylene block copolymer, for example, contains a sea component made of polypropylene and island components made of an ethylene-propylene copolymer rubber component. The sea component can contribute to improving the blocking resistance, heat resistance, rigidity, seal strength, etc. of the propylene-ethylene block copolymer. The island components can also contribute to improving the impact resistance of the propylene-ethylene block copolymer. Therefore, by adjusting the ratio of the sea component to the island component, the mechanical properties of a sealant layer containing a propylene-ethylene block copolymer can be adjusted.

[0083] In the propylene-ethylene block copolymer, the mass ratio of the sea part made of polypropylene is higher than the mass ratio of the island part made of ethylene-propylene copolymer rubber component. For example, in the propylene-ethylene block copolymer, the mass ratio of the sea part made of polypropylene is at least 51 mass% or more, preferably 60 mass% or more, and more preferably 70 mass% or more.

[0084] The single-layer sealant layer may further contain a second thermoplastic resin in addition to the first thermoplastic resin consisting of a propylene-ethylene block copolymer. Examples of the second thermoplastic resin include α-olefin copolymers and polyethylene. An example of an α-olefin copolymer is linear low-density polyethylene. Examples of polyethylene include low-density polyethylene, medium-density polyethylene, and high-density polyethylene. The second thermoplastic resin may contribute to increasing the impact resistance of the sealant layer.

[0085] Low density polyethylene has a density of 0.910 g / cm 3 or more and 0.925g / cm 3 Medium density polyethylene has a density of 0.926 g / cm 3 or more and 0.940 g / cm 3 High density polyethylene is polyethylene with a density of 0.941 g / cm 3 or more and 0.965g / cm 3The following polyethylenes are available: Low-density polyethylene is obtained by polymerizing ethylene at a high pressure, for example, of 1000 atmospheres or more and less than 2000 atmospheres; medium-density polyethylene and high-density polyethylene are obtained by polymerizing ethylene at a medium or low pressure, for example, of 1 atmosphere or more and less than 1000 atmospheres.

[0086] It should be noted that medium-density polyethylene and high-density polyethylene may partially contain a copolymer of ethylene and an α-olefin. Even when ethylene is polymerized under medium or low pressure, medium-density or low-density polyethylene can be produced if it contains a copolymer of ethylene and an α-olefin. Such polyethylene is referred to as the linear low-density polyethylene mentioned above. Linear low-density polyethylene is obtained by copolymerizing an α-olefin with a linear polymer obtained by polymerizing ethylene under medium or low pressure to introduce short-chain branches. Examples of α-olefins include 1-butene (C4), 1-hexene (C6), 4-methylpentene (C6), and 1-octene (C8). The density of linear low-density polyethylene is, for example, 0.915 g / cm. 3 or more and 0.945 g / cm 3 The following is the result.

[0087] The α-olefin copolymer constituting the second thermoplastic resin of the propylene-ethylene block copolymer is not limited to the linear low-density polyethylene described above. The α-olefin copolymer refers to a material having the structural formula shown in formula (IV) below.

[0088] [ka] Both R1 and R2 are H (hydrogen atom) or alkyl groups such as CH3 and C2H5. Furthermore, both j and k are integers of 1 or greater. Furthermore, j is greater than k. That is, in the α-olefin copolymer represented by formula (IV), the structure on the left side including R1 is the base. R1 is, for example, H, and R2 is, for example, C2H5.

[0089] In the sealant layer, the mass ratio of the first thermoplastic resin comprising a propylene-ethylene block copolymer is higher than the mass ratio of the second thermoplastic resin containing at least an α-olefin copolymer or polyethylene. For example, in a single sealant layer, the mass ratio of the first thermoplastic resin comprising a propylene-ethylene block copolymer is at least 51 mass% or more, preferably 60 mass% or more, and more preferably 70 mass% or more.

[0090] As described above, the second thermoplastic resin can contribute to increasing the impact resistance of the sealant layer. Therefore, by adjusting the mass ratio of the second thermoplastic resin containing at least an α-olefin copolymer or polyethylene in the single sealant layer, the mechanical properties of the sealant layer can be adjusted.

[0091] The sealant layer 70 may further contain a thermoplastic elastomer. By using a thermoplastic elastomer, the impact resistance and puncture resistance of the sealant layer 70 can be further improved.

[0092] The thermoplastic elastomer is, for example, a hydrogenated styrene-based thermoplastic elastomer. The hydrogenated styrene-based thermoplastic elastomer has a structure consisting of a polymer block A mainly composed of at least one vinyl aromatic compound and a polymer block B mainly composed of at least one hydrogenated conjugated diene compound. The thermoplastic elastomer may also be an ethylene-α-olefin elastomer. The ethylene-α-olefin elastomer is a low-crystalline or amorphous copolymer elastomer, and is a random copolymer of 50 to 90% by mass of ethylene as the main component and an α-olefin as a copolymerization monomer.

[0093] The content of the propylene-ethylene block copolymer in the sealant layer 70 is, for example, 80% by mass or more, and preferably 90% by mass or more.

[0094] Propylene-ethylene block copolymers can be produced by polymerizing the raw materials propylene and ethylene using a catalyst, such as a Ziegler-Natta catalyst or a metallocene catalyst.

[0095] The thickness of the sealant layer 70 is preferably 30 μm or more, and more preferably 40 μm or more. The thickness of the sealant layer 70 is preferably 100 μm or less, and more preferably 80 μm or less.

[0096] In the following, preferred mechanical properties of the sealant film when the sealant layer 70 is made of a single layer sealant film containing a propylene-ethylene block copolymer will be described. The tensile elongation of the sealant film in the machine direction (MD) at 25°C is preferably 600% or more and 1300% or less. The product of the tensile elongation (%) of the sealant film in the machine direction (MD) and its thickness (μm) is preferably 35,000 or more and 80,000 or less. The tensile elongation of the sealant film in the transverse direction (TD) at 25°C is preferably 700% or more and 1400% or less. The product of the tensile elongation (%) of the sealant film in the transverse direction (TD) and its thickness (μm) is preferably 40,000 or more and 85,000 or less. The tensile modulus of elasticity of the sealant film in the machine direction (MD) at 25°C is preferably 400 MPa or more and 1100 MPa or less. The product of the tensile modulus (MPa) of the sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably 30,000 or more and 55,000 or less. The tensile modulus of the sealant film in the transverse direction (TD) at 25°C is preferably 250 MPa or more and 900 MPa or less. The product of the tensile modulus (MPa) of the sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably 20,000 or more and 45,000 or more. 1, the first direction D1 corresponds to the machine direction (MD) of the sealant film, and the second direction D2 corresponds to the perpendicular direction (TD) of the sealant film.

[0097] The tensile modulus and tensile elongation can be measured in accordance with JIS K7127. A tensile tester STA-1150 manufactured by Orientec Co., Ltd. can be used as a measuring device. In the bag 10 shown in FIG. 1 , the direction in which the upper portion 11 and the lower portion 12 extend is the machine direction of the film constituting the bag 10, such as a sealant film, and the direction in which the side portion 13 extends is perpendicular to the film constituting the bag 10, such as a sealant film. Although not shown, the bag 10 may be configured so that the direction in which the upper portion 11 and the lower portion 12 extend is perpendicular to the film and the direction in which the side portion 13 extends is the machine direction of the film.

[0098] There are two main types of single-layer sealant films containing propylene-ethylene block copolymers. The first type is a type that has high tensile elongation and impact resistance, such as unstretched polypropylene film ZK500 manufactured by Toray Advanced Film Co., Ltd. The first type of sealant film preferably also has the property of low hot seal strength. This prevents excessive internal pressure in the storage section 17 when the bag 10 is heated, thereby preventing damage to the packaging material 30. The second type is a type with a high tensile modulus, such as unstretched polypropylene film ZK207 manufactured by Toray Advanced Film Co., Ltd. Use of the second type of sealant film can improve tearability when a consumer tears bag 10 along first direction D1 to open bag 10.

[0099] The product of the tensile elongation (%) of the first type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably 45,000 or more, more preferably 50,000 or more, or may be 55,000 or more, or 60,000 or more. The product of the tensile elongation (%) of the first type sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably 53,000 or more, more preferably 60,000 or more. When the sealant film has a high tensile elongation, it is possible to prevent the bag 10 from breaking due to an impact when dropped, for example. Furthermore, the product of the tensile modulus (MPa) of the first type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably not more than 38,000, more preferably not more than 35,000. Furthermore, the product of the tensile modulus (MPa) of the first type sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably not more than 30,000, more preferably not more than 25,000.

[0100] The product of the tensile modulus (MPa) of the second type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably 35,000 or more, more preferably 38,000 or more, and even more preferably 45,000 or more. The product of the tensile modulus (MPa) of the second type sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably 25,000 or more, more preferably 30,000 or more, even more preferably 35,000 or more, and may be 38,000 or more. When the sealant film has a high tensile modulus, the tearability when opening the bag 10 can be improved. Furthermore, the product of the tensile elongation (%) of the second type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably not more than 55,000, more preferably not more than 50,000. Furthermore, the product of the tensile elongation (%) of the second type sealant film in the transverse direction (TD) and the thickness (μm) of the sealant film is preferably not more than 60,000, more preferably not more than 55,000.

[0101] The sealant layer 70 may have easy-peel properties. Easy-peel properties refer to the property that, when a packaging material 30 having a sealant layer 70 is used to form a lid for a container, the lid can be easily peeled from the flange of the container at its underside, i.e., at the sealant layer 70. Easy-peel properties can be achieved, for example, by forming the sealant layer 70 from two or more types of resins, with one resin being incompatible with the other resins. Examples of resins that can achieve easy-peel properties include mixed resins of polyethylene and polypropylene, such as high-density polyethylene.

[0102] 10, the sealant layer 70 may include a first layer 71 located on the metal foil 50 side and a second layer 72 located inside the first layer 71 and constituting the inner surface 30x of the packaging material 30. The first layer 71 and second layer 72 of the sealant layer 70 having easy peel properties can be mainly of two types, such as Type A and Type B described below.

[0103] In the A-type sealant layer 70, the first layer 71 is a layer containing polyethylene as a main component, and the second layer 72 is a layer containing a mixed resin of polyethylene and polypropylene. In the second layer 72, the blend ratio of polypropylene is higher than the blend ratio of polyethylene. The mass ratio of polypropylene to polyethylene in the second layer 72 is 6:4 to 8:2.

[0104] When the packaging material 30 having the A-type sealant layer 70 is used in a packaged product for heat sterilization, the density of the polyethylene in the sealant layer 70 is set to 0.940 g / cm 3 It is preferable that the above is set.

[0105] The polypropylene in the second layer 72 of the A-type sealant layer 70 may be, for example, an ethylene-propylene random copolymer.

[0106] In the A-type sealant layer 70, the ratio of the thickness of the first layer 71 to the thickness of the second layer 72 can be set to 5:1 to 10:1.

[0107] In the B-type sealant layer 70, the first layer 71 is a layer containing polypropylene as a main component, and the second layer 72 is a layer containing a mixed resin of polyethylene and polypropylene. In the second layer 72, the blend ratio of polypropylene is higher than the blend ratio of polyethylene. The mass ratio of polypropylene to polyethylene in the second layer 72 is 6:4 to 8:2.

[0108] When the packaging material 30 having the B-type sealant layer 70 is used in a packaged product for heat sterilization, the density of the polyethylene in the sealant layer 70 is set to 0.940 g / cm 3 It is preferable that the above is set.

[0109] The polypropylene in the first layer 71 of the B-type sealant layer 70 may be, for example, an ethylene-propylene block copolymer. The polypropylene in the second layer 72 of the B-type sealant layer 70 may be, for example, an ethylene-propylene random copolymer.

[0110] In the B-type sealant layer 70, the ratio of the thickness of the first layer 71 to the thickness of the second layer 72 can be set to 3:1 to 8:1.

[0111] The sealant layer 70 may be a resin layer provided by an extrusion method or the like on the inner surface side of the metal foil 50. In this case, the second adhesive layer 55 described above does not need to be present between the metal foil 50 and the sealant layer 70.

[0112] (Other layers) The substrate 35 of the packaging material 30 may further include a printed layer 32. In the example shown in Fig. 2, the printed layer 32 is located on the surface of the biaxially stretched plastic film 40 on the first adhesive layer 45 side.

[0113] The printed layer 32 is a layer for displaying information about the contents or packaged product, and for adding aesthetic appeal to a packaged product such as the bag 10. The printed layer expresses letters, numbers, symbols, figures, pictures, etc. The printed layer contains a binder resin and a coloring material such as a dye or pigment dispersed in the binder resin. Materials that can be used to form the printed layer include gravure printing ink and flexographic printing ink. A specific example of gravure printing ink is Finart, manufactured by DIC Graphics Corporation.

[0114] Packaging material manufacturing method Next, an example of a method for producing the packaging material 30 will be described.

[0115] First, prepare the biaxially stretched plastic film 40 and the metal foil 50. The biaxially stretched plastic film 40 is provided with a print layer 32 or the like as needed.

[0116] Next, the biaxially oriented plastic film 40 and the metal foil 50 are laminated together by dry lamination via the first adhesive layer 45. After that, the laminate including the biaxially oriented plastic film 40 and the metal foil 50 is laminated together with the sealant layer 70 by dry lamination via the second adhesive layer 55. In this way, a packaging material 30 including the biaxially oriented plastic film 40, the metal foil 50, and the sealant layer 70 can be obtained.

[0117] Alternatively, the packaging material 30 may be produced by first laminating the metal foil 50 and the sealant layer 70 via the second adhesive layer 55 using a dry lamination method, and then laminating the biaxially oriented plastic film 40 and a laminate including the metal foil 50 and the sealant layer 70 via the first adhesive layer 45 using a dry lamination method.

[0118] In the dry lamination method, an adhesive composition is first applied to one of the two films to be laminated. The applied adhesive composition is then dried to volatilize the solvent. The two films are then laminated together via the dried adhesive composition. The two laminated films are then rolled up and aged, for example, at 20°C or higher for 24 hours or more.

[0119] Bag manufacturing method Next, a method for manufacturing bag 10 using the above-mentioned packaging material 30 will be described. First, front film 14 and back film 15 made of packaging material 30 are prepared. Next, the inner surfaces of each film are heat-sealed to form seals such as bottom seal 12a and side seal 13a. The films joined together by heat sealing are then cut into an appropriate shape to obtain bag 10 shown in FIG. 1.

[0120] Next, the contents 18 are filled into the bag 10 through the opening 11b of the top 11. Specifically, as shown in FIG. 11 , the pair of side seal portions 13a of the bag 10, which are closest to the top 11, are gripped by a pair of zippers 105. Furthermore, as shown by arrow P in FIG. 11 , the zippers 105 are moved in a direction that narrows the gap between the pair of zippers 105 in the width direction of the bag 10. This causes the front film 14 and the back film 15 to deform so as to form the opening 11b in the top 11. At this time, as shown in FIG. 11 , suction units 106 may be attached to the outer surfaces of the front film 14 and the back film 15, and the suction units 106 may be moved in the direction of arrow Q. This facilitates the formation of the opening 11b. Next, the contents 18 are filled into the bag 10 through the opening 11b. The top 11 is then heat-sealed to form the top seal portion 11a. In this manner, a bag 10 containing and sealed with the contents 18 can be obtained.

[0121] In this embodiment, the biaxially oriented plastic film 40 of the substrate 35 of the packaging material 30 contains polyester as a primary component. This allows the moisture content of the substrate 35 to be reduced compared to when the substrate 35 includes a biaxially oriented plastic film containing nylon as a primary component. This prevents the moisture in the substrate 35 from evaporating and causing bubbles during heat sealing. This prevents the substrate 35 from becoming cloudy due to bubbles, making it easier to maintain the transparency of the substrate 35.

[0122] Contents 18 are, for example, cooked foods containing water, such as curry, stew, soup, etc. Contents 18 may also contain ingredients with a high oil content, such as meat, fish, and seasonings for those. In addition to food, items that can be heated in a hot water bath or the like can also be placed in bag 10 as contents. Contents that do not require heating may also be placed in bag 10.

[0123] Subsequently, the bag 10 containing the contents may be subjected to a sterilization treatment such as boiling or retorting. In this embodiment, the biaxially oriented plastic film 40 of the substrate 35 of the packaging material 30 contains polyester as a primary component. Therefore, compared to a case in which the substrate 35 includes a biaxially oriented plastic film containing nylon as a primary component, absorption of moisture by the substrate 35 during sterilization can be suppressed. This suppresses the occurrence of cloudiness in the substrate 35 due to moisture, making it easier to maintain the transparency of the substrate 35. Furthermore, an increase in the static and dynamic friction coefficients of the outer surface 30y of the packaging material 30 caused by moisture absorption by the substrate 35 can be suppressed. This suppresses a decrease in the slipperiness of the packaging material 30 and the packaged product when the packaging material 30 and the packaged product are exposed to a high-temperature, high-humidity environment.

[0124] Furthermore, in this embodiment, a high-stiffness polyester film is used as the biaxially oriented plastic film 40 of the substrate 35 of the packaging material 30 that constitutes the bag 10. This allows the packaging material 30 and the bag 10 to have excellent puncture strength. This makes it possible to prevent the bag 10 from being torn, for example, when it comes into contact with a sharp object having a pointed tip. The puncture strength of the packaging material 30 is preferably 15.0 N or more, more preferably 16.0 N or more, even more preferably 17.0 N or more, and still more preferably 18.0 N or more. A method for measuring the puncture strength will be described in the examples below.

[0125] Furthermore, in this embodiment, the use of a high-stiffness polyester film as the biaxially oriented plastic film 40 of the substrate 35 facilitates increasing the rigidity of the packaging material 30. When the packaging material 30 is rigid, it becomes easier to form the opening 11b in the upper portion 11 when the chuck portion 105 is moved, as shown in FIG. 11 . For example, the front and back films 14 and 15 are each more likely to deform into a curved shape that is convex toward the outer surface. This makes it easier to ensure the opening width K of the opening 11b. Furthermore, when the packaging material 30 constituting the front and back films 14 and 15 is rigid, the front and back films 14 and 15 are less likely to wrinkle. This allows the suction portion 106 to easily adhere to the outer surfaces of the front and back films 14 and 15. This also contributes to ensuring the opening width K of the opening 11b.

[0126] In the present embodiment, the packaging material 30 includes a metal foil 50. This allows the packaging material 30 and the bag 10 to have gas barrier properties that prevent the transmission of oxygen gas, water vapor, and the like, and light-blocking properties that prevent the transmission of visible light, ultraviolet light, and the like.

[0127] How to open the bag Next, a method for opening the bag 10 will be described. A consumer can open the bag 10 by tearing the bag 10 along the first direction D1. To improve the tearability of the bag 10, it is preferable to use the second type of sealant film described above, which has a high tensile modulus.

[0128] It should be noted that various modifications can be made to the above-described embodiment. Below, modifications will be described with reference to the drawings as necessary. In the following description and the drawings used in the following description, parts that can be configured similarly to the above-described embodiment will be designated by the same reference numerals as those used for the corresponding parts in the above-described embodiment, and duplicated explanations will be omitted. Furthermore, if it is clear that the effects obtained in the above-described embodiment can also be obtained in the modified embodiment, the explanations thereof may be omitted.

[0129] (Variations of the bag) Figure 12 is a diagram showing another example of bag 10 provided with packaging material 30. Bag 10 shown in Figure 12 differs only in that it further includes a lower film 16, and other configurations are substantially the same as bag 10 shown in Figure 1. In bag 10 shown in Figure 12, the same parts as bag 10 shown in Figure 1 are designated by the same reference numerals and detailed description thereof will be omitted.

[0130] The bag 10 shown in Figure 12 is a gusset-type bag configured to be self-standing. In addition to the components of the bag 10 shown in Figure 1, the bag 10 includes a lower film 16 that configures the lower portion 12. The lower film 16 is folded back at a folded-back portion 16f and disposed between the front film 14 and the back film 15. In this case, the sealed portion includes a lower sealed portion 12a that extends across the lower portion 12. The lower sealed portion 12a includes a sealed portion configured by joining the inner surfaces of the front film 14 and the lower film 16, and a sealed portion configured by joining the inner surfaces of the back film 15 and the lower film 16.

[0131] Bag manufacturing method A method for manufacturing the bag 10 shown in Figure 12 will be described. First, a front film 14 and a back film 15 made of packaging material 30 are prepared. A folded-over bottom film 16 is inserted between the front film 14 and the back film 15. Next, the inner surfaces of the films are heat-sealed to form seals such as a bottom seal 12a and a side seal 13a. The films joined together by heat sealing are then cut into an appropriate shape to obtain the bag 10 shown in Figure 12.

[0132] 13A and 13B are a longitudinal cross-sectional view and a plan view showing a lidded container 110, which is an example of an application of the packaging material 30. The lidded container 110 includes a container body 112 fabricated by sheet molding such as drawing or injection molding, and a lid member 114 joined to the container body 112. The container body 112 has a bottom surface 112a, a side surface 112b, and a flange portion 113 extending horizontally outward from the upper end of the side surface 112b. The lid member 114 is joined to the upper surface of the flange portion 113 of the container body 112 via a seal portion 116. The lid member 114 may include the above-described packaging material 30 having at least one high-stiffness polyester film. Using the above-described packaging material 30 to form the lid member 114 can provide the lid member 114 with excellent puncture resistance. This can prevent the lid member 114 from being torn when it comes into contact with a sharp object.

[0133] The sealant layer 70 of the packaging material 30 constituting the lid member 114 may have easy-peel properties. That is, the sealant layer 70 of the packaging material 30 constituting the lid member 114 may have a first layer 71 containing polyethylene or polypropylene as a main component, and a second layer 72 containing a mixed resin of polyethylene and polypropylene and constituting the inner surface 30x.

[0134] FIG. 14 is a perspective view showing a container 120, which is an example of an application of the packaging material 30. The container 120 includes an outer box 122 and a bag-in-box 124 housed in the outer box 122. The outer box 122 is made of, for example, cardboard. The bag-in-box 124 can house contents such as water. The bag-in-box 124 may include the above-described packaging material 30 having at least one high-stiffness polyester film. By using the above-described packaging material 30 to form the bag-in-box 124, it is possible to impart excellent puncture resistance to the bag-in-box 124. This makes it possible to prevent the lid material 114 from being torn when a sharp object with a pointed tip comes into contact with the bag-in-box 124.

[0135] The inside of the bag-in-box 124 may be cleaned with a cleaning solution containing hydrogen peroxide or the like. In this embodiment, the biaxially oriented plastic film 40 of the substrate 35 of the packaging material 30 contains polyester as a primary component. Therefore, compared to when the substrate 35 includes a biaxially oriented plastic film containing nylon as a primary component, the occurrence of cloudiness in the substrate 35 during cleaning can be suppressed, making it easier to maintain the transparency of the substrate 35.

[0136] 14, the bag-in-box 124 may have a spout 125 for pouring out the contents. In this case, the outer box 122 may have an opening 123 formed therein for exposing the spout 125 to the outside of the outer box 122.

[0137] In this application, products for packaging items, such as the bag 10, the container with lid 110, and the container 120, are also referred to as packaging products. [Example]

[0138] Next, the present invention will be explained in more detail with reference to examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention.

[0139] The packaging material 30 of the present invention was evaluated for puncture strength, loop stiffness, tensile properties, appearance, and slipperiness in Examples 1 to 5 and Comparative Examples 1 to 3.

[0140] Example 1 A high-stiffness polyester film (hereinafter also referred to as high-stiffness PET film) having a loop stiffness of 0.0017 N or more, containing 90% by mass or more of PET, and provided with a printed layer 32 was prepared as the biaxially stretched plastic film 40. Specifically, XP-55 manufactured by Toray Industries, Inc. was used as the high-stiffness PET film. The thickness of the high-stiffness PET film was 16 μm. The measured loop stiffness of the high-stiffness PET film was 0.0021 N in both the machine direction and the perpendicular direction. The Young's modulus of the high-stiffness PET film in the machine direction was 4.8 GPa, and the Young's modulus of the high-stiffness PET film in the perpendicular direction was 4.7 GPa. The tensile strength of the high-stiffness PET film in the machine direction was 292 MPa, and the tensile strength of the high-stiffness PET film in the perpendicular direction was 257 MPa. The tensile elongation of the high-stiffness PET film in the machine direction was 107%, and the tensile elongation of the high-stiffness PET film in the perpendicular direction was 102%. In this case, the tensile strength of the high-stiffness PET film in the machine direction divided by the tensile elongation was 2.73 [MPa / %], and the tensile strength of the high-stiffness PET film in the perpendicular direction divided by the tensile elongation was 2.52 [MPa / %]. The heat shrinkage of the high-stiffness PET film in both the machine direction and the perpendicular direction was 0.4%.

[0141] As the metal foil 50, an aluminum foil having a thickness of 7 μm was prepared.

[0142] Furthermore, an unstretched polypropylene film ZK500 manufactured by Toray Advanced Film Co., Ltd. was prepared as the sealant layer 70. ZK500 contains the above-mentioned propylene-ethylene block copolymer. The thickness of the sealant layer 70 was 60 μm.

[0143] ZK500 has a higher tensile elongation than general unstretched polypropylene films. Specifically, the tensile elongation of ZK500 in the machine direction (MD) is 1180% when the thickness is 50 μm and 1100% when the thickness is 60 μm. The tensile elongation of ZK500 in the transverse direction (TD) is 1240% when the thickness is 50 μm and 1150% when the thickness is 60 μm. Therefore, the product of the tensile elongation (%) of ZK500 in the machine direction and the thickness (μm) is 59,000 when the thickness is 50 μm and 66,000 when the thickness is 60 μm. The product of the tensile elongation (%) of ZK500 in the transverse direction and the thickness (μm) is 62,000 when the thickness is 50 μm and 69,000 when the thickness is 60 μm.

[0144] Furthermore, ZK500 has a lower tensile modulus than general unstretched polypropylene films. Specifically, the tensile modulus of ZK500 in the machine direction (MD) is 640 MPa when the thickness is 50 μm and 550 MPa when the thickness is 60 μm. The tensile modulus of ZK500 in the transverse direction (TD) is 480 MPa when the thickness is 50 μm and 400 MPa when the thickness is 60 μm. Therefore, the product of the tensile modulus (MPa) of ZK500 in the machine direction and the thickness (μm) is 32,000 when the thickness is 50 μm and 33,000 when the thickness is 60 μm. The product of the tensile modulus (MPa) of ZK500 in the transverse direction and the thickness (μm) is 24,000 when the thickness is 50 μm and 35,000 when the thickness is 60 μm.

[0145] Next, the biaxially oriented plastic film 40 provided with the printed layer 32, the metal foil 50, and the sealant layer 70 were laminated in this order by dry lamination to produce the packaging material 30. The printed layer was laminated so that it faced the metal foil 50. A two-component polyurethane adhesive (main agent: RU-40, curing agent: H-4) manufactured by Rock Paint Co., Ltd. was used for the first adhesive layer 45 and the second adhesive layer 55. The main agent RU-40 is a polyester polyol. The thickness of the first adhesive layer 45 and the second adhesive layer 55 was 3 μm. The overall thickness of the packaging material 30 was 90 μm.

[0146] [Evaluation of puncture resistance] Next, the puncture strength of the packaging material 30 was measured in accordance with JIS Z1707 7.4. A Tensilon universal testing machine RTC-1310 manufactured by A&D was used as the measuring instrument. Specifically, as shown in FIG. 15 , a test piece of the fixed packaging material 30 was pierced from the outer surface 30y side with a semicircular needle 90 having a diameter of 1.0 mm and a tip radius of 0.5 mm at a speed of 50 mm / min (50 mm per minute), and the maximum stress until the needle 90 penetrated the packaging material 30 was measured. The maximum stress was measured for five or more test pieces, and the average value was taken as the puncture strength of the packaging material 30. The measurement was performed in an environment of 23°C and 50% relative humidity. The resulting puncture strength was 17.3 N.

[0147] [Evaluation of tensile properties] The tensile properties of the packaging material 30 were also evaluated in the machine direction and perpendicular directions. Specifically, the Young's modulus of the packaging material 30 was measured in the machine direction and perpendicular directions. The tensile properties of the packaging material 30 can be measured in accordance with JIS K7127. A tensile tester RTC-1310A manufactured by Orientec Co., Ltd. can be used as a measuring instrument. A rectangular film cut from the packaging material with a width of 15 mm and a length of 150 mm can be used as a test piece. The distance between the pair of chucks holding the test piece at the start of the measurement was 50 mm, and the tensile speed was 300 mm / min. The measurement was performed in an environment with a temperature of 23°C and a relative humidity of 50%. As a result, the Young's modulus in the machine direction was 4005 MPa, and the Young's modulus in the perpendicular direction was 4352 MPa.

[0148] [Evaluation of loop stiffness] The loop stiffness of the packaging material 30 was also measured in the machine direction and perpendicular direction. The measuring device used was a No. 581 Loop Stiffness Tester (registered trademark) LOOP STIFFNESS TESTER DA type manufactured by Toyo Seiki Seisakusho. The measurement was performed in an environment with a temperature of 23°C and a relative humidity of 50%. As a result, the loop stiffness of the packaging material 30 in the machine direction was 0.112 N, and the loop stiffness in the perpendicular direction was 0.103 N.

[0149] [Evaluation of Slipperiness] Next, the slipperiness of the outer surface 30y of the packaging material 30 was evaluated. Here, the coefficient of friction of the outer surface 30y of the packaging material 30 was measured. Specifically, the static friction coefficient and the dynamic friction coefficient between the outer surface 30y of the packaging material 30 and a metal surface were measured. The measurements were performed using a friction measuring instrument TR-2 manufactured by Toyo Seiki Seisaku-sho, Ltd. in accordance with JIS K-7125. Aluminum was used as the metal constituting the metal surface.

[0150] The specific measurement method will be described below. First, the packaging material 30 was cut to prepare a test piece with a width of 70 mm and a length of 152 mm. Next, the following first and second measurements were carried out using the test piece.

[0151] In the first measurement, the test specimen was stored for at least 24 hours in a room with a temperature of 20-30°C and a humidity of 40-60%. The test specimen was then placed on a metal surface so that its outer surface was in contact with the metal surface. A sled with a mass of 200 g and a 63 mm wide and 63 mm long member was then placed on top of the test specimen. The test specimen was then slid across the metal surface at a speed of 100 mm / min. The static and dynamic coefficients of friction of the outer surface of the test specimen were calculated based on the force applied to the test specimen at the start of sliding and the force applied to the test specimen during sliding. The measurement was performed under the standard conditions specified in JIS K7100: a temperature of 23°C and humidity of 50%.

[0152] In the second measurement, the test specimen was stored in a high-temperature constant temperature bath at a temperature of 40°C and a humidity of 90% for 24 hours, and then the static and dynamic friction coefficients of the outer surface of the test specimen were measured in the same manner as in the first measurement, except that the test specimen was placed on a metal surface. The measurement was carried out within 5 minutes after the test specimen was removed from the high-temperature constant temperature bath.

[0153] The ratio of the static friction coefficient in the second measurement to the static friction coefficient in the first measurement was 1.05 or less. The ratio of the kinetic friction coefficient in the second measurement to the kinetic friction coefficient in the first measurement was also 1.05 or less. In other words, there was almost no increase in the friction coefficient due to exposing the test specimen to an environment of 40°C temperature and 90% humidity.

[0154] [Evaluation of appearance] Next, bags 10 were produced using the packaging material 30 as the front film 14, back film 15, and bottom film 16, and the appearance of the bags 10 was evaluated. Specifically, first, the bag 10 shown in FIG. 11 was produced using the packaging material 30. The height S1 of the bag 10 was 160 mm, and the width S2 was 147 mm. The height S3 of the folded-back bottom film 16, i.e., the height from the bottom end of the bag 10 to the folded-back portion 16f, was 46 mm. Next, 200 g of water was filled into the bag 10 through the opening 11b of the top portion 11. The top portion 11 was then heat-sealed to form the top seal portion 11a. In this manner, multiple bags 10 shown in FIG. 11 containing 200 g of water were produced.

[0155] Next, the bag 10 containing the water was subjected to a heat sterilization treatment. Specifically, a spray-type retort treatment was performed on the bag 10. The retort temperature was 121°C, and the retort time was 30 minutes.

[0156] Next, the bags 10 that had been subjected to the heat sterilization treatment were visually inspected to see if they had become cloudy. As a result, no cloudiness was found.

[0157] Example 2 A packaging material 30 was produced in the same manner as in Example 1, except that an unstretched polypropylene film ZK207 manufactured by Toray Advanced Film Co., Ltd. was used as the sealant layer 70. ZK207 contains the above-mentioned propylene-ethylene block copolymer. The thickness of the sealant layer 70 was 70 μm. The overall thickness of the packaging material 30 was 100 μm.

[0158] ZK207 has a high tensile modulus. Specifically, the tensile modulus of ZK207 in the machine direction (MD) is 780 MPa when the thickness is 50 μm and 680 MPa when the thickness is 60 μm. The tensile modulus of ZK207 in the transverse direction (TD) is 630 MPa when the thickness is 50 μm and 560 MPa when the thickness is 60 μm. Therefore, the product of the tensile modulus (MPa) and thickness (μm) of ZK207 in the machine direction is 39,000 when the thickness is 50 μm and 40,800 when the thickness is 60 μm. The product of the tensile modulus (MPa) and thickness (μm) of ZK207 in the transverse direction is 31,500 when the thickness is 50 μm and 33,600 when the thickness is 60 μm.

[0159] ZK207 also has low tensile elongation. Specifically, the tensile elongation of ZK207 in the machine direction (MD) is 790% when the thickness is 50 μm and 730% when the thickness is 60 μm. The tensile elongation of ZK207 in the transverse direction (TD) is 1020% when the thickness is 50 μm and 870% when the thickness is 60 μm. Therefore, the product of the tensile elongation (%) of ZK207 in the machine direction and the thickness (μm) is 39,500 when the thickness is 50 μm and 43,800 when the thickness is 60 μm. The product of the tensile elongation (%) of ZK207 in the transverse direction and the thickness (μm) is 51,000 when the thickness is 50 μm and 52,200 when the thickness is 60 μm.

[0160] Next, in the same manner as in Example 1, the biaxially stretched plastic film 40 provided with the printed layer, the metal foil 50, and the sealant layer 70 were laminated in this order by dry lamination to produce the packaging material 30. The printed layer was laminated so that it faced the surface of the metal foil 50.

[0161] Subsequently, the puncture strength of the packaging material 30 was measured in the same manner as in Example 1. As a result, the puncture strength was 17.0 N.

[0162] The tensile properties of the packaging material 30 in the machine direction and perpendicular direction were evaluated in the same manner as in Example 1. As a result, the Young's modulus in the machine direction was 4113 MPa, and the Young's modulus in the perpendicular direction was 4235 MPa.

[0163] The loop stiffness of the packaging material 30 in the machine direction and perpendicular direction was measured in the same manner as in Example 1. As a result, the loop stiffness in the machine direction was 0.131 N, and the loop stiffness in the perpendicular direction was 0.124 N.

[0164] The slipperiness of the packaging material 30 was evaluated in the same manner as in Example 1. As a result, the ratio of the static friction coefficient in the second measurement to the static friction coefficient in the first measurement was 1.05 or less. The ratio of the dynamic friction coefficient in the second measurement to the dynamic friction coefficient in the first measurement was also 1.05 or less.

[0165] Furthermore, in the same manner as in Example 1, bags 10 containing 200 g of water were produced using packaging material 30, and the bags 10 were subjected to a heat sterilization treatment. Subsequently, the bags 10 that had been subjected to the heat sterilization treatment were visually inspected to see if they had become cloudy. As a result, no cloudiness was found to have occurred.

[0166] Example 3 A packaging material 30 was produced in the same manner as in Example 1, except that an unstretched polypropylene film ZK500R manufactured by Toray Advanced Film Co., Ltd. was used as the sealant layer 70. The thickness of the sealant layer 70 was 50 μm. The overall thickness of the packaging material 30 was 80 μm.

[0167] ZK500R has a high tensile modulus. Specifically, the tensile modulus of ZK500R in the machine direction (MD) is 980 MPa when the thickness is 50 μm. Furthermore, the tensile modulus of ZK500R in the transverse direction (TD) is 780 MPa when the thickness is 50 μm. Therefore, the product of the tensile modulus (MPa) of ZK500R in the machine direction and the thickness (μm) is 49,000 when the thickness is 50 μm. Furthermore, the product of the tensile modulus (MPa) of ZK500R in the transverse direction and the thickness (μm) is 39,000 when the thickness is 50 μm.

[0168] ZK500R also has low tensile elongation. Specifically, the tensile elongation of ZK500R in the machine direction (MD) is 770% when the thickness is 50 μm. Furthermore, the tensile elongation of ZK500R in the transverse direction (TD) is 870% when the thickness is 50 μm. Therefore, the product of the tensile elongation (%) of ZK500R in the machine direction and the thickness (μm) is 38,500 when the thickness is 50 μm. Furthermore, the product of the tensile elongation (%) of ZK500R in the transverse direction and the thickness (μm) is 43,500 when the thickness is 50 μm. Thus, in ZK500R, the product of the tensile modulus (MPa) and the thickness (μm) of the sealant layer 70 in at least one direction is 42,000 or more.

[0169] Next, in the same manner as in Example 1, the biaxially stretched plastic film 40 provided with the printed layer, the metal foil 50, and the sealant layer 70 were laminated in this order by dry lamination to produce the packaging material 30. The printed layer was laminated so that it faced the surface of the metal foil 50.

[0170] Subsequently, the puncture strength of the packaging material 30 was measured in the same manner as in Example 1. As a result, the puncture strength was 16.4 N.

[0171] The tensile properties of the packaging material 30 in the machine direction and perpendicular direction were evaluated in the same manner as in Example 1. As a result, the Young's modulus in the machine direction was 3994 MPa, and the Young's modulus in the perpendicular direction was 4119 MPa.

[0172] The loop stiffness of the packaging material 30 in the machine direction and the perpendicular direction was measured in the same manner as in Example 1. As a result, the loop stiffness in the machine direction was 0.100 N, and the loop stiffness in the perpendicular direction was 0.101 N.

[0173] The slipperiness of the packaging material 30 was evaluated in the same manner as in Example 1. As a result, the ratio of the static friction coefficient in the second measurement to the static friction coefficient in the first measurement was 1.05 or less. The ratio of the dynamic friction coefficient in the second measurement to the dynamic friction coefficient in the first measurement was also 1.05 or less.

[0174] Furthermore, in the same manner as in Example 1, bags 10 containing 200 g of water were produced using packaging material 30, and the bags 10 were subjected to a heat sterilization treatment. Subsequently, the bags 10 that had been subjected to the heat sterilization treatment were visually inspected to see if they had become cloudy. As a result, no cloudiness was found to have occurred.

[0175] Example 4 The packaging material 30 was produced in the same manner as in Example 1, except that a polyethylene film having a thickness of 50 μm was used as the sealant layer 70. The polyethylene film had a density of 0.922 g / cm 3 The packaging material 30 had a total thickness of 80 μm.

[0176] Subsequently, the puncture strength of the packaging material 30 was measured in the same manner as in Example 1. As a result, the puncture strength was 15.4 N.

[0177] The tensile properties of the packaging material 30 in the machine direction and perpendicular direction were evaluated in the same manner as in Example 1. As a result, the Young's modulus in the machine direction was 3898 MPa, and the Young's modulus in the perpendicular direction was 4002 MPa.

[0178] The loop stiffness of the packaging material 30 in the machine direction and the perpendicular direction was measured in the same manner as in Example 1. As a result, the loop stiffness in the machine direction was 0.092 N, and the loop stiffness in the perpendicular direction was 0.098 N.

[0179] The slipperiness of the packaging material 30 was evaluated in the same manner as in Example 1. As a result, the ratio of the static friction coefficient in the second measurement to the static friction coefficient in the first measurement was 1.05 or less. The ratio of the dynamic friction coefficient in the second measurement to the dynamic friction coefficient in the first measurement was also 1.05 or less.

[0180] Furthermore, in the same manner as in Example 1, bags 10 containing 200 g of water were produced using packaging material 30, and the bags 10 were subjected to a heat sterilization treatment. Subsequently, the bags 10 that had been subjected to the heat sterilization treatment were visually inspected to see if they had become cloudy. As a result, no cloudiness was found to have occurred.

[0181] Example 5 A packaging material 30 was produced in the same manner as in Example 1, except that a co-extruded film having easy-peel properties and including a first layer 71 and a second layer 72 as shown in FIG. 10 was used as the sealant layer 70. The first layer 71 was a 45 μm thick layer made of polyethylene. The second layer 72 was a 5 μm thick layer containing a mixed resin of polyethylene and polypropylene. The polyethylene had a density of 0.950 g / cm. 3 High-density polyethylene having a density of 1000 MPa was used. An ethylene-propylene random copolymer was used as the polypropylene. The mass ratio of polypropylene to polyethylene in the second layer 72 was 7:3. The thickness of the sealant layer 70 was 50 μm. The overall thickness of the packaging material 30 was 80 μm.

[0182] Subsequently, the puncture strength of the packaging material 30 was measured in the same manner as in Example 1. As a result, the puncture strength was 15.8 N.

[0183] The tensile properties of the packaging material 30 in the machine direction and perpendicular direction were evaluated in the same manner as in Example 1. As a result, the Young's modulus in the machine direction was 3928 MPa, and the Young's modulus in the perpendicular direction was 4080 MPa.

[0184] The loop stiffness of the packaging material 30 in the machine direction and the perpendicular direction was measured in the same manner as in Example 1. As a result, the loop stiffness in the machine direction was 0.096 N, and the loop stiffness in the perpendicular direction was 0.100 N.

[0185] The slipperiness of the packaging material 30 was evaluated in the same manner as in Example 1. As a result, the ratio of the static friction coefficient in the second measurement to the static friction coefficient in the first measurement was 1.05 or less. The ratio of the dynamic friction coefficient in the second measurement to the dynamic friction coefficient in the first measurement was also 1.05 or less.

[0186] Furthermore, in the same manner as in Example 1, bags 10 containing 200 g of water were produced using packaging material 30, and the bags 10 were subjected to a heat sterilization treatment. Subsequently, the bags 10 that had been subjected to the heat sterilization treatment were visually inspected to see if they had become cloudy. As a result, no cloudiness was found to have occurred.

[0187] (Comparative Example 1) Packaging material 30 was produced in the same manner as in Example 1, except that a biaxially oriented PET film with a thickness of 12 μm was used as base material 35 of packaging material 30. The biaxially oriented PET film used had approximately the same tensile strength in the machine direction (MD) and the transverse direction (TD). The overall thickness of packaging material 30 was 86 μm.

[0188] Subsequently, the puncture strength of the packaging material 30 was measured in the same manner as in Example 1. As a result, the puncture strength was 14.1 N.

[0189] The tensile properties of the packaging material 30 in the machine direction and perpendicular direction were evaluated in the same manner as in Example 1. As a result, the Young's modulus in the machine direction was 3724 MPa, and the Young's modulus in the perpendicular direction was 3819 MPa.

[0190] The loop stiffness of the packaging material 30 in the machine direction and perpendicular direction was measured in the same manner as in Example 1. As a result, the loop stiffness in the machine direction was 0.091 N, and the loop stiffness in the perpendicular direction was 0.087 N.

[0191] The slipperiness of the packaging material 30 was evaluated in the same manner as in Example 1. As a result, the ratio of the static friction coefficient in the second measurement to the static friction coefficient in the first measurement was 1.05 or less. The ratio of the dynamic friction coefficient in the second measurement to the dynamic friction coefficient in the first measurement was also 1.05 or less.

[0192] Furthermore, in the same manner as in Example 1, bags 10 containing 200 g of water were produced using packaging material 30, and the bags 10 were subjected to a heat sterilization treatment. Subsequently, the bags 10 that had been subjected to the heat sterilization treatment were visually inspected to see if they had become cloudy. As a result, no cloudiness was found to have occurred.

[0193] (Comparative Example 2) A packaging material 30 was produced in the same manner as in Example 2, except that a biaxially oriented PET film having a thickness of 12 μm was used as the substrate 35 of the biaxially oriented plastic film 40. The biaxially oriented PET film used had approximately the same tensile strength in the machine direction (MD) and the transverse direction (TD). The overall thickness of the packaging material 30 was 96 μm.

[0194] Subsequently, the puncture strength of the packaging material 30 was measured in the same manner as in Example 1. As a result, the puncture strength was 13.8 N.

[0195] The tensile properties of the packaging material 30 in the machine direction and perpendicular direction were evaluated in the same manner as in Example 1. As a result, the Young's modulus in the machine direction was 3779 MPa, and the Young's modulus in the perpendicular direction was 3915 MPa.

[0196] The loop stiffness of the packaging material 30 in the machine direction and perpendicular direction was measured in the same manner as in Example 1. As a result, the loop stiffness in the machine direction was 0.108 N, and the loop stiffness in the perpendicular direction was 0.101 N.

[0197] The slipperiness of the packaging material 30 was evaluated in the same manner as in Example 1. As a result, the ratio of the static friction coefficient in the second measurement to the static friction coefficient in the first measurement was 1.05 or less. The ratio of the dynamic friction coefficient in the second measurement to the dynamic friction coefficient in the first measurement was also 1.05 or less.

[0198] Furthermore, in the same manner as in Example 1, bags 10 containing 200 g of water were produced using packaging material 30, and the bags 10 were subjected to a heat sterilization treatment. Subsequently, the bags 10 that had been subjected to the heat sterilization treatment were visually inspected to see if they had become cloudy. As a result, no cloudiness was found to have occurred.

[0199] (Comparative Example 3) A packaging material 30 was produced in the same manner as in Example 1, except that the substrate 35 further included a biaxially oriented nylon film (thickness 15 μm) positioned closer to the metal foil 50 than the biaxially oriented plastic film 40. The overall thickness of the packaging material 30 was 104 μm.

[0200] Subsequently, the puncture strength of the packaging material 30 was measured in the same manner as in Example 1. As a result, the puncture strength was 18.4 N.

[0201] The tensile properties of the packaging material 30 in the machine direction and perpendicular direction were evaluated in the same manner as in Example 1. As a result, the Young's modulus in the machine direction was 3645 MPa, and the Young's modulus in the perpendicular direction was 3382 MPa.

[0202] The loop stiffness of the packaging material 30 in the machine direction and the perpendicular direction was measured in the same manner as in Example 1. As a result, the loop stiffness in the machine direction was 0.136 N, and the loop stiffness in the perpendicular direction was 0.131 N.

[0203] The slipperiness of the packaging material 30 was evaluated in the same manner as in Example 1. As a result, the ratio of the static friction coefficient in the second measurement to the static friction coefficient in the first measurement was 1.05 or less. The ratio of the dynamic friction coefficient in the second measurement to the dynamic friction coefficient in the first measurement was also 1.05 or less.

[0204] Furthermore, in the same manner as in Example 1, bags 10 containing 200 g of water were produced using packaging material 30, and the bags 10 were subjected to a heat sterilization treatment. Subsequently, it was visually confirmed whether or not cloudiness had occurred in the bags 10 that had been subjected to the heat sterilization treatment. As a result, cloudiness had occurred.

[0205] The layer structures and evaluation results of the packaging materials 30 of Examples 1 to 5 are summarized in FIG. 16. The layer structures and evaluation results of the packaging materials 30 of Comparative Examples 1 to 3 are summarized in FIG. 17. In FIGS. 16 and 17, the "Layer Structure" column lists the components of the packaging material 30 in order from the outermost layer to the top. In the "Appearance" column of FIGS. 16 and 17, "great" means that the bag 10 that had been subjected to heat sterilization treatment was not cloudy, and "not good" means that the bag 10 that had been subjected to heat sterilization treatment was cloudy. In the "Slipperiness" column of FIGS. 16 and 17, "great" means that the ratio of the static and dynamic friction coefficients in the second measurement to the static and dynamic friction coefficients in the first measurement was 1.05 or less.

[0206] As can be seen from a comparison between Examples 1 to 5 and Comparative Examples 1 to 3, when packaging material 30 contains a high-stiffness polyester film, the puncture strength of packaging material 30 could be increased to a level equivalent to that of packaging material 30 containing a nylon film. Specifically, the puncture strength could be increased to 15.0 N or more. In Examples 1, 2, and 3, the puncture strength of packaging material 30 was 16.0 N or more. Furthermore, in Examples 1 and 2, the puncture strength of packaging material 30 was 17.0 N or more.

[0207] Furthermore, as can be seen from a comparison between Examples 1 to 5 and Comparative Example 3, the absence of nylon film in packaging material 30 prevented bags 10 that had been subjected to heat sterilization treatment from becoming cloudy. [Explanation of symbols]

[0208] 10 bags 11 Upper 12 Lower 12a Lower seal 13 Side 13a Side seal 14 Surface film 15 Back film 16 Lower film 17 Storage section 18 Contents 25 Easy-to-open means 26 notches 30 Packaging materials 35 Base material 40 Biaxially oriented plastic film 45 First adhesive layer 50 Metallic foil 55 Second adhesive layer 70 Sealant Layer

Claims

1. A packaging material comprising a substrate, an aluminum foil, and a sealant layer in this order from the outer surface side to the inner surface side, The packaging material constitutes a lid material for a container, The substrate has only one biaxially stretched plastic film containing polyester as a main component, The thickness of the aluminum foil is 15 μm or less, The Young's modulus of the packaging material in one direction and in a direction perpendicular to the one direction is 3800 MPa or more. A packaging material having a puncture strength of 15.0 N or more.

2. A packaging material comprising a substrate, an aluminum foil, and a sealant layer in this order from the outer surface side to the inner surface side, The packaging material constitutes a bag-in-box, The substrate has only one biaxially stretched plastic film containing polyester as a main component, The thickness of the aluminum foil is 15 μm or less, The Young's modulus of the packaging material in one direction and in a direction perpendicular to the one direction is 3800 MPa or more. A packaging material having a puncture strength of 15.0 N or more.

3. The packaging material according to claim 1 or 2, wherein the aluminum foil has a thickness of 15 μm or less (excluding the case where the aluminum foil has a thickness of 15 μm).

4. The packaging material according to claim 1 , wherein the packaging material has a puncture strength of 17.0 N or more.

5. The packaging material according to claim 1 , wherein the Young's modulus of the packaging material in the one direction is 4000 MPa or more.

6. The packaging material according to claim 1 , wherein the biaxially oriented plastic film has a thickness of 14 μm or more and 30 μm or less.

7. The packaging material according to claim 1 , wherein the biaxially oriented plastic film contains 90% by mass or more of polyethylene terephthalate.

8. The packaging material according to claim 1 , wherein the sealant layer contains polypropylene as a main component.

9. The packaging material according to claim 1 , wherein the sealant layer comprises polyethylene having a melting point of 100° C. or higher.

10. 8. The packaging material according to claim 1, wherein the sealant layer comprises a first layer containing polyethylene or polypropylene as a main component, and a second layer located on the inner side of the first layer and containing a mixed resin of polyethylene and polypropylene.

11. A lid material comprising the packaging material according to claim 1.

12. A bag-in-box comprising the packaging material according to claim 2.

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