Packaging materials and pouches

Abstract

To provide a pouch that can enhance the appearance and suppress the occurrence of pinholes.SOLUTION: A packaging material 30 according to an aspect of the present invention comprises a biaxially oriented plastic film 31, a metal foil layer 32, and a sealant film 33 in this order. The biaxially oriented plastic film 31 contains polyester as the main component, the sealant film 33 contains polypropylene as the main component, and there is only one biaxially oriented plastic film 31 in the packaging material 30. A Young's modulus of the packaging material 30 in one direction when measured in an environment of 25°C is 3,600 MPa or more, and the piercing strength of the packaging material 30 when measured in the environment of 25°C is 15.0 N or more.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a packaging material and a pouch.

Background Art

[0002] Conventionally, many products in the market are pouches made of plastic packaging materials filled and sealed with cooked or semi-cooked liquid, viscous substances, or mixtures of liquid and solid. In a pouch, a non-sealed portion where the packaging materials are not joined constitutes a storage portion for containing the contents, and a sealed portion where the packaging materials are joined seals the storage portion (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] <00000(5]]Currently, in pouches, in order to enhance the purchasing desire, it is required to improve the appearance of the pouches. However, when the Young's modulus of the packaging material constituting the pouch is small, wrinkles may occur in the pouch during heat sterilization treatment (boiling treatment) or heat and pressure sterilization treatment (retort treatment), and the appearance of the pouch may be impaired.

[0005] Also, due to vibrations during transportation, the pouch may rub against the surface of the cardboard box in which it is packed, or the corners of the pouch may rub against each other, resulting in pinholes in the packaging material constituting the pouch. If pinholes occur in the pouch, the preservability of the contents may be impaired, so it is required to suppress the occurrence of pinholes.

[0006] It should be noted that there seems to be a small error in the original text where "[[ID=2(4]]" should probably be "". This has been corrected in the translation for clarity.This invention was made to solve the above problems. Specifically, it aims to provide a packaging material that can improve appearance and suppress the occurrence of pinholes, and a pouch equipped with the same. [Means for solving the problem]

[0007] This invention includes the following inventions. [1] A packaging material comprising, in this order, a biaxially oriented plastic film, a metal foil layer, and a sealant film, wherein the biaxially oriented plastic film is mainly composed of polyester, the sealant film is mainly composed of polypropylene, there is only one biaxially oriented plastic film in the packaging material, the unidirectional Young's modulus of the packaging material measured at 25°C is 3600 MPa or more, and the puncture strength of the packaging material measured at 25°C is 15.0 N or more.

[0008] [2] The packaging material according to [1] above, wherein the product of the tensile elongation (%) and thickness (μm) of the sealant film in the unidirectional direction is 30,000 or more and 50,000 or less.

[0009] [3] The packaging material according to [1] or [2] above, wherein the product of the tensile elongation (%) and thickness (μm) of the sealant film in a direction perpendicular to the aforementioned one direction is 45,000 or more and 55,000 or less.

[0010] [4] The packaging material according to any one of the above [1] to [3], wherein the sealant film comprises a propylene-ethylene block copolymer.

[0011] [5] The packaging material according to any one of the above [1] to [4], wherein the biaxially oriented plastic film is a biaxially oriented polyethylene terephthalate film.

[0012] [6] A pouch containing the packaging material described in any one of the above items [1] through [5].

[0013] [7] The pouch according to any one of the above items [1] to [6], wherein the pouch contains contents. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a packaging material that can improve appearance and suppress the occurrence of pinholes, and a pouch equipped therewith. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a front view of the pouch according to the embodiment. [Figure 2] Figure 2 is a diagram illustrating the dimensions of each component of the pouch shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view of the packaging material according to the embodiment. [Figure 4] Figure 4 shows how a test specimen for measuring the Young's modulus of the packaging material is cut from the front surface of the pouch. [Figure 5] Figure 5 shows how a test specimen for measuring the Young's modulus of the packaging material is cut from the back of the pouch. [Figure 6] Figure 6 shows how Young's modulus is measured using a test specimen. [Figure 7] Figure 7 shows how to cut a test specimen from the front of a pouch to measure the puncture strength of the packaging material. [Figure 8] Figure 8 shows how to cut out a test specimen from the back of a pouch to measure the puncture strength of the packaging material. [Figure 9] Figure 9 shows how puncture strength is measured using a test specimen. [Modes for carrying out the invention]

[0016] Hereinafter, the pouch according to the embodiment of the present invention will be described with reference to the drawings. In this specification, terms such as "film" and "sheet" are not distinguished from each other based only on the difference in name. Therefore, for example, "film" is used in the sense that it also includes a member that may also be called a sheet. FIG. 1 is a front view of the pouch according to this embodiment, FIG. 2 is a diagram for explaining the dimensions of each component of the pouch shown in FIG. 1, and FIG. 3 is a cross-sectional view of the packaging material according to this embodiment. FIG. 4 is a diagram when a test piece for measuring the Young's modulus of the packaging material is cut out from the front surface of the pouch, FIG. 5 is a diagram when a test piece for measuring the Young's modulus of the packaging material is cut out from the back surface of the pouch, and FIG. 6 is a diagram showing a state of measuring the Young's modulus using the test piece. FIG. 7 is a diagram when a test piece for measuring the puncture strength of the packaging material is cut out from the front surface of the pouch, FIG. 8 is a diagram when a test piece for measuring the puncture strength of the packaging material is cut out from the back surface of the pouch, and FIG. 9 is a diagram showing a state of measuring the puncture strength using the test piece.

[0017] <<<Pouch>>> The pouch 10 shown in FIG. 1 is a standing-type pouch and has an accommodation space 10A for accommodating the contents. The contents are not particularly limited, and examples include solids, liquids, or mixtures thereof. Examples of the contents include cooked foods such as curry, stew, and soup. The cooked food may be subjected to heat sterilization treatment such as boiling treatment or retort treatment. That is, heat sterilized foods or pressure-heat sterilized foods may be accommodated as the contents. The "retort treatment" is a treatment in which after filling the contents into the pouch and sealing the pouch, the pouch is heated in a pressurized state using steam or heated warm water. The temperature of the retort treatment is, for example, 120°C or higher. The pouch is a concept that includes not only a pouch in a state where the contents are not filled but also a pouch in a state where the contents are filled.

[0018] The pouch 10 shown in FIG. 1 has a front film 11, a back film 12, and a bottom film 13. The front film 11 and the back film 12 have a rectangular outline. In the state shown in FIG. 1, the bottom film 13 is in a double-folded state.

[0019] The pouch 10 has an upper part 10B, a bottom part 10C opposite to the upper part 10B, a first side part 10D and a second side part 10E extending between the upper part 10B and the bottom part 10C. The second side part 10E is a side part opposite to the first side part 10D. Also, the positions of "upper", "lower", "side", and "bottom" in this specification mean the positions in the state where the pouch stands on its own.

[0020] The ratio (H / W1) of the height H1 (see FIG. 2) of the pouch 10 to the width W1 (see FIG. 2) of the pouch 10 is preferably 0.6 or more and 2.0 or less. If H1 / W1 is 0.6 or more, more contents can be accommodated, and if H1 / W1 is 2.0 or less, the pouch 10 can be stably made to stand on its own before opening. The height H1 of the pouch 10 is the length from the lower edge 10G of the pouch 10 to the upper edge 10F in the Y direction DRY parallel to the direction in which the first side seal part 16 described later extends. When the length of the pouch is not constant, the height of the pouch is taken as the maximum value. The width W1 of the pouch 10 is the length from the side edge 10H on the first side part 10D side of the pouch 10 to the side edge 10I of the second side part 10E in the X direction DRX orthogonal to the Y direction DRY. When the width W1 of the pouch is not constant, the width of the pouch is taken as the minimum value. The dimensions of the pouch and the dimensions of each component constituting the pouch in the present embodiment are all values measured in the state where the pouch is made substantially flat without expanding the gusset part 14 described later.

[0021] As shown in FIG. 1, the pouch 10 has a gusset part 14 at the bottom 10C. By providing the gusset part 14, it is possible to accommodate larger contents or increase the accommodation capacity of the contents, and at the same time, the pouch 10 can be made to stand on its own.

[0022] As shown in Figure 1, the pouch 10 is equipped with a sealing portion 15 for sealing the pouch 10. The sealing portion 15 in the pouch 10 includes a first side sealing portion 16 formed on the first side portion 10D, a second side sealing portion 17 formed on the second side portion 10E, a first bottom sealing portion 20 provided on the first pleat portion 18 (described later), a second bottom sealing portion 21 provided on the second pleat portion 19 (described later), and a third bottom sealing portion 22 provided on the sides of the first pleat portion 18 and the second pleat portion 19. In Figure 1, the top of the pouch 10 is open, but after the contents are filled into the storage space 10A, it is heat-sealed to form an upper sealing portion in the upper edge 10F and the upper sealing portion area R enclosed by the dashed line in Figure 1, thereby sealing the pouch 10. When an upper seal portion is formed, it is preferable that the width W3 of the upper seal portion (see Figure 2) is, for example, 2 mm or more and 15 mm or less.

[0023] <First side sealing portion and second side sealing portion> The first side seal portion 16 is the portion where the front film 11 and the back film 12 are joined together at the first side portion 10D, and is formed from the fold line 14A to the upper edge 10F. The second side seal portion 17 is the portion where the front film 11 and the back film 12 are joined together at the second side portion 10E, and is formed from the fold line 14A to the upper edge 10F of the pouch 10. The joining of the front film 11 and the back film 12 during the formation of the first side seal portion 16 and the second side seal portion 17 is performed by heat sealing (heat fusion).

[0024] The width W2 of the first side seal portion 16 and the second side seal portion 17 (see Figure 2) is preferably, for example, 2 mm or more and 15 mm or less. If the width W2 of the first side seal portion 16 and the second side seal portion 17 is 2 mm or more, a reliable seal can be achieved at the first side seal portion 16 and the second side seal portion 17, and if it is 15 mm or less, a wider accommodation space 10A can be secured. In this specification, "width" of each seal portion means the length in the direction perpendicular to the direction in which the seal portion extends. If the width of the seal portion is not constant, the width of the seal portion shall be the shortest value among the lengths in the direction perpendicular to the direction in which the seal portion extends. The lower limit of the width W2 is more preferably 4 mm or more, and the upper limit is more preferably 10 mm or less.

[0025] The pouch 10 includes a first pleat 18 and a second pleat 19 located below the first side sealing portion 16 and the second side sealing portion 17.

[0026] <First and second folds> The first pleat 18 and the second pleat 19 are parts for forming the gusset portion 14. The first pleat 18 is formed by joining the front film 11 and the first portion of the bottom film 13, which is the part on the front film 11 side, to each other, and the second pleat 19 is formed by joining the back film 12 and the second portion of the bottom film 13, which is the part on the back film 12 side, to each other. The joining of the front film 11 and the first portion of the bottom film 13 when forming the first pleat 18 and the joining of the back film 12 and the second portion of the bottom film 13 when forming the second pleat 19 is performed by heat sealing (heat fusion). The first pleat 18 and the second pleat 19 may be rectangular in shape, for example.

[0027] In the Y-direction DRY, the ratio of the height H2 of the first pleat 18 (see Figure 2) to the height H1 of the pouch 10 (H2 / H1) is preferably 0.1 or more and 0.5 or less. If H2 / H1 is 0.1 or more, more contents can be contained. Also, if H2 / H1 is 0.5 or less, the pouch 10 can stand upright stably when it is placed upright. The height H2 of the first pleat 18 is the length in the Y-direction DRY. Specifically, it is the length from the fold line 14A to the lower edge 10G of the pouch 10. If the height of the first pleat 18 is not constant, the height of the first pleat should be the smallest value. The height H2 of the first pleat 18 may be 20 mm or more and 50 mm or less. In the Y-direction DRY, the ratio of the height of the second pleat 19 to the height H1 of the pouch 10 is the same as H2 / H1.

[0028] The first pleated portion 18 has a first bottom sealing portion 20 formed by joining the first portion of the front film 11 and the bottom film 13, and the second pleated portion 19 has a second bottom sealing portion 21 formed by joining the second portion of the front film 11 and the bottom film 13.

[0029] Parts of the sides of the first pleat 18 and part of the sides of the second pleat 19 are joined by a third bottom seal portion 22, which is formed by joining the sealant film 33 of the packaging material 30 constituting the front film 11 (described later) and the sealant film 33 of the packaging material 30 constituting the back film 12. The joining of the sealant films 33 during the formation of the third bottom seal portion 22 is performed by heat sealing (heat fusion).

[0030] The third bottom seal portion 22 is a portion for joining a part of the side of the first pleat portion 18 and a part of the side of the second pleat portion 19 to each other. The third bottom seal portion 22 is formed by joining the front film 11 and the back film 12 through a notch provided in the bottom film 13. From the viewpoint of spreading the bottom film when filling the contents into the storage space, it is necessary for the first pleat portion and the second pleat portion to be separated in the center of the bottom of the pouch. However, if the first pleat portion and the second pleat portion are completely separated, when the contents are filled into the storage space, the first pleat portion and the second pleat portion may not be able to withstand the weight of the contents, causing a gap to form between the first pleat portion and the second pleat portion, which may make it difficult for the pouch to stand on its own. Also, since biaxially oriented plastic films cannot be heat-sealed to each other, the first pleat portion and the second pleat portion, where biaxially oriented plastic films face each other, cannot be heat-sealed as they are. Therefore, by forming the third bottom seal portion 22, parts of both sides of the first pleat portion 18 and the second pleat portion 19 are joined together. This prevents the bottom film 13 from spreading when filling with contents, and allows the pouch 10 to stand upright stably.

[0031] As shown in Figure 1, the first side seal portion 16 and the second side seal portion 17 are provided with an opening initiation means 23 that can serve as a starting point for opening. The opening initiation means 23 may be provided in either the first side seal portion 16 or the second side seal portion 17.

[0032] <<How to start opening>> The opening initiation means 23 can serve as the starting point for opening the pouch 10. Examples of the opening initiation means 23 include notches and slits. The opening initiation means 23 shown in Figure 1 is a slit.

[0033] <<Packaging materials>> The front film 11, back film 12, and bottom film 13 are made of the packaging material 30 shown in Figure 3. The bottom film 13 may also be made of the packaging material 30 shown in Figure 3. The packaging material 30 comprises at least a biaxially oriented plastic film 31, a metal foil layer 32, and a sealant film 33 in that order. The packaging material 30 contains only one biaxially oriented plastic film. The sealant film is a layer that forms the inner surface of the pouch 10. The packaging material 30 shown in Figure 3 comprises, for example, a biaxially oriented plastic film 31, a printing layer 34, a first adhesive layer 35, a metal foil layer 32, a second adhesive layer 36, and a sealant film 33 in that order. The packaging material may further include a functional layer that performs a desired function between the biaxially oriented plastic film 31 and the sealant film 33. The pouch 10 can be manufactured by continuously conveying the packaging material 30 wound in a roll.

[0034] The packaging material 30 has a unidirectional Young's modulus of 3600 MPa or more when measured in an environment of 25°C. The unidirectional Young's modulus of the packaging material 30 is preferably 3700 MPa or more, and more preferably 3800 MPa or more. The Young's modulus of the packaging material 30 in the direction perpendicular to the unidirectional direction is preferably 3500 MPa or more, and more preferably 3600 MPa or more. The unidirectional direction of the packaging material 30 may be, for example, the X-direction DRX of the pouch 10, and the direction perpendicular to the unidirectional direction of the packaging material 30 may be, for example, the Y-direction DRY of the pouch 10. Also, for example, the flow direction (MD) of the packaging material 30 may correspond to the X-direction DRX of the pouch 10, and for example, the width direction (TD) of the packaging material 30 may correspond to the Y-direction DRY of the pouch 10. Also, for example, the unidirectional direction of the packaging material 30 may correspond to the flow direction (MD), and for example, the direction perpendicular to the unidirectional direction of the packaging material 30 may correspond to the width direction (TD).

[0035] The Young's modulus of the packaging material 30 shall be measured in accordance with JIS K7127, except for the lengths of the test pieces S1 and S2 described later. First, five rectangular test pieces S1 (see Figure 4) are cut from the front film 11 of the pouch 10, excluding the seal portion 15, with one side L1 (see Figure 4) of 15 mm and the other side L2 (see Figure 4) extending perpendicular to side L1 of 100 mm. The test piece S1 is cut so that the other side L2 is parallel to the X direction DRX (the direction perpendicular to the direction in which the first side seal portion 16 extends). Next, five rectangular test pieces S2 (see Figure 5) are cut from the back film 12 of the pouch 10, excluding the seal portion 15, with one side L1 (see Figure 5) of 15 mm and the other side L2 (see Figure 5) extending perpendicular to side L1 of 100 mm. Specimen S2 is cut out so that its other side L2 is parallel to the Y direction DRY (the direction parallel to the direction in which the first side seal portion 16 extends). Then, each specimen S1 and S2 is held in an environment of 25°C for 24 hours. The Young's modulus of specimens S1 and S2 is then measured using a Tensilon universal material testing machine RTC-1310A (manufactured by A&D Co., Ltd.). Specifically, first, both ends of the longitudinal direction of specimen S1 are gripped with grippers 51 and 52 as shown in Figure 6. Note that in Figure 6, the layer structure of specimens S1 and S2 is partially omitted. Then, in an environment of 25°C and 50% relative humidity, with an initial gripper-to-grip distance D1 (see Figure 6) of 50 mm, a tensile test is performed on specimen S1 at a tensile speed of 300 mm / min in the longitudinal direction of specimen S1, and the Young's modulus of specimen S1 is measured. The Young's modulus of test specimen S2 is also measured under the same measurement conditions as for test specimen S1. Then, the Young's modulus is measured for five test specimens S1, and the average value is taken as the Young's modulus of the packaging material 30 in the X direction (DRX). Similarly, the Young's modulus is measured for five test specimens S2, and the average value is taken as the Young's modulus of the packaging material 30 in the Y direction (DRY).

[0036] The packaging material 30 has a puncture strength of 15.0 N or higher when measured in an environment of 25°C. Preferably, the puncture strength is 16.0 N or higher, more preferably 16.3 N or higher, and even more preferably 16.5 N or higher.

[0037] The puncture strength of the packaging material 30 shall be measured in accordance with JIS K1707:1999 7.4. First, three pieces are prepared for each pouch 10. From one pouch 10, one square test piece S3 (see Figure 7) is cut out from the front film 11, excluding the seal portion 15, with one side L3 (see Figure 7) measuring 75 mm and the other side L4 (see Figure 7) extending perpendicular to side L3 measuring 75 mm. Additionally, one square test piece S3 (see Figure 8) is cut out from the back film 12, excluding the seal portion 15, with one side L3 (see Figure 8) measuring 75 mm and the other side L4 (see Figure 8) extending perpendicular to side L3 measuring 75 mm. Test pieces S3 are cut out from the remaining two pouches in the same manner, to prepare a total of six test pieces S3. Test specimen S3 is cut so that one side L3 is parallel to the Y direction DRY (the direction parallel to the direction in which the first side seal portion 16 extends). Then, each test specimen S3 is kept in an environment of 25°C for 24 hours. Then, using a Tensilon universal material testing machine RTC-1310A (manufactured by A&D Co., Ltd.), a semicircular needle 53 (see Figure 9) with a diameter of 1.0 mm and a tip shape radius of 0.5 mm is pierced into the test specimen S3 from the outer surface (biaxially oriented plastic film 31) side of the packaging material 30 at a speed of 50 mm / min, and the maximum stress until the needle 53 penetrates the test specimen S3 is measured. Note that in Figure 9, the layer structure of test specimen S3 is partially omitted. The maximum stress is measured for 5 of the 6 test specimens S3, and the average value is taken as the puncture strength of the packaging material.

[0038] <Biaxially oriented plastic film> A biaxially oriented plastic film is a plastic film that has been intentionally stretched to improve its mechanical strength. In this invention, a biaxially oriented plastic film refers to one that satisfies at least one of the following conditions (a) or (b). (a) Young's modulus is 1000 MPa or more in one direction and in a direction perpendicular to that direction. (b) Tensile elongation is 200% or less in one direction and in a direction perpendicular to that direction.

[0039] The Young's modulus and tensile elongation of biaxially oriented plastic films shall be measured in accordance with JIS K7127. First, a rectangular test specimen with one side measuring 15 mm and the other side extending perpendicular to that side measuring 150 mm shall be cut from the biaxially oriented plastic film, and this specimen shall be kept in an environment of 25°C for 24 hours. Then, the Young's modulus and tensile elongation of the specimen shall be measured using a Tensilon universal material testing machine RTC-1310A (manufactured by A&D Co., Ltd.) in an environment of 25°C and 50% relative humidity. The initial gripping distance shall be 100 mm, and the tensile speed shall be 300 mm / min. The length in the direction perpendicular to one side may be adjusted as long as measurement can be performed with an initial gripping distance of 100 mm.

[0040] The biaxially oriented plastic film 31 is a plastic film that has been stretched in two predetermined directions. The biaxially oriented plastic film 31 functions as a base film for providing the packaging material 30 with a predetermined strength. The stretching direction of the biaxially oriented plastic film 31 is not particularly limited. For example, the biaxially oriented plastic film 31 may be stretched in the direction in which the side edge 10H extends and in a direction perpendicular to this direction. The stretching ratio of the biaxially oriented plastic film 31 is, for example, 1.05 times or more.

[0041] The biaxially oriented plastic film 31 contains polyester as its main component. In this specification, "contains polyester as its main component" means that the biaxially oriented plastic film contains more than 50% by mass of polyester. Examples of polyester include polyethylene terephthalate (hereinafter also referred to as PET) and polybutylene terephthalate (hereinafter also referred to as PBT). The more than 50% by mass of polyester in the biaxially oriented plastic film 31 may be composed of one type of polyester or of two or more types of polyester. A biaxially oriented PET film can be used as the biaxially oriented plastic film. The biaxially oriented PET film preferably contains 80% by mass or more of PET. Furthermore, the biaxially oriented PET film is more preferably 90% by mass or more of PET, and even more preferably 95% or more.

[0042] The thickness of the biaxially oriented plastic film 31 is preferably 8 μm or more, more preferably 9 μm or more, and even more preferably 12 μm or more. Furthermore, the thickness of the biaxially oriented plastic film 31 is preferably 30 μm or less, and more preferably 25 μm or less. By making the thickness of the biaxially oriented plastic film 31 8 μm or more, the biaxially oriented plastic film 31 gains sufficient strength. Also, by making the thickness of the biaxially oriented plastic film 31 30 μm or less, the biaxially oriented plastic film 31 exhibits excellent moldability. Therefore, the process of processing the packaging material 30 to manufacture the pouch 10 can be carried out efficiently.

[0043] <Metal foil layer> As the metal constituting the metal foil layer 32, aluminum, iron, copper, tin, or alloys thereof can be used, from the viewpoint of gas barrier properties that suppress the transmission of oxygen and water vapor, and light-shielding properties that suppress the transmission of visible light and ultraviolet rays. From the viewpoint of cost, an aluminum foil layer is preferred as the metal foil layer.

[0044] The thickness of the metal foil layer 32 is preferably 5 μm or more and 30 μm or less. If the thickness of the metal foil layer 32 is 5 μm or more, gas barrier properties and pinhole resistance can be ensured for the packaging material 30, and the transmission of visible light, etc. can be suppressed. If the thickness is 30 μm or less, a good tactile feel and ease of opening can be achieved for the packaging material 30. The lower limit of the thickness of the metal foil layer 32 is more preferably 6 μm or more, and the upper limit of the thickness of the metal foil layer 32 is more preferably 15 μm or less.

[0045] <Sealant film> Next, the sealant film 33 will be described. The sealant film 33 may be a single layer or a multi-layer film. Preferably, the sealant film 33 consists of an unstretched film. The term "unstretched" includes not only films that are not stretched at all, but also films that are slightly stretched due to the tension applied during film formation.

[0046] A sealant film refers to a film that satisfies at least one of the following conditions (c) or (d): (c) Young's modulus is less than 1000 MPa in one direction and in a direction perpendicular to that direction. (d) Tensile elongation of 300% or more in one direction and in a direction perpendicular to that direction.

[0047] The Young's modulus and tensile elongation of sealant film shall be measured in accordance with JIS K7127. First, a rectangular test piece with one side measuring 15 mm and the other side extending perpendicular to that side measuring 150 mm shall be cut from the sealant film, and this test piece shall be kept in an environment of 25°C for 24 hours. Then, Young's modulus and tensile elongation shall be measured using a Tensilon universal material testing machine RTC-1310A (manufactured by A&D Co., Ltd.) in an environment of 25°C and 50% relative humidity. The initial gripping distance shall be 100 mm, and the tensile speed shall be 300 mm / min. The length in the direction perpendicular to one side may be adjusted as long as measurements can be taken with an initial gripping distance of 100 mm.

[0048] The pouch 10, which is made of packaging material 30, is subjected to sterilization treatment such as retort processing at high temperatures. Therefore, the sealant film 33 used has heat resistance that can withstand these high-temperature treatments.

[0049] The melting point of the material constituting the sealant film 33 is preferably 150°C or higher, and more preferably 160°C or higher. By increasing the melting point of the sealant film 33, it becomes possible to perform the retort treatment of the pouch 10 at a high temperature, and thus the time required for retort treatment can be shortened. Note that the melting point of the material constituting the sealant film 33 is lower than the melting point of the resin constituting the biaxially oriented plastic film 31.

[0050] The sealant film 33 contains polypropylene as its main component. In this specification, "contains polypropylene as its main component" means that the sealant film contains more than 50% by mass of polypropylene. Specifically, materials containing propylene as their main component include polypropylene such as propylene-ethylene block copolymer, propylene-ethylene random copolymer, and homopolypropylene, or mixtures of polypropylene and polyethylene. Here, "propylene-ethylene block copolymer" means a material having the structural formula shown in formula (1) below. Also, "propylene-ethylene random copolymer" means a material having the structural formula shown in formula (2) below. Also, "homopolypropylene" means a material having the structural formula shown in formula (3) below.

[0051] [ka] In equation (1) above, m1, m2, and m3 represent integers greater than or equal to 1.

[0052] [ka] In equation (2) above, m and n represent integers greater than or equal to 1.

[0053] [ka] In equation (3) above, m represents an integer greater than or equal to 1.

[0054] When using a material primarily composed of propylene, which is a mixture of polypropylene and polyethylene, the material may have a sea-island structure. Here, "sea-island structure" refers to a structure in which polyethylene is discontinuously dispersed within continuous regions of polypropylene.

[0055] Preferably, the sealant film 33 is a single-layer film containing a propylene-ethylene block copolymer. For example, the sealant film 33 is a single-layer unstretched film mainly composed of a propylene-ethylene block copolymer. By using a propylene-ethylene block copolymer, the impact resistance of the sealant film 33 can be increased, thereby preventing the pouch 10 from tearing due to impact during a fall. In addition, the puncture resistance of the packaging material 30 can be increased.

[0056] The propylene-ethylene block copolymer includes, for example, a marine component made of polypropylene and an island component made of ethylene-propylene copolymer rubber. The marine component can contribute to improving the blocking resistance, heat resistance, rigidity, and seal strength of the propylene-ethylene block copolymer. The island component can also contribute to improving the impact resistance of the propylene-ethylene block copolymer. Therefore, the mechanical properties of the sealant film 33 containing the propylene-ethylene block copolymer can be adjusted by adjusting the ratio of the marine component to the island component.

[0057] In a propylene-ethylene block copolymer, the mass ratio of the polypropylene component is higher than the mass ratio of the ethylene-propylene copolymer rubber component. For example, in a propylene-ethylene block copolymer, the mass ratio of the polypropylene component is at least 51% by mass, preferably 60% by mass or more, and more preferably 70% by mass or more.

[0058] The content of propylene-ethylene block copolymer in the sealant film 33 is, for example, 80% by mass or more, and preferably 90% by mass or more.

[0059] One method for producing propylene-ethylene block copolymers involves polymerizing the raw materials, such as propylene and ethylene, using a catalyst. Suitable catalysts include Ziegler-Natta type catalysts and metallocene catalysts.

[0060] The thickness of the sealant film 33 is preferably 30 μm or more, and more preferably 40 μm or more. Furthermore, the thickness of the sealant film 33 is preferably 100 μm or less, and more preferably 80 μm or less.

[0061] As a single-layer sealant film 33 containing a propylene-ethylene block copolymer, there are types with a high tensile modulus, such as ZK207, which will be described later. By using this type of sealant film 33, the tearability when consumers tear the pouch 10 along the flow direction (MD) can be improved when opening the pouch 10.

[0062] The tensile elongation (%) of the sealant film 33 in the flow direction (MD), measured at 25°C after being held at 25°C for 24 hours, is preferably 1100% or less, more preferably 1000% or less, and may also be 900% or less, or 800% or less. Furthermore, the product of the tensile elongation (%) of the sealant film 33 in the flow direction (MD) and the thickness (μm) of the sealant film 33 is preferably 30000 or more and 50000 or less. The lower limit of this product in the flow direction (MD) is more preferably 34000 or more, 36000 or more, or 38000 or more.

[0063] The tensile elongation (%) of the sealant film 33 in the width direction (TD), measured at 25°C after being held at 25°C for 24 hours, is preferably 1200% or less, more preferably 1100% or less, and may also be 1000% or less, or 900% or less. Furthermore, the product of the tensile elongation (%) of the sealant film 33 in the width direction (TD) and the thickness (μm) of the sealant film 33 is preferably 45000 or more and 55000 or less. The lower limit of this product in the width direction (TD) is more preferably 47000 or more, or 49000 or more.

[0064] The tensile modulus (MPa) of the sealant film 33 in the flow direction (MD), measured at 25°C after being held at 25°C for 24 hours, is preferably 500 MPa or higher, more preferably 600 MPa or higher, and may be 650 MPa or higher, or 700 MPa or higher. Furthermore, the product of the tensile modulus (MPa) of the sealant film 33 in the flow direction (MD) and the thickness (μm) of the sealant film 33 is preferably 35,000 or higher, more preferably 38,000 or higher, and even more preferably 45,000 or higher. The sealant film 33 having a high tensile modulus improves the tearability when opening the pouch 10.

[0065] The tensile modulus (MPa) of the sealant film 33 in the width direction (TD), measured at 25°C after being held at 25°C for 24 hours, is preferably 450 MPa or higher, more preferably 500 MPa or higher, and may be 550 MPa or higher, or 600 MPa or higher. Furthermore, the product of the tensile modulus (MPa) of the sealant film 33 in the width direction (TD) and the thickness (μm) of the sealant film 33 is preferably 28,000 or higher, more preferably 30,000 or higher.

[0066] The tensile modulus of the sealant film 33 shall be measured using the same measurement method and conditions as the tensile elongation of the sealant film 33.

[0067] <Print layer> The printing layer 34 is a layer for adding information about the contents or packaging product, or for adding aesthetic appeal to the pouch, and includes, for example, a colorant and a binder resin. By forming the printing layer 34, a pattern can be formed on the pouch 10. The term "pattern" as used herein is not particularly limited and broadly includes, for example, figures, letters, patterns, symbols, designs, marks, etc. As the ink for gravure printing, Finart manufactured by DIC Graphics Co., Ltd. can be used.

[0068] The printed layer 34 may also contain any other additives. Examples of additives include lubricants, anti-blocking agents, fillers, curing agents, pigment dispersants, defoamers, leveling agents, waxes, silane coupling agents, preservatives, antioxidants, UV absorbers, rust inhibitors, plasticizers, flame retardants, and color developers. These additives are used particularly to improve printability and printing effect, and their type and amount can be appropriately selected depending on the printing method, printing substrate, and printing conditions. The printed layer 34 can be formed on the biaxially oriented plastic film 31 by a printing method such as gravure printing.

[0069] (Colorants) The colorants are not particularly limited; known pigments and dyes can be used and selected appropriately according to the desired color.

[0070] (Binder resin) Examples of binder resins include linseed oil, tung oil, soybean oil, hydrocarbon oil, rosin, rosin ester, rosin-modified resin, shellac, alkyd resin, phenolic resin, maleic acid resin, natural resin, hydrocarbon resin, polyvinyl chloride resin, polyacetic acid resin, polystyrene resin, polyvinyl butyral resin, (meth)acrylic resin, polyamide resin, polyester resin, polyurethane resin, epoxy resin, urea resin, melamine resin, aminoalkyd resin, nitrocellulose, ethylcellulose, chlorinated rubber, cyclized rubber, polymers of (meth)acrylate compounds, or mixtures thereof.

[0071] <First adhesive layer and second adhesive layer> The first adhesive layer 35 contains an adhesive for bonding the biaxially oriented plastic film 31 and the metal foil layer 32 by dry lamination. The second adhesive layer 36 contains an adhesive for bonding the metal foil layer 32 and the sealant film 33 by dry lamination.

[0072] The adhesives constituting the first adhesive layer 35 and the second adhesive layer 36 are produced from adhesive compositions prepared by mixing a first composition containing a main component and a solvent, and a second composition containing a curing agent and a solvent, respectively. Specifically, the adhesive includes a cured product produced by the reaction of the main component and the solvent in the adhesive composition.

[0073] Examples of adhesives include polyurethane. Polyurethane is a cured product of a polyol, which is the main component, reacting with an isocyanate compound, which is the curing agent. Examples of polyurethane include polyether polyurethane and polyester polyurethane. Polyether polyurethane is a cured product produced by the reaction of a polyether polyol, which is the main component, with an isocyanate compound, which is the curing agent. Polyester polyurethane is a cured product produced by the reaction of a polyester polyol, which is the main component, with an isocyanate compound, which is the curing agent.

[0074] As isocyanate compounds, 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 isocyanate compounds can be used.

[0075] The thickness of the first adhesive layer 35 and the second adhesive layer 36 is preferably 2 μm or more, and more preferably 3 μm or more. Furthermore, the thickness of the first adhesive layer 35 and the second adhesive layer 36 is preferably 6 μm or less, and more preferably 5 μm or less.

[0076] Incidentally, as mentioned above, the isocyanate compounds that constitute the curing agent of the adhesive include aromatic isocyanate compounds and aliphatic isocyanate compounds. Of these, aromatic isocyanate compounds may leach components that are unsuitable for food use under high-temperature environments such as heat sterilization. Furthermore, the second adhesive layer 36 is in contact with the sealant film 33. Therefore, if the second adhesive layer 36 contains an aromatic isocyanate compound, components leached from the aromatic isocyanate compound may adhere to the contents contained in the containment space 10A that is in contact with the sealant film 33. Considering these issues, it is preferable to use a cured product produced by the reaction of a polyol as the main component and an aliphatic isocyanate compound as the curing agent as the adhesive constituting the second adhesive layer 36. This prevents components unsuitable for food use caused by the second adhesive layer 36 from adhering to the contents.

[0077] Specific examples of packaging material 30 include the following packaging materials. Note that " / " is used to indicate the boundary between layers when listing them. The layers should be listed from the outside to the inside of the pouch. That is, the layer listed on the far right is the sealant film. Also, "Al foil layer" below refers to the aluminum foil layer. Biaxially oriented PET film / Printed layer / Adhesive layer / Aluminum foil layer / Adhesive layer / Sealant film

[0078] According to this embodiment, the Young's modulus of the packaging material 30 in one direction (e.g., the flow direction (MD)) is 3600 MPa or higher when measured in an environment of 25°C, resulting in a high Young's modulus in one direction. This suppresses the occurrence of wrinkles when heat sterilization (boiling) or heat pressurized sterilization (retorting) is performed, thereby improving the appearance of the pouch 10. Furthermore, when a standing-type pouch 10 is made using the packaging material 30, its self-standing ability can be improved.

[0079] According to this embodiment, the puncture strength of the packaging material 30, measured in a 25°C environment after being held in a 25°C environment for 1 minute, is 15.0 N or higher. Therefore, the puncture strength is high, which suppresses the occurrence of pinholes. [Examples]

[0080] To illustrate the present invention in detail, examples are given below, but the present invention is not limited to these examples.

[0081] <Example 1> First, a 12 μm thick biaxially oriented polyethylene terephthalate film (product name "E5100", manufactured by Toyobo Co., Ltd.) was prepared as the biaxially oriented plastic film. Next, a printed layer was formed on this film. The thickness of the printed layer was 1.0 μm. In addition, a 7 μm thick aluminum (Al) foil layer was prepared as the metal foil layer. Furthermore, a 70 μm thick unoriented polypropylene film (product name "ZK207", manufactured by Toray Film Processing Co., Ltd.) was prepared as the sealant film. ZK207 contained the propylene-ethylene block copolymer mentioned above.

[0082] ZK207 has low tensile elongation. Specifically, the tensile elongation of ZK207 in the flow direction (MD) is 790% when the thickness is 50 μm and 730% when the thickness is 60 μm. Therefore, the product of the tensile elongation (%) and thickness (μm) of ZK207 in the flow direction is 39500 when the thickness is 50 μm and 43800 when the thickness is 60 μm. In addition, the tensile elongation of ZK207 in the width direction (TD) is 1020% when the thickness is 50 μm and 870% when the thickness is 60 μm. Therefore, the product of the tensile elongation (%) and thickness (μm) of ZK207 in the width direction is 51000 when the thickness is 50 μm and 52200 when the thickness is 60 μm.

[0083] Next, a packaging material was prepared by dry lamination, sequentially laminating a biaxially oriented polyethylene terephthalate film, a printed layer, a first adhesive layer, an Al foil layer, a second adhesive layer, and an unstretched polypropylene film. For the first and second adhesive layers, a two-component polyurethane adhesive (main component: RU-40, curing agent: H-4) manufactured by Rock Paint Co., Ltd. was used. The main component, RU-40, is a polyester polyol. The thickness of the first and second adhesive layers was 3.0 μm.

[0084] Then, using the three packaging materials prepared as described above, 200 ml of water was added to create the standing pouch shown in Figure 1. Specifically, first, the packaging material that would form the bottom was folded in half so that the unstretched polypropylene film, which is the sealant film, was on the outside, forming a first and second section connected by the fold line. In addition, while still folded, circular holes with a diameter of 10 mm were punched out near the lower ends of both lateral edges of the bottom surface when cut and made into a pouch, to form through holes.

[0085] Then, a folded bottom film packaging material was placed at a predetermined position between the front film packaging material and the back film packaging material, and heat-sealed under the following conditions to form a first pleat portion having a first side seal portion, a second side seal portion, a first bottom seal portion, and a second pleat portion having a second bottom seal portion. This resulted in a pouch with an open top. In the area of ​​the through-hole, since there is no folded bottom film packaging material, the front film packaging material and the back film packaging material are directly fused together to form a third bottom seal portion. (Heat fusion conditions) • Heat sealing equipment: Heat sealer TP-701-A (manufactured by Tester Sangyo Co., Ltd.) ·Heat fusion temperature: 220℃ • Heat fusion pressure: 0.1 MPa • Heat fusion time: 1 second

[0086] Subsequently, 200 ml of water was filled into the pouch through the opening, and then the upper seal portion was formed by heat sealing under the same conditions as described above, thereby sealing the pouch. After that, the pouch was subjected to retort processing under the following conditions to produce the packaging material and pouch according to Example 1 that had undergone retort processing. In Example 1, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch. (Retort processing) • Method: Spray type • Retort temperature: 135℃ • Retort preparation time: 40 minutes

[0087] In the fabricated pouch, the pouch height H1 was 160 mm, the pouch width W1 was 147 mm, the height of the first pleat H2 and the height of the second pleat were 46 mm, the width W2 of the first and second side seals was 7.0 mm, and the width W3 of the top seal was 10.0 mm.

[0088] <Example 2> Packaging material was prepared in the same manner as in Example 1, except that a 60 μm thick unoriented polypropylene film (product name "ZK207", manufactured by Toray Film Processing Co., Ltd.) was used as a sealant film instead of a 70 μm thick unoriented polypropylene film (product name "ZK207", manufactured by Toray Film Processing Co., Ltd.). Then, using three of these packaging materials, a pouch according to Example 2 was prepared in the same manner as in Example 1. In Example 2, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

[0089] <Example 3> Packaging material was prepared in the same manner as in Example 1, except that a 12 μm thick biaxially oriented polyethylene terephthalate film (product name "FE2001," manufactured by Futamura Chemical Co., Ltd.) was used as the biaxially oriented plastic film instead of a 12 μm thick biaxially oriented polyethylene terephthalate film (product name "E5100," manufactured by Toyobo Co., Ltd.). Then, using three of these packaging materials, a pouch according to Example 3 was prepared in the same manner as in Example 1. In Example 3, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

[0090] <Comparative Example 1> The packaging material was prepared in the same manner as in Example 1, except that a 60 μm thick unoriented polypropylene film (product name "ZK500", manufactured by Toray Film Processing Co., Ltd.) was used as a sealant film instead of a 70 μm thick unoriented polypropylene film (product name "ZK207", manufactured by Toray Film Processing Co., Ltd.). Then, using three of these packaging materials, a pouch according to Comparative Example 1 was prepared in the same manner as in Example 1. In Comparative Example 1, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

[0091] <Measuring Young's modulus> The Young's modulus of the packaging material constituting the pouches after retort processing in Examples 1-3 and Comparative Example 1 was measured. Except for the length of the test specimens described later, the measurement of Young's modulus was performed in accordance with JIS K7127. As shown in Figure 4, five rectangular test specimens S1 were cut from the front surface of each pouch, excluding the seal portion, with one side L1 measuring 15 mm and the other side L2 extending perpendicular to side L1 measuring 100 mm. The test specimens S1 were cut so that the other side L2 was parallel to the X direction (the direction perpendicular to the direction in which the first side seal portion extends). Subsequently, as shown in Figure 5, five rectangular test specimens S2 were cut from the back surface of each pouch, excluding the seal portion, with one side L1 measuring 15 mm and the other side L2 extending perpendicular to side L1 measuring 100 mm. Test specimen S2 was cut so that its other side L2 was parallel to the Y direction (the direction parallel to the direction in which the first side seal extends). Then, each test specimen S1 and S2 was held in an environment of 25°C for 24 hours. Then, a tensile test was performed using a Tensilon universal material tester RTC-1310A (manufactured by A&D Co., Ltd.) at a temperature of 25°C and a relative humidity of 50%, with an initial gripping distance D1 of 50 mm and a tensile speed of 300 mm / min, and the Young's modulus of test specimen S1 was measured. The Young's modulus was measured for five test specimens S1, and the average value was taken as the Young's modulus in the X direction of the packaging material. The Young's modulus of test specimen S2 was measured in the same manner. The Young's modulus was measured for five test specimens S2, and the average value was taken as the Young's modulus in the Y direction of the packaging material. Note that L1, L2, S1, S2, and D1 are as shown in Figures 4 to 6.

[0092] <Puncture strength> The puncture strength of the packaging material constituting the retort-treated pouches in Examples 1-3 and Comparative Example 1 was measured in accordance with JIS K1707:1999 7.4. First, three retort-treated pouches were prepared for each of Examples 1-3 and Comparative Example 1. For one pouch, as shown in Figure 7, one square test piece S3 was cut from the front surface, excluding the seal portion, with one side L3 of 75 mm and the other side L4 extending perpendicular to side L3 of 75 mm. Also, as shown in Figure 8, one square test piece S3 was cut from the back surface, excluding the seal portion, with one side L3 of 75 mm and the other side L4 extending perpendicular to side L3 of 75 mm. Test pieces S3 were cut from the remaining two pouches in the same manner, for a total of six test pieces S3. Test specimen S3 was cut so that one side L3 was parallel to the Y direction (the direction parallel to the direction in which the first side seal extends). Then, each test specimen S3 was kept in an environment of 25°C for 24 hours. Then, using a Tensilon universal material testing machine RTC-1310A (manufactured by A&D Co., Ltd.), a semicircular needle with a diameter of 1.0 mm and a tip radius of 0.5 mm was inserted into the test specimen S3 from the outer surface (biaxially oriented PET film) side of the packaging material at a speed of 50 mm / min, at a temperature of 25°C and a relative humidity of 50%, and the maximum value of stress until the needle penetrated the test specimen S3 was measured. The maximum value of stress was measured for 5 of the 6 test specimens S3, and the average value was taken as the puncture strength of the packaging material. L3, L4, and S3 are as shown in Figures 7 and 8.

[0093] <Exterior Evaluation> The appearance of the pouches after retort processing for Examples 1-3 and Comparative Example 1 was evaluated. The appearance evaluation was performed as follows: First, 10 pouches of each type were prepared after retort processing, and the presence or absence of wrinkles in the pouches was visually checked. Of the 10 pouches, the number of pouches without wrinkles and the number of pouches with wrinkles that were at a practically acceptable level were counted.

[0094] The composition of the packaging materials is shown in Table 1, and the evaluation results are shown in Table 2. [Table 1]

[0095] [Table 2]

[0096] The results are described below. As shown in Table 2, the packaging materials of Examples 1 to 3 suppressed the occurrence of wrinkles in the pouch after retort processing compared to the packaging material of Comparative Example 1. In addition, the packaging materials constituting the pouches of Examples 1 to 3 have high puncture strength, which can suppress the occurrence of pinholes. [Explanation of Symbols]

[0097] 10... Pouch 10A...Accommodation space 11…Front surface film 12…Backside film 13…Bottom film 15...Seal part 30...Packaging materials 31…First biaxially oriented plastic film 32...Metal foil layer 33...Sealant film

Claims

1. A packaging material comprising, in this order, a biaxially oriented plastic film, a printed layer, a metal foil layer, and a sealant film, The aforementioned biaxially oriented plastic film is mainly composed of polyester, The sealant film is mainly composed of polypropylene, The packaging material contains only one biaxially oriented plastic film. The unidirectional Young's modulus of the packaging material, measured in an environment of 25°C, is 3600 MPa or more and 3915 MPa or less. The puncture strength of the packaging material measured in an environment of 25°C is 15.0 N or more and 17.0 N or less. A packaging material wherein the product of the tensile elongation (%) and thickness (μm) of the sealant film in the aforementioned unidirectional direction is 30,000 or more and 50,000 or less.

2. The packaging material according to claim 1, wherein the product of the tensile elongation (%) and thickness (μm) of the sealant film in a direction perpendicular to the aforementioned one direction is 45,000 or more and 55,000 or less.

3. The packaging material according to claim 1 or 2, wherein the sealant film comprises a propylene-ethylene block copolymer.

4. The packaging material according to any one of claims 1 to 3, wherein the biaxially oriented plastic film is a biaxially oriented polyethylene terephthalate film.

5. A pouch comprising the packaging material described in any one of claims 1 to 4.

6. The pouch according to claim 5, wherein the contents are contained within the pouch.

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