Packaging materials and pouches

Abstract

To increase the heat resistance of a packaging material.SOLUTION: The packaging material comprises a first oriented plastic film, a second oriented plastic film, a third oriented plastic film, and a sealant film in this order. The first and third oriented plastic films are biaxially oriented polyethylene terephthalate films. The second oriented plastic film is a uniaxially orientation polyethylene terephthalate film. The sealant film is a non-oriented polypropylene film having tensile elongation of 1000% or more in a flowing direction, tensile elongation of 1100% or more in a perpendicular direction, and a thickness of 50 μm or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Embodiments of this disclosure relate to packaging materials and pouches. [Background technology]

[0002] Conventionally, many products on the market consist of pre-cooked or semi-cooked liquids, viscous substances, or mixtures of liquids and solids, sealed in pouches made of laminated plastic. In a pouch, the non-sealed sections, where the laminated layers are not joined, constitute the storage area where the contents are contained. The sealed sections, where the laminated layers are joined, seal the storage area. The contents are, for example, pre-cooked foods such as curry, stew, and soup. The contents are heated in a microwave oven or similar device while contained in the pouch.

[0003] When contents contained in a sealed pouch are heated in a microwave oven, the moisture in the contents evaporates as heating occurs, increasing the pressure inside the pouch. When the pressure inside the pouch increases, there is a risk that the pouch may burst, scattering the contents and contaminating the microwave oven. Considering this problem, for example, Patent Document 1 proposes providing the pouch with a steam venting mechanism that automatically connects the contents to the outside when the pressure inside the contents increases, allowing the steam inside the contents to escape. In Patent Document 1, the steam venting mechanism has an intermediate seal portion located between the upper and lower side seal portions of the pouch, and an unsealed portion that is isolated from the contents by the intermediate seal portion and extends to the side edge of the pouch. When the pressure inside the contents increases, the intermediate seal portion peels off, and the contents and the unsealed portion communicate. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-101154 [Overview of the project] [Problems that the invention aims to solve]

[0005] When heating the contents of a pouch using a microwave oven, the temperature of the packaging material also rises. If the packaging material has low heat resistance, it may deform due to the heat.

[0006] The embodiments of this disclosure aim to provide a packaging material that can effectively solve the aforementioned problems. [Means for solving the problem]

[0007] Embodiments of this disclosure relate to the following [1] to

[10] . [1] A packaging material comprising, in this order, at least a first stretched plastic film, a second stretched plastic film, a third stretched plastic film, and a sealant film, The first stretched plastic film and the third stretched plastic film are biaxially oriented polyethylene terephthalate films. The second stretched plastic film is a uniaxially oriented polyethylene terephthalate film, The sealant film is a packaging material that is an unoriented polypropylene film having a tensile elongation of 1000% or more in the flow direction and 1100% or more in the vertical direction, and a thickness of 50 μm or more.

[0008] [2] A packaging material comprising, in this order, at least a first stretched plastic film, a second stretched plastic film, a third stretched plastic film, and a sealant film, The first stretched plastic film and the third stretched plastic film are biaxially oriented polyethylene terephthalate films. The second stretched plastic film is a uniaxially oriented polyethylene terephthalate film, The sealing film is a non-stretched polypropylene film having a tensile elongation of less than 1000% in the flow direction and a tensile elongation of less than 1100% in the perpendicular direction, and having a thickness of 60 μm or more, and is a packaging material.

[0009] [3] In the packaging material according to [1] or [2], the third stretched plastic film may include an inner surface facing the sealing film and an outer surface facing the second stretched plastic film, and the packaging material may include a transparent vapor deposition layer located on the inner surface or the outer surface of the third stretched plastic film.

[0010] [4] The packaging material according to [3] may include a gas barrier coating film located on the transparent vapor deposition layer.

[0011] [5] In the packaging material according to [1] or [2], the first stretched plastic film may include an inner surface facing the second stretched plastic film and an outer surface located on the opposite side of the inner surface, and the packaging material may include a transparent vapor deposition layer located on the inner surface of the first stretched plastic film.

[0012] [6] The packaging material according to [5] may include a gas barrier coating film located on the transparent vapor deposition layer.

[0013] [7] In the packaging material according to [1] or [2], the tensile strength of the second stretched plastic film in the perpendicular direction may be smaller than the tensile strength of the second stretched plastic film in the flow direction.

[0014] [8] A pouch in which a storage portion for storing contents is defined between a front film and a back film, equipped with a steam venting mechanism for discharging the steam of the storage portion to the outside when the pressure of the storage portion increases, wherein the front film and the back film are made of the packaging material according to [1] or [2].

[0015] The pouches described in [9] and [8] are A first side sealing portion located on the first side of the pouch, which joins the inner surface of the surface film and the inner surface of the back film, A second side seal portion is located on the second side of the pouch, facing the first side in the first direction, and defines the housing portion between it and the first side seal portion, The pouch may also include a first non-seal portion located near the top of the pouch and isolated from the housing portion by the first side seal portion, the first non-seal portion extending to reach the first side edge of the first side portion of the pouch. The first side sealing portion may include an upper sealing portion extending along the first side toward the upper part of the pouch from the first non-seal portion, a lower sealing portion extending along the first side toward the lower part of the pouch from the first non-seal portion, and an intermediate sealing portion having one end connected to the upper sealing portion and the other end connected to the lower sealing portion, and located between the housing portion and the first non-seal portion. The first non-sealed portion and the intermediate sealed portion may constitute the steam venting mechanism.

[0016] The pouch described in

[10] [9] may include an upper seal portion located at the top of the pouch and connected to the first side seal portion and the second side seal portion. The distance from the center point of the housing portion to the upper seal portion may be shorter than the distance from the center point to the intermediate seal portion. [Effects of the Invention]

[0017] According to the form of this disclosure, the heat resistance of the packaging material can be improved. [Brief explanation of the drawing]

[0018] [Figure 1] This is a cross-sectional view showing an example of a packaging material according to this embodiment. [Figure 2] This is a cross-sectional view showing an example of a packaging material according to this embodiment. [Figure 3]This is a cross-sectional view showing an example of a packaging material according to this embodiment. [Figure 4] This is a front view showing an example of a pouch according to this embodiment. [Figure 5] This is a front view showing the pouch with its contents inside. [Figure 6] This figure shows the pouch configuration and evaluation results for Examples 1-8. [Figure 7] This figure shows an example of the evaluation results for ease of opening. [Figure 8] This figure shows an example of the evaluation results for ease of opening. [Figure 9] This figure shows an example of the results of the heat resistance evaluation. [Figure 10] This figure shows an example of the results of the heat resistance evaluation. [Modes for carrying out the invention]

[0019] The embodiments will be described with reference to the drawings. Note that, for the sake of illustration and ease of understanding, the scale and aspect ratios of the drawings attached to this specification have been appropriately modified and exaggerated from those of the actual objects.

[0020] Furthermore, terms used in this specification to specify shapes, geometric conditions, and their degrees, such as "parallel," "orthogonal," and "identical," as well as values ​​for lengths and angles, should not be interpreted strictly, but rather to include a range that allows for the expectation of similar functionality.

[0021] In this specification, if two or more upper limit candidates and two or more lower limit candidates are given for a certain parameter, the numerical range of that parameter may be constructed by combining any one upper limit candidate and any one lower limit candidate. For example, consider the case where it is stated that "Parameter B is, for example, A1 or greater and may be A2 or greater. Parameter B is, for example, A3 or less and may be A4 or less." In this case, the numerical range of parameter B may be A1 or greater and A3 or less, A1 or greater and A4 or less, A2 or greater and A3 or less, or A2 or greater and A4 or less.

[0022] <Packaging materials> The packaging material according to this embodiment comprises at least a first stretched plastic film, a second stretched plastic film, a third stretched plastic film, and a sealant film in this order. The packaging material may further comprise other layers such as an adhesive layer, a printed layer, and a transparent vapor deposition layer.

[0023] The packaging material according to this embodiment will be described with reference to the drawings. Examples of schematic cross-sectional views of the packaging material according to this embodiment are shown in Figures 1 to 3.

[0024] The packaging material 50 shown in Figure 1 comprises, in this order from the outer surface 50y toward the inner surface 50x, a first stretched plastic film 51, a printed layer 61, a first adhesive layer 56, a second stretched plastic film 52, a second adhesive layer 57, a gas barrier coating film 63, a transparent vapor deposition layer 62, a third stretched plastic film 53, a third adhesive layer 58, and a sealant film 55. The inner surface 50x faces the containment portion in a pouch made of the packaging material 50.

[0025] The third stretched plastic film 53 includes an inner surface 53x facing the sealant film 55 and an outer surface 53y facing the second stretched plastic film 52. The transparent vapor deposition layer 62 is located on the outer surface 53y of the third stretched plastic film 53. The gas barrier coating film 63 is located on the transparent vapor deposition layer 62.

[0026] As shown in Figure 1, the outer surface 51y of the first stretched plastic film 51 may constitute the outer surface 50y of the packaging material 50. The printing layer 61 may be located on the inner surface 51x of the first stretched plastic film 51. The printing layer 61 may be in contact with the first adhesive layer 56. The outer surface 52y of the second stretched plastic film 52 may be in contact with the first adhesive layer 56. The inner surface 52x of the second stretched plastic film 52 may be in contact with the second adhesive layer 57. The gas barrier coating film 63 may be in contact with the second adhesive layer 57. The inner surface 53x of the third stretched plastic film 53 may be in contact with the third adhesive layer 58. The outer surface 55y of the sealant film 55 may be in contact with the third adhesive layer 58. The inner surface 55x of the sealant film 55 may constitute the inner surface 50x of the packaging material 50.

[0027] As shown in Figure 2, the transparent vapor deposition layer 62 may be located on the inner surface 53x of the third stretched plastic film 53. The gas barrier coating film 63 is located on the transparent vapor deposition layer 62.

[0028] As shown in Figure 2, the outer surface 53y of the third stretched plastic film 53 may be in contact with the second adhesive layer 57. The gas barrier coating film 63 may be in contact with the third adhesive layer 58.

[0029] As shown in Figure 3, the transparent vapor deposition layer 62 may be located on the inner surface 51x of the first stretched plastic film 51. The gas barrier coating film 63 is located on the transparent vapor deposition layer 62.

[0030] As shown in Figure 3, the printed layer 61 may be located on the gas barrier coating film 63. The outer surface 53y of the third stretched plastic film 53 may be in contact with the second adhesive layer 57. The inner surface 53x of the third stretched plastic film 53 may be in contact with the third adhesive layer 58.

[0031] The films and layers that make up the packaging material 50 will be described below.

[0032] [First stretched plastic film and third stretched plastic film] The first stretched plastic film 51 and the third stretched plastic film 53 are both biaxially oriented polyethylene terephthalate films. The biaxially oriented polyethylene terephthalate film is stretched in two predetermined directions. The biaxially oriented polyethylene terephthalate film mainly contains polyethylene terephthalate (hereinafter also referred to as PET). In the following description, the biaxially oriented polyethylene terephthalate film will also be referred to as a biaxially oriented PET film.

[0033] The first stretched plastic film 51 and the third stretched plastic film 53 have a flow direction and a perpendicular direction. The flow direction is the direction in which the film flows when the film is formed, and is known as MD (Machine Direction). The perpendicular direction is the direction perpendicular to the flow direction, and is known as TD (Transverse Direction). The second stretched plastic film 52 and the sealant film 55 also have a flow direction and a perpendicular direction. When manufacturing a pouch 10, which will be described later, using the packaging material 50, the first direction is the flow direction and the second direction is the perpendicular direction.

[0034] The stretching ratio of biaxially oriented PET film in the flow direction and perpendicular direction is, for example, 1.05 times or more.

[0035] The tensile strength TS2T of a biaxially oriented PET film in the vertical direction is greater than or equal to the tensile strength TS2M of the biaxially oriented PET film in the flow direction. The ratio of the tensile strength TS2T in the vertical direction to the tensile strength TS2M in the flow direction, TS2T / TS2M, is 1.00 or greater, and may be 1.05 or greater. TS2T / TS2M may be, for example, 1.20 or less, and may be 1.15 or less.

[0036] The tensile modulus TM2T of a biaxially oriented PET film in the vertical direction is, for example, 3500 MPa or more, may be 3700 MPa or more, or 3900 MPa or more. The tensile modulus TM2T of a biaxially oriented PET film in the vertical direction is, for example, 4500 MPa or less, may be 4300 MPa or less, or 4100 MPa or less.

[0037] The tensile elongation TE2M of a biaxially oriented PET film in the flow direction may be greater than or equal to the tensile elongation TE2T of a biaxially oriented PET film in the vertical direction. The ratio TE2M / TE2T, which is the ratio of the tensile elongation TE2M in the flow direction to the tensile elongation TE2T in the vertical direction, may be, for example, 1.00 or more, and may be 1.01 or more. TE2M / TE2T may be, for example, 1.15 or less, and may be 1.10 or less, and may be 1.05 or less. The tensile elongation TE2M and TE2T may be, for example, 100% or more, and may be 105% or more. The tensile elongation TE2M and TE2T may be, for example, 120% or less, and may be 115% or less.

[0038] Tensile strength, tensile modulus, and tensile elongation are measured in accordance with JIS K7127. An Orientec RTC-1310A tensile testing machine is used as the measuring instrument. The test specimens are made from biaxially oriented PET film cut into rectangular pieces with a width of 15 mm and a length of 150 mm. The initial distance between the pair of chucks holding the test specimen is 100 mm, and the tensile speed is 300 mm / min. The length of the test specimen is adjustable as long as it can be gripped by the pair of chucks. Unless otherwise specified in this application, the ambient temperature during testing is 25°C and the relative humidity is 50%. The average values ​​of the measurements from five test specimens are used as the tensile strength, tensile modulus, and tensile elongation in this application.

[0039] Biaxially oriented PET film contains PET as its main component. The PET content in biaxially oriented PET film is, for example, 51% by mass or more, may be 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 99% by mass or more. Biaxially oriented PET film may contain components other than PET. For example, biaxially oriented PET film may contain polyester other than PET.

[0040] The thickness of the biaxially oriented PET film is, for example, 8 μm or more, but may be 10 μm or more, 11 μm or more, or 12 μm or more. The thickness of the biaxially oriented PET film is, for example, 25 μm or less, but may be 20 μm or less. The strength of the packaging material 50 can be ensured by having a biaxially oriented PET film with a thickness of 8 μm or more. The moldability of the packaging material 50 can be ensured by having a biaxially oriented PET film with a thickness of 25 μm or less.

[0041] [Second-stage stretched plastic film] The second stretched plastic film 52 is a uniaxially oriented polyethylene terephthalate film. The uniaxially oriented polyethylene terephthalate film is stretched in a predetermined one direction. The uniaxially oriented polyethylene terephthalate film mainly contains polyethylene terephthalate (hereinafter also referred to as PET). In the following description, the uniaxially oriented polyethylene terephthalate film will also be referred to as a uniaxially oriented PET film.

[0042] The stretching ratio of a uniaxially oriented PET film in the flow direction is, for example, 1.05 times or more.

[0043] The tensile strength TS1T of a uniaxially oriented PET film in the vertical direction is less than the tensile strength TS1M of a uniaxially oriented PET film in the flow direction. Therefore, a uniaxially oriented PET film is tearable in the flow direction. By including a uniaxially oriented film in the packaging material 50, the packaging material 50 can be tearable in the flow direction. For example, the force that a consumer applies to the packaging material 50 along the flow direction is more likely to act as a tearing force. The ratio of the tensile strength TS1T in the vertical direction to the tensile strength TS1M in the flow direction, TS1T / TS1M, is less than 1.00, preferably 0.90 or less, and more preferably 0.80 or less. TS1T / TS1M is, for example, 0.50 or more, may be 0.60 or more, or 0.70 or more.

[0044] The tensile modulus TM1T of a uniaxially oriented PET film in the vertical direction is, for example, 3500 MPa or more, and may be 3600 MPa or more. The tensile modulus TM1T of a uniaxially oriented PET film in the vertical direction is, for example, 4000 MPa or less, and may be 3900 MPa or less.

[0045] The tensile elongation TE1T of a uniaxially oriented PET film in the vertical direction may be greater than the tensile elongation TE1M of a uniaxially oriented PET film in the flow direction. The ratio of the tensile elongation TE1T in the vertical direction to the tensile elongation TE1M in the flow direction, TE1T / TE1M, is, for example, 1.01 or more, may be 1.05 or more, or may be 1.08 or more. TE1T / TE1M is, for example, 1.20 or less, may be 1.15 or less, or may be 1.12 or less. The tensile elongation TE1M in the flow direction is, for example, 110% or more, may be 115% or more, or may be 120% or more. The tensile elongation TE1M in the flow direction is, for example, 130% or less, or may be 125% or less. The tensile elongation TE1T in the vertical direction is, for example, 120% or more, may be 125% or more, or may be 130% or more. The tensile elongation TE1T in the vertical direction is, for example, 145% or less, and may also be 140% or less.

[0046] The methods for measuring the tensile strength, tensile modulus, and tensile elongation of uniaxially oriented PET film are the same as those for biaxially oriented PET film, so the explanation will be omitted.

[0047] Uniaxially oriented PET film contains PET as its main component. The PET content in the uniaxially oriented PET film is, for example, 51% by mass or more, may be 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 99% by mass or more. Uniaxially oriented PET film may contain components other than PET. For example, uniaxially oriented PET film may contain polyester other than PET.

[0048] The thickness of the uniaxially oriented PET film is, for example, 8 μm or more, but may be 10 μm or more, 11 μm or more, or 12 μm or more. The thickness of the uniaxially oriented PET film is, for example, 25 μm or less, but may be 20 μm or less.

[0049] [Sealant film] The sealant film 55 forms the seal portion of the pouch by melting through heat sealing. The sealant film 55 is an unoriented polypropylene film. The term "unoriented" 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.

[0050] An unoriented polypropylene film may be a single layer; that is, an unoriented polypropylene film may consist of one layer. An unoriented polypropylene film may be multilayered; that is, an unoriented polypropylene film may contain multiple layers. Preferably, the unoriented polypropylene film is a single layer.

[0051] The pouch 10, composed of packaging material 50, is subjected to sterilization treatments such as boiling or retorting at high temperatures. The unoriented polypropylene film has heat resistance that can withstand these high-temperature treatments.

[0052] The melting point of the materials constituting the unoriented polypropylene film is preferably 150°C or higher, and more preferably 160°C or higher. By increasing the melting point of the unoriented polypropylene film, it becomes possible to perform retort processing of pouch 10 at a high temperature, thereby shortening the time required for retort processing. Note that the melting point of the materials constituting the unoriented polypropylene film is lower than the melting point of PET.

[0053] Unoriented polypropylene film contains propylene as its main component. The propylene content in unoriented polypropylene film is, for example, 90% by mass or more. Specific examples of propylene include propylene-ethylene block copolymer, propylene-ethylene random copolymer, and homopolypropylene. "Propylene-ethylene block copolymer" refers to a material having the structural formula shown in formula (I) below. "Propylene-ethylene random copolymer" refers to a material having the structural formula shown in formula (II) below. "Homopolypropylene" refers to a material having the structural formula shown in formula (III) below.

[0054] [ka]

[0055] [ka]

[0056] [ka]

[0057] Preferably, the unoriented polypropylene film contains a propylene-ethylene block copolymer. This helps to prevent the pouch 10 from rupturing due to impact during a fall.

[0058] A 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 an unoriented polypropylene film can be adjusted by adjusting the ratio of the marine component to the island component.

[0059] 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.

[0060] There are mainly two types of single-layer, unoriented polypropylene films containing propylene-ethylene block copolymer. The first type is one that has high tensile elongation and impact resistance, such as the ZK500 described later. The first type of unoriented polypropylene film preferably also has the characteristic of low hot seal strength. This prevents the internal pressure of the containment section 18 from becoming excessive when the pouch 10 is heated. Therefore, damage to the packaging material 50 can be suppressed. The second type is one with a high tensile modulus, such as ZK207, which will be described later. By using the second type of unoriented polypropylene film, the tear resistance of the packaging material 50 in the flow direction can be improved.

[0061] (Type 1 unoriented polypropylene film) The first type of unoriented polypropylene film will be described in detail.

[0062] The tensile elongation of the first type of unoriented polypropylene film in the flow direction is, for example, 1000% or more, and may be 1100% or more. The tensile elongation of the first type of unoriented polypropylene film in the flow direction is, for example, 1400% or less, and may be 1300% or less. The tensile elongation of the first type of unoriented polypropylene film in the perpendicular direction is, for example, 1100% or more, and may be 1200% or more. The tensile elongation of the first type of unoriented polypropylene film in the perpendicular direction is, for example, 1500% or less, and may be 1400% or less.

[0063] The tensile modulus of the first type of unoriented polypropylene film in the flow direction is, for example, less than 650 MPa and may be 600 MPa or less. The tensile modulus of the first type of unoriented polypropylene film in the flow direction is, for example, 450 MPa or more and may be 500 MPa or more. The tensile modulus of the first type of unoriented polypropylene film in the vertical direction is, for example, less than 500 MPa and may be 450 MPa or less. The tensile modulus of the first type of unoriented polypropylene film in the vertical direction is, for example, 350 MPa or more and may be 400 MPa or more.

[0064] The tensile modulus and tensile elongation of unoriented polypropylene film are measured in accordance with JIS K7127. An Orientec RTC-1310A tensile testing machine is used as the measuring instrument. The test specimens are rectangular pieces of unoriented polypropylene film cut to a width of 15 mm and a length of 150 mm. The initial distance between the pair of chucks holding the test specimen is 100 mm, and the tensile speed is 300 mm / min. The length of the test specimen is adjustable as long as it can be gripped by the pair of chucks. Unless otherwise specified in this application, the ambient temperature during testing is 25°C and the relative humidity is 50%. The average values ​​of the measurements from five test specimens are used as the tensile modulus and tensile elongation in this application.

[0065] The content of propylene-ethylene block copolymer in the first type of unoriented polypropylene film is, for example, 70% by mass or more, and may be 75% by mass or more. The content of propylene-ethylene block copolymer in the first type of unoriented polypropylene film is, for example, 85% by mass or less, and may be 80% by mass or less.

[0066] The first type of unoriented polypropylene film may contain a second thermoplastic resin in addition to a first thermoplastic resin consisting of a propylene-ethylene block copolymer. The content of the second thermoplastic resin is lower than the content of the first thermoplastic resin. The second thermoplastic resin is, for example, polyethylene. The polyethylene may be low-density polyethylene or linear low-density polyethylene. The density of the polyethylene is 0.900 g / cm³. 3 It may be greater than or equal to 0.910 g / cm³. 3 It may be greater than this. The density of polyethylene is 0.930 g / cm³. 3 It may also be less than 0.920 g / cm³. 3 The following is also acceptable.

[0067] The thickness of the first type of unoriented polypropylene film is, for example, 45 μm or more, may be 50 μm or more, may be 55 μm or more, or may be 60 μm or more. The thickness of the first type of unoriented polypropylene film is, for example, 80 μm or less, may be 70 μm or less.

[0068] (Second type of unoriented polypropylene film) The second type of unoriented polypropylene film will be described in detail.

[0069] The tensile elongation of the second type of unoriented polypropylene film in the flow direction may be, for example, less than 1000%, and may be 900% or less, or 800% or less. The tensile elongation of the second type of unoriented polypropylene film in the flow direction may be, for example, 600% or more, or 700% or more. The tensile elongation of the second type of unoriented polypropylene film in the perpendicular direction may be, for example, less than 1100%, and may be 1050% or less, or 1000% or less. The tensile elongation of the second type of unoriented polypropylene film in the perpendicular direction may be, for example, 700% or more, or 800% or more.

[0070] The tensile modulus of the second type of unoriented polypropylene film in the flow direction is, for example, 650 MPa or more, and may be 700 MPa or more. The tensile modulus of the second type of unoriented polypropylene film in the flow direction is, for example, 850 MPa or less, and may be 800 MPa or less. The tensile modulus of the first type of unoriented polypropylene film in the vertical direction is, for example, 500 MPa or more, and may be 550 MPa or more. The tensile modulus of the second type of unoriented polypropylene film in the vertical direction is, for example, 700 MPa or less, and may be 650 MPa or less.

[0071] In the second type of unstretched polypropylene film, the content of the propylene-ethylene block copolymer is, for example, 80% by mass or more, and may be 85% by mass or more. In the first type of unstretched polypropylene film, the content of the propylene-ethylene block copolymer is, for example, 96% by mass or less, and may be 90% by mass or less.

[0072] The second type of unstretched polypropylene film may contain a second thermoplastic resin in addition to the first thermoplastic resin composed of a propylene-ethylene block copolymer. The content of the second thermoplastic resin is lower than the content of the first thermoplastic resin. The second thermoplastic resin is, for example, a thermoplastic elastomer. The thermoplastic elastomer may 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 α-olefin as the comonomer. The density of the thermoplastic elastomer is 0.860 g / cm 3 or more, and may be 0.870 g / cm 3 or more. The density of the thermoplastic elastomer is 0.900 g / cm 3 or less, and may be 0.890 g / cm 3 or less.

[0073] The second type of unstretched polypropylene film may contain a third thermoplastic resin in addition to the first thermoplastic resin composed of a propylene-ethylene block copolymer. The content of the third thermoplastic resin is lower than the content of the first thermoplastic resin. The third thermoplastic resin is, for example, polyethylene. The density of polyethylene is 0.940 g / cm 3 or more, and may be 0.950 g / cm 3 or more. The density of polyethylene is 0.970 g / cm 3 or less, and may be 0.960 g / cm 3 or less.

[0074] The thickness of the second type of unoriented polypropylene film is, for example, 55 μm or more, and may be 60 μm or more. The thickness of the second type of unoriented polypropylene film is, for example, 80 μm or less, and may be 70 μm or less.

[0075] [Transparent vapor deposited layer] Next, the transparent vapor-deposited layer 62 will be described. The transparent vapor-deposited layer 62 is a transparent layer formed by a vapor deposition method, etc. The transparent vapor-deposited layer 62 enhances the gas barrier properties of the packaging material 50. For example, the transparent vapor-deposited layer 62 suppresses the permeation of gases such as oxygen gas and water vapor through the packaging material 50.

[0076] The material used to constitute the transparent vapor deposition layer 62 is one or more materials selected from the group consisting of metal oxides such as aluminum oxide and inorganic compounds such as silicon oxide.

[0077] The transparent vapor-deposited layer 62 may consist of a single layer or multiple layers. Each layer of the single layer and multiple layers contains one or more materials selected from the group described above. If the transparent vapor-deposited layer 62 consists of multiple layers, each layer may contain the same material or different materials.

[0078] The transparent deposition layer 62 may be an amorphous thin film of aluminum oxide. Specifically, the transparent deposition layer 62 may be a film of the formula AlO X The amorphous thin film of aluminum oxide may be represented by the formula AlO (wherein X represents a number in the range of 0.5 to 1.5). As the transparent deposition layer 62, an amorphous thin film of aluminum oxide in which the value of X decreases in the depth direction from the film surface toward the inner surface can also be used. The amorphous thin film of aluminum oxide is represented by the formula AlO X(In the formula, X represents a number in the range of 0.5 to 1.5.) It is preferable that the value of X increases in the depth direction from the surface of the thin film toward the interior. In general, a value of X of 0.5 or more can be used as the value of X in the above formula, but if X is less than 1.0, the coloring becomes severe and the transparency is poor, so it is preferable to use X of 1.0 or more. Also, since X = 1.5 represents a state in which Al and oxygen are completely oxidized, the upper limit for using X is up to 1.5. When the value of X in the above formula is 0, it is a completely inorganic element (pure substance) and is not transparent.

[0079] The value of X is calculated by analyzing the transparent deposition layer 62 in the depth direction using an X-ray photoelectron spectroscopy (XPS) instrument.

[0080] The thickness of the transparent vapor deposition layer 62 is, for example, 3 nm or more, may be 10 nm or more, or 15 nm or more. The thickness of the transparent vapor deposition layer 62 is, for example, 50 nm or less, may be 40 nm or less, or 30 nm or less.

[0081] The method for forming the transparent vapor-deposited layer 62 may be, for example, physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, or chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition, thermochemical vapor deposition, and photochemical vapor deposition.

[0082] The surface of the first stretched plastic film 51 or the third stretched plastic film 53 on which the transparent vapor deposition layer 62 is formed may be treated to improve adhesion, or a layer for improving adhesion may be formed thereon. The treatment may be, for example, plasma treatment.

[0083] [Gas barrier coating film] Next, the gas barrier coating film 63 provided on the surface of the transparent vapor deposition layer 62 will be described.

[0084] The gas barrier coating film 63 consists of a gas barrier composition formed by polycondensation using a sol-gel method. The gas barrier composition comprises at least one alkoxide and a polyvinyl alcohol resin and / or an ethylene-vinyl alcohol copolymer. The gas barrier composition further comprises a sol-gel catalyst, an acid, water, and an organic solvent. The gas barrier coating film 63 is preferably transparent.

[0085] The above general formula R 1 n M(OR 2 ) m The alkoxide represented by can be at least one of a partially hydrolyzed alkoxide or a condensate of hydrolyzed alkoxide. In the case of a partially hydrolyzed alkoxide, it is not necessary for all alkoxy groups to be hydrolyzed. A partially hydrolyzed alkoxide may be one in which one or more alkoxy groups have been hydrolyzed, or a mixture thereof. As a condensate of hydrolyzed alkoxide, a dimer or more of a partially hydrolyzed alkoxide, specifically a 2 to 6-mer, can be used.

[0086] The above general formula R 1 n M(OR 2 ) m In the alkoxide represented by , the metal atom represented by M can be silicon, zirconium, titanium, aluminum, or others. Preferred metals include, for example, silicon and titanium. In this embodiment, the alkoxide can be used alone or by mixing alkoxides of two or more different metal atoms in the same solution.

[0087] Furthermore, the above general formula R 1 n M(OR 2 ) m In the alkoxide represented by R, 1Specific examples of organic groups represented by the above general formula R include alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, n-hexyl, n-octyl, and others. 1 n M(OR 2 ) m In the alkoxide represented by R, 2 Specific examples of organic groups represented by include, for example, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group, and others. Note that these alkyl groups may be the same or different within the same molecule.

[0088] When preparing the above gas barrier composition, for example, a silane coupling agent may be added. As the silane coupling agent, known organic reactive group-containing organoalkoxysilanes can be used. In particular, organoalkoxysilanes having an epoxy group are preferably used, and specifically, for example, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, or β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane can be used. One or more of the above silane coupling agents may be used.

[0089] [Adhesive layer] The first adhesive layer 56 is formed by applying an adhesive to the surface of the film to be laminated, which is one of a film containing a first stretched plastic film 51 and a film containing a second stretched plastic film 52, and drying it. The second adhesive layer 57 is formed by applying an adhesive to the surface of the film to be laminated, which is one of a film containing a second stretched plastic film 52 and a film containing a third stretched plastic film 53, and drying it. The third adhesive layer 58 is formed by applying an adhesive to the surface of the film to be laminated, which is one of a film containing a third stretched plastic film 53 and a film containing a sealant film 55, and drying it. As adhesives constituting the adhesive layers such as the first adhesive layer 56, the second adhesive layer 57, and the third adhesive layer 58, for example, solvent-type, water-type, or emulsion-type adhesives such as one-component or two-component curing or non-curing vinyl-based, (meth)acrylic-based, polyamide-based, polyester-based, polyether-based, polyurethane-based, epoxy-based, rubber-based, and others can be used. As a two-component curing adhesive, a cured product of a polyol and an isocyanate compound can be used. The above laminating adhesive can be applied by methods such as the direct gravure roll coating method, gravure roll coating method, kiss coating method, reverse roll coating method, fontein method, transfer roll coating method, and others.

[0090] The adhesive layers 56, 57, and 58 preferably have a thickness of 0.1 μm to 10 μm, more preferably 1 μm to 5 μm, and even more preferably 1 μm to 3 μm.

[0091] [Print layer] The printing layer 61 is a layer that forms any desired printed pattern, such as letters, numbers, pictures, figures, symbols, and designs, for purposes such as decoration, displaying contents, displaying expiration dates, displaying manufacturer and seller information, and for adding aesthetic appeal. The printing layer 61 is provided as needed. For example, the printing layer 61 is provided between the first stretched plastic film 51 and the first adhesive layer 56. The printing layer 61 may be provided over the entire surface of the first stretched plastic film 51 or on a part of it. The printing layer 61 can be formed using conventionally known pigments and dyes, and the method of formation is not particularly limited.

[0092] The printed layer 61 preferably has a thickness of 0.1 μm to 10 μm, more preferably 1 μm to 5 μm, and even more preferably 1 μm to 3 μm.

[0093] <Manufacturing method for packaging materials> Next, an example of a method for manufacturing the packaging material 50 will be described.

[0094] First, the first stretched plastic film 51 and the second stretched plastic film 52 described above are prepared. The first stretched plastic film 51 may have a printed layer 61 provided in advance. Next, the first stretched plastic film 51 and the second stretched plastic film 52 are laminated together via a first adhesive layer 56 using a dry lamination method.

[0095] Next, a laminate containing the first stretched plastic film 51 and the second stretched plastic film 52 is laminated with the third stretched plastic film 53 via a second adhesive layer 57 using a dry lamination method. The third stretched plastic film 53 may have a transparent vapor deposition layer 62 pre-applied to it. A gas barrier coating film 63 may be provided on the surface of the transparent vapor deposition layer 62.

[0096] Subsequently, a laminate containing the first stretched plastic film 51, the second stretched plastic film 52, and the third stretched plastic film 53 is laminated with a sealant film 55 via a third adhesive layer 58. This makes it possible to obtain a packaging material 50 comprising the first stretched plastic film 51, the second stretched plastic film 52, the third stretched plastic film 53, and the sealant film 55.

[0097] The order in which the first stretched plastic film 51, the second stretched plastic film 52, the third stretched plastic film 53, and the sealant film 55 are laminated by the dry lamination method is not limited to the order described above. For example, the packaging material 50 may be manufactured by laminating a first laminate containing the first stretched plastic film 51 and the second stretched plastic film 52 and a second laminate containing the third stretched plastic film 53 and the sealant film 55 by the dry lamination method.

[0098] In the dry lamination method, first, an adhesive composition is applied to one of the two films to be laminated. Next, the applied adhesive composition is dried to evaporate the solvent. Then, the two films are laminated together via the dried adhesive composition. Subsequently, the two laminated films are wound up and aged for 24 hours or more in an environment of, for example, 20°C or higher.

[0099] The packaging material 50 can also be subjected to secondary processing for the purpose of imparting chemical functions, electrical functions, magnetic functions, mechanical functions, friction / wear / lubrication functions, optical functions, thermal functions, biocompatibility, and other surface functions. Examples of secondary processing include embossing, painting, bonding, printing, metallizing (plating, etc.), machining, and surface treatment (antistatic treatment, corona discharge treatment, plasma treatment, photochromism treatment, physical vapor deposition, chemical vapor deposition, coating, etc.). Furthermore, molded products can be manufactured by laminating (dry lamination or extrusion lamination), pouch manufacturing, and other post-processing processes to the packaging material 50.

[0100] <Pouch> The packaging material 50 is used as the material for forming the pouch. Figure 4 is a front view showing an example of a pouch 10 equipped with the packaging material 50. The pouch 10 has a storage section 18 for containing the contents. Note that Figure 4 shows the pouch 10 without any contents inside. The configuration of the pouch 10 will be described below.

[0101] As shown in Figure 4, the pouch 10 includes an upper part 11, a lower part 12, a first side part 13, and a second side part 14, and has a substantially rectangular outline in the front view. The names such as "upper part," "lower part," and "side part," as well as terms such as "upper" and "downward," merely describe the relative position and orientation of the pouch 10 and its components, with the lower part defined as the side that can be positioned downward when the pouch 10 is heated. The orientation of the pouch 10 is not limited by the names and terms used herein.

[0102] The pouch 10 comprises a surface film 15 that constitutes the surface of the pouch 10, a back film 16 that constitutes the back of the pouch 10, and a bottom film 17 that constitutes the bottom 12. Each film may be made of the packaging material 50 described above.

[0103] The terms "front film," "back film," and "bottom film" are merely ways of defining each film according to its positional relationship, and the method of providing the film when manufacturing the pouch 10 is not limited by these terms. For example, the pouch 10 may be manufactured using a single film in which the front film 15, back film 16, and bottom film 17 are connected; it may be manufactured using a total of two films: a single film in which the front film 15 and bottom film 17 are connected and a single back film 16; or it may be manufactured using a total of three films: a single front film 15, a single back film 16, and a single bottom film 17.

[0104] The surface film 15, the back film 16, and the bottom film 17 are joined together on their inner surfaces by a sealing portion. In plan views of the pouch 10, such as in Figure 4, the sealing portion is hatched. The space enclosed by the sealing portion, the surface film 15, the back film 16, and the bottom film 17 can function as a storage portion 18 for containing the contents.

[0105] The method for forming a seal is not particularly limited, as long as it is possible to join opposing films together. For example, a seal may be formed by melting the inner surfaces of the films by heating and welding the inner surfaces together, i.e., by heat sealing. Alternatively, a seal may be formed by bonding the inner surfaces of opposing films together using an adhesive or the like.

[0106] As shown in Figure 4, the sealing portion of the pouch 10 has a first side sealing portion 30, a second side sealing portion 35, and a lower sealing portion 12a. The first side sealing portion 30 is located on the first side portion 13. The second side sealing portion 35 is located on the second side portion 14. The second side portion 14 faces the first side portion 13 in the first direction D1. The lower sealing portion 12a is located on the lower portion 12. The lower sealing portion 12a is connected to the first side sealing portion 30 and the second side sealing portion 35. The unsealed portion surrounded by the first side sealing portion 30, the second side sealing portion 35, and the lower sealing portion 12a functions as a storage portion 18 that contains the contents.

[0107] In the pouch 10 before it is filled with contents (when it does not contain contents), as shown in Figure 4, the top 11 of the pouch 10 is an opening 11b. After the contents are placed in the pouch 10, the inner surface of the surface film 15 and the inner surface of the back film 16 are joined at the top 11 to form the top seal and seal the pouch 10.

[0108] The first side sealing portion 30, the second side sealing portion 35, and the upper sealing portion are sealing portions formed by joining the inner surface of the surface film 15 and the inner surface of the backing film 16. The lower sealing portion 12a includes a sealing portion formed by joining the inner surface of the surface film 15 and the inner surface of the lower film 17, and a sealing portion formed by joining the inner surface of the backing film 16 and the inner surface of the lower film 17.

[0109] The sealing portion may include a sealing portion 34 located at the lower part 12 below the first side sealing portion 30. At the location of the sealing portion 34, a hole or notch is formed in the lower film 17. The sealing portion 34 is a sealing portion formed by joining the inner surface of the surface film 15 and the inner surface of the back film 16. The sealing portion may also include a sealing portion 39 located at the lower part 12 below the second side sealing portion 35. At the location of the sealing portion 39, a hole or notch is formed in the lower film 17. The sealing portion 39 is a sealing portion formed by joining the inner surface of the surface film 15 and the inner surface of the back film 16. The sealing portions 34 and 39 partially join the surface film 15 and the back film 16 at the lower part 12. This enhances the self-supporting ability of the pouch 10.

[0110] In addition to the non-sealed portion that functions as the containment portion 18, the pouch 10 includes a first non-sealed portion 40 isolated from the containment portion 18 by a first side seal portion 30, as shown in Figure 4. The non-sealed portion is the part of the film where opposing inner surfaces are not joined together. The first non-sealed portion 40 is located closer to the upper part 11 of the pouch 10. "Closer to the upper part 11" means that the first non-sealed portion 40 is located closer to the upper part 11 than the center point C of the containment portion 18.

[0111] As shown in Figure 4, the first non-seal portion 40 extends to the first side edge 13x of the first side portion 13 of the pouch 10. In other words, the first non-seal portion 40 overlaps the first side edge 13x and has an open edge portion 41 that opens to the outside. Steam generated in the containment portion 18 and flowing into the first non-seal portion 40 can be discharged to the outside through the open edge portion 41.

[0112] The first side seal portion 30 is configured to define the first non-seal portion 40. For example, as shown in Figure 4, the first side seal portion 30 has an upper seal portion 31, a lower seal portion 32, and an intermediate seal portion 33. The upper seal portion 31 extends along the first side portion 13 from the first non-seal portion 40 toward the upper part 11 of the pouch 10. The lower seal portion 32 extends along the first side portion 13 toward the lower part 12 of the pouch 10 from the first non-seal portion 40. The intermediate seal portion 33 is located between the housing portion 18 and the first non-seal portion 40. The intermediate seal portion 33 includes one end connected to the upper seal portion 31 and the other end connected to the lower seal portion 32.

[0113] When the pouch 10 is heated and steam is generated in the containment section 18, increasing the pressure in the containment section 18, the intermediate seal portion 33 partially peels off, allowing the containment section 18 and the first unsealed portion 40 to communicate. The steam that flows from the containment section 18 into the first unsealed portion 40 can be discharged to the outside through the opening edge portion 41. In this way, the intermediate seal portion 33 and the first unsealed portion 40 function as a steam venting mechanism that discharges steam from the containment section 18 to the outside.

[0114] As shown in Figure 4, a second non-seal portion 45 may be formed between the second side edge 14x of the second side portion 14 and the second side sealing portion 35. In this case, the second non-seal portion 45 may extend to reach the second side edge 14x. In other words, the second non-seal portion 45 may overlap the second side edge 14x and have an open edge portion 46 that opens to the outside.

[0115] The second side seal portion 35 may have an upper seal portion 36, a lower seal portion 37, and an intermediate seal portion 38. The upper seal portion 36 extends along the second side portion 14 from the second non-seal portion 45 toward the upper part 11 of the pouch 10. The lower seal portion 37 extends along the second side portion 14 from the second non-seal portion 45 toward the lower part 12 of the pouch 10. The intermediate seal portion 38 is located between the housing portion 18 and the second non-seal portion 45. The intermediate seal portion 38 includes one end connected to the upper seal portion 36 and the other end connected to the lower seal portion 37.

[0116] As shown in Figure 4, the pouch 10 may be provided with an opening means 30a located on the upper sealing portion 31. The opening means 30a penetrates the surface film 15 and the back film 16. The opening means 30a is a notch, a cut, etc. The opening means 30a can serve as a starting point when the user tears the pouch 10. The opening means 30a extends from the first side edge 13x toward the containment portion 18.

[0117] As shown in Figure 4, the pouch 10 may be provided with an opening means 35a located in the second side seal portion 35. The opening means 35a penetrates the surface film 15 and the back film 16. The opening means 35a is a notch, a cut, etc. Like the opening means 30a, the opening means 35a can serve as a starting point when the user tears the pouch 10. The opening means 35a extends from the second side edge 14x toward the containment portion 18. The opening means 35a may be formed in the portion of the second side seal portion 35 that faces the opening means 30a in the first direction D1. For example, the opening means 35a may be formed in the upper seal portion 36.

[0118] Figure 5 shows the pouch 10 with its contents contained and its top 11 sealed. After the contents are filled into the pouch 10 through the opening 11b at the top 11, the inner surface of the surface film 15 and the inner surface of the back film 16 are joined at the top 11. This forms the top seal portion 11a, sealing the pouch 10.

[0119] In Figure 5, the virtual line L1 is the line connecting the center point C of the housing section 18 and the first non-sealed section 40 by the shortest distance. The extension of the virtual line L1 may intersect the opening edge 41.

[0120] The distance H1 in the first direction D1 from the center point C to the inner edge 32a of the lower seal portion 32 is equal to the distance H2 in the first direction D1 from the center point C to the inner edge 37a of the lower seal portion 37. The distance H2 in the second direction D2 from the center point C to the inner edge of the upper seal portion 11a is equal to the distance H4 in the second direction D2 from the center point C to the inner edge of the lower seal portion 12a.

[0121] The symbol H5 represents the distance from the center point C to the intermediate seal portion 33. Distance H5 is the distance from the intersection of the virtual line L1 and the inner edge 33a of the intermediate seal portion 33 to the center point C. Distance H5 may be smaller than or larger than distance H3. The ratio of distance H5 to distance H3, H5 / H3, is, for example, 0.95 or more, may be 0.98 or more, may be greater than 1.00, may be 1.01 or more, may be 1.03 or more, or may be 1.05 or more. H5 / H3 is, for example, 1.10 or less, may be 1.05 or less, may be less than 1.00, or may be 0.98 or less.

[0122] The symbol H6 represents the distance from the center point C to the first non-sealed portion 40. Distance H6 is the distance from the intersection of the virtual straight line L1 and the outer edge of the intermediate seal portion 33 to the center point C.

[0123] The contents contained in pouch 10 are heated in a microwave oven. The contents may include solid ingredients and liquid components. The solid ingredients may include oil-containing components such as meat. Examples of contents include cooked foods such as sweet and sour pork, curry, stew, soup, boiled dishes, and hamburgers.

[0124] The weight of the contents contained in pouch 10 is, for example, 50g or more, may be 100g or more, or 130g or more. The weight of the contents contained in pouch 10 is, for example, 300g or less, may be 250g or less, or 220g or less.

[0125] The ratio of the weight of the ingredients to the total weight of the contents may be, for example, 1% or more, 5% or more, or 10% or more. The ratio of the weight of the ingredients to the total weight of the contents may be, for example, 95% or less, 90% or less, or 70% or less. The ingredients are obtained by removing the liquid components from the contents. For example, the ingredients can be obtained by filtering the liquid components in the contents using a sieve. The mesh size of the sieve may be, for example, 0.7 mm.

[0126] [How to heat the pouch] Next, the method for heating the pouch 10 described above will be explained. First, the pouch 10 is placed in the microwave oven with the lower part 12 facing downwards. That is, the pouch 10 is made to stand upright in the microwave oven. Then, the pouch 10 is heated using the microwave oven. The moisture contained in the contents evaporates, and the pressure in the containment section 18 increases.

[0127] As the pressure in the containment section 18 increases, the pouch 10 expands, for example, in a circular shape, around the center point C of the containment section 18. As a result, a force is applied to each position of the seal portion in the direction from the center point C toward the seal portion. When a force is applied to the intermediate seal portion 33, the intermediate seal portion 33 peels off. When the peeling of the intermediate seal portion 33 reaches the first non-seal portion 40, a flow path is formed in the intermediate seal portion 33. The steam generated in the containment section 18 flows into the first non-seal portion 40 through the flow path and is released to the outside from the opening edge portion 41. This suppresses the increase in pressure in the containment section 18.

[0128] When heating the contents using a microwave oven, the temperatures of the surface film 15 and back film 16 of the pouch 10 also rise. For example, while heating the contents using a microwave oven, the contents may splatter and adhere to the inner surface of the surface film 15. If the contents adhering to the inner surface are further heated, the temperature of the inner surface of the surface film 15 in contact with the contents will also rise. The heat resistance of the sealant film 55 that makes up the inner surface of the surface film 15 is lower than that of the stretched plastic film. Therefore, it is possible that a part of the sealant film 55 that makes up the surface film 15 may deform due to the effects of heat. If the effect of the deformation of the sealant film 55 extends to the outer surface of the surface film 15, it is possible that holes may form in the surface film 15 or wrinkles may be formed in the surface film 15.

[0129] In this embodiment, the third stretched plastic film 53 adjacent to the sealant film 55 is made of a biaxially stretched PET film. The heat resistance of a biaxially stretched PET film is higher than that of a uniaxially stretched PET film. For example, the melting point of a biaxially stretched PET film is higher than that of a uniaxially stretched PET film. Therefore, according to this embodiment, deformation of the third stretched plastic film 53 due to the deformation of the sealant film 55 can be suppressed. This prevents the deformation of the sealant film 55 from extending to the outer surface of the surface film 15. Consequently, it is possible to prevent holes from forming in the surface film 15 or wrinkles from forming in the surface film 15.

[0130] The sealant film 55 preferably has a thickness of 45 μm or more, and more preferably 50 μm or more. Increasing the thickness of the sealant film 55 can increase its heat capacity. Therefore, the third stretched plastic film 53 adjacent to the sealant film 55 can be suppressed from being affected by heat.

[0131] After heating the contents, the user tears the pouch 10 starting from the opening means 30a. In this embodiment, the packaging material 50 constituting the pouch 10 includes a second-oriented plastic film 52 which is a uniaxially oriented PET film. The tearability of uniaxially oriented PET film is higher than that of biaxially oriented PET film. Therefore, the force applied by the consumer to the pouch 10 is more likely to act as a force to tear the packaging material 50. This suppresses the stretching of the sealant film 55 when the consumer tears open the pouch 10. This makes it easier for the user to tear the pouch 10 from the first side 13 to the second side 14 along the first direction D1.

[0132] Preferably, as described above, the sealant film 55 of the packaging material 50 constituting the pouch 10 contains a propylene-ethylene block copolymer. This suppresses the pouch 10 from rupturing due to impact when dropped.

[0133] Preferably, as described above, the packaging material 50 constituting the pouch 10 includes a transparent vapor-deposited layer 62. This prevents gases such as oxygen gas and water vapor from permeating the packaging material 50 and entering the containment section 18. It also prevents odors from the film or layers constituting the packaging material 50 from adhering to the contents. For example, when the contents are heated during retort processing, odors generated from the adhesive layers 56, 57, and 58 from adhering to the contents can be prevented. This prevents changes in the flavor of the contents. From the viewpoint of preventing odors from adhering to the contents, it is preferable that the transparent vapor-deposited layer 62 is close to the inner surface 50x of the packaging material 50. For example, the packaging material 50 shown in Figures 1 and 2 is preferable to the packaging material 50 shown in Figure 3.

[0134] Various modifications can be made to the embodiments described above. The following descriptions will explain the modifications, referring to the drawings as needed. In the following descriptions and the drawings used therein, parts that can be configured similarly to the embodiments described above will be given the same reference numerals as those used for the corresponding parts in the embodiments described above, and redundant explanations will be omitted. Furthermore, if it is clear that the effects and advantages obtained in the embodiments described above can also be obtained in the modifications, the explanation may be omitted.

[0135] In the above-described embodiment, an example was shown in which the pouch 10 is a gusset-type pouch comprising a surface film 15, a back film 16, and a bottom film 17, and configured to be self-supporting. The pouch 10 may have other structures. For example, the pouch 10 may be a three-sided sealed pouch, a four-sided sealed pouch, etc., composed of a surface film 15 and a back film 16. [Examples]

[0136] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention.

[0137] (Example 1) A biaxially oriented PET film with a thickness of 12 μm was prepared as the first oriented plastic film 51. E5102 manufactured by Toyobo Co., Ltd. was used as the biaxially oriented PET film.

[0138] The tensile strength of E5102 in the flow direction is 224 MPa, and the tensile strength of E5102 in the vertical direction is 246 MPa. The tensile elongation of E5102 in the flow direction is 97%, and the tensile elongation of E5102 in the vertical direction is 82%. The tensile modulus of E5102 in the flow direction is 3920 MPa, and the tensile modulus of E5102 in the vertical direction is 4020 MPa.

[0139] As the second stretched plastic film 52, a uniaxially oriented PET film with a thickness of 12 μm was prepared. For the uniaxially oriented PET film, we used Emblet® PC manufactured by Unitika Ltd.

[0140] Emblet® PC has higher tear resistance in the flow direction compared to biaxially oriented PET film. The tensile strength of Emblet® PC in the flow direction is 200 MPa, and the tensile strength of Emblet® PC in the vertical direction is 180 MPa. The tensile elongation of Emblet® PC in the flow direction is 130%, and the tensile elongation of Emblet® PC in the vertical direction is 130%. The tensile modulus of Emblet® PC in the flow direction is 3700 MPa, and the tensile modulus of Emblet® PC in the vertical direction is 3600 MPa.

[0141] A biaxially oriented PET film with a thickness of 12 μm was prepared as the third-oriented plastic film 53. E5102 manufactured by Toyobo Co., Ltd. was used as the biaxially oriented PET film. Next, the outer surface 53y of the third-oriented plastic film 53 was subjected to corona discharge treatment, and then a transparent vapor-deposited layer 62 made of silicon oxide with a thickness of 10 nm was formed. Subsequently, the transparent vapor-deposited layer 62 was subjected to plasma treatment with a mixed gas of oxygen and argon, and then a coating solution mainly composed of ethyl silicate and polyvinyl alcohol was applied with a gravure roll coater to form a gas barrier coating film 63 with a thickness of 300 nm after drying.

[0142] A 40 μm thick unoriented polypropylene film was prepared as sealant film 55. ZK500, manufactured by Toray Film Processing Co., Ltd., was used as the unoriented polypropylene film.

[0143] ZK500 has a higher tensile elongation compared to general unoriented polypropylene films. The tensile elongation of ZK500 in the flow direction is 1180% when the thickness is 50 μm and 1100% when the thickness is 60 μm. The tensile elongation of ZK500 in the perpendicular direction is 1240% when the thickness is 50 μm and 1150% when the thickness is 60 μm.

[0144] ZK500 has a lower tensile modulus compared to general unoriented polypropylene films. The tensile modulus of ZK500 in the flow direction is 640 MPa for a thickness of 50 μm and 550 MPa for a thickness of 60 μm. The tensile modulus of ZK500 in the perpendicular direction is 480 MPa for a thickness of 50 μm and 400 MPa for a thickness of 60 μm.

[0145] A packaging material was prepared by sequentially laminating a first stretched plastic film 51, a first adhesive layer 56, a second stretched plastic film 52, a second adhesive layer 57, a gas barrier coating film 63, a transparent vapor deposition layer 62, a third stretched plastic film 53, a third adhesive layer 58, and a sealant film 55 using a dry lamination method. For the adhesive layers 56, 57, and 58, a two-component polyurethane adhesive manufactured by Rock Paint Co., Ltd., with RU-004 as the main component and H-1 as the curing agent, was used. The thickness of the adhesive layers 56, 57, and 58 was 3.0 μm.

[0146] (Example 2) The packaging material was prepared in the same manner as in Example 1, except that the thickness of the sealant film 55 was changed from 40 μm to 50 μm.

[0147] (Example 3) The packaging material was prepared in the same manner as in Example 1, except that the thickness of the sealant film 55 was changed from 40 μm to 60 μm.

[0148] (Example 4) The packaging material was prepared in the same manner as in Example 3, except that the transparent vapor-deposited layer 62 and the gas barrier coating film 63 were not formed on the third stretched plastic film 53.

[0149] (Example 5) The packaging material was prepared in the same manner as in Example 3, except that the arrangement of the transparent vapor-deposited layer 62 and the gas barrier coating film 63 was changed from the outer surface 53y of the third stretched plastic film 53 to the inner surface 51x of the first stretched plastic film 51.

[0150] (Example 6) Except for the points listed below, the packaging material was prepared in the same manner as in Example 3. • A biaxially oriented PET film was used as the second stretched plastic film 52. - The arrangement of the transparent vapor deposition layer 62 and the gas barrier coating film 63 was changed from the outer surface 53y of the third stretched plastic film 53 to the outer surface 52y of the second stretched plastic film 52. • Uniaxially oriented PET film was used as the third-oriented plastic film 53.

[0151] (Example 7) The packaging material was prepared in the same manner as in Example 1, except that a 50 μm thick, unoriented polypropylene film ZK207 manufactured by Toray Film Processing Co., Ltd. was used as the sealant film 55.

[0152] (Example 8) The packaging material was prepared in the same manner as in Example 7, except that the thickness of the sealant film 55 was changed from 50 μm to 60 μm.

[0153] Using the packaging materials from Examples 1 to 8, evaluations were conducted regarding ease of opening, drop strength, heat resistance, and flavor change.

[0154] (openability) Using the packaging materials from Examples 1 to 8, a pouch 10 as shown in Figure 4 was prepared. Subsequently, 100 ml of water was filled into the storage section 18 of the pouch 10, and then the upper seal section 11a was formed to create the pouch 10 shown in Figure 5.

[0155] The heat sealing conditions for forming the seal portion of pouch 10 are as follows: • Heat sealing device: Heat sealer TP-701-A (manufactured by Tester Sangyo Co., Ltd.) • Heat seal temperature: 225℃ • Heat seal pressure: 0.1 MPa • Heat sealing time: 1 second

[0156] The dimensions of each part of pouch 10 are as follows: • Dimensions S1 of pouch 10 in the first direction D1: 150 mm • Dimensions of pouch 10 in the second direction D2: S2: 145 mm • Dimension S3 of the lower part 12 in the second direction D2: 43 mm • Width of upper sealing portion 31 and upper sealing portion 36: 10 mm • Width of lower seal portion 32 and lower seal portion 37: 6 mm • Width of upper seal portion 11a: 10 mm • Minimum dimension of the lower seal portion 12a in the second direction D2: 10 mm • Dimensions of the opening edge 41 in the second direction D2: 15 mm • Distance H1 and distance H2: 69mm • Distance H3 and distance H4: 62.5mm ·Distance H5: 65.0mm ·Distance H6: 68.1mm

[0157] Pouch 10 containing water was heated in a 600W microwave oven for 150 seconds. A SHARP RE-TS3 microwave oven was used.

[0158] Next, the ease of opening the pouch 10 was evaluated by tearing the pouch 10 starting from the opening means 30a. Specifically, it was evaluated whether the pouch 10 was continuously torn along the first direction D1 from the first side 13 to the second side 14. The results are shown in the "Ease of Opening" column of Figure 6. In the "Ease of Opening" column, "great" means that all 10 pouches 10 were continuously torn along the first direction D1 from the first side 13 to the second side 14. "good" means that 5 to 9 of the 10 pouches 10 were continuously torn along the first direction D1 from the first side 13 to the second side 14. "not good" means that 6 or more of the 10 pouches 10 were not continuously torn along the first direction D1 from the first side 13 to the second side 14. An example of a pouch 10 that was evaluated as "good" is shown in Figure 7. An example of a pouch 10 that was evaluated as "not good" is shown in Figure 8. In the example shown in Figure 8, a misalignment occurred between the tearing path of the surface film 15 and the tearing path of the back film 16. The tearing stopped when one of the tearing paths reached the upper seal portion 11a.

[0159] (Drop strength) Using the packaging materials from Examples 1 to 8, a pouch 10 as shown in Figure 4 was prepared. Subsequently, 200 ml of water was filled into the containment section 18 of the pouch 10, and then the upper seal section 11a was formed to create the pouch 10 shown in Figure 5. After that, the pouch 10 was left undisturbed for one day at a temperature of 5°C. The heat sealing conditions and the dimensions of each part of the pouch 10 were the same as those used for the evaluation of ease of opening.

[0160] Subsequently, a drop test was conducted on pouch 10. Specifically, pouch 10 was dropped from a height of 1.2m. At this time, the orientation of pouch 10 was set so that the lower part 12 of pouch 10 was facing downwards.

[0161] Afterward, it was checked whether any of the pouches 10 had ruptured. This drop test was performed on 10 pouches 10. The results are shown in the "Drop Strength" column of Figure 6. In the "Drop Strength" column, "great" means that none of the 10 pouches 10 ruptured. "good" means that 5 to 9 of the 10 pouches 10 did not rupture. "not good" means that 6 or more of the 10 pouches 10 ruptured.

[0162] (Heat resistance) Using the packaging materials from Examples 1 to 8, a pouch 10 as shown in Figure 4 was prepared. Subsequently, 140g of sweet and sour pork was filled into the storage section 18 of the pouch 10, and then the upper seal section 11a was formed to create the pouch 10 shown in Figure 5. The heat sealing conditions and the dimensions of each part of the pouch 10 were the same as those used for the evaluation of ease of opening.

[0163] Pouch 10 containing sweet and sour pork was heated in a 600W microwave oven for 160 seconds. A SHARP RE-TS3 microwave oven was used.

[0164] Next, we evaluated whether the packaging material of pouch 10 was damaged. Specifically, first, a sample of the packaging material was prepared by cutting off a portion of the packaging material. Then, the cross-section of the sample was observed using a digital microscope VHX-6000. The results are shown in the "Heat Resistance" column of Figure 6. In the "Heat Resistance" column, "good" means that the deformation of the sealant film 55 did not extend to the third stretched plastic film 53. "Not good" means that the deformation of the sealant film 55 extended to the outer surface of the surface film 15. That is, it means that the first stretched plastic film 51, the second stretched plastic film 52, and the third stretched plastic film 53 were deformed. An example of a cross-section of a sample evaluated as "good" is shown in Figure 9. An example of a cross-section of a sample evaluated as "not good" is shown in Figure 10.

[0165] (Changes in flavor) Using the packaging materials from Examples 1 to 8, a pouch 10 as shown in Figure 4 was prepared. Subsequently, 250 g of white rice porridge was filled into the storage section 18 of the pouch 10, and then the upper seal section 11a was formed to create the pouch 10 shown in Figure 5. The heat sealing conditions and the dimensions of each part of the pouch 10 were the same as those used for the evaluation of ease of opening.

[0166] The following conditions were used to retort the pouch containing the white rice porridge (10 pouches). • Method: Spray type • Retort temperature: 121℃ • Retort preparation time: 30 minutes

[0167] Next, five testers evaluated the flavor of the white rice porridge contained in pouch 10 after retort processing. The results are shown in the "Flavor Change" column of Figure 6. In the "Flavor Change" column, "good" means that three or more of the five testers did not perceive any change in the flavor of the white rice porridge. "bad" means that three or more of the five testers perceived a change in the flavor of the white rice porridge.

[0168] In the "Layer Composition" column of Figure 6, "Biaxial PET" refers to biaxially oriented PET film. "Uniaxial PET" refers to uniaxially oriented PET film. "CPP" refers to unoriented polypropylene film. The text in parentheses after "CPP" indicates the product name of the CPP. The number after the product name indicates the thickness of the CPP. "Barrier film" refers to the gas barrier coating film 63. "Vapor deposition" refers to the transparent vapor deposition layer 62. "DL" refers to the adhesive layer.

[0169] A comparison of Example 6 with the other examples shows that it is effective for the third-oriented plastic film 53 to be a biaxially oriented PET film in order to improve heat resistance. A comparison of Example 6 with Examples 3-5 shows that it is also effective for the third-oriented plastic film 53 to be a biaxially oriented PET film in order to improve drop strength.

[0170] From a comparison of Examples 4-6 with other examples, it can be seen that providing a transparent vapor-deposited layer 62 on the third stretched plastic film 53 is effective in suppressing changes in flavor. [Explanation of Symbols]

[0171] 10 pouches 11 Top 11a Upper seal section 12 Lower part 12a Lower seal section 13. First side 13x 1st side edge 14. Second side 14x 2nd side edge 15 Surface film 16 Backside film 17 Lower film 18. Detention Unit 30 First side sealing portion 31 Upper seal portion 31a Inner margin 32 Lower seal portion 32a Inner margin 33 Intermediate sealing section 33a Inner border 35 Second side seal section 36 Upper seal portion 36a Inner border 37 Lower seal portion 37a Inner margin 38 Intermediate seal section 38a Inner margin 40 First non-sealed section 41 Opening edge 45 Second non-sealed section 46 Opening edge 50 Packaging materials 50x inner 50y external surface 51 First stretched plastic film 52. Second-oriented plastic film 53 Third-Oriented Plastic Film 55 Sealant film 56 First adhesive layer 57 Second adhesive layer 58 Third adhesive layer 61 Printing layer 62 Transparent vapor deposition layer 63 Gas barrier coating film

Claims

1. A packaging material comprising, at least, a first stretched plastic film, a second stretched plastic film, a third stretched plastic film, and a sealant film in this order, The first stretched plastic film and the third stretched plastic film are biaxially oriented polyethylene terephthalate films. The second stretched plastic film is a uniaxially oriented polyethylene terephthalate film. The tensile strength of the second stretched plastic film in the vertical direction is less than the tensile strength of the second stretched plastic film in the flow direction. The sealant film is a packaging material that is an unoriented polypropylene film having a tensile elongation of 1000% or more in the flow direction and 1100% or more in the vertical direction, and a thickness of 50 μm or more.

2. A packaging material comprising, at least, a first stretched plastic film, a second stretched plastic film, a third stretched plastic film, and a sealant film in this order, The first stretched plastic film and the third stretched plastic film are biaxially oriented polyethylene terephthalate films. The second stretched plastic film is a uniaxially oriented polyethylene terephthalate film. The third stretched plastic film includes an inner surface facing the sealant film and an outer surface facing the second stretched plastic film, The packaging material comprises a transparent vapor-deposited layer located on the inner or outer surface of the third stretched plastic film. The sealant film is a packaging material that is an unoriented polypropylene film having a tensile elongation of less than 1000% in the flow direction and less than 1100% in the vertical direction, and a thickness of 60 μm or more.

3. The third stretched plastic film includes an inner surface facing the sealant film and an outer surface facing the second stretched plastic film, The packaging material according to claim 1, wherein the packaging material comprises a transparent vapor-deposited layer located on the inner surface or outer surface of the third stretched plastic film.

4. The packaging material according to claim 2 or 3, wherein the packaging material comprises a gas barrier coating film located on the transparent vapor deposition layer.

5. The first stretched plastic film includes an inner surface facing the second stretched plastic film and an outer surface located on the opposite side of the inner surface. The packaging material according to claim 1 or 2, wherein the packaging material comprises a transparent vapor-deposited layer located on the inner surface of the first stretched plastic film.

6. The packaging material according to claim 5, wherein the packaging material comprises a gas barrier coating film located on the transparent vapor deposition layer.

7. The packaging material according to claim 2, wherein the tensile strength of the second stretched plastic film in the vertical direction is less than the tensile strength of the second stretched plastic film in the flow direction.

8. A pouch in which a compartment for containing contents is defined between a surface film and a back film, The storage compartment is equipped with a steam venting mechanism that discharges steam from the storage compartment to the outside when the pressure in the storage compartment increases. A pouch wherein the surface film and the back film are made of the packaging material described in claim 1 or 2.

9. A first side sealing portion located on the first side of the pouch, which joins the inner surface of the surface film and the inner surface of the back film, A second side seal portion is located on the second side of the pouch, facing the first side in the first direction, and defines the housing portion between it and the first side seal portion, A first non-seal portion located near the top of the pouch and isolated from the housing portion by the first side seal portion, the first non-seal portion extending to reach the first side edge of the first side portion of the pouch, The first side sealing portion includes an upper sealing portion extending along the first side toward the upper part of the pouch from the first non-seal portion, a lower sealing portion extending along the first side toward the lower part of the pouch from the first non-seal portion, and an intermediate sealing portion having one end connected to the upper sealing portion and the other end connected to the lower sealing portion, and located between the housing portion and the first non-seal portion. The pouch according to claim 8, wherein the first non-sealed portion and the intermediate sealed portion constitute the steam venting mechanism.

10. The pouch is provided with an upper sealing portion located at the upper part and connected to the first side sealing portion and the second side sealing portion, The pouch according to claim 9, wherein the distance from the center point of the housing portion to the upper sealing portion is shorter than the distance from the center point to the intermediate sealing portion.

Images