Pouch

Abstract

To provide a pouch that can prevent the pouch from breaking when heated in a microwave oven and can stably release steam.SOLUTION: A pouch 10 according to an aspect of the present invention includes a packaging material 30. The packaging material 30 comprises a first biaxially oriented plastic film 31, a second biaxially oriented plastic film 32, a third biaxially oriented plastic film 33, and a sealant film 34 in this order. The sealant film 33 contains polypropylene as the main component. There are only two biaxially oriented plastic films 31, 32 in the packaging material 30. The packaging material 30 has a breaking strength of 50.0 MPa or more in one direction when measured in an environment of 100°C after being held for 1 minute in the environment of 100°C. A seal portion 15 has a seal strength of 15.0 N or less when measured in the environment of 100°C after being held for 1 minute in the environment of 100°C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a pouch. [Background technology]

[0002] Conventionally, standing pouches that can be heated in a microwave oven and can contain the contents of retort foods, frozen foods, etc., have been widely used. Such pouches are configured to stand upright in a microwave oven and are equipped with a steam venting mechanism that automatically releases steam generated during microwave heating to the outside of the pouch (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 4029590 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] When these pouches are heated in a microwave oven, excessive pressure is applied, preventing steam from escaping through the steam release mechanism, which can cause the pouch to burst. Even if the pouch doesn't burst, other parts of it may open.

[0005] This invention was made to solve the above problems. The objective is to provide a pouch that can suppress rupture during microwave heating and allows for stable steam release. [Means for solving the problem]

[0006] This invention includes the following inventions. [1] A pouch comprising packaging material and having a containment space, wherein the packaging material comprises, in this order, a first biaxially oriented plastic film, a second biaxially oriented plastic film, a third biaxially oriented plastic film, and a sealant film, wherein the first biaxially oriented plastic film is mainly composed of polyester, the second biaxially oriented plastic film is mainly composed of polyester or polyamide, and if the second biaxially oriented plastic film is mainly composed of polyester, the third biaxially oriented plastic film is mainly composed of polyester or polyamide, and if the second biaxially oriented plastic film is mainly composed of polyamide, the third biaxially oriented plastic film The packaging material comprises a pouch in which the packing film is mainly composed of polyester, the sealant film is mainly composed of polypropylene, there are only three biaxially oriented plastic films in the packaging material, the pouch is equipped with a seal portion for sealing the pouch, the seal portion is equipped with a vapor-venting seal portion configured to peel off when the pressure in the containment space increases, the pouch is configured to allow vapor to escape by peeling off the vapor-venting seal portion, the packaging material has a unidirectional breaking strength of 50.0 MPa or more when measured in a 100°C environment after being held in a 100°C environment for 1 minute, and the seal strength of the seal portion is 15.0 N or less when measured in a 100°C environment after being held in a 100°C environment for 1 minute.

[0007] [2] The pouch according to [1] above, wherein the product of the tensile elongation (%) and thickness (μm) of the sealant film in the unidirectional direction exceeds 50,000.

[0008] [3] The pouch 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 exceeds 55,000.

[0009] [4] The pouch according to any one of the above [1] to [3], wherein the sealant film comprises a propylene-ethylene block copolymer and an elastomer.

[0010] [5] The first biaxially stretched plastic film is a biaxially stretched polyethylene terephthalate film, the second biaxially stretched plastic film is a biaxially stretched polyethylene terephthalate film or a biaxially stretched nylon film, and when the second biaxially stretched plastic film is the biaxially stretched polyethylene terephthalate film, the third biaxially stretched plastic film is a biaxially stretched polyethylene terephthalate film or a biaxially stretched nylon film, and when the second biaxially stretched plastic film is the biaxially stretched nylon film, the third biaxially stretched plastic film is a biaxially stretched polyethylene terephthalate film. The pouch according to any one of the above [1] to [4].

[0011] [6] The packaging material further includes a transparent vapor deposition layer provided between the first biaxially stretched plastic film and the second biaxially stretched plastic film or between the second biaxially stretched plastic film and the third biaxially stretched plastic film, and the transparent vapor deposition layer contains a metal oxide or an inorganic oxide. The pouch according to any one of the above [1] to [5].

[0012] [7] The packaging material further includes a transparent gas barrier coating film provided on the surface of the transparent vapor deposition layer. The pouch according to [6] above.

[0013] [8] Contents are contained in the accommodation space of the pouch. The pouch according to any one of the above [1] to [7].

Advantages of the Invention

[0014] According to one aspect of the present invention, a pouch can be provided that can suppress the bursting of the pouch during heating in a microwave oven and can stably vent steam.

Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a front view of a pouch according to an 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 used in pouches. [Figure 4] Figure 4 shows how to cut a test specimen from the front of a pouch to measure the hot breaking strength of the packaging material. [Figure 5] Figure 5 shows how a test specimen for measuring the hot breaking strength of the packaging material is cut from the back of the pouch. [Figure 6] Figure 6 shows the process of measuring the hot fracture strength using a test specimen. [Figure 7] Figure 7 shows the process of cutting a test specimen from a pouch to measure the hot seal strength of the packaging material. [Figure 8] Figure 8 shows the process of measuring hot seal strength using a test specimen. [Figure 9] Figure 9 illustrates the hot seal strength (maximum tensile strength). [Modes for carrying out the invention]

[0016] Hereinafter, a pouch according to an 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 solely on the basis of differences in name. Therefore, for example, "film" is used to include components that may also be called sheets. Figure 1 is a front view of a pouch according to an embodiment, Figure 2 is a diagram illustrating the dimensions of each component of the pouch shown in Figure 1, and Figure 3 is a cross-sectional view of the packaging material used in the pouch. Figure 4 shows a test piece for measuring the hot breaking strength of the packaging material being cut from the front of the pouch, Figure 5 shows a test piece for measuring the hot breaking strength of the packaging material being cut from the back of the pouch, and Figure 6 shows the process of measuring the hot breaking strength using the test piece. Figure 7 shows a test piece for measuring the hot seal strength of the packaging material being cut from the pouch, Figure 8 shows the process of measuring the hot seal strength using the test piece, and Figure 9 is a diagram illustrating the hot seal strength (maximum tensile strength).

[0017] <<<Pouch>>> The pouch 10 shown in Figure 1 is a standing-type pouch and has a storage space 10A for containing contents. The contents are not particularly limited, but may include solids, liquids, or mixtures thereof. Examples of contents include cooked foods such as curry, stew, and soup. The cooked foods may have undergone heat sterilization treatment such as boiling or retorting. That is, the contents may include heat-sterilized foods or pressurized heat-sterilized foods. "Retorting" is a process in which the contents are filled into the pouch, the pouch is sealed, and then the pouch is heated under pressure using steam or hot water. The temperature for retorting is, for example, 120°C or higher. The term "pouch" is a concept that includes not only pouches that are empty but also pouches that are filled with contents.

[0018] The pouch 10 shown in Figure 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 Figure 1, the bottom film 13 is folded in half.

[0019] The pouch 10 has an upper part 10B, a bottom part 10C opposite to the upper part 10B, and 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 the side opposite to the first side part 10D. In this specification, the positions of "upper," "lower," "side," and "bottom" refer to the position when the pouch is standing upright.

[0020] The ratio (H1 / W1) of the height H1 (see Figure 2) of the pouch 10 to the width W1 (see Figure 2) is preferably 0.6 or more and 2.0 or less. If H1 / W1 is 0.6 or more, more contents can be contained, and if H1 / W1 is 2.0 or less, the pouch 10 can stand upright stably before opening. The height H1 of the pouch 10 is the length from the lower edge 10G to the upper edge 10F of the pouch 10 in the Y direction DRY, which is parallel to the direction in which the first side seal portion 16 described later extends. If the length of the pouch is not constant, the height of the pouch shall be the largest value. The width W1 of the pouch 10 is the length from the side edge 10H on the first side portion 10D side of the pouch 10 to the side edge 10I on the second side portion 10E in the X direction DRX, which is perpendicular to the Y direction DRY. If the width W1 of the pouch is not constant, the width of the pouch shall be the shortest value. In this embodiment, the dimensions of the pouch and the dimensions of each component constituting the pouch are all measured with the pouch in a nearly flat state without expanding the gusset portion 14, which will be described later.

[0021] As shown in Figure 1, the pouch 10 has a gusset portion 14 at its bottom 10C. By providing the gusset portion 14, it is possible to accommodate larger contents or increase the capacity of the contents, and the pouch 10 can 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 pleated portion 18 (described later), a second bottom sealing portion 21 provided on the second pleated portion 19 (described later), a third bottom sealing portion 22 provided on the sides of the first pleated portion 18 and the second pleated portion 19, and a vapor vent sealing portion 26 configured to peel off when the pressure in the containment space 10A of the pouch 10 increases. In Figure 1, the top of the pouch 10 is open. However, after the contents are filled into the storage space 10A, the pouch is heat-sealed to form an upper seal in the upper edge 10F and the upper seal area R enclosed by the dashed line in Figure 1, thereby sealing the pouch 10. When an upper seal is formed, the width W4 of the upper seal (see Figure 2) is preferably, 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 34 of the packaging material 30 constituting the front film 11 (described later) and the sealant film 34 of the packaging material 30 constituting the back film 12. The joining of the sealant films 34 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. In addition, since the first biaxially oriented plastic films cannot be heat-sealed to each other, the first pleat portion and the second pleat portion, where the first 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 notch.

[0033] The first side portion 10D of the pouch 10 is provided with a steam release mechanism 24 to release steam from inside the pouch 10 to the outside when the pressure inside the pouch 10 increases due to steam generated during heating in a microwave oven.

[0034] <<Steam release mechanism>> The steam venting mechanism 24 shown in Figure 1 consists of an unsealed first unsealed portion 25 isolated from the containment space 10A, and a steam venting seal portion 26 that isolates the first unsealed portion 25 from the containment space 10A and extends further toward the containment space 10A than the first side seal portion 16.

[0035] <First unsealed section> The first unsealed portion 25 has an opening 25A that reaches the side edge of the front film 11 and the back film 12, and is in communication with the outside through the opening 25A.

[0036] <Steam vent seal section> The steam vent seal section 26 is connected to the first side seal section 16. As shown in Figure 1, one end of the steam vent seal section 26 is connected to the upper part 16A of the first side seal section 16, and the other end is connected to the lower part 16B. This isolates the first unsealed section 25 from the containment space 10A. The width W3 of the steam vent seal section 26 (see Figure 2) is set to, for example, 2.5 mm or more and 6 mm or less.

[0037] The steam vent seal portion 26 detaches when the pressure inside the pouch 10 reaches a predetermined pressure due to heating, thereby connecting the containment space 10A with the first unsealed portion 25, and allowing steam inside the containment space 10A to be automatically released to the outside of the pouch 10 through the first unsealed portion 25. Furthermore, since the steam vent seal portion 26 protrudes further towards the containment space 10A than the first side seal portion 16, stress tends to concentrate on the steam vent seal portion 26 when the pressure inside the pouch 10 increases due to heating in a microwave oven. In addition, since delamination progresses more easily from the steam vent seal portion 26, it is possible to suppress the progression of delamination from the first side seal portion 16 and other parts.

[0038] Furthermore, the steam venting mechanism 24 only needs to be configured to allow steam to escape by peeling off the steam venting seal portion 26, and is not limited to the example described above.

[0039] Furthermore, the pouch 10 has a second unsealed portion 27 formed in the second side seal portion 17. This is provided to ensure that the first unsealed portion 25 forms an opening 25A at the side edge of the front film 11 and the back film 12 when manufacturing the pouch 10. In other words, the second unsealed portion 27 is provided to improve the manufacturing efficiency of the pouch 10. The second unsealed portion 27 reaches the side edge of the front film 11 and the back film 12 and opens. Note that the second unsealed portion 27 is not necessarily required.

[0040] <<Packaging materials>> The front film 11 and the back film 12 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 first biaxially oriented plastic film 31, a second biaxially oriented plastic film 32, a third biaxially oriented plastic film 33, and a sealant film 34 in this order. The packaging material 30 contains only three biaxially oriented plastic films. The sealant film 34 is a layer that forms the inner surface of the pouch 10. The packaging material 30 shown in Figure 3 comprises, for example, a first biaxially oriented plastic film 31, a printing layer 35, a first adhesive layer 36, a second biaxially oriented plastic film 32, a second adhesive layer 37, a third biaxially oriented plastic film 33, a third adhesive layer 38, and a sealant film 34 in this order. The packaging material may further include a functional layer that exhibits a desired function, such as a transparent gas barrier layer, between the first biaxially oriented plastic film 31 and the sealant film 34. The pouch 10 can be manufactured by continuously conveying the packaging material 30 wound into a roll.

[0041] The packaging material 30 has a unidirectional breaking strength (hot breaking strength) of 50.0 MPa or higher when measured in a 100°C environment after being held in a 100°C environment for 1 minute. The above unidirectional hot breaking strength of the packaging material 30 is preferably 51.0 MPa or higher, more preferably 53.0 MPa or higher, and even more preferably 56.0 MPa or higher. The above unidirectional hot breaking strength of the packaging material 30 in a direction perpendicular to the unidirectional direction is preferably 46.0 MPa or higher, more preferably 50.0 MPa or higher, even more preferably 53.0 MPa or higher, and most preferably 54.0 MPa or higher. The unidirectional direction of the packaging material 30 is, for example, the X direction DRX in the pouch 10 (see Figure 1), and the direction perpendicular to the unidirectional direction of the packaging material 30 may be, for example, the Y direction DRY in the pouch 10. Furthermore, 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, one direction of the packaging material 30 may correspond to the flow direction (MD), and for example, a direction perpendicular to one direction of the packaging material may correspond to the width direction (TD).

[0042] The hot breaking strength 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, the hot fracture strength of specimen S1 is 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, after holding specimen S1 in an environment of 100°C and 5% relative humidity for 1 minute, a tensile test is performed on specimen S1 in the longitudinal direction of specimen S1 at a tensile speed of 300 mm / min with an initial gripper distance D1 (see Figure 6) of 50 mm in an environment of 100°C and 5% relative humidity, and the hot fracture strength of specimen S1 is measured. The hot fracture strength of test specimen S2 is measured under the same measurement conditions as for test specimen S1. The hot fracture strength of five test specimens S1 is measured, and the average value is taken as the hot fracture strength of the packaging material 30 in the X direction (DRX). The hot fracture strength of five test specimens S2 is measured, and the average value is taken as the hot fracture strength of the packaging material 30 in the Y direction (DRY).

[0043] The packaging material 30 has a seal strength (hot seal strength) of 15.0 N or less when measured in a 100°C environment after being held in a 100°C environment for 1 minute. The hot seal strength is preferably 12.0 N or less, and more preferably 10.0 N or less. If the hot seal strength is too low, the steam vent seal portion 26 may peel off before the contents are sufficiently heated and pressurized, causing a decrease in the pressure and temperature of the containment space 10A. Considering this point, the hot seal strength of the seal portion 15 of the pouch 10 is preferably 4 N or more, and more preferably 5 N or more. Note that the seal strength of the steam vent seal portion 26 may also change due to sterilization treatment such as retort treatment, but if the pouch 10 is subjected to retort treatment, unless otherwise specified, "seal strength of the seal portion" refers to the seal strength of the seal portion of the pouch after retort treatment.

[0044] In measuring the hot seal strength of the packaging material 30, first, one pouch is prepared. From the pouch, five rectangular test pieces S3 (see Figure 7) are cut out, each with one side L3 (see Figure 7) of 15 mm and the other side L4 (see Figure 7) extending perpendicular to side L3, in a state where the front film 11 and the back film 12 are joined, including the first side seal portion 16 or the second side seal portion 17. For example, as shown in Figure 7, three test pieces S3 are cut out including the first side seal portion 16, and two test pieces S3 are cut out including the second side seal portion 17. Three test pieces S3 are cut from the first side seal portion 16 side and two from the second side seal portion 17 side, such that the other side L4 is parallel to the X direction DRX (the direction perpendicular to the direction in which the first side seal portion 16 extends), and the steam vent seal portion 26 is not included. The hot seal strength will be measured using this test specimen S3. The hot seal strength will be measured using a Tensilon universal material tester RTC-1310A (manufactured by A&D Co., Ltd.) in accordance with JIS Z1707:1997 7.5. First, the two layers of packaging material 30 in the unsealed portion of the test specimen S3 will be gripped by the grippers 53 and 54 of the tester (see Figure 8). Note that the layer structure of test specimen S3 is partially omitted in Figure 8. Then, the grippers 53 and 54 will be pulled at a speed of 300 mm / min in opposite directions perpendicular to the surface direction of the sealed portion of test specimen S3, and the maximum value of the tensile stress will be measured. The average of the maximum values ​​will be taken as the seal strength (see Figure 9). The hot seal strength will be measured after holding the test specimen S3 in an environment of 100°C and 5% relative humidity for 1 minute, and then in an environment of 100°C and 5% relative humidity. The hot seal strength of five test specimens S3 is measured, and the average value is taken as the hot seal strength of the pouch.

[0045] <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.

[0046] 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.

[0047] (First biaxially oriented plastic film) The first biaxially oriented plastic film 31 is a plastic film that is stretched in two predetermined directions. The first biaxially oriented plastic film 31 functions as a base film for giving the packaging material 30 a predetermined strength. The stretching direction of the first biaxially oriented plastic film 31 is not particularly limited. For example, the first 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 first biaxially oriented plastic film 31 is, for example, 1.05 times or more.

[0048] The first 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 first 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 first 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.

[0049] The thickness of the first 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. Alternatively, the thickness of the first biaxially oriented plastic film 31 is preferably 30 μm or less, and more preferably 25 μm or less. By making the thickness of the first biaxially oriented plastic film 31 8 μm or more, the first biaxially oriented plastic film 31 will have sufficient strength. Furthermore, by making the thickness of the first biaxially oriented plastic film 31 30 μm or less, the first biaxially oriented plastic film 31 will exhibit excellent moldability. Therefore, the process of processing the packaging material 30 to manufacture the pouch 10 can be carried out efficiently.

[0050] (Second biaxially oriented plastic film) The second biaxially oriented plastic film 32 is, for example, a base film stretched in two predetermined directions, similar to the first biaxially oriented plastic film 31. For example, the second biaxially oriented plastic film 32 may be stretched in the direction in which the side edge 10H extends and in a direction perpendicular to this direction. The second biaxially oriented plastic film 32, like the first 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 second biaxially oriented plastic film 32 is not particularly limited, similar to the case of the first biaxially oriented plastic film 31.

[0051] The second biaxially oriented plastic film 32 is preferably a biaxially oriented plastic film containing polyamide as a main component, or a biaxially oriented plastic containing polyester as a main component. In this specification, "containing polyamide as a main component" means that the biaxially oriented plastic film contains more than 50% by mass of polyamide. Examples of polyamides include aliphatic polyamides and aromatic polyamides. Examples of aliphatic polyamides include nylon such as nylon-6, nylon-6,6, and copolymers of nylon-6 and nylon-6,6, while examples of aromatic polyamides include polymetaxylene adipamide (MXD6). By containing polyamide as a main component in the second biaxially oriented plastic film 32, the puncture strength of the packaging material 30 equipped with the second biaxially oriented plastic film 32 can be increased. Examples of polyesters include the polyesters described in the section for the first biaxially oriented plastic film 31. As the second biaxially oriented plastic film 32, a biaxially oriented nylon film or a biaxially oriented polyethylene terephthalate film can be used. The biaxially oriented nylon film preferably contains 80% by mass or more of polyamide. Furthermore, the biaxially oriented nylon film is more preferably containing 90% by mass or more of polyamide, and even more preferably containing 95% or more.

[0052] When a film mainly composed of polyester is used as the second biaxially oriented plastic film 32, the thickness of the second biaxially oriented plastic film 32 can be the same as the thickness of the first biaxially oriented plastic film 31. When a film mainly composed of polyamide is used as the second biaxially oriented plastic film 32, the thickness of the second biaxially oriented plastic film 32 is preferably 12 μm or more, and more preferably 15 μm or more. Furthermore, the thickness of the second biaxially oriented plastic film 32 is preferably 30 μm or less, and more preferably 25 μm or less.

[0053] The second biaxially oriented plastic film 32 may be configured to have tear resistance in the flow direction (MD). In the following description, a biaxially oriented plastic film having tear resistance in the flow direction (MD) will also be referred to as a biaxially oriented straight-cut film. By using a biaxially oriented straight-cut film, tear resistance in the flow direction (MD) can be given to the packaging material 30. The tensile strength of the biaxially oriented straight-cut film in the flow direction (MD) is greater than the tensile strength of the biaxially oriented straight-cut film in the width direction (TD). The tensile strength of the biaxially oriented straight-cut film in the flow direction (MD) is preferably 1.05 times or more, more preferably 1.10 times or more, and even more preferably 1.20 times or more, than the tensile strength of the biaxially oriented straight-cut film in the width direction (TD). Furthermore, the tensile strength of the biaxially oriented straight-cut film in the flow direction (MD) is, for example, 200 MPa or more and 300 MPa or less.

[0054] (Third biaxially oriented plastic film) The third biaxially oriented plastic film 33 is, for example, a base film stretched in two predetermined directions, similar to the first biaxially oriented plastic film 31. For example, the third biaxially oriented plastic film 33 may be stretched in the direction in which the side edge 10H extends and in a direction perpendicular to this direction. The third biaxially oriented plastic film 33, like the first 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 third biaxially oriented plastic film 33 is not particularly limited, similar to the case of the first biaxially oriented plastic film 31.

[0055] If the second biaxially oriented plastic film 32 is mainly composed of polyester, the third biaxially oriented plastic film 33 is mainly composed of polyester or polyamide, and if the second biaxially oriented plastic film 32 is mainly composed of polyamide, the third biaxially oriented plastic film 33 is mainly composed of polyester. By including polyamide as the main component of the third biaxially oriented plastic film 33, the puncture strength of the packaging material 30 comprising the third biaxially oriented plastic film 33 can be increased.

[0056] The thickness of the third biaxially oriented plastic film 33 is the same as that of the second biaxially oriented plastic film 32, so it will be omitted here. The third biaxially oriented plastic film 33 may also be the biaxially oriented straight-cut film described above.

[0057] <Sealant film> Next, the sealant film 34 will be described. The sealant film 34 may be a single layer or a multi-layer film. Preferably, the sealant film 34 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.

[0058] 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.

[0059] The Young's modulus and tensile elongation of sealant film 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 sealant 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.

[0060] The pouch 10, which is made up of packaging material 30, is subjected to sterilization treatment such as retort processing at high temperatures. Therefore, the sealant film 34 used has heat resistance that can withstand these high-temperature treatments.

[0061] The melting point of the material constituting the sealant film 34 is preferably 150°C or higher, and more preferably 160°C or higher. By increasing the melting point of the sealant film 34, 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. The melting point of the material constituting the sealant film 34 is lower than the melting point of the resin constituting the first biaxially oriented plastic film 31, the second biaxially oriented plastic film 32, and the third biaxially oriented plastic film 33.

[0062] The sealant film 34 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.

[0063] [ka] In equation (1) above, m1, m2, and m3 represent integers greater than or equal to 1.

[0064] [ka] In equation (2) above, m and n represent integers greater than or equal to 1.

[0065] [ka] In equation (3) above, m represents an integer greater than or equal to 1.

[0066] When a mixture of polypropylene and polyethylene is used as a material with propylene as the main component, the material may have a sea-island structure. Here, "sea-island structure" refers to a structure in which polyethylene is discontinuously dispersed within a continuous region of polypropylene.

[0067] Preferably, the sealant film 34 is a single-layer film containing a propylene-ethylene block copolymer. For example, the sealant film 34 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 34 can be increased, thereby preventing the pouch 10 from rupturing due to impact during a fall. In addition, the puncture resistance of the packaging material 30 can be increased.

[0068] Furthermore, by using a propylene-ethylene block copolymer, the strength of the seal portion formed by the sealant film 34 at high temperatures, for example 100°C, i.e., the hot seal strength mentioned above, becomes extremely low compared to low temperatures, for example, the room temperature seal strength. Due to the low hot seal strength, when heating the pouch 10 using a microwave oven, the steam vent seal portion 26 is more likely to peel off, and the steam in the containment space 10A can easily escape to the outside of the pouch 10. This prevents the internal pressure of the containment space 10A from becoming excessive, thereby preventing damage to the packaging material 30 during heating.

[0069] The propylene-ethylene block copolymer includes, for example, a marine component made of polypropylene and an island component made of an ethylene-propylene copolymer rubber component. 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 34 containing the propylene-ethylene block copolymer can be adjusted by adjusting the ratio of the marine component to the island component.

[0070] 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.

[0071] The single-layer sealant film 34 further comprises a second thermoplastic resin in addition to a first thermoplastic resin consisting of a propylene-ethylene block copolymer. Examples of the second thermoplastic resin include α-olefin copolymers and polyethylene. An example of an α-olefin copolymer is linear low-density polyethylene. Examples of polyethylene include low-density polyethylene, medium-density polyethylene, and high-density polyethylene. The second thermoplastic resin can contribute to improving the impact resistance of the sealant film 34. Furthermore, by using the second thermoplastic resin, the hot seal strength can be made even lower at low temperatures, for example, at room temperature.

[0072] Low-density polyethylene has a density of 0.910 g / cm³. 3 More than 0.925g / cm 3 The following polyethylenes are used. Medium-density polyethylene has a density of 0.926 g / cm³. 3 More than 0.940g / cm 3 The following polyethylenes are used. High-density polyethylene has a density of 0.941 g / cm³. 3 More than 0.965g / cm 3 The following types of polyethylene are used. Low-density polyethylene is obtained, for example, by polymerizing ethylene at a high pressure of 1000 atmospheres or more but less than 2000 atmospheres. Medium-density polyethylene and high-density polyethylene are obtained, for example, by polymerizing ethylene at a medium or low pressure of 1 atmosphere or more but less than 1000 atmospheres.

[0073] In addition, medium-density polyethylene and high-density polyethylene may partially contain a copolymer of ethylene and an α-olefin. Also, even when ethylene is polymerized at medium or low pressure, if a copolymer of ethylene and an α-olefin is included, medium-density or low-density polyethylene can be produced. Such polyethylene is referred to as the above-mentioned linear low-density polyethylene. Linear low-density polyethylene is obtained by copolymerizing an α-olefin with a linear polymer obtained by polymerizing ethylene at medium or low pressure to introduce short-chain branches. Examples of α-olefins include 1-butene (C4), 1-hexene (C6), 4-methylpentene (C6), 1-octene (C8), and the like. The density of linear low-density polyethylene is, for example, 0.915 g / cm 3 or more and 0.945 g / cm 3 or less.

[0074] Note that the α-olefin copolymer constituting the second thermoplastic resin of the propylene-ethylene block copolymer is not limited to the above-mentioned linear low-density polyethylene. The α-olefin copolymer means a material having a structural formula shown in the following formula (4).

[0075] [Chemical formula] R 1 , R 2 are both H (hydrogen atom) or an alkyl group such as CH3 or C2H5. Also, both j and k are integers of 1 or more. Also, j is larger than k. That is, in the α-olefin copolymer shown in formula (4), the structure on the left side containing R 1 serves as the base. R 1 is, for example, H, and R 2 is, for example, C2H5.

[0076] In the sealant film 34, the mass ratio of the first thermoplastic resin made of propylene-ethylene block copolymer is higher than the mass ratio of the second thermoplastic resin containing at least α-olefin copolymer or polyethylene. For example, in a single-layer sealant film 34, the mass ratio of the first thermoplastic resin made of propylene-ethylene block copolymer is at least 51% by mass, preferably 60% by mass or more, and more preferably 70% by mass or more.

[0077] As described above, the second thermoplastic resin can contribute to improving the impact resistance of the sealant film 34. Therefore, the mechanical properties of the sealant film 34 can be adjusted by adjusting the mass ratio of the second thermoplastic resin, which contains at least an α-olefin copolymer or polyethylene, in the single-layer sealant film 34.

[0078] Furthermore, the sealant film 34 may further contain an elastomer such as a thermoplastic elastomer. By using a thermoplastic elastomer, the impact resistance and puncture resistance of the sealant film 34 can be further enhanced. In addition, by using a thermoplastic elastomer, the hot seal strength described above can be made even lower than the seal strength at low temperatures, for example, at room temperature.

[0079] Thermoplastic elastomers are, for example, hydrogenated styrene-based thermoplastic elastomers. Hydrogenated styrene-based thermoplastic elastomers have a structure consisting of polymer block A mainly composed of at least one vinyl aromatic compound and polymer block B mainly composed of at least one hydrogenated conjugated diene compound. Alternatively, thermoplastic elastomers may also be ethylene-α-olefin elastomers. Ethylene-α-olefin elastomers are low-crystallinity or amorphous copolymer elastomers, and are random copolymers of 50-90% by mass of ethylene as the main component and α-olefin as the copolymer monomer.

[0080] The content of propylene-ethylene block copolymer in the sealant film 34 is, for example, 80% by mass or more, and preferably 90% by mass or more.

[0081] 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.

[0082] The thickness of the sealant film 34 is preferably 30 μm or more, and more preferably 40 μm or more. Furthermore, the thickness of the sealant film 34 is preferably 100 μm or less, and more preferably 80 μm or less.

[0083] The single-layer sealant film 34 containing a propylene-ethylene block copolymer includes types such as ZK500, described later, which have high tensile elongation and impact resistance. Preferably, this type of sealant film 34 also has the characteristic of low hot seal strength. This makes it possible to suppress the internal pressure of the containment space 10A from becoming excessive when the pouch 10 is heated.

[0084] The tensile elongation (%) of the sealant film 34 in the flow direction (MD), measured at 25°C after being held at 25°C for 24 hours, is preferably 800% or more, more preferably 900% or more, and may be 1000% or more, or 1100% or more. Furthermore, the product of the tensile elongation (%) of the sealant film 34 in the flow direction (MD) and the thickness (μm) of the sealant film 34 is preferably greater than 50,000, more preferably 55,000 or more, or may be 60,000 or more.

[0085] The tensile elongation of the sealant film 34 in the width direction (TD), measured at 25°C after being held at 25°C for 24 hours, is preferably 1050% or more, and more preferably 1100% or less. Furthermore, the product of the tensile elongation (%) of the sealant film in the width direction (TD) and the thickness (μm) of the sealant film is preferably greater than 55000, and more preferably 60000 or more. The high tensile elongation of the sealant film 34 helps to prevent the pouch 10 from rupturing due to impacts such as drops.

[0086] The tensile modulus of the sealant film 34 in the flow direction (MD), measured at 25°C after being held at 25°C for 24 hours, is preferably 670 MPa or less, and more preferably 650 MPa or less. Furthermore, the product of the tensile modulus of the sealant film 34 in the flow direction (MD) (MPa) and the thickness of the sealant film 34 (μm) is preferably less than 35,000, and more preferably 34,000 or less.

[0087] The tensile modulus of the sealant film 34 in the width direction (TD), measured at 25°C after being held at 25°C for 24 hours, is preferably 550 MPa or less, and more preferably 500 MPa or less. Furthermore, the product of the tensile modulus of the sealant film 34 in the width direction (TD) (MPa) and the thickness of the sealant film 34 (μm) is preferably less than 28,000, and more preferably 25,000 or less.

[0088] The tensile modulus of the sealant film 34 shall be measured using the same measurement method and conditions as the tensile elongation of the sealant film 34.

[0089] <Print layer> The printing layer 35 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 35, 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.

[0090] The printed layer 35 may also contain other optional 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 effects, and their type and amount can be appropriately selected depending on the printing method, printing substrate, and printing conditions. The printed layer 35 can be formed on the first biaxially oriented plastic film 31 by a printing method such as gravure printing.

[0091] (Colorants) The colorants are not particularly limited; known pigments and dyes can be used and selected appropriately according to the desired color.

[0092] (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.

[0093] <First adhesive layer to third adhesive layer> The first adhesive layer 36 contains an adhesive for bonding the first biaxially oriented plastic film 31 and the second biaxially oriented plastic film 32 by dry lamination. The second adhesive layer 37 contains an adhesive for bonding the second biaxially oriented plastic film 32 and the third biaxially oriented plastic film 33 by dry lamination. The third adhesive layer 38 contains an adhesive for bonding the third biaxially oriented plastic film 33 and the sealant film 34 by dry lamination.

[0094] The adhesives constituting the first adhesive layer 36, the second adhesive layer 37, and the third adhesive layer 38 are each produced from an adhesive composition prepared by mixing a first composition containing a main component and a solvent with a second composition containing a curing agent and a solvent. Specifically, the adhesive includes a cured product produced by the reaction of the main component and the solvent in the adhesive composition.

[0095] 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.

[0096] 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.

[0097] The thickness of the first adhesive layer 36, the second adhesive layer 37, and the third adhesive layer 38 is preferably 2 μm or more, and more preferably 3 μm or more. Furthermore, the thickness of the first adhesive layer 36, the second adhesive layer 37, and the third adhesive layer 38 is preferably 6 μm or less, and more preferably 5 μm or less.

[0098] 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 third adhesive layer 38 is in contact with the sealant film 34. Therefore, if the third adhesive layer 38 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 34. 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 third adhesive layer 38. This makes it possible to prevent components unsuitable for food use caused by the third adhesive layer 38 from adhering to the contents.

[0099] <Gas barrier film> The first biaxially oriented plastic film 31, the second biaxially oriented plastic film 32, or the third biaxially oriented plastic film 33 may be a gas barrier film having at least a transparent vapor deposition layer. The gas barrier film may further include a transparent gas barrier coating film formed on the surface of the transparent vapor deposition layer and having transparency.

[0100] The transparent vapor-deposited layer functions as a gas barrier layer that prevents the permeation of oxygen gas and water vapor. Two or more transparent vapor-deposited layers may be provided. If there are two or more transparent vapor-deposited layers, each may have the same composition or different compositions. Methods for forming the transparent vapor-deposited layer include, 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. Specifically, the vapor-deposited layer can be formed on a deposition roller using a roller-type vapor deposition apparatus.

[0101] The transparent vapor-deposited layer is composed of a transparent inorganic material. Examples of inorganic materials include metal oxides and inorganic oxides. Examples of metal oxides include oxides of metals such as aluminum (Al), magnesium (Mg), calcium (Ca), potassium (K), tin (Sn), sodium (Na), boron (B), titanium (Ti), lead (Pb), zirconium (Zr), and yttrium (Y). Examples of inorganic oxides include silicon (Si) oxide. As the inorganic material constituting the transparent vapor-deposited layer, aluminum oxide (aluminum oxide) or silicon oxide is preferred.

[0102] The thickness of the transparent vapor-deposited layer is preferably 40 Å to 130 Å, and more preferably 50 Å to 120 Å.

[0103] A transparent gas barrier coating is a layer that functions as a layer that suppresses the permeation of oxygen gas and water vapor. The transparent gas barrier coating is generally formulated with the formula R 3 n M(OR 4 ) m (However, in the formula, R 3 , R 4The transparent gas barrier composition is obtained by polycondensing a polyvinyl alcohol resin and / or ethylene-vinyl alcohol copolymer as described above, in the presence of a sol-gel catalyst, acid, water, and an organic solvent. (where represents an organic group having 1 to 8 carbon atoms, M represents a metal atom, n represents an integer of 0 or more, m represents an integer of 1 or more, and n+m represents the valence of M.)

[0104] The above general formula R 3 n M(OR 4 ) m As the alkoxide represented by , at least one of the following can be used: a partially hydrolyzed alkoxide or a condensate of the hydrolyzed alkoxide. Furthermore, as the partially hydrolyzed alkoxide, it is not necessary for all alkoxy groups to be hydrolyzed; it may be a product in which one or more alkoxy groups are hydrolyzed, or a mixture thereof. As the condensate of the hydrolyzed alkoxide, dimers or more of the partially hydrolyzed alkoxide, specifically 2 to 6-mers, can be used.

[0105] The above general formula R 3 n M(OR 4 ) m In the alkoxide represented by , the metal atom represented by M can be silicon, zirconium, titanium, aluminum, or others. In this embodiment, 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.

[0106] Furthermore, the above general formula R 3 n M(OR 4 ) m In the alkoxide represented by R, 3Specific 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. 3 n M(OR 4 ) m In the alkoxide represented by R, 4 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.

[0107] 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 this embodiment, organoalkoxysilanes having epoxy groups are particularly preferred, and specifically, for example, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, etc., can be used. One or more of the above silane coupling agents may be used.

[0108] 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. Biaxially oriented PET film / Printing layer / Adhesive layer / Biaxially oriented nylon film / Adhesive layer / Biaxially oriented PET film / Adhesive layer / Sealant film Biaxially oriented PET film / Printed layer / Adhesive layer / Biaxially oriented PET film / Adhesive layer / Biaxially oriented nylon film / Adhesive layer / Sealant film Biaxially oriented PET film / Printed layer / Adhesive layer / Biaxially oriented PET film / Adhesive layer / Biaxially oriented PET film / Adhesive layer / Sealant film Biaxially oriented PET film / Printed layer / Adhesive layer / Biaxially oriented nylon film / Adhesive layer / Biaxially oriented straight-cut PET film / Adhesive layer / Sealant film Biaxially oriented PET film / Printed layer / Adhesive layer / Biaxially oriented PET film / Adhesive layer / Biaxially oriented straight-cut nylon film / Adhesive layer / Sealant film Biaxially oriented PET film / Printed layer / Adhesive layer / Biaxially oriented PET film / Adhesive layer / Biaxially oriented straight-cut PET film / Adhesive layer / Sealant film Biaxially oriented PET film / Transparent vapor deposition layer / Transparent gas barrier coating film / Printed layer / Adhesive layer / Biaxially oriented nylon film / Adhesive layer / Biaxially oriented PET film / Adhesive layer / Sealant film Biaxially oriented PET film / Transparent vapor deposition layer / Transparent gas barrier coating film / Printed layer / Adhesive layer / Biaxially oriented PET film / Adhesive layer / Biaxially oriented nylon film / Adhesive layer / Sealant film Biaxially oriented PET film / Printed layer / Adhesive layer / Transparent gas barrier coating film / Transparent vapor deposition layer / Biaxially oriented PET film / Adhesive layer / Biaxially oriented PET film / Adhesive layer / Sealant film

[0109] According to this embodiment, the hot breaking strength in one direction (e.g., the flow direction (MD)) measured in a 100°C environment after being held for 1 minute is 50.0 MPa or higher, indicating high hot breaking strength. This suppresses the tearing of the pouch 10 when heated in a microwave oven.

[0110] When the seal strength of the steam vent seal portion of a pouch heated to a high temperature in a microwave oven becomes moderately low, the steam vent seal portion becomes easier to peel off based on the force exerted by the pressure of the water vapor generated in the containment space. In other words, the steam vent seal portion peels off at lower pressures. According to this embodiment, the hot seal strength of the pouch 10 measured in a 100°C environment is 15.0 N or less, so the hot seal strength is low, which makes it easier for steam to escape from the steam vent seal portion 26, and allows for stable steam removal. [Examples]

[0111] To illustrate the present invention in detail, examples are given below, but the present invention is not limited to these examples.

[0112] <Example 1> First, three sheets of 12 μm thick biaxially oriented polyethylene terephthalate film (product name "E5100", manufactured by Toyobo Co., Ltd.) were prepared as the first, second, and third biaxially oriented plastic films. Next, a printed layer was formed on one of these films. The thickness of the printed layer was 1.0 μm. In addition, an unoriented polypropylene film (product name "ZK500", manufactured by Toray Film Processing Co., Ltd.) with a thickness of 60 μm was prepared as a sealant film. ZK500 contained the aforementioned propylene-ethylene block copolymer and elastomer.

[0113] ZK500 has a higher tensile elongation compared to general unoriented polypropylene films. Specifically, the tensile elongation of ZK500 in the flow direction (MD) is 1180% when the thickness is 50 μm and 1100% when the thickness is 60 μm. In the width direction (TD), the tensile elongation of ZK500 is 1240% when the thickness is 50 μm and 1150% when the thickness is 60 μm. Therefore, the product of the tensile elongation (%) and thickness (μm) of ZK500 in the flow direction is 59000 when the thickness is 50 μm and 66000 when the thickness is 60 μm. In the width direction, the product of the tensile elongation (%) and thickness (μm) of ZK500 is 62000 when the thickness is 50 μm and 69000 when the thickness is 60 μm.

[0114] Next, a packaging material was prepared by dry lamination, sequentially laminating a biaxially oriented polyethylene terephthalate film, a printed layer, a first adhesive layer, a biaxially oriented polyethylene terephthalate film, a second adhesive layer, a biaxially oriented polyethylene terephthalate film, a third adhesive layer, and an unstretched polypropylene film. For the first to third 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, second, and third adhesive layers was 3.0 μm.

[0115] 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 become the bottom film 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 a 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.

[0116] 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 side seal portion, a second side seal portion, a first pleat portion having a first bottom seal portion, a second pleat portion having a second bottom seal portion, and a steam vent seal portion. This resulted in a pouch with an open top. In the area of ​​the through-hole, since there was no folded bottom film packaging material, the front film packaging material and the back film packaging material fused directly 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

[0117] Subsequently, 200 ml of water was filled into each 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, each pouch was subjected to retort processing under the following conditions to produce pouches 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

[0118] In the pouch according to the first example that was produced, the pouch height H1 was 160 mm, the pouch width W1 was 147 mm, the height H2 of the first pleat and the height of the second pleat were 46 mm each, the width W2 of the first side seal and the second side seal was 7.0 mm, the width W3 of the steam vent seal was 5 mm, and the width W4 of the top seal was 10.0 mm.

[0119] <Example 2> In Example 2, the packaging material was prepared in the same manner as in Example 1, except that a 15 μm thick biaxially oriented nylon film (product name "Bonel QC," Kojin Film & Chemicals Co., Ltd.) was used as the second biaxially oriented plastic film, instead of a 12 μm thick biaxially oriented polyethylene terephthalate film (product name "E5200," manufactured by Toyobo 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.

[0120] <Example 3> In Example 3, the packaging material was prepared in the same manner as in Example 1, except that a 15 μm thick biaxially oriented nylon film (product name "Bonel QC," Kojin Film & Chemicals Co., Ltd.) was used as the third biaxially oriented plastic film, instead of a 12 μm thick biaxially oriented polyethylene terephthalate film (product name "E5200," 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.

[0121] <Comparative Example 1> In Comparative Example 1, the packaging material was prepared in the same manner as in Example 1, except that a 70 μm thick unoriented polypropylene film (product name "ZK99S," 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.

[0122] <Hot fracture strength measurement> The breaking strength (hot breaking strength) at 100°C of the packaging material constituting the retort-treated pouches according to Examples 1-3 and Comparative Example 1 was measured. First, one retort-treated pouch according to Examples 1-3 and Comparative Example 1 was prepared. As shown in Figure 4, five rectangular test pieces S1 were cut from the front surface of each pouch, excluding the seal portion, with one side L1 of 15 mm and the other side L2 extending perpendicular to side L1 of 100 mm. The test pieces S1 were cut so that the other side L2 was parallel to the X direction DRX (the direction perpendicular to the direction in which the first side seal portion extends). Next, as shown in Figure 5, five rectangular test pieces S2 were cut from the back surface of each pouch, excluding the seal portion, with one side L1 of 15 mm and the other side L2 extending perpendicular to side L1 of 100 mm. Test specimen S2 was cut so that its other side L2 was parallel to the Y direction DRY (the direction parallel to the direction in which the first side seal extends). Then, using a Tensilon universal material testing machine RTC-1310A (manufactured by A&D Co., Ltd.), each test specimen S1 was held for 1 minute in an environment of 100°C and 5% relative humidity. After that, a tensile test was performed in an environment of 100°C and 5% relative humidity with an initial gripping distance D1 of 50 mm and a tensile speed of 300 mm / min, and the hot breaking strength of test specimen S1 was measured. The hot breaking strength of test specimen S2 was measured in the same manner. The hot breaking strength of five test specimens S1 was measured, and the average value was taken as the hot breaking strength in the X direction of the packaging material. Similarly, the hot breaking strength of five test specimens S2 was measured, and the average value was taken as the hot breaking strength in the Y direction of the packaging material.

[0123] <Hot seal strength measurement> The seal strength (hot seal strength) at 100°C was measured for the retort-treated pouches according to Examples 1-3 and Comparative Example 1. First, one retort-treated pouch according to Examples 1-3 and Comparative Example 1 was prepared. For each pouch, five rectangular test pieces S3 were cut out, each with a side L3 of 15 mm and another side L4 extending perpendicular to side L3 of 70 mm, including the first side seal portion and with the front and back films joined together. Specifically, as shown in Figure 7, three test pieces S3 were cut out including the first side seal portion, and two test pieces S3 were cut out including the second side seal portion. The test pieces S3 were cut so that the other side L4 was parallel to the X direction DRX (the direction perpendicular to the direction in which the first side seal portion extends), and so as not to include the steam vent seal portion. The hot seal strength was measured using these test pieces. The hot seal strength was measured using a Tensilon universal material tester RTC-1310A (manufactured by A&D Co., Ltd.) in accordance with JIS Z1707:1997 7.5. First, two pieces of packaging material in the unsealed portion of the test specimen were each gripped with the grippers of the tensile tester. Then, each gripper was pulled at a speed of 300 mm / min in opposite directions perpendicular to the surface direction of the sealed portion of test specimen S3, and the maximum value of the tensile stress was measured. The average of the maximum values ​​was then taken as the seal strength. The hot seal strength was measured by holding the specimens in an environment of 100°C and 5% relative humidity for 1 minute, and then returning to an environment of 100°C and 5% relative humidity. The hot seal strength was measured for five or more test specimens S3, and the average value was taken as the hot seal strength of the pouch.

[0124] The composition of the packaging materials and the evaluation results are shown in Table 1 below. [Table 1]

[0125] The results are described below. As shown in Table 1, the packaging materials constituting the pouches in Examples 1 to 3 have higher hot breaking strength in the X direction compared to the packaging material constituting the pouch in Comparative Example 1. Therefore, even if the pouch expands due to steam during heating in a microwave oven, it is possible to suppress the pouch from bursting. In addition, the packaging materials constituting the pouches in Examples 1 to 3 have lower hot seal strength compared to the packaging material constituting the pouch in Comparative Example 1. This allows steam to escape more easily from the steam vent seal, enabling stable steam release. [Explanation of Symbols]

[0126] 10... Pouch 10A...Accommodation space 11…Front surface film 12…Backside film 13…Bottom film 15...Seal part 26... Steam vent seal section 30...Packaging materials 31…First biaxially oriented plastic film 32…Second biaxially oriented plastic film 33…Third biaxially oriented plastic film 34...Sealant film

Claims

1. A pouch containing packaging material and having a storage space, The packaging material comprises a first biaxially oriented plastic film, a second biaxially oriented plastic film, a third biaxially oriented plastic film, and a sealant film in this order. The first biaxially oriented plastic film is mainly composed of polyester, The second biaxially oriented plastic film is a film mainly composed of polyamide (excluding stretched polyamide films that include a first layer made of polyester, a second layer made of polyamide, and a third layer made of polyester), The third biaxially oriented plastic film is mainly composed of polyester, The sealant film is mainly composed of polypropylene, The aforementioned packaging material contains only three biaxially oriented plastic films. The pouch is equipped with a sealing portion for sealing the pouch, The sealing portion includes a vapor venting sealing portion configured to peel off due to an increase in the pressure of the containment space, The pouch is configured such that the steam can escape by peeling off the steam vent seal portion. The packaging material, after being held in a 100°C environment for 1 minute, has a unidirectional breaking strength of 50.0 MPa or more when measured in a 100°C environment. A pouch in which the seal strength of the sealed portion, measured in a 100°C environment after being held in a 100°C environment for 1 minute, is 15.0 N or less.

2. A pouch containing packaging material and having a storage space, The packaging material comprises a first biaxially oriented plastic film, a second biaxially oriented plastic film, a third biaxially oriented plastic film, and a sealant film in this order. The first biaxially oriented plastic film is mainly composed of polyester, The second biaxially oriented plastic film is mainly composed of polyester, The third biaxially oriented plastic film is a film mainly composed of polyamide (excluding stretched polyamide films that include a first layer made of polyester, a second layer made of polyamide, and a third layer made of polyester), The sealant film is mainly composed of polypropylene, The aforementioned packaging material contains only three biaxially oriented plastic films. The pouch is equipped with a sealing portion for sealing the pouch, The sealing portion includes a vapor venting sealing portion configured to peel off due to an increase in the pressure of the containment space, The pouch is configured such that the steam can escape by peeling off the steam vent seal portion. The packaging material, after being held in a 100°C environment for 1 minute, has a unidirectional breaking strength of 50.0 MPa or more when measured in a 100°C environment. A pouch in which the seal strength of the sealed portion, measured in a 100°C environment after being held in a 100°C environment for 1 minute, is 15.0 N or less.

3. The pouch according to claim 1 or 2, wherein the product of the tensile elongation (%) and thickness (μm) of the sealant film in the aforementioned unidirectional direction exceeds 50,000.

4. The pouch according to any one of claims 1 to 3, wherein the product of the tensile elongation (%) and thickness (μm) of the sealant film in a direction perpendicular to the aforementioned one direction exceeds 55,000.

5. The pouch according to any one of claims 1 to 4, wherein the sealant film comprises a propylene-ethylene block copolymer and an elastomer.

6. The pouch according to claim 1, wherein the first biaxially oriented plastic film is a biaxially oriented polyethylene terephthalate film, the second biaxially oriented plastic film is a biaxially oriented nylon film, and the third biaxially oriented plastic film is a biaxially oriented polyethylene terephthalate film.

7. The pouch according to claim 2, wherein the first biaxially oriented plastic film is a biaxially oriented polyethylene terephthalate film, the second biaxially oriented plastic film is a biaxially oriented polyethylene terephthalate film, and the third biaxially oriented plastic film is a biaxially oriented nylon film.

8. The pouch according to any one of claims 1 to 7, wherein the packaging material further comprises a transparent vapor deposition layer provided between the first biaxially oriented plastic film and the second biaxially oriented plastic film or between the second biaxially oriented plastic film and the third biaxially oriented plastic film, and the transparent vapor deposition layer comprises a metal oxide or an inorganic oxide.

9. The pouch according to claim 8, wherein the packaging material further comprises a transparent gas barrier coating film provided on the surface of the transparent vapor deposition layer.

10. The pouch according to any one of claims 1 to 9, wherein the packaging material further comprises a printed layer provided on the side of the first biaxially oriented plastic film that is on the side of the second biaxially oriented plastic film.

11. The pouch according to any one of claims 1 to 10, wherein the contents are contained in the containment space of the pouch.

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