Microwave packaging bag and method for manufacturing a microwave packaging bag

Abstract

To suppress the occurrence of bursting or popping sounds when heating in a microwave oven. [Solution] The microwave packaging bag has a sealed portion formed by heat-sealing at least a portion of the peripheral edge of a laminated sheet arranged front to back, and a vent portion formed in a portion of the sealed portion. The laminated sheet has a base layer, an anchor coat layer, a heat-adhesive resin layer, and an extruded resin layer formed between the anchor coat layer and the heat-adhesive resin layer. The vent portion has an easily peelable portion formed in a portion of the anchor coat layer and having a lower density than other portions, and a plurality of holes that penetrate at least the base layer in the thickness direction.

Description

Technical Field

[0001] The present invention relates to a packaging bag for a microwave oven and a method for manufacturing the packaging bag for a microwave oven.

Background Art

[0002] There is a packaging bag made of a plastic film, which contains food and is sealed and then put into circulation in a sealed state. Among this type of packaging bag, there is one that can correspond to a microwave oven and can be directly heated in the microwave oven in a sealed state. When heating a sealed packaging bag in a microwave oven, the internal pressure of the packaging bag increases and it bulges due to the water vapor evaporated from the food by heating and the thermal expansion of the air inside the packaging bag.

[0003] In a packaging bag corresponding to a microwave oven, an invention has been proposed in which a foamed ink layer composed of foamed ink is laminated as an intermediate layer on a portion for releasing the pressure of the plastic film, and the structure is configured to extract steam from the foamed ink layer (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the case of a structure in which a foamed ink layer is formed in the intermediate layer of the plastic film, when a material that is easy to stretch is selected for the base material layer among the two resin layers sandwiching the foamed ink layer, especially when the base material layer is a polyolefin-based resin, it may rupture.

[0006] The present invention aims to provide a microwave packaging bag in which, even if the base material layer is made of a material that easily expands with increasing temperature, such as a polyolefin resin, when the internal pressure rises during microwave heating, the bag is configured to reliably release internal steam and air to the outside, thereby suppressing the occurrence of bursting or popping noises. [Means for solving the problem]

[0007] To achieve the above objective, the microwave packaging bag of the present invention has a storage section for storing contents, a sealed section formed by heat-sealing at least a portion of the peripheral edge of laminated sheets arranged front to back, and a permeable section formed in a part of the sealed section that allows steam from the storage section to pass through. The laminated sheet has a base layer, an anchor coat layer formed on the inside of the base layer and formed by printing, a heat-adhesive resin layer formed inside the anchor coat layer, and an extruded resin layer formed between the anchor coat layer and the heat-adhesive resin layer, and the permeable section has an easily peelable section formed in a part of the anchor coat layer and having a lower density than other parts of the anchor coat layer, and a plurality of holes formed in the portion of the laminated sheet constituting the permeable section that penetrate at least the base layer in the thickness direction. [Effects of the Invention]

[0008] According to the microwave packaging bag of the present invention, when the internal pressure increases during heating in a microwave oven, the steam and air inside are quickly released, thereby suppressing the occurrence of bursting or popping noises. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a rear view of an example of a microwave-safe packaging bag. [Figure 2] Figure 2 is an exploded perspective view of the microwave packaging bag shown in Figure 1. [Figure 3] Figure 3 is a plan view of the resin sheet used in the packaging bag shown in Figure 1. [Figure 4]Figure 4 illustrates the state of the raw material before it is wound up and the state of it being unwound before it is formed into a resin sheet. [Figure 5] Figure 5 is a cross-sectional view of the vicinity of the vapor-permeable portion of the resin sheet in the first embodiment. [Figure 6] Figure 6 is an enlarged cross-sectional view showing the steam vent portion of the microwave packaging bag of the first embodiment. [Figure 7] Figure 7 is a magnified view of the easily peeled area. [Figure 8] Figure 8 is a flowchart showing an example of the manufacturing process for microwaveable packaging bags. [Figure 9] Figure 9 is a schematic diagram showing the process of forming the anchor coat layer. [Figure 10] Figure 10 is a cross-sectional view of the vicinity of the vapor-permeable portion of the resin sheet in Modification Example 1. [Figure 11] Figure 11 is a cross-sectional view of the vicinity of the vapor-permeable section of the resin sheet in Modification Example 2. [Figure 12] Figure 12 is an enlarged cross-sectional view of the steam vent portion of the microwave packaging bag according to the second embodiment. [Figure 13] Figure 13 is an enlarged cross-sectional view of the steam-permeable portion of a microwave-safe packaging bag, a modified example of the second embodiment. [Figure 14] Figure 14 shows a modified example of the shape of the holes in the steam passage section. [Figure 15] Figure 15 shows a modified example of the shape of the holes in the steam passage section. [Modes for carrying out the invention]

[0010] <First Embodiment> Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a rear view of an example of a microwave oven packaging bag 1. Figure 2 is an exploded perspective view of the microwave oven packaging bag 1 shown in Figure 1. Figure 3 is a plan view of the resin sheet 10 used in the packaging bag shown in Figure 1. Figure 4 is a diagram illustrating the state in which the raw material roll 20 is wound and unwound before it is formed into the resin sheet 10.

[0011] The packaging bag 1 for a microwave oven is a so-called pillow-type packaging bag and is rectangular when viewed from the back. The packaging bag 1 for a microwave oven has a back seal portion 21 and an end seal portion 22. The back seal portion 21 and the end seal portion 22 are formed by thermally bonding a part of the resin sheet 10 that constitutes the packaging bag 1 for a microwave oven. The back seal portion 21 is formed at the center in the short side direction of the back surface portion of the packaging bag 1 for a microwave oven and extends in the longitudinal direction. The end seal portion 22 extends along the sides at both ends in the longitudinal direction of the packaging bag 1 for a microwave oven.

[0012] As shown in FIGS. 2 and 3, the packaging bag 1 for a microwave oven is composed of a single rectangular resin sheet 10. The resin sheet 10 has a first strip portion 101 disposed at both ends in the longitudinal direction and formed along the short side, and a second strip portion 102 disposed at both ends in the short side direction and formed along the long side.

[0013] The resin sheet 10 is bent so that the heat-adhesive resin layers 12 of the first strip portions 101 at both ends in the longitudinal direction come into contact with each other. Then, the first strip portions 101 are heated, pressurized, and thermally bonded. As a result, the resin sheet 10 is formed into a cylindrical body 100 in which the back seal portion 21 is formed. In the cylindrical body 100, the second strip portions 102 are disposed at both openings (see FIG. 2).

[0014] Then, the content S is disposed inside the cylindrical body 100, the heat-adhesive resin layers 12 of the second strip portions 102 disposed at both openings of the cylindrical body 100 are brought into contact with each other, and the second strip portions 102 are thermally bonded by heating and pressurizing. As a result, the end seal portion 22 is formed. As a result, the packaging bag 1 for a microwave oven in which the content S is accommodated and sealed in the accommodation portion 103 is formed.

[0015] When the microwaveable packaging bag 1 is viewed from the front and back, a steam-permeable portion 23 is formed at the point where the back seal portion 21 of the end seal portion 22 intersects with the end seal portion 22. More specifically, a back seal portion 21 is formed on a part of the end seal portion 22. The end seal portion 22 is formed by heat-bonding two second strip-shaped portions 102, one at a time. The steam-permeable portion 23 is formed on the second strip-shaped portion 102 on the side of the end seal portion 22 opposite to the side where the back seal portion 21 is located.

[0016] As shown in Figure 2, a steam passage section 23 is formed in the longitudinal center of the second strip-shaped section 102. The steam passage section 23 is configured to release air and steam from inside the containment section 103 to the outside when the internal pressure of the containment section 103 rises. The detailed configuration of the steam passage section 23 will be described later.

[0017] Next, the detailed configuration of the resin sheet 10 will be described. Figure 5 is a cross-sectional view of the vicinity of the steam-permeable portion 23 of the resin sheet 10 of the first embodiment. The resin sheet 10 has a laminated structure in which a heat-adhesive resin layer 12 is laminated on the inner surface. As shown in Figure 5, the resin sheet 10 has a structure in which a base layer 11, an extruded resin layer 14, an anchor coat layer 13, and a heat-adhesive resin layer 12 are laminated in order from the outside to the inside of the microwave packaging bag 1.

[0018] The base layer 11 is formed, for example, from polypropylene (PP) with a thickness of approximately 20 μm. The polypropylene constituting the base layer 11 can be, for example, a uniaxially or biaxially oriented polypropylene (OPP) film. The polypropylene (OPP) film used in the base layer 11 of this embodiment has, for example, a breaking strength in the MD direction of 100 MPa and an elongation of 300% at a temperature of 80°C. Alternatively, it has a breaking strength in the MD direction of 80 MPa and an elongation of 400% at a temperature of 100°C.

[0019] The heat-adhesive resin layer 12 is formed, for example, from polyethylene (PE) with a thickness of approximately 40 μm. Examples of polyethylene constituting the heat-adhesive resin layer 12 include linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE). Furthermore, inorganic agents such as titanium dioxide and carbon black may be contained in these films. This allows for light-shielding properties to be imparted to the laminate. The heat-adhesive resin layer 12, for example, has a tensile elongation at break in the MD direction of 10%-100% resin at a 100°C environment, and is characterized by being relatively difficult to stretch and prone to breakage in high-temperature environments.

[0020] The anchor coat layer 13 is formed from, for example, polyethyleneimine with a thickness of approximately 0.1-1 μm. The extruded resin layer 14 is a polyethylene (PE) layer of approximately 10 μm-20 μm, formed by extruded sandwich lamination. The extruded resin layer 14 is made of the same material as the heat-adhesive resin layer 12. When the base layer 11 and the heat-adhesive resin layer 12 are laminated via the extruded resin layer 14, heating and pressurizing are applied to form the resin sheet 10. Furthermore, the heating and pressurizing at this time bond the anchor coat layer 13 and the extruded resin layer 14. Since the extruded resin layer 14 and the heat-adhesive resin layer 12 are made of the same material, the heating and pressurizing bond the extruded resin layer 14 to the heat-adhesive resin layer 12. In the resin sheet 10, the base layer 11 and the heat-adhesive resin layer 12 are bonded by the anchor coat layer 13 and the extruded resin layer 14.

[0021] In the resin sheet 10, a printing layer 15 for printing patterns, etc., is formed at a predetermined position on the lower surface (heat-adhesive resin layer 12 side) of the base material layer 11. The printing layer 15 may also be provided on the upper surface (outside) of the base material layer 11. The printing layer 15 is formed to a thickness of approximately 1 μm to 3 μm by ink placed at a predetermined position on the base material layer 11. On the lower surface (inside) of the base material layer 11, a layer with a transparent vapor-deposited film, a barrier coat layer using polyvinyl alcohol, etc., may be formed. Examples of transparent vapor-deposited films include those formed from silica or alumina.

[0022] As shown in Figure 4, the resin sheet 10 is formed by cutting a continuous, long roll of raw material 20 with the same layer structure at a predetermined pitch P. When the raw material 20 is cut at the predetermined pitch P, the portion adjacent to the adjacent resin sheet 10 is the second strip portion 102. The raw material 20 is provided as a roll of raw material 201 wound in a roll shape. The resin sheet 10 is formed by pulling the raw material 20 from the roll of raw material 201 and cutting it. The direction in which the raw material 20 is pulled from the roll of raw material 201 is defined as the film pulling direction (MD direction), and the direction perpendicular to the MD direction is defined as the TD direction.

[0023] In the resin sheet 10, a vapor-permeable portion 23 is formed in the center of the second strip-shaped portion 102 in the TD direction. The breaking strength of the base layer 11 of the resin sheet 10 in the MD direction is different from the breaking strength in the TD direction. More specifically, the breaking strength of the base layer 11 in the TD direction is higher than the breaking strength in the MD direction. Also, the elongation of the base layer 11 in the MD direction is formed to be greater than the elongation in the TD direction. Furthermore, the breaking strength of the base layer 11 in the MD and TD directions decreases with increasing temperature, while the elongation (deformation) increases with increasing temperature.

[0024] As shown in Figure 3, the resin sheet 10 constituting the microwave packaging bag 1 is formed such that end seal portions 22 are arranged at both ends in the MD direction. When the microwave packaging bag 1 is heated, the base material layer 11 of the resin sheet 10 stretches more in the MD direction than in the TD direction and is more prone to tearing in the MD direction.

[0025] Next, the structure of the steam-permeable portion 23 of the resin sheet will be described. Figure 6 is an enlarged cross-sectional view of the steam-permeable portion of the microwaveable packaging bag of the first embodiment. Figure 7 is an enlarged view of the easily peelable portion 16 formed in the steam-permeable portion 23.

[0026] As shown in Figures 5 and 6, an easily peelable portion 16 is formed in the same layer as the anchor coat layer 13 in the steam-permeable portion 23. The easily peelable portion 16 is formed of a patterned anchor coat. A patterned anchor coat is a configuration in which the anchor coat is formed in a predetermined pattern.

[0027] As shown in Figure 7, the patterned anchor coat Ptn in the easily peelable section 16 has a dotted structure in which dotted sections 161, each composed of anchor coat material arranged in a dotted (columnar) pattern, are arranged in the MD and TD directions. In the easily peelable section 16, the density of the anchor coat material is lower than that of the anchor coat layer 13 formed in the same layer. Therefore, the adhesive strength between the heat-adhesive resin layer 12 and the substrate layer 11 is lower in the area where the easily peelable section 16 is formed compared to the area where the anchor coat layer 13 is formed. In other words, the easily peelable section 16 can be described as an area of ​​the anchor coat layer 13 with a lower density of anchor coat material. In this embodiment, the easily peelable section 16 is configured to be arranged throughout the entire vapor-permeable section 23, but it is not limited to this configuration. For example, the easily peelable section 16 may be formed in a part of the vapor-permeable section 23.

[0028] Multiple holes 3 are formed in the steam-permeable section 23, penetrating the base layer 11 and the easily peelable section 16 in the thickness direction. For example, the holes 3 are cylindrical and penetrate from the upper surface (outer surface) to the lower surface (inner surface) of the base layer 11. Note that the shape of the holes 3 is just an example and is not limited to a cylindrical shape. In addition, in the resin sheet 10 of this embodiment, the holes 3 also penetrate the easily peelable section 16. Note that the holes 3 may not reach the easily peelable section 16, and a portion may be formed in the easily peelable section 16, that is, the ends of the holes 3 may reach the middle part of the easily peelable section 16. The holes 3 only need to penetrate at least the base layer 11. However, as will be described in detail later, it is preferable for the holes 3 to penetrate the easily peelable section 16 for manufacturing purposes.

[0029] In the steam-permeable section 23, the multiple holes 3 are arranged at intervals in the MD direction and the TD direction. Some or all of the holes 3 are provided so as to penetrate the easy-peel section 16 in the thickness direction of the resin sheet 10. In the microwave packaging bag 1, heating generates steam inside the containment section 103 and the gas filled inside expands. As a result, the base layer 11 and the anchor coat layer 13 deform in the MD direction and the TD direction. Because the holes 3 are formed in the base layer 11 and the anchor coat layer 13, the displacement in the MD direction and the TD direction due to the deformation of the base layer 11 and the anchor coat layer 13 is discontinuous due to the holes 3.

[0030] In this way, because the easily peelable portion 16 and the multiple holes 3 are formed, the heat-adhesive resin layer 12 and the base material layer 11 are more easily separated in the steam-permeable portion 23 compared to other parts of the end seal portion 22.

[0031] <Manufacturing process for microwaveable packaging bag 1> The manufacturing process of microwave packaging bag 1 will be explained with reference to the drawings. Figure 8 is a flowchart showing an example of the manufacturing process of microwave packaging bag 1. As shown in Figure 7, a printed layer 15 is formed on the lower surface of the resin film 111 that constitutes the base layer 11 made of biaxially oriented polypropylene by printing (printing process: S101).

[0032] An anchor coat layer 13 is formed on the lower surface of the substrate layer 11 on which the printed layer 15 is formed (anchor coat layer formation step: step S102). Here, an example of the process for forming the anchor coat layer 13 will be explained with reference to the drawings. Figure 9 is a schematic diagram showing the process for forming the anchor coat layer 13.

[0033] As shown in Figure 9, the anchor coat layer 13 is applied using a roller R1. More specifically, the anchor coat agent 131 constituting the anchor coat layer 13 is applied to the outer surface of the roller R1. Then, the roller R1 is moved while the lower surface of the resin film 111 on which the printed layer 15 is formed is in contact with the roller R1. As a result, the anchor coat agent 131 applied to the surface of the roller R1 is applied to the lower surface of the resin film 111.

[0034] As shown in Figure 9, when the anchor coating agent 131 is applied to the roller R1, the anchor coating agent 131 is applied to the portion of the resin film 111 that comes into contact with the easily peelable portion 16, so as to have the same shape as the pattern anchor coating Ptn described above. The lower surface of the resin film 111 on which the printed layer 15 is formed is moved while in contact with the roller R1. As a result, the easily peelable portion 16 made of pattern anchor coating Ptn is formed on the lower surface of the base layer 11 adjacent to the anchor coating layer 13. In other words, in the anchor coating layer formation process S102 in which the anchor coating layer 13 is formed, the easily peelable portion 16 is formed at the same time as the anchor coating layer 13 is formed.

[0035] It is also possible to print the printing layer 15 and the anchor coat layer 13 using the same printing method. In this case, the printing layer 15 and the anchor coat layer 13 may be formed simultaneously with the ink for forming the printing layer 15 attached to the outside of the anchor coat agent 131 that is attached to the roller R1. Even in this case, the easily peelable portion 16 is formed by forming the same pattern as the pattern anchor coat Ptn on a part of the anchor coat agent 131. The anchor coat layer formation process includes a drying process.

[0036] Then, a hole 3 is formed in the portion of the second strip-shaped portion 102 where the steam-permeable portion 23 is formed, penetrating the base material layer 11 and the easily peelable portion 16 (hole formation step: step S103). The hole 3 is configured to penetrate the base material layer 11 and the easily peelable portion 16 from the top surface to the bottom surface, but is not limited to this. For example, the hole 3 only needs to penetrate the base material layer 11, and may be a hole that reaches the middle part of the easily peelable portion 16. The hole 3 may be formed by a mechanical processing method using a machining center, or by a chemical method. Here, it is assumed that the hole 3 is formed by drilling using a machining center.

[0037] Subsequently, a heat-adhesive resin layer 12 is positioned opposite the lower surface of the anchor coat layer 13 of the base material layer 11, and a high-temperature molten extruded resin layer 14 is extruded in a film-like manner and positioned between the anchor coat layer 13 and the heat-adhesive resin layer 12 (extruded resin layer formation process: step S104).

[0038] With the extruded resin layer 14 positioned between the anchor coat layer 13 and the heat-adhesive resin layer 12, the base layer 11 and the heat-adhesive resin layer 12 are pressed together. This causes the heat-adhesive resin layer 12 to adhere to the lower surface of the anchor coat layer 13 of the base layer 11 via the extruded resin layer 14 (heat-adhesive resin layer formation step: S105). The pressing of the base layer 11 and the heat-adhesive resin layer 12 can be performed using, for example, a pair of rollers (not shown) to apply pressure, but is not limited to this. Furthermore, the extruded resin layer 14 is made of the same material as the heat-adhesive resin layer 12 and is at a high temperature during pressing. Therefore, the extruded resin layer 14 can be integrated with the heat-adhesive resin layer 12.

[0039] In this way, a raw material roll 20 is produced from the biaxially oriented polypropylene resin film 111 before forming the resin sheet 10. Subsequently, a raw material roll 201 is formed by winding the raw material roll 20 into a roll shape (winding process: step S106).

[0040] The manufacturing process described above is carried out in an apparatus that forms a printed layer 15 and an anchor coat layer 13 including an easily peelable portion 16 on a resin film constituting the base layer 11, and then adheres a heat-adhesive resin layer 12 via the anchor coat layer 13 and the extruded resin layer 14. After this, the raw material roll 201 is transferred to an apparatus that manufactures packaging bags, and after forming a resin sheet 10, a packaging bag manufacturing process is carried out in which a microwave-safe packaging bag 1 is manufactured. Note that if the process of laminating each of the above layers onto the resin film and the process of manufacturing the packaging bag, which will be described later, are carried out as a series of processes, the winding process described above may be omitted.

[0041] The raw material 20 is cut at a predetermined pitch P in the MD direction (cutting process: step S107). The raw material 20 may be cut mechanically using a blade, or it may be cut by irradiating it with a laser. In addition, a wide range of cutting methods that can accurately cut at a predetermined pitch P can be used. The resin sheet 10 is formed by cutting in the cutting process of step S107. In order to cut accurately in the cutting process, cutting lines may be provided on the raw material 20 at a predetermined pitch P. In this case, the cutting process can be configured to cut along the cutting lines.

[0042] The rectangular resin sheet 10 is positioned with its first strip-shaped portions 101 at both ends in the TD direction abutted together (sheet bending process: step S108). At this time, the sheets are positioned so that the heat-adhesive resin layers 12 of the first strip-shaped portions 101 are in contact with each other. Then, by heating and pressurizing the abutted first strip-shaped portions 101, the first strip-shaped portions 101 are heat-bonded, and a back seal portion 21 is formed (heat bonding process: step S109). As a result, a cylindrical body 100 is formed from the resin sheet 10.

[0043] Second strip-shaped portions 102 are positioned at the ends of both openings of the cylindrical body 100. In this state, the second strip-shaped portions 102 positioned at one end of one opening are placed on top of each other front and back. At this time, the inner surfaces of the second strip-shaped portions 102 are in contact with each other. In addition, both ends of the back seal portion 21 are positioned so as to overlap the steam-permeable portions 23 formed on the second strip-shaped portions 102 front and back. Then, the heat-adhesive resin layers 12 of the second strip-shaped portions 102 are in contact with each other, and the second strip-shaped portions 102 are heated and pressurized, causing the front and back positioned second strip-shaped portions 102 to be heat-bonded (heat bonding process: step S110).

[0044] As a result, the cylindrical body 100 becomes a bag-like shape with one opening closed. After the contents S are placed inside the cylindrical body 100 through the closed opening, the second strip-shaped portions 102 located at the ends of the opening are heat-sealed together (heat sealing process: step S111). In the heat sealing process of step S111, the same process as in the heat sealing process of step S110 is performed. As a result, a microwave-safe packaging bag 1 is formed with the contents S contained in the storage portion 103 and sealed. In other words, a microwave-safe packaging bag 1 is formed in which steam-permeable portions 23 are formed in the portion of the end seal portion 22 that overlaps with the back seal portion 21 and in the portions facing each other front and back.

[0045] In the manufacturing process of the microwave packaging bag 1 described above, one of the second strip-shaped portions 102 is heat-sealed to close one opening of the cylindrical body 100, the contents S are placed inside, and the other second strip-shaped portion 102 is heat-sealed. However, the process is not limited to this. For example, the contents S may be placed inside the cylindrical body 100, and then the second strip-shaped portions 102 forming both openings may be heat-sealed. In the microwave packaging bag 1, the air inside the containment portion 103 may be removed, or the containment portion 103 may be filled with an inert gas such as nitrogen gas.

[0046] <Regarding steaming during heating of microwave packaging bag 1> When the microwave-safe packaging bag 1 is heated in a microwave oven, the pressure inside the containment section 103 increases due to the thermal expansion of the air inside the containment section 103 and the steam generated by the evaporation of moisture contained in the contents S. As the pressure inside the containment section 103 increases, the microwave-safe packaging bag 1 swells, and the stress acting on the resin sheet 10 increases. The stress acting on the resin sheet 10 is concentrated near the end seal section 22.

[0047] The resin sheet 10 expands significantly (stretches) due to heating and the increase in pressure inside the housing section 103. As described above, the base layer 11 is made of polypropylene (PP), and the heat-adhesive resin layer 12 and the extruded resin layer 14 are made of polyethylene (PE). The base layer 11 is a material that stretches easily, while the heat-adhesive resin layer 12 and the extruded resin layer 14 are materials that break when heated. Note that the heat-adhesive resin layer 12 and the extruded resin layer 14 break at relatively low temperatures.

[0048] Therefore, when the microwave packaging bag 1 is heated in a microwave oven, the heat-adhesive resin layer 12 and the base layer 11 deform. The base layer 11 elongates greater in the MD direction than in the TD direction. The end seal portion 22 is elongated and extends along the TD direction, and when the base layer 11 deforms due to the increase in pressure inside the housing portion 103, the deformation (displacement) in the MD direction is greater than the deformation (displacement) in the TD direction in the steam-through portion 23.

[0049] In the case of a packaging bag without a ventilation section 23, if the internal pressure of the containment section 103 increases and a force exceeding the breaking strength acts on the heat-adhesive resin layer 12, the heat-adhesive resin layer 12 will break. Also, the base layer 11 deforms due to the increase in internal pressure of the containment section 103. At this time, the base layer 11 is stretched at a high temperature, but because the base layer 11 has a high tensile elongation rate at high temperatures, the film thickness becomes thinner, and the base layer 11 breaks following the breakage of the heat-adhesive resin layer 12. For example, the stress acting on the heat-adhesive resin layer 12 due to the increase in internal pressure of the containment section 103 is concentrated at the boundary of the end seal section 22. At the boundary of the end seal section 22, the stress acting on the center of the heat-adhesive resin layer 12 in the TD direction is greater than that acting on both ends in the TD direction. Therefore, the base layer 11 and the heat-adhesive resin layer 12 are prone to breaking near the center of the end seal section 22 in the TD direction.

[0050] If the heat-adhesive resin layer 12 and the base layer 11 rupture while the internal pressure of the containment section 103 is high, the air and steam inside the containment section 103 will be forcefully ejected to the outside. At this time, the contents S contained in the containment section 103 may be ejected to the outside, guided by the ejection of air and steam. Also, if the base layer 11, which is a stretched film, ruptures, a popping sound may occur when air and steam are ejected, even if the contents S are not ejected. In either case, the convenience for the user is reduced.

[0051] In contrast, the microwave packaging bag 1 according to this embodiment has a steam-permeable portion 23 in the central part of the TD direction where stress tends to concentrate in the end seal portion 22. Multiple holes 3 are formed in the steam-permeable portion 23, and an easy-peel portion 16 is arranged between the base material layer 11 and the extruded resin layer 14. As described above, since the easy-peel portion 16 is formed of pattern anchor coat Ptn, the base material layer 11 and the extruded resin layer 14 are easily peeled off.

[0052] In the steam passage section 23, when the resin sheet 10 deforms due to the increase in pressure inside the containment section 103, the laminate strength between the base material layer 11 and the extruded resin layer 14 is weak in the steam passage section 23, causing the base material layer 11 and the polyethylene resin (heat-adhesive resin layer 12 and extruded resin layer 14) to deform.

[0053] In the steam-permeable section 23, the presence of an easily peelable section 16 separates the base layer 11 from the heat-adhesive resin layer 12 and the extruded resin layer 14. As a result, the heat-adhesive resin layer 12 and the extruded resin layer 14 are ruptured by thermal expansion from the seal edge 221 of the end seal section 22. Since the heat-adhesive resin layer 12 and the extruded resin layer 14 are made of unstretched resin, the popping sound associated with their rupture is milder compared to that of a stretched film and is less likely to be recognized as a popping sound.

[0054] In other words, in the vapor-permeable portion 23, the laminated sheet is divided in the thickness direction by the easily peelable portion 16, compared to the portion of the end seal portion 22 where the vapor-permeable portion 23 is not formed. Therefore, deformation of the base material layer 11 due to deformation of the heat-adhesive resin layer 12 is suppressed.

[0055] Furthermore, in the microwave packaging bag 1, the lamination strength is reduced in the steam-permeable section 23 by the easy-peel section 16, and the presence of the holes 3 reduces deformation due to thermal expansion in the easily stretchable base layer 11. If the easily stretchable base layer 11 does not have holes, the film thickness of the base layer 11 will decrease due to thermal expansion in the MD direction until the steam is released to the outside, and it will eventually break. As a result, rupture occurs. Note that if the base layer 11 is made of a material such as biaxially oriented polyester or biaxially oriented polyamide, which has a tensile elongation in the MD direction of less than 300% at a 100°C environment, it is not necessary to provide the holes 3.

[0056] A fractured portion 120 (see Figure 6) is formed in the heat-adhesive resin layer 12 due to stress and a decrease in tear strength resulting from the reduction in thickness due to thermal deformation of the heat-adhesive resin layer 12. However, since the base layer 11 is provided with an easily peelable portion 16, the displacement associated with the deformation of the heat-adhesive resin layer 12 is not easily transmitted, and even if the heat-adhesive resin layer 12 and the extruded resin layer 14 fracture, the base layer 11 will not fracture.

[0057] As a result of the formation of the fractured section 120, the high-temperature steam generated in the containment section 103 penetrates through the fractured section 120 to the boundary between the easily peelable section 16 and the extruded resin layer 14. In the steam-through section 23, holes 3 are formed that penetrate the base material layer 11 and the anchor coat layer 13. Therefore, the steam that has penetrated to the boundary between the easily peelable section 16 and the extruded resin layer 14 is discharged to the outside through the holes 3.

[0058] A portion of the steam passing through the hole 3 flows into the area where the easy-peel section 16 is formed. The incoming high-temperature steam causes the base material layer 11 and the extruded resin layer 14 to separate in the easy-peel section 16. As a result, the air and steam inside the containment section 103 that flow into the steam passage section 23 are discharged to the outside through the gap between the base material layer 11 and the extruded resin layer 14 that have been separated in the easy-peel section 16.

[0059] The same applies even if the hole 3 is not formed up to the anchor coat layer 13.

[0060] In other words, the steam passage section 23 has the above-described configuration, which suppresses the rupture of the base material layer 11 due to an increase in the internal pressure of the containment section 103 and allows the internal steam and air to be discharged to the outside. As a result, even if the internal pressure of the containment section 103 increases due to heating in a microwave oven, the scattering of contents S and the generation of a rupture sound due to the rupture of the base material layer 11 can be suppressed.

[0061] Furthermore, it is preferable that the total cross-sectional area of ​​the holes 3 is such that, when the extruded resin layer 14 ruptures, it can achieve a flow rate that allows sufficient air and vapor to be released to the outside from between the base layer 11 and the easily peelable portion 16. For example, such an area ratio can be 1% or more and less than 50%.

[0062] In this embodiment, the steam passage 23 is formed at the portion where both end seal portions 22 intersect with the back seal portion 21, but is not limited to this. The steam passage 23 may be formed at the portion where one end seal portion 22 intersects with the back seal portion 21. Furthermore, the portion where the steam passage 23 is formed is not limited to the portion where the end seal portion 22 intersects with the back seal portion 21, but may be formed at a position offset from the portion where the end seal portion 22 intersects with the back seal portion 21. In addition, the steam passage 23 may be formed in the middle portion in the longitudinal direction of the back seal portion 21. Moreover, a plurality of steam passages 23 may be formed in the microwave packaging bag 1. It is preferable that the steam passage 23 is formed near the portion where stress concentrates in the heat-adhesive resin layer 12 when the internal pressure of the containment portion 103 increases.

[0063] In this embodiment, the microwave packaging bag 1 is a pillow-type packaging bag, but is not limited to this. For example, it can be widely used for packaging bags constructed by heat-sealing predetermined positions of overlapping resin sheets, such as a gusset type with gussets on the sides, a three-sided sealed type made by folding a single resin sheet and heat-sealing three sides, a four-sided sealed type made by overlapping two resin sheets and heat-sealing the periphery, and a self-standing type with a bottom.

[0064] In this embodiment, the steam vent section 23 of the microwave packaging bag 1 is configured to release air and steam from inside the containment section 103 to the outside through the holes 3. However, the invention is not limited to this configuration, and the base layer 11 may be configured such that cracks are formed to increase the flow rate as air and steam flow out. Here, a crack configuration could be such that the holes 3 connect to each other and the opening slowly enlarges.

[0065] <Example 1> Figure 10 is a cross-sectional view of the vicinity of the vapor-permeable portion 23 of the resin sheet 10A of Modified Example 1. As shown in Figure 10, the resin sheet 10A has a perforated structure in which no anchor coating agent is placed, which is designated as an easy-peel portion 16A. With this configuration, the base layer 11 and the heat-adhesive resin layer 12 are not bonded in the easy-peel portion 16A. Therefore, when the microwave packaging bag 1 is heated in a microwave oven and a rupture portion 120 is formed in the heat-adhesive resin layer 12, air and steam from the containment portion 103 flow into the easy-peel portion 16A through the rupture portion 120 and are released to the outside through the unbonded easy-peel portion 16A. As a result, the stress acting on the base layer 11 is suppressed, and the spillage of contents S due to the rupture of the base layer 11 and the generation of a rupture sound are suppressed.

[0066] <Modification 2> Figure 11 is a cross-sectional view of the vicinity of the vapor-permeable portion 23 of the resin sheet 10B of Modification 2. As shown in Figure 11, in the resin sheet 10B, the easily peelable portion 16B is filled with a laminate strength reducing material that reduces the laminate strength, instead of the pattern anchor coat Ptn. As the laminate strength reducing material that reduces the laminate strength, appropriate options include a plaster containing a release agent, a foaming ink in which the gas in microcapsules contained in the ink foams up due to the heat and pressure during filling and sealing, and a brightness ink containing aluminum paste. The easily peelable portion 16 may also be constructed by applying multiple coats of ink such as silver ink, pearl ink, or white ink.

[0067] By filling the easily peelable section 16B with a laminate strength-reducing material that lowers the laminate strength, when the microwaveable packaging bag 1 is heated in a microwave oven and a rupture 120 is formed in the heat-adhesive resin layer 12, air and steam from the containment section 103 flow into the easily peelable section 16B through the rupture 120. Since the easily peelable section 16B is filled with a laminate strength-reducing material that lowers the laminate strength, the base layer 11 and the heat-adhesive resin layer 12 are easily separated in the easily peelable section 16B. Therefore, the steam that flows into the easily peelable section 16B separates through the easily peelable section 16B before the base layer 11 bursts, and the steam and air are discharged to the outside through the separated easily peelable section 16B. As a result, the stress acting on the base layer 11 is suppressed, and the spillage of contents S and the generation of a rupture sound due to the rupture of the base layer 11 are suppressed.

[0068] The easily peelable portions 16A and 16B shown in the above-described modified examples 1 and 2 can be formed in the same manner as the method for forming the patterned anchor coat Ptn shown in Figure 9 when forming the anchor coat layer 13.

[0069] <Second Embodiment> The microwave packaging bag of the second embodiment will be described with reference to the drawings. Figure 12 is an enlarged cross-sectional view of the steam vent 24 of the microwave packaging bag 1C of the second embodiment. As shown in Figure 12, the microwave packaging bag 1C differs from the microwave packaging bag 1 in that it has a steam vent 24. The other parts of the microwave packaging bag 1C are the same as those of the microwave packaging bag 1. Therefore, in the microwave packaging bag 1C, the same reference numerals are used for parts that are substantially the same as those of the microwave packaging bag 1, and detailed descriptions of these same parts are omitted.

[0070] In the microwave packaging bag 1C, the steam vent portion 24 is provided at the point where the back seal portion 21 of the end seal portion 22 intersects. The steam vent portion 24 is provided with a hole 4. In the steam vent portion 24, the hole 4 is formed to penetrate the end seal portion 22.

[0071] The manufacturing process for microwave packaging bag 1C, as shown in Figure 8, involves forming the heat-adhesive resin layer in step S105, followed by the hole-forming step in step S103. Alternatively, after step S109, a hole-forming step may be performed to form holes 4 in the steam-permeable portions 25 provided in both end seal portions 22.

[0072] As described above, even when a microwave-safe packaging bag 1C having a steam-through section 24 with a hole 4 that penetrates the end seal section 22 is heated in a microwave oven, air and steam from the containment section 103 are easily discharged through the hole 4. Furthermore, even if the heat-adhesive resin layer 12 is deformed by the hole 4, this displacement is not easily transmitted to the base material layer 11. Therefore, the rupture of the microwave-safe packaging bag 1C can be suppressed.

[0073] Alternatively, after sealing the end seal portion 22 in step S110 or step S111, the hole forming step in step S103 to form the hole portion 5 may be performed to manufacture the microwave packaging bag 1D. With this configuration, the hole portion 5 penetrates the end seal portion 22 in which the steam vent portion 25 is formed (see Figure 13). As a result, steam can be easily released from the hole portion 5 in the microwave packaging bag 1D, and the rupture of the base material layer 11 can be suppressed.

[0074] <Variation 3> Figure 14 shows the shape of the holes 3E in the steam passage section 23E of Modification 3. As shown in Figure 14, the steam passage section 23E has holes 3E formed in a slit shape. The slit-shaped holes 3E may be, for example, perforated. In this case, the length of one hole is preferably 3 mm or less.

[0075] <Modification 4> Figure 15 shows the shape of the holes 3F of the steam passage section 23F in Modification 4. As shown in Figure 15, the steam passage section 23F has holes 3F arranged in a row that are further apart from each other as you move from one end to the other. The holes 3F may be formed, for example, by perforations. In this case, the length of one hole is preferably 3 mm or less. The above modification is just one example, and the holes may have other shapes.

[0076] Although the heat-adhesive resin layer 12 described above is made of polyethylene (PE), the heat-adhesive resin layer 12 may also be made of polypropylene (unoriented polypropylene: CPP) instead of polyethylene film. Furthermore, the heat-adhesive resin layer 12 is not limited to polyethylene or polypropylene, but can be made of a wide range of materials with heat-adhesive properties.

[0077] In a resin sheet, if each layer is made of polyolefin, the microwave packaging bag can be constructed as a monoolefin. This is advantageous for recycling the microwave packaging bag.

[0078] Although embodiments of the present invention have been described above, the present invention is not limited thereto. Furthermore, various modifications can be made to the embodiments of the present invention, as long as they do not depart from the spirit of the invention. [Industrial applicability]

[0079] According to the present invention, a packaging bag that can be used for cooking in a microwave oven can be provided. [Explanation of symbols]

[0080] 1, 1C, 1D Microwave-safe packaging bags 3, 3A, 3E, 3F, 4, 5 holes 10, 10A, 10B resin sheets 11 Base material layer 12 Heat adhesive resin layer 13 Anchor Coat Layer 131 Anchor coating agent 14. Extruded resin layer 15 Printing layer 16, 16A, 16B Easily peelable part 161 Point-like part 20 Original fabric 201 Roll of raw material 21 Spine seal section 22 End seal section 221 Seal edge section 23, 23A, 23B, 23C, 23D, 23E, 23F, 24, 25 Steaming section 100 cylindrical body 101 First band-shaped section 102 Second band-shaped section 103 Storage Unit S Contents R1 Laura Ptn Pattern Anchor Coat

Claims

1. A microwaveable packaging bag having a compartment for containing contents, A sealed portion formed by heat-sealing at least a portion of the peripheral edge of the laminated sheets arranged front and rear, It has a steam passage formed in a part of the seal portion that allows steam from the containment portion to pass through, The aforementioned laminated sheet is A base layer and An anchor coat layer formed on the inside of the aforementioned substrate layer and formed by printing, A heat-adhesive resin layer formed inside the anchor coat layer, The system comprises an extruded resin layer formed between the anchor coat layer and the heat-adhesive resin layer, The aforementioned steaming section includes, A portion of the anchor coat layer is formed, and has a lower density than the rest of the anchor coat layer, A microwave packaging bag having a plurality of holes that penetrate at least the base material layer in the thickness direction in the portion of the laminated sheet that constitutes the steam-permeable portion.

2. The microwave packaging bag according to claim 1, wherein in the steam-permeable portion, the hole penetrates the anchor coat layer.

3. The microwave packaging bag according to claim 1, wherein in the steam-permeable portion, the hole penetrates the heat-adhesive resin layer.

4. Microwave packaging bag according to claim 1, wherein the easily peelable portion in the steam-permeable portion is formed by a patterned anchor coat which is a pattern shape formed by the anchor coat agent constituting the anchor coat layer.

5. Microwave packaging bag according to claim 1, wherein in the steam-permeable portion, the easily peelable portion is a pore-like structure in which the anchor coating agent constituting the anchor coating layer is not filled.

6. Microwave packaging bag according to claim 1, wherein in the steam-permeable portion, the easily peelable portion is filled with a laminate strength reducing material that is lower than the laminate strength of the anchor coat layer and the extruded resin layer.

7. The microwave packaging bag according to claim 1, wherein the base layer is made of a resin that exhibits a tensile elongation at break of 300 percent or more in the MD direction under conditions of 100°C.

8. The microwave packaging bag according to claim 1, wherein the heat-adhesive resin layer is made of a resin having a tensile elongation at break of 10 to 100 percent in the MD direction at a 100°C environment.

9. A method for manufacturing microwave packaging bags, which are formed to have a storage section capable of holding articles, which is sealed at a sealing portion, An anchor coat layer forming step, in which an anchor coat layer is formed on one surface of a resin sheet constituting the base layer, such that an easily peelable portion is formed in a part of the sealing portion that is a vapor-permeable portion for allowing steam generated in the containment portion to pass through, In the portion where the steam passage is formed, a hole forming step is performed to form a hole that penetrates at least the base material layer, An extrusion resin forming step is performed by bringing a sheet for forming a heat-adhesive resin layer into contact with the surface of the substrate layer on which the anchor coat layer is formed, and extruding the sheet with molten resin between the anchor coat layer and the heat-adhesive resin layer. A heat-adhesive resin layer forming step, in which a heat-adhesive resin layer is formed by pressing the substrate layer and the sheet on which the heat-adhesive resin layer is formed, A sheet arrangement step of arranging the resin sheets so that the heat-adhesive resin layers are arranged facing each other, A method for manufacturing a microwave-safe packaging bag, comprising a heat bonding step of heat bonding a predetermined portion of the resin sheet to form the sealed portion.

10. A method for manufacturing microwave packaging bags, which are formed to have a storage section capable of holding articles, which is sealed at a sealing portion, An anchor coat layer forming step, which involves forming an anchor coat layer on one surface of a resin sheet constituting the base layer such that an easily peelable portion is formed in a part of the sealing portion that is a vapor-permeable portion for allowing steam generated in the containment portion to pass through, An extrusion resin forming step is performed by bringing a sheet for forming a heat-adhesive resin layer into contact with the surface of the substrate layer on which the anchor coat layer is formed, and extruding the sheet with molten resin between the anchor coat layer and the heat-adhesive resin layer. A heat-adhesive resin layer forming step, in which a heat-adhesive resin layer is formed by pressing the substrate layer and the sheet on which the heat-adhesive resin layer is formed, In the portion where the steam-through portion is formed, a hole-forming step is performed to form a hole that penetrates the base material layer and the heat-adhesive resin layer, A sheet arrangement step of arranging the resin sheets so that the heat-adhesive resin layers are arranged facing each other, A method for manufacturing a microwave-safe packaging bag, comprising a heat bonding step of heat bonding a predetermined portion of the resin sheet to form the sealed portion.

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