Packaging bag

Abstract

To provide a packaging bag that is excellent in heat insulating properties and that can inhibit contents from leaking out.SOLUTION: According to the present invention, a packaging bag is constituted by making a film with flexibility welded in a seal part. The packaging bag comprises a steam removal seal part that forms a steam channel in association with an increase in internal pressure. The film comprises a foam layer, and the steam removal seal part is provided in the seal part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a packaging bag suitable for heating the contents in a microwave oven.

Background Art

[0002] Patent Document 1 discloses a laminated film formed by co-extruding a foamed layer made of a polyolefin resin and a solid layer made of a polyolefin resin using an inflation molding machine. By hermetically packaging frozen food and heating it directly in a microwave oven, when it is time to eat, a packaging bag for frozen food that ruptures with a popping sound and generates water vapor by heating is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the internal pressure of the packaging bag in Patent Document 1 increases during heating in a microwave oven, the packaging bag ruptures, and the steam inside the packaging bag is released. Although Patent Document 1 is characterized in that the size of the rupture opening formed at the time of rupture is reduced by combining a foamed layer and a solid layer, it is difficult to completely control where the rupture opening is formed in the packaging bag. Depending on the location where the rupture opening is formed, it is difficult to completely eliminate the risk of the contents leaking out.

[0005] The present invention has been made in view of such circumstances, and provides a packaging bag having excellent heat insulation properties and capable of suppressing leakage of the contents.

Means for Solving the Problems

[0006] According to the present invention, there is provided a packaging bag formed by welding a flexible film at a seal portion, the packaging bag including a steam vent seal portion that forms a steam flow path as the internal pressure increases, the film including a foam layer, and the steam vent seal portion being provided at the seal portion.

[0007] Since the packaging bag of the present invention is composed of a film having a foam layer, it has excellent heat insulation properties. Further, since a steam vent seal portion is provided at the seal portion of the film, when the internal pressure increases with heating in a microwave oven, a steam flow path is formed in the steam vent seal portion, and the steam inside the packaging bag is released. Therefore, it is always possible to form a steam flow path at a specific position, and leakage of the contents is suppressed.

[0008] Hereinafter, various embodiments of the present invention will be exemplified. The embodiments shown below can be combined with each other. Preferably, the packaging bag is the packaging bag described above, wherein a cut is provided in the film at a position outside the packaging bag and adjacent to the inner edge, rather than the inner edge of the steam vent seal portion. Preferably, the packaging bag is the packaging bag described above, wherein the film includes a base material layer, the foam layer, and a sealant layer in this order from the outer surface side of the packaging bag, and the sealant layer is made of a resin having a lower melting point than the base material layer. Preferably, the packaging bag is the packaging bag described above, wherein the steam vent seal portion includes a point seal portion, and the thickness of the sealant layer at the point seal portion is smaller than the thickness of the sealant layer at other portions of the steam vent seal portion. Preferably, the packaging bag is the packaging bag described above, wherein the thickness of the sealant layer at the point seal portion is 50 μm or less.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described. Various characteristic matters shown in the following embodiments can be combined with each other. Also, an invention can be established independently for each characteristic matter.

[0011] 1. First Embodiment As shown in FIG. 1A, the packaging bag 1 of the first embodiment of the present invention is formed by making a flexible film 9 into a bag shape. The packaging bag 1 includes a front part 2 and a back part 3. The front part 2 and the back part 3 are welded by heat sealing at the seal part 4. The seal part 4 includes a top seal part 4t formed along the upper side 1t of the packaging bag 1 and a side seal part 4s formed along the right side 1r or the left side 1l. The lower side 1b of the packaging bag 1 is not welded before the contents are accommodated, and is welded after the contents are accommodated in the packaging bag 1 to form a bottom seal part 4b. Thereby, the seal part 4 is provided on the entire circumference of the packaging bag 1, and the inside of the packaging bag 1 is sealed.

[0012] As shown in FIG. 2, the film 9 is a laminated film preferably composed of a plurality of layers including a base material layer 9a, a foamed layer 9b, and a sealant layer 9c, with the sealant layer 9c being the innermost layer. The sealant layer 9c is preferably a non-foamed (solid) layer. At the seal portion 4, the sealant layers 9c are welded together. The film 9 can be formed, for example, by laminating the films constituting the base material layer 9a, the foamed layer 9b, and the sealant layer 9c respectively.

[0013] The base material layer 9a is preferably composed of a resin such as nylon, ethylene-α-olefin copolymer, polypropylene, high-density polyethylene, linear low-density polyethylene, polyethylene terephthalate, etc. The thickness of the base material layer 9a outside the seal portion 4 is, for example, 30 to 100 μm, and preferably 40 to 80 μm.

[0014] The sealant layer 9c is preferably composed of a resin having a melting point lower than that of the base material layer 9a. The sealant layer 9c is, for example, preferably composed of an olefin resin such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, propylene-ethylene copolymer, or an olefin resin graft-modified with an ethylene-based unsaturated carboxylic acid or its anhydride, a polyamide-based resin having a relatively low melting point or low softening point, a polyester-based resin, or an ethylene-vinyl acetate copolymer resin. The thickness of the sealant layer 9c outside the seal portion 4 is, for example, 25 to 60 μm, and preferably 30 to 50 μm.

[0015] The foamed layer 9b can be composed of the resins mentioned in the above description of the base material layer 9a or the sealant layer 9c, and is preferably composed of a resin having a melting point lower than that of the base material layer 9a. The foamed layer 9b is preferably composed of an olefin resin (preferably polyethylene).

[0016] The expansion ratio of the foam layer 9b is, for example, 1.2 to 3.5 times, preferably 2.0 to 3.0 times, and more preferably 2.3 to 2.8 times. If the expansion ratio is less than 1.2 times, it becomes difficult to form foam. On the other hand, if it exceeds 3.5 times, it becomes difficult to form uniform foam. Incidentally, the expansion ratio is the density of the resin before foaming / the density (bulk density) of the foam layer after foaming. The foam layer 9b preferably includes, in addition to single bubbles, interconnected bubbles in which a plurality of bubbles communicate and are connected. In this case, it becomes easy to form a vapor flow path through the foam layer 9b. The thickness of the foam layer 9b other than the seal portion 4 is, for example, 30 to 80 μm, preferably 40 to 70 μm.

[0017] On the surface of the foam layer 9b, there are uneven shapes derived from bubbles. Since the sealant layer 9c covers the foam layer 9b, the uneven shape of the foam layer 9b is also reflected in the sealant layer 9c, and an uneven shape is also formed on the surface of the sealant layer 9c. This uneven shape enhances the slipperiness of the contents.

[0018] Since the foam layer 9b contains a large number of bubbles, its light transmittance is low. Therefore, the contents sealed in the packaging bag 1 cannot be visually recognized from the outside, and it has excellent aesthetics.

[0019] The foam layer 9b has excellent heat insulation properties. Therefore, when frozen food is stored in the packaging bag 1, frosting on the surface of the packaging bag 1 is suppressed. Also, the rise in the surface temperature of the packaging bag 1 when heating the contents in a microwave oven is suppressed. Therefore, the risk of getting burned when touching the surface of the packaging bag 1 immediately after heating in a microwave oven is reduced.

[0020] Note that the configuration of the film 9 is not limited to that shown in FIG. 2, and it may be a configuration in which the base material layer 9a, the sealant layer 9c, and the foam layer 9b are arranged in this order. Also, at least one of the base material layer 9a and the sealant layer 9c may be omitted. Furthermore, it may include layers other than the base material layer 9a, the foam layer 9b, and the sealant layer 9c. For example, a printing layer or an adhesive layer may be provided between the base material layer 9a and the foam layer 9b. Also, the base material layer 9a may be composed of multiple layers.

[0021] As shown in FIG. 1A, the front portion 2 includes a lower front portion 2d and an upper front portion 2u. The lower front portion 2d and the upper front portion 2u are each welded to the back portion 3. As shown in FIG. 2, the lower front portion 2d and the upper front portion 2u are connected at a clasp portion 5 formed by overlapping each other in a folded state. As shown in FIG. 1A, at the clasp portion 5, the lower front portion 2d and the upper front portion 2u are welded at a pair of side seal portions 6a, a pair of end seal portions 6b, and a steam vent seal portion 6c. The side seal portions 6a are provided at positions along the right side 1r and the left side 1l at the clasp portion 5. The end seal portions 6b are provided so as to connect the side seal portions 6a and the steam vent seal portion 6c. The end seal portions 6b become narrower from the side seal portions 6a toward the steam vent seal portion 6c. As shown in FIG. 1B, the steam vent seal portion 6c has a substantially V shape, and its inner edge 6c1 also has a substantially V shape that curves toward the inside of the packaging bag 1. A cut 12 is provided outside the packaging bag 1 and adjacent to the inner edge 6c1 with respect to the inner edge 6c1.

[0022] As shown in FIG. 1B, a point seal portion 6c2 is provided near the tip of the steam vent seal portion 6c. The point seal portion 6c2 preferably protrudes inside the packaging bag 1 more than the inner edge 6c1 of the steam vent seal portion 6c. The point seal portion 6c2 can be formed by heat-sealing with a force stronger than the compression strength when forming the steam vent seal portion 6c after forming the steam vent seal portion 6c. At this time, a thick portion (not shown) may be formed at the periphery of the point seal portion 6c2 due to the resin flowing around when forming the point seal portion 6c2. Further, since the sealant layer 9c is formed of a resin having a lower melting point than the base material layer 9a, the degree of thinning of the sealant layer 9c is particularly high in the point seal portion 6c2. The thickness of the sealant layer 9c at the point seal portion 6c2 is smaller than the thickness of the sealant layer 9c at other portions of the steam vent seal portion 6c. In the point seal portion 6c2, the foam layer 9b may become a solid layer by the bubbles bursting during pressing. In the point seal portion 6c2, since the seal strength is weakened by the thinning of the sealant layer 9c, a steam flow path is likely to be formed in the steam vent seal portion 6c. The thickness of the sealant layer 9c at the point seal portion 6c2 is preferably 50 μm or less. This thickness is, for example, 1 to 50 μm, specifically, for example, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 μm, and may be within the range between any two of the values exemplified here. This is because if it is too thick, it is difficult for steam to escape, and peeling may progress at the side seal portion 6a.

[0023] After the packaging bag 1 is filled with the contents, as shown in FIG. 3, a bottom seal portion 4b is formed on the lower side 1b of the packaging bag 1. Thereby, the inside of the packaging bag 1 is sealed.

[0024] When the packaging bag 1 filled with the contents is heated in a microwave oven, the internal pressure of the packaging bag 1 rises due to the steam generated from the moisture contained in the contents, and as shown in FIG. 3, the packaging bag 1 expands. As a result, the seal is peeled off near the substantially V-shaped tip of the steam vent seal portion 6c, a steam flow path is formed, and the steam is released to the outside through the steam flow path.

[0025] In the packaging bag 1 without the foamed layer 9b, the films welded at the steam vent seal portion 6c (here, the film constituting the lower front portion 2d and the film constituting the upper front portion 2u) are completely peeled off, and a gap is formed between them, thereby forming a steam flow path. Therefore, the cross-sectional area of the steam flow path tends to be large. For this reason, when the steam flow path is formed, a large amount of steam is immediately released, and the internal pressure of the packaging bag 1 rapidly decreases, whereby the steaming effect of the contents is likely to be reduced.

[0026] On the other hand, in the packaging bag 1 having the foamed layer 9b as in the present embodiment, as shown in FIG. 4, when the peeling at the steam vent seal portion 6c starts with the increase in the internal pressure and the steam flow path 6d communicating the inside of the packaging bag 1 and the foamed layer 9b is formed, the steam can be discharged to the outside through the steam flow path 6d, the foamed layer 9b, and the cut 12. A large number of air bubbles exist in the foamed layer 9b, and the partition walls separating the adjacent air bubbles are very thin in thickness, so they are easily broken by the pressure of the steam to form a steam flow path. Since the cut 12 is provided at a position adjacent to the inner edge of the steam vent seal portion 6c, the steam that has passed through the steam flow path in the foamed layer 9b is quickly discharged from the cut 12. The cross-sectional area of the steam flow path formed by such a principle is very small. For this reason, the discharge rate of the steam in the packaging bag 1 is low, and the steaming effect of the contents is enhanced. In addition, when the cut 12 is not provided in the packaging bag 1, the steam that has passed through the steam flow path in the foamed layer 9b can be discharged from the end face of the film 9.

[0027] 2. Second Embodiment The second embodiment of the present invention will be described with reference to FIGS. 5 to 6. This embodiment is similar to the first embodiment, and the main difference is the configuration of the point seal portion 6c2. Hereinafter, the description will focus on the differences.

[0028] In the first embodiment, the point seal portion 6c2 is formed by heating while pressing from both sides of the clasp portion 5, but in this embodiment, as shown in FIG. 5, the point seal portion 6c2 is formed by heating while pressing from one side of the clasp portion 5 (preferably the lower front portion 2d side).

[0029] When the point seal portion 6c2 is formed in such a manner, the foam layer 9b1 on the pressed side (the lower front side 2d in this embodiment) is more heated than the foam layer 9b2 on the non-pressed side (the upper front side 2u in this embodiment), and thus the bubbles are more likely to collapse. For this reason, the foam layer 9b2 has higher air permeability than the foam layer 9b1. Further, when the internal pressure of the packaging bag 1 increases, as shown in FIG. 6, a vapor flow path 6d extending toward the foam layer 9b2 is likely to be formed. For this reason, as the internal pressure of the packaging bag 1 increases, the vapor inside the packaging bag 1 is discharged to the outside through the vapor flow path 6d, the foam layer 9b2, and the cut 12.

[0030] Since the upper front portion 2u of the clasping portion 5 is formed by valley-folding the film, when a steam vent is formed in the upper front portion 2u of the clasping portion 5, it is difficult for the contents to leak out when the steam escapes and the packaging bag 1 shrinks.

[0031] 3. Other Embodiments The present invention can also be implemented in the following aspects. · The packaging bag 1 may have a self-standing shape. · The steam vent seal portion 6c is not limited to a substantially V-shaped, and may be U-shaped or the like. · In the above embodiment, the outer edge 6c3 of the steam vent seal portion 6c has a similar shape (that is, a substantially V-shaped) to the inner edge 6c1, but the outer edge 6c3 may have another shape. For example, as shown in FIG. 7, the outer edge 6c3 may be a straight shape. Further, in the above embodiment, the cut 12 is provided in the unsealed portion, but in the form of FIG. 7, the cut 12 is provided in the sealed portion. · The clasping portion 5 can be omitted. In this case, the steam vent seal portion 6c is provided at another portion. For example, a convex shape serving as the steam vent seal portion 6c may be provided in the seal portion 4 (the top seal portion 4t, the side seal portion 4s, or the bottom seal portion 4b) at the peripheral edge of the packaging bag 1, a steam vent seal portion 6c connected to the seal portion 4 at the peripheral edge may be provided, or a steam vent seal portion 6c independent of the seal portion 4 at the peripheral edge may be provided.

Explanation of Reference Numerals

[0032] 1: Packaging bag 1b: Lower side 1l: Left side 1r: Right side 1t: Upper side 2: Front part 2d: Lower front part 2u: Upper front part 3: Back part 4: Seal part 4b: Bottom seal part 4s: Side seal part 4t: Top seal part 5: Clasp part 6a: Side seal part 6b: End seal part 6c: Steam vent seal part 6c1: Inner edge 6c2: Point seal part 6d: Steam flow path 7: Steam vent seal part 9: Film 9a: Base material layer 9b: Foam layer 9b1: Foam layer 9b2: Foam layer 9c: Sealant layer 12: Cut

Claims

1. A packaging bag formed by welding a flexible film at a seal portion, comprising a steam vent seal portion that forms a steam flow path as the internal pressure rises, wherein the film comprises a foaming layer, the steam vent seal portion is provided at the seal portion, a cut is provided in the film at a position outside the packaging bag and adjacent to the inner edge, relative to the inner edge of the steam vent seal portion, the film comprises a base material layer, the foaming layer, and a sealant layer in order from the outer surface side of the packaging bag, the sealant layer is composed of a resin having a lower melting point than the base material layer, the steam vent seal portion comprises a point seal portion, the thickness of the sealant layer at the point seal portion is smaller than the thickness of the sealant layer at other portions of the steam vent seal portion, the packaging bag is configured such that as the internal pressure of the packaging bag rises, peeling at the steam vent seal portion is initiated to form the steam flow path that communicates the inside of the packaging bag with the foaming layer, and the steam that has passed through the steam flow path in the foaming layer is discharged to the outside through the cut.

2. The packaging bag according to Claim 1, wherein the thickness of the sealant layer at the point seal portion is 50 μm or less.

3. The packaging bag according to Claim 1 or Claim 2, wherein the packaging bag comprises a front portion and a back portion, the front portion and the back portion are welded by heat sealing at the seal portion, the front portion comprises a lower front portion and an upper front portion, the lower front portion and the upper front portion are each welded to the back portion, the lower front portion and the upper front portion are connected at a clasp portion formed by overlapping each other in a folded-back state, the point seal portion is formed by heating while pressing from one side of the clasp portion.

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