Microwave pouch

Abstract

To provide a pouch for a microwave oven in which a cut-in processed part is free from unintentional fracture during heating while giving an excellent opening property.SOLUTION: There is provided a pouch for a microwave oven which is formed into a bag shape by thermally bonding laminated films to each other and has a steam venting mechanism for automatically venting steam in a storage part when heated, in which the laminated film has a vapor deposition polyethylene terephthalate layer, a polybutylene terephthalate layer, and a non-oriented polypropylene layer in order from the outer layer. At least a part of the intermediate layer of the laminated film has a cut-in processed part. The outer layer of the laminated film has no cut-in processed part. In a state where at least a part of the polybutylene terephthalate layer of the laminated film in the thickness direction is not cut-in processed, the cutting depth of the polybutylene terephthalate layer is such a depth that the thickness of the polybutylene terephthalate layer remaining without being cut is 2 μm or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pouch for a microwave oven that is formed into a bag shape by thermally bonding laminated films and has an automatic steam venting mechanism that automatically vents internal steam when heated.

Background Art

[0002] Conventionally, there has been on the market a packaged food that is formed into a bag shape by thermally bonding laminated films and contains cooked or semi-cooked food, and the food is heated and cooked by a microwave oven when eating the food.

[0003] In such a pouch, when heated in a microwave oven, the internal pressure of the pouch increases due to steam generated from the food and thermal expansion of the internal air, and there is a risk that the pouch may burst or deform, or the food inside the pouch may scatter due to bursting.

[0004] Therefore, in recent years, an automatic steam venting mechanism that automatically vents internal steam when heated is generally provided in pouches for microwave ovens. As such a pouch having an automatic steam venting mechanism, there is known a pouch in which a part of the laminated films is thermally bonded to provide an annular steam venting seal portion, and a steam venting hole is provided in a steam release portion surrounded by the annular steam venting seal portion (see, for example, Patent Documents 1 and 2).

[0005] In the pouch of this Patent Document 1, when the internal pressure of the pouch increases with heating by a microwave oven, a part of the steam venting seal portion starts to break, and due to stress concentration caused by the increase in the internal pressure of the pouch, the steam venting seal portion retreats, and when peeling reaches the weakened portion, water vapor and the like are discharged to the outside.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] On the other hand, some pouches are known to be processed in a way that allows users to open them by hand without using scissors or other tools to remove the contents. One such process is a half-cut process, which involves creating linear cuts in the film. However, if a microwave pouch is subjected to the aforementioned half-cut process, there is a risk that it may rupture at the processed area when the internal pressure of the pouch increases due to heating in a microwave oven.

[0008] The present invention aims to solve the above-mentioned problems and provide a microwave pouch that offers excellent opening capabilities while preventing the perforated portion from unintentionally breaking during heating. [Means for solving the problem]

[0009] The microwave pouch of the present invention is formed into a bag shape by heat bonding laminated films to create a peripheral seal portion that surrounds the four sides of the containment area, and is equipped with an automatic steam release mechanism that automatically releases steam from inside the containment area during heating. The automatic steam venting mechanism comprises a steam venting seal portion configured to begin peeling when the internal pressure of the containment portion increases during heating, and a steam release portion surrounded by the steam venting seal portion. The aforementioned steam vent seal portion is The short side of the peripheral sealing portion is not continuous with the aforementioned portion, and The aforementioned peripheral seal portion The longer side It is formed in a continuous ring shape, The laminated film is composed of, in order from the outer layer, a vapor-deposited polyethylene terephthalate layer, a polybutylene terephthalate layer, and an unstretched polypropylene layer. The laminated film has a notched portion in at least a part of the intermediate layer, and the notched portion passes through the space between the upper short side of the peripheral seal portion and the steam vent seal portion in the laminated film. Connecting the long sides on both sides of the peripheral seal portion, so as to cross the housing portion It extends in one direction along the direction of the formed surface. consecutive It is a straight line, The above problem is solved by ensuring that no notched portions are formed in the outer layer of the laminated film, and that at least a portion of the thickness direction of the polybutylene terephthalate layer of the laminated film is uncut, and that the depth of the cut in the polybutylene terephthalate layer is such that the thickness of the remaining uncut polybutylene terephthalate layer is 2 μm or more. [Effects of the Invention]

[0010] The microwave pouch of the present invention is equipped with an automatic steam release mechanism that automatically releases steam from the contents during heating, thereby ensuring reliable steam release. Furthermore, the laminated film constituting the microwave pouch has a polybutylene terephthalate layer in the intermediate layer, and at least a portion of the intermediate layer of the laminated film has a notched portion. As a result, at least a portion of the thickness direction of the polybutylene terephthalate layer is not notched, which allows the polybutylene terephthalate to exhibit its characteristic of being stretchable and difficult to tear at high temperatures. This provides excellent ease of opening while preventing the notched portion from unintentionally breaking during heating. [Brief explanation of the drawing]

[0011] [Figure 1] This is a plan view showing a microwave pouch according to one embodiment of the present invention. [Figure 2] Figure 1 is an enlarged view showing the configuration of the automatic steam release mechanism for microwaveable pouches. [Figure 3] This diagram illustrates the process of venting vapor from a pouch, and is a schematic diagram showing a cross-section along a straight line connecting the center point of the pouch and the seal peeling start point. [Modes for carrying out the invention]

[0012] The pouch for a microwave oven of the present invention is formed by heat-sealing laminated films stacked on top of each other so as to form a bag shape, and is configured to have an automatic steam venting mechanism that automatically vents the steam inside the pouch to the outside during heating.

[0013] Hereinafter, the pouch for a microwave oven according to an embodiment of the present invention will be described based on the drawings.

[0014] FIG. 1 is a plan view showing a pouch for a microwave oven according to an embodiment of the present invention. This pouch for a microwave oven (hereinafter simply referred to as "pouch") 100 has an outer shape that is, for example, rectangular in a plan view, and a peripheral seal portion 105 formed by thermally bonding a front-side laminated film 110 (see FIG. 3) and a back-side laminated film 115 (see FIG. 3) is formed so as to surround the four sides of a storage portion 101 located at the center of the pouch 100.

[0015] The laminated film has a layer structure of (1) a polybutylene terephthalate layer (PBT layer) / a vapor-deposited polyethylene terephthalate layer (vapor-deposited PET layer) / an unstretched polypropylene layer (CPP layer), or (2) a vapor-deposited polyethylene terephthalate layer (vapor-deposited PET layer) / a polybutylene terephthalate layer (PBT layer) / an unstretched polypropylene layer (CPP layer). The thickness of the polybutylene terephthalate layer is, for example, 10 μm or more and 50 μm or less. The vapor-deposited polyethylene terephthalate layer is a vapor-deposited film-containing film in which a vapor-deposited film made of a metal oxide such as alumina or silicon oxide is formed on a polyethylene terephthalate film. The thickness of the vapor-deposited polyethylene terephthalate layer is, for example, 10 μm or more and 50 μm or less. The unstretched polypropylene layer is an inner layer that functions as a sealant layer. The thickness of the unstretched polypropylene layer is, for example, 20 μm or more and 150 μm or less.

[0016] In the laminated film, a cut portion 130 is formed in at least a part of its intermediate layer (when having the layer structure of (1) above, it is a vapor-deposited PET layer; when having the layer structure of (2) above, it is a PBT layer). The cut portion 130 is linear and extends in one direction in the plane direction formed on the laminated film, and is arranged to connect two notches 135 formed on both sides of the peripheral seal portion 105 and cross the accommodating portion 101. When the laminated film has the layer structure of (1) above, the cut portion 130 may be a cut that penetrates the vapor-deposited polyethylene terephthalate layer, which is the intermediate layer, in the thickness direction, and further, a part of the inner layer (sealant layer) in the thickness direction may be cut. When the laminated film has the layer structure of (2) above, it is preferable that only a part of the PBT layer in the thickness direction is cut. When the cut portion 130 is a cut where only a part of the PBT layer in the thickness direction is cut, the depth of the cut may be such that the thickness of the remaining PBT layer that is not cut is ensured to be, for example, 2 μm or more. The cut portion 130 can be formed by, for example, half-cut processing. The cut portion 130 is not limited to being linear, and may be curved or bent. Also, the cut portion 130 does not have to be continuous. For example, it may be formed intermittently in a chain line shape on a virtual straight line.

[0017] The pouch 100 is provided with an automatic steam venting mechanism 120 that automatically vents the steam in the accommodating portion 101 to the outside during heating. As shown in FIGS. 2 and 3, the automatic steam venting mechanism 120 includes a steam venting seal portion 121 configured such that the surface-side laminated film 110 and the back-side laminated film 115 start to peel off when the internal pressure of the accommodating portion 101 rises during heating, a steam release portion 122 surrounded by the steam venting seal portion 121, and a steam venting portion 123 formed in the steam release portion 122.

[0018] The steam venting seal portion 121 is formed, for example, in an annular shape by heat bonding the surface laminated film 110 and the back laminated film 115, and has a seal peeling start portion S at the outer edge closest to the center of the housing portion 101, which is initiated by the steam generated inside the housing portion 101 when heated in a microwave oven. The formation of the steam vent seal portion 121 can be performed simultaneously with or separately from the formation of the peripheral seal portion 105.

[0019] The steam release section 122 is formed as an unsealed section where, for example, the surface laminated film 110 and the back laminated film 115 are not heat-bonded. The specific form of the steam release portion 122 is not limited to this, and for example, the steam release portion may be formed as a weakly bonded portion that is heat-bonded to have a lower sealing strength than the peripheral seal portion 105 and the steam release seal portion 121, or as a patterned bonded portion that has knurled seals or the like applied to the surface laminated film 110 and the back laminated film 115.

[0020] The steam vent section 123 is formed as a hole or slit, and in this embodiment, for example, the opening shape is formed as a circular through-hole. The steam vent section 123 may be provided on only one of the surface laminated film 110 and the back laminated film 115, or it may be provided on both the surface laminated film 110 and the back laminated film 115.

[0021] The seal peeling start point S of the steam vent seal portion 121 is preferably located on or inside the circumference of a virtual circle R that is inscribed in the center of the inner end of the peripheral seal portions 105 on the two short sides of the pouch 100. With this configuration, it becomes possible to discharge water vapor inside the pouch 100 from the weakened portion, and the automatic opening by the automatic steam vent mechanism 120 can be made even more reliable. In the pouch 100 of this embodiment, the steam vent seal portion 121 is provided to be continuous with the peripheral seal portion 105 while satisfying the above conditions.

[0022] When the pouch 100 is heated, the steam generated from the contents causes the pouch 100 to expand from the center point P toward the peripheral seal portion 105, resulting in radial stress concentration as shown by the virtual circle R in Figure 1, whose radius is the distance from the center point P to the inner end of the shorter peripheral seal portion 105. Due to this stress concentration, the peeling of the surface laminated film 110 and the back laminated film 115 begins at the steam vent seal portion 121, which is the part closest to the center point P of the pouch 100, at the seal peeling start portion S. Then, as shown in Figure 3, the steam vent seal portion 121 retracts due to the stress concentration caused by the increase in internal pressure of the pouch 100, and when the peeling reaches the steam release portion 122, the pouch 100 partially opens and steam is discharged to the outside through the steam vent portion 123.

[0023] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various design modifications can be made without departing from the present invention as described in the claims. For example, the pouch of the present invention is not limited to the four-sided seal type described above, but can be applied to various types of pouches such as standing pouches, flat pouches, three-sided seal types, pillow types, and gusset types. Furthermore, the shape of the pouch may be any shape other than the rectangular shape shown in the above-described embodiment, such as a trapezoid or an irregular shape with some unevenness.

[0024] Furthermore, the steam vent seal portion does not need to be provided in a continuous manner with the peripheral seal portion; it may be provided independently inside the outer seal portion. Also, the steam vent seal portion may be formed in other shapes, such as a rectangular ring, and its dimensions can be selected as appropriate. Furthermore, when forming a steam vent as a hole, the opening shape of the hole does not have to be circular; it can be any shape, such as oval, triangular, square, trapezoidal, or triangular, and its dimensions can be selected as appropriate.

[0025] The following describes examples taken to confirm the effects of the present invention.

[0026] [Example 1] Referring to the configuration shown in Figure 1, a four-sided sealed microwave pouch equipped with an automatic steam release mechanism (hereinafter referred to as "Sample A") was manufactured. Sample A has a width dimension (horizontal dimension in Figure 1) of 130 mm and a length (vertical dimension in Figure 1) of 175 mm. The laminated film used in this sample A consists of a 15 μm thick PBT layer (outer layer), a 12 μm thick vapor-deposited PET layer (intermediate layer), and a 70 μm thick CPP layer (inner layer), all laminated in this order, with a notched section (130) formed at the position shown in Figure 1. The notched section (130) penetrates the entire intermediate layer in the thickness direction.

[0027] As a heating test, sample A, containing 180g of water, was heated under heating conditions of rated power of 500W for 3 minutes, and the presence or absence of breakage in the notched area and the presence or absence of automatic opening (steam passage) in the steam vent seal area were checked. In Sample A, it was confirmed that no rupture occurred at the notched portion even when the internal pressure of the pouch increased due to heating. Furthermore, in Sample A, it was confirmed that the automatic opening mechanism performed correctly.

[0028] [Example 2] In Example 1, a film was used in which a 12 μm thick vapor-deposited PET layer (outer layer), a 15 μm thick PBT layer (intermediate layer), and a 70 μm thick CPP layer (inner layer) were laminated in this order. Sample B was prepared in the same manner as Sample A, except that a notched section (130) was formed by cutting a portion of the intermediate layer (PBT layer) in the thickness direction to a depth of 13 μm. A heating test was performed on Sample B in the same manner as in Example 1. The presence or absence of breakage in the notched portion and the presence or absence of automatic opening (steam release) of the steam vent seal portion were checked. It was confirmed that breakage did not occur from the notched portion even when the internal pressure of the pouch increased due to heating. Furthermore, it was confirmed that the automatic opening by the automatic steam release mechanism worked properly in Sample B. [Explanation of Symbols]

[0029] 100 ··· Microwave pouch 101 ··· Storage Unit 105 ··· Peripheral seal section 110 ··· Surface laminated film 115 ··· Laminated film on the back side 120 ··· Automatic steam release mechanism 121... Steam vent seal section 122... Steam release section 123... Steam vent section 130 ··· Cutting section 135 ··· Notch P... Center point of the pouch R ··· Virtual Yen S... Seal peeling start point

Claims

[Claim 1] A microwave pouch is formed into a bag shape by heat-bonding laminated films to create a peripheral seal that surrounds the four sides of the containment area, and is equipped with an automatic steam release mechanism that automatically releases steam from inside the containment area during heating. The automatic steam venting mechanism comprises a steam venting seal portion configured to begin peeling when the internal pressure of the containment portion increases during heating, and a steam release portion surrounded by the steam venting seal portion. The steam venting seal portion is not continuous with the short side of the peripheral seal portion, but is formed to form an annular shape continuous with the long side of the peripheral seal portion. The laminated film is composed of, in order from the outer layer, a vapor-deposited polyethylene terephthalate layer, a polybutylene terephthalate layer, and an unstretched polypropylene layer. The laminated film has a notched portion in at least a part of the intermediate layer, and the notched portion is a continuous straight line extending in one direction in the planar direction, formed in the laminated film to pass between the upper short side of the peripheral seal portion and the steam vent seal portion, connecting the long sides on both sides of the peripheral seal portion and traversing the housing portion. A microwave pouch characterized in that no notched portion is formed in the outer layer of the laminated film, at least a portion of the thickness direction of the polybutylene terephthalate layer of the laminated film is uncut, and the depth of the cut in the polybutylene terephthalate layer is such that the thickness of the remaining uncut polybutylene terephthalate layer is 2 μm or more.

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