Microwave-safe food packaging bags

Abstract

To provide a for-food electronic oven-compatible packaging bag having an inner film made not become obstructive when unsealed.SOLUTION: A for-food electronic oven-compatible packaging bag comprises a laminate film having a base-material layer P2 and a sealant layer P1 that is bent into the form of a cylinder having a joining part 1 centrally of a back-lining portion of a bag, to thereby provide a heat-sealing portion between opposed films in the joining part and a heat-sealing portion between opposed films in both opening ends of the cylinder, so that the heat-sealing portions are sealed after a food S is received inside. An inner film covering the food is arranged between the food and the film positioned on a front side of the packaging bag such that both ends are heat-sealed in the heat-sealing portion between the opposed films in both opening ends of the bag. Furthermore, a foam-ink layer 5 containing a thermally expandable micro-capsule to foam by the heat of heat-sealing is provided in a manner traversing from inside to outside of the packaging bag between the base-material layer and the sealant layer of the film positioned on a back side of the packaging bag in both opening ends of the cylinder.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a packaging bag made of plastic film, and more particularly to a microwave-safe packaging bag for food that is used when distributing food that can be heated in a microwave oven in a packaging bag. [Background technology]

[0002] Packaged foods are known in which food is placed in a microwave-safe plastic bag, which is then sealed and distributed in that sealed state. In this case, consumers who purchase the food heat the food in a microwave oven without opening the sealed bag. As a result, the internal pressure of the bag increases due to water vapor evaporated from the food and the thermal expansion of the air inside the bag, causing the bag to expand and eventually burst, posing a risk of accidents in which food and other items are scattered throughout the microwave.

[0003] However, the former known invention has a problem in that the manufacturing cost of the packaging bag increases due to the labor, process and material costs required for attaching the valve body.

[0004] On the other hand, in the latter known invention, it is difficult to set the heat seal strength, and if the internal pressure rises suddenly due to reasons such as high output from the microwave oven's magnetron or high moisture content in the food, there is a risk that other parts will peel off at the same time and the package will be destroyed before the pressure relief provided by the weak heat seal can function.

[0005] Furthermore, if the material is suddenly peeled off and steamed, there is a risk of a popping sound being generated.

[0006] Microwave-safe food packaging bags have the problem that they cannot be made without using easy-peel film or specially shaped seal bars. When using easy-peel film, there are drawbacks such as difficulty in controlling the seal strength due to variations in the quality of the easy-peel film, which weakens the seal strength on the easy-peel side and makes the bag more likely to tear.

[0007] On the other hand, when using a specially shaped seal bar, a unique seal bar must be made for each bag size, which means the seal must protrude inside the bag, which inevitably creates the problem of the seal easily retracting when external pressure is applied.

[0008] In order to prevent this type of accident, an invention has been proposed in which a valve is attached to the packaging bag in advance to release the pressure generated by the heating (Patent Document 1), and an invention in which the heat seal strength of part of the heat-sealed joint of the packaging body is weakened to make it easier to peel off due to the increase in internal pressure caused by water vapor evaporated by heating, and pressure is released by steaming through this point (Patent Document 2).

[0009] In order to solve the above problems, the applicant of the present application has proposed a microwave-safe packaging bag for food in which a laminated film of two or more layers, having at least a heat-resistant base layer and a sealant layer, is folded into a tube with the center of the back seal of the bag as the grommet, thereby creating a heat-seal section between opposing films at the grommet and between opposing films at both open ends of the tube, and the heat-seal section is sealed after food is placed inside.The microwave-safe packaging bag for food has a foaming ink layer that foams when heated during heat sealing, on the base layer side of the sealant layer that makes up the front film opposite the back seal, running across the bag from the inside to the outside (Patent Document 3).

[0010] According to the above-mentioned microwave-safe packaging bag for food, by partially providing a foaming ink layer that foams when heated by the heat seal, the interlayer strength of the laminated film is partially weakened, allowing steam that generates internal pressure to escape from there.This allows steam to escape from a specified location before internal pressure that would cause the heat seal portion to peel off is generated, preventing irregular ruptures. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Patent No. 3006528 [Patent Document 1] Patent No. 3006528 [Patent Document 3] Patent No. 7022468 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0012] Incidentally, the film on the front side of the packaging bag is printed with a design or trademark for sales purposes so that it can be seen by consumers. However, if the food comes into direct contact with the film, external shaking during transport can cause the food to move around, and the film can be rubbed, causing some of the food to adhere to the film and become dirty, which can impair the effectiveness of the design or trademark.

[0013] The above problem can be prevented by placing an inner film that covers all or part of the food between the food and the film on the front side of the packaging bag so that both ends of the inner film are positioned in the heat-sealed area between the opposing films at both open ends of the tube.

[0014] However, in this case, when the film on the front side and the film on the back side are peeled off to expose the food after heating the food, if the inner film remains on the film on the back side, the food will be covered by the inner film and become a hindrance, which is a problem. [Means for solving the problem]

[0015] The present invention was created with the objective of providing a microwave-safe food packaging bag that solves the above-mentioned problems.

[0016] In other words, the microwave-safe packaging bag for food of the present invention is made by folding a two-layer or more laminated film having at least a heat-resistant base layer and a sealant layer into a tubular shape with the center of the back seal of the bag as the grommet, thereby creating a heat-seal section between the opposing films at the grommet and heat-seal sections between the opposing films at both open ends of the tube, and the heat-seal section is sealed after the food is placed inside.In this microwave-safe packaging bag for food, an inner film that covers all or part of the food is arranged between the food and the film on the front side of the packaging bag so that both ends are heat-sealed at the heat-seal sections between the opposing films at both open ends of the tube, and a foaming ink layer containing heat-expandable microcapsules that foam when heated during heat sealing is arranged on the base layer side of the sealant layer, between the base layer and sealant layer of the film on the back side of the packaging bag at both open ends of the tube, crossing from the inside to the outside of the packaging bag.

[0017] In addition, the invention described in claim 2 is characterized in that, in the microwave-safe packaging bag for food, the microcapsule-containing foaming ink layer foams to 20 to 100 μm at temperatures of approximately 100°C for 30 to 60 seconds, 150°C for 1 second, and 160°C for 0.5 seconds.

[0018] The invention described in claim 3 is characterized in that in the microwave-safe food packaging bag, the microcapsule-containing foamed ink layer is provided by gravure printing.

[0019] The invention described in claim 4 is characterized in that in the microwave-safe food packaging bag, a brittle film that is easily torn is used as the sealant layer. [Effects of the Invention]

[0020] The thermally expandable microcapsules contained in the foaming ink layer foam due to the heat generated during heat sealing, which inhibits lamination at that point.

[0021] Therefore, in the microwave-safe packaging bag for food of the present invention, a foaming ink layer containing heat-expandable microcapsules that foam when heated during heat sealing is provided on the base layer side of the sealant layer, between the base layer and sealant layer of the film located on the back side of the packaging bag at both open ends of the tube, so that it runs across from the inside to the outside of the packaging bag.This partially weakens the interlayer strength of the laminated film, allowing steam that generates internal pressure to escape.This allows steam to escape from a designated location before internal pressure sufficient to cause the heat-sealed portion to peel off is generated, preventing irregular ruptures.

[0022] In this case, the layer for weakening the interlayer strength is applied by printing as a foaming ink layer, so microwave-safe packaging bags for food can be manufactured at low cost without the need for special separate parts or cutting processes.

[0023] Furthermore, the interlayer strength weakens due to heating, and peeling progresses due to the passage of steam caused by internal pressure between the base material layer and sealant layer of the film located on the back of the packaging bag, while heat seals are maintained between the base material layer and sealant layer of the film located on the front side, between the sealant layer and inner film, and between the inner film and the sealant layer of the film located on the back side.Therefore, when the film located on the front side and the film located on the back side are peeled off to expose the food after heating, the inner film remains interlocked between the sealant layers of the film located on the front side and the film located on the back side, and is removed along with the film located on the back side that is being peeled off, so the food is not covered by the inner film and does not get in the way. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a perspective view of the film side located on the back side of the microwave-safe packaging bag for food of the present invention. FIG. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] FIG. 10 is a cross-sectional view of the open end of the tube that constitutes the bag. [Figure 5] FIG. 10 is a perspective view of the film side located on the back side before bag making. BEST MODE FOR CARRYING OUT THE INVENTION

[0025] Specific embodiments of the present invention will be described below with reference to the accompanying drawings. Figure 1 is a perspective view showing a pouch body P of the present invention, a microwave-safe packaging bag for food, in the state before opening. This pouch body P is based on a known pouch body constructed by folding a plastic film into a cylindrical shape with a seam 1 in the center of the back sealing part S of the pouch body, and then bonding together the seam and the inner surfaces of the open ends 4, 4 of the tube (see Figures 2 and 3).

[0026] The plastic film that makes up the bag body P is made of a laminated film of two or more layers, having at least a heat-resistant base layer and a sealant layer, and has a heat-seal section between opposing films at the seam 1 and between opposing films at both open ends of the tube, and the heat-seal sections are sealed after the food S is placed inside. In the figure, symbol F1 is the film located on the front side of the packaging bag P, and a design or trademark for sales purposes is printed on it so that it can be visually recognized by consumers. In the figure, symbol F2 is the film located on the back side of the packaging bag P, where the seam 1 is located.

[0027] FIG. 4 shows an example of lamination of plastic films constituting the bag body P, in which a two-layer structure is used in which a sealant layer P1 is laminated on a heat-resistant base material layer P2.

[0028] Examples of the film that constitutes the base material layer P2 include OPP, PET, and ONY, and examples of the film that constitutes the sealant layer P1 include CPP and LL.

[0029] It is also possible to use a brittle film that is easily torn as the sealant layer.

[0030] Figure 2 is a longitudinal cross-sectional view of the microwave-safe packaging bag for food of the present invention during bag production. In the figure, the symbol F denotes the food to be placed inside, and an inner film 10 that covers all or part of the food is placed between the food and film F1 located on the front side of the packaging bag P so that both ends of the inner film 10 are heat-sealed in the heat-sealed areas between the opposing films F1 and F2 at both opening ends 4 of the tube. During bag production, the inner film 10 is sandwiched and fixed between film F1 located on the front side and film F2 located on the back side.

[0031] The inner film 10 may be made of, for example, CPP or LL.

[0032] In the figure, the symbol 5 denotes a foamed ink layer, which is arranged across the packaging bag from the inside to the outside, on the base layer side of the sealant layer between the base layer P2 and the sealant layer P1 of the film F2 located on the back side of the packaging bag P at both open ends 4 of the tube.

[0033] The foaming ink layer 5 is an ink containing thermally expandable microcapsules that expand due to the heat generated during heat sealing. For example, microcapsules based on a thermoplastic resin such as vinyl chloride resin, ethylene vinyl acetate resin, or acrylic resin may contain aliphatic hydrocarbons such as isobutane, butane, isopentane, or n-pentane (a specific product is LG-MC Bubble Agent E, manufactured by Tokyo Ink Co., Ltd.). Here, we use an ink that expands to 20 to 100 μm at temperatures of approximately 100°C for 30 to 60 seconds, 150°C for 1 second, and 160°C for 0.5 seconds.

[0034] The foamed ink layer 5 is placed across the heat seal portion of the top and bottom of the opposing films at both open ends 4, 4 of the tube, from the inside to the outside of the packaging bag, and based on the results of the following experiment, it is desirable that the width of the layer be 15.4% to 23.0% of the top and bottom seal width.

[0035] The experiment was carried out on a bag containing Chinese buns, measuring 130mm wide x 170mm long, with the foamed ink layer placed in the center of the 130mm wide top and bottom seal. The results are shown below, where the width of the foamed ink layer was varied within the range of 20mm to 40mm. 20mm → 15.4% of the top and bottom seal width. The result was an explosion. 30mm → 23.0% of the top and bottom seal width. The bag was successfully steamed without exploding. 40mm → 30.7% of the top and bottom seal width. The bag was successfully steamed without exploding.

[0036] In the above process, the foamed ink layer 5 is applied by gravure printing. In addition, although not shown, printing for whitening or design is performed between the layers.

[0037] Figure 4 shows the operation of the present invention, i.e., the steaming process. When food S sealed in a packaging bag P is heated in a microwave oven, water vapor evaporates, and the resulting pressure and the thermal expansion of the air cause the internal pressure of the packaging bag to increase, causing it to swell and burst. However, the sealant edge breaks at the foaming ink area located at the three-point intersection X, allowing steam to escape between the layers and preventing bursting.

[0038] Furthermore, the interlayer strength weakens due to heating, and peeling progresses due to the passage of steam caused by internal pressure between the base material layer P2 of film F2 located on the back side of the packaging bag P and the sealant layer P1, while heat seals are maintained between the base material layer P2 of film F1 located on the front side and the sealant layer P1, between the sealant layer P1 and inner film 10, and between the inner film 10 and the sealant layer P1 of film F2 located on the back side.Therefore, when the film F1 located on the front side and the film F2 located on the back side are peeled off to expose the food S after heating, the inner film remains interlocked between the sealant layers of the film located on the front side and the film located on the back side, and is removed together with the film located on the back side that is being peeled off, so the food is not covered by the inner film and does not get in the way.

[0039] Table 1 shows the laminated structure of the plastic film that constitutes the bag body, and the seal strength, lamination strength, and steam permeability results for each structure. [Table 1]

[0040] As a result of experiments, the inventors of the present application have found that a film constituting the sealant layer P1 on which the foamed ink layer 5 is provided, which has tear strength in Elmendorf tear strength measurement (in accordance with JIS K7128) of MD 1.2 (N) or less and TD 2.7 (N) or less when MD and TD are 30μ, MD 1.5 (N) or less and TD 3.1 (N) or less when MD and TD are 40μ, and MD 2.1 (N) or less and TD 3.7 or less when MD and TD are 50μ, and which has a dart impact strength (in accordance with JIS K7124) of 3.5 (J) or less, is suitable for achieving the effect of the present invention of realizing vapor permeability and not producing popping sounds.

[0041] Table 2 shows the tear strength and impact strength of commercially available films from various manufacturers. [Table 2]

[0042] The plastic film constituting the bag body P may have a three-layer structure, for example, a sealant layer may be laminated onto two heat-resistant base layers. In this case, the foamed ink layer is provided on the base layer side of the sealant layer constituting the film located on the back side of the packaging bag. [Explanation of symbols]

[0043] P bag body S food F1 Film located on the front side F2 Film behind P1 sealant layer P2 base material layer 1. Prayer point 4 Open End 5 Foamed ink layer

Claims

1. This microwave-safe packaging bag for food is made by folding a two- or more-layer laminated film having at least a heat-resistant base layer and a sealant layer into a cylindrical shape with the center of the back-attached part of the bag as the grommet, thereby providing a heat-seal section between the opposing films at the grommet section and heat-seal sections between the opposing films at both open ends of the tube, and the heat-seal section is then sealed after the food is placed inside. This microwave-safe packaging bag for food is characterized in that an inner film that covers all or part of the food is arranged between the food and the film located on the front side of the packaging bag so that both ends of the inner film are heat-sealed at the heat-seal sections between the opposing films at both open ends of the tube, and a foaming ink layer containing heat-expandable microcapsules that foam when heated during heat sealing is provided on the base layer side of the sealant layer between the base layer and sealant layer of the film located on the back side of the packaging bag at both open ends of the tube, so that the foaming ink layer crosses from the inside to the outside of the packaging bag. The foaming ink layer is made of heat-expandable microcapsules that foam when heated during heat-sealing and is provided on the base layer side of the sealant layer so that the foaming ink layer crosses from the inside to the outside of the packaging bag between the base layer and sealant layer of the film located on the back side of the packaging bag at both open ends of the tube.

2. 2. The microwave-safe packaging bag for food according to claim 1, wherein the microcapsule-containing foamable ink layer foams to a thickness of 20 to 100 μm at temperatures of about 100° C. for 30 to 60 seconds, 150° C. for 1 second, and 160° C. for 0.5 seconds.

Images