Manufacturing method for microwave heating packaging

Abstract

The present invention provides a method for manufacturing microwave heating packaging that includes a pressure release section capable of safely and reliably releasing high-pressure steam during microwave cooking. [Solution] The method for manufacturing the packaging includes a complete cutting step S24 in which a U-shaped cut is made to penetrate the sheet member in the thickness direction from the outer surface to the inner surface, and a heat welding step S25 in which the sealant layers are partially heat-welded together to form a heat-sealed area so that a food storage space is formed in the packaging. In the partial rejoining step S25A, the divided area of ​​the sealant layer among the cuts that penetrated each sheet member is rejoined. The cut is formed in a protruding area that protrudes into the food storage space, and the U-shaped folded curved portion is formed by a first arc, and the outer edge of the protruding area is formed by a second arc concentric with the first arc, and when the radius of the first arc is r1 and the radius of the second arc is r2, r1:r2 = 2 to 4:8.

Description

[[Technical Field]]

[0001] The present invention relates to a method for producing a package for microwave heating, and more specifically to a method for producing a package for microwave heating that is provided with a pressure releasing portion (cut portion) that automatically releases vapor pressure (internal pressure) when heated by a microwave oven. [[Background Art]]

[0002] (Conventional package for microwave heating) Conventionally, packages for microwave heating in which two heat-resistant resin films are heat-sealed (thermally bonded) along the peripheral edge, and cooked or semi-cooked food materials are hermetically sealed inside the package are commercially available. This type of package allows food materials to be heated and cooked by directly heating the package in a microwave oven.

[0003] (Conventional steam venting mechanism) Usually, such a package is provided with a mechanism (pressure releasing portion) for releasing water vapor to the outside when the internal pressure reaches or exceeds a certain value, in order to prevent the bag from bursting (bag breakage) due to increased internal pressure caused by water vapor generated from food materials during heating.

[0004] (Known vent hole (Patent Document 1)) As a package for microwave having such a steam venting mechanism, for example, as disclosed in Patent Document 1, a package having a through hole (vent hole) provided in a part of a heat-sealed surface is known.

[0005] (Problems of known vent holes 1 (causes of product damage and breakage)) However, in the conventional product provided with the above through-hole, there is a risk that a part of an adjacent product enters the through-hole during the manufacturing process, thereby causing damage or breakage to the product. Furthermore, the through-hole can also cause accidental catching and damage during transportation and storage of the product.

[0006] (Problems of known vent holes 2 (risk of foreign matter mixing into the product)) Furthermore, punching is required during manufacturing to create through-holes, and there is a risk that the punched-out material (circular film) may become mixed in as foreign matter inside the packaging. In addition, there is a risk that foreign matter may enter the through-holes or the unheat-sealed areas around the through-holes during product transportation and display.

[0007] (Cuts made only in the base layer (Patent Documents 2, 3)) Other known prior art with a steam venting mechanism includes packaging in which V-shaped or U-shaped notches are formed in all or part of the heat-resistant base material layer of one side of the film (see Patent Documents 2 and 3). These notches can usually be formed by irradiating them with a laser using a laser processing machine after the base material layer and sealant layer are overlapped and heat-sealed in the bag-making process following the sheet material manufacturing process.

[0008] (Known problem with the cut section 1 (Inadequate release of internal pressure)) However, in these prior art packaging structures, the portion directly below the cut in the base layer is not weakened at all, and the strength of the sealant layer itself is no different from that of other parts. Therefore, in these packaging structures, there is no guarantee that the opening will occur directly below the cut as expected when the internal pressure rises, and there is a risk that the high-temperature steam generated during microwave cooking cannot be safely and reliably released.

[0009] (Known problem with the cut-out section 2 (Poor appearance of the product upon shipment)) Furthermore, additional laser processing after the bag-making process melts part of the product, negatively affecting the appearance of the product at the time of shipment. In other words, it is preferable that the pressure-releasing cutouts be formed before or during the bag-making process.

[0010] (Disclosure of prior art by the inventors) To address these problems, the present inventors have already proposed a steam venting mechanism in which, during the manufacturing process of the packaging, a portion of the upper and lower films is completely cut in the thickness direction, and then only the sealant layer is heat-sealed again to form a cut section (see Patent Document 4). This steam venting mechanism reduces the likelihood of poor release of internal pressure in the packaging during microwave cooking and eliminates the risk of damage or contamination during manufacturing and transportation.

[0011] (Problems with prior art) However, the inventors believe that the manufacturing process of the packaging described in Patent Document 4 still has room for improvement, as the internal pressure release capacity of the steam venting mechanism varies depending on the manufacturing conditions. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2002-249176 [Patent Document 2] Japanese Patent Publication No. 2001-287774 [Patent Document 3] Japanese Patent Publication No. 2007-331816 [Patent Document 4] Patent No. 6578329 [Overview of the project] [Problems that the invention aims to solve]

[0013] This invention was proposed in view of the above circumstances, and aims to provide a method for manufacturing microwave heating packaging equipped with a pressure release section that can safely and reliably release high-pressure steam during microwave cooking.

[0014] Another objective of the present invention is to provide a method for manufacturing microwave heating packaging that minimizes damage and rupture during manufacturing and transportation, and eliminates the risk of foreign matter contamination. [Means for solving the problem]

[0015] That is, the present invention employs, for example, the following configuration and features. (Aspect 1) A method for manufacturing a package for microwave heating comprising a plurality of sheet members, wherein each of the sheet members comprises at least a sealant layer, a base material layer laminated on an outer side of the sealant layer in the thickness direction, and an adhesive layer connecting the sealant layer and the base material layer, and a half-folding step of half-folding a conveying sheet to overlap the sheet members in the thickness direction; a complete cutting step of providing a notch portion, which forms a U-shaped character shape and is formed such that an opening of the character shape faces outward from the center of the package, in a part of a predetermined heat-sealing region of the overlapped sheet members over the entire thickness direction from the outer surface to the inner surface of the sheet members; a heat-sealing step of partially heat-welding the sealant layers of the sheet members to each other to form a heat-sealed region such that a food storage space is formed in the package; in the heat-sealing step, a partial re-bonding step of re-bonding a divided region of the sealant layer among the notch portions formed in each sheet member in the complete cutting step; comprising, in the heat-sealing step, the sealant layers of the sheet members are welded to each other such that the heat-sealed region is formed along a peripheral edge of the sheet member and a protruding region protruding from a part of the peripheral edge into the food storage space, the notch portion is formed in the protruding region, and the U-shaped folded curved portion is formed by a first circular arc, an outer edge of the protruding region is formed by a second circular arc concentric with the first circular arc, and when a radius of the first circular arc is r1 and a radius of the second circular arc is r2, r1:r2 = 2 to 4:8, a method for manufacturing a package for microwave heating, characterized by the above. (Aspect 2) in the heat-sealing step, heat welding is performed in n separate steps by sequentially pressing n (n≧2) heat-sealing plates arranged in series in a conveying direction of the sheet members against the predetermined heat-sealing region of the sheet members, and In the n-th heat welding step, at least one of the heat sealing plates also performs heat welding on the predetermined heat seal region of the sheet member disposed forward or rearward in the conveyance direction, The method for producing a package for microwave heating according to aspect 1, characterized by the above-mentioned feature. (Aspect 3) In the complete cutting step, the notched portion is formed by mechanical means using a blade, and the sheet member is arranged such that the character-shaped opening of the notched portion faces forward with respect to the conveyance direction of the production line, The method for producing a package for microwave heating according to aspect 1 or 2, characterized by the above-mentioned feature. Effects of the Invention

[0016] According to the package for microwave heating produced by the production method of the present invention, since it has the notched portion (i.e., the pressure releasing portion) having the above configuration, high-temperature and high-pressure steam generated during microwave cooking can be released automatically, safely and reliably.

[0017] Furthermore, since the pressure releasing portion of the present invention is not formed by conventional through-holes or the like, it does not cause unintended catching or foreign matter contamination during production or transportation of the product.

[0018] Furthermore, in the pressure releasing portion of the present invention, both the base material layer and the sealant layer are once cut in the thickness direction, and thereafter only the sealant layer is re-welded (with reduced strength, however), so that when the internal pressure of the package increases, a crack (pressure release passage) is reliably formed at the re-welded portion.

[0019] Furthermore, since the package for microwave heating provided with the pressure releasing portion of the present invention can release steam at a desired internal pressure, uneven heating of food materials sealed in the package can be prevented, and the food materials can be finished deliciously.

[0020] Furthermore, according to a preferred embodiment of the present invention, by moving the sheet member in the conveying direction of the manufacturing line and performing heat welding of the sheet member in multiple stages using multiple heating sealing plates, and simultaneously performing heat welding of the sheet members before and after the stage, the cycle time is shortened and productivity is improved. In addition, because the heat welding time per stage is short, melting of the base material layer can be prevented. [Brief explanation of the drawing]

[0021] [Figure 1] A schematic diagram showing the front view and cross-sectional structure of the packaging body of the present invention. [Figure 2] This is an enlarged schematic diagram showing the pressure release portion and protruding region of the present invention. [Figure 3] This figure schematically illustrates the method for manufacturing the packaging of the present invention. [Figure 4] This is a flowchart showing the detailed steps in the manufacturing method of the packaging material of the present invention (particularly the bag-making process). [Figure 5] This figure shows the state of the package at each step of the manufacturing method of the present invention. [Figure 6] This is a schematic diagram showing the cross-sectional structure of the notched portion in Example 3 and the Comparative Example. [Figure 7] This diagram shows the location of the test specimen for tensile testing and the results of the tensile test. [Modes for carrying out the invention]

[0022] The present invention will be described below based on the embodiments shown in the drawings, but the present invention is not limited in any way to the specific embodiments described below. In each figure, the same or corresponding components are denoted by the same reference numerals. [Examples]

[0023] (Outline of the packaging of the present invention) Figures 1(a) and 1(b) are schematic diagrams showing the front view and cross-sectional structure of the packaging body of the present invention.

[0024] The microwave heating packaging 1 of the present invention (Example 1) (hereinafter also simply referred to as "packaging") is a three-sided sealed bag made by overlapping two sheet members 2,2 made of laminated film having a sealant layer 3 and a base material layer 5 described later, and heat-sealing three sides of its peripheral edge (left and right sides and bottom side) (see Figure 1(a)).

[0025] (Laminated structure of sheet material) Each sheet member 2 comprises, as shown in Figure 1(b), at least a sealant layer 3, a heat-resistant base material layer 5, and an adhesive layer 4 connecting the sealant layer 3 and the base material layer 5. Here, the base material layer 5 may be laminated in multiple layers from a commercial standpoint. For example, a printing layer 8 and an adhesive layer 7 may be further provided between the first base material layer 6 and the second base material layer 9.

[0026] (Material of the base layer) The base material 5 can be made of nylon, polypropylene, polyethylene terephthalate, polybutylene terephthalate, etc., but is not limited to these.

[0027] (Materials for the sealant layer) For example, unoriented polypropylene is envisioned as the material for the sealant layer 3, but it is not necessarily limited to this.

[0028] (Cross-sectional structure of the packaging) To illustrate the cross-sectional structure of the packaging 1 of Example 1, Figure 1(a) is divided into regions A, B, and C1 (or C2). Here, region C1 (or C2) is a heat-sealed region 11 where sheet members 2,2 are heat-welded together. Region B is a region where the sheet members 2,2 are not bonded together and can move freely from one another, and a food storage space 10 for storing food (not shown) is formed between these members 2,2. The opening of the food storage space 10 is normally sealed when food is placed inside.

[0029] Region A is a heat-sealed region 11 similar to region C1 (or C2), in which a notch (pressure release portion 12), described later, is further formed. This region A includes a protruding region 11C that extends toward the food storage space 10.

[0030] (Preferred shape of pressure release portion and heat seal protruding region) The shape and structure of the packaging body 1 described above have some commonalities with the packaging body disclosed in Patent Document 4. However, through subsequent improvements, the inventors have found that by setting the shape of the pressure release portion 12 and the surrounding heat seal protruding region 11C, and their relative dimensional ratios, as follows, the steam release performance (internal pressure release capacity) of the packaging body 1 can be dramatically improved, and the packaging performance during manufacturing and use of the packaging body can be sufficiently maintained.

[0031] (Notched area) As shown in Figure 2, the pressure release portion 12 is a U-shaped notch, and the folded curved portion 12A of the U is formed by a circular arc (first circular arc) with the center point O as the base point. On the other hand, the outer edge 11Ca of the tip of the protruding region 11C is also a circular arc (second circular arc, that is, a circular arc concentric with the first circular arc) with the aforementioned center point O as the base point. Furthermore, if the radius of the first circular arc is r1 and the radius of the second circular arc is r2, then preferably r1:r2 = 2 to 4:8 (i.e., 2:8 to 4:8), and even more preferably r1:r2 = 3:8.

[0032] By configuring the folded-over curved portion 12A and the outer edge 11Ca as described above, when the internal pressure in the food storage space 10 of the packaging body 1 increases due to water vapor, pressure concentration is more likely to occur at the folded-over curved portion 12A. This ensures that the pressure release portion 12, including the folded-over curved portion 12A, ruptures reliably and safely, and water vapor is released from the packaging body 1 to the outside through the pressure release portion 12. [Examples]

[0033] (Method for manufacturing the present invention's packaging) Next, the method for manufacturing the packaging 1 of the present invention will be described. Figure 3(a) shows an overview of the method for manufacturing the packaging 1 of the present invention. For the sake of explanation, it is broadly divided into the manufacturing process S1 of the sheet member 2 and the bag-making process S2 of the packaging 1. Figure 3(b) is a flowchart showing the main processes S11 to S14 included in the manufacturing process S1 of the sheet member 2.

[0034] (Preparation process for each film S11) First, the films constituting the sheet member 2 (each of the layers 3 and 5 described above) are prepared (step S11). Each of the films 3 and 5 may be obtained by purchasing commercially available products from a film manufacturer. The base material layers 5 (each of the base material layers 6 and 9 in the case of a multilayer structure as in Example 1) and sealant layers 3 (each of the films) constituting the sheet member 2 are usually manufactured by a known inflation method or casting method and wound into a roll. The first and second base material layers 6 and 9 may also be subjected to biaxial stretching.

[0035] (Printing layer formation process S12) A printed layer 8 is formed (transferred) on one surface (the inner surface facing the first substrate layer 6) of the substrate layer 5 (the second substrate layer 9 in the example shown in Figure 1(b)) using a known printing technique such as gravure printing or flexographic printing (step S12).

[0036] (First lamination process (formation of laminated film (substrate layer)) S13A) Next, a lamination process (S13) is carried out. Specifically, the second substrate layer 9 on which the printed layer 8 described above is formed and the first substrate layer 6 are laminated using an adhesive (first lamination process S13A). Known lamination techniques such as dry lamination or extrusion coating lamination can be used. For example, an adhesive is applied to one surface of the second substrate layer 9 (the surface on which the printed layer 8 described above is formed) unwound from a roller (not shown), and while drying, the second substrate layer 9 is bonded to the surface of the first substrate layer 6. This allows the printed layer 8 and the adhesive layer 7 to be formed between the first and second substrate layers 6 and 9, as shown in Figure 1(b). Note that the substrate layer 5 may be a single substrate layer (for example, only the second substrate layer 9), in which case this process S13A may be omitted and the process may proceed to the next process S13B.

[0037] (Second lamination process (lamination of sealant layer and substrate layer) S13B) Using the same method as the lamination method for the first and second base material layers 6 and 9 (first lamination step S13A), the integrated base material layer 5 and the sealant layer 3 can be bonded together with an adhesive (adhesive layer 4) (second lamination step S13B). Upon completion of this step S13B, a sheet member 2 is formed in which the sealant layer 3 and the base material layer 5 are integrally laminated.

[0038] (Slitting process S14) At the start of manufacturing the packaging body 1, each sheet member 2,2 that forms both sides of the packaging body 1 is arranged and transported on a single transport sheet 13 in a spread-out state (see, for example, Figure 5(a)). The transport sheet 13 usually has an extra area (also called an edge) not shown in addition to the area of ​​the spread-out sheet members 2,2, and these edges are cut off by a slitter (not shown) (step S14).

[0039] (Bag making process S2) Figure 4 is a flowchart showing the main steps S21 to S29 included in the bag-making process S2 for the packaging 1. In each of the steps S21 to S29 described later, the conveying sheet 13 is basically transported by driving rollers or the like (not shown) in a flow-line operation. Therefore, in most of these steps, it is preferable to transport the conveying sheet 13 from the upstream process to the downstream process while applying appropriate tension and oscillation to the conveying sheet 13.

[0040] (Half-folding process S21) As shown in Figure 5(a), the sheet members 2,2, which are unfolded on a single transport sheet 13, are cut and separated along the unfolding line UF and then folded (half-folding process S21).

[0041] (First heat welding step S22) The folded sheet members 2,2 are heat-sealed (first heat sealing step S22) by pressing a heated sealing plate (not shown) against a desired location 11A (for example, the straight portion of the bottom shown in Figure 5(b)) to form a package 1.

[0042] (1st cooling step S23) Then, the portion 11A that was heat-sealed in the first heat-welding step S22 is brought into contact (clamped) with a metal plate 15 having a large heat capacity, as shown in Figure 5(b), thereby cooling the portion 11A (first cooling step S23).

[0043] (Complete cutting process of the pressure release notch S24) Next, as shown in Figure 5(c), the aforementioned U-shaped cut portion 12 is provided in a part of the heat-sealing area 11F of the folded sheet members 2,2, extending along the entire thickness direction from the outer surface to the inner surface of the sheet members 2,2. That is, a cut portion 12 is formed that penetrates the upper and lower sheet members 2,2 in the thickness direction (complete cutting step S24).

[0044] (Use of mechanical means, such as bladed tools) In the complete cutting process S24, it is preferable that the U-shaped opening of the cut portion 12 (see reference numeral 12B in Figure 2) is formed so that it faces outward from the center of the packaging body 1 (i.e., the food storage space 10). Furthermore, in the complete cutting process S24, it is preferable that the cut portion 12 is formed by punching out a desired area 11F of the conveying sheet 13 using mechanical means such as a blade 14 (see Figure 5(c)). In this complete cutting process S24, it is even more preferable that the sheet member 2 is cut with a blade 14 or the like so that the area to be heat-sealed 11F includes a protruding area 11C (see Figure 5(c)) and the cut portion 12 is formed in the protruding area 11C.

[0045] (Arrangement of the cuts relative to the transport direction) Furthermore, it is preferable to position the sheet member 2 such that the U-shaped opening 12B of the notch 12 faces forward (downstream) with respect to the conveying direction of the manufacturing line. In other words, the U-shaped folded curved portion 12A faces backward (upstream). This prevents the notch 12 from catching and curling up, even if the sheet member 2 comes into contact with the aforementioned sealing plate or metal plate 15 during conveyance, thus preventing the notch 12 from being heat-welded in that state.

[0046] (Second heat welding step S25) In the first heat welding process S22 alone, it is usually impossible to heat-weld all desired areas. Therefore, a heated sealing plate (not shown) is pressed against the remaining desired areas (for example, the left and right side edges 11B, 11B of the sheet member 2) to heat-weld (heat-seal) them (second heat welding process S25).

[0047] When this second heat welding process S25 is performed, it is preferable that not only are the opposing sealant layers 3,3 of each sheet member 2,2 heat-welded together, but that the side walls of the sealant layers 3,3 that demarcate the aforementioned cut portion 12 (the area 12R enclosed by the dashed line drawn within the sealant layer 3 in Figure 1(b)) are heat-welded again (partial rejoining process S25A of a portion 12R of the cut portion 12). If the cut portion 12 is formed in the bottom portion 11A, the complete cutting process S24 described above is performed before the first heat welding process S22, and when this first heat welding process S22 is performed, the partial rejoining process S25A is performed on a portion of the cut portion 12 that has been completely cut in the thickness direction (a portion 12R of the sealant layer 3).

[0048] In the second heat welding step S25 of this embodiment, it is preferable to heat-weld the sealant layers 3, 3 of the sheet members 2, 2 together in the area between the peripheral edge 11B of the sheet member 2 and the protruding region 11C that partially protrudes from the peripheral edge 11B into the food storage space 10 (see Figure 5(d)).

[0049] (Manufacturing conditions for the second heat welding process S25) In the second heat welding process S25, it is necessary not only to heat-weld the contact surfaces of the upper and lower sealant layers 3, 3 together, but also to reliably heat-weld (re-bond) a portion 12R (sealant layer portion) of the cut portion 12, and it is preferable to set and control the following manufacturing conditions.

[0050] (Temperature range for heat welding) The temperature of the heat-sealing plate, which is the heat-sealing temperature T, is preferably in the range of 200°C ≤ T ≤ 250°C, and more preferably in the range of 230°C ≤ T ≤ 240°C. If the temperature T falls below the lower limit, the melting of the individual sealant layers 3,3 becomes insufficient, making heat welding between the sealant layers 3,3 less likely. On the other hand, if the temperature T exceeds the upper limit, the base material layers 5,5 also begin to melt, which is undesirable. Focusing on the completely cut portion of the notch 12, by setting the temperature T within the above range, only the sealant layers 3,3 can be selectively recombined, while the base material layers 5,5 remain cut.

[0051] (Time and number of heat welding applications) Furthermore, when performing heat welding of any sheet member 2 using only one heated sealing plate, the required heat welding time t is preferably t = 1.05 to 1.35 seconds. Alternatively, multiple (n) heated sealing plates may be used to simultaneously heat-weld a sheet member 2 and an adjacent sheet member 2, dividing the heat welding time t.

[0052] (Multiple heat welding processes using multiple heating sheets) Focusing on a single sheet member 2, it is preferable to heat-seal the sheet member 2 in n steps using n heat-sealing plates (more preferably, n=3 heat-sealing steps). Specifically, n heat-sealing plates corresponding to the n heat-sealing steps (first, second, and third sealing plates in the case of n=3) are arranged sequentially in the conveying direction of the manufacturing line, and heat-sealing is performed by simultaneously pressing the first, second, and third sealing plates against a series of sheet members 2 arranged continuously on the conveying sheet 13.

[0053] The pressing (heat welding) time per application is the time t obtained by dividing the above-mentioned heat welding time t by the number of heat welding applications n. d = t / n. When n=3, t d = 0.35 to 0.45 seconds. When the sheet member 2 pressed against the first sealing plate is moved in the transport direction so that it is positioned directly below the second sealing plate before the next heat sealing, the respective heating sealing plates are positioned apart so that the sheet members 2, 2 before and after the sheet member 2 are positioned directly below the third sealing plate and the first sealing plate.

[0054] In this way, by moving the sheet member 2 in the conveying direction of the manufacturing line and performing heat welding of the sheet member 2 in multiple stages using multiple heating sealing plates, and simultaneously performing heat welding of the sheet members 2, 2 before and after, the cycle time is shortened and productivity is improved. Furthermore, in this method, the heat welding time per stage is t d Because the distance is short, it is also possible to prevent melting of the base material layers 5,5.

[0055] (Second cooling step S26) In the second heat sealing step S25, the heat-sealed portions 11B, 11B are brought into contact (clamped) with a metal plate 16 having a large heat capacity, thereby cooling the heated portions 11B, 11B (second cooling step S26). After completing the steps S21 to S26, a continuous series of packages 1 with heat-sealed peripheral portions 11A, 11B, 11B on three sides are formed on a single long transport sheet 13.

[0056] (Notch machining process S27) If necessary, as shown in Figures 5(e) and (f), notches may be made (step S27) on both side edges 11B, 11B of the sheet member 2 to form an opening notch 17.

[0057] (Shearing process S28) Furthermore, the boundary portion of adjacent sheet members 2,2 formed on a single long conveying sheet 13 (the dividing line SL shown by the dashed line in Figure 5(e)) can be cut along the dividing line SL, as shown in Figure 5(f), by applying shearing force with a guillotine-shaped or scissor-shaped blade (not shown) (shearing process S28). This allows individual packages 1 to be separated and obtained from a single conveying sheet 13. If necessary, the corners of the packages 1 may be punched out to form rounded corners 18 (corner rounding cut process S29).

[0058] If the packaging body 1 is a self-standing type (not shown), in order to form a bowl-shaped base portion, it is preferable to perform additional processing in addition to the above steps S21 to S29, such as inserting a separate film (not shown) between each base portion 11A, 11A of the sheet members 2, 2 and heat-sealing them, or punching holes (not shown) in a part of the film before inserting it into the base portions 11A, 11A. [Examples]

[0059] (Test specimen from Example 3) The packaging body 1 of the present invention was manufactured according to the manufacturing method described above (Example 3). In Example 3, biaxially oriented nylon was used for the first base material layer 6, and biaxially oriented polyethylene terephthalate was used for the second base material layer 9. Unoriented polypropylene was used as the sealant layer 3. Figure 6(a) is a schematic diagram illustrating the cross-sectional structure of the cut portion 12 of Example 3. A part of the U-shaped cut portion 12 of this packaging body 1 (a 2 mm wide strip shown in Figure 7(a)) was cut out as a test piece SP1 for the tensile test described later.

[0060] (Test specimen for comparative example) Meanwhile, a comparative example specimen SP2 was also prepared using the same materials as in Example 3. However, the sealant layer 3 was used in its intact state without the complete cutting and recombination described above. A U-shaped cut was made only in the base layer 5. A portion of this cut section 12 (a 2 mm wide strip) was cut out as specimen SP2. Figure 6(b) is a schematic diagram illustrating the cross-sectional structure of the cut section 12 of the comparative example. Note that in Figures 6(a) and 6(b), the adhesive layers 4 and 7 and the printed layer 8 shown in Figure 1(b) are omitted for the sake of explanation.

[0061] (Tensile test) Tensile tests were performed using the specimens SP1 and SP2 from Example 3 and Comparative Example described above. Specifically, each specimen SP1 and SP2 was pulled outwards at a speed of 100 mm / min to the left and right at room temperature.

[0062] (Results of tensile test) Figure 7(b) shows the tensile test results (displacement and tensile load for each specimen SP1 and SP2). In the comparative example specimen SP2, even when pulled with a load of approximately 0.9 kgf, it continued to stretch for more than 10 mm without breaking. On the other hand, in the example specimen SP1, with a tensile load of approximately 0.4 kgf, it stretched only 0.5 mm before breaking. From this, it was found that the cut portion of the comparative example, which had an intact sealant layer, continued to stretch when pulled and did not break easily. On the other hand, in the cut portion 12 of example 3, which had a sealant layer 3 that had been completely cut and rejoined, it was found that about half the tensile force (maximum load) required to break was needed compared to the comparative example, and the rejoined portion 12R broke (opened) with only a small stretch.

[0063] (Consideration of the optimal ratio of the first and second circular arcs) Furthermore, the inventors also evaluated the influence of the relative radius ratio r1:r2 between the first arc of the notch 12 and the second arc of the outer edge 11Ca of the protruding region 11C on various performance characteristics of the packaging 1. Specifically, the various capabilities of the packaging 1 were evaluated by microwave heating tests (Test 1 in Table 1), pressure resistance tests (Test 2 in Table 1), and horizontal drop tests (Test 3 in Table 1). Seven different packaging 1 samples with varying radius ratios were prepared for each test. Specifically, in all samples, the radius r2 of the second arc was kept constant (4.0 mm), and pressure release sections 12 were created with radii r1 of the first arc of 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm, and 3.5 mm.

[0064] (Test 1: Microwave heating test) The microwave heating test aims to evaluate the steam release capacity of the pressure release section 12 (steam vent). A sample (package 1) was prepared by filling the food storage space 10 with 100g of water, and the sample was heated in a microwave oven set to each power level shown in Table 1 for 30 seconds after steam release began. The presence or absence of malfunctions was evaluated. In Table 1, a "×" is used to indicate conditions in which a malfunction occurred, and a "○" is used to indicate conditions in which the device performed adequately. The interpretation of the test results described later in Table 1 is also in the same manner.

[0065] [Table 1]

[0066] (Results of microwave heating test) As shown in the Test1 column of Table 1, in the sample where the radius r1 of the first arc was 0.5 mm, the cross-sectional area of ​​the water vapor flow path was reduced, causing the water-filled food container space 10 to reach a pressurized state that exceeded the strength of the packaging 1, resulting in deformation or damage to a part of the packaging 1. In the sample where the radius r1 of the first arc was 1.0 mm or greater, no steam leakage problems occurred at any output level.

[0067] (Test 2: Pressure resistance test) The pressure resistance test aims to evaluate whether the packaging 1 has sufficient strength during transportation and in-store display. In this test, a sample was prepared with 200g of water filled into the food storage space 10. The sample was kept horizontal to the ground and sandwiched between two plates (not shown) from above and below. The presence or absence of defects was evaluated when each load shown in Table 1 was applied perpendicular to the horizontal part of the sample for 60 seconds.

[0068] (Results of pressure resistance test) As shown in the Test2 column of Table 1, no problems occurred with samples where the first arc was relatively small (r1 = 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm) even when each load was applied. However, with samples where the radius r1 was 2.5 mm or larger, a problem occurred in which the steam vent broke under increased load conditions. This is thought to be due to the fact that as the radius r1 of the first arc (the U-shaped folded curved portion 12A) becomes relatively large, the distance between the second arc and the first arc shortens, and the heat-welded area between the tip outer edge 11Ca of the protruding region 11C (the boundary with the food storage space 10) and the notched portion 12 (the weakened portion that serves as a passage to the outside) narrows.

[0069] (Test 3: Horizontal Drop Test) The horizontal drop test aims to evaluate whether the packaging 1 has sufficient strength against instantaneous impact. Using the same sample as in the pressure resistance test, the sample was dropped from a height of 1m above the ground with the flat surface of the packaging parallel to the ground, and the presence or absence of defects was evaluated.

[0070] (Results of horizontal drop test) As shown in the Test3 column of Table 1, for samples with a relatively small first arc (r1 = 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm), no damage was found to the entire sample or the area around the cut 12 even after more than 10 drops. In particular, the sample with r1 = 1.5 mm withstood more than 20 drops. However, for samples with a radius r1 of 2.5 mm or more, the bag ruptured after fewer than 10 drops, resulting in the water contained inside splashing out. The cause of the malfunction due to the increase in radius r1 is thought to be the same as the cause of the malfunction in the pressure resistance test described above.

[0071] Based on the test results above, it was found that from the viewpoint of promoting steam escape, it is desirable to increase the radius r1 relative to the radius r2, but from the viewpoint of packaging strength, it is desirable to decrease the radius r1 relative to the radius r2. The range of radius ratio that satisfies these two conflicting requirements simultaneously is r1:r2 = 2 to 4:8 (i.e., 2:8 to 4:8), and preferably r1:r2 = 3:8. [Industrial applicability]

[0072] As described above, the microwave heating packaging manufactured by the manufacturing method of the present invention has a slit (pressure release section) with the above configuration, so that the high-temperature, high-pressure steam generated during microwave cooking can be automatically, safely, and reliably released.

[0073] Furthermore, since the pressure release portion of the present invention is not formed by conventional through holes or the like, it does not cause accidental snagging or contamination of foreign matter during product manufacturing or transportation.

[0074] The present invention's method for manufacturing packaging that exhibits such remarkable effects is not found in the industry or market, and therefore has very high industrial value and potential for industrial application. [Explanation of Symbols]

[0075] 1. Packaging for microwave heating 2. Sheet material (laminated film) 3. Sealant layer 4 Adhesive layer 5 Base material layer 6 First base layer 7 Adhesive layer 8 printing layer 9 Second base layer 10 Food storage space 11 Heat seal area 11A, 11B Heat sealing area at the periphery (bottom and side edges) 11C,11Ca protruding region, outer edge of the protruding region 11F Heat seal planned area 12, 12A, 12B: Cut-out section (pressure release section), folded curved section, opening 12R Partial recombination region of the incision 13. Transport sheets used during manufacturing 14. Cutting tools for mechanical cutting means 15,16 Metal plate for cooling the heat-welded area 17 Notches 18 Corner R section A, B, C1, C2 are regions classified to explain the cross-sectional structure of the packaging body of the present invention. n Number of sealing plates (number of heat welding cycles) O Center point of the 1st and 2nd arcs r1, r2 Radius of the first and second circular arcs SP1, SP2, Test specimens for Example 3, and comparative specimens. SL Disconnected Line T Thermal welding temperature t,t d Heat welding time, heat welding time per application UF Development Line

Claims

1. A method for manufacturing a microwave heating packaging body comprising multiple sheet members, Each of the sheet members comprises at least a sealant layer, a base material layer laminated on the outer side in the thickness direction of the sealant layer, and an adhesive layer connecting the sealant layer and the base material layer, A folding step involves folding the transport sheet in half and overlapping the sheet members in the thickness direction, A complete cutting step is performed in which a cut portion is formed in the thickness direction from the outer surface to the inner surface of the sheet members, in a part of the area of ​​the overlapping sheet members to be heat-sealed, forming a U-shaped character with the opening of the character shape facing outward from the center of the packaging body, A heat welding step is performed to partially heat-weld the sealant layers of the sheet members together to form a heat-sealed region so that a food storage space is formed in the packaging body, The heat welding process includes a partial rejoining step in which the divided region of the sealant layer among the cut portions formed in each sheet member in the complete cutting step is rejoined, Includes, In the heat welding process, the sealant layers of the sheet members are welded together such that the heat seal region is formed along the periphery of the sheet member and the protruding region that extends from a part of the periphery into the food storage space. The aforementioned notch is formed in the protruding region, and The U-shaped folded curved portion is formed by a first circular arc, the outer edge of the protruding region is formed by a second circular arc concentric with the first circular arc, and the radius of the first circular arc is r １ Let the radius of the second arc be r. ２ In that case, r １ :r ２ = 2-4:8 A method for manufacturing microwave heating packaging, characterized by the following features.

2. In the heat sealing process, n (n≧2) heating seal plates arranged in series in the conveying direction of the sheet member are sequentially pressed onto the area of ​​the sheet member to be heat sealed, thereby performing the heat sealing in n steps, and During the n heat sealing cycles, at least one of the heat sealing plates also heat-seals the area of ​​the sheet member that is positioned in front of or behind the conveying direction. A method for manufacturing a microwave heating packaging according to feature 1.

3. In the complete cutting process, the notch is formed by mechanical means using a cutting tool, and The sheet member is arranged such that the opening of the letter shape in the cut portion faces forward with respect to the conveying direction of the manufacturing line. A method for manufacturing a microwave heating packaging according to claim 1 or 2.

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