Method for manufacturing package for microwave oven heating

Abstract

Provided is a method for manufacturing a package for microwave oven heating provided with a pressure release part capable of safely and reliably releasing high-pressure steam during cooking in a microwave oven.　A method for manufacturing a package comprises: a complete cutting step S24 for causing a U-shaped cut part to penetrate a sheet member in the thickness direction from an outer surface to an inner surface; and a heat welding step S25 for forming a heat seal region by partially heat welding sealant layers to each other such that a food material accommodation space is formed in the package. In a partial recombination step S25A, the divided regions of the sealant layer are recombined among cut parts penetrating respective sheet members. Each cut part is formed in a protruding region protruding into the food material accommodation space. A U-shaped folded curved part is formed by a first circular arc. The outer edge of each protruding region is formed by a second circular arc concentric with the first circular arc. It is preferable that r1:r2 = 3:8, where r1 is the radius of the first circular arc, and r2 is the radius of the second circular arc.

Description

Manufacturing method for microwave heating packaging

[0001] The present invention relates to a method for manufacturing microwave heating packaging, and more specifically, to a method for manufacturing microwave heating packaging equipped with a pressure release section (notch) that automatically releases steam pressure (internal pressure) when heated in a microwave oven.

[0002] (Conventional microwave heating packaging) Conventionally, microwave heating packaging has been sold in which two heat-resistant resin films are heat-sealed along the edges, and cooked or partially cooked food is sealed inside. Food can be cooked by heating this type of packaging directly in a microwave oven.

[0003] (Conventional steam release mechanism) Typically, such packaging is equipped with a mechanism (pressure release section) that releases steam to the outside when the internal pressure exceeds a certain value, in order to prevent the bag from bursting (rupturing) due to the rise in internal pressure caused by the steam generated from the food during heating.

[0004] (Known perforations (Patent Document 1)) As a microwave heating package having such a steam venting mechanism, for example, as shown in Patent Document 1, a through hole (perforation) is known in which a part of the heat-seal surface is provided.

[0005] (Problem 1 of known through-holes (cause of product damage or breakage)) However, in conventional products equipped with the above-mentioned through-holes, there is a risk that the product may be damaged or broken during the manufacturing process if a part of an adjacent product enters the through-hole. Furthermore, during transportation and storage of the product, the through-hole can cause accidental snagging and damage.

[0006] (Problem with known punch holes 2 (Risk of foreign matter contamination in the product)) In addition, punching is required during manufacturing to form through holes, and there is a risk that the punched material (circular film) may be mixed into the packaging as foreign matter. Furthermore, 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 in the base layer only (Patent Documents 2, 3)) As prior art with other known steam venting mechanisms, there is a known packaging in which cuts such as V-shapes or U-shapes are formed in all or part of the heat-resistant base layer of one side of the film (see Patent Documents 2, 3). These cuts can usually be formed by irradiating them with a laser using a laser processing machine after the base 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 (failure to release internal pressure)) However, in these prior art packaging materials, the portion directly below the cut section in the base layer is not weakened at all, and the strength of the sealant layer itself does not differ from that of other parts. Therefore, in these packaging materials, there is no guarantee that the opening will occur directly below the cut section 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 section 2 (poor appearance of the product at the time of shipment)) Furthermore, additional laser processing after the bag-making process melts part of the product, which negatively affects the appearance of the product at the time of shipment. In other words, it is preferable that the pressure-releasing cut section be formed before or during the bag-making process.

[0010] (Disclosure of Prior Art by the Inventors) In response to these problems, the 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 during manufacturing and transportation, as well as contamination by foreign matter.

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

[0012] Japanese Unexamined Patent Publication No. 2002-249176, Japanese Unexamined Patent Publication No. 2001-287774, Japanese Unexamined Patent Publication No. 2007-331816, Japanese Patent No. 6578329

[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.

[0015] In other words, the present invention adopts, for example, the following configuration and features: (Aspect 1) A method for manufacturing a microwave heating package comprising a plurality of sheet members, wherein each sheet member comprises at least a sealant layer, a base material layer laminated on the outside in the thickness direction of the sealant layer, and an adhesive layer connecting the sealant layer and the base material layer, and the method includes: a folding step of folding a transport sheet in half to overlap the sheet members in the thickness direction; a complete cutting step of providing a cut portion in a part of the heat-sealing area of ​​the overlapped sheet members, forming a U-shape with the opening of the character shape facing outward from the center of the package, extending from the outer surface to the inner surface in the thickness direction of the sheet members; a heat-sealing step of partially heat-sealing the sealant layers of the sheet members to each other to form a heat-sealing area so as to form a food-containing space in the package; and a partial re-joining step of re-joining the divided area of ​​the sealant layer among the cut portions formed in each sheet member in the complete cutting step. In the heat welding process, the sealant layers of the sheet member are welded together such that the heat seal region is formed along the periphery of the sheet member and a protruding region that extends from a part of the periphery into the food storage space, the notch is formed in the protruding region, the U-shaped folded curved portion is formed by a first arc, the outer edge of the protruding region is formed by a second arc concentric with the first arc, and the radius of the first arc is r １ Let the radius of the second arc be r. ２ In that case, r１ : r ２ = 3:8, and a method for manufacturing a packaging body for microwave heating, characterized in that. (Aspect 2) When the heat welding temperature of the heat welding step is T, it is within the range of 200 ° C ≦ T ≦ 250 ° C, and the method for manufacturing a packaging body for microwave heating according to Aspect 1, characterized in that.

[0016] According to the packaging body for microwave heating manufactured by the manufacturing method of the present invention, since it has the cut portion (that is, the pressure release portion) having the above configuration, high-temperature and high-pressure water vapor generated during range cooking can be automatically and safely and surely released.

[0017] Further, since the pressure release portion of the present invention is not formed by a conventional through-hole or the like, it does not cause accidental snagging or foreign matter mixing during product manufacturing or transportation.

[0018] Further, in the pressure release portion of the present invention, both the base material layer and the sealant layer are once cut in the thickness direction, and then only the sealant layer is re-welded (however, the strength is weakened). Therefore, when the internal pressure of the packaging body increases, a crack (pressure release passage) is surely formed at the re-welded portion.

[0019] Further, since the packaging body for microwave heating provided with the pressure release portion of the present invention can release water vapor at a desired internal pressure, uneven heating of the food sealed in the packaging body can be prevented, and the food can be finished deliciously.

[0020] Furthermore, according to the manufacturing method of a preferred aspect of the present invention, while moving the sheet member in the conveyance direction of the manufacturing line, the heat welding of the sheet member is divided into a plurality of times using a plurality of heating seal plates, and the heat welding of the sheet members before and after that is also performed simultaneously, so that the tact time is shortened and the productivity is improved. In addition, since the heat welding time per time is short, melting prevention of the base material layer can also be achieved.

[0021] This is a schematic diagram showing the front view and cross-sectional structure of the packaging of the present invention. This is an enlarged schematic diagram showing the pressure release portion and protruding region of the present invention. This is a schematic diagram showing the manufacturing method of the packaging of the present invention. This is a flowchart showing the detailed steps in the manufacturing method of the packaging of the present invention (particularly the bag-making process). This is a diagram showing the state of the packaging at each step of the manufacturing method of the present invention. This is a schematic diagram showing the cross-sectional structure of the cut portion of Example 3 and the comparative example. This is a diagram showing the location of the test piece for tensile testing and the tensile test results.

[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.

[0023] (Schematic diagram of the packaging body 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 body 1 of the present invention (Example 1) (hereinafter also simply referred to as "packaging body") 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 members) Each sheet member 2 comprises 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, as shown in Figure 1(b). Here, the base material layer 5 may be laminated in multiple layers from the viewpoint of product sales. 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 layer 5 can be made of nylon, polypropylene, polyethylene terephthalate, polybutylene terephthalate, etc., but is not limited to these.

[0027] (Material of the sealant layer) As the material of the sealant layer 3, for example, non-stretched polypropylene is assumed to be used, but it is not necessarily limited to this.

[0028] (Cross-sectional structure of the package) To explain the cross-sectional structure of the package 1 of Example 1, in FIG. 1(a), A, B, and C １ (or C ２ ) are divided into regions. Here, region C １ (or C ２ ) is the heat seal region 11 where the sheet members 2, 2 are heat-sealed to each other. Region B is a region where the sheet members 2, 2 are not adhered to each other and can move freely relative to each other, and a food accommodation space 10 for accommodating food (not shown) is formed between these members 2, 2. The opening of the food accommodation space 10 is usually sealed when food is accommodated.

[0029] Region A is a region in which a cut portion (pressure release portion 12) described later is further formed in the heat seal region 11 similar to region C １ (or C ２ ). This region A includes a protruding region 11C that protrudes toward the food accommodation space 10.

[0030] (Preferred shapes of the pressure release portion and the heat seal protruding region) Although the shape and structure of the above-described package 1 have a common part with the package disclosed in Patent Document 4, the inventors of the present invention have further improved it, and by setting the shape of the pressure release portion 12 and the heat seal protruding region 11C around it and their relative dimensional ratios as follows, the steam escape performance (internal pressure release ability) of the package 1 is dramatically improved and the bagging performance during the manufacture and use of the package can be sufficiently maintained.

[0031] (Cut portion) The pressure release portion 12 is a U-shaped cut portion as shown in FIG. 2, and the bent curved portion 12A of the U shape is formed by an arc (first arc) with the center point O as a base point. On the other hand, the outer edge 11Ca of the tip of the protruding region 11C is also an arc (second arc, that is, an arc concentric with the first arc) with the above-described center point O as a base point. Further, when the radius of the first arc is r １ and the second arc is r ２ , preferably r１ :r ２ = 2 to 4:8 (i.e., 2:8 to 4:8), and more preferably r １ :r ２ The ratio is 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.

[0033] (Method for Manufacturing the Packaging of the Present Invention) 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 prepared by purchasing commercially available products from a film manufacturer. The base material layer 5 (each of the base material layers 6 and 9 in the case of a multilayer structure as in Example 1) and sealant layer 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 step 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 Laminating Process (Formation of Laminated Film (Substrate Layer)) S13A) Next, the laminating process (S13) is carried out. Specifically, the second substrate layer 9 on which the above-mentioned printed layer 8 is formed and the first substrate layer 6 are laminated using an adhesive (first laminating process S13A). Known laminating 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 unwound from a roller (not shown) (the surface on which the above-mentioned printed layer 8 is formed), and while drying, the second substrate layer 9 is bonded to the surface of the first substrate layer 6. As a result, as shown in Figure 1(b), the printed layer 8 and the adhesive layer 7 can be formed between the first and second substrate layers 6 and 9. 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 Laminating Process (Lamination of Sealant Layer and Base Layer) S13B) Using the same method as the lamination method for the first and second base layers 6 and 9 (first laminating process S13A), the base layer 5, which has been integrated as described above, and the sealant layer 3 can be bonded together with an adhesive (adhesive layer 4) (second laminating process S13B). Upon completion of this process S13B, a sheet member 2 is formed in which the sealant layer 3 and the base layer 5 are integrally laminated.

[0038] (Slitting process S14) At the start of manufacturing the packaging body 1, each sheet member 2, 2 that makes up both sides of the packaging body 1 is arranged and transported on a single transport sheet 13 in a state where many of them are spread out (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 (process S14).

[0039] (Bag-making process S2) Figure 4 is a flowchart showing the main processes S21 to S29 included in the bag-making process S2 for the packaging body 1. In each of the processes 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 processes, it is preferable to transport the conveying sheet 13 from the upstream process to the downstream process while applying appropriate tension and appropriate oscillation to the conveying sheet 13.

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

[0041] (First heat sealing step S22) The folded sheet members 2, 2 are heat-sealed together 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 the packaging body 1 (first heat sealing step S22).

[0042] (First 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 S24 for pressure release cuts) Next, as shown in Figure 5(c), the above-mentioned U-shaped cut 12 is made 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 12 is formed that penetrates the upper and lower sheet members 2, 2 in the thickness direction (complete cutting process S24).

[0044] (Use of mechanical means such as a blade) 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). 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 transport sheet 13 with 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 notch relative to the conveying direction) Furthermore, it is preferable to arrange the sheet member 2 such that the U-shaped opening 12B of the notch 12 faces forward (downstream) relative 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 seal plate or metal plate 15 during conveying, thus preventing the notch 12 from being heat-welded in that state.

[0046] (Second heat welding step S25) In the first heat welding step S22 alone, it is usually impossible to heat-weld all the 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 step 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 define 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 range 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 heated sealing plate that becomes the heat welding 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, and heat welding between the sealant layers 3, 3 becomes difficult. 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 cut section 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 passes) When performing heat welding of any sheet member 2 using only one heated sealing plate, the required heat welding time is preferably t = 1.05 to 1.35 seconds. Multiple (n) heated sealing plates may be used to heat-weld the sheet member 2 and adjacent sheet member 2 simultaneously, dividing the heat welding time t.

[0052] (Performing multiple heat welding operations using multiple heating sheets) Focusing on a single sheet member 2, it is preferable to heat-weld the sheet member 2 in n separate operations using n heating sheets (more preferably, the number of heat welding operations n = 3). Specifically, n heating sheets corresponding to the number of heat welding operations n (first, second, and third sealing sheets in the case of n = 3) are arranged sequentially in the conveying direction of the manufacturing line, and heat welding is performed by simultaneously pressing the first, second, and third sealing sheets 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 This results in a time of 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 beneath the second sealing plate before the next heat sealing, the respective heating sealing plates are separated so that the sheet members 2, 2 before and after the sheet member 2 are positioned directly beneath 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) The heated portions 11B, 11B, which were heat-sealed in the second heat-welding step S25, 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 number 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 processing step 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, by applying shearing force to 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)) with a guillotine-shaped or scissor-shaped blade (not shown), the sheet can be cut along the dividing line SL as shown in Figure 5(f) (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 (R-shaped corner cutting 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.

[0059] (Test specimen of 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 used as a test specimen SP for the tensile test described later. １ He started it by saying that.

[0060] (Test specimen of comparative example) On the other hand, using the same material as in Example 3, a test specimen SP of the comparative example was prepared. ２ A sample was also prepared. However, the sealant layer 3 was used in its undamaged state without the complete cutting and recombination described above. A U-shaped cut was made only in the base layer 5. A part of this cut 12 (a 2 mm wide strip) was used for the test piece SP. ２ It was cut out as shown. Figure 6(b) is a schematic diagram illustrating the cross-sectional structure of the cut portion 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) have been omitted for the sake of explanation.

[0061] (Tensile test) Test specimen SP of Example 3 and Comparative Example described above １ SP ２ Tensile tests were performed using the following method: Specifically, each test specimen SP was subjected to a tensile test at room temperature. １ SP ２ The object was pulled so that it moved outwards to the left and right at a speed of 100 mm per minute (100 mm / min).

[0062] (Tensile test results) Figure 7(b) shows the tensile test results (each test piece SP １ SP ２ The displacement and tensile load are shown. Comparative example: Test specimen SP ２ In contrast, 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, the test piece SP of Example 3 １In the comparative example, a tensile load of approximately 0.4 kgf caused it to stretch only 0.5 mm before breaking. This indicates that when the cut portion of the comparative example, which had an intact sealant layer, was pulled, it continued to stretch and did not break easily. On the other hand, in the cut portion 12 of Example 3, which had a completely cut and rejoined sealant layer 3, it was found that about half the tensile force (maximum load) required to break the cut portion required in the comparative example was needed, and the rejoined portion 12R broke (opened) with only a small amount of stretching.

[0063] (Investigation of the optimal ratio of the first and second arcs) Furthermore, the inventors investigated the relative radius ratio r between the first arc of the notched portion 12 and the second arc of the outer edge 11Ca of the protruding region 11C. １ :r ２ The influence of on various performance aspects of packaging 1 was also evaluated. Specifically, the various capabilities of 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 samples of packaging 1 with different radius ratios were prepared for each test. Specifically, the radius r of the second arc was the same for all samples. ２ The radius of the first arc is kept constant (4.0 mm) １ Pressure release sections 12 were fabricated with dimensions 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 purpose of the microwave heating test is 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 the start of steam release. 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 the same.

[0065]

[0066] (Results of microwave heating test) As shown in the Test1 column in Table 1, the radius r of the first arc １In the sample with a diameter of 0.5 mm, the cross-sectional area of ​​the water vapor flow path becomes small, causing the food-containing space 10 filled with water to reach a pressurized state that exceeds the strength of the packaging 1, resulting in deformation or damage to a part of the packaging 1. Radius r of the first arc １ For samples with a thickness of 1.0 mm or more, no steam leakage problems occurred at any output level.

[0067] (Test 2 Pressure Resistance Test) The purpose of the pressure resistance test is to evaluate whether the packaging 1 has sufficient strength during transportation and in-store display. In this test, a sample was prepared by filling the food storage space 10 with 200g of water. 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 Test 2 column in Table 1, the first arc is relatively small for the sample (r １ No problems occurred when applying loads of 0.5 mm, 1.0 mm, 1.5 mm, and 2.0 mm. However, with radius r １ In samples with a diameter of 2.5 mm or more, a malfunction occurred where the steam vent broke under increased load conditions. This was due to the radius r of the first arc. １ It is believed that the relatively large size of the U-shaped folded curved portion 12A shortens the distance between the second arc and the first arc, which in turn narrows the heat-welding area between the 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).

[0069] (Test 3 Horizontal Drop Test) The purpose of the horizontal drop test is 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 1 m 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 Test 3 column in Table 1, the first arc is relatively small for the sample (r １Even after repeated drops (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 notched portion 12. In particular, r １ A sample of 1.5 mm withstood more than 20 drops. However, the radius r １ However, with samples larger than 2.5 mm, the bag ruptured after fewer than 10 drops, causing the contained water to spill out. １ The cause of the malfunction due to the increase in is thought to be the same as the cause of the malfunction in the pressure resistance test described above.

[0071] Based on the results of each test, from the perspective of promoting steam release, radius r ２ With respect to radius r １ It is desirable to increase the radius r, but from the viewpoint of packaging strength ２ With respect to radius r １ It was found that it is desirable to reduce the value. The range of radius ratios that satisfies these two contradictory requirements simultaneously is r １ :r ２ = 2 to 4:8 (i.e., 2:8 to 4:8), and preferably r １ :r ２ The ratio is 3:8.

[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 on the market, and therefore has very high industrial value and potential for industrial application.

[0075] 1 Microwave heating packaging 2 Sheet material (laminated film) 3 Sealant layer 4 Adhesive layer 5 Base material layer 6 First base material layer 7 Adhesive layer 8 Printed layer 9 Second base material layer 10 Food storage space 11 Heat seal area 11A, 11B Heat seal area at the periphery (bottom and side edges) 11C, 11Ca Protruding area, outer edge of the leading edge of the protruding area 11F Area to be heat sealed 12, 12A, 12B Cut-out section (pressure release section), folded and curved section, opening 12R Partial rejoining area of ​​the cut-out section 13 Conveying sheet transported during manufacturing 14 Cutting blade of mechanical cutting means 15, 16 Metal plate for cooling the heat-sealed area 17 Notch 18 Corner radius section A, B, C １ , C ２ The regions classified to explain the cross-sectional structure of the packaging body of the present invention are: n - Number of sealing plates (number of heat welding cycles) O - Center points of the first and second arcs r １ ,r ２ Radius of the first and second arcs SP １ SP ２ Test specimen of Example 3, test specimen of Comparative Example SL dividing line T heat welding temperature t, t ｄ Heat welding time, heat welding time per pass, UF development line

Claims

1. A method for manufacturing a microwave heating package comprising a plurality of sheet members, wherein each sheet member comprises at least a sealant layer, a base layer laminated on the outer side of the sealant layer in the thickness direction, and an adhesive layer connecting the sealant layer and the base layer, and the method includes: a folding step of folding a transport sheet in half to overlap the sheet members in the thickness direction; a complete cutting step of providing a cut portion in a part of the heat-sealing area of ​​the overlapped sheet members, forming a U-shape with the opening of the character shape facing outward from the center of the package, extending from the outer surface to the inner surface in the thickness direction of the sheet members; a heat-sealing step of partially heat-sealing the sealant layers of the sheet members to form a heat-sealing area so as to form a food-containing space in the package; and a partial re-joining step of re-joining the divided areas of the sealant layer in the cut portion formed in each sheet member in the complete cutting step, In the heat welding process, the sealant layers of the sheet member are welded together such that the heat seal region is formed along the periphery of the sheet member and a protruding region that extends from a part of the periphery into the food storage space, the notch is formed in the protruding region, the U-shaped folded curved portion is formed by a first arc, the outer edge of the protruding region is formed by a second arc concentric with the first arc, and the radius of the first arc is r １ Let the radius of the second arc be r. ２ In that case, r １ :r ２ A method for manufacturing microwave heating packaging, characterized in that the ratio is 3:

8.

2. The method for manufacturing a microwave heating packaging according to claim 1, characterized in that when the heat welding temperature of the heat welding step is T, it is within the range of 200°C ≤ T ≤ 250°C.

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