Square-bottom packaging bag and method for manufacturing a square-bottom packaging bag

Abstract

To provide a square bottom packaging bag that is less likely to warp and a method for manufacturing the square bottom packaging bag.SOLUTION: The square bottom packaging bag includes: a square-tubular side portion 11 made of a laminate A having at least an outermost layer made of a paper layer; and a bottom portion 12 that closes one end of the square-tubular opening of the side portion 11 by joining the side portion 11 to the bottom seal portion. The bottom portion 12 is made of a laminate B that is different from the laminate A that constitutes the side portion 11 and has an outermost layer made of a biaxially oriented film and an innermost layer made of a sealant layer and does not have paper, and the side portion 11 is formed by joining a pair of opposing flat portions and a pair of opposing side portions by four side seal portions, and in the outermost layer of the laminate A that constitutes the pair of opposing flat portions, there is no difference in the inclination of the molecular orientation of the film or the difference in thermal shrinkage of the film between the bottom seal portion and the four side seal portions. The other end of the square-tubular opening is an opening K, and when the opening K is open, the laminates of the side portion 11 overlap only at the four side seal portions.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a square-bottom packaging bag and a method for manufacturing the same.

Background Art

[0002] As packaging for foods, medical products, sundries, etc., a packaging bag made of a soft film such as resin may be used. As such a packaging bag, a square-bottom packaging bag having a pair of flat portions, a pair of side portions, and a bottom portion is known. Square-bottom packaging bags exist in various forms depending on differences in manufacturing methods such as the joining form of each surface portion constituting the packaging bag and the conveying direction of the soft film (for example, Patent Documents 1 and 2). In many forms, the square-bottom packaging bag is manufactured in a folded flat shape, and the folding method of the flat shape is also different for each.

[0003] Patent Document 1 describes a method for manufacturing a square tubular stand-up bag (square-bottom packaging bag) from a laminated film such as a plastic film. This method intermittently supplies a strip-shaped tubular body one unit length at a time in the method for manufacturing a square tubular stand-up bag, and makes cuts in the rear material and both side materials with the front material left. Then, the cut edge portion is folded back by the width of the fold of the side material, the bottom material is polymerized on the opening surface, and only the left and right side edges of the bottom material with respect to the opening surface are heat-sealed. Further, the folded-back piece is folded back together with the bottom material, the two edge portions of the bottom material are heat-sealed to the opening surface, and the bag body with the bottom material attached is separated from the strip-shaped tubular body. In the method for manufacturing the square tubular stand-up bag of Patent Document 1, the vertical direction of the stand-up bag coincides with the flow direction of the laminated film.

[0004] Patent Document 2 describes a method for manufacturing packaging material (square-bottom packaging bag) from laminate film such as plastic film. In this method, the front wall, rear wall, and side wall are each formed from separate material sections joined by weld seams. The front wall and rear wall material sections are formed by flat first and second material main webs that overlap each other and are transported in a common first transport direction. Side-fold sections are cut to a fixed length from a flat third material web that has been folded to form a side-fold web, and are transported in a second transport direction lateral to the first transport direction so as to be placed on one of the material main webs. A flat fourth material web that forms a separate material section forming the bottom of the bag is integrated into at least one of the two material main webs and then transported parallel to the first transport direction and welded along the side-fold section and the side edges adjacent to both material main webs. In the packaging material manufacturing method of Patent Document 2, the vertical direction of the packaging material is perpendicular to the flow direction of the laminate film. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2000-334861 [Patent Document 2] Japanese Patent Publication No. 2000-254984 [Overview of the project] [Problems that the invention aims to solve]

[0006] Conventionally, as shown in Patent Documents 1 and 2, a laminate is used as the laminate film for square-bottom packaging bags, etc., in which a stretched film is provided as the outermost layer. However, when square-bottom packaging bags are manufactured using this laminate, the folded and flattened square-bottom packaging bags immediately after manufacture may develop curls at the four corners. This curl is generally called an S-curl. When this curl occurs, for example, when bundling multiple square-bottom packaging bags together and storing them in a box for shipment, they become bulky and do not fit well. Also, when such a curl occurs in a square-bottom packaging bag, it may become difficult to open the opening for filling the bag with food or other contents. The present invention aims to provide a square-bottom packaging bag and a method for manufacturing a square-bottom packaging bag that are less prone to warping compared to using a laminate in which a stretched film is provided as the outermost layer. [Means for solving the problem]

[0007] Thus, according to the present invention, a rectangular tubular side portion made of a laminate A in which at least the outermost layer is made of paper, and a bottom portion that closes one end of the rectangular tubular opening of the side portion by joining the side portion with a bottom sealing portion. For food and medical products A square-bottomed packaging bag, wherein the bottom portion differs from the laminate A that constitutes the side portion, and consists of a laminate B in which the outermost layer is made of a biaxially oriented film and the innermost layer is made of a sealant layer and does not contain paper. The aforementioned bottom portion, when folded, is trapezoidal in a plan view. The aforementioned side portion is formed by joining a pair of opposing planar portions and a pair of opposing side portions with four side sealing portions. The pair of side portions are folded in half to form a rectangle, and the area where the bottom portion of the side portion folded in half to form a rectangle overlaps with the bottom portion folded in a trapezoidal shape is a triangular portion, and in this triangular portion, only the bottom portion of the side portion is folded while being sandwiched by the bottom portion, and in a plan view, four layers of laminate A and four layers of laminate B are stacked on top of each other. In the outermost layer of the laminate A constituting the pair of opposing planar portions, there is no difference in the tilt of the molecular orientation of the film, and no difference in the thermal shrinkage of the film in the bottom seal portion and the four side seal portions, and the other end of the square tubular opening is The aforementioned square-bottom packaging bag A square-bottom packaging bag is provided, characterized in that it has an opening, and when the opening is open, the laminated side portions overlap only at the four side sealing portions. Here, the laminate A may further have an innermost layer and an intermediate layer made of a biaxially oriented film with a thickness of 6 μm to 50 μm.

[0008] Furthermore, the present invention provides a method for manufacturing a square-bottom packaging bag in which the flat portion film and the side portion film are conveyed along the vertical direction of the packaging bag. Furthermore, the present invention provides a method for manufacturing a square-bottom packaging bag in which the flat portion film is conveyed along the left-right direction of the packaging bag. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a square-bottom packaging bag that is less prone to warping and a method for manufacturing a square-bottom packaging bag. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows an example of the packaging bag configuration in this embodiment. [Figure 2] This diagram shows the packaging bag in a folded state. [Figure 3] Figures (a) to (c) provide a more detailed explanation of the base. [Figure 4] (a) to (c) are cross-sectional views of the laminated material that makes up the side surface. [Figure 5] This diagram illustrates an S-shaped curl. [Figure 6] This diagram shows an example of a packaging bag manufacturing method. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described in detail below with reference to the attached drawings. <Overall description of the packaging bag> Figure 1 shows an example of the configuration of the square-bottom packaging bag 10 (hereinafter simply referred to as "packaging bag 10") in this embodiment. As shown in the figure, the packaging bag 10 of this embodiment includes a side portion 11 that constitutes the side of the packaging bag 10 and a bottom portion 12 that constitutes the bottom of the packaging bag 10. The side surface portion 11 is a square tubular shape in which a pair of flat portions 11a and a pair of side portions 11b are alternately joined, and each of the two side portions 11b is disposed at a position facing each other. The bottom surface portion 12 is joined so as to close one end of the square tubular opening of the side surface portion 11.

[0012] The joining of the flat portion 11a and the side portion 11b of the side surface portion 11 is by heat welding of the laminates constituting them. As a result, side seal portions SL and SR protruding outward are formed by heat welding of the laminates to each other. By providing such seal portions SL and SR on the side surface portion 11, the self-standing property of the packaging bag 10 is improved.

[0013] Also, the other end of the square tubular opening of the side surface portion 11, which is opposite to the bottom surface portion 12 side closing one end, is an opening K. And, a filling material can be filled into the packaging bag 10 through the opening K. The filling material is not particularly limited, but for example, it is food, medical products, miscellaneous goods, etc. And, by sealing the opening K after filling, the filling material filled in the packaging bag 10 can be circulated in a sealed state. Also, above the packaging bag 10, cut openings 11c, which are incisions, are provided in the side seal portions SL and SR. And, a consumer can take out the filling material filled in the packaging bag 10 by tearing the side surface portion 11 with the opening 11c as a tear start portion.

[0014] Also, the side portions 11b and the bottom surface portion 12 of the packaging bag 10 can be bent along predetermined fold lines. And, in the folded state, the two opposing flat portions 11a of the packaging bag 10 are close to each other, and the internal space of the packaging bag 10 is almost eliminated. And, the packaging bag 10 becomes a flat shape. On the contrary, in the state where the side portions 11b and the bottom surface portion 12 are not bent and are stretched, the packaging bag 10 is in an expanded state, and in this state, the side surface portion 11 is square tubular.

[0015] FIG. 2 is a view showing the folded state of the packaging bag 10. The side part 11b is rectangular, extends in the direction connecting one end and the other end of the square tube shape, is half-folded into a V shape by valley-folding along the folding line T, and can be folded while protruding the top V1 of the V shape inwardly of the packaging bag 10. In this case, as shown in FIG. 2, the tops V1 of the two side parts 11b face each other.

[0016] FIGS. 3(a) to (c) are diagrams for explaining the bottom surface part 12 in more detail. FIG. 3(a) shows the state where the bottom surface part 12 is extended. As shown in the drawing, the bottom surface part 12 is rectangular, and in the state where the packaging bag 10 is folded, it is bent so as to protrude inwardly of the bag. The bottom surface part 12 has a folding line T which is a valley fold that is bent so as to protrude inwardly of the bag, and a folding line Y which is a mountain fold that is bent so as to protrude outwardly of the bag. In FIG. 3(a), the folding line T is shown as a dotted line, and the folding line Y is shown as a one-dot chain line. The folding line T has a straight part T1 that is parallel to the pair of flat parts 11a and terminates inside the peripheral edge of the bottom surface part 12 in the middle part with the pair of flat parts 11a, and a V-shaped part T3 that extends from both ends T2 of the straight part T1 toward the corresponding corner parts of the bottom surface part 12. The folding line Y extends substantially perpendicularly from both ends T2 of the straight part T1 in the folding line T toward the short side of the bottom surface part 12. By bending the bottom surface part 12 so as to protrude inwardly of the bag, the bottom surface part 12 is folded so that each of the pair of flat parts 11a is close to each other, and the state shown in FIG. 3(b) is obtained. In the folded state, as shown in FIG. 2, the bottom surface part 12 is folded into a trapezoidal shape in plan view. If the upper side of this trapezoid corresponding to the straight part T1 is taken as the top V2, the bottom surface part 12 is folded while protruding the top V2 in the inward direction of the packaging bag 10 and in the direction of the opening K. As shown in FIG. 2, the overlapping part of the side part 11b that is half-folded and folded into a rectangular shape and the bottom surface part 12 that is folded into a trapezoidal shape is a triangular part W. In this triangular part W, the side part 11b is folded and overlapped while being sandwiched by the bottom surface part 12.

[0017] Figure 3(c) shows the bottom seal portion SD of the bottom surface portion 12. This bottom seal portion SD is provided along each of the four sides of the rectangular bottom surface portion 12, and joins the bottom surface portion 12 to the flat portion 11a and the side portion 11b by heat welding of the laminates that constitute them.

[0018] <Explanation of the layer structure of the side portion 11 and the bottom portion 12> Next, the layer structure of the side portion 11 and the bottom portion 12 will be described. Figures 4(a) to 4(c) are cross-sectional views of the laminated material constituting the side portion 11. Of these, Figures 4(a) and 4(b) show the cross-sectional configuration of the laminated side portion 11 of this embodiment, and Figure 4(c) shows the cross-sectional configuration of an example of a conventionally used laminated side portion. In the figures, the lower part is the inside of the packaging bag 10, and the upper part is the outside of the packaging bag 10. Furthermore, the side portion 11 described herein includes both the flat portion 11a and the side portion 11b. Conventional square-bottom packaging bags typically use a biaxially oriented film for the outermost layer of their sides, considering printability and strength. Printing is applied to the biaxially oriented film, and the printed layer (Pr) is often located inside the biaxially oriented film. In this case, the biaxially oriented film can cause warping at the four corners of the packaging bag immediately after manufacturing. Specifically, at adjacent corners, one side curls upwards and the other downwards. This is also known as an S-shaped curl.

[0019] Figure 5 shows an S-shaped curl. In this case, the flat portion of the conventional packaging bag 10J curls upward on one side (the front side) and downward on the other side (the back side) at the top. The sealing portions SLJ, SRJ, and SDJ are less prone to warping because they have more rigidity than the portions without sealing portions SLJ, SRJ, and SDJ, while warping is more likely to occur at the corners of the upper opening KJ where there are no sealing portions.

[0020] The warping is thought to occur for the following reasons: Biaxially oriented films are stretched by being pulled in both the longitudinal and transverse directions during film manufacturing, causing the resin molecules to orient themselves in these directions. At this time, near the center of the film in the width direction, the orientation of the molecules coincides with the longitudinal or transverse direction of the film, but near the edges in the width direction, it does not coincide with the longitudinal or transverse direction of the film, and the molecules may be oriented in a direction that is inclined from these directions. In a conventional packaging bag 10J in which the side parts are formed from a laminate using biaxially oriented film as the outermost layer, as shown in Figure 1, when a pair of flat parts are arranged facing each other, the orientation of the molecules of the outermost layer of biaxially oriented film in each flat part will be different, and it is thought that warping occurs when this difference is large. The same can be said for a pair of side parts. Furthermore, during the heat sealing process for forming each seal section SLJ, SRJ, and SDJ in the manufacturing of the packaging bag 10J, the significant difference in the orientation of the outermost layer of the biaxially oriented film on opposing pairs of flat surfaces results in differences in thermal shrinkage. This leads to areas within each seal section SLJ, SRJ, and SDJ having higher and lower thermal shrinkage rates, which is also considered a cause of warping at the four corners of the packaging bag 10J. As mentioned above, warping is most likely to occur at the corners of the upper opening KJ, which is not sealed.

[0021] As a result, when the packaging bag 10J is folded immediately after manufacturing, curling may occur at the four corners of the packaging bag 10J. In other words, the aforementioned S-shaped curl occurs. When an S-shaped curl occurs, as mentioned above, for example, when dozens of packaging bags 10J are bundled together for shipping, the bundle becomes bulky, and it may be difficult to store this bundle in a box or the like. Furthermore, when filling the packaging bag 10J with food or other contents, it may become difficult to open the top opening KJ used for filling. In particular, the S-shaped curl is more likely to occur when the direction connecting one end and the other end of the rectangular tubular opening on the side of the packaging bag 10J coincides with the flow direction of the film that makes up the laminate. Therefore, in this embodiment, this problem is mitigated by using a side portion 11 that does not use a biaxially oriented film for the outermost layer.

[0022] In this embodiment, the laminate constituting the side portion 11 is a laminate A with the outermost layer 112 being paper. Furthermore, if printing is to be performed on the side portion 11, the printing is applied to the outer surface of the paper. Furthermore, a protective coating may be applied to the print.

[0023] The type of paper that can be used to make up the outermost layer 112 is not particularly limited and can be appropriately selected depending on the appearance and form of the product, but examples include bleached kraft paper, glossy bleached kraft paper, coated paper (kraft paper coated with paint), foil base paper, fine paper, rayon paper, and pure white roll paper. Among these, coated paper is preferred because it has strength, a smooth surface, and excellent printability. Furthermore, in the process of manufacturing the packaging bag 10, it is preferable to use paper that generates little paper dust when cutting the packaging bag 10 into individual bags. Paper that generates little paper dust is also preferable because it makes the cut lines look better. From this viewpoint as well, coated paper is preferred. In addition, the side portion 11b of the side portion 11 is folded, so it is preferable that it has excellent foldability. From this viewpoint as well, kraft paper and pure white roll paper are preferred. Furthermore, the paper's basis weight is 20 g / m². 2 More than 70g / m 2 The following is preferable:

[0024] The innermost layer 111 of the laminate A constituting the side portion 11 is a sealant layer. The innermost layer 111 is a layer for forming the respective seal portions SL, SR, and SD by heat welding, and is made of an unstretched film of synthetic resin or a layered extruded synthetic resin. The material of the synthetic resin forming the innermost layer 111 is not particularly limited as long as it can be heat-welded. For example, resins such as polyethylene (PE) resins, ethylene-vinyl acetate copolymers, ionomer resins, ethylene-acrylic acid copolymers, ethylene-methyl acrylate copolymers, ethylene-methacrylic acid copolymers, polypropylene (PP) resins, and ethylene-polypropylene copolymers can be used. In addition, any of the polyethylene resins, such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene, can be used. Note that only one of these resins may be used, but two or more may be used in combination. Furthermore, the thickness of the innermost layer 111 is preferably 15 μm or more and 200 μm or less.

[0025] The innermost layer 111 is positioned on the inner surface side of the packaging bag 10. As described above, when the laminates constituting the flat portion 11a and the laminates constituting the side portion 11b are joined alternately, the innermost layers 111 are joined to each other by heat welding. Similarly, when the laminates constituting the side portion 11 and the laminates constituting the bottom portion 12 are joined, the innermost layers 111 and 121 are joined to each other by heat welding. For this reason, it is preferable that the innermost layers 111 and 121 constituting each surface are made of resins that can be heat-welded to each other, and it is preferable that they are made of the same type of resin.

[0026] The laminate A constituting the side portion 11 has an outermost layer 112 made of paper. Therefore, there is no difference in the tilt of molecular orientation or thermal shrinkage of the biaxially oriented film, and thus the aforementioned S-shaped curl does not occur. As a result, the bundle of dozens of packaging bags 10 bound together for shipment does not become bulky, and when this bundle is stored in a box or the like, it fits well. Furthermore, when filling the packaging bag 10 with food or other contents, the opening for filling is easy to open. Even if the direction connecting one end and the other end of the rectangular tubular opening of the side portion 11 of the packaging bag 10 of the present invention coincides with the flow direction of the film constituting the laminate A, the S-shaped curl does not occur. Furthermore, by using paper for the outermost layer 112 of the laminated A that constitutes the side portion 11, the amount of plastic used can be reduced, resulting in a packaging bag 10 with a lower environmental impact. From this perspective, it is preferable that the weight of the paper constituting the outermost layer 112 accounts for 50% or more of the weight of the packaging bag 10.

[0027] Furthermore, in the laminate A constituting the side portion 11 of this embodiment, an intermediate layer 113 may be used between the outermost layer 112 (paper) and the innermost layer 111, if necessary.

[0028] The intermediate layer 113 is a layer that can impart functionalities such as gas barrier properties, water vapor barrier properties, mechanical toughness, bending resistance, puncture resistance, impact resistance, abrasion resistance, and cold resistance. It may be a stretched film made of synthetic resin, a vapor-deposited film in which a metal such as aluminum or magnesium, or an inorganic substance such as silicon oxide or aluminum oxide is deposited on a stretched film, or a film coated with polyvinylidene chloride on a stretched film. Examples of synthetic resins used to form the stretched film for the intermediate layer 113 include films made of polyethylene terephthalate (PET), polyamide, polyvinyl chloride, polycarbonate, polyvinyl alcohol, and ethylene-vinyl acetate copolymer saponified products. These stretched films may be uniaxially oriented or biaxially oriented. When tear resistance is required, it is preferable to use a uniaxially oriented film stretched in the tearing direction. Metal foils such as aluminum and magnesium can also be used. The thickness of the intermediate layer 113 can be any thickness that can impart these functionalities, for example, 6 μm or more and 50 μm or less.

[0029] A biaxially oriented film may be used as the intermediate layer 113. When a biaxially oriented film is used as the intermediate layer 113, S-shaped curling is less likely to occur than when a biaxially oriented film is used for the outermost layer 112. This is because the outermost layer 112, made of paper, is located outside the biaxially oriented film of the intermediate layer 113, thus reducing the effect of thermal shrinkage due to heat sealing.

[0030] For the bottom portion 12, it is preferable to use a laminate B that uses a biaxially oriented film instead of paper for the outermost layer 122. In this embodiment, if a laminate with paper as the outermost layer is used for the bottom portion 12, when manufacturing the packaging bag 10 described later, if there is a cutting process for the bottom portion 12 before applying each seal, paper dust released from the paper during cutting is likely to get mixed into the inside of the packaging bag 10. Also, in this embodiment, the folding method of the bottom portion 12 is complex, as explained in Figure 3(a). And, in the case of a bottom portion 12 made of a laminate with paper as the outermost layer, the strength to withstand this folding is likely to be insufficient. For this reason, it is preferable to use a laminate B with a biaxially oriented film for the outermost layer 122 for the bottom portion 12.

[0031] For the innermost layer 121 of the laminate B that constitutes the bottom portion 12, various materials used for the innermost layer 111 of the laminate A that constitutes the side portion 11 can be used. However, from the viewpoint of performing heat welding with the side portion 11, it is preferable to use the same type of material as the innermost layer 111 of the side portion 11.

[0032] As the material for the biaxially oriented film used in the outermost layer 122 of the laminate B that constitutes the bottom surface 12, polyester-based resins such as polyethylene terephthalate, polyamide-based resins, polypropylene-based resins, polycarbonate-based resins, and polyacetal-based resins can be used. While only one of these resins may be used, two or more can be used in combination. Furthermore, cellophane, nonwoven fabrics, etc., can be used in combination as needed. Furthermore, while biaxially oriented film was used in the examples given here, uniaxially oriented film may also be used. However, if printing is to be performed, printability is required, and for that purpose, uniaxially oriented or biaxially oriented film is preferable. Laminate B, like laminate A, may also have an intermediate layer. Both laminate A and laminate B are laminated using known methods such as dry lamination or extrusion lamination.

[0033] <Explanation of the manufacturing method of the packaging bag 10> Next, we will explain the manufacturing method of the packaging bag 10. The manufacturing method for the packaging bag 10 is not particularly limited, but for example, it may be manufactured as follows. Herein, we present an example of a manufacturing method that includes a conveying step in which the conveying direction of the laminate A constituting the side portion 11 of the packaging bag 10 coincides with the direction connecting one end and the other end of the rectangular tubular opening of the side portion 11. Prepare a side film, which is a laminate A with paper as the outermost layer 112, that constitutes the side portion 11 of the packaging bag 10. Also, prepare a bottom film, which is a laminate B with biaxially oriented film as the outermost layer 122, that constitutes the bottom portion 12 of the packaging bag 10. The side film may be pre-separated into the side film and the flat film, or it may be cut during the manufacturing process.

[0034] The side film is folded in half. The bottom portion 12 is made by cutting the bottom film into a rectangular shape and folding the bottom portion 12 into a trapezoidal shape in plan view, as described above.

[0035] Next, the folded side film and bottom portion 12 are sandwiched between a pair of flat films at predetermined positions.

[0036] A more detailed explanation will be provided using Figure 6. Figure 6 shows an example of a method for manufacturing the packaging bag 10. The apparatus 200 in this manufacturing method has rolls 210 and 220, and the rotation of rolls 210 and 220 conveys the fed film in the direction of arrow C. This direction of arrow C is the flow direction of the film that constitutes the laminate A. Here, a pair of long side films 11bF, folded along the flow direction, are transported so that the tops V1 of their respective V shapes face each other, and are held between the folded portions at both ends of the bottom portion 12, which is folded into a trapezoidal shape in plan view. Then, a pair of flat films HF1 and HF2 are fed between rolls 210 and 220 from above and below. The side film 11bF and the bottom film 12 are sandwiched between the flat film HF1 and the flat film HF2, and then the side seals SL and SR and the bottom seal is applied. As a result, the flat film HF1, the flat film HF2, the side film 11bF, and the bottom film 12 are integrated to form a strip film BF.

[0037] Next, if the product is manufactured with two or more packaging bags 10 in the width direction, the strip-shaped film BF is cut along the conveying direction. This forms a strip-shaped bag in which the packaging bags 10 are connected in the longitudinal direction. Furthermore, an opening 11c is formed by making cuts in a portion of the side seal sections SL and SR. Then, the strip-shaped bag is cut in a direction perpendicular to the conveying direction, below the bottom seal portion SD. This separates it into individual packaging bags 10, and the packaging bags 10 are manufactured.

[0038] In the case of a laminate containing paper, paper dust is likely to be released from the cut surface during the manufacturing process, depending on the type of paper. The bottom portion 12 is cut from the bottom film before it is sandwiched between the pair of flat films HF1 and HF2 to form the respective seal portions SL, SR, and SD. Therefore, when it is sandwiched between the pair of flat films HF1 and HF2, paper dust may get mixed into the inside of the strip-shaped film BF, and ultimately the paper dust may get mixed into the inside of the packaging bag 10. For this reason, when forming the packaging bag 10 by this manufacturing method, it is preferable that the bottom portion 12 is a laminate that does not contain paper. On the other hand, the flat portion 11a and the side portion 11b are cut after the respective seal portions have been formed and the strip-shaped film BF has been created, so even if paper dust is released by cutting, the paper dust will not get mixed into the inside of the packaging bag 10.

[0039] Furthermore, as shown in Figure 6, in this embodiment, when the packaging bag 10 is placed with the bottom portion 12 facing downwards, the flat portion films HF1, HF2 and the side portion film 11bF are transported along the vertical direction. When this manufacturing method is used with a flat portion film and side portion film made of a laminate with a biaxially oriented film as the outermost layer, the flat portion film and side portion film are transported along the vertical direction of the packaging bag, which makes the aforementioned S-shaped curl particularly likely to occur. In this embodiment, even when the packaging bag 10 is manufactured using this method, the S-shaped curl can be suppressed. At least, it is preferable that the transport direction of the flat portion film constituting the flat portion 11a of the side portion 11 coincides with the direction connecting one end and the other end of the rectangular tubular opening of the side portion 11, that is, along the vertical direction of the packaging body 10.

[0040] In the configuration described in detail above, the side portion 11 was formed into a rectangular tube shape by joining four films, but the number of films is not particularly limited. For example, a rectangular tube-shaped side portion may be formed by winding and joining a single film. In this case, the side seal portion may be provided at the corner of the side portion, as shown in Figure 1, or it may be formed within any plane. Furthermore, when the side seal portion is provided at the corner, it may or may not protrude outward, as shown in Figure 1. When a flat film and side film using a biaxially oriented film as the outermost layer are used, the effects of the present invention are clearly evident when the manufacturing method described in this embodiment involves conveying the flat film and side film along the vertical direction of the packaging bag, as S-shaped curls are likely to occur. However, the present invention is not limited to this manufacturing method, and the packaging bag may also be one in which the flat film is conveyed along the left-right direction of the packaging bag. Furthermore, in the configurations described above, the packaging bag 10 was folded using the folding method shown in Figures 1 to 3, but the folding method is not limited to this, and other folding methods can also be applied.

[0041] Although this embodiment has been described above, the technical scope of the present invention is not limited to the scope described in the above embodiment. It is clear from the claims that various modifications or improvements made to the above embodiment are also included in the technical scope of the present invention. [Explanation of symbols]

[0042] 10...Packaging bag, 11...Side section, 11a...Flat section, 11b...Side section, 12...Bottom section, 111, 121...Innermost layer, 112, 122...Outermost layer, 113...Middle layer, SL, SR, SD...Seal section, K...Opening, Pr...Printed layer, T, Y...Fold line

Claims

1. A rectangular cylindrical side section made of a laminate A, in which at least the outermost layer is made of paper, By joining the aforementioned side portion and bottom sealing portion, the bottom portion closes one end of the rectangular tubular opening in the side portion, A square-bottom packaging bag for food and medical products, The bottom portion differs from the laminate A that constitutes the side portion, and consists of a laminate B in which the outermost layer is made of a biaxially oriented film and the innermost layer is made of a sealant layer and does not contain paper. The aforementioned bottom portion, when folded, is trapezoidal in a plan view. The aforementioned side portion is formed by joining a pair of opposing planar portions and a pair of opposing side portions with four side sealing portions. The pair of sides are folded in half and folded into a rectangular shape, The area where the bottom surface of the side portion, which is folded in half and into a rectangular shape, and the bottom portion, which is folded into a trapezoidal shape, overlap is a triangular portion, and in this triangular portion, only the bottom surface of the side portion is folded while being sandwiched by the bottom portion, and in a plan view, four layers of the laminate A and four layers of the laminate B are stacked on top of each other. In the outermost layer of the laminate A constituting the pair of opposing planar portions, there is no difference in the tilt of the molecular orientation of the film, nor is there any difference in the thermal shrinkage of the film in the bottom seal portion and the four side seal portions. The other end of the aforementioned rectangular tubular opening is the opening of the square-bottomed packaging bag. When the opening is open, the laminated bodies on the side overlap only at the four side sealing portions. A square-bottomed packaging bag characterized by the following features.

2. The square-bottom packaging bag according to claim 1, characterized in that the laminate A further comprises an innermost layer and an intermediate layer made of a biaxially oriented film with a thickness of 6 μm or more and 50 μm or less.

3. A method for manufacturing a square-bottom packaging bag according to claim 1, A method for manufacturing a square-bottom packaging bag, wherein the flat film and the side film are conveyed along the vertical direction of the packaging bag.

4. A method for manufacturing a square-bottom packaging bag according to claim 1, A method for manufacturing a square-bottom packaging bag, wherein the flat film is conveyed along the left-right direction of the packaging bag.

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