JP7843580B2 - Square-bottom packaging bag and method for manufacturing a square-bottom packaging bag - Google Patents

Description

This invention relates to a square-bottom packaging bag and a method for manufacturing a square-bottom packaging bag.

For packaging food, medical supplies, and general merchandise, flexible film bags made of resin or similar materials are sometimes used. Among such bags, the square-bottomed bag, having a pair of flat sections, a pair of side sections, and a bottom section, is known. Square-bottomed bags exist in various forms depending on differences in manufacturing methods, such as the joining configuration of each section and the direction of transport of the flexible film (for example, Patent Documents 1 and 2). In many forms, square-bottomed bags are manufactured in a flattened, folded state, and the way they are folded into this flattened shape varies.

Patent Document 1 describes a method for manufacturing a rectangular tubular self-standing bag (square-bottom packaging bag) from a laminate film such as a plastic film. This method involves intermittently supplying a strip-shaped tubular body in one-unit lengths, making cuts in the rear and side panels while leaving the front panel intact. The cut edges are then folded back by the width of the pleats in the side panels, the bottom panel is superimposed on the opening, and only the left and right edges of the bottom panel are heat-sealed to the opening. Furthermore, the folded-back pieces are folded back together with the bottom panel, the two edges of the bottom panel are heat-sealed to the opening, and the bag with the bottom panel attached is separated from the strip-shaped tubular body. In the method for manufacturing a rectangular tubular self-standing bag described in Patent Document 1, the vertical direction of the self-standing bag coincides with the flow direction of the laminate film.

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 walls are each formed from separate material sections joined by weld seams. The front 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. A flat third material web, folded to form a side-fold web, is cut to a fixed length and 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, forming a separate material section that constitutes 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 edges adjacent to the side-fold section and 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.

Japanese Patent Publication No. 2000-334861 Japanese Patent Publication No. 2000-254984

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.

Thus, according to the present invention, a square-bottom packaging bag for food and medical products is provided, having 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 being joined to the side portion by a bottom seal portion, wherein the bottom portion is different from the laminate A that constitutes the side portion, and is made 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 have paper , the bottom portion is trapezoidal in a plan view when folded, the side portion is made of a pair of opposing planar portions and a pair of opposing side portions joined by four side seal portions, the pair of side portions are folded in half to form a rectangular shape, and The bottom portion of the side portion, which is folded into a rectangular shape, and the bottom portion, which is folded into a trapezoidal shape, overlap at 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, and in the outermost layer of laminate A that constitutes the pair of opposing planar portions, there is no difference in the inclination of the molecular orientation of the film or a difference in the thermal shrinkage of the film of the bottom seal portion and the four side seal portions, the other end of the square tubular opening is the opening of the square bottom packaging bag , and when the opening is open, the laminates of the side portions overlap only at the four side seal 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.

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.

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.

This figure shows an example of the packaging bag configuration in this embodiment. This diagram shows the packaging bag in a folded state. Figures (a) to (c) provide a more detailed explanation of the bottom surface. (a) to (c) are cross-sectional views of the laminated material that constitutes the side surface. This is a diagram illustrating an S-shaped curl. This diagram shows an example of a packaging bag manufacturing method.

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 portion 11 is a rectangular tube shape in which a pair of flat portions 11a and a pair of side portions 11b are joined alternately, with each of the two side portions 11b positioned opposite to the other.
The bottom portion 12 is joined to the side portion 11 so as to close one end of the rectangular tubular opening.

The joint between the flat portion 11a and the side portion 11b of the side portion 11 is achieved by heat welding of the laminates that constitute them. As a result, the heat welding of the laminates creates outwardly protruding side seal portions SL and SR. Providing such seal portions SL and SR on the side portion 11 improves the self-supporting ability of the packaging bag 10.

Furthermore, the other end of the rectangular tubular opening in the side portion 11, opposite to the bottom portion 12 that seals one end, is an opening K. The contents can be filled into the packaging bag 10 through this opening K. The contents are not particularly limited, but examples include food, medical supplies, and general merchandise. By sealing the opening K after filling, the contents of the packaging bag 10 can be distributed in a sealed state. Additionally, an opening 11c, which is a notch, is provided in the side seal portions SL and SR at the top of the packaging bag 10. Consumers can then remove the contents from the packaging bag 10 by tearing the side portion 11, using the opening 11c as the starting point for tearing.

Furthermore, the packaging bag 10 has sides 11b and bottom 12 that can be folded along predetermined fold lines. When folded, the two opposing flat surfaces 11a of the packaging bag 10 come into close proximity, and the internal space of the packaging bag 10 almost disappears. The packaging bag 10 then becomes flattened.
In contrast, when the side portion 11b and bottom portion 12 are not folded but extended, the packaging bag 10 becomes unfolded, and in this state, the side portion 11 is in the shape of a rectangular tube.

Figure 2 shows the packaging bag 10 in a folded state.
The side portion 11b is rectangular in shape, extending in the direction connecting one end and the other end of the rectangular tube, and can be folded in half along the fold line T to form a V-shape, with the top V1 of the V-shape protruding inward towards the packaging bag 10. In this case, as shown in Figure 2, the tops V1 of the two side portions 11b face each other.

Figures 3(a) to 3(c) illustrate the bottom portion 12 in more detail. Figure 3(a) shows the bottom portion 12 in an extended state. As shown in the figure, the bottom portion 12 is rectangular and is folded so as to be convex inward when the packaging bag 10 is folded. The bottom portion 12 has a fold line T which is a valley fold that is folded so as to be convex inward, and a fold line Y which is a mountain fold that is folded so as to be convex outward. In Figure 3(a), the fold line T is shown as a dotted line and the fold line Y is shown as a dashed line. The fold line T is formed with a straight section T1 in the middle of the pair of flat sections 11a that is parallel to the pair of flat sections 11a and ends inward from the periphery of the bottom portion 12, and V-shaped sections T3 that extend from both ends T2 of the straight section T1 toward the corresponding corners of the bottom portion 12. The fold line Y extends almost perpendicularly from both ends T2 of the straight portion T1 in the fold line T toward the shorter side of the bottom portion 12. When the bottom portion 12 is folded so that it is convex inward of the bag, the bottom portion 12 is folded so that each of the pair of flat portions 11a is close to each other, resulting in the state shown in Figure 3(b).
When folded, the bottom portion 12 folds into a trapezoidal shape in plan view, as shown in Figure 2. If the top edge of this trapezoid, which corresponds to the straight portion T1, is called the apex V2, the bottom portion 12 is folded so that the apex V2 protrudes in the direction of the inside of the packaging bag 10 and toward the opening K.
As shown in Figure 2, the area where the side portion 11b, which is folded in half to form a rectangle, and the bottom portion 12, which is folded into a trapezoid shape, overlap is a triangular portion W. In this triangular portion W, the side portion 11b is folded and overlapped while being sandwiched between the bottom portion 12.

Furthermore, 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 constituting them.

<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 as the outermost layer on the 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, due to the biaxially oriented film, curling may occur at the four corners of the packaging bag immediately after manufacturing. More specifically, at adjacent corners, one side curls upward and the other downward. This is also known as an S-shaped curl.

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 parts 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.

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 planar parts are arranged facing each other, the orientation of the molecules of the outermost layer of biaxially oriented film in each planar 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 portion 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 can lead to areas within each seal portion 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.

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 shipment, 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 upper 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 constituting 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.

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.

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 that the amount of paper dust generated is small 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 good. 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 basis weight of the paper is preferably 20 g/ ^m² or more and 70 g/ ^m² or less.

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 heat welding to form the respective seal portions SL, SR, and SD, 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.

The innermost layer 111 is positioned on the inner surface 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 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 by heat welding. Therefore, it is preferable that the innermost layers 111 and 121 constituting each surface be made of a resin that can be heat-welded to each other, and preferably of the same type of resin.

The laminate A constituting the side portion 11 has a paper outermost layer 112. 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 when 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 body 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 viewpoint, 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.

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

The intermediate layer 113 is a layer that can impart functionalities such as gas barrier properties, water vapor barrier properties, mechanical toughness, flexibility, 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.

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 compared to 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.

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 mix into the inside of the packaging bag 10. Furthermore, 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 often insufficient. Therefore, it is preferable to use a laminate B with a biaxially oriented film for the outermost layer 122 for the bottom portion 12.

For the innermost layer 121 of the laminate B constituting the bottom portion 12, various materials used for the innermost layer 111 of the laminate A constituting the side portion 11 can be used. However, from the viewpoint of 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.

As the material for the biaxially oriented film used in the outermost layer 122 of the laminate B that constitutes the bottom portion 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 may also have an intermediate layer, similar to laminate A.
Laminate A and laminate B are both laminated using known methods such as dry lamination or extrusion lamination.

<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 in which the transport direction of the laminated film A constituting the side portion 11 of the packaging bag 10 is transported in a direction that 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.

The side film is folded in half. The bottom portion 12 is created 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.

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

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 a roll 210 and a roll 220, and the rotation of the 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 their respective V-shaped apex V1s 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 become one, forming a strip film BF.

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 portions 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.

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 the sealing portions SL, SR, and SD are formed by sandwiching it between the pair of flat films HF1 and HF2. Therefore, when sandwiched between the pair of flat films HF1 and HF2, paper dust may become mixed into the strip-shaped film BF, and ultimately, this paper dust may enter the packaging bag 10. For this reason, when forming the packaging bag 10 using this manufacturing method, it is preferable that the bottom portion 12 is a laminate without paper. In contrast, the flat portion 11a and side portion 11b are cut after the sealing portions have been formed and the strip-shaped film BF has been created; therefore, even if paper dust is released during cutting, it will not enter the packaging bag 10.

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 and HF2 and the side portion film 11bF are transported along the vertical direction. When this manufacturing method is used with a laminate consisting of a flat portion film and side portion film 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, making 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.

In the embodiment 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 in detail above, the packaging bag 10 was folded in the manner shown in Figures 1 to 3, but the folding method is not limited to this, and other folding methods can also be applied.

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 to the above embodiment are also included within the technical scope of the present invention.

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 (4)

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 .
A square-bottom packaging bag characterized in that, when the opening is open, the laminated bodies of the side portions overlap only at the four side sealing portions. 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 to 50 μm. 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. 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.