Bag container using non-oriented pet film

Abstract

To provide a highly transparent bag container having a desired film thickness and optimum rigidity (flexibility), i.e., a bag container imparting a high-grade feeling as compared with a conventional bag container by easily performing bag making processing such as thermal welding processing or folding processing.SOLUTION: A bag container formed of at least one sheet, the sheet including a non-stretched PET film layer and a stretched PET film layer as at least one of a base material layer and an adhesive layer, the non-stretched PET film layer being formed by heating and melting a PET resin as a raw material and extruding the PET resin from a mold, the bag container is a PET film layer containing amorphous PET formed in an amorphous state by rapidly cooling the formed film by a cooling drum, and a part or the whole of the amorphous PET is isophthalic acid-modified PET, or isophthalic acid-modified PET and glycol-modified PET.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a flexible packaging container, i.e., a bag container, using a sheet having at least a non-stretched PET film layer, and more particularly to a bag container in which heat welding processing, folding processing, etc. are applied to the non-stretched PET film when producing the bag container, i.e., when making the bag container. [Background technology]

[0002] As is well known, there are bag containers made of synthetic resin films such as polyethylene (PE) film, polypropylene (PP) film, polyvinyl chloride (PVC), etc. These bag containers are used for a variety of purposes, taking advantage of the properties of each film, such as flexibility and transparency.

[0003] For example, PE bags made from PE film or PP bags made from PP film are generally called plastic bags and are inexpensive and highly flexible bags (see, for example, Patent Document 1). Such PE or PP bags are used, for example, as food packaging bags, garbage bags, etc. PVC bags made from PVC film are available in two types: soft and hard. Soft PVC bags are used as stretch film to wrap food trays, while hard PVC bags are used to package miscellaneous goods, clothing, etc. For these bag containers made from synthetic resin films, the material is selected taking into consideration transparency and flexibility depending on the intended use.

[0004] The flexibility of a film depends primarily on its thickness, and naturally, thinner films are more flexible when made of the same material. In other words, thicker films can be used to form bags with higher rigidity. However, thicker films make it difficult to apply conventional bag-making processes and also increase the amount of material used, making bag-making more expensive. Therefore, bags made from films classified as soft plastics, such as PP film and PE film, are highly flexible but are unsuitable for producing bags that require a certain level of rigidity.

[0005] On the other hand, PET film is a film that is more rigid and transparent than soft plastic films such as PP film and PE film, and has been used as a bag container. For such PET film, oriented PET is used because it is easy to control the film thickness, especially to make it thinner. Here, the term "PET" refers to another name for polyethylene terephthalate, and hereafter, unless otherwise specified, it will be used to mean polyethylene terephthalate.

[0006] However, due to its properties, stretched PET has poor low-temperature heat-sealing properties, making it difficult to heat-seal it to form a bag container, and furthermore, its oriented crystals make it difficult to fold it. Therefore, bags cannot be made from stretched PET film alone, and so bags are made by laminating it with other synthetic resin films that have excellent processability to create a multilayer sheet, which allows for heat-sealing and folding as a sheet (see, for example, Patent Documents 2 and 3). In other words, stretched PET film alone cannot be heat-sealed or folded, making it unsuitable for making bags.

[0007] In addition to oriented PET film, there is also non-oriented PET film. Unlike oriented PET film, non-oriented PET film can be heat-sealed over a wide temperature range, and since the crystals are not oriented, it can be folded. However, with conventional non-oriented PET film, it is difficult to control the film thickness, especially to make it thinner. Because it is not possible to make the film thinner than a certain thickness, containers made from non-oriented PET lack flexibility and end up being hard packaging containers like boxes. In other words, it was unthinkable to make bag containers from non-oriented PET film. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-118177 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-55243 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-134491 Summary of the Invention [Problem to be solved by the invention]

[0009] As described above, some conventional synthetic resin films cannot easily achieve a certain level of rigidity, or are difficult to process with heat welding and creases, etc., and some cannot be formed to a desired film thickness. Therefore, it has not been possible to produce a highly transparent bag container with the desired film thickness and optimal rigidity (flexibility).

[0010] The present invention has been made to solve the problems associated with bag manufacturing using synthetic resin films as described above, and aims to provide a highly transparent bag container that can be easily manufactured using processes such as heat welding and folding, has optimal rigidity (flexibility) at a desired film thickness, and that has a more luxurious feel than conventional bag containers. [Means for solving the problem]

[0011] (1) The present invention provides a bag container formed from at least one sheet, the sheet including an unstretched PET film layer as at least one of a base layer and an adhesive layer, and having a joint where the unstretched PET film layers are joined together, the unstretched PET film layer being a PET film layer containing amorphous PET.

[0012] In other words, since the unstretched PET film layer is a PET film layer containing amorphous PET, the amorphous PET in this bag container has moderate rigidity (flexibility) and high transparency, and can achieve bag container functions that could not be achieved with films made of other synthetic resin materials, namely, characteristic functions such as high toughness, self-standing, foldability, and use for advertising.

[0013] A typical example of non-crystalline PET is A-PET, which is a non-oriented PET and is also called amorphous PET. PET film containing A-PET is formed by heating and melting PET resin, extruding it through a mold, and then rapidly cooling the formed film on a cooling drum, resulting in a non-crystalline film. The process of forming it into a film is also called film formation.

[0014] (2) The bag container may have at least one exposed surface of the non-stretched PET film, and the joint may be formed by joining the exposed surfaces of the non-stretched PET film together using a heat welding process. According to this bag container, the sheets are joined together to form a bag using a heat welding process such as a heat press process, an impulse process, or an ultrasonic process. While heat welding is difficult with stretched PET film, heat welding is possible with non-stretched PET film at low temperatures, making bag production easier. Furthermore, by welding the exposed surfaces of the non-stretched PET film layers together, the joint is firmly joined. This type of heat welding process is also called heat sealing, or simply sealing.

[0015] (3) This bag container has a pair of opposing front portions and a bottom portion that is continuous with the lower ends of each front portion and connects the lower ends of the opposing front portions, and the bottom portion has the joint portion. With this bag container, at least the bottom portion functions as a gusset portion, significantly increasing the storage space of the bag container. Furthermore, because the bottom portion includes a highly tenacity unstretched PET film layer, deformation and breakage of the bottom of the bag container, which bears the greatest weight of the contents, are prevented.

[0016] (4) This bag has side sections that are continuous with the side edges of each front section and connect the side edges of the opposing front sections, and the side sections have folds that can be folded inward. With this bag, the side sections function as gussets, significantly increasing the storage space of the bag. Meanwhile, when the bag is not in use, the bag can be folded by folding the side sections inward along the folds.

[0017] In conventional bag containers made with stretched PET film, it was necessary to layer the stretched PET film with another film that can be folded in order to create a crease.However, with this bag container, creases can be formed even if it is a single layer or without being layered with another film that can be folded in, and creases can be formed that extend in the desired direction so that the side portions can be folded inward in a V shape.

[0018] (5) The bag container may be formed from a single sheet, and the joint portion of the bottom portion may be formed by overlapping and joining the folded sheet surfaces. This allows folds to be formed without layering with another film that can be folded, making it possible to produce a bottom gusset bag using a non-stretched PET film. Furthermore, because the bottom portion includes a highly tenacity non-stretched PET film layer, deformation or breakage of the bottom of the bag container, which bears the greatest weight of the contents, is prevented.

[0019] (6) One of the front portions may have the joint extending from the upper end to the lower end. This bag container has a joint extending from the upper end to the lower end of the front portion. A sheet having a non-stretched PET film layer is easier to heat-seal and fold than a sheet having a stretched PET film layer, so this bag body makes it easy to produce a two-sided bag or the like.

[0020] (7) The non-stretched PET film layer may have two or more pairs of opposing exposed surfaces bonded together in the sheet thickness direction at some or all of the bonded portions. Since the exposed surfaces of the non-stretched PET film layer can be heat-sealed at low temperatures, two or more pairs of exposed surfaces overlapping in the thickness direction can be sealed together. This allows, for example, a heater provided in a bag-making machine to seal two or more pairs of exposed surfaces at once, enabling efficient bag-making.

[0021] (8) In the non-stretched PET film layer, four pairs of opposing exposed surfaces may be bonded together in the sheet thickness direction at some or all of the bonded portions.

[0022] That is, when four pairs of opposing exposed surfaces are joined together, for example, eight sheets can be stacked in multiple layers at one location, resulting in a bag container with a complex structure and assembly. Even with such a complex structure and assembly of bag containers, for example, a heater provided in a bag making machine can seal two or more pairs of exposed surfaces at once, allowing for efficient bag making processing.

[0023] (9) The non-oriented PET film layer may be a film layer formed by mixing glycol-modified PET. Glycol-modified PET is PET in which part of the ethylene glycol is replaced with cyclohexanedimethanol, and is also called G-PET. If the amorphous PET is A-PET, the non-oriented PET film layer is a film layer formed by mixing glycol-modified PET and A-PET.

[0024] Glycol-modified PET is known to be resistant to crystallization, so by mixing glycol-modified PET with amorphous PET, crystallization of the non-oriented PET film layer is suppressed even when heated during heat welding, and the lack of sealing ability caused by crystallization can be reduced.

[0025] Furthermore, the suppression of crystallization allows the transparency of the unstretched PET film layer to be maintained, which makes it easy to adjust the bag-making processing conditions while maintaining high transparency.

[0026] (10) A part or all of the amorphous PET may be isophthalic acid-modified PET, which is PET in which part of the terephthalic acid is replaced with isophthalic acid.

[0027] If part of the amorphous PET is isophthalic acid-modified PET, the non-stretched PET film layer is a film layer formed from isophthalic acid-modified PET and, for example, A-PET, or may be a film layer formed from isophthalic acid-modified PET and a PET mixture of glycol-modified PET and A-PET.

[0028] It is known that isophthalic acid-modified PET is difficult to crystallize, and by suppressing crystallization, the transparency of the non-stretched PET film layer can be improved.

[0029] (11) The joint of the bottom surface may be heat-sealed by ultrasonic heating. Heat-sealing methods include heat pressing, welding, and ultrasonic heating. Generally, heat pressing allows for easy control of the welding temperature and reduces welding costs. On the other hand, ultrasonic heating allows for pinpoint heating of areas that are difficult to heat by heat pressing due to the shape of the object to be heated.

[0030] (12) The bag container may have a pair of opposing front faces, and the front faces may have the joints at both ends. This bag container is a so-called side-seal bag, and has joints on the sides of the bag container where exposed surfaces of the unstretched PET film are joined together, making it easy to manufacture the bag.

[0031] (13) The joints at both ends may be heat-sealed by a heat-cutting method. Heat-sealing by the heat-cutting method is a highly efficient heat-sealing method in which a heated blade is used to join the sheets by heat welding and simultaneously cut the joined sheets. The heat-sealing method is known to be a method that can be used when the heat welding is stable.

[0032] (14) The non-stretched PET film layer may be a film layer formed by mixing glycol-modified PET.

[0033] Because glycol-modified PET is mixed into the non-oriented PET film layer, the lack of sealing ability due to crystallization is reduced, and the non-oriented PET film layer can be stably thermally cut. This allows for easy adjustment of bag-making processing conditions using the thermal cutting method. Furthermore, suppressing crystallization helps maintain transparency.

[0034] (15) A part or all of the amorphous PET may be isophthalic acid-modified PET. For example, the non-stretched PET film layer may be a film layer formed from isophthalic acid-modified PET and A-PET.

[0035] At this time, the crystallization of the isophthalic acid-modified PET is suppressed, and the transparency of the unstretched PET film layer can be improved.

[0036] (16) The unstretched PET film layer may have a thickness of 30 μm to 150 μm. By making the unstretched PET film layer 30 μm to 150 μm thick, a bag container with the desired rigidity can be produced. For example, by making the unstretched PET film layer 30 μm to 150 μm thick, the bag container 100 has a certain level of rigidity while still having the desired toughness to allow elastic deformation. This allows the bag container 100 to maintain its independence even when empty, which was difficult to achieve with conventional PP or PE bags.

[0037] (17) The present invention provides a bag container formed from at least one sheet, the sheet including an unstretched PET film layer as either a base layer or an adhesive layer, the unstretched PET film layer being a PET film layer including amorphous PET.

[0038] The bag container according to the present invention is formed by folding and joining at least one sheet including a non-stretched PET film layer. In this bag container, the non-stretched PET film is used as a base layer, and the non-stretched PET film layer is a PET film layer including amorphous PET, which has appropriate rigidity (flexibility) and high transparency, and therefore can achieve the functions of a bag container that could not be achieved with films of other synthetic resin materials, namely, characteristic functions such as high toughness, self-standing, foldability, and use for advertising.

[0039] (18) The non-stretched PET film layer may be a PET film layer formed by mixing glycol-modified PET. By mixing glycol-modified PET, crystallization of the non-stretched PET film layer is suppressed even when heated during heat welding, thereby reducing the lack of processability caused by crystallization. Furthermore, suppressing crystallization allows the transparency of the non-stretched PET film layer to be maintained. This allows bag-making processing conditions to be easily adjusted while maintaining high transparency.

[0040] (19) A part or all of the amorphous PET may be isophthalic acid-modified PET. Isophthalic acid-modified PET is known to be difficult to crystallize. Therefore, by suppressing crystallization, the transparency of the non-stretched PET film layer can be improved.

[0041] (20) The bag container may have an opening for putting in and taking out the contents, and a sealed structure may be formed by sealing the opening. The non-oriented PET film layer has superior properties in terms of oxygen permeability, water vapor permeability, and aroma retention compared to polyethylene film, polypropylene film, etc. Therefore, when the bag container is formed into a sealed structure, even if the contents are food or drink, the contents can be stored for a long period of time without deterioration in quality compared to polyethylene film, polypropylene film, etc. [Effects of the Invention]

[0042] The bag container of the present invention can be easily manufactured through processes such as heat welding and folding, and is a highly transparent bag container with the desired film thickness and optimal rigidity (flexibility), i.e., a bag container that gives a more luxurious feel than conventional bag containers. [Brief explanation of the drawings]

[0043] [Figure 1] 1 is a perspective view showing a bag container (square-bottom bag) according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing the bag container shown in FIG. 1 from the bottom side. [Figure 3] FIG. 2 is a development view of the bag container shown in FIG. 1. [Figure 4] 2 is a perspective view showing the bag container shown in FIG. 1 in a folded state. FIG. [Figure 5] 10A and 10B are perspective views showing a bag container (Box Pouch (registered trademark)) according to a second embodiment of the present invention, where (A) is a perspective view showing the bag container from the top side and (B) is a perspective view showing the bag container from the bottom side. [Figure 6] FIG. 6 is a development view of the bag container shown in FIG. 5. [Figure 7] FIG. 6 is a cross-sectional view showing the layer structure of the sheet of the bag container shown in FIG. 5. [Figure 8] 6 is a front view and a longitudinal cross-sectional view of the bag container shown in FIG. 5. [Figure 9] 6 is a cross-sectional view showing a layer structure according to a modified example of the sheet of the bag container shown in FIG. 5. FIG. [Figure 10] FIG. 10 is a perspective view showing a bag container (stand-up bag) according to a third embodiment of the present invention. [Figure 11] 11A and 11B are explanatory diagrams of a front view and a longitudinal section of the pouch container (stand-up pouch) shown in FIG. [Figure 12] FIG. 10 is a perspective view showing a bag container (a two-sided bag) according to a fourth embodiment of the present invention. [Figure 13] FIG. 10 is a perspective view showing a bag container (two-sided bag) according to a fifth embodiment of the present invention. [Figure 14] FIG. 10 is a perspective view showing a bag container (three-sided bag) according to a sixth embodiment of the present invention. [Figure 15] FIG. 10 is a perspective view showing a bag container (side-seal bag) according to a seventh embodiment of the present invention. [Figure 16] 16 is an explanatory view showing a thermal fusion cutting process for the bag container (side-seal bag) shown in FIG. 15. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0044] A pouch container 100 according to a first embodiment of the present invention will be described in detail with reference to Figures 1 to 4. The pouch container 100 is a so-called square-bottom bag with gussets (gusseted portions) on the sides and bottom. Square-bottom bags form a roughly rectangular storage space, and although they have a larger storage volume than other bags such as flat bags, they are characterized by being foldable when not containing any contents, i.e., when not in use. Furthermore, square-bottom bags are stable and self-standing when in use.

[0045] 1 and 2, the bag container 100 is formed in a substantially rectangular parallelepiped shape and includes a pair of front portions 120 that form the front and back sides of the rectangular parallelepiped, a pair of side portions 140 that form both sides of the rectangular parallelepiped, and a bottom portion 160 that forms the bottom of the rectangular parallelepiped. These form an opening in the bag container 100 that opens upward in Fig. 1. Contents can be put in and taken out of the bag container 100 through the opening.

[0046] Each side of the bag container 100 is rectangular, although the aspect ratios are different. However, each side may be trapezoidal or have another shape as long as it functions as a bag container. Such a bag container may have, for example, a rectangular front and bottom with trapezoidal sides, or a rectangular bottom with trapezoidal front and sides.

[0047] The bag container 100 is formed by folding a single sheet as shown in FIG. 3. The sheet includes a first front sheet portion 120a forming one of the front portions 120, a first side sheet portion 140a forming one of the side portions 140, a second front sheet portion 120b forming the other of the front portions 120, a second side sheet portion 140b forming the other side portion 140, and a joint sheet portion 180, which are arranged in this order and are continuous. The first and second front sheet portions 120a, 120b, the first and second side sheet portions 140a, 140b, and the joint sheet portion 180 are each formed into a rectangular shape, although they have different aspect ratios. Note that, in this specification, the terms "rectangle" and "quadrilateral" used to specify the shape of the sheet also include those with rounded corners, i.e., so-called "rounded corners."

[0048] The sheet further includes first, second, third, and fourth bottom sheet portions 160a, 160b, 160c, and 160d that are continuous with the lower sides of the front and side portions 120 and 140 (the lower side in FIG. 3 ) and form the bottom portion 160. Each of the bottom sheet portions 160a to 160d is formed in a substantially trapezoidal shape. As will be described later, the bottom sheet portions 160a to 160d are stacked on top of each other to form the bottom portion 160. However, other shapes may be used as long as the bottom portion 160 can be formed. In other words, the shape is not limited to a quadrangle such as a trapezoid, and may be a convex, concave, or other shape.

[0049] Each front sheet portion 120a, 120b has an oval-shaped hole 122a, 122b cut out. The holes 122a, 122b are located opposite each other when the bag container 100 is formed from the sheet. As a result, by passing fingers through both holes 122a, 122b, both holes 122a, 122b function as the handle 122 (see Figures 1 and 2). However, the handle may be achieved by other configurations. For example, the handle can be created by drilling two desired holes in the bag container, passing both ends of a string through the holes, securing each end with a caulking or the like, and forming a loop with the string.

[0050] Each side sheet portion 140a, 140b has a first fold 142 extending vertically and a second fold 144 extending diagonally downward and diagonally downward, branching from a point below the first fold 142. The first fold 142 and the second fold 144 form an inverted Y-shaped fold. Each fold is creasing-processed, a type of folding process, to form, for example, a V-shaped groove in the cross-section of the sheet. This allows the sheet to be easily folded along the fold. The groove may be formed as a dotted line or a continuous line. However, the folds 142, 144 may be folded without being creasing-processed.

[0051] The first fold 142 extends downward from the upper end in the longitudinal direction of each side sheet portion 140a, 140b, and at the center position in the short direction of the side sheet portions 140a, 140b, and the second fold 144 extends from halfway along the first fold 142 to one lower end (lower left end) and the other lower end (lower right end) of the side sheet portions 140a, 140b.

[0052] By folding the side sheet portions 140a, 140b along the first and second creases 142, 144, the side portion 140 is formed so that it can be folded in a V-shape inside the bag container, allowing the bag container 100 to be folded when not in use (see Figure 4). As will be described later, the sheet is formed as a thin sheet with a base layer of unstretched PET film containing amorphous PET, and can be folded in the same way as conventional plastic films. With stretched PET film, the crystals are oriented by stretching, making it impossible to fold in the desired direction. However, with unstretched PET film containing amorphous PET, the crystals are not oriented by stretching, so it can be fold in the desired direction.

[0053] The surface sheet portions of the sheet are folded at right angles at the boundary lines of the surface sheet portions, thereby forming the sheet into a substantially rectangular parallelepiped bag container 100, as shown in Figures 1 and 2. The boundary lines of the surface sheet portions may be creased by a scoring process similar to the first and second folds 142, 144.

[0054] An auxiliary sheet 100A having the same shape as the bottom portion 160 is placed in the bag container 100 with the first to fourth bottom sheet portions 160a to 160d overlapping each other (see FIG. 1). With the auxiliary sheet 100A overlapping the first to fourth bottom sheet portions 160a to 160d, the bottom portion 160 is bonded at multiple locations using an adhesive or the like to form multiple first joint portions 162 (see FIG. 2).

[0055] Furthermore, the bag container 100 has a second joint portion 182 on one front surface portion 120 made of the first front surface sheet portion 120a. The second joint portion 182 is formed by overlapping the joint sheet portion 180 with a portion of the side edge of the first front surface sheet portion 120a and bonding the overlapped portion together. This bonds the unstretched PET film layers together.

[0056] Furthermore, these joints 162, 182 may be formed by adhesion using an adhesive or the like, or by thermal welding using an impulse method, ultrasonic method or the like.

[0057] The sheet forming the bag container 100 has a single-layer structure consisting of only an unstretched PET film layer. That is, both sides of the unstretched PET film layer of the sheet are exposed. As a result, the unstretched PET film functions as a base layer and an adhesive layer in a single layer. Here, the base layer refers to the layer with the highest rigidity among the multiple layers of a single sheet, and generally controls the rigidity and toughness of the sheet. Furthermore, the adhesive layer refers to a layer with one side bonded to the surface of another sheet or the like. Therefore, the bag container 100 according to this embodiment includes an unstretched PET film layer that functions as a base layer or adhesive layer, and has a joint where the unstretched PET film layers are bonded together.

[0058] This non-oriented PET film layer uses PET resin as its raw material. The non-oriented PET film layer is a PET film layer containing amorphous PET, which is formed by heating and melting the PET resin and extruding it through a mold to form a film, and then rapidly cooling the film using a cooling drum to form an amorphous state. An example of amorphous PET formed through this process is A-PET (amorphous PET), which is unoriented PET.

[0059] At this time, the recycled PET resin may be heated and melted to form a film.

[0060] The non-stretched PET film layer of the pouch container 100 may be composed of a film layer formed by mixing glycol-modified PET and A-PET. Because it is less likely to crystallize, it is possible to maintain high transparency.

[0061] A film layer formed by blending glycol-modified PET and A-PET can be obtained, for example, by melt-extrusion, where the heated and melted glycol-modified PET resin and A-PET resin are extruded through a T-die. In this process, the glycol-modified PET resin and A-PET resin are fed in a mixed state into a hopper provided in an extrusion device and melted therein, or are fed into two separate hoppers provided in the extrusion device and mixed during the melt-extrusion process.

[0062] Glycol-modified PET is a PET film in which part of the ethylene glycol is replaced with cyclohexanedimethanol, and is also called G-PET. Glycol-modified PET is known to be resistant to crystallization. Therefore, by mixing glycol-modified PET, crystallization of the non-oriented PET film layer is suppressed even when heated, for example, during heat welding processing, and the lack of sealing ability caused by crystallization can be reduced.

[0063] Furthermore, suppressing crystallization helps maintain the transparency of the unstretched PET film layer, which makes bag-making easier and maintains high transparency.

[0064] When glycol-modified PET is mixed, the aforementioned crystallization is suppressed, thereby reducing the lack of sealing ability during heat welding and maintaining high transparency in the pouch container 100. In this way, the pouch manufacturing process can be easily performed, and a pouch container having rigidity or flexibility and high transparency can be obtained.

[0065] In this case, recycled glycol-modified PET resin may be used.

[0066] Furthermore, the unstretched PET film layer of the pouch container 100 may be a PET film layer containing a part or all of isophthalic acid-modified PET. That is, the unstretched PET film layer may be a film layer formed from A-PET and isophthalic acid-modified PET, or a film layer formed from a mixture of glycol-modified PET and A-PET and isophthalic acid-modified PET.

[0067] Isophthalic acid-modified PET is known to be resistant to crystallization, so suppressing crystallization can improve the transparency of the unstretched PET film layer.

[0068] Crystallization can also be suppressed by using a special modifying agent.

[0069] When in use, i.e., when an item is contained, the bag container 100 is used in the shape of a roughly rectangular parallelepiped as shown in Fig. 1. On the other hand, when not in use, i.e., when no item is contained, the side portions are folded inward in a V-shape, and the bag container 100 is folded into a sheet shape as shown in Fig. 4.

[0070] Each front surface portion 120 is formed in the same rectangular shape, and faces each other so that each side corresponds to the other. That is, the lower ends of the rectangular front surfaces 120 correspond to each other, and the bottom surface portion 160 is formed to connect these lower ends. In addition, the side ends of the rectangular front surfaces 120 correspond to each other, and each side surface portion 140 is formed to connect these two side ends.

[0071] In this embodiment, the unstretched PET film layer has a thickness of 80 μm. The 80 μm thick unstretched PET film has a certain level of rigidity while still providing the desired toughness to allow elastic deformation. This allows the bag container 100 to stand on its own even when empty, something that was difficult to achieve with conventional PP or PE bags.

[0072] However, the non-stretched PET film layer may have a thickness of 30 μm to 150 μm. A thickness within this range maintains toughness sufficient to allow elastic deformation, while providing flexibility sufficient to prevent the container from becoming a box. Furthermore, the non-stretched PET film layer may have a thickness of 80 μm to 120 μm. A thickness within this range maintains toughness sufficient to allow the container to stand on its own, while providing flexibility sufficient to allow appropriate deformation depending on the contents contained therein. The relationship between thickness and toughness will also depend on the thickness of the other film layers when a synthetic resin film is laminated in addition to the non-stretched PET film layer, but when the non-stretched PET layer forms the base layer, the non-stretched PET layer generally determines the toughness.

[0073] The pouch 100 according to the embodiment of the present invention is formed from a single sheet in which a non-stretched PET film layer containing amorphous PET functions as a base layer and an adhesive layer. Therefore, the non-stretched PET film has high transparency, gloss, and toughness (so-called stiffness), and a pouch made from a sheet with a non-stretched PET film as a base layer evokes a sense of luxury compared to sheets made from conventional synthetic resins. The sheets on each side of the pouch 100 may have a two-layer structure in which a stretched PET film layer 200b is laminated to a non-stretched PET film 200a, as employed in the pouch 200 according to the second embodiment described below.

[0074] The bag container 100 according to the present embodiment is formed by cutting out a predetermined shape from a sheet cut into a rectangular shape of a predetermined size, a so-called cut sheet. However, the sheet may also be formed by cutting out a long sheet wound into a roll, a so-called roll sheet.

[0075] Next, a bag container 200 according to a second embodiment of the present invention will be described with reference to Figures 5 to 9. The bag container 200 is a box pouch (registered trademark), which is a type of square-bottom bag. Like the bag container 100, the bag container 200 has gussets (gusset portions) on the sides and bottom. However, the bag container 200 is formed by a different manufacturing method from that of the bag container 100.

[0076] The box pouch can be formed, for example, by cutting, folding, and heat-sealing two roll sheets. The front part of the box pouch may be formed into another shape. For example, by forming the front part into the shape of a character and joining the periphery of the front part, a bag container can be formed that evokes the impression that the character is standing upright.

[0077] 5 and 6, like the bag container 100, the bag container 200 is formed in a substantially rectangular parallelepiped shape, and includes a pair of substantially rectangular front portions 220, a pair of substantially rectangular side portions 240, and a substantially rectangular bottom portion 260. However, whereas the bag container 100 is formed from a single sheet, the bag container 200 is formed from a plurality of sheets. In addition, the bag container 200 includes a joint portion 280 joining the front portion 220 and the side portion 240, a joint portion 282 joining the front portion 220 and the bottom portion 260, and a joint portion 284 joining the side portion 240 and the bottom portion 260.

[0078] Joints 280 are formed on both side edges of the front surface portion 220 and on both side edges of the side surface portion 240. Joints 282 are provided at the bottom end of the front surface portion 220 and at the front and rear ends of the bottom surface portion 260. Joints 284 are provided at the bottom end of the side surface portion 240 and at the left and right ends of the bottom surface portion 260.

[0079] As shown in Fig. 7, the sheet 200S on each surface of the pouch container 200 has a two-layer structure in which a stretched PET film layer 200b is laminated to a non-stretched PET film layer 200a. The stretched PET film layer functions as a decorative layer, and the non-stretched PET film layer functions as a base layer and an adhesive layer. Here, the decorative layer refers to a layer on which decorative portions such as letters, figures, patterns, etc. are formed and which is laminated to another layer to decorate the sheet.

[0080] The stretched PET film is produced by a conventionally well-known molding method using uniaxial or biaxial stretching, and the stretched PET film layer refers to a layer formed by the stretched PET film.

[0081] In contrast, non-stretched PET films are produced by a conventional film forming method using a roll device (see, for example, JP-A-11-235747). In other words, in this specification, "stretched PET film" refers to a film that has been intentionally stretched to achieve uniform crystal orientation, while "non-stretched PET" refers to a film that has not been intentionally stretched or that does not have properties that make crystallization difficult. Furthermore, "non-stretched PET film layer" refers to a layer formed from non-stretched PET film.

[0082] The stretched PET film layer 200b has a partial opaque portion 202 (for example, the "ABC" portion in FIG. 5) and serves as a decorative layer. That is, in the sheet 200S, the stretched PET film layer 200b having the opaque portion 202 is laminated to the transparent unstretched PET film layer 200a, and the opaque portion has a display function for displaying letters, figures, patterns, etc.

[0083] The opaque portion 202 is made by printing desired characters, figures, patterns, etc. on the stretched PET film, and then laminating the printed stretched PET film onto the non-stretched PET film to produce a sheet bearing the desired characters, figures, patterns, etc. The non-stretched PET film 200a and the stretched PET film 200b are laminated together using a conventionally well-known laminating device.

[0084] In the bag container 200, the unstretched PET film layer is exposed on the inner surface of each side portion of the bag. Therefore, at the joints 280, 282, and 284, the exposed surfaces of the unstretched PET film layer are directly joined together. However, heat welding may be difficult between the unstretched PET film layer and the stretched PET film layer or other synthetic resin film layer due to differences in melting temperature and the effect of intermolecular bonding. Therefore, the joints are firmly joined by directly joining the exposed surfaces of the unstretched PET film layer.

[0085] Since each joint of the bag container 200 is formed around the periphery of each surface, it is heat-sealed from the outside of the bag container 200 using a heat press method. An example of a device that can make such bags is the bag making machine described in Japanese Patent Application Laid-Open No. 2011-67997. However, each joint may be heat-sealed using other methods.

[0086] By joining the bag container 200 in this manner, the pair of front portions 220 of the bag container 200 face each other, the bottom portion 260 is continuous with the lower ends of both front portions 220 and connects the lower ends of both front portions 220, and the side portion 240 is continuous with the side ends of both front portions 220 and connects the side ends of both front portions 220. The other configurations are the same as those in the first embodiment.

[0087] Fig. 8(a) shows a front view of the bag container 200 assembled by joining in this manner. Fig. 8(b) shows an explanatory diagram of a longitudinal section of section A-A' shown in the front view of Fig. 8(a). Fig. 8(c) shows an explanatory diagram of a longitudinal section of section B-B'. Arrows L and R indicate left and right directions in the left-right direction of the front view of the bag container 200. Arrows U and D indicate up and down directions in the up-down direction, respectively. Arrows F and B indicate front and back directions in the depth direction when viewed from the front of the bag container 200.

[0088] The bag container 200 is assembled by arranging the front surface portion 220, side surface portion 240, and bottom surface portion 260 as shown in Figure 6, then overlapping them at their respective joints 280, 282, and 284 and heat welding them in the depth direction. In Figures 8(b) and (c), the joints 280, 282, and 284 are indicated by thick arrows. At these joints 280, 282, and 284, the sheets 200S of the surface portions 220, 240, and 260 are joined to each other in the sheet thickness direction.

[0089] At this time, the sheets 200S of the surface portions 220, 240, 260 are arranged so that the exposed side of each unstretched PET film layer 200a faces the respective joining portions 220, 240, 260.

[0090] Cross section A-A' is a cross section in the vertical direction of Figure 8(a), and is a cross section passing through the edge of left-facing L. Therefore, cross section A-A' represents a state in which joint 280 joining front portion 220 and side portion 240 is cut in the depth direction, a state in which joint 284 joining side portion 240 and bottom portion 260 is cut in the depth direction, and a state in which joint 282 joining front portion 220 and bottom portion 260 is cut in the depth direction. Figures 8(b) and (c) are diagrams that emphasize the dimension of bag container 200 in the depth direction, and also show the state just before joining portions 280, 282, and 284 are overlapped.

[0091] 8(b), in the cross section A-A', in the portion where the bottom surface portion 260 is not joined, from the front side F to the back side B, the front portion 220 of the front side F, the side surface portion 240 of the front side F, the side surface portion 240 of the back side B, and the front portion 220 of the back side B are overlapped four times via the respective joining portions 280, 280. As a result, two pairs of opposing exposed surfaces of the unstretched PET film layer are joined at the respective joining portions 280, 280 in the sheet thickness direction of the respective surface portions 220, 220, 240, 240.

[0092] In addition, in the upper U region of the part where the bottom surface portion 260 is joined, from the front side F to the back side B, the front portion 220 of the front side F, the side portion 240a of the front side F facing most forward F, the side portion 240b of the front side F facing more rearward B than this, the bottom surface portion 260 of the front side F, the bottom surface portion 260 of the back side B, the side portion 240c of the back side B facing most forward F, the side portion 240d of the back side B facing more rearward B than this, and the front portion 220 of the back side B are overlapped eight times via each joint 280, 280, 284, 284. As a result, the four pairs of opposing exposed surfaces of the unstretched PET film layer are joined together at the joining portions 280, 280, 284, 284 in the sheet thickness direction of the surface portions 220, 220, 240a, 240c, 240c, 240d, 260, 260.

[0093] Furthermore, in the region of the lower side D of the portion where the bottom surface portion 260 is joined, the front surface portion 220 on the front side F, the bottom surface portion 260 on the front side F, the bottom surface portion 260 on the back side B, and the front surface portion 220 on the back side B are overlapped four times via the respective joints 282, 282 from the front side F to the back side B. As a result, two pairs of opposing exposed surfaces of the unstretched PET film layer are joined in the sheet thickness direction of the respective surface portions 220, 220, 260, 260 at the respective joints 282, 282.

[0094] 8(c), in the section B-B' where the bottom surface portion 260 is joined, the front surface portion 220 on the front side F, the bottom surface portion 260 on the front side F, the bottom surface portion 260 on the back side B, and the front surface portion 220 on the back side B are overlapped four times via the joints 282, 282 from the front side F to the back side B. As a result, two pairs of opposing exposed surfaces of the unstretched PET film layer are joined in the sheet thickness direction of the surface portions 220, 220, 260, 260 at the joints 282, 282.

[0095] The heat sealing at each joint 280, 282, 284 is performed, for example, by applying a high-temperature heater in the depth direction and crimping the bag container 200. As described above, the exposed surfaces of the non-stretched PET film layers are directly joined together at these joints 280, 282, 284. Because the exposed surfaces of the non-stretched PET film layers can be heat-sealed together, it is possible to seal exposed surfaces that overlap in the sheet thickness direction. This allows, for example, a heater provided in a bag making machine to seal multiple pairs of exposed surfaces at once, enabling efficient bag making.

[0096] This non-oriented PET film layer uses PET resin as its raw material. The non-oriented PET film layer is a PET film layer containing amorphous PET, which is formed by heating and melting the PET resin and extruding it through a mold to form a film, and then rapidly cooling the film using a cooling drum to form an amorphous state. An example of amorphous PET formed through this process is A-PET (amorphous PET), which is unoriented PET.

[0097] In the bag container 200, the exposed surfaces of the unstretched PET film layers containing A-PET are heat-sealed together, so that the joints 280, 282, 284 are firmly joined.

[0098] In addition, unstretched PET films containing A-PET have high transparency, gloss, and toughness (so-called stiffness), and bag containers made from sheets with unstretched PET films containing A-PET as the base layer evoke a sense of luxury compared to sheets made from conventional synthetic resins.

[0099] At this time, the recycled PET resin may be heated and melted to form a film.

[0100] However, depending on the bag-making process conditions, such as heater temperature and heating time, the thermal history of the unstretched PET film layer can cause crystallization, resulting in insufficient sealing. Therefore, to improve sealing performance, the bag-making process conditions must be adjusted. In particular, when sealing two or more pairs of exposed surfaces, the entire sheet thickness is heated to a high temperature, so the greater the number of pairs of exposed surfaces to be sealed, the greater the risk of excessive heating.

[0101] Furthermore, in the upper U region of the portion where the bottom surface portion 260 is joined, four pairs of opposing exposed surfaces are joined in the sheet thickness direction, so they are welded together in an overheated state, and there is a higher risk of insufficient sealing due to crystallization.

[0102] Therefore, measures may be taken to prevent excessive crystallization due to thermal history by performing heat welding in multiple steps, such as joining each front portion 220, 220 to the bottom portion 260, joining each side portion 240, 240 to the bottom portion 260, and joining each front portion 220, 220 to each side portion 240, 240 separately, and then heating each joining portion 280, 280, 282, 282, 284, 284 at once.

[0103] The non-stretched PET film layer of the bag container 200 is made of a film layer formed by mixing glycol-modified PET and A-PET.

[0104] A film layer formed by blending glycol-modified PET and A-PET can be obtained, for example, by melt-extrusion, where the heated and melted glycol-modified PET resin and A-PET resin are extruded through a T-die. In this process, the glycol-modified PET resin and A-PET resin are fed in a mixed state into a hopper provided in an extrusion device and melted therein, or are fed into two separate hoppers provided in the extrusion device and mixed during the melt-extrusion process.

[0105] Glycol-modified PET is PET in which part of the ethylene glycol is replaced with cyclohexanedimethanol, and is also called G-PET. Glycol-modified PET is known to be resistant to crystallization. Therefore, by mixing glycol-modified PET, crystallization of the non-oriented PET film layer is suppressed even when it is excessively heated during heat welding processing, and the lack of sealing ability caused by crystallization can be reduced.

[0106] Furthermore, suppressing crystallization helps maintain the transparency of the unstretched PET film layer, making it easier to adjust bag-making processing conditions while maintaining high transparency.

[0107] In this case, recycled PET resin or glycol-modified PET resin may be used.

[0108] For these reasons, even when sealing is performed at high temperatures or for a long time at each of the joints 280, 282, 284 where two or four sets of opposing exposed surfaces are joined in the sheet thickness direction, crystallization is suppressed, and insufficient sheet properties due to progress of crystallization can be reduced, and high transparency can be maintained. In this way, bag manufacturing can be easily performed, and a bag container having rigidity or flexibility and high transparency can be obtained.

[0109] Furthermore, the non-stretched PET film layer of the pouch container 200 may be a PET film layer containing part or all of isophthalic acid-modified PET. That is, the non-stretched PET film layer may be a film layer formed from A-PET and isophthalic acid-modified PET, or a film layer formed from a mixture of glycol-modified PET and A-PET and isophthalic acid-modified PET. Furthermore, by strictly adjusting the bag-making processing conditions, the non-stretched PET film layer of the pouch container 200 may be a film layer formed from A-PET or A-PET and isophthalic acid-modified PET without mixing glycol-modified PET.

[0110] Isophthalic acid-modified PET is known to be resistant to crystallization, so suppressing crystallization can improve the transparency of the unstretched PET film layer.

[0111] Crystallization can also be suppressed by using a special modifying agent.

[0112] Similar to the side surface portion 140 of the bag container 100 according to the first embodiment, the side surface portion 240 of the bag container 200 has a first fold 242 extending vertically and a second fold 244 extending diagonally downward and diagonally downward so as to branch off from the first fold 242, with the first fold 242 and the second fold 244 forming an inverted Y-shaped fold. The bottom surface portion 260 also has a third fold 246. Each fold is so-called scored. However, the folds 242, 244, and 246 may be folded without being scored.

[0113] This allows the sheet to be easily folded along the creases. Side surface portion 240 is folded along first to third creases 242, 244, and 246, so that side surface portion 240 and bottom surface portion 260 can be folded into a V-shape inside the bag-container, making bag-container 200 foldable when not in use.

[0114] Although the sheet 200S has a two-layer structure in which a stretched PET film layer is laminated to a non-stretched PET film layer, it may have a single-layer structure consisting of only a non-stretched PET film layer, or may have other multi-layer structures as long as one side of the non-stretched PET film layer is exposed. When joining sheets of a single-layer structure, they are thermally welded using an impulse method or an ultrasonic method, or are bonded using an adhesive or the like.

[0115] Furthermore, in the pouch container 200, the unstretched PET film functions as both a base layer and an adhesive layer, but it is sufficient that it functions as at least one of the base layer and the adhesive layer. That is, either the base layer or the adhesive layer may be formed from an unstretched PET film layer, and the other may be formed from another synthetic resin film layer or a stretched PET film layer.

[0116] Although all of the sheets in the bag container 200 are formed from sheets having the same layer structure, the sheets may have different layer structures. For example, the front surface portion 220 may be formed from a sheet having a two-layer structure of an unstretched PET film layer and a stretched PET film layer, and the side surface portions 240 and the bottom surface portion 260 may be formed from a sheet having a single-layer structure of only the unstretched PET film layer.

[0117] A modified example of the sheet 200S of the pouch container 200 is the sheet 200T shown in Fig. 9. While the sheet 200S has a two-layer structure, the sheet 200T has a three-layer structure. The sheet 200T includes, for example, a PE film layer 200c that functions as a base layer, an unstretched PET film layer 200d that functions as an adhesive layer, and an oriented PET film layer 200e that functions as a decorative layer.

[0118] Even with such a sheet 200T, one side of the unstretched PET film layer 200d is exposed, so if the sheet is made so that this side is placed inside the bag container 200, the unstretched PET film layers can be joined together.

[0119] Next, bag containers 300, 400, 500, 600, and 700 according to third to seventh embodiments will be described with reference to Figures 10 to 16. These bag containers can be made by a conventionally well-known bag making method.

[0120] The bag container 300 according to the third embodiment shown in FIG. 10 is called a stand-up bag and includes a pair of substantially rectangular front portions 320 and a substantially circular bottom portion 360. The bag container 300 is formed from multiple sheets. For example, the stand-up bag can be formed by folding, cutting, and heat-sealing two rolled sheets. The front portion of the stand-up bag may be formed in a different shape. For example, by forming the front portion in the shape of a character and joining the periphery of the front portion, a bag container can be formed that evokes the impression of the character standing upright.

[0121] The sheet forming the front surface portion 320 has a two-layer structure consisting of an unstretched PET film layer and an oriented PET film layer, similar to the sheet 200S. The unstretched PET film layer functions as a base layer and an adhesive layer, and the oriented PET film layer functions as a decorative layer. As a result, the front surface portion 320 of the bag container 300 displays the letters "ABC" as the opaque portion 302, similar to the bag container 200.

[0122] As in the second embodiment, the sheet may have a single layer structure consisting of only an unstretched PET film layer.

[0123] Each sheet forming the bag container 300 may have a different layer configuration as long as at least one surface of the unstretched PET film layer is exposed. Furthermore, when each sheet forming the bag container 300 has two or more layers, it is sufficient that the unstretched PET film layer functions at least as a base layer or an adhesive layer.

[0124] Each surface of the bag container 300 is joined by heat welding. That is, the front surface 320 has a joint 380 where both sides are joined together by heat welding, and the front surface 320 and the bottom surface 360 ​​have a joint 382 where the peripheries of each are overlapped and joined by heat welding. At the joint 380, the exposed surfaces of the unstretched PET film layers are directly joined together. Since each joint of the bag container 300 is formed around the periphery of each surface, it is heat-sealed from the outside of the bag container 300 using a heat press method. However, each joint may be heat-sealed using other methods.

[0125] However, when joining the above-mentioned single-layered sheets, they are thermally welded by an impulse method or an ultrasonic method, or are bonded using an adhesive or the like.

[0126] By joining the bag container 300 in this manner, the pair of front portions 320 of the bag container 300 face each other, and the bottom portion 360 is formed so as to continue from the lower ends of both front portions 320 and connect the lower ends of both front portions 320.

[0127] The bottom surface 360 ​​of the bag container 300 forms a bottom gusset (gusset portion). The bottom surface 360 ​​also has a fold 362 extending in one direction. The fold 362 is so-called scored, and for example, a V-shaped groove is formed in the thickness direction of the sheet. This allows the sheet to be easily folded along the fold. By folding the bottom surface along the fold 362, it is possible to fold it into a V-shape inside the bag container, making the bag container 300 foldable when not in use. However, the fold 362 may be simply folded without being scored. The other configurations are the same as those in the second embodiment.

[0128] Fig. 11(a) shows a front view of the bag container 300 that has been joined, folded, and assembled in this manner. Fig. 11(b) shows an explanatory diagram of a longitudinal section of section A-A' shown in the front view of Fig. 11(a). Fig. 11(c) shows an explanatory diagram of a longitudinal section of section B-B'. Arrows L and R indicate left and right directions in the left-right direction of the front view of the bag container 300. Arrows U and D indicate up and down directions in the up-down direction, respectively. Arrows F and B indicate front and back directions in the depth direction of the front view of the bag container 300.

[0129] The bag container 300 is assembled by folding the front panel 320 and the bottom panel 360, overlapping them at their respective joints 380, 382, ​​and heat welding them in the depth direction. In Figures 11(b) and (c), the joints 380, 382 are indicated by thick arrows. At these joints 380, 382, ​​the sheets of the front panel 320, 360 are joined to each other in the sheet thickness direction.

[0130] At this time, the sheets of the surface portions 320 and 360 are arranged so that the exposed side of each unstretched PET film layer faces the respective joint portions 380 and 382 .

[0131] Cross section A-A' is a cross section in the vertical direction of Figure 11(a), and is a cross section passing through the edge of left-facing L. Therefore, cross section A-A' represents a state in which joint 380 joining opposing front portions 320, 320 is cut in the depth direction, and also represents a state in which joint 382 joining front portion 320 and bottom portion 360 is cut in the depth direction. Figures 11(b) and (c) are diagrams that emphasize the depth dimension of bag container 300, and also show the state just before joints 380, 382 are overlapped.

[0132] Therefore, although the cross section of the folded portion of the bottom surface portion 360 is shown as an inverted U-shape in FIGS. 11(b) and 11(c), when the bag container 300 is folded, it is folded at an acute angle along the crease 362.

[0133] 11(b), in the cross section A-A', in the portion where the bottom surface portion 360 is not joined, the front surface portion 320 on the front side F and the front surface portion 320 on the back side B are overlapped in this order from the front side F to the back side B via the joint 380. As a result, a pair of opposing exposed surfaces of the unstretched PET film layer are joined at the joint 380 in the sheet thickness direction of the surface portions 320, 320.

[0134] Furthermore, in the portion where the bottom surface portion 360 is joined, the front surface portion 320 on the front side F, the bottom surface portion 360 on the front side F, the bottom surface portion 360 on the back side B, and the front surface portion 320 on the back side B are overlapped four times via the joints 382, ​​382 from the front side F to the back side B. As a result, two pairs of opposing exposed surfaces of the unstretched PET film layer are joined in the sheet thickness direction of the surface portions 320, 320, 360, 360 at the joints 382, ​​382.

[0135] However, in the cutout region indicated by S1 in the figure, the left end L and the right end R of the bottom surface portion 360 on the front side F and the bottom surface portion 360 on the back side B are cut out so as to form semicircular shapes that open to the left L and right R. Therefore, in the cutout region S1, the exposed surfaces of the unstretched PET film layers of the front portion 320 on the front side F and the front portion 320 on the back side B are directly overlapped and welded together via the joint 380a.

[0136] By directly joining the notched regions S1, the front portions 320 of the bag container 300 stand on the ground and a gusset (gusset portion) can be formed at the bottom.

[0137] 11(c), in the seal region indicated by S2 in the figure where the bottom surface portion 360 is joined, the front surface portion 320 on the front side F, the bottom surface portion 360 on the front side F, the bottom surface portion 360 on the back side B, and the front surface portion 320 on the back side B are overlapped four times via respective joints 382, ​​382 from the front side F to the back side B. As a result, two pairs of opposing exposed surfaces of the unstretched PET film layer are joined at each joint 382, ​​382 in the sheet thickness direction of the surface portions 320, 320, 360, 360.

[0138] The heat sealing at each joint 380, 382 is performed, for example, by applying a high-temperature heater in the depth direction and crimping the bag container 300. As described above, the exposed surfaces of the non-stretched PET film layers are directly joined together at these joints 380, 382. Because the exposed surfaces of the non-stretched PET film layers can be heat-sealed together, it is possible to seal exposed surfaces that overlap in the sheet thickness direction. This allows, for example, a heater provided in a bag making machine to seal multiple pairs of exposed surfaces at once, enabling efficient bag making.

[0139] The non-stretched PET film layer is a PET film layer containing A-PET, and therefore the exposed surfaces of the non-stretched PET film layer are heat-sealed together, thereby firmly joining the joints 380 and 382.

[0140] However, depending on the bag-making processing conditions, such as heater temperature and heating time, crystallization may progress due to the thermal history of the unstretched PET film layer, resulting in insufficient sealing. In particular, when sealing two or more pairs of exposed surfaces together, as in the case of the bag container 300, the entire sheet thickness direction is heated to a high temperature, and the greater the number of pairs of exposed surfaces to be sealed, the greater the risk of excessive heating.

[0141] Incidentally, the unstretched PET film layer of the bag container 300 is made of a film layer formed by mixing glycol-modified PET and A-PET, similar to the bag container 200.

[0142] Therefore, even when sealing is performed at high temperatures or for a long time at each joint 380, 382 where two pairs of opposing exposed surfaces are joined in the sheet thickness direction, crystallization is suppressed, and insufficient sheet properties due to progress of crystallization can be reduced, and high transparency can be maintained. In this way, bag-making processing conditions can be easily adjusted, and a bag container with rigidity or flexibility and high transparency can be obtained.

[0143] In this case, recycled PET resin or glycol-modified PET resin may be used.

[0144] Furthermore, the non-stretched PET film layer of the pouch container 300 may be a PET film layer containing part or all of isophthalic acid-modified PET. That is, the non-stretched PET film layer may be a film layer formed from A-PET and isophthalic acid-modified PET, or a film layer formed from a mixture of glycol-modified PET and A-PET and isophthalic acid-modified PET. Furthermore, by strictly adjusting the bag-making processing conditions, the non-stretched PET film layer of the pouch container 300 may be a film layer formed from A-PET or A-PET and isophthalic acid-modified PET without mixing glycol-modified PET.

[0145] Isophthalic acid-modified PET is known to be resistant to crystallization, so suppressing crystallization can improve the transparency of the unstretched PET film layer.

[0146] Crystallization can also be suppressed by using a special modifying agent.

[0147] In this embodiment, the bag container 300, which is a stand-up bag, has a square front portion 320, but the front portion may be formed in other shapes. For example, by forming the front portion in the shape of a character and joining the periphery of the front portion, a bag container can be formed that evokes the impression that the character is standing upright. The bag container 300 may also be formed from a single sheet. In this case, for example, the front portion 320 on the front side F, the bottom portion 360, and the front portion 320 on the back side B may be continuous at the bottom of the bag container 300, forming a W-shape in the vertical cross section of Figures 11(b) and 11(c).

[0148] The bag container 400 according to the fourth embodiment shown in Figure 12 is called a two-pronged bag and has a pair of substantially rectangular front portions 420. The bag container 400 is a so-called flat bag, but may also be formed as a gusseted bag with a gusset portion. The bag container 400 is formed from a single sheet. That is, a single rectangular sheet is folded at approximately one-quarter positions on both the left and right sides, and both ends of the sheet are overlapped and joined.

[0149] The bag container 400 is formed from a two-layer sheet with an exposed unstretched PET film layer. The unstretched PET film layer also functions as at least a base layer or an adhesive layer. For example, if the sheet of the bag container 400 has a two-layer structure similar to the sheet 200S, with the unstretched PET film layer serving as a base layer and adhesive layer and the stretched PET film layer serving as a decorative layer, then, similar to the bag container 200, letters, figures, patterns, etc. can be displayed on the opaque portion.

[0150] The bag container 400 has a joint 480 extending from the top to the bottom in the center of the left-right direction of one of the front portions 420, and a joint 482 extending left-right at the bottom. That is, one of the front portions 420 has the joint 480 formed by overlapping and heat-sealing both ends of the single rectangular sheet described above, and both front portions 420 have joints 482 formed by heat-sealing at their bottom edges. The joints 480 and 482 are formed by directly bonding the exposed surfaces of the unstretched PET film layers together. Each joint of the bag container 400 is heat-sealed from the outside of the bag container 400 using a heat press method. However, each joint may be heat-sealed using other methods. The other configurations are the same as those of the third embodiment.

[0151] With a joint 480 extending from the top to the bottom leaning toward either the left or right side of the front portion 420, in a region near the bottom, this joint 480 overlaps in the sheet thickness direction with a region near the center of a joint 482 extending left and right at the bottom. In this overlapping region, four sheets are overlapped in four layers, from top to bottom in the figure, via the joints 480, 482. As a result, two pairs of opposing exposed surfaces of the unstretched PET film layer are joined in the sheet thickness direction of the front portion 420 at each of the joints 480, 482.

[0152] The heat sealing at each joint 480, 482 is performed, for example, by applying a high-temperature heater in the depth direction and crimping the bag container 400. Furthermore, at these joints 480, 482, the exposed surfaces of the non-stretched PET film layers are directly joined together. Because the exposed surfaces of the non-stretched PET film layers can be heat-sealed together, it is possible to seal the exposed surfaces that overlap in the sheet thickness direction. This allows, for example, a heater provided in a bag making machine to simultaneously seal multiple pairs of exposed surfaces in the overlapping regions described above, enabling efficient bag making.

[0153] At this time, the joints 480 and 482 can be welded individually in this order, for example, the joints 480 and 482, and then the overlapping regions can be heated.

[0154] Furthermore, when providing a gusset portion on the side such as in the bag container 200, by joining each front portion 420, 420 to a side portion not shown, two sets of exposed surfaces of the unstretched PET film layer may be joined and heat-sealed in the sheet thickness direction as in the joints 280, 280 shown in Figure 8(b).

[0155] These non-stretched PET film layers are PET film layers containing A-PET, and therefore, by heat welding the exposed surfaces of the non-stretched PET film layers together, the respective joints 480, 482 are firmly joined.

[0156] Furthermore, because the unstretched PET film layer of the bag container 400 is composed of a film layer formed by mixing glycol-modified PET and A-PET, even when sealing the joint where two pairs of opposing exposed surfaces are joined in the sheet thickness direction at high temperatures or for a long time, crystallization is suppressed, reducing insufficient sheet properties due to advanced crystallization and maintaining high transparency. In this way, bag-making processing conditions can be easily adjusted, and a bag container with rigidity or flexibility and high transparency can be obtained.

[0157] Furthermore, the non-stretched PET film layer of the bag container 400 may be a PET film layer containing part or all of isophthalic acid-modified PET. That is, the non-stretched PET film layer may be a film layer formed from A-PET and isophthalic acid-modified PET, or a film layer formed from a mixture of glycol-modified PET and A-PET and isophthalic acid-modified PET. Furthermore, the non-stretched PET film layer of the bag container 400 may be a film layer formed from A-PET or A-PET and isophthalic acid-modified PET without mixing glycol-modified PET, by strictly adjusting the bag-making processing conditions.

[0158] Isophthalic acid-modified PET is known to be resistant to crystallization, so suppressing crystallization can improve the transparency of the unstretched PET film layer.

[0159] Crystallization can also be suppressed by using a special modifying agent.

[0160] The bag container 400 is formed by folding the single rectangular sheet at two points, the left and right quarters, so that the joint 480 is located approximately in the center of the front portion 420, but by changing the folding position, the joint 480 can be located in the desired position.

[0161] In this embodiment, the bag container 400, which is a folded bag, has a square front portion 420, but the front portion may be formed in another shape. For example, by forming the front portion in the shape of a character, a bag container in the shape of that character can be formed.

[0162] The bag container 500 according to the fifth embodiment shown in Figure 13 is called a two-sided bag and has a pair of generally rectangular front sections 520. The bag container 500 is formed from a single sheet. That is, both front sections 520 of the bag container 500 are formed by folding a single rectangular sheet in the center and overlapping the two sections. The fold of the bag container 500 functions as the bottom of the bag container and may be formed by scoring similarly to the first and second folds 142, 144.

[0163] The pouch 500 is formed from a two-layer sheet with an exposed unstretched PET film layer. The unstretched PET film layer functions as at least a base layer or an adhesive layer. For example, if the sheet of the pouch 500 has a two-layer structure similar to the sheet 200S, with the unstretched PET film layer serving as a base layer and adhesive layer and the stretched PET film layer serving as a decorative layer, then, similar to the pouch 200, letters, figures, patterns, etc. can be displayed on the opaque portion.

[0164] The pouch 500 also has a joint 580 where both sides of the overlapping front portion 520 are joined together by heat welding. The joint 580 is formed by directly joining the exposed surfaces of the unstretched PET film layers. Each joint 580 of the pouch 500 is formed around the periphery of each face portion, and is therefore heat-sealed from the outside of the pouch 500 by a heat press method. However, each joint 580 may be heat-sealed by other methods. The other configurations are the same as those in the third embodiment.

[0165] The heat welding at the joints 580 is performed, for example, by applying a high-temperature heater in the depth direction and pressing the bag container 500. Furthermore, exposed surfaces of the unstretched PET film layers are directly joined together at these joints 580. Because the exposed surfaces of the unstretched PET film layers can be heat-welded together, it is possible to seal the exposed surfaces that overlap in the sheet thickness direction.

[0166] Furthermore, this non-stretched PET film layer is a PET film layer containing A-PET, and therefore, the exposed surfaces of the non-stretched PET film layers are heat-welded together, thereby firmly joining the joint 580.

[0167] The unstretched PET film layer of the pouch container 500 may be formed from a film layer formed by mixing glycol-modified PET and A-PET. In this case, even when the joint 580 is sealed at high temperatures or for a long time, crystallization is suppressed, reducing insufficient sheet properties due to crystallization and maintaining high transparency. In this way, bag-making processing conditions can be easily adjusted, and a pouch container with rigidity or flexibility and high transparency can be obtained.

[0168] Furthermore, the non-stretched PET film layer of the pouch container 500 may be a PET film layer containing a part or all of isophthalic acid-modified PET. That is, the non-stretched PET film layer may be a film layer formed from A-PET and isophthalic acid-modified PET, or a film layer formed from a mixture of glycol-modified PET and A-PET and isophthalic acid-modified PET.

[0169] Isophthalic acid-modified PET is known to be resistant to crystallization, so suppressing crystallization can improve the transparency of the unstretched PET film layer.

[0170] Crystallization can also be suppressed by using a special modifying agent.

[0171] In this embodiment, the bag container 500, which is a two-sided bag, has a pair of substantially rectangular front portions 520, but the front portions may be formed in other shapes. For example, a pair of front portions may be formed in the shape of a character, and a common side of both front portions may be folded back and the other peripheries of the front portions joined together except for a portion that will become an opening, thereby forming a bag container in the shape of that character.

[0172] A bag container 600 according to a sixth embodiment shown in Fig. 14 is called a three-sided bag, and has a pair of substantially rectangular front portions 620. The bag container 600 is formed from two sheets of the same shape.

[0173] The bag container 600 is formed from a two-layer sheet with an exposed unstretched PET film layer. The unstretched PET film layer also functions as at least a base layer or an adhesive layer. For example, if the sheet of the bag container 600 has a two-layer structure similar to the sheet 200S, with the unstretched PET film layer serving as a base layer and adhesive layer and the stretched PET film layer serving as a decorative layer, then, similar to the bag container 200, letters, figures, patterns, etc. can be displayed on the opaque portion.

[0174] The bag container 600 has joints 680, 682 formed by joining both side edges and the bottom edge of the overlapping front portion 620 together by heat welding. The joints 680, 682 are formed by directly joining the exposed surfaces of the unstretched PET film layers. Since the joints 680, 682 of the bag container 600 are formed around the periphery of the front portion 620, they are heat-sealed from the outside of the bag container 600 by a heat press method. However, the joints may be heat-sealed by other methods. The other configurations are the same as those in the third embodiment.

[0175] The heat welding at each joint 680, 682 is performed, for example, by applying a high-temperature heater in the depth direction and pressing the bag container 600. Furthermore, exposed surfaces of the unstretched PET film layers are directly joined together at these joints 680, 682. Because the exposed surfaces of the unstretched PET film layers can be heat-sealed together, the exposed surfaces that overlap in the sheet thickness direction can be sealed together.

[0176] The non-stretched PET film layer is a PET film layer containing A-PET, and therefore the exposed surfaces of the non-stretched PET film layer are heat-sealed together, thereby firmly joining the joints 680 and 682.

[0177] The unstretched PET film layer of the bag container 600 may be formed from a film layer formed by mixing glycol-modified PET and A-PET. In this case, even when the joints 680, 682 are sealed at high temperatures or for long periods of time, crystallization is suppressed, reducing insufficient sheet properties due to crystallization and maintaining high transparency. In this way, bag-making processing conditions can be easily adjusted, and a bag container with rigidity or flexibility and high transparency can be obtained.

[0178] Furthermore, the unstretched PET film layer of the bag container 600 may be a PET film layer containing a part or all of isophthalic acid-modified PET. That is, the unstretched PET film layer may be a film layer formed from A-PET and isophthalic acid-modified PET, or a film layer formed from a mixture of glycol-modified PET and A-PET and isophthalic acid-modified PET.

[0179] Isophthalic acid-modified PET is known to be resistant to crystallization, so suppressing crystallization can improve the transparency of the unstretched PET film layer.

[0180] Crystallization can also be suppressed by using a special modifying agent.

[0181] In this embodiment, the bag container 600, which is a three-sided bag, has a pair of substantially rectangular front portions 620, but the front portions may be formed in other shapes. For example, a pair of front portions may be formed in the shape of a character, and the two front portions may be overlapped and then joined around the periphery of the front portions except for a portion that will become an opening, thereby forming a bag container in the shape of that character.

[0182] The bag container 700 according to the seventh embodiment shown in Figure 15 is called a side-seal bag and has a pair of substantially rectangular front faces 720. The bag container 700 is formed from a single sheet. That is, both front faces 720 of the bag container 700 are formed by folding a single rectangular sheet in the center and overlapping the two faces. The folds may be scored.

[0183] The pouch container 700 also has a joint 780 where the sides of the overlapping front portions 720 are joined together by heat welding. At the joint 780, the unstretched PET film layers are directly joined together. Each joint 780 of the pouch container 700 is heat-sealed from the outside of the pouch container 700 by a heat cutting method. The heat cutting method using a heated blade allows the sheet to be cut at the same time as heat welding, making it easy to form the desired joint.

[0184] The thermal cutting can be performed by a heat press method using a heated blade, but other methods of thermal cutting, such as an impulse method or an ultrasonic method, may also be used.

[0185] The sheet forming the bag container 700 has a single-layer structure consisting of only a non-stretched PET film layer. However, other layer structures are also possible as long as at least one surface of the non-stretched PET film layer is exposed. Therefore, for example, the bag container 700 may be formed from a sheet having a two-layer structure consisting of a non-stretched PET film layer and a stretched PET film layer. The other configurations are the same as those in the third embodiment.

[0186] 16 shows how a heating blade K, for example for thermal cutting by a heat press method, thermally cuts the overlapping sheets to form two bag containers 700(i) and 700(ii). The high-temperature heating blade K moves downward, as indicated by the downward arrow Wd in the figure, so as to abut against the two overlapping sheets that will become the front portions 720, 720, 720, 720 of each bag container 700(i) and 700(ii). After thermal cutting, the blade returns to an upward direction Wu, which is opposite to the downward direction Wd.

[0187] At this time, while moving downward Wd, the tip Kt of the heating blade K heats and heat-welds the sheets facing each other in the sheet thickness direction. Then, as the tip Kt moves downward as shown by the imaginary line, the heating blade K melts and cuts the upper and lower sheets in the figure, separating the bag container 700(i) on the left side of the figure from the bag container 700(ii) on the right side of the figure.

[0188] Furthermore, in the area near the contact point of the heating blade K, a joint 780(i) of the left bag container 700(i) and a joint 780(ii) of the right bag container 700(ii) are formed.

[0189] When the sheets forming the pouch containers 700(i), 700(ii) are two-layer sheets, an unstretched PET film layer is disposed below the upper sheet in the figure, and an unstretched PET film layer is disposed above the lower sheet in the figure. As a result, the exposed surfaces of the unstretched PET film layers are directly bonded to each other at each bonding portion 780(i), 780(ii). Because the exposed surfaces of the unstretched PET film layers can be heat-sealed to each other, the exposed surfaces that overlap in the sheet thickness direction can be sealed to each other.

[0190] Furthermore, this non-stretched PET film layer is a PET film layer containing A-PET. Therefore, by heat welding the exposed surfaces of the non-stretched PET film layers together, each joint 780(i), 780(ii) is firmly joined. Furthermore, even when each joint 780(i), 780(ii) formed by the heating blade K is formed only in a narrow area or when processing is performed for a short time due to simultaneous fusion cutting, a sufficiently strong joint is possible.

[0191] The unstretched PET film layer of the bag container 700 may be composed of a film layer formed by mixing glycol-modified PET and A-PET. Since the heating blade K simultaneously melts and cuts the bag container 700, crystallization is suppressed even when high-temperature processing is performed on each joint 780(i), 780(ii) in a short period of time, reducing insufficient sealing due to crystallization and maintaining high transparency. This facilitates bag manufacturing, and allows for the production of a bag container that is rigid or flexible and highly transparent.

[0192] Furthermore, the unstretched PET film layer of the bag container 700 may be a PET film layer containing a part or all of isophthalic acid-modified PET. That is, the unstretched PET film layer may be a film layer formed from A-PET and isophthalic acid-modified PET, or a film layer formed from a mixture of glycol-modified PET and A-PET and isophthalic acid-modified PET.

[0193] Isophthalic acid-modified PET is known to be resistant to crystallization, so suppressing crystallization can improve the transparency of the unstretched PET film layer.

[0194] Crystallization can also be suppressed by using a special modifying agent.

[0195] When each sheet forming the bag container 700 has two or more layers, the unstretched PET film layer only needs to function as at least a base layer or an adhesive layer. For example, if the sheet of the bag container 700 has a two-layer structure in which the unstretched PET film layer serves as a base layer and an adhesive layer, and the stretched PET film layer serves as a decorative layer, similar to the sheet 200S, then, similar to the bag container 200, letters, figures, patterns, etc. can be displayed as an opaque portion.

[0196] In this embodiment, bag container 700, which is a side seal, has a pair of substantially rectangular front portions 720, but the front portions may be formed in other shapes. For example, a pair of front portions may be formed in the shape of a character, and the two front portions may be overlapped and then joined around the periphery of the front portions except for a portion that will become an opening, thereby forming a bag container in the shape of that character.

[0197] In the bag containers according to each of these embodiments, the opening for putting in and taking out the contents may be sealable by a zipper or heat welding. This forms the bag container into an airtight structure. The non-oriented PET film layer used in the bag containers according to the embodiments of the present invention has excellent properties in terms of oxygen permeability, water vapor permeability, and aroma retention compared to conventional polyethylene films, polypropylene films, etc.

[0198] Therefore, when the bag containers of each of these embodiments are formed into a sealed structure, even if the contents are food or drink, the contents can be stored for a long period of time without deterioration in quality, compared to polyethylene film, polypropylene film, etc.

[0199] The bag container according to the embodiment of the present invention may be made manually without using a bag making machine. One of the features of the bag container according to the embodiment of the present invention is that a non-stretched PET film layer is used for at least one of the base layer and the adhesive layer. This makes it possible to provide a bag container that utilizes the physical properties of the non-stretched PET film.

[0200] The above describes the embodiments of the present invention. However, the present invention is not limited to these descriptions. Design modifications made by those skilled in the art to the above-described embodiments are also included within the scope of the present invention as long as they incorporate the features of the present invention. [Industrial Applicability]

[0201] The present invention can be used to make bags for synthetic resin containers. [Explanation of symbols]

[0202] 100, 200, 300, 400, 500, 600, 700 bag containers 200S seat 200a unstretched PET film layer 200b Stretched PET film layer 120,220,320,420,520,620,720 Front 140,240, side part 142,144,242,244,246,342,442,562,762 folds 160,260,360 Bottom part 162,182,280,282,284,380,382,480,482,580,680,682,780 Joint

Claims

1. A bag container formed from at least one sheet, the sheet includes at least a non-stretched PET film layer and a stretched PET film layer as either a base layer or an adhesive layer; The unstretched PET film layer is The raw material, PET resin, is heated and melted, then extruded through a mold to form a film. The film is rapidly cooled by a cooling drum after the film formation, and the film is formed in an amorphous state, thereby forming a PET film layer containing amorphous PET. The amorphous PET is partially or entirely isophthalic acid-modified PET, or isophthalic acid-modified PET and glycol-modified PET; Bag container.

2. A method for manufacturing a bag container formed from at least one sheet, comprising: The method for producing the sheet includes a step of laminating a non-stretched PET film layer and a stretched PET film layer as at least one of a base layer and an adhesive layer, The unstretched PET film layer is The raw material, PET resin, is heated and melted, then extruded through a mold to form a film. The film is rapidly cooled by a cooling drum after the film formation, and the film is formed in an amorphous state, thereby forming a PET film layer containing amorphous PET. The amorphous PET is partially or entirely isophthalic acid-modified PET, or isophthalic acid-modified PET and glycol-modified PET; Manufacturing method of bag containers.

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