JP7473935B2 - Bag containers made from non-oriented PET film - Google Patents

Description

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 specifically, to a bag container in which heat welding, folding, etc. are applied to the non-stretched PET film during the production of the bag container, i.e., during bag making.

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

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

The flexibility of a film depends mainly on the thickness of the film, and if the material is the same, naturally the thinner the film, the more flexible it is. In other words, by making the film thicker, it is possible to form a bag container with high rigidity. However, if the film is made thicker, it becomes difficult to apply conventional bag-making processes, and the amount of material used increases, making the bag-making cost more expensive. Therefore, bag containers made from films classified as soft plastics, such as PP film and PE film, are very flexible, but are not suitable for making bag containers that require a certain level of rigidity.

On the other hand, there is PET film, which is more rigid and transparent than soft plastic films such as PP film and PE film, and this has been used as a bag container. For such PET films, oriented PET is used because of the ease of controlling the film thickness, especially the ease of making it thinner. Here, the term "PET" refers to another name for polyethylene terephthalate, and hereafter will be used to mean polyethylene terephthalate unless otherwise specified.

However, due to its characteristics, stretched PET has poor low-temperature heat welding properties, making it difficult to heat-seal it to form a bag container, and furthermore, because the crystals are oriented, folding is difficult. Therefore, bags cannot be made from stretched PET film alone, so bags are made by laminating other synthetic resin films with excellent workability to create multi-layer sheets, which can be heat-sealed and folded as a sheet (see, for example, Patent Documents 2 and 3). In other words, stretched PET film is not suitable for making bag containers because it cannot be heat-sealed or folded by itself.

In addition to stretched PET film, there is also non-stretched PET film. Unlike stretched PET film, non-stretched 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-stretched PET film, it is difficult to control the film thickness, especially to make it thinner, and it is not possible to make the film thinner than a certain thickness. Therefore, even if containers are made from non-stretched PET, they lack flexibility and end up becoming hard packaging containers such as box containers. In other words, it was unthinkable to make bag containers from non-stretched PET film.

JP 2014-118177 A JP 2001-55243 A JP 2015-134491 A

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

The present invention was made to solve the problems associated with making bags using synthetic resin films as described above, and aims to provide a highly transparent bag container that can be easily processed for bag making, such as by heat welding and creasing, and has optimal rigidity (flexibility) at a desired film thickness, i.e., a bag container that gives a more luxurious feel than conventional bag containers.

(1) The present invention provides a bag container formed from at least one sheet, the sheet including a non-stretched PET film layer as at least one of a base layer and an adhesive layer, and having a joint where the non-stretched PET film layers are joined together, the non-stretched PET film layer being a PET film layer that includes amorphous PET.

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 appropriate rigidity (flexibility) and high transparency, and the bag container can achieve functions that could not be achieved with films made of other synthetic resin materials, namely, characteristic functions such as high toughness, self-supporting, foldability, and use for advertising.

A typical example of non-crystalline PET is A-PET, which is unoriented PET, and is also called amorphous PET. A PET film containing A-PET is a film that is formed into a non-crystalline state by heating and melting PET resin, extruding it from a mold, and then quenching the formed film on a cooling drum. Forming it into a film is also called film formation.

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

(3) This bag container has a pair of opposing front portions and a bottom portion that is continuous with the lower end of each front portion and connects the lower ends of the opposing front portions, and the bottom portion has the joint portion. According to this bag container, at least the bottom portion functions as a gusset portion, and the storage space of the bag container is significantly increased. In addition, because the bottom portion includes a highly tough unstretched PET film layer, deformation and destruction of the bottom of the bag container, which is most susceptible to the load of the contents, is prevented.

(4) This bag container 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 creases that allow them to be folded inward. With this bag container, the side sections function as gussets, greatly increasing the storage space of the bag container. Meanwhile, when the bag container is not in use, the side sections can be folded inward along the creases to fold the bag container.

Conventional bag containers using stretched PET film required the stretched PET film to be multi-layered with another film that can be folded in order to create creases, but this bag container can form creases even if it is a single layer or is not multi-layered with another film that can be folded in, and it is possible to form creases that extend in the desired direction so that the side portions can be folded inward in a V shape.

(5) The bag container may be formed from a single sheet, and the joint of the bottom portion may be formed by overlapping and joining the sheet surfaces of the folded sheet. This allows folds to be formed without multi-layering with other films that can be folded, making it possible to manufacture bottom gusset bags using unstretched PET film. In addition, because the bottom portion includes a highly tough unstretched PET film layer, deformation or destruction of the bottom of the bag container, which bears the greatest load of the contents, is prevented.

(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. Since 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, this bag body makes it easy to manufacture a two-handled bag, etc.

(7) The non-stretched PET film layer may have two or more pairs of opposing exposed surfaces bonded together in the sheet thickness direction of the sheet at some or all of the joints. Since the exposed surfaces of the non-stretched PET film layer can be heat-sealed together 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 processing.

(8) The unstretched PET film layer may have four pairs of opposing exposed surfaces bonded together in the sheet thickness direction of the sheet at some or all of the joints.

That is, when four sets 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 a bag container, for example, a heater provided in a bag making machine can seal two or more sets of exposed surfaces at once, allowing for efficient bag making processing.

(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 non-crystalline PET is A-PET, the non-oriented PET film layer is a film layer formed by mixing glycol-modified PET and A-PET.

Glycol-modified PET is known to be difficult to crystallize. Therefore, by mixing glycol-modified PET with amorphous PET, crystallization of the unstretched PET film layer is suppressed even when it is heated by heat welding processing, and the lack of sealing ability caused by crystallization can be reduced.

In addition, by suppressing crystallization, the transparency of the unstretched PET film layer can be maintained. This makes it easy to adjust the bag-making processing conditions while maintaining high transparency.

(10) A part or all of the amorphous PET may be isophthalic acid modified PET. Isophthalic acid modified PET is PET in which a part of the terephthalic acid is replaced with isophthalic acid.

If part of the amorphous PET is isophthalic acid modified PET, the unstretched PET film layer is a film layer formed from isophthalic acid modified PET and, for example, A-PET. It may also be a film layer formed from isophthalic acid modified PET and a PET mixture of glycol modified PET and A-PET.

It is known that isophthalic acid-modified PET is difficult to crystallize. By suppressing crystallization, the transparency of the unstretched PET film layer can be improved.

(11) The joint of the bottom surface may be heat-sealed by ultrasonic heating. Heat-sealing methods include heat pressing, welding and sealing, and ultrasonic heating. In general, the heat pressing method makes it easy to control the welding temperature and the cost of welding low. On the other hand, the ultrasonic heating method can pinpoint heating of areas that are difficult to heat by the heat pressing method due to the shape of the non-heated object, etc.

(12) This bag container has a pair of opposing front portions, and the front portions 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 the exposed surfaces of the unstretched PET film are joined together, making it easy to manufacture the bag.

(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 process in which a heated blade is used to cut the joined sheets at the same time as joining by heat welding. The heat-sealing method is known to be a method that can be used when the heat welding is stable.

(14) The non-oriented PET film layer may be a film layer formed by mixing glycol-modified PET.

Since glycol-modified PET is mixed into the non-oriented PET film layer, the lack of sealing ability caused by crystallization is reduced, and the non-oriented PET film layer can be stably thermally cut. This makes it possible to easily adjust the bag-making processing conditions using the thermal cutting method. In addition, transparency can be maintained by suppressing crystallization.

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

At this time, the crystallization of the isophthalic acid-modified PET is suppressed, thereby improving the transparency of the unstretched PET film layer.

(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 manufactured. For example, by making the unstretched PET film layer 30 μm to 150 μm thick, the bag container has a certain level of rigidity while still having the desired toughness to allow elastic deformation. This allows the bag container 100 to ensure self-supporting when no contents are placed inside, which was difficult to achieve with conventional PP bags or PE bags.

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

In the bag container of the present invention, at least one sheet including a non-stretched PET film layer is folded and joined to form the bag container. In this bag container, a 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, and has appropriate rigidity (flexibility) and high transparency, so that the bag container can achieve the functions that could not be achieved with films of other synthetic resin materials, namely, characteristic functions such as high toughness, self-supporting, foldability, and use for advertising.

(18) The non-stretched PET film layer may be a PET film layer formed by mixing glycol-modified PET. That is, by mixing glycol-modified PET, crystallization of the non-stretched PET film layer is suppressed even when it is heated by heat welding processing, and the lack of processability caused by the progress of crystallization can be reduced. Furthermore, by suppressing crystallization, the transparency of the non-stretched PET film layer can be maintained. As a result, it is easy to adjust the bag making processing conditions and maintain high transparency.

(19) A part or all of the amorphous PET may be isophthalic acid modified PET. It is known that isophthalic acid modified PET is difficult to crystallize. Therefore, by suppressing crystallization, the transparency of the unstretched PET film layer can be improved.

(20) The bag container may have an opening for inserting and removing 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.

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

FIG. 1 is a perspective view showing a bag container (square bottom bag) according to a first embodiment of the present invention. FIG. 2 is a perspective view showing the bag container shown in FIG. 1 from the bottom side. FIG. 2 is a development view of the bag container shown in FIG. 1 . FIG. 2 is a perspective view showing the bag container shown in FIG. 1 in a folded state. 11A and 11B are perspective views showing a bag container (Box Pouch (registered trademark)) according to a second embodiment of the present invention, in which (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. FIG. 6 is a development view of the bag container shown in FIG. 5 . FIG. 6 is a cross-sectional view showing a layer structure of the sheet of the bag container shown in FIG. 5 . 6 is a front view and a longitudinal sectional view of the bag container shown in FIG. 5 . 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. FIG. 11 is a perspective view showing a bag container (stand bag) according to a third embodiment of the present invention. 11A and 11B are explanatory diagrams of a front view and a longitudinal section of the bag container (stand bag) shown in FIG. 10 . FIG. 11 is a perspective view showing a bag container (a two-sided bag) according to a fourth embodiment of the present invention. FIG. 13 is a perspective view showing a bag container (two-sided bag) according to a fifth embodiment of the present invention. FIG. 13 is a perspective view showing a bag container (three-sided bag) according to a sixth embodiment of the present invention. FIG. 13 is a perspective view showing a bag container (side seal bag) according to a seventh embodiment of the present invention. 16 is an explanatory diagram showing a thermal fusion cutting process for the bag container (side-seal bag) shown in FIG. 15 .

The bag container 100 according to the first embodiment of the present invention will be described in detail with reference to Figs. 1 to 4. The bag container 100 is a so-called square bottom bag with gussets (gusseted portions) on the sides and bottom. The square bottom bag forms a roughly rectangular storage space, and although it has a larger storage volume than other bags such as flat bags, it has the characteristic of being foldable when not storing anything, i.e., when not in use. In addition, the square bottom bag has stable self-supporting ability when in use.

As shown in Figs. 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. As a result, the bag container 100 is formed with an opening that opens upward in Fig. 1. Contents can be put in and taken out of the bag container 100 through the opening.

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

The bag container 100 is formed by folding one sheet shown in FIG. 3. The sheet is provided with a first front sheet portion 120a forming one front portion 120, a first side sheet portion 140a forming one side portion 140, a second front sheet portion 120b forming the other front portion 120, a second side sheet portion 140b forming the other side portion 140, and a joint sheet portion 180, which are arranged in sequence and continuously. 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 rectangle, although the aspect ratios are different. In this specification, the terms rectangle and square that specify the shape of the sheet also include those having so-called corners R, which are rounded corners.

The sheet further includes first, second, third and fourth bottom sheet portions 160a, 160b, 160c, 160d that are continuous with the lower side (lower side in FIG. 3) of each front portion 120 and each side portion 140 and form the bottom portion 160. Each of the bottom sheet portions 160a to 160d is formed in a substantially trapezoidal shape. As described below, each of the bottom sheet portions 160a to 160d is overlapped with each other to form the bottom portion 160. However, other shapes are also acceptable as long as the bottom portion 160 can be formed. In other words, they are not limited to a quadrilateral shape such as a trapezoid, and may be convex, concave or other shapes.

Each front sheet portion 120a, 120b has an oval-shaped hole 122a, 122b. The holes 122a, 122b are provided in opposing positions 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 portion 122 (see Figures 1 and 2). However, the handle portion may be achieved by other configurations. For example, the handle portion can be created by drilling two desired holes in the bag container, passing both ends of a string through the holes, fixing each end with a rivet or the like, and forming a loop with the string.

Each of the side sheet portions 140a, 140b has a first fold 142 extending in the vertical direction and a second fold 144 extending diagonally downward and diagonally downward so as to branch off from the middle below the first fold 142, and the first fold 142 and the second fold 144 form an inverted Y-shaped fold. Each fold is lined, which is a type of folding process, and a V-shaped groove is formed 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 lined.

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 lateral direction of the side sheet portion 140a, 140b, and the second fold 144 extends from the middle of the first fold 142 to one lower end (lower left end) and the other lower end (lower right end) of the side sheet portion 140a, 140b.

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

By folding each surface sheet portion at a right angle at the boundary line of each surface sheet portion, the sheet becomes a roughly rectangular bag container 100 as shown in Figures 1 and 2. The boundary line of each surface sheet portion may be formed by crease processing similar to the first and second folds 142, 144.

In the bag container 100, an auxiliary sheet 100A having the same shape as the bottom portion 160 is placed in a state in which the first to fourth bottom sheet portions 160a to 160d are stacked on top of each other (see FIG. 1). With the auxiliary sheet 100A stacked on the first to fourth bottom sheet portions 160a to 160d, multiple locations on the bottom portion 160 are bonded using an adhesive or the like to form multiple first joints 162 (see FIG. 2).

In addition, the bag container 100 has a second joint portion 182 on one front portion 120 consisting of the first front sheet portion 120a. The second joint portion 182 is formed by overlapping the joint sheet portion 180 with a part of the side end of the first front sheet portion 120a and bonding the overlapped portion together. This bonds the unstretched PET film layers together.

In addition to bonding using an adhesive or the like, these joints 162, 182 may be formed by thermal welding using an impulse method, ultrasonic method, or the like.

The sheet forming the bag container 100 has a single-layer structure consisting of only a non-stretched PET film layer. In other words, both sides of the non-stretched PET film layer of the sheet are exposed. As a result, the non-stretched PET film functions as a base layer and an adhesive layer in a single layer. Here, the base layer means the layer with the highest rigidity among the multiple layers of one sheet, and generally controls the rigidity and toughness of the sheet. Also, the adhesive layer means 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 a non-stretched PET film layer in which the sheet functions as a base layer or an adhesive layer, and has a joint where the non-stretched PET film layers are bonded to each other.

This unstretched PET film layer uses PET resin as the raw material. The unstretched PET film layer is a PET film layer that contains amorphous PET, and is formed into an amorphous state by heating and melting the PET resin and extruding it from a mold to form a film, and then quenching the film after film formation using a cooling drum. An example of amorphous PET formed by this process is A-PET (amorphous PET), which is unoriented PET.

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

The non-oriented PET film layer of the bag container 100 may also be composed of a film layer formed by mixing glycol-modified PET and A-PET. Since it is less prone to crystallization, it is possible to maintain high transparency.

The film layer formed by mixing glycol-modified PET and A-PET is obtained, for example, by extruding heated and molten glycol-modified PET resin and A-PET resin through a T-shaped die using a melt extrusion method. At this time, the glycol-modified PET resin and A-PET resin are fed in a mixed state into a hopper installed in the extrusion device and melted, or are fed into two separate hoppers installed in the extrusion device and mixed during the melt extrusion process.

Glycol-modified PET is PET in which part of the ethylene glycol has been 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 heated, for example, during heat welding processing, and the lack of sealing ability caused by crystallization can be reduced.

In addition, by suppressing crystallization, the transparency of the unstretched PET film layer can be maintained. This makes bag-making easy and maintains high transparency.

When glycol-modified PET is mixed into the bag container 100, the crystallization described above is suppressed, thereby reducing the lack of sealing during heat welding and maintaining high transparency. In this way, bag manufacturing can be easily performed, and a bag container having rigidity or flexibility and high transparency can be obtained.

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

Furthermore, the non-stretched PET film layer of the bag container 100 may be a PET film layer that contains 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.

It is known that isophthalic acid-modified PET is difficult to crystallize. Therefore, by suppressing crystallization, the transparency of the unstretched PET film layer can be improved.

Crystallization can also be suppressed by using special modification agents.

When the bag container 100 is in use, i.e., when it contains an item, it is used in the shape of a roughly rectangular parallelepiped as shown in FIG. 1. In contrast, when it is not in use, i.e., when it does not contain an item, 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.

Each front portion 120 is formed in the same rectangular shape, with each side facing each other. That is, the bottom ends of the rectangles of the front portions 120 correspond to each other, and the bottom portion 160 is formed to connect these bottom ends. In addition, the side ends of the rectangles of the front portions 120 correspond to each other, and each side portion 140 is formed to connect these two side ends.

In this embodiment, the unstretched PET film layer has a thickness of 80 μm. The unstretched PET film with a thickness of 80 μm has a certain level of rigidity while having the desired toughness to allow elastic deformation. This allows the bag container 100 to ensure self-supporting even when no contents are placed inside, which was difficult to achieve with conventional PP bags or PE bags.

However, the non-stretched PET film layer may have a thickness of 30 μm to 150 μm. If the thickness is within this range, the toughness is maintained to an extent that the film can be elastically deformed, while the film has flexibility to the extent that the film does not become a box container. Furthermore, the non-stretched PET film layer may have a thickness of 80 μm to 120 μm. If the thickness is within this range, the film has flexibility to deform appropriately depending on the contents, while the toughness is maintained to an extent that the film can be self-supporting. The relationship between film thickness and toughness also depends 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 toughness is generally dominated by the non-stretched PET layer.

The bag container 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 bag container made of a sheet with a non-stretched PET film as a base layer evokes a sense of luxury compared to conventional sheets made of synthetic resin. The sheets on each surface that make up the bag container 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 adopted in the bag container 200 according to the second embodiment described below.

The bag container 100 according to this 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.

Next, a bag container 200 according to a second embodiment of the present invention will be described with reference to Figs. 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 (gusseted portions) on the sides and bottom. However, the bag container 200 is formed by a manufacturing method different from that of the bag container 100.

The box pouch can be formed, for example, by cutting, folding, and heat welding 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.

As shown in Figs. 5 and 6, the bag container 200 is formed in a substantially rectangular parallelepiped shape similar to the bag container 100, 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 multiple sheets. In addition, the bag container 200 includes a joint portion 280 that joins the front portion 220 and the side portion 240, a joint portion 282 that joins the front portion 220 and the bottom portion 260, and a joint portion 284 that joins the side portion 240 and the bottom portion 260.

The joints 280 are formed on both side ends of the front portion 220 and both side ends of the side portion 240. The joints 282 are provided at the bottom end of the front portion 220 and the front and rear ends of the bottom portion 260. The joints 284 are provided at the bottom end of the side portion 240 and the left and right ends of the bottom portion 260.

As shown in FIG. 7, the sheet 200S on each surface of the bag 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 parts such as letters, figures, patterns, etc. are formed and which is laminated to other layers to decorate the sheet.

Stretched PET film is produced by the well-known molding method of uniaxial or biaxial stretching. And the stretched PET film layer refers to a layer formed by stretched PET film.

In contrast, non-stretched PET film is produced by a conventional film forming method using a roll device (see, for example, JP-A-11-235747). In other words, in this specification, a stretched PET film refers to one that has been intentionally stretched to align the crystal orientation, and non-stretched PET refers to one that has not been intentionally stretched or one that does not have properties that make it difficult to crystallize. And a non-stretched PET film layer refers to a layer formed by a non-stretched PET film.

The stretched PET film layer 200b has an 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 of displaying characters, figures, patterns, etc.

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

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

Since each joint of the bag container 200 is formed around 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 JP 2011-67997 A. However, each joint may be heat-sealed using other methods.

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.

Figure 8(a) shows a front view of the bag container 200 assembled by joining in this manner. Figure 8(b) shows an explanatory diagram of a vertical section of section A-A' shown in the front view of Figure 8(a). Figure 8(c) shows an explanatory diagram of a vertical section of section B-B'. The leftward and rightward directions in the left-right direction of the front view of the bag container 200 are indicated by arrows L and R, respectively. The upward and downward directions in the up-down direction are indicated by arrows U and D, respectively. The frontward and rearward directions in the depth direction when viewed from the front of the bag container 200 are indicated by arrows F and B, respectively.

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

At this time, the sheets 200S of each surface portion 220, 240, 260 are positioned so that the exposed side of each unstretched PET film layer 200a faces each joint portion 220, 240, 260.

Cross section A-A' is a vertical cross section in FIG. 8(a), and is a cross section passing through the edge of the left-facing L. Therefore, cross section A-A' represents a state in which the joint 280 joining the front portion 220 and the side portion 240 is cut in the depth direction, a state in which the joint 284 joining the side portion 240 and the bottom portion 260 is cut in the depth direction, and a state in which the joint 282 joining the front portion 220 and the bottom portion 260 is cut in the depth direction. FIGS. 8(b) and (c) are figures emphasizing the depth dimension of the bag container 200, and also show the state immediately before the joints 280, 282, and 284 are overlapped.

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

In the upper U region of the portion where the bottom surface portion 260 is joined, the front portion 220 of the front side F, the side portion 240a of the front side F facing most forward, the side portion 240b of the front side F facing more backward B, the bottom portion 260 of the front side F, the bottom 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 backward B, and the front portion 220 of the back side B are overlapped eight times through the respective joints 280, 280, 284, 284. As a result, the four pairs of opposing exposed surfaces of the non-stretched PET film layer are joined in the sheet thickness direction of each surface portion 220, 220, 240a, 240c, 240c, 240d, 260, 260 at each joint 280, 280, 284, 284.

Furthermore, in the region of the lower side D 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 from the front side F to the back side B via each joint 282, 282. As a result, the two sets of opposing exposed surfaces of the unstretched PET film layer are joined in the sheet thickness direction of each of the surface portions 220, 220, 260, 260 at each joint 282, 282.

In the cross section B-B', as shown in FIG. 8(c), in the portion where the bottom surface portion 260 is joined, the front 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 portion 220 on the back side B are overlapped four times from the front side F to the back side B via the respective joints 282, 282. As a result, the two sets 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.

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 unstretched PET film layer are directly bonded to each other at these joints 280, 282, 284. Because the exposed surfaces of the unstretched PET film layer can be heat-sealed to each other, exposed surfaces that overlap in the sheet thickness direction can be sealed to each other. This allows, for example, a heater equipped in a bag making machine to seal multiple pairs of exposed surfaces at once, enabling efficient bag making processing.

This unstretched PET film layer uses PET resin as the raw material. The unstretched PET film layer is a PET film layer that contains amorphous PET, and is formed into an amorphous state by heating and melting the PET resin and extruding it from a mold to form a film, and then quenching the film after film formation using a cooling drum. An example of amorphous PET formed by this process is A-PET (amorphous PET), which is unoriented PET.

The exposed surfaces of the unstretched PET film layers containing A-PET in the bag container 200 are heat-welded together, so that each joint 280, 282, 284 is firmly joined.

In addition, non-stretched PET films containing A-PET have high transparency, gloss, and toughness (known as stiffness), and bags and containers made from sheets with a base layer of non-stretched PET films containing A-PET evoke a sense of luxury compared to sheets made from conventional synthetic resins.

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

However, depending on the bag-making processing conditions, such as the 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, it is necessary to adjust the bag-making processing conditions. In particular, when sealing two or more pairs of exposed surfaces together, the entire sheet thickness direction 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.

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

For this reason, measures may be taken to prevent crystallization due to thermal history from progressing too far by, for example, joining each of the front portions 220, 220 to the bottom portion 260, joining each of the side portions 240, 240 to the bottom portion 260, and joining each of the front portions 220, 220 to each of the side portions 240, 240 separately, and then heating each of the joining portions 280, 280, 282, 282, 284, 284 all at once to perform heat welding in multiple steps.

Incidentally, the unstretched PET film layer of the bag container 200 is composed of a film layer formed by mixing glycol-modified PET and A-PET.

The film layer formed by mixing glycol-modified PET and A-PET is obtained, for example, by extruding heated and molten glycol-modified PET resin and A-PET resin through a T-shaped die using a melt extrusion method. At this time, the glycol-modified PET resin and A-PET resin are fed in a mixed state into a hopper installed in the extrusion device and melted, or are fed into two separate hoppers installed in the extrusion device and mixed during the melt extrusion process.

Glycol-modified PET is PET in which part of the ethylene glycol has been 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 by heat welding processing, and the lack of sealing ability caused by crystallization can be reduced.

In addition, by suppressing crystallization, the transparency of the unstretched PET film layer can be maintained. This makes it easy to adjust the bag-making processing conditions while maintaining high transparency.

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

For these reasons, even when sealing each joint 280, 282, 284, in which two or four sets of opposing exposed surfaces are joined in the sheet thickness direction, at high temperatures and for a long period of time, crystallization is suppressed, and the sheet property deficiency caused by the progression 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.

Furthermore, the non-stretched PET film layer of the bag container 200 may be a PET film layer that contains 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. Also, the non-stretched PET film layer of the bag container 200 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.

It is known that isophthalic acid modified PET is difficult to crystallize. Therefore, by suppressing crystallization, the transparency of the unstretched PET film layer can be improved.

Crystallization can also be suppressed by using special modification agents.

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 middle of the first fold 242, as in the side surface portion 140 of the bag container 100 according to the first embodiment, and the first fold 242 and the second fold 244 form 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.

This allows the sheet to be easily folded along the creases. The side surface portion 240 is folded along the first to third creases 242, 244, and 246, so that the side surface portion 240 and the bottom surface portion 260 are formed in a V-shape so that they can be folded inside the bag container, making it possible to fold the bag container 200 when not in use.

The sheet 200S has a two-layer structure in which a non-stretched PET film layer is laminated with a stretched PET film layer, but it may have a single-layer structure consisting of only a non-stretched PET film layer, or may have other layer configurations of multiple layers 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.

In addition, in the bag container 200, the non-stretched PET film functions as a base layer and an adhesive layer, but it is sufficient if it functions as at least one of the base layer and the adhesive layer. In other words, either the base layer or the adhesive layer may be formed from a non-stretched PET film layer, and the other may be formed from another synthetic resin film layer or a stretched PET film layer.

The bag container 200 is formed from sheets that all have the same layer structure, but each sheet may have a different layer structure. For example, the front portion 220 may be formed from a sheet with a two-layer structure of an unstretched PET film layer and a stretched PET film layer, and the side portion 240 and the bottom portion 260 may be formed from a sheet with a single layer structure of only the unstretched PET film layer.

As an example of a modified example of the sheet 200S of the bag container 200, there 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 has, for example, a PE film layer 200c that functions as a base layer, a non-stretched PET film layer 200d that functions as an adhesive layer, and a stretched PET film layer 200e that functions as a decorative layer.

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 on the inside of the bag container 200, the unstretched PET film layers can be bonded together.

Next, the bag containers 300, 400, 500, 600, and 700 according to the third to seventh embodiments will be described with reference to Figs. 10 to 16. These bag containers can be manufactured using a conventional bag manufacturing method.

The bag container 300 according to the third embodiment shown in FIG. 10 is called a stand-up bag, and has a pair of substantially rectangular front portions 320 and a substantially circular bottom portion 360. The bag container 300 is formed from a plurality of sheets. For example, the stand-up bag can be formed by folding, cutting, and heat welding two rolled sheets. Note that the front portion of the stand-up bag may be formed in another 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 that evokes the impression that the character is standing upright can be formed.

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

Also, as in the second embodiment, the sheet may have a single-layer structure consisting of only a non-oriented PET film layer.

Each sheet forming the bag container 300 may have a different layer structure as long as at least one surface of the unstretched PET film layer is exposed. Also, when each sheet forming the bag container 300 has two or more layers, the unstretched PET film layer only needs to function as at least a base layer or an adhesive layer.

The bag container 300 has each surface joined by heat welding. That is, the front portion 320 has a joint 380 where both sides are joined together by heat welding, and the front portion 320 and the bottom portion 360 have a joint 382 where the peripheries of the front portion 320 and the bottom portion 360 are overlapped and joined by heat welding. The joint 380 is formed by directly joining the exposed surfaces of the unstretched PET film layer. Since each joint of the bag container 300 is formed on the periphery of each surface, it is heat-sealed from the outside of the bag container 300 by a heat press method. However, each joint may be heat-sealed by other methods.

However, when joining the aforementioned single-layered sheets, they are thermally welded using the impulse or ultrasonic method, or they are bonded using adhesives, etc.

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.

The bottom surface 360 of the bag container 300 forms a bottom gusset (gusset portion). The bottom surface 360 also has a crease 362 extending in one direction. The crease 362 is so-called lined, 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 crease. By folding the bottom surface along the crease 362, it is possible to fold it into a V-shape inside the bag container, making it possible to fold the bag container 300 when not in use. However, the crease 362 may be folded without being lined. The other configurations are the same as those in the second embodiment.

Figure 11(a) shows a front view of the bag container 300 that is joined, folded, and assembled in this manner. Figure 11(b) shows an explanatory diagram of a vertical section of section A-A' shown in the front view of Figure 11(a). Figure 11(c) shows an explanatory diagram of a vertical section of section B-B'. The leftward and rightward directions in the left-right direction of the front view of the bag container 300 are indicated by arrows L and R, respectively. The upward and downward directions in the up-down direction are indicated by arrows U and D, respectively. The frontward and rearward directions in the depth direction when viewed from the front of the bag container 300 are indicated by arrows F and B, respectively.

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

At this time, the sheets of each surface portion 320, 360 are positioned so that the exposed side of each unstretched PET film layer faces each joint portion 380, 382.

Cross section A-A' is a vertical cross section in FIG. 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 sections 320, 320 is cut in the depth direction, and also represents a state in which joint 382 joining front section 320 and bottom section 360 is cut in the depth direction. FIGS. 11(b) and (c) are figures emphasizing the depth dimension of bag container 300, and also show the state immediately before joints 380, 382 are overlapped.

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

As shown in FIG. 11(b), in the cross section A-A', in the portion where the bottom surface portion 360 is not joined, the front portion 320 on the front side F and the front portion 320 on the back side B are overlapped via the joint 380 from the front side F to the back side B. 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 each surface portion 320, 320.

In addition, in the portion where the bottom surface portion 360 is joined, the front surface portion 320 of the front side F, the bottom surface portion 360 of the front side F, the bottom surface portion 360 of the back side B, and the front surface portion 320 of the back side B are overlapped four times from the front side F to the back side B via each joint 382, 382. As a result, two sets of opposing exposed surfaces of the unstretched PET film layer are joined in the sheet thickness direction of each surface portion 320, 320, 360, 360 at each joint 382, 382.

However, in the cutout region shown by S1 in the figure, the left side L end and the right side R end 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 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.

By directly joining the notch areas S1, the bag container 300 can stand with each front portion 320 in contact with the ground and form a gusset (gusset portion) at the bottom.

In cross section B-B', as shown in FIG. 11(c), in the sealing region indicated by S2 in the figure where the bottom surface portion 360 is joined, the front portion 320 of the front side F, the bottom surface portion 360 of the front side F, the bottom surface portion 360 of the back side B, and the front portion 320 of the back side B are overlapped four times from the front side F to the back side B via each joint 382, 382. As a result, two sets of opposing exposed surfaces of the unstretched PET film layer are joined in the sheet thickness direction of each of the surface portions 320, 320, 360, 360 at each joint 382, 382.

The heat welding 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 unstretched PET film layer are directly bonded to each other at these joints 380, 382. Because the exposed surfaces of the unstretched PET film layer can be heat welded to each other, it is possible to seal exposed surfaces that overlap in the sheet thickness direction. This allows, for example, a heater equipped in a bag making machine to seal multiple pairs of exposed surfaces at once, enabling efficient bag making processing.

In addition, this unstretched PET film layer is a PET film layer that contains A-PET. Therefore, the exposed surfaces of the unstretched PET film layer are heat-welded to each other, so that each joint 380, 382 is firmly joined.

However, depending on the bag-making processing conditions such as the heater temperature and heating time, the thermal history of the unstretched PET film layer can cause crystallization, resulting in insufficient sealing. In particular, when sealing two or more pairs of exposed surfaces, such as in the bag container 300, the entire sheet thickness direction 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.

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

Therefore, even when sealing each joint 380, 382, in which two pairs of opposing exposed surfaces are joined in the sheet thickness direction, at high temperatures and for a long time, crystallization is suppressed, and the sheet property deficiency caused by the progression of crystallization can be reduced, and high transparency can be maintained. In this way, the bag manufacturing processing conditions can be easily adjusted, and a bag container having rigidity or flexibility and high transparency can be obtained.

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

Furthermore, the non-stretched PET film layer of the bag container 300 may be a PET film layer that contains 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. The non-stretched PET film layer of the bag container 300 may also 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.

It is known that isophthalic acid-modified PET is difficult to crystallize. Therefore, by suppressing crystallization, the transparency of the unstretched PET film layer can be improved.

Crystallization can also be suppressed by using special modification agents.

In this embodiment, the bag container 300, which is a stand-up bag, has a front portion 320 formed in a square shape, but the front portion may be formed in another 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 that evokes the impression that the character is standing upright can be formed. 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, and may be configured to form a W-shape in the vertical cross section of Figures 11 (b) and (c).

The bag container 400 according to the fourth embodiment shown in FIG. 12 is called a folded bag and has a pair of approximately rectangular front portions 420. The bag container 400 is a so-called flat bag, but may be formed as a gusseted bag provided with a gusset portion. The bag container 400 is formed from a single sheet. That is, a single rectangular sheet is folded at approximately 1/4 positions on both the left and right sides, and both ends of the sheet are overlapped and joined.

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

The bag container 400 has a joint 480 that extends from the top to the bottom in the center of the left-right direction of one of the front parts 420, and a joint 482 that extends in the left-right direction at the bottom. That is, one of the front parts 420 has a joint 480 in which both ends of the above-mentioned one rectangular sheet are overlapped and joined by heat welding, and both front parts 420 have joints 482 at their bottoms that are joined by heat welding. The joints 480 and 482 are directly joined to each other at the exposed surfaces of the non-stretched PET film layer. Each joint of the bag container 400 is heat-sealed from the outside of the bag container 400 by a heat press method. However, each joint may be heat-sealed by other methods. The other configurations are the same as those in the third embodiment.

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

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. In addition, at these joints 480, 482, the exposed surfaces of the unstretched PET film layer are directly bonded to each other. Because the exposed surfaces of the unstretched PET film layer can be heat-sealed to each other, it is possible to seal exposed surfaces that overlap in the sheet thickness direction. This allows, for example, a heater equipped in a bag making machine to seal multiple pairs of exposed surfaces in the overlapping areas as described above at once, enabling efficient bag making processing.

At this time, each joint 480, 482 can be welded individually, for example, in the order of joint 480 and joint 482, and then the overlapping area can be heated.

When providing a side gusset portion such as in the bag container 200, the front portions 420, 420 may be joined to the side portions (not shown) so that two sets of exposed surfaces of the unstretched PET film layer are joined and heat-sealed in the sheet thickness direction, as in the joints 280, 280 shown in FIG. 8(b).

These unstretched PET film layers are PET film layers that contain A-PET. Therefore, the exposed surfaces of the unstretched PET film layers are heat-welded to each other, so that each joint 480, 482 is firmly joined.

In addition, since 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 a joint where two pairs of opposing exposed surfaces are joined in the sheet thickness direction at high temperatures or for a long period of time, crystallization is suppressed, and the lack of sheet properties caused by crystallization can be reduced, and transparency can be maintained at a high level. In this way, bag manufacturing processing conditions can be easily adjusted, and a bag container with rigidity or flexibility and high transparency can be obtained.

Furthermore, the non-stretched PET film layer of the bag container 400 may be a PET film layer that contains 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. The non-stretched PET film layer of the bag container 400 may also 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.

It is known that isophthalic acid-modified PET is difficult to crystallize. Therefore, by suppressing crystallization, the transparency of the unstretched PET film layer can be improved.

Crystallization can also be suppressed by using special modification agents.

The bag container 400 is made 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 part 420, but by changing the folding position, the joint 480 can be located in any desired position.

In this embodiment, the bag container 400, which is a folded bag, has a front portion 420 formed in a rectangular shape, 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.

The bag container 500 according to the fifth embodiment shown in FIG. 13 is called a two-sided bag and has a pair of substantially rectangular front portions 520. The bag container 500 is formed from a single sheet. That is, both front portions 520 of the bag container 500 are formed by folding a single rectangular sheet in the center and overlapping them. The fold of the bag container 500 functions as the bottom of the bag container and may be formed by a scoring process similar to the first and second folds 142, 144.

The bag container 500 is formed from a two-layered sheet with an exposed non-stretched PET film layer. The non-stretched PET film layer also functions as at least a base layer or adhesive layer. For example, if the sheet of the bag container 500 has a two-layered structure with the non-stretched PET film layer as the base layer and adhesive layer, and the stretched PET film layer as the decorative layer, similar to the sheet 200S, then letters, figures, patterns, etc. can be displayed as opaque parts, similar to the bag container 200.

The bag container 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 bag container 500 is formed around the periphery of each surface, and is therefore heat-sealed from the outside of the bag container 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.

The heat welding at the joints 580 is performed, for example, by applying a high-temperature heater in the depth direction and crimping the bag container 500. Furthermore, at these joints 580, the exposed surfaces of the unstretched PET film layers are directly bonded together. 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.

In addition, this unstretched PET film layer is a PET film layer that contains A-PET. Therefore, the exposed surfaces of the unstretched PET film layer are heat-welded together, and the joint 580 is firmly joined.

The non-oriented PET film layer of the bag container 500 may be composed of 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, and the lack of sheet property caused by the progression of crystallization can be reduced, and transparency can be maintained at a high level. In this way, the bag manufacturing processing conditions can be easily adjusted, and a bag container having rigidity or flexibility and high transparency can be obtained.

Furthermore, the non-stretched PET film layer of the bag container 500 may be a PET film layer that contains 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.

It is known that isophthalic acid modified PET is difficult to crystallize. Therefore, by suppressing crystallization, the transparency of the unstretched PET film layer can be improved.

Crystallization can also be suppressed by using special modification agents.

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

The bag container 600 according to the 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.

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

The bag container 600 has joints 680, 682 where both sides and the bottom of the overlapping front portion 620 are joined together by heat welding. The joints 680, 682 are directly joined between the exposed surfaces of the unstretched PET film layers. Each joint 680, 682 of the bag container 600 is formed around the periphery of the front portion 620, and is therefore heat-sealed from the outside of the bag container 600 by a heat press method. However, each joint may be heat-sealed by other methods. The other configurations are the same as those in the third embodiment.

The heat welding at each joint 680, 682 is performed, for example, by applying a high-temperature heater in the depth direction and crimping the bag container 600. Furthermore, at these joints 680, 682, the exposed surfaces of the unstretched PET film layer are directly bonded to each other. Since the exposed surfaces of the unstretched PET film layer can be heat welded to each other, it is possible to seal the exposed surfaces that overlap in the sheet thickness direction.

In addition, this unstretched PET film layer is a PET film layer that contains A-PET. Therefore, the exposed surfaces of the unstretched PET film layer are heat-welded to each other, so that each joint 680, 682 is firmly joined.

The non-oriented PET film layer of the bag container 600 may be composed of a film layer formed by mixing glycol-modified PET and A-PET. In this case, even when each joint 680, 682 is sealed at high temperature or for a long time, crystallization is suppressed, and the lack of sheet property caused by the progress of crystallization can be reduced, and high transparency can be maintained. In this way, the bag manufacturing processing conditions can be easily adjusted, and a bag container having rigidity or flexibility and high transparency can be obtained.

Furthermore, the non-stretched PET film layer of the bag container 600 may be a PET film layer that contains 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.

It is known that isophthalic acid-modified PET is difficult to crystallize. Therefore, by suppressing crystallization, the transparency of the unstretched PET film layer can be improved.

Crystallization can also be suppressed by using special modification agents.

In this embodiment, the bag container 600, which is a three-sided bag, has a pair of roughly rectangular front portions 620, but the front portions may be formed in other shapes. For example, a pair of front portions are formed in the shape of a character, and the periphery of the front portions is joined together with the exception of a portion that will become an opening, to form a bag container in the shape of that character.

The bag container 700 according to the seventh embodiment shown in FIG. 15 is called a side-seal bag, and has a pair of substantially rectangular front portions 720. The bag container 700 is formed from a single sheet. That is, both front portions 720 of the bag container 700 are formed by folding a single rectangular sheet in the center and overlapping them. The folds may be lined.

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

Thermal cutting can be performed by a heat press method using a heated blade. However, other methods of thermal cutting, such as an impulse method or an ultrasonic method, may also be used.

The sheet forming the bag container 700 has a single-layer structure consisting of only a non-stretched PET film layer. However, other layer configurations are also acceptable 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.

Figure 16 shows how a heating blade K for thermal cutting by a heat press method, for example, thermally cuts overlapping sheets to form two bag containers 700(i), 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 two front portions 720, 720, 720, 720 of each bag container 700(i), 700(ii). Then, after thermal cutting, it returns to the upward direction Wu, which is opposite to the downward direction Wd.

At this time, while moving in the downward direction 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 the upper sheet and the lower sheet in the figure, and cuts the bag container 700(i) on the left side of the figure and the bag container 700(ii) on the right side of the figure into separate entities.

In addition, in the area near where the heating blade K comes into contact, 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.

When the sheets forming the bag containers 700(i), 700(ii) are two-layered sheets, a non-stretched PET film layer is disposed below the top sheet in the figure, and a non-stretched PET film layer is disposed above the bottom sheet in the figure. As a result, the exposed surfaces of the non-stretched PET film layers are directly bonded to each other at each bonding portion 780(i), 780(ii). Since the exposed surfaces of the non-stretched PET film layers can be heat-welded to each other, the exposed surfaces that overlap in the sheet thickness direction can be sealed to each other.

This unstretched PET film layer is a PET film layer that contains A-PET. Therefore, the exposed surfaces of the unstretched PET film layer are heat-welded together, and the joints 780(i), 780(ii) are firmly joined. Even if the joints 780(i), 780(ii) formed by the heating blade K are formed only in a narrow area, or if processing is performed for a short period of time in order to simultaneously perform melt cutting, a sufficiently strong joint is possible.

The non-oriented 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 bag container 700 is also melted and cut by the heating blade K at the same time, crystallization is suppressed even when high-temperature processing is performed on each joint 780(i), 780(ii) in a short period of time, and the lack of sealing ability caused by the progression of crystallization can be reduced, and transparency can be maintained at a high level. In this way, bag manufacturing can be easily performed, and a bag container having rigidity or flexibility and high transparency can be obtained.

Furthermore, the non-stretched PET film layer of the bag container 700 may be a PET film layer that contains 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.

It is known that isophthalic acid-modified PET is difficult to crystallize. Therefore, by suppressing crystallization, the transparency of the unstretched PET film layer can be improved.

Crystallization can also be suppressed by using special modification agents.

Incidentally, when each sheet forming the bag container 700 is 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, as in the sheet 200S, then, like the bag container 200, letters, figures, patterns, etc. can be displayed as opaque parts.

In this embodiment, the 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 can be formed in the shape of a character, and the periphery of the front portions can be joined together with the front portions overlapping each other, except for a portion that will become an opening, to form a bag container in the shape of that character.

In the bag container according to each of these embodiments, the opening through which the contents are put in and taken out may be made sealable by a zipper or heat welding. This allows the bag container to be formed into a sealed structure. Here, the non-oriented PET film layer used in the bag container according to the embodiment of the present invention has superior properties in terms of oxygen permeability, water vapor permeability, and aroma retention compared to conventional polyethylene films, polypropylene films, etc.

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

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.

The above describes the embodiments of the present invention. However, the present invention is not limited to these descriptions. Any design modifications made by a person skilled in the art to the above-described embodiments are also included within the scope of the present invention as long as they have the characteristics of the present invention.

This invention can be used to make bags for synthetic resin containers.

100, 200, 300, 400, 500, 600, 700 Bag container 200S Sheet 200a Non-stretched PET film layer 200b Stretched PET film layer 120, 220, 320, 420, 520, 620, 720 Front portion 140, 240 Side portion 142, 144, 242, 244, 246, 342, 442, 562, 762 Fold 160, 260, 360 Bottom portion 162, 182, 280, 282, 284, 380, 382, 480, 482, 580, 680, 682, 780 Joint portion

Claims (19)

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 non-oriented PET film layer is a PET film layer containing amorphous PET,
The PET film layer containing the amorphous PET is
A film layer formed in an amorphous state by heating and melting A-PET and isophthalic acid-modified PET, extruding the mixture through a mold to form a film, and then quenching the formed film on a cooling drum; or
The bag container is characterized in that the film layer is formed in an amorphous state by heating and melting A-PET, isophthalic acid-modified PET, and glycol-modified PET, extruding the mixture through a mold to form a film, and then quenching the formed film with a cooling drum. The bag container according to claim 1, wherein the sheet further has a joint where the unstretched PET film layers are joined together. 3. The bag container according to claim 2, wherein the unstretched PET film layer has at least one exposed surface, and the exposed surfaces of the unstretched PET film layer are joined to each other by a heat welding process at the joint. The bag container according to claim 3 , wherein at least two pairs of opposing exposed surfaces of the unstretched PET film layer are joined in a thickness direction of the sheet at some or all of the joints. The bag container according to claim 4 , wherein in the non-oriented PET film layer, four pairs of opposing exposed surfaces are joined to each other in a sheet thickness direction of the sheet at some or all of the joints. A pair of opposing front portions,
The bag container according to claim 3 , wherein the front portion has the joint portions at both side ends. The bag container according to claim 6 , wherein the joints at both ends are heat-welded by a heat cutting method. The bag container according to any one of claims 1 to 7 , wherein the non-oriented PET film layer has a thickness of 30 µm to 150 µm. It has an opening for inserting and removing contents,
The bag container according to claim 1 , wherein the opening is sealed to form a sealed structure. The device has a pair of opposing front portions and a bottom portion that is continuous with the lower ends of the front portions and connects the lower ends of the opposing front portions,
The bag container according to claim 3 , wherein the bottom portion includes the joint portion. a side surface portion continuing from a side end of each of the front surfaces and connecting the side ends of the opposing front surfaces;
The bag container according to claim 10 , wherein the side portion has a fold that allows the side portion to be folded inward. It is formed from a single sheet,
The bag container according to claim 10 or 11 , wherein the joint portion of the bottom portion is formed by overlapping and joining the folded sheet. The bag container according to claim 10 , wherein one of the front portions has the joint portion extending from an upper end to a lower end. The bag container according to any one of claims 10 to 13 , wherein at some or all of the joints, two or more pairs of opposing exposed surfaces of the non-oriented PET film layer are joined in the sheet thickness direction of the sheet. The bag container according to claim 14 , wherein in the non-oriented PET film layer, four pairs of opposing exposed surfaces are joined to each other in a sheet thickness direction of the sheet at some or all of the joints. The bag container according to any one of claims 10 to 15 , wherein the joint of the bottom portion is heat-sealed by ultrasonic heating. The bag container according to any one of claims 10 to 16 , wherein the non-oriented PET film layer has a thickness of 30 µm to 150 µm. It has an opening for inserting and removing contents,
The bag container according to claim 10 , wherein a sealed structure is formed by sealing the opening. A method for manufacturing a bag container formed from at least one sheet, comprising the steps of:
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 non-oriented PET film layer is a PET film layer containing amorphous PET,
The PET film layer containing the amorphous PET is
A film layer formed in an amorphous state by heating and melting A-PET and isophthalic acid-modified PET, extruding the mixture through a mold to form a film, and then quenching the formed film on a cooling drum; or
The method for producing a bag container is characterized in that A-PET, isophthalic acid-modified PET, and glycol-modified PET are heated and melted, extruded through a mold to form a film, and the film after film formation is quenched by a cooling drum to form a film layer in an amorphous state.

Images