Packaging bag and manufacturing method thereof

Abstract

To provide a packaging bag which is made of a mono-material and prevents a blocking.SOLUTION: A bag body 3 is formed by overlapping the inner surfaces of packaging films 2A and 2B made of a single material or a laminated film of the same material and bonding the peripheral edge parts of each film together by heat sealing, the packaging films 2A and 2B have a base layer that forms an outer surface of the bag body 3 and a heat-sealing layer that forms the inner surface of the bag body 3, the bag body 3 has a pair of planar parts 4 facing each other and gusset parts 5 and 6 folded inward between the pair of planar parts 4, the gusset part 6 is composed of a packaging film 2B having a coating layer on the outer surface at least at a position corresponding to a peripheral edge part, the coating layer containing a resin component selected from nitrocellulose, polyamide, shellac, epoxy, polyurethane, chlorinated polyolefin, a mixture of silicone and acrylic, or a mixture of silicone and polyamide.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a packaging bag and a method for manufacturing the same. [Background technology]

[0002] For example, packaging bags are produced by overlapping the inner surfaces of packaging films and bonding their peripheral edges together by heat sealing. Also, among packaging bags, there is a gusset bag, which has a pair of opposing flat surfaces and a gusset portion folded inward between the pair of flat surfaces, and is produced by overlapping the flat surfaces with the gusset portion folded inward between the pair of flat surfaces and bonding their peripheral edges together.

[0003] Recently, mono-material packaging films have been gaining attention as a way to effectively use plastics while reducing environmental impact. Mono-material packaging films mean that packaging bags are manufactured using packaging films made of a single or homogeneous material. Mono-material packaging films make recycling easier, making it possible to provide environmentally friendly packaging bags.

[0004] For example, Patent Document 1 listed below discloses a method for producing a packaging bag having a gusset portion using a laminated film obtained by laminating two layers of biaxially oriented polypropylene and a thermoplastic resin film such as unoriented polypropylene or polyethylene film, as an example of a packaging bag that can be made into a mono-material.

[0005] However, when producing a packaging bag having such a gusset portion, blocking may occur, in which the outer surfaces of the packaging film that constitutes the gusset portion melt and bond or pseudo-bond together.

[0006] If blocking occurs between the surfaces of the packaging film that make up the gusset, the packaging bag will not expand as designed when filled with contents, resulting in a packaging bag that does not reach the specified volume, which could cause the contents to overflow from the opening of the packaging bag or the contents to be pinched by the seal when the opening of the packaging bag is heat-sealed, resulting in defective filling. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 51-120880 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been proposed in view of the above-mentioned conventional circumstances, and aims to provide a packaging bag that achieves mono-materialization while preventing the occurrence of blocking, and a method for manufacturing the same. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides the following means. [1] A bag body is provided which is constructed by overlapping the inner surfaces of packaging films made of a single or laminated film of the same material and bonding the peripheral portions of each other by heat sealing, The packaging film has a base layer that forms the outer surface of the bag body and a heat-sealing layer that forms the inner surface of the bag body, The bag body has a pair of planar portions facing each other and a gusset portion folded inward between the pair of planar portions, The gusset portion is characterized in that it is made of a packaging film having a coating layer on the outer surface at least at a position corresponding to the peripheral edge portion, the coating layer containing a resin component selected from nitrocellulose, polyamide, shellac, epoxy, polyurethane, chlorinated polyolefin, a mixture of silicone and acrylic, or a mixture of silicone and polyamide. [2] The gusset portion is provided on the side and bottom of the bag body, The bag body is configured by overlapping the gusset portion on the side portion and the gusset portion on the bottom portion between the pair of flat portions in a state where the gusset portion on the side portion and the gusset portion on the bottom portion are folded inward, and bonding the peripheral edge portions on the side portion and the peripheral edge portions on the bottom portion together, The packaging bag described in [1] is characterized in that the coating layer is provided on the outer surface of the packaging film at a position corresponding to at least the peripheral edge of the side or bottom side, on the side where the gusset portion on the side and the gusset portion on the bottom side overlap between the pair of flat portions. [3] The packaging bag according to [1], wherein the coating layer is provided over an area larger than the area overlapping the bonded portion of the peripheral edge portion in a plan view. [4] The packaging bag according to [1], characterized in that the difference in melting point between the base material layer and the heat-sealable layer, which has a melting point lower than that of the base material layer, is 45°C or less. [5] The packaging bag according to any one of [1] to [4], characterized in that contents are accommodated inside the bag body. [6] A method for producing the packaging bag according to any one of [1] to [4], providing the coating layer on an outer surface of the gusset portion at least at a position corresponding to the peripheral edge portion; a step of overlapping the pair of flat portions with the gusset portion folded inward and bonding the peripheral edges of the flat portions together by heat sealing. [7] The method for manufacturing the packaging bag according to [6], characterized in that it includes a step of overlapping the pair of flat portions with the gusset portion folded inward between them, and spot-heat-sealing the peripheral portions that are to be heat-sealed to each other. [Effects of the Invention]

[0010] As described above, according to the present invention, it is possible to provide a packaging bag that achieves mono-material construction while preventing the occurrence of blocking, and a method for manufacturing the same. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view showing a packaging bag according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view of the packaging bag shown in FIG. 1, seen from the bottom side. [Figure 3] 2 is a plan view showing the folded state of the packaging bag shown in FIG. 1.

[0023] FIG. [Figure 4] 2 is a plan view of the packaging bag shown in FIG. 1 as seen from the bottom side. [Figure 5] FIG. 2A is a cross-sectional view showing a first packaging film, and FIG. 2B is a cross-sectional view showing a second packaging film. [Figure 6] FIG. 2 is a perspective view for explaining a method of manufacturing the packaging bag shown in FIG. [Figure 7] 2 is a perspective view showing a state in which the gusset portion on the side and the gusset portion on the bottom of the packaging bag shown in FIG. 1 are overlapped. FIG. [Figure 8] 2 is a perspective view showing a state in which peripheral portions of the packaging bag shown in FIG. 1 are bonded together by heat sealing in the manufacturing method thereof. FIG. [Figure 9] FIG. 4 is a perspective view showing a packaging bag according to a second embodiment of the present invention. [Figure 10] 10 is a plan view showing the folded state of the packaging bag shown in FIG. 9. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings used in the following description, the dimensions of the components may be shown at different scales to make them easier to see, and the dimensional ratios of the components may not be the same as in reality. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not necessarily limited to them, and can be implemented with appropriate changes within the scope of the present invention.

[0013] [First embodiment] (packaging bag) First, as a first embodiment of the present invention, a packaging bag 1A shown in, for example, FIGS. 1 to 5 will be described.

[0014] Fig. 1 is a perspective view showing the packaging bag 1A. Fig. 2 is a perspective view showing the bottom side of the packaging bag 1A. Fig. 3 is a plan view showing the packaging bag 1A in a folded state. Fig. 4 is a plan view of the packaging bag 1A as seen from the bottom side. Fig. 5(A) is a cross-sectional view showing the first packaging film 2A. Fig. 5(B) is a cross-sectional view showing the second packaging film 2B.

[0015] As shown in Figures 1 to 4, the packaging bag 1A of this embodiment has a bag body 3 formed by overlapping the inner surfaces of multiple packaging films 2A, 2B and bonding their peripheral edges together by heat sealing.

[0016] The bag body 3 has a pair of opposing flat sections 4, a pair of side gusset sections 5 that are folded inward between the pair of flat sections, and a bottom gusset section 6 that is folded inward between the pair of flat sections. Of these, the pair of flat sections 4 and the pair of side gusset sections 5 are made of a first packaging film 2A, which will be described later, and the bottom gusset section 6 is made of a second packaging film 2B, which will be described later.

[0017] The bag body 3 is constructed by overlapping the side gusset portion 5 and the bottom gusset portion 6 between a pair of flat portions 4 with the gusset portion 5 on the side and the bottom portion folded inward, and then bonding the peripheral edges of the side and bottom portions together.

[0018] In the packaging bag 1A of this embodiment, side edge seal portions 7 are formed between the pair of flat portions 4 and the pair of side gusset portions 5 by bonding together the peripheral edges of the side portions.

[0019] In addition, in the packaging bag 1A of this embodiment, a bottom edge seal portion 8 is formed between a pair of flat portions 4 and a bottom side gusset portion 6, and between a pair of side side gusset portions 5 and a bottom side gusset portion 6, by bonding the peripheral portions of the bottom side of each other.

[0020] Furthermore, an opening 3a is formed on the upper side of the bag body 3. That is, the peripheral edge on the upper side of the bag body 3 is not sealed when the bag body 3 is in an unused folded state, and contents can be filled into the bag body 3 through the opening 3a.

[0021] In the packaging bag 1A of this embodiment, when the bag body 3 is in a folded state, an overlapping portion S is formed on the bottom side, where the gusset portion 5 on the side folded inward between the pair of flat portions 4 and the gusset portion 6 on the bottom side are overlapped. The overlapping portion S has a right-angled triangular shape in a plan view.

[0022] As a result, in the folded state, the bag body 3 is divided into a two-ply area E1 where a pair of flat portions 4 overlap in the center of the bag body 3, a four-ply area E2 where a pair of flat portions 4 and a side gusset portion 5 overlap near each side edge seal portion 7, a four-ply area E3 where a pair of flat portions 4 and a bottom gusset portion 6 overlap near the bottom edge seal portion 8, and an eight-ply area E4 where a pair of flat portions 4 and a side gusset portion 5 and a bottom gusset portion 6 overlap near the intersection of each side edge seal portion 7 and the bottom edge seal. Therefore, the overlapping portion S constitutes the thickest eight-ply area E4.

[0023] In the packaging bag 1A of this embodiment, a user, such as a food manufacturer, fills the contents into the inside of the bag body 3 through the opening 3a, and then seals the opening 3a by heat-sealing the peripheral portion of the upper side of the bag body 3.

[0024] As a result, the packaging bag 1A of this embodiment is distributed as a content-filled packaging bag in which the content is accommodated (sealed) inside the bag body 3. Furthermore, the packaging bag 1A of this embodiment forms a self-standing flat-bottom bag that is composed of five surfaces, namely a pair of flat surfaces 4, a pair of side surfaces 5, and a bottom surface 6, when the content is accommodated (sealed) inside the bag body 3.

[0025] (packaging film) The bag body 3 is composed of four first packaging films 2A that form a pair of flat portions 4 and a pair of side gusset portions 5, and one second packaging film 2B that forms a bottom gusset portion 6. That is, the second packaging film 2B is used for the bottom gusset portion 6 where the overlapping portion S is located.

[0026] As shown in Fig. 5(A), the first packaging film 2A is made of a monomaterial film, which is a laminated film made of a single material, in which a base material layer 21, a printing layer 22, an adhesive layer 23, and a heat-sealing layer 24 are laminated in that order. The base material layer 21 forms the outer surface of the bag body 3, and the heat-sealing layer 24 forms the inner surface of the bag body 3. A monomaterial film is preferable in that it reduces the environmental impact, such as being easy to recycle and dispose of.

[0027] On the other hand, the second packaging film 2B has a structure in which a coating layer 25 is provided on the outer surface of the first packaging film 2A, as shown in FIG. 5(B).

[0028] In the present invention, the term "single material" refers to, for example, a packaging film in which multiple plastic films are laminated together, and the same resin material is used for the outer base layer and the inner heat-sealing layer. Specifically, a packaging film made of a single material is composed of only polyethylene, only polypropylene, or only polyester resin material.

[0029] In the present invention, the term "same material" refers to, for example, a packaging film in which multiple plastic films are laminated together, in which the same type of resin material is used for the outer base layer and the inner heat-sealing layer, specifically, a packaging film in which polypropylene is used for the base layer and polyethylene is used for the heat-sealing layer, or a packaging film in which polybutylene terephthalate is used for the base layer and polyethylene terephthalate is used for the heat-sealing layer.

[0030] In this way, for example, a film in which the base layer and the heat-sealing layer are both formed of the same type of resin material classified as polyolefin or polyester, but are not formed of the same resin material, is considered to be a packaging film made of the same material in the present invention.

[0031] In the present invention, a packaging film made of a single material or the same type of material is referred to as a mono-material film.

[0032] The higher the mono-material ratio of the packaging bag of the present invention, the better, and it is preferably 80% or more, and more preferably 90% or more.

[0033] The mono-material rate of a packaging bag is the percentage of a single or homogeneous material in terms of mass of the materials used.

[0034] If the mono-material ratio of the packaging bag of the present invention is 90% or more, it will be possible to meet the guidelines required by CEFLEX (Circular Economy for Flexible Packaging), a European consortium (joint venture) that aims to realize a circular society in the flexible packaging field, which state that "at least 90% of the materials making up flexible packaging containers should be mono-materials," making it possible to provide flexible packaging containers that are easy to recycle.

[0035] The base layer 21 is made of a plastic film with a melting point higher than at least the heat-sealing layer 24. Furthermore, it is preferable to use a plastic film for the base layer 21 that has excellent properties such as printability, puncture strength, tensile strength, and impact resistance. Specific examples include plastic films based on synthetic resin materials, such as polyolefins such as high-density polyethylene (HDPE) and polypropylene (PP), and polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Among these, polypropylene is most preferable in terms of versatility. Furthermore, the melting point of the polypropylene used for the base layer is preferably 160°C or higher and 175°C or lower.

[0036] The substrate layer 21 may be either a stretched film or an unstretched film. Alternatively, the substrate layer 21 may be a vapor-deposited film having a metal such as aluminum or magnesium, or an oxide such as aluminum oxide or silicon oxide, deposited on one surface. Alternatively, the substrate layer 21 may be a coated film having a barrier coating agent such as polyvinylidene chloride coated on one surface.

[0037] The thickness of the base layer 21 is preferably 6 μm to 100 μm, and more preferably 12 μm to 50 μm.

[0038] The printed layer 22 is made of a coating film formed by applying ink. That is, the printed layer 22 is formed by printing ink on one or both surfaces of the base layer 21. Known printing inks can be used as the ink. The ink contains a solvent, a resin, a pigment, and an additive.

[0039] Examples of methods for forming the printed layer 22 include gravure printing, offset printing, and flexographic printing. Among these printing methods, gravure printing is preferably used because it has excellent reproducibility of colors and designs.

[0040] The coating amount per unit area of ​​the ink constituting the printing layer 22 after the solvent has dried is 0.3 g / m 2~2.0g / m 2 That's about it.

[0041] The printed layer 22 is formed by printing indications such as characters, figures, decorations, and symbols for management related to the contents, as well as designs that serve as the background of these indications, on the base material layer 21. The printed layer 22 may also be formed by printing ink having functionality such as an antistatic agent on the base material layer 21.

[0042] The adhesive layer 23 is formed using an adhesive that bonds the materials that make up the laminated film together. Examples of methods for forming the adhesive layer 23 include dry lamination, non-solvent lamination, and extrusion lamination, in which a resin material such as molten polyethylene is extruded from a T-die into a film and laminated. Among these formation methods, the dry lamination method is preferably used from the viewpoint of adhesive strength.

[0043] The thickness of the adhesive layer 23 is preferably 0.5 μm to 50 μm, and more preferably 1 μm to 30 μm.

[0044] The heat-sealable layer 24 is made of a plastic film that has a melting point at least lower than that of the base layer 21 and is heat-sealable. Specific examples include single-layer plastic films made of polyolefins such as low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene, linear low-density polyethylene (LLDPE), or polypropylene, or heat-sealable polyesters such as polyethylene terephthalate. Polypropylene may be a homopolymer, random copolymer, or block copolymer. Among these, polypropylene is most preferred as the synthetic resin constituting the heat-sealable layer 24 in terms of versatility. The melting point of the polypropylene used for the heat-sealable layer is preferably 130°C or higher and lower than 160°C.

[0045] The heat-sealing layer 24 is preferably an unstretched film, but may also be a multi-layer plastic film of two or more layers obtained by co-extrusion of the above-mentioned synthetic resin materials.

[0046] The thickness of the heat-sealing layer 24 is preferably 15 μm to 200 μm, and more preferably 20 μm to 150 μm.

[0047] The first packaging film 2A may have a configuration in which an intermediate layer (not shown) is provided between the base material layer 21 and the heat-sealing layer 24, if necessary. The intermediate layer is made of a plastic film having a melting point higher than that of at least the heat-sealing layer 24.

[0048] The intermediate layer is provided when it is necessary to impart physical strength such as puncture strength, tensile strength, and impact resistance to the laminate film, or when it is necessary to impart gas barrier properties to the laminate film, etc. In other words, the intermediate layer serves as a functional layer that imparts functionality to the laminate film.

[0049] Examples of the intermediate layer include a plastic film made of a synthetic resin material such as polyolefin, such as medium-density polyethylene, high-density polyethylene, or polypropylene, polyester, such as polyethylene terephthalate or polybutylene terephthalate, or ethylene-vinyl alcohol copolymer (EVOH), etc. The intermediate layer may be either a stretched film or an unstretched film.

[0050] The intermediate layer may be a vapor-deposited film formed by vapor-depositing a metal such as aluminum or magnesium, or an oxide such as aluminum oxide or silicon oxide. The intermediate layer may also be a coated film coated with a barrier coating agent such as polyvinylidene chloride. By providing such an intermediate layer, gas barrier properties can be imparted to the laminated film.

[0051] The intermediate layer may also be a multi-layer plastic film obtained by co-extrusion of a combination of the above-mentioned synthetic resin materials, i.e., the intermediate layer may be a single layer or two or more layers.

[0052] The thickness of the intermediate layer is preferably 4 μm to 50 μm, and more preferably 7 μm to 30 μm.

[0053] The coating layer 25 is made of a coating film coated with a coating agent for preventing blocking. That is, the coating layer 25 is formed by applying a coating agent to the outer surface of the base layer 21.

[0054] The coating agent preferably has heat resistance at least equal to or higher than the melting point of the base layer 21. Here, heat resistance means that the resin contained in the coating agent does not melt when heated at a temperature equal to or higher than the melting point of the base layer 21.

[0055] The coating agent preferably has heat resistance at least equal to or higher than the melting point of the heat-sealable layer 24. Furthermore, the coating agent more preferably has heat resistance at least equal to or higher than the set temperature of the bag-making machine. This effectively prevents blocking between the base material layers 21 of the gusset portions 5, 6 caused by melting of the resin contained in the coating agent during bag making.

[0056] Known inks for surface printing can be suitably used for the coating layer 25. Specific examples include varnish, medium ink, and matte ink. The ink used for the coating layer 25 is not limited to being transparent or translucent, and may also be colored.

[0057] The coating agent contains a solvent, a resin, a pigment, and additives, similar to ink. Various solvents commonly used in the field of printing inks can be used for the coating agent. Specific examples include organic solvents such as methyl ethyl ketone, ethyl acetate, methanol, ethanol, and isopropyl alcohol.

[0058] The resin contained in the coating agent of the present invention is nitrocellulose, polyamide, shellac, epoxy, polyurethane, chlorinated polyolefin, a mixture of silicone and acrylic, or a mixture of silicone and polyamide. By using a coating agent containing these resins, it is possible to provide a packaging bag that prevents blocking. Among these resins, shellac, a mixture of silicone and polyamide, and nitrocellulose are preferred in terms of heat resistance and blocking resistance. In particular, coating agents using nitrocellulose as the resin have the best blocking resistance between the film and the coating agent, as well as between the coating agent and the coating agent.

[0059] The coating agent can be any of various inorganic pigments, organic pigments, etc. that are commonly used in the field of printing inks. In addition, the coating agent can contain additives such as curing agents such as melamine-based curing agents, epoxy-based curing agents, and epoxymelamine-based curing agents, dispersants, antifoaming agents, plasticizers, and antistatic agents, as needed.

[0060] Examples of methods for forming the coating layer 25 include gravure printing, offset printing, and flexographic printing. Among these printing methods, gravure printing is preferred because it has excellent reproducibility of colors and designs.

[0061] The coating thickness of the coating agent (coating layer 25) is preferably 0.05 μm to 5.0 μm, and more preferably 0.1 μm to 3.0 μm. If the coating thickness is in the range of 0.05 μm to 5.0 μm, blocking between the base material layers 21 of the gusset portions 5, 6 during bag production can be effectively prevented.

[0062] The coating layer 25 may be so-called solid printing or halftone printing. Solid printing refers to a state in which the coating agent is printed with halftone dots without gaps over a certain area. The dot area ratio of solid printing is 100%. Halftone printing refers to a state in which the coating agent is printed with gaps between halftone dots at a certain density over a certain area, or as a collection of fine dots. The dot area ratio of halftone printing is 10% to less than 100%.

[0063] The coating layer 25 may also be printed with a pattern such as a geometric pattern, a lattice pattern, a check pattern, or a gradation. By printing the coating layer with halftone printing or a pattern, the degree (severity) of blocking can be controlled.

[0064] As a result, the packaging bag 1A is in a weak blocking state immediately after production, so the size of a bundle of accumulated packaging bags 1A can be reduced, improving the volume efficiency relative to the cardboard used for packaging, which in turn leads to improved transportation efficiency.

[0065] On the other hand, when a user such as a food manufacturer fills the packaging bag 1A with contents, the blocking is easily released, so there is no effect on filling.

[0066] Incidentally, if there is a large difference in melting point between the base material layer 21 and the heat-sealing layer 24 of the packaging films 2A, 2B that constitute the bag body 3, when the peripheral portions of each film are bonded together by heat sealing, the base material layer 21 will not melt at the time the heat-sealing layer 24 melts, so blocking will not occur and quality control of bag production (the manufacturing process of packaging bags) will be easier.

[0067] On the other hand, if the difference in melting point between the base material layer 21 and the heat-sealing layer 24 is small, when the peripheral edges of the base material layer 21 and the heat-sealing layer 24 are bonded together by heat sealing, the base material layer 21 will also approach a molten state when the heat-sealing layer 24 melts, which increases the possibility of blocking. Furthermore, the seal portions 7 and 8 may be thermally shrunk or holes may be formed in the seal portions 7 and 8, which will impair the appearance of the bag body 3.

[0068] In particular, when the packaging films 2A, 2B are made of mono-material films, the base material layer 21 and the heat-sealing layer 24 are made of the same or similar materials and have close melting points, which makes blocking more pronounced.

[0069] In contrast, in the packaging bag 1A of this embodiment, a second packaging film 2B is used in the gusset portion 6 on the bottom side where the above-mentioned overlapping portion S is located, in which an anti-blocking coating layer 25 having heat resistance equal to or greater than that of the above-mentioned base material layer 21 is provided.

[0070] This makes it possible to prevent the outer surfaces of the bottom gusset portion 6 (second packaging film 2B) from melting and adhering to each other when the inner surfaces of multiple packaging films 2A, 2B are overlapped and their peripheral edges are bonded together by heat sealing.

[0071] In other words, in the packaging bag 1A of this embodiment, even if the packaging films 2A and 2B are made of monomaterial films, the coating layer 25 provided on the outer surface of the bottom gusset portion 6 (second packaging film 2B) can prevent blocking from occurring.

[0072] The coating layer 25 only needs to be provided on the outer surface of the bottom gusset portion 6 (second packaging film 2B) at a position corresponding to at least the bottom edge seal portion 8 (bottom side peripheral edge portion). In addition, taking into consideration the seal width during heat sealing, the coating layer 25 is preferably provided over an area larger than the area overlapping with the bottom edge seal portion 8 in a plan view. In this embodiment, the coating layer 25 is provided over the entire outer surface of the bottom gusset portion 6 (second packaging film 2B).

[0073] Blocking is more likely to occur when the difference in melting point between the base layer 21 and the heat-sealing layer 24 is 45°C or less, and blocking becomes more pronounced when the difference is 20°C or less.

[0074] (Manufacturing method of packaging bags) Next, a method for manufacturing the packaging bag 1A will be described with reference to FIGS. Fig. 6 is a perspective view for explaining a manufacturing method of the packaging bag 1A. Fig. 7 is a perspective view showing a state in which the gusset portion 5 on the side side of the packaging bag 1A and the gusset portion 6 on the bottom side are overlapped. Fig. 8 is a perspective view showing a state in which the peripheral portions of the packaging bag 1A are bonded together by heat sealing in the manufacturing method of the packaging bag 1A.

[0075] When manufacturing the above-mentioned packaging bag 1A, first, a long first packaging film 2A that forms a pair of flat portions 4, a long first packaging film 2A that forms a pair of side gusset portions 5, and a second packaging film 2B that forms a bottom gusset portion 6 are prepared.

[0076] The coating layer 25 is formed on the outer surface of the second packaging film 2B, which becomes the gusset portion 6 on the bottom side, by applying the above-mentioned anti-blocking coating agent.

[0077] Next, as shown in Fig. 6, the first packaging film 2A that will become the pair of side gusset portions 5 shown in Fig. 7 and the second packaging film 2B that will become the bottom gusset portion 6 are folded inward and sandwiched between the pair of first packaging films 2A that will become the pair of flat portions 4. The second packaging films 2B that will become the bottom gusset portion 6 are arranged side by side at a fixed interval in the longitudinal direction of the first packaging films 2A that will become the pair of side gusset portions 5. The packaging films 2A and 2B are overlapped with their inner surfaces facing each other.

[0078] Next, while the packaging films 2A and 2B overlapped in this state are being conveyed, the peripheral edges of each of the portions that will become the bag bodies 3 are bonded together by heat sealing using a bag making machine (not shown).

[0079] Specifically, a heat seal bar heated to a predetermined sealing temperature is pressed against both sides of the first packaging film 2A, which becomes the pair of flat portions 4, along the contour of the portion that will become the bag body 3, and then a cooled cooling bar is pressed against the film.

[0080] In the portion heated by the heat seal bar, the inner surfaces of the packaging films 2A and 2B melt together, and are thereby brought into close contact with each other.

[0081] As a result, as shown in Fig. 8, side edge seal portions 7 are formed by bonding the peripheral edges of the side portions between the pair of flat portions 4 and the pair of side gusset portions 5. In addition, bottom edge seal portions 8 are formed by bonding the peripheral edges of the bottom portions between the pair of flat portions 4 and the bottom gusset portion 6 and between the pair of side gusset portions 5 and the bottom gusset portion 6.

[0082] Next, after the heat sealing, the overlapped packaging films 2A, 2B are cut to fit the shape of the bag body 3 and divided into individual bag bodies 3. By going through the above steps, it is possible to manufacture a plurality of packaging bags 1A at once.

[0083] In the manufacturing method of the packaging bag 1A of this embodiment, a second packaging film 2B is used in which the above-mentioned anti-blocking coating layer 25 is provided in the gusset portion 6 on the bottom side where the above-mentioned overlapping portion S is located.

[0084] This makes it possible to prevent the outer surfaces of the gusset portion 6 on the bottom side, which is made up of the second packaging film 2B, from melting and adhering to each other when the inner surfaces of multiple packaging films 2A, 2B are overlapped and their peripheral edges are bonded together by heat sealing.

[0085] Furthermore, in the manufacturing method of the packaging bag 1A of this embodiment, even when the packaging films 2A and 2B are made of monomaterial films, the occurrence of blocking can be prevented by the coating layer 25 provided on the outer surface of the bottom side gusset portion 6 made of the second packaging film 2B.

[0086] Incidentally, when manufacturing the above-mentioned packaging bag 1A, as shown in Figure 8, before or after the above-mentioned heat sealing process, spot heat sealing is performed on the peripheral portion of the bag body 3 on the bottom side where the above-mentioned overlapping portion S is located, among the peripheral portions that are heat sealed to each other.

[0087] That is, since this overlapping portion S constitutes the above-mentioned thickest eight-ply area E4, when heat-sealing this overlapping portion S, more thermal energy (temperature, time, pressure) is required.

[0088] Therefore, when manufacturing the above-mentioned packaging bag 1A, point sealing is performed on the four boundaries P between the eight-ply area E4 and the four-ply areas E2 and E3 on the peripheral edge of the bottom side of the bag body 3, with a pressure per unit area higher than when pressing a heat seal bar.

[0089] As a result, in the packaging bag 1A of this embodiment, as shown in Figures 3 and 4, it is possible to improve the adhesion of the bottom edge seal portion 8 formed in the bag body 3 at a position corresponding to the boundary P (hereinafter referred to as the point seal portion 9).

[0090] The shape of the point seal portion 9 may be, for example, circular, elliptical, or polygonal. On the other hand, the point seal portion 9 is preferably sized to fit within the width of at least the bonding portion of the peripheral edge.

[0091] If the point seal portion 9 protrudes from the bottom edge seal portion 8, not only will the appearance be poor, but cracks may occur in the heat-sealing layer 24 starting from the outer edge of the point seal portion 9, making it impossible to maintain sufficient sealing.

[0092] In the packaging bag 1A of this embodiment, the point seal portion 9 is a portion to which more heat energy is applied as described above, and therefore is a location where blocking is likely to occur.

[0093] In contrast, in the manufacturing method of packaging bag 1A of this embodiment, even when point sealing is performed at the above-mentioned boundary P, it is possible to prevent blocking from occurring by means of coating layer 25 provided on the outer surface of bottom gusset portion 6 made of second packaging film 2B. This makes it possible to manufacture high-quality packaging bag 1A with excellent appearance.

[0094] Second Embodiment (packaging bag) Next, as a second embodiment of the present invention, a packaging bag 1B shown in, for example, FIGS. 9 and 10 will be described.

[0095] Fig. 9 is a perspective view showing packaging bag 1B. Fig. 10 is a plan view showing packaging bag 1B in a folded state. In the following description, the same parts as those in packaging bag 1A will not be described and will be denoted by the same reference numerals in the drawings.

[0096] As shown in Figures 9 and 10, in the folded state of the packaging bag 1B of this embodiment, the overlapping portion S between the side gusset portion 5 and the bottom gusset portion 6, which are folded inward between a pair of flat portions 4, is folded toward the side.

[0097] In addition, in the packaging bag 1B of this embodiment, the bag body 3 is composed of three first packaging films 2A that form a pair of flat portions 4 and a bottom side gusset portion 6, and two second packaging films 2B that form a pair of side side gusset portions 5.

[0098] That is, the second packaging film 2B is used for the gusset portions 5 on the pair of side portions where the overlapping portion S is located. Other than that, the configuration is basically the same as that of the packaging bag 1A.

[0099] In the packaging bag 1B of this embodiment, the second packaging film 2B provided with the above-mentioned anti-blocking coating layer 25 is used in the gusset portion 5 on the side where the overlapping portion S is located.

[0100] This makes it possible to prevent the outer surfaces of the gusset portion 5 on the side of the second packaging film 2B from melting and adhering to each other when the inner surfaces of multiple packaging films 2A, 2B are overlapped and their peripheral edges are bonded together by heat sealing.

[0101] Furthermore, in the packaging bag 1B of this embodiment, even when the packaging films 2A and 2B are made of monomaterial films, the occurrence of blocking can be prevented by the coating layer 25 provided on the outer surface of the gusset portion 5 on the side side made of the second packaging film 2B.

[0102] (Manufacturing method of packaging bags) Next, the manufacturing method of the packaging bag 1B is basically the same as that of the packaging bag 1A, and therefore the description thereof will be omitted.

[0103] In the manufacturing method of the packaging bag 1B of this embodiment, a second packaging film 2B is used in which the above-mentioned anti-blocking coating layer 25 is provided in the gusset portion 5 on the side where the above-mentioned overlapping portion S is located.

[0104] This makes it possible to prevent the outer surfaces of the gusset portion 5 on the side of the second packaging film 2B from melting and adhering to each other when the inner surfaces of multiple packaging films 2A, 2B are overlapped and their peripheral edges are bonded together by heat sealing.

[0105] Furthermore, in the manufacturing method of the packaging bag 1B of this embodiment, even when the packaging films 2A, 2B are made of monomaterial films, the occurrence of blocking can be prevented by the coating layer 25 provided on the outer surface of the gusset portion 5 on the side side made of the second packaging film 2B.

[0106] When the packaging bag 1B is manufactured, four boundaries P between the eight-ply area E4 and the four-ply areas E2 and E3 are point-sealed on the peripheral edge of the side of the bag body 3.

[0107] As a result, in the packaging bag 1B of this embodiment, as shown in Figure 10, it is possible to improve the adhesion of the point seal portion 9, which is located at a position corresponding to the boundary P, among the side edge seal portions 7 formed on the bag body 3.

[0108] Therefore, in the manufacturing method of packaging bag 1B of this embodiment, even when point sealing is performed at the above-mentioned boundary P, it is possible to prevent blocking from occurring by means of coating layer 25 provided on the outer surface of gusset portion 5 on the side portion side made of second packaging film 2B. This makes it possible to manufacture high-quality packaging bag 1B with excellent appearance.

[0109] The present invention is not necessarily limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0110] For example, in the above-mentioned packaging bags 1A, 1B, the second packaging film 2B is used in either the gusset portion 5 on the side side or the gusset portion 6 on the bottom side, but the second packaging film 2B may also be used in both the gusset portion 5 on the side side and the gusset portion 6 on the bottom side.

[0111] Furthermore, although the above-mentioned packaging bags 1A and 1B are configured with a pair of side gusset portions 5 and a bottom gusset portion 6, the present invention can also be applied to packaging bags that have only one of the side gusset portion 5 and the bottom gusset portion 6.

[0112] Furthermore, while the packaging bags 1A and 1B are configured using mono-material films for the packaging films 2A and 2B, the present invention is not limited to such configurations and can be applied to packaging bags in which the above-mentioned blocking is likely to occur. That is, the packaging films 2A and 2B are not limited to those made of a laminated film of a single material, and the present invention can be suitably used when packaging films 2A and 2B are used in which the difference in melting point between the base layer 21 and the heat-sealing layer 24 is small, such as laminated films made of the same material. [Example]

[0113] The effects of the present invention will be made clearer by the following examples. Note that the present invention is not limited to the following examples and can be practiced with appropriate modifications within the scope of the present invention.

[0114] Example 1 In Example 1, a first packaging film was prepared by first forming a printed layer on one side of a 20 μm thick base layer made of biaxially oriented polypropylene by printing, and then bonding the printed layer to a 40 μm thick heat-sealable layer made of unoriented polypropylene using a dry laminating adhesive made of a polyurethane-based two-component curing adhesive to produce a mono-material film with a thickness of approximately 64 μm.

[0115] In addition, as a second packaging film, a monomaterial film with a coating layer formed was produced by applying XGS-3622OP Varnish NT (main agent) / No. 5000 (hardener) manufactured by Sakata Inx Corporation, which has a resin component of nitrocellulose, as a coating agent to the outer surface of the first packaging film.

[0116] Next, a first packaging film forming a pair of flat portions 4, a first packaging film forming a pair of side gusset portions, and a second packaging film forming a bottom gusset portion were prepared, and then the side gusset portions and the bottom gusset portions were overlapped between the pair of flat portions with the gusset portions folded inward, and the peripheral edges of the side portions and the bottom portion were bonded together by heat sealing to produce a bag body.

[0117] At this time, the width of the side edge seal portion and bottom edge seal portion of the bag body was 5 mm, and the temperature of each seal portion in the bag making machine was set to 170°C. The melting point of the base material layer was 172°C, and the melting point of the heat-sealable layer was 135°C, with a difference in their melting points of 37°C.

[0118] Furthermore, since the overlapping portion of the bag body between the gusset portion on the side and the gusset portion on the bottom side, which are folded inward between a pair of flat portions, is folded toward the bottom side, point sealing was performed on the four boundaries between the eight-ply area and the four-ply area on the peripheral edge of the bottom side of the bag body before the above-mentioned heat sealing process. The packaging bag of Example 1 was produced through the above steps.

[0119] Example 2 A packaging bag made of a monomaterial film was obtained in the same manner as in Example 1, except that the coating agent for the second packaging film was changed to Riofresh (registered trademark), an edible ink manufactured by Toyochem Co., Ltd., whose resin component is shellac.

[0120] Example 3 A packaging bag made of a monomaterial film was obtained in the same manner as in Example 1, except that the coating agent for the second packaging film was changed to X218 Hakuri Varnish C manufactured by Toyo Ink Mfg. Co., Ltd., whose resin component is a mixture of silicone and polyamide.

[0121] (Comparative Example 1) In Comparative Example 1, a packaging bag was produced under the same conditions as in Example 1, except that a second packaging film was used in which no coating layer was provided on the gusset portion on the bottom side.

[0122] (Comparative Example 2) In Comparative Example 2, a laminated film was produced by first forming a printed layer on one side of a base layer made of polyethylene terephthalate with a thickness of 12 μm by printing, and then laminating an intermediate layer made of low-density polyethylene with a thickness of 15 μm and a heat-sealing layer made of unstretched polypropylene with a thickness of 40 μm on top of the printed layer.

[0123] Next, a packaging film is prepared that forms a pair of flat portions, a pair of side gusset portions, and a bottom gusset portion, and then the side gusset portions and the bottom gusset portions are overlapped between the pair of flat portions with the side gusset portions and the bottom gusset portions folded inward, and the peripheral edges of the side portions and the bottom portion are bonded together by heat sealing.

[0124] At this time, the width of the side edge seal portion and the bottom edge seal portion was 5 mm, and the temperature of each seal portion in the bag making machine was set to 170°C. The melting point of the base material layer was 240°C, and the melting point of the heat-sealing layer was 135°C, with a difference in their melting points of 105°C.

[0125] This produced a packaging bag having a bag body in which the overlapping portion of the gusset portion on the side and the gusset portion on the bottom side, which were folded inward between a pair of flat portions, were folded toward the bottom side.

[0126] Next, the packaging bags of Examples 1 to 3 and Comparative Examples 1 and 2 were subjected to an evaluation test for occurrence of blocking.

[0127] In this evaluation test, a tensile strength test was conducted on the overlapping portion of each packaging bag in accordance with "JIS Z0238" to measure the tensile strength.The measurement results were rated as "no blocking" when the tensile strength was less than 3.0N / 15mm, and "blocking" when it was 3.0N / 15mm or more.

[0128] As a result, the packaging bag of Example 1 showed good results with no occurrence of blocking, and the packaging bags of Examples 2 and 3 also showed good results with no occurrence of blocking.

[0129] In addition, in the packaging bag of Example 1, no abnormalities were found in the coating layer itself after the evaluation test for the occurrence of blocking. In the packaging bag of Example 2, it was discovered that part of the coating layer had peeled off from the second packaging film after the test. The packaging bag of Example 3 tended to block slightly compared to Examples 1 and 2. In terms of blocking resistance and coating layer stability, Example 1 was the most excellent among Examples 1 to 3.

[0130] On the other hand, in the packaging bag of Comparative Example 1, blocking occurred in the point seal portion.

[0131] On the other hand, in the packaging bag of Comparative Example 2, the difference in melting point between the base material layer and the heat-sealable layer was large, and blocking did not occur.

[0132] The monomaterial ratio of the packaging bags of Examples 1 to 3 and Comparative Example 1 was approximately 92%, which met the CEFLEX guideline of 90%, whereas the monomaterial ratio of the packaging bag of Comparative Example 2 was approximately 72%, which did not meet the CEFLEX guideline. [Explanation of symbols]

[0133] DESCRIPTION OF SYMBOLS 1A, 1B... Packaging bag 2A... First packaging film 2B... Second packaging film 3... Bag body 3a... Opening 4... Flat portion 5... Side gusset portion 6... Bottom gusset portion 7... Side edge seal portion 8... Bottom edge seal portion 9... Point seal portion 21... Base material layer 22... Printed layer 23... Adhesive layer 24... Heat-sealed layer 25... Coating layer S... Overlap portion P... Boundary

Claims

1. The bag body is constructed by overlapping inner surfaces of packaging films made of a single material or a laminated film of the same material and bonding the peripheral portions of each other by heat sealing, The packaging film has a base layer that forms the outer surface of the bag body and a heat-sealing layer that forms the inner surface of the bag body, The bag body has a pair of planar portions facing each other and a gusset portion folded inward between the pair of planar portions, The gusset portion is characterized in that it is made of a packaging film having a coating layer on the outer surface at least at a position corresponding to the peripheral edge portion, the coating layer containing a resin component selected from nitrocellulose, polyamide, shellac, epoxy, polyurethane, chlorinated polyolefin, a mixture of silicone and acrylic, or a mixture of silicone and polyamide.

2. The gusset portion is provided on the side and bottom of the bag body, The bag body is configured by overlapping the gusset portion on the side portion and the gusset portion on the bottom portion between the pair of flat portions in a state where the gusset portion on the side portion and the gusset portion on the bottom portion are folded inward, and bonding the peripheral edge portions on the side portion and the peripheral edge portions on the bottom portion together, The packaging bag according to claim 1, characterized in that the coating layer is provided on the outer surface of the packaging film at a position corresponding to at least the peripheral edge of the side or bottom side, on the side where the gusset portion on the side and the gusset portion on the bottom side overlap between the pair of flat portions.

3. The packaging bag according to claim 1 , wherein the coating layer is provided over an area larger than an area overlapping the bonded portion of the peripheral edge portion in a plan view.

4. 2. The packaging bag according to claim 1, wherein the difference in melting point between the base material layer and the heat-sealable layer, which has a melting point lower than that of the base material layer, is 45° C. or less.

5. 5. The packaging bag according to claim 1, wherein the bag body contains a content.

6. A method for manufacturing the packaging bag according to any one of claims 1 to 4, providing the coating layer on an outer surface of the gusset portion at least at a position corresponding to the peripheral edge portion; a step of overlapping the pair of flat portions with the gusset portion folded inward and bonding the peripheral edges of the flat portions together by heat sealing.

7. 7. The method for manufacturing a packaging bag according to claim 6, further comprising a step of overlapping the pair of flat portions with the gusset portion folded inward, and spot-heat-sealing the peripheral portions that are to be heat-sealed to each other.

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