Packaging bag and method for manufacturing same

Abstract

There is provided a packaging bag in which the occurrence of blocking is prevented while achieving mono-materialization. A packaging bag includes a bag body 3 formed by overlapping inner surfaces of packaging films 2A and 2B made of a laminated film of one or a same kind of material and bonding peripheral edge portions of the films to each other by heat seal. The packaging films 2A and 2B include a base material layer that forms an outer surface of the bag body 3 and a heat seal layer that forms an inner surface of the bag body 3. The bag body 3 includes a pair of flat portions 4 facing each other and gusset portions 5 and 6 folded inward between the pair of flat portions 4. The gusset portion 6 is formed of the packaging film 2B in which a coating layer containing a resin component selected from cellulose nitrate, polyamide, shellac, epoxy, polyurethane, chlorinated polyolefin, a mixture of silicone and acrylic, or a mixture of silicone and polyamide is provided on an outer surface at least at a position corresponding to the peripheral edge portion.

Description

PACKAGING BAG AND METHOD FOR MANUFACTURING SAME

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

[0002] For example, a packaging bag is manufactured by overlapping the inner surfaces of packaging films with each other and bonding the peripheral edge portions to each other by heat seal. In addition, the packaging bag includes a gusset bag that includes a pair of flat portions facing each other and a gusset portion folded inward between the pair of flat portions, and is manufactured by overlapping the gusset portions in a state where the gusset portions are folded inward between the pair of flat portions and bonding the peripheral edge portions to each other.

[0003] Recently, mono-materialization of packaging films has become a hot topic as one of schemes that effectively uses plastics while reducing environmental loads. Mono-materialization means that a packaging bag is manufactured using a packaging film made of one or the same kind of material. By mono-materialization of the packaging film, recycling is facilitated, so that it is possible to provide a packaging bag in consideration of environments.

[0004] For example, Patent Literature 1 below discloses a method for manufacturing 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 non-oriented polypropylene or a polyethylene film as an example of a packaging bag that enables mono-materialization.

[0005] However, in the case of manufacturing a packaging bag having such a gusset portion, blocking may occur in which the outer surfaces of packaging films constituting the gusset portion are melted and bonded or pseudo bonded.

[0006] When blocking occurs between the surfaces of the packaging films constituting the gusset portion, the packaging bag is not inflated as designed when contents are filled into the packaging bag. For this reason, the packaging bag may be in a state where its volume is less than a predetermined volume, and contents may overflow from the opening of the packaging bag, or filling failure may occur in which the contents are sandwiched by the seal portion when the opening of the packaging bag is heat-sealed.

[0007] Patent Literature 1: JP-A-51-120880Problems to be Solved by Invention

[0008] The present invention has been proposed in view of such conventional circumstances, and an object of the present invention is to provide a packaging bag in which the occurrence of blocking is prevented while mono-materialization is achieved, and a method for manufacturing the packaging bag.Solution to Problems

[0009] In order to achieve the above object, the present invention provides the following schemes. [1] A packaging bag including a bag body formed by overlapping inner surfaces of packaging films made of a laminated film of one or a same kind of material and bonding peripheral edge portions of the inner surfaces of the packaging films to each other by heat seal, in which the packaging film includes a base material layer that forms an outer surface of the bag body and a heat seal layer that forms an inner surface of the bag body, the bag body includes a pair of flat portions facing each other and a gusset portion folded inward between the pair of flat portions, and the gusset portion is formed of a packaging film in which a coating layer containing a resin component selected from cellulose nitrate, polyamide, shellac, epoxy, polyurethane, chlorinated polyolefin, a mixture of silicone and acrylic, or a mixture of silicone and polyamide is provided on an outer surface at least at a position corresponding to the peripheral edge portion. [2] The packaging bag according to [1], in which the gusset portion is provided on a side portion and a bottom of the bag body, and the bag body is formed by overlapping the side gusset portion and the bottom gusset portion, with the side gusset portion and the bottom gusset portion folded inward between the pair of flat portions, and bonding the side peripheral edge portion and the bottom peripheral edge portion to each other, and the coating layer is provided on an outer surface of the packaging film at a position corresponding to at least the side peripheral edge portion or the bottom peripheral edge portion on a side where the side gusset portion and the bottom gusset portion overlap each other between the pair of flat portions. [3] The packaging bag according to [1], in which the coating layer is provided in a range larger than a range overlapping a bonded portion of the peripheral edge portion in a planar view. [4] The packaging bag according to [1], in which a difference in a melting point between the base material layer and the heat seal layer having a melting point lower than the base material layer is 45°C or less. [5] The packaging bag according to any one of [1] to [4], in which a content is accommodated inside the bag body. [6] A method for manufacturing the packaging bag according to any one of [1] to [4], the method including the steps of: providing the coating layer on an outer surface of the gusset portion at a position corresponding to at least the peripheral edge portion; and overlapping the gusset portions between the pair of flat portions in a state where the gusset portions are folded inward to bond the peripheral edge portions to each other by heat seal. [7] The method for manufacturing a packaging bag according to [6], further including the step of overlapping the gusset portions between the pair of flat portions in a state where the gusset portions are folded inward to heat-fuse the gusset portions in a spot manner with respect to the peripheral edge portions to be heat-sealed to each other.Effects of Invention

[0010] As described above, according to the present invention, it is possible to provide a packaging bag in which the occurrence of blocking is prevented while mono-materialization is achieved, and a method for manufacturing the packaging bag.

[0011] Fig. 1 is a perspective view showing a packaging bag according to a first embodiment of the present invention. Fig. 2 is a perspective view of the packaging bag shown in Fig. 1 as viewed from a bottom side. Fig. 3 is a plan view showing a folded state of the packaging bag shown in Fig. 1. Fig. 4 is a plan view of the packaging bag shown in Fig. 1 as viewed from the bottom side. Fig. 5(A) is a cross-sectional view showing a first packaging film, and Fig. 5(B) is a cross-sectional view showing a second packaging film. Fig. 6 is a perspective view for explaining a method for manufacturing the packaging bag shown in Fig. 1. Fig. 7 is a perspective view showing a state in which a side gusset portion and a bottom gusset portion of the packaging bag shown in Fig. 1 are overlapped with each other. Fig. 8 is a perspective view showing a state in which peripheral edge portions are bonded to each other by heat seal in the method for manufacturing the packaging bag shown in Fig. 1. Fig. 9 is a perspective view showing a packaging bag according to a second embodiment of the present invention. Fig. 10 is a plan view showing a folded state of the packaging bag shown in Fig. 9.

[0012] In the following, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the drawings used in the following description, in order to make each component easily viewable, scales of dimensions may be different depending on the components, and dimensional ratios and the like of each component are not necessarily the same as actual ones. In addition, materials, dimensions, and the like exemplified in the following description are merely examples, and the present invention is not necessarily limited to them, and are appropriately changeable and implementable without changing the gist of the present invention.

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

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

[0015] As shown in Figs. 1 to 4, the packaging bag 1A of the present embodiment includes a bag body 3 formed by overlapping inner surfaces of a plurality of packaging films 2A and 2B with each other and bonding (heat sealing) peripheral edge portions of the packaging films 2A and 2B to each other by heat fusion (heat seal).

[0016] The bag body 3 includes a pair of flat portions 4 facing each other, a pair of side gusset portions 5 folded inward between the pair of flat portions 4, and a bottom gusset portion 6 folded inward between the pair of flat portions. Among them, the pair of flat portions 4 and the pair of side gusset portions 5 are formed of the first packaging film 2A described later, and the bottom gusset portion 6 is formed of the second packaging film 2B described later.

[0017] The bag body 3 is formed by overlapping the side gusset portion 5 and the bottom gusset portion 6, with the side gusset portion 5 and the bottom gusset portion 6 folded inward between the pair of flat portions 4, and bonding the side peripheral edge portion and the bottom peripheral edge portion to each other.

[0018] In the packaging bag 1A of the present embodiment, the side peripheral edge portions are bonded to each other between the pair of flat portions 4 and the side gusset portions 5 to form the side edge seal portion 7.

[0019] In addition, in the packaging bag 1A of the present embodiment, a bottom edge seal portion 8 is formed by bonding the bottom peripheral edge 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.

[0020] Further, an opening 3a is formed on the upper side of the bag body 3. That is, the peripheral edge portion on the upper side of the bag body 3 is not bonded in an unused folded state, and the contents can be filled from the opening 3a of the bag body 3 into the inside.

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

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

[0023] In the packaging bag 1A of the present embodiment, for example, a user such as a food manufacturer fills the contents inside the bag body 3 from the opening 3a, and then the opening 3a is sealed by bonding the peripheral edge portion on the upper side of the bag body 3 by heat seal.

[0024] As a result, the packaging bag 1A of the present embodiment is distributed as a packaging bag containing contents in which the contents are accommodated in the bag body 3 and the opening 3a is sealed. In addition, the packaging bag 1A of the present embodiment constitutes a self-standable flat bottom bag constituted of five surfaces including the pair of flat portions 4, the pair of side surface portions 5, and the bottom surface portion 6 in a state where contents are accommodated and sealed in the bag body 3.

[0025] Packaging film The bag body 3 includes four pieces of the first packaging films 2A constituting the pair of flat portions 4 and the pair of side gusset portions 5, and one piece of the second packaging film 2B constituting the 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 mono-material film that is a laminated film of a single material in which a base material layer 21, an ink layer 22, an adhesive layer 23 and a heat seal layer 24 are sequentially laminated. In addition, the base material layer 21 forms the outer surface of the bag body 3, and the heat seal layer 24 forms the inner surface of the bag body 3. The mono-material film is preferable in that environmental loads such as the recyclability and the disposal is lowered.

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

[0028] In the present invention, the single material refers to, for example, a packaging film in which a plurality of plastic films is laminated, in which the same resin material is used for the base material layer on the outer surface side and the heat seal layer on the inner surface side. Specifically, the packaging film made of a single material is made of a resin material with only polyethylene, only polypropylene, or only polyester.

[0029] In addition, in the present invention, the same kind of material refers to, for example, a packaging film in which a plurality of plastic films is laminated, in which the same kind of resin material is used for the base material layer on the outer surface side and the heat seal layer on the inner surface side. Specifically, polypropylene is used for the base material layer and polyethylene is used for the heat seal layer, or polybutylene terephthalate is used for the base material layer and polyethylene terephthalate is used for the heat seal layer.

[0030] As described above, for example, a packaging film having the base material layer and the heat seal layer made of the same kind of resin material classified as polyolefin or polyester and not made of the same resin material is referred to as a packaging film made of the same type of material in the present invention.

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

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

[0033] Note that the mono-material rate of the packaging bag is a ratio of single or the same kind of material in terms of mass among the materials to be used.

[0034] In the case in which the mono-material rate of the packaging bag of the present invention is 90% or more, it is possible to satisfy the guideline that "at least 90% of materials constituting flexible packaging containers are mono-material" required by CEFLEX (Circular Industry for Flexible Packaging), which is a consortium (joint entity) aiming at achievement of a circular society in the flexible packaging field in Europe, and it is possible to provide a flexible packaging container of easy material recycling.

[0035] The base material layer 21 is made of at least a plastic film having a melting point higher than that of the heat seal layer 24. In addition, for the base material layer 21, it is preferable to use a plastic film excellent in characteristics such as printability, puncture strength, tensile strength, and impact resistance. Specific examples include plastic films having, as a base material, a synthetic resin material including a polyolefin such as high density polyethylene (HDPE) or polypropylene (PP), or a polyester such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT). Among them, polypropylene is most preferable from the viewpoint of versatility. In addition, the melting point of the polypropylene used for the base material layer is preferably 160°C or higher and 175°C or lower.

[0036] The base material layer 21 may be an oriented film or a non-oriented film. In addition, the base material layer 21 may be a vapor-deposited film in which a metal such as aluminum or magnesium or an oxide such as aluminum oxide or silicon oxide is vapor-deposited on any one surface. In addition, the base material layer 21 may be a coating film in which any one surface is coated with a barrier coating agent such as polyvinylidene chloride.

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

[0038] The ink layer 22 is made of a film-like coating with a coating ink. That is, the ink layer 22 is formed by printing ink on any one surface or both surfaces of the base material layer 21. As the ink, a known printing ink can be used. The ink contains a solvent, a resin, a pigment, and an additive.

[0039] Examples of the method for printing the ink layer 22 include a gravure printing method, an offset printing method, and a flexographic printing method. Among these printing methods, the gravure printing method excellent in color and design reproducibility is suitably used.

[0040] The coating amount of the ink constituting the ink layer 22 per unit area after solvent drying is about 0.3 g / m2to 2.0 g / m2.

[0041] The ink layer 22 is formed by printing characters and figures related to contents, displays such as symbols for decoration and management, patterns serving as backgrounds of these displays, and the like on the base material layer 21. The ink layer 22 may be formed by printing a functional ink such as an antistatic agent on the base material layer 21.

[0042] The adhesive layer 23 is formed using an adhesive that bonds materials constituting the laminated film to each other. Examples of the method for forming the adhesive layer 23 include a dry lamination method, a non-solvent lamination method, and an extrusion lamination method in which a resin material such as polyethylene melted from a T-die is extruded into a film shape and laminated. Among these forming methods, a dry lamination method is suitably used from the viewpoint of adhesive strength.

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

[0044] For the heat seal layer 24, a plastic film having a melting point lower than that of at least the base material layer 21 and capable of heat seal is used. Specifically, examples include a monolayer plastic film made of a polyolefin such as low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene, linear low density polyethylene (LLDPE), or polypropylene, or a polyester such as polyethylene terephthalate having a heat seal property. Note that the polypropylene may be any of a homopolymer, a random copolymer, and a block copolymer. Among them, polypropylene is most preferable as the synthetic resin constituting the heat seal layer 24 from the viewpoint of versatility. In addition, the melting point of the polypropylene used for the heat seal layer is preferably 130°C or higher and lower than 160°C.

[0045] The heat seal layer 24 is preferably the non-oriented film. In addition, the heat seal layer 24 may be a multilayer plastic film of two or more layers obtained by combining and co-extruding the above-described synthetic resin materials.

[0046] The thickness of the heat seal layer 24 is preferably 15 μm to 200 μm, 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 seal layer 24 as necessary. The intermediate layer is made of at least a plastic film having a melting point higher than that of heat seal layer 24.

[0048] The intermediate layer is provided in the case in which it is necessary to impart physical strength such as puncture strength, tensile strength, and impact resistance to the laminated film, or in the case in which gas barrier properties are imparted to the laminated film. In other words, the intermediate layer has a role as a functional layer that imparts a function to the laminated film.

[0049] Examples of the intermediate layer include a plastic film made of a synthetic resin material made of 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). In addition, the intermediate layer may be any of the oriented film or the non-oriented film.

[0050] In addition, the intermediate layer may be, for example, a vapor deposited film on which a metal such as aluminum or magnesium or an oxide such as aluminum oxide or silicon oxide is deposited. In addition, the intermediate layer may be a coating 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] In addition, the intermediate layer may be a multilayer plastic film obtained by combining and co-extruding the above-described synthetic resin materials. That is, the intermediate layer may be one layer or two or more layers.

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

[0053] The coating layer 25 is formed of a coating film with an applied coating agent that prevents blocking. That is, the coating layer 25 is formed by applying a coating agent to the outer surface of the base material layer 21.

[0054] The coating agent preferably has heat resistance at least equal to or higher than the melting point of the base material layer 21. Here, the 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 material layer 21.

[0055] The coating agent preferably has heat resistance at least equal to or higher than the melting point of the heat seal layer 24. In addition, the coating agent more preferably has heat resistance at least equal to or higher than the set temperature of a bag making machine. As a result, this makes it possible to effectively prevent blocking between the base material layers 21 of the gusset portions 5 and 6 due to melting of the resin contained in the coating agent at the time of bag production.

[0056] For the coating layer 25, a known ink for surface printing can be suitably used. Specifically, examples include varnish, medium, and mat ink. In addition, the ink used for the coating layer 25 is not limited to transparent or translucent, and may be colored.

[0057] Similarly to the ink, the coating agent contains a solvent, a resin, a pigment, and an additive. For the coating agent, various solvents generally used in the field of printing ink can be used. Specifically, examples include organic solvents such as methyl ethyl ketone, ethyl acetate, methanol, ethanol, and isopropyl alcohol.

[0058] The resin contained in the coating agent in the present invention is cellulose nitrate (nitrocellulose), polyamide, shellac, epoxy, polyurethane, chlorinated polyolefin, a mixture of silicone and acrylic, or a mixture of silicone and polyamide. With the use of a coating agent containing these resins, it is possible to provide a packaging bag in which the occurrence of blocking is prevented. Among these resins, shellac, a mixture of silicone and polyamide, and cellulose nitrate are preferable from the viewpoint of heat resistance and blocking resistance. In particular, in the coating agent using the cellulose nitrate as the resin, the blocking resistance of the film-to-coating agent and the blocking resistance of the coating agent to coating agent are the most excellent.

[0059] For the coating agent, various inorganic pigments, organic pigments, and the like generally used in the field of printing ink can be used. In addition, for the coating agent, additives such as a curing agent and a dispersant such as a melamine-based curing agent, an epoxy-based curing agent, and an epoxy melamine-based curing agent, an antifoaming agent, a plasticizer, and an antistatic agent can be used as necessary.

[0060] Examples of the method for forming the coating layer 25 include a gravure printing method, an offset printing method, and a flexographic printing method. Among these printing methods, a gravure printing method excellent in color and design reproducibility is preferable.

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

[0062] In addition, the coating layer 25 may be a so-called solid printing, or may be a halftone printing. Note that solid printing means a state in which the coating agent is printed with halftone dots without gaps in a certain area. In addition, the dot area ratio in solid printing is 100%. The halftone printing means a state in which the coating agent has gaps of halftone dots at a constant concentration with respect to a constant area, or a state in which the coating agent is printed as a set of fine dots. In addition, the halftone printing has a dot area ratio of 10% to less than 100%.

[0063] In addition, the coating layer 25 may be printed with a pattern such as a geometric pattern, a lattice pattern, a check pattern, a gradation pattern, or the like. The degree of blocking can be controlled by making the coating layer halftone printed or pattern printed.

[0064] As a result, since the packaging bag 1A is in a weak blocking state immediately after manufactured, the size of the bundle in which the packaging bags 1A are accumulated can be reduced, and the volume efficiency for the cardboard for packaging is improved. Consequently, transportation efficiency is improved.

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

[0066] Meanwhile, when the difference in a melting point between the base material layer 21 and the heat seal layer 24 of the packaging films 2A and 2B constituting the bag body 3 is large, the base material layer 21 is not melted at the time when the heat seal layer 24 is melted in bonding the peripheral edge portions of the packaging films 2A and 2B to each other by heat seal, so that blocking does not occur and quality control of bag production (manufacturing process of packaging bag) is facilitated.

[0067] On the other hand, when the difference in a melting point between the base material layer 21 and the heat seal layer 24 is small, the base material layer 21 also approaches the molten state at the time of the melting heat seal layer 24 at the time of bonding the peripheral edge portions to each other by heat seal, so that the possibility of the occurrence of blocking increases. In addition, the appearance of the bag body 3 is impaired, for example, the seal portions 7 and 8 are thermally contracted or holes are formed in the seal portions 7 and 8.

[0068] In particular, in the case in which the packaging films 2A and 2B are made of a mono-material film, the base material layer and the heat seal layer are made of the identical or the same material, and the melting points of the base material layer 21 and the heat seal layer 24 are close to each other, so that the occurrence of blocking becomes more noticeable.

[0069] On the other hand, the packaging bag 1A of the present embodiment uses the second packaging film 2B provided with the anti-blocking coating layer 25 having heat resistance equal to or higher than that of the base material layer 21 provided in the bottom gusset portion 6 where the overlapping portion S is located.

[0070] As a result, when the inner surfaces of the plurality of packaging films 2A and 2B are overlapped with each other and the peripheral edge portions are bonded to each other by heat seal, it is possible to prevent the outer surfaces of the bottom gusset portions 6 (second packaging films 2B) from melting and adhering to each other.

[0071] That is, in the packaging bag 1A of the present embodiment, even in the case in which the packaging films 2A and 2B are made of a mono-material film, it is possible to prevent the occurrence of blocking with the coating layer 25 provided on the outer surface of the bottom gusset portion 6 (second packaging film 2B).

[0072] Note that the coating layer 25 may be provided on an outer surface at a position corresponding to at least the bottom edge seal portion 8 (bottom peripheral edge portion) of the outer surface of the bottom gusset portion 6 (second packaging film 2B). In addition, the coating layer 25 is preferably provided in a range larger than a range overlapping the bottom edge seal portion 8 in a planar view in consideration of the seal width at the time of heat seal. In the present 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 in the case in which the difference in a melting point between the base material layer 21 and the heat seal layer 24 is 45°C or lower, and the occurrence of blocking is more noticeable in the case in which the difference in a melting point is 20°C or lower.

[0074] Method for manufacturing a packaging bag Next a method for manufacturing the packaging bag 1A will be described with reference to Figs. 6 to 8. Note that Fig. 6 is a perspective view for explaining a method for manufacturing the packaging bag 1A. Fig. 7 is a perspective view showing a state in which the side gusset portion 5 and the bottom gusset portion 6 of the packaging bag 1A are overlapped with each other. Fig. 8 is a perspective view showing a state in which the peripheral edge portions are bonded to each other by heat seal in the method for manufacturing the packaging bag 1A.

[0075] When the packaging bag 1A is manufactured, first, a long first packaging film 2A forming the pair of flat portions 4, a long first packaging film 2A forming the pair of side gusset portions 5, and the second packaging film 2B forming the bottom gusset portion 6 are prepared.

[0076] The coating layer 25 is formed on the outer surface of the second packaging film 2B to be the bottom gusset portion 6 by applying the above-described coating agent that prevents blocking.

[0077] Subsequently, as shown in Fig. 6, the first packaging film 2A serving as the pair of side gusset portions 5 shown in Fig. 7 and the second packaging film 2B serving as the bottom gusset portion 6, which are folded inward and overlapped with each other, are sandwiched between the first packaging films 2A serving as the pair of flat portions 4. In addition, the second packaging film 2B serving as the bottom gusset portion 6 is arranged side by side at a constant interval in the longitudinal direction of the first packaging film 2A serving as the pair of the side gusset portions 5. In addition, the packaging films 2A and 2B are overlapped with each other in a state where the inner surfaces face each other.

[0078] Subsequently, while conveying the overlapped packaging films 2A and 2B in such a state, the peripheral edge portions are bonded to each other by heat seal for each portion to be the bag body 3 using a bag making machine (not shown).

[0079] Specifically, a heat seal bar heated to a predetermined seal temperature is pressed from both surfaces of the first packaging film 2A to be the pair of flat portions 4 along the contour of the portion to be the bag body 3, and then a cooled cooling bar is pressed.

[0080] The portions heated by the heat seal bars are brought into close contact with each other by melting the inner surfaces of the packaging films 2A and 2B.

[0081] As a result, as shown in Fig. 8, the side edge seal portion 7 in which the side peripheral edge portions are bonded to each other is formed between the pair of flat portions 4 and the pair of side gusset portions 5. In addition, 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, the bottom edge seal portion 8 in which the bottom peripheral edge portions are bonded to each other is formed.

[0082] Subsequently, after the heat seal, the packaging films 2A and 2B overlapped with each other are cut in accordance with the shape of the bag body 3 and divided into individual bag bodies 3. Through the above steps, it is possible to collectively manufacture the plurality of packaging bags 1A.

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

[0084] As a result, when the inner surfaces of the plurality of packaging films 2A and 2B are overlapped with each other and the peripheral edge portions are bonded to each other by heat seal, it is possible to prevent the outer surfaces of the bottom gusset portions 6 formed of the second packaging film 2B from melting and adhering to each other.

[0085] In addition, in the method for manufacturing the packaging bag 1A of the present embodiment, even in the case in which the packaging films 2A and 2B are formed of a mono-material film, it is possible to prevent the occurrence of blocking with the coating layer 25 provided on the outer surface of the bottom gusset portion 6 formed of the second packaging film 2B.

[0086] Meanwhile, when the packaging bag 1A is manufactured, as shown in Fig. 8, before or after the step of performing the heat seal described above, heat seal in a spot manner is performed on the bottom peripheral edge portion where the overlapping portion S is located among the peripheral edge portions of the bag body 3 to be heat-sealed to each other.

[0087] That is, since the overlapping portion S constitutes the above-described thickest eight-layered area E4, more thermal energy (temperature, time, pressure) is necessary when the overlapping portion S is heat-sealed.

[0088] Therefore, when the packaging bag 1A is manufactured, point sealing having a higher pressure per unit area than when the heat seal bar is pressed is performed on the four boundaries P of the eight-layered area E4 and the four-layered areas E2 and E3 in the bottom peripheral edge portion of the bag body 3.

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

[0090] Note that the shape of the point seal portion 9 may be, for example, any of a circle, an ellipse, and a polygon. On the other hand, the point seal portion 9 preferably has a size that fits at least the width of the heat sealed portion of the peripheral edge portion.

[0091] When the point seal portion 9 protrudes from the bottom edge seal portion 8, not only the appearance is deteriorated, but also a crack is generated in the heat seal layer 24 starting from the outer edge of the point seal portion 9, and sufficient sealabilities may not be maintained.

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

[0093] On the other hand, in the method for manufacturing the packaging bag 1A of the present embodiment, even in the case in which point sealing is performed on the boundary P described above, it is possible to prevent the occurrence of blocking with the coating layer 25 provided on the outer surface of the bottom gusset portion 6 formed of the second packaging film 2B. Accordingly, it is possible to manufacture the high-quality packaging bag 1A having an excellent appearance.

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

[0095] Note that Fig. 9 is a perspective view showing the packaging bag 1B. Fig. 10 is a plan view showing a folded state of the packaging bag 1B. In addition, in the following description, a description of a portion equivalent to the packaging bag 1A is omitted, and the same reference numerals are given in the drawings.

[0096] As shown in Figs. 9 and 10, in the packaging bag 1B of the present embodiment, in the folded state of a bag body 3, an overlapping portion S of a side gusset portion 5 folded inward between a pair of flat portions 4 and a bottom gusset portion 6 is folded into the side portion side.

[0097] In addition, in the packaging bag 1B of the present embodiment, the bag body 3 includes three first packaging films 2A constituting the pair of flat portions 4 and the bottom gusset portion 6, and two second packaging films 2B constituting the pair of side gusset portions 5.

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

[0099] The packaging bag 1B of the present embodiment uses the second packaging film 2B in which the above-described anti-blocking coating layer 25 is provided in the side gusset portion 5 where the overlapping portion S is located.

[0100] As a result, when the inner surfaces of the plurality of packaging films 2A and 2B are overlapped with each other and the peripheral edge portions are bonded to each other by heat seal, it is possible to prevent the outer surfaces of the side gusset portions 5 formed of the second packaging film 2B from melting and adhering to each other.

[0101] In addition, in the packaging bag 1B of the present embodiment, even in the case in which the packaging films 2A and 2B are formed of a mono-material film, it is possible to prevent the occurrence of blocking with the coating layer 25 provided on the outer surface of the side gusset portion 5 formed of the second packaging film 2B.

[0102] Method for manufacturing a packaging bag Next, since the method for manufacturing the packaging bag 1B is basically the same as the method for manufacturing the packaging bag 1A, the description will be omitted.

[0103] In the method for manufacturing the packaging bag 1B of the present embodiment, the second packaging film 2B in which the above-described coating layer 25 that prevents blocking is provided in the side gusset portion 5 where the above-described overlapping portion S is located is used.

[0104] As a result, when the inner surfaces of the plurality of packaging films 2A and 2B are overlapped with each other and the peripheral edge portions are bonded to each other by heat seal, it is possible to prevent the outer surfaces of the side gusset portions 5 formed of the second packaging film 2B from melting and adhering to each other.

[0105] In addition, in the method for manufacturing the packaging bag 1B of the present embodiment, even in the case in which the packaging films 2A and 2B are made of a mono-material film, it is possible to prevent the occurrence of blocking with the coating layer 25 provided on the outer surface of the side gusset portion 5 formed of the second packaging film 2B.

[0106] When the packaging bag 1B is manufactured, point sealing is performed on the four boundaries P of the eight-layered area E4 and the four-layered areas E2 and E3 in the side peripheral edge portion of the bag body 3.

[0107] As a result, in the packaging bag 1B of the present embodiment, as shown in Fig. 10, it is possible to enhance the adhesion of the point seal portion 9 that is a position corresponding to the boundary P in the side edge seal portion 7 formed in the bag body 3.

[0108] Therefore, in the method for manufacturing the packaging bag 1B of the present embodiment, even in the case in which point sealing is performed on the boundary P described above, it is possible to prevent the occurrence of blocking with the coating layer 25 provided on the outer surface of the side gusset portion 5 formed of the second packaging film 2B. As a result, it is possible to manufacture the high-quality packaging bag 1B excellent in appearance.

[0109] Note that the present invention is not necessarily limited to the embodiments described above, and various modifications can be made without deviating from the gist of the present invention.

[0110] For example, in the packaging bags 1A and 1B, the second packaging film 2B is used for any one of the side gusset portion 5 and the bottom gusset portion 6, but the second packaging film 2B may be used for both the side gusset portion 5 and the bottom gusset portion 6.

[0111] In addition, the packaging bags 1A and 1B are configured to include the pair of side gusset portions 5 and the bottom gusset portion 6, but the present invention is also applicable to a packaging bag including only one of the side gusset portion 5 and the bottom gusset portion 6.

[0112] In addition, in the packaging bags 1A and 1B, a mono-material film is used for the packaging films 2A and 2B, but the present invention is not limited to such a configuration, and the present invention is also applicable to a packaging bag in which the above-described blocking easily occurs. That is, the packaging films 2A and 2B are not limited to those formed of a laminated film of a single material, and the present invention can be suitably used in the case in which the packaging films 2A and 2B having a small difference in a melting point between the base material layer 21 and the heat seal layer 24, such as a laminated film of the same kind of material, are used.

[0113] In the following, the effects of the present invention will be more apparent from Examples. Note that the present invention is not limited to the following examples, and can be appropriately modified without changing the gist of the present invention.

[0114] Example 1 In Example 1, first, as a first packaging film, an ink layer was formed by printing on one surface of a base material layer made of biaxially oriented polypropylene having a thickness of 20 μm, and then a mono-material film having a thickness of about 64 μm was prepared by bonding the ink layer to a heat seal layer made of non-oriented polypropylene having a thickness of 40 μm using a polyurethane-based two-component curable adhesive for dry lamination on the ink layer.

[0115] As a second packaging film, XGS-3622OP varnish NT (main agent) / No. 5000 (curing agent) manufactured by SAKATA INX CO., LTD., in which a resin component was cellulose nitrate, was applied as a coating agent to the outer surface of the first packaging film, thus preparing a mono-material film on which a coating layer was formed.

[0116] Subsequently, a first packaging film forming the pair of flat portions 4, a first packaging film forming the pair of side gusset portions, and a second packaging film forming the bottom gusset portion were prepared, and then the side gusset portion and the bottom gusset portion were folded inward and overlapped between the pair of flat portions, and the side peripheral edge portion and the bottom peripheral edge portion were bonded to each other by heat seal, thus preparing a bag body.

[0117] At this time, the widths of the side edge seal portion and the bottom edge seal portion of the bag body were set to 5 mm, and the temperature of the heat seal bar in the bag making machine was set to 170°C. Note that the base material layer has a melting point of 172°C, the heat seal layer has a melting point of 135°C, and the difference between the melting points is 37°C.

[0118] In addition, in the bag body, since the overlapping portion of the side gusset portion and the bottom gusset portion folded inward between the pair of flat portions is folded toward the bottom side, point sealing was performed on four boundaries between the eight-layered area and the four-layered area among the bottom peripheral edge portion of the bag body before the above-described heat seal step. A packaging bag of Example 1 was prepared through the above steps.

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

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

[0121] Comparative Example 1 In Comparative Example 1, a packaging bag was prepared under the same conditions as in Example 1 except that the second packaging film in which the coating layer was not provided at the bottom gusset portion was used.

[0122] Comparative Example 2 In Comparative Example 2, first, as a packaging film, an ink layer was formed on one surface of a base material layer made of polyethylene terephthalate having a thickness of 12 μm by printing, and then a laminated film was prepared in which an intermediate layer made of low-density polyethylene having a thickness of 15 μm and a heat seal layer made of non-oriented polypropylene having a thickness of 40 μm were laminated in this order.

[0123] Subsequently, a packaging film for forming a pair of flat portions, a pair of side gusset portions, and a bottom gusset portion was prepared, and then the side gusset portion and the bottom gusset portion were overlapped with the side gusset portions and the bottom gusset portion folded inward between the pair of flat portions, and the side peripheral edge portions and the bottom peripheral edge portions were bonded to each other by heat seal.

[0124] At this time, the widths of the side edge seal portion and the bottom edge seal portion were set to 5 mm, and the temperature of the heat seal bar in the bag making machine was set to 170°C. Note that the base material layer has a melting point of 240°C, the heat seal layer has a melting point of 135°C, and the difference between the melting points is 105°C.

[0125] As a result, a packaging bag including a bag body in which an overlapping portion of a side gusset portion and a bottom gusset portion folded inward between a pair of flat portions was folded toward a bottom side was prepared.

[0126] Subsequently, an evaluation test for the occurrence of blocking was performed on the packaging bags of Example 1 to 3 and Comparative Examples 1 and 2.

[0127] In this evaluation test, a tensile strength test in accordance with "JIS Z0238" was performed on the overlapping portion of each packaging bag, and the tensile strength was measured. As for the measurement results, in the case in which the tensile strength was less than 3.0 N / 15 mm, it was determined as "no blocking", and in the case in which the tensile strength was 3.0 N / 15 mm or more, it was determined as "blocking".

[0128] As a result, the packaging bag of Example 1 exhibited a good result without the occurrence of blocking. In addition, the packaging bags of Examples 2 and 3 exhibited good results without the occurrence of blocking.

[0129] Note that in the packaging bag of Example 1, no abnormality was observed in the coating film itself of the coating layer after the evaluation test for the occurrence of blocking. In the packaging bag of Example 2, it was found that a part of the coating layer was peeled off from the second packaging film after the test. The packaging bag of Example 3 was slightly blocked as compared with Examples 1 and 2. Among Example 1 to 3, Example 1 was the most excellent in terms of blocking resistance and stability of the coating layer.

[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 a melting point between the base material layer and the heat seal layer was large, and blocking did not occur.

[0132] The mono-material rate of the packaging bag of Example 1 to 3 and Comparative Example 1 was about 92%, which met the CEFLEX guideline of 90%, whereas the mono-material rate of the packaging bag of Comparative Example 2 was about 72%, which did not meet the CEFLEX guideline.List of Reference Signs

[0133] 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 Ink layer 23 Adhesive layer 24 Heat seal layer 25 Coating layer S Overlapping portion P Boundary

Claims

1. A packaging bag comprising a bag body formed by overlapping inner surfaces of packaging films made of a laminated film of one or a same kind of material and bonding peripheral edge portions of the inner surfaces to each other by heat seal, wherein the packaging film includes a base material layer that forms an outer surface of the bag body and a heat seal layer that forms an inner surface of the bag body, the bag body includes a pair of flat portions facing each other and a gusset portion folded inward between the pair of flat portions, and the gusset portion is formed of a packaging film in which a coating layer containing a resin component selected from cellulose nitrate, polyamide, shellac, epoxy, polyurethane, chlorinated polyolefin, a mixture of silicone and acrylic, or a mixture of silicone and polyamide is provided on an outer surface at least at a position corresponding to the peripheral edge portion.

2. The packaging bag according to claim 1, wherein the gusset portion is provided on a side portion and a bottom portion of the bag body, the bag body is configured such that a side gusset portion and a bottom gusset portion are overlapped, with the side gusset portion and the bottom gusset portion folded inward between the pair of flat portions, and the side peripheral edge portion and the bottom peripheral edge portion are bonded to each other, and the coating layer is provided on an outer surface of the packaging film at a position corresponding to at least the side peripheral edge portion or the bottom peripheral edge portion on a side where the side gusset portion and the bottom gusset portion overlap each other between the pair of flat portions.

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

4. The packaging bag according to claim 1, wherein a difference in a melting point between the base material layer and the heat seal layer having a melting point lower than the base material layer is 45°C or less.

5. The packaging bag according to any one of claims 1 to 4, wherein a content is accommodated inside the bag body.

6. A method for manufacturing the packaging bag according to any one of claims 1 to 4, wherein the method comprising the steps of: providing the coating layer on an outer surface of the gusset portion at a position corresponding to at least the peripheral edge portion; and overlapping the gusset portions between the pair of flat portions in a state where the gusset portions are folded inward to bond the peripheral edge portions to each other by heat seal.

7. The method for manufacturing the packaging bag according to claim 6, further comprising the step of overlapping the gusset portions between the pair of flat portions with the gusset portions folded inward to heat-fuse the gusset portions in a spot manner with respect to a peripheral edge portion to be heat-sealed to each other.

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