Heat sealing agent, packaging material containing the heat sealing agent, and packaging bag

Abstract

To provide a heat sealant contained in a wrapping material of a packaging bag excellent in air-tightness, in addition, to provide a wrapping material containing such a heat sealant, and a method for preparing the packaging material, furthermore, a method for preparing a packaging bag prepared from the wrapping material, and a method for preparing the packaging bag.SOLUTION: A heat sealant of the present invention contains a heat sealant and foaming particles in a mass ratio of 90 / 10-30 / 70. Further, a packaging material of the present invention includes a heat sealing layer containing the heat sealant and a base material. The method for preparing a packaging material of the present invention includes a preparation step for preparing a heat sealing layer coating liquid containing the heat sealant, and a coating process for coating on a substrate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heat-sealing agent, a packaging material including the heat-sealing agent, and a method for producing the packaging material.The present invention also relates to a packaging bag produced from the packaging material, and a method for producing the packaging bag. [Background technology]

[0002] In recent years, efforts have been actively made to reduce the amount of plastic used, which has a significant impact on the environment. For example, Patent Document 1 discloses a packaging material (packaging paper) in which a predetermined amount of a coating liquid for a heat seal layer containing an ionomer or the like is applied to at least one side of a paper substrate having an opacity of 75% or less. According to the configuration of Patent Document 1, it is said that the amount of plastic used in the heat seal layer is reduced, and a packaging material with good heat sealability can be obtained.

[0003] 8 is a schematic cross-sectional view of a conventional packaging material (packaging material composed of a heat seal layer and a substrate) similar to the packaging material (wrapping material) described in Patent Document 1. As shown in FIG. 8, packaging material 100 includes a paper substrate 101 and a heat seal layer 102.

[0004] For example, a two-handled bag 103 as shown in Fig. 9(a) is generally produced by heat sealing (thermocompression bonding) a packaging material 100. When the two-handled bag 103 is produced using the packaging material 100, a back-attached portion 104 and a bottom-attached portion 105 are formed in the two-handled bag 103 as shown in Fig. 9(a). The back-attached portion 104 is a portion where one end and the other end of the packaging material 100 are shaped into a tube and attached together. The bottom-attached portion 105 is a portion where the opening at the bottom end or top end of the packaging material 100 is attached together.

[0005] At the back-attached portion 104 and the bottom-attached portion 105, two sheets of the packaging material 100 are overlapped. Therefore, if the adhesion between the packaging material 100 at the back-attached portion 104 and the bottom-attached portion 105 is weak, the sealability of the two-sided bag 103 cannot be ensured. In particular, the overlapping portion 106 (the portion surrounded by a solid line in FIG. 9(a)) where the back-attached portion 104 and the bottom-attached portion 105 overlap is a portion where four sheets of packaging material overlap. The cross section of the overlapping portion 106 as viewed from a direction parallel to the longitudinal direction of the bottom-attached portion 105 is shown in FIG. 9(b) as a schematic diagram. As shown in FIG. 9(b), the packaging material 100 is more overlapped at the overlapping portion 106 than at other portions, so that a gap 107 (the portion with dense hatching in FIG. 9(b)) is likely to occur. The presence of the gap 107 in the two-sided bag 103 means that the sealability of the two-sided bag 103 is not ensured. For this reason, the two-handled bag 103 is easily torn, or there is a risk that the contents stored in the two-handled bag 103 may leak out.

[0006] A different type of packaging bag from the two-sided bag 103 is a gusset bag 110 shown in Fig. 10(a). As shown in Fig. 10(a), like the two-sided bag 103, the gusset bag 110 has a back-attached portion 111 and a bottom-attached portion 112. The gusset bag 110 also has fold-in portions 113 from the top to the bottom on both sides. Note that Fig. 10(a) shows the back-attached portion 111, bottom-attached portion 112, fold-in portion 113, and overlapping portion 114 (described below) from the entire gusset bag 110.

[0007] The gusset bag 110 may also have the same problem as the above-mentioned two-piece bag 103. That is, a cross section of an overlapping portion 114 (encircled by a solid line in FIG. 10(a)) where the bottom bonding portion 112 and the fold-in portion 113 overlap in a direction parallel to the longitudinal direction of the bottom bonding portion 112 is shown in FIG. 10(b) as a schematic diagram. As shown in FIG. 10(b) , four packaging materials overlap at the overlapping portion 114 where the bottom bonding portion 112 and the fold-in portion 113 overlap. Gaps 115 (densely hatched portion in FIG. 10(b)) are likely to occur in this overlapping portion, and therefore the sealability of the gusset bag 110 cannot be ensured. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2022-160165 A Summary of the Invention [Problem to be solved by the invention]

[0009] In view of the above problems, the present invention aims to provide a heat sealant capable of producing a packaging material for a packaging bag having excellent sealing properties. It also aims to provide a packaging material containing such a heat sealant and a method for producing the packaging material. It also aims to provide a packaging bag produced from the packaging material and a method for producing the packaging bag. [Means for solving the problem]

[0010] A first aspect of the present invention relates to a heat-sealing agent. The heat-sealing agent according to this aspect contains a heat-sealing material and expandable particles in a mass ratio of heat-sealing material / expandable particles=90 / 10 to 30 / 70.

[0011] The heat-sealing agent according to this embodiment contains the heat-sealing material and the expandable particles in a mass ratio within the range described above. As a result, when the heat-sealing agent is heated, the expandable particles expand appropriately and increase in volume. As a result, the packaging bag made from the packaging material containing the heat-sealing agent of the present invention is prevented from having gaps at the overlapping portions of the packaging material. As a result, the packaging bag has excellent sealing properties.

[0012] In the heat sealant according to this embodiment, the maximum expansion diameter of the expandable particles is preferably 35 to 130 μm. This allows the expandable particles to expand appropriately when a predetermined temperature is applied to the heat sealant. Therefore, the packaging bag made from the packaging material containing the heat sealant of the present invention is more prevented from generating gaps at the overlapping portions of the packaging material. As a result, the packaging bag has excellent sealing properties.

[0013] In the heat sealant according to this embodiment, the maximum expansion temperature of the expandable particles is preferably 110 to 220°C. When such expandable particles are contained in the heat sealant, the expandable particles expand appropriately. This makes it easier for the expandable particles to expand when the heat sealant is heated. Therefore, in a packaging bag made from a packaging material containing the heat sealant of the present invention, the occurrence of gaps in the overlapping portions of the packaging material is further suppressed. As a result, a packaging bag with excellent sealing properties is obtained.

[0014] The second aspect of the present invention relates to a packaging material. The packaging material according to this aspect includes a heat seal layer containing any one of the heat seal agents described above, and a substrate. The packaging material according to this aspect has the same effect as the first aspect. In this case, the substrate is preferably paper. Thus, the substrate of the packaging material according to this aspect is preferably paper, not plastic. Therefore, the amount of plastic used can be reduced.

[0015] The third aspect of the present invention relates to a method for producing a packaging material comprising a heat seal layer containing any one of the heat seal agents described above and a substrate. The method for producing a packaging material according to this aspect includes a preparation step for preparing a heat seal layer coating liquid containing a heat seal agent, and a coating step for coating the heat seal layer coating liquid on the substrate. The method for producing a packaging material according to this aspect has the same effects as those of the first and second aspects.

[0016] The fourth aspect of the present invention relates to a packaging bag. The packaging bag according to this aspect is obtained by thermocompression bonding a layer containing a heat-sealing agent of a packaging material including a layer containing any one of the heat-sealing agents described above and a substrate. The packaging material according to this aspect has the same effects as the first to third aspects.

[0017] In this case, the packaging bag preferably has a portion where the packaging material overlaps. In this way, the packaging bag according to the present embodiment has excellent sealing properties even if the packaging material has a portion where the packaging material overlaps.

[0018] A fifth aspect of the present invention relates to a method for producing a packaging bag. The method for producing a packaging bag according to this aspect includes a thermocompression bonding step of thermocompressing the packaging material described above. The method for producing a packaging bag according to this aspect provides the same effects as the first to fourth aspects. Effect of the Invention

[0019] According to the present invention, a heat seal agent capable of producing a packaging material for a packaging bag having excellent sealing properties can be obtained. It is also possible to provide a packaging material containing such a heat seal agent and a method for producing the packaging material. It is also possible to provide a packaging bag produced from the packaging material and a method for producing the packaging bag. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a schematic configuration of a packaging material according to an embodiment. [Diagram 2] FIG. 2 is a flow chart showing a process for producing a packaging bag according to an embodiment. [Diagram 3] Fig. 3(a) is a perspective view of a two-pronged bag made from a packaging material according to an embodiment, and Fig. 3(b) is a schematic cross-sectional view of the part surrounded by a solid line in Fig. 3(a) as viewed from a direction parallel to the longitudinal direction of the bottom pasting part. [Figure 4] Fig. 4(a) is a perspective view of a gusset bag having a bottom-pasted portion and a folded-in portion, which is made from a packaging material according to an embodiment. Fig. 4(b) is a schematic diagram showing a cross section of the portion surrounded by a solid line in Fig. 4(a), as viewed from a direction parallel to the longitudinal direction of the bottom-pasted portion. [Diagram 5] FIG. 5 is a graph showing the relationship between the temperature and the volume change rate of the expandable particles contained in the heat sealing agent according to the embodiment. [Figure 6] 6(a) to (d) are optical microscope photographs of the cross section showing the state of the overlapping portion between the back and bottom adhesive portions of the two-piece bags (Examples) for Tests 2 to 5, respectively. [Figure 7] 7(a) and (b) are optical microscope photographs of the cross section showing the state of the overlapping portion between the back and bottom adhesive portions of the two-piece bags of Comparative Examples 1 and 2, respectively. [Figure 8] FIG. 8 is a cross-sectional view that illustrates a schematic configuration of a conventional packaging material. [Figure 9] 9(a) and 9(b) are diagrams relating to a conventional packaging material. Fig. 9(a) is a perspective view of a two-pronged bag made from the conventional packaging material. Fig. 9(b) is a schematic diagram showing a cross section of the part surrounded by a solid line in Fig. 9(a) as viewed from a direction parallel to the longitudinal direction of the bottom pasting part. [Figure 10] Figures 10(a) and 10(b) are diagrams relating to a conventional packaging material. Figure 10(a) is a perspective view of a gusset bag made from the conventional packaging material. Figure 10(b) is a schematic diagram showing a cross section of the part surrounded by a solid line in Figure 10(a) as viewed from a direction parallel to the longitudinal direction of the bottom pasting part. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] As described above, the present invention relates to a packaging bag having excellent sealing properties. First, an outline of the packaging bag according to the present invention will be described with reference to Figs. 1 to 4(b).

[0022] FIG. 1 is a cross-sectional view showing a schematic configuration of a packaging material 1 that is mainly applied to packaging bags. FIG. 2 is a flow showing a manufacturing process of a packaging bag. FIG. 3(a) and (b) are diagrams for explaining a two-hand bag 10 when the packaging bag is a two-hand bag type. FIG. 3(a) is a perspective view showing the configuration of the two-hand bag 10, and FIG. 3(b) is a diagram showing a schematic cross section of the part surrounded by a solid line in FIG. 3(a) when viewed from a direction parallel to the longitudinal direction of the bottom-attached part 12. FIG. 4(a) and (b) are diagrams for explaining a gusset bag 20 when the packaging bag is a gusset bag type. FIG. 4(a) is a perspective view showing the configuration of the gusset bag 20, and FIG. 4(b) is a diagram showing a schematic cross section of the part surrounded by a solid line in FIG. 4(a) when viewed from a direction parallel to the longitudinal direction of the bottom-attached part 22. Note that the flow in FIG. 2 shows only the steps related to this embodiment, and detailed steps are omitted. In addition, the gusset bag 20 shown in FIG. 4(a) is illustrated with respect to the back affixed portion 21, the bottom affixed portion 22, the fold-in portion 23, and the overlapping portion 24 from the entirety.

[0023] As shown in Fig. 1, a packaging material 1 applied to the packaging bag according to this embodiment includes a heat seal layer 2 and a base material 3. Then, as shown in the flow of Fig. 2, the packaging bag is produced through a preparation step, a coating step, and a thermocompression bonding step.

[0024] The preparation process in Fig. 2 is a process for preparing a heat-seal layer coating liquid for forming the heat-seal layer 2 of the packaging material 1 shown in Fig. 1. Specifically, a heat-sealing agent is prepared so that the heat-sealing material and the expandable particles have an appropriate mass ratio, and then a heat-sealing layer coating liquid containing this heat-sealing agent is prepared.

[0025] The mass ratio of the heat-sealing material to the expandable particles in the heat-sealing agent is very important in this embodiment, as will be described in detail later.

[0026] In the coating step, the heat seal layer coating liquid prepared in the preparation step is applied to the substrate 3. Through these steps, the packaging material 1 is obtained.

[0027] The thermocompression bonding process is a process for producing a packaging bag of a desired shape using the packaging material 1 obtained in the coating process. Examples of the types of packaging bags include a two-sided bag 10 shown in Fig. 3(a) and a gusset bag 20 shown in Fig. 4(a).

[0028] When producing the two-sided bag 10 shown in Fig. 3(a), the two-sided bag 10 is formed with a back affixed portion 11, a bottom affixed portion 12, and an overlapping portion 13 of the back affixed portion 11 and the bottom affixed portion 12, in the same manner as described with reference to Fig. 9(a). The packaging material 1 overlaps in all of these portions. For this reason, if the packaging materials 1 in the back affixed portion 11 and the bottom affixed portion 12 are not securely in contact with each other, the resulting packaging bag will have poor sealing properties. In particular, because four sheets of packaging material 1 overlap in the overlapping portion 13, a gap 107 as shown in Fig. 9(b) is likely to occur as in the conventional case.

[0029] The inventors of the present application thought that if the expandable particles contained in the heat sealant expand when the overlapping portions of the packaging materials 1 are thermocompression-bonded to form the back-bonding portion 11, the bottom-bonding portion 12, and the overlapping portion 13, the expandable particles will evenly fill the gaps between the packaging materials 1. As a result, they discovered that the gaps 107 shown in Fig. 9(b) and the gaps 115 shown in Fig. 10(b) are suppressed in the overlapping portions of the packaging materials 1. In other words, the expandable particles are appropriately expanded by thermocompression bonding, so that the packaging materials 1 come into close contact with each other with the occurrence of gaps suppressed, as shown in Fig. 3(b). As a result, a two-handled bag 10 with excellent sealing properties is obtained.

[0030] The same is true for the production of the gusset bag 20 in Fig. 4(a). That is, similarly to what has been described with reference to the gusset bag 110 in Fig. 10(a), the gusset bag 20 is formed with a back affixed portion 21, a bottom affixed portion 22, a fold-in portion 23, and an overlapping portion 24 of the bottom affixed portion 22 and the fold-in portion 23. In the gusset bag 110, when gaps are generated due to overlapping of the packaging materials 100, the adhesion between the packaging materials 100 is weakened, and for example, a gap 115 as shown in Fig. 10(b) is generated.

[0031] However, as described above, when the expandable particles contained in the heat sealing agent are expanded by thermocompression, the packaging materials 1 are tightly adhered to each other with the occurrence of gaps suppressed, as shown in Figure 4(b), and a gusseted bag 20 with excellent sealing properties is obtained.

[0032] The gusset bag 20 also has an overlapping portion between the back lining 21 and the bottom lining 22. This portion is similar to the overlapping portion 13 of the two-handled bag 10 in Figures 3(a) and (b), so a description thereof will be omitted. In this embodiment, attention is focused on the overlapping portion 24 as a characteristic portion of the gusset bag 20 that is not present in the two-handled bag 10.

[0033] Hereinafter, with regard to packaging material 1 that is preferably applied to a packaging bag having excellent sealing properties, first, a heat seal agent contained in a heat seal layer constituting packaging material 1 that the inventors of the present application focused on will be described, and then the packaging material 1 and the production of packaging material 1 will be described. After that, a packaging bag produced from packaging material 1 and a method for producing the packaging bag will be described.

[0034] <Heat sealant> As shown in Fig. 1, the packaging material 1 includes a heat seal layer 2 and a substrate 3. The heat seal layer 2 includes a heat seal agent. The heat seal agent includes a heat seal material and expandable particles. The inventors of the present application have found that by appropriately adjusting the blending ratio of the heat seal material and the expandable particles in the heat seal agent, the occurrence of gaps (see Figs. 9(b) and 10(b)) in a packaging bag made from the packaging material 1 can be suppressed.

[0035] The blending ratio of the heat seal material and the expandable particles in such a heat seal agent is 90 / 10 to 30 / 70 by mass ratio. If the mass ratio of the heat seal material and the expandable particles is adjusted to be within this range, the expandable particles will expand appropriately. Then, in the production of a packaging bag, when the overlapping parts of the packaging materials 1 are heat-pressed (the heat-pressing step in FIG. 2), the expandable particles contained in the heat seal agent will expand appropriately. This suppresses the occurrence of gaps in the overlapping parts of the packaging materials 1 in the two-sided bag 10 (packaging bag) (see FIG. 3(a)). In particular, the occurrence of gaps is suppressed even in the overlapping part 13 where four packaging materials 1 are overlapped and gaps are likely to occur (see FIG. 3(b)). The same is true for the back affixed part 21, bottom affixed part 22, and overlapping part 24 of the gusset bag 20 (packaging bag) shown in FIG. 4(a) (see FIG. 4(b)).

[0036] If the ratio of expandable particles to the heat seal material is less than 90 / 10 by mass, the amount of expandable particles is small, so even if the overlapping parts of the packaging material 1 are heat-pressed and the expandable particles expand, it is not possible to uniformly densely seal the overlapping parts of the packaging material 1 in the two-piece bag 10.

[0037] On the other hand, if the ratio of expandable particles to the heat-sealing material is greater than 30 / 70 by mass, the heat-sealing layer coating liquid prepared by mixing the expandable particles and the heat-sealing material is likely to become gel-like. This is thought to be because the amount of expandable particles is excessive, making it difficult for the expandable particles to stably disperse in the heat-sealing layer coating liquid. Thus, if the ratio of expandable particles to the heat-sealing material is greater than 30 / 70 by mass, the heat-sealing layer coating liquid becomes unstable (gel-like), making it difficult to produce the packaging material 1 itself.

[0038] When heat is applied to the expandable particles, the expandable particles expand, and the diameter at that time has a unique value for each expandable particle. This is the so-called "maximum expansion diameter." The maximum expansion diameter of the expandable particles contained in the heat seal layer 2 (i.e., the layer containing the heat seal agent) of this embodiment is preferably in the range of 35 to 130 μm. If the maximum expansion diameter is smaller than 35 μm, when the overlapping portions of the packaging materials 1 are thermocompressed (thermocompression bonding step in FIG. 2), the expandable particles expand, but the expansion diameter may not be sufficient, making it difficult to sufficiently fill the gaps between the packaging materials 1 (see FIG. 9(b) and FIG. 10(b)).

[0039] On the other hand, if the maximum foaming diameter is greater than 130 μm, the foamable particles may expand more than necessary during the thermocompression process of FIG. 2, making it difficult to properly bond the packaging materials 1 together, and making it difficult to produce the desired packaging bag (such as the two-handled bag 10 and the gusseted bag 20).

[0040] Furthermore, the temperature at which the expandable particles reach the above-mentioned maximum expansion diameter (hereinafter referred to as the "maximum expansion temperature" in this specification) is preferably 110 to 220°C. When the maximum expansion temperature is in this range, the expandable particles expand more appropriately to the maximum expansion diameter. If the maximum expansion temperature is lower than 110°C, when the overlapping parts of the packaging material 1 are thermocompression-bonded (thermocompression bonding step in FIG. 2), the expandable particles will expand, but the maximum expansion diameter may not be sufficient, making it difficult to fill the gaps between the packaging materials 1 (see FIG. 9(b) and FIG. 10(b)).

[0041] On the other hand, if the maximum expansion temperature is higher than 220°C, the expandable particles can expand to the maximum expansion diameter, but the temperature may be too high and the expandable particles may become unstable. Therefore, even if the thermocompression bonding step (see FIG. 2) is performed, it may be difficult to produce a packaging bag from the packaging material 1.

[0042] The expandable particles contained in the heat sealing agent may be commercially available. For example, in this embodiment, EXPANCEL 031-DU40 (maximum expansion diameter is φ40 μm), EXPANCEL 909-DU80 (maximum expansion diameter is φ80 μm), EXPANCEL 930-DU120 (maximum expansion diameter is φ120 μm), and EXPANCEL 551-DU40 (maximum expansion diameter is φ50 μm) manufactured by Nippon Phillite Co., Ltd. are used. However, it is not limited to these, and it is preferable to use appropriate expandable particles. In addition, the average diameter of EXPANCEL 551-DU40 when expanded is φ30 to 50 μm. For this reason, the maximum expansion diameter is set to φ50 μm.

[0043] Fig. 5 is a graph showing the relationship between the temperature and the volume change rate of the expandable particles manufactured by Nippon Phillite Co., Ltd. used in this embodiment. The graph in Fig. 5 shows the relationship between the temperature and the volume change rate of four types of expandable particles, EXPANCEL 031-DU40, EXPANCEL 551-DU40, EXPANCEL 909-DU80, and EXPANCEL 930-DU120. The graph in Fig. 5 is quoted from the catalog of Expancel Microsphere published by Nippon Phillite Co., Ltd. in January 2013.

[0044] Here, when each expandable particle has the maximum volume, it is when the volume change rate of each expandable particle is the largest. Therefore, when checking the graph of Fig. 5, the temperature when the volume change rate of each of the four expandable particles is the maximum is about 125°C for EXPANCEL 031-DU40, about 140°C for EXPANCEL 551-DU40, about 180°C for EXPANCEL 909-DU80, and about 200°C for EXPANCEL 930-DU120. In other words, each expandable particle has the maximum expansion diameter when it reaches the above-mentioned temperature.

[0045] As described above, the expandable particles in this embodiment preferably have a maximum expansion diameter of 35 to 130 μm and a maximum expansion temperature of 110 to 220° C. The maximum expansion diameters and maximum expansion temperatures of the four expandable particles, EXPANCEL 031-DU40, EXPANCEL 551-DU40, EXPANCEL 909-DU80, and EXPANCEL 930-DU120, described with reference to the graph in Fig. 5, are within the above-mentioned preferred numerical ranges. Therefore, the above-mentioned four expandable particles can be more preferably used in this embodiment.

[0046] The heat seal material is not particularly limited as long as it is a heat-sealable polymer, and examples thereof include any desired polymer component such as olefin polymers, vinyl acetate ethylene, polyvinyl acetate, polyvinyl acetate polyvinyl alcohol, dextrin-stabilized polyvinyl acetate, polyvinyl acetate copolymers, vinyl acetate ethylene copolymers, vinyl acrylic resins, styrene acrylic resins, acrylic resins, styrene butyl rubber, polyurethane, and mixtures thereof.

[0047] Various additives may be added to the heat-sealing agent in which the blending ratio of the heat-sealing material and the expandable particles is adjusted. Examples of additives include antioxidants, ultraviolet absorbers, lubricants, drying agents, wetting agents, surfactants, dispersants, and waxes. These additives may be used alone or in combination of two or more. In this way, a heat-sealing layer coating liquid for forming the heat-sealing layer 2 of the packaging material 1 shown in FIG. 1 is prepared.

[0048] <Packaging materials and packaging material production> Next, a packaging material 1 containing the heat-sealing agent will be described. As described with reference to Fig. 1, the packaging material 1 includes a heat-sealing layer 2 and a substrate 3. The heat-sealing layer 2 is formed by applying a heat-sealing layer coating liquid containing the heat-sealing agent prepared in a preparation step to the substrate 3 in a coating step.

[0049] Examples of the substrate 3 include paper substrates such as fine paper, recycled paper, one-sided glossy paper, greaseproof paper, coated paper, art paper, kraft paper, glassine paper, and cass coated paper.

[0050] The amount of the heat seal layer coating liquid to be applied is appropriately adjusted depending on the shape and size of the packaging bag to be produced.

[0051] <Packaging bags and their production> Various packaging bags are produced from the packaging material 1 obtained as described above. The packaging bag has a configuration in which the packaging material 1 has overlapping portions. For example, the two-piece bag 10 in Fig. 3(a) and the gusset bag 20 in Fig. 4(a) have portions in which four sheets of the packaging material 1 overlap (overlap portion 13 in Fig. 3(a) and overlap portion 24 in Fig. 4(a)). Other examples include pillow bags, bottom gusset bags, and stand-up bags.

[0052] Next, the production of a packaging bag using the packaging material 1 will be described.

[0053] 2, the packaging material 1 is subjected to thermocompression bonding at predetermined locations where the packaging materials 1 overlap (thermocompression bonding step). In the thermocompression bonding step, a seal bar (not shown) is used.

[0054] For example, when producing a two-handled bag 10 shown in FIG. 3(a) from a packaging material 1, a seal bar is applied to the packaging material 1 at locations corresponding to the back-attached portion 11, the bottom-attached portion 12, and the overlapping portion 13. As described above, these are the locations where the packaging materials 1 overlap. At these locations, the heat from the seal bar causes the heat seal layers 2 of the overlapping packaging materials 1 to be crimped together. That is, the heat seal agents forming the heat seal layers 2 are preferably crimped together. In this manner, a two-handled bag 10 (packaging bag) is obtained. The same applies to a gusseted bag 20 shown in FIG. 4(a).

[0055] The temperature in the thermocompression step is appropriately set depending on the size and thickness of the packaging material 1, the expandable particles used, and the like.

[0056] In the thermocompression bonding step, the pressure of the seal bar is preferably set to 0.4 to 0.6 MPa. Thermocompression bonding of overlapping portions of the packaging material 1 is preferably performed for 0.5 to 1.5 seconds. The pressure and thermocompression bonding time can be appropriately changed depending on the size of the packaging bag, the thickness and number of packaging materials 1, etc.

[0057] In the packaging bag of the present embodiment, the substrate is preferably a paper substrate. In this case, the amount of plastic is reduced compared to conventional packaging bags. For example, soft packaging materials such as plastic films have a thick sealant layer, so gaps between packaging materials are easily blocked. On the other hand, the heat sealant applied to the paper substrate is thinner than the soft packaging material, so it may not be able to fully fill the gaps between packaging materials. However, in the packaging bag of the present embodiment, even if the substrate is paper, the occurrence of gaps is suppressed in the overlapping portions of the packaging materials, and the bag has excellent sealing properties. Therefore, the present inventors conducted a test to verify that the packaging bag of the present embodiment has excellent sealing properties, suppressing the occurrence of gaps in the overlapping portions of the packaging materials. EXAMPLES

[0058] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0059] [Verification 1] Nine heat seal agents, No. 1 to No. 9, were prepared using expandable particles EXPANCEL 031-DU40 (manufactured by Nippon Phillite Co., Ltd.) and heat seal material AQUENCE EPIX BC9220HS (manufactured by Henkel Co., Ltd.). These nine heat seal agents were prepared by adjusting the mass ratio of the heat seal material to the expandable particles to 90 / 10, 80 / 20, 70 / 30, 60 / 40, 50 / 50, 40 / 60, 30 / 70, 20 / 80, and 10 / 90, starting from No. 1. Then, as described in the above embodiment, a heat seal layer coating liquid containing each heat seal agent was prepared.

[0060] The heat-sealing agent No. 8 and No. 9 (comparative examples) turned into a gel during preparation of the heat-sealing layer coating solution, so preparation of the heat-sealing layer coating solution was discontinued. Therefore, the following operations were performed on the heat-sealing agents No. 1 to No. 7 (examples).

[0061] Next, a packaging material was produced using these heat seal layer coating liquids (heat seal layer coating liquids prepared using the heat seal agents No. 1 to No. 7). The production of this packaging material was carried out in the same manner as the production of the packaging material described in the above embodiment. That is, the heat seal layer coating liquid was applied to the base material, unbleached kraft paper (weighing 60 g / m 2 The coating amount of the heat seal layer coating solution was 5 g / m2 in a dry state. 2 The coating amount of the heat seal layer coating solution was 5 g / m2 in a dry state. 2 Therefore, the thickness of the heat seal layer of the produced packaging material was 5 μm.

[0062] In the first test, the heat seal layer coating liquid prepared using the No. 1 heat seal agent was applied to unbleached kraft paper to prepare a packaging material. This process was repeated four times to prepare four packaging materials. Then, the heat compression bonding process described in the above embodiment was carried out on each packaging material at different temperatures to prepare a two-sided bag. The temperatures at this time were 150°C, 160°C, 170°C, and 180°C. At each temperature, the pressure was set to 0.5 MPa, and the time for heat compression bonding (i.e., the time for applying the heat seal bar to the packaging material) was 1 second. In this way, four two-sided bags were prepared using the No. 1 heat seal agent. As with No. 1, four two-sided bags were prepared for each of the No. 2 to No. 7 heat seal agents.

[0063] Next, the back seal part (see Fig. 3(a)), which is the overlapping part of the packaging material of the two-sided pouches made using the heat seal agents No. 1 to No. 7, was pulled using a tool (Orientec Co., Ltd. Tensilon universal material testing machine RTC-1210A) to measure the strength at which the back seal part peeled off. The condition of the back seal part at that time was also visually observed.

[0064] [Verification 2] In verification 2, nine heat-sealing agents No. 10 to No. 18 were prepared using the same expandable particles and heat-sealing material as in verification 1, and a heat-sealing layer coating liquid was prepared. In verification 2, similarly to verification 1, heat-sealing agents No. 17 and No. 18 (comparative examples) were prepared so that the mass ratio of the heat-sealing material to the expandable particles was 20 / 80 and 10 / 90, respectively. During the preparation of the heat-sealing layer coating liquid, the heat-sealing layer coating liquid changed to a gel state, so the preparation of the heat-sealing layer coating liquid was stopped. Therefore, the subsequent operations were performed on heat-sealing agents No. 10 to No. 16 (embodiments).

[0065] In verification 2, like verification 1, four two-sided bags were made using heat seal agents No. 10 to No. 16. However, in verification 2, the coating amount of the heat seal layer coating liquid on the unbleached kraft paper was 10 g / m2 in a dry state. 2 In the second test, the thickness was 5 g / m 2 By applying the heat seal layer twice, the dry weight is 10g / m 2 The thickness of the heat seal layer of the produced packaging material was 10 μm.

[0066] Next, the back seal part (see Fig. 3(a)), which is the overlapping part of the packaging material of the two-sided pouches made using the heat seal agents No. 10 to No. 16, was pulled using a tool (Orientec Co., Ltd. Tensilon universal material testing machine RTC-1210A) to measure the strength at which the back seal part peeled off. The condition of the back seal part at that time was also visually observed.

[0067] The results of verification 1 and verification 2 are shown in Table 1. In Table 1, the item "peeling form" refers to the state of the back adhesive part when the back adhesive part of the gambrel bag is pulled with the above-mentioned tool. "Interface" in "peeling form" means "interface peeling". As explained in the above embodiment, this means that there are two overlapping packaging materials at the back adhesive part, and these two packaging materials peel off at the heat seal layer. In other words, since the packaging materials peel off so as to be separated from each other, when the examiner visually observed the peeled part, he / she judged it to be "cleanly peeled off", and it was judged to be "interface".

[0068] "Material break" means "substrate destruction." This is different from the above-mentioned "interface," and refers to a state in which the two packaging materials at the back adhesive part do not separate cleanly, and the substrate is broken. In other words, when the inspector visually observed the peeled part, it was deemed to be "material break" if it could not be judged to have been "cleanly peeled off."

[0069] In addition, since it was not possible to prepare a heat seal layer coating liquid for No. 8 and No. 9 in Verification 1, and for No. 17 and No. 18 in Verification 2, only the results of No. 1 to No. 7 and No. 10 to No. 16 are shown in Table 1.

[0070] [Table 1]

[0071] As shown in Table 1, the peeling morphology of the back adhesive of the two-handled bags produced by carrying out the heat-compression bonding process at 150°C to 170°C using the heat sealants No. 1 to No. 7 in Verification 1 was "material breakage". In particular, in the two-handled bags produced by carrying out the heat-compression bonding process at temperatures set to 150°C and 160°C, the strength at which the back adhesive could be peeled off ("material breakage") was large at 3.48 to 5.10 N / 15 mm. This means that the above two-handled bags cannot be peeled off unless a large strength of about 3.48 to 5.10 N / 15 mm is applied to the back adhesive.

[0072] In addition, the back adhesive portion of the two-handled bags produced by carrying out the heat-compression bonding process at 150°C to 170°C using the heat seal agents No. 10 to No. 16 in verification 2 all showed a "material break" in the peeling form. In particular, in the two-handled bags produced by carrying out the heat-compression bonding process at temperatures set to 150°C and 160°C, the strength at which the back adhesive portion could be peeled off ("material break") was large at 3.84 to 5.64 N / 15 mm. This means that the above two-handled bags cannot be peeled off unless a large strength of about 3.84 to 5.64 N / 15 mm is applied to the back adhesive portion.

[0073] In verification 1, the strength of the two-sided bags produced by the heat-pressing process at 170°C when the back adhesive portion could be peeled off ("material breakage") was 2.21-4.20N / 15mm. In verification 2, the strength was 2.88-5.19N / 15mm. These results showed that although the strength was slightly lower than at 150°C and 160°C, the peeling mode was "material breakage" and the bag was strongly pressed.

[0074] Figure 6(a) shows an enlarged photograph of the overlapping area where the back and bottom are overlapped when a two-sided bag is made by thermocompression bonding the overlapping areas of packaging materials at 170°C using a heat sealant No. 11, which is a heat sealant and expandable particles adjusted to a mass ratio of 80 / 20. In Figure 6(a), the gap between the packaging materials is filled, especially in the area surrounded by the black circle, and no gaps can be seen. Note that Figure 6(a) was observed with an optical microscope (Keyence Corporation, shape analysis laser microscope VK-X1000), and the photograph in Figure 6(a) was magnified 500 times.

[0075] In this way, it was found that the two-handled bags produced by carrying out the heat-compression bonding process at 150°C to 170°C using the heat-sealing agents No. 1 to No. 7 in Verification 1 and No. 10 to No. 16 in Verification 2 were particularly strongly heat-compressed at the back and bottom sections where the packaging material overlaps like the back and bottom sections, and at the overlapping sections where the back and bottom sections overlap. This is because the expandable particles were appropriately expanded and effectively filled the gaps between the packaging materials.

[0076] On the other hand, using heat sealing agents No. 1 to No. 7 in Verification 1 and No. 10 to No. 16 in Verification 2, heat compression was performed on the overlapping parts of the packaging materials at 180°C, and the back seal parts of the produced agasmic bags had peeling patterns in both ``material breakage'' and ``interface'' cases.

[0077] More specifically, in verification 1, there was a case where the strength was 2.22 N / 15 mm and the material broke (No. 3), while the strength was 2.47 N / 15 mm (No. 7), which was greater than 2.22 N / 15 mm, and the interface broke. The expandable particles EXPANCEL 031-DU40 used in verification 1 have a maximum expansion temperature of about 120°C, which is about 60°C lower than the 180°C at which the heat-compression bonding process was performed, and the set temperature of the heat-compression bonding process is slightly higher than when the heat-compression bonding process is set to 150°C to 170°C. For this reason, in the case of packaging bags made using a heat seal agent containing a small amount of expandable particles, such as No. 1 to No. 3, it is presumed that even if the expandable particles are expanded to the maximum diameter, the gaps between the packaging materials as described above will be appropriately filled, improving the sealing performance of the two-sided bag. In contrast, when the proportion of expandable particles is increased, as in Nos. 4 to 7, the amount of expandable particles is excessive, and it is presumed that the expandable particles expand, making it difficult to obtain heat seal strength, and the peel morphology becomes "interface."

[0078] In addition, in verification 2, when a packaging bag was made at 170℃ using heat seal agent No. 14, the strength was 2.88N / 15mm, resulting in "material breakage." However, when a packaging bag was made at 180℃ using heat seal agent No. 11, the strength was 2.80N / 15mm, resulting in "interface breakage." Although the strength of the two did not differ significantly, the peeling morphology was different.

[0079] As with the above-mentioned Verification 1, the peeling form is related to the compounding ratio in the heat sealing agent, and is also presumably influenced by the temperature during the thermocompression bonding process and the maximum expansion temperature of the expandable particles.

[0080] However, even if the thermocompression bonding process is performed at 180°C, the peel strength is high and a two-handled bag with excellent sealability can be produced by using a heat sealing agent containing a small amount of expandable particles, such as No. 1 to No. 3 in Verification 1 and No. 10 in Verification 2. Therefore, it was found that by taking into consideration the proportion of expandable particles and the set temperature in the thermocompression bonding process, a two-handled bag with high peel strength and excellent sealability can be produced.

[0081] [Verification 3] In verification 1 and verification 2, the temperature for the heat compression bonding process when producing a two-sided bag, which is a packaging bag, was set to 150° C. to 180° C. As shown in Table 1 and Fig. 6(a), by appropriately adjusting the mass ratio of the heat seal material and the expandable particles in the heat seal agent, a two-sided bag with excellent sealing properties could be produced.

[0082] In verification 3, the sealing ability of packaging bags produced by a thermocompression process at 190°C, which is higher than in verifications 1 and 2, was verified.

[0083] In preparing the heat seal agent in verification 3 (referred to as No. 19), the same heat seal material and expandable particles as those in verification 1 were used, and the mass ratio of the heat seal material to the expandable particles was adjusted to 90 / 10. The procedure was the same as verification 1, except that the temperature in the heat compression bonding process in producing the packaging bag was set to 190°C. However, in verification 3, only one packaging material was produced using the heat seal agent No. 19 (Example).

[0084] Figure 6(b) shows the overlapping area (see Figure 3(b)) where the back and bottom seals of a two-sided pouch made using the No. 17 heat seal agent are overlapping, as observed with an optical microscope (Keyence Corporation, shape analysis laser microscope VK-X1000), and the photograph in Figure 6(b) is enlarged 500 times. In Figure 6(b), it can be confirmed that the gaps between the packaging materials have been filled, particularly in the area circled in black, and the occurrence of gaps has been suppressed.

[0085] [Comparative Example 1] A two-pronged bag was produced in the same manner as in Verification 3, except that a heat seal agent containing only a heat seal material without containing expandable particles (this is referred to as Comparative Example 1) was used.

[0086] Figure 7(a) shows the overlapping portion (see Figure 9(b)) of the back and bottom sealing portions of the two-sided bag made using the heat seal agent of Comparative Example 1, observed with an optical microscope (Keyence Corporation, shape analysis laser microscope VK-X1000), and the photograph in Figure 7(a) was magnified 500 times. In Figure 7(a), gaps were confirmed between the packaging materials, particularly in the area circled in black.

[0087] The results of Verification 3 and Comparative Example 1 show that even when the heat-compression bonding process is carried out at 190°C, packaging bags made by appropriately adjusting the ratio of heat-sealing material and expandable particles to prepare a heat-sealing agent have excellent sealing properties.

[0088] [Verification 4] In verification 4, the sealing ability of packaging bags produced by performing a thermocompression process at a higher temperature than in verification 3 was verified.

[0089] In verification 4, a heat seal agent (referred to as No. 20) was prepared using expandable particles EXPANCEL 909-DU80 (manufactured by Nippon Phillite Co., Ltd.) and a heat seal agent AQUENCE EPIX BC9220HS (manufactured by Henkel). The mass ratio of the heat seal material and expandable particles in the heat seal agent No. 20 was adjusted to 90 / 10. The procedure was the same as in verification 1, except that the temperature in the thermocompression process in producing the packaging bag was set to 250°C. However, in verification 4, only one packaging material was produced using the heat seal agent No. 18 (Example).

[0090] Figure 6(c) shows the overlapping area (see Figure 3(b)) where the back and bottom adhesives of a two-sided bag made using the No. 20 heat sealant are attached, as observed with an optical microscope (Keyence Corporation, shape analysis laser microscope VK-X1000). The photograph in Figure 6(c) was magnified 500 times.

[0091] In Figure 6(c), it can be seen that the gaps between the packaging materials have been filled, particularly in the areas surrounded by black circles, and the occurrence of gaps has been suppressed.

[0092] [Verification 5] In verification 5, the expandable particles in the heat seal agent No. 20 were changed to EXPANCEL 930-DU120 (manufactured by Nippon Phillite Co., Ltd.) to prepare a heat seal agent (referred to as No. 21). The mass ratio of the heat seal material to the expandable particles in the heat seal agent No. 21 was adjusted to 90 / 10. And, the same as in verification 4, except that the temperature in the thermocompression bonding process in the production of the packaging bag was set to 250°C. In verification 5, as in verifications 3 and 4, only one packaging material using a heat seal agent was produced (Example).

[0093] Figure 6(d) shows the overlapping area (see Figure 3(b)) where the back and bottom adhesives of a two-sided bag made using the No. 21 heat seal agent were observed with an optical microscope (Keyence Corporation, shape analysis laser microscope VK-X1000). The photograph in Figure 6(d) was magnified 500 times.

[0094] In Figure 6(d), it can be seen that the gaps between the packaging materials have been filled, particularly in the areas surrounded by black circles, and the occurrence of gaps has been suppressed.

[0095] [Comparative Example 2] A two-pronged bag was produced in the same manner as in Verification 5, except that a heat seal agent containing only a heat seal material without containing expandable particles (this is referred to as Comparative Example 2) was used.

[0096] Figure 7(b) shows the overlapping portion (see Figure 9(b)) where the back and bottom adhesive portions of a two-sided bag made using the heat sealing agent of Comparative Example 2 are overlapped, as observed with an optical microscope (Keyence Corporation, shape analysis laser microscope VK-X1000). The photograph in Figure 7(b) is magnified 500 times.

[0097] In FIG. 7(b), gaps were observed between the packaging materials, particularly in the areas circled in black.

[0098] Therefore, it was found that even when the heat-compression bonding process was carried out at a high temperature of 250°C, packaging bags made by appropriately adjusting the ratio of heat-sealing material and expandable particles to prepare a heat-sealing agent had excellent sealing properties.

[0099] In this way, the packaging bag produced using the heat sealing agent of this embodiment has excellent sealing properties, with the occurrence of gaps being suppressed even in overlapping areas where multiple packaging materials overlap. [Explanation of symbols]

[0100] 1 Packaging material 2 Heat seal layer 3 Base material 10 Gassho bag (packaging bag) 20 Gusset bag (packaging bag)

Claims

1. A heat-sealing agent comprising a heat-sealing material and expandable particles in a mass ratio of heat-sealing material / expandable particles of 90 / 10 to 30 / 70.

2. 2. The heat-sealing agent according to claim 1, wherein the expandable particles have a maximum expansion diameter of 35 to 130 μm.

3. The heat-sealing agent according to claim 1, wherein the expandable particles have a maximum expansion temperature of 110 to 220°C.

4. A packaging material comprising a heat seal layer containing the heat sealant according to any one of claims 1 to 3 and a substrate.

5. The packaging material according to claim 4 , wherein the substrate is paper.

6. A packaging bag formed from a packaging material comprising a heat seal layer formed from a heat seal agent containing a heat seal material and expandable particles in a mass ratio of heat seal material / expandable particles = 90 / 10 to 30 / 70, and a substrate, The packaging bag is formed by heat-pressing the overlapping portions of the packaging materials.

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