Laminate for bottom tape and self-standing packaging bag

Abstract

To provide a laminate for a bottom tape that can form a self-standing packaging bag with excellent drop impact resistance while achieving mono-materialization by a polyethylene resin, and a self-standing packaging bag with excellent drop impact resistance.SOLUTION: A laminate for a bottom tape includes a base material layer A and a heat seal layer B. The base material layer A contains a polyethylene resin with a density of 0.93 g / cm3 or more and a melting point of 120°C or more. The heat seal layer B contains, from an opposite side to the base material layer A, a resin layer B1 containing a polyethylene resin with a melting point of 100°C or less, and a resin layer B2 containing linear low-density polyethylene with a density of 0.92 g / cm3 or less and a melting point of more than 100°C, in this order.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a laminate for a bottom tape that can be applied to a bottom tape of a self-supporting packaging bag, and to a self-supporting packaging bag. [Background technology]

[0002] Conventionally, self-supporting packaging bags called standing pouches, which are obtained by processing a flexible packaging material made of a laminate of synthetic resin films, have been widely used as storage containers for various liquid foods and toiletries. Since the standing pouches are self-supporting, they are excellent in display effect at the time of sale, convenient for storage and use after purchase, and also have excellent storage efficiency as packaging bags.

[0003] Conventional standing pouches were manufactured using a laminate having at least a heat-resistant base film and a sealant layer having low-temperature fusion properties. As the heat-resistant base film, polyethylene terephthalate (PET) resin film, oriented polypropylene (OPP) resin film, oriented nylon (ONy) resin film, etc. were used, and as the sealant layer, polyolefin resins such as low-density polyethylene (LDPE) resin were often used. However, soft packaging materials combining these different materials are difficult to separate after disposal, so they cannot be recycled as materials, or even if they are mechanically separated, the purity of the recovered materials is reduced, and the only disposal methods are to landfill or incinerate them to recover the thermal energy.

[0004] In recent years, as the need for global environmental protection has led to a growing trend away from incineration (thermal recycling) and toward recycling of materials (material recycling), attention has been focused on mono-material packaging materials made of a combination of a single material, rather than a combination of different materials. For example, the following Patent Document 1 proposes a packaging bag made by heat-sealing a laminate made of layers containing only polyethylene as a resin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2021-120204 A Summary of the Invention [Problem to be solved by the invention]

[0006] Packaging bags for liquid refill pouches and the like are required to have excellent drop impact resistance. In general, a self-supporting packaging bag is produced by arranging two main sheets with their sealant layers facing each other, inserting a bottom tape folded in an inverted V shape with the sealant layer facing outward between the sheets, and heat sealing the periphery. The present inventors have therefore investigated the possibility of making such a self-supporting packaging bag into a mono-material form using polyethylene resin, and have found that there are the following problems with drop impact resistance. Specifically, in a drop test of a packaging bag filled with liquid, it has been found that cracks and breakage are likely to occur at the folded portion of the bottom tape and at the intersection between the bottom tape and the main sheet.

[0007] The present invention aims to provide a laminate for a bottom tape that can form a self-supporting packaging bag that has excellent drop impact resistance while being made into a mono-material using polyethylene resin, and a self-supporting packaging bag that has excellent drop impact resistance. [Means for solving the problem]

[0008] One aspect of the present invention is a laminate used as a bottom tape for forming the bottom of a self-supporting packaging bag having a body and a bottom, the laminate comprising a base material layer A and a heat seal layer B, the base material layer A having a density of 0.93 g / cm 3 and a polyethylene resin having a melting point of 120°C or more. The heat seal layer B is made of a resin layer B1 containing a polyethylene resin having a melting point of 100°C or less and a polyethylene resin having a density of 0.92 g / cm3 from the side opposite to the substrate layer A. 3 and a resin layer B2 containing a linear low-density polyethylene having a melting point of more than 100°C, in this order.

[0009] According to the laminate for the bottom tape of the present invention, by having the above-mentioned configuration, it is possible to achieve mono-materialization using polyethylene resin while providing sufficient impact resistance and low-temperature sealing properties, thereby improving the drop impact resistance of the self-supporting packaging bag.

[0010] In the bottom tape laminate of the present invention, the layer thickness T B1 and the thickness T of the resin layer B2 B2 Relative to T B1 / T B2 may be 0.1 to 1. In this case, it is possible to achieve both high levels of impact resistance and low-temperature sealability, and the drop impact resistance of the self-supporting packaging pouch can be further improved.

[0011] From the viewpoint of blocking resistance, the density difference between the base layer A and the resin layer B1 is 0.01 g / cm 3 More than 0.08g / cm 3 It may be the following.

[0012] Furthermore, from the viewpoint of impact resistance, the linear low-density polyethylene constituting the resin layer B2 may be a 4-methylpentene-1 based copolymer.

[0013] The base layer A may have a multi-layer structure. In this case, lamination can be achieved by changing the anisotropy of the film and bonding it together, and the tensile break resistance and puncture resistance can be improved more than by simply increasing the film thickness.

[0014] Another aspect of the present invention provides a self-supporting packaging bag formed by heat sealing a pair of main body sheets and a bottom tape having a mountain fold portion, wherein the bottom tape is composed of a laminate for a bottom tape according to one aspect of the present invention described above.

[0015] The self-supporting packaging bag of the present invention can have excellent drop impact resistance since the bottom tape is composed of the laminate for a bottom tape of the present invention.

[0016] The self-supporting packaging bag of the present invention is a laminate comprising a pair of main body sheets each having a base layer C and a heat seal layer D, and the base layer C has a density of 0.93 g / cm 3 or more, and contains a polyethylene resin having a melting point of 120°C or more, and the heat seal layer D is provided with a resin layer D1 containing a polyethylene resin having a melting point of 100°C or less from the side opposite to the base layer C, and a density of 0.92 g / cm 3 or less, and a resin layer D2 containing a linear low-density polyethylene having a melting point of more than 100° C. In this case, it is possible to make the self-supporting packaging bag mono-material, and further improve the drop impact resistance. Effect of the Invention

[0017] According to the present invention, it is possible to provide a laminate for a bottom tape that can form a self-supporting packaging bag that has excellent drop impact resistance while being made into a mono-material using polyethylene resin, and a self-supporting packaging bag that has excellent drop impact resistance. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a laminate according to one embodiment of the present invention. [Diagram 2] 1 is a front view showing a schematic diagram of a self-supporting packaging bag according to one embodiment of the present invention. [Diagram 3] 3 is a perspective view showing a pair of main body sheets and a bottom tape constituting the self-supporting packaging bag shown in FIG. 2. FIG. [Figure 4] FIG. 2 is a diagram showing a heat-sealed portion of a test packaging bag used in a drop test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings where necessary. However, the present invention is not limited to the following embodiments.

[0020] <Laminate for bottom tape> The laminate for the bottom tape in this embodiment is a laminate comprising a base material layer A and a heat seal layer B, and is used as a bottom tape for forming the bottom of a self-supporting packaging bag (standing pouch) having a main body portion (also called a trunk portion) and a bottom portion.

[0021] Fig. 1 is a schematic cross-sectional view showing a laminate according to one embodiment. The laminate 100 for a bottom tape shown in Fig. 1 comprises a base layer 10 and a heat seal layer 20, the base layer 10 including a first base layer 12 and a second base layer 14 in this order from the side closer to the heat seal layer 20, and the heat seal layer 20 including a first heat seal layer 22 and a second heat seal layer 24 in this order from the side opposite to the base layer 10. In the laminate 100 for a bottom tape, the second base layer 14 and the first heat seal layer 22 each form the outermost layer (the outermost layer).

[0022] [Base material layer A] The base layer A has a density of 0.93 g / cm 3 The polyethylene resin has a density of 0.93 to 0.97 g / cm3 and a melting point of 120°C or higher. 3 From the viewpoints of bottom opening property during sealing heating and prevention of welding of the main body, the melting point of the high density polyethylene may be 120 to 150°C, or 125 to 140°C.

[0023] The base layer A may contain additives such as antistatic agents, ultraviolet absorbers, plasticizers, lubricants, antioxidants, and colorants.

[0024] The base layer A may be formed of a film composed of the above-mentioned polyethylene resin. The film may be a stretched film or an unstretched (non-stretched) film. From the viewpoint of making it difficult to break due to external stress such as a drop impact or a puncture, the base layer A may be formed of a stretched film. Also, from the viewpoint of making it difficult to tear and absorbing impact by deforming in response to a strain due to a tensile load, the base layer A may be formed of an unstretched film. The thickness of the film may be 5 to 100 μm, or 10 to 80 μm.

[0025] The above-mentioned film may be provided with a vapor-deposited layer of an inorganic oxide such as aluminum oxide or silicon oxide. In this case, the film provided with the vapor-deposited layer may function as a barrier film. A strong adhesion coating layer may be provided between the film and the vapor-deposited layer, and wettability improving treatment (corona treatment, etc.) may be performed.

[0026] The substrate layer A may have a multi-layer structure, as in the substrate layer 10 shown in Fig. 1. In this case, lamination can be achieved by changing the anisotropy of the film and laminating it, and the tensile break resistance and puncture resistance can be improved more than simply increasing the film thickness. In the substrate layer 10, for example, the first substrate layer 12 and the second substrate layer 14 are laminated to a thickness of about 20 µm or more, and functionality can be imparted by providing printing or a functional layer (barrier, light shielding, etc.) between the layers.

[0027] When the base layer A has a multi-layer structure, each layer may be laminated via an adhesive or an adhesive assistant. Examples of the lamination method include dry lamination, non-solvent lamination, and extrusion lamination.

[0028] The thickness of the base layer A may be 5 to 100 μm, or may be 10 to 80 μm.

[0029] [Heat seal layer B] The heat seal layer B is made up of a resin layer B1 (for example, the first heat seal layer 22 shown in FIG. 1) containing a polyethylene resin having a melting point of 100° C. or less and a polyethylene terephthalate resin having a density of 0.92 g / cm 3 from the side opposite to the base layer A. 3 or less, and a resin layer B2 (for example, the second heat seal layer 24 shown in FIG. 1) containing a linear low-density polyethylene having a melting point of more than 100° C. in this order.

[0030] The polyethylene resin forming the resin layer B1 may have a melting point of 70 to 125°C, or 80 to 120°C.

[0031] The polyethylene resin forming the resin layer B1 has a density of 0.88 to 0.92 g / cm 3 and may be 0.90 to 0.92 g / cm 3 may be also possible.

[0032] As the polyethylene resin forming the resin layer B1, at least one of linear low density polyethylene (L-LDPE) and very low density polyethylene (VLDPE) can be used. These polyethylenes are copolymers of ethylene and α-olefins, and examples of the α-olefins include propylene (C3), butene (C4), pentene (C5), hexene (C6), heptene (C7) and octene (C8). In this specification, the density of VLDPE is 0.88 to 0.92 g / cm. 3 It is defined as follows.

[0033] From the viewpoints of impact resistance and low-temperature heat sealability, the polyethylene resin forming the resin layer B1 may be an ultra-low density polyethylene containing hexene-1 as a comonomer component (in other words, an ultra-low density polyethylene obtained by copolymerizing a monomer composition containing ethylene and hexene-1).

[0034] The resin layer B1 may contain additives such as a heat stabilizer, an antioxidant, an ultraviolet absorber, an antiblocking agent, a lubricant, and an antistatic agent.

[0035] Thickness T of resin layer B1 B1From the viewpoint of low-temperature sealing property and retention of seal strength, the thickness may be 10 to 100 μm or 15 to 100 μm.

[0036] The linear low density polyethylene forming the resin layer B2 may have a melting point of 100 to 135°C, or 110 to 130°C.

[0037] The linear low-density polyethylene forming the resin layer B2 has a density of 0.90 to 0.93 g / cm 3 and may be 0.91 to 0.92 g / cm 3 may be also possible.

[0038] The linear low-density polyethylene forming the resin layer B2 may be a 4-methylpentene-1 based copolymer (in other words, a copolymer obtained by copolymerizing a monomer composition containing ethylene and 4-methylpentene-1) from the viewpoint of impact resistance.

[0039] From the viewpoint of improving the drop impact resistance of the self-supporting packaging bag, the linear low-density polyethylene forming the resin layer B2 has a polydispersity (Mw / Mn) of 2 or more, and may be 3 to 12, or may be 7 to 12. The polydispersity of the polyethylene resin means a value determined in terms of polystyrene using gel permeation chromatography (GPC). From the same viewpoint as above, the linear low-density polyethylene forming the resin layer B2 may be one polymerized with a single catalyst system (for example, a metallocene catalyst system).

[0040] Thickness T of resin layer B2 B2 From the viewpoints of impact resistance and stretchability when pressure is applied, the thickness may be 20 to 200 μm or 50 to 150 μm.

[0041] In the bottom tape laminate according to this embodiment, the layer thickness T B1 and the thickness T of the resin layer B2 B2 Relative to T B1 / T B2 may be 0.1 to 1, or may be 0.1 to 0.5. B1 / TB2 However, within such a range, both impact resistance and low-temperature sealability can be achieved at a high level, and the drop impact resistance of the self-supporting packaging bag can be further improved.

[0042] The thickness of the heat seal layer B may be 30 to 200 μm, or may be 50 to 150 μm.

[0043] The method for forming the heat seal layer B is to mix the material constituting the resin layer B1 and the material constituting the resin layer B2 in the ratio T B1 / T B2 a method of extruding one of the resin layers B1 and B2 as a single layer and forming the other resin layer thereon in a thickness satisfying the above-mentioned ratio T B1 / T B2 and a method of laminating the layers to a thickness that satisfies the above.

[0044] In the bottom tape laminate according to this embodiment, from the viewpoint of blocking resistance, the density difference between the base layer A and the resin layer B1 is 0.01 g / cm 3 More than 0.08g / cm 3 It may be less than 0.03 g / cm 3 More than 0.08g / cm 3 When the base layer A has a multi-layer structure, the density difference between the outermost layer (for example, the second base layer 14 shown in FIG. 1) and the resin layer B1 may be within the above range.

[0045] From the viewpoint of blocking resistance, the bottom tape laminate according to this embodiment may have a melting point difference between the base layer A and the resin layer B1 of 10° C. or more, or may have a melting point difference of 20° C. or more. When the base layer A has a multi-layer structure, the melting point difference between the outermost layer (for example, the second base layer 14 shown in FIG. 1) and the resin layer B1 may be within the above range.

[0046] The bottom tape laminate according to this embodiment can be formed by laminating the base layer A and the heat seal layer B. Examples of the lamination method include dry lamination, non-solvent lamination, and extrusion lamination. The base layer A and the heat seal layer B may be laminated via an adhesive auxiliary such as an adhesive or an anchor coat.

[0047] The content of the polyethylene resin in the bottom tape laminate according to this embodiment may be 85% by mass or more, or 90% by mass or more, from the viewpoint of mono-materialization.

[0048] As described above, the bottom tape laminate of this embodiment comprises a base layer, a heat seal layer, and, if necessary, an adhesive layer containing an adhesive, an anchor coat layer containing an adhesive auxiliary material, and a vapor deposition layer containing a metal oxide, but may further comprise a pattern layer (printed layer), a light-shielding layer, a molecular adsorption layer, a reflective layer, etc.

[0049] The pattern layer (printed layer) can be provided, for example, between the substrate layers (for example, between layer 12 and layer 14 shown in FIG. 1), between the substrate layer and resin layer B2 (for example, between layer 12 and layer 24 shown in FIG. 1), or on the surface of substrate layer A. The light-shielding layer, the adsorption layer, and the reflective layer can be provided, for example, between resin layer B1 and resin layer B2 (for example, between layer 22 and layer 24 shown in FIG. 1), between the substrate layer and resin layer B2 (for example, between layer 12 and layer 24 shown in FIG. 1), on the surface of substrate layer A, inside substrate layer A, or inside resin layer B.

[0050] The thickness of the bottom tape laminate according to this embodiment may be 50 to 300 μm, or 70 to 250 μm.

[0051] <Standing pouch> The self-supporting packaging bag according to the present embodiment is a self-supporting packaging bag formed by heat-sealing a pair of main body sheets and a bottom tape having a mountain fold, the bottom tape being composed of the laminate for the bottom tape according to the present embodiment. The self-supporting packaging bag has a main body formed by the pair of main body sheets, and a bottom formed by a part of the pair of main body sheets and the bottom tape.

[0052] Fig. 2 is a front view showing a self-supporting packaging bag according to the present embodiment, and Fig. 3 is a perspective view showing a pair of main body sheets and a bottom tape which constitute the self-supporting packaging bag shown in Fig. 2.

[0053] The self-supporting packaging bag 50 shown in Fig. 2 is formed by heat-sealing a pair of main body sheets 2, 3 (first and second main body sheets) and a bottom tape 1. The bottom tape 1 may be formed from the bottom tape laminate 100 shown in Fig. 1, in which case the bottom tape is arranged so that the heat seal layer 20 is on the inner surface side of the self-supporting packaging bag 50. The main body sheets 2, 3 can also be formed from a laminate including a base layer and a heat seal layer, and the pair of main body sheets are arranged so that their respective heat seal layers face each other and are on the inner surface side of the self-supporting packaging bag 50.

[0054] The sides of the self-supporting packaging pouch 50 are formed by side seal portions 7. The width of the side seal portions 7 is, for example, 3 to 15 mm, and may be 5 to 15 mm, from the viewpoint of achieving both sufficient seal strength and sufficient content capacity.

[0055] The bottom of the self-supporting packaging bag 50 is composed of a bottom seal portion 5 and a bottom seal portion 6. The bottom seal portion 5 is a portion where a part of the main body sheet 2 and one bottom portion of the bottom tape 1 (1c shown in FIG. 3) are heat-sealed to each other, and the bottom seal portion 6 is a portion where a part of the main body sheet 3 and the other bottom portion of the bottom tape 1 (1b shown in FIG. 3) are heat-sealed to each other.

[0056] The bottom tape 1 has one mountain fold 1a and two bottom sides 1d. That is, when the self-supporting packaging pouch 50 is in a self-supporting state, the bottom tape 1 is arranged in an inverted V shape (see FIG. 3).

[0057] As shown in Fig. 2, the self-supporting packaging bag 50 has fused portions 9 on both sides of the bottom. The fused portions 9 join the main body sheets 2 and 3. The fused portions 9 are locations where the heat seal layers of the main body sheets 2 and 3 are locally fused to each other through cutout portions 8 provided in the base tape 1. As shown in Fig. 3, the cutout portions 8 of the base tape 1 are located in the region between the mountain fold portion 1a and the bottom edge 1d, and on the side portions of the base tape 1.

[0058] In the self-supporting packaging bag according to the present embodiment, the main body sheet may have a configuration similar to that of the bottom tape laminate according to the present embodiment. For example, a pair of main body sheets may be formed of a laminate including a base layer C and a heat seal layer D, and the base layer C has a density of 0.93 g / cm 3 or more, and contains a polyethylene resin having a melting point of 120°C or more, and the heat seal layer D is provided with a resin layer D1 containing a polyethylene resin having a melting point of 100°C or less from the side opposite to the base layer C, and a density of 0.92 g / cm 3 or less, and a resin layer D2 containing a linear low-density polyethylene having a melting point of more than 100° C. In this case, it is possible to make the self-supporting packaging bag mono-material, and further improve the drop impact resistance. EXAMPLES

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0060] <Preparation of laminate for bottom tape> (Laminate for bottom tape 1) The first base layer is made of a non-oriented high-density polyethylene film (thickness: 32 μm, density: 0.951 g / cm 3, melting point: 132°C) and a non-oriented high-density polyethylene film (thickness 30 μm, density: 0.948 g / cm) constituting the second base layer. 3 , melting point: 128° C.) by a dry lamination method using an adhesive (LX-500 / KW-75 (manufactured by DIC, product name)) to form a film-like base layer.

[0061] On the other hand, the ultra-low density polyethylene (density: 0.909 g / cm 3 ) constituting the first heat seal layer 3 , melting point: 97°C, C6-VLDPE of single catalyst system (metallocene catalyst system) containing hexene-1 as a comonomer component) and linear low-density polyethylene (density: 0.914 g / cm) constituting the second heat seal layer. 3 A film-like heat seal layer with a total thickness of 100 μm was formed by co-extrusion of this copolymer with a multi-catalyst system (C6-LLDPE, melting point: 120°C, containing 4-methylpentene-1 as a comonomer component) at a layer thickness ratio of 1:4.

[0062] The film-like base layer and the film-like heat seal layer were laminated by a dry lamination method using an adhesive (LX-500 / KW-75 (manufactured by DIC, product name)) to obtain a laminate for a bottom tape having a layered structure of a first heat seal layer / a second heat seal layer / a first base layer / a second base.

[0063] (Laminate 2 for bottom tape) The base layer is a non-oriented high-density polyethylene film (thickness: 70 μm, density: 0.948 g / cm 3 A laminate for a bottom tape having a laminate structure of a first heat seal layer / second heat seal layer / base material layer was obtained in the same manner as for bottom tape laminate 1, except that a polyester resin (melting point: 128°C) was used.

[0064] (Bottom tape laminate 3) The first heat seal layer is made of ultra-low density polyethylene (density: 0.909 g / cm 3, melting point: 97°C, single catalyst system (metallocene catalyst system) C6-VLDPE containing hexene-1 as a comonomer component) and linear low density polyethylene (density: 0.913 g / cm) constituting the second heat seal layer. 3 A laminate for a bottom tape having a laminate structure of a first heat seal layer / second heat seal layer / first base layer / second base material was obtained in the same manner as for the laminate for a bottom tape 1, except that a film-like heat seal layer having a total thickness of 100 μm was used, which was formed by co-extruding a first heat seal layer / second heat seal layer / first base material layer / second base material with a thickness ratio of 1:4 and a single catalyst system LLDPE (melting point: 110°C, single catalyst system containing hexene-1 as a comonomer component).

[0065] (Bottom tape laminate 4) The first base layer is made of a non-oriented high-density polyethylene film (thickness: 32 μm, density: 0.951 g / cm 3 , melting point: 132°C) and a non-oriented high-density polyethylene film (thickness: 32 μm, density: 0.951 g / cm) constituting the second base layer. 3 , melting point: 130° C.) was laminated by a dry lamination method using an adhesive (LX-500 / KW-75 (manufactured by DIC, product name)) to form a film-like base layer.

[0066] On the other hand, the linear low density polyethylene (density: 0.913 g / cm 3 ) constituting the first heat seal layer 3 , melting point: 110°C, single catalyst type LLDPE containing hexene-1 as a comonomer component) and linear low density polyethylene (density: 0.916g / cm3) constituting the second heat seal layer. 3 A film-like heat seal layer with a total thickness of 100 μm was formed by co-extrusion of this copolymer with a 1:4 butene-1-containing C4-LLDPE (melting point: 104° C., comonomer component butene-1).

[0067] The film-like base layer and the film-like heat seal layer were laminated by a dry lamination method using an adhesive (LX-500 / KW-75 (manufactured by DIC, product name)) to obtain a laminate for a bottom tape having a layered structure of a first heat seal layer / a second heat seal layer / a first base layer / a second base.

[0068] (Bottom Tape Laminate 5) The first heat seal layer is made of linear low density polyethylene (density: 0.913 g / cm 3 , melting point: 110°C, single catalyst type LLDPE containing hexene-1 as a comonomer component) and linear low density polyethylene (density: 0.916g / cm3) constituting the second heat seal layer. 3 A laminate for a bottom tape having a laminate structure of a first heat seal layer / second heat seal layer / first base material layer / second base material was obtained in the same manner as for the laminate for a bottom tape 1, except that a film-like heat seal layer having a total thickness of 100 μm was used, which was formed by co-extruding a first heat seal layer / second heat seal layer / first base material layer / second base material with a thickness ratio of 1:4.

[0069] <Preparing the main sheet> (Main sheet 1) A laminate was prepared in the same manner as the bottom tape laminate 3, and this was used as the main body sheet 1.

[0070] (Main sheet 2) A laminate was prepared in the same manner as the bottom tape laminate 1, and this was used as the main sheet 2.

[0071] (Main sheet 3) A laminate was prepared in the same manner as the bottom tape laminate 5, and this was used as the main body sheet 3.

[0072] [Creating self-supporting packaging bags] (Examples 1 to 4, Comparative Examples 1 and 2) A self-supporting packaging bag was produced by combining the main body sheet and the bottom tape laminate shown in Table 1. The size of the packaging bag was 135 mm wide, 225 mm high, and 40 mm folded, and the width of the side seal was 5 mm.

[0073] [Drop test] The self-supporting packaging bag thus produced was filled with 400 mL of water as the content, and the top of the self-supporting packaging bag was heat-sealed to obtain a test packaging bag with a heat-sealed portion as shown in FIG. 4. The test packaging bag, which had been stored in an environment of 5°C for 24 hours or more, was dropped from a height of 100 cm onto a concrete floor with the bottom tape facing down, and the number of times it was dropped before it broke was counted. If the bag broke within 10 drops and there was a problem with the bottom (such as cracks in the bottom tape, pinholes at the intersection of the bottom tape and the main sheet, or cracks along the seal edge from near the intersection of the bottom tape and the main sheet), it was deemed to be "defective." Eight samples were evaluated under the same conditions, and the failure rate (%) was calculated.

[0074] [Table 1] [Explanation of symbols]

[0075] 1...bottom tape, 1a...mountain fold portion, 1b, 1c...bottom portion, 1d...bottom edge, 2, 3...main body sheet, 5, 6...bottom seal portion, 7...side seal portion, 8...cutout portion, 9...fusion portion, 10...base material layer, 12...first base material layer, 14...second base material layer, 20...heat seal layer, 22...first heat seal layer, 24...second heat seal layer, 50...self-supporting packaging bag, 100...laminate for bottom tape.

Claims

1. A laminate used as a bottom tape for forming a bottom of a self-supporting packaging bag having a body and a bottom, The present invention comprises a base material layer A and a heat seal layer B, The base layer A has a density of 0.93 g / cm ３ or more, and contains a polyethylene resin having a melting point of 120°C or more, The heat seal layer B is made of a resin layer B1 containing a polyethylene resin having a melting point of 100° C. or less and a density of 0.92 g / cm 3 from the side opposite to the base layer A. ３ and a resin layer B2 containing a linear low-density polyethylene having a melting point of more than 100°C, in this order.

2. Layer thickness T of resin layer B1 Ｂ１ and the layer thickness T of the resin layer B2 Ｂ２ Ratio to T Ｂ１ / T Ｂ２ The laminate for the bottom tape according to claim 1, wherein is 0.1 to 1.

3. The density difference between the base layer A and the resin layer B1 is 0.01 g / cm ３ 0.08g / cm or more ３ 2. The bottom tape laminate of claim 1, wherein:

4. The laminate for bottom tape according to claim 1, wherein the linear low-density polyethylene constituting the resin layer B2 is a 4-methylpentene-1 based copolymer.

5. The laminate for a bottom tape according to claim 1 , wherein the base layer A has a multi-layer structure.

6. A pair of main sheets; A bottom tape having a mountain fold; A self-supporting packaging bag formed by heat sealing the A self-supporting packaging bag, wherein the bottom tape is composed of the laminate for the bottom tape according to any one of claims 1 to 5.

7. The pair of main body sheets are composed of a laminate including a base material layer C and a heat seal layer D, The base layer C has a density of 0.93 g / cm ３ and a polyethylene resin having a melting point of 120° C. or more, and the heat seal layer D is provided with a resin layer D1 containing a polyethylene resin having a melting point of 100° C. or less from the side opposite to the base layer C, and a density of 0.92 g / cm ３ The self-supporting packaging bag according to claim 6, further comprising, in this order, a resin layer D1 having a melting point of 100° C. or less and a resin layer D2 containing a linear low-density polyethylene having a melting point of more than 100° C.

Images