JP7795719B2 - Laminate and packaging bag - Google Patents

Description

This disclosure relates to a laminate and a packaging bag.

Packaging bags are used to store fluid contents such as liquids and powders. Packaging bags are composed of a laminate including a base material and a sealant layer. For example, resin films made from polyethylene are widely used as sealant layers because they are flexible, transparent, and have excellent heat-sealing properties. Resin films made from polyester or polyamide are also widely used as base materials because they have excellent strength and heat resistance.

In recent years, there has been a growing demand for packaging bags to be recycled in order to reduce environmental impact. From the perspective of recycling, it is preferable for the base material and sealant layer to be made from the same type of resin material (mono-materialization). For example, Patent Document 1 proposes making the base material and sealant layer from polyethylene.

Japanese Patent Application Laid-Open No. 2020-55156

In order to make it easier to open a packaging bag by hand, an easy-open line is sometimes formed on the packaging bag. The present inventors have investigated forming an easy-open line by irradiating a laminate with a laser to form an altered portion. It is believed that the laminate can be easily torn along the altered portion (easy-open line).

When the substrate contains a different type of resin material from the resin material that makes up the sealant layer, it is possible to selectively form an altered portion in the substrate by selecting a laser that is absorbed by the substrate but not by the sealant layer. However, from the perspective of recycling, when the substrate and sealant layer are made of the same type of resin material, polyethylene, the substrate does not adequately absorb the laser, and an altered portion tends not to form well in the substrate. As a result, the improvement in tearability due to laser irradiation is insufficient.

One objective of the present disclosure is to provide a laminate that is highly recyclable and whose tearability can be improved by laser irradiation.

The laminate of the present disclosure comprises at least a stretched substrate and a sealant layer, the stretched substrate containing polyethylene as a primary component, and the sealant layer comprising at least a first layer and a second layer, the first layer containing ethylene/α-olefin copolymer as a primary component and having a melting point of 112°C or less, the second layer containing polyethylene as a primary component and having a melting point of 114°C or higher, one surface layer of the laminate being the first layer, and the laminate further comprising a heat-generating layer between the stretched substrate and the sealant layer that contains a heat-generating substance that absorbs laser light and generates heat.

The present disclosure provides a laminate that is highly recyclable and can be effectively improved in tearability by laser irradiation. By using the laminate of the present disclosure, packaging bags that are highly recyclable and easy to open can be produced.

FIG. 1 is a schematic cross-sectional view showing one embodiment of a laminate. FIG. 2 is a schematic cross-sectional view showing one embodiment of the sealant layer. FIG. 3 is a schematic cross-sectional view showing one embodiment of the sealant layer. FIG. 4 is a schematic cross-sectional view showing one embodiment of the sealant layer. FIG. 5 is a front view showing one embodiment of a packaging bag. FIG. 6 is a cross-sectional view showing an example of a through hole of an easy-open line. FIG. 7 is a diagram for explaining a method for measuring the width of the altered portion. FIG. 8 is a front view showing an example of an easy-open line. FIG. 9 is a front view showing one embodiment of a packaging bag. FIG. 10 is a front view showing one embodiment of a packaging bag. FIG. 11 is a front view showing one embodiment of a packaging bag. FIG. 12 is a front view of a test piece for measuring tear strength. FIG. 13 is an observation image of the cross-sectional shape of the laminate.

Embodiments of the present disclosure are described in detail below. The present disclosure can be implemented in many different forms and should not be construed as being limited to the description of the embodiments exemplified below. For clarity of explanation, the drawings may show the width, thickness, shape, etc. of each layer more schematically than in the embodiments, but these are merely examples and do not limit the interpretation of the present disclosure. In this specification and each figure, elements similar to those already described in the previous figures are designated by the same reference numerals, and detailed descriptions may be omitted where appropriate.

In the following description, each of the components (for example, polyolefins such as polyethylene, α-olefins, resin materials, additives, and exothermic substances) may be used alone or in combination of two or more.
The term "main component" means a component that is contained in a layer or substrate in an amount of 50% by mass or more.

[Laminate]
The laminate of the present disclosure comprises at least an oriented substrate and a sealant layer.
The laminate of the present disclosure can be suitably used as a packaging material.

The stretched substrate contains polyethylene as a main component.
The sealant layer includes at least a first layer and a second layer, each of which will be described later.
The laminate of the present disclosure further includes a heat-generating layer between the stretched substrate and the sealant layer, which contains a heat-generating substance that absorbs laser light and generates heat. With this configuration, for example, an altered portion can be formed by irradiating the laminate with a laser, improving the hand tearability of the laminate and thus the ease of opening a packaging bag including the laminate. For example, by forming an altered portion along the longitudinal direction (MD), transverse direction (direction perpendicular to the MD, or TD), or a direction diagonal at 45° to the MD, tearability in each direction can be improved. In particular, tearability of the laminate can be improved not only in the MD and TD but also in the direction diagonal at 45° to the MD.

In one embodiment, the resin constituting the stretched substrate and the resin constituting the sealant layer are both primarily composed of polyethylene, which can improve the recyclability of the laminate, for example.

The polyethylene content of the entire laminate of the present disclosure is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. This allows, for example, the laminate to be used to produce mono-material packaging bags, improving the recyclability of the packaging bags. There is no particular upper limit to the polyethylene content, but it may be 99% by mass or 95% by mass.

<Stretched base material>
The stretched substrate contains polyethylene as a main component.

In this disclosure, polyethylene refers to a polymer in which the content of ethylene-derived structural units among all repeating structural units is 50 mol% or more. In this polymer, the content of ethylene-derived structural units is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more. The above content can be measured by NMR.

In this disclosure, polyethylene may be a homopolymer of ethylene or a copolymer of ethylene and an ethylenically unsaturated monomer other than ethylene. Examples of ethylenically unsaturated monomers other than ethylene include α-olefins having 2 to 20 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methyl-1-butene, 4-methyl-1-pentene, and 6-methyl-1-heptene; vinyl monomers such as vinyl acetate and vinyl propionate; and (meth)acrylic acid esters such as methyl (meth)acrylate and ethyl (meth)acrylate.

In the present disclosure, examples of polyethylene include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, and very low-density polyethylene. From the viewpoint of the strength and heat resistance of the stretched substrate, high-density polyethylene and medium-density polyethylene are preferred. From the viewpoint of the film-forming ability and processability of the stretched substrate, linear low-density polyethylene and medium-density polyethylene are preferred. Medium-density polyethylene is particularly preferred. From the viewpoint of reducing the environmental impact, biomass-derived polyethylene and mechanically recycled or chemically recycled polyethylene may also be used as the polyethylene.

In the present disclosure, the density of polyethylene is as follows:
The density of the high-density polyethylene is preferably greater than 0.945 g/cm ^3. The upper limit of the density of the high-density polyethylene is, for example, 0.965 g/cm ^3. The density of the medium-density polyethylene is preferably greater than 0.930 g/cm ³ and not greater than 0.945 g/cm ^3. The density of the low-density polyethylene is preferably greater than 0.900 g/cm ³ and not greater than 0.930 g/cm ^3. The density of the linear low-density polyethylene is preferably greater than 0.900 g/cm ³ and not greater than 0.930 g/cm ^3. The density of the very low-density polyethylene is preferably not greater than 0.900 g/cm ^3. The lower limit of the density of the very low-density polyethylene is, for example, 0.860 g/cm ^3. The density of the polyethylene is measured in accordance with JIS K7112 (particularly Method D (density gradient tube method, 23°C)).

Low-density polyethylene is typically polyethylene obtained by polymerizing ethylene using a high-pressure polymerization method (high-pressure low-density polyethylene). Linear low-density polyethylene is typically polyethylene obtained by polymerizing ethylene and a small amount of α-olefins using a polymerization method that uses a multi-site catalyst such as a Ziegler-Natta catalyst or a single-site catalyst such as a metallocene catalyst.

Polyethylenes with different densities or branching can be obtained by appropriately selecting the polymerization method. For example, it is preferable to use a multi-site catalyst such as a Ziegler-Natta catalyst or a single-site catalyst such as a metallocene catalyst as the polymerization catalyst, and to carry out polymerization in one stage or two or more stages using any of gas phase polymerization, slurry polymerization, solution polymerization, and high-pressure ionic polymerization.

From the viewpoint of film-forming properties and processability, the melt flow rate (MFR) of the polyethylene is preferably 0.1 g/10 min or more, more preferably 0.2 g/10 min or more, even more preferably 0.5 g/10 min or more, and is preferably 50 g/10 min or less, more preferably 30 g/10 min or less, even more preferably 10 g/10 min or less, and particularly preferably 5.0 g/10 min or less. The MFR of the polyethylene is measured by Method A in accordance with JIS K7210 under a load of 2.16 kg. The MFR measurement temperature is 190°C.
The above description of polyethylene can also be applied to other parts.

From the viewpoint of heat resistance, the melting point (Tm) of polyethylene is preferably 100°C or higher, more preferably 105°C or higher, even more preferably 110°C or higher, and particularly preferably 120°C or higher, and preferably 140°C or lower. Tm is the melting peak temperature obtained by differential scanning calorimetry (DSC) in accordance with JIS K7121.

The polyethylene content in the stretched substrate is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, and particularly preferably 90% by mass or more or 95% by mass or more. This configuration can, for example, improve the recyclability of the laminate.

The stretched substrate may contain a resin material other than polyethylene. Examples of such resin materials include polyolefins other than polyethylene, (meth)acrylic resins, vinyl resins, cellulose resins, polyamides, polyesters, and ionomer resins.

The stretched substrate may contain additives. Examples of additives include crosslinkers, antioxidants, antiblocking agents, slip agents, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, compatibilizers, pigments, and modifying resins.

A stretched substrate is a substrate that has been stretched. This can improve, for example, the strength, heat resistance, and transparency of the substrate. The stretching process can be uniaxial or biaxial. When stretching in the machine direction (the flow direction of the substrate, MD), the stretching ratio can be 2x or more, 3x or more, 10x or less, or 7x or less. When stretching in the transverse direction (the direction perpendicular to the MD, TD), the stretching ratio can be 2x or more, 3x or more, 10x or less, or 7x or less. A stretched substrate is, for example, a uniaxially stretched film that has been stretched in the machine direction (MD).

The stretched substrate may have a single-layer structure or a multi-layer structure. The stretched substrate may have one or more polyethylene layers containing polyethylene as a main component. Polyethylene substrates having a multi-layer structure are preferred, for example, from the viewpoint of achieving an excellent balance of strength, heat resistance, printability, and stretchability. In the case of a polyethylene substrate having a multi-layer structure, the number of polyethylene layers may be two or more, three or more, seven or fewer, or five or fewer, for example, three, five, or seven layers.

The polyethylene content in the polyethylene layer is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, and particularly preferably 90% by mass or more or 95% by mass or more.

The haze value of the stretched substrate may be 25% or less, 15% or less, or 10% or less. The lower limit of the haze value may be 0.1% or 1%. The haze value of the stretched substrate is measured in accordance with JIS K7136.

The thickness of the stretched substrate is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and preferably 200 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less. If the thickness is equal to or greater than the lower limit, for example, the strength and heat resistance of the laminate can be improved. If the thickness is equal to or less than the upper limit, for example, the processability of the laminate can be improved.

The stretched substrate can be produced, for example, by forming a film from polyethylene or a resin composition thereof using an inflation method, T-die molding, or the like, and then stretching the film. Using inflation molding, film formation and stretching can be carried out simultaneously. In one embodiment, the stretched substrate is a co-extruded resin film. In one embodiment, the stretched substrate is a resin film obtained by co-extrusion of two or more materials that make up the polyethylene layer using a co-extrusion inflation method, followed by a stretching treatment.

The stretched substrate may be surface-treated. This can improve adhesion between the stretched substrate and other layers, for example. Surface treatment methods include physical treatments such as corona treatment, ozone treatment, low-temperature plasma treatment using oxygen gas and/or nitrogen gas, and glow discharge treatment; and chemical treatments such as oxidation treatment using chemicals.

Examples of polyethylene substrates having a multilayer structure include the following.
(1) A substrate comprising, in this order, a medium-density polyethylene layer, a high-density polyethylene layer, a blend layer of medium-density polyethylene and high-density polyethylene, a high-density polyethylene layer, and a medium-density polyethylene layer;
(2) A substrate comprising, in this order, a medium-density polyethylene layer, a medium-density polyethylene layer, a blend layer of medium-density polyethylene and linear low-density polyethylene, a medium-density polyethylene layer, and a medium-density polyethylene layer;
(3) A substrate comprising, in this order, a blend layer of medium-density polyethylene and high-density polyethylene, a blend layer of medium-density polyethylene and linear low-density polyethylene, a linear low-density polyethylene layer, a blend layer of medium-density polyethylene and linear low-density polyethylene, and a blend layer of medium-density polyethylene and high-density polyethylene;
(4) A substrate comprising, in this order, a blend layer of medium-density polyethylene and high-density polyethylene, a blend layer of medium-density polyethylene and linear low-density polyethylene, a blend layer of medium-density polyethylene and linear low-density polyethylene, a blend layer of medium-density polyethylene and linear low-density polyethylene, and a blend layer of medium-density polyethylene and high-density polyethylene;
(5) A substrate comprising, in this order, a blend layer of high-density polyethylene and medium-density polyethylene, a medium-density polyethylene layer, a blend layer of linear low-density polyethylene and medium-density polyethylene, a medium-density polyethylene layer, and a blend layer of high-density polyethylene and medium-density polyethylene;
(6) A substrate comprising, in this order, a blend layer of medium-density polyethylene and high-density polyethylene, a high-density polyethylene-containing layer, a linear low-density polyethylene layer, a high-density polyethylene layer, and a blend layer of medium-density polyethylene and high-density polyethylene;
(7) A substrate comprising, in this order, a blend layer of medium-density polyethylene and high-density polyethylene, a blend layer of medium-density polyethylene and linear low-density polyethylene, a linear low-density polyethylene layer, a high-density polyethylene layer, and a blend layer of medium-density polyethylene and high-density polyethylene;
(8) A substrate comprising, in this order, a high-density polyethylene layer, a medium-density polyethylene layer, a low-density polyethylene layer, a linear low-density polyethylene layer or an ultra-low-density polyethylene layer, a medium-density polyethylene layer, and a high-density polyethylene layer;
(9) A substrate comprising, in this order, a high-density polyethylene layer, a blend layer of high-density polyethylene and medium-density polyethylene, a low-density polyethylene layer, a linear low-density polyethylene layer or an ultra-low-density polyethylene layer, a blend layer of high-density polyethylene and medium-density polyethylene, and a high-density polyethylene layer;
(10) A substrate comprising, in this order, a high-density polyethylene layer, a high-density polyethylene layer, a blend layer of medium-density polyethylene and high-density polyethylene, a high-density polyethylene layer, and a high-density polyethylene layer;
(11) A substrate comprising, in this order, a medium-density polyethylene layer, a high-density polyethylene layer, a linear low-density polyethylene layer, a high-density polyethylene layer, and a medium-density polyethylene layer.

The substrates (1) to (11) above each have five layers. Starting from the outside, the layers are referred to as the first to fifth layers. The thickness of each of the first and fifth layers may be 0.5 μm or more, 1 μm or more, 10 μm or less, 8 μm or less, or 5 μm or less. The thickness of each of the second and fourth layers may be 0.5 μm or more, 1 μm or more, 15 μm or less, 10 μm or less, or 8 μm or less. The thickness of the third layer may be 1 μm or more, 2 μm or more, 5 μm or more, 50 μm or less, 40 μm or less, or 30 μm or less.

Examples of polyethylene substrates having a multilayer structure include the following.
(12) A substrate comprising a high-density polyethylene layer and a medium-density polyethylene layer in this order;
(13) A substrate comprising a high-density polyethylene layer, a medium-density polyethylene layer, and a high-density polyethylene layer in this order.

<Anchor coat layer>
The laminate of the present disclosure may include an anchor coat layer between the stretched substrate and the heat generating layer, which can improve adhesion between the layers, for example.

Examples of anchor coating agents include isocyanate-based, polyurethane-based, polyolefin-based, polyethyleneimine-based, and epoxy resin-based anchor coating agents. In one embodiment, the anchor coating agent is a two-component curing resin, consisting of, for example, a polyol base and a polyisocyanate curing agent. In one embodiment, the anchor coating agent contains a polyisocyanate. Examples of polyols include polyether polyols, polyester polyols, and (meth)acrylic polyols. Examples of polyisocyanates include aromatic polyisocyanates such as tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, and polymethylene polyphenylene polyisocyanate, as well as aliphatic polyisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate. In one embodiment, the anchor coating layer is made of polyurethane obtained by reacting a polyol with a polyisocyanate. Specific examples of polyurethane include polyether polyurethane, polyester polyurethane, and poly(meth)acrylic polyurethane.

The anchor coat layer can be formed, for example, by applying an anchor coat agent to the stretched substrate. The anchor coat agent can be applied by coating methods such as roll coating, gravure roll coating, and kiss coating, or by printing.

The thickness of the anchor coat layer is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.2 μm or more, and preferably 3.0 μm or less, more preferably 2.0 μm or less, even more preferably 1.0 μm or less.

<Heat generating layer>
The laminate of the present disclosure includes a heat-generating layer containing a heat-generating substance that absorbs laser light and generates heat. For example, by irradiating the laminate with a laser, an easy-open line including an altered portion can be formed, improving the ease of opening a packaging bag. The heat-generating layer is provided between the stretched substrate and the sealant layer. The heat-generating layer may further contain a binder resin.

Examples of exothermic substances that absorb laser light and generate heat include metal oxides, bismuth-based compounds, molybdenum or molybdenum-based compounds, copper or copper-based compounds, and carbon black. Among these, inorganic substances are preferred, and metal oxides are more preferred.

Examples of metal oxides include titanium oxide, magnesium oxide, zinc oxide, aluminum oxide, silicon oxide, nickel oxide, tin oxide, neodymium oxide, mica, zeolite, kaolinite, copper-molybdenum composite oxide, and copper-tungsten composite oxide. Of these, titanium oxide is preferred. The heat-generating layer may be, for example, a white layer or a white layer containing titanium oxide.

Examples of bismuth-based compounds include bismuth oxide, bismuth nitrate-based compounds such as bismuth nitrate and bismuth oxynitrate, bismuth halides such as bismuth chloride, bismuth oxychloride, bismuth sulfate, bismuth acetate, bismuth citrate, bismuth hydroxide, bismuth titanate, and bismuth subcarbonate.

Molybdenum compounds include, for example, molybdenum oxides such as molybdenum dioxide and molybdenum trioxide, molybdenum chloride, and metal molybdates. Metal components in metal molybdates include, for example, potassium, zinc, calcium, nickel, bismuth, and magnesium.

Examples of copper-based compounds include copper oxide, copper halides, organic acid copper salts such as formic acid, citric acid, salicylic acid, lauric acid, oxalic acid, and maleic acid, copper phosphate, and copper hydroxyphosphate.

The content of the heat-generating substance in the heat-generating layer may be 5% by mass or more, 10% by mass or more, 20% by mass or more, 50% by mass or more, 85% by mass or less, 80% by mass or less, or 75% by mass or less.

Examples of binder resins include polyurethane, polyester, (meth)acrylic resin, and cellulose resin. The binder resin content in the heat-generating layer may be 15% by mass or more, 20% by mass or more, 25% by mass or more, 95% by mass or less, 90% by mass or less, 80% by mass or less, or 50% by mass or less.

The thickness of the heat-generating layer may be 0.5 μm or more, 1.0 μm or more, 4.0 μm or less, 3.5 μm or less, or 3.0 μm or less. If the thickness is equal to or greater than the lower limit, for example, the ease of opening a packaging bag can be improved. If the thickness is equal to or less than the upper limit, for example, the recyclability of the laminate can be improved.

The heat-generating layer is located, for example, between the stretched substrate and the sealant layer. Furthermore, when the laminate is viewed in plan, the heat-generating layer may be provided over the entire surface, or only in the area where the easy-open line will be formed when a packaging bag is made from the laminate.

The heat-generating layer can be formed, for example, by applying a composition containing a binder resin and a heat-generating substance to a stretched substrate or the like and drying it. Examples of application methods include printing methods such as gravure printing, offset printing, and flexographic printing. In other words, the heat-generating layer may be a printed layer provided on the stretched substrate. Furthermore, when the laminate is viewed in plan, the printed layer may be provided over the entire surface, or only in areas where an easy-open line will be formed when a packaging bag is made from the laminate.

<Print layer>
The laminate of the present disclosure may include a printed layer other than the heat-generating layer. The printed layer includes an image. Examples of the image include letters, figures, patterns, symbols, and combinations thereof. The image may include text information such as the product name, the name of the contents in the packaging bag, the manufacturer, and the names of ingredients. The image may be a single, solid color (a so-called solid image).

The printing layer contains coloring materials such as pigments and dyes. The printing layer may be formed using, for example, ink derived from biomass. This can further reduce the environmental impact, for example. The heat-generating layer may also function as a printing layer containing an image.

Methods for forming the printed layer include conventionally known printing methods such as gravure printing, offset printing, and flexographic printing. Flexographic printing may also be used from the perspective of reducing environmental impact.

The thickness of the printing layer may be 0.5 μm or more, 1.0 μm or more, 10 μm or less, 6.0 μm or less, or 4.0 μm or less.

The printed layer may be formed on either side of the stretched substrate. It is preferable that the printed layer be formed on the side of the stretched substrate facing the sealant layer, as this prevents the printed layer from coming into contact with the outside air and prevents deterioration of the printed layer over time.

<Sealant layer>
The laminate of the present disclosure includes a sealant layer.
In one embodiment, the sealant layer contains polyethylene as a main component. This allows the packaging bag to be made of a single material. After collecting used packaging bags, there is no need to separate the stretched substrate and the sealant layer, improving the recyclability of the packaging bag.

Examples of polyethylene include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, and very low-density polyethylene. From the viewpoint of heat-sealability, low-density polyethylene, linear low-density polyethylene, and very low-density polyethylene are preferred. From the viewpoint of reducing the environmental impact, biomass-derived polyethylene and mechanically or chemically recycled polyethylene may also be used as the polyethylene.

From the viewpoint of heat sealability, the sealant layer preferably contains low-density polyethylene and linear low-density polyethylene. From the viewpoint of tearability, the sealant layer preferably contains low-density polyethylene. When the sealant layer contains low-density polyethylene and linear low-density polyethylene, the content (mass %) of the linear low-density polyethylene may be greater than the content (mass %) of the low-density polyethylene.

From the viewpoint of balancing heat resistance and heat sealability, the melting point (Tm) of the polyethylene constituting the sealant layer is preferably 90°C or higher, more preferably 95°C or higher, and preferably 140°C or lower, more preferably 130°C or lower.

From the viewpoint of film-forming ability and processability, the MFR of the polyethylene constituting the sealant layer is preferably 0.1 g/10 min or more, more preferably 0.3 g/10 min or more, even more preferably 0.5 g/10 min or more, and preferably 50 g/10 min or less, more preferably 30 g/10 min or less, and even more preferably 10 g/10 min or less. An MFR of at least the lower limit can improve, for example, the processability of the sealant layer. An MFR of at most the upper limit can improve, for example, film-forming ability.

The polyethylene content in the sealant layer is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. This can improve the recyclability of the packaging bag, for example.

The sealant layer may contain the above-mentioned additives.

The thickness of the sealant layer is preferably 10 μm or more, more preferably 30 μm or more, even more preferably 50 μm or more, and particularly preferably 80 μm or more, and is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 150 μm or less. It is preferable that the total thickness of a sealant layer having a multilayer structure be within the above range. If the thickness is equal to or greater than the lower limit, for example, the heat sealability of the sealant layer and the recyclability of the packaging bag can be improved. If the thickness is equal to or less than the upper limit, for example, the processability of the laminate can be improved.

From the standpoint of heat-sealability, the sealant layer is preferably an unstretched resin film, more preferably an unstretched co-extruded resin film, and each layer constituting the sealant layer is a co-extruded resin layer. The above-mentioned resin film can be produced using, for example, a casting method, a T-die method, or an inflation method. The term "unstretched" encompasses not only films that are not stretched at all, but also films that are slightly stretched due to the tension applied during film formation.

For example, an unstretched resin film corresponding to the sealant layer may be laminated onto the stretched substrate, if necessary, via an adhesive layer, or the sealant layer may be formed by melt-extruding polyethylene or a resin composition thereof onto the stretched substrate. In the latter case, an adhesive layer may not be provided. Examples of adhesive layers include those described below.

In the laminate of the present disclosure, the sealant layer comprises a first layer and a second layer, as described below. The first layer contains an ethylene/α-olefin copolymer as a primary component and has a melting point of 112°C or less. The second layer contains polyethylene as a primary component and has a melting point of 114°C or more. The first layer improves low-temperature sealing properties, while the second layer improves rigidity and hand tearability.

Stretched substrates containing polyethylene as the primary component are made from polyethylene, which has a lower melting point than conventional resin films such as polyester and nylon, so the heat-sealing temperature cannot be set too high when manufacturing packaging bags using the laminate. In the case of a sealant layer comprising a first layer and a second layer, the first layer can be heat-sealed at a lower temperature than the second layer, so the sealing properties of the packaging bag can be maintained even when combined with a stretched substrate made of polyethylene.

Stretched substrates made of polyethylene have higher tear strength than resin films such as polyester or nylon, so when the laminate is processed into a packaging bag, the hand tearability (tearability) of the bag may be reduced upon opening. Combining the stretched substrate with the sealant layer of the above embodiment improves the tearability of the laminate. While the reason for this is unclear, it is presumed that the sealant layer has improved toughness by including a second layer with a melting point of 114°C or higher, further improving the tearability of the laminate. In this disclosure, while tearability can be improved by providing an easy-open line in the laminate as described above, tearability can be further improved by using the sealant layer.

In this specification, the melting point of a layer is a value determined using a differential scanning calorimeter in accordance with JIS K7121:2012. Specifically, a sample is taken from each layer of the sealant layer, and the melting point is measured using the method described in the Examples section.

(First layer)
The first layer of the sealant layer contains an ethylene/α-olefin copolymer as a main component and has a melting point of 112°C or less. This improves the low-temperature sealing property of the sealant layer, as described above. The first layer is one of the surface layers of the sealant layer and also one of the surface layers of the laminate. The first layer is the layer facing the contents to be placed in the packaging bag.

An example of an ethylene/α-olefin copolymer is linear polyethylene. Linear polyethylene is a copolymer of ethylene and an α-olefin obtained using, for example, a multi-site catalyst such as a Ziegler-Natta catalyst or a single-site catalyst such as a metallocene catalyst. An example of a linear polyethylene having a density of 0.930 g/cm ^or less is linear low-density polyethylene.

The α-olefin comonomer of the copolymer is, for example, an α-olefin having 3 to 20 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-nonene, and 4-methylpentene. The higher the carbon number, the better the tear resistance tends to be. Considering low-temperature sealing properties and tear resistance, 1-hexene and 1-octene are preferred α-olefins.

Polyethylene can be produced, for example, using a multi-site catalyst such as a Ziegler-Natta catalyst or a single-site catalyst such as a metallocene catalyst as the polymerization catalyst. A single-site catalyst is a catalyst capable of forming a uniform active species and is typically prepared by contacting a metallocene transition metal compound or a non-metallocene transition metal compound with an activating cocatalyst. Single-site catalysts are preferred because, compared to multi-site catalysts, the structure of the active sites is more uniform, allowing for the production of polymers with high molecular weights and highly uniform structures. Metallocene catalysts are preferred as single-site catalysts. Furthermore, using an ethylene/α-olefin copolymer produced using a metallocene catalyst in the first layer can improve, for example, low-temperature sealability compared to using an ethylene/α-olefin copolymer produced using a Ziegler-Natta catalyst. Using an ethylene/α-olefin copolymer produced using a metallocene catalyst in the second or third layer (described below) can improve, for example, impact resistance compared to using an ethylene/α-olefin copolymer produced using a Ziegler-Natta catalyst.

From the viewpoint of the low-temperature sealing properties of the sealant layer, the melting point of the first layer is preferably 110°C or lower, more preferably 105°C or lower, and even more preferably 100°C or lower, and may be 80°C or higher, or 90°C or higher.

From the viewpoint of the balance between the low-temperature sealing properties and rigidity of the sealant layer, the difference between the melting points of the second layer and the first layer is preferably 4°C or more, more preferably 15°C or more, and even more preferably 20°C or more, and is preferably 50°C or less, more preferably 48°C or less, and even more preferably 46°C or less, and may be, for example, 40°C or less.

The density of the first layer is preferably 0.915 g/cm ^or less, more preferably 0.912 g/cm ^or less, and even more preferably 0.908 g/cm ^or less, and may be 0.890 g/cm ^or more, or may be 0.900 g/cm ^or more. By setting the density of the first layer to 0.915 g/cm ^or less, for example, the low-temperature sealing property of the sealant layer can be improved. By setting the density of the first layer to 0.890 g/cm ^or more, for example, the blocking resistance of the laminate can be improved.

The content of ethylene/α-olefin copolymer in the first layer is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more.

In one embodiment, the first layer contains an ethylene/α-olefin copolymer having a density of preferably 0.912 g/ ^cm3 or less, more preferably 0.908 g/ ^cm3 or less, and even more preferably 0.905 g/ ^cm3 or less. The density of the ethylene/α-olefin copolymer is preferably 0.890 g/ ^cm3 or more, and more preferably 0.895 g/ ^cm3 or more. When the first layer contains an ethylene/α-olefin copolymer having a density of 0.912 g/ ^cm3 or less, for example, the low-temperature sealability of the sealant layer can be improved. When the ethylene/α-olefin copolymer has a density of 0.890 g/ ^cm3 or more, for example, the blocking resistance of the laminate can be improved.

The thickness of the first layer may be 5 μm or more, 15 μm or more, 50 μm or less, or 30 μm or less. The first layer may be a single layer or a multilayer structure in which each layer has the same composition. If the first layer is a multilayer structure, the thickness of the first layer is the total thickness of each layer.

The ratio of the thickness of the first layer to the thickness of the sealant layer is preferably 3% or more, more preferably 5% or more, even more preferably 10% or more, and particularly preferably 15% or more, and is preferably 40% or less, more preferably 35% or less, even more preferably 30% or less, and particularly preferably 25% or less. This can, for example, further improve the balance between the low-temperature sealing properties and rigidity of the sealant layer.

In one embodiment, the first layer is preferably in contact with the second layer or the third layer, and more preferably in contact with the second layer. That is, in one embodiment, the first layer is preferably in contact with the second layer or the third layer without an adhesive layer therebetween.
In one embodiment, the first layer is an unstretched resin layer.

The first layer may contain the above-mentioned additives.

(Second layer)
The second layer of the sealant layer contains polyethylene as a main component and has a melting point of 114° C. or higher, which can improve the rigidity of the sealant layer as described above.

From the viewpoint of the rigidity of the sealant layer, the melting point of the second layer is preferably 117°C or higher, more preferably 120°C or higher, and may be 150°C or lower, or 135°C or lower.

The density of the second layer is preferably 0.916 g/cm or ^more , more preferably 0.917 g/cm ^or more, even more preferably 0.920 g/cm or ^more , and particularly preferably 0.930 g/cm ^or more, and may be 0.950 g/ ^cm or less, or may be 0.945 g/cm or ^less . By setting the density of the second layer to 0.916 g/cm ^or more, for example, the rigidity and tear resistance of the sealant layer can be improved. By setting the density of the second layer to 0.950 g/cm ^or less, for example, the impact resistance of the sealant layer can be improved.

The polyethylene content in the second layer is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

In one embodiment, the second layer preferably contains polyethylene having a density of 0.915 g/cm ^or more, more preferably 0.935 g/cm or ^more . The density of the polyethylene is preferably 0.970 g/ ^cm or less, more preferably 0.960 g/cm ^or less. When the second layer contains polyethylene having a density of 0.915 g/cm ^or more, for example, the rigidity and tear resistance of the sealant layer can be improved. When the density of the polyethylene is 0.970 g/cm ^or less, for example, the impact resistance of the sealant layer can be improved.

The second layer may contain an ethylene/α-olefin copolymer as the polyethylene. The content of the ethylene/α-olefin copolymer in the second layer is preferably 50% by mass or more, more preferably 70% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less, based on the entire second layer. By making the content of the ethylene/α-olefin copolymer 50% by mass or more, it is possible to improve, for example, the impact resistance of the sealant layer. By making the content of the ethylene/α-olefin copolymer 90% by mass or less, it is possible to improve, for example, the tear resistance of the sealant layer.

The second layer may contain an ethylene homopolymer as the polyethylene. The ethylene homopolymer content in the second layer is preferably 10% by mass or more, more preferably 15% by mass or more, and preferably 50% by mass or less, more preferably 25% by mass or less, based on the entire second layer. By making the ethylene homopolymer content 10% by mass or more, it is possible to improve, for example, the tear resistance of the sealant layer. By making the ethylene homopolymer content 50% by mass or less, it is possible to improve, for example, the impact resistance of the sealant layer.

In one embodiment, when the sealant layer is composed of two layers, the second layer is the surface layer of the sealant layer facing the stretched substrate. In one embodiment, when the sealant layer is composed of three or more layers, the second layer is the surface layer of the sealant layer facing the stretched substrate and/or the intermediate layer. In this case, it is preferable that the first layer and the intermediate layer be made of different materials from the viewpoint of balancing low-temperature sealing properties and rigidity.

An intermediate layer refers to a layer located between one surface layer and the other surface layer of the sealant layer. The intermediate layer may be a single layer or multiple layers. If the intermediate layer is multiple layers, the composition of each intermediate layer may be the same or different.

The second layer may be present in multiple layers within the sealant layer, as long as it contains polyethylene as its main component and has a melting point of 114°C or higher. For example, both the surface layer and the intermediate layer on the stretched substrate side may be second layers.

The thickness of the second layer may be 10 μm or more, 45 μm or more, 250 μm or less, or 170 μm or less. If the second layer is multi-layered, the thickness of the second layer is the total thickness of each layer.

In one embodiment, the second layer is an unstretched resin layer.

The second layer may contain the above-mentioned additives.

(Third layer)
The sealant layer may further include a third layer in addition to the first and second layers. The third layer contains polyethylene as a main component and is a layer that does not fall under the category of the first or second layer.

In one embodiment, the third layer is a surface layer and/or an intermediate layer on the stretched substrate side.
The third layer may be a layer present in multiple locations within the sealant layer.

In one embodiment, the third layer is an unstretched resin layer.

The third layer may contain the above-mentioned additives.

(Configuration of sealant layer)
The layer structure of the sealant layer containing polyethylene as the main component is, for example,
First layer/second layer,
first layer/second layer/first layer,
first layer/second layer/second layer,
First layer/second layer/third layer,
first layer/third layer/second layer,
"/" means between layers.

For example, when the sealant layer comprises a first layer, an intermediate layer, and a surface layer on the stretched substrate side, it is preferable that the melting point of the intermediate layer be higher than that of the surface layer on the stretched substrate side. It is also preferable that the melting point of the intermediate layer be higher than that of the first layer. It is also preferable that the melting point of the surface layer on the stretched substrate side be higher than that of the first layer. This configuration can further improve, for example, the low-temperature sealing properties, rigidity, and impact resistance of the sealant layer.

For example, the difference between the melting point of the intermediate layer and the melting point of the surface layer on the stretched substrate side may be 0°C or higher and 30°C or lower, 1°C or higher, 2°C or higher, 25°C or lower, 20°C or lower, 15°C or lower, or 10°C or lower. For example, the difference between the melting point of the intermediate layer and the melting point of the first layer may be 2°C or higher and 50°C or lower, 4°C or higher, 15°C or higher, 40°C or lower, or 35°C or lower. For example, the difference between the melting point of the surface layer on the stretched substrate side and the melting point of the first layer may be 2°C or higher and 40°C or lower, 4°C or higher, 15°C or higher, 35°C or lower, or 30°C or lower.

In a sealant layer comprising a first layer, an intermediate layer, and a surface layer facing the stretched substrate, the ratio of the thickness of the first layer to the thickness of the sealant layer and the ratio of the thickness of the surface layer facing the stretched substrate are each independently preferably 3% or more, more preferably 5% or more, even more preferably 10% or more, and particularly preferably 15% or more, and preferably 40% or less, more preferably 35% or less, even more preferably 30% or less, and particularly preferably 25% or less.

In a sealant layer comprising a first layer, an intermediate layer, and a surface layer on the stretched substrate side, the ratio of the thickness of the intermediate layer to the thickness of the sealant layer is preferably 20% or more, more preferably 30% or more, even more preferably 40% or more, and particularly preferably 50% or more, and is preferably 94% or less, more preferably 90% or less, even more preferably 80% or less, and particularly preferably 70% or less.

In one embodiment, the sealant layer does not have an adhesive layer between each layer selected from the first layer, the second layer, and optionally the third layer that make up the sealant layer. For example, the sealant layer is a coextruded resin film.

The content of the ethylene/α-olefin copolymer in the sealant layer is preferably 50% by mass or more, more preferably 70% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less, based on the total sealant layer. By making the ethylene/α-olefin copolymer content 50% by mass or more, it is possible to improve, for example, the impact resistance of the sealant layer. By making the ethylene/α-olefin copolymer content 90% by mass or less, it is possible to improve, for example, the tear resistance of the sealant layer.

The content of ethylene homopolymer in the sealant layer is preferably 10% by mass or more, more preferably 15% by mass or more, and preferably 50% by mass or less, more preferably 25% by mass or less, based on the total sealant layer. By making the content of ethylene homopolymer 10% by mass or more, it is possible to improve, for example, the tear resistance of the sealant layer. By making the content of ethylene homopolymer 50% by mass or less, it is possible to improve, for example, the impact resistance of the sealant layer.

The surface of the sealant layer opposite the first layer may be surface treated. This improves adhesion to the adjacent layer. Specific examples of surface treatments are as described above.

<Adhesive layer>
The laminate of the present disclosure may include an adhesive layer between any layers, such as between the stretched substrate and the sealant layer, for example, between the heat generating layer and the sealant layer, thereby improving the adhesion between the stretched substrate and the sealant layer.

The thickness of the adhesive layer may be 0.1 μm or more, 0.2 μm or more, 0.5 μm or more, 10 μm or less, 8.0 μm or less, or 6.0 μm or less. The thickness of the adhesive layer may be 2.0 μm or less.

In one embodiment, the adhesive layer may be an adhesive layer made of an adhesive. The adhesive may be a one-component curing adhesive, a two-component curing adhesive, or a non-curing adhesive. The adhesive may be a solventless adhesive or a solvent-based adhesive.

Solvent-free adhesives, i.e., non-solvent laminating adhesives, include, for example, polyether-based adhesives, polyester-based adhesives, silicone-based adhesives, epoxy-based adhesives, and urethane-based adhesives. Of these, urethane-based adhesives are preferred, and two-component curing urethane-based adhesives are more preferred.

In one embodiment, the solventless adhesive is a two-component curing adhesive containing a base agent and a curing agent. From the standpoint of coatability, the weight-average molecular weight (Mw) of the polymer component contained in the base agent is preferably 800 to 10,000, more preferably 1,200 to 4,000. The polydispersity index (Mw/Mn) of the polymer component contained in the base agent is preferably 2.8 or less, more preferably 1.2 to 2.7, even more preferably 1.5 to 2.6, and particularly preferably 2.0 to 2.5. Here, Mn is the number-average molecular weight of the polymer component contained in the base agent. Each average molecular weight is measured by gel permeation chromatography (GPC) in accordance with JIS K7252-1 (2008) and is expressed in polystyrene equivalents.

Examples of solvent-based adhesives include rubber-based adhesives, vinyl-based adhesives, olefin-based adhesives, silicone-based adhesives, epoxy-based adhesives, phenol-based adhesives, and urethane-based adhesives.

In one embodiment, forming an adhesive layer using a solvent-free adhesive can further reduce the amount of residual solvent in the laminate, specifically the amount of residual organic solvent. Examples of organic solvents include hydrocarbon solvents such as toluene, xylene, n-hexane, and methylcyclohexane; ester solvents such as ethyl acetate, n-propyl acetate, n-butyl acetate, and isobutyl acetate; alcohol solvents such as methanol, ethanol, isopropyl alcohol, n-butyl alcohol, and isobutyl alcohol; and ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

In one embodiment, by using a solvent-free adhesive, for example, the adhesive layer can be made thinner than when a solvent-based adhesive is used. This allows the polyolefin content in the entire laminate to be further increased. Such a laminate is suitable for producing mono-material packaging bags. In one embodiment, by using a solvent-free adhesive, the tearability of the laminate can be further improved compared to when a solvent-based adhesive is used.

The following describes a two-component curing urethane adhesive. A preferred urethane adhesive is one that contains a base agent that includes a polyol compound, such as polyester polyol, and a curing agent that includes an isocyanate compound.

Examples of polyol compounds include polyester polyols, polyether polyols, polycarbonate polyols, and (meth)acrylic polyols. Of these, polyester polyols are preferred.

Polyester polyols have two or more hydroxyl groups per molecule. They have, for example, a polyester structure or a polyester polyurethane structure as their main backbone. Polyester polyols can be obtained, for example, by a dehydration condensation reaction, transesterification, or ring-opening reaction between a polyhydric alcohol component and a polycarboxylic acid component.

Examples of polyhydric alcohol components include diols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, and cyclohexanedimethanol; and tri- or higher functional polyols such as glycerin, triethylolpropane, trimethylolpropane, pentaerythritol, and sorbitol.

Examples of polycarboxylic acid components include aliphatic polycarboxylic acids, alicyclic polycarboxylic acids, and aromatic polycarboxylic acids, as well as their ester derivatives and acid anhydrides. Examples of aliphatic polycarboxylic acids include aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, and dimer acid. Examples of alicyclic polycarboxylic acids include 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid. Examples of aromatic polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, and 1,2-bis(phenoxy)ethane-p,p'-dicarboxylic acid.

If necessary, the polyester polyol can be pre-chain-lengthened with a polyisocyanate. Examples of polyisocyanates include diisocyanates such as 1,6-hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, m-xylylene diisocyanate, α,α,α'α'-tetramethyl-m-xylylene diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, and diphenylmethane diisocyanate; as well as biuret, nurate, or trimethylolpropane adducts of diisocyanates.

From the viewpoint of coatability, the weight-average molecular weight (Mw) of polyol compounds such as polyester polyols is preferably 800 to 10,000, more preferably 1,200 to 4,000. The polydispersity (Mw/Mn) of polyol compounds such as polyester polyols is preferably 2.8 or less, more preferably 1.2 to 2.7, even more preferably 1.5 to 2.6, and particularly preferably 2.0 to 2.5. Here, Mn is the number-average molecular weight of the polyol compound. Each average molecular weight is measured by gel permeation chromatography (GPC) in accordance with JIS K7252-1 (2008) and is expressed in terms of polystyrene.

The isocyanate compound has two or more isocyanate groups in one molecule.
Examples of the isocyanate compound include aromatic isocyanates and aliphatic isocyanates. The isocyanate compound may be a blocked isocyanate compound obtained by addition reaction using a known isocyanate blocking agent by a known, conventional, appropriate method.

Examples of isocyanate compounds include diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, norbornene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, m-xylylene diisocyanate, hydrogenated xylylene diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, and α,α,α'α'-tetramethyl-m-xylylene diisocyanate; trimers of these diisocyanates; and adducts, biuret compounds, and allophanate compounds obtained by reacting these diisocyanate compounds with low-molecular-weight active hydrogen compounds or their alkylene oxide adducts, or high-molecular-weight active hydrogen compounds.

Examples of low-molecular-weight active hydrogen compounds include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexamethylene glycol, 1,8-octamethylene glycol, 1,4-cyclohexanedimethanol, meta-xylylene alcohol, 1,3-bishydroxyethylbenzene, 1,4-bishydroxyethylbenzene, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, erythritol, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, and meta-xylylenediamine. Examples of high-molecular-weight active hydrogen compounds include polyesters, polyether polyols, and polyamides.

The adhesive layer may be an adhesive resin layer containing a thermoplastic resin. Examples of thermoplastic resins include high-density polyethylene, medium-density polyethylene, high-pressure low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-methyl(meth)acrylate copolymer, ethylene-ethyl(meth)acrylate copolymer, ethylene-maleic acid copolymer, ionomer resin, and resins obtained by graft polymerizing or copolymerizing polyolefin with an unsaturated carboxylic acid, unsaturated carboxylic anhydride, or ester monomer. The thermoplastic resin may be derived from a fossil fuel, a biomass-derived material, or both.

In one embodiment, the laminate of the present disclosure may be produced by laminating a stretched substrate and a resin film corresponding to the sealant layer using a non-solvent lamination method with a solvent-free adhesive, or by dry lamination using a solvent-based adhesive.

<Layer structure of laminate>
Specific examples of the layer structure of the laminate of the present disclosure are given below. The laminate 30 shown in Fig. 1 includes, in this order, a stretched substrate 40, a heat-generating layer 50, an adhesive layer 60, and a sealant layer 70. In Fig. 1, the stretched substrate 40 may have a multi-layer structure. The sealant layer 70 in Fig. 1 has, for example, the layer structure shown in Figs. 2 to 4.

The sealant layer 70 shown in FIG. 2 includes, in this order, a first layer 72 as a sealing layer and a second layer 74 as a laminate layer. The sealant layer 70 shown in FIG. 3 includes, in this order, a first layer 72 as a sealing layer, a second layer 74 as an intermediate layer, and a second layer 74 as a laminate layer. The two second layers 74 may be the same as or different from each other. The sealant layer 70 shown in FIG. 4 includes, in this order, a first layer 72 as a sealing layer, a second layer 74 as an intermediate layer, and a third layer 76 as a laminate layer.

[Packaging bag]
The laminate of the present disclosure can be suitably used for packaging material applications. The packaging material is used to produce packaging bags. By using at least the laminate of the present disclosure, a packaging bag with excellent tearability can be produced. The packaging bag may be a refill pouch, particularly a stand-up pouch, that contains fluid contents such as liquids or powders and is refilled into containers such as bottles.

Packaging bags include various types, such as standing pouch, side seal, two-sided seal, three-sided seal, four-sided seal, envelope seal, palm seal (pillow seal), pleated seal, flat bottom seal, square bottom seal, and gusset seal.

The packaging bag of the present disclosure comprises the laminate of the present disclosure.
The packaging bag of the present disclosure comprises:
a storage section for storing contents;
a seal portion where the sealant layers of the laminate are joined together;
and an easy-open line including the altered portion of the laminate.
The seal portion includes an inner edge that defines the receptacle portion.
The easy-open line includes a first intersection and a second intersection that intersect with the inner edge of the sealed portion, and is a line that crosses the containing portion when the packaging bag is viewed in plan.
The packaging bag may further have a notch portion that serves as a tearing starting point.

<Sealing section>
The packaging bag has a seal portion where the sealant layers of the laminate are joined together.
Examples of methods for forming the sealed portion include heat sealing, in which the sealant layer of the laminate is melted by heating or the like to fuse the sealant layers together.Specific examples of methods include bar sealing, rotary roll sealing, belt sealing, impulse sealing, high-frequency sealing, and ultrasonic sealing.

<Easy-to-open line>
The packaging bag has an easy-open line as a path for tearing the packaging bag.
The easy-open line includes a deteriorated portion where the laminate has deteriorated.
The width W1 of the altered portion included in the easy-open line is preferably 30 μm or more, more preferably 50 μm or more, and even more preferably 70 μm or more, and may be 250 μm or less, 230 μm or less, or 200 μm or less. This, for example, can improve the ease of opening the packaging bag. The width W1 is measured at the end face of the stretched substrate on the sealant layer side. The greater the energy absorbed by the heat-generating layer from the laser, the greater the width W1 tends to be.
A specific example of a method for calculating the width W1 will be described later.

The laminate constituting the packaging bag may have two or more easy-open lines. The number of easy-open lines may be one or more, two or more, three or more, ten or less, eight or less, or five or less. The easy-open lines may be formed on both the surface film and the back film, which will be described later. In this case, the surface film and the back film may each have the above-mentioned number of easy-open lines.

An easy-open line including an altered portion can be formed, for example, by irradiating a laser onto the laminate that constitutes the packaging bag. The reason why an altered portion is formed in the laminate is presumed to be as follows: When a laser is irradiated onto the laminate, the heat-generating substance contained in the heat-generating layer absorbs the laser, causing the temperature of the heat-generating layer to rise. This generates gas, for example, around the heated heat-generating layer. As the temperature of the gas rises and the gas pressure increases, part of the stretched substrate is scattered, forming an altered portion. The altered portion may penetrate the stretched substrate, may further penetrate the heat-generating layer, or may further penetrate the adhesive layer. Even if no through-holes are formed, the altered portion may be formed, for example, by the heat-generating layer expanding and partially raising or peeling off the stretched substrate. Note that the altered portion may also be formed by a different principle.

The laser can be irradiated while moving the laser irradiation position on the laminate. For example, a laser irradiation device that emits a laser toward the laminate can be moved relative to the laminate. This causes an altered portion to be formed along the movement path of the laser irradiation device. As a result, an easy-open line extending in a direction corresponding to the movement path of the laser irradiation device is formed on the laminate. The relative movement may include moving the laser irradiation device relative to the laminate, or may include moving the laminate relative to the laser irradiation device. The laser irradiation position on the laminate may also be moved by changing the trajectory of the laser using a galvanometer mirror or the like.

The laminate may be irradiated with a laser from the sealant layer side.
The laminate may be irradiated with a laser from the stretched substrate side.

The scanning speed of the laser irradiation may be 10 mm/s or more, 20 mm/s or more, or 50 mm/s or more. By setting the scanning speed at a certain value or more, it is possible to prevent the heating layer from absorbing excessive laser energy, for example. This prevents damage to the sealant layer and prevents the width W1 of the altered portion from becoming too large. The scanning speed of the laser irradiation can be selected appropriately depending on the type and wavelength of the laser.

The scanning speed of the laser irradiation may be 2000 mm/s or less, 1500 mm/s or less, or 1000 mm/s or less. This allows, for example, the heat-generating layer to properly absorb the laser energy.

The laser output may be 1 W or more, 2 W or more, 100 W or less, 80 W or less, or 50 W or less. The laser line width may be 40 μm or more, 60 μm or more, 500 μm or less, 200 μm or less, or 100 μm or less.

The laser may be a UV laser, a visible light laser, or an infrared laser. The wavelength of the laser may be 200 nm or more, 300 nm or more, 500 nm or more, 800 nm or more, 1000 nm or more, 20 μm or less, 15 μm or less, 2000 nm or less, 1800 nm or less, or 1500 nm or less.

Examples of the laser include a fiber laser, a YAG laser, a _YVO4 laser, a semiconductor laser, and a carbon dioxide laser ( _CO2 laser). From the viewpoint of tearability (particularly tearability in a 45° diagonal direction, which will be described later), a fiber laser is preferred, and from the viewpoint of productivity, a _CO2 laser is preferred.

<Contents>
The contents to be placed in the packaging bag include, for example, liquids, solids, powders, and gels. The contents may be food or beverages, or non-food or beverages such as chemicals, cosmetics, and pharmaceuticals. After the contents are placed in the packaging bag, the opening of the packaging bag can be heat-sealed to seal the packaging bag.

Examples of contents include shampoo, rinse, conditioner, hand soap, body soap, air freshener, deodorant, insect repellent, detergent; sauce, soy sauce, dressing, cooking oil, mayonnaise, ketchup, syrup, cooking alcohol, and other liquid or viscous condiments; fruit juice; spices; liquid beverages, jelly-like beverages, liquid soups, powdered soups, instant foods, other food and beverages; and cream.

<Making packaging bags>
In one embodiment, a packaging bag can be produced by folding the laminate of the present disclosure in half and overlapping it so that the stretched substrate is on the outside and the sealant layer is on the inside, and then heat-sealing the edges, etc. In another embodiment, a packaging bag can be produced by overlapping multiple laminates of the present disclosure so that the sealant layers face each other, and then heat-sealing the edges, etc. The entire packaging bag may be made of the above-mentioned laminate, or only a portion of the packaging bag may be made of the above-mentioned laminate.

<Embodiment of packaging bag>
Hereinafter, several examples of embodiments of the packaging bag of the present disclosure will be described with reference to the drawings.
FIG. 5 is a front view of a packaging bag 10 according to one embodiment. FIG. 5 shows the packaging bag 10 before it is filled with contents (i.e., no contents are contained therein). The packaging bag 10 is a gusset-type pouch configured to be self-standing. The packaging bag 10 includes an upper portion 11, a lower portion 12, and a side portion 13, and has a generally rectangular outline in a front view. Terms such as "upper portion,""lowerportion," and "side portion," as well as terms such as "above" and "below," merely describe the relative positions and directions of the packaging bag 10 and its components relative to a state in which the packaging bag 10 is self-standing with the gusset portion facing downward. The names and terms used in this specification do not limit the orientation of the packaging bag 10 during transportation or use.

The packaging bag 10 has a storage section 17, a seal section 19, and an easy-open line 26. The storage section 17 stores the contents. The seal section 19 includes an inner edge 19x that defines the storage section 17. The seal section 19 is formed by joining the sealant layers of the laminate that makes up the packaging bag 10. In plan views such as Figure 5, the seal section 19 is hatched.

The storage section 17 may include a spout section 20. The spout section 20 is the section through which the contents pass when removing them from the packaging bag 10. The width of the spout section 20 is narrower than the width of the rest of the storage section 17. This allows the user to accurately determine the pouring direction of the contents as they are poured from the packaging bag 10 through the spout section 20.

The easy-open line 26 is formed on the packaging bag 10 to improve the tearability of the packaging bag 10. The easy-open line 26 crosses the storage section 17 in a plan view of the packaging bag 10. The direction of the easy-open line 26 crossing the storage section 17 is not particularly limited; for example, it may be in the MD direction of the laminate, or in a direction at any angle to the MD direction (for example, the TD direction or a direction at 45°). In the example shown in Figure 5, the easy-open line 26 crosses the spout section 20 in a plan view. As shown in Figure 5, a notch 28 adjacent to the easy-open line 26 may be formed on the outer edge of the packaging bag 10. Instead of the notch 28, a slit may be formed on the outer edge of the packaging bag 10.

When a user tears the packaging bag 10 along the easy-open line 26, a shear force is applied to the film that constitutes the packaging bag 10. The tearing of the sealant layer 70 progresses along the easy-open line 26, causing the film to tear. Tearability refers to the ease with which tearing of the packaging bag 10 progresses based on the shear force applied to the film. If a film has high tearability, the user can tear the film of the packaging bag 10 along the easy-open line 26 by applying an appropriate shear force to the packaging bag 10. If a film has low tearability, tearing of the packaging bag 10 along the easy-open line 26 is unlikely to progress even if the user applies a large shear force to the packaging bag 10. For example, the shear force applied to the packaging bag 10 may be used to stretch some layers of the packaging bag 10 or to peel some layers of the packaging bag 10 from other layers. This makes it difficult for the film to tear.

The packaging bag 10 comprises a surface film 14 that forms the surface, a back film 15 that forms the back, and a lower film 16 that forms the lower portion 12. The lower film 16 is folded back at the fold portion 16f and is positioned between the surface film 14 and the back film 15.

Either or both of the front film 14 and the back film 15 are composed of the laminate 30 of the present disclosure. The lower film 16 may also be composed of the laminate 30 of the present disclosure. In one embodiment, the laminate 30 includes an oriented substrate 40, a heat-generating layer 50, an adhesive layer 60, and a sealant layer 70, as shown in FIG. 6 .

The laminate 30 includes an inner surface 30x and an outer surface 30y. The inner surface 30x is the surface that contacts the contents. The outer surface 30y is the surface located opposite the inner surface 30x. The sealant layer 70 is located on the inner surface 30x side of the stretched substrate 40. The heat-generating layer 50 is located between the stretched substrate 40 and the sealant layer 70.

The terms "surface film," "back film," and "bottom film" merely refer to the respective films according to their positional relationships, and the above terms do not limit the method of providing the films when manufacturing the packaging bag 10. For example, the packaging bag 10 may be manufactured using a single film in which the surface film 14, back film 15, and bottom film 16 are connected together; it may be manufactured using a total of two films: one film in which the surface film 14 and bottom film 16 are connected together and one back film 15; or it may be manufactured using a total of three films: one surface film 14, one back film 15, and one bottom film 16.

As shown in FIG. 5, the seal portion 19 includes a bottom seal portion 12a, a side seal portion 13a, and a spout seal portion 20a. The bottom seal portion 12a extends across the bottom portion 12. The side seal portion 13a extends along the pair of side portions 13. The spout seal portion 20a defines the spout portion 20. The distance between the inner edges of the spout seal portion 20a is smaller than the distance between the inner edges of the pair of side seal portions 13a. When the spout portion 20 is formed at a corner between the top portion 11 and side portions 13 of the packaging bag 10, the spout seal portion 20a is connected to the side seal portion 13a.

As shown in FIG. 5, when the packaging bag 10 does not contain any contents, the top 11 of the packaging bag 10 forms an opening 11b. After the contents are placed in the packaging bag 10 through the opening 11b, the sealant layer of the front film 14 and the sealant layer of the back film 15 are joined at the top 11 to form an upper seal at the opening 11b. This seals the storage area 17 from the outside of the packaging bag 10.

The side seal portion 13a, the spout seal portion 20a, and the upper seal portion are formed by joining the sealant layer of the surface film 14 and the sealant layer of the back film 15. The lower seal portion 12a includes a portion where the sealant layer of the surface film 14 and the sealant layer of the bottom film 16 are joined, and a portion where the sealant layer of the back film 15 and the sealant layer of the bottom film 16 are joined. As shown by the dotted line labeled 13c in Figure 5, a cutout may be formed in part of the bottom film 16. The sealant layer of the surface film 14 and the sealant layer of the back film 15 may be joined at the position of the cutout.

The easy-open line 26 will now be described in detail. Figure 6 is a diagram showing the easy-open line 26 formed in the surface film 14. Figure 6 is a cross-sectional view showing the surface film 14 cut in a direction perpendicular to the direction in which the easy-open line 26 extends, as indicated by the symbol A in Figure 5. Although not shown, an easy-open line 26 may also be formed in the back film 15. The easy-open line 26 in the surface film 14 and the easy-open line 26 in the back film 15 may overlap when viewed in the normal direction of the surface film 14. The easy-open line 26 includes a through-hole 27 that penetrates the stretched substrate 40. The easy-open line 26 is formed by irradiating the laminate 30 with a laser. As shown in Figure 8, the packaging bag 10 may have multiple easy-open lines 26 that cross the storage section 17.

The method for calculating the width of the altered portion will be explained with reference to Figure 7. As shown in Figure 7, the easy-open line 26 intersects with the inner edge 19x of the sealed portion 19 at the first intersection 261 and the second intersection 262. Points P1, P2, and P3 are located at the boundaries when the section of the easy-open line 26 from the first intersection 261 to the second intersection 262 is divided into four parts. The packaging bag 10 is cut along a straight line that is perpendicular to the direction in which the easy-open line 26 extends and passes through points P1, P2, and P3. The three cut surfaces are observed, and the widths are measured. The average of the three width measurements is used as the width W1 of the altered portion. For example, a Keyence VHX-6000 digital microscope is used to observe the cut surface. The observation magnification is 1000x. The width of the altered portion is measured using the length measurement function of the VHX-6000.

Next, the layer structure of the lower film 16 will be described.
The layer configuration of the lower film 16 is arbitrary as long as it has an inner surface that can be bonded to the sealant layer of the front film 14 and the sealant layer of the back film 15. For example, the above-described laminate 30 may be used as the lower film 16, similar to the front film 14 and the back film 15. A film having a different configuration from the laminate 30 of the present disclosure may also be used as the lower film 16.

The packaging bag 10 can be produced, for example, as follows: A laminate 30 is prepared. Next, a laser is irradiated onto the laminate 30 to form an easy-open line 26. The laminate 30 with the easy-open line 26 formed thereon is cut in two. This results in a surface film 14 and a back film 15. Next, a folded-over bottom film 16 is inserted between the surface film 14 and the back film 15. Next, the sealant layers of each film are heat-sealed to form seals such as a bottom seal 12a, a side seal 13a, and a spout seal 20a. The films joined together by heat sealing are then cut into an appropriate shape. This results in the packaging bag 10 shown in Figure 5.

Next, the contents are filled into the storage section 17 of the packaging bag 10. The top section 11 is then heat-sealed to form the top seal section. In this way, the packaging bag 10 is obtained, with the contents stored and sealed.

In the above description of the embodiment, an example was shown in which the packaging bag 10 is a gusset-type pouch, but the specific configuration of the packaging bag 10 is not particularly limited.

For example, as shown in Figures 9 and 10, the packaging bag 10 does not need to have a bottom film 16. In Figures 9 and 10, the bottom seal portion 12a and the side seal portion 13a of the packaging bag 10 are formed by joining the sealant layers of the front film 14 and the back film 15, respectively, which are made up of a laminate 30. After the contents are placed in the packaging bag 10, the sealant layer of the front film 14 and the sealant layer of the back film 15 are joined at the opening 11b of the top 11, thereby sealing the packaging bag 10. In Figures 9 and 10, the packaging bag 10 also has an easy-open line 26 that crosses the storage portion 17 in a plan view. This improves the tearability of the packaging bag 10.

As shown in FIG. 11, the packaging bag 10 may be a pillow pouch. The packaging bag 10 includes a seam 18 formed by overlapping the ends of a laminate 30 that constitutes the front film 14 and the back film 15. The seam 18 includes a seam seal portion 18a where the sealant layers of the laminate 30 are joined together. In the example shown in FIG. 11, the easy-open line 26 is formed to cross the storage section 17 and the seam 18. As shown in FIG. 11, a notch 28 or a notch (not shown) that contacts the easy-open line 26 may be formed on the outer edge of the seam.

The present disclosure relates to, for example, the following [1] to [8].
[1] A laminate comprising at least a stretched substrate and a sealant layer, wherein the stretched substrate contains polyethylene as a main component, and the sealant layer comprises at least a first layer and a second layer, wherein the first layer contains an ethylene/α-olefin copolymer as a main component and has a melting point of 112°C or less, and the second layer contains polyethylene as a main component and has a melting point of 114°C or more, one surface layer of the laminate is the first layer, and the laminate further comprises a heat-generating layer between the stretched substrate and the sealant layer, the heat-generating layer containing a heat-generating substance that absorbs laser light and generates heat.
[2] The laminate according to [1], wherein the density of the first layer is 0.915 g/cm ³ or less, and the density of the second layer is 0.916 g/cm ³ or more.
[3] The laminate according to [1] or [2], wherein the exothermic substance is at least one selected from metal oxides, bismuth-based compounds, molybdenum, molybdenum-based compounds, copper, copper-based compounds, and carbon black.
[4] The laminate according to any one of [1] to [3], wherein the exothermic substance is a metal oxide.
[5] The laminate according to any one of [1] to [4], wherein the heat generating layer is a printed layer provided on the stretched substrate.
[6] The laminate according to any one of [1] to [5], further comprising an adhesive layer between the heat generating layer and the sealant layer.
[7] The laminate according to any one of [1] to [6], wherein the content of polyethylene in the entire laminate is 80% by mass or more.
[8] A packaging bag comprising the laminate described in any one of [1] to [7], wherein the packaging bag has a storage section for storing contents, a seal section where the sealant layers of the laminate are joined together, and an easy-open line including the altered part of the laminate, the seal section including an inner edge that defines the storage section, the easy-open line including a first intersection and a second intersection that intersect with the inner edge of the seal section, and is a line that crosses the storage section when the packaging bag is viewed in a plane.

The laminate of the present disclosure will be described in more detail below using examples, but the laminate of the present disclosure is not limited to the following examples.

[Preparation of stretched substrate]
The following materials were used in making the stretched substrate:
- Medium density polyethylene (MDPE)
Product name: Elite 5538G, manufactured by Dow Chemical
Density: 0.941 g/cm ³ , Melting point: 129°C, MFR: 1.3 g/10 min. High density polyethylene (HDPE)
Product name: Elite 5960G, manufactured by Dow Chemical
Density: 0.960 g/cm ³ , Melting point: 134°C, MFR: 0.8 g/10 min. Linear low-density polyethylene (LLDPE)
Product name: Elite 5400G, manufactured by Dow Chemical
Density: 0.916 g/cm ³ , melting point: 123° C., MFR: 1.3 g/10 min

<Polyethylene base material>
Blend PE (A) was obtained by blending 70 parts of MDPE and 30 parts of LLDPE with an average density of 0.934 g/ ^cm3 . Blend PE (B) was obtained by blending 70 parts of MDPE and 30 parts of HDPE with an average density of 0.947 g/ ^cm3 . The LLDPE, blend PE (A), and blend PE (B) were coextruded into five layers by inflation molding with a layer thickness ratio of blend PE (B) layer 15 μm/blend PE (A) layer 22.5 μm/LLDPE layer 50 μm/blend PE (A) layer 22.5 μm/blend PE (B) layer 15 μm to form a tubular film with a total thickness of 125 μm. The tubular film was then folded at the nip to form a two-ply film. The obtained polyethylene film was stretched 5 times in the machine direction (MD), and one of the blended PE (B) layers was subjected to a corona treatment. The end was then slit and divided into two pieces to obtain a polyethylene substrate (hereinafter also referred to as "PE substrate") having a thickness of 25 μm.

<Other stretched substrates>
Ny substrate: 15 μm thick biaxially oriented nylon substrate (Idemitsu Unitech, G-100)

[Preparation of sealant film]
The following materials were used in making the sealant film:
Ethylene/α-olefin copolymer (hereinafter referred to as "Copolymer A")
Copolymers of ethylene and C8 olefins,
Density: 0.902g/cm ³ , MFR: 1.0g/10min,
Polymerization catalyst: metallocene catalyst-ethylene/α-olefin copolymer (hereinafter referred to as “Copolymer B”)
Copolymers of ethylene and C8 olefins,
Density: 0.918g/cm ³ , MFR: 0.8g/10min,
Polymerization catalyst: metallocene catalyst-ethylene/α-olefin copolymer (hereinafter referred to as “Copolymer C”)
Copolymers of ethylene and C8 olefins,
Density: 0.941g/cm ³ , MFR: 1.3g/10min,
Polymerization catalyst: Metallocene catalyst, high-pressure low-density polyethylene (LDPE)
Density: 0.919 g/cm ³ , MFR: 2.0 g/10 min. Slip agent masterbatch (slip agent MB)
Base material: Polyethylene,
Slip agent: erucic acid amide, slip agent content: 2.0% by mass,
Density: 0.921 g/cm ³ , MFR: 5.4 g/10 min. Antiblocking agent masterbatch (AB agent MB)
Base material: polyethylene, anti-blocking agent: acrylic resin,
Antiblocking agent content: 30% by mass,
Density: 0.959g/cm ³ , MFR: 2.5g/10min

A mixture of 93 parts by weight of copolymer A, 1 part by weight of slip agent MB, and 6 parts by weight of AB agent MB was used for the first layer (sealing layer). A mixture of 69 parts by weight of copolymer C, 30 parts by weight of LDPE, and 1 part by weight of slip agent MB was used for the second layer (intermediate layer). A mixture of 89 parts by weight of copolymer B, 10 parts by weight of LDPE, and 1 part by weight of slip agent MB was used for the second layer (laminating layer). A sealant film (hereinafter also referred to as "PE film (A)") having a thickness of 130 μm was obtained by three-layer extrusion film formation such that the thickness ratio of the first layer (sealing layer):second layer (intermediate layer):second layer (laminating layer) was 1:3:1.
The laminate layer surface of the PE film (A) was subjected to a corona treatment.

The melting points of each layer in the obtained PE film (A) were determined using a differential scanning calorimeter in accordance with JIS K7121:2012 using the following method. As a result, the melting points of the first layer (sealing layer) were 99°C, the second layer (intermediate layer) was 122°C, and the second layer (laminate layer) was 117°C. In addition, the densities of the first layer (sealing layer) were 0.906 g/ ^cm3 , the second layer (intermediate layer) was 0.934 g/ ^cm3 , and the second layer (laminate layer) was 0.918 g/ ^cm3 .

(Melt point measurement)
The melting points of each layer in the sealant film were determined using a differential scanning calorimeter in accordance with JIS K7121:2012. A Hitachi High-Tech Science TA7000 series thermal analyzer was used as the differential scanning calorimeter. Specifically, samples of each layer were collected from the sealant film. Approximately 10 mg of the sample was placed in an aluminum cell and heated in a nitrogen atmosphere from 20°C to a temperature (e.g., 200°C) sufficiently higher than the melting point at a heating rate of 10°C/min. The temperature was then maintained at this temperature for 10 minutes, and the sample was then cooled to 20°C at a cooling rate of 10°C/min. This heating, maintaining, and cooling process was repeated once more, and the melting peak temperature of the maximum endothermic peak observed during the second heating was determined and used as the melting point.

[glue]
The following adhesives were used:
Solvent-free adhesive (NSL): Rock Paint, two-component curing urethane solvent-free adhesive, base: RN-920, hardener: HN-920 = 1:1. The weight-average molecular weight (Mw) of the polymer component contained in the base was in the range of 2,000 to 2,500, and the polydispersity (Mw/Mn) of the polymer component contained in the base was in the range of 2.0 to 2.5.

Solvent-based adhesive (DL): Rock Paint, two-component curing urethane solvent-based adhesive, base: RU-80, hardener: H-5, blended at a ratio of 10:1.15. The weight-average molecular weight (Mw) of the polymer component contained in the base was in the range of 30,000 to 34,000, and the number-average molecular weight (Mn) was in the range of 7,500 to 9,500.

[Preparation of coating liquid]
A coating liquid for a white layer having the following composition was prepared.
(White layer coating liquid)
Synthetic resin 12 parts by weight Titanium oxide 30 parts by weight Solvent 58 parts by weight

[Preparation of laminate]
In the following description of the examples and comparative examples, detailed explanations of the previously mentioned layers (for example, layer formation conditions and thicknesses) may be omitted as appropriate.

[Example 1]
A white layer coating solution was applied to the corona-treated surface of the PE substrate using a gravure printing machine and then dried with hot air to form a 1.0 μm thick white layer. A solvent-free adhesive was applied to the white layer surface of the substrate to form a 1.0 μm thick adhesive layer, and the adhesive layer surface was then bonded to the corona-treated surface of the PE film (A). After bonding, an aging treatment was performed at 40°C for 4 days. In this manner, a laminate was produced.

[Examples 2 to 4]
Using a gravure printing machine, the corona treated surface of the PE substrate is printed.
In Example 2, an oil-based gravure ink (manufactured by DIC Graphics, trade name: Finart) was applied and dried with hot air to form a printed layer, and a white layer coating liquid was applied thereon and dried with hot air to form a white layer;
In Example 3, the oil-based gravure ink was applied and dried with hot air to form a printed layer, and then the white layer coating liquid was applied thereon and dried with hot air to form a white layer, and then the oil-based gravure ink was applied thereon and dried with hot air to form a printed layer;
In Example 4, the white layer coating liquid was applied and dried with hot air to form a white layer, and the oil-based gravure ink was applied thereon and dried with hot air to form a print layer.
The thickness of each layer is 1.0 μm.

A solventless adhesive was applied to the white layer or printed layer of the PE substrate to form an adhesive layer with a thickness of 1.0 μm, and the adhesive layer surface was then bonded to the corona-treated surface of the PE film (A). After bonding, the bonded surfaces were subjected to aging treatment at 40° C. for 4 days.
In this manner, a laminate was produced.

[Comparative Examples 1 and 2]
A solvent-based adhesive was applied to the corona-treated surface of a PE or Ny substrate and dried with hot air to form an adhesive layer 3.0 μm thick. The adhesive layer surface was then bonded to the corona-treated surface of a PE film (A). After bonding, the laminate was subjected to aging treatment at 40°C for 4 days. In this manner, a laminate was produced.

[Production of packaging bags]
Two sheets of the resulting laminate were prepared, and the laminates were stacked together with the sealant layers facing each other, and two sides were heat-sealed to form a body. Next, another laminate was folded into a V shape with the sealant layer facing outward, and one end of the body was sandwiched between the two sheets and heat-sealed to form a bottom, producing a standing pouch. The heat-sealing conditions were a temperature of 140°C, a pressure of 1 kgf/ ^cm2 , and a time of 1 second.

[Tear strength]
In accordance with JIS P8116 and JIS K7128, the laminates prepared in the examples and comparative examples were cut to a size of 63 mm x 76 mm to prepare test specimens. The laminates were cut so that the short sides of the laminate, each 63 mm long, were aligned in the machine direction (MD), the transverse direction (TD), or a direction diagonal at 45° to the MD. A laser was irradiated from the substrate side of the laminate at 80% of the (average) output of each device and at a scanning speed of 100 mm/s or 1000 mm/s along the short side of the test specimen at the center of the long side to form a linear easy-to-cut line (easy-to-open line). Five easy-to-open lines were formed (see FIG. 12). The spacing between the easy-to-open lines was 4 mm.

The following laser irradiation device was used.
・_CO2 laser irradiation device (Keyence, 3-Axis _CO2 laser marker ML-Z9520,
_CO2 laser, wavelength 10.6 μm, average power 30 W),
・Fiber laser irradiation device (Panasonic, LP-Z250,
Yb: fiber laser, wavelength 1060 nm, average power 25 W,
Printing pulse period 10 μs, line width 70 μm)
・UV laser irradiation device (Keyence, 3-Axis UV laser marker MD-U1000C,
_YVO4 laser, wavelength 355nm, output 2.5W)

The tear strength along the easy-open line was measured in accordance with the Elmendorf tear method of JIS K7128-2:1998. The measuring device used was an Elmendorf tear tester (Toyo Seiki Seisakusho S-01). Four laminates were stacked to prepare test pieces, and measurements were taken on two test pieces. The results were multiplied by four to convert to a value for 16 sheets, and the average of the obtained values was used as the tear strength (N). An evaluation of the laminate of Example 1 in which an easy-open line was not formed is described as Reference Example 1.

[Evaluation of hand tearability]
The hand tearability of the laminate was evaluated based on the tear strength.
A: Less than 3.0N B: 3.0N or more C: OVER (cannot be measured)

[Monomaterial rate]
A laminate containing 90% or more by mass of polyethylene was evaluated as "A," and a laminate containing less than 90% by mass of polyethylene was evaluated as "B."

[Cross-section observation of altered portion and measurement of width W1]
Points P1, P2, and P3 were set at the boundaries when the easy-open line formed along the short side of the test piece was divided into four parts. The laminate was cut along straight lines that were perpendicular to the direction in which the easy-open line extended and passed through points P1, P2, and P3. The three cut surfaces were observed, and the width of the altered part was measured. The average value of the three width measurements was used as the width W1 of the altered part. In the table, width W1 is referred to as "line width."
The cross-sectional shape of the laminate of Example 1 ( _CO2 laser irradiation, output: 80%, scanning speed: 1000 mm/sec) was observed (observation magnification: 1000x) using a digital microscope VHX-6000 manufactured by Keyence Corporation. The observation results of the laminate are shown in Figure 13. Figure 13 is an image of a cross section perpendicular to the MD direction of a laminate irradiated with a laser along the MD direction. The width W1 of the altered portion in Figure 13 was measured using the length measurement function of the VHX-6000. The result was 109 μm.

10 Packaging bag 11 Upper part 12 Lower part 12a Lower seal part 13 Side part 13a Side seal part 14 Surface film 15 Back film 16 Lower film 17 Storage part 20 Spout part 20a Spout seal part 26 Easy-open line 27 Through hole 28 Notch 30 Laminate 30x Inner surface 30y Outer surface 40 Stretched substrate 50 Heat generating layer 60 Adhesive layer 70 Sealant layer

Claims (8)

A laminate comprising at least a stretched substrate and a sealant layer,
The stretched substrate contains polyethylene as a main component,
The sealant layer comprises:
At least a first layer and a second layer are included,
the first layer contains an ethylene/α-olefin copolymer as a main component,
the melting point of the first layer is 112°C or less;
the second layer contains polyethylene as a main component,
The melting point of the second layer is 114°C or higher,
one surface layer of the laminate is the first layer,
The laminate further includes a heat-generating layer between the stretched substrate and the sealant layer, the heat-generating layer containing a heat-generating substance that absorbs a laser and generates heat.
Laminate. The density of the first layer is 0.915 g/cm ³ or less,
The density of the second layer is 0.916 g/cm ³ or more.
The laminate according to claim 1 . The laminate according to claim 1 or 2, wherein the heat-generating substance is at least one selected from metal oxides, bismuth-based compounds, molybdenum, molybdenum-based compounds, copper, copper-based compounds, and carbon black. The laminate according to any one of claims 1 to 3, wherein the heat-generating substance is a metal oxide. The laminate described in any one of claims 1 to 4, wherein the heat-generating layer is a printed layer provided on the stretched substrate. The laminate described in any one of claims 1 to 5, further comprising an adhesive layer between the heat-generating layer and the sealant layer. The laminate described in any one of claims 1 to 6, wherein the polyethylene content in the entire laminate is 80% by mass or more. A packaging bag comprising the laminate according to any one of claims 1 to 7,
The packaging bag
a storage section for storing contents;
a seal portion where the sealant layers of the laminate are joined together;
An easy-open line including a deteriorated portion of the laminate,
the sealing portion includes an inner edge that defines the receiving portion;
The easy-open line includes a first intersection and a second intersection that intersect with the inner edge of the sealed portion, and is a line that crosses the containing portion when the packaging bag is viewed in a plane.
packaging bag.