Laminate and packaging material

Abstract

To provide a laminate that has strength, heat sealability, and recyclability, and can be suitably used as a packaging material.SOLUTION: A laminate includes a base material and a heat seal layer, in which the base material and the heat seal layer are made of the same resin materials, the base material has a multilayer structure, the base material is a base material subjected to drawing processing, and the heat seal layer is a layer not subjected to drawing processing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to laminates and packaging materials. [Background technology]

[0002] Conventionally, packaging materials and the like have been produced using resin films made of resin materials. The packaging materials include, for example, a base material and a heat-sealing layer. For example, resin films made of polyolefins have suitable flexibility and transparency, as well as excellent heat-sealing properties, and are therefore used as the heat-sealing layer in packaging materials.

[0003] Generally, resin films made of polyolefins are inferior in strength and heat resistance and therefore cannot be used as a base material for constituting packaging materials, etc. Therefore, resin films excellent in strength and heat resistance, such as polyester film and polyamide film, are generally used as the base material for packaging materials. Therefore, different types of resin films are used for the base material and the heat seal layer in ordinary packaging materials (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-202519 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, with the growing demand for the creation of a recycling-oriented society, attempts have been made to recycle and reuse packaging materials. However, laminates comprising two or more different types of resin films as described above are difficult to separate by type of resin material, making them unsuitable for recycling.

[0006] The problem to be solved by the present disclosure is to provide a laminate that combines strength, heat-sealability, and recyclability and can be suitably used as a packaging material, and a packaging material including the laminate. [Means for solving the problem]

[0007] The laminate of the present disclosure comprises a substrate and a heat seal layer, the substrate and the heat seal layer being made of the same type of resin material, the substrate having a multilayer structure, the substrate being a substrate that has been subjected to a stretching treatment, and the heat seal layer being a layer that has not been subjected to a stretching treatment.

[0008] The packaging material of the present disclosure comprises the laminate. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a laminate that combines strength, heat sealability, and recyclability and can be suitably used as a packaging material, and a packaging material including the laminate. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional schematic diagram showing one embodiment of a laminate according to the present disclosure. [Figure 2] FIG. 2 is a cross-sectional schematic diagram showing one embodiment of a laminate of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Laminate] The laminate of the present disclosure comprises a substrate and a heat seal layer. In the laminate of the present disclosure, the substrate and the heat seal layer are made of the same resin material. That is, the substrate is made of a resin material, and the heat seal layer is made of the same resin material as the resin material constituting the substrate. By using a laminate having such a configuration, for example, a packaging material with excellent recyclability can be produced.

[0012] The term "same type of resin material" refers to resin materials that share a common basic structure and is not limited to completely identical resin materials. The term "same type of resin material" includes resin materials that share the same main monomer among the monomers that form the resin material. For example, if the main monomer is referred to as "monomer A," a homopolymer of monomer A, a copolymer of monomer A and monomer B, and a copolymer of monomer A, monomer B, and monomer C are all classified as the same type of resin material.

[0013] For example, polyethylene includes high-density polyethylene and linear low-density polyethylene, which are classified as the same type of resin material. For example, polyester includes polyethylene terephthalate and polyethylene naphthalate, which are classified as the same type of resin material.

[0014] The content of the same type of resin material in 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. Since such a laminate uses the same type of resin material, it can be classified as a so-called mono-material material, and the recyclability of the laminate can be improved.

[0015] In one embodiment, the same type of resin material is polyolefin. In this case, the content of polyolefin in the entire laminate is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. In one embodiment, the content of polyethylene or polypropylene in the entire laminate is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more.

[0016] In one embodiment, the same type of resin material is polyester. In this case, the content of polyester in the entire laminate is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more.

[0017] In one embodiment, a laminate 10 of the present disclosure includes a substrate 12 and a heat seal layer 14, as shown in Figure 1. In one embodiment, a laminate 10 of the present disclosure further includes a printed layer (not shown) on the substrate 12. The printed layer is usually formed on a surface layer of the substrate on which the heat seal layer is provided. In one embodiment, a laminate 10 of the present disclosure includes an adhesive layer 16 between the substrate 12 and the heat seal layer 14, as shown in Figure 2. The substrate 12 has a multilayer structure, but this multilayer structure is not shown.

[0018] <Base material> The substrate constituting the laminate of the present disclosure is a substrate that has been subjected to a stretching treatment and has a multilayer structure. Hereinafter, such a substrate will also be referred to as a "stretched multilayer substrate."

[0019] The stretching treatment can significantly improve the heat resistance and strength of the substrate, and such a stretched multilayer substrate can satisfy the physical properties required for, for example, the outer layer of a packaging material, etc. The stretching may be uniaxial or biaxial.

[0020] In one embodiment, the stretching ratio in the longitudinal direction (MD) of the stretched multilayer substrate is preferably 2 to 10, more preferably 3 to 7. In one embodiment, the stretching ratio in the transverse direction (TD) of the stretched multilayer substrate is preferably 2 to 10, more preferably 3 to 7.

[0021] A stretching ratio of 2 times or more can improve, for example, the rigidity, strength, and heat resistance of the substrate, improve the printability of the substrate, and improve the transparency of the substrate.A stretching ratio of 10 times or less can achieve good stretching without causing breakage of the film, for example.

[0022] In one embodiment, the stretched multilayer substrate constituting the laminate of the present disclosure is a uniaxially stretched film, more specifically, a uniaxially stretched film that has been stretched in the machine direction (MD).

[0023] The stretched multilayer substrate has a multilayer structure of two or more layers. In one embodiment, the number of layers in the stretched multilayer substrate is preferably 2 to 7, more preferably 3 to 5. The multilayer structure of the stretched multilayer substrate can improve the balance of the rigidity, strength, heat resistance, printability, and stretchability of the substrate. Each layer of the stretched multilayer substrate is also made of the same type of resin material.

[0024] Examples of resin materials constituting the stretched multilayer substrate include polyolefins such as polyethylene, polypropylene, and polymethylpentene; and polyesters. Among these, polyolefins are preferred, and polyethylene and polypropylene are more preferred.

[0025] Examples of polyethylene include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, and very low-density polyethylene. Among these, high-density polyethylene and medium-density polyethylene are preferred from the viewpoint of the strength and heat resistance of the substrate, and medium-density polyethylene is more preferred from the viewpoint of stretchability.

[0026] The density of the high density polyethylene is preferably 0.945 g / cm 3 The upper limit of the density of high density polyethylene is, for example, 0.965 g / cm 3 The density of the medium density polyethylene is preferably 0.925 g / cm 3 Exceeds 0.945g / cm 3 The density of the low density polyethylene is preferably 0.900 g / cm or less. 3 Exceeds 0.925g / cm 3 The density of the linear low density polyethylene is preferably 0.900 g / cm or less. 3 Exceeds 0.925g / cm 3 The density of the ultra-low density polyethylene is preferably 0.900 g / cm or less. 3 The lower limit of the density of the ultra-low density polyethylene is, for example, 0.860 g / cm 3 The density of polyethylene is measured in accordance with JIS K7112 (1999).

[0027] From the viewpoints of film-forming properties and substrate processability, the melt flow rate (MFR) of the polyethylene is preferably 0.1 g / 10 min or more and 50 g / 10 min or less, more preferably 0.3 g / 10 min or more and 30 g / 10 min or less. In the present disclosure, the MFR of the polyethylene is measured in accordance with ASTM D1238 at a temperature of 190°C and a load of 2.16 kg.

[0028] Polypropylene may be any of a propylene homopolymer, a propylene random copolymer, and a propylene block copolymer. A propylene homopolymer is a polymer of propylene alone. A propylene random copolymer is a random copolymer of propylene and an ethylenically unsaturated monomer other than propylene (e.g., an α-olefin such as ethylene, 1-butene, or 4-methyl-1-pentene). A propylene block copolymer is a copolymer having a polymer block of propylene and a polymer block of an ethylenically unsaturated monomer other than propylene (e.g., an α-olefin such as ethylene, 1-butene, or 4-methyl-1-pentene). For example, it is preferable to use a homopolymer when emphasis is placed on the rigidity and heat resistance of the packaging material, and to use a random copolymer when emphasis is placed on the impact resistance of the packaging material.

[0029] From the viewpoints of film-forming properties and substrate processability, the MFR of polypropylene is preferably 0.1 g / 10 min or more and 50 g / 10 min or less, more preferably 0.3 g / 10 min or more and 30 g / 10 min or less. In the present disclosure, the MFR of polypropylene is measured in accordance with ASTM D1238 at a temperature of 230°C and a load of 2.16 kg.

[0030] Examples of polyolefins include copolymers of ethylene and ethylenically unsaturated monomers other than ethylene, and copolymers of propylene and ethylenically unsaturated monomers other than propylene (however, excluding copolymers corresponding to the above-mentioned polyethylene and polypropylene).

[0031] Examples of the ethylenically unsaturated monomer include α-olefins having 2 to 20 carbon atoms, such as ethylene, 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.

[0032] Polyolefins with different densities or branching can be obtained by appropriately selecting a 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 a polymerization catalyst and carry out polymerization in one or more stages by any of gas phase polymerization, slurry polymerization, solution polymerization, and high-pressure ionic polymerization.

[0033] A single-site catalyst is a catalyst capable of forming a uniform active species, and is usually 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 they have a more uniform structure of the active site than multi-site catalysts, making it possible to obtain polymers with high molecular weights and highly uniform structures.

[0034] The single-site catalyst is preferably a metallocene catalyst, which comprises a transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, a cocatalyst, an organometallic compound as needed, and a support as needed.

[0035] Examples of the transition metal in the transition metal compound include zirconium, titanium, and hafnium, with zirconium and hafnium being preferred.

[0036] The cyclopentadienyl skeleton in the transition metal compound is a cyclopentadienyl group or a substituted cyclopentadienyl group. The substituted cyclopentadienyl group has at least one substituent selected from, for example, a hydrocarbon group having from 1 to 30 carbon atoms, a silyl group, a silyl-substituted alkyl group, a silyl-substituted aryl group, a cyano group, a cyanoalkyl group, a cyanoaryl group, a halogen group, a haloalkyl group, and a halosilyl group. The substituted cyclopentadienyl group has one or more substituents, and the substituents may be bonded to each other to form a ring, such as an indenyl ring, a fluorenyl ring, an azulenyl ring, or a hydrogenated product thereof. The ring formed by bonding the substituents to each other may further have a substituent.

[0037] The transition metal compound usually has two ligands having a cyclopentadienyl skeleton. The ligands having each cyclopentadienyl skeleton are preferably bonded to each other via a bridging group. Examples of the bridging group include alkylene groups having 1 to 4 carbon atoms, silylene groups, substituted silylene groups such as dialkylsilylene groups and diarylsilylene groups, and substituted germylene groups such as dialkylgermylene groups and diarylgermylene groups. Among these, substituted silylene groups are preferred.

[0038] The co-catalyst refers to a component that enables a transition metal compound of Group IV of the periodic table to function effectively as a polymerization catalyst or a component that balances the ionic charge in a catalytically activated state. Examples of the co-catalyst include benzene-soluble aluminoxanes or benzene-insoluble organoaluminum oxy-compounds, ion-exchangeable layered silicates, boron compounds, ionic compounds consisting of a cation with or without an active hydrogen group and a non-coordinating anion, lanthanoid salts such as lanthanum oxide, tin oxide, and phenoxy compounds containing a fluoro group.

[0039] Examples of organometallic compounds that may be used as needed include organoaluminum compounds, organomagnesium compounds, and organozinc compounds. Of these, organoaluminum compounds are preferred.

[0040] The transition metal compound may be used by being supported on an inorganic or organic carrier, preferably a porous oxide of an inorganic or organic compound, such as montmorillonite or other ion-exchangeable layered silicates, SiO2, Al2O3, MgO, ZrO2, TiO2, BO3, CaO, ZnO, BaO, ThO2, or mixtures thereof.

[0041] As the polyolefin, a biomass-derived polyolefin may be used. That is, as a raw material for obtaining the polyolefin, a biomass-derived olefin may be used instead of an olefin obtained from a fossil fuel. Since the biomass-derived polyolefin is a carbon-neutral material, the environmental impact of packaging materials can be reduced. The biomass-derived polyolefin (e.g., polyethylene) can be produced, for example, by the method described in JP 2013-177531 A. Commercially available biomass-derived polyolefin (e.g., Green PE commercially available from Braskem) may also be used.

[0042] Polyolefins that have been recycled through mechanical recycling may also be used. Mechanical recycling generally involves crushing recovered polyolefin films and washing them with alkali to remove dirt and foreign matter from the film surface, and then drying them at high temperature and reduced pressure for a certain period of time to diffuse any contaminants remaining inside the film, thereby decontaminating the film and removing the dirt from the polyolefin film, which is then returned to polyolefin.

[0043] Examples of polyesters used as resin materials for forming the stretched multilayer substrate include copolymers of dicarboxylic acid compounds and diol compounds. As monomers forming the copolymer, monomers other than dicarboxylic acid compounds and diol compounds may be used as needed.

[0044] Examples of dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, pimelic acid, azelaic acid, methylmalonic acid, ethylmalonic acid, adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, decalindicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodiumsulfoisophthalic acid, phenylendanedicarboxylic acid, anthracenedicarboxylic acid, phenanthrenedicarboxylic acid, 9,9'-bis(4-carboxyphenyl)fluorene acid, and ester derivatives thereof.

[0045] Examples of diol compounds include ethylene glycol, 1,2-propanediol, 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, hexanediol, neopentyl glycol, cyclohexanedimethanol, cyclohexanediethanol, decahydronaphthalenedimethanol, decahydronaphthalenediethanol, norbornanedimethanol, norbornanediethanol, tricyclodecanedimethanol, tricyclodecaneethanol, tetracyclododecanedimethanol, tetracyclododecanediethanol, decalindimethanol, and decalindiethanol. , 5-methylol-5-ethyl-2-(1,1-dimethyl-2-hydroxyethyl)-1,3-dioxane, cyclohexanediol, bicyclohexyl-4,4'-diol, 2,2-bis(4-hydroxycyclohexylpropane), 2,2-bis(4-(2-hydroxyethoxy)cyclohexyl)propane, cyclopentanediol, 3-methyl-1,2-cyclopentadiol, 4-cyclopentene-1,3-diol, adamantanediol, paraxylene glycol, bisphenol A, bisphenol S, styrene glycol, trimethylolpropane, and pentaerythritol.

[0046] Among the above, polyethylene terephthalate, which is a copolymer of terephthalic acid and its ester derivatives with ethylene glycol, is preferred.

[0047] The polyester may be a biomass-derived polyester, which contains a diol compound as a copolymerization component derived from biomass, and can significantly reduce the amount of fossil fuel used, thereby effectively reducing the environmental impact of producing the laminate.

[0048] Biomass-derived diol compounds, such as biomass-derived ethylene glycol, are made from ethanol (biomass ethanol) produced from biomass as a raw material. Biomass-derived ethylene glycol can be obtained by converting biomass ethanol into ethylene oxide using a conventionally known method, or by other methods to produce ethylene glycol. Commercially available biomass ethylene glycol may also be used; for example, biomass ethylene glycol sold by India Glycoal Limited can be suitably used.

[0049] As the polyester, recycled polyester may be used. Examples of recycled polyester include chemically recycled polyester and mechanically recycled polyester. Chemically recycled polyester refers to polyester obtained by breaking down polyester containers to the monomer level and polymerizing the monomers again. Mechanically recycled polyester refers to polyester obtained by sorting, crushing, and washing polyester containers to remove contaminants and foreign matter, obtaining flakes, and further treating the flakes at high temperature and reduced pressure for a certain period of time to remove contaminants from within the resin.

[0050] The content of the same resin material in each layer constituting the stretched multilayer base material is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, which can improve the recyclability of the laminate.

[0051] The content of the same resin material in the stretched multilayer substrate is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, which can improve the recyclability of the laminate.

[0052] The stretched multi-layer substrate may contain one or more additives. Examples of additives include crosslinking agents, antiblocking agents, slip agents, antioxidants, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, dyes, and modifying resins. Each layer constituting the stretched multi-layer substrate may independently contain the above-mentioned additives.

[0053] The haze value of the stretched multilayer substrate is preferably 25% or less, more preferably 15% or less, and even more preferably 10% or less. The smaller the haze value, the better, but in one embodiment, the lower limit may be 0.1% or 1%. The haze value of the stretched multilayer substrate is measured in accordance with JIS K7136.

[0054] The total thickness of the stretched multilayer substrate is preferably 10 μm or more and 60 μm or less, more preferably 15 μm or more and 50 μm or less. When the thickness of the stretched multilayer substrate is 10 μm or more, the rigidity and strength of the laminate can be improved. When the thickness of the stretched multilayer substrate is 60 μm or less, the processability of the laminate can be improved.

[0055] The stretched multilayer substrate is preferably subjected to a surface treatment. This can improve the adhesion between the surface layer of the stretched multilayer substrate and the layer laminated on the stretched multilayer substrate. Examples of surface treatment methods include physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using gases such as oxygen gas and nitrogen gas, and glow discharge treatment; and chemical treatments such as oxidation treatment using chemicals. In addition, an anchor coating layer may be formed on the surface of the stretched multilayer substrate using a conventional anchor coating agent.

[0056] A stretched multilayer substrate can be produced by forming a laminate from multiple resin materials or resin compositions using, for example, an inflation method or a T-die method, and then stretching the resulting laminate. The stretching treatment can improve the transparency, rigidity, strength, and heat resistance of the substrate, making it suitable for use as, for example, a substrate for packaging materials.

[0057] In one embodiment, the stretched multilayer substrate is obtained by stretching a laminate (precursor) having a multilayer structure. Specifically, the layers can be co-extruded into a tubular shape to form a film, thereby producing a laminate. Alternatively, the layers can be co-extruded into a tubular shape, and then the opposing layers can be pressure-bonded together using a rubber roll or the like to produce a laminate. By producing a laminate using such a method, the number of defective products can be significantly reduced, and production efficiency can be improved.

[0058] For example, when the stretched multilayer substrate is made of polyethylene and is produced by the T-die method, the melt flow rate (MFR) of the polyethylene constituting each layer of the multilayer substrate is preferably 3 g / 10 min or more and 20 g / 10 min or less, from the viewpoints of film-forming properties and processability of the multilayer substrate.

[0059] For example, when the stretched multi-layer substrate is made of polyethylene and is produced by an inflation method, the MFR of the polyethylene constituting each layer of the multi-layer substrate is preferably 0.5 g / 10 min or more and 5 g / 10 min or less, from the viewpoints of film-forming properties and processability of the multi-layer substrate.

[0060] The stretched multilayer substrate can be obtained, for example, by stretching the above-mentioned laminate. The preferred stretching ratio is as described above. Note that the laminate can also be stretched in an inflation film-forming machine. This allows the production of a stretched multilayer substrate, thereby further improving production efficiency.

[0061] Hereinafter, several examples of embodiments of the stretched multilayer substrate will be described. Hereinafter, a layer made of polyethylene will be referred to as a "polyethylene layer". The stretched multilayer substrate of the first embodiment includes, in the thickness direction, 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, in this order. This configuration can improve the printability, strength, and heat resistance of the substrate, and can improve the stretchability of the pre-stretched laminate.

[0062] In the blend layer of medium-density polyethylene and high-density polyethylene, the mass ratio of medium-density polyethylene to high-density polyethylene (medium-density polyethylene / high-density polyethylene) is preferably 0.25 or more and 4 or less, more preferably 0.4 or more and 2.4 or less.

[0063] The stretched multilayer substrate of the second embodiment includes, in the thickness direction, 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 another medium-density polyethylene layer, in this order. This configuration can improve the printability, strength, and heat resistance of the substrate, and can improve the stretchability of the pre-stretched laminate.

[0064] In the blend layer of medium-density polyethylene and linear low-density polyethylene, the mass ratio of medium-density polyethylene to linear low-density polyethylene (medium-density polyethylene / linear low-density polyethylene) is preferably 0.25 or more and 4 or less, more preferably 0.4 or more and 2.4 or less.

[0065] The stretched multilayer substrate of the third embodiment includes, in the thickness direction, 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, in this order. This configuration can improve the printability, strength, and heat resistance of the substrate, and can improve the stretchability of the pre-stretched laminate.

[0066] In the blend layers of medium-density polyethylene and high-density polyethylene, the mass ratio of medium-density polyethylene to high-density polyethylene (medium-density polyethylene / high-density polyethylene) is preferably 0.25 or more and 4 or less, more preferably 0.4 or more and 2.4 or less. In the blend layer of medium-density polyethylene and linear low-density polyethylene, the mass ratio of medium-density polyethylene to linear low-density polyethylene (medium-density polyethylene / linear low-density polyethylene) is preferably 0.25 or more and 4 or less, more preferably 0.4 or more and 2.4 or less.

[0067] The stretched multilayer substrate of the fourth embodiment includes, in the thickness direction, 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. This configuration can improve the printability, strength, and heat resistance of the substrate, and can improve the stretchability of the pre-stretched laminate.

[0068] In the blend layers of high-density polyethylene and medium-density polyethylene, the mass ratio of medium-density polyethylene to high-density polyethylene (medium-density polyethylene / high-density polyethylene) is preferably 0.25 or more and 4 or less, more preferably 0.4 or more and 2.4 or less. In the blend layer of linear low-density polyethylene and medium-density polyethylene, the mass ratio of linear low-density polyethylene to medium-density polyethylene (linear low-density polyethylene / medium-density polyethylene) is preferably 0.25 or more and 4 or less, more preferably 0.4 or more and 2.4 or less.

[0069] In the stretched multilayer substrates of the first to fourth embodiments, the thickness of each of the two surface layers is preferably from 0.5 μm to 10 μm, more preferably from 1 μm to 8 μm, and even more preferably from 1 μm to 5 μm, which can further improve the heat resistance and printability of the substrate.

[0070] In the stretched multilayer substrates of the first to fourth embodiments, the thickness of each of the two surface layers is preferably smaller than the total thickness of the three inner layers (the multilayer intermediate layer). The ratio of the thickness of each of the two surface layers to the total thickness of the multilayer intermediate layer (surface layer / multilayer intermediate layer) is preferably 0.05 to 0.8, more preferably 0.1 to 0.7, and even more preferably 0.1 to 0.4. This can further improve the rigidity, strength, and heat resistance of the substrate.

[0071] The stretched multilayer substrate of the fifth embodiment comprises a high-density polyethylene layer and a medium-density polyethylene layer in this order in the thickness direction. The high-density polyethylene layer as the surface layer of the substrate can improve the strength and heat resistance of the substrate. The medium-density polyethylene layer in the substrate can improve the stretchability of the pre-stretch laminate.

[0072] The stretched multilayer substrate of the sixth embodiment includes a high-density polyethylene layer, a medium-density polyethylene layer, and a high-density polyethylene layer in this order in the thickness direction. This configuration improves the strength and heat resistance of the substrate, suppresses curling in the substrate, and improves the stretchability of the pre-stretched laminate.

[0073] In the stretched multilayer base materials of the fifth and sixth embodiments, the thickness of the high-density polyethylene layer is preferably equal to or less than the thickness of the medium-density polyethylene layer, and the ratio of the thickness of the high-density polyethylene layer to the thickness of the medium-density polyethylene layer is preferably 0.1 or more and 1 or less, more preferably 0.2 or more and 0.5 or less.

[0074] The stretched multilayer substrate of the seventh embodiment comprises, in this order in the thickness direction, 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 (for simplicity, these three layers are collectively referred to as the "low-density polyethylene layer, etc."), a medium-density polyethylene layer, and a high-density polyethylene layer. This configuration can improve the stretchability of the laminate before stretching, improve the strength and heat resistance of the substrate, and suppress curling in the substrate.

[0075] In the stretched multilayer substrate of the seventh embodiment, the thickness of the high-density polyethylene layer is preferably equal to or less than the thickness of the medium-density polyethylene layer, and the ratio of the thickness of the high-density polyethylene layer to the thickness of the medium-density polyethylene layer is preferably 0.1 or more and 1 or less, more preferably 0.2 or more and 0.5 or less.

[0076] In the stretched multilayer substrate of the seventh embodiment, the thickness of the high-density polyethylene layer is preferably equal to or greater than the thickness of the low-density polyethylene layer, etc. The ratio of the thickness of the high-density polyethylene layer to the thickness of the low-density polyethylene layer is preferably 1 or more and 4 or less, more preferably 1 or more and 2 or less.

[0077] Other embodiments of the stretched multilayer substrate include a substrate comprising, in this order in the thickness direction, 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; and a substrate comprising, in this order in the thickness direction, 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.

[0078] <Barrier layer> In one embodiment, the laminate of the present disclosure includes a barrier layer between the stretched multilayer substrate and the heat seal layer, which can improve the gas barrier properties, specifically the oxygen barrier properties and water vapor barrier properties, of the laminate.

[0079] The barrier layer is formed, for example, on the surface of the stretched multilayer substrate. A barrier layer may be provided between the stretched multilayer substrate and the heat-sealing layer via an adhesive or the like. For example, a barrier film comprising a second substrate and a barrier layer formed on the second substrate may be provided between the stretched multilayer substrate and the heat-sealing layer via an adhesive or the like. In this embodiment, from the viewpoint of recyclability, the second substrate in the barrier film is preferably made of the same type of resin material as the resin material constituting the stretched multilayer substrate. The content of the same type of resin material in the second substrate is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. This improves the recyclability of the laminate.

[0080] In one embodiment, the barrier layer is a vapor-deposited layer. Vapor-deposited layers are made of, for example, metals such as aluminum, or inorganic oxides such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, and barium oxide. Among these, an aluminum vapor-deposited layer is preferred.

[0081] The thickness of the vapor-deposited layer is preferably 1 nm or more and 150 nm or less, more preferably 5 nm or more and 60 nm or less, and even more preferably 10 nm or more and 40 nm or less. By making the thickness of the vapor-deposited layer 1 nm or more, the oxygen barrier property and water vapor barrier property of the laminate can be further improved. By making the thickness of the vapor-deposited layer 150 nm or less, the occurrence of cracks in the vapor-deposited layer can be suppressed and the recyclability of the laminate can be improved.

[0082] Examples of methods for forming the vapor-deposited layer include physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating; and chemical vapor deposition (CVD) methods such as plasma-enhanced chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition. The vapor-deposited layer may be a composite film containing two or more vapor-deposited layers of different inorganic oxides, formed by combining physical vapor deposition and chemical vapor deposition.

[0083] The vacuum level in the deposition chamber was 10-2 ~10 -8 After oxygen is introduced, the pressure is preferably about 10 -1 ~10 -6 The pressure is preferably about mbar. The amount of oxygen introduced varies depending on the size of the deposition machine. An inert gas such as argon gas, helium gas, or nitrogen gas may be used as a carrier gas for the introduced oxygen, provided that this does not cause any problems. The conveying speed of the stretched multilayer substrate is, for example, about 10 to 800 m / min.

[0084] The surface of the vapor-deposited layer is preferably subjected to the above-mentioned surface treatment, which can improve the adhesion between the vapor-deposited layer and the adjacent layer.

[0085] When the vapor-deposited layer is composed of an inorganic oxide such as aluminum oxide or silicon oxide, a barrier coat layer may be provided on the surface of the vapor-deposited layer to form a barrier layer comprising the vapor-deposited layer and the barrier coat layer. In one embodiment, the laminate of the present disclosure comprises, in the thickness direction, a stretched multilayer substrate, an inorganic oxide vapor-deposited layer, a barrier coat layer, and a heat-seal layer, in this order. By adopting such a configuration, for example, the oxygen barrier property and water vapor barrier property of the laminate can be improved, and the occurrence of cracks in the inorganic oxide vapor-deposited layer can be effectively suppressed.

[0086] In one embodiment, the barrier coat layer is made of a gas barrier resin, such as ethylene-vinyl alcohol copolymer (EVOH), polyvinyl alcohol, polyacrylonitrile, polyamide resins such as nylon 6, nylon 6,6, and polymetaxylylene adipamide (MXD6), polyester resins, polyurethane resins, and (meth)acrylic resins.

[0087] The thickness of the barrier coat layer is preferably 0.01 μm or more and 10 μm or less, more preferably 0.1 μm or more and 5 μm or less. By making the thickness of the barrier coat layer 0.01 μm or more, the gas barrier property can be further improved. By making the thickness of the barrier coat layer 10 μm or less, the processability of the laminate can be improved. Furthermore, the laminate can be suitably used for producing mono-material packaging containers.

[0088] The barrier coat layer can be formed, for example, by dissolving or dispersing a material such as a gas barrier resin in water or an appropriate organic solvent, applying the resulting coating liquid, and drying it.

[0089] In another embodiment, the barrier coat layer is a gas barrier coating film formed from a composition containing a hydrolyzate of a metal alkoxide or a hydrolyzed condensate of a metal alkoxide obtained by polycondensing a mixture of a metal alkoxide and a water-soluble polymer by a sol-gel method in the presence of a sol-gel catalyst, water, an organic solvent, etc. By providing such a barrier coating layer on the vapor deposition layer, it is possible to effectively prevent cracks from occurring in the vapor deposition layer.

[0090] In one embodiment, the metal alkoxide is represented by the following general formula: R 1 n M(OR 2 ) m In the above formula, R 1 and R 2 each independently represents an organic group having 1 to 8 carbon atoms; M represents a metal atom; n represents an integer of 0 or more; m represents an integer of 1 or more; and n+m represents the valence of M.

[0091] R 1 and R 2 Examples of the organic group represented by the formula (I) include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl. Examples of the metal atom M include silicon, zirconium, titanium, and aluminum.

[0092] Examples of metal alkoxides that satisfy the above general formula include tetramethoxysilane (Si(OCH3)4), tetraethoxysilane (Si(OC2H5)4), tetrapropoxysilane (Si(OC3H7)4), and tetrabutoxysilane (Si(OC4H9)4).

[0093] It is preferable to use a silane coupling agent together with the metal alkoxide, and as the silane coupling agent, a known organoalkoxysilane containing an organic reactive group can be used.

[0094] The water-soluble polymer is preferably polyvinyl alcohol or an ethylene-vinyl alcohol copolymer. Depending on the desired physical properties such as oxygen barrier property, water vapor barrier property, water resistance, and weather resistance, either polyvinyl alcohol or an ethylene-vinyl alcohol copolymer may be used, or both may be used in combination. Alternatively, a gas barrier coating film obtained using polyvinyl alcohol and a gas barrier coating film obtained using an ethylene-vinyl alcohol copolymer may be laminated.

[0095] As the catalyst for the sol-gel method, an acid or amine compound is suitable.

[0096] The composition may further contain an acid. The acid is used as a catalyst for the hydrolysis of sol-gel process catalysts, mainly metal alkoxides and silane coupling agents. Examples of the acid include mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as acetic acid and tartaric acid.

[0097] The composition may contain an organic solvent, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and n-butanol.

[0098] The thickness of the gas barrier coating film is preferably 0.01 μm or more and 100 μm or less, more preferably 0.1 μm or more and 50 μm or less. This further improves the gas barrier properties. By making the thickness of the gas barrier coating film 0.01 μm or more, the oxygen barrier properties and water vapor barrier properties of the laminate can be improved, and the occurrence of cracks in the vapor deposition layer can be prevented. By making the thickness of the gas barrier coating film 100 μm or less, the laminate can be made suitable for use in producing mono-material packaging containers.

[0099] The gas barrier coating film can be formed by applying a composition containing the above-mentioned materials by a conventionally known means such as roll coating using a gravure roll coater or the like, spray coating, spin coating, dipping, brush coating, bar coating, or applicator, and then polycondensing the composition by a sol-gel method.

[0100] An embodiment of the method for forming a gas barrier coating film will be described below. First, a composition is prepared by mixing a metal alkoxide, a water-soluble polymer, a sol-gel catalyst, water, an organic solvent, and optionally a silane coupling agent, etc. A polycondensation reaction gradually proceeds in the composition.

[0101] Next, the composition is applied onto the vapor-deposited layer by the conventionally known means and dried. This drying further promotes the polycondensation reaction of the metal alkoxide and the water-soluble polymer (and the silane coupling agent, if the composition contains one) to form a composite polymer layer. Finally, heating is performed to form a gas barrier coating film.

[0102] In the case of an adhesive layer adjacent to a barrier layer such as an aluminum vapor-deposited layer, the adhesive layer is preferably formed from a cured product of a resin composition containing a polyester polyol, an isocyanate compound, and a phosphoric acid-modified compound. By forming the adhesive layer in this manner, the oxygen barrier property and water vapor barrier property of the laminate of the present disclosure can be further improved.

[0103] <Print layer> In one embodiment, the laminate of the present disclosure further includes a printed layer formed on the above-described stretched multilayer substrate. In one embodiment, the printed layer is preferably formed on the side of the stretched multilayer substrate where the heat seal layer is provided, since this can suppress deterioration of the image over time. When the laminate includes a barrier layer on the stretched multilayer substrate, for example, a printed layer may be provided on the barrier layer. In this case, the laminate of the present disclosure includes, for example, a stretched multilayer substrate, a barrier layer, a printed layer, and a heat seal layer in this order in the thickness direction.

[0104] The printed layer includes, for example, an image. Examples of images include letters, figures, symbols, and combinations thereof. Examples of methods for forming the printed layer include gravure printing, offset printing, and flexographic printing. In one embodiment, flexographic printing is preferred from the viewpoint of reducing environmental impact. Furthermore, from the viewpoint of reducing environmental impact, the printed layer may be formed on the surface of the stretched multilayer substrate using a biomass-derived ink.

[0105] <Heat seal layer> The laminate of the present disclosure includes a heat seal layer. The heat seal layer of the present disclosure is a layer that has not been subjected to a stretching treatment. The heat seal layer is composed of the same type of resin material as the resin material that constitutes the stretched multilayer substrate. A laminate having such a configuration has both heat sealability and recyclability.

[0106] For example, when the stretched multi-layer substrate is made of polyolefin, the heat seal layer is made of the same type of resin material as the stretched multi-layer substrate, i.e., polyolefin. Among the above-mentioned polyolefins, polyethylene and polypropylene are preferred.

[0107] In an embodiment in which the stretched multilayer substrate is made of polyethylene, examples of polyethylene constituting the heat seal layer 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 load, biomass-derived polyethylene and / or recycled polyethylene may also be used.

[0108] In an embodiment in which the stretched multilayer substrate is made of polyethylene, the polyethylene content in the heat seal layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, which can improve the recyclability of the laminate.

[0109] In an embodiment in which the stretched multilayer substrate is made of polypropylene, examples of the polypropylene constituting the heat seal layer include propylene homopolymer, propylene random copolymer, and propylene block copolymer. From the viewpoint of heat sealability, the density of the polypropylene is preferably 0.88 g / cm. 3 More than 0.92g / cm 3 or less, more preferably 0.90 g / cm 3 More than 0.91g / cm 3 From the viewpoint of reducing the environmental load, biomass-derived polypropylene and / or recycled polypropylene may be used.

[0110] In an embodiment in which the stretched multilayer substrate is made of polypropylene, the content of polypropylene in the heat seal layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, which can improve the recyclability of the laminate.

[0111] For example, when the stretched multilayer substrate is made of polyester, the heat seal layer is made of polyester, which is the same type of resin material as the stretched multilayer substrate. Among the above-mentioned polyesters, polyethylene terephthalate is preferred. From the viewpoint of reducing the environmental load, biomass-derived polyester and / or recycled polyester may also be used.

[0112] In an embodiment in which the stretched multilayer substrate is made of polyester, the heat seal layer is preferably made of a low-crystalline or amorphous polyester from the viewpoint of heat sealability. The crystallinity of the polyester constituting the heat seal layer is preferably 12% or less, more preferably 10% or less. This further improves heat sealability.

[0113] The crystallinity of a polyester is determined by dividing the heat of fusion of a low-crystalline or amorphous polyester when melted using a differential scanning calorimeter by the heat of fusion of a completely crystalline polyester (140 J / g for polyethylene terephthalate) and multiplying the result by 100.

[0114] The glass transition temperature (Tg) of the polyester constituting the heat seal layer is preferably 60°C or higher and 90°C or lower, more preferably 63°C or higher and 80°C or lower. When Tg is 90°C or lower, the heat sealability of the heat seal layer can be improved. When Tg is 60°C or higher, the occurrence of blocking can be suppressed. Tg is a value determined by differential scanning calorimetry in accordance with JIS K7121.

[0115] In an embodiment in which the stretched multilayer substrate is made of polyester, the content of polyester in the heat seal layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, which can improve the recyclability of the laminate.

[0116] The heat seal layer may contain one or more additives. Examples of additives include crosslinking agents, antiblocking agents, slip agents, antioxidants, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, dyes, and modifying resins. Each layer constituting the heat seal layer may independently contain the above-mentioned additives.

[0117] The heat seal layer may be a single layer or may have a multi-layer structure of two or more layers. In one embodiment, the number of layers in the heat seal layer is 2 to 7 in the case of a multi-layer structure. Each layer of the heat seal layer is also made of the same type of resin material.

[0118] In one embodiment, the heat seal layer is a multilayer resin film made of the same resin material as the resin material constituting the stretched multilayer substrate. This multilayer resin film is an unstretched resin film. This provides excellent heat sealability. The resin film can be produced by, for example, a casting method, a T-die method, or an inflation method.

[0119] In one embodiment, the heat seal layer is a multi-layer melt-extruded layer made of the same type of resin material as the resin material that makes up the stretched multi-layer substrate.

[0120] For example, a heat-sealable layer can be formed by laminating an unstretched film onto a stretched multilayer substrate, optionally via an adhesive layer, or by melt-extruding a heat-sealable resin material onto a stretched multilayer substrate. Examples of adhesive layers include those described below.

[0121] The thickness of the heat seal layer is preferably 10 μm or more and 300 μm or less, more preferably 15 μm or more and 250 μm or less. From the viewpoint of the strength of the heat seal layer and the processability of the laminate, it is preferable that the thickness of the heat seal layer be appropriately changed depending on the mass of the contents to be filled in the packaging material produced from the laminate of the present disclosure.

[0122] For example, when the packaging material is a pouch, the thickness of the heat seal layer is preferably 20 μm or more and 60 μm or less, so that the pouch can be well filled with contents of, for example, 1 g or more and 200 g or less.

[0123] For example, when the packaging material is a stand-up pouch, the thickness of the heat seal layer is preferably 40 μm or more and 200 μm or less, in which case, for example, 50 g or more and 2000 g or less of contents can be filled well into the stand-up pouch.

[0124] In the laminate of the present disclosure, the stretched multilayer substrate satisfies the rigidity, strength, and heat resistance required for an outer layer film of a packaging material, and the heat seal layer enables packaging. Furthermore, the stretched multilayer substrate and the heat seal layer are composed of the same type of resin material. Therefore, the laminate is suitable as a material for constituting packaging materials that require recyclability.

[0125] In one embodiment, the laminate of the present disclosure comprises only a stretched multilayer substrate on which a printing layer is formed as needed, and a heat-seal layer. In one embodiment, the laminate of the present disclosure comprises only a stretched multilayer substrate on which a printing layer is formed as needed, an adhesive layer, and a heat-seal layer. As a result, the laminate of the present disclosure can be particularly improved in recyclability because each resin layer is composed of the same type of resin material.

[0126] <Adhesive layer> In one embodiment, the laminate of the present disclosure includes an adhesive layer between any layers, such as between the stretched multilayer substrate and the heat-sealing layer, between the stretched multilayer substrate and the barrier film, between the barrier film and the heat-sealing layer, etc. This can improve the adhesion between the stretched multilayer substrate and the heat-sealing layer and the adhesion between other layers.

[0127] The adhesive layer contains one or more types of adhesives, such as one-component curing adhesives, two-component curing adhesives, and non-curing adhesives.

[0128] The adhesive may be a solvent-free adhesive or a solvent-based adhesive, with solvent-free adhesives being preferred from the standpoint of environmental impact. Examples of solvent-free adhesives include polyether adhesives, polyester adhesives, silicone adhesives, epoxy adhesives, and urethane adhesives. Among these, two-component curing urethane adhesives are preferred. Examples of solvent-based adhesives include rubber adhesives, vinyl adhesives, silicone adhesives, epoxy adhesives, phenol adhesives, and olefin adhesives.

[0129] In one embodiment, from the viewpoint of recyclability, when the stretched multilayer substrate and the heat seal layer constituting the laminate of the present disclosure are each made of polyolefin, the adhesive layer is made of an olefin-based adhesive.

[0130] In one embodiment, from the viewpoint of recyclability, when the stretched multilayer substrate and the heat seal layer constituting the laminate of the present disclosure are each made of polyester, the adhesive layer is made of a polyester-based adhesive.

[0131] The adhesive layer may contain one or more additives, such as pigments, dyes, lubricants, colorants, wetting agents, thickeners, coagulants, gelling agents, anti-settling agents, softeners, hardeners, plasticizers, leveling agents, antioxidants, UV absorbers, light stabilizers, and flame retardants.

[0132] From the viewpoint of the adhesiveness of the adhesive layer and the processability of the laminate, the thickness of the adhesive layer is preferably 0.5 μm or more and 6 μm or less, more preferably 0.8 μm or more and 5 μm or less, and even more preferably 1 μm or more and 4.5 μm or less.

[0133] The adhesive layer can be formed by applying an adhesive to the stretched multilayer substrate and drying it using a method such as direct gravure roll coating, gravure roll coating, kiss coating, reverse roll coating, Fontaine coating, or transfer roll coating.

[0134] [Application] The laminate of the present disclosure can be suitably used for packaging materials such as packaging bags. The packaging material of the present disclosure comprises the laminate of the present disclosure.

[0135] For example, a packaging material can be produced by folding the laminate of the present disclosure in half and overlapping it so that the stretched multilayer substrate is on the outside and the heat seal layer is on the inside, and then heat sealing the edges, etc. Alternatively, a packaging material can be produced by overlapping multiple laminates of the present disclosure so that the heat seal layers face each other, and then heat sealing the edges, etc. The entire packaging material may be composed of the above-mentioned laminate, or only a part of the packaging material may be composed of the above-mentioned laminate.

[0136] Examples of heat-sealing methods for packaging materials include side seals, two-sided seals, three-sided seals, four-sided seals, envelope seals, palm seals (pillow seals), pleated seals, flat-bottom seals, square-bottom seals, and gusset seals. Self-standing packaging bags (stand-up pouches) are also possible. Examples of heat-sealing methods include bar seals, rotary roll seals, belt seals, impulse seals, high-frequency seals, and ultrasonic seals.

[0137] For example, a stand-up pouch having a body and a bottom can be produced as follows: First, one or more laminates of the present disclosure are formed into a cylindrical shape with the heat-sealable layer facing inward, and heat-sealed to form the body. Next, another laminate of the present disclosure is folded into a V shape with the heat-sealable layer facing outward. The V-shaped laminate is sandwiched into one end of the body, and the bottom is formed by heat-sealing.

[0138] In the stand-up pouch, only the body portion may be formed from the laminate of the present disclosure, only the bottom portion may be formed from the laminate of the present disclosure, or both the body portion and the bottom portion may be formed from the laminate of the present disclosure.

[0139] The contents to be filled into the packaging material include, for example, liquids, powders, and gels, and may be food or non-food. After the contents are filled into the packaging material, the opening of the packaging material is heat-sealed to obtain a package.

[0140] The present disclosure relates to, for example, the following [1] to

[12] . [1] A laminate comprising a substrate and a heat seal layer, wherein the substrate and the heat seal layer are made of the same type of resin material, the substrate has a multi-layer structure, the substrate is a substrate that has been subjected to a stretching treatment, and the heat seal layer is a layer that has not been subjected to a stretching treatment. [2] The laminate according to [1] above, wherein the same type of resin material is polyolefin. [3] The laminate according to [1] or [2] above, wherein the same type of resin material is polyethylene or polypropylene. [4] The laminate according to [1] above, wherein the same type of resin material is polyester. [5] The laminate according to any one of the above [1] to [4], further comprising a printed layer formed on the substrate. [6] The laminate according to any one of the above [1] to [5], wherein the heat seal layer has a multilayer structure. [7] The laminate according to any one of the above [1] to [6], wherein the heat seal layer is an unstretched resin film or a melt-extruded layer of the above resin material. [8] The laminate according to any one of the above [1] to [7], further comprising a barrier layer formed on the substrate. [9] The laminate according to any one of the above [1] to [7], further comprising a barrier film between the substrate and the heat seal layer, the barrier film comprising a second substrate and a barrier layer formed on the second substrate.

[10] The laminate according to any one of the above [1] to [9], wherein the content of the same type of resin material in the entire laminate is 90 mass % or more.

[11] The laminate according to any one of the above [1] to

[10] , which is a laminate for use as a packaging material.

[12] A packaging material comprising the laminate according to any one of [1] to

[11] above. [Example]

[0141] The laminate of the present disclosure will be described in more detail based on examples, but the laminate of the present disclosure is not limited to the examples. Hereinafter, "parts by mass" will be simply referred to as "parts".

[0142] The polyethylene used in the following examples is described below. Medium-density polyethylene (hereinafter referred to as "MDPE"): Product name: Elite5538G Density: 0.941g / cm 3 , Melting point: 129℃, MFR: 1.3g / 10min, Dowchemical High-density polyethylene (hereinafter referred to as "HDPE"): Product name: Elite5960G Density: 0.960g / cm 3 , Melting point: 134℃, MFR: 0.8g / 10min, Dowchemical Linear low-density polyethylene (hereinafter referred to as "LLDPE"): Product name: Elite5400G Density: 0.916g / cm 3 , Melting point: 123℃, MFR: 1.3g / 10min, Dowchemical Blended polyethylene A 50 parts MDPE and 50 parts HDPE were mixed to give an average density of 0.951 g / cm 3 A blended polyethylene A (hereinafter referred to as "blended PE(A)") was obtained. Blended polyethylene B 50 parts MDPE and 50 parts LLDPE were mixed to give an average density of 0.929 g / cm 3 A blended polyethylene B (hereinafter referred to as "blended PE(B)") was obtained. Blended polyethylene B1 70 parts MDPE and 30 parts LLDPE were mixed to give an average density of 0.934 g / cm 3 A blended polyethylene B1 (hereinafter referred to as "blended PE (B1)") was obtained. Blended polyethylene C 70 parts MDPE and 30 parts HDPE were mixed to give an average density of 0.947 g / cm 3 A blended polyethylene C (hereinafter referred to as "blended PE(C)") was obtained. Blended polyethylene D A mixture of 30 parts MDPE and 70 parts HDPE gave an average density of 0.954 g / cm 3 A blended polyethylene D (hereinafter referred to as "blended PE(D)") was obtained.

[0143] [Example 1] MDPE, HDPE, and blended PE (A) were co-extruded into a tubular film with a layer thickness ratio of MDPE layer (15 μm) / HDPE layer (22.5 μm) / blended PE (A) layer (50 μm) / HDPE layer (22.5 μm) / MDPE layer (15 μm) using an inflation molding method to obtain a polyethylene film with a total thickness of 125 μm. The tubular film was then folded at the nip to form two layers. The numbers in parentheses indicate the layer thicknesses. The polyethylene film prepared above was stretched in the machine direction (MD) at a stretch ratio of 5 times, and then the MDPE layer (surface layer) on one side was subjected to a corona discharge treatment. The edge was then slit and divided into two pieces to obtain a stretched multilayer substrate with a thickness of 25 μm.

[0144] First, linear low-density polyethylene (Prime Polymer Co., Ltd., SP2520, density: 0.925 g / cm 3 , melting point: 122°C) and a second linear low-density polyethylene (Prime Polymer Co., Ltd., SP1520, density: 0.913 g / cm 3A multilayer extrusion film was formed from a first linear low-density polyethylene layer having a thickness of 20 μm and a second linear low-density polyethylene layer having a thickness of 20 μm by inflation molding. This multilayer unstretched polyethylene film was used as a heat-sealing layer as described below.

[0145] The first linear low-density polyethylene layer side of the unstretched polyethylene film (heat seal layer) having the multilayer structure prepared above and the stretched multilayer substrate prepared above were dry laminated using a two-component curing urethane adhesive (Ru-77T / H-7, manufactured by Rock Paint Co., Ltd.) to obtain a laminate.

[0146] [Examples 2 to 7] A laminate was obtained in the same manner as in Example 1, except that the layer structure of the stretched multilayer base material was changed as shown in Table 1.

[0147] [Recyclability evaluation] The content of polyethylene in the entire laminate produced above was determined, and the recyclability thereof was evaluated based on the following evaluation criteria.

[0148] (Evaluation criteria) AA: The polyethylene content in the entire laminate was 90 mass % or more. BB: The polyethylene content in the entire laminate is 80% by mass or more but less than 90% by mass. there were. CC: The polyethylene content in the entire laminate was less than 80 mass %.

[0149] [Heat sealability evaluation] The laminate prepared above was cut to a size of 220 mm length x 130 mm width. Two sheets of the laminate thus cut were overlapped with the heat-sealed layers facing each other, and the laminate prepared above was folded into a V shape with the heat-sealed layer facing outward, and sandwiched into one end of the body. Next, the two vertical sides and the side sandwiching the V-shaped laminate were heat-sealed (140°C, 1 kgf, 1 second). 300 mL of liquid detergent was filled into the resulting packaging bag, and the remaining side was heat-sealed (140°C, 1 kgf, 1 second) to obtain a package.

[0150] The above-mentioned package was dropped from a height of 100 cm onto a hard floor 10 times with the body of the package held horizontally to the ground. This test was carried out for 10 bags at a time, and the presence or absence of damage was visually observed, and the heat sealability was evaluated based on the following evaluation criteria.

[0151] (Evaluation criteria) AA: No damage was found in any of the 10 bags. NG: Breakage was confirmed in one or more of the 10 bags, posing a practical problem.

[0152] [Haze Rating] The haze value of the stretched multilayer substrate prepared above was measured in accordance with JIS K7136.

[0153] [Rigidity evaluation] The stretched multilayer substrate prepared above was cut into test pieces with a width of 10 mm, and the stiffness of the test pieces was measured using a loop stiffness measuring tester (manufactured by Toyo Seiki Seisakusho, product name: Loop Stiffness Tester). The loop length was 60 mm.

[0154] [Strength evaluation] A 10 mm wide dumbbell-shaped test piece was cut from the stretched multilayer substrate prepared above. The tensile strength of this test piece in the MD direction was measured using a tensile tester (Orientec Co., Ltd., RTC-1310A). The chuck distance was 10 mm and the pulling speed was 300 mm / min.

[0155] [Table 1]

[0156] As is clear from the results in Table 1, it is evident that the laminate of the present disclosure makes it possible to produce packaging bags that are excellent in strength, heat sealability and recyclability. [Explanation of symbols]

[0157] 10: Laminate 12: Base material (stretched multilayer base material) 14: Heat seal layer 16: Adhesive layer

Claims

1. A laminate comprising a substrate and a heat seal layer, the base material and the heat seal layer are made of the same type of resin material, The substrate has a multilayer structure, the substrate is a substrate that has been subjected to a stretching treatment, The heat seal layer is a layer that has not been subjected to a stretching treatment. Laminate.

2. The laminate according to claim 1 , wherein the homogeneous resin material is a polyolefin.

3. The laminate according to claim 1 or 2, wherein the same type of resin material is polyethylene or polypropylene.

4. The laminate according to claim 1 , wherein the homogeneous resin material is polyester.

5. The laminate according to any one of claims 1 to 4, further comprising a printed layer formed on the substrate.

6. The laminate according to any one of claims 1 to 5, wherein the heat seal layer has a multi-layer structure.

7. The laminate according to any one of claims 1 to 6, wherein the heat seal layer is an unstretched resin film or a melt-extruded layer of the resin material.

8. The laminate according to any one of claims 1 to 7, further comprising a barrier layer formed on the substrate.

9. The laminate according to any one of claims 1 to 7, further comprising a barrier film between the substrate and the heat seal layer, the barrier film comprising a second substrate and a barrier layer formed on the second substrate.

10. The laminate according to any one of claims 1 to 9, wherein the content of the same type of resin material in the entire laminate is 90 mass% or more.

11. The laminate according to any one of claims 1 to 10, which is a laminate for packaging materials.

12. A packaging material comprising the laminate according to any one of claims 1 to 11.

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