Laminate and packaging material

Abstract

To provide a laminate comprising a polyethylene multilayer substrate and a heat seal layer primarily composed of polyethylene, the laminate having excellent heat resistance.SOLUTION: A laminate comprises a polyethylene multilayer substrate and a heat seal layer primarily composed of polyethylene. The polyethylene multilayer substrate has been drawn and comprises a first polyethylene layer, a second polyethylene layer, and a third polyethylene layer in the stated order in a thickness direction, where the first polyethylene layer has an indentation elastic modulus of 1.0 GPa or more and the third polyethylene layer has an indentation elastic modulus of 1.0 GPa or more.SELECTED DRAWING: Figure 2

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 polyethylene are widely used as heat-sealing layers in packaging materials because they are flexible, transparent, and have excellent heat-sealing properties (see, for example, Patent Document 1).

[0003] On the other hand, polyethylene is a resin that softens at a relatively low temperature compared to other thermoplastic resins, and therefore, when used as a base material for packaging materials, it may deform or even melt during heat sheet processing. Furthermore, polyethylene film may lack strength compared to other thermoplastic resin films. For this reason, resin films with excellent strength and heat resistance, such as polyester film and nylon film, are generally used as base materials for packaging materials. For example, bags are made by laminating a base material such as polyester film or nylon film with a polyethylene film, and then heat-sealing the polyethylene film side so that it is on the inside of the packaging bag (see, for example, the background art of Patent Document 2).

[0004] In recent years, along with the growing demand for the creation of a recycling-oriented society, attempts have been made to recycle and reuse packaging materials. However, laminates obtained by laminating different types of resin films as described above are difficult to separate by type of resin, and are therefore not suitable for recycling. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-202519 [Patent Document 2] Japanese Patent Application Publication No. 2017-031233 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, the present inventors discovered that the strength and heat resistance of a resin film made of polyethylene can be improved by stretching, and considered using a polyethylene multilayer substrate as the substrate, which has multiple layers containing polyethylene and has been stretched.

[0007] Heat is applied to substrates used in packaging materials, for example, during heat sealing of the packaging material. However, the present inventors have found that laminates including the polyethylene multilayer substrate may experience significant heat shrinkage due to the application of heat, and thus have insufficient heat resistance.

[0008] One object of the present disclosure is to provide a laminate having excellent heat resistance, which includes a polyethylene multilayer substrate and a heat seal layer containing polyethylene as a main component. [Means for solving the problem]

[0009] The laminate of the present disclosure comprises a polyethylene multilayer substrate and a heat seal layer containing polyethylene as a main component. The polyethylene multilayer substrate comprises a first polyethylene layer, a second polyethylene layer, and a third polyethylene layer in this order in the thickness direction, and is formed by stretching. In one embodiment of the multilayer substrate, the first polyethylene layer has an indentation modulus of 1.0 GPa or more, and the third polyethylene layer has an indentation modulus of 1.0 GPa or more. In one embodiment of the multilayer substrate, the first polyethylene layer has an indentation hardness of 45 MPa or more, and the third polyethylene layer has an indentation hardness of 45 MPa or more. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a laminate having excellent heat resistance, which includes a polyethylene multilayer base material and a heat seal layer containing polyethylene as a main component. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional schematic diagram illustrating one embodiment of a polyethylene multilayer substrate. [Figure 2] 1 is a cross-sectional schematic diagram illustrating one embodiment of a laminate of the present disclosure. [Figure 3] 1 is a cross-sectional schematic diagram illustrating one embodiment of a laminate of the present disclosure. [Figure 4] 1 is a cross-sectional schematic diagram illustrating one embodiment of a laminate of the present disclosure. [Figure 5] 1 is a cross-sectional schematic diagram illustrating one embodiment of a laminate of the present disclosure. [Figure 6] FIG. 2 is a schematic diagram illustrating a method for measuring the thermal shrinkage rate of a laminate. DETAILED DESCRIPTION OF THE INVENTION

[0012] [term] The terms used in this disclosure are explained below. "Polyethylene" refers to a polymer in which the content of ethylene-derived structural units is 50 mol% or more of all repeating structural units. In such a 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 content is measured by nuclear magnetic resonance (NMR) spectroscopy.

[0013] The "polyethylene layer" is a layer containing polyethylene as a main component, i.e., a layer containing more than 50% by mass of polyethylene. The polyethylene content in the polyethylene layer is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more.

[0014] 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, particularly Method D (density gradient tube method, 23°C).

[0015] In the present disclosure, examples of polyethylene include ethylene homopolymers and copolymers of ethylene with other monomers. Examples of other monomers include α-olefins having 3 to 20 carbon atoms, vinyl acetate, and (meth)acrylic acid esters. Examples of α-olefins having 3 to 20 carbon atoms include 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. Examples of (meth)acrylic acid esters include alkyl (meth)acrylates such as methyl (meth)acrylate and ethyl (meth)acrylate.

[0016] Examples of the copolymer include a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, a copolymer of ethylene and at least one selected from vinyl acetate and (meth)acrylic acid esters, and a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms, and at least one selected from vinyl acetate and (meth)acrylic acid esters.

[0017] Polyethylenes with different densities or branches 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.

[0018] 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.

[0019] 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.

[0020] Examples of the transition metal in the transition metal compound include zirconium, titanium, and hafnium, with zirconium and hafnium being preferred.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] Examples of organometallic compounds that may be used as needed include organoaluminum compounds, organomagnesium compounds, and organozinc compounds. Of these, organoaluminum compounds are preferred.

[0025] 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.

[0026] Biomass-derived ethylene may be used as a raw material for obtaining polyethylene, instead of ethylene obtained from fossil fuels. Biomass-derived polyethylene is a carbon-neutral material, and therefore can reduce the environmental impact of packaging materials produced using a polyethylene multilayer substrate. Biomass-derived polyethylene can be produced, for example, by the method described in JP 2013-177531 A. Commercially available biomass-derived polyethylene (e.g., Green PE available from Braskem) may also be used.

[0027] You can also use polyethylene recycled through mechanical recycling. Mechanical recycling generally involves crushing collected polyethylene film, washing it with alkali to remove dirt and foreign matter from the film surface, and then drying it at high temperature and reduced pressure for a certain period of time to diffuse any contaminants remaining inside the film, thereby decontaminating it and removing the dirt from the polyethylene film and returning it to polyethylene.

[0028] In the following description, each of the components (for example, polyethylene such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene, additives, colorants, resin materials, and adhesives) that appear may be used alone or in combination of two or more types. Below, the polyethylene multilayer substrate included in the laminate of the present disclosure will be described, and then the laminate of the present disclosure will be described.

[0029] [Polyethylene multi-layer base material] The polyethylene multilayer substrate is a first polyethylene layer; a second polyethylene layer; and a third polyethylene layer; and the like are provided in this order in the thickness direction and are subjected to a stretching treatment. Hereinafter, the polyethylene multilayer substrate will also be simply referred to as "multilayer substrate."

[0030] The multilayer substrate may further include a 2a polyethylene layer between the first and second polyethylene layers, and a 2b polyethylene layer between the second and third polyethylene layers. In this case, the multilayer substrate includes the first polyethylene layer, the 2a polyethylene layer, the second polyethylene layer, the 2b polyethylene layer, and the third polyethylene layer in this order in the thickness direction. The 2a polyethylene layer, the second polyethylene layer, and the 2b polyethylene layer constitute an intermediate layer (multilayer intermediate layer) in the multilayer substrate.

[0031] In one embodiment, the surface layer on one side of the multilayer substrate is a first polyethylene layer, and the surface layer on the other side of the multilayer substrate is a third polyethylene layer. The multilayer substrate may have another layer between at least one of the first polyethylene layer, the 2a polyethylene layer, the second polyethylene layer, the 2b polyethylene layer, and the third polyethylene layer. In one embodiment, the multilayer substrate consists only of the first polyethylene layer, the 2a polyethylene layer, the second polyethylene layer, the 2b polyethylene layer, and the third polyethylene layer.

[0032] Hereinafter, the polyethylene layer will also be referred to as the "PE layer."

[0033] Examples of polyethylene contained in the multilayer substrate include high-density polyethylene, medium-density polyethylene, low-density polyethylene (high-pressure low-density polyethylene), linear low-density polyethylene, and very low-density polyethylene.

[0034] From the viewpoint of film-forming properties and processability of the multilayer substrate, the melt flow rate (MFR) of the polyethylene contained in the multilayer substrate is preferably 0.1 g / 10 min to 50 g / 10 min, more preferably 0.2 g / 10 min to 30 g / 10 min, even more preferably 0.2 g / 10 min to 15 g / 10 min, still more preferably 0.2 g / 10 min to 10 g / 10 min, and particularly preferably 0.2 g / 10 min to 5 g / 10 min. In the present disclosure, MFR is measured in accordance with ASTM D1238 at a temperature of 190°C and a load of 2.16 kg.

[0035] FIG. 1 shows one embodiment of a multi-layer substrate. The multilayer substrate 10 of FIG. a first PE layer 12; a 2a PE layer 18; a second PE layer 20; a second PE layer 22; the third PE layer 14; are provided in this order in the thickness direction. In the multilayer substrate 10 of Fig. 1, the 2a PE layer 18 and the 2b PE layer 22 may be omitted.

[0036] For example, the first PE layer may contain medium-density polyethylene and high-density polyethylene, and the third PE layer may contain medium-density polyethylene and high-density polyethylene. By adjusting the ratio of the medium-density polyethylene and high-density polyethylene, for example, it is possible to adjust the indentation modulus and indentation hardness, which will be described later. This allows for further improvement in the ink adhesion and heat resistance of the multilayer substrate.

[0037] The mass ratio of the medium-density polyethylene to the high-density polyethylene (medium-density polyethylene / high-density polyethylene) in the first PE layer and the third PE layer is preferably 1.1 or more and 5 or less, more preferably 1.5 or more and 3 or less, thereby further improving the balance between ink adhesion and heat resistance.

[0038] The total content of medium-density polyethylene and high-density polyethylene in the first PE layer and the third PE layer is independently preferably at least 80% by mass, more preferably at least 90% by mass, and even more preferably at least 95% by mass, thereby further improving the ink adhesion and heat resistance of the multilayer substrate.

[0039] For example, the second PE layer may contain linear low-density polyethylene. This configuration tends to allow the indentation modulus and indentation hardness (described later) to be adjusted to a low range, thereby improving the stretchability of the laminate, which is the precursor of the multilayer substrate.

[0040] The content of the linear low-density polyethylene in the second PE layer is preferably more than 50% by mass, more preferably at least 60% by mass, even more preferably at least 70% by mass, and even more preferably at least 80%, 90%, or 95% by mass, thereby further improving the balance between heat resistance, rigidity, and extensibility.

[0041] In one embodiment, the 2a PE layer and the 2b PE layer may each contain high-density polyethylene. This configuration tends to allow the indentation modulus and indentation hardness (described later) to be adjusted to a high range. These layers contribute to improving the heat resistance of the multilayer substrate. That is, by incorporating high-density polyethylene into the 2a PE layer and the 2b PE layer in addition to the first and third PE layers, the heat resistance of the multilayer substrate can be further improved.

[0042] In one embodiment, the 2a PE layer and the 2b PE layer may each further contain low-density polyethylene. This configuration may adjust, for example, the indentation modulus and indentation hardness described below. This further improves the balance between heat resistance, rigidity, and processability of the multilayer substrate.

[0043] The mass ratio of high-density polyethylene to low-density polyethylene (high-density polyethylene / low-density polyethylene) in the 2a PE layer and the 2b PE layer is preferably from 1 to 4, more preferably from 1.5 to 3. This allows the multilayer substrate to have a better balance of heat resistance, rigidity, and processability.

[0044] The content of high-density polyethylene in the 2a PE layer and the 2b PE layer is preferably greater than 50% by mass, more preferably at least 55% by mass, and even more preferably at least 60% by mass, which can further improve the heat resistance of the multilayer substrate.

[0045] The total content of high-density polyethylene and low-density polyethylene in the 2a PE layer and the 2b PE layer is independently preferably at least 80 mass%, more preferably at least 90 mass%, and even more preferably at least 95 mass%, which can further improve the balance of heat resistance, rigidity, and processability of the multilayer substrate.

[0046] In another embodiment, the 2a PE layer may contain a medium-density polyethylene and a linear low-density polyethylene, and the 2b PE layer may contain a medium-density polyethylene and a linear low-density polyethylene. By adjusting the ratio of the medium-density polyethylene and the linear low-density polyethylene, for example, the indentation modulus and indentation hardness described below can be adjusted. These layers contribute to improving the stretchability of the laminate, which is the precursor to the multilayer substrate.

[0047] The mass ratio of medium-density polyethylene to linear low-density polyethylene (medium-density polyethylene / linear low-density polyethylene) in the 2a PE layer and the 2b PE layer is preferably 0.25 or more and 4 or less, more preferably 0.4 or more and 2.4 or less, thereby further improving the balance between heat resistance, rigidity, and extensibility.

[0048] The total content of medium-density polyethylene and linear low-density polyethylene in the 2a PE layer and the 2b PE layer is independently preferably at least 80% by mass, more preferably at least 90% by mass, and even more preferably at least 95% by mass, thereby further improving the stretchability of the precursor laminate.

[0049] The thickness of each of the first PE layer and the third PE layer is independently 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, thereby further improving the ink adhesion and heat resistance of the multilayer substrate.

[0050] The thickness of each of the first PE layer and the third PE layer is preferably smaller than the total thickness of the 2a PE layer, the second PE layer, and the 2b PE layer (hereinafter, the 2a, 2b, and 2b layers are collectively referred to as the "multilayer intermediate layer"). The ratio of the thickness of each of the first PE layer and the third PE layer to the total thickness of the multilayer intermediate layer (first PE layer or third PE 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 further improves the rigidity, strength, and heat resistance of the multilayer substrate.

[0051] The thickness of the second PE layer is preferably from 1 μm to 50 μm, more preferably from 2 μm to 40 μm, and even more preferably from 5 μm to 30 μm, thereby improving the balance between heat resistance, rigidity, and stretchability.

[0052] The thickness of each of the 2a PE layer and the 2b PE layer is independently preferably from 0.5 μm to 15 μm, more preferably from 1 μm to 10 μm, and even more preferably from 1 μm to 8 μm, which can further improve the heat resistance of the multilayer substrate or the stretchability of the precursor laminate.

[0053] The ratio of the total thickness of the 2a PE layer and the 2b PE layer to the thickness of the second PE layer (total thickness of the 2a PE layer and the 2b PE layer / thickness of the second PE layer) is preferably 0.1 to 10, more preferably 0.2 to 5, and even more preferably 0.5 to 2. This can further improve the rigidity, strength, and heat resistance of the multilayer substrate. The thickness of each of the above layers is the thickness after stretching treatment.

[0054] Each layer constituting the multilayer substrate may independently contain additives, such as crosslinkers, antioxidants, antiblocking agents, slip agents, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

[0055] At least one layer selected from the first PE layer, the second PE layer, and the third PE layer in the multilayer substrate, specifically at least one layer selected from the first PE layer, the 2a PE layer, the second PE layer, the 2b PE layer, and the third PE layer, may contain a slip agent. This, for example, can improve the processability of the multilayer substrate. For example, the second PE layer may contain a slip agent, or all of the above layers may contain a slip agent.

[0056] Examples of slip agents include amide-based lubricants, fatty acid esters such as glycerin fatty acid esters, hydrocarbon waxes, higher fatty acid waxes, metal soaps, hydrophilic silicones, silicone-modified (meth)acrylic resins, silicone-modified epoxy resins, silicone-modified polyethers, silicone-modified polyesters, block-type silicone (meth)acrylic copolymers, polyglycerol-modified silicones, and paraffins.

[0057] Among lubricants, amide-based lubricants are preferred. Examples of amide-based lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylol amides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides.

[0058] Examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide. Examples of methylol amides include methylol stearic acid amide. Examples of saturated fatty acid bisamides include methylene bisstearamide, ethylene biscapric amide, ethylene bislauric amide, ethylene bisstearamide, ethylene bishydroxystearamide, ethylene bisbehenic amide, hexamethylene bisstearamide, hexamethylene bisbehenic amide, hexamethylene hydroxystearamide, N,N'-distearyl adipamide, and N,N'-distearyl sebacamide. Examples of unsaturated fatty acid bisamides include ethylene bisoleic amide, ethylene biserucic amide, hexamethylene bisoleic amide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacamide. Examples of fatty acid ester amides include stearamidoethyl stearate. Examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, and N,N'-distearylisophthalic acid amide. Among the slip agents, erucamide is preferred.

[0059] To improve the dispersibility of the slip agent in the resin composition forming each layer, a masterbatch containing the slip agent and polyethylene may be used. The content of the slip agent in the masterbatch is preferably 1% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 20% by mass or less, and even more preferably 3% by mass or more and 10% by mass or less. Specific examples of polyethylene include those mentioned above. The preferred physical properties (density, MFR, etc.) that the polyethylene should satisfy are also as described above.

[0060] In the multilayer substrate, the slip agent content in the layer containing the slip agent may be, for example, 0.01% by mass to 3% by mass, or 0.03% by mass to 1% by mass, which can further improve the processability of the multilayer substrate.

[0061] When a layer contains multiple types of polyethylene with different densities (n types; n is an integer of 2 or more), the density of the polyethylene constituting the layer may be measured in accordance with the above-mentioned JIS K7112, and the average density D calculated according to the following formula (1) may be calculated. av may be the density of the polyethylene that constitutes the layer.

[0062] D av = ΣW i ×D i …(1) In equation (1), Σ is W for i from 1 to n. i ×D i where n is an integer greater than or equal to 2, and W i denotes the mass fraction of the i-th polyethylene, and D i is the density of the i-th polyethylene (g / cm 3 ) is shown.

[0063] The multilayer substrate has been stretched and has unique physical properties, and therefore is superior in rigidity, strength, heat resistance, and ink adhesion to conventional polyethylene films. Therefore, the polyethylene multilayer substrate can be used, for example, as a substrate for packaging materials, and a clear image can be formed on the surface of the multilayer substrate.

[0064] The haze value of the 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 multilayer substrate is measured in accordance with JIS K7136.

[0065] The content of polyethylene in the 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 multilayer substrate.

[0066] Specific embodiments of the polyethylene multilayer substrate will be described below. The polyethylene multilayer substrate of the first embodiment comprises a first PE layer, a 2a PE layer, a second PE layer, a 2b PE layer, and a third PE layer in this order in the thickness direction, and is stretched; the first PE layer contains medium density polyethylene and high density polyethylene; the 2a PE layer contains high density polyethylene and optionally low density polyethylene; the second PE layer contains linear low-density polyethylene; the 2b PE layer contains high density polyethylene and optionally low density polyethylene; The third PE layer contains medium density polyethylene and high density polyethylene.

[0067] The polyethylene multilayer substrate of the second embodiment comprises a first PE layer, a 2a PE layer, a second PE layer, a 2b PE layer, and a third PE layer in this order in the thickness direction, and is stretched; the first PE layer contains medium density polyethylene and high density polyethylene; The 2a PE layer contains medium density polyethylene and linear low density polyethylene, the second PE layer contains linear low-density polyethylene; The 2b PE layer contains medium density polyethylene and linear low density polyethylene, The third PE layer contains medium density polyethylene and high density polyethylene.

[0068] The medium-density polyethylene contained in the first PE layer and the medium-density polyethylene contained in the third PE layer may be the same or different, but from the viewpoint of facilitating the production of the multilayer base material, it is preferable that they are the same. The high-density polyethylene contained in the first PE layer and the high-density polyethylene contained in the third PE layer may be the same or different, but from the viewpoint of facilitating the production of the multilayer base material, it is preferable that they are the same.

[0069] In the first embodiment, the high-density polyethylene contained in the 2a PE layer and the high-density polyethylene contained in the 2b PE layer may be the same or different, and from the viewpoint of facilitating the production of the multilayer base material, it is preferable that they are the same.

[0070] In the second embodiment, the linear low-density polyethylene contained in the second PE layer may be the same as or different from the linear low-density polyethylene contained in the 2a PE layer and the 2b PE layer. In the second embodiment, the medium-density polyethylene contained in the 2a PE layer and the medium-density polyethylene contained in the 2b PE layer may be the same or different, and from the viewpoint of facilitating the production of the multilayer base material, it is preferable that they are the same. In the second embodiment, the linear low-density polyethylene contained in the 2a PE layer and the linear low-density polyethylene contained in the 2b PE layer may be the same or different, and from the viewpoint of facilitating the production of the multilayer base material, it is preferable that they are the same. In the second embodiment, the medium-density polyethylene contained in the 2a PE layer and the 2b PE layer may be the same as or different from the medium-density polyethylene contained in the first PE layer and the third PE layer.

[0071] <Method of manufacturing polyethylene multilayer substrate> The polyethylene multilayer substrate can be produced by forming a laminate from multiple polyethylene materials 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 multilayer substrate, making it suitable for use as, for example, a substrate for packaging materials.

[0072] The polyethylene multilayer substrate of the first embodiment is obtained, for example, by stretching a laminate (precursor) having, in the thickness direction, a layer containing medium-density polyethylene and high-density polyethylene, a layer containing high-density polyethylene, a layer containing linear low-density polyethylene, a layer containing high-density polyethylene, and a layer containing medium-density polyethylene and high-density polyethylene, in this order.

[0073] Specifically, a laminate can be produced by co-extruding from the outside a layer containing medium-density polyethylene and high-density polyethylene, a layer containing high-density polyethylene, a layer containing linear low-density polyethylene, a layer containing high-density polyethylene, and a layer containing medium-density polyethylene and high-density polyethylene into a tubular shape. Alternatively, a laminate can be produced by co-extruding from the outside a layer containing medium-density polyethylene and high-density polyethylene, a layer containing high-density polyethylene, and a layer containing linear low-density polyethylene into a tubular shape, and then pressing the opposing layers containing linear low-density polyethylene together using a rubber roll or the like. By producing a laminate using such a method, the number of defective products can be significantly reduced and production efficiency can be improved.

[0074] The polyethylene multilayer substrate of the second embodiment and other polyethylene multilayer substrates can also be produced, for example, by the method described above.

[0075] When a laminate is produced by the T-die method, the melt flow rate (MFR) of the polyethylene constituting each layer is preferably 3 g / 10 min or more and 20 g / 10 min or less from the viewpoint of film-forming properties and processability of the multilayer substrate.

[0076] When a laminate is produced by an inflation method, the MFR of the polyethylene constituting each layer is preferably 0.2 g / 10 min or more and 5 g / 10 min or less from the viewpoint of film-forming properties and processability of the multilayer substrate.

[0077] The multilayer substrate can be obtained, for example, by stretching the laminate described above. Note that the stretching of the laminate can also be performed in an inflation film-forming machine. This allows the multilayer substrate to be produced, thereby further improving production efficiency.

[0078] The multilayer substrate may be a uniaxially stretched film or a biaxially stretched film. In one embodiment, the multilayer substrate is a uniaxially stretched film, more specifically, a uniaxially stretched film that has been stretched in the machine direction (MD).

[0079] In one embodiment, the stretching ratio in the machine direction (MD) of the 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 multilayer substrate is preferably 2 to 10, more preferably 3 to 7.

[0080] A stretching ratio of 2 or more can improve, for example, the rigidity, strength, and heat resistance of the multilayer substrate, improve the ink adhesion to the multilayer substrate, and improve the transparency of the multilayer substrate.A stretching ratio of 10 or less can ensure good stretching of the laminate.

[0081] The laminate or multilayer substrate is preferably subjected to a surface treatment. This can improve the adhesion between the surface layer of the multilayer substrate and the layer laminated on the 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.

[0082] An anchor coating layer may be formed on the surface of the laminate or multilayer substrate using a conventionally known anchor coating agent.

[0083] The total thickness of the 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 multilayer substrate is 10 μm or more, the rigidity and strength of the multilayer substrate can be improved. When the thickness of the multilayer substrate is 60 μm or less, the processability of the multilayer substrate can be improved. A small thickness of the multilayer substrate within a range in which the above-mentioned effects can be obtained is preferable, for example, from the viewpoint of cost reduction.

[0084] [Laminate] The laminate of the present disclosure comprises: The polyethylene multilayer substrate described above; A heat seal layer containing polyethylene as a main component. Equipped with.

[0085] In this disclosure, the indentation moduli of the first PE layer, the second PE layer, the second PE layer, the second PE layer, the third PE layer, and the third PE layer are also referred to as indentation modulus 1, indentation modulus 2a, indentation modulus 2, indentation modulus 2b, and indentation modulus 3, respectively. The ratio of the indentation modulus of the first PE layer to the indentation modulus of the second PE layer is also referred to as the ratio (modulus 1 / modulus 2). The same applies to other cases.

[0086] In this disclosure, the indentation hardnesses of the first PE layer, the second PE layer, the second PE layer, the second PE layer, the third PE layer, and the third PE layer are also referred to as indentation hardness 1, indentation hardness 2a, indentation hardness 2, indentation hardness 2b, and indentation hardness 3, respectively. The ratio of the indentation hardness of the first PE layer to the indentation hardness of the second PE layer is also referred to as the ratio (hardness 1 / hardness 2). The same applies to other cases.

[0087] The laminate according to the first aspect of the present disclosure is characterized in that the first PE layer has an indentation modulus of 1.0 GPa or more, and the third PE layer has an indentation modulus of 1.0 GPa or more, thereby improving the heat resistance of the laminate and suppressing thermal shrinkage of the laminate during application of heat, for example, during heat sealing.

[0088] The indentation modulus 1 and indentation modulus 3 in the laminate of the first embodiment are each independently 1.0 GPa or more, preferably 1.05 GPa or more, more preferably 1.1 GPa or more, even more preferably 1.15 GPa or more, and particularly preferably 1.3 GPa or more; and preferably 4.5 GPa or less, more preferably 4.0 GPa or less, even more preferably 3.5 GPa or less, even more preferably 3.0 GPa or less, and particularly preferably 2.5 GPa or less, 2.0 GPa or less, or 1.8 GPa or less. This tends to further suppress thermal shrinkage of the laminate during heat sealing, for example. The ranges of the indentation modulus 1 and indentation modulus 3 may each independently be any combination of the above lower and upper limits, for example, 1.0 GPa or more and 4.5 GPa or less.

[0089] The indentation modulus 2 of the laminate of the first embodiment is preferably 0.03 GPa or more, more preferably 0.05 GPa or more, even more preferably 0.1 GPa or more, even more preferably 0.13 GPa or more, and particularly preferably 0.15 GPa or more; and preferably 0.7 GPa or less, more preferably 0.6 GPa or less, even more preferably 0.5 GPa or less, even more preferably 0.4 GPa or less, and particularly preferably 0.3 GPa or less. With such a design, for example, the stretchability of the laminate before stretching tends to be better. The range of the indentation modulus 2 may be any combination of the above lower and upper limits, for example, 0.03 GPa or more and 0.7 GPa or less.

[0090] The indentation modulus 2a and the indentation modulus 2b of the laminate of the first embodiment are each independently preferably 0.3 GPa or more, more preferably 0.4 GPa or more, even more preferably 0.5 GPa or more, and even more preferably 0.6 GPa or more; and preferably 3.5 GPa or less, more preferably 3.0 GPa or less, even more preferably 2.5 GPa or less, even more preferably 2.0 GPa or less, and particularly preferably 1.5 GPa or less. This tends to further suppress thermal shrinkage of the laminate during heat sealing, for example. The ranges of the indentation modulus 2a and the indentation modulus 2b may each independently be any combination of the above lower and upper limits, for example, 0.3 GPa or more and 3.5 GPa or less.

[0091] In the laminate of the first aspect, the magnitude of the indentation modulus of each PE layer preferably satisfies the relationship of Indentation modulus 1 > Indentation modulus 2a > Indentation modulus 2, and more preferably satisfies the relationship of Indentation modulus 3 > Indentation modulus 2b > Indentation modulus 2. This tends to further improve the balance between the heat resistance and stretchability (processability, productivity) of the multilayer substrate, for example.

[0092] In the laminate of the first aspect, the indentation modulus of the first PE layer is preferably at least 3.5 times that of the second PE layer, and the indentation modulus of the third PE layer is preferably at least 3.5 times that of the second PE layer, thereby improving the heat resistance of the laminate and further suppressing thermal shrinkage of the laminate during heat application, for example, during heat sealing.

[0093] The ratios (elastic modulus 1 / elastic modulus 2) and (elastic modulus 3 / elastic modulus 2) in the laminate of the first embodiment are each independently preferably 3.5 or more, more preferably 4.0 or more, even more preferably 4.5 or more, still more preferably 5.0 or more, and particularly preferably 5.5 or more; and are preferably 16.0 or less, more preferably 14.0 or less, even more preferably 12.0 or less, still more preferably 10.0 or less, and particularly preferably 9.0 or less. The ranges of the ratio (elastic modulus 1 / elastic modulus 2) and the ranges of the ratio (elastic modulus 3 / elastic modulus 2) may each independently be any combination of the above lower and upper limits, for example, 3.5 or more and 16.0 or less.

[0094] In the laminate of the first aspect, the indentation modulus of the 2a PE layer is preferably at least 2.0 times that of the second PE layer, and the indentation modulus of the 2b PE layer is preferably at least 2.0 times that of the second PE layer, which tends to further suppress thermal shrinkage of the laminate during heat sealing, for example.

[0095] In the laminate of the first embodiment, the ratios (elastic modulus 2a / elastic modulus 2) and (elastic modulus 2b / elastic modulus 2) are each independently preferably 2.0 or more, more preferably 2.5 or more, and even more preferably 3.0 or more; and are preferably 14.0 or less, more preferably 12.0 or less, even more preferably 10.0 or less, still more preferably 9.0 or less, and particularly preferably 8.5 or less. The ranges of the ratio (elastic modulus 2a / elastic modulus 2) and the ranges of the ratio (elastic modulus 2b / elastic modulus 2) may each independently be any combination of the above lower and upper limits, for example, from 2.0 to 14.0.

[0096] In the laminate of the first aspect, the ratio (elastic modulus 1 / elastic modulus 3) is preferably 0.6 to 1.7, more preferably 0.7 to 1.4, even more preferably 0.8 to 1.2, and even more preferably 0.9 to 1.1, which tends to improve the symmetry of the layer structure of the multilayer substrate, thereby suppressing curling of the multilayer substrate and improving processability in printing, lamination, and the like.

[0097] In the laminate of the first aspect, the ratio (elastic modulus 2a / elastic modulus 2b) is preferably 0.6 to 1.7, more preferably 0.7 to 1.4, even more preferably 0.8 to 1.2, and still more preferably 0.9 to 1.1, which tends to improve the symmetry of the layer structure of the multilayer substrate, thereby suppressing curling of the multilayer substrate and improving processability in printing, lamination, and the like.

[0098] The laminate according to the second aspect of the present disclosure is characterized in that the first PE layer has an indentation hardness of 45 MPa or more, and the third PE layer has an indentation hardness of 45 MPa or more, thereby improving the heat resistance of the laminate and suppressing thermal shrinkage of the laminate when heat is applied, for example, during heat sealing.

[0099] The indentation hardness 1 and indentation hardness 3 of the laminate of the second embodiment are each independently 45 MPa or more, preferably 48 MPa or more, more preferably 50 MPa or more, and even more preferably 52 MPa or more; and preferably 110 MPa or less, more preferably 90 MPa or less, even more preferably 80 MPa or less, even more preferably 75 MPa or less, and particularly preferably 70 MPa or less. This tends to further suppress thermal shrinkage of the laminate during heat sealing, for example. The ranges of the indentation hardness 1 and the indentation hardness 3 may each independently be any combination of the above lower and upper limits, for example, 45 MPa or more and 110 MPa or less. The laminate of the first embodiment may further satisfy the above requirements for the indentation hardness 1 and the indentation hardness 3.

[0100] The indentation hardness 2 of the laminate of the second embodiment is preferably 1 MPa or more, more preferably 3 MPa or more, even more preferably 7 MPa or more, even more preferably 10 MPa or more, and particularly preferably 15 MPa or more; and preferably 40 MPa or less, more preferably 35 MPa or less, even more preferably 30 MPa or less, even more preferably 26 MPa or less, and particularly preferably 23 MPa or less. With such a design, for example, the stretchability of the laminate before stretching tends to be better. The range of the indentation hardness 2 may be any combination of the above lower and upper limits, for example, 1 MPa or more and 40 MPa or less. The laminate of the first embodiment may further satisfy the above requirements for indentation hardness 2.

[0101] The indentation hardness 2a and the indentation hardness 2b of the laminate of the second embodiment are each independently preferably 20 MPa or more, more preferably 30 MPa or more, even more preferably 35 MPa or more, and even more preferably 37 MPa or more; and preferably 100 MPa or less, more preferably 80 MPa or less, even more preferably 70 MPa or less, even more preferably 65 MPa or less, and particularly preferably 60 MPa or less. This tends to further suppress thermal shrinkage of the laminate during heat sealing, for example. The ranges of the indentation hardness 2a and the indentation hardness 2b may each independently be any combination of the above lower and upper limits, for example, 20 MPa or more and 100 MPa or less. The laminate of the first embodiment may further satisfy the above requirements for the indentation hardness 2a and the indentation hardness 2b.

[0102] In the laminate of the second aspect, the magnitude of the indentation hardness of each PE layer preferably satisfies the relationship of Indentation Hardness 1 > Indentation Hardness 2a > Indentation Hardness 2, and more preferably satisfies the relationship of Indentation Hardness 3 > Indentation Hardness 2b > Indentation Hardness 2. This tends to further improve the balance between the heat resistance and stretchability (processability, productivity) of the multilayer substrate, for example.

[0103] In the laminate of the second aspect, the indentation hardness of the first PE layer is preferably at least 2.0 times that of the second PE layer, and the indentation hardness of the third PE layer is preferably at least 2.0 times that of the second PE layer, thereby improving the heat resistance of the laminate and further suppressing thermal shrinkage of the laminate when heat is applied, for example, during heat sealing.

[0104] The ratios (Hardness 1 / Hardness 2) and (Hardness 3 / Hardness 2) in the laminate of the second embodiment are each independently preferably 2.0 or greater, more preferably 2.2 or greater, even more preferably 2.4 or greater, still more preferably 2.6 or greater, and particularly preferably 2.8 or greater; and are preferably 6.0 or less, more preferably 5.5 or less, even more preferably 5.0 or less, still more preferably 4.5 or less, and particularly preferably 4.0 or less or 3.5 or less. The ranges of the ratio (Hardness 1 / Hardness 2) and the ratio (Hardness 3 / Hardness 2) may each independently be any combination of the above-mentioned lower and upper limits, for example, 2.0 or greater and 6.0 or less. The laminate of the first embodiment may further satisfy the above-mentioned requirements for the ratio (Hardness 1 / Hardness 2) and the ratio (Hardness 3 / Hardness 2).

[0105] In the laminate of the second aspect, the indentation hardness of the 2a PE layer is preferably at least 1.5 times that of the second PE layer, and the indentation hardness of the 2b PE layer is preferably at least 1.5 times that of the second PE layer, which tends to further suppress thermal shrinkage of the laminate during heat sealing, for example.

[0106] The ratios (hardness 2a / hardness 2) and (hardness 2b / hardness 2) in the laminate of the second embodiment are each independently preferably 1.5 or more, more preferably 1.7 or more, and even more preferably 1.9 or more; and are preferably 6.0 or less, more preferably 5.5 or less, even more preferably 5.0 or less, even more preferably 4.5 or less, and particularly preferably 4.0 or less or 3.5 or less. This tends to further suppress thermal shrinkage of the laminate during heat sealing, for example. The ranges of the ratio (hardness 2a / hardness 2) and the ratio (hardness 2b / hardness 2) may each independently be any combination of the above-mentioned lower and upper limits, for example, 1.5 or more and 6.0 or less. The laminate of the first embodiment may further satisfy the above-mentioned requirements for the ratio (hardness 2a / hardness 2) and the ratio (hardness 2b / hardness 2).

[0107] In the laminate of the second aspect, the ratio (hardness 1 / hardness 3) is preferably 0.6 to 1.7, more preferably 0.7 to 1.4, even more preferably 0.8 to 1.2, and even more preferably 0.9 to 1.1, which tends to improve the symmetry of the layer structure of the multilayer substrate, thereby suppressing curling of the multilayer substrate and improving processability in printing, lamination, and the like.

[0108] In the laminate of the second aspect, the ratio (hardness 2a / hardness 2b) is preferably 0.6 to 1.7, more preferably 0.7 to 1.4, even more preferably 0.8 to 1.2, and even more preferably 0.9 to 1.1, which tends to improve the symmetry of the layer structure of the multilayer substrate, thereby suppressing curling of the multilayer substrate and improving processability in printing, lamination, and the like.

[0109] In the present disclosure, the indentation modulus and indentation hardness of each PE layer can be adjusted, for example, by appropriately selecting the polyethylene contained in each PE layer. Increasing the content of high-density polyethylene, such as high-density polyethylene, in the PE layer tends to increase the indentation modulus and indentation hardness. Increasing the content of low-density polyethylene, such as low-density polyethylene and linear low-density polyethylene, in the PE layer tends to decrease the indentation modulus and indentation hardness. The indentation modulus and indentation hardness of each PE layer can also be adjusted by the stretch ratio. For example, increasing the stretch ratio tends to increase the indentation modulus and indentation hardness of each PE layer, while decreasing the stretch ratio tends to decrease the indentation modulus and indentation hardness of each PE layer.

[0110] In the present disclosure, the indentation modulus and indentation hardness of each PE layer are measured by nanoindentation. Specifically, the indentation modulus and indentation hardness of the laminate are measured using a nanoindenter, with the cross section parallel to the TD direction of each PE layer of the polyethylene multilayer substrate as the measurement surface. The measurement conditions are as follows: A Berkovich indenter (triangular pyramidal indenter) is used as the indenter. The indenter is pressed into the PE layer from the cross section parallel to the TD direction of the laminate to a depth of 200 nm over 10 seconds, held in that state for 5 seconds, and then unloaded over 10 seconds to obtain the maximum load Pmax, the contact projected area A at the maximum depth, and a load-displacement curve. The elastic modulus and hardness values ​​are calculated from the obtained load-displacement curve. Measurements are performed at room temperature (25°C). Measurements are performed at five locations on the same cross section, and the average value of the elastic modulus is taken as the indentation modulus, and the average value of the hardness is taken as the indentation hardness. Details of the measurement conditions are described in the Examples section.

[0111] 2, a laminate 30 of the present disclosure includes a polyethylene multilayer substrate 10 and a heat seal layer 32. In the multilayer substrate 10, an intermediate layer including the second polyethylene layer and, if necessary, polyethylene layers 2a and 2b is referred to as an intermediate layer 16.

[0112] In one embodiment, the laminate 30 further includes a printed layer (not shown) on the multilayer substrate 10. The printed layer is usually formed on a surface layer of the multilayer substrate on which a heat seal layer is provided, for example, on the first polyethylene layer described above.

[0113] 3, the laminate 30 includes a barrier layer 34 and an adhesive layer 36 between the multi-layer substrate 10 and the heat seal layer 32. In this embodiment, the barrier layer 34 is formed on the surface of the multi-layer substrate 10. 4, the laminate 30 includes an adhesive layer 36 and a barrier layer 34 between the multilayer substrate 10 and the heat seal layer 32. In this embodiment, the barrier layer 34 is formed on the surface of the heat seal layer 32. In one embodiment, as shown in FIG. 5, the laminate 30 includes an adhesive layer 36 between the multi-layer substrate 10 and the heat seal layer 32 .

[0114] In the laminate of the present disclosure, the polyethylene content is preferably 90% by mass or more. This improves the recyclability of the laminate. The polyethylene content in the laminate refers to the ratio of the polyethylene content to the sum of the contents of the resin materials in each layer constituting the laminate.

[0115] The laminates of the present disclosure, in one embodiment, exhibit the following heat shrinkage values: MD refers to the longitudinal or machine direction of the laminate, and TD refers to the direction perpendicular to MD.

[0116] The MD heat shrinkage (MD) of the laminate is, for example, 15% or less, preferably 13% or less, more preferably 11% or less, even more preferably 10% or less, still more preferably 8% or less, and particularly preferably 7% or less. The lower limit of the MD heat shrinkage (MD) is preferably as low as possible, but may be, for example, 0.5%, 1%, 2%, or 3%. A laminate with such a low MD heat shrinkage is excellent in, for example, printability and bag-making suitability when producing packaging bags by heat sealing.

[0117] The TD heat shrinkage (TD) of the laminate is, for example, 15% or less, preferably 13% or less, more preferably 11% or less, even more preferably 10% or less, still more preferably 8% or less, and particularly preferably 7% or less. The lower limit of the MD heat shrinkage (TD) is preferably as low as possible, but may be, for example, 0.5%, 1%, 2%, or 3%. A laminate with such a low TD heat shrinkage (TD) is excellent in, for example, printability and bag-making suitability when producing packaging bags by heat sealing.

[0118] The ratio (MD / TD) of the thermal shrinkage (MD) to the thermal shrinkage (TD) of the laminate is preferably 0.5 to 2.0, more preferably 0.7 to 1.4, even more preferably 0.8 to 1.2, and particularly preferably 0.9 to 1.1. If the ratio (MD / TD) is within this range, the laminate will shrink relatively uniformly in MD and TD even when subjected to heat treatment, and therefore, for example, image distortion in the printed layer of the laminate can be suppressed.

[0119] The heat shrinkage of the laminate is measured as follows: The laminate is cut into 10 cm x 10 cm pieces to prepare three sample pieces. Each sample piece is folded in half parallel to the MD or TD so that the heat seal layer side is on the inside, and then tested at a temperature of 120°C and a pressure of 1 kgf / cm using a heat seal tester. 2 A 1.5 cm x 10 cm area is heat-sealed under the conditions of 1 second, 1 minute, and 1 minute (see Figure 6). In Figure 6, the shaded area indicates the heat-sealed area. After heat-sealing, the seal width of the sample is measured, and the MD shrinkage rate (see Figure 6(a)) and TD shrinkage rate (see Figure 6(b)) are calculated. The average value of the three sample pieces is taken as each heat shrinkage rate.

[0120] Each heat shrinkage rate is calculated by the following formula. Heat shrinkage rate (MD) (%) = {(length in MD direction of the portion to be heat-sealed of the laminate (1.5 cm) - length in MD direction of the heat-sealed portion of the laminate after heat sealing) / length in MD direction of the portion to be heat-sealed of the laminate (1.5 cm)} × 100 Heat shrinkage rate (TD) (%) = {(length in the TD direction of the portion of the laminate to be heat-sealed (1.5 cm) - length in the TD direction of the heat-sealed portion of the laminate after heat sealing) / length in the TD direction of the portion of the laminate to be heat-sealed (1.5 cm)} × 100

[0121] For example, if the laminate is sealed with a 1.5 cm heat seal bar and the seal width of the sample is 1.4 cm, the heat shrinkage rate will be (1.5-1.4) / 1.5×100=6.7%.

[0122] <Heat seal layer> The heat seal layer is a layer containing polyethylene as a main component, i.e., a layer containing more than 50% by mass of polyethylene. The polyethylene content in the heat seal layer is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more. By using such a configuration, a laminate for packaging materials can be obtained that has sufficient rigidity, strength, and heat resistance, and is excellent in recyclability.

[0123] The laminate of the present disclosure comprises a polyethylene multilayer substrate and a heat-sealable layer containing polyethylene as a main component (hereinafter also referred to as a "heat-sealable polyethylene layer"). In one embodiment, a printed layer (image) is formed on at least one surface of the multilayer substrate. Since this can prevent deterioration of the image over time, it is preferable that the printed layer is formed on the side of the multilayer substrate where the heat-sealable polyethylene layer is provided.

[0124] In one embodiment, the first polyethylene layer or the third polyethylene layer constitutes the surface layer on one side of the laminate, and the heat seal layer constitutes the surface layer on the other side of the laminate.

[0125] In one embodiment, the resin layers included in the laminate, which includes a polyethylene multilayer substrate and a heat-sealable polyethylene layer, are all polyethylene layers, and the laminate does not include a different type of resin film, such as a polyester film or a nylon film. The polyethylene multilayer substrate meets the rigidity, strength, and heat resistance required for an outer layer film of a packaging material, and the heat-sealable polyethylene layer enables packaging. Therefore, the laminate is suitable as a material for constituting packaging materials that require recyclability.

[0126] In one embodiment, the laminate of the present disclosure comprises only a polyethylene multilayer substrate on which a print layer is optionally formed and a heat-sealable polyethylene layer, whereby each resin layer of the laminate of the present disclosure is made of the same polyethylene material, thereby improving recyclability.

[0127] The heat-seal layer is usually a non-stretched layer. For example, the heat-seal layer can be formed by laminating an unstretched polyethylene film onto a multilayer substrate or the like, optionally via an adhesive layer, or by melt-extruding a polyethylene-containing resin material onto a multilayer substrate or the like. Examples of the adhesive layer include the adhesive layer described below.

[0128] 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 or recycled polyethylene may also be used.

[0129] The content of polyethylene 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. The heat seal layer may contain the above-mentioned additives.

[0130] The heat seal layer may be one layer or two or more layers. In one embodiment, the number of heat seal layers is one to three. The thickness of the heat seal layer is, for example, 10 μm or more and 300 μm or less. From the viewpoint of the strength of the heat seal layer and the processability of the laminate, it is preferable to change the thickness of the heat seal layer appropriately depending on the mass of the contents to be filled in, for example, a packaging material produced using the laminate of the present disclosure.

[0131] 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. For example, when the packaging material is a stand-up pouch, the thickness of the heat seal layer is preferably 50 μm or more and 200 μm or less, so that the stand-up pouch can be well filled with contents of, for example, 50 g or more and 2000 g or less.

[0132] <Barrier layer> In one embodiment, the laminate of the present disclosure includes a barrier layer between the multilayer substrate and the heat-sealing layer. This improves the gas barrier properties of the laminate, specifically the oxygen barrier properties and water vapor barrier properties. The barrier layer may be formed on the surface of the multilayer substrate or on the surface of the heat-sealing layer. Alternatively, the barrier layer may be provided between the multilayer substrate and the heat-sealing layer via an adhesive or the like.

[0133] 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.

[0134] The thickness of the barrier 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 barrier 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 barrier layer 150 nm or less, the occurrence of cracks in the barrier layer can be suppressed and the recyclability of the laminate can be improved.

[0135] Examples of methods for forming the barrier 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 barrier layer may be a composite film containing two or more barrier layers made of different inorganic oxides, formed by combining physical vapor deposition and chemical vapor deposition.

[0136] 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 A pressure of about mbar is preferred. 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 no problems occur. The conveying speed of the multilayer substrate is, for example, about 10 to 800 m / min.

[0137] The surface of the barrier layer is preferably subjected to the above-mentioned surface treatment, which can improve the adhesion between the barrier layer and the adjacent layer.

[0138] When the vapor-deposited layer is made 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] 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 2each 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.

[0144] 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.

[0145] 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).

[0146] 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.

[0147] 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.

[0148] As the catalyst for the sol-gel method, an acid or amine compound is suitable.

[0149] The composition may further contain an acid. The acid is used as a catalyst for the sol-gel process, mainly for the hydrolysis of 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.

[0150] The composition may contain an organic solvent, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and n-butanol.

[0151] 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.

[0152] 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.

[0153] 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, if necessary, a silane coupling agent. A polycondensation reaction gradually progresses within the composition. Next, the composition is applied to the vapor-deposited layer by the conventionally known method and dried. This drying process 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, the mixture is heated to form a gas barrier coating film.

[0154] <Adhesive layer> In one embodiment, the laminate of the present disclosure includes an adhesive layer between any of the layers (for example, between the multilayer substrate and the barrier layer, between the barrier layer and the heat seal layer, or between the multilayer substrate and the heat seal layer), which can improve the adhesion between the layers included in the laminate.

[0155] The adhesive layer contains an adhesive, such as a one-component curing adhesive, a two-component curing adhesive, or a non-curing adhesive.

[0156] 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. Examples of solvent-based adhesives include rubber adhesives, vinyl adhesives, silicone adhesives, epoxy adhesives, phenolic adhesives, olefin adhesives, and urethane adhesives. Among these, two-component curing urethane adhesives are preferred.

[0157] 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.

[0158] 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.

[0159] The adhesive layer can be formed by applying an adhesive to a multilayer substrate or the like by a method such as direct gravure roll coating, gravure roll coating, kiss coating, reverse roll coating, Fontaine coating, or transfer roll coating, and then drying the adhesive.

[0160] <Print layer> The laminate of the present disclosure may include a printing layer formed on a polyethylene multilayer substrate. The printing layer is formed, for example, on the first PE layer or the third PE layer of the multilayer substrate. The multilayer substrate has excellent ink adhesion, allowing for the formation of good images. The multilayer substrate has excellent heat resistance, including heat shrinkage resistance, making it suitable for printing applications.

[0161] 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 multilayer substrate using a biomass-derived ink.

[0162] In one embodiment, the print layer contains a colorant. Examples of the colorant include pigments such as inorganic pigments and organic pigments; and dyes such as acid dyes, direct dyes, disperse dyes, oil-soluble dyes, metal-containing oil-soluble dyes, and sublimation dyes. Examples of the colorant include fluorescent materials such as ultraviolet light-emitting materials that emit fluorescence by absorbing ultraviolet light, and infrared light-emitting materials that emit fluorescence by absorbing infrared light.

[0163] In one embodiment, the print layer may contain a resin material, such as cellulose resin, (meth)acrylic resin, urethane resin, alkyd resin, polyester, polycarbonate, polyolefin, polystyrene, norbornene-based resin, polyvinyl chloride, polyvinyl acetate, and vinyl chloride-vinyl acetate copolymer.

[0164] [Application] The laminate of the present disclosure can be suitably used for packaging material applications such as packaging bags, etc. The packaging material of the present disclosure includes the laminate of the present disclosure.

[0165] For example, a packaging material can be produced by folding the laminate in half and overlapping it so that the multilayer base material 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 so that the heat seal layers face each other and heat-sealing the edges, etc. The entire packaging material may be composed of the laminate, or only a part of the packaging material may be composed of the laminate.

[0166] 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.

[0167] For example, a stand-up pouch having a body and a bottom can be manufactured as follows: First, one or more of the above laminates are formed into a cylindrical shape with the heat-sealable layer facing inward, and the body is formed by heat-sealing. Next, another of the above laminates 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 heat-sealed to form the bottom.

[0168] In the stand-up pouch, only the body may be formed from the laminate, only the bottom may be formed from the laminate, or both the body and the bottom may be formed from the laminate.

[0169] 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.

[0170] The present disclosure relates to, for example, the following [1] to

[13] . [1] A laminate comprising a polyethylene multilayer substrate and a heat seal layer containing polyethylene as a main component, wherein the polyethylene multilayer substrate comprises a first polyethylene layer, a second polyethylene layer, and a third polyethylene layer in that order in the thickness direction, and is stretched, and the indentation modulus of the first polyethylene layer is 1.0 GPa or more, and the indentation modulus of the third polyethylene layer is 1.0 GPa or more. [2] The laminate according to [1] above, wherein the first polyethylene layer has an indentation modulus of 4.5 GPa or less, and the third polyethylene layer has an indentation modulus of 4.5 GPa or less. [3] The laminate according to [1] or [2] above, wherein the second polyethylene layer has an indentation modulus of 0.03 GPa or more and 0.7 GPa or less. [4] The laminate according to any one of the above [1] to [3], wherein the polyethylene multilayer substrate further comprises a 2a polyethylene layer between the first polyethylene layer and the second polyethylene layer, and a 2b polyethylene layer between the second polyethylene layer and the third polyethylene layer, and the indentation modulus of the 2a polyethylene layer and the 2b polyethylene layer are each independently 0.3 GPa or more and 3.5 GPa or less. [5] A laminate comprising a polyethylene multilayer substrate and a heat seal layer containing polyethylene as a main component, wherein the polyethylene multilayer substrate comprises a first polyethylene layer, a second polyethylene layer, and a third polyethylene layer in that order in the thickness direction and is stretched, and wherein the indentation hardness of the first polyethylene layer is 45 MPa or more, and the indentation hardness of the third polyethylene layer is 45 MPa or more. [6] The laminate according to [5] above, wherein the first polyethylene layer has an indentation hardness of 110 MPa or less, and the third polyethylene layer has an indentation hardness of 110 MPa or less. [7] The laminate according to [5] or [6] above, wherein the second polyethylene layer has an indentation hardness of 1 MPa or more and 40 MPa or less. [8] The laminate according to any one of the above [5] to [7], wherein the polyethylene multilayer substrate further comprises a 2a polyethylene layer between the first polyethylene layer and the second polyethylene layer, and a 2b polyethylene layer between the second polyethylene layer and the third polyethylene layer, and the indentation hardness of the 2a polyethylene layer and the 2b polyethylene layer are each independently 20 MPa or more and 100 MPa or less. [9] The laminate according to any one of the above [1] to [8], wherein the heat shrinkage rate of the laminate in the longitudinal direction (MD) is 15% or less, and the heat shrinkage rate of the laminate in the direction perpendicular to the MD (TD) is 15% or less.

[10] The laminate according to any one of the above [1] to [9], further comprising a printed layer on the polyethylene multilayer substrate.

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

[10] , further comprising a barrier layer formed on the surface of the polyethylene multilayer substrate or on the surface of the heat seal layer.

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

[11] , further comprising an adhesive layer between the polyethylene multilayer substrate and the heat seal layer.

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

[12] above. [Example]

[0171] 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".

[0172] The polyethylene used in the following examples and comparative examples will be described. Medium-density polyethylene (hereinafter referred to as "MDPE"): Product name Enable4002MC Density: 0.940g / cm 3 , Melting point: 128℃, MFR: 0.25g / 10min, ExxonMobil High-density polyethylene (1) (hereinafter referred to as "HDPE (1)"): Product name: Elite5960G Density: 0.960g / cm 3 , Melting point: 134℃, MFR: 0.8g / 10min, Dowchemical High-density polyethylene (2) (hereinafter referred to as "HDPE (2)"): Product name H619F Density: 0.965g / cm 3 , Melting point: 135℃, MFR: 0.7g / 10min, Made by SCG Linear low-density polyethylene (hereinafter referred to as "LLDPE"): Product name: Exceed XP8656ML Density: 0.916g / cm 3 , Melting point: 121℃, MFR: 0.5g / 10min, ExxonMobil Low-density polyethylene (hereinafter referred to as "LDPE"): Product name LD2420F Density: 0.922g / cm 3 , Melting point: 112℃, MFR: 0.75g / 10min, Made by PTT MB containing slip agent: Product name SLIP61 10061-K Density: 0.910g / cm 3, MFR:10g / 10min, Polyethylene base, contains 5% by weight of erucic acid amide slip agent Ampacet

[0173] [Preparation of blended polyethylene] Blended Polyethylene A1 70 parts MDPE and 30 parts HDPE (1) were mixed to give an average density of 0.948 g / cm 3 A blended polyethylene A1 (hereinafter referred to as "blended PE(A1)") was obtained. Blended polyethylene B1 70 parts of HDPE (2) and 30 parts of LDPE were mixed to give an average density of 0.950 g / cm 3 A blended polyethylene B1 (hereinafter referred to as "blended PE (B1)") was obtained. Blended polyethylene B2 50 parts MDPE and 50 parts LLDPE were mixed to give an average density of 0.929 g / cm 3 Blend polyethylene B2 (hereinafter referred to as "blend PE (B2)") was obtained. Blended polyethylene C1 98 parts LLDPE and 2 parts MB containing slip agent were mixed to give an average density of 0.916 g / cm 3 A blended polyethylene C1 (hereinafter referred to as "blended PE(C1)") was obtained.

[0174] [Manufacturing Example 1] Blend PE (A1), blend PE (B1), and blend PE (C1) were coextruded into a five-layer tube using an inflation molding method with a layer thickness ratio of blend PE (A1) layer (15 μm) / blend PE (B1) layer (22.5 μm) / blend PE (C1) layer (50 μm) / blend PE (B1) layer (22.5 μm) / blend PE (A1) layer (15 μm). A polyethylene film with a total thickness of 125 μm was obtained, and the tube-shaped film was folded at the nip to form two layers. The numbers in parentheses indicate the layer thicknesses.

[0175] The polyethylene film prepared above was stretched in the machine direction (MD) at a stretch ratio of 5 times, and the blend PE (A1) 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 polyethylene multilayer substrate (stretched multilayer substrate) with a thickness of 25 μm.

[0176] [Production Examples 2 and 3] A polyethylene film and a stretched multilayer base material were obtained in the same manner as in Production Example 1, except that the layer structure was changed as shown in Table 3.

[0177] [Examples and Comparative Examples: Preparation of Laminates] 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., SP0510, density: 0.903 g / cm 3 A multilayer extrusion film was formed from the above-mentioned polyethylene (melting point: 98°C) by inflation molding to produce an unstretched polyethylene film having 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. This unstretched polyethylene film was used as a heat-sealing layer as described below.

[0178] The first linear low-density polyethylene layer side of the unstretched polyethylene film (heat seal layer) prepared above was dry laminated to the corona discharge treated side of the stretched multilayer substrate obtained in the Production Example using a two-component curing urethane adhesive (Ru-77T / H-7, manufactured by Rock Paint Co., Ltd.) to obtain a laminate. The adhesive layer had a thickness of 3.0 μm.

[0179] [Ink adhesion evaluation] An image was formed on the corona discharge treated surface of the stretched multilayer substrate obtained in the production example by gravure printing using oil-based gravure ink (manufactured by DIC Graphics Corporation, trade name: Finart). The image formed on the stretched multilayer substrate was visually observed and evaluated based on the following evaluation criteria.

[0180] (Evaluation criteria) AA: When Cellotape (registered trademark) was applied to the image forming surface of the stretched multilayer substrate and then peeled off, the ink adhered well to the stretched multilayer substrate and no ink peeling occurred on the Cellotape (registered trademark). BB: When Cellotape (registered trademark) was applied to the image forming surface of the stretched multilayer substrate and then peeled off, the ink did not adhere well to the stretched multilayer substrate, and the ink peeled off from the Cellotape (registered trademark).

[0181] [Shrinkage evaluation] The laminate prepared above was cut into 10 cm x 10 cm pieces to prepare three sample pieces. Each sample piece was folded in half with the heat seal layer side facing inward, and tested at a temperature of 120°C and a pressure of 1 kgf / cm using a heat seal tester. 2 A 1.5 cm x 10 cm area was heat-sealed for 1 second. After heat sealing, the seal width of the sample was measured, and the shrinkage rates in the MD and TD directions were calculated. The average values ​​of the three sample pieces were used as the heat shrinkage rates for each sample.

[0182] [Heat resistance evaluation] The heat resistance was evaluated according to the following criteria. AA: There was no significant shrinkage of the stretched multilayer substrate during printing, dry lamination, and heat sealing of the laminate produced above, and the target product was produced cleanly. BB: The stretched multilayer substrate significantly shrunk during printing, dry lamination, and heat sealing of the laminate produced above, and the target product could not be produced cleanly.

[0183] [Haze Rating] The haze value of the stretched multilayer substrate obtained in the production examples was measured in accordance with JIS K7136.

[0184] [Rigidity evaluation] The stretched multilayer substrate obtained in the production example was cut into a 10 mm wide test piece, and the stiffness of the test piece was measured using a loop stiffness measuring tester (manufactured by Toyo Seiki Seisakusho, trade name: Loop Stiffness Tester). The loop length was 60 mm.

[0185] [Strength evaluation] A 10 mm wide dumbbell-shaped test piece was cut out from the stretched multilayer substrate obtained in the production example. The tensile strength of the 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.

[0186] [Indentation modulus and indentation hardness evaluation] For the laminates obtained in the examples and comparative examples, a nanoindenter (HYSITRON's "TI950 TriboIndenter") was used to measure the cross section parallel to the TD direction of each polyethylene layer of the stretched multilayer substrate at five points on the same cross section, and the elastic modulus and hardness values ​​were averaged to determine the indentation elastic modulus and indentation hardness, respectively. A Berkovich indenter (triangular pyramid indenter) was used as the indenter for the nanoindenter.

[0187] The measurement conditions were as follows: The indenter was pressed into the polyethylene layer from a cross section parallel to the TD direction of the laminate to a depth of 200 nm over 10 seconds, and held in that state for 5 seconds. The load was then released over 10 seconds. This allowed the maximum load Pmax, the contact projected area A at the maximum depth, and the load-displacement curve to be obtained, and the elastic modulus and hardness values ​​were calculated from the obtained load-displacement curve. The measurement was carried out at room temperature (25°C). The cross section was prepared by cutting the laminate parallel to the TD direction using a cryo-ultramicrotome at -100°C. Finishing was carried out with a diamond knife. The thickness of each layer could also be measured by observing the cross section.

[0188] The above evaluation results are shown in Tables 1 to 3.

[0189] [Table 1]

[0190] [Table 2]

[0191] [Table 3] [Explanation of symbols]

[0192] 10: Polyethylene multilayer base material 12: First polyethylene layer 14: Third polyethylene layer 16: Intermediate layer including second polyethylene layer 18: 2a polyethylene layer 20: Second polyethylene layer 22: 2nd b polyethylene layer 30: Laminate 32: Heat seal layer 34: Barrier layer 36: Adhesive layer

Claims

1. a polyethylene multilayer substrate; A heat seal layer containing polyethylene as a main component. A laminate comprising: The polyethylene multilayer substrate is a first polyethylene layer containing at least medium density polyethylene and high density polyethylene; a 2a polyethylene layer containing at least a linear low-density polyethylene; a second polyethylene layer containing at least a linear low density polyethylene; a second polyethylene layer (2b) containing at least a linear low-density polyethylene; a third polyethylene layer containing at least medium density polyethylene and high density polyethylene; It has a five-layer structure having the following in this order in the thickness direction, At least one of the five polyethylene layers is made of a blend of at least two or more polyethylenes having different densities, the polyethylene multilayer substrate has been stretched at a stretching ratio of 2 to 10 times in each of the longitudinal direction (MD) and / or the transverse direction (TD), the indentation hardness of the first polyethylene layer is 45 MPa or more and 110 MPa or less; The indentation hardness of the third polyethylene layer is 45 MPa or more and 110 MPa or less. Laminate.

2. The laminate according to claim 1 , wherein the second polyethylene layer has an indentation hardness of 1 MPa or more and 40 MPa or less.

3. the indentation hardness of the 2a polyethylene layer and the indentation hardness of the 2b polyethylene layer are each independently 20 MPa or more and 100 MPa or less; The laminate according to claim 1 or 2.

4. The heat shrinkage rate of the laminate in the longitudinal direction (MD) is 15% or less, The thermal shrinkage rate of the laminate in the direction perpendicular to the MD (TD) is 15% or less. The laminate according to any one of claims 1 to 3.

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

6. The laminate according to any one of claims 1 to 5, further comprising a barrier layer formed on a surface of the polyethylene multilayer substrate or on a surface of the heat seal layer.

7. The laminate according to any one of claims 1 to 6, further comprising an adhesive layer between the polyethylene multilayer substrate and the heat seal layer.

8. A packaging material comprising the laminate according to any one of claims 1 to 7.

Images