Polyethylene multilayer substrate, printing substrate, laminate and wrapping material

Abstract

To provide a polyethylene multilayer substrate excellent in ink adhesion and manufacturability.SOLUTION: A polyethylene multilayer substrate includes a first layer including a medium-density polyethylene, a second layer including a medium-density polyethylene, a third layer including a medium-density polyethylene and a linear low-density polyethylene, a fourth layer including a medium-density polyethylene, and a fifth layer including a medium-density polyethylene, in this order in a thickness direction. A drawing treatment is applied to the polyethylene multilayer substrate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to polyethylene multi-layer substrates, printed substrates, laminates and packaging materials. [Background technology]

[0002] Conventionally, packaging materials and the like are manufactured using resin films made of resin materials. The packaging materials include, for example, a base material and a heat seal layer. For example, a resin film made of polyethylene has flexibility and transparency as well as excellent heat sealability, and is therefore widely used as a heat seal layer in packaging materials (for example, see Patent Document 1).

[0003] On the other hand, polyethylene is a resin that softens at a relatively low temperature compared to other thermoplastic resins, so when used as a base material for packaging materials, it may deform or even melt during heat sheet processing. In addition, polyethylene film may have insufficient 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, a bag is made by laminating a base material such as a polyester film or nylon film with a polyethylene film, and heat sealing the polyethylene film side so that it is on the inside of the packaging bag (for example, see 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, in the case of a laminate obtained by laminating different kinds of resin films as described above, it is difficult to separate the resins by type, and therefore the laminate is not suitable for recycling. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2009-202519 A [Patent Document 2] JP 2017-031233 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present inventors therefore discovered that the strength and heat resistance of a resin film made of polyethylene can be improved by stretching treatment, and investigated the use of a polyethylene multilayer substrate as the substrate, which has multiple layers containing polyethylene and has been subjected to a stretching treatment. Meanwhile, images such as characters and figures are usually printed with ink on substrates used for packaging materials, etc. However, further studies by the present inventors have revealed that polyethylene multi-layer substrates may have insufficient ink adhesion.

[0007] Furthermore, in the case of a polyethylene multi-layer base material, the physical properties such as transparency, strength, and heat resistance can be improved by stretching the precursor laminate. If the stretchability of the laminate can be improved, the manufacturability of the polyethylene multi-layer base material can be improved, and it becomes easier to adjust the physical properties, for example.

[0008] One object of the present disclosure is to provide a polyethylene multi-layer substrate that has excellent ink adhesion and manufacturability. [Means for solving the problem]

[0009] The polyethylene multi-layer substrate of the present disclosure is a first layer comprising a medium density polyethylene; a second layer comprising a medium density polyethylene; a third layer containing medium density polyethylene and linear low density polyethylene; a fourth layer containing a medium density polyethylene; a fifth layer containing medium density polyethylene; in the thickness direction in this order, and is subjected to a stretching treatment. Effect of the Invention

[0010] According to the present disclosure, it is possible to provide a polyethylene multilayer substrate having excellent ink adhesion and manufacturability. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional schematic diagram illustrating one embodiment of a polyethylene multi-layer substrate of the present disclosure. [Diagram 2] 1 is a cross-sectional schematic diagram showing one embodiment of a laminate of the present disclosure. [Diagram 3] 1 is a cross-sectional schematic diagram showing one embodiment of a laminate of the present disclosure. [Figure 4] 1 is a cross-sectional schematic diagram showing one embodiment of a laminate of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The terms used in this disclosure are explained below. "Polyethylene" refers to a polymer in which the content of ethylene-derived structural units in all repeating structural units is 50 mol% or more. In the polymer, the content of ethylene-derived structural units is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more. The content is measured by nuclear magnetic resonance (NMR) method.

[0013] 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 It is. The density of the medium density polyethylene is preferably 0.925 g / cm 3 Exceeds 0.945g / cm 3 The following is the result. The density of the low density polyethylene is preferably 0.900 g / cm 3 Exceeds 0.925g / cm 3 The following is the result. The density of the linear low density polyethylene is preferably 0.900 g / cm3 Exceeds 0.925g / cm 3 The following is the result. The density of the very low density polyethylene is preferably 0.900 g / cm 3 The lower limit of the density of the very low density polyethylene is, for example, 0.860 g / cm 3 It is. The density of polyethylene is measured in accordance with JIS K7112 (1999).

[0014] [Polyethylene multi-layer base material] As shown in FIG. 1, the polyethylene multilayer substrate 10 of the present disclosure has the following features: a first layer 12 containing medium density polyethylene; a second layer 18 containing medium density polyethylene; a third layer 20 containing medium density polyethylene and linear low density polyethylene; a fourth layer 22 containing medium density polyethylene; a fifth layer 14 containing medium density polyethylene; in the thickness direction in this order, and is subjected to a stretching treatment. Hereinafter, the above-mentioned polyethylene multi-layer substrate will be simply referred to as "multi-layer substrate".

[0015] In one embodiment, the surface layer on one side of the multilayer substrate is the first layer, and the surface layer on the other side of the multilayer substrate is the fifth layer. The multilayer substrate may have other layers between the first to fifth layers, but in one embodiment, the multilayer substrate is composed of only the first to fifth layers.

[0016] In the present disclosure, examples of polyethylene include homopolymers of ethylene and copolymers of ethylene and 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.

[0017] 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.

[0018] Polyethylenes with different densities or branches can be obtained by appropriately selecting a polymerization method. For example, it is preferable to carry out polymerization in one stage or two or more stages by any of gas phase polymerization, slurry polymerization, solution polymerization, and high pressure ion polymerization using a multi-site catalyst such as a Ziegler-Natta catalyst or a single-site catalyst such as a metallocene catalyst as a polymerization catalyst.

[0019] 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 nonmetallocene transition metal compound with an activating cocatalyst. A single-site catalyst is preferred because it has a uniform structure of the active site compared to a multi-site catalyst, and therefore can produce a polymer having a high molecular weight and a highly uniform structure.

[0020] 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.

[0021] Examples of the transition metal in the transition metal compound include zirconium, titanium and hafnium, with zirconium and hafnium being preferred.

[0022] 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 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, forming 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.

[0023] A transition metal compound usually has two ligands having a cyclopentadienyl skeleton. The ligands having each cyclopentadienyl skeleton are preferably bonded to each other by a bridging group. Examples of the bridging group include an alkylene group having 1 to 4 carbon atoms, a silylene group, a substituted silylene group such as a dialkylsilylene group or a diarylsilylene group, and a substituted germylene group such as a dialkylgermylene group or a diarylgermylene group. Among these, a substituted silylene group is preferred.

[0024] The cocatalyst refers to a component that allows 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 cocatalyst 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.

[0025] Examples of the organometallic compound that may be used as needed include organoaluminum compounds, organomagnesium compounds, and organozinc compounds. Of these, organoaluminum compounds are preferred.

[0026] The transition metal compound may be used by being supported on an inorganic or organic carrier. The carrier is preferably an inorganic or organic porous oxide, and specific examples thereof include ion-exchangeable layered silicates such as montmorillonite, SiO2, Al2O3, MgO, ZrO2, TiO2, B2O3, CaO, ZnO, BaO, ThO2, and mixtures thereof.

[0027] 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, so that the environmental impact of packaging materials produced using a multilayer substrate can be reduced. Biomass-derived polyethylene can be produced, for example, by the method described in JP 2013-177531 A. Commercially available biomass-derived polyethylene (for example, Green PE available from Braskem) may be used.

[0028] Polyethylene recycled by mechanical recycling may be used. Mechanical recycling is a method in which collected polyethylene films are generally crushed, washed with an alkali to remove dirt and foreign matter from the film surface, and then dried at high temperature and reduced pressure for a certain period of time to diffuse and decontaminate the contaminants remaining inside the film, removing dirt from the polyethylene film and returning it to polyethylene. The melt flow rate (MFR) of the polyethylene contained in the multilayer substrate of the present disclosure is preferably 0.1 g / 10 min to 50 g / 10 min, more preferably 0.3 g / 10 min to 30 g / 10 min, from the viewpoints of film formability and processability of the multilayer substrate. In the present disclosure, the MFR is measured in accordance with ASTM D1238 at a temperature of 190° C. and a load of 2.16 kg.

[0029] Examples of polyethylene include high density polyethylene, medium density polyethylene, low density polyethylene (high pressure low density polyethylene), linear low density polyethylene, and very low density polyethylene. Each layer constituting the multi-layered base material will now be described.

[0030] <First layer and fifth layer> The first layer contains one or more medium density polyethylenes. The fifth layer contains one or more medium density polyethylenes. When printing an image on a substrate, a surface treatment such as a corona discharge treatment is usually performed on the substrate as a pretreatment. A layer containing medium-density polyethylene tends to have higher durability against surface treatment than a layer containing only high-density polyethylene as polyethylene. Therefore, the layer containing medium-density polyethylene has excellent ink adhesion during printing after the surface treatment. In addition, the layer containing medium-density polyethylene also has the heat resistance required during printing and heat sealing. In addition, the layer containing medium-density polyethylene contributes to improving the stretchability of the laminate, which is a precursor of the multilayer substrate.

[0031] The medium-density polyethylene contained in the first layer and the medium-density polyethylene contained in the fifth 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.

[0032] The first layer and the fifth layer may each independently contain, in addition to the medium density polyethylene, another polyethylene other than the medium density polyethylene. Examples of the other polyethylene other than the medium density polyethylene include high density polyethylene, low density polyethylene (high pressure low density polyethylene), linear low density polyethylene, and very low density polyethylene. From the viewpoint of further improving the ink adhesion of the multilayer substrate and the stretchability of the laminate, which is the precursor, the first layer preferably contains only medium density polyethylene as the polyethylene. From the viewpoint of further improving the ink adhesion of the multilayer substrate and the stretchability of the laminate, which is the precursor, the fifth layer preferably contains only medium density polyethylene as the polyethylene.

[0033] The content of medium-density polyethylene in the first 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 further improve the ink adhesion of the multilayer substrate and the stretchability of the laminate, which is the precursor. The content of the medium-density polyethylene in the fifth 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 further improve the ink adhesion of the multilayer base material and the stretchability of the laminate, which is the precursor.

[0034] The thickness of each of the first layer and the fifth layer is preferably from 0.5 μm to 10 μm, more preferably from 1 μm to 8 μm, and even more preferably from 1 μm to 5 μm, which can further improve the ink adhesion and heat resistance of the multilayer substrate.

[0035] The thickness of each of the first layer and the fifth layer is preferably smaller than the total thickness of the second layer, the third layer, and the fourth layer (hereinafter, the second to fourth layers are also collectively referred to as the "multilayer intermediate layer"). The ratio of the thickness of each of the first layer and the fifth layer to the total thickness of the multilayer intermediate layer (first layer or fifth layer / multilayer intermediate layer) is preferably 0.05 to 0.8, more preferably 0.1 to 0.7, and even more preferably 0.1 to 0.4. This can further improve the rigidity, strength, and heat resistance of the multilayer substrate.

[0036] <Second layer and fourth layer> The second layer contains one or more medium density polyethylenes. The fourth layer contains one or more medium density polyethylenes. The second layer and the fourth layer each contribute to improving the extensibility of the laminate, which is a precursor of the multi-layer substrate.

[0037] The medium-density polyethylene contained in the second layer and the medium-density polyethylene contained in the fourth 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. The medium-density polyethylene in the second layer, the medium-density polyethylene in the fourth layer, the medium-density polyethylene in the first layer, and the medium-density polyethylene in the fifth 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.

[0038] The second layer and the fourth layer may each independently contain, in addition to the medium density polyethylene, another polyethylene other than the medium density polyethylene. Examples of the other polyethylene other than the medium density polyethylene include high density polyethylene, low density polyethylene (high pressure low density polyethylene), linear low density polyethylene, and very low density polyethylene. From the viewpoint of further improving the stretchability of the laminate, which is the precursor of the multilayered base material, the second layer preferably contains only medium density polyethylene as the polyethylene. From the viewpoint of further improving the stretchability of the laminate, which is the precursor of the multilayered base material, the fourth layer preferably contains only medium density polyethylene as the polyethylene.

[0039] The content of medium-density polyethylene in the second 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 further improve the stretchability of the laminate, which is the precursor. The content of medium-density polyethylene in the fourth 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 further improve the stretchability of the laminate, which is a precursor.

[0040] The thickness of each of the second layer and the fourth layer is preferably 0.5 μm or more and 15 μm or less, more preferably 1 μm or more and 10 μm or less, and even more preferably 1 μm or more and 8 μm or less, which can further improve the stretchability of the laminate, which is the precursor.

[0041] <Third Layer> The third layer contains one or more types of medium density polyethylene and one or more types of linear low density polyethylene. The third layer contributes to improving the stretchability of the laminate, which is a precursor of the multilayer substrate.

[0042] The medium density polyethylene contained in the third layer may be the same as or different from the medium density polyethylene contained in the first, second, fourth and fifth layers.

[0043] The third layer may further contain, in addition to the medium density polyethylene and linear low density polyethylene, other polyethylenes other than these polyethylenes. Examples of the other polyethylenes other than the medium density polyethylene and linear low density polyethylene include high density polyethylene, low density polyethylene (high pressure low density polyethylene) and very low density polyethylene. From the viewpoint of further improving the stretchability of the laminate, which is the precursor of the multilayer base material, it is preferable that the third layer contains only medium density polyethylene and linear low density polyethylene as the polyethylenes.

[0044] The mass ratio of the medium density polyethylene to the linear low density polyethylene in the third layer (medium density polyethylene / linear low density polyethylene) is preferably 0.25 to 4, more preferably 0.4 to 2.4, thereby enabling a further improvement in the balance of heat resistance, rigidity, and extensibility. The total content of the medium density polyethylene and the linear low density polyethylene in the third layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, thereby enabling the stretchability of the precursor laminate to be further improved.

[0045] The thickness of the third 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, which can improve the balance of heat resistance, rigidity, and stretchability.

[0046] The ratio of the total thickness of the second layer and the fourth layer to the thickness of the third layer (total thickness of the second layer and the fourth layer / thickness of the third 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.

[0047] The first to fifth layers constituting the multilayer base material may each independently contain one or more additives, such as crosslinking agents, antioxidants, antiblocking agents, slip agents, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

[0048] In one embodiment, in the multilayer substrate of the present disclosure, the density of the polyethylene in the third layer is lower than the density of the polyethylene in the second layer, and the density of the polyethylene in the fourth layer is higher than the density of the polyethylene in the third layer. A multilayer substrate having such a configuration has excellent ink adhesion and manufacturability (stretchability of the laminate, which is the precursor).

[0049] When a layer contains multiple types of polyethylene with different densities (n types; n is an integer of 2 or more), the average density D is calculated according to the following formula (1). av is the density of the polyethylene constituting the layer.

[0050] D av = ΣW i ×D i …(1) In formula (1), Σ is W for i from 1 to n. i ×D i where n is an integer equal to or greater than 2, and W i indicates the mass fraction of the i-th polyethylene, and D i is the density of the i-th polyethylene (g / cm 3 ) is shown.

[0051] When any mutually adjacent layers selected from the first to fifth layers in the multilayer substrate are referred to as layer (1) and layer (2), the absolute value of the difference between the density of the polyethylene constituting layer (1) and the density of the polyethylene constituting layer (2) is preferably 0.030 g / cm 3 More preferably, it is 0.025 g / cm 3 More preferably, 0.020 g / cm 3The following is the requirement. Hereinafter, this requirement is also referred to as the "density difference requirement." In other words, it is preferable that any pair of adjacent layers in the thickness direction selected from the first to fifth layers included in the multilayer base material (for example, the pair of the first layer and the second layer, the pair of the second layer and the third layer, the pair of the third layer and the fourth layer, and the pair of the fourth layer and the fifth layer) satisfies the density difference requirement. In the following description, density differences always refer to absolute values ​​of the differences.

[0052] A multilayer substrate that satisfies the above density difference requirement has a small density difference between the first to fifth layers as described above, and therefore exhibits high interlayer strength.

[0053] <Manufacturing method of multi-layer substrate> The multi-layer substrate of the present disclosure can be produced, for example, by forming a laminate from a plurality of polyethylene materials by an inflation method or a T-die method, and stretching the resulting laminate. The stretching treatment can improve the transparency, rigidity, strength, and heat resistance of the multi-layer substrate, and the multi-layer substrate can be suitably used, for example, as a substrate for packaging materials.

[0054] The multilayer substrate can be obtained, for example, by stretching a laminate (precursor) having, in the thickness direction, a layer containing medium-density polyethylene, a layer containing medium-density polyethylene, a layer containing medium-density polyethylene and linear low-density polyethylene, a layer containing medium-density polyethylene, and a layer containing medium-density polyethylene, in that order.

[0055] Specifically, a laminate can be produced by co-extruding from the outside a layer containing medium density polyethylene, a layer containing medium density polyethylene, a layer containing medium density polyethylene and linear low density polyethylene, a layer containing medium density polyethylene, and a layer containing medium density polyethylene into a tubular shape. Alternatively, a laminate can be produced by co-extruding from the outside a layer containing medium density polyethylene, a layer containing medium density polyethylene, and a layer containing medium density polyethylene and linear low density polyethylene into a tubular shape, and then pressing the opposing layers containing medium density polyethylene and linear low density polyethylene together with a rubber roll or the like. By producing a laminate by such a method, the number of defective products can be significantly reduced and production efficiency can be improved.

[0056] When producing a laminate 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 viewpoints of film formability and processability of the multilayer base material.

[0057] When a laminate is produced by an inflation method, the MFR of the polyethylene constituting each layer is preferably 0.5 g / 10 min or more and 5 g / 10 min or less from the viewpoints of film formability and processability of the multi-layered base material.

[0058] The multilayer substrate of the present disclosure can be obtained, for example, by stretching the above-mentioned laminate. Note that the laminate can also be stretched in an inflation film forming machine. This allows the multilayer substrate to be produced, thereby further improving production efficiency.

[0059] The multi-layer substrate of the present disclosure may be a uniaxially stretched film or a biaxially stretched film. In one embodiment, the multi-layer substrate is a uniaxially stretched film, more specifically, a uniaxially stretched film that has been stretched in the machine direction (MD).

[0060] In one embodiment, the stretching ratio in the longitudinal direction (MD) of the multilayer substrate is preferably from 2 to 10, more preferably from 3 to 7. In one embodiment, the stretching ratio in the transverse direction (TD) of the multilayer substrate is preferably from 2 to 10, more preferably from 3 to 7.

[0061] When the stretching ratio is 2 times or more, for example, the rigidity, strength, and heat resistance of the multilayer substrate can be improved, the ink adhesion to the multilayer substrate can be improved, and the transparency of the multilayer substrate can be improved. When the stretching ratio is 10 times or less, the laminate can be stretched well.

[0062] The haze value of the multi-layered substrate is preferably 25% or less, more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less. The smaller the haze value, the more preferable it is, but in one embodiment, the lower limit may be 0.1% or 1%. The haze value of the multi-layered substrate is measured in accordance with JIS K7136.

[0063] The content of polyethylene in the multi-layered base material is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, which can improve the recyclability of the multi-layered base material.

[0064] The laminate or the multi-layer substrate is preferably subjected to a surface treatment. This can improve the adhesion between the surface layer of the multi-layer substrate and the layer laminated on the multi-layer substrate. Examples of the surface treatment method include physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using gas such as oxygen gas and nitrogen gas, and glow discharge treatment; and chemical treatments such as oxidation treatment using chemicals.

[0065] An anchor coat layer may be formed on the surface of the laminate or multilayer substrate using a conventionally known anchor coat agent.

[0066] The total thickness of the multi-layered 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 multi-layered substrate is 10 μm or more, the rigidity and strength of the multi-layered substrate can be improved. When the thickness of the multi-layered substrate is 60 μm or less, the processability of the multi-layered substrate can be improved.

[0067] [Printing base material] The printing substrate of the present disclosure comprises the polyethylene multilayer substrate of the present disclosure and a printing layer formed on the multilayer substrate. The printing layer is formed, for example, on the first layer or the fifth layer of the multilayer substrate. The multilayer substrate has excellent ink adhesion, and therefore can form a good image.

[0068] The printed layer includes, for example, an image. Examples of the image include characters, figures, symbols, and combinations thereof. Examples of the method for forming the printed layer include gravure printing, offset printing, and flexographic printing. In one embodiment, from the viewpoint of reducing the environmental load, the flexographic printing method is preferred. Also, from the viewpoint of reducing the environmental load, a printed layer may be formed on the surface of the multilayer substrate using ink derived from biomass.

[0069] [Laminate] 2, a laminate 30 of the present disclosure includes a polyethylene multi-layer substrate 10 of the present disclosure and a heat seal layer 32. In the multi-layer substrate 10, the second layer 18, the third layer 20, and the fourth layer 22 are collectively referred to as a multi-layer intermediate layer 16.

[0070] In one embodiment, the laminate 30 further includes a printed layer (not shown) on the multi-layer substrate 10. The printed layer is usually formed on a surface layer of the multi-layer substrate on which a heat seal layer is provided, for example, on the first layer described above.

[0071] In one embodiment, as shown in FIG. 3, the laminate 30 includes a barrier layer 34 and an adhesive layer 36 between the multi-layer substrate 10 and a heat seal layer 32 . In one embodiment, as shown in FIG. 4, the laminate 30 includes an adhesive layer 36 between the multi-layer substrate 10 and the heat seal layer 32 .

[0072] In the laminate of the present disclosure, the content of polyethylene is preferably 90% by mass or more. This can improve the recyclability of the laminate. The content of polyethylene in the laminate means the ratio of the content of polyethylene to the sum of the contents of the resin materials in each layer constituting the laminate.

[0073] <Heat seal layer> The heat seal layer is preferably made of polyethylene, which provides a laminate for packaging materials having sufficient rigidity, strength and heat resistance, and excellent recyclability.

[0074] The recyclability will now be described. Compared with other thermoplastic resin films, polyethylene film has poor heat resistance, and therefore, when used as a base material for packaging materials, it may deform during heat sheeting. In addition, polyethylene film has poor rigidity, so it has low printability and it is not possible to form a clear image on its surface. In addition, polyethylene film does not have high strength and does not meet the durability required for the outer layer of packaging materials. For this reason, a laminate is obtained by laminating a resin film (base material) having excellent rigidity, strength, and heat resistance, such as a polyester film or a nylon film, with a polyethylene film (heat seal layer), and the end of the laminate is heat sealed so that the polyethylene film side of the laminate is on the inside, thereby producing a packaging material.

[0075] In recent years, with the growing demand for the creation of a recycling-oriented society, attempts have been made to recycle and reuse packaging materials. However, when a laminate is manufactured by laminating different types of resin films as described above, it is difficult to separate the resin films from each other. For this reason, such a laminate is not suitable for recycling.

[0076] In contrast, the polyethylene multilayer substrate of the present disclosure is stretched as described above, and therefore has superior rigidity, strength, and heat resistance as well as superior ink adhesion compared to conventional polyethylene films. Therefore, the polyethylene multilayer substrate of the present disclosure 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.

[0077] In one embodiment, the laminate of the present disclosure comprises the polyethylene multilayer substrate of the present disclosure and a heat seal layer containing polyethylene (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 deterioration of the image over time can be prevented, it is preferable that the printed layer is formed on the side of the multilayer substrate where the heat sealable polyethylene layer is provided.

[0078] In the laminate comprising the polyethylene multi-layer base material and the heat-sealable polyethylene layer of the present disclosure, in one embodiment, the resin layers contained in the laminate are all polyethylene layers, and the laminate does not comprise different types of resin films such as polyester films and nylon films. In addition, the polyethylene multi-layer base material satisfies the rigidity, strength, and heat resistance required for an outer layer film of a packaging material, and the heat-sealable polyethylene layer enables packaging. For this reason, the laminate is suitable as a material for constituting a packaging material that requires recyclability.

[0079] In one embodiment, the laminate of the present disclosure comprises only the multi-layer base material on which a print layer is formed as necessary, and a heat seal layer made of polyethylene, whereby the laminate of the present disclosure has improved recyclability, since each resin layer is made of the same material, polyethylene.

[0080] The heat seal layer is usually a layer that is not stretched. For example, the heat seal layer can be formed by laminating an unstretched polyethylene film onto a multi-layer substrate or the like, optionally via an adhesive layer, or by melt-extruding a resin material containing polyethylene onto a multi-layer substrate or the like. Examples of the adhesive layer include the adhesive layer described below.

[0081] 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, and 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 be used.

[0082] 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 one or more of the above additives.

[0083] The heat seal layer may be one layer or two or more layers. In one embodiment, the number of heat seal layers is 1 to 3. 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 appropriately change the thickness of the heat seal layer depending on the mass of the contents to be filled in, for example, a packaging material produced using the laminate of the present disclosure.

[0084] 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. In this case, for example, 1 g or more and 200 g or less of contents can be filled well in the pouch. 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. In this case, for example, 50 g or more and 2000 g or less of contents can be filled well in the stand-up pouch.

[0085] <Barrier layer> In one embodiment, the laminate of the present disclosure includes a barrier layer between the multilayer substrate and the heat seal layer. This can improve 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 seal layer. In addition, the barrier layer may be provided between the multilayer substrate and the heat seal layer via an adhesive or the like.

[0086] In one embodiment, the barrier layer is a vapor deposition layer. The vapor deposition layer is composed of, for example, a metal such as aluminum, and an inorganic oxide 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 deposition layer is preferable.

[0087] The thickness of the barrier layer is preferably 1 nm to 150 nm, more preferably 5 nm to 60 nm, and even more preferably 10 nm to 40 nm. 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.

[0088] 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 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, which is formed by using both physical vapor deposition and chemical vapor deposition in combination.

[0089] The vacuum level in the deposition chamber was 10 -2 ~10 -8 After oxygen is introduced, the pressure is preferably about 10 -1 ~10 -6 The pressure is preferably about mbar. The amount of oxygen introduced varies depending on the size of the deposition machine. For the oxygen introduced, an inert gas such as argon gas, helium gas, or nitrogen gas may be used as a carrier gas to the extent that no problems occur. The conveying speed of the multilayer substrate is, for example, about 10 to 800 m / min.

[0090] 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.

[0091] 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 including the vapor-deposited layer and the barrier coat layer.

[0092] 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.

[0093] 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. In addition, the laminate can be made suitable for use in the production of mono-material packaging containers.

[0094] 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.

[0095] In another embodiment, the barrier coat layer is a gas barrier coating film formed from a composition containing a hydrolysate 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 coat layer on the vapor deposition layer, the occurrence of cracks in the vapor deposition layer can be effectively prevented.

[0096] In one embodiment, the metal alkoxide is represented by the following general formula: R 1 n M(OR 2 ) m In the above formula, R 1 and R 2 each independently represents an organic group having 1 to 8 carbon atoms, M represents a metal atom, n represents an integer of 0 or more, m represents an integer of 1 or more, and n+m represents the atomic valence of M.

[0097] R 1 and R 2 Examples of the organic group represented by the formula (1) include alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, and i-butyl. Examples of the metal atom M include silicon, zirconium, titanium, and aluminum.

[0098] Examples of metal alkoxides satisfying the above general formula include tetramethoxysilane (Si(OCH3)4), tetraethoxysilane (Si(OC2H5)4), tetrapropoxysilane (Si(OC3H7)4), and tetrabutoxysilane (Si(OC4H9)4).

[0099] 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.

[0100] As the water-soluble polymer, polyvinyl alcohol and an ethylene-vinyl alcohol copolymer are preferred, and from the viewpoints of oxygen barrier property, water vapor barrier property, water resistance and weather resistance, it is preferred to use these in combination.

[0101] As the sol-gel catalyst, an acid or amine compound is preferable.

[0102] The composition may further contain an acid. The acid is used as a catalyst for the sol-gel process, mainly for 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.

[0103] The composition may contain an organic solvent, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and n-butanol.

[0104] 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 can further improve 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 deposition layer can be prevented. By making the thickness of the gas barrier coating film 100 μm or less, the laminate can be suitably used for the production of mono-material packaging containers.

[0105] 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, brushing, bar coating, or an applicator, and then polycondensing the composition by a sol-gel method.

[0106] Hereinafter, one embodiment of the method for forming a gas barrier coating film will be described. First, a composition is prepared by mixing a metal alkoxide, a water-soluble polymer, a sol-gel catalyst, water, an organic solvent, and optionally a silane coupling agent, etc. In the composition, a polycondensation reaction gradually proceeds.

[0107] Next, the composition is applied onto the deposition layer by the above-mentioned conventionally known means and dried. This drying further advances the polycondensation reaction of the metal alkoxide and the water-soluble polymer (and the silane coupling agent, if the composition contains a silane coupling agent) to form a composite polymer layer. Finally, the composition is heated to form a gas barrier coating film.

[0108] <Adhesive layer> In one embodiment, the laminate of the present disclosure includes an adhesive layer between any 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.

[0109] The adhesive layer contains one or more types of adhesives, such as one-component curing adhesives, two-component curing adhesives, and non-curing adhesives.

[0110] The adhesive may be a solvent-free adhesive or a solvent-based adhesive, and from the viewpoint of environmental load, a solvent-free adhesive is preferred. Examples of the solvent-free adhesive include polyether adhesives, polyester adhesives, silicone adhesives, epoxy adhesives, and urethane adhesives. Among these, two-liquid curing urethane adhesives are preferred. Examples of the solvent-based adhesive include rubber adhesives, vinyl adhesives, silicone adhesives, epoxy adhesives, phenol adhesives, and olefin adhesives.

[0111] In the case of an adhesive layer adjacent to a barrier layer such as an aluminum vapor deposition layer, the adhesive layer is preferably made of a cured product of a resin composition containing a polyester polyol, an isocyanate compound, and a phosphoric acid-modified compound. By configuring the adhesive layer in this way, the oxygen barrier property and water vapor barrier property of the laminate of the present disclosure can be further improved.

[0112] 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 to 6 μm, more preferably 0.8 μm to 5 μm, and even more preferably 1 μm to 4.5 μm.

[0113] The adhesive layer can be formed by applying and drying an adhesive onto a multi-layer substrate or the like by a method such as direct gravure roll coating, gravure roll coating, kiss coating, reverse roll coating, Fontaine method, or transfer roll coating.

[0114] [Application] The polyethylene multilayer substrate, printed substrate, and 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 polyethylene multilayer substrate, printed substrate, or laminate of the present disclosure.

[0115] For example, the laminate can be folded in half so that the multilayer base material is on the outside and the heat seal layer is on the inside, and the ends are heat sealed to produce a packaging material. Alternatively, a plurality of the laminates can be stacked so that the heat seal layers face each other, and the ends are heat sealed to produce a packaging material. The entire packaging material may be composed of the laminate, or only a part of the packaging material may be composed of the laminate.

[0116] Examples of heat seal forms for packaging materials include side seal type, two-sided seal type, three-sided seal type, four-sided seal type, envelope seal type, hem seal type (pillow seal type), pleated seal type, flat bottom seal type, square bottom seal type, and gusset type. Self-supporting packaging bags (stand-up pouches) are also possible. Examples of heat seal methods include bar seal, rotary roll seal, belt seal, impulse seal, high frequency seal, and ultrasonic seal.

[0117] For example, a stand pouch having a body and a bottom can be manufactured as follows. First, one or more of the above laminates are shaped into a tube with the heat seal layer on the inside and heat sealed to form a body. Next, another of the above laminates is folded into a V shape with the heat seal layer on the outside. The V-shaped laminate is sandwiched into one end of the body and heat sealed to form a bottom.

[0118] In the stand pouch, only the body portion may be formed from the laminate, only the bottom portion may be formed from the laminate, or both the body portion and the bottom portion may be formed from the laminate.

[0119] 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.

[0120] The present disclosure relates to, for example, the following [1] to

[14] . [1] A multilayer polyethylene substrate comprising, in the thickness direction, a first layer containing medium-density polyethylene, a second layer containing medium-density polyethylene, a third layer containing medium-density polyethylene and a linear low-density polyethylene, a fourth layer containing medium-density polyethylene, and a fifth layer containing medium-density polyethylene, in that order, and which has been subjected to a stretching treatment. [2] The polyethylene multi-layer substrate according to [1] above, wherein the mass ratio of the medium-density polyethylene to the linear low-density polyethylene (medium-density polyethylene / linear low-density polyethylene) in the third layer is 0.25 or more and 4 or less. [3] The polyethylene multilayer substrate according to [1] or [2] above, wherein the first layer contains 80% by mass or more of medium-density polyethylene, the second layer contains 80% by mass or more of medium-density polyethylene, the third layer contains 80% by mass or more of the combined total of medium-density polyethylene and linear low-density polyethylene, the fourth layer contains 80% by mass or more of medium-density polyethylene, and the fifth layer contains 80% by mass or more of medium-density polyethylene. [4] In the multilayer base material, when any adjacent layers selected from the first to fifth layers are referred to as layer (1) and layer (2), the absolute value of the difference between the density of the polyethylene constituting layer (1) and the density of the polyethylene constituting layer (2) is 0.030 g / cm 3 The polyethylene multilayer substrate according to any one of the above [1] to [3], which is: [5] A printing substrate comprising the polyethylene multilayer substrate according to any one of [1] to [4] above and a printing layer formed on the multilayer substrate. [6] A laminate comprising the polyethylene multilayer base material according to any one of the above [1] to [4] and a heat seal layer. [7] The laminate according to [6] above, wherein the heat seal layer contains polyethylene. [8] The laminate according to [6] or [7] above, further comprising a printed layer on the multilayer substrate. [9] The laminate according to any one of the above [6] to [8], further comprising a barrier layer between the multilayer substrate and the heat seal layer.

[10] The laminate according to [9] above, wherein the barrier layer is a vapor deposition layer.

[11] The laminate according to [9] or

[10] above, further comprising an adhesive layer between the multilayer substrate and the barrier layer.

[12] The laminate according to any one of the above [6] to [8], further comprising an adhesive layer between the multilayer substrate and the heat seal layer.

[13] The laminate according to any one of the above [6] to

[12] , which is used for packaging material applications.

[14] A packaging material comprising the polyethylene multilayer substrate described in any one of [1] to [4] above, the printing substrate described in [5] above, or the laminate described in any one of [6] to

[13] above. EXAMPLES

[0121] The multilayer substrate of the present disclosure will be described in more detail with reference to examples, but the multilayer substrate of the present disclosure is not limited to the examples. Hereinafter, "parts by mass" will be simply referred to as "parts".

[0122] The polyethylene used in the following examples and comparative examples will be described. Medium Density Polyethylene (MDPE): Product name: Elite5538G Density: 0.941g / cm 3 , Melting point: 129℃, MFR: 1.3g / 10min, Dowchemical High density polyethylene (hereinafter referred to as "HDPE"): Product name Elite5960G Density: 0.960g / cm 3 , Melting point: 134℃, MFR: 0.8g / 10min, Dowchemical Linear low density polyethylene (hereinafter referred to as "LLDPE"): Product name Elite5400G Density: 0.916g / cm 3 , Melting point: 123℃, MFR: 1.3g / 10min, Dowchemical Blended polyethylene A A mixture of 50 parts MDPE and 50 parts HDPE had an average density of 0.951 g / cm 3 Thus, a blended polyethylene A (hereinafter referred to as "blended PE(A)") was obtained. Blended polyethylene B A mixture of 50 parts MDPE and 50 parts LLDPE had an average density of 0.929 g / cm 3 Thus, blended polyethylene B (hereinafter referred to as "blended PE(B)") was obtained.

[0123] [Reference Example 1 and Example 1]

[0124] MDPE and blended PE (B) were extruded into a tubular film by inflation molding with a layer thickness ratio of MDPE layer (15 μm) / MDPE layer (22.5 μm) / blended PE (B) layer (50 μm) / MDPE layer (22.5 μm) / MDPE layer (15 μm). A polyethylene film with a total thickness of 125 μm was obtained, and the tubular film was folded at the nip to make two layers. The numbers in parentheses indicate the layer thickness. The polyethylene film prepared above was stretched in the machine direction (MD) at a stretch ratio of 5 times, and the MDPE layer (surface layer) on one side was subjected to a corona discharge treatment, and then the end was slit and divided into two pieces to obtain a stretched multilayer substrate (Example 1) with a thickness of 25 μm. In addition, the MDPE layer (surface layer) on one side of the polyethylene film prepared above was subjected to a corona discharge treatment (Reference Example 1).

[0125] [Comparative Example 1] A polyethylene film and a stretched multilayer base material were obtained in the same manner as in Example 1, except that the layer structure was changed as shown in Table 1.

[0126] [Extensibility evaluation] The stretchability was evaluated according to the following criteria. AA: The substrate (polyethylene film) did not break during stretching, and was able to be stretched stably. BB: The substrate (polyethylene film) breaks during stretching. It was not possible to extend it stably.

[0127] [Ink adhesion evaluation] Images were formed by gravure printing using oil-based gravure ink (manufactured by DIC Graphics Corporation, trade name: Finart) on the corona discharge treated surface of the stretched multilayer substrates obtained in the Examples and Comparative Examples, and the polyethylene film obtained in the Reference Example. The images formed on the stretched multilayer substrates and the polyethylene film were visually observed and evaluated based on the following evaluation criteria.

[0128] (Evaluation Criteria) AA: When Scotch tape (registered trademark) was applied to the image-forming side of the stretched multilayer substrate or polyethylene film and then peeled off, the ink adhered well to the stretched multilayer substrate or polyethylene film and no ink peeling off from the Scotch tape (registered trademark) occurred. BB: When Scotch tape (registered trademark) was applied to the image-forming side of the stretched multilayer substrate or polyethylene film and then peeled off, the ink did not adhere well to the stretched multilayer substrate or polyethylene film, and the ink peeled off to the Scotch tape (registered trademark).

[0129] [Delamination evaluation] 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, SP1520, density: 0.913 g / cm 3 A multi-layer extrusion film was produced from the polyethylene film (melting point: 116°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 seal layer as described below.

[0130] The first linear low-density polyethylene layer side of the unstretched polyethylene film (heat seal layer) prepared above and the stretched multilayer substrate obtained in the Examples and Comparative Examples, or the polyethylene film obtained in the Reference Examples were dry laminated via a two-component curing urethane adhesive (Ru-77T / H-7, manufactured by Rock Paint Co., Ltd.) to obtain a laminate.

[0131] The laminate prepared above was cut into 10 cm x 10 cm pieces to prepare three sample pieces each. Each sample piece was folded in half so that the heat seal layer side was on the inside, and tested at a temperature of 140°C and a pressure of 1 kgf / cm using a heat seal tester. 2 An area of ​​1 cm x 10 cm was heat sealed under the conditions of 100° C., 1 sec.

[0132] The heat-sealed sample pieces were cut into strips with a width of 15 mm, and both ends that were not heat-sealed were clamped in a tensile tester. A tensile test was carried out at a speed of 300 mm / min and a load range of 50 N to check for the occurrence of delamination of the stretched multilayer substrate or polyethylene film. AA: Interlaminar delamination of stretched multi-layer substrate or polyethylene film during tensile testing Did not occur. BB: Delamination occurred between the stretched multilayer substrate or the polyethylene film during the tensile test.

[0133] [Haze Rating] The haze values ​​of the stretched multilayer substrates obtained in the Examples and Comparative Examples, and the polyethylene films obtained in the Reference Examples were measured in accordance with JIS K7136.

[0134] [Rigidity evaluation] The stretched multilayer substrates obtained in the Examples and Comparative Examples, and the polyethylene films obtained in the Reference Examples were cut into test pieces with a width of 10 mm, and the stiffness of the test pieces was measured using a loop stiffness measuring tester (manufactured by Toyo Seiki Seisakusho, product name: Loop Stiffness Tester). The length of the loop was 60 mm.

[0135] [Strength evaluation] Dumbbell-shaped test pieces with a width of 10 mm were cut out from the stretched multilayer substrates obtained in the Examples and Comparative Examples, and the polyethylene film obtained in the Reference Examples. The tensile strength of the test pieces in the MD direction was measured using a tensile tester (ORIENTEC Co., Ltd., RTC-1310A). The chuck distance was 10 mm, and the tensile speed was 300 mm / min. The evaluation results are shown in Table 1.

[0136] [Table 1] [Explanation of symbols]

[0137] 10: Polyethylene multi-layer base material 12: A first layer containing medium density polyethylene 14: A fifth layer containing medium density polyethylene 16: A multi-layer intermediate layer consisting of a second layer, a third layer, and a fourth layer 18: A second layer containing medium density polyethylene 20: A third layer containing medium density polyethylene and linear low density polyethylene 22: A fourth layer containing medium density polyethylene 30: Laminate 32: Heat seal layer 34: Barrier layer 36: Adhesive layer

Claims

1. a first layer comprising a medium density polyethylene; a second layer comprising a medium density polyethylene; a third layer containing medium density polyethylene and linear low density polyethylene; a fourth layer containing a medium density polyethylene; a fifth layer containing medium density polyethylene; A polyethylene multilayer substrate having the above in this order in the thickness direction and subjected to a stretching treatment.

2. 2. The polyethylene multi-layer substrate according to claim 1, wherein the mass ratio of the medium density polyethylene to the linear low density polyethylene in the third layer (medium density polyethylene / linear low density polyethylene) is 0.25 or more and 4 or less.

3. The content ratio of the medium density polyethylene in the first layer is 80% by mass or more, The content of the medium density polyethylene in the second layer is 80% by mass or more, a total content ratio of the medium density polyethylene and the linear low density polyethylene in the third layer is 80 mass% or more, The content ratio of the medium density polyethylene in the fourth layer is 80% by mass or more, The polyethylene multi-layer substrate according to claim 1 or 2, wherein the content of the medium-density polyethylene in the fifth layer is 80 mass % or more.

4. In the multilayer base material, when any adjacent layers selected from the first to fifth layers are referred to as layer (1) and layer (2), the absolute value of the difference between the density of the polyethylene constituting layer (1) and the density of the polyethylene constituting layer (2) is 0.030 g / cm ３ Below is the The polyethylene multi-layer substrate according to any one of claims 1 to 3.

5. A polyethylene multilayer substrate according to any one of claims 1 to 4, A printing layer formed on the multilayer substrate; A printing substrate comprising:

6. A polyethylene multilayer substrate according to any one of claims 1 to 4, Heat seal layer A laminate comprising:

7. The laminate of claim 6 wherein the heat seal layer comprises polyethylene.

8. The laminate according to claim 6 or 7, further comprising a printed layer on the multi-layer substrate.

9. The laminate according to any one of claims 6 to 8, further comprising a barrier layer between the multilayer substrate and the heat seal layer.

10. The laminate of claim 9 , wherein the barrier layer is a vapor-deposited layer.

11. 11. The laminate of claim 9 or 10, further comprising an adhesive layer between the multilayer substrate and the barrier layer.

12. The laminate according to any one of claims 6 to 8, further comprising an adhesive layer between the multilayer substrate and the heat seal layer.

13. The laminate according to any one of claims 6 to 12, which is used for packaging material applications.

14. A packaging material comprising a polyethylene multilayer substrate according to any one of claims 1 to 4, a printing substrate according to claim 5, or a laminate according to any one of claims 6 to 13.

Images