Polyethylene laminate for packaging material and packaging material including the laminate

Abstract

To provide a polyethylene laminate for a packaging material that can remarkably reduce load on an environment and has high-printability and strength.SOLUTION: A polyethylene laminate for a packaging material includes at least a stretched polyethylene film, an adhesion layer and a heat-sealing polyethylene layer. An image is formed on at least one surface of the stretched polyethylene film by a flexographic printing method. The adhesion layer includes solventless type adhesive.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to polyethylene laminates for packaging materials and packaging materials made from said laminates. [Background technology]

[0002] Polyethylene film is used in various packaging materials because it has moderate flexibility, excellent transparency, moisture resistance, and chemical resistance, and is inexpensive. Although the melting point of polyethylene varies slightly depending on the type, it is generally around 100-140°C, so it is commonly used as a heat-sealable film in the packaging materials field.

[0003] On the other hand, compared to other thermoplastic resin films, polyethylene film has inferior rigidity, resulting in poor printability and making it difficult to form clear images on its surface. Furthermore, polyethylene film does not possess sufficient strength to meet the durability requirements for outer packaging materials. Therefore, packaging materials are manufactured by laminating a resin film with excellent rigidity and strength, such as polyester film or nylon film, with a polyethylene film to form a laminate, and then heat-sealing the edges of the laminate so that the polyethylene film side of the laminate faces inward (for example, Japanese Patent Publication No. 2005-104525).

[0004] Incidentally, in recent years, with the growing demand for the creation of a circular economy, attempts have been made to recycle and reuse packaging materials. However, when different types of resin films are laminated together as described above, it is difficult to separate the resin films from each other, making them unsuitable for recycling. There has also been a demand for using packaging materials with a lower environmental impact. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2005-104525 [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention was made to solve the above-mentioned problems, and aims to provide a polyethylene laminate for packaging materials that significantly reduces the burden on the environment while possessing high printability and strength. [Means for solving the problem]

[0007] The polyethylene laminate for packaging materials of the present invention comprises at least a stretched polyethylene film, an adhesive layer, and a heat-sealable polyethylene layer, wherein an image is formed on at least one surface of the stretched polyethylene film by flexographic printing, and the adhesive layer contains a solvent-free adhesive.

[0008] In one embodiment, the stretched polyethylene film comprises at least one of high-density polyethylene (HDPE) and medium-density polyethylene (MDPE).

[0009] In one embodiment, the stretching ratio in the longitudinal direction (MD) of the stretched polyethylene film is 2 times or more and 10 times or less.

[0010] In one embodiment, the stretched polyethylene film is a biaxially oriented film.

[0011] In one embodiment, the thickness of the stretched polyethylene film is 9 μm or more and 50 μm or less.

[0012] In one embodiment, the stretched polyethylene film has a structure consisting of a high-density polyethylene layer / medium-density polyethylene layer / high-density polyethylene layer.

[0013] In one embodiment, the ratio of the thickness of the high-density polyethylene layer to the thickness of the medium-density polyethylene layer is 1 / 10 or more and 1 / 1 or less.

[0014] In one embodiment, the stretched polyethylene film is produced by an inflation molding method.

[0015] In one embodiment, the heat-sealable polyethylene layer contains at least one of low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE).

[0016] The packaging material of the present invention is characterized by being composed of the above laminate.

Effect of the Invention

[0017] According to the present invention, it is possible to significantly reduce the environmental load and provide a polyethylene laminate for a packaging material having high printability and strength.

Brief Description of the Drawings

[0018] [Figure 1] It is a schematic cross-sectional view showing an embodiment of the polyethylene laminate for a packaging material according to the present invention. [Figure 2] It is a schematic cross-sectional view showing an embodiment of the polyethylene laminate for a packaging material according to the present invention.

Mode for Carrying Out the Invention

[0019] <Polyethylene Laminate for Packaging Material> The polyethylene laminate for a packaging material according to the present invention will be described while referring to the drawings. As shown in FIG. 1, the polyethylene laminate 10 for a packaging material includes at least a stretched polyethylene film 20, an adhesive layer 30, and a heat-sealable polyethylene layer 40. Further, in one embodiment, between the stretched polyethylene film 20 and the heat-sealable polyethylene layer 40, a polyethylene layer 50 provided with a vapor deposition film is provided. The following describes each layer of the polyethylene laminate used for packaging materials.

[0020] <Stretched polyethylene film> Stretched polyethylene film may be uniaxially oriented or biaxially oriented, but from the viewpoint of strength, biaxially oriented film is preferred.

[0021] The stretching ratio in the longitudinal direction (MD) of the stretched polyethylene film is preferably 2 times or more and 10 times or less, and preferably 3 times or more and 7 times or less. This can further improve the printability and strength of the polyethylene laminate. In addition, this can improve the transparency of the stretched polyethylene film. Furthermore, the stretching ratio in the transverse direction (TD) is preferably 2 times or more and 10 times or less, and preferably 3 times or more and 7 times or less. This can further improve the printability and strength of the polyethylene laminate. In addition, this can improve the transparency of the stretched polyethylene film.

[0022] Examples of polyethylenes included in stretched polyethylene films include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE). Furthermore, stretched polyethylene films may contain two or more of these types. Among these, high-density polyethylene (HDPE) and medium-density polyethylene (MDPE) are preferred from the viewpoint of printability, strength, heat resistance, and stretchability of polyethylene laminates, and medium-density polyethylene is more preferred from the viewpoint of stretchability. In this invention, high-density polyethylene has a density of 0.945 g / cm³. 3 The above refers to medium-density polyethylene, which has a density of 0.925 to 0.944 g / cm³. 3 Low-density polyethylene has a density of 0.925 g / cm³. 3 It refers to something less than [amount].

[0023] Polyethylenes with different densities and branching patterns, as described above, 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 the polymerization catalyst, and to carry out the polymerization in one or more stages using one of the following methods: gas-phase polymerization, slurry polymerization, solution polymerization, or high-pressure ionic polymerization.

[0024] The single-site catalyst described above 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 activation co-catalyst. Single-site catalysts are preferred over multi-site catalysts because they have a more uniform active site structure, allowing for the polymerization of polymers with high molecular weight and high uniformity. As a single-site catalyst, metallocene catalysts are particularly preferred. A metallocene catalyst is a catalyst comprising a transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, a co-catalyst, an organometallic compound if necessary, and each catalytic component of a support.

[0025] In the transition metal compounds of Group IV of the periodic table containing the ligand having the cyclopentadienyl skeleton described above, the cyclopentadienyl skeleton is a cyclopentadienyl group, a substituted cyclopentadienyl group, etc. The substituted cyclopentadienyl group has at least one substituent selected from hydrocarbon groups having 1 to 30 carbon atoms, silyl groups, silyl-substituted alkyl groups, silyl-substituted aryl groups, cyano groups, cyanoalkyl groups, cyanoaryl groups, halogen groups, haloalkyl groups, halosilyl groups, etc. The substituted cyclopentadienyl group may have two or more substituents, and the substituents may bond to each other to form a ring, forming an indenyl ring, a fluorenyl ring, an azlenyl ring, or a hydrogenated version thereof. The ring formed by the bonding of substituents may further have substituents on each other.

[0026] In a transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, examples of the transition metal include zirconium, titanium, and hafnium, with zirconium and hafnium being particularly preferred. The transition metal compound usually has two ligands having a cyclopentadienyl skeleton, and it is preferable that each ligand having a cyclopentadienyl skeleton is bonded to each other by a bridging group. Examples of bridging groups 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. A substituted silylene group is preferred. The above transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton can be used as a catalyst component, either individually or as a mixture of two or more.

[0027] Co-catalysts are those that can effectively utilize the transition metal compounds of Group IV of the periodic table mentioned above as polymerization catalysts, or that can balance the ionic charge of the catalytically activated state. Examples of co-catalysts include benzene-soluble aluminoxanes and benzene-insoluble organoaluminum oxy compounds, ion-exchangeable layered silicates, boron compounds, ionic compounds consisting of cations containing or not containing active hydrogen groups and non-coordinating anions, lanthanide salts such as lanthanum oxide, tin oxide, and phenoxy compounds containing fluoro groups.

[0028] Transition metal compounds of Group IV of the periodic table containing ligands having a cyclopentadienyl skeleton may be used by being supported on an inorganic or organic compound. Preferred supports are porous oxides of inorganic or organic compounds, specifically including ion-exchange layered silicates such as montmorillonite, SiO2, Al2O3, MgO, ZrO2, TiO2, B2O3, CaO, ZnO, BaO, ThO2, or mixtures thereof. Further organometallic compounds that may be used as needed include organoaluminum compounds, organomagnesium compounds, and organozinc compounds. Of these, organoaluminum compounds are preferred.

[0029] Furthermore, copolymers of ethylene and other monomers can be used, as long as they do not impair the properties of the present invention. Examples of ethylene copolymers include copolymers consisting of ethylene and α-olefins having 3 to 20 carbon atoms. 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, 6-methyl-1-heptene, and the like. Also, copolymers with vinyl acetate, acrylic acid esters, etc., are acceptable, as long as they do not impair the objectives of the present invention.

[0030] Furthermore, in this invention, biomass-derived ethylene may be used as a raw material for obtaining the above-mentioned high-density polyethylene, etc., instead of ethylene obtained from fossil fuels. Since such biomass-derived polyethylene is a carbon-neutral material, it can be used as a packaging material with an even lower environmental impact. Such biomass-derived polyethylene can be manufactured, for example, by a method described in Japanese Patent Application Publication No. 2013-177531. Alternatively, commercially available biomass-derived polyethylene (for example, Green PE, commercially available from Braschem) may be used.

[0031] The polyethylene content in the stretched polyethylene film is preferably 50% by mass or more, and more preferably 70% by mass or more.

[0032] The stretched polyethylene film may contain additives to the extent that they do not impair the properties of the present invention. Examples include crosslinking agents, antioxidants, antiblocking agents, lubricants, ultraviolet absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

[0033] In one embodiment, the stretched polyethylene film has a multilayer structure. Preferably, it comprises a layer containing high-density polyethylene (HDPE) and a layer containing medium-density polyethylene (MDPE). For example, the structure may consist of a high-density polyethylene layer / medium-density polyethylene layer / high-density polyethylene layer. By using such a structure, the printability and strength of the polyethylene laminate can be further improved. In this case, the ratio of the thickness of the high-density polyethylene layer to the medium-density polyethylene layer is preferably 1 / 10 or more and 1 / 1 or less, and more preferably 1 / 5 or more and 1 / 2 or less.

[0034] The thickness of the stretched polyethylene film is preferably 9 μm or more and 50 μm or less, and more preferably 12 μm or more and 30 μm or less. By setting the thickness of the stretched polyethylene film within the above numerical range, the printability, strength, and heat resistance of the polyethylene laminate can be further improved.

[0035] In one embodiment, the stretched polyethylene film has a vapor-deposited film on one side containing a metal such as aluminum, or an inorganic oxide such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, or barium oxide. This improves the gas barrier properties of the polyethylene laminate according to the present invention. Conventional known methods can be used for deposition, such as physical vapor deposition (PVD) methods including vacuum deposition, sputtering, and ion plating, or chemical vapor deposition (CVD) methods including plasma chemical vapor deposition, thermochemical vapor deposition, and photochemical vapor deposition.

[0036] Also, the film thickness of the vapor deposition film is preferably 0.002 μm or more and 0.4 μm or less, and more preferably 0.005 μm or more and 0.1 μm or less. By setting the thickness of the vapor deposition film within the above numerical range, it is possible to prevent the occurrence of cracks and the like in the vapor deposition film while maintaining the gas barrier property.

[0037] Also, for example, a composite film composed of two or more layers of vapor deposition films of different inorganic oxides can be formed and used by combining both physical vapor deposition and chemical vapor deposition methods. As the degree of vacuum in the vapor deposition chamber, before oxygen introduction, it is about 10 -2 ~10 -8 mbar, particularly preferably about 10 -3 ~10 -7 mbar. After oxygen introduction, it is about 10 -1 ~10 -6 mbar, particularly preferably about 10 -2 ~10 -5 mbar. Note that the amount of oxygen introduced and the like vary depending on the size of the vapor deposition machine and the like. For the oxygen to be introduced, inert gases such as argon gas, helium gas, and nitrogen gas may be used as carrier gases within a non-obstructive range. As the film conveyance speed, it is about 10 to 800 m / min, particularly preferably about 50 to 600 m / min.

[0038] The stretched polyethylene film is characterized in that an image is formed on at least one surface by the flexographic printing method. By performing image formation by the flexographic printing method, the environmental load can be reduced. The image to be formed is not particularly limited, and characters, patterns, symbols, etc. may be formed. Also, since it is possible to prevent the deterioration of the image over time, it is preferable to form the image on the side where the heat-sealing polyethylene layer of the stretched polyethylene film is laminated.

[0039] Stretched polyethylene film can be obtained by melting a polyethylene-containing resin material, forming a film using a melt extrusion molding method such as inflation molding or T-die molding, and then stretching it. It is preferable to produce it by inflation molding because the stretching process is easier. Stretched polyethylene film having a multilayer structure can be produced by melt co-extrusion of multiple resin materials.

[0040] The melt flow rate (MFR) of the resin material is preferably 0.5 g / 10 min or more and 20 g / 10 min or less, and more preferably 0.8 g / 10 min or more and 5 g / 10 min or less. By setting the MFR of the resin material within the above numerical range, the stretching process can be carried out more easily.

[0041] <Adhesive layer> The polyethylene laminate for packaging materials of the present invention comprises an adhesive layer containing a solvent-free adhesive between a stretched polyethylene film and a heat-sealable polyethylene layer. Furthermore, if the polyethylene laminate for packaging materials of the present invention comprises a polyethylene layer having a vapor-deposited film, the adhesive layer is provided between the stretched polyethylene film and the polyethylene layer having the vapor-deposited film, and between the polyethylene layer having the vapor-deposited film and the heat-sealable polyethylene layer. The adhesive layer of the polyethylene laminate for packaging materials of the present invention contains a solvent-free adhesive, thereby reducing the environmental burden.

[0042] Examples of adhesives include polyvinyl acetate adhesives, polyacrylic acid ester adhesives, cyanoacrylate adhesives, ethylene copolymer adhesives, cellulose adhesives, polyester adhesives, polyether adhesives, polyamide adhesives, polyimide adhesives, amino resin adhesives, phenolic resin adhesives, epoxy adhesives, urethane adhesives, rubber adhesives, and silicone adhesives.

[0043] The thickness of the adhesive layer is not particularly limited, but it can be between 0.5 μm and 5 μm.

[0044] <Heat-sealable polyethylene layer> The heat-sealable polyethylene layer comprises at least one of high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or copolymers of ethylene and other monomers. Among these, low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE) are preferred from the viewpoint of heat-sealability. From the viewpoint of environmental impact, it is preferable that these polyethylenes are derived from biomass.

[0045] The polyethylene content in the heat-sealable polyethylene layer is preferably 50% by mass or more, and more preferably 70% by mass or more.

[0046] The heat-sealable polyethylene layer may contain additives, to the extent that they do not impair the properties of the present invention. Examples include crosslinking agents, antioxidants, ultraviolet absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

[0047] The thickness of the heat-sealable polyethylene layer is preferably 20 μm or more and 200 μm or less, and more preferably 30 μm or more and 150 μm or less. By setting the thickness of the heat-sealable polyethylene layer within the above numerical range, its heat-sealability can be improved.

[0048] A heat-sealable polyethylene layer can be formed by creating a polyethylene film from a polyethylene-containing resin material using a melt extrusion molding method such as inflation molding or T-die molding, and then laminating this film onto a polyethylene layer having a stretched polyethylene film or a vapor-deposited film via an adhesive layer.

[0049] <Polyethylene layer with vapor-deposited film> In one embodiment, the polyethylene laminate according to the present invention comprises a polyethylene layer having a vapor-deposited film between a stretched polyethylene film and a heat-sealable polyethylene layer. This makes it possible to improve the gas barrier properties of the polyethylene laminate according to the present invention.

[0050] The polyethylene layer with a vapor-deposited film may be composed of a stretched film or an unstretched film, but from the viewpoint of printability, strength, and heat resistance of the polyethylene laminate, it is preferable that it be stretched. Furthermore, it may be uniaxially stretched or biaxially stretched, but from the viewpoint of strength, it is preferable that it be biaxially stretched.

[0051] The polyethylene layer comprising the vapor-deposited film contains at least one of high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a copolymer of ethylene and other monomers. Among these, high-density polyethylene (HDPE) and medium-density polyethylene (MDPE) are preferred from the viewpoint of printability, strength, and heat resistance, and high-density polyethylene (HDPE) is more preferred. From the viewpoint of environmental impact, it is preferable that these polyethylenes are derived from biomass.

[0052] The polyethylene content in the polyethylene layer equipped with the vapor-deposited film is preferably 50% by mass or more, and more preferably 70% by mass or more.

[0053] The polyethylene layer having a vapor-deposited film may contain additives to the extent that they do not impair the properties of the present invention, such as crosslinking agents, antioxidants, ultraviolet absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

[0054] From the viewpoint of productivity and economics, the thickness of the polyethylene layer with the vapor-deposited film is preferably 9 μm or more and 50 μm or less, and more preferably 12 μm or more and 30 μm or less. Furthermore, the thickness of the deposited film is preferably 0.002 μm or more and 0.4 μm or less, and more preferably 0.005 μm or more and 0.1 μm or less. By keeping the thickness of the deposited film within the above numerical range, it is possible to prevent the occurrence of cracks and other defects in the deposited film while maintaining gas barrier properties.

[0055] A polyethylene layer equipped with a vapor-deposited film may have an image formed on its surface. The image formation method is as described above.

[0056] A polyethylene layer with a vapor-deposited film can be formed by creating a polyethylene film from a polyethylene-containing resin material using a melt extrusion molding method such as inflation molding or T-die molding, forming a vapor-deposited film on at least one surface of the polyethylene film using the method described above, and then laminating it onto a stretched polyethylene film via an adhesive layer. In this case, the polyethylene film may be subjected to stretching treatment before vapor deposition and before lamination.

[0057] <Packaging materials> In one embodiment, the packaging material according to the present invention can be manufactured by folding the polyethylene laminate in half and overlapping the two halves so that the heat-sealable polyethylene layer faces inward, and then heat-sealing the edges. Furthermore, it can be manufactured by overlapping two polyethylene laminates so that the heat-sealable polyethylene layers face each other, and then heat-sealing the edges. Depending on the sealing method, various types of packaging materials can be manufactured by heat sealing using heat sealing methods such as side seal type, two-side seal type, three-side seal type, four-side seal type, envelope seal type, gusset seal type (pillow seal type), pleated seal type, flat-bottom seal type, square-bottom seal type, gusset type, and others. Other options include, for example, self-standing packaging bags (standing pouches). Heat sealing can be carried out using known methods such as bar sealing, rotary roll sealing, belt sealing, impulse sealing, high-frequency sealing, and ultrasonic sealing.

[0058] The polyethylene laminate according to the present invention, even if it is a laminate consisting of only one type of resin (i.e., polyethylene), has a stretched polyethylene film that satisfies the strength and printability required for an outer film of packaging material, and a heat-sealable polyethylene layer that enables packaging. Therefore, it is extremely suitable as a material for packaging materials where recyclability is required. [Examples]

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

[0060] <Example 1> Medium-density polyethylene (density: 0.941 g / cm³) 3 A polyethylene film with a thickness of 100 μm was obtained by using inflation molding with a material (melting point 129°C, MFR: 1.3 g / 10 min, manufactured by Dowchemical, trade name: Elite5538G). This polyethylene film was stretched in the longitudinal direction (MD) at a stretching ratio of 5 times to obtain a stretched polyethylene film with a thickness of 20 μm.

[0061] The stretched polyethylene film described above and an unstretched linear low-density polyethylene (LLDPE) film with a thickness of 40 μm (manufactured by Toyobo Co., Ltd., product name: L6100) were laminated together using a two-component, solvent-free polyester adhesive (manufactured by Rock Paint Co., Ltd., product name: RN-920 / HN:920) to obtain a polyethylene laminate.

[0062] <Example 2> High-density polyethylene (density: 0.961 g / cm³) 3(Melting point 135℃, MFR: 0.7g / 10min, manufactured by ExxonMobil, product name: HTA108) and medium-density polyethylene (density: 0.941g / cm³) 3 A polyethylene film consisting of a high-density polyethylene layer, a medium-density polyethylene layer, and a high-density polyethylene layer was prepared by inflation molding using a material with a melting point of 129°C, an MFR of 1.3 g / 10 min, manufactured by Dowchemical, and trade name: Elite5538G. The thickness of the high-density polyethylene layer was 20 μm, and the thickness of the medium-density polyethylene layer was 60 μm. This polyethylene film was stretched in the longitudinal direction (MD) at a stretching ratio of 5 times to obtain a stretched polyethylene film with a thickness of 20 μm.

[0063] The stretched polyethylene film described above and an unstretched linear low-density polyethylene (LLDPE) film with a thickness of 40 μm (manufactured by Toyobo Co., Ltd., product name: L6100) were laminated together using a two-component, solvent-free polyester adhesive (manufactured by Rock Paint Co., Ltd., product name: RN-920 / HN:920) to obtain a polyethylene laminate.

[0064] <Example 3> Medium-density polyethylene (density: 0.941 g / cm³) 3 A polyethylene film with a thickness of 100 μm was obtained by using inflation molding with a material (melting point 129°C, MFR: 1.3 g / 10 min, manufactured by Dowchemical, trade name: Elite5538G). This polyethylene film was stretched in the longitudinal (MD) and widthwise (TD) directions at a stretching ratio of 2.24 times to obtain a stretched polyethylene film with a thickness of 20 μm. The stretched polyethylene film described above and an unstretched linear low-density polyethylene (LLDPE) film with a thickness of 40 μm (manufactured by Toyobo Co., Ltd., product name: L6100) were laminated together using a two-component, solvent-free polyester adhesive (manufactured by Rock Paint Co., Ltd., product name: RN-920 / HN:920) to obtain a polyethylene laminate.

[0065] <Comparative Example 1> Medium-density polyethylene (density: 0.941 g / cm³) 3 A polyethylene film with a thickness of 20 μm was obtained by using inflation molding with a material (melting point 129°C, MFR: 1.3 g / 10 min, manufactured by Dowchemical, trade name: Elite5538G).

[0066] The above polyethylene film and a 40 μm thick unstretched linear low-density polyethylene (LLDPE) film (manufactured by Toyobo Co., Ltd., product name: L6100) were laminated together using a two-component, solvent-free polyester adhesive (manufactured by Rock Paint Co., Ltd., product name: RN-920 / HN:920) to obtain a polyethylene laminate.

[0067] <Comparative Example 2> High-density polyethylene (density: 0.961 g / cm³) 3 (Melting point 135℃, MFR: 0.7g / 10min, manufactured by ExxonMobil, product name: HTA108) and medium-density polyethylene (density: 0.941g / cm³) 3 A polyethylene film consisting of a high-density polyethylene layer, a medium-density polyethylene layer, and a high-density polyethylene layer was prepared by inflation molding using a material with a melting point of 129°C, an MFR of 1.3 g / 10 min, manufactured by Dowchemical, and trade name: Elite5538G. The thickness of each high-density polyethylene layer was 4 μm, and the thickness of the medium-density polyethylene layer was 12 μm.

[0068] The above polyethylene film and a 40 μm thick unstretched linear low-density polyethylene (LLDPE) film (manufactured by Toyobo Co., Ltd., product name: L6100) were laminated together using a two-component, solvent-free polyester adhesive (manufactured by Rock Paint Co., Ltd., product name: RN-920 / HN:920) to obtain a polyethylene laminate.

[0069] <Printability Evaluation> Images were formed on one side of the stretched polyethylene film and polyethylene film prepared in the above examples and comparative examples using a water-based flexographic ink (manufactured by Toyo Ink Co., Ltd., product name: Aquariona) by flexographic printing. The formed images were observed visually, and the printability of the stretched polyethylene film and polyethylene film was evaluated based on the following evaluation criteria. The evaluation results are summarized in Table 1. (Evaluation Criteria) ○: The dimensional stability during printing was good, and a good image was formed without smudging, bleeding, etc. ×: The film expanded and contracted during printing, resulting in smudging and blurring of the resulting image.

[0070] <Rigidity Evaluation> The stretched polyethylene films and polyethylene films prepared in the above examples and comparative examples were prepared as 15 mm wide test pieces, and their stiffness was measured using a loop stiffness tester (manufactured by Toyo Seiki Seisakusho, product name: Loop Stiffness Tester). The loop length was set to 60 mm. The measurement results are summarized in Table 1.

[0071] <Strength Evaluation> The stretched polyethylene films and polyethylene films prepared in the above examples and comparative examples were used to create 10 mm wide dumbbell-shaped test specimens. The tensile strength of these specimens in the MD direction was measured using a tensile testing machine (Orientec Co., Ltd., RTC-1310A). The distance between the chucks was 10 mm, and the tensile speed was 300 mm / min. The measurement results are summarized in Table 1.

[0072] [Table 1] [Explanation of Symbols]

[0073] 10: Polyethylene laminate for packaging materials, 20: Stretched polyethylene film, 30: Adhesive layer, 40: Heat-sealable polyethylene layer, 50: Polyethylene layer with vapor-deposited film

Claims

1. The film comprises at least a stretched polyethylene film, an adhesive layer, and a heat-sealable film, the heat-sealable film is made of polyethylene, At least one surface of the stretched polyethylene film is printed by a flexographic printing method, 1. A polyethylene laminate for packaging materials, wherein the adhesive layer contains a solventless adhesive.

2. 2. The polyethylene laminate for packaging materials according to claim 1, wherein the oriented polyethylene film comprises at least one of high density polyethylene (HDPE) and medium density polyethylene (MDPE).

3. 3. The polyethylene laminate for packaging materials according to claim 1, wherein the stretched polyethylene film has a stretching ratio in the machine direction (MD) of 2 times or more and 10 times or less.

4. The polyethylene laminate for packaging materials according to any one of claims 1 to 3, wherein the stretched polyethylene film is a biaxially stretched film.

5. The polyethylene laminate for packaging materials according to any one of claims 1 to 4, wherein the thickness of the stretched polyethylene film is 9 µm or more and 50 µm or less.

6. The polyethylene laminate for packaging materials according to any one of claims 1 to 5, wherein the stretched polyethylene film has a configuration consisting of a high-density polyethylene layer / a medium-density polyethylene layer / a high-density polyethylene layer.

7. 7. The polyethylene laminate for packaging materials according to claim 6, wherein the ratio of the thickness of said high-density polyethylene layer to that of said medium-density polyethylene layer is 1 / 10 or more and 1 / 1 or less.

8. The polyethylene laminate for packaging materials according to any one of claims 1 to 7, wherein the stretched polyethylene film is produced by inflation molding.

9. The polyethylene laminate for packaging materials according to any one of claims 1 to 8, wherein the heat-sealable film comprises at least one of low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE).

10. A packaging material comprising the laminate according to any one of claims 1 to 9.

Images