Laminate and packaging material

Abstract

To provide a laminate excellent in recyclability and having good printability and impact resistance.SOLUTION: A laminate comprising a base material layer and a sealant layer, wherein the base material layer has a core layer and a skin layer on the sealant layer side in this order, a probe descent temperature of the core layer is higher than 180°C, a probe descent temperature of the skin layer is 180°C or lower, and the core layer, the skin layer and the sealant layer contain a polyethylene resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate and a packaging material. [Background technology]

[0002] In recent years, growing environmental awareness stemming from issues such as marine plastic waste has led to calls for further improvements in the efficiency of the sorted collection and recycling of plastic materials, and there is also a growing demand for mono-material packaging materials used for packaging foods, medicines, etc. From this perspective, laminates primarily composed of polyethylene films have been proposed as laminates for use in packaging materials, instead of laminates composed of different types of resin films (e.g., Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-189333 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the inventors attempted to produce packaging materials using conventional laminates, they found that there was room for improvement in the conventional laminates in terms of achieving both printability, i.e., resistance to distortion of the pattern (printed layer) due to heat received during the laminate production process, and impact resistance, i.e., physical resistance to external impacts such as being dropped.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laminate that is excellent in recyclability and has good printability and impact resistance, and to provide a packaging material including the laminate. [Means for solving the problem]

[0006] The present invention includes, for example, the following [1] to [8]. [1] A laminate comprising a substrate layer and a sealant layer, the base material layer has a core layer and a skin layer on the sealant layer side in this order, the core layer has a probe drop temperature of more than 180°C, and the skin layer has a probe drop temperature of 180°C or less; The laminate, wherein the core layer, the skin layers, and the sealant layer comprise a polyethylene resin. [2] The laminate according to [1], wherein the thickness of the skin layer is 0.3 μm or more and 50 μm or less. [3] The laminate comprises the base material layer, an intermediate layer having an inorganic oxide layer, and the sealant layer in this order; The laminate according to [1] or [2], wherein the intermediate layer contains a polyethylene resin. [4] The laminate according to any one of [1] to [3], wherein the thickness of the core layer is 33% or more of the thickness of the base layer. [5] The laminate according to any one of [1] to [4], wherein the base layer is a stretched film. [6] The laminate according to any one of [1] to [5], further comprising a printed layer on the surface of the base material layer. [7] The laminate according to any one of [1] to [6], wherein the substrate layer has another skin layer, the core layer, and the skin layer in this order, the probe drop temperature of the other skin layer is 180°C or less, and the other skin layer contains a polyethylene resin. [8] A packaging material comprising the laminate according to any one of [1] to [7]. [Effects of the Invention]

[0007] According to the present invention, a laminate having excellent recyclability, good printability, and good impact resistance is provided. Also, according to the present invention, a packaging material including the laminate is provided. [Brief explanation of the drawings]

[0008] [Figure 1]FIG. 1 is a cross-sectional view of a laminate according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the drawings are schematic, and for example, the relationship between thickness and planar dimensions, and the thickness ratio of each layer may differ from the actual ones. Furthermore, the embodiments shown below exemplify configurations for embodying the technical idea of ​​the present disclosure, and the technical idea of ​​the present disclosure is not limited to the materials, shapes, structures, etc. of the components described below.

[0010] [Laminate] Fig. 1 is a cross-sectional view of a laminate according to one embodiment of the present invention. The laminate 100 includes a substrate layer 10 and a sealant layer 30. As shown in the figure, the laminate 100 may include a gas barrier layer 20 (an intermediate layer 21 and an inorganic oxide layer 22) between the substrate layer 10 and the sealant layer 30, and may include a printed layer 40 on the inner surface side of the substrate layer 10 (the side facing the sealant layer 30). The laminate 100 may further include a heat-resistant layer on the outer surface side of the substrate layer 10 (the side not facing the sealant layer 30), and may also include adhesive layers between the layers as needed (neither of which is shown).

[0011] The content of polyethylene resin in the laminate 100 can be 90% by mass or more, or may be 95% by mass or more, based on the total amount of the laminate 100, in order to achieve mono-materialization and excellent recyclability.

[0012] The thickness of the laminate 100 is not particularly limited and can be determined appropriately depending on the cost and application. The thickness of the laminate 100 may be 50 μm or more, 60 μm or more, or 70 μm or more, or may be 300 μm or less, 250 μm or less, or 200 μm or less.

[0013] <Base material layer> The substrate layer 10 can have three layers, in this order: a skin layer (another skin layer) 11 on the side opposite the sealant layer, a core layer 12, and a skin layer 13 on the sealant layer side, each containing a polyethylene resin. The substrate layer 10 does not necessarily have to have the other skin layer 11. The other skin layer 11 and the skin layer 13 can each be the outermost layer of the substrate layer 10. The substrate layer 10 is a multilayer film that can be obtained by coextrusion, and therefore can also be called a coextruded multilayer film.

[0014] From the viewpoint of more easily achieving both printability and impact resistance, the core layer 12 and the skin layer 13 can be laminated adjacent to each other. From the same viewpoint, the core layer 12 and the other skin layer 11 can be laminated adjacent to each other.

[0015] The base material layer 10 may have layers other than the three layers of the other skin layer 11, the core layer 12, and the skin layer 13. For example, a resin layer may be provided between the core layer 12 and the skin layer 13, or another resin layer may be provided between the other skin layer 11 and the core layer 12. The resin layer is, for example, a layer containing a polyethylene resin and having a different composition from the core layer 12 and the skin layer 13. The other resin layer is, for example, a layer containing a polyethylene resin and having a different composition from the other skin layer 11 and the core layer 12. The resin layer and the other resin layer have the function of bonding different layers (between the core layer and the skin layer), and therefore can also be called adhesive resin layers. The base layer 10 may have, for example, three, five, seven or more layers (preferably layers containing polyethylene resin).

[0016] The content of polyethylene resin in the base material layer 10 may be 90% by mass or more, or 95% by mass or more, based on the total amount of the base material layer 10, from the viewpoint of realizing mono-materialization and excellent recyclability.

[0017] The substrate layer 10 may be a stretched film or a non-stretched film. When the substrate layer 10 is a stretched film, a laminate having good printability and impact resistance can be easily obtained. Examples of stretched films include uniaxially stretched films and biaxially stretched films, with biaxially stretched films being preferred from the viewpoint of impact resistance.

[0018] The thickness of the base layer 10 is not particularly limited and can be appropriately determined according to the cost and application, taking into consideration suitability as a packaging material and suitability for lamination with other layers. The thickness of the base layer 10 may be 3 μm or more, 5 μm or more, 6 μm or more, or 10 μm or more, or may be 200 μm or less, 120 μm or less, 100 μm or less, or 40 μm or less.

[0019] (core layer) The core layer 12 is a layer containing a polyethylene resin. Hereinafter, the polyethylene resin constituting the core layer 12 is also referred to as a first polyethylene resin. The content of the first polyethylene resin in the core layer 12 may be 90% by mass or more, 95% by mass or more, or 98% by mass or more, based on the total amount of the core layer 12, or may be 100% by mass (an embodiment in which the core layer 12 is substantially composed of the first polyethylene resin). When the core layer 12 is composed of multiple polyethylene resins (for example, multiple polyethylene resins with different average molecular weights, densities, etc.), a mixture of the multiple polyethylene resins is referred to as the first polyethylene resin. The first polyethylene resin may be a high-density polyethylene resin (HDPE).

[0020] The core layer 12 has a probe drop temperature of more than 180° C., from the viewpoint of being less likely to wrinkle when heat is applied and having better printing stability (heat resistance). The probe drop temperature is a value measured by the method described below.

[0021] The higher the probe drop temperature of the core layer 12, the easier it is to achieve excellent printability. The probe drop temperature of the core layer 12 may be 185°C or higher, 190°C or higher, or 200°C or higher, from the viewpoint of making wrinkles less likely to occur and achieving better printability. On the other hand, the probe drop temperature of the core layer 12 may be 250° C. or less, 230° C. or less, or 220° C. or less from the viewpoint of impact resistance.

[0022] The tip drop temperature is a parameter related to localized thermal analysis of materials using a probe and can be obtained by measuring the tip's rise and fall behavior. To measure the tip drop temperature, an atomic force microscope (AFM) equipped with a cantilever (probe) with a heating mechanism and a nanothermal microscope is used. The cantilever is placed in contact with the surface of a solid sample fixed to a sample stage. When a voltage is applied to the cantilever in contact mode to heat the surface, the sample surface thermally expands, causing the cantilever to rise. Further heating of the cantilever softens the sample surface, significantly changing its hardness. As a result, the cantilever descends and penetrates the sample surface. The point at which the sudden displacement detected at this point is the tip drop start point, and the voltage is converted into temperature to obtain the tip drop temperature. This method allows us to determine the tip drop temperature locally in the nanoscale region, near the surface.

[0023] Usable AFMs include the MPF-3D-SA and Ztherm systems from Oxford Instruments, and the Nano Thermal Analysis and nanoIR series from Bruker Japan. Measurements are also possible with AFMs from other manufacturers if they are fitted with a Nano Thermal Analysis. Examples of cantilevers that can be used include the AN2-200 from Anasys Instruments. Cantilevers other than those listed above can also be used as long as they are capable of sufficiently reflecting laser light and allowing voltage to be applied.

[0024] The temperature range for measuring the probe drop temperature varies depending on the material being measured, but for example, the starting temperature can be around room temperature, 25° C., and the ending temperature can be around 400° C. The temperature range for measuring the probe drop temperature may be between 25° C. and 300° C.

[0025] The spring constant of the cantilever may be 0.1 to 3.5 N / m, and is preferably 0.5 to 3.5 N / m for measurements in both tapping mode and contact mode. In AFM, the deflection of the cantilever is sometimes measured in voltage units. In contact mode, the deflection of the cantilever changes before and after contact between the cantilever and the sample. By keeping this change within the range of 0.1 to 3.0 V, it is possible to keep the cantilever in contact with the sample while preventing damage to the sample surface.

[0026] The cantilever temperature rise rate varies depending on the heating mechanism, etc., but may be 0.1 to 10 V / sec, preferably 0.2 to 5 V / sec. When the sample surface softens, the tip of the cantilever sinks into the sample and descends. The amount of cantilever sinking affects the detection sensitivity of the peak top of the softening curve and can be set to 3 to 500 nm. From the viewpoint of preventing cantilever damage, it is more preferable to set the amount of sinking to 5 to 100 nm.

[0027] In order to calculate the probe drop temperature, it is necessary to create a calibration curve. In the examples described below, calibration curves were created using polycaprolactone, low-density polyethylene, polypropylene, and polyethylene terephthalate as calibration samples. The materials for the calibration samples are not limited to those mentioned above; they may be any material whose thermal conductivity is not significantly different from that of common polymers and whose melting point is at least one of approximately 60°C, approximately 250°C, and an intermediate melting point. For example, it is also possible to remove polypropylene from the four calibration samples mentioned above and use only polycaprolactone, low-density polyethylene, and polyethylene terephthalate as calibration samples.

[0028] A core layer 12 having the desired probe drop temperature can be obtained, for example, by adjusting the density, melt flow rate (MFR), stretching ratio during film formation, heat treatment and cooling conditions, etc. of the first polyethylene resin, or by subjecting the core layer 12 to treatments such as annealing or electron beam (EB) irradiation.

[0029] The density of the first polyethylene resin is not particularly limited, but is preferably 0.942 g / cm 3 More than 0.945g / cm 3 or more, or 0.950 g / cm 3 or more, 0.980 g / cm 3 Below, 0.975g / cm 3 Below, 0.970g / cm 3 or less, or 0.965 g / cm 3 The first polyethylene resin may be a medium to high density polyethylene resin. The density of the resin (resin film) is a value measured based on JIS Z 8837.

[0030] The melt flow rate MFR of the first polyethylene resin at 190°C under a load of 2.16 kg is not particularly limited, and may be 10 g / 10 min or less, 5 g / 10 min or less, 3 g / 10 min or less, or 2 g / 10 min or less, or may be 0.1 g / 10 min or more, 0.3 g / 10 min or more, or 0.5 g / 10 min or more. The melt flow rate of a resin (resin film) is a value measured in accordance with JIS K6921-2.

[0031] The difference between the probe drop temperature of the core layer 12 and the probe drop temperature of the other skin layer 11 and / or skin layer 13 may be 10°C or more, 30°C or more, or 40°C or more from the viewpoint of achieving both heat resistance and impact resistance. On the other hand, from the viewpoint of interlayer adhesion between the core layer and the skin layer, the difference between the probe drop temperature of the core layer 12 and the probe drop temperature of the other skin layer 11 and / or skin layer 13 may be 100°C or less, 70°C or less, or 50°C or less.

[0032] The thickness of the core layer 12 is not particularly limited and can be appropriately determined according to the cost and application, taking into consideration the suitability of the manufacturing method and apparatus, and the suitability for lamination with other layers. From a practical standpoint, the thickness of the core layer 12 may be 5 μm or more, 8 μm or more, 10 μm or more, 12 μm or more, or 15 μm or more, or may be 80 μm or less, 50 μm or less, 40 μm or less, or 30 μm or less.

[0033] The thickness of the core layer 12 may be 33% or more, 40% or more, 50% or more, 55% or more, or 60% or more of the thickness of the base material layer 10, from the viewpoint of making wrinkles less likely to occur and improving printing stability. On the other hand, from the viewpoint of achieving better impact resistance, the thickness of the core layer 12 may be 90% or less, 85% or less, or 80% or less of the thickness of the base material layer 10.

[0034] From the viewpoint of making wrinkles less likely to occur and improving printing stability, the thickness of core layer 12 may be greater than the thickness of other skin layer 11 and / or skin layer 13. The thickness of core layer 12 may be more than 1 time, 1.5 times or more, 2 times or more, or 3 times or more the thickness of other skin layer 11 and / or skin layer 13. On the other hand, from the viewpoint of achieving better impact resistance, the thickness of the core layer 12 may be 20 times or less, 10 times or less, or 5 times or less than the thickness of the other skin layer 11 and / or skin layer 13.

[0035] The other skin layer 11, core layer 12, and skin layer 13 may contain a resin other than polyethylene resin as long as it does not impair recyclability. Examples of such resins include olefin-based resins such as ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, ethylene-(meth)acrylic acid copolymer, homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-α-olefin copolymer, and polybutene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; ethylene-vinyl alcohol copolymer, polyamide, and various modifying resins. Each layer may independently contain one or more additives. Examples of additives include crosslinkers, antioxidants, antiblocking agents, lubricants (slip agents), UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, and pigments.

[0036] (skin layer) The skin layer 13 is a layer containing a polyethylene resin. Hereinafter, the polyethylene resin constituting the skin layer 13 is also referred to as the second polyethylene resin. The content of the second polyethylene resin in the skin layer 13 may be 90% by mass or more, 95% by mass or more, or 98% by mass or more, based on the total amount of the skin layer 13, or may be 100% by mass (an embodiment in which the skin layer 13 is substantially composed of the second polyethylene resin). When the skin layer 13 is composed of multiple polyethylene resins (for example, multiple polyethylene resins with different average molecular weights, densities, etc.), the second polyethylene resin is a mixture of the multiple polyethylene resins. The second polyethylene resin may be a medium-density polyethylene resin (MDPE).

[0037] The skin layer 13 has a probe drop temperature of 180° C. or less, from the viewpoint of improving adhesion with the laminated sealant layer 30 and the like, thereby realizing physical resistance to external impacts such as dropping.

[0038] The probe drop temperature of the skin layer 13 may be 170° C. or less, 160° C. or less, or 150° C. or less, from the viewpoint of achieving excellent impact resistance as described above. On the other hand, the probe drop temperature of the skin layer 13 may be 90° C. or higher, 110° C. or higher, or 130° C. or higher from the viewpoint of printability.

[0039] A skin layer 13 having the desired probe drop temperature can be obtained, for example, by adjusting the density, melt flow rate (MFR), stretching ratio during film formation, heat treatment and cooling conditions, etc. of the second polyethylene resin, or by subjecting the skin layer 13 to treatments such as annealing or electron beam (EB) irradiation.

[0040] The density of the second polyethylene resin is not particularly limited, but is preferably 0.926 g / cm 3 More than 0.930g / cm 3 More than 0.935g / cm 3 or more, or 0.940 g / cm 3 or more, 0.970 g / cm 3 Below, 0.965g / cm 3 or less, or 0.960 g / cm 3 The second polyethylene resin may be a low to medium density polyethylene resin.

[0041] The melt flow rate MFR of the second polyethylene resin at 190°C under a load of 2.16 kg is not particularly limited, and may be 15 g / 10 min or less, 10 g / 10 min or less, 5 g / 10 min or less, or 3 g / 10 min or less, or may be 0.5 g / 10 min or more, 0.8 g / 10 min or more, or 1 g / 10 min or more.

[0042] The thickness of skin layer 13 is not particularly limited and can be determined appropriately according to the cost and application, taking into consideration the suitability of the manufacturing method and apparatus, and the suitability for lamination with other layers. From a practical standpoint, the thickness of skin layer 13 may be 0.3 μm or more, 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more, or may be 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less.

[0043] (other skin layers) The other skin layer 11 may be a layer containing a polyethylene resin. The other skin layer 11 may contain, for example, a second polyethylene resin, similar to the skin layer 13. As described above, the base layer 10 does not necessarily have to include the other skin layer 11, but including the other skin layer 11 tends to improve film formation stability during film production.

[0044] The probe drop temperature of the other skin layer 11 may be 180° C. or less, 160° C. or less, or 150° C. or less, from the viewpoint of film formability and impact resistance. On the other hand, the probe drop temperature of the other skin layer 11 may be 100° C. or higher, 120° C. or higher, or 130° C. or higher from the viewpoint of heat resistance.

[0045] From the viewpoint of heat resistance and film formability, the other skin layer 11 may be a layer containing a polypropylene resin. In this case, the probe drop temperature of the other skin layer 11 may be 200 to 260°C.

[0046] The thickness of the other skin layer 11 is not particularly limited and can be appropriately determined according to the cost and application, taking into consideration the suitability of the manufacturing method and apparatus, and the suitability for lamination with other layers. From a practical standpoint, the thickness of the other skin layer 11 may be 0.3 μm or more, 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more, or may be 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less.

[0047] The base layer 10 can be produced by a known co-extrusion method such as an air-cooled inflation method, a water-cooled inflation method, or a T-die casting method. From the viewpoint of versatility, the base layer 10 may be produced by either an inflation method or an air-cooled inflation method. The air-cooled inflation method is a method in which a mold with an annular lip called a ring die (or a crosshead die) is installed at the tip of an extruder, and material is extruded into a tubular shape and continuously molded. More specifically, an air hole is installed in the center of the ring die, and compressed air is blown through the air hole to expand the tube, which is then cooled while being pulled by rollers called pinch rolls, and the film is wound up, thereby producing the base layer 10.

[0048] The obtained substrate layer 10 may be subjected to a surface modification treatment to improve suitability for subsequent processes, as necessary. For example, the surface of the substrate layer 10 may be modified to improve printability or lamination suitability during lamination. Examples of modification treatments include treatments that generate functional groups by oxidizing the film surface, such as corona discharge treatment, plasma treatment, and flame treatment, and modification treatments using a wet process that forms an easy-adhesion layer by coating.

[0049] <Gas barrier layer> The gas barrier layer 20 is a layer provided between the substrate layer 10 and the sealant layer 30 from the viewpoint of improving gas barrier properties against water vapor and oxygen. The gas barrier layer 20 is preferably a transparent layer. The gas barrier layer 20 has an intermediate layer 21 and an inorganic oxide layer 22. The gas barrier layer 20 may further have a gas barrier coating layer or an anchor coat layer, which will be described later.

[0050] (middle class) The intermediate layer 21 is a layer containing a polyethylene resin. Examples of the polyethylene resin include low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), high-density polyethylene resin (HDPE), linear low-density polyethylene resin (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, and ethylene-(meth)acrylic acid copolymer. The polyethylene resin contained in the intermediate layer may be high-density polyethylene resin (HDPE).

[0051] The intermediate layer 21 may contain additives such as antistatic agents, ultraviolet absorbers, plasticizers, lubricants, etc. as trace components. The intermediate layer 21 may be subjected to a surface treatment such as plasma treatment to improve adhesion to the layer to be laminated.

[0052] The intermediate layer 21 may be a stretched film or a non-stretched film, but a stretched film is preferred from the viewpoint of processability for imparting gas barrier properties, and a non-stretched film is preferred from the viewpoint of adhesion of the laminate. Examples of stretched films include uniaxially stretched films and biaxially stretched films, but a biaxially stretched film is preferred from the viewpoint of impact resistance of the gas barrier layer 20.

[0053] The thickness of the intermediate layer 21 is not particularly limited, but may be, for example, 100 μm or less, 40 μm or less, or 35 μm or less from the viewpoint of further improving the flexibility of the gas barrier layer 20. On the other hand, the thickness of the intermediate layer 21 may be 10 μm or more, 12 μm or more, or 15 μm or more from the viewpoint of strength.

[0054] (inorganic oxide layer) The inorganic oxide layer 22 contains an inorganic oxide. Examples of inorganic oxides include aluminum oxide, silicon oxide, tin oxide, magnesium oxide, and mixtures thereof. From the viewpoints of more easily maintaining gas barrier properties even after heat sterilization treatment, more excellent heat resistance, and transparency, the inorganic oxide layer 22 may contain at least one selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide.

[0055] The thickness of the inorganic oxide layer 22 may be 5 to 150 nm. If the thickness of the inorganic oxide layer 22 is 5 nm or more, it is easy to form a layer with a uniform and sufficient film thickness, and sufficient gas barrier properties can be achieved. If the thickness of the inorganic oxide layer 22 is 150 nm or less, flexibility can be imparted to the inorganic oxide layer 22, and even if an external load such as bending or pulling is applied to the inorganic oxide layer 22 after its formation, the generation of cracks in the inorganic oxide layer 22 can be suppressed. The thickness of the inorganic oxide layer 22 may be 6 nm or more, or 8 nm or more, or may be 100 nm or less, or 50 nm or less.

[0056] The inorganic oxide layer 22 can be formed by a typical vacuum deposition method. It can also be formed by other thin film formation methods such as sputtering, ion plating, plasma vapor deposition (CVD), etc. The inorganic oxide layer 22 may be formed by vacuum deposition from the viewpoint of excellent productivity.

[0057] The heating method for the vacuum deposition method can be any of electron beam heating, resistance heating, and induction heating. The vacuum deposition method may be electron beam heating in view of the wide range of evaporation material options. In view of improving the adhesion between the intermediate layer 21 and the inorganic oxide layer 22 and the density of the inorganic oxide layer 22, deposition may be performed by a plasma-assisted method, an ion-beam-assisted method, or the like. In view of improving the transparency of the inorganic oxide layer 22, deposition may be performed by reactive deposition.

[0058] (Gas barrier coating layer) The gas barrier coating layer is a layer provided on the inorganic oxide layer 22 for the purpose of protecting the inorganic oxide layer 22 and complementing the gas barrier properties.

[0059] The gas barrier coating layer may be a heat-cured product of a composition containing at least one of a water-soluble polymer and a hydrolyzate thereof, and at least one selected from the group consisting of a metal alkoxide, a silane coupling agent, and a hydrolyzate thereof.

[0060] Examples of the water-soluble polymer include hydroxyl group-containing polymer compounds such as polyvinyl alcohol, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, etc. The water-soluble polymer may be polyvinyl alcohol (PVA) from the viewpoint of excellent gas barrier properties.

[0061] Examples of metal alkoxides include compounds represented by the following general formula: M(OR 11 ) m (R 12 ) n-m …(1) In the above formula (1), R 11 and R 12 R are each independently a monovalent organic group having 1 to 8 carbon atoms. 11 and R 12 may each independently be an alkyl group such as a methyl group or an ethyl group. M represents an n-valent metal atom such as Si, Ti, Al, or Zr. m is an integer of 1 to n. 11 and R 12 If there are multiple, R 11 Comrades or R 12 They may be the same or different.

[0062] Examples of metal alkoxides include tetraethoxysilane [Si(OC2H5)4], triisopropoxyaluminum [Al(O-2'-C3H7)3], etc. The metal alkoxide may be tetraethoxysilane or triisopropoxyaluminum, from the viewpoint that it is relatively stable in an aqueous solvent after hydrolysis.

[0063] Examples of the silane coupling agent include compounds represented by the following general formula: Si(OR 21 ) p (R 22 ) 3-p R 23 …(2) In the above formula (2), R 21represents an alkyl group such as a methyl group or an ethyl group, and R 22 represents a monovalent organic group such as an alkyl group, an aralkyl group, an aryl group, an alkenyl group, an alkyl group substituted with an acryloxy group, or an alkyl group substituted with a methacryloxy group, and R 23 represents a monovalent organic functional group, and p represents an integer of 1 to 3. 21 or R 22 If there are multiple, R 21 Comrades or R 22 R may be the same or different. 23 Examples of the monovalent organic functional group represented by the formula (I) include a monovalent organic functional group containing a glycidyloxy group, an epoxy group, a mercapto group, a hydroxyl group, an amino group, an alkyl group substituted with a halogen atom, and an isocyanate group.

[0064] Examples of the silane coupling agent include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and 3-isocyanate alkylalkoxysilane.

[0065] The silane coupling agent may be a multimer, such as a dimer or trimer, of the above-mentioned silane coupling agent. A preferred multimer is a trimer, such as 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate, which is a condensation polymer of 3-isocyanatoalkylalkoxysilane. Adding 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate to a water-soluble polymer can improve the water resistance of the gas barrier coating layer through hydrogen bonding.

[0066] The gas barrier coating layer can be formed using a composition (hereinafter referred to as an overcoat agent) obtained by adding a water-soluble polymer and a metal alkoxide and / or a silane coupling agent to water or a water / alcohol mixture. The overcoat agent can be prepared, for example, by mixing a solution of a hydroxyl-containing polymer compound, which is a water-soluble polymer, in an aqueous solvent (water or a water / alcohol mixture) with a metal alkoxide and / or a silane coupling agent directly, or with a solution that has been previously treated, such as by hydrolysis. Additives such as an isocyanate compound, a dispersant, a stabilizer, a viscosity modifier, and a colorant may also be added to the overcoat agent.

[0067] The amount of metal alkoxide in the overcoating agent can be 1 to 4 parts by mass, or may be 2 to 3 parts by mass, per 1 part by mass of the water-soluble polymer, from the viewpoints of maintaining adhesion to the inorganic oxide layer 22 and gas barrier properties. Similarly, the amount of silane coupling agent can be 0.01 to 1 part by mass, or may be 0.1 to 0.5 parts by mass, per 1 part by mass of the water-soluble polymer. When a silane compound (alkoxysilane) is used as the metal alkoxide, the amount of the silane compound (metal alkoxide and silane coupling agent) in the overcoating agent can be 1 to 4 parts by mass, or may be 2 to 3 parts by mass, per 1 part by mass of the water-soluble polymer.

[0068] The overcoating agent can be applied onto the inorganic oxide layer 22 by, for example, dipping, roll coating, gravure coating, reverse gravure coating, air knife coating, comma coating, die coating, screen printing, spray coating, gravure offset, etc. The coating film obtained by applying the overcoating agent can be dried by, for example, hot air drying, hot roll drying, high frequency irradiation, infrared irradiation, UV irradiation, or a combination thereof.

[0069] The temperature at which the coating film is dried can be, for example, 50 to 150° C., and preferably 70 to 100° C. By keeping the drying temperature within the above range, the occurrence of cracks in the gas barrier layer 20 can be further suppressed, and excellent barrier properties can be achieved.

[0070] The gas barrier coating layer may be formed using an overcoat agent containing a water-soluble polymer (e.g., polyvinyl alcohol-based resin) and a silane compound. The overcoat agent may contain an acid catalyst, an alkali catalyst, a photopolymerization initiator, or the like, as needed. Examples of the silane compound include silane coupling agents, polysilazanes, and siloxanes, such as tetramethoxysilane, tetraethoxysilane, glycidoxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, and hexamethyldisilazane.

[0071] The gas barrier coating layer described above can maintain excellent gas barrier properties even after heat sterilization. Therefore, when the laminate 100 is used as a packaging material for heat sterilization, the packaging material has excellent adhesion even after heat sterilization. In addition, the gas barrier coating layer described above is preferable because it has sufficient transparency, flex resistance, and stretch resistance, and there is no risk of generating harmful substances such as dioxins.

[0072] The thickness of the gas barrier coating layer may be 0.05 μm or more, or 0.1 μm or more, from the viewpoint of excellent gas barrier properties, and may be 1 μm or less, or 0.5 μm or less, from the viewpoints of easily forming a uniform coated surface, reducing the load due to drying, flexibility, and production costs.

[0073] (Anchor coat layer) In order to improve the adhesion between the intermediate layer 21 and the inorganic oxide layer 22, an anchor coat layer may be provided between the intermediate layer 21 and the inorganic oxide layer 22.

[0074] The anchor coat layer can be formed from a coating liquid containing a resin such as an acrylic resin, an epoxy resin, an acrylic urethane resin, a polyester polyurethane resin, a polyether polyurethane resin, etc. From the viewpoints of heat resistance and interlayer adhesive strength, the anchor coat layer may be formed from a coating liquid containing an acrylic urethane resin or a polyester polyurethane resin.

[0075] The method for applying the coating liquid that forms the anchor coat layer may be a known coating method, such as an immersion method (dipping method), or a method using a spray, a coater, a printer, a brush, etc. In addition, examples of the types of coaters and printers used in these methods and the coating methods thereof include gravure coaters such as direct gravure, reverse gravure, kiss reverse gravure, and offset gravure, reverse roll coaters, microgravure coaters, coaters combined with a chamber doctor, air knife coaters, dip coaters, bar coaters, comma coaters, and die coaters.

[0076] The method for drying the anchor coat layer is not particularly limited, but examples include natural drying, drying in an oven set at a predetermined temperature, and using a dryer attached to a coater, such as an arch dryer, floating dryer, drum dryer, infrared dryer, etc. Drying conditions can be selected appropriately depending on the drying method, and for example, in a method of drying in an oven, drying may be performed at 60 to 100°C for about 1 second to 2 minutes.

[0077] The thickness of the anchor coat layer may be 0.01 μm or more, 0.03 μm or more, or 0.05 μm or more from the viewpoint of easily obtaining sufficient adhesion between layers, and may be 5 μm or less, 3 μm or less, or 2 μm or less from the viewpoint of excellent gas barrier properties.

[0078] <Heat-resistant layer> The heat-resistant layer is provided to prevent defects during heat sealing during bag making and filling / sealing, and to ensure heat-sealing suitability. Specifically, it can prevent appearance defects such as wrinkles that occur when the base material layer comes into contact with the heat seal bar, and the base material layer from adhering (being removed) to the heat seal bar due to thermal welding. Furthermore, in a packaging bag in the form of a standing pouch, it can prevent thermal welding between the base material layers when the base material layers are placed face to face at the base material portion and bottom sealed. For this purpose, the heat-resistant layer may be provided as the outermost layer of the laminate.

[0079] The thickness of the heat-resistant layer is adjusted according to the total thickness of the laminate, but from the viewpoint of improving heat resistance and reducing the amount of heat required for heat sealing, it may be, for example, 0.1 to 5.0 μm, 0.2 to 4.0 μm, or 0.3 to 2.0 μm.

[0080] The heat-resistant layer provided on the outer surface of the base layer must be heat-resistant enough to withstand heat, for example, 140°C, without softening, melting, or decomposition during heat sealing. Therefore, the heat-resistant layer preferably contains a thermosetting resin or a resin with a melting point of 160°C or higher. The resin is preferably at least one resin selected from the group consisting of polyacrylic, polyurethane, polyester, polyamide, polyamideimide, vinyl chloride-vinyl acetate copolymer, and epoxy. Among these, acrylic resin, urethane resin, vinyl chloride-vinyl acetate copolymer, polyester resin, and mixtures thereof are more preferred.

[0081] In order to form a urethane bond, a two-component curing resin is preferred, and the curing agent is not particularly limited as long as it can react with the two-component curing resin and cure it, but polyvalent isocyanate compounds are preferred, and examples include aromatic diisocyanate compounds such as tolylene diisocyanate and 4,4-diphenylmethane diisocyanate, aliphatic diisocyanate compounds such as xylylene diisocyanate and hexamethylene diisocyanate, polymers of these, and derivatives of these.

[0082] The heat-resistant layer may contain a matting agent component. By containing the matting agent component in the heat-resistant layer, it is possible to improve heat resistance and adjust slip properties. Examples of the matting agent component include inorganic particles. Examples of inorganic particles include silica, talc, calcium carbonate, precipitated barium sulfate, alumina, acid clay, clay, magnesium carbonate, carbon black, tin oxide, titanium white, mica, and glass.

[0083] The heat-resistant layer may contain a wax such as polyethylene wax, polypropylene wax, polytetrafluoroethylene wax, montan wax, paraffin wax, microcrystalline wax, amide wax, petroleum wax, etc., or a lubricant such as liquid paraffin, white petrolatum, castor oil, etc. When the heat-resistant layer contains a lubricant, it can impart appropriate slipperiness to the laminate when dried, thereby improving the production efficiency of the packaging material.

[0084] The heat-resistant layer can be formed by applying a coating liquid for the heat-resistant layer. The coating amount of the coating liquid for the heat-resistant layer after drying is 0.1 to 5 g / m 2 It is preferable that the density is 0.3 to 3 g / m 2 If the coating amount is within the above range, the amount of residual solvent is small, and blocking during film formation can be suppressed.

[0085] The method for applying the heat-resistant layer coating solution is not particularly limited, and coating methods such as roll coating, gravure coating, knife coating, dip coating, and spray coating can be used.

[0086] Suitable examples of the solvent include alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, n-butyl alcohol, and isobutyl alcohol; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as ethyl acetate, n-propyl acetate, n-butyl acetate, and isobutyl acetate; glycol-based solvents such as 2-butoxyethanol and propylene glycol monomethyl ether; and hydrocarbon-based solvents such as toluene, xylene, n-hexane, and methylcyclohexane.

[0087] When a heat-resistant layer is formed by applying and drying (curing) a coating agent, an adhesion-imparting layer may be formed on the substrate layer to improve adhesion between the substrate layer and the heat-resistant layer, as long as recyclability is not impaired.

[0088] <Adhesive layer> The adhesive layer is a layer containing at least one type of adhesive and is provided, for example, between the base layer 10 and the gas barrier layer 20, between the base layer 10 and the sealant layer 30 (when the gas barrier layer 20 is not provided), or between the gas barrier layer 20 and the sealant layer 30 to bond the two layers together. The adhesive layer can be formed using a known adhesive. The adhesive may be, for example, a dry lamination adhesive. The dry lamination adhesive is not particularly limited, and examples include ester-based adhesives, ether-based adhesives, and urethane-based adhesives. These adhesives may be one-component curing types or two-component curing types.

[0089] The adhesive layer may be formed using a gas barrier adhesive from the viewpoint of excellent gas barrier properties. Even if minute cracks occur in the inorganic oxide layer 22 or the gas barrier coating layer, the gas barrier adhesive can fill in the cracks and fill in the gaps, thereby preventing a decrease in the gas barrier properties of the laminate 100.

[0090] Gas barrier adhesives are adhesives that can exhibit gas barrier properties after curing. Examples of gas barrier adhesives include epoxy adhesives and polyester / polyurethane adhesives. Specific examples of gas barrier adhesives include "Maxieve" manufactured by Mitsubishi Gas Chemical Company, Inc. and "Paslim" manufactured by DIC Corporation.

[0091] The oxygen permeability of the gas barrier adhesive is, for example, 150 cc / m 2 ·day·atm or less is preferable, and 100cc / m 2 ·day·atm or less is more preferable, and 80cc / m 2 ·day·atm or less is more preferable, and 50cc / m 2 It is particularly preferable that the oxygen permeability is 100 / day / atm or less. When the oxygen permeability is within the above range, the gas barrier properties of the laminate 100 can be sufficiently improved.

[0092] The adhesive layer can be formed using a solvent-based adhesive (an adhesive containing an organic solvent) or a solventless adhesive (an adhesive not containing an organic solvent). These adhesives may be either one-component curing or two-component curing. Examples of such adhesives include urethane-based adhesives, epoxy-based adhesives, and silicone-based adhesives. From the viewpoint of impact resistance, urethane-based adhesives are preferred, and two-component curing urethane-based adhesives are particularly preferred. Furthermore, from the viewpoint of improving oxygen barrier properties, gas barrier adhesives are preferred, and examples of such adhesives include solvent-based epoxy adhesives. From the viewpoint of reducing environmental impact, solventless adhesives can be used.

[0093] The polyol component may be one or a mixture of two or more selected from the group consisting of polyester polyols, polyether polyols, polyether ester polyols, and polyurethane polyols.

[0094] The polyester polyol may be, for example, an ester reaction product of a polycarboxylic acid, a dialkyl ester of a polycarboxylic acid, or a mixture thereof with a glycol-based solvent. The polycarboxylic acid may be, for example, succinic acid, glutaric acid, isophthalic acid, terephthalic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, or dimer acid. The glycol-based solvent may be, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butylene glycol, neopentyl glycol, or 1,6-hexanediol.

[0095] The polyether polyol may be, for example, a polymer of an oxirane compound and a low-molecular-weight polyol. The oxirane compound may be, for example, ethylene oxide, propylene oxide, butylene oxide, or tetrahydrofuran. The low-molecular-weight polyol may be, for example, water, ethylene glycol, propylene glycol, trimethylolpropane, or glycerin.

[0096] The polyetherester polyol may be obtained by reacting, for example, a polycarboxylic acid, a dialkyl ester of a polycarboxylic acid, or a mixture thereof with a polyether polyol.

[0097] The polyurethane polyol may be, for example, the reaction product of a polyester polyol, a polyether polyol, or a polyetherester polyol with a polyisocyanate monomer.

[0098] The polyisocyanate component may be an aliphatic polyisocyanate, an aromatic polyisocyanate, or a mixture thereof.

[0099] The aliphatic polyisocyanate may be, for example, a polyisocyanate monomer, a polyisocyanate derivative, or a polyisocyanate-terminated prepolymer. The polyisocyanate monomer may be, for example, tetramethylene diisocyanate, isopropylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, or trimethylhexamethylene diisocyanate. The polyisocyanate derivative may be, for example, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, lysine diisocyanate, or isophorone diisocyanate.

[0100] The aromatic polyisocyanate may be, for example, a polyisocyanate monomer, a polyisocyanate derivative, or a polyisocyanate-terminated prepolymer. The polyisocyanate monomer may be, for example, tolylene diisocyanate, phenylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, or tetramethylxylylene diisocyanate. The polyisocyanate derivative may be, for example, an isocyanurate derived from the polyisocyanate monomer. The polyisocyanate-terminated prepolymer may be a bifunctional polyisocyanate containing terminal isocyanate groups obtained by reacting a polyisocyanate monomer with a bifunctional polyol compound such as polypropylene glycol. The polyisocyanate-terminated prepolymer may also be a multifunctional polyisocyanate containing terminal isocyanate groups obtained by reacting a polyisocyanate monomer with a trifunctional or higher functional polyol compound such as trimethylolpropane.

[0101] When the laminate 100 comprises a base layer 10, a gas barrier layer 20, and a sealant layer 30, it is preferable to provide an adhesive layer formed from a solvent-free adhesive between the base layer 10 and the gas barrier layer 20, from the viewpoint of suppressing dimensional changes in the printed layer provided on the base layer. Furthermore, from the viewpoint of suppressing the effects of the contents components on the solvent-free adhesive layer, such as a decrease in adhesion, it is preferable to provide an adhesive layer formed from a gas barrier adhesive between the gas barrier layer 20 and the sealant layer 30. On the other hand, although the adhesive components are similar, solvent-based adhesives generally have higher molecular weights than solventless adhesives, so solvent-based adhesives are superior in terms of initial adhesion immediately after lamination and adhesion strength after aging and hardening. Solvent-based adhesives also have excellent resistance to contents, so they have the advantage of being less likely to lose adhesive strength after the contents are stored.

[0102] The adhesive layer can be formed by applying an adhesive to a target layer by, for example, a bar coating method, a dipping method, a roll coating method, a gravure coating method, a reverse coating method, an air knife coating method, a comma coating method, a die coating method, a screen printing method, a spray coating method, a gravure offset method, or the like to form a coating film, and then drying and curing the coating film.

[0103] When a solvent-based adhesive is used as the adhesive, a laminated film can be obtained by applying the solvent-based adhesive to the intermediate layer 21 by a general dry lamination method, bonding it to the sealant layer 30, and then thermally drying to remove the solvent. Thermal drying can be carried out using an oven or the like under conditions such as a temperature of 50 to 80°C, an oven length of 5 to 20 m, and a processing speed of 50 to 200 m / min.

[0104] When a solvent-free adhesive is used as the adhesive, the solvent-free adhesive can be applied to the intermediate layer 21 and then bonded to the sealant layer 30 by the method described above, thereby obtaining a laminated film.

[0105] Next, the base layer 10 and the laminated film obtained above are bonded together using a solventless adhesive. The bonding of the base layer 10 and the laminated film can be carried out, for example, by using a solventless adhesive laminator equipped with a device for applying a heated and melted solventless adhesive to a substrate by roll coating.

[0106] When the solventless adhesive is, for example, a two-component curing urethane adhesive, a base agent containing a polyol component and a curing agent containing a polyisocyanate component are typically supplied separately and mixed before reaching the coating section of the laminating device. The mixed adhesive is supplied, for example, between a doctor roll and a metering roll, which rotate in opposite directions in the laminating device. The supplied adhesive is transferred from the metering roll to a coating roll and coated on the surface of the substrate layer 10 (on the side of the printed layer, if any) supplied between the coating roll and the impression roll.

[0107] The adhesive-coated substrate layer 10 is bonded to a laminate film and wound up by a winder to obtain a laminate 100. The obtained laminate 100 is preferably aged at 20 to 50° C. for 24 to 96 hours. The doctor roll, metering roll, and coating roll described above are examples of the configuration of a laminating device, and the configuration may vary depending on the laminating device used.

[0108] Here, in order to make the solvent-free adhesive have a low viscosity so that it can be applied without a solvent, it is preferable to heat a metal roll such as a doctor roll or a coating roll to melt the solvent-free adhesive and reduce the viscosity before applying and laminating.

[0109] Therefore, it is preferable to set the heating temperature of the solvent-free adhesive within the range of 50 to 100°C. Furthermore, the heating temperature is preferably set within the range of 50 to 100°C so that the viscosity of the solvent-free adhesive at that heating temperature is 200 to 2000 mPa·s. From the viewpoint of obtaining a laminate 100 having a more uniform coating appearance, the heating temperature is more preferably a temperature at which the viscosity of the solvent-free adhesive is 300 to 1500 mPa·s, and even more preferably a temperature at which the viscosity is 500 to 1000 mPa·s. Furthermore, from the viewpoint of further improving the lamination strength of the laminate 100 and further suppressing the expansion and contraction of the base material layer 10, the heating temperature is more preferably 50 to 90°C, and even more preferably 50 to 80°C.

[0110] Because a solvent-free adhesive is used to bond the base layer 10 and the laminate film, long-term thermal drying (such as oven drying) at high temperatures to remove the solvent is not required, which prevents the base layer 10 from expanding and contracting, resulting in a laminate 100 with good dimensional stability of the pattern on the printing layer, for example.

[0111] When a solvent-based adhesive is used, the temperature at which the coating film is dried may be, for example, 30 to 200° C., and preferably 50 to 180° C. The temperature at which the coating film is cured may be, for example, 20 to 70° C., and preferably 30 to 60° C. By keeping the drying and curing temperatures within the above ranges, it is possible to prevent cracks from occurring in the inorganic oxide layer 22 and the adhesive layer, and it is possible to sufficiently improve the gas barrier properties of the laminate 100.

[0112] The thickness of the adhesive layer is preferably 0.1 to 20 μm, more preferably 0.5 to 10 μm, and even more preferably 1 to 5 μm. When the thickness of the adhesive layer is 0.1 μm or more, cushioning properties that absorb external impacts can be obtained, making it easier to prevent cracking of the inorganic oxide layer 22 and further improving the gas barrier properties of the laminate 100. When the thickness of the adhesive layer is 20 μm or less, the flexibility of the laminate 100 tends to be sufficiently maintained.

[0113] When an adhesive layer is provided between the gas barrier layer 20 and the sealant layer 30, the adhesive layer can be formed directly on the surface of the inorganic oxide layer 22 or the gas barrier coating layer from the viewpoint of suppressing cracking of the inorganic oxide layer 22. That is, the adhesive layer may be formed by applying an adhesive directly to the surface of the inorganic oxide layer 22 or the gas barrier coating layer, followed by drying and curing. In this case, the thickness of the adhesive layer is preferably 50 times or more the thickness of the inorganic oxide layer 22. When the thickness of the adhesive layer is 50 times or more the thickness of the inorganic oxide layer 22, cushioning properties that absorb external impacts can be obtained, making it easier to prevent the inorganic oxide layer 22 from cracking and further improving the gas barrier properties of the laminate 100. The thickness of the adhesive layer is preferably 300 times or less the thickness of the inorganic oxide layer 22. When the thickness of the adhesive layer is 300 times or less the thickness of the inorganic oxide layer 22, the laminate 100 has excellent flexibility and processability and can reduce costs.

[0114] <Sealant layer> The sealant layer 30 is a layer made of, for example, a polyethylene resin. The sealant layer 30 is a layer that is bonded by heat sealing when the laminate 100 is used to form a packaging material such as a packaging bag. The polyethylene resin that makes up the sealant layer 30 may be low-density polyethylene resin (LDPE), linear low-density polyethylene resin (LLDPE), or very-low-density polyethylene resin (VLDPE) from the viewpoint of excellent heat sealing properties. From the viewpoint of environmental impact, the sealant layer 30 may be made of biomass-derived polyethylene resin or recycled polyethylene resin. The sealant layer 30 may be made of, for example, a non-oriented polyethylene film.

[0115] Low-density polyethylene resin has a density of 0.900 g / cm 3 More than 0.925g / cm 3 As a linear low-density polyethylene resin, polyethylene having a density of 0.900 g / cm3 or less can be used. 3 More than 0.925g / cm 3 Ultra-low density polyethylene resins can be used with a density of 0.900 g / cm or less. 3 Less than 100% polyethylene can be used.

[0116] The sealant layer 30 may contain a resin other than polyethylene resin. Examples of resins other than polyethylene resin include olefin-based resins such as ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, ethylene-(meth)acrylic acid copolymer, homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-α-olefin copolymer, and polybutene. The sealant layer 30 may contain additives such as antioxidants, lubricants, antiblocking agents, and antistatic agents.

[0117] The thickness of the sealant layer 30 may be, for example, 20 μm or more, 40 μm or more, or 50 μm or more. When the thickness of the sealant layer 30 is 20 μm or more, sufficient heat seal strength can be achieved. The thickness of the sealant layer 30 may be, for example, 200 μm or less, 170 μm or less, or 150 μm or less. When the thickness of the sealant layer 30 is 200 μm or less, excellent processability can be achieved.

[0118] <Print layer> The printed layer 40 is provided at a position visible from the outside of the laminate 100 for the purpose of displaying information about the contents, identifying the contents, or improving the design of the packaging bag. The printed layer 40 can be provided on the surface of the skin layer 13 of the base material layer 10 or on the surface of another skin layer 11, depending on the purpose.

[0119] There are no particular limitations on the method for forming the printed layer 40, and known printing methods and printing inks can be applied. The printing method and printing ink are appropriately selected in consideration of, for example, printability for each layer of the laminate 100, design such as color tone, adhesion, and safety as a food container.

[0120] Examples of printing methods include gravure printing, offset printing, gravure offset printing, flexographic printing, and inkjet printing. Among these, gravure printing is preferred from the viewpoints of productivity and high-definition patterns. Furthermore, examples of curing methods for printing inks include heat curing, UV curing, and EB curing.

[0121] In order to improve the adhesion of the printing layer 40, the surface of the layer forming the printing layer may be subjected to pretreatment such as corona treatment, plasma treatment, or flame treatment, or a coating layer such as an easy-adhesion layer may be provided.

[0122] The thickness of the printed layer 40 can be set to, for example, 1 to 3 μm from the viewpoint of realizing good tone of the image.

[0123] <Packaging materials> The laminate 100 can be used as a packaging material for forming packaging bags, etc. Specifically, it can be used as a packaging material for flat bags, three-sided bags, two-sided bags, gusseted bags, standing pouches, pouches with spouts, pouches with beaks, etc. It can be said that the packaging material made into bags from the laminate 100 is a packaging material that is excellent in recyclability, has no distortion of the pattern (little distortion), and is excellent in impact resistance.

[0124] The laminate 100 can be used as a packaging material as well as a film for electronic devices, a film for solar cells, a film for fuel cells, a substrate film, and the like. [Example]

[0125] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0126] <Preparation of base layer> A polyethylene (PE) film having the structure shown in Table 1 was prepared as the substrate layer. In the table, MDPE stands for medium density polyethylene, HDPE stands for high density polyethylene, and the numbers in parentheses following the material names indicate the density (g / cm 3The column for the thickness of the base layer indicates the "total thickness (thickness of other skin layers / thickness of core layer / thickness of skin layer)."

[0127] A printed layer (thickness: 1 μm) was formed on the skin layer side of each film by corona treating the skin layer, printing a design using flexographic printing, and drying it in a drying oven at 70°C. A heat-resistant layer was formed on the surface of the other skin layer of the film of Example 3. The heat-resistant layer was formed by mixing a base agent (LG6720 weak matte varnish) and a curing agent (LG curing agent D) manufactured by Tokyo Ink Co., Ltd. in a mass ratio of 9:1, applying the mixture using a coater, and drying it (thickness: 1.2 μm).

[0128] <Preparation of gas barrier layer> An unstretched film of high-density polyethylene (HDPE) was prepared as the intermediate layer. One side of this film was corona-treated, and then a transparent silica vapor-deposited film (inorganic oxide layer) made of silicon oxide was formed on it using a vacuum deposition device with electron beam heating.

[0129] <Preparing the sealant layer> As the sealant layer, an unstretched film of linear low-density polyethylene resin (LLDPE) was prepared.

[0130] <Preparing the adhesive> A urethane adhesive, which is a solvent-free adhesive, and an epoxy adhesive, which is a gas barrier adhesive, were prepared. (Urethane adhesive: solvent-free adhesive) A urethane adhesive was obtained by mixing 100 parts by mass of Takelac A670B (manufactured by Mitsui Chemicals, Inc.) with 100 parts by mass of Takenate A670A (manufactured by Mitsui Chemicals, Inc.). (Epoxy adhesive: gas barrier adhesive) An epoxy adhesive was obtained by mixing 23 parts by mass of a solvent made by mixing ethyl acetate and methanol in a mass ratio of 1:1 with 16 parts by mass of Maxieve C93T (manufactured by Mitsubishi Gas Chemical Co., Ltd.) and 5 parts by mass of Maxieve M-100 (manufactured by Mitsubishi Gas Chemical Co., Ltd.).

[0131] <Preparation of laminate> The substrate layer (printed layer side) and the gas barrier layer (intermediate layer side) were laminated using a dry lamination method with a urethane adhesive, and the gas barrier layer (silica vapor deposition film side) and the sealant layer were laminated using a dry lamination method with an epoxy adhesive. This resulted in a laminate with a layer structure of (heat-resistant layer) / substrate layer / printed layer / urethane adhesive layer / intermediate layer / silica vapor deposition film / epoxy adhesive layer / sealant layer. The resulting laminate was aged at 40°C for 4 days. The layer structure of each laminate is shown in Table 1.

[0132] [evaluation] The laminates obtained in each example were evaluated for the following items, and the results are shown in Table 1.

[0133] <Recyclability> The content (mass%) of polyethylene resin in the laminate obtained in each example was calculated based on the following formula: All laminates were rated A (polyethylene resin content of 90 mass% or more). {(mass of base layer + mass of intermediate layer + mass of sealant layer) / mass of entire laminate} x 100

[0134] <Tip drop temperature> The probe drop temperature (softening point) of each layer of the substrate was measured using an atomic force microscope equipped with a nanothermal microscope consisting of a cantilever (probe) with a heating mechanism. First, the substrate layer was embedded in a visible light curing resin to obtain a measurement sample, which was then cross-sectioned in a direction parallel to the TD direction using a diamond knife of a cryo-ultramicrotome in a −140°C environment.

[0135] After measuring the shape of the measurement sample with a 10 μm field of view in AC mode after cross-section cutting, the cantilever (probe) was separated from the sample by 5 to 10 μm in the Z direction. In this state, the detrend correction function of the instrument was used in contact mode with a maximum applied voltage of 6 V and a heating rate of 0.5 V / s to correct for changes in the deflection of the cantilever (probe) due to the applied voltage. Then, in contact mode, the cantilever was brought into contact with the sample so that the change in deflection before and after contact between the cantilever and the sample was 0.2 V. While maintaining a constant deflection value, a voltage was applied to the cantilever at a maximum applied voltage of 6 V and a heating rate of 0.5 V / s to heat the sample. The change in Z displacement during this time was recorded, and the measurement was stopped when the Z displacement changed from rising to falling and fell by 50 nm from the point of change. If the Z displacement did not drop by 50 nm from the change point and reached the maximum applied voltage, the maximum applied voltage during detrend correction and measurement was increased by 0.5 V and the measurement was repeated. The applied voltage at which the recorded Z displacement was maximized was converted into a temperature and used as the probe drop temperature. This measurement was performed at 10 points within a 10 μm field of view, and the average value was used. To convert the applied voltage to temperature, calibration curves were created using polycaprolactone (melting point 60°C), low-density polyethylene resin (112°C), polypropylene resin (166°C), and polyethylene terephthalate resin (255°C). The melting points were measured using a differential scanning calorimeter (DSC) at a heating rate of 5°C / min. The measurement method was the same as for the samples, except that the maximum applied voltages during detrend correction and measurement were 3.5 V for polycaprolactone, 5.5 V for low-density polyethylene resin, 6.5 V for polypropylene, and 7.8 V for polyethylene terephthalate resin. The relationship between the applied voltage and melting point at which the Z displacement was maximized during measurement of each calibration sample was approximated by a cubic function using the least-squares method to create a calibration curve, and the applied voltage during sample measurement was converted to temperature.

[0136] <Printability (heat resistance)> The pattern on the laminate obtained in each example was visually observed, and the dimensional change of the pattern was evaluated using a Mylar scale based on the following evaluation criteria. ○: The difference between the dimensions (circumferential length) of the plate cylinder in flexographic printing and the corresponding dimensions of the image on the laminate was ±3 mm or less, and the image distortion was small. In addition, the image was not rubbed or blurred. ×: The difference between the peripheral length of the plate cylinder in flexographic printing and the corresponding dimensions of the image on the laminate exceeded ±3 mm, resulting in significant distortion of the image. In addition, the image was rubbed or blurred.

[0137] <Adhesion> A 15 mm wide strip test piece was cut out from the laminate obtained in each example, and the laminate strength between the base layer and intermediate layer was measured in accordance with JIS Z 1707 using a Tensilon universal testing machine RTC-1250 manufactured by Orientec Co., Ltd. The measurement was performed using a T-peel test at a peel rate of 300 mm / min, and the results were evaluated according to the following criteria. ◯: The laminate strength was 2N / 15mm or more. ×: The laminate strength was less than 2 N / 15 mm.

[0138] <Impact resistance (drop test)> Using the laminate obtained in each example, a standing packaging bag measuring 300 mm in height, 200 mm in width, and 50 mm in width at the bottom was produced. 1200 ml of cold water was filled into this packaging bag and dropped from a height of 1 m up to 10 times. After each drop, it was checked whether water had leaked from the packaging bag, and the results were evaluated according to the following criteria. ○: The bag did not break even after being dropped 10 times, and no water leakage was observed. ×: The bag broke and water leakage was observed within 10 drops.

[0139] [Table 1] [Explanation of symbols]

[0140] 10...substrate layer, 11...other skin layer, 12...core layer, 13...skin layer, 20...gas barrier layer, 21...intermediate layer, 22...inorganic oxide layer, 30...sealant layer, 40...printed layer, 100...laminated body.

Claims

1. A laminate comprising a substrate layer and a sealant layer, the base material layer has a core layer and a skin layer on the sealant layer side in this order, the core layer has a probe drop temperature of more than 180°C, and the skin layer has a probe drop temperature of 180°C or less; The laminate, wherein the core layer, the skin layers, and the sealant layer comprise a polyethylene resin.

2. The laminate according to claim 1 , wherein the thickness of the skin layer is 0.3 μm or more and 50 μm or less.

3. the laminate comprises the base material layer, an intermediate layer having an inorganic oxide layer, and the sealant layer in this order; The laminate of claim 1 , wherein the intermediate layer comprises a polyethylene resin.

4. The laminate according to claim 1 , wherein the thickness of the core layer is 33% or more of the thickness of the substrate layer.

5. The laminate according to claim 1 , wherein the substrate layer is a stretched film.

6. The laminate according to claim 1 , further comprising a printed layer on the surface of the base layer.

7. 2. The laminate according to claim 1, wherein the substrate layer has another skin layer, the core layer, and the skin layer in this order, the other skin layer having a probe drop temperature of 180°C or less, and the other skin layer contains a polyethylene resin.

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

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