Multilayer sheet and container

Abstract

To provide a multilayer sheet which can be easily broken.SOLUTION: Provided is a multilayer sheet comprising: a first laminate having a surface layer, a first adhesive layer, an oxygen barrier layer, and a second adhesive layer in the stated order; and a second laminate bonded to the second adhesive layer of the first laminate, wherein the second laminate has at least two layers containing a styrene polymer and a plurality of rubber particles, and the tensile elastic modulus of the first laminate is 450 MPa or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to multilayer sheets and containers. [Background technology]

[0002] Packaging containers for packaging food are manufactured, for example, by molding a multilayer sheet having an oxygen barrier layer to prevent food deterioration due to oxygen (see Patent Document 1). In recent years, packaging containers (also called dispensing packages) have been provided in which food such as seasonings is stored in a container body and a lid covering the container body has a slit (hereinafter referred to as a "notch") formed in the lid (see Patent Document 2). When this packaging container is pinched and bent with the fingers, the lid breaks at the notch, allowing the food to be extracted from the broken portion. The multilayer sheet disclosed in Patent Document 1 can be used for the lid of such a packaging container (dispensing package). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 054567 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-83120 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the investigations of the present inventors, there is room for improvement in terms of ease of tearing in the multilayer sheet disclosed in Patent Document 1. Therefore, one aspect of the present invention aims to provide a multilayer sheet that can be easily torn. [Means for solving the problem]

[0005] The present invention includes the following aspects. [1] A multilayer sheet comprising a first laminate having a surface layer, a first adhesive layer, an oxygen barrier layer, and a second adhesive layer in that order, and a second laminate adhered to the second adhesive layer of the first laminate, wherein the second laminate has at least two layers containing a styrene-based polymer and a plurality of rubber particles, and the tensile modulus of the first laminate is 450 MPa or less. [2] The multilayer sheet according to [1], wherein the average particle size of the plurality of rubber particles is 2 μm or less. [3] The multilayer sheet according to [1] or [2], wherein the standard deviation of the average particle size of the plurality of rubber particles is 1 μm or less. [4] The multilayer sheet according to any one of [1] to [3], wherein the thickness of the surface layer is 10 μm or more and 50 μm or less, and the thickness of the oxygen barrier layer is 5 μm or more and 15 μm or less. [5] The multilayer sheet according to any one of [1] to [4], wherein the thickness of each of the first adhesive layer and the second adhesive layer is 10 μm or more and 20 μm or less. [6] A container comprising a container body having an opening and a lid body that closes the opening of the container, wherein the lid body is formed from the multilayer sheet described in any one of [1] to [5].

[0006] The present inventors have investigated the possibility of improving the ease of breaking of the multilayer sheet by improving the ease of breaking of the first laminate, among the first and second laminates described in [1] above. When the second laminate has the same configuration, if the first laminate can be easily broken, the entire multilayer sheet can naturally be easily broken. Therefore, improving the ease of breaking of the first laminate is important. One aspect of the present invention is to improve the ease of breaking of the first laminate by devising the configuration of the first laminate when the second laminate has the same configuration. As a result of the investigation, it was found that when the tensile modulus of the first laminate is 450 MPa or less, the first laminate can be broken more easily than when the tensile modulus exceeds 450 MPa. This means that when the tensile modulus of the first laminate is 450 MPa or less, the entire multilayer sheet can be broken more easily than when the tensile modulus exceeds 450 MPa. In other words, the main feature of one aspect of the present invention is that by using a first laminate having a tensile modulus of elasticity of 450 MPa or less, the ease of breaking of the first laminate is improved, and ultimately the ease of breaking of the entire multilayer sheet is improved. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide a multilayer sheet that can be easily torn. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one embodiment of a multilayer sheet. [Figure 2] FIG. 1 is a perspective view illustrating one embodiment of a container. [Figure 3] FIG. 3 is a schematic cross-sectional view of the lid of the container shown in FIG. 2. [Figure 4] FIG. 3 is a schematic diagram showing an example of use of the container shown in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0010] FIG. 1 is a schematic cross-sectional view showing one embodiment of a multilayer sheet. As shown in FIG. 1, a multilayer sheet 1 according to one embodiment has a structure in which a first laminate 2 and a second laminate 3 are laminated together. The first laminate 2 has a surface layer 21 exposed on one surface (surface) of the multilayer sheet 1, a first adhesive layer 22 provided on the surface opposite the one surface (surface) of the surface layer 21, an oxygen barrier layer 23 bonded to the surface layer 21 via the first adhesive layer 22, and a second adhesive layer 24 provided on the surface of the oxygen barrier layer 23 opposite the surface layer 21. The second laminate 3 has a base layer 31 bonded to the oxygen barrier layer via the second adhesive layer 24, and a back layer 32 provided on the surface of the base layer 31 opposite the second adhesive layer 24 and exposed on the other surface (back) of the multilayer sheet 1.

[0011] The overall thickness of the multilayer sheet 1 may be 200 μm or more, 250 μm or more, or 300 μm or more from the viewpoint of ensuring the strength of molded articles obtained from the multilayer sheet 1. The overall thickness of the multilayer sheet 1 may be 600 μm or less, 500 μm or less, or 400 μm or less from the viewpoint of reducing the production costs of the multilayer sheet 1 and the molded articles obtained from the multilayer sheet 1.

[0012] The thickness of the surface layer 21 may be 10 μm or more, 13 μm or more, or 15 μm or more, and may be 50 μm or less, 48 μm or less, or 46 μm or less. The thickness of the surface layer 21 may be 4% or more of the overall thickness of the multilayer sheet 1, and, if the surface layer 21 has water vapor barrier properties, from the viewpoint of further improving the water vapor barrier properties, the thickness of the surface layer 21 may be preferably 5% or more, more preferably 6% or more. The thickness of the surface layer 21 may be 20% or less, 18% or less, or 16% or less of the overall thickness of the multilayer sheet 1 from the viewpoint of reducing the occurrence of burrs on the edge surfaces during punching of the multilayer sheet and suppressing the problem of poor appearance.

[0013] The thickness of the first adhesive layer 22 and the second adhesive layer 24 may each be 10 μm or more, 12 μm or more, or 14 μm or more to obtain excellent interlayer adhesive strength, and the thickness of the first adhesive layer 22 and the second adhesive layer 24 may each be 20 μm or less, 18 μm or less, or 16 μm or less to suppress problems with poor appearance. The thicknesses of the first adhesive layer 22 and the second adhesive layer 24 may be the same as or different from each other. The thickness of the first adhesive layer 22 and the second adhesive layer 24 may each be 2% or more, 3% or more, or 4% or more, and 10%, 8%, or 6% or less, of the total thickness of the multilayer sheet 1.

[0014] The thickness of the oxygen barrier layer 23 may be 5 μm or more, 6 μm or more, or 7 μm or more from the viewpoint of improving oxygen barrier properties. The thickness of the oxygen barrier layer 23 may be 15 μm or less, 13 μm or less, or 11 μm or less from the viewpoint of obtaining a molded product from the multilayer sheet that is smoother and has a better appearance. The thickness of the oxygen barrier layer 23 may be 1% or more or 2% or more, or 8%, 6%, or 4% or less, of the total thickness of the multilayer sheet 1.

[0015] The thickness of the base layer 31 may be 100 μm or more, 150 μm or more, 170 μm or more, or 190 μm or more from the viewpoint of improving the rigidity of the multilayer sheet. The thickness of the base layer 31 may be 300 μm or less, 270 μm or less, or 250 μm or less from the viewpoint of improving thermal conductivity during thermoforming of the multilayer sheet and obtaining a molded product with a better appearance. The thickness of the base layer 31 may be 50% or more, 53% or more, 55% or more, or 57% or more of the overall thickness of the multilayer sheet 1, and may be 80% or less, 75% or less, 70% or less, or 65% or less.

[0016] The thickness of the back surface layer 32 may be 20 μm or more, 30 μm or more, or 40 μm or more from the viewpoint of improving the appearance. When a pigment is contained in the back surface layer 32 so that the back surface layer 32 can be printed by laser processing, the thickness of the back surface layer 32 may be 90 μm or less, 80 μm or less, or 70 μm or less from the viewpoint of reducing the amount of pigment used and thereby suppressing costs. The thickness of the back surface layer 32 may be 10% or more, 12% or more, or 14% or more, or 30% or less, 25% or less, or 20% or less, of the total thickness of the multilayer sheet 1.

[0017] The thickness of the first laminate 2 may be 20 μm or more, 30 μm or more, 40 μm or more, or 50 μm or more, and may be 120 μm or less, 110 μm or less, 100 μm or less, or 90 μm or less. The thickness of the first laminate 2 may be 10% or more, 12% or more, or 15% or more, and may be 30% or less, 28% or less, or 26% or less, of the overall thickness of the multilayer sheet 1.

[0018] The thickness of the second laminate 3 may be 200 μm or more, 220 μm or more, or 240 μm or more, and may be 300 μm or less, 290 μm or less, or 280 μm or less. The thickness of the second laminate 3 may be 50% or more, 60% or more, or 70% or more, and may be 90% or less, 88% or less, or 86% or less of the overall thickness of the multilayer sheet 1.

[0019] The surface layer 21 preferably contains an olefin polymer in order to impart water vapor barrier properties to the multilayer sheet 1. The olefin polymer contains one or more olefins as monomer units. Examples of the olefin polymer include low-density polyethylene (density: 0.91 g / cm 3 More than 0.93g / cm 3 less than 0.93 g / cm 3 More than 0.94g / cm 3 less than 0.94g / cm 3 More than 0.97g / cm 3Examples of the olefin polymer include linear polyethylene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-based ionomer resin, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-propylene copolymer, homopolypropylene, block polypropylene, and random polypropylene. These olefin-based polymers may be used alone or in combination of two or more. The surface layer 21 preferably contains low-density polyethylene and high-density polyethylene.

[0020] The content of the olefin polymer in the surface layer 21 may be 80 parts by mass or more, 90 parts by mass or more, 95 parts by mass or more, or 100 parts by mass, relative to 100 parts by mass of the total mass of the surface layer 21.

[0021] When the surface layer 21 contains low-density polyethylene and high-density polyethylene, the content ratio of the high-density polyethylene to the total mass of the low-density polyethylene and high-density polyethylene may be 30% by mass or more, 35% by mass or more, or 40% by mass or more, and may be 70% by mass or less, 65% by mass or less, or 60% by mass or less. In this case, the density of the mixture of low-density polyethylene and high-density polyethylene is 0.915 g / cm 3 More than 0.92g / cm 3 or more, or 0.93 g / cm 3 or more, and 3 Below, 0.96g / cm 3 or less, or 0.95 g / cm 3 It may be the following:

[0022] The surface layer 21 may further contain a polymer other than the olefin polymer, and may further contain additives. Examples of the additives include colorants such as pigments and dyes, release agents such as silicone oil and alkyl esters, fibrous reinforcing agents such as glass fibers, granular lubricants such as talc, clay and silica, antistatic agents such as salt compounds of sulfonic acid and alkali metals or polyalkylene glycols, ultraviolet absorbers, and antibacterial agents.

[0023] The first adhesive layer 22 and the second adhesive layer 24 preferably contain a modified olefin polymer from the viewpoint of favorably bonding different layers together. The modified olefin polymer is a polymer obtained by modifying an olefin polymer containing one or more olefins as monomer units. Examples of the modified olefin polymer include a polymer obtained by modifying a homopolymer of an olefin (e.g., an olefin having 2 to 8 carbon atoms), a polymer obtained by modifying a copolymer of an olefin (e.g., an olefin having 2 to 20 carbon atoms), and a polymer obtained by modifying a copolymer of an olefin (e.g., an olefin having 2 to 20 carbon atoms) and a vinyl compound.

[0024] Examples of the olefin include ethylene, propylene, butene-1, 3-methylbutene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, and decene-1. Examples of the vinyl compound include vinyl acetate, vinyl chloride, acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters. The olefin copolymer may be an olefin-based rubber such as an ethylene-butene-1 copolymer or a propylene-butene-1 copolymer.

[0025] The modification method may be an acid modification method under grafting reaction conditions. The acid used for the acid modification may be an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, or tetrahydrophthalic acid, or a derivative thereof such as an acid halide, amide, imide, anhydride, or ester. The derivative may be malenyl chloride, maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, or glycidyl maleate.

[0026] The modified olefin polymer is preferably one or more selected from modified ethylene polymers, modified propylene polymers, modified ethylene-propylene copolymer rubbers, and modified ethylene-butene-1 copolymer rubbers, which are modified with an unsaturated dicarboxylic acid or an anhydride thereof, more preferably maleic acid or an anhydride thereof.

[0027] The modified olefin polymer may be used alone or in combination of two or more. The modified olefin polymer used in the first adhesive layer 22 and the modified olefin polymer used in the second adhesive layer 24 may be the same or different.

[0028] The content of the modified olefin polymer in the first adhesive layer 22 may be 80 parts by mass or more, 90 parts by mass or more, 95 parts by mass or more, or 100 parts by mass, relative to 100 parts by mass of the total mass of the first adhesive layer 22. The content of the modified olefin polymer in the second adhesive layer 24 may be 80 parts by mass or more, 90 parts by mass or more, 95 parts by mass or more, or 100 parts by mass, relative to 100 parts by mass of the total mass of the second adhesive layer 24.

[0029] The first adhesive layer 22 and the second adhesive layer 24 may further contain additives. Examples of the additives are the same as the examples of the additives that the surface layer 21 may contain.

[0030] The oxygen barrier layer 23 has an oxygen barrier property. Specifically, the oxygen barrier layer 23 has an oxygen barrier property of 5 cc / m 2 The oxygen permeability in this specification means the oxygen permeability measured in accordance with JIS K7126-2.

[0031] The oxygen barrier layer 23 contains a polymer that can impart oxygen barrier properties (oxygen barrier polymer). Examples of oxygen barrier polymers include ethylene-vinyl alcohol copolymer, polyamide, polyvinyl alcohol, and polyvinylidene chloride. The oxygen barrier polymers may be used alone or in combination of two or more. From the viewpoint of facilitating extrusion molding of the oxygen barrier layer 23, the oxygen barrier layer 23 preferably contains an ethylene-vinyl alcohol copolymer.

[0032] The ethylene-vinyl alcohol copolymer can be obtained, for example, by saponifying an ethylene-vinyl acetate copolymer. From the viewpoints of further improving the oxygen barrier property of the oxygen barrier layer 23 and facilitating extrusion molding of the oxygen barrier layer 23, the content of ethylene units in the ethylene-vinyl alcohol copolymer may be 10 mol% or more or 20 mol% or less, and 65 mol% or less or 50 mol% or less, based on the total mass of monomer units contained in the copolymer. The saponification degree of the ethylene-vinyl alcohol copolymer may be 90 mol% or more, or 95 mol% or more.

[0033] The content of the oxygen barrier polymer in the oxygen barrier layer 23 may be 80 parts by mass or more, 90 parts by mass or more, 95 parts by mass or more, or 100 parts by mass, relative to 100 parts by mass of the total mass of the oxygen barrier layer 23.

[0034] The oxygen barrier layer 23 may further contain a polymer other than the oxygen barrier polymer, and may further contain additives. Examples of the additives are the same as the examples of the additives that the surface layer 21 may contain.

[0035] The base layer 31 contains a styrene-based polymer and a plurality of rubber particles dispersed in the styrene-based polymer. One example of a method for dispersing a plurality of rubber particles in the styrene-based polymer is graft polymerization of a styrene-based monomer in the presence of a diene-based rubber. This method makes it possible to obtain a graft polymer having a structure in which a plurality of rubber particles are dispersed in the styrene-based polymer. Examples of styrene-based monomers include styrene, α-methylstyrene, p-methylstyrene, dimethylstyrene, pt-butylstyrene, and chlorostyrene. Examples of diene-based rubbers include polybutadiene rubber, polystyrene-butadiene copolymer rubber, polyisoprene rubber, and polychloroprene rubber.

[0036] Examples of styrene polymers in which multiple rubber particles are dispersed include high impact polystyrene (HIPS) and polystyrene-acrylonitrile graft polymer (ABS). HIPS is obtained, for example, by polymerizing styrene monomer in the presence of a diene rubber (typically polybutadiene), and has a sea-island structure in which the styrene polymer forms a continuous phase (sea) and rubber formed by graft polymerization of a portion of the styrene monomer forms dispersed layers (islands). ABS is obtained by polymerizing styrene monomer and acrylonitrile monomer in the presence of a diene rubber (typically polybutadiene), and has a sea-island structure in which a styrene-acrylonitrile copolymer (AS) forms a continuous phase (sea) and rubber formed by graft polymerization of a portion of the styrene monomer and acrylonitrile monomer forms dispersed layers (islands).

[0037] The base layer 31 may further contain a styrene-based polymer in which rubber particles are not dispersed. Examples of the styrene-based polymer in which rubber particles are not dispersed include homopolymers or copolymers of styrene-based monomers such as styrene, α-methylstyrene, p-methylstyrene, dimethylstyrene, pt-butylstyrene, and chlorostyrene, and copolymers of styrene-based monomers with other monomers. Examples of the copolymers of styrene-based monomers with other monomers include styrene-acrylonitrile copolymers. The styrene-based polymers may be used alone or in combination of two or more.

[0038] The base layer 31 preferably contains high impact polystyrene (HIPS) and styrene homopolymer (general-purpose polystyrene, GPPS) from the viewpoints of facilitating thermoforming of a molded article from the multilayer sheet 1 and achieving excellent rigidity of the molded article. In addition, mixing GPPS into HIPS also has the advantage of making it easier to adjust the content of rubber particles in the HIPS.

[0039] In the base layer 31, the content of the styrene-based polymer in which a plurality of rubber particles are dispersed may be 60 parts by mass or more, 65 parts by mass or more, or 70 parts by mass or more, and may be 95 parts by mass or less, 90 parts by mass or less, or 85 parts by mass or less, relative to 100 parts by mass of the total mass of the base layer 31. In the base layer 31, the content of the styrene-based polymer in which rubber particles are not dispersed may be 5 parts by mass or more, 10 parts by mass or more, or 15 parts by mass or more, and may be 40 parts by mass or less, 35 parts by mass or less, or 30 parts by mass or less, relative to 100 parts by mass of the total mass of the base layer 31.

[0040] The content of the styrene-based polymer in the base layer 31 (the total content of the styrene-based polymer in which rubber particles are dispersed and the styrene-based polymer in which rubber particles are not dispersed) may be 90 parts by mass or more, 95 parts by mass or more, or 98 parts by mass or more, relative to 100 parts by mass of the total mass of the base layer 31.

[0041] The average particle size of the multiple rubber particles dispersed in the styrene-based polymer (also referred to as the "average rubber particle size") may be 2 μm or less, 1.8 μm or less, 1.6 μm or less, 1.4 μm or less, or 1.2 μm or less. When the second laminate 3 is formed with a notch and used as a lid (details will be described later), a crack is more likely to propagate from the notch into the second laminate 3 when the lid is bent. As a result, the multilayer sheet can be easily broken regardless of the breaking speed. The average rubber particle size may be 0.1 μm or more, 0.5 μm or more, or 0.8 μm or more. The "average rubber particle size" herein refers to the arithmetic average particle size based on a volume-based particle size distribution measured using a laser diffraction / scattering particle size distribution analyzer.

[0042] The standard deviation of the average particle size of the rubber particles may be 1.0 μm or less, 0.8 μm or less, 0.6 μm or less, or 0.4 μm or less, from the viewpoint of making it possible to break the multilayer sheet 1 more easily without depending on the breaking speed when breaking the multilayer sheet 1. The standard deviation of the average particle size of the rubber particles may be 0.05 μm or more, 0.1 μm or more, or 0.15 μm or more.

[0043] From the viewpoint of improving crack propagation resistance, the content of rubber particles in the base layer 31 may be 7% by mass or less or 6% by mass or less based on the total mass of the base layer 31. From the viewpoint of improving the impact resistance of the multilayer sheet 1, the content of rubber particles in the base layer 31 may be 3% by mass or more or 4% by mass or more based on the total mass of the base layer 31.

[0044] When the multilayer sheet 1 or a molded product thereof is subjected to a printing process such as laser irradiation, the base layer 31 may further contain a white pigment (or a masterbatch containing the white pigment). Examples of white pigments include titanium oxide (titanium white), zinc white (zinc white), lithopone, and white lead.

[0045] The content of the white pigment may be 1 phr or more, 2 phr or more, or 3 phr or more from the viewpoints of obtaining hiding properties and improving the color development of printed characters, and of obtaining light-blocking properties and suppressing discoloration and deterioration of the contents due to light. The content of the white pigment may be 7 phr or less, or 6 phr or less from the viewpoints of suppressing aggregation of the white pigment and suppressing poor appearance of the multilayer sheet 1 and its molded products due to aggregates, etc. The unit phr used here means the parts by mass of the white pigment per 100 parts by mass of the total mass of the polymer contained in the base layer 31.

[0046] The substrate layer 31 may further contain a polymer other than the above-mentioned polymers, and may further contain additives. Examples of additives include compatibilizers that make different components compatible, colorants such as pigments and dyes, release agents such as silicone oil and alkyl esters, fibrous reinforcing agents such as glass fiber, granular lubricants such as talc, clay, and silica, antistatic agents such as salt compounds of sulfonic acid and alkali metals or polyalkylene glycols, ultraviolet absorbers, and antibacterial agents. The substrate layer 31 may also contain scrap resin generated during the manufacturing process of the multilayer sheet or container.

[0047] The back surface layer 32 contains a styrene-based polymer in which a plurality of rubber particles are dispersed. Details of the styrene-based polymer in which a plurality of rubber particles are dispersed are the same as those of the styrene-based polymer in which a plurality of rubber particles are dispersed described for the base material layer 31.

[0048] In the back surface layer 32, the content of the styrene-based polymer in which rubber particles are dispersed may be 90 parts by mass or more, 95 parts by mass or more, or 98 parts by mass or more, relative to 100 parts by mass of the total mass of the back surface layer 32.

[0049] The content of rubber particles in the back surface layer 32 may be 8% by mass or less or 7% by mass or less, based on the total mass of the base layer 31, from the viewpoint of improving crack propagation resistance. The content of rubber particles in the base layer 31 may be 4% by mass or more or 5% by mass or more, from the viewpoint of improving the impact resistance of the multilayer sheet 1.

[0050] When the multilayer sheet 1 or a molded product thereof is subjected to a laser printing process, the back surface layer 32 may further contain a pigment (or a masterbatch containing the pigment) that develops color upon irradiation with a laser (e.g., a YAG laser). Examples of the pigment include mica, titanium oxide, antimony oxide, metal salts such as copper phosphate and sulfate, and black pigments such as carbon black. The content of the pigment may be 0.007% by mass or more or 0.009% by mass, and may be 4.6% by mass or less or 3.2% by mass or less.

[0051] The back surface layer 32 may further contain a polymer other than the above-mentioned polymers, and may further contain an additive. Examples of the additive are the same as the examples of the additive that may be contained in the base material layer 31.

[0052] In the multilayer sheet 1 described above, the first laminate 2 has a tensile modulus of 450 MPa or less. This allows the first laminate 2 to be easily torn, and as a result, the multilayer sheet 1 to be easily torn. The tensile modulus of the first laminate 2 may be 440 MPa or less, 430 MPa or less, 420 MPa or less, 330 MPa or less, or 200 MPa or less, or may be 100 MPa or more, 150 MPa or more, 200 MPa or more, 250 MPa or more, 300 MPa or more, or 340 MPa or more. The tensile modulus here refers to the larger of the tensile modulus of the multilayer sheet 1 in the machine direction (MD) or the tensile modulus in the cross direction (TD), which is perpendicular to the MD direction.

[0053] The layer structure of the multilayer sheet is not limited to the layer structure shown in FIG. 1 described in the above embodiment. For example, in the above embodiment, the second laminate 3 has two layers, a base layer 31 and a back surface layer 32, which are layers containing a styrene-based polymer and a plurality of rubber particles. However, the layer containing a styrene-based polymer and a plurality of rubber particles may have at least two layers, and in other embodiments, may have three or more layers. Also, for example, in the above embodiment, the back surface layer 32 is exposed. However, in other embodiments, a design layer (printed layer) bearing letters or a pattern may be further provided on the surface of the back surface layer opposite the base material layer. This design layer may be a PET film, and may be provided by lamination.

[0054] The method for producing the multilayer sheet is not particularly limited, and a general method can be used. For example, the multilayer sheet can be produced by a melt co-extrusion molding method in which the raw materials for each layer are laminated in a molten state using multiple extruders. More specifically, examples include a method in which the raw materials for each layer are melt-extruded using multiple single-screw or twin-screw extruders, and a multilayer sheet is obtained using a feed block and a T-die equipped with a selector plug, and a method in which a multilayer sheet is obtained using a multi-manifold die.

[0055] Since the multilayer sheet is thermoformable, a molded product can be obtained by molding the multilayer sheet. The type of molded product is not particularly limited, but examples thereof include container lids, and in particular, lids for food packaging containers are preferred embodiments.

[0056] FIG. 2 is a perspective view showing one embodiment of a container. As shown in FIG. 2, a container 10 according to one embodiment includes a container body 11 having a space capable of accommodating contents, and a lid 12. In this embodiment, the container body 11 has two spaces capable of accommodating two types of contents, and has openings 11a on its top surface corresponding to the positions of the spaces. The lid 12 is fixed to the top surface of the container body 11 so as to cover the openings 11a. The lid 12 has notches 13 so that the lid 12 can be broken by bending it. A communication section 14 is provided between the space in which the contents are accommodated and the notch 13. Each communication section 14 has an easily peelable section 15. The easily peelable section 15 is a section at which the lid 12 is attached so that it is easier to peel the lid 12 from the container body 11 than other sections. Before use, the lid 12 is attached to the container body 11 at the easily peelable section 15, so that the two spaces in which the contents are accommodated are independent of each other. Such a container 10 is also called a dispensing package. In another embodiment, when one type of content is contained in two spaces, the easily separable portion 15 does not need to be provided, and the two spaces may be connected.

[0057] Fig. 3 is a schematic cross-sectional view of the lid body 12. As shown in Fig. 3, the lid body 12 is formed from the above-described multilayer sheet 1 and has the same layer structure as the multilayer sheet 1. The lid body 12 is provided with a notch (cut) 13 extending from the back surface layer 32 to the base material layer 31. The lid body 12 is placed on the container body 11 so that the surface layer 21 faces the container body 11 (contents) and the back surface layer 32 is exposed.

[0058] FIG. 4 is a schematic diagram showing an example of how the container 10 is used. The container 10 contains a first content C1 and a second content C2, which are independently contained therein. When a user U pinches the container 10 with their fingers and bends it (folding it so that the lid 12 faces outward), a crack propagates from the notch 13 shown in FIGS. 2 and 3 in the stacking direction of the lid 12, and the first content C1 and the second content C2 apply pressure to the lid 12 from the surface layer 21 side. This crack and pressure cause the lid 12 to break near the notch 13 and peel from the container body 11 at the easily peelable portion 15. This establishes communication between the space containing the first content C1 and the second content C2 and the broken portion of the lid 12 at the communication portion 14. As a result, the first content C1 and the second content C2 are discharged from the container 10 through the communication portion 14 and the broken portion of the lid 12. At this time, since the lid body 12 is formed of a multilayer sheet 1 having the above-mentioned easily breakable first laminate 2, the lid body 12 easily breaks due to the pressure of the first contents C1 and the second contents C2. [Example]

[0059] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the contents of the examples or the like.

[0060] <1. Preparation of multilayer sheet> The raw materials used in the examples and comparative examples are as follows. (1) Surface layer Low-density polyethylene (LDPE): "LC522" (Japan Polyethylene Co., Ltd.) High-density polyethylene (HDPE): "HF562" (Japan Polyethylene Co., Ltd.) (2) First adhesive layer and second adhesive layer Modified polyolefin (modified PO): "Modic F502C" (Mitsubishi Chemical Corporation) (3) Oxygen barrier layer Ethylene-vinyl alcohol copolymer (EVOH): "EVAL J171B" (Kuraray Co., Ltd.) (4) Second laminate High impact polystyrene (HIPS) 1: "H485" (Toyo Styrene Co., Ltd., average rubber particle size: 1 μm) High impact polystyrene (HIPS) 2: "E640N" (Toyo Styrene Co., Ltd., average rubber particle size: 3 μm) High impact polystyrene (HIPS) 3: "H850N" (Toyo Styrene Co., Ltd., average rubber particle size: 4 μm) Styrene homopolymer (GPPS): "HRM23" (Toyo Styrene Co., Ltd.) White pigment masterbatch: "ET3627" (Nikko Bix Co., Ltd., white pigment (titanium oxide) concentration in masterbatch: 50% by mass) Printing masterbatch: "TT3344" (Resinocolor Kogyo Co., Ltd.)

[0061] Example 1 A mixture of HDPE and LDPE in a mass ratio of 50 / 50 (density of polyethylene: 0.941 g / cm 3 ) was melt extruded from a φ75mm single-screw extruder, the modified PO from a φ45mm single-screw extruder, EVOH from a φ45mm single-screw extruder, a mixture of HIPS1 and GPPS mixed in a mass ratio of 80 / 20 and further mixed with 5 phr of white pigment masterbatch from a φ120mm single-screw extruder, and a mixture of HIPS mixed with 7 phr of printing masterbatch from a φ65mm single-screw extruder, and a multilayer sheet 330 μm thick and 640 mm wide was obtained by the feed block method, with a layer structure of surface layer 30 μm / adhesive layer 15 μm / oxygen barrier layer 10 μm / adhesive layer 15 μm / base layer 210 μm / back layer 50 μm.

[0062] (Example 2 and Comparative Examples 1 and 2) A multilayer sheet was obtained in the same manner as in Example 1, except that the thickness of each layer was changed as shown in Table 1.

[0063] Example 3 The mixing ratio of HDPE and LDPE in the surface layer was changed to HDPE / LDPE = 30 / 70 (mass ratio) and the density of polyethylene was 0.934 g / cm 3A multilayer sheet was obtained in the same manner as in Example 1, except that the thickness of each layer was changed as shown in Table 1.

[0064] (Comparative Example 3) A multilayer sheet was obtained in the same manner as in Comparative Example 1, except that HIPS2 was used instead of HIPS1.

[0065] Comparative Example 4 A multilayer sheet was obtained in the same manner as in Comparative Example 1, except that HIPS3 was used instead of HIPS1.

[0066] <2. Characterization> The obtained multilayer sheets according to the examples and comparative examples were evaluated in various ways by the following methods.

[0067] (A) Thickness of each layer Test pieces were cut out from the multilayer sheet at five equally spaced positions across the entire width direction (TD), which is perpendicular to the machine direction (MD), and the cross sections of the test pieces were cut using a single-edged knife. The cross sections of the obtained test pieces were observed with a stereo microscope (Profile Measuring Laser Microscope VK-X100, manufactured by Keyence Corporation), and the thickness of each layer was measured. The thickness of each layer was calculated as the average thickness of each layer at five positions across the width of the multilayer sheet.

[0068] (B) Average particle size of rubber in the base layer and backing layer A test piece was cut out at a desired position from the multilayer sheet, and layers other than the base layer and back layer were scraped off with a single-edged knife to remove the base layer and back layer, respectively. Next, components other than the rubber particles were dissolved in a solvent (N,N-dimethylformamide) to separate the rubber particles, and the average particle size of the rubber particles in the base layer and back layer was measured using a laser diffraction / scattering particle size distribution analyzer (Horiba, Ltd., Model: LA-920).

[0069] (C) Tensile modulus of the first laminate A 10 mm x 150 mm rectangular test piece (Type 2) according to JIS K7127:1999 was cut out from any position of the first laminate. According to JIS K7161:2014, the test piece was pulled in the longitudinal direction using a tensile tester (Model VE1D, manufactured by Toyo Seiki Seisakusho, Ltd.), and the tensile modulus (MPa) was measured at a temperature of 23°C, a humidity of 50% RH, a chuck distance of 50 mm, and a pulling speed of 200 mm / min. The tensile modulus was measured in both the MD and TD directions of the first laminate (test piece).

[0070] (D) Ease of breaking of the first laminate (breaking strength) In the same manner as for the tensile modulus, the test piece was pulled in the longitudinal direction, and the strength at which the test piece broke was evaluated as the breaking strength (MPa). The smaller the breaking strength of the first laminate, the more easily the first laminate breaks.

[0071] The obtained multilayer sheets according to the examples and comparative examples were evaluated in various ways using the methods for evaluating multilayer sheets described above. The results are shown in Table 1.

[0072] [Table 1]

[0073] The ease of breaking of each second laminate used in the examples and comparative examples was also evaluated. Specifically, a test piece measuring 15 mm × 150 mm was cut out from an arbitrary position of the second laminate, and both longitudinal ends of the test piece were chucked to an MIT folding endurance tester (MIT-D, manufactured by Toyo Seiki Seisaku-sho, Ltd.). With a load (250 g) applied to the test piece, the test piece was bent at a bending angle of 135° at two bending speeds (high speed: 175 rpm, low speed: 90 rpm). The number of bendings until the test piece (second laminate) broke in two was measured. Evaluation was performed according to the following criteria depending on the number of bendings. The fewer the number of bendings, the more easily the second laminate broke. A: Less than 50 bending times B: Number of flexions: 50 to less than 100 C: Number of bending times: 100 to 1000 D: The number of bending times exceeds 1000

[0074] As a result, the second laminates in Examples 1 to 3 and Comparative Examples 1 and 2 were rated "A" at both high and low speeds. The second laminate in Comparative Example 3 was rated "B" at high speed and "C" at low speed. The second laminate in Comparative Example 4 was rated "C" at both high and low speeds. [Explanation of symbols]

[0075] 1...multilayer sheet, 2...first laminate, 21...surface layer, 22...first adhesive layer, 23...oxygen barrier layer, 24...second adhesive layer, 3...second laminate, 31...base material layer, 32...back surface layer, 10...container, 11...container body, 12...lid body, 13...notch, 14...communicating portion, 15...easily peelable portion, U...user, C1...first content, C2...second content.

Claims

1. a first laminate having a surface layer, a first adhesive layer, an oxygen barrier layer, and a second adhesive layer in this order; a second laminate adhered to the second adhesive layer of the first laminate; A multilayer sheet comprising: the second laminate has at least two layers containing a styrene-based polymer and a plurality of rubber particles, A multilayer sheet, wherein the first laminate has a tensile modulus of 450 MPa or less.

2. The multilayer sheet according to claim 1 , wherein the average particle size of the plurality of rubber particles is 2 μm or less.

3. 3. The multilayer sheet according to claim 1, wherein the standard deviation of the average particle size of the plurality of rubber particles is 1 μm or less.

4. 3. The multilayer sheet according to claim 1, wherein the surface layer has a thickness of 10 μm or more and 50 μm or less, and the oxygen barrier layer has a thickness of 5 μm or more and 15 μm or less.

5. 3. The multilayer sheet according to claim 1, wherein the first adhesive layer and the second adhesive layer each have a thickness of 10 μm or more and 20 μm or less.

6. a container body having an opening; a lid that closes the opening of the container, A container, wherein the lid is formed from the multilayer sheet according to claim 1 or 2.

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