Laminate for lid material, lid material, and packaging container

Abstract

Provided is a laminate for a lid material, the laminate comprising a base material layer at least one surface layer of which is a polyethylene-based resin layer, an easily peelable layer, and a sealant layer adjacent to the easily peelable layer, wherein: the easily peelable layer contains a high-pressure, low-density polyethylene (A1) and a propylene homopolymer (B1); the content of the high-pressure, low-density polyethylene (A1) is more than 50 mass% with respect to 100 mass% of the total mass of the high-pressure low-density polyethylene (A1) and the propylene homopolymer (B1) contained in the easily peelable layer; the content of the propylene homopolymer (B1) in the easily peelable layer is more than 0 mass% and less than 40 mass% with respect to the total mass of the easily peelable layer; and the sealant layer contains a propylene-based resin (B) and is an outermost layer on an adherend-contacting side of the laminate for a lid material. Also, provided are: a lid material using said laminate for a lid material; and a packaging container using said lid material.

Description

Laminate for lid material, lid material, and packaging container

[0001] The present disclosure relates to a lid material laminate, a lid material, and a packaging container.

[0002] Paper containers in which the surface of a paper base is coated with polyethylene, impact-resistant polystyrene sheets, expanded polystyrene sheets, or those in which an impact-resistant polystyrene film is laminated thereto, are widely used as container materials for foods, pharmaceuticals, etc. In general, the container and the lid material are hermetically sealed by heat sealing using a sealant resin composition, thereby protecting the contents. Among packaging containers, paper cups with a polyethylene surface coating are excellent from the viewpoint of reducing the environmental load by reducing the amount of plastic used, and are also excellent in terms of insulation, heat retention, design, etc., and are therefore used in a wide range of applications, such as cup noodle containers, dessert containers, and beverage containers.

[0003] Lids for packaging containers require high adhesion to protect the contents and easy opening when opened. Patent Document 1 discloses a coextruded multilayer film suitable for use as a lid for airtight packaging containers, which has high transparency and allows easy confirmation of whether the container has been opened. The multilayer film has a sealant layer primarily composed of a polyethylene-based resin and a support layer containing a propylene-based resin and a polyethylene-based resin, each having a melting point of 155°C or higher. Patent Documents 2 and 3 disclose composite films suitable for use as lids for packaging volatile chemicals and the like, which have barrier properties against volatile components during storage and distribution, and which are useful for leaving only a seal layer with low barrier properties against volatile components when used. Patent Document 4 also discloses a sealant film with easy peel properties and stable sealing properties.

[0004] Patent Document 1: JP 2010-94860 A Patent Document 2: JP 2004-268491 A Patent Document 3: JP 2004-267493 A Patent Document 4: JP 2008-150541 A

[0005] The technical standards required for easily openable lid materials for containers, etc., whose surfaces are formed from polypropylene sheets, are becoming increasingly stringy. Specifically, high sealing strength is required to prevent the lid from opening and leaking the contents during transportation or storage, and easy peelability is required to allow the lid to be easily opened when used. Furthermore, the peeling state of the lid after peeling has sometimes been problematic. Regarding the peeling state of the lid after peeling, stringiness, filmy residue, etc., has sometimes been observed at the peeled portion. Stringiness is a phenomenon in which thin resin threads are formed at the peeled portion, while filmy residue, also known as feathering, is a phenomenon in which a thin film remains at the peeled surface. The occurrence of stringiness, filmy residue, etc. has led to problems such as poor appearance, contamination of food with threads when removing food contents, and poor tactile feel at the edge of the cup, significantly damaging the impression of the packaging container.

[0006] The problem that one embodiment of the present disclosure aims to solve is to provide a laminate for a lid material, a lid material, and a packaging container that, when used as a lid material for a container, has high sealing strength, good peelability, and is less likely to leave residue at the peeled portion after peeling.

[0007] Specific means for solving the above problems include the following aspects: <1> A lid material laminate comprising a base layer, at least one surface layer of which is a polyethylene-based resin layer, an easily peelable layer adjacent to the polyethylene-based resin layer, and a sealant layer adjacent to the easily peelable layer, wherein the easily peelable layer contains a high-pressure low-density polyethylene (A1) and a propylene homopolymer (B1), the content of the high-pressure low-density polyethylene (A1) in the easily peelable layer is more than 50% by mass relative to 100% by mass, which is the total mass of the high-pressure low-density polyethylene (A1) and the propylene homopolymer (B1) contained in the easily peelable layer, the content of the propylene homopolymer (B1) in the easily peelable layer is more than 0% by mass and less than 40% by mass relative to the total mass of the easily peelable layer, and the sealant layer contains a propylene-based resin (B) and is the outermost layer of the lid material laminate on the side that comes into contact with an adherend. <2> The lid material laminate according to <1>, wherein the high-pressure low-density polyethylene (A1) has a melt flow rate of 3.0 g / 10 min or more and 100 g / 10 min or less, measured at 190°C under a load of 2160 g in accordance with JIS K 7210-1: 2014. <3> The lid material laminate according to <1> or <2>, wherein the propylene homopolymer (B1) has a melt flow rate of 0.1 g / 10 min or more and 100 g / 10 min or less, measured at 230°C under a load of 2160 g in accordance with JIS K 7210-1: 2014. <4> The lid material laminate according to any one of <1> to <3>, wherein the easily peelable layer contains a tackifier resin (D). <5> The lid material laminate according to <4>, wherein the total content of the high-pressure low-density polyethylene (A1), the propylene homopolymer (B1), and the tackifier resin (D) in the easily peelable layer is more than 98% by mass and 100% by mass or less, based on the total mass of the resin components contained in the easily peelable layer. <6> The lid material laminate according to any one of <1> to <5>, wherein the content of the propylene-based resin (B) in the sealant layer is 90% by mass or more, based on the total mass of the sealant layer. <7> The lid material laminate according to any one of <1> to <6>, wherein the thickness of the sealant layer is 3 μm or more and 20 μm or less.<8> The lid material laminate according to any one of <1> to <7>, wherein the propylene-based resin (B) is a propylene homopolymer (B2) or a propylene-α-olefin random copolymer (B3). <9> The lid material laminate according to any one of <1> to <8>, wherein the propylene-based resin (B) has a melt flow rate of 0.1 g / 10 min or more and 100 g / 10 min or less, measured in accordance with JIS K 7210-1:2014 at 230°C under a load of 2,160 g. <10> The lid material laminate according to any one of <1> to <9>, wherein the polyethylene-based resin layer is made of high-pressure low-density polyethylene (A2) or linear low-density polyethylene (C). <11> A lid material comprising the lid material laminate according to any one of <1> to <10>. <12> A packaging container comprising: the lid material according to <11>; and a container having a cylindrical body with one end closed and the other end having an opening, wherein the lid material is heat-sealed to the opening via a sealant layer, thereby covering the opening with the lid material.

[0008] According to one embodiment of the present disclosure, it is possible to provide a lid material laminate, a lid material, and a packaging container that, when used as a lid material for a container, have high sealing strength, good easy peelability, and are less likely to leave residue at the peeled portion after peeling.

[0009] 1 is a schematic diagram illustrating an example of a lid material laminate according to the present disclosure. 2 is a schematic diagram illustrating an example of a packaging container including the lid material according to the present disclosure.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to the following embodiments.

[0011] In the present disclosure, numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in numerical ranges described in the present disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple corresponding substances. When multiple substances corresponding to each component exist, the content or amount of each component means the total content or amount of the multiple substances, unless otherwise specified. In the present disclosure, "layer" and "film" include configurations of shapes that are formed over the entire surface when observed in a plan view, as well as configurations of shapes that are formed only on a portion of the surface.

[0012] In the present disclosure, high-pressure low-density polyethylene (hereinafter sometimes referred to as LDPE) is a polyethylene having a density of 910 kg / m3 synthesized by radical polymerization under a high pressure of 100 MPa to 400 MPa. ３ More than 930kg / m ３ LDPE refers to polyethylene with a density of less than 1000 kJ / cm. LDPE is synthesized by a high-pressure method and has a structure in which repeating ethylene units are randomly branched. For this reason, it has the characteristics of a lower melting point and greater flexibility than linear low-density polyethylene (hereinafter sometimes referred to as L-LDPE), which is a copolymer generally obtained by copolymerizing ethylene with an α-olefin such as 1-butene using a metallocene catalyst.

[0013] [Lid material laminate] The lid material laminate of the present disclosure comprises a substrate layer, at least one surface layer of which is a polyethylene-based resin layer, an easily peelable layer adjacent to the polyethylene-based resin layer, and a sealant layer adjacent to the easily peelable layer, wherein the easily peelable layer comprises a high-pressure low-density polyethylene (A1) and a propylene homopolymer (B1), and the content of the high-pressure low-density polyethylene (A1) in the easily peelable layer is more than 50 mass% relative to 100 mass% which is the total mass of the high-pressure low-density polyethylene (A1) and the propylene homopolymer (B1) contained in the easily peelable layer, and the content of the propylene homopolymer (B1) in the easily peelable layer is more than 0 mass% and less than 40 mass% relative to the total mass of the easily peelable layer, and the sealant layer comprises a propylene-based resin (B) and is the outermost layer of the lid material laminate on the side that comes into contact with an adherend. The lid material laminate of the present disclosure is suitable for use as a lid material for containers, and is adhered to a flange provided at the opening of the container via a sealant layer to seal the opening of the container. The lid material laminate of the present disclosure is suitable for use as a lid material for various containers, particularly cup containers, and has high sealing strength, good peelability, and is less likely to leave residue at the peeled portion after peeling. Even if the lid is peeled by cohesive failure, the surface condition of the peeled surface is excellent.

[0014] The lid material laminate of the present disclosure has a substrate layer having a polyethylene-based resin layer disposed on the surface layer adjacent to the peelable layer, and an easily peelable layer containing a specific amount of high-pressure low-density polyethylene (A1), thereby improving interlayer adhesion between the substrate layer and the easily peelable layer. Furthermore, since both the easily peelable layer and the sealant layer adjacent to the easily peelable layer contain a propylene-based resin, the interlayer adhesion between the easily peelable layer and the sealant layer is also improved. Furthermore, the easily peelable layer contains a propylene homopolymer (B1) that has low compatibility with the high-pressure low-density polyethylene (A1), forming a sea-island structure of two resins in the easily peelable layer, achieving an appropriately low peel strength due to cohesive failure and suppressing the generation of residues such as stringiness at the peeled portion. It is believed that these advantages combined result in high sealing strength, easy peelability, and suppressed generation of residues at the peeled portion after peeling.

[0015] <Substrate Layer> In the substrate layer of the lid material laminate of the present disclosure, at least the surface layer is a polyethylene-based resin layer. The substrate layer is provided adjacent to the easily peelable layer on the side opposite to the side of the easily peelable layer having the sealant layer, and the polyethylene-based resin layer, which is the surface layer of the substrate layer, is adjacent to the easily peelable layer. The substrate layer can be provided for the purpose of improving the handleability, mechanical properties, heat resistance, etc. of the lid material laminate having the easily peelable layer. The substrate layer may not only have a single-layer structure consisting of only the surface layer, but also a laminate structure of two or more layers including the surface layer depending on the purpose. Whether the substrate layer has a single-layer structure or a laminate structure, it has a surface layer on the side of the substrate layer adjacent to the easily peelable layer. When the substrate layer has a single-layer structure, it consists of only the surface layer.

[0016] -Surface Layer- The polyethylene-based resin layer, which is the surface layer of the base layer, is preferably made of, for example, high-density polyethylene, medium-density polyethylene, high-pressure low-density polyethylene (A2), or linear low-density polyethylene (C). The polyethylene-based resin layer is more preferably made of high-pressure low-density polyethylene (A2) or linear low-density polyethylene (C). The surface layer can be formed by forming a film of a resin composition for forming a surface layer, which contains other components that are used in combination as desired. The components of the surface layer are described below.

[0017] -High-Pressure Low-Density Polyethylene (A2) (LDPE (A2))- The LDPE (A2) used in the surface layer of the present disclosure is polyethylene obtained by polymerizing ethylene by a high-pressure radical method.

[0018] The polymerization of LDPE (A2) can be carried out by a known method. Examples of the reactor used for the polymerization include an autoclave reactor and a tubular reactor, and either may be used.

[0019] The LDPE (A2) that forms the surface layer has a density of 910 kg / m as measured in accordance with JIS K7112:1999 "Measurement of density and specific gravity of non-foamed plastics." ３ More than 930kg / m ３ and preferably 915 kg / m ３ More than 925kg / m ３By using LDPE (A2) having a density within the above range for the resin composition for forming the surface layer, a resin composition excellent in extrusion processability can be obtained.

[0020] Furthermore, the LDPE (A2) to be used for the surface layer preferably has a melt flow rate (hereinafter sometimes referred to as MFR) measured in accordance with JIS K 7210-1:2014 at 190°C under a load of 2160 g of 1.0 g / 10 min or more and 100 g / 10 min or less, more preferably 1.0 g / 10 min or more and 50 g / 10 min or less, and even more preferably 3.0 g / 10 min or more and 30 g / 10 min or less. By using LDPE (A2) having a melt flow rate within the above range for the resin composition for forming the surface layer, the extrusion processability when forming the surface layer becomes better.

[0021] The LDPE (A2) in the surface layer may be a commercially available product, such as Mirason M11P (manufactured by Mitsui-Dow Polychemicals Co., Ltd.).

[0022] - Linear Low-Density Polyethylene (C) (L-LDPE (C)) - The L-LDPE (C) used in the surface layer of the present disclosure is generally a copolymer obtained by copolymerizing ethylene with an α-olefin such as 1-butene using a metallocene catalyst.

[0023] The polymerization of L-LDPE (C) can be carried out by a known method. L-LDPE (C) may be obtained by either gas phase polymerization or liquid phase polymerization, but is preferably obtained by gas phase polymerization using a metallocene catalyst.

[0024] The L-LDPE (C) that forms the surface layer has a density of 900 kg / m as measured in accordance with JIS K7112:1999 "Measurement of density and specific gravity of non-foamed plastics." ３ More than 940kg / m ３ and preferably 900 kg / m ３ More than 930kg / m ３ By using L-LDPE (C) having a density within the above range for the resin composition for forming the surface layer, a resin composition excellent in extrusion processability can be obtained.

[0025] Furthermore, the L-LDPE (C) to be the surface layer preferably has a melt flow rate (hereinafter sometimes referred to as MFR) of 0.1 g / 10 min or more and 100 g / 10 min or less, and more preferably 0.2 g / 10 min or more and 50 g / 10 min or less, as measured at 190°C and a load of 2160 g in accordance with JIS K 7210-1: 2014. By using an L-LDPE (C) having a melt flow rate within the above range in the resin composition for forming the surface layer, the extrusion processability when forming the surface layer becomes better.

[0026] The L-LDPE (C) in the surface layer may be a commercially available product, such as Evolue SP1071C (manufactured by Prime Polymer Co., Ltd.).

[0027] The surface layer of the substrate layer is formed from the above-mentioned LDPE (A2) or L-LDPE (C), which allows the substrate layer to function favorably and has good adhesion to the easily peelable layer, thereby forming a favorable laminate for a lid material.

[0028] -Configuration of Surface Layer- When the substrate layer has a laminate structure of two or more layers, the layers other than the surface layer can be plate-shaped materials such as sheets and films. Examples of materials include paper such as fine paper, medium-quality paper, pure white roll paper, coated paper, single-sided art paper, double-sided art paper, mixed paper, synthetic paper, and paperboard; metals such as aluminum foil; polyesters such as polyethylene terephthalate; polyethylenes such as high-pressure low-density polyethylene; polypropylenes such as polypropylene homopolymers and polypropylene copolymers; and resins such as polyamides. Furthermore, depending on the purpose of more effectively suppressing gas permeability, a material combining different materials, such as aluminum-vapor-deposited polyester, aluminum-vapor-deposited polypropylene, and silica-vapor-deposited polyester, may also be used. In particular, the substrate layer preferably includes a paper substrate from the viewpoint of reducing environmental impact, and preferably includes a film or sheet made of polyethylene or polyester from the viewpoint of processability.

[0029] When a base layer is provided, the thickness of the base layer can be, for example, from 5 μm to 100 μm, and preferably from 10 μm to 50 μm, from the viewpoints of mechanical strength and workability. For the purpose of further improving the adhesive strength with the easily peelable layer, the surface of the base layer on the side to be laminated with the easily peelable layer may be subjected to corona treatment, plasma treatment, flame treatment, ozone treatment, or the like, or may be subjected to anchor coating treatment.

[0030] <Easy-to-peel layer> The easy-to-peel layer in the covering laminate of the present disclosure comprises a high-pressure low-density polyethylene (A1) and a propylene homopolymer (B1), and the content of the high-pressure low-density polyethylene (A1) in the easy-to-peel layer is greater than 50% by mass relative to the total mass of the high-pressure low-density polyethylene (A1) and the propylene homopolymer (B1) contained in the easy-to-peel layer (100% by mass), and the content of the propylene homopolymer (B1) in the easy-to-peel layer is greater than 0% by mass and less than 40% by mass relative to the total mass of the easy-to-peel layer. The easy-to-peel layer can be formed by forming a film of a resin composition for forming an easy-to-peel layer, which comprises a high-pressure low-density polyethylene (A1) and a propylene homopolymer (B1), and further comprises other components that are used in combination as desired. Hereinafter, each component contained in the easy-to-peel layer will be described.

[0031] —High-Pressure Low-Density Polyethylene (A1) (LDPE (A1))— The LDPE (A1) contained in the easily peelable layer of the present disclosure is polyethylene obtained by polymerizing ethylene by a high-pressure radical method, and the polymerization method is the same as that for the LDPE (A2) described above.

[0032] The LDPE (A1) contained in the easily peelable layer in the present disclosure has a density of 910 kg / m as measured in accordance with JIS K7112:1999 "Measurement of density and specific gravity of non-foamed plastics." ３ More than 930kg / m ３ and preferably 915 kg / m ３ More than 925kg / m ３ The density is in the following range: By using LDPE (A1) having a density in the above range for the resin composition for forming the easily peelable layer, a resin composition having excellent extrusion processability can be obtained.

[0033] The LDPE (A1) contained in the easily peelable layer preferably has a melt flow rate (hereinafter sometimes referred to as MFR) measured in accordance with JIS K 7210-1: 2014 at 190°C under a load of 2160 g of 1.0 g / 10 min or more and 100 g / 10 min or less, and more preferably 3.0 g / 10 min or more and 100 g / 10 min or less. By using an LDPE (A1) having a melt flow rate within the above range in the resin composition for forming the easily peelable layer, the extrusion processability when forming the easily peelable layer becomes better.

[0034] The content of LDPE (A1) in the peelable layer is preferably more than 50% by mass and less than 80% by mass, and more preferably 55% by mass or more and 75% by mass or less, relative to 100% by mass, which is the total mass of the high-pressure low-density polyethylene (A1) and the propylene homopolymer (B1) contained in the peelable layer. When the content of LDPE (A1) in the peelable layer is in the above range, it becomes easy to control the heat resistance and adhesive strength to the adherend of the peelable layer within appropriate ranges.

[0035] The LDPE (A1) in the peelable layer may contain only one type, or may contain two or more different types. From the viewpoint of ensuring both sealing strength and peelability as a lid material laminate, a mixture of two or more different LDPEs (A1) is preferred. For example, the LDPE (A1) may be a mixture of LDPE (HP-LDPE-2) and LDPE (HP-LDPE-3) having different MFRs. In this mixture, it is believed that the effect of controlling the peelability of the peelable layer and the sealant layer is easily exerted, peelability is easily ensured, interlayer adhesion between the peelable layer and the sealant layer is easily maintained, and sealing strength is easily ensured. Note that the blending ratio, where the total of HP-LDPE-2 and HP-LDPE-3 is 100 parts by mass, is preferably 20:80 to 80:20, in terms of HP-LDPE-2:HP-LDPE-3.

[0036] - Propylene homopolymer (PP (B1)) - The easily peelable layer contains PP (B1). The PP (B1) may be a propylene homopolymer. Only one type of PP (B1) may be contained, or two or more types of PP (B1) having different molecular weights may be contained. The PP (B1) preferably has a crystallinity of 30% or more as determined by X-ray. From the viewpoint of heat resistance, the PP (B1) is preferably a polymer having a melting peak of 120°C to 170°C as determined by a differential scanning calorimeter (DSC), more preferably a polymer having a melting peak of 150°C to 170°C.

[0037] PP (B1) can be produced by polymerizing propylene in the presence of a stereoregular olefin polymerization catalyst containing a transition metal compound component such as a titanium-based or metallocene-based compound, an organoaluminum component, and, if necessary, an electron donor, a carrier, etc.

[0038] The melt flow rate (MFR) of PP (B1) measured under a load of 2.16 kg at a temperature of 230°C is preferably 0.1 g / 10 min to 500 g / 10 min, more preferably 0.1 g / 10 min to 100 g / 10 min, and even more preferably 1 g / 10 min to 50 g / 10 min, from the viewpoints of moldability and impact resistance. The MFR of PP (B1) is a value measured in accordance with JIS K 7210-1:2014 under conditions of a test load of 2.16 kg and a temperature of 230°C.

[0039] The density of PP (B1) is 870 kg / m to 930 kg / m from the viewpoint of excellent impact resistance and a low linear expansion coefficient. ３ is preferred, and 880 kg / m ３ ~920 kg / m ３ More preferably, 890 kg / m ３ ~910 kg / m ３ The density of PP (B1) is a value measured by the underwater displacement method in accordance with JIS K 7112:1999.

[0040] The content of PP (B1) in the peelable layer is more than 0% by mass and less than 40% by mass, based on the total mass of the peelable layer.The content of PP (B1) in the peelable layer is preferably 20% by mass or more and 39% by mass or less, more preferably 25% by mass or more and 38% by mass or less, based on the total mass of the peelable layer.Within the above range, the balance between the sealing strength and the peelability of the peelable layer is particularly good.

[0041] It is believed that the inclusion of PP (B1) having low compatibility with the above-mentioned LDPE (A1) in the peelable layer provides a good balance between the sealing strength and releasability of the peelable layer. There are three types of peeling mechanisms when peeling a lid from a container: interfacial peeling, interlayer peeling, and cohesive peeling. In the lid laminate of the present disclosure, it is believed that peeling of the lid, which is heat-sealed via the peelable layer, from the container occurs due to cohesive failure of the peelable layer. Although the mechanism is unclear in the present disclosure, a peelable layer-forming resin composition is formed by mixing LDPE (A1) and PP (B1) having low compatibility with LDPE (A1) to form the peelable layer. When the peelable layer is formed, a sea-island structure is formed in which the LDPE (A1) forms the sea and the PP (B1) forms the islands, both of which are poorly compatible with each other. The flexible LDPE (A1) provides high sealing strength to the container. Furthermore, when the lid material is peeled off from the container, cohesive peeling occurs at the interface between the PP (B1) and LDPE (A1) that form the islands, resulting in good easy peeling properties. Furthermore, even if cohesive peeling occurs, which is said to leave noticeable residues such as strings due to the properties of the flexible LDPE (A1), it is thought that the generation of residues such as strings when opening is suppressed.

[0042] From the viewpoint of enabling favorable cohesive failure, the content ratio of the LDPE (A1) to the PP (B1) in the easily peelable layer ((A1):(B1)=) is preferably 80:20 to 51:49 in mass terms, and more preferably 75:25 to 55:45 in mass terms.

[0043] - Tackifier resin (D) - The peelable layer may contain a tackifier resin (D). The tackifier resin (D) has the function of imparting tackiness to the resin. This makes it easy to adjust the adhesive strength of the resin composition for forming the peelable layer. The tackifier resin (D) is compatible with the LDPE (A1) and is contained in the sea portion of the sea-island structure in the peelable layer, which is thought to improve the sealing strength. The tackifier resin (D) is selected from resins that have the function of imparting tackiness. Examples of the tackifier resin (D) include aromatic hydrocarbon resins, alicyclic hydrocarbon resins, aliphatic hydrocarbon resins, terpene resins, rosins, styrene resins, and coumarone-indene resins.

[0044] Examples of aromatic hydrocarbon resins include resins obtained by polymerizing fractions containing at least one vinyl aromatic hydrocarbon having 8 to 10 carbon atoms, such as vinyltoluene, indene, and α-methylstyrene, and resins obtained by copolymerizing these fractions with aliphatic hydrocarbon fractions. Examples of alicyclic hydrocarbon resins include resins obtained by cyclodimerizing and then polymerizing diene components in spent C4-C5 fractions, resins obtained by polymerizing cyclic monomers such as cyclopentadiene, and resins obtained by intranuclear hydrogenation of aromatic hydrocarbon resins (e.g., hydrogenated petroleum resins). Examples of aliphatic hydrocarbon resins include resins obtained by polymerizing fractions containing at least one mono- or diolefin having 4 to 5 carbon atoms, such as 1-butene, isobutene, butadiene, 1,3-pentadiene, and isoprene. Examples of terpene resins include α-pinene polymers, β-pinene polymers, dipentene polymers, terpene-phenol copolymers, α-pinene-phenol copolymers, and hydrogenated versions of these. Examples of rosins include rosins such as gum rosin, wood rosin, and tall oil, as well as modified products thereof, and examples of modified products include those that have been subjected to modifications such as hydrogenation, disproportionation, dimerization, esterification, etc. Examples of styrene-based resins include low-molecular-weight resinous polymers obtained by polymerizing styrene-based monomers such as styrene, vinyltoluene, α-methylstyrene, and isopropyltoluene.

[0045] The tackifier resin (D) is preferably a resin having a softening point of 85°C to 130°C, more preferably 100°C to 125°C, and even more preferably 110°C to 120°C. In general, a softening point of 85°C or higher tends to provide excellent heat resistance, while a softening point of 130°C or lower tends to provide excellent tackifying properties. The softening point of the tackifier resin (D) can be a value measured based on the softening point test method (ring and ball method) in accordance with JIS K 2207:2006.

[0046] The content of the tackifier resin (D) is preferably more than 0% by mass and less than 25% by mass, relative to the total mass of the resin composition for forming the peelable layer. When the content of the tackifier resin (D) exceeds 0% by mass, relative to the total mass of the resin composition for forming the peelable layer, variation in adhesive strength to the adherend is suppressed. From the viewpoint of uniforming adhesive strength, the content of the tackifier resin (D) is more preferably 3% by mass or more, even more preferably 5% by mass or more, and particularly preferably 7% by mass or more, relative to the total mass of the resin composition for forming the peelable layer. Furthermore, from the viewpoint of achieving a good balance between adhesion and releasability, the content of the tackifier resin (D) is preferably less than 25% by mass, more preferably 20% by mass or less, even more preferably 18% by mass or less, and particularly preferably less than 16% by mass, relative to the total mass of the resin composition for forming the peelable layer. That is, the content of the tackifier resin (D) is more preferably 3% by mass or more and 20% by mass or less, even more preferably 5% by mass or more and 18% by mass or less, and particularly preferably 7% by mass or more and less than 16% by mass, relative to the total mass of the resin composition for forming the easily peelable layer.

[0047] The tackifier resin (D) in the easily peelable layer may be a commercially available product. Examples of commercially available tackifier resin (D) include hydrogenated alicyclic resins such as Alcon (registered trademark: the same applies hereinafter) P140 (manufactured by Arakawa Chemical Industries, Ltd., softening point 140 ° C.), Alcon P125 (manufactured by Arakawa Chemical Industries, Ltd., softening point 125 ° C.), Alcon P115 (manufactured by Arakawa Chemical Industries, Ltd., softening point 115 ° C.), Alcon P100 (manufactured by Arakawa Chemical Industries, Ltd., softening point 100 ° C.), and Alcon P90 (manufactured by Arakawa Chemical Industries, Ltd., softening point 90 ° C.).

[0048] Other Components—The peelable layer, specifically the resin composition for forming the peelable layer, may contain, in addition to the LDPE (A1), PP (B1), and tackifier resin (D), other components (also referred to as other components) as long as the effects of the present disclosure are not impaired. The other components are not particularly limited, but examples include antistatic agents, antiblocking agents, slip agents, antioxidants, heat stabilizers, light stabilizers, pigments, dyes, etc. The other components may be used alone or in combination of two or more. Examples of antistatic agents include conductive polymers, nonionic surfactants, and anionic surfactants. Examples of antiblocking agents include silica and aluminosilicates (e.g., zeolites). Examples of slip agents include polyalkylene glycols such as polyethylene glycol and polypropylene glycol; hydrogenated castor oil, etc. When the peelable layer contains a slip agent, the content of the slip agent is preferably less than 1% by mass, and more preferably 0.5% by mass or less, relative to the total mass of the resin composition.

[0049] The content of the other components is preferably less than 2% by mass relative to the total mass of the peelable layer. In other words, the total content of the LDPE (A2), PP (B1), and tackifier resin (D) in the peelable layer is preferably more than 98% by mass and less than 100% by mass, more preferably 99% by mass or more and less than 100% by mass, and even more preferably 99.5% by mass or more and less than 100% by mass, relative to the total mass of the resin components contained in the peelable layer. Within the above range, the balance between the sealing strength and ease of releasability in the peelable layer is particularly good. Furthermore, the MFR of the resin composition for forming the peelable layer is preferably 1.0 g / 10 min to 70 g / 10 min, more preferably 3.0 g / 10 min to 50 g / 10 min, and even more preferably 3.0 g / 10 min to 40 g / 10 min. The MFR of the resin composition for forming the easily peelable layer is a value measured in accordance with JIS K 7210-1:2014 under conditions of a test load of 2.16 kg and a temperature of 190°C.

[0050] From the viewpoint of the balance between sealing strength and ease of peeling, the thickness of the easily peelable layer is preferably 3 μm or more and less than 20 μm, more preferably 4 μm to 15 μm, and even more preferably 5 μm to 12 μm.

[0051] <Sealant layer> The lid material laminate of the present disclosure has a sealant layer adjacent to the easily peelable layer. The sealant layer is a layer for imparting heat sealability to the lid material laminate. In the lid material laminate, the sealant layer is the outermost layer on the side that comes into contact with an adherend such as a container. That is, in the lid material laminate, the sealant layer is the layer that comes into direct contact with an adherend such as a container.

[0052] - Propylene-based resin (B) - The sealant layer contains a propylene-based resin (B) (hereinafter also referred to as PP(B)). PP(B) may be one selected from the group consisting of propylene-based resins, i.e., copolymers and homopolymers having structural units derived from propylene. PP(B) may contain only one type, or may contain two or more types having different molecular weights. PP(B) may be a propylene homopolymer (B1). When the sealant layer contains PP(B), high sealing strength of the covering laminate can be obtained.

[0053] The PP (B) is preferably a propylene homopolymer (B2) or a propylene-α-olefin random copolymer (B3). When the PP (B) of the sealant layer is a propylene homopolymer (B2) or a propylene-α-olefin random copolymer (B3), the covering laminate can achieve high sealing strength. When the PP (B) is a propylene homopolymer (B2), it may be the same propylene homopolymer PP (B1) as the propylene homopolymer PP (B1) contained in the easily peelable layer described above. In this case, preferred physical properties such as MFR are also the same as those of the PP (B1).

[0054] Examples of the propylene-α-olefin random copolymer (B3) include copolymers of propylene and α-olefins such as ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Among these, propylene-ethylene random copolymers composed of propylene and a small amount of ethylene and having a content of structural units derived from ethylene of 5 mol% or less are preferred. Among these olefin polymers, propylene-ethylene random copolymers, propylene homopolymers, and ethylene-based polymers are particularly preferred. These olefin polymers may be used alone or in combination of two or more.

[0055] From the viewpoint of heat resistance, PP (B) is preferably a polymer having a melting point of 120°C to 170°C, more preferably 130°C to 170°C, as measured by a differential scanning calorimeter (DSC) in accordance with JIS K7121:1987.

[0056] The melt flow rate (MFR) of PP(B) measured under a load of 2.16 kg and at a temperature of 230°C is preferably 0.1 g / 10 min to 500 g / 10 min, more preferably 0.1 g / 10 min to 100 g / 10 min, and even more preferably 3 g / 10 min to 50 g / 10 min, from the viewpoint of moldability and impact resistance. The MFR of PP(B) is a value measured in accordance with JIS K 7210-1:2014 under conditions of a test load of 2.16 kg and a temperature of 230°C.

[0057] The density of PP (B) is 870 kg / m from the viewpoint of excellent impact resistance and a low linear expansion coefficient. ３ ~930 kg / m ３ is preferred, and 880 kg / m ３ ~920 kg / m ３ More preferably, 890 kg / m ３～ 910 kg / m ３ The density of PP(B) is a value measured by the underwater displacement method in accordance with JIS K 7112:1999.

[0058] The content of PP(B) in the sealant layer is preferably 90% by mass or more relative to the total mass of the sealant layer. A PP(B) content of 90% by mass or more in the sealant layer indicates that PP(B) is the main component in the layer. The content of PP(B) in the sealant layer is preferably 90% by mass or more and 100% by mass or less, more preferably more than 95% by mass and 100% by mass or less, even more preferably 98% by mass to 100% by mass, particularly preferably 99% by mass to 100% by mass, and even more preferably more than 99% by mass and 100% by mass or less. Within the above range, the function of the sealant layer is more favorably exhibited, and the covering material laminate has high sealing strength, good easy peelability, and is less likely to leave residue in the peeled area after peeling.

[0059] -Antiblocking Agent- The sealant layer preferably contains an antiblocking agent, which reduces blocking of the covering laminate.

[0060] Examples of antiblocking agents include silica, aluminosilicates (such as zeolite), talc, calcium carbonate, and starch. Silica and zeolite are preferred because they efficiently exhibit antiblocking effects even when incorporated in small amounts and because of transparency. The sealant layer may contain only one type of antiblocking agent, or two or more types. When the sealant layer contains an antiblocking agent, the content of the antiblocking agent is preferably 0.1% by mass or more and 5.0% by mass or less, more preferably 0.1% by mass or more and 4.0% by mass or less, and even more preferably 0.1% by mass or more and 3.0% by mass or less, relative to the total mass of the sealant layer. By having the content of the antiblocking agent in the sealant layer within the above range, stickiness of the sealant layer is suppressed, blocking is suppressed, and the transparency of the film is maintained at a high level.

[0061] Other Components—The sealant layer may further contain other components in addition to PP (B) and the antiblocking agent described above, which is a preferred additional component, as long as the effects are not impaired. Examples of other components include thermoplastic resins other than PP (B), thermosetting resins, plasticizers, antioxidants, UV absorbers, antistatic agents, surfactants, colorants, light stabilizers, foaming agents, lubricants, crystal nucleating agents, crystallization accelerators, crystallization retarders, catalyst deactivators, inorganic fillers, organic fillers, impact modifiers, slip agents, crosslinking agents, crosslinking aids, tackifiers, silane coupling agents, processing aids, mold release agents, hydrolysis inhibitors, heat stabilizers, antifogging agents, flame retardants, flame retardant aids, light diffusing agents, antibacterial agents, antifungal agents, and dispersants. The other components may be used alone or in combination of two or more.

[0062] Examples of thermoplastic resins other than PP (B) that the sealant layer may contain (also referred to as other thermoplastic resins) include polyolefins, ethylene-unsaturated carboxylic acid copolymers or ionomers thereof, ethylene-vinyl acetate copolymers (EVA), ethylene-α-olefin copolymer elastomers, etc. Examples of the α-olefins include polyethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, etc. Commercially available products may be used as the other thermoplastic resins.

[0063] The thickness of the sealant layer is preferably 3 μm to 20 μm, more preferably 4 μm to 15 μm, and even more preferably 4 μm to 12 μm. Within the above range, the function of the sealant layer is more favorably exhibited, and the covering laminate has high sealing strength, good easy peelability, and is less likely to leave residue at the peeled portion after peeling.

[0064] <Layer structure of lid material laminate> The lid material laminate of the present disclosure is not particularly limited in its layer structure as long as it has the above-mentioned base material layer, easily peelable layer, and sealant layer, and may further have other optional layers. The structure of the lid material laminate will be described with reference to the drawings.

[0065] Fig. 1 is a schematic diagram showing one embodiment of a lid material laminate of the present disclosure. The lid material laminate 10 shown in Fig. 1 has a substrate layer 16, and an easily peelable layer 14 and a sealant layer 12 are provided in this order on the surface of the substrate layer 16. The presence of the substrate layer 16 further improves the strength and stability of the lid. In the lid material laminate 10 shown in Fig. 2, the sealant layer 12 is the outermost surface and is the layer that comes into contact with the container, which is the adherend.

[0066] Other Layers Examples of other layers that may be optionally provided in the covering material laminate of the present disclosure include a barrier layer intended to provide gas barrier properties, water vapor barrier properties, odor blocking properties, etc., an adhesive layer intended to improve adhesion between different layers, a foam layer, an inorganic layer, a hard coat layer, an anti-reflection layer, an anti-fouling layer, an anchor coat layer, etc.

[0067] The barrier layer may be made of a metal foil such as aluminum foil, aluminum-deposited polyester, aluminum-deposited polypropylene, silica-deposited polyester, etc. The thickness of the barrier layer is preferably 3 μm to 20 μm, more preferably 4 μm to 15 μm, and even more preferably 5 μm to 15 μm.

[0068] From the viewpoint of increasing the adhesive strength with adjacent layers, the surface of the barrier layer on which another resin layer is laminated or the surface on which an optional adhesive layer is laminated may be subjected to a surface treatment. Examples of surface treatments include physical treatments such as corona treatment, plasma treatment, and flame treatment, and chemical treatments such as anchor coat treatment. Among these, it is preferable that the surface of the barrier layer on which the adhesive layer is laminated is subjected to corona treatment.

[0069] The adhesive layer is a layer for improving adhesion between two adjacent layers, for example, the barrier layer and the substrate layer. When the covering material laminate of the present disclosure has an adhesive layer, the adhesive layer may be a single layer or two or more layers. Furthermore, the adhesive layer may contain a known adhesive. The adhesive layer may contain, for example, an ionomer of an ethylene-unsaturated carboxylic acid copolymer. The thickness of the adhesive layer is preferably 5 μm to 50 μm, more preferably 10 μm to 30 μm, and even more preferably 10 μm to 20 μm.

[0070] The position of the other layer is not particularly limited as long as the effects of the present disclosure are achieved. The number of other layers may be one or two or more.

[0071] <Preferred physical properties of lid material laminate> When used as a lid material for a container, the lid material laminate of the present disclosure preferably has high sealing strength and easy peelability, i.e., low peel strength. Preferred physical properties for the sealing strength and peel strength, which is an index of easy peelability, of the lid material laminate of the present disclosure are listed below.

[0072] - Sealing Strength - When the lid material laminate of the present disclosure is heat-sealed to the surface of a container having a surface formed from a polypropylene sheet, such as a commercially available product under the trade name of Lamicon Cup LR72-71T (manufactured by Tokan Kogyo Co., Ltd.), at a gauge pressure of 0.1 MPa, a heating temperature of 180°C, and a sealing time of 1.0 second, the sealing strength between the lid material laminate and the polypropylene container preferably exceeds 30 kPa, more preferably 31 kPa or more, and even more preferably 32 kPa or more. If the sealing strength according to the test method described below is less than 30 kPa, for example, due to vibration, temperature conditions, stress, etc. during transport of the container, the container may not be able to maintain its sealing, potentially reducing the protection of the contents.

[0073] The sealing strength test method will be described in more detail. First, a container (72 mm diameter) whose surface is formed from a polypropylene sheet is placed in a cup holder, and the sealant layer side of a sample cut into a size of 100 mm x 100 mm from the lid material laminate of the present disclosure is placed on the flange of the polypropylene container so that the center of the sample faces the center of the opening of the polypropylene container. Next, heat sealing is performed under the following heat sealing conditions to obtain a test sample of easy-peel layer / sealant layer / polypropylene container. Thereafter, the test sample is left in an environment of 23°C and 50% RH for 24 hours. (Heat sealing conditions) Sealing device: Cup sealer (PACH SEALER Model 0L, manufactured by Eishin Pack Kogyo Co., Ltd.) Sealing temperature: 180°C Sealing time: 1.0 second Sealing pressure (gauge pressure): 0.1 MPa

[0074] Next, a certain amount of air is blown into the test sample under the following conditions until the lid material laminate peels off, and the maximum pressure when the lid material laminate peels off is measured. The average value of the maximum pressure measured three times is taken as the sealing strength (kPa). (Air blowing conditions) Testing equipment: Bursting strength tester manufactured by Sun Scientific Co., Ltd. Flow rate: 0.8 L / min Temperature: 23°C Humidity: 50% RH

[0075] - Peel Strength - When the lid material laminate of the present disclosure is heat-sealed to the surface of a container formed from a polypropylene sheet at a gauge pressure of 0.1 MPa, a heating temperature of 180°C, and a sealing time of 1.0 second, the peel strength when peeling the lid material laminate from the polypropylene container is preferably 5 N or more and 20 N or less, more preferably 5 N or more and 15 N or less, even more preferably 7 N or more and 15 N or less, and particularly preferably 8 N or more and 15 N or less. If the peel strength is less than 5 N using the test method described below, for example, the lid material of the container may be easily opened due to vibration, stress, etc. during transport of the container, which may reduce the protection of the contents. Furthermore, if the peel strength exceeds 20 N, for example, it may become difficult to open the lid, and there is a concern that stringiness or the like may easily occur at the peeled portion.

[0076] The peel strength test method will be described in more detail. First, a container (72 mm diameter) whose surface is formed from a polypropylene sheet is set in a cup holder, and the sealant layer side of a sample cut into a size of 100 mm x 100 mm from the lid material laminate of the present disclosure is placed on the flange of the polypropylene container so that the center of the sample faces the center of the opening of the polypropylene container. Next, heat sealing is performed under the following heat sealing conditions to obtain a test sample of easily peelable layer / sealant layer / polypropylene container. Thereafter, the test sample is left in an environment of 23°C and 50% RH for 24 hours. (Heat sealing conditions) Sealing device: Cup sealer (PACH SEALER Model 0L, manufactured by Eishin Pack Kogyo Co., Ltd.) Sealing temperature: 180°C Sealing time: 1.0 second Sealing pressure (gauge pressure): 0.1 MPa

[0077] Next, the lid material laminate is peeled from the polypropylene container from a corner of the test sample under the following peeling conditions, and the maximum peel strength during peeling is measured. The average value of the maximum peel strengths measured three times is taken as the peel strength (N). (Peeling conditions) Peeling tester: Peel tester manufactured by Imada Co., Ltd. Test speed: 500 mm / min Peel angle: 45° Temperature: 23°C Humidity: 50% RH

[0078] [Lid Material] The lid material of the present disclosure includes the lid material laminate of the present disclosure described above. The lid material of the present disclosure includes the lid material laminate of the present disclosure described above and is suitable for use as a lid material for packaging containers. The lid material of the present disclosure may use the lid material laminate of the present disclosure described above as the lid material itself, or may be configured with a support and the lid material laminate of the present disclosure described above, or may further include other layers. Examples of the lid material structure include a laminate structure including a substrate layer / easily peelable layer / sealant layer laminate structure, and may have a structure having different resin films as the substrate layer, such as a laminate structure of a stretched polyester film / polyethylene film / laminate layer / easily peelable layer / sealant layer, or a laminate structure of a paper substrate layer / laminate layer / easily peelable layer / adhesive layer / sealant layer. The "laminate layer" is a polyethylene-based resin layer. Note that the "laminate layer" or "stretched polyester film / polyethylene film / laminate layer" in the above layer structure functions as the resin substrate layer of the lid body. In this case, the substrate layer of the present disclosure corresponds to "stretched polyester film / polyethylene film / laminate layer" or "paper substrate layer / laminate layer." Note that, since the lid material laminate of the present disclosure includes a substrate layer, it may or may not have a separate support. Furthermore, in order to improve water vapor barrier properties and odor blocking properties, the lid material may further have a barrier layer.

[0079] When the lid material laminate of the present disclosure, or further, a lid material including the lid material laminate, is manufactured, a laminate is formed. It can be obtained by appropriately applying a known laminate manufacturing method, such as a method of multi-layer coating of a coating liquid for forming each layer on a support or substrate layer, or a method of forming a film by co-extrusion of molten resins for forming each layer constituting the laminate. Among these, from the viewpoint of ease of manufacturing, a method of forming a laminate on a support or substrate layer by co-extrusion is preferred. A suitable example of a use in which a lid material is applied is a lid material that adheres to a storage container to close the opening.

[0080] [Packaging Container] The packaging container of the present disclosure comprises the lid material of the present disclosure described above and a container having a cylindrical body with one end closed and the other end having an opening, and the opening is covered by the lid material by heat-sealing the lid material to the opening (e.g., the peripheral surface of the opening) via a sealant layer.

[0081] The base material of the packaging container of the present disclosure is not particularly limited, and any base material can be used as long as the surface that contacts the sealant layer of the lid material is heat-sealable. A container having a base material with an opening and a storage section that can be used in the packaging container of the present disclosure is preferably a container in which at least the outermost surface, i.e., the outermost surface that contacts the sealant layer of the lid material, is molded from a resin material. Of these, a container in which the surface of the base material that contacts the lid material is formed from a polypropylene sheet is preferred. The packaging container of the present disclosure is a container that has suitable peel strength and good easy peelability when the heat-sealed lid material is peeled off, and is unlikely to leave residue at the peeled portion after peeling. Furthermore, when sealed, it has stable sealing strength, suppresses undesired peeling during storage or transportation, and provides excellent protection for the contents.

[0082] <Polypropylene Container> A polypropylene container, which is a suitable base material for the packaging container of the present disclosure, will be described. A polypropylene container is a container in which the surface of the container, which is heat-sealed via the sealant layer of the lid material, is formed from a polypropylene sheet. The sheet for forming the polypropylene container is not particularly limited as long as it can be used to form a container. The polypropylene container may have another layer other than polypropylene on the side opposite the polypropylene side. Examples of the other layer include a polyethylene layer, a paper substrate, a substrate layer, an adhesive layer, an anti-fouling layer, a barrier layer, etc. The other layer may be one layer or two or more layers.

[0083] The polypropylene on the surface of the container to be heat-sealed is not particularly limited as long as it is a propylene polymer containing mainly propylene-derived structural units. The propylene polymer is preferably a propylene homopolymer or a propylene copolymer containing 50% by mass or more of propylene-derived structural units relative to the entire polymer, and more preferably a propylene homopolymer. The surface of the container to be heat-sealed may contain components other than polypropylene.

[0084] The container may have a flange that is heat-sealed via a sealant layer of the lid material. When the container has a flange, the surface of the flange is preferably also made of polypropylene.

[0085] The packaging container can be suitably used as a packaging container for packaging, for example, food, beverages, liquids other than beverages, medicines, industrial goods, daily necessities, cosmetics, etc., and can be particularly suitably used as a packaging container for food and medicines. The container may contain food, beverages, liquids other than beverages, medicines, industrial goods, daily necessities, cosmetics, etc., or may contain food, beverages, or medicines.

[0086] An example of a packaging container according to the present disclosure will be described below with reference to the drawings.

[0087] FIG. 2 is a schematic diagram showing an example of a packaging container using a lid material laminate 10 including the base material layer 16 shown in FIG. 1 as a lid material laminate. The packaging container 20 shown in FIG. 2 uses the lid material laminate 10 shown in FIG. 1 as a lid material. The packaging container 20 includes a lid material and a polypropylene container 18, and contents such as food can be stored in a space corresponding to the storage section of the polypropylene container 18. The polypropylene container 18 has a polypropylene layer on its surface. The polypropylene container 18 has a flange at its opening. The sealant layer 12 of the lid material is heat-sealed to the polypropylene layer on the surface of the flange, thereby covering the opening with the lid material. When the lid material is peeled from the packaging container 20, the generation of residues such as stringiness is suppressed, thereby suppressing the incorporation of foreign matter such as resin into the contents and the deterioration of the texture when eating the contents by placing the flange portion in the mouth.

[0088] The present embodiment will be described in detail below with reference to examples, etc. However, the present embodiment is not limited to the descriptions of these examples.

[0089] [Materials] The following components were used for the laminate: The melt flow rate (MFR) was measured in accordance with JIS K 7210-1:2014.

[0090] <High-pressure low-density polyethylene (A1) or (A2)> HP-LDPE-1: low-density polyethylene, MFR (190°C, 2160 g load): 7.2 g / 10 min, density: 918 kg / m ３ , Melting point: 108°C HP-LDPE-2: Low density polyethylene, MFR (190°C, 2160g load): 23g / 10min, Density: 918kg / m ３ , Melting point: 106 ° C. HP-LDPE-3: Low density polyethylene, MFR (190 ° C, 2160 g load): 70 g / 10 min, Density: 916 kg / m ３ , Melting point: 104°C HP-LDPE-4: Low density polyethylene, MFR (190°C, 2160g load): 1.6g / 10min, Density: 920kg / m ３ , melting point: 110 ° C.

[0091] <Propylene-based resin (B1) or (B2)> h-PP-1: MFR (230°C, 2160 g load): 30 g / 10 min, density: 910 kg / m ３ , Melting point: 162°C h-PP-2: MFR (230°C, 2160g load): 3.0g / 10min, Density: 910kg / m ３ , Melting point: 165°C r-PP-1: MFR (230°C, 2160g load): 25g / 10min, Density: 910kg / m ３ , Melting point: 137°C r-PP-2: MFR (230°C, 2160g load): 9.6g / 10min, Density: 910kg / m ３ , melting point: 140 ° C.

[0092] <Linear low-density polyethylene (C)> LLDPE: linear low-density polyethylene, MFR (190°C, 2160 g load): 10 g / 10 min, density: 910 kg / m ３ , melting point: 112 ° C.

[0093] <Tackifier Resin (D)> Tackifier Resin 1: Alicyclic hydrocarbon resin (manufactured by Arakawa Chemical Industries, Ltd., Alcon (registered trademark) P115)

[0094] <Additives> Release agent: polyethylene glycol (PEG, manufactured by Nippon Fine Chemical Co., Ltd.) Slip agent: erucic acid amide (ELA, manufactured by NOF Corporation)

[0095] [Examples 1 to 5 and Comparative Examples 1 to 3] <Preparation of Resin Composition 1 for Forming Peelable Layer> The materials were pre-mixed in a blending ratio of 17 parts by mass of HP-LDPE-2, 33 parts by mass of HP-LDPE-3, 34.8 parts by mass of h-PP-2, 15 parts by mass of tackifier resin (D), 0.1 part by mass of release roll agent, and 0.1 part by mass of slip agent, so that the charged amount was 10 kg. The mixture was then charged into a single-screw extruder having a screw diameter of 65 mmφ (effective screw length: L / D = 28) and melt-kneaded at a processing temperature of 240°C, to prepare Resin Composition 1 for Forming Peelable Layer (hereinafter also referred to as Composition 1). Of all the components in Composition 1, the total content of HP-LDPE (A1), h-PP, and tackifier resin (D) was 99.8 mass%, and the content of HP-LDPE (A1) was 59.0 mass% relative to the total content of HP-LDPE and h-PP.

[0096] <Preparation of Resin Composition 2 for Forming Peelable Layer> The materials were pre-mixed in a blending ratio of 21 parts by mass of HP-LDPE-2, 41 parts by mass of HP-LDPE-3, and 38 parts by mass of h-PP-2 so that the charged amount was 10 kg, and the mixture was melt-kneaded under the same conditions as for Composition 1, to prepare Resin Composition 2 for forming a peelable layer (hereinafter also referred to as Composition 2). Of all the components in Composition 2, the content of HP-LDPE (A1) was 62.0% by mass relative to the total amount of HP-LDPE and h-PP.

[0097] <Preparation of Resin Composition 3 for Forming Peelable Layer> The materials were pre-mixed in a blending ratio of 30 parts by mass of HP-LDPE-4 and 70 parts by mass of h-PP-1 so that the charged amount was 10 kg, and the mixture was melt-kneaded under the same conditions as for Composition 1, to prepare Resin Composition 3 for forming peelable layer (hereinafter also referred to as Composition 3). Of all the components in Composition 3, the content of HP-LDPE (A1) was 30.0% by mass relative to the total amount of HP-LDPE and h-PP.

[0098] The formulations of Compositions 1 to 3 constituting the easily peelable layer are shown in Table 1 below. In the table, "-" indicates that the component in question is not contained.

[0099]

[0100] The MFR of composition 1 measured under conditions of 190°C and a load of 2160 g was 32 g / 10 min, the MFR of composition 2 measured under the same conditions was 18 g / 10 min, and the MFR of composition 3 measured under the same conditions was 7.3 g / 10 min.

[0101] <Preparation of Laminate> A molten film consisting of a laminate layer (polyethylene resin layer) / an easily peelable layer / a sealant layer was prepared using a multilayer cast film molding machine. The T-die setting temperature was 230 ° C., and a portion of a substrate layer made of a 12 μm stretched polyester film (manufactured by Toray Industries, Inc., Lumirror (registered trademark)) laminated with a 15 μm low-density polyethylene was extrusion laminated onto the laminate layer side of the molten film so as to be bonded to the low-density polyethylene side of the substrate layer, thereby preparing a lid material laminate. In each example and comparative example, the compositions shown in Table 2 were used for the laminate layer, the easily peelable layer, and the sealant layer. The three-layer cast film molding machine used above was a three-layer cast molding machine manufactured by Tanabe Plastics Machinery Co., Ltd., and all molding machines had a screw diameter of 40 mmφ, a T-die width of 500 mm, and a coextrusion feed block manufactured by EDI.

[0102] [Evaluation of Peel Strength (Cup Seal Strength)] A polypropylene cup container (Lamicon Cup LR72-71T, manufactured by Tokan Kogyo Co., Ltd.) was set in a cup holder, and the sealant layer side of a lid material sample cut into a size of 100 mm x 100 mm from the lid material laminate was placed on the flange of the polypropylene cup container so that the center of the cup container and the center of the sample faced each other. Next, heat sealing was performed under the following heat sealing conditions to obtain a test sample having a layer structure of stretched polyester film / polyethylene / laminate layer (polyethylene-based resin layer) / easy-peel layer / sealant layer / polypropylene cup. Thereafter, the sample was left in an environment of 23°C and 50% RH for 24 hours. <Heat Sealing Conditions> Sealing device: Cup sealer (PACH SEALER Model 0L, manufactured by Eishin Pack Kogyo Co., Ltd.) Sealing temperature: 180°C Sealing time: 1.0 second Sealing pressure (gauge pressure): 0.1 MPa

[0103] Next, the lid material laminate was peeled from the polypropylene cup at a corner of the test sample prepared above under the following peeling conditions, and the maximum peel strength during peeling was measured. The average value of the maximum peel strengths measured three times was taken as the peel strength (N).

[0104] <Peel conditions> Peel tester: Peel tester manufactured by Imada Co., Ltd. Test speed: 500 mm / min Peel angle: 45° Temperature: 23° C. Humidity: 50% RH

[0105] The peel strength was evaluated according to the following criteria: <Evaluation criteria> A: The peel strength was 7N or more and 14N or less. B: The peel strength was less than 7N or more than 14N.

[0106] [Visual evaluation of peeling state] A skilled technician observed the sealant layer side surface of the laminate (sample in which the sealant layer and polypropylene cup were peeled off) used in the above peel strength measurement after peel strength measurement. Thin thread-like resin may be formed at the peeled portion. This is commonly known as stringing. The occurrence of stringing was recorded visually. The stringing phenomenon is not preferable not only because it deteriorates the appearance but also because it is undesirable from the viewpoint of foreign matter contamination, such as pieces of thread adhering to the contents when removing food or other contents. The peeling state was evaluated according to the following criteria. Grades AA to B are levels that are not problematic in practical use, with grades AA and A being preferable levels. <Evaluation criteria> AA: No stringing was observed at all A: Almost no stringing was observed B: Scattered stringing was observed C: Scattered film was observed D: Film residue was observed on the cup

[0107] [Evaluation of Weight Change] In the evaluation of peel strength, the weights of the polypropylene cup container alone before the lid material laminate was heat-sealed and the polypropylene cup container alone after the lid material laminate was heat-sealed and peeled off were measured, and the weight change was evaluated. The weight change was evaluated according to the following criteria. <Evaluation criteria> A: Weight change was 0% or more and less than 0.14% B: Weight change was 0.14% or more

[0108] [Evaluation of Sealing Strength] A polypropylene cup container (Lamicon Cup LR72-71T, manufactured by Tokan Kogyo Co., Ltd.) was set in a cup holder, and the sealant layer side of a lid material sample cut into a size of 100 mm x 100 mm from the lid material laminate was placed on the flange of the polypropylene cup container so that the center of the cup container and the center of the sample faced each other. Next, heat sealing was performed under the following heat sealing conditions to obtain a test sample having a layer structure of stretched polyester film / polyethylene / laminate layer (polyethylene-based resin layer) / easy-peel layer / sealant layer / polypropylene cup. Thereafter, the sample was left in an environment of 23°C and 50% RH for 24 hours. <Heat Sealing Conditions> Sealing device: Cup sealer (PACH SEALER Model 0L, manufactured by Eishin Pack Kogyo Co., Ltd.) Sealing temperature: 180°C Sealing time: 1.0 second Sealing pressure (gauge pressure): 0.1 MPa

[0109] Next, a certain amount of air was blown into the test sample prepared above under the following conditions until the laminate peeled off, and the maximum pressure at which the laminate peeled off was measured. The average of the maximum pressures measured three times was taken as the sealing strength (kPa). <Air blowing conditions> Testing equipment: Bursting strength tester manufactured by Sun Scientific Co., Ltd. Flow rate: 0.8 L / min Temperature: 23°C Humidity: 50% RH

[0110] The sealing strength was evaluated according to the following criteria: <Evaluation criteria> AA: The maximum pressure when the laminate peeled off exceeded 40 kPa. A: The maximum pressure when the laminate peeled off was 30 kPa or more and 40 kPa or less. B: The maximum pressure when the laminate peeled off was less than 30 kPa.

[0111]

[0112] As is clear from Table 2, Examples 1 to 5 had higher sealing strength and lower peel strength than Comparative Examples 1 to 3. Furthermore, stringiness and weight change after peeling were suppressed, and the peeling state was at a level that poses no practical problems. From the above, it was confirmed that, according to this embodiment, when the obtained lid material laminate is used as a lid material for a packaging container, high sealing strength and low peel strength are achieved, i.e., both sealing strength and easy peelability are achieved, and residue is less likely to be left in the peeled portion after peeling.

[0113] The disclosure of Japanese Patent Application No. 2024-005700, filed on January 17, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A base material layer in which at least one surface layer is a polyethylene-based resin layer, a peelable layer adjacent to the polyethylene-based resin layer, and a sealant layer adjacent to the peelable layer, wherein the peelable layer contains high-pressure low-density polyethylene (A1) and a propylene homopolymer (B1), and the content of the high-pressure low-density polyethylene (A1) in the peelable layer exceeds 50% by mass with respect to the total mass of 100% by mass of the mass of the high-pressure low-density polyethylene (A1) and the mass of the propylene homopolymer (B1) contained in the peelable layer, and the content of the propylene homopolymer (B1) in the peelable layer exceeds 0% by mass and is less than 40% by mass with respect to the total mass of the peelable layer, and the sealant layer contains a propylene-based resin (B) and is the outermost layer on the side in contact with the adherend of the laminate for lid materials.

2. The laminate for lid materials according to claim 1, wherein the high-pressure low-density polyethylene (A1) conforms to JIS K 7210-1:2014 and has a melt flow rate measured under the conditions of 190°C and a load of 2160 g of 3.0 g / 10 min or more and 100 g / 10 min or less.

3. The laminate for lid materials according to claim 1, wherein the propylene homopolymer (B1) conforms to JIS K 7210-1:2014 and has a melt flow rate measured under the conditions of 230°C and a load of 2160 g of 0.1 g / 10 min or more and 100 g / 10 min or less.

4. The laminate for lid materials according to claim 1, wherein the peelable layer contains a tackifier resin (D).

5. The laminate for lid materials according to claim 4, wherein the total content of the high-pressure low-density polyethylene (A1), the propylene homopolymer (B1), and the tackifier resin (D) in the peelable layer exceeds 98% by mass and is 100% by mass or less with respect to the total mass of the resin components contained in the peelable layer.

6. The laminate for lid materials according to claim 1, wherein the content of the propylene-based resin (B) in the sealant layer is 90% by mass or more with respect to the total mass of the sealant layer.

7. The laminate for lid materials according to claim 1, wherein the thickness of the sealant layer is 3 μm or more and 20 μm or less.

8. The laminate for lid materials according to claim 1, wherein the propylene-based resin (B) is a propylene homopolymer (B2) or a propylene / α-olefin random copolymer (B3).

9. The propylene-based resin (B) conforms to JIS K 7210-1:2014 and has a melt flow rate measured under the conditions of 230°C and a load of 2160 g of 0.1 g / 10 min or more and 100 g / 10 min or less. The laminate for a lid material according to claim 1.

10. The polyethylene-based resin layer is composed of high-pressure low-density polyethylene (A2) or linear low-density polyethylene (C). The laminate for a lid material according to claim 1.

11. A lid material including the laminate for a lid material according to any one of claims 1 to 10.

12. The lid material according to claim 11, and a container having one of the cylindrical bodies closed and an opening at the other, wherein the opening is covered with the lid material by heat-sealing the lid material through a sealant layer. A packaging container.

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