Resin composition for sealant, sealant, laminate, and skin pack packaging body

Abstract

A resin composition for a sealant according to the present invention contains an ethylene-vinyl acetate copolymer (A) having a melting point of 65°C or more, a high-pressure, low-density polyethylene (B), and a propylene-based polymer (C). The high-pressure low-density polyethylene (B) content is 5-25 parts by mass relative to 100 parts by mass of the entire resin composition for a sealant.

Description

Resin composition for sealant, sealant, laminate, and packaging material for skin pack

[0001] The present disclosure relates to a resin composition for a sealant, a sealant, a laminate, and a packaging body for a skin pack.

[0002] Skin pack packaging is a process in which a base tray carrying the contents (i.e., the packaged items) is placed in a vacuum chamber, a vacuum is created inside the vacuum chamber, a heated lid film is heated, and the upper chamber is opened to create a differential pressure, causing the lid film to adhere closely or pseudo-adhere to the contents, thereby vacuum-packaging the contents. Conventionally, films having a laminated structure of polyvinyl chloride (PVC) / polyvinylidene chloride (PVDC) / ethylene-vinyl acetate copolymer (EVA) have generally been used as films for skin packing sliced ​​ham, bacon, processed seafood products, etc.

[0003] Disclosed as a multilayer film for food packaging is a flexible multilayer film that includes at least a nylon layer (A), a gas barrier layer (B), an adhesive layer (C), an ionomer layer (D), and an ethylene-vinyl acetate copolymer layer (E) having a vinyl acetate content of 10% or more, and has a layer structure of (A)-(B)-(C)-(D)-(E), (A)-(C)-(B)-(C)-(D)-(E), (B)-(A)-(C)-(D)-(E), (B)-(C)-(A)-(C)-(D)-(E), or (A)-(B)-(A)-(C)-(D)-(E) (see, for example, Patent Document 1). Furthermore, a coextruded multilayer film for skin pack lid material has been disclosed, which is composed of an outermost layer (A) made of an oxygen gas barrier resin and having a thickness of 5 to 30 μm, an intermediate layer (B) made of an ionomer resin and having a thickness of 5 to 80 μm, an intermediate layer (C) made of an ethylene-vinyl acetate copolymer and having a thickness of 5 to 80 μm, and an innermost layer (D) made of an ethylene-based heat-sealable resin and having a thickness of 5 to 80 μm laminated together in this order, and which has an adhesive layer between each of the layers as needed (see, for example, Patent Document 2).

[0004] Patent Document 1: Patent No. 3085626 Patent Document 2: Patent No. 5034237

[0005] Films used in skin pack packaging require excellent adhesion, while also requiring adequate peelability when removing contents from vacuum packaging. Furthermore, resin compositions used to form the film are required to be suitable for manufacturing when forming the film. However, it has been difficult for the multilayer films described in Patent Documents 1 and 2 to satisfy all of the above-mentioned required properties. The present disclosure has been made in view of the above-mentioned conventional circumstances, and one aspect of the present disclosure aims to provide a sealant resin composition that has adequate peel strength and excellent manufacturing suitability when forming a film. Another aspect of the present disclosure aims to provide a sealant, a laminate, and a skin pack packaging body using this sealant resin composition.

[0006] Specific means for achieving the above object include the following aspects. <1> A sealant resin composition comprising an ethylene-vinyl acetate copolymer (A) having a melting point of 65°C or higher, a high-pressure low-density polyethylene (B), and a propylene polymer (C), wherein the content of the high-pressure low-density polyethylene (B) is 5 to 25 parts by mass per 100 parts by mass of the total sealant resin composition. <2> The sealant resin composition according to <1>, wherein the ethylene-vinyl acetate copolymer (A) has a melting point of 85°C or lower. <3> The sealant resin composition according to <1> or <2>, wherein the propylene polymer (C) is a propylene homopolymer. <4> A sealant comprising the sealant resin composition according to any one of <1> to <3>. <5> A laminate having a sealant layer comprising the sealant according to <4> and a substrate layer. <6> The laminate according to <5>, wherein the substrate layer includes a resin layer in contact with the sealant layer. <7> The laminate according to <5>, wherein the base layer includes a paper base layer. <8> The laminate according to <6>, wherein the base layer includes a paper base layer. <9> A skin pack packaging comprising a lid material and a base material, for skin-packing contents by bringing the lid material and the base material into close contact with each other, wherein at least one of the lid material and the base material has the sealant according to <4> or the laminate according to any one of <5> to <8>.

[0007] According to one aspect of the present disclosure, it is possible to provide a sealant resin composition that has appropriate peel strength and excellent manufacturability when forming a film. Also, according to another aspect of the present disclosure, it is possible to provide a sealant, a laminate, and a skin pack packaging body using the sealant resin composition.

[0008] Hereinafter, an embodiment of the present disclosure will be described. The present disclosure is not limited to the following embodiment, and can be implemented with appropriate modifications within the scope of the object of the present disclosure.

[0009] In the present disclosure, the term "to" in a numerical range means that the numerical values ​​before and after "to" are included. In the numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples. In the present disclosure, when the composition contains multiple substances corresponding to each component, the amount of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0010] [Sealant Resin Composition] The sealant resin composition of the present disclosure is a sealant resin composition comprising an ethylene-vinyl acetate copolymer (A) having a melting point of 65°C or higher, a high-pressure low-density polyethylene (B), and a propylene polymer (C), wherein the content of the high-pressure low-density polyethylene (B) is 5 to 25 parts by mass relative to 100 parts by mass of the total sealant resin composition. By providing the sealant resin composition of the present disclosure with the above configuration, it is believed that a sealant resin composition can be obtained that has appropriate peel strength and excellent manufacturability when forming a film, compared to conventional sealant resin compositions.

[0011] Each component contained in the sealant resin composition of the present disclosure will be described in detail below. Unless otherwise specified, the melt flow rate (MFR) is a value [g / 10 min] measured at 190°C under a load of 2160 g in accordance with JIS K7210:1999.

[0012] <Ethylene-vinyl acetate copolymer (A)> The ethylene-vinyl acetate copolymer (A) used in the present disclosure has a melting point of 65°C or higher. When the melting point of the ethylene-vinyl acetate copolymer (A) is 65°C or higher, excellent cuttability during granulation is achieved. The melting point of the ethylene-vinyl acetate copolymer (A) is preferably 66°C or higher, more preferably 68°C or higher, and even more preferably 71°C or higher. From the viewpoint of adequate peel strength, the melting point of the ethylene-vinyl acetate copolymer (A) is preferably 100°C or lower, more preferably 95°C or lower, even more preferably 90°C or lower, even more preferably 85°C or lower, particularly preferably 82°C or lower, extremely preferably 79°C or lower, and most preferably 75°C or lower. The melting point of the ethylene-vinyl acetate copolymer (A) is preferably 65°C to 100°C, more preferably 65°C to 95°C, even more preferably 65°C to 90°C, still more preferably 65°C to 85°C, particularly preferably 65°C to 82°C, extremely preferably 65°C to 79°C, and most preferably 65°C to 75°C.

[0013] In the present disclosure, the melting point Tm of the ethylene-vinyl acetate copolymer (A) refers to a value measured with a differential scanning calorimeter (DSC) in accordance with JIS K7121: 1987. When multiple peaks are detected, the peak detected at the highest temperature is used.

[0014] The ethylene-vinyl acetate copolymer (A) used in the present disclosure contains at least structural units derived from ethylene and structural units derived from vinyl acetate (VA). The ethylene-vinyl acetate copolymer (A) may be a random copolymer, a block copolymer, or an alternating copolymer. The ethylene-vinyl acetate copolymer (A) may further contain structural units derived from a monomer other than vinyl acetate and ethylene. In the present disclosure, it is preferred that the ethylene-vinyl acetate copolymer does not contain any monomer units other than vinyl acetate and ethylene, and is composed of structural units derived from vinyl acetate and structural units derived from ethylene.

[0015] The ethylene-vinyl acetate copolymer (A) in the present disclosure contains structural units derived from ethylene and structural units derived from vinyl acetate, and may optionally further contain structural units derived from other monomers. Examples of structural units derived from other monomers include structural units derived from unsaturated carboxylic acid esters, unsaturated hydrocarbons other than ethylene (e.g., propylene, butene, 1,3-butadiene, pentene, 1,3-pentadiene, 1-hexene, etc.), vinyl esters other than vinyl acetate (e.g., vinyl propionate, etc.), oxides such as vinyl sulfate and vinyl nitrate, halogen compounds (e.g., vinyl chloride, vinyl fluoride, etc.), vinyl group-containing primary and secondary amine compounds, carbon monoxide, sulfur dioxide, etc. Among these, structural units derived from other monomers are preferably structural units derived from unsaturated carboxylic acid esters.

[0016] The unsaturated carboxylic acid ester is not particularly limited as long as it is copolymerizable with ethylene and vinyl acetate, and examples thereof include unsaturated carboxylic acid alkyl esters. Examples of the unsaturated carboxylic acid alkyl ester include alkyl acrylates such as methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, n-butyl acrylate, and isooctyl acrylate, alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, and isooctyl methacrylate, and alkyl maleates such as dimethyl maleate and diethyl maleate, and other unsaturated carboxylic acid alkyl esters in which the alkyl group has 1 to 12 carbon atoms.

[0017] Among these, as the unsaturated carboxylic acid alkyl ester, alkyl esters of acrylic acid or methacrylic acid such as methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, n-butyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, and isooctyl methacrylate are preferred, and lower alkyl esters of acrylic acid or methacrylic acid (for example, alkyl esters in which the alkyl group has 2 to 5 carbon atoms) are more preferred.

[0018] From the viewpoint of adequate peel strength, the content of structural units derived from vinyl acetate in the ethylene-vinyl acetate copolymer (A) is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 8% by mass or more, and particularly preferably 10% by mass or more, based on the total structural units of the ethylene-vinyl acetate copolymer (A). From the viewpoint of film production suitability, the content of structural units derived from vinyl acetate in the ethylene-vinyl acetate copolymer (A) is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less, and particularly preferably 30% by mass or less, based on the total structural units of the ethylene-vinyl acetate copolymer (A). The content of structural units derived from vinyl acetate in the ethylene-vinyl acetate copolymer (A) is preferably 3% to 50% by mass, more preferably 5% to 40% by mass, even more preferably 8% to 35% by mass, and particularly preferably 10% to 30% by mass, based on the total structural units of the ethylene-vinyl acetate copolymer (A).

[0019] The ethylene-vinyl acetate copolymer (A) preferably has a content of structural units derived from ethylene of 50% to 97% by mass, more preferably 60% to 95% by mass, even more preferably 65% ​​to 92% by mass, and particularly preferably 70% to 90% by mass, based on all structural units of the ethylene-vinyl acetate copolymer (A). Furthermore, the ethylene-vinyl acetate copolymer (A) may have a content of structural units derived from other monomers of 10% by mass or less, preferably 0% by mass, based on all structural units of the ethylene-vinyl acetate copolymer (A).

[0020] The melt flow rate (MFR) of the ethylene-vinyl acetate copolymer (A) in the present disclosure is preferably 0.5 g / 10 min to 800 g / 10 min, more preferably 1 g / 10 min to 400 g / 10 min, and even more preferably 2 g / 10 min to 200 g / 10 min, from the viewpoint of suitability for film production.

[0021] The ethylene-vinyl acetate copolymer (A) may be used alone or in combination of two or more types differing in copolymerization ratio, etc. The proportion of the ethylene-vinyl acetate copolymer (A) in the entire sealant resin composition of the present disclosure is preferably 30% by mass to 80% by mass, more preferably 40% by mass to 70% by mass, and even more preferably 50% by mass to 60% by mass, from the viewpoints of appropriate peel strength and suitability for film production.

[0022] <High-Pressure Low-Density Polyethylene (B)> The high-pressure low-density polyethylene (B) used in the present disclosure is polyethylene obtained by polymerizing ethylene by a high-pressure radical method.

[0023] The polymerization of the high-pressure low-density polyethylene (B) can be carried out by a known method. The reactor used for the polymerization includes, for example, an autoclave reactor and a tubular reactor, and either may be used.

[0024] The high-pressure low-density polyethylene (B) 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 ~930 kg / m ３ and preferably 915 kg / m ３ ~925 kg / m ３ By using the high-pressure low-density polyethylene (B) having a density within the above range in a resin composition for sealants, a resin composition having excellent extrusion processability can be obtained.

[0025] The high-pressure low-density polyethylene (B) preferably has a melt flow rate (MFR) of 1.0 g / 10 min to 100 g / 10 min, more preferably 1.0 g / 10 min to 50 g / 10 min, and even more preferably 3.0 g / 10 min to 30 g / 10 min. By using a high-pressure low-density polyethylene (B) having a melt flow rate within the above range in the sealant resin composition, the extrusion processability when forming a film becomes better.

[0026] The high-pressure low-density polyethylene (B) may be a commercially available product, such as Mirason M11P (manufactured by Dow Mitsui Polychemicals Co., Ltd.).

[0027] The content of the high-pressure low-density polyethylene (B) is 5 to 25 parts by mass relative to 100 parts by mass of the entire sealant resin composition. When the content of the high-pressure low-density polyethylene (B) is 25 parts by mass or less relative to 100 parts by mass of the entire sealant resin composition, appropriate peel strength is obtained. When the content of the high-pressure low-density polyethylene (B) is 5 parts by mass or more relative to 100 parts by mass of the entire sealant resin composition, there is an advantage in terms of film production suitability. The content of the high-pressure low-density polyethylene (B) is preferably 8 parts by mass or more, more preferably 10 parts by mass or more, relative to 100 parts by mass of the entire sealant resin composition. The content of the high-pressure low-density polyethylene (B) is preferably 23 parts by mass or less, more preferably 20 parts by mass or less, relative to 100 parts by mass of the entire sealant resin composition.

[0028] The content of the high-pressure low-density polyethylene (B) is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, relative to the total content of the high-pressure low-density polyethylene (B) and the propylene polymer (C) described below in the sealant resin composition. There is no particular upper limit to the content of the high-pressure low-density polyethylene (B) relative to the total content of the high-pressure low-density polyethylene (B) and the propylene polymer (C) described below, but it can be 55% by mass or less, and preferably 45% by mass or less. The content of the high-pressure low-density polyethylene (B) relative to the total content of the high-pressure low-density polyethylene (B) and the propylene polymer (C) described below is preferably 5% to 55% by mass. By setting the content of the high-pressure low-density polyethylene (B) within the above range, it becomes easy to control the heat resistance and peel strength of a film formed using the sealant resin composition within appropriate ranges.

[0029] <Propylene-Based Polymer (C)> The propylene-based polymer (C) used in the present disclosure may be one selected from the group consisting of propylene-based resins, i.e., copolymers having propylene-derived structural units and propylene homopolymers. The propylene-based polymer (C) may contain only one type, or may contain two or more types having different molecular weights. Examples of the propylene-based polymer (C) include propylene homopolymers, copolymers of propylene and other α-olefins (e.g., ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, etc.) containing propylene as the main component, and the like. Here, the term "main component" means that the content of propylene-derived structural units is 50% by mass or more of the total structural units of the propylene-based polymer (C).

[0030] The propylene polymer (C) may be a propylene homopolymer. The propylene polymer (C) preferably contains a propylene homopolymer from the viewpoint of appropriate peel strength. The propylene homopolymer, which is a preferred embodiment of the propylene polymer (C), preferably has a crystallinity of 30% or more by X-ray analysis.

[0031] From the viewpoint of heat resistance, the propylene polymer (C) is preferably a polymer having a melting point of 120°C to 170°C, more preferably 150°C to 170°C, as measured by a differential scanning calorimeter (DSC) in accordance with JIS K7121:1987.

[0032] A propylene homopolymer, which is a preferred embodiment of the propylene polymer (C), can be produced by polymerizing propylene in the presence of a stereoregular olefin polymerization catalyst containing a titanium-based or metallocene-based or other transition metal compound component, an organoaluminum component, and, if necessary, an electron donor, a carrier, and the like.

[0033] The melt flow rate (MFR) of the propylene polymer (C) measured under a load of 2.16 kg at a temperature of 230°C is preferably 1 g / 10 min to 500 g / 10 min, more preferably 2 g / 10 min to 100 g / 10 min, and even more preferably 3 g / 10 min to 50 g / 10 min, from the viewpoints of moldability and impact resistance. The MFR of the propylene polymer (C) 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.

[0034] The density of the propylene polymer (C) is 870 kg / m from the viewpoint of excellent impact resistance and a reduced 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 the propylene polymer (C) is a value measured by the underwater displacement method in accordance with JIS K 7112:1999.

[0035] The content of the propylene polymer (C) is preferably more than 0 mass% and less than 40 mass%, more preferably 20 mass% to 39 mass%, and even more preferably 25 mass% to 38 mass%, based on the total mass of the sealant resin composition.

[0036] It is believed that the sealant resin composition contains the propylene polymer (C) which has poor compatibility with the high-pressure low-density polyethylene (B), thereby achieving a good balance between peel strength and easy releasability.

[0037] <Tackifier Resin (D)> The sealant resin composition of the present disclosure may further contain a tackifier resin (D). Examples of the tackifier resin (D) include aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, aromatic hydrocarbon resins, styrene hydrocarbon resins, terpene resins, and rosins.

[0038] Examples of aliphatic hydrocarbon resins include C olefins such as 1-butene, isobutylene, butadiene, 1,3-pentadiene, isoprene, and piperylene. ４ ~C ５ Examples of the alicyclic hydrocarbon resin include polymers containing mono- or diolefins as the main component. ４ ~C ５ Examples of the resins include resins obtained by cyclodimerizing and then polymerizing diene components in the fraction, resins obtained by polymerizing cyclic monomers such as cyclopentadiene, and resins obtained by intranuclear hydrogenation of aromatic hydrocarbon resins. Examples of aromatic hydrocarbon resins include C olefins such as vinyl toluene, indene, and α-methylstyrene. ９ ~C １０ Here, the term "major component" means that the content of the structural unit is 50% by mass or more based on the total structural units of the hydrocarbon resin.

[0039] Examples of styrene hydrocarbon resins include polymers of styrene, vinyltoluene, α-methylstyrene, isopropenyltoluene, and the like.

[0040] Examples of terpene resins include α-pinene polymers, β-pinene polymers, dipentene polymers, terpene-phenol copolymers, α-pinene-phenol copolymers, and hydrogenated terpene resins.

[0041] Examples of rosins include rosin, polymerized rosin, hydrogenated rosin, rosin ester, rosin phenolic resin and its ester.

[0042] Among these, it is particularly preferable to use hydrogenated resins such as hydrogenated aromatic hydrocarbon resins and hydrogenated terpene resins.

[0043] From the viewpoint of maintaining good releasability, the content of the tackifier resin (D) is preferably 0% by mass to 25% by mass, with the total sealant resin composition being 100% by mass.

[0044] <Additives> In addition to the above components, any additives may be blended into the sealant resin composition of the present disclosure. Examples of such additives include antioxidants, heat stabilizers, light stabilizers, antistatic agents, lubricants, and colorants. In particular, blending a lubricant is desirable to improve the processability of the composition. Examples of such lubricants include fatty acid amides, high-molecular-weight polyethylene glycols, hydrogenated castor oil, and silica.

[0045] It is effective to blend such lubricants in an amount of about 100 ppm to 10,000 ppm for organic compound lubricants, or about 0.1 to 3 parts by mass for inorganic compound lubricants such as silica, relative to 100 parts by mass of the total amount of the sealant resin composition. The use of a lubricant has the advantage of preventing blocking of films and sticking to metal rolls when the sealant resin composition is extrusion coated onto a substrate, as well as improving the workability of subsequent processes such as rewinding.

[0046] In consideration of moldability and sealing properties, the sealant resin composition preferably has a melt flow rate of 1 g / 10 min to 400 g / 10 min, more preferably 1 g / 10 min to 150 g / 10 min.

[0047] [Sealant] The sealant of the present disclosure includes the sealant resin composition of the present disclosure. The sealant may be used as a single layer, or may be used in the form of a laminate having a sealant layer made of the sealant described below and a substrate layer.

[0048] The thickness of the sealant is preferably 1 μm to 200 μm, more preferably 2 μm to 100 μm, and even more preferably 5 μm to 50 μm.

[0049] The method for forming a sealant using the sealant resin composition is not particularly limited. Examples include a method in which the sealant resin composition is extrusion laminated onto a temporary support to form a sealant layer, and then the sealant layer is peeled off from the temporary support to form a sealant, and a method in which the sealant resin composition is formed into a film by inflation or T-die casting to form a sealant. The temporary support is not particularly limited, and various films, etc., listed below as examples of the base layer can be used.

[0050] [Laminate] The laminate of the present disclosure has a sealant layer made of the sealant of the present disclosure and a substrate layer. The substrate layer constituting the laminate is a stretched or unstretched film, and examples thereof include resin films such as polyesters such as polyethylene terephthalate, polyamides, polypropylene, polyethylene, ethylene-vinyl acetate copolymers, ethylene-unsaturated carboxylic acid ester copolymers, ethylene-unsaturated carboxylic acid copolymers or ionomers thereof, and ethylene-vinyl alcohol copolymers; paper; aluminum foil; films vapor-deposited with aluminum, silica, alumina, magnesia, etc.; and films coated with a gas barrier material such as polyvinylidene chloride or polyvinyl alcohol. These substrate layers may be single layers or laminates of two or more layers.

[0051] When the substrate layer includes a paper substrate layer, examples of the paper substrate constituting the paper substrate layer include 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. Known paperboard can be used as the paper substrate layer from the viewpoint of strength, durability, etc. It is preferable to use cup base paper made of virgin pulp as the paper substrate, but the raw material of the paper substrate layer is not limited to this. The paper substrate used for the paper substrate layer has a basis weight of 100 g / m ２ ~800g / m ２ , preferably 200 g / m ２ ~500g / m ２ , more preferably 200 g / m ２ ~450g / m ２ and the density is 0.2 g / cm３ ~2.0 g / cm ３ , preferably 0.6 g / cm ３ ~1.1 g / cm ３ Examples of suitable paperboard include:

[0052] The substrate layer constituting the laminate preferably has a resin layer in contact with the sealant layer. Examples of the resin layer include resin films such as the above-mentioned polyesters, polyamides, polypropylene, polyethylene, ethylene-vinyl acetate copolymers, ethylene-unsaturated carboxylic acid ester copolymers, ethylene-unsaturated carboxylic acid copolymers or ionomers thereof, and ethylene-vinyl alcohol copolymers, as well as gas barrier materials such as the above-mentioned polyvinylidene chloride and polyvinyl alcohol. The thickness of the resin layer in contact with the sealant layer is not particularly limited. The thickness of the resin layer can be, for example, 5 μm to 30 μm, and preferably 10 μm to 20 μm.

[0053] The substrate layer may include a paper substrate layer and a resin layer in contact with the sealant layer. Preferred lamination structures of the substrate layer include, for example, a resin layer / paper substrate layer structure and a resin layer / paper substrate layer / resin layer structure.

[0054] The method for producing the laminate is not particularly limited. The laminate of the present disclosure can be obtained by laminating the sealant resin composition of the present disclosure as a sealant layer on a substrate layer. Methods for laminating the sealant resin composition on a substrate layer include extrusion lamination of the sealant resin composition directly onto the substrate, and general methods such as thermal lamination, dry lamination, sand lamination, co-extrusion inflation, and co-extrusion T-die lamination, in which a film of the sealant resin composition formed by inflation or T-die casting is laminated onto the substrate. Any of these methods is applicable. The thickness of the sealant layer constituting the laminate is preferably 1 μm to 200 μm, more preferably 2 μm to 100 μm, and even more preferably 5 μm to 50 μm. Furthermore, the thickness of the substrate layer is preferably approximately 30 μm to 500 μm from the viewpoint of ease of peeling. When the substrate layer is used as a base material, there are no particular limitations on the thickness of the substrate layer.

[0055] [Skin pack packaging] The skin pack packaging of the present disclosure is a skin pack packaging that includes a lid material and a base material, and is used to skin-package contents by bringing the lid material and the base material into close contact with each other, and at least one of the lid material and the base material has the sealant of the present disclosure or the laminate of the present disclosure.

[0056] In one embodiment, the sealant layer constituting the sealant or laminate is preferably disposed on at least a portion of the surface of at least one of the lid material and the base material that comes into contact with the contents. In another embodiment, the sealant layer constituting the sealant or laminate is preferably disposed on at least a portion of the surface of at least one of the lid material and the base material that faces the lid material and the base material. Here, the contents include a variety of items such as various foods and beverages and medicines, and are not particularly limited as long as they can be used as a skin pack.

[0057] The skin pack packaging of the present disclosure includes at least a lid material and a base material, and may have a sealant containing the sealant resin composition of the present disclosure or a laminate of the present disclosure on both the lid material and the base material, or may have the sealant or laminate of the present disclosure only on the lid material, or may have the sealant or laminate of the present disclosure only on the base material.

[0058] The layer configuration of the lid material and the base material (tray) can be a conventionally known layer configuration. Here, when expressed as an ionomer-containing layer (IO), a saponified ethylene-vinyl acetate copolymer (EVOH) layer (B), an ethylene-vinyl acetate copolymer resin layer (EVA), a hot-melt resin layer (HM), a polyethylene-containing layer (PE), a polypropylene-containing layer (PP), a nylon-containing layer (Ny), a glycol-modified polyethylene terephthalate resin layer (PET-G), a foam substrate, and a sealant layer (EZP) composed of the sealant resin composition of the present disclosure, the following layer configuration can be formed, for example. Note that although notation of the adhesive layer is omitted, it can be used appropriately between each layer as needed.

[0059] <Lid material> (1-1) IO / B / EVA (content side) (1-2) PE / IO / B / EVA / IO (content side) (1-3) IO / B / HM (content side) (1-4) IO / B / IO / EVA (content side) (1-5) IO / EVA / IO / EZP (content side) (1-6) Ny / IO / B / EVA / IO (content side) (1-7) PE / IO / Ny / B / EVA / IO (content side) (1-8) Ny / IO / Ny / B / Ny / EVA / IO (content side) (1-9) PET-G / B / IO / EZP (content side) <Tray (bottom material)> (2-1) Foam base material / PP / B / EZP (content side) (2-2) PP / B / PP / IO (content side) (2-3) PP / B / PP / EZP (content side)

[0060] For example, when the lid material is the above-mentioned (1-1), the layer structure of the lid material indicates that the ionomer-containing layer (IO), the EVOH layer (B), and the ethylene-vinyl acetate copolymer resin layer (EVA) are laminated in this order, and among these layers, the ethylene-vinyl acetate copolymer resin layer (EVA) is located closest to the contents. In this case, the ethylene-vinyl acetate copolymer resin layer (EVA) may be in direct contact with the contents, or another layer may be interposed between the ethylene-vinyl acetate copolymer resin layer (EVA) and the contents.

[0061] Of the above-mentioned lid materials and tray (base materials), preferred combinations are [(1-1) or (1-2) or (1-6) or (1-7)] and [(2-1) or (2-3)], (1-5) and [((2-1) or (2-2)], more preferred combinations are [(1-1) or (1-2)] and [(2-1) or (2-3)], and even more preferred combinations are (1-2) and (2-1).

[0062] In other words, the combination of (1-2) and (2-1) above is an embodiment in which the lid material has at least one layer containing at least an ionomer, while the tray (base material) has a sealant layer (EZP) composed of the sealant resin composition of the present disclosure. This embodiment can be suitably used for skin packing of foods, medicines, etc.

[0063] The present disclosure will be specifically described below based on examples, but the present disclosure is not limited to these examples.

[0064] The components used to prepare the sealant resin composition (P) are as follows.

[0065] <Ethylene-vinyl acetate copolymer (A)> EVA1 (VA content: 33% by mass, MFR (190°C, 2160g load): 90g / 10 min, melting point: 56°C) EVA2 (VA content: 33% by mass, MFR (190°C, 2160g load): 14g / 10 min, melting point: 63°C) EVA3 (VA content: 28% by mass, MFR (190°C, 2160g load): 150g / 10 min, melting point: 65°C) EVA4 (VA content: 28% by mass, MFR (190°C, 2160g load): 15g / 10 min, melting point: 71°C) EVA5 (VA content: 25% by mass, MFR (190°C, 2160g load): 2g / 10min, melting point: 77°C), EVA6 (VA content: 10% by mass, MFR (190°C, 2160g load): 9g / 10min, melting point: 94°C), EVA7 (VA content: 16% by mass, MFR (190°C, 2160g load): 2.7g / 10min, melting point: 89°C).

[0066] <High-pressure low-density polyethylene (B)> HP-LDPE1 (MFR (190°C, 2160 g load): 6.5 g / 10 min, density: 918 kg / m ３ , melting point: 106 ° C.)

[0067] <Propylene-based resin (C)> Homo PP1 (propylene homopolymer, MFR (230°C, 2160 g load): 3.0 g / 10 min, density: 910 kg / m ３ , melting point: 165°C) Homo PP2 (Prime Polymer Co., Ltd., product number: Y400-GP, propylene homopolymer, MFR (230°C, 2160g load): 4.0g / 10min, density: 900kg / m ３ , melting point: 160°C) <Other components> m-PE (Prime Polymer Co., Ltd., product number: SP4030, metallocene linear low-density polyethylene, MFR (190°C, 2160g load): 3.2g / 10min, density: 938kg / m ３ , melting point: 127 ° C.)

[0068] The components were melt-kneaded at 180°C in an extruder (with a Dulmage flight screw tip) at the blending ratios shown in Table 1 or Table 2, and strands were cut at an extrusion rate of 10 kg / hour and a cutting speed of 20 m / min to obtain pellets of the sealant resin composition (P). In Examples and Comparative Examples 1, 2, and 6, the melt-blended sealant resin composition (P) was formed into a tube-like structure consisting of a PE / adhesive layer (Admer SF741 manufactured by Mitsui Chemicals, Inc.) / sealant layer using a multi-layer inflation molding machine (150 mm diameter, 40 mm extruder screw diameter) under conditions of a die temperature of 180°C, a melt zone temperature of 180°C, a line speed (LS) of 13.5 m / min, and a blow-up ratio (BUR) of 1.7, yielding a film with a folded diameter of 400 mm and a thickness of 50 μm. The resulting films of the sealant resin composition (P) were then laminated under the following conditions to produce laminates. A PE layer was melt-extruded onto a substrate layer (a two-layer laminate of a polyethylene terephthalate (PET) layer (12 μm) / polyethylene (PE) layer (15 μm)), and then the film prepared above was laminated thereon to obtain a laminate for evaluation testing consisting of a PET layer / PE layer (substrate layer) / PE layer / film (sealant layer).

[0069] In Comparative Example 8, the sealant resin composition (P) was prepared by dry-blending the components in the proportions shown in Table 3. The composition was then molded into a sheet of PE / adhesive layer (Admer SF741 manufactured by Mitsui Chemicals, Inc.) / sealant layer using a multilayer film molding machine (lip width 450 mm, extruder screw diameter 40 mm) at a die temperature of 200°C, a melting zone temperature of 200°C, and a line speed (LS) of 10.0 m / min, yielding a 50 μm thick film. The composition of Comparative Example 8 was the same as that of Comparative Example 7. The resulting film of the sealant resin composition (P) was then laminated under the following conditions to produce laminates. A PE layer was melt-extruded onto a substrate layer (a two-layer laminate of a polyethylene terephthalate (PET) layer (12 μm) / polyethylene (PE) layer (15 μm)), and then the film prepared above was laminated thereon to obtain a laminate for evaluation testing consisting of a PET layer / PE layer (substrate layer) / PE layer / film (sealant layer).

[0070] <Evaluation of cutting properties during granulation> Cutting properties were evaluated when cutting was performed under the above conditions. A: Good cutting properties. B: Some short, string-like pellets were observed, but this is not a problem in practical use. C: Poor cutting resulted in string-like pellets, making the pellets unsuitable for practical use.

[0071] <Evaluation of Peel Strength> The laminate prepared above was cut into a size of 100 mm in length and 300 mm in width. An adherend was cut into a size of 50 mm in length and 300 mm in width. The sealant layer side of the laminate and the sealant layer side of the adherend were overlapped and heat-sealed under the following heat-sealing conditions to obtain a test sample, which was then left to stand for 24 hours in an environment of 23°C and 50% RH. The adherends used were (1) BOPS sheet G90 (BOPS, manufactured by Daicel Miraize Co., Ltd., thickness 300 μm), (2) HIPS sheet NS-100 (HIPS, manufactured by Kyoei Sangyo Co., Ltd., thickness 550 μm), and (3) PET sheet NOACRYSTAL-V (APET, manufactured by RP Topla Co., Ltd., thickness 300 μm).

[0072] (Heat sealing conditions) Sealing device: Heat seal tester (TP-701S manufactured by Tester Sangyo Co., Ltd.) Sealing temperature: 100°C to 140°C Sealing time: 1.0 second Sealing pressure (actual pressure): 0.2 MPa

[0073] Next, the test sample prepared above was cut into a size of 15 mm wide and peeled under the following peeling conditions to measure the maximum peel strength during peeling. The measurement was performed five times, and the average of the maximum peel strengths during measurement was taken as the peel strength (N / 15 mm) of the laminate. (Peel conditions) Peel test device: small tabletop tester (Shimadzu Corporation EZ-SX) Test speed: 300 mm / min Peel angle: 180 degrees Temperature: 23°C Humidity: 50% RH

[0074] The peel strength was evaluated according to the following evaluation criteria. Level A indicates performance with no practical problems. (Evaluation criteria) A: Peel strength at 100°C and 120°C is in the range of 1.0 N or more and 15 N or less. B: Not equivalent to A.

[0075]

[0076]

[0077]

[0078] In Tables 1 and 2, when a component constituting the sealant resin composition (P) is marked "-", it means that the corresponding component is not contained. In Tables 1 and 2, when a peel strength under each temperature condition is marked "-", it means that a peel strength test at the corresponding temperature has not been carried out.

[0079] As is clear from the evaluation results shown in Tables 1 and 2, the laminates obtained from the sealant resin compositions of the Examples have adequate peel strength even at low temperatures (e.g., 100°C). It is also clear that the sealant resin compositions of the Examples have excellent cuttability during granulation and excellent manufacturability when forming a film. On the other hand, the laminates obtained from the sealant resin compositions of Comparative Examples 1, 2, and 6 did not have sufficient peel properties. The sealant resin compositions of Comparative Examples 3-5 and 7 had poor cuttability during granulation and poor manufacturability when forming a film. Furthermore, as is clear from the evaluation results shown in Table 3, the laminate obtained from the sealant resin composition of Comparative Example 8, in which the components were dry-blended, did not have sufficient peel properties.

[0080] The disclosure of Japanese Patent Application No. 2024-102338, filed on June 25, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated by reference into this specification 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 resin composition for sealants comprising an ethylene-vinyl acetate copolymer (A) having a melting point of 65°C or higher, a high-pressure low-density polyethylene (B), and a propylene polymer (C), wherein the content of the high-pressure low-density polyethylene (B) is 5 to 25 parts by mass per 100 parts by mass of the total resin composition for sealants.

2. The sealant resin composition according to claim 1, wherein the melting point of the ethylene-vinyl acetate copolymer (A) is 85°C or lower.

3. The sealant resin composition according to claim 1, wherein the propylene polymer (C) is a propylene homopolymer.

4. A sealant comprising the sealant resin composition according to claim 1.

5. A laminate comprising a sealant layer made of the sealant of claim 4 and a substrate layer.

6. The laminate according to claim 5, wherein said substrate layer includes a resin layer in contact with said sealant layer.

7. The laminate according to claim 5, wherein the substrate layer comprises a paper substrate layer.

8. The laminate according to claim 6, wherein the substrate layer comprises a paper substrate layer.

9. A skin pack packaging comprising a lid material and a base material, for skin-packing contents by bringing the lid material and the base material into close contact with each other, wherein at least one of the lid material and the base material has the sealant described in claim 4 or the laminate described in any one of claims 5 to 8.

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