Stretched film, laminate, packaging material, packaging body, and method for producing stretched film
Patent Information
- Application Number
- JP2025511259
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Filing Date
- 2025-09-24
- Publication Date
- 2025-12-15
Abstract
Description
Stretched film, laminate, packaging material, and method for producing stretched film
[0001] The present invention relates to a stretched film, a laminate, a package, and a method for producing a stretched film.
[0002] In recent years, against the backdrop of environmental issues, laws regarding the disposal of various plastics have been enacted, and there is an increasing need for recycling packaging materials, and various recyclable packaging materials have been studied. Among these, mono-material materials (e.g., all PE) made of a single material have attracted attention as recyclable packaging materials.
[0003] While films made from various resins are commonly used as base materials for general packaging materials, rigidity is a necessary characteristic for an all-PE base material. From the perspective of rigidity, high-density polyethylene (HDPE) is a suitable resin, but HDPE has the problem of low gloss. Furthermore, stretching is often performed to improve rigidity, but necking (width loss) during stretching narrows the film width that can be obtained, resulting in reduced productivity.
[0004] In view of the above-mentioned conventional techniques, an object of the present invention is to provide a film that can be used as a base material for packaging materials, which has excellent rigidity and gloss, and which reduces neck-in.
[0005] In view of the above problems, the present inventors have conducted extensive research and have found that the above problems can be solved by a stretched film made of a polyethylene resin composition having specific physical properties, thereby completing the present invention.
[0006] The stretched film of the present invention is as follows. [1] A stretched film comprising an ethylene polymer and 100 to 2500 ppm of a nucleating agent relative to 100 parts by mass of the ethylene polymer, which satisfies the following requirements (a1) and (a2): Requirement (a1) The melt flow rate (MFR) measured at 190°C under a load of 2.16 kg is 0.2 to 10 g / 10 min. Requirement (a2) The density is 940 to 970 kg / m 3[2] The stretched film according to [1] above, characterized in that the stretching ratio is 2 times or more and less than 6 times. [3] The stretched film according to [1] or [2] above, wherein the Mw / Mn of the ethylene polymer is 2 to 15. [4] The stretched film according to any one of [1] to [3] above, characterized in that the stretched film has a gloss of 30% or more, a modulus of elasticity (in the MD direction) of 3,000 MPa or more, and a tear strength (in the MD direction) of 8 N / cm or more. [5] A laminate comprising the stretched film according to any one of [1] to [4] above. [6] The laminate according to [5] above, characterized in that the stretched film according to any one of [1] to [4] above is located in at least one outermost layer of the laminate. [7] The laminate according to [6] above, characterized in that the stretched film according to any one of [1] to [4] above is located in both outermost layers of the laminate. [8] A packaging material comprising the stretched film according to any one of [1] to [4] above or the laminate according to any one of [5] to [7] above. [9] A packaged product packaged with a packaging material comprising the stretched film according to any one of [1] to [4] above or the laminate according to any one of [5] to [7] above.
[10] A method for producing the stretched film according to any one of [1] to [4] above, the method comprising the steps of producing, by melt extrusion molding, a film containing an ethylene polymer that satisfies the following requirements (a1) and (a2) and 100 to 2500 ppm of a nucleating agent per 100 parts by mass of the ethylene polymer, and stretching the film: (a1) The melt flow rate (MFR) measured at 190°C under a load of 2.16 kg is 0.2 to 10 g / 10 min. (a2) The density is 940 to 970 kg / m 3 is.
[0007] The stretched film of the present invention has an excellent balance of rigidity, low shrinkage and longitudinal tear strength, has excellent gloss, and can be suitably used as a recyclable packaging material, and can reduce neck-in.
[0008] The present invention will be described in detail below. The stretched film of the present invention contains an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms (hereinafter sometimes abbreviated as an ethylene-based polymer).
[0009] Regarding requirement (a1), the lower limit of the MFR (190°C, 2.16 kg load) of the ethylene polymer is 0.2 g / 10 min or more, preferably 0.4 g / 10 min or more, and more preferably 0.8 g / 10 min or more, and the upper limit is 10 g / 10 min or less, preferably 5 g / 10 min or less, and more preferably 3 g / 10 min or less. By having the MFR (190°C, 2.16 kg load) within this range, stretching stability and glossiness can be obtained.
[0010] Regarding the requirement (a2), the lower limit of the density of the ethylene polymer is usually 940 kg / m 3 or more, preferably 942 kg / m 3 More preferably, 943 kg / m 3 or more, and among them, 946 kg / m 3 The upper limit is 970 kg / m 3 Preferably 965 kg / m or less 3 or less, more preferably 962 kg / m 3 The density is within this range, whereby rigidity and stretching stability can be obtained. The density is a value measured in accordance with JIS K7112 (density gradient tube method).
[0011] Regarding molecular weight distribution (Mw / Mn): The molecular weight distribution (Mw / Mn) of the ethylene polymer is not particularly limited, but the upper limit is preferably 15 or less, more preferably 13 or less, and particularly preferably 7 or less. The lower limit is preferably 2 or more, more preferably 2.1 or more. When the molecular weight distribution of the ethylene polymer is within this range, a stretched film having an excellent balance of extrudability and gloss can be obtained. The molecular weight distribution can be obtained by measurement using gel permeation chromatography. The molecular weight distribution of the ethylene polymer is preferably such that the proportion of molecular weights of 10,000 or less exceeds 8.5% by mass of the total. This proportion is more preferably 8.7% by mass or more, more preferably 8.9% by mass or more, and even more preferably 25% by mass or less, and even more preferably 20% by mass or less. This is preferred because it reduces the pressure of the molten resin during the production of the raw film, enabling efficient molding.
[0012] The weight average molecular weight and molecular weight distribution of the ethylene polymer can be measured by gel permeation chromatography (GPC) calibrated using a standard substance (monodisperse polystyrene) of known molecular weight.
[0013] The ethylene polymer of the stretched film is not particularly limited as long as it satisfies the above requirements (a1) and (a2), but an ethylene homopolymer and a copolymer of ethylene and an α-olefin having 3 or more carbon atoms (ethylene-α-olefin copolymer) are preferred. The α-olefin in the ethylene-α-olefin copolymer is preferably at least one selected from α-olefins having 3 to 20 carbon atoms, and specific examples include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-octene.
[0014] The ethylene-based polymer contains 50 mol % or more and 100 mol % or less, preferably more than 50 mol % and 100 mol % or less, more preferably 55 to 100 mol %, and even more preferably 60 to 100 mol % of structural units derived from ethylene.
[0015] Ethylene-based polymers can be produced using known catalysts such as Ziegler-Natta catalysts and metallocene catalysts. Furthermore, in addition to the copolymer of ethylene and an α-olefin, other low-density polyethylenes may be used as the resin component. In the present invention, one or a combination of two or more polyethylenes satisfying the above-mentioned properties can be selected from commercially available polyethylene-based resins and used as the resin component. An example of a polyethylene-based resin containing an ethylene-α-olefin copolymer is linear low-density polyethylene.
[0016] The ethylene polymer may contain structural units derived from one or more types of biomass-derived monomers (ethylene). The same type of monomers constituting the polymer may be biomass-derived monomers only, or may be both biomass-derived monomers and fossil fuel-derived monomers. The biomass-derived monomer is a monomer derived from any renewable natural raw material, such as a plant-derived or animal-derived material, including fungi, yeast, algae, and bacteria, and its residues, and contains carbon. 14 C isotope 1×10 -14 The biomass carbon concentration (pMC) measured in accordance with ASTM D6866 is about 100 (pMC). The biomass-derived monomer (ethylene) can be obtained, for example, by a conventionally known method.
[0017] It is preferable from the viewpoint of reducing the environmental load that the ethylene-based polymer contains a structural unit derived from a biomass-derived monomer. As long as the polymer production conditions, such as the polymerization catalyst and polymerization temperature, are the same, even if the raw material olefin contains a biomass-derived olefin, 14 C isotope 1×10 -12 Other than the proportion of ethylene glycol in the polymer, its molecular structure is the same as that of polyethylene polymers made from fossil fuel-derived monomers, and therefore its performance is said to be unchanged.
[0018] Furthermore, the units constituting the ethylene-based polymer may contain chemically recycled monomers (ethylene, α-olefins). The monomers constituting the polymer may consist solely of chemically recycled monomers, or may contain chemically recycled monomers together with fossil fuel-derived monomers and / or biomass-derived monomers. The chemically recycled monomers are obtained by conventionally known methods. It is preferable for the ethylene-based polymer to contain chemically recycled monomers from the perspective of reducing environmental impact (mainly waste reduction). Even if the raw material monomer contains chemically recycled monomers, the chemically recycled monomers are monomers obtained by depolymerizing or pyrolyzing polymers such as waste plastics back into monomer units such as ethylene, or monomers produced using such monomers as raw materials. Therefore, if the polymer production conditions, such as the polymerization catalyst, polymerization process, and polymerization temperature, are equivalent, the molecular structure will be equivalent to that of an ethylene-α-olefin copolymer composed of fossil fuel-derived monomers. Therefore, performance is also expected to be unchanged.
[0019] The stretched film of the present invention is characterized by containing a nucleating agent in an amount of 100 to 2500 ppm relative to 100 parts by mass of the ethylene-based polymer. Examples of the nucleating agent (B) include sorbitol-based nucleating agents, phosphorus-based nucleating agents, cyclic dicarboxylate-based nucleating agents, metal carboxylate-based nucleating agents, polymer-based nucleating agents, inorganic compound-based nucleating agents, and rosin-based nucleating agents.
[0020] Specific examples of sorbitol-based nucleating agents include 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol, 1,3,2,4-dibenzylidene sorbitol, 1,3,2,4-di-(p-methylbenzylidene) sorbitol, and 1,3-p-chlorobenzylidene-2,4-p-methylbenzylidene sorbitol.
[0021] Specific examples of phosphorus-based nucleating agents include sodium bis-(4-t-butylphenyl) phosphate, potassium bis-(4-t-butylphenyl) phosphate, sodium 2,2'-ethylidene bis(4,6-di-t-butylphenyl) phosphate, sodium 2,2'-methylene bis(4,6-di-t-butylphenyl) phosphate, bis(2,4,8,10-tetra-t-butyl-6-hydroxy-12H-dibenzo[d,g][1,3,2]dioxaphosphocin-6-oxide) sodium salt, and bis(2,4,8,10-tetra-t-butyl-6-hydroxy-12H-dibenzo[d,g][1,3,2]dioxaphosphocin-6-oxide) aluminum hydroxide salt.
[0022] Specific examples of cyclic dicarboxylate nucleating agents include 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, bicyclo[2,2,1]heptenedicarboxylic acid, and sodium and calcium salts thereof.
[0023] Specific examples of metal carboxylate nucleating agents include aluminum pt-butylbenzoate, aluminum hydroxy-di(pt-butylbenzoate) (trade name "AL-PTBBA", manufactured by Japan Chemtech), aluminum adipate, and sodium benzoate.
[0024] As the polymer nucleating agent, a branched α-olefin polymer is preferably used. Examples of branched α-olefin polymers include homopolymers of 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, and 3-ethyl-1-hexene, as well as copolymers thereof and copolymers thereof with other α-olefins. Among these, high-melting point polymers include polyvinylcycloalkanes such as polyvinylcyclohexane and polyvinylcyclopentane, poly3-methyl-1-pentene, poly3-methyl-1-butene, and polyalkenylsilanes.
[0025] Specific examples of inorganic compound nucleating agents include talc, mica, and calcium carbonate.
[0026] Examples of rosin-based nucleating agents include metal salts of rosin acid, which are reaction products of rosin acid and metal compounds. Examples of rosin acids include natural rosins such as gum rosin, tall oil rosin, and wood rosin; various modified rosins such as disproportionated rosin, hydrogenated rosin, dehydrogenated rosin, polymerized rosin, and α,β-ethylenically unsaturated carboxylic acid-modified rosin; and purified products of the above natural rosins and modified rosins. Examples of unsaturated carboxylic acids used to prepare the α,β-ethylenically unsaturated carboxylic acid-modified rosins include maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, citraconic acid, acrylic acid, and methacrylic acid. Among these, at least one rosin acid selected from the group consisting of natural rosin, modified rosin, purified products of natural rosin, and purified products of modified rosin is preferred. Here, the rosin acid contains a plurality of resin acids selected from pimaric acid, sandaracopimaric acid, palustric acid, isopimaric acid, abietic acid, dehydroabietic acid, neoabietic acid, dihydropimaric acid, dihydroabietic acid, tetrahydroabietic acid, and the like.
[0027] Examples of the metal compound that reacts with rosin acid to form a metal salt include compounds containing a metal element such as sodium, potassium, or magnesium, which form a salt with the rosin acid. Specific examples include chlorides, nitrates, acetates, sulfates, carbonates, oxides, and hydroxides of the metals.
[0028] Among these nucleating agents, cyclic dicarboxylate nucleating agents are preferred, and a particularly preferred commercial product is "Hyperform HPN-20E" (manufactured by Milliken), which is primarily composed of calcium 1,2-cyclohexanedicarboxylate. These nucleating agents may be used alone or in combination of two or more. The stretched film of the present invention contains 100 to 2500 ppm of nucleating agent per 100 parts by mass of the ethylene polymer. The lower limit of the nucleating agent content is preferably 200 ppm or more, and the upper limit is preferably 2000 ppm or less. Furthermore, in one embodiment of the present invention, the nucleating agent content may be 900 ppm or less. Note that if the content is less than 100 ppm, gloss tends to be insufficient, and if it exceeds 2500 ppm, strength tends to be reduced.
[0029] Regarding Other Polymers: The stretched film may further contain other polymers besides the ethylene-based polymer, as long as the object of the present invention is not impaired. Examples of other polymers include thermoplastic resins other than ethylene-based polymers. Examples of thermoplastic resins include olefin-based polymers other than ethylene-based polymers, (meth)acrylic resins, polyvinyl chloride, polystyrene, polyester, polyamide, polyimide, polyacetal, polyvinyl alcohol, polyacrylonitrile, and polycarbonate. When other polymers are contained, the content of the other polymers is typically 0.1 parts by mass or more, more preferably 1 part by mass or more, and typically 30 parts by mass or less, preferably 20 parts by mass or less, and more preferably 10 parts by mass or less, based on 100 parts by mass of the total content of the ethylene-based polymer and other polymers. However, when the film of the present invention is used as a monomaterial material consisting of a single material, there are embodiments in which the other polymers are substantially free of other polymers or in which the content of the other polymers is 0 parts by mass.
[0030] The stretched film of the present invention may contain, as needed, at least one of various additives typically added to polyolefin resins, such as neutralizing agents, weather stabilizers, heat stabilizers, antistatic agents, anti-fogging agents, anti-blocking agents, slip agents, lubricants, pigments, and anti-dripping agents, as long as the purpose of the film is not impaired.
[0031] When an additive is added to the stretched film, the content thereof is usually 5 parts by mass or less, and preferably 1 part by mass or less, based on 100 parts by mass of the ethylene polymer.
[0032] The stretched film of the present invention may be a uniaxially stretched film or a biaxially stretched film. The stretching ratio in the stretched film of the present invention is preferably 2.0 times or more, more preferably 2.5 times or more, particularly preferably 3.0 times or more, and most preferably 3.1 times or more. The upper limit of the stretching ratio is not particularly limited, but is preferably 10 times or less, more preferably less than 6 times. A stretching ratio within the above range ensures rigidity and strength. The thickness of the stretched film of the present invention can be appropriately set depending on various applications, but generally, the lower limit is preferably 5 μm or more, more preferably 10 μm or more, and the upper limit is preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 60 μm or less. A thickness of the stretched film within the above range ensures a balance between rigidity and strength as a packaging material.
[0033] The method for producing the stretched film of the present invention is not particularly limited, and examples thereof include a method of stretching a film (raw sheet) obtained by a known melt extrusion molding method, etc. Examples of methods for stretching the raw sheet include a method of simultaneous or sequential biaxial stretching in the longitudinal and transverse directions by a tenter method, a method of simultaneous biaxial stretching in the longitudinal and transverse directions by a tubular method, and a method of uniaxial stretching in the machine direction of the film by using two or more rolls with different rotation speed ratios.
[0034] In the uniaxial stretching, it is preferable to unwind the film into a roll stretching machine, preheat it with a preheating roll, and then uniaxially stretch it in the MD direction (take-up speed direction). From the viewpoint of improving production efficiency, it is preferable to preheat the raw film to be stretched and then immediately uniaxially stretch it in the MD direction. In the present invention, uniaxial stretching means stretching in a uniaxial direction, but it may be stretched in a direction different from the uniaxial direction to the extent that the effect of the present invention is not impaired. This is because, depending on the stretching equipment used, even if uniaxial stretching is attempted, it may actually be stretched in a direction different from the uniaxial direction.
[0035] The stretched film may be annealed, if necessary, by bringing the stretched sheet into contact with a heated roll.
[0036] Regarding Gloss: The stretched film of the present invention has excellent gloss, and its gloss (measured in accordance with JIS Z 8741 at a 20-degree measurement angle) is preferably 30% or more. It is more preferably 35% or more, and even more preferably 40% or more. Regarding Elastic Modulus: The stretched film of the present invention has an excellent balance of rigidity, low shrinkage, and longitudinal tear strength, and the elastic modulus in the MD direction is preferably greater than 1600 MPa, more preferably 1700 MPa or more, and even more preferably 2000 MPa or more. Of these, stretched films with excellent rigidity are preferably those with an elastic modulus (in the MD direction) of 3000 MPa or more, more preferably 3500 MPa or more, and even more preferably 4000 MPa or more. The upper limit of this elastic modulus (in the MD direction) is not particularly limited, but in practice it is 7000 MPa or less. Having the elastic modulus in the MD direction within the above-mentioned range ensures the rigidity of the film. Tear Strength: The tear strength in the machine direction (MD) of the stretched film of the present invention is preferably 8 N / cm or more, more preferably 10 N / cm or more, and even more preferably 15 N / cm or more. The stretched film of the present invention is preferably one in which the gloss, modulus, and tear strength are all within the above ranges.
[0037] [Laminate] The laminate of the present invention is characterized by including a layer made of the stretched film of the present invention described above. The laminate of the present invention may have a plurality of layers made of the stretched film of the present invention. Other layers in the laminate including the stretched film of the present invention described above can be appropriately adopted depending on the application.
[0038] Examples of other layers in the laminate of the present invention include other plastic films, metal foils such as aluminum, paper, cellophane, etc. By laminating other layers to the multilayer stretched film of the present invention to form a laminate, various additional functions can be imparted. For example, the multilayer stretched film may be co-extruded with a barrier resin (e.g., EVOH, Ny, etc.) or an adhesive resin (e.g., acid-modified polyethylene such as acrylic acid or maleic anhydride), or may be coated on the surface (e.g., a vapor-deposited film, etc.).
[0039] The vapor-deposited film may be made of a metal or an inorganic oxide. Examples of metals constituting the metal vapor-deposited film include aluminum, chromium, tin, nickel, copper, silver, gold, and platinum. Examples of metal oxides include aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, and barium oxide.
[0040] Examples of plastic films include thermoplastic resin plastic films such as polyolefins such as crystalline polypropylene, crystalline propylene-ethylene copolymer, crystalline polybutene-1, crystalline poly-4-methylpentene-1, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), and ionically cross-linked olefin copolymer (ionomer); polyamides such as nylon 6 and nylon 66; polyesters such as polyethylene terephthalate (PET) and polytetramethylene terephthalate; and polyacetals such as various polycarbonates.
[0041] To produce a laminate in which the other layers described above are laminated on the stretched film of the present invention, an adhesive or anchoring agent can be interposed between the layers as needed. Metal oxides or the like can also be vapor-deposited on the entire surface or a portion of the surface, or an ink layer can be provided. The method for laminating the stretched film of the present invention and the other layers is not particularly limited, but examples include direct lamination by extrusion lamination, ozone treatment in an oxidizing atmosphere (e.g., a gas containing oxygen, particularly ozone (air, etc.)), and lamination via an adhesive by dry lamination. It is preferred that the stretched film of the present invention be present in at least one of the outermost layers on both sides of the laminate.
[0042] In addition, in the laminate of the present invention, it is also one of the preferred embodiments that the stretched film of the present invention is present as the outermost layer on both sides thereof. In this case, the layer sandwiched between the outermost layers is not particularly limited, but for example, a layer made of an olefin polymer can be used. The density is not particularly limited, but a density of 940 kg / m is preferred. 3 Less than 870 kg / m 3 A layer made of the above ethylene polymer can be used. In this case, the tear strength is excellent. For example, since a surface having excellent gloss tends to be required to have not only excellent appearance but also excellent printability, a packaging material in which the outermost layers on both sides are the stretched film of the present invention is a packaging material in which the outermost layer has excellent appearance and the innermost layer has excellent printability.
[0043] The thickness of the laminate is generally about 8 μm to 2000 μm. The laminate of the present invention is widely used for various purposes, and is particularly suitable for use as a packaging material.
[0044] [Packaging Material] The packaging material of the present invention comprises the stretched film of the present invention or the multilayer stretched film of the present invention. In particular, for example, a packaging material made of the laminate of the present invention is suitable for packaging various products and parts. Such packaging material can be produced, for example, by overlapping the laminates of the present invention so that at least partial edges thereof contact each other and integrating them by heat sealing. The packaging material of the present invention is used for a wide range of applications, for example, for packaging various products and parts such as daily necessities, machine parts, electrical parts, food, and beverages. By using the stretched film having excellent gloss of the present invention as the outermost layer of the packaging material of the present invention, the commercial value of the packaging material can be further increased. [Packaging] A packaging material in which various products, parts, food, and beverages are packaged in a packaging material containing the stretched film or laminate of the present invention can be a product with excellent appearance.
[0045] EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following examples, MFR, density, molecular weight distribution (Mw / Mn), gloss, elastic modulus, heat shrinkage, tear strength, and neck-in were measured as follows.
[0046] <Melt flow rate (MFR: [g / 10 min])> Measurement was carried out in accordance with JIS K7210 under conditions of 190°C and a load of 2.16 kg (kgf).
[0047] <Density [kg / m 3 The measurement was carried out in accordance with JIS K7112 using the strand obtained when measuring the MFR.
[0048] <Weight Average Molecular Weight (Mw), Number Average Molecular Weight (Mn), and Molecular Weight Distribution (Mw / Mn)> The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the ethylene polymer are values measured by gel permeation chromatography (GPC), and were calculated based on a polyethylene conversion method using a calibration curve prepared using commercially available monodisperse polystyrene.
[0049] <Gloss> Measurement was carried out in accordance with JIS Z 8741 at a measurement angle of 20 degrees.
[0050] <Elastic modulus> A dumbbell-shaped test piece was punched out from the film in accordance with JIS K6781. The direction punched parallel to the film take-up direction was defined as the MD (machine direction). The test piece was set in the air chuck of a universal testing machine, and a tensile test was performed at a chuck distance of 80 mm and a tensile speed of 200 mm / min. The slope of the initial stress versus displacement was defined as the elastic modulus.
[0051] <Tear Strength> The Elmendorf tear strength was measured in accordance with JIS K 7128-2 using an Elmendorf tear tester manufactured by Toyo Seiki Seisakusho Co., Ltd. The MD direction is defined as the direction in which the cut is made in the direction in which the film is taken off.
[0052] <Neck-in> Neck-in was calculated using the following formula: Neck-in [%] = 100 - (original film width / stretched film width x 100)
[0053] Examples 1-7, Reference Examples 1-4, Comparative Examples 1-3 The following nucleating agents were used in the proportions shown in Tables 1-1 and 1-2. The ethylene-based polymers shown in Tables 1-1 and 1-2 were used. The ethylene-based polymers containing the nucleating agents were melt-kneaded at 200°C using an extruder, and then a 125 μm-thick raw film was formed using an inflation molding machine. The resin pressure was measured at an extrusion rate of 49 kg / h. This raw film was uniaxially stretched using a heated roll at the stretching temperature and stretch ratio shown in Tables 1-1 and 1-2 to obtain a uniaxially stretched film. The gloss, modulus, tear strength, and neck-in of the resulting stretched film were measured. The results are shown in Tables 1-1 and 1-2. Note that in some Reference Examples and Comparative Examples, a nucleating agent was not added, and in Reference Examples 1 and 2, a 25 μm-thick raw film was used as is without stretching.
[0054] <Film molding conditions> Molding machine: Modern Machinery inflation molding machine Die: 125 mmφ (diameter), 4 mm (lip width) Air ring: 2 gap type Resin temperature during molding: 195°C Extrusion rate: 49 kg / h
[0055] Nucleating agent: trade name "Hyperform HPN-20E" (manufactured by Milliken Co.), containing calcium salt of 1,2-cyclohexanedicarboxylic acid as the main component. Note that, for example, in Example 1, 0.1920 parts by mass, i.e., 1920 ppm, of the nucleating agent was blended with respect to 100 parts by mass of the ethylene polymer.
[0056] Ethylene polymer Hi-Zex 3600F manufactured by Prime Polymer Co., Ltd. (MFR 1 g / 10 min, density 958 g / m 3 Evolue H SP4505 manufactured by Prime Polymer Co., Ltd. (MFR 0.4 g / 10 min, density 944 g / m 3 , Mw / Mn 4.5) Hi-Zex 5000SR manufactured by Prime Polymer Co., Ltd. (MFR 0.37 g / 10 min, density 955 g / m 3 Evolue H SP6011 manufactured by Prime Polymer Co., Ltd. (MFR 1 g / 10 min, density 956 g / m 3 , Mw / Mn 2.6) Hi-Zex 5000H manufactured by Prime Polymer Co., Ltd. (MFR 0.1 g / 10 min, density 958 g / m 3 Evolue SP3010 manufactured by Prime Polymer Co., Ltd. (MFR 0.75 g / 10 min, density 926 g / m 3 , Mw / Mn 10.57) Evolue SP0510 manufactured by Prime Polymer Co., Ltd. (MFR 1.2 g / 10 min, density 903 kg / m 3 )
[0057] Example 8 The raw materials for both outer layers were prepared by mixing 100 parts by mass of an ethylene polymer, Hi-Zex 3600F (manufactured by Prime Polymer Co., Ltd.), with 1920 ppm of a nucleating agent (trade name Hyperform HPN-20E, manufactured by Milliken).
[0058] Evolue SP0510 (manufactured by Prime Polymer Co., Ltd.) was used as the raw material for the intermediate layer as an ethylene-based polymer. A multilayer inflation film extruder was then used to obtain a three-layer film with a thickness of 25 μm, consisting of a surface layer / intermediate layer / surface layer ratio of 1 / 1 / 1, stretched at a stretching ratio of 5 and a stretching temperature of 126°C. The physical properties of the resulting three-layer film were measured using the following methods. The results are shown in Table 2.
[0059] <Film molding conditions> Molding machine: Alpine 3-type 3-layer inflation molding machine Die: 225 mmφ (diameter), 3 mm (lip width) Air ring: 2-gap type Resin temperature during molding: 210°C Extrusion rate: 121 kg / h
[0060]
[0061]
[0062]
[0063]
[0064] The stretched film of the present invention is a film that can be used as a base material for packaging materials that have an excellent balance of rigidity, low shrinkage, and longitudinal tear strength, and also have excellent gloss, and laminates containing the film can be used in a variety of applications, particularly as packaging materials for a wide range of uses, including food products.
Claims
1. A stretched film comprising an ethylene-based polymer and 100 to 2500 ppm of a nucleating agent per 100 parts by mass of the ethylene-based polymer, the stretched film satisfying the following requirements (a1) and (a2): Requirement (a1) The melt flow rate (MFR) measured at 190° C. under a load of 2.16 kg is 0.2 to 10 g / 10 min. Requirement (a2) Density is 940 to 970 kg / m 3 is.
2. 2. The stretched film according to claim 1, wherein the stretching ratio is 2 times or more but less than 6 times.
3. 2. The stretched film according to claim 1, wherein the ethylene polymer has an Mw / Mn ratio of 2 to 15.
4. 2. The stretched film according to claim 1, wherein the stretched film has a gloss of 30% or more, an elastic modulus (MD direction) of 3000 MPa or more, and a tear strength (MD direction) of 8 N / cm or more.
5. A laminate comprising the stretched film according to claim 1.
6. 6. The laminate according to claim 5, wherein the stretched film according to claim 1 is positioned as at least one outermost layer of the laminate.
7. 7. The laminate according to claim 6, wherein the stretched film according to claim 1 is positioned as both outermost layers of the laminate.
8. A packaging material comprising the stretched film according to claim 1 or the laminate according to claim 5.
9. A packaged product obtained by packaging with a packaging material comprising the stretched film according to claim 1 or the laminate according to claim 5.
10. A method for producing the stretched film according to any one of claims 1 to 4, comprising the steps of producing, by melt extrusion molding, a film containing an ethylene-based polymer satisfying the following requirement (a1) and requirement (a2) and 100 to 2500 ppm of a nucleating agent per 100 parts by mass of the ethylene-based polymer, and stretching the film: (a1) The melt flow rate (MFR) measured at 190°C under a load of 2.16 kg is 0.2 to 10 g / 10 min. (a2) Density is 940 to 970 kg / m 3 is.