Film, laminate, packaging material, and method for producing film

Abstract

[Problem] To provide a film excellent in heat resistance, transparency, and transparency after retort treatment. [Solution] Provided is a film characterized by containing: an ethylene-based polymer having a melt flow rate [g / 10 min] that is within a specific range, a density [g / cm3] that is within a specific range, a melting point [°C] that is within a specific range, and a ΔH50% melting temperature [°C] (melting temperature [°C] at 50% melting heat) that is within a specific range; and a nucleating agent in the amount of 100-2500 ppm with respect to 100 parts by mass of the ethylene-based polymer. Also provided are a laminate including the same, and a packaging material comprising the same.

Description

Film, laminate, packaging material, and film manufacturing method

[0001] The present invention relates to a film, a laminate, a packaging material, and a method for producing a film.

[0002] To enable long-term storage, packaging bags containing medical products or food products are sometimes sterilized at high temperatures of approximately 100 to 140°C after filling and sealing. For example, such packaging bags are made from a laminate (laminate film) formed by laminating multiple resin films. These packaging bags must be heat-resistant enough to withstand sterilization under high temperature and pressure, and transparent enough to allow the contents to be seen.

[0003] General packaging materials use films made from various resins as the base material, and while transparency is required for packaging materials, when highly transparent LLDPE is used for packaging materials, it has poor heat resistance, and when laminated with other layers, deformation occurs when treated at the retort sterilization temperature (121°C), causing the packaging material to swell, wrinkle, and fuse.

[0004] The middle layer of the laminate has a density of 935 kg / m ３ It has also been proposed that the use of the above LLDPE and a nucleating agent can prevent whitening of the laminate during retort treatment up to 120°C (Patent Document 1). However, this is still insufficient in terms of heat resistance. Furthermore, if high-density polyethylene is used to enable retort treatment at high temperatures, the laminate will have excellent heat resistance and will be less likely to deform, and even when treated at the retort sterilization temperature (121°C), deformation (wrinkles, wrinkles, etc.) can be prevented. However, this results in poor transparency, which worsens further when treated with retort sterilization.

[0005] Japanese Patent Application Publication No. 8-25594

[0006] As a result of investigating films that have excellent heat resistance, transparency, and transparency after retort treatment, the inventors discovered that a film with these excellent properties can be produced by adding a specific amount of a nucleating agent to polyethylene that has a specific density, a specific melting point, and a specific melting behavior, and thus completed the present invention.

[0007] The present invention has the following aspects. [1] A film comprising an ethylene polymer satisfying the following requirements (a1) to (a4) and a nucleating agent in an amount of 100 to 2,500 ppm per 100 parts by mass of the ethylene polymer: (a1) A melt flow rate (MFR, 190°C, load 2.16 kg) of 0.1 to 10 g / 10 min. (a2) A density of 936 to 970 kg / m. ３ (a3) The melting point (Tm) determined by differential scanning calorimetry (DSC) is 124°C or higher. (a4) In a heat of fusion curve obtained by differential scanning calorimetry (DSC), a baseline is drawn in the temperature range from 40°C to 150°C, and the value of that baseline is subtracted from the heat of fusion curve. The remaining area is taken as the total heat of fusion (ΔH). The temperature at which this area becomes 50% (ΔH50% melting temperature [°C]) is 120°C or higher. [2] A laminate comprising the film described in [1] above. [3] A laminate comprising the film described in [1] above, wherein the innermost layer is made of the film described in [1] above. [4] A packaging material comprising the laminate described in [2] or [3] above. [5] A method for producing the film described in [1] above by melt extrusion molding.

[0008] According to the present invention, a film having excellent heat resistance, transparency, and transparency after retort treatment is provided.

[0009] The present invention will be described below. [Film] The ethylene polymer used in the film of the present invention is preferably an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms (hereinafter sometimes abbreviated as ethylene polymer). This ethylene polymer satisfies the following requirements (a1) to (a4):

[0010] Regarding requirement (a1): Requirement (a1) is that the melt flow rate (MFR, 190°C, load 2.16 kg) is 0.1 to 10 g / 10 min. The lower limit of the MFR (190°C, load 2.16 kg) of the ethylene polymer is preferably 0.5 g / 10 min or more, more preferably 1.0 g / 10 min or more, and the upper limit is preferably 5 g / 10 min or less, more preferably 4 g / 10 min or less. When the MFR (190°C, load 2.16 kg) is within this range, excellent gloss can be obtained.

[0011] Regarding the requirement of (a2), the requirement of (a2) is that (a2) the density is 936 to 970 kg / m ３ That is, the lower limit of the density of the ethylene polymer is 936 kg / m ３ or more, preferably 940 kg / m ３ More preferably, 946 kg / m ３ The upper limit is 970 kg / m ３ and preferably 965 kg / m ３ or less, more preferably 960 kg / m ３ More preferably, it is 955 kg / m or less. ３ and particularly preferably 950 kg / m ３ or less, and most preferably 949 kg / m ３ The density is within this range, whereby excellent rigidity and transparency can be obtained. The density is a value measured in accordance with JIS K7112 (density gradient tube method).

[0012] Regarding Requirement (a3): The requirement (a3) ​​is that the melting point (Tm) determined by a differential scanning calorimeter (DSC) is 124°C or higher. That is, the melting point of the ethylene polymer is 124°C or higher, preferably 126°C or higher, more preferably 128°C or higher, and of these, preferably 130°C or higher. The melting point is measured using a differential scanning calorimeter (DSC) in accordance with JIS-K7121. Details of the measurement will be described in the Examples. In order to satisfy the requirements (a2) and (a3), the ethylene content of the ethylene polymer used in the present invention is preferably 90 mol% or higher, more preferably 93 mol% or higher, and even more preferably 100 mol%.

[0013] Regarding requirement (a4), requirement (a4) is that a baseline is drawn in the region of 40°C to 150°C in a calorie curve of fusion obtained by a differential scanning calorimeter (DSC), the value of that baseline is subtracted from the calorie curve, and the remaining area is taken as the total heat of fusion (ΔH). The temperature at which this area becomes 50% (ΔH50% melting temperature [°C]) is 120°C or higher. That is, the ΔH50% melting temperature [°C] (melting temperature at 50% heat of fusion [°C]) is 120°C or higher, preferably 122°C or higher, more preferably 123°C or higher, and of these, more preferably 124°C or higher.

[0014] In the present invention, an ethylene polymer satisfying the above requirements (a1) to (a4) is used. Furthermore, it is preferable that the ethylene polymer of the present invention further satisfy the following requirement (a5). Regarding requirement (a5): Requirement (a5) is that Mw / Mn, which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), each measured by gel permeation chromatography (GPC), is 5.0 to 10.0. That is, the lower limit of Mw / Mn of the ethylene polymer is 5.0 or more, preferably 5.5 or more, and more preferably 6.0 or more. The upper limit is 10.0 or less, preferably 9.0 or less, and more preferably 8.0 or less. Having Mw / Mn in this range provides an excellent balance between formability during film production and film strength.

[0015] The ethylene polymer of the film is not particularly limited as long as it satisfies the above requirements (a1) to (a4), but ethylene homopolymers and copolymers of ethylene and α-olefins having 3 or more carbon atoms (ethylene-α-olefin copolymers) 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.

[0016] The ethylene-based polymer preferably contains 90 mol % or more, and more preferably 95 mol % or more and 100 mol % or less, of structural units derived from ethylene.

[0017] The ethylene polymer of the present invention may be a single ethylene polymer or a composition of two or more ethylene polymers. When the ethylene polymer of the present invention is a composition of two or more ethylene polymers, the composition must satisfy the above-mentioned requirements (a1) to (a4).

[0018] The ethylene polymer of the present invention has a density of 950 to 970 kg / m ３ and a high density component (A1) having a density of 901 to 925 kg / m ３ The density of the high density component (A1) is preferably 955 to 965 kg / m ３ is particularly preferred, and the density of the low-density component (A2) is 910 to 920 kg / m ３ The amount of (A1) present relative to 100 parts by mass of the total of (A1) and (A2) is 99 to 1 part by mass, preferably 98 to 30 parts by mass, more preferably 97 to 40 parts by mass, even more preferably 96 to 50 parts by mass, and particularly preferably 95 to 60 parts by mass. In this case, the transparency after sterilization treatment is good, and an excellent balance between heat sealability and heat resistance is achieved.

[0019] 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.

[0020] The ethylene polymer may contain structural units derived from one or more biomass-derived monomers (ethylene). The same type of monomer constituting the polymer may be only biomass-derived monomers, 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 or residue thereof, such as a plant-derived or animal-derived material, including fungi, yeast, algae, and bacteria, and contains, as 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.

[0021] 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.

[0022] 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. Chemically recycled monomers can be obtained by conventionally known methods. It is preferable for ethylene-based polymers 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.

[0023] The 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 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] Specific examples of inorganic compound-based nucleating agents include talc, mica, and calcium carbonate. Rosin-based nucleating agents include, for example, 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.

[0030] 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.

[0031] Among these nucleating agents, cyclic dicarboxylate nucleating agents are preferred, and a particularly preferred commercially available product is "Hyperform HPN-20E" (manufactured by Milliken), which contains 1,2-cyclohexanedicarboxylic acid calcium salt as its main ingredient. HPN-20E contains 1,2-cyclohexanedicarboxylic acid calcium salt as its active ingredient. These nucleating agents may be used alone or in combination. The 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, the upper limit is preferably 2300 ppm, and particularly preferably 2000 ppm or less. If the content is less than 100 ppm, gloss tends to be insufficient, and if it exceeds 2500 ppm, strength tends to be reduced.

[0032] <Other Polymers> The 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 usually 0.1 parts by mass or more, more preferably 1 part by mass or more, and usually 30 parts by mass or less, preferably 20 parts by mass or less, more preferably 10 parts by mass or less, relative to 100 parts by mass of the total content of the ethylene-based polymer and other polymers.

[0033] The film of the present invention may contain, as necessary, within a range that does not impair the object of the present invention, at least one of various additives that are added to general polyolefin resins, such as a neutralizing agent, a weather stabilizer, a heat stabilizer, an antistatic agent, an antifogging agent, an antiblocking agent, a slip agent, a lubricant, a pigment, a dripping agent, etc. When an additive is added to the film, the content thereof is usually 5 parts by mass or less, preferably 1 part by mass or less, per 100 parts by mass of the ethylene polymer.

[0034] The film of the present invention can also be used as a stretched film. When used as a stretched film, it may be a uniaxially stretched film or a biaxially stretched film. The stretch 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. There is no particular upper limit to the stretch ratio, but it is preferably 10 times or less, more preferably less than 6 times. By having the stretch ratio within the above range, rigidity and strength can be obtained.

[0035] The thickness of the film of the present invention can be appropriately set depending on various applications, and in general, the lower limit is preferably 5 μm or more, more preferably 10 μm or more, and the upper limit is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. When the film thickness is within the above range, a balance between rigidity and strength as a packaging material can be achieved.

[0036] The method for producing the film of the present invention is not particularly limited, but it can be obtained by a known melt extrusion molding method. For example, a laminate can be obtained by melt extruding the resin components constituting each layer separately or simultaneously, and then stretching the obtained film (raw film for stretching). Cast molding is preferred as the method for producing the film of the present invention.

[0037] When the film of the present invention is a stretched film, examples of the method for stretching the raw stretched film 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 flow direction of the film by using a difference in the rotation speed ratio of two or more rolls.

[0038] 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.

[0039] The stretched film may be annealed, if necessary, by contacting the stretched sheet with a heated roll.

[0040] The film of the present invention is preferably a non-stretched film.

[0041] [Laminate] The film of the present invention may be used as a laminate laminated with other layers. That is, the laminate of the present invention is a laminate including the above-mentioned film, and may have a plurality of layers made of the above-mentioned film in the laminate. The other layers constituting the laminate can be appropriately adopted depending on the application. When the film of the present invention is used as a laminate laminated with other layers, it is preferable that the film is located in the innermost layer of the laminate. The innermost layer refers to the layer that comes into contact with the contents when a package is obtained from the laminate. In an embodiment in which the laminate is heat-sealed and used as a packaging bag, the innermost layer functions as a heat-seal layer.

[0042] The method for producing the laminate of the present invention is not particularly limited. For example, the laminate can be obtained by melt extrusion molding the resin components constituting each layer separately or simultaneously. Cast molding is preferred as the method for producing the laminate of the present invention.

[0043] To produce the laminate of the present invention, an adhesive or anchoring agent may be interposed between the layers as needed. Metal oxides or the like may also be vapor-deposited on the entire surface or a portion of the surface, or an ink layer may be provided. There are no particular limitations on the method for producing the laminate of the present invention, 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.

[0044] [Packaging Material] The laminate of the present invention has excellent heat resistance and transparency, and transparency after retort treatment. Therefore, it is useful for various applications requiring heat resistance and impact resistance, such as in the food and medical fields. Specifically, it can be suitably used as a packaging material for fluid or solid packaged items, such as retort foods, pharmaceuticals, medical devices, electrical components, foods, and beverages. Such packaging materials can be used, for example, by overlapping the laminate of the present invention so that at least partial edges thereof contact each other and integrating them by heat fusion. When a laminate including the film of the present invention is integrated by heat fusion for use, it is preferable that the layer made of the film of the present invention is a heat seal layer.

[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, melting point, ΔH50% melting temperature, haze, haze (after heat resistance at 121°C), and heat resistance temperature (5N) were measured as follows.

[0046] Physical Properties of Ethylene-Based Polymers <Melt Flow Rate (MFR: [g / 10 min])> In accordance with JIS K7210, an ethylene-based polymer sample was measured under conditions of 190° C. and a load of 2.16 kg (kgf).

[0047] <Density [kg / m ３ ]> Measurement was carried out in accordance with JIS K7112 by the density gradient tube method using the strand obtained when measuring MFR.

[0048] <Melting Point [°C]> The melting point of an ethylene polymer sample is measured in accordance with JIS-K7121 using a differential scanning calorimeter (DSC, manufactured by PerkinElmer) under the following measurement conditions. The melting point (Tm) is determined as the apex of the endothermic peak in the second run when the measurement is performed under the following measurement conditions. When there are multiple endothermic peaks, the melting point (Tm) is determined as the apex of the endothermic peak with the greatest peak height. (Measurement Conditions) Measurement environment: nitrogen gas atmosphere Sample amount: 5 mg First run: The temperature is increased from 30°C at a rate of 10°C / min to 230°C, and maintained at that temperature for 10 minutes. Thereafter, the temperature is decreased at a rate of 10°C / min to -30°C, and maintained at that temperature for 1 minute. Second run: The temperature is increased from -30°C at a rate of 10°C / min to 230°C. In determining the magnitude of the peak height, a baseline was drawn in the temperature range of 40°C to 150°C, and the value of that baseline was subtracted from the heat of fusion curve, and the magnitude of the peak height was determined, as in the case of requirement (a4) below.

[0049] <ΔH50% Melting Temperature [°C]> The ΔH50% melting temperature [°C] (melting temperature at 50% heat of fusion [°C]) is the temperature [°C] at which the heat of fusion of the total heat of fusion (ΔH) obtained from the DSC curve in DSC measurement is 50%. This measurement was performed by performing heating and cooling (first run, second run) in the same manner as in the measurement of the melting point, and determining the temperature from the DSC curve in the second run. That is, a baseline was drawn in the region from 40°C to 150°C in the DSC curve, and the value of that baseline was subtracted from the DSC curve. The remaining area was defined as the total heat of fusion (ΔH). It was determined whether the temperature (ΔH50% melting temperature [°C]) at which that area became 50% was 120°C or higher.

[0050] <Molecular weight distribution (Mw / Mn)> The weight average molecular weight (Mw) and number average molecular weight (Mn) were measured by gel permeation chromatography (GPC) and calculated in terms of polyethylene. The molecular weight distribution (Mw / Mn) was calculated from the obtained Mw and Mn. The GPC measurement conditions were as follows: (Measurement conditions) Measurement apparatus: Gel permeation chromatograph GPC / HT type (manufactured by Tosoh) Analysis software: Data processing software Empower3 (manufactured by Waters) Column: 2 x TSKgel GMH6-HT + 2 x TSKgel GMH6-HTL (both 7.5 mm inner diameter x 30 cm length, manufactured by Tosoh) Column temperature: 140°C Mobile phase: o-dichlorobenzene (containing 0.025% by mass of BHT) Detector: Differential refractometer Flow rate: 1.0 mL / min Sample concentration: 0.1% (w / v) Injection volume: 400 μL Sampling time interval: 0.5 seconds Column calibration: Monodisperse polystyrene (manufactured by Tosoh) Molecular weight conversion: Polyethylene conversion / general calibration method

[0051] ...Physical properties of film and dry laminate... <Haze [%]> The haze [%] of each sample of film and dry laminate was measured in accordance with ASTM D1003. <Haze (after heat resistance at 121°C) [%]> The haze (after heat resistance at 121°C) [%] of the dry laminate sample was measured after sterilization at 121°C for 5 minutes.

[0052] <Heat Resistance Temperature (5N) [°C]> Two film samples are stacked with their inner surfaces facing each other and heat-sealed by applying temperature and load for a predetermined time. The heat resistance temperature (5N) is determined as the temperature at which the force (N / 15 mm) required to separate the heat-sealed portion where the two film samples are fused reaches 5 N / 15 mm. (Measurement conditions) Heat sealing pressure: 0.2 MPa Heat sealing time: 1 second Test speed (separation speed of two film samples): 300 mm / min Film sample thickness / width: 80 μm / 15 mm width Measurement temperature: 100 to 170°C (in 5°C increments)

[0053] [Example 1, Comparative Examples 1 and 2] The following nucleating agents were used in the proportions shown in Table 1. The following ethylene-based polymers were used. The ethylene-based polymers containing the nucleating agents were melt-kneaded at 230°C using an extruder, and then a raw film having a thickness of 80 μm was formed using a cast molding machine. Next, a substrate (15 μm thick) made of a biaxially oriented nylon film (ONy) was bonded as the substrate layer (D) to the films of the Examples and Comparative Examples using an anchor coating agent to obtain dry laminates. The following tests were performed on the dry laminates obtained as described above. The results are shown in Table 1.

[0054] The MFR, density, melting point, ΔH50% melting temperature, haze, and heat resistance temperature (5N) of the obtained film, and the haze, haze (after heat resistance at 121°C), and heat resistance temperature (5N) of the dry laminate were measured. The results are shown in Table 1. In the comparative example, no nucleating agent was added.

[0055] (Film molding conditions) Molding machine: Modern Machinery cast molding machine Resin temperature during molding: 230°C, Cooling temperature: 40°C Film thickness: 80 μm

[0056] Ethylene polymer: Trade name: Evolue SP1510, manufactured by Prime Polymer Co., Ltd. Linear low-density polyethylene (ethylene-1-hexene copolymer) (MFR: 1.0 g / 10 min, density: 915 kg / m ３ Product name: Hi-Zex 2200J, manufactured by Prime Polymer Co., Ltd. High density polyethylene (MFR: 5.2 g / 10 min, density: 964 kg / m ３ Product name: Evolue SP3530, manufactured by Prime Polymer Co., Ltd. Linear low-density polyethylene (ethylene-1-hexene copolymer) (MFR: 3.2 g / 10 min, density: 931 kg / m ３ , melting point: 122 ° C.)

[0057] Nucleating agent: trade name "Hyperform HPN-20E" (manufactured by Milliken Co.), containing calcium salt of 1,2-cyclohexanedicarboxylic acid as the main component. For example, in Example 1, 0.1920 parts by mass, i.e., 1920 ppm, of the nucleating agent was blended with 100 parts by mass of the ethylene polymer.

[0058]

[0059] The film of the present invention is a film that is excellent in heat resistance, transparency, and transparency after retort treatment, and laminates containing the film can be used in a variety of applications, particularly as packaging materials for a wide range of applications including food products.

Claims

1. A film comprising an ethylene polymer satisfying the following requirements (a1) to (a4), and a nucleating agent in an amount of 100 to 2,500 ppm per 100 parts by mass of the ethylene polymer: (a1) a melt flow rate (MFR, 190°C, load 2.16 kg) of 0.1 to 10 g / 10 min; (a2) a density of 936 to 970 kg / m ３ (a3) The melting point (Tm) determined by a differential scanning calorimeter (DSC) is 124°C or higher. (a4) In a calorie of fusion curve obtained by a differential scanning calorimeter (DSC), a baseline is drawn in the region from 40°C to 150°C, the value of that baseline is subtracted from the calorie of fusion curve, and the remaining area is taken as the total heat of fusion (ΔH). The temperature at which that area becomes 50% (ΔH50% melting temperature [°C]) is 120°C or higher.

2. A laminate comprising the film of claim 1.

3. A laminate comprising the film of claim 1, wherein the innermost layer is made of the film of claim 1.

4. A packaging material comprising the laminate according to claim 2 or 3.

5. A method for producing the film of claim 1 by melt extrusion.

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