Packaging film, packaging material and food package

Abstract

To provide a packaging film having improved heat seal peeing energy, a packaging material, and a food package.SOLUTION: A packaging film 100 includes a biaxially stretched film layer 101 containing an olefinic polymer and at least one filler selected from the group consisting of an organic filler and an inorganic filler, and a heat seal layer 103 provided on at least one surface of the biaxially stretched film layer 101, wherein the heat seal layer 103 contains a propylene-based polymer and an olefin copolymer, the propylene-based polymer contained in the heat seal layer 103 contains at least one selected from the group consisting of homopolypropylene, and a block copolymer of propylene and α-olefin having 2 or more and 10 or less carbon atoms (excluding propylene).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a packaging film, a packaging material, and a food package. [Background technology]

[0002] Polyolefin films have an excellent balance of performance characteristics, such as processability, water vapor barrier properties, transparency, mechanical strength, and rigidity, and are used, for example, as packaging films for packaging food. As a technique relating to such a polyolefin film, for example, the technique described in Patent Document 1 can be mentioned.

[0003] Patent Document 1 describes a heat-sealable polyolefin-based foamed film that is characterized by including at least two layers, a seal layer and a foam layer, and when the film has a thickness of 30 μm or less, the total light transmittance according to JIS K7105 is 15% or less and the seal strength is 5.0 N / 15 mm. 2 The document describes a heat-sealable polyolefin-based foamed film characterized by the above. According to the heat-sealable polyolefin-based foamed film described in Patent Document 1, it is described that a heat-sealable polyolefin-based foamed film having good heat-sealability and hiding property can be obtained. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-30471 A Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, from the viewpoint of environmental issues, there has been a demand for reducing the amount of plastic used in plastic packaging materials. One method for reducing the amount of plastic used in plastic packaging materials is to reduce the density of the packaging film used in the packaging material. However, packaging films with reduced density sometimes have insufficient heat seal peel energy.

[0006] The present invention has been made in view of the above circumstances, and provides a packaging film, a packaging material, and a food package having improved heat seal peel energy. [Means for solving the problem]

[0007] According to the present invention, there are provided the following packaging film, packaging material, and food package.

[0008] [1] a biaxially stretched film layer containing an olefin-based polymer and at least one filler selected from the group consisting of an organic filler and an inorganic filler; A packaging film comprising: a heat seal layer provided on at least one surface of the biaxially oriented film layer, The heat seal layer contains a propylene-based polymer and an olefin copolymer, The propylene-based polymer contained in the heat seal layer includes at least one selected from the group consisting of homopolypropylene and block copolymers of propylene and an α-olefin having 2 to 10 carbon atoms (however, α-olefin excludes propylene). [2] The packaging film according to [1], wherein the content of the olefin copolymer in the heat seal layer is 25.0% by mass or more and 65.0% by mass or less, when the total amount of all components contained in the heat seal layer is 100% by mass. [3] The packaging film according to [1] or [2], wherein the olefin copolymer comprises a copolymer of 1-butene and an α-olefin having 2 to 10 carbon atoms (wherein the α-olefin excludes 1-butene). [4] The copolymer of 1-butene and an α-olefin having 2 to 10 carbon atoms (wherein the α-olefin is excluding 1-butene) has a content of 1-butene-derived structural units of 20.0 mol % to 95.0 mol % when the total number of moles of structural units derived from all monomers contained in the copolymer is taken as 100 mol %. [3] The packaging film described in. [5] The packaging film according to any one of [1] to [4] above, wherein the number of moles of structural units derived from 1-butene is 20.0 mol % or more and 60.0 mol % or less when the total number of moles of structural units in all polymers contained in the heat seal layer is 100 mol %. [6] The packaging film according to any one of the above [1] to [5], wherein the melting point of the olefin copolymer contained in the heat seal layer is 60° C. or higher and 130° C. or lower, as measured by DSC. [7] The packaging film according to any one of [1] to [6] above, wherein the MFR of the olefin copolymer contained in the heat seal layer, measured in accordance with ASTM D1238 under conditions of 230°C and a load of 2.16 kg, is 0.01 g / 10 min or more and 20.0 g / 10 min or less. [8] The packaging film according to any one of the above [1] to [7], wherein the olefin-based polymer contained in the biaxially oriented film layer includes a propylene copolymer. [9] The packaging film according to [8] above, wherein the propylene copolymer is a block copolymer of propylene and an α-olefin having 2 to 10 carbon atoms (wherein α-olefin excludes propylene).

[10] The packaging film according to any one of the above [1] to [9], wherein the filler comprises at least one selected from the group consisting of calcium carbonate, calcium sulfate, barium carbonate, barium sulfate, titanium oxide, magnesium hydroxide, magnesium carbonate, aluminum hydroxide, zinc oxide, magnesium oxide, silica, potassium titanate, calcium sulfite, calcium silicate, wollastonite, talc, mica, clay, kaolinite, montmorillonite, hydrotalcite, polystyrene-based resin particles, and poly(meth)acrylic resin particles.

[11] The packaging film according to any one of [1] to

[10] above, wherein the content of the filler in the biaxially oriented film layer is 1.5% by mass or more and 30.0% by mass or less, when the entire biaxially oriented film layer is taken as 100% by mass.

[12] The packaging film according to any one of the above [1] to

[11] , wherein the biaxially oriented film layer has voids.

[13] The packaging film according to any one of the above [1] to

[12] , wherein the heat seal layer is provided so as to be in direct contact with the one surface of the biaxially stretched film layer.

[14] The packaging film according to any one of [1] to

[13] above, wherein the puncture strength when a needle is pierced from the heat seal layer surface of the packaging film is 4 N or more, as measured in accordance with JIS Z 1707 (2019) at a temperature of 23°C and a humidity of 50%.

[15] The pinhole resistance of the packaging film is measured using a Gelbo flex tester under the conditions of an ambient temperature of -20°C and 3,000 flex cycles, and is 600 pinholes / m 2 The packaging film according to any one of the above [1] to

[14] ,

[16] 55℃, 1kg / 4cm 2 The packaging film according to any one of items [1] to

[15] above, wherein the blocking resistance between the heat seal layers of the packaging film is 5.0 N / 20 mm or less when measured using a tensile tester after storage for 24 hours under a load of 1.0 N / 20 mm or less.

[17] The packaging film according to any one of the above [1] to

[16] , wherein the thickness of the packaging film is 5.0 μm or more and 50.0 μm or less.

[18] The packaging film according to any one of the above [1] to

[17] , wherein the heat seal layer has a thickness of 1.0 μm or more and 13.0 μm or less.

[19] The packaging film according to any one of the above [1] to

[18] , wherein the packaging film is milky white.

[20] The packaging film according to any one of the above [1] to

[19] , which is a packaging film for food. [twenty one] A packaging material using the packaging film according to any one of [1] to

[20] above. [twenty two] The packaging material according to

[21] above, and a food product within the packaging material. Effect of the Invention

[0009] According to the present invention, it is possible to provide a packaging film, a packaging material, and a food package having improved heat seal peel energy. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a cross-sectional view showing a schematic example of the structure of the packaging film of the present embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing a schematic example of the structure of the packaging film of the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the drawings are simplified and do not correspond to the actual dimensional ratio. Note that "~" between numbers in the text indicates "above" to "below" unless otherwise specified.

[0012] [Packaging film] 1 and 2 are cross-sectional views that diagrammatically show an example of the structure of a packaging film 100 according to the present embodiment. The packaging film 100 of this embodiment is a packaging film comprising a biaxially oriented film layer 101 containing an olefin-based polymer and at least one type of filler selected from the group consisting of organic fillers and inorganic fillers, and a heat seal layer 103 provided on at least one surface of the biaxially oriented film layer 101, wherein the heat seal layer 103 contains a propylene-based polymer and an olefin copolymer, and the propylene-based polymer contained in the heat seal layer 103 includes at least one selected from the group consisting of homopolypropylene and a block copolymer of propylene and an α-olefin having a carbon number of 2 or more and 10 or less (however, the α-olefin excludes propylene).

[0013] As described above, from the viewpoint of environmental issues, there is a demand for packaging materials using packaging films with reduced density. For example, a method for obtaining a packaging film with reduced density may include a method for forming voids in a biaxially stretched film layer. However, packaging materials using packaging films with reduced density may not have sufficient strength.

[0014] According to the study by the present inventors, it was found that it is effective to improve the heat seal peel energy of the packaging film in order to improve the strength of the packaging material. The packaging material using the packaging film is obtained, for example, by bonding the heat seal layers of two packaging films together. However, the strength of the packaging material using the conventional packaging film having a biaxially stretched film layer in which voids are formed tends to decrease. The present inventors considered that the strength of the packaging material is decreased when the packaging material using the conventional packaging film having a biaxially stretched film layer in which voids are formed is weak between the biaxially stretched film layer and the heat seal layer, and the biaxially stretched film layer and the heat seal layer are peeled off. That is, the present inventors considered that when the packaging material using the conventional packaging film having a biaxially stretched film layer in which voids are formed is peeled off, the interlayer between the biaxially stretched film layer and the heat seal layer becomes the peeling surface. According to the study by the present inventors, it was found that the strength of the packaging material is improved by increasing the heat seal peel energy of the packaging film. The present inventors consider the reason for this as follows. First, by improving the heat seal peeling energy of the packaging film, the strength between the biaxially oriented film layer and the heat seal layer is improved. As a result, the peeling surface is not between the biaxially oriented film layer and the heat seal layer, but is the interface between the heat seal layers of the two packaging films. The strength of the packaging material is improved by the peeling surface being the heat seal layers of the two packaging films. The present invention has been made in view of the above circumstances, and provides a packaging film having improved heat seal peeling energy.

[0015] Packaging films used in food packaging materials are required to have improved puncture strength and pinhole resistance. The packaging film of the present embodiment can also improve the balance of puncture strength and pinhole resistance. Furthermore, the packaging film of this embodiment can also have improved blocking resistance.

[0016] The density D of the packaging film 100 of the present embodiment is preferably 0.50 g / cm from the viewpoint of further improving the strength of the packaging material. 3 More preferably, 0.55 g / cm 3 More preferably, 0.58 g / cm 3More preferably, 0.60 g / cm 3 More preferably, 0.63 g / cm 3 From the viewpoint of environmental issues, it is preferably 0.90 g / cm 3 Less than or equal to 0.85 g / cm 3 More preferably, 0.80 g / cm 3 More preferably, 0.75 g / cm 3 More preferably, 0.70 g / cm 3 More preferably, 0.68 g / cm 3 The following is the result. The density D of the packaging film can be measured by the method described in the Examples.

[0017] When the packaging film 100 of this embodiment is subjected to differential scanning calorimetry using a differential scanning calorimeter in succession to a process of increasing the temperature from -50°C to 250°C at a heating rate of 10°C / min (1st run), a process of decreasing the temperature from 250°C to -50°C at a heating rate of 10°C / min (temperature decrease measurement), and a process of increasing the temperature from -50°C to 250°C at a heating rate of 10°C / min (2nd run), it is preferable that an endothermic peak and an exothermic peak, as described below, are observed.

[0018] In a DSC curve 2 (2nd Run) obtained by differential scanning calorimetry of the packaging film 100, an endothermic peak A is preferably observed in the range of 130.0°C or higher and 180.0°C or lower. From the viewpoint of further improving the heat seal peeling energy, the temperature range at which endothermic peak A is observed is preferably 140.0°C or higher, more preferably 150.0°C or higher, even more preferably 155.0°C or higher, even more preferably 158.0°C or higher, even more preferably 161.0°C or higher, and preferably 175.0°C or lower, more preferably 170.0°C or lower, even more preferably 168.0°C or lower, even more preferably 165.0°C or lower.

[0019] The heat of fusion ΔH at endothermic peak A observed in DSC curve 2 (2nd Run) obtained by differential scanning calorimetry of the packaging film 100 is preferably 65.0 J / g or more, more preferably 67.0 J / g or more, even more preferably 69.0 J / g or more, even more preferably 70.0 J / g or more, and preferably 90.0 J / g or less, more preferably 87.0 J / g or less, even more preferably 85.0 J / g or less, even more preferably 82.0 J / g or less, even more preferably 80.0 J / g or less, even more preferably 78.0 J / g or less.

[0020] In a DSC curve 2 (2nd Run) obtained by differential scanning calorimetry of the packaging film 100, an endothermic peak B is preferably observed in the range of 50.0°C or more and 100.0°C or less. The temperature range at which endothermic peak B is observed is preferably 60.0°C or higher, more preferably 65.0°C or higher, even more preferably 70.0°C or higher, even more preferably 73.0°C or higher, and even more preferably 75.0°C or higher, and from the viewpoint of further improving the heat seal peeling energy, it is preferably 90.0°C or lower, more preferably 85.0°C or lower, even more preferably 80.0°C or lower, and even more preferably 78.0°C or lower.

[0021] The heat of fusion ΔH at endothermic peak B observed in DSC curve 2 (2nd Run) obtained by differential scanning calorimetry of the packaging film 100 is preferably 1.0 J / g or more, more preferably 1.2 J / g or more, and even more preferably 1.4 J / g or more, from the viewpoint of further improving the heat seal peel energy, and is preferably 6.0 J / g or less, more preferably 5.5 J / g or less, even more preferably 5.0 J / g or less, even more preferably 4.5 J / g or less, even more preferably 4.0 J / g or less, and even more preferably 3.7 J / g or less, from the viewpoint of further improving the heat seal peel energy.

[0022] In the DSC curve (cool) of the temperature drop measurement obtained by differential scanning calorimetry of the packaging film 100, an exothermic peak C is preferably observed in the range of 110.0° C. or more and 130.0° C. or less. From the viewpoint of further improving the heat seal peeling energy, the temperature range at which exothermic peak C is observed is preferably 112.0°C or higher, more preferably 114.0°C or higher, even more preferably 116.0°C or higher, even more preferably 118.0°C or higher, and is preferably 128.0°C or lower, more preferably 125.0°C or lower, even more preferably 123.0°C or lower.

[0023] The ΔH of the exothermic peak C observed in the DSC curve (cool) of the temperature-lowering measurement obtained by differential scanning calorimetry of the packaging film 100 is preferably 65.0 J / g or more, more preferably 68.0 J / g or more, even more preferably 70.0 J / g or more, even more preferably 72.0 J / g or more, and is preferably 90.0 J / g or less, more preferably 85.0 J / g or less, even more preferably 80.0 J / g or less, even more preferably 78.0 J / g or less.

[0024] In the DSC curve (cool) of the temperature drop measurement obtained by differential scanning calorimetry of the packaging film 100, an exothermic peak D is preferably observed in the range of 25.0° C. or more and 75.0° C. or less. The temperature range in which exothermic peak D is observed is preferably 30.0°C or higher, more preferably 35.0°C or higher, even more preferably 38.0°C or higher, even more preferably 40.0°C or higher, even more preferably 42.0°C or higher, and preferably 70.0°C or lower, more preferably 65.0°C or lower, even more preferably 60.0°C or lower, even more preferably 55.0°C or lower, even more preferably 53.0°C or lower.

[0025] From the viewpoint of further improving the heat seal peeling energy, ΔH of the exothermic peak D observed in the DSC curve (cool) of the temperature decreasing measurement obtained by differential scanning calorimetry of the packaging film 100 is preferably 2.5 J / g or more, more preferably 2.8 J / g or more, even more preferably 3.0 J / g or more, and even more preferably 3.1 J / g or more, and from the viewpoint of further improving the heat seal peeling energy, it is preferably 8.5 J / g or less, more preferably 8.0 J / g or less, even more preferably 7.5 J / g or less, even more preferably 7.0 J / g or less, even more preferably 6.5 J / g or less, even more preferably 6.3 J / g or less, even more preferably 6.0 J / g or less, even more preferably 5.8 J / g or less, and even more preferably 5.6 J / g or less.

[0026] From the viewpoint of further improving the strength of the packaging material, the heat seal strength of the packaging film 100 of this embodiment is preferably 3.0 N / 15 mm or more, more preferably 3.5 N / 15 mm or more, and even more preferably 3.8 N / 15 mm or more, and the upper limit is not particularly limited, but may be, for example, 10.0 N / 15 mm or less, 9.0 N / 15 mm or less, or 8.0 N / 15 mm or less. In this specification, the heat seal strength of the packaging film refers to a value measured by the method described in the Examples section, i.e., the heat seal strength when a peel test is performed on a sample obtained by laminating a packaging film and a biaxially oriented polypropylene film with a two-component curing polyurethane adhesive (a mixture of a urethane resin as the main agent, an isocyanate curing agent, and an ethyl acetate solvent in a ratio of 9.0:1.0:7.5 (mass ratio)) using a tensile tester.

[0027] The heat seal peel energy of the packaging film 100 of this embodiment is preferably 500 mJ or more, more preferably 530 mJ or more, and even more preferably 550 mJ or more, from the viewpoint of further improving the strength of the packaging material, and the upper limit is not particularly limited, but may be, for example, 1500 mJ or less, or 1400 mJ or less. In this specification, the heat seal peel energy of the packaging film refers to a value measured by the method described in the Examples section, i.e., the heat seal peel energy when a peel test is performed on a sample obtained by laminating a packaging film and a biaxially oriented polypropylene film with a two-component curing polyurethane adhesive (a mixture of a urethane resin as the main agent, an isocyanate curing agent, and an ethyl acetate solvent in a ratio of 9.0:1.0:7.5 (by mass)) using a tensile tester.

[0028] The puncture strength of the packaging film 100 of this embodiment is preferably 4N or more, more preferably 5N or more, from the viewpoint of further improving the strength of the packaging material, and the upper limit is not particularly limited, but may be, for example, 10N or less, or 7N or less. Here, the puncture strength of the packaging film refers to the puncture strength when a needle is pierced from the heat seal layer surface of the packaging film, measured in accordance with JIS Z 1707 (2019) under conditions of temperature: 23°C and humidity: 50%.

[0029] The pinhole resistance of the packaging film 100 of the present embodiment is preferably 600 pinholes / m from the viewpoint of further improving the strength of the packaging material. 2 Less than or equal to 500 pieces / m 2 Less than 400 / m, more preferably 2 Less than 300 / m, more preferably 2 Less than or equal to 250 pieces / m 2 The lower limit is not particularly limited, but may be, for example, 10 particles / m 2 More than 50 pieces / m 2 It may be more than that. Here, the pinhole resistance of the packaging film refers to a value measured by the method described in the Examples, that is, the pinhole resistance measured using a Gelbo flex tester under the conditions of an atmospheric temperature of -20°C and a number of flexes of 3000.

[0030] From the viewpoint of further improving the handleability of the packaging film, the blocking resistance of the packaging film 100 of this embodiment is preferably 5.0 N / 20 mm or less, more preferably 4.8 N / 20 mm or less, and even more preferably 4.6 N / 20 mm or less. The lower limit is not particularly limited, but may be, for example, 0.5 N / 20 mm or more, or 0.8 N / 20 mm or more. Here, the blocking resistance of the packaging film is 55°C, 1kg / 4cm 2 This refers to the blocking resistance between heat seal layers measured using a tensile tester after storing the sample for 24 hours under a load of 1000 g / m².

[0031] The color of the packaging film 100 of the present embodiment is not particularly limited, but is preferably milky white. If the packaging film is milky white, it is not necessary to print the packaging film in white, which is preferable from the viewpoint of environmental issues. Here, the packaging film being milky white means, for example, that the whiteness is 60% or more, or that the total light transmittance of the packaging film is 90.0% or less. From the standpoint of environmental concerns, the whiteness of the packaging film 100 of this embodiment is preferably 65% ​​or more, more preferably 70% or more, even more preferably 80% or more, and even more preferably 90% or more, and the upper limit is not particularly limited, but is, for example, 99% or less. The whiteness index refers to a value measured in accordance with JIS L 1916 (2000). From the standpoint of environmental considerations, the total light transmittance of the packaging film 100 of this embodiment is preferably 70.0% or less, more preferably 60.0% or less, even more preferably 55.0% or less, and even more preferably 50.0% or less, and the lower limit is not particularly limited, but may be, for example, 20.0% or more, or 30.0% or more. The total light transmittance means a value measured in accordance with JIS K 7136 (2000).

[0032] From the viewpoint of further improving the handleability of the packaging film, the thickness of the packaging film 100 of this embodiment is preferably 5.0 μm or more, more preferably 10.0 μm or more, even more preferably 15.0 μm or more, even more preferably 20.0 μm or more, even more preferably 22.0 μm or more, and even more preferably 24.0 μm or more, and from the viewpoint of environmental issues, it is preferably 50.0 μm or less, more preferably 40.0 μm or less, even more preferably 35.0 μm or less, even more preferably 32.0 μm or less, and even more preferably 30.0 μm or less.

[0033] Each layer constituting the packaging film 100 will now be described.

[0034] <Biaxially oriented film layer> The biaxially stretched film layer 101 contains an olefin-based polymer and at least one type of filler selected from the group consisting of organic fillers and inorganic fillers. The biaxially stretched film layer 101 is formed, for example, by biaxially stretching a film made of an olefin-based polymer composition containing an olefin-based polymer and a filler. The biaxially stretched film layer 101 may be a single layer or a multilayer, but it is necessary that it is biaxially stretched.

[0035] The biaxially stretched film layer 101 contains an olefin-based polymer. The olefin-based polymer in the biaxially stretched film layer 101 includes homopolyolefins, olefin copolymers, etc., and more specifically, includes homopolyethylene, homopolypropylene, homopolybutene, ethylene copolymers, propylene copolymers, 1-butene copolymers, etc. Here, unless otherwise specified, the olefin copolymer of the present embodiment refers to an olefin copolymer in which the most abundant olefin-derived structural unit in the olefin copolymer is 98.5 mol% or less when the total number of moles of the structural units derived from all monomers contained in the olefin copolymer is 100 mol%. Unless otherwise specified, the homopolyolefin of the present embodiment refers to an olefin homopolymer and an olefin copolymer in which the most abundant olefin-derived structural unit in the olefin copolymer is more than 98.5 mol% when the total number of moles of the structural units derived from all monomers contained in the olefin copolymer is 100 mol%.

[0036] The olefin-based polymer contained in the biaxially stretched film layer 101 preferably includes an olefin copolymer, more preferably includes a propylene copolymer, even more preferably includes a block copolymer of propylene, even more preferably includes a block copolymer of propylene and an α-olefin having a carbon number of 2 to 10 (however, α-olefins exclude propylene), even more preferably includes a block copolymer of propylene and an α-olefin having a carbon number of 2 to 6 (however, α-olefins exclude propylene), even more preferably includes at least one selected from the group consisting of a block copolymer of propylene and ethylene and a block copolymer of propylene and 1-butene, and even more preferably includes a block copolymer of propylene and ethylene.

[0037] In the propylene copolymer in the biaxially oriented film layer 101, when the total number of moles of structural units derived from all monomers contained in the propylene copolymer is taken as 100 mol%, the total number of moles of structural units derived from α-olefins having a carbon number of 2 to 10 (however, α-olefins exclude propylene) is preferably 2.0 mol% or more, more preferably 4.0 mol% or more, and even more preferably 6.0 mol% or more, from the viewpoint of further improving the heat seal peel energy, and is preferably 10.0 mol% or less, more preferably 9.5 mol% or less, even more preferably 9.0 mol% or less, and even more preferably 8.5 mol% or less, from the viewpoint of further improving the heat seal peel energy.

[0038] The content of the olefin copolymer contained in the biaxially oriented film layer 101, when the total of all components contained in the biaxially oriented film layer 101 is taken as 100% by mass, is preferably 50.0% by mass or more, more preferably 60.0% by mass or more, even more preferably 70.0% by mass or more, even more preferably 75.0% by mass or more, even more preferably 80.0% by mass or more, and is preferably 97.0% by mass or less, more preferably 96.0% by mass or less, from the viewpoint of further improving the heat seal peel energy.

[0039] The melting point of the olefin copolymer in the biaxially oriented film layer 101 as measured by DSC is preferably 125°C or higher, more preferably 135°C or higher, even more preferably 140°C or higher, even more preferably 145°C or higher, even more preferably 150°C or higher, even more preferably 155°C or higher, and even more preferably 160°C or higher, from the viewpoint of further improving the thermal dimensional stability of the packaging material, and is preferably 180°C or lower, more preferably 175°C or lower, even more preferably 170°C or lower, and even more preferably 168°C or lower, from the viewpoint of further improving the formability of the packaging film 100. When two or more kinds of olefin copolymers are used as the olefin copolymer, the melting point of the olefin copolymer is the peak temperature of the maximum melting peak.

[0040] The MFR of the olefin copolymer in the biaxially oriented film layer 101, measured in accordance with ASTM D1238 under conditions of 230°C and a load of 2.16 kg, is preferably 0.01 g / 10 min or more, more preferably 0.1 g / 10 min or more, even more preferably 0.5 g / 10 min or more, even more preferably 1.0 g / 10 min or more, and even more preferably 2.0 g / 10 min or more, from the viewpoint of further improving the formability of the packaging film 100, and is preferably 20.0 g / 10 min or less, more preferably 15.0 g / 10 min or less, even more preferably 12.0 g / 10 min or less, even more preferably 10.0 g / 10 min or less, even more preferably 8.0 g / 10 min or less, and even more preferably 5.0 g / 10 min or less, from the viewpoint of further improving the thermal dimensional stability of the packaging material. When two or more types of olefin copolymers are used as the olefin copolymer, the MFR of the olefin copolymer can be the MFR of a mixture obtained by melt blending two or more types of olefin copolymers by a known method or the like.

[0041] The olefin copolymer of the present embodiment can be produced by various methods, for example, by using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst.

[0042] The olefin polymer contained in the biaxially oriented film layer 101 preferably contains a homopolyolefin. Examples of homopolyolefins include homopolyethylene, homopolypropylene, homopolybutene, and the like, and among these, it is preferable to include homopolypropylene.

[0043] The content of homopolyolefin contained in the biaxially oriented film layer 101, when the total amount of all components contained in the biaxially oriented film layer 101 is 100 mass%, is preferably 0.5 mass% or more, more preferably 1.0 mass% or more, even more preferably 3.0 mass% or more, even more preferably 5.0 mass% or more, and is preferably 25.0 mass% or less, more preferably 20.0 mass% or less, even more preferably 15.0 mass% or less, and even more preferably 10.0 mass% or less.

[0044] The isotactic mesopentad fraction (mmmm) of the homopolyolefin in the biaxially stretched film layer 101 is preferably 96.0% or more, more preferably 96.5% or more, even more preferably 97.0% or more, and even more preferably 97.3% or more, from the viewpoint of further improving the balance of thermal dimensional stability, heat resistance, water vapor barrier properties, mechanical properties, rigidity, bag formability, etc. of the packaging film 100. The upper limit of the isotactic mesopentad fraction (mmmm) of the homopolyolefin is not particularly limited, but from the viewpoint of ease of production, it is preferably 99.5% or less, more preferably 99.0% or less, even more preferably 98.5% or less, and even more preferably 98.0% or less. The isotactic mesopentad fraction (mmmm) is an index of stereoregularity, 13 It can be determined from C-nuclear magnetic resonance (NMR) spectrum by a known method. When two or more types of homopolyolefins are used as the homopolyolefin, the isotactic mesopentad fraction of the homopolyolefin can be the isotactic mesopentad fraction of a mixture obtained by melt blending two or more types of homopolyolefins by a known method.

[0045] The melting point of the homopolyolefin in the biaxially oriented film layer 101 as measured by DSC is preferably 150°C or higher, more preferably 155°C or higher, and even more preferably 157°C or higher, from the viewpoint of further improving the balance of the thermal dimensional stability, heat resistance, water vapor barrier properties, mechanical properties, rigidity, bag formability, fluidity, moldability, etc. of the packaging film 100, and is preferably 180°C or lower, more preferably 175°C or lower, even more preferably 170°C or lower, even more preferably 165°C or lower, and even more preferably 160°C or lower. When two or more kinds of homopolyolefins are used as the homopolyolefin, the melting point of the homopolyolefin is the peak temperature of the maximum melting peak.

[0046] The MFR of the homopolyolefin in the biaxially oriented film layer 101, measured in accordance with ASTM D1238 under conditions of 230°C and a load of 2.16 kg, is preferably 0.01 g / 10 min or more, more preferably 0.1 g / 10 min or more, even more preferably 0.5 g / 10 min or more, even more preferably 1.0 g / 10 min or more, and even more preferably 2.0 g / 10 min or more, from the viewpoint of further improving the formability of the packaging film 100, and is preferably 20.0 g / 10 min or less, more preferably 15.0 g / 10 min or less, even more preferably 12.0 g / 10 min or less, even more preferably 10.0 g / 10 min or less, even more preferably 8.0 g / 10 min or less, and even more preferably 5.0 g / 10 min or less, from the viewpoint of further improving the thermal dimensional stability of the packaging material. When two or more kinds of homopolyolefins are used as the homopolyolefin, the MFR of the homopolyolefin can be the MFR of a mixture obtained by melt blending two or more kinds of homopolyolefins by a known method or the like.

[0047] Homopolyolefins can be produced by various methods, for example, by using known catalysts such as Ziegler-Natta catalysts and metallocene catalysts.

[0048] The olefin-based polymer contained in the biaxially oriented film layer 101 preferably contains an olefin copolymer and a homopolyolefin.

[0049] The total content of the olefin-based polymer contained in the biaxially oriented film layer 101 is preferably 70.0 mass% or more, more preferably 75.0 mass% or more, even more preferably 80.0 mass% or more, even more preferably 85.0 mass% or more, and is preferably 97.0 mass% or less, more preferably 96.0 mass% or less, when the total amount of all components contained in the biaxially oriented film layer is 100 mass%.

[0050] The biaxially stretched film layer 101 contains at least one filler selected from the group consisting of organic fillers and inorganic fillers. The filler in the biaxially stretched film layer 101 preferably includes at least one selected from the group consisting of calcium carbonate, calcium sulfate, barium carbonate, barium sulfate, titanium oxide, magnesium hydroxide, magnesium carbonate, aluminum hydroxide, zinc oxide, magnesium oxide, silica, potassium titanate, calcium sulfite, calcium silicate, wollastonite, talc, mica, clay, kaolinite, montmorillonite, hydrotalcite, polystyrene-based resin particles, and poly(meth)acrylic resin particles, and more preferably includes at least one selected from the group consisting of calcium carbonate and titanium oxide.

[0051] The content of the filler contained in the biaxially oriented film layer 101, when the total amount of all components contained in the biaxially oriented film layer is taken as 100% by mass, is preferably 1.5% by mass or more, more preferably 2.0% by mass or more, more preferably 3.0% by mass or more, even more preferably 5.0% by mass or more, and even more preferably 7.0% by mass or more, from the viewpoint of making the density D of the packaging film 100 more appropriate, and is preferably 30.0% by mass or less, more preferably 25.0% by mass or less, even more preferably 23.0% by mass or less, even more preferably 20.0% by mass or less, and even more preferably 15.0% by mass or less, from the viewpoint of further improving the heat seal peel energy.

[0052] The shape of the filler in the biaxially oriented film layer 101 is not particularly limited, and examples thereof include cubic, rod-like, spherical, elliptical, amorphous, conical, plate-like, needle-like, etc., but a cubic shape is preferable from the viewpoint of making the density D of the packaging film 100 more appropriate. The shape of the filler can be evaluated, for example, by observing the biaxially stretched film layer using a scanning electron microscope.

[0053] The average particle diameter of the filler in the biaxially oriented film layer 101 is preferably 0.5 μm or more, more preferably 1.0 μm or more, and even more preferably 1.5 μm or more, from the viewpoint of making the density D of the packaging film 100 more appropriate, and is preferably 5.0 μm or less, more preferably 4.0 μm or less, even more preferably 3.5 μm or less, and even more preferably 3.0 μm or less, from the viewpoint of further improving the heat seal strength and heat seal peel energy. The average particle size of the filler means a value measured by a light transmission measurement method using centrifugal sedimentation.

[0054] The filler in the biaxially stretched film layer 101 may be used untreated, or may be surface-treated with a silane coupling agent, a titanium coupling agent, a surfactant, or the like to improve dispersibility in the olefin-based polymer.

[0055] The biaxially stretched film layer 101 preferably has voids from the viewpoint of reducing the density D of the packaging film 100. The maximum pore size of the voids in the biaxially stretched film layer 101 is preferably 2.0 μm or more, more preferably 3.0 μm or more, and even more preferably 5.0 μm or more from the viewpoint of making the density D of the packaging film 100 more appropriate, and is preferably 50.0 μm or less, more preferably 30.0 μm or less, and even more preferably 10.0 μm or less from the viewpoint of further improving the heat seal strength and heat seal peel energy. Here, the maximum pore size means the maximum value of the pore size of one void. The presence or absence of voids in the biaxially stretched film layer 101 and the maximum diameter of the voids can be evaluated by observing the biaxially stretched film layer using a scanning electron microscope. The voids can be formed, for example, by adjusting the content of the filler in the biaxially oriented film layer, the thickness of the biaxially oriented film layer, the stretching ratio, and the like.

[0056] From the viewpoint of further improving the balance of the thermal dimensional stability, formability, water vapor barrier properties, cost, mechanical properties, transparency, bag formability, handleability, appearance, and lightness of the packaging film 100, the thickness of the biaxially oriented film layer 101 is preferably 5.0 μm or more, more preferably 10.0 μm or more, even more preferably 12.0 μm or more, and even more preferably 15.0 μm or more, and is preferably 100.0 μm or less, more preferably 50.0 μm or less, even more preferably 40.0 μm or less, even more preferably 30.0 μm or less, and even more preferably 25.0 μm or less.

[0057] The ratio of the thickness of the biaxially oriented film layer 101 to the total thickness of the packaging film 100 is preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, and preferably 95% or less, more preferably 90% or less, even more preferably 85% or less.

[0058] The biaxially stretched film layer 101 may contain various additives such as tackifiers, heat stabilizers, weather stabilizers, antioxidants, UV absorbers, lubricants, slip agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, etc., as necessary, within the scope that does not impair the purpose of this embodiment.

[0059] The olefin polymer composition for constituting the biaxially stretched film layer 101 can be prepared by mixing or melt-kneading each component using a dry blend, a tumbler mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, a heat roll, or the like.

[0060] <Heat seal layer> The packaging film 100 of this embodiment includes a biaxially oriented film layer 101 and a heat seal layer 103 provided on at least one surface of the biaxially oriented film layer 101 . From the viewpoint of further simplifying the manufacturing process of the packaging film 100, the heat seal layer 103 is preferably provided so as to be in direct contact with one surface of the biaxially oriented film layer 101.

[0061] In order to improve the heat sealability of the packaging film 100, the heat seal layer 103 is preferably provided on the outermost layer of the packaging film 100.

[0062] The heat seal layer 103 may be a single layer or a multilayer, but from the viewpoint of further simplifying the manufacturing process of the packaging film 100, it is preferable that it is a single layer.

[0063] The heat seal layer 103 is preferably formed by biaxially stretching simultaneously with the biaxially stretched film layer 101 in a state before biaxial stretching. This allows the packaging film 100 to be produced using a molding method such as coextrusion, i.e., a laminated film produced in a single molding operation, thereby further simplifying the manufacturing process of the packaging film 100. Therefore, the heat seal layer 103 is preferably biaxially stretched.

[0064] The heat seal layer 103 contains a propylene-based polymer and an olefin copolymer, and the propylene-based polymer contained in the heat seal layer 103 contains at least one selected from the group consisting of homopolypropylene and a block copolymer of propylene and an α-olefin having 2 to 10 carbon atoms (however, the α-olefin excludes propylene).

[0065] The total content of the propylene-based polymers contained in the heat seal layer 103, when the total amount of all components contained in the heat seal layer 103 is taken as 100% by mass, is preferably 20.0% by mass or more, more preferably 25.0% by mass or more, even more preferably 30.0% by mass or more, and even more preferably 35.0% by mass or more, from the viewpoint of further improving the heat sealability of the heat seal layer 103, and is preferably 75.0% by mass or less, more preferably 73.0% by mass or less, and even more preferably 71.0% by mass or less.

[0066] The melting point of the propylene-based polymer contained in the heat seal layer 103, as measured by DSC, is preferably 125°C or higher, more preferably 135°C or higher, even more preferably 140°C or higher, even more preferably 145°C or higher, even more preferably 150°C or higher, and even more preferably 155°C or higher, from the viewpoint of further improving the heat seal peel energy, and is preferably 180°C or lower, more preferably 175°C or lower, even more preferably 170°C or lower, and even more preferably 168°C or lower, from the viewpoint of further improving the formability of the packaging film 100. When two or more kinds of propylene polymers are used as the propylene polymer, the melting point of the propylene polymer is the peak temperature of the maximum melting peak.

[0067] The preferred aspects of the isotactic mesopentad fraction (mmmm), melting point, MFR, etc. of the homopolypropylene contained in the heat seal layer 103 are the same as those of the homopolyolefin contained in the biaxially oriented film layer 101 described above.

[0068] The content of homopolypropylene contained in the heat seal layer 103, when the total amount of all components contained in the heat seal layer 103 is taken as 100% by mass, is preferably 20.0% by mass or more, more preferably 25.0% by mass or more, even more preferably 30.0% by mass or more, and even more preferably 35.0% by mass or more, from the viewpoint of further improving the heat seal peel energy, and is preferably 75.0% by mass or less, more preferably 70.0% by mass or less, even more preferably 65.0% by mass or less, even more preferably 60.0% by mass or less, and even more preferably 55.0% by mass or less, from the viewpoint of further improving the heat sealability of the heat seal layer 103.

[0069] The block copolymer of propylene and an α-olefin having a carbon number of 2 or more and 10 or less (however, α-olefins exclude propylene) contained in the heat seal layer 103 preferably includes a block copolymer of propylene and an α-olefin having a carbon number of 2 or more and 6 or less (however, α-olefins exclude propylene), more preferably includes at least one selected from the group consisting of a block copolymer of propylene and ethylene and a block copolymer of propylene and 1-butene, and even more preferably includes a block copolymer of propylene and ethylene.

[0070] In the block copolymer of propylene and an α-olefin having a carbon number of 2 to 10 (α-olefin excluding propylene) contained in the heat seal layer 103, when the total number of moles of constituent units derived from all monomers contained in the block copolymer is taken as 100 mol%, the total number of moles of constituent units derived from an α-olefin having a carbon number of 2 to 10 (α-olefin excluding propylene) is preferably 2.0 mol% or more, more preferably 4.0 mol% or more, even more preferably 6.0 mol% or more, and preferably 20.0 mol% or less, more preferably 18.0 mol% or less, even more preferably 15.0 mol% or less, even more preferably 12.0 mol% or less, even more preferably 10.0 mol% or less, even more preferably 9.0 mol% or less.

[0071] The preferred aspects of the melting point, MFR, etc. of the block copolymer of propylene and an α-olefin having 2 to 10 carbon atoms (however, α-olefin excludes propylene) contained in the heat seal layer 103 are the same as those of the olefin copolymer contained in the biaxially oriented film layer 101 described above.

[0072] The content of the block copolymer of propylene and an α-olefin having a carbon number of 2 to 10 (excluding propylene) contained in the heat seal layer 103 is, when the total amount of all components contained in the heat seal layer 103 is taken as 100 mass%, from the viewpoint of further improving the heat seal peel energy, preferably 20.0 mass% or more, more preferably 25.0 mass% or more, even more preferably 30.0 mass% or more, even more preferably 35.0 mass% or more, even more preferably 40.0 mass% or more, and even more preferably 45.0 mass% or more, and from the viewpoint of further improving the heat sealability of the heat seal layer 103, it is preferably 75.0 mass% or less, more preferably 73.0 mass% or less, and even more preferably 71.0 mass% or less.

[0073] The heat seal layer 103 comprises an olefin copolymer. The olefin copolymer contained in the heat seal layer 103 may be, for example, a copolymer of α-olefins such as ethylene, propylene, 1-butene, hexene-1, 4-methyl-pentene-1, and octene-1. However, the olefin copolymer contained in the heat seal layer 103 excludes block copolymers of propylene and an α-olefin having a carbon number of 2 or more and 10 or less (however, α-olefins exclude propylene).

[0074] The content of the olefin copolymer in the heat seal layer 103 is preferably 25.0% by mass or more, more preferably 27.0% by mass or more, and even more preferably 29.0% by mass or more, when the total amount of all components contained in the heat seal layer 103 is 100% by mass, and from the viewpoint of further improving the heat seal peel energy, it is preferably 65.0% by mass or less, more preferably 63.0% by mass or less, even more preferably 60.0% by mass or less, even more preferably 58.0% by mass or less, even more preferably 55.0% by mass or less, and even more preferably 52.0% by mass or less.

[0075] The olefin copolymer contained in the heat seal layer 103 is preferably an elastomer.

[0076] The olefin copolymer contained in the heat seal layer 103 is preferably a butene copolymer, more preferably a copolymer of 1-butene and an α-olefin having a carbon number of 2 or more and 10 or less (however, α-olefins exclude 1-butene), even more preferably a copolymer of 1-butene and an α-olefin having a carbon number of 2 or more and 6 or less (however, α-olefins exclude 1-butene), and even more preferably a copolymer of 1-butene and propylene. In the above-mentioned copolymer of 1-butene and 2 to 10 α-olefins (wherein α-olefins exclude 1-butene), when the total number of moles of structural units derived from all monomers contained in the copolymer is taken as 100 mol%, the content of structural units derived from 1-butene is preferably 20.0 mol% or more, more preferably 40.0 mol% or more, even more preferably 60.0 mol% or more, even more preferably 70.0 mol% or more, even more preferably 75.0 mol% or more, even more preferably 80.0 mol% or more, even more preferably 85.0 mol% or more, and preferably 95.0 mol% or less, more preferably 93.0 mol% or less, even more preferably 90.0 mol% or less.

[0077] The melting point of the olefin copolymer in the heat seal layer 103 as measured by DSC is preferably 60°C or higher, more preferably 65°C or higher, even more preferably 70°C or higher, even more preferably 75°C or higher, even more preferably 80°C or higher, even more preferably 85°C or higher, even more preferably 90°C or higher, even more preferably 95°C or higher, and preferably 130°C or lower, more preferably 120°C or lower, even more preferably 110°C or lower, even more preferably 105°C or lower. When two or more kinds of olefin copolymers are used as the olefin copolymer, the melting point of the olefin copolymer is the peak temperature of the maximum melting peak.

[0078] The MFR of the olefin copolymer in the heat seal layer 103, measured in accordance with ASTM D1238 under conditions of 230°C and a load of 2.16 kg, is preferably 0.01 g / 10 min or more, more preferably 0.1 g / 10 min or more, even more preferably 1.0 g / 10 min or more, even more preferably 3.0 g / 10 min or more, even more preferably 5.0 g / 10 min or more, even more preferably 7.0 g / 10 min or more, and is preferably 20.0 g / 10 min or less, more preferably 15.0 g / 10 min or less, even more preferably 12.0 g / 10 min or less, and even more preferably 10.0 g / 10 min or less.

[0079] When the total number of moles of structural units in all polymers contained in the heat seal layer 103 is taken as 100 mol%, the number of moles of structural units derived from 1-butene is preferably 20.0 mol% or more, more preferably 23.0 mol% or more, and even more preferably 25.0 mol% or more, and from the viewpoint of further improving the heat seal peel energy, it is preferably 60.0 mol% or less, more preferably 55.0 mol% or less, even more preferably 50.0 mol% or less, even more preferably 48.0 mol% or less, and even more preferably 45.0 mol% or less.

[0080] When the total number of moles of all polymer structural units contained in the heat seal layer 103 is taken as 100 mol %, the number of moles of ethylene-derived structural units is preferably 0.1 mol % or more, more preferably 0.3 mol % or more, and preferably 10.0 mol % or less, more preferably 8.0 mol % or less, and even more preferably 6.0 mol % or less.

[0081] From the viewpoint of further improving the heat sealability, the thickness of the heat seal layer 103 is preferably 1.0 μm or more, more preferably 3.0 μm or more, and even more preferably 4.0 μm or more, and from the viewpoint of further improving the blocking properties and slip properties of the packaging film 100, the thickness is preferably 13.0 μm or less, more preferably 11.0 μm or less, even more preferably 10.0 μm or less, even more preferably 8.0 μm or less, and even more preferably 6.0 μm or less.

[0082] The heat seal layer 103 may contain various additives such as tackifiers, heat stabilizers, weather stabilizers, antioxidants, UV absorbers, lubricants, slipping agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, and inorganic or organic fillers, as necessary, within the scope that does not impair the purpose of this embodiment.

[0083] The polyolefin resin composition for constituting the heat seal layer 103 can be prepared by mixing or melt-kneading each component using a dry blend, a tumbler mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, a heat roll, or the like.

[0084] <Surface layer> The packaging film 100 may further include a surface layer 105 from the viewpoint of imparting functions such as heat adhesion resistance, antistatic properties, blocking resistance, printability, and slip properties depending on the purpose. The surface layer 105 is preferably provided on the side of the biaxially oriented film layer 101 opposite the heat seal layer 103, and from the viewpoint of further simplifying the manufacturing process of the packaging film 100, it is more preferable that the surface layer 105 is provided so as to be in direct contact with the side of the biaxially oriented film layer 101 opposite the heat seal layer 103.

[0085] The surface layer 105 may be a single layer or a multilayer, but from the viewpoint of further simplifying the manufacturing process of the packaging film 100, it is preferable that the surface layer 105 be a single layer.

[0086] The surface layer 105 is preferably formed by biaxially stretching simultaneously with the biaxially stretched film layer 101 in a state before biaxial stretching. This allows the packaging film 100 to be produced using a molding method such as coextrusion, i.e., a laminated film produced in a single molding operation, thereby further simplifying the manufacturing process of the packaging film 100. Therefore, the surface layer 105 is preferably biaxially stretched.

[0087] The surface layer 105 may be subjected to a surface treatment. Specifically, a surface activation treatment such as a corona treatment, a flame treatment, a plasma treatment, a primer coat treatment, or an ozone treatment may be performed, and the corona treatment is preferably performed.

[0088] The surface layer 105 is made of a polyolefin-based resin composition containing a polyolefin. The polyolefin constituting the surface layer 105 includes at least one selected from the group consisting of homopolymers or copolymers of α-olefins such as ethylene, propylene, 1-butene, hexene-1, 4-methyl-pentene-1, 1-octene, etc.; high-pressure low-density polyethylene; linear low-density polyethylene (LLDPE); high-density polyethylene; homopolypropylene; random copolymers of propylene and α-olefins having 2 to 10 carbon atoms; ethylene-vinyl acetate copolymers (EVA); and ionomer resins. Among these, homopolyolefins are preferred as the polyolefins constituting the surface layer 105, and homopolypropylene is more preferred among them, from the viewpoint of further improving the balance of heat fusion resistance, thermal dimensional stability, heat resistance, water vapor barrier properties, transparency, mechanical properties, rigidity, bag formability, flowability, moldability, etc. of the packaging film 100. Here, the preferred embodiment of the homopolyolefin constituting the surface layer 105 is the same as the homopolyolefin contained in the biaxially oriented film layer 101 described above.

[0089] The content of homopolyolefin contained in surface layer 105, when the total amount of all components contained in surface layer 105 is taken as 100% by mass, is preferably 75% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of further improving the balance of heat resistance, thermal dimensional stability, heat resistance, water vapor barrier property, transparency, mechanical properties, rigidity, bag formability, fluidity, formability, etc. of the packaging film 100, and is preferably 98% by mass or less, and more preferably 96% by mass or less.

[0090] The thickness of the surface layer 105 is preferably 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.5 μm or more, and even more preferably 1.0 μm or more, from the viewpoint of further improving the functions of the packaging film 100 such as heat resistance, heat sealability, antistatic properties, blocking resistance, printability, and slip properties, and is preferably 10.0 μm or less, more preferably 8.0 μm or less, even more preferably 6.0 μm or less, even more preferably 5.0 μm or less, and even more preferably 2.0 μm or less, from the viewpoint of further improving the balance of the heat resistance, thermal dimensional stability, formability, cost, mechanical properties, transparency, environmental compatibility, and light weight of the packaging film 100.

[0091] The surface layer 105 may contain various additives, such as a tackifier, a heat stabilizer, a weather stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, a slip agent, a nucleating agent, an antiblocking agent, an antistatic agent, an antifogging agent, a pigment, a dye, and an inorganic or organic filler, as necessary, within a range that does not impair the purpose of this embodiment. From the viewpoint of further improving the handling properties during production of the packaging film 100, the surface layer 105 preferably contains an antiblocking agent.

[0092] The polyolefin resin composition for constituting the surface layer 105 can be prepared by mixing or melt-kneading the components using a dry blend, a tumbler mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, a heat roll, or the like.

[0093] <Other layers> The packaging film 100 may further include other layers, such as an adhesive layer.

[0094] [Manufacturing method of packaging film] When the packaging film 100 is multilayered, for example, an olefin-based polymer composition for constituting the biaxially oriented film layer 101 and a polyolefin-based composition for constituting the heat seal layer 103 are co-extruded onto a film to obtain a film, and the film can be biaxially stretched using a known biaxially oriented film manufacturing method such as a simultaneous biaxial stretching method, a sequential biaxial stretching method, or an inflation biaxial stretching method. The molding device and molding conditions are not particularly limited, and conventionally known molding devices and molding conditions can be adopted. As the molding device, a T-die extruder, a multi-layer T-die extruder, an inflation molding machine, a multi-layer inflation molding machine, etc. can be used. As the biaxial stretching conditions, for example, known OPP film manufacturing conditions can be adopted. More specifically, in the sequential biaxial stretching method, for example, the MD stretching temperature may be 80°C to 145°C, the MD stretching ratio may be in the range of 4.5 to 6 times, the TD stretching temperature may be 130°C to 190°C, and the TD stretching ratio may be in the range of 9 to 11 times. The packaging film 100 can also be obtained by separately forming the biaxially oriented film layer 101 and the heat seal layer 103, laminating them together, and heat forming them.

[0095] [Uses of packaging film] Since the packaging film 100 has a good balance of puncture strength and pinhole resistance, it is preferably a packaging film for food, and more preferably a packaging film for frozen food. That is, it is preferably used as a packaging film constituting a packaging material for food, and more preferably used as a packaging film constituting a packaging material for frozen food.

[0096] [Packaging material] The packaging material of this embodiment is a packaging material using the packaging film 100 of this embodiment. In addition, the packaging material of this embodiment may use the packaging film 100 for a part thereof or may use the packaging film 100 for the entire packaging material depending on the application.

[0097] The packaging material of the present embodiment is preferably a packaging material used for the purpose of containing food, and more preferably a packaging material used for the purpose of containing frozen food.

[0098] The packaging material of this embodiment is produced, for example, by bonding the heat seal layers 103 of the packaging film 100 of this embodiment together and processing them into a bag shape. In addition, the packaging material of this embodiment can also be produced, for example, by bonding the packaging film 100 of this embodiment with a surface substrate film for lamination (e.g., OPP film, PET film, etc.), a sealant film, etc., and processing them into a bag shape.

[0099] [Food packaging] The food package of the present embodiment includes the packaging material of the present embodiment and food contained in the packaging material. That is, the food package of the present embodiment is the food packaging material of the present embodiment that contains food. In the food packaging product of this embodiment, the food is preferably a frozen food.

[0100] Although the embodiments of the present invention have been described above with reference to the drawings, these are merely examples of the present invention, and various configurations other than those described above can also be adopted. EXAMPLES

[0101] The present embodiment will be described in detail below with reference to examples and comparative examples, but the present embodiment is not limited to the descriptions of these examples.

[0102] 1. Raw materials The raw materials used in the examples and comparative examples are shown below. (1) Homopolypropylene h-PP1: homopolypropylene (MFR: 3.0 g / 10 min, melting point: 159°C, isotactic mesopentad fraction (mmmm): 97.5%, content of ethylene-derived structural units: 1.2 mol%, content of propylene-derived structural units: 98.8 mol%) (2) Copolymer b-PP1: Propylene block copolymer (MFR: 3.0 g / 10 min, melting point: 165°C, content of ethylene-derived structural units: 8.0 mol%, content of propylene-derived structural units: 92.0 mol%) r-PP1: Propylene random copolymer (MFR: 7.0 g / 10 min, melting point: 139°C, content of ethylene-derived structural units: 3.2 mol%, content of 1-butene-derived structural units: 2.9 mol%, content of propylene-derived structural units: 93.9 mol%) r-PP2: Propylene random copolymer (MFR: 7.0 g / 10 min, melting point: 131°C, content of ethylene-derived structural units: 3.6 mol%, content of 1-butene-derived structural units: 2.8 mol%, content of propylene-derived structural units: 93.6 mol%) BPR1: 1-butene-propylene copolymer elastomer (MFR: 9.0 g / 10 min, melting point: 100°C, content of 1-butene-derived structural units: 88.9 mol%, content of propylene-derived structural units: 11.1 mol%) (3) Masterbatch MB1: A masterbatch made by mixing homopolypropylene and calcium carbonate, produced by the manufacturing method described below (melting point: 161°C, calcium carbonate content in the masterbatch: 60% by mass, homopolypropylene content in the masterbatch: 40% by mass) MB2: Masterbatch made by mixing homopolypropylene and titanium oxide (melting point: 156°C, titanium oxide content in masterbatch: 60% by mass, polypropylene content in masterbatch: 40% by mass) (4) Additives A1: Anti-blocking agent

[0103] [MB1 Manufacturing] Limestone was crushed and spheroidized using a jet mill with a high-pressure jet air flow swirling vortex method to obtain calcium carbonate. The obtained calcium carbonate was detected by wide-angle X-ray diffraction to have a crystal peak of calcium carbonate (calcite (rhombohedral crystal of trigonal system)), and no other peaks were detected, confirming that it was substantially composed entirely of calcium carbonate. The physical properties of the obtained calcium carbonate are as follows. Average particle size: 2 μm Shape: cubic (2 μm × 2 μm × 1 - 2 μm) Phosphorus content: 16 ppm Sulfur content: <10 ppm The average particle size was measured by a light transmission measurement method using centrifugal sedimentation with an ultracentrifugal automatic particle size distribution measuring device (manufactured by Horiba, Ltd., product name: CAPA - 700).

[0104] <Preparation of MB1> The above calcium carbonate was kneaded with h-PP1 under the conditions of 160°C to 220°C using a twin-screw extruder (manufactured by Japan Steel Works, Ltd., product name: TEX 44SS - 38, 58 - 3V 38 mmφ) to obtain MB1. MB1 was prepared so that the calcium carbonate was 60% by mass and h-PP1 was 40% by mass.

[0105] 2. Measurement and evaluation methods (1) Content of constitutional units derived from α-olefins having 2 to 10 carbon atoms in homopolypropylene and copolymers The measurement of the content of constitutional units derived from α-olefins having 2 to 10 carbon atoms in homopolypropylene and copolymers was carried out using a nuclear magnetic resonance apparatus (manufactured by Bruker BioSpin, product name: AVANCE III cryo - 500 type), 13 and measured by C-NMR. The sample was dissolved in the following measurement solvent for measurement, and evaluation was made from the integrated intensity of each signal. The obtained 13Using C-NMR spectra, signals were assigned with reference to the literature, Macromolecules (1982) Ethylene-1-Butene Copolymers. 1. Monomer Sequence Distribution and Macromolecules (1977) Carbon-13 Nuclear Magnetic Resonance Determination of Monomer Composition and Sequence Distributions in Ethylene-Propylene Copolymers Prepared with a Stereoregular Catalyst System, and the contents [mol %] of ethylene-derived structural units, propylene-derived structural units, and 1-butene-derived structural units in the homopolypropylene and copolymers were quantified. [Measurement conditions] Measurement nuclei: 13 C(125MHz) Measurement mode: Single pulse proton broadband decoupling Pulse width: 45° Number of points: 64k Repeat time: 5.5 seconds Measurement solvent: orthodichlorobenzene / heavy benzene (4:1) Sample concentration: 50mg / 0.6mL Measurement temperature: 120℃ Window function: exponential (BF: 0.5Hz)

[0106] (2) Content of ethylene-derived and 1-butene-derived structural units in the heat seal layer A sample is cut out from the heat seal layer, and the sample is dissolved in a measurement solvent under the same measurement conditions as in (1) above. 13 Measurements were performed by C-NMR.

[0107] (3) MFR of homopolypropylene and copolymer Measured in accordance with ASTM D1238 at 230°C and a load of 2.16 kg.

[0108] (4) Melting points of homopolypropylene, copolymers and masterbatches Using a differential scanning calorimeter (manufactured by TA Instruments, product name: Q200DSC), the homopolypropylene, copolymer and masterbatch were subjected to the following consecutive measurements: a first run in which the temperature was increased from -50°C to 250°C at a rate of 10°C / min, a second run in which the temperature was decreased from 250°C to -50°C at a rate of 10°C / min (temperature decrease measurement), and a third run in which the temperature was increased from -50°C to 250°C at a rate of 10°C / min. The peak temperature of the maximum melting peak in the DSC curve in the second run was taken as the melting point.

[0109] (5) Isotactic mesopentad fraction of homopolypropylene (mmmm) The isotactic mesopentad fraction (mmmm) was measured using a nuclear magnetic resonance spectrometer (Bruker Biospin, product name: AVANCE III cryo-500 model). 13 The measurement was performed by C-NMR. The sample was dissolved in the measurement solvent described below, and the measurement was performed, and the evaluation was performed based on the integrated intensity of each signal. [Measurement conditions] Measurement nuclei: 13 C(125MHz) Measurement mode: Single pulse proton broadband decoupling Pulse width: 45° Number of points: 64k Repeat time: 5.5 seconds Measurement solvent: orthodichlorobenzene / heavy benzene (4:1) Sample concentration: 50mg / 0.6mL Measurement temperature: 120℃ Window function: exponential (BF: 0.5Hz) Chemical shift standard: mmmm(CH3): 21.59ppm

[0110] (6) Thickness and density of packaging film D The thickness of the packaging film was measured using a micrometer (manufactured by Hybrid Manufacturing Co., Ltd., product name: Automatic Micrometer). The thickness of the packaging film was measured at five points, and the average value was taken as the thickness [μm] of the packaging film. 1m from packaging film 2 A sample was cut out to have an area of ​​1 m 2 Mass of sample for measurement per unit [g / m 2 The density of the packaging film D [g / cm 3 ] was calculated. Packaging film density D [g / cm 3 ]=1m 2 Mass of sample for measurement per unit [g / m 2 ] / Packaging film thickness [μm]

[0111] (7) DSC measurement of packaging film A sample of about 5.0 mg was cut out from the packaging film. Next, using a differential scanning calorimeter (manufactured by TA Instruments, product name: Q200DSC), the sample was subjected to a process of increasing the temperature from -50°C to 250°C at a rate of 10°C / min (1st run), a process of decreasing the temperature from 250°C to -50°C at a rate of 10°C / min (temperature decrease measurement), and a process of increasing the temperature from -50°C to 250°C at a rate of 10°C / min (2nd run). From the obtained DSC curve 2 of the 2nd run, the peak temperature [°C] and the heat of fusion ΔH [J / g] were determined for the endothermic peak A and the endothermic peak B, respectively. The peak temperature [°C] and ΔH [J / g] were calculated for the obtained DSC curve (cool) of the temperature-drop measurement, exothermic peak C, and exothermic peak D, respectively.

[0112] (8) Total light transmittance of packaging film The total light transmittance [%] of one sheet of packaging film was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name: NDH-5000) in accordance with JIS K 7136 (2000).

[0113] (9) Heat seal strength of packaging film The corona-treated surface of a 20 μm-thick biaxially oriented polypropylene film (Mitsui Chemicals Tohcello, Inc., product name: U-1) was bonded to the surface layer of the packaging film coated with an adhesive so that the MD direction of the biaxially oriented polypropylene film and the MD direction of the packaging film were aligned, to produce a packaging film after lamination. The adhesive used was a two-component curing polyurethane adhesive (a blend of 9.0 parts by mass of urethane resin (Mitsui Chemicals, Inc., product name: Takelac A525S), 1.0 part by mass of isocyanate curing agent (Mitsui Chemicals, Inc., product name: Takenate A50), and 7.5 parts by mass of ethyl acetate). The dry coating amount of the adhesive was 2.7 g / m 2 It was decided. After lamination, the heat seal layers of the two packaging films were stacked together so that the MD directions of the two packaging films were aligned, and the films were heat-sealed using an impulse sealer manufactured by Fuji Impulse Co., Ltd. (model: OPL-300-10) at a temperature of 140°C and a sealing time of 0.5 seconds to obtain a sample for measuring heat seal strength. A 15 mm wide test piece was cut out from the sample for measuring heat seal strength, and the two packaging films were peeled off using an Orientec tensile tester under the conditions of 90 degree peel, peel speed of 300 mm / min, and tension in the MD direction, and the peel strength at this point was recorded as the heat seal strength [N / 15 mm].

[0114] (10) Heat seal peeling energy of packaging film When the heat seal strength (9) was measured, the heat seal peel energy (mJ) was calculated from the heat seal strength (N / 15 mm) and the peel distance (mm) according to the following formula (1). The method for calculating the heat seal peel energy in this specification is a measurement method that complies with the literature: Journal of the Japan Society of Welding, 2006, Vol. 42, No. 4, pp. 146-152, “Proposal for measurement and evaluation method of peel energy at welded surface of heat seal.”

[0115]

number

[0116] In equation (1), S is the peel energy [mJ], F is the tensile strength at each peel distance [N], ΔL is the unit distance [mm] for energy calculation, and Ld is the tensile distance at which fracture occurs [mm].

[0117] (11) Pinhole resistance of packaging film A test piece measuring 297 mm in width and 210 mm in length was cut out from the packaging film and subjected to a bending test 3,000 times at an ambient temperature of -20°C using a Gelbo Flex Tester (manufactured by Tester Sangyo Co., Ltd.) with a twist angle of 440 degrees, a stroke of 152 mm, and a bending frequency of 40 times / min. After the bending test, the heat-sealed layers of the test piece were heat-sealed to each other to make a bag, and the number of pinholes [pieces / m 2 ] was counted using an Ageless Seal Check (manufactured by Mitsubishi Gas Chemical Co., Ltd.). 2 ] was measured.

[0118] (12) Puncture strength of packaging film A test piece 60 mm wide and 200 to 300 mm long was cut out from the packaging film. Next, a tensile tester (manufactured by Orientec Co., Ltd., product name: Tensilon RTC-1225) was used to measure the puncture strength [N] when a needle was pierced from the heat seal layer surface under conditions of temperature: 23°C and humidity: 50% in accordance with JIS Z 1707 (2019).

[0119] (13) Blocking resistance of packaging film Two pieces of packaging film cut to a width of 20 mm were stacked together so that the heat-sealed layers were in contact with each other, and then heated at 55°C, 1 kg / 4 cm 2 After storing the film for 24 hours under this load, the peel strength [N / 20 mm] of the two packaging films was measured using a tensile tester (manufactured by A&D Co., Ltd.).

[0120] [Examples 1 to 6 and Comparative Examples 1 to 2] Polypropylene films were extruded with the compositions shown in Table 1, and then biaxially stretched to produce packaging films, which were then evaluated. The evaluation results are shown in Table 1. In Table 1, "-" means that the value was not measured. In addition, a corona treatment was performed on the surface layer opposite the biaxially stretched film layer. Extrusion molding machine: 60mmφ multi-layer T-die extrusion molding machine (screw: L / D=27, manufactured by Screw Seiki Co., Ltd.) Extrusion temperature setting: 230~250℃ Processing speed: 20m / min (winding speed) MD stretching temperature [℃]: 90℃~120℃ Stretching ratio in MD direction [times]: 5 times TD stretching temperature [℃]: 150℃~170℃ Stretching ratio in TD direction [times]: 9.3 times

[0121] [Table 1]

[0122] As can be seen from Table 1, the packaging films of the examples have improved heat seal peel energy values ​​compared to the packaging films of the comparative examples. That is, it can be seen that the packaging film of this embodiment has improved heat seal peel energy.

[0123] In addition, the packaging film of the embodiment has a smaller number of pinholes than the packaging film of the comparative example, which indicates that the pinhole resistance is improved. Also, the packaging film of the embodiment has an improved puncture strength compared to the packaging film of the comparative example. That is, according to the packaging film of this embodiment, the performance balance between the puncture strength and pinhole resistance of the packaging film is improved, and it can be understood that it can be suitably used as a packaging film for food.

[0124] Furthermore, the packaging films of the Examples have lower peel strengths as measured by blocking resistance compared to the packaging films of the Comparative Examples, and therefore it can be seen that blocking resistance is improved. That is, according to the packaging film of this embodiment, the blocking resistance of the packaging film is improved. [Explanation of symbols]

[0125] 100 Packaging Film 101 Biaxially oriented film layer 103 Heat seal layer 105 Surface layer

Claims

1. A biaxially oriented film layer comprising an olefin polymer and at least one filler selected from the group consisting of organic fillers and inorganic fillers, A packaging film comprising a heat seal layer provided on at least one surface of the biaxially oriented film layer, The heat seal layer comprises a propylene polymer and an olefin copolymer. A packaging film in which the propylene-based polymer contained in the heat-seal layer includes at least one selected from the group consisting of homopolypropylene and block copolymers of propylene and α-olefins having 2 to 10 carbon atoms (wherein α-olefins exclude propylene).

2. The packaging film according to claim 1, wherein the content of the olefin copolymer in the heat seal layer is 25.0% by mass or more and 65.0% by mass or less, when the total amount of all components contained in the heat seal layer is taken as 100% by mass.

3. The packaging film according to claim 1 or 2, wherein the olefin copolymer comprises a copolymer of 1-butene and an α-olefin having 2 to 10 carbon atoms (wherein the α-olefin is excluding 1-butene).

4. The packaging film according to claim 3, wherein the copolymer of 1-butene and an α-olefin having 2 to 10 carbon atoms (where the α-olefin excludes 1-butene) has a content of 1-butene-derived constituent units of 20.0 mol% to 95.0 mol% when the total number of moles of constituent units derived from all monomers contained in the copolymer is 100 mol%.

5. The packaging film according to claim 1 or 2, wherein, when the total number of moles of constituent units in all polymers contained in the heat-seal layer is taken as 100 mol%, the number of moles of constituent units derived from 1-butene is 20.0 mol% or more and 60.0 mol% or less.

6. The packaging film according to claim 1 or 2, wherein the melting point of the olefin copolymer contained in the heat seal layer, as determined by DSC measurement, is 60°C or higher and 130°C or lower.

7. The packaging film according to claim 1 or 2, wherein the MFR of the olefin copolymer contained in the heat seal layer, measured in accordance with ASTM D1238 under conditions of 230°C and a 2.16 kg load, is 0.01 g / 10 min or more and 20.0 g / 10 min or less.

8. The packaging film according to claim 1 or 2, wherein the olefin polymer contained in the biaxially oriented film layer includes a propylene copolymer.

9. The packaging film according to claim 8, wherein the propylene copolymer is a block copolymer of propylene and an α-olefin having 2 to 10 carbon atoms (wherein the α-olefin is excluding propylene).

10. The packaging film according to claim 1 or 2, wherein the filler comprises at least one selected from the group consisting of calcium carbonate, calcium sulfate, barium carbonate, barium sulfate, titanium dioxide, magnesium hydroxide, magnesium carbonate, aluminum hydroxide, zinc oxide, magnesium oxide, silica, potassium titanate, calcium sulfite, calcium silicate, wollastonite, talc, mica, clay, kaolinite, montmorillonite, hydrotalcite, polystyrene resin particles, and poly(meth)acrylic resin particles.

11. The packaging film according to claim 1 or 2, wherein the content of the filler in the biaxially oriented film layer is 1.5% by mass or more and 30.0% by mass or less, when the total mass of the biaxially oriented film layer is 100% by mass.

12. The packaging film according to claim 1 or 2, wherein the biaxially oriented film layer has voids.

13. The packaging film according to claim 1 or 2, wherein the heat seal layer is provided so as to be in direct contact with one of the surfaces of the biaxially oriented film layer.

14. The packaging film according to claim 1 or 2, wherein the puncture strength when a needle is inserted into the heat-sealed layer surface of the packaging film is 4N or greater, as measured in accordance with JIS Z 1707 (2019) under conditions of temperature: 23°C and humidity: 50%.

15. Using a Gelboflex tester, the pinhole resistance of the packaging film was measured under the conditions of ambient temperature: -20°C and number of bends: 3000 times, and the pinhole resistance was 600 pins / m². ２ The packaging film according to claim 1 or 2, which is as follows:

16. 55℃, 1kg / 4cm ２ The packaging film according to claim 1 or 2, wherein the blocking resistance performance between the heat-seal layers of the packaging film, measured using a tensile testing machine after being stored for 24 hours under the applied load, is 5.0 N / 20 mm or less.

17. The packaging film according to claim 1 or 2, wherein the thickness of the packaging film is 5.0 μm or more and 50.0 μm or less.

18. The packaging film according to claim 1 or 2, wherein the thickness of the heat-seal layer is 1.0 μm or more and 13.0 μm or less.

19. The packaging film according to claim 1 or 2, wherein the packaging film is milky white.

20. A packaging film according to claim 1 or 2, which is a food packaging film.

21. A packaging material using the packaging film described in claim 1 or 2.

22. The packaging material according to claim 21, A food package containing the food within the aforementioned packaging material.

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