Packaging film, packaging material, and food package

Abstract

To provide a packaging film having improved heat seal strength in a packaging film having the same density, 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. In the packaging film 100, the olefinic polymer contains an olefin copolymer, the olefin copolymer contains a propylene copolymer, the propylene copolymer contains at least one kind selected from the group consisting of a block copolymer of propylene and α-olefin having 2 or more and 10 or less carbon atoms (excluding propylene), and a random 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 often do not have sufficient heat seal strength.

[0006] The present invention has been made in consideration of the above circumstances, and provides a packaging film, a packaging material, and a food package that have improved heat seal strength when used in a packaging film of the same density. [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 packaging film comprising 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, The olefin polymer includes an olefin copolymer, The olefin copolymer comprises a propylene copolymer; The propylene copolymer comprises at least one selected from the group consisting of 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), and random copolymers of propylene and an α-olefin having a carbon number of 2 or more and 10 or less (however, α-olefins exclude propylene). [2] The packaging film according to [1] above, wherein the propylene copolymer has a total molar number of constituent units derived from α-olefins having a carbon number of 2 or more and 10 or less (α-olefins exclude propylene) of 2.0 mol % or more and 10.0 mol % or less when the total molar number of constituent units derived from all monomers contained in the propylene copolymer is taken as 100 mol %. [3] The packaging film according to [1] or [2], wherein the total number of moles of structural units derived from monomers in all polymers contained in the biaxially oriented film layer is taken as 100 mol %, and the total number of moles of structural units derived from α-olefins (α-olefins excluding propylene) having a carbon number of 2 or more and 10 or less is 2.0 mol % or more and 10.0 mol % or less. [4] The packaging film according to any one of the above [1] to [3], wherein the melting point of the olefin copolymer as measured by DSC is in the range of 125° C. or higher and 180° C. or lower. [5] The packaging film according to any one of [1] to [4] above, wherein the MFR of the olefin copolymer, 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. [6] The packaging film according to any one of the above [1] to [5], 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. [7] The packaging film according to any one of [1] to [6], 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 amount of all components in the biaxially oriented film layer is 100% by mass. [8] The packaging film according to any one of the above [1] to [7], wherein the biaxially oriented film layer has voids. [9] When differential scanning calorimetry was performed on the packaging film using a differential scanning calorimeter, the following steps were performed in succession: a first run of heating the packaging film from -50°C to 250°C at a heating rate of 10°C / min, a second run of heating the packaging film from 250°C to -50°C at a heating rate of 10°C / min, and a third run of heating the packaging film from -50°C to 250°C at a heating rate of 10°C / min: The packaging film according to any one of [1] to [8] above, wherein an endothermic peak A is observed in the range of 130.0°C or higher and 170.0°C or lower in a DSC curve 2 (2nd Run) obtained by the differential scanning calorimetry.

[10] The density D of the packaging film is 0.50 g / cm 3 More than 0.90g / cm 3 The packaging film according to any one of the above [1] to [9],

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

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

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

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

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

[12] , further comprising a heat seal layer on at least one surface of the biaxially stretched film layer.

[14] The packaging film described in

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

[15] The packaging film according to

[13] or

[14] , wherein the heat seal layer contains a random copolymer of propylene and an α-olefin having 2 to 10 carbon atoms (provided that the α-olefin does not include propylene).

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

[15] , which is a packaging film for food.

[17] A packaging material using the packaging film according to any one of [1] to

[16] above.

[18] The packaging material according to

[17] 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 strength for a packaging film of the same density. [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 having a biaxially stretched film layer 101 containing an olefin-based polymer and at least one filler selected from the group consisting of organic fillers and inorganic fillers, wherein the olefin-based polymer includes an olefin copolymer, the olefin copolymer includes a propylene copolymer, and the propylene copolymer includes at least one selected from the group consisting of a block copolymer of propylene and an α-olefin having a carbon number of 2 to 10 (however, the α-olefin excludes propylene) and a random copolymer of propylene and an α-olefin having a carbon number of 2 to 10 (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. According to the studies of the present inventors, it has been found that in order to improve the strength of the packaging material, it is effective to improve the heat seal strength of the packaging film. According to the packaging film of this embodiment, it is possible to improve the heat seal strength of a packaging film having the same density.

[0014] Furthermore, 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. A packaging material using a packaging film can be 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. Furthermore, according to the packaging film of this embodiment, the heat seal peeling energy of the packaging film can be improved.

[0015] 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 heat seal strength and the heat seal peel energy. 3 More preferably, 0.53 g / cm 3 More preferably, 0.55 g / cm 3 More preferably, 0.56 g / cm 3 From the viewpoint of environmental issues, it is preferably 0.90 g / cm 3 More preferably, 0.87 g / cm 3 More preferably, 0.85 g / cm 3 More preferably, 0.83 g / cm 3 More preferably, 0.80 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.

[0016] The tensile modulus T1 in the MD direction of the packaging film 100 of this embodiment is, from the viewpoint of further improving the strength of the packaging material, preferably 200 MPa or more, more preferably 350 MPa or more, even more preferably 500 MPa or more, and even more preferably 580 MPa or more, and from the viewpoint of further improving the heat seal strength and the heat seal peel energy, preferably 3000 MPa or less, more preferably 2000 MPa or less, even more preferably 1500 MPa or less, even more preferably 1200 MPa or less, and even more preferably 1100 MPa or less. The tensile modulus T2 in the TD direction of the packaging film 100 of this embodiment is, from the viewpoint of further improving the strength of the packaging material, preferably 500 MPa or more, more preferably 800 MPa or more, even more preferably 1000 MPa or more, and even more preferably 1050 MPa or more, and from the viewpoint of further improving the heat seal strength and the heat seal peel energy, is preferably 3000 MPa or less, more preferably 2000 MPa or less, and even more preferably 1800 MPa or less. The tensile modulus of the packaging film means a value measured in accordance with JIS K7127 (1999) using a tensile tester under conditions of a measurement temperature of 23±2° C., 50±5% RH, and a tensile speed of 5 mm / min.

[0017] The sum of the tensile modulus of elasticity in the MD direction T1 [MPa] and the tensile modulus of elasticity in the TD direction T2 [MPa] is defined as T3 [MPa], and the density of the packaging film is defined as D [g / cm 3 ], T3 / D [MPa / (g / cm 3 )] is preferably 1500 or more, more preferably 2000 or more, even more preferably 2500 or more, and even more preferably 2700 or more from the viewpoint of further improving the strength of the packaging material, and is preferably 5000 or less, more preferably 4500 or less, even more preferably 4400 or less, even more preferably 4000 or less, even more preferably 3800 or less, even more preferably 3600 or less, even more preferably 3500 or less, and even more preferably 3400 or less, from the viewpoint of further improving the heat seal strength and the heat seal peel energy.

[0018] When the packaging film 100 of this embodiment is subjected to differential scanning calorimetry using a differential scanning calorimeter, which successively includes 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 A is observed in DSC curve 2 (2nd run) obtained by the differential scanning calorimetry. The temperature range in which endothermic peak A is observed is preferably 130.0°C or higher, more preferably 133.0°C or higher, even more preferably 135.0°C or higher, even more preferably 137.0°C or higher, and is preferably 170.0°C or lower, 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, from the viewpoint of further improving the heat seal strength and heat seal peel energy, preferably 90.0 J / g or less, more preferably 88.0 J / g or less, and even more preferably 85.0 J / g or less, and the lower limit is not particularly limited, but may be, for example, 60.0 J / g or more, or 65.0 J / g or more.

[0020] The heat of fusion ΔH [J / g] at the endothermic peak A observed in the DSC curve 2 (2nd Run) obtained by differential scanning calorimetry of the packaging film 100 is defined as the density of the packaging film D [g / cm 3 ], ΔH / D[(J / g) / (g / cm 3 )] is preferably 122.0 or less, more preferably 121.5 or less, and even more preferably 121.2 or less, from the viewpoint of further improving the heat seal strength and the heat seal peel energy, and the lower limit is not particularly limited, but may be, for example, 95.0 or more, 98.5 or more, or 102.0 or more.

[0021] 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 3.5 N / 15 mm or more, more preferably 4.0 N / 15 mm or more, and even more preferably 4.5 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. The density of the packaging film is D [g / cm 3], the heat seal strength [N / 15 mm] of the packaging film 100 of this embodiment divided by D [(N / 15 mm) / (g / cm 3 From the viewpoint of further improving the strength of the packaging material, the saturation coefficient (ratio) is preferably 6.0 or more, more preferably 7.0 or more, even more preferably 7.5 or more, even more preferably 7.8 or more, and even more preferably 8.0 or more, and the upper limit is not particularly limited, but may be, for example, 12.0 or less, 11.0 or less, 10.0 or less, or 9.8 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.

[0022] The heat seal peel energy of the packaging film 100 of this embodiment is, from the viewpoint of further improving the strength of the packaging material, preferably 200 mJ or more, more preferably 300 mJ or more, even more preferably 350 mJ or more, and even more preferably 370 mJ or more, and the upper limit is not particularly limited, but may be, for example, 1500 mJ or less, 1300 mJ or less, or 1100 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.

[0023] 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 85.0% or less, more preferably 80.0% or less, even more preferably 75.0% or less, and even more preferably 70.0% or less, and the lower limit is not particularly limited, but may be, for example, 20.0% or more, or 30.0% or more. Here, the total light transmittance refers to a value measured in accordance with JIS K 7136 (2000).

[0024] 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.

[0025] Each layer constituting the packaging film 100 will now be described.

[0026] <Biaxially oriented film layer> The biaxially stretched film layer 101 comprises an olefin-based polymer and at least one filler selected from the group consisting of organic fillers and inorganic fillers, the olefin-based polymer comprises an olefin copolymer, the olefin copolymer comprises a propylene copolymer, and the propylene copolymer comprises at least one selected from the group consisting of a block copolymer of propylene and an α-olefin having 2 to 10 carbon atoms (however, the α-olefin excludes propylene) and a random copolymer of propylene and an α-olefin having 2 to 10 carbon atoms (however, the α-olefin excludes propylene). 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.

[0027] The olefin-based polymer in the biaxially stretched film layer 101 includes an olefin copolymer. Here, the olefin copolymer of the present embodiment refers to an olefin copolymer in which the olefin-derived structural unit contained most abundantly in the olefin copolymer is 98.5 mol % or less when the total number of moles of structural units derived from all monomers contained in the olefin copolymer is 100 mol %. The olefin copolymer in the biaxially oriented film layer 101 includes a propylene copolymer. The olefin copolymer in the biaxially stretched film layer 101 may contain, in addition to the propylene copolymer, for example, an ethylene copolymer, a 1-butene copolymer, or the like.

[0028] 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 65.0% by mass or more, even more preferably 68.0% by mass or more, from the viewpoint of further improving the heat seal strength and heat seal peel energy, and is preferably 98.0% by mass or less, more preferably 96.0% by mass or less.

[0029] The propylene copolymer in the biaxially oriented film layer 101 includes at least one selected from the group consisting of block copolymers of propylene and an α-olefin having a carbon number of 2 or more and 10 or less (however, the α-olefin excludes propylene), and random copolymers of propylene and an α-olefin having a carbon number of 2 or more and 10 or less (however, the α-olefin excludes propylene). The propylene copolymer in the biaxially stretched film layer 101 preferably contains at least one selected from the group consisting of block copolymers of propylene and an α-olefin having 2 to 6 carbon atoms (however, the α-olefins exclude propylene) and random copolymers of propylene and an α-olefin having 2 to 6 carbon atoms (however, the α-olefins exclude propylene), more preferably contains at least one selected from the group consisting of block copolymers of propylene and ethylene, block copolymers of propylene and 1-butene, block copolymers of propylene, ethylene and 1-butene, random copolymers of propylene and ethylene, random copolymers of propylene and 1-butene, and random copolymers of propylene, ethylene and 1-butene, and even more preferably contains at least one selected from the group consisting of block copolymers of propylene and ethylene and random copolymers of propylene, ethylene and 1-butene.

[0030] In the propylene copolymer in the biaxially stretched 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, from the viewpoint of further improving the heat seal strength and heat seal peel energy, preferably 2.0 mol% or more, more preferably 3.0 mol% or more, even more preferably 4.0 mol% or more, even more preferably 5.0 mol% or more, and even more preferably 5.5 mol% or more, and from the viewpoint of further improving the heat seal strength and heat seal peel energy, 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.

[0031] 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 132°C or higher, even more preferably 135°C or higher, and even more preferably 137°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.

[0032] 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, and even more preferably 8.0 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.

[0033] 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.

[0034] The olefin-based polymer of the biaxially oriented film layer 101 may further contain a homopolyolefin. Here, the homopolyolefin of the present embodiment refers to an olefin homopolymer, or an olefin copolymer in which the olefin-derived structural unit contained most abundantly in the olefin copolymer exceeds 98.5 mol % when the total number of moles of structural units derived from all monomers contained in the olefin copolymer is taken as 100 mol %. Examples of homopolyolefins include homopolyethylene, homopolypropylene, homopolybutene, and the like, and among these, it is preferable to include homopolypropylene.

[0035] The content of homopolyolefin contained in the biaxially oriented film layer 101 is preferably 0.5 mass% or more, more preferably 1.0 mass% or more, and even more preferably 2.0 mass% or more, when the total amount of all components contained in the biaxially oriented film layer 101 is 100 mass%, and from the viewpoint of further improving the heat seal strength and heat seal peel energy, it is preferably 25.0 mass% or less, more preferably 20.0 mass% or less, and even more preferably 15.0 mass% or less.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] Homopolyolefins can be produced by various methods, for example, by using known catalysts such as Ziegler-Natta catalysts and metallocene catalysts.

[0040] The total content of the olefin-based polymers contained in the biaxially oriented film layer 101, when the total amount of all components contained in the biaxially oriented film layer is 100 mass%, is preferably 70.0 mass% or more, more preferably 72.0 mass% or more, even more preferably 75.0 mass% or more, even more preferably 80.0 mass% or more, and is preferably 97.0 mass% or less, more preferably 96.7 mass% or less, even more preferably 96.5 mass% or less.

[0041] When the total number of moles of monomer-derived structural units in all polymers contained in the biaxially oriented film layer 101 is taken as 100 mol%, the total number of moles of structural units derived from α-olefins (however, α-olefins exclude propylene) having a carbon number of 2 or more and 10 or less is preferably 2.0 mol% or more, more preferably 3.0 mol% or more, even more preferably 3.5 mol% or more, and even more preferably 4.0 mol% or more, from the viewpoint of further improving the heat seal strength and heat seal peel energy, and is preferably 10.0 mol% or less, more preferably 9.0 mol% or less, even more preferably 8.5 mol% or less, and even more preferably 8.0 mol% or less, from the viewpoint of further improving the heat seal strength and heat seal peel energy.

[0042] 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.

[0043] 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, even more preferably 2.5% by mass or more, and even more preferably 3.0% 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, and even more preferably 20.0% by mass or less, from the viewpoint of further improving the heat seal strength and the heat seal peel energy.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] <Heat seal layer> The packaging film 100 of this embodiment preferably further comprises a heat seal layer 103 on at least one surface of the biaxially oriented film layer 101 in order to impart heat sealability. From the viewpoint of further simplifying the manufacturing process of the packaging film 100, it is more preferable that the heat seal layer 103 is provided so as to be in direct contact with one surface of the biaxially oriented film layer 101.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] The heat seal layer 103 is made of, for example, a polyolefin-based resin composition containing polyolefin. Examples of the polyolefin constituting the heat seal layer 103 include homopolymers or copolymers of α-olefins such as ethylene, propylene, 1-butene, hexene-1, 4-methyl-pentene-1, and octene-1; olefin-based elastomers; high-pressure low-density polyethylene; linear low-density polyethylene (LLDPE); high-density polyethylene; polypropylene; random copolymers of propylene and α-olefins having 2 to 10 carbon atoms (however, α-olefins exclude propylene); propylene-based elastomers; ethylene-vinyl acetate copolymers (EVA); and ionomer resins.

[0057] From the viewpoint of further improving the heat sealability, the heat seal layer 103 preferably contains a random copolymer of propylene and an α-olefin having 2 to 10 carbon atoms (however, α-olefins exclude propylene), more preferably contains a random copolymer of propylene and an α-olefin having 2 to 6 carbon atoms (however, α-olefins exclude propylene), and even more preferably contains at least one selected from the group consisting of a random copolymer of propylene and ethylene, a random copolymer of propylene and 1-butene, and a random copolymer of propylene, ethylene and 1-butene.

[0058] The melting point of the random 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) in the heat seal layer 103 is, from the viewpoint of further improving the blocking resistance of the packaging film 100, preferably 60°C or higher, more preferably 80°C or higher, even more preferably 100°C or higher, and even more preferably 120°C or higher, and from the viewpoint of further improving the heat sealability of the packaging film 100, preferably 170°C or lower, more preferably 160°C or lower, even more preferably 150°C or lower, and even more preferably 140°C or lower.

[0059] The MFR of the random copolymer of propylene and an α-olefin having 2 to 10 carbon atoms (wherein α-olefins exclude propylene) 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 0.5 g / 10 min or more, 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 fluidity and moldability, and is preferably 20.0 g / 10 min or less, more preferably 15.0 g / 10 min or less, and even more preferably 10.0 g / 10 min or less, from the viewpoint of further stabilizing moldability. When two or more types of random copolymers are used as the random copolymer, the MFR of the random copolymer can be the MFR of a mixture obtained by melt blending two or more types of random copolymers by a known method or the like.

[0060] From the viewpoint of further improving the heat sealability, the heat seal layer 103 preferably contains an olefin-based elastomer. Examples of the olefin-based elastomer include an α-olefin polymer having 2 to 20 carbon atoms, the melting point of which is preferably 110° C. or less, more preferably 100° C. or less, and even more preferably 80° C. or less, or no melting point is observed; a copolymer of ethylene and an unsaturated carboxylic acid or an unsaturated carboxylate; and the like. Specifically, the olefin elastomer includes ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-4-methylpentene-1 copolymer, ethylene-1-octene copolymer, propylene homopolymer, propylene-ethylene copolymer, propylene-ethylene-1-butene copolymer, 1-butene homopolymer, 1-butene-ethylene copolymer, 1-butene-propylene copolymer, 4-methylpentene-1 homopolymer, 4-methylpentene-1-propylene copolymer, 4-methylpentene-1-1-butene copolymer, 4-methylpentene-1-propylene-1-butene copolymer, propylene-1-butene copolymer, ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, and the like. From the viewpoint of further improving the heat sealability, it is preferable to include a propylene-1-butene copolymer.

[0061] The heat seal layer 103 more preferably contains a random 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), and an olefin-based elastomer.

[0062] The content of the random copolymer of propylene and an α-olefin having a carbon number of 2 or more and 10 or less (however, α-olefin excludes propylene) contained in the heat seal layer 103 is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, when the total amount of all components contained in the heat seal layer 103 is taken as 100% by mass. The content of the olefin-based elastomer contained in the heat seal layer 103 is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, when the total amount of all components contained in the heat seal layer 103 is 100% by mass.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] <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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] <Other layers> The packaging film 100 may further include other layers, such as an adhesive layer.

[0076] [Manufacturing method of packaging film] The packaging film 100 can be obtained, for example, by extruding an olefin polymer composition to form the biaxially oriented film layer 101, and then biaxially stretching the extruded film using a known biaxially oriented film manufacturing method such as simultaneous biaxial stretching, sequential biaxial stretching, or inflation biaxial stretching. When the packaging film 100 is multilayered, for example, an olefin polymer composition for constituting the biaxially oriented film layer 101 and a resin composition for constituting each layer 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 other layers, laminating them, and heat forming them.

[0077] [Uses of packaging film] The packaging film 100 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.

[0078] [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.

[0079] 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.

[0080] 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.

[0081] [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.

[0082] 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

[0083] 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.

[0084] 1. Raw materials The raw materials used in the examples and comparative examples are shown below. (1) Homopolyolefin 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%) PBR1: Propylene-1-butene copolymer elastomer (MFR: 7.0 g / 10 min, melting point: 75°C, content of 1-butene-derived structural units: 27.0 mol%, content of propylene-derived structural units: 73.0 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) (4) Additives ·A1: Anti-blocking agent

[0085] [Manufacture of MB1] [Preparation of Calcium Carbonate]< Limestone was pulverized 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 with a calcium carbonate crystal peak (calcite (rhombohedral crystal of trigonal system)) by wide-angle X-ray diffraction, and no other peaks were detected, confirming that substantially all was composed 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 by centrifugal sedimentation using an ultracentrifugal automatic particle size distribution measuring device (manufactured by Horiba, Ltd., product name: CAPA-700).

[0086] [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. Note that MB1 was prepared such that the calcium carbonate was 60% by mass and h-PP1 was 40% by mass.

[0087] 2. Measurement and Evaluation Methods (1) Content of constitutional units derived from α-olefins having 2 or more and 10 or less carbon atoms in homopolypropylene and copolymers The measurement of the content of constitutional units derived from α-olefins having 2 or more and 10 or less 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 by C-NMR. The sample was dissolved in the following measurement solvent for measurement and evaluated 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)

[0088] (2) The content of structural units derived from α-olefins (excluding propylene) having a carbon number of 2 to 10 in the biaxially stretched film layer. A sample is cut out from the biaxially stretched film 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.

[0089] (3) MFR of homopolypropylene and copolymer Measured in accordance with ASTM D1238 at 230°C and a load of 2.16 kg.

[0090] (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.

[0091] (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

[0092] (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]

[0093] (7) Tensile modulus of packaging film A test piece measuring 15 mm x 15 cm was cut out from the packaging film. The tensile modulus of elasticity in the MD direction (T1) and the tensile modulus of elasticity in the TD direction (T2) of the test piece were measured using a tensile tester manufactured by Orientec Co., Ltd., in accordance with JIS K7127 (1999), under the conditions of a measurement temperature of 23±2°C, 50±5% RH, and a tensile speed of 5 mm / min. From the measured values ​​of the density D of the packaging film, the tensile modulus T1 [MPa] in the MD direction, and the tensile modulus T2 [MPa] in the TD direction, T3 / D [MPa / (g / cm 3 )] was calculated.

[0094] (8) 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] of the endothermic peak and the heat of fusion ΔH [J / g] of the endothermic peak were determined. From the density D of the packaging film and the heat of fusion ΔH of the endothermic peak, ΔH / D [(J / g) / (g / cm 3 )] was calculated.

[0095] (9) Total light transmittance of packaging film The total light transmittance [%] of one 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).

[0096] (10) 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]. Packaging film density D [g / cm 3] and heat seal strength [N / 15mm], the value obtained by dividing the heat seal strength by density D [(N / 15mm) / (g / cm 3 )] was calculated.

[0097] (11) Heat seal peeling energy of packaging film When the heat seal strength (10) 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.”

[0098]

number

[0099] 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].

[0100] [Examples 1 to 6 and Comparative Examples 1 to 3] 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 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

[0101] [Table 1]

[0102] From Table 1, the packaging films of the examples have an improved value of the heat seal strength of the packaging film divided by the density D, compared to the packaging films of the comparative examples. That is, it can be seen that the packaging film of this embodiment has an improved heat seal strength in packaging films of the same density. It can also be seen that the packaging film of the example has improved heat seal peel energy compared to the packaging film of the comparative example having the same density. That is, it can be seen that the packaging film of the present embodiment has improved heat seal peel energy. [Explanation of symbols]

[0103] 100 Packaging Film 101 Biaxially oriented film layer 103 Heat seal layer 105 Surface layer

Claims

1. A packaging film comprising a biaxially oriented film layer containing an olefin polymer and at least one filler selected from the group consisting of organic fillers and inorganic fillers, The olefin polymer includes an olefin copolymer. The olefin copolymer includes a propylene copolymer. The propylene copolymer comprises at least one selected from the group consisting of a block copolymer of propylene and an α-olefin having 2 to 10 carbon atoms (where the α-olefin is excluding propylene), and a random copolymer of propylene and an α-olefin having 2 to 10 carbon atoms (where the α-olefin is excluding propylene), wherein the propylene copolymer comprises at least one selected from the group.

2. The packaging film according to claim 1, wherein the propylene copolymer has a total mole count of 2.0 mol% to 10.0 mol% of constituent units derived from α-olefins (excluding propylene) having 2 to 10 carbon atoms, when the total mole count of constituent units derived from all monomers contained in the propylene copolymer is set to 100 mol%.

3. The packaging film according to claim 1 or 2, wherein, when the total number of moles of monomer-derived constituent units in all polymers contained in the biaxially oriented film layer is taken as 100 mol%, the total number of moles of constituent units derived from α-olefins having 2 to 10 carbon atoms (where α-olefins exclude propylene) is 2.0 mol% to 10.0 mol%.

4. The packaging film according to claim 1 or 2, wherein the melting point of the olefin copolymer, as determined by DSC measurement, is in the range of 125°C to 180°C.

5. The packaging film according to claim 1 or 2, wherein the MFR of the olefin copolymer, 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.

6. 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.

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

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

9. When differential scanning calorimetry is performed on the aforementioned packaging film using a differential scanning calorimeter, consisting of a process of raising the temperature from -50°C to 250°C at a heating rate of 10°C / min (1st Run), a process of lowering the temperature from 250°C to -50°C at a cooling rate of 10°C / min (cooling measurement), and a process of raising the temperature from -50°C to 250°C at a heating rate of 10°C / min (2nd Run), The packaging film according to claim 1 or 2, wherein an endothermic peak A is observed in the range of 130.0°C to 170.0°C in the DSC curve 2 (2nd Run) obtained by the differential scanning calorimetry.

10. The density D of the aforementioned packaging film is 0.50 g / cm³. ３ 0.90g / cm or more ３ The packaging film according to claim 1 or 2, which is as follows:

11. 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.

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

13. The packaging film according to claim 1 or 2, further comprising a heat-seal layer on at least one surface of the biaxially oriented film layer.

14. The packaging film according to claim 13, 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.

15. The packaging film according to claim 13, wherein the heat-seal layer comprises a random copolymer of propylene and an α-olefin having 2 to 10 carbon atoms (wherein the α-olefin is excluding propylene).

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

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

18. The packaging material according to claim 17, A food package containing the food within the aforementioned packaging material.

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