Biaxially oriented polypropylene film, package for food, and food package

Abstract

To provide a biaxially oriented polypropylene film with improved thermal dimensional stability.SOLUTION: A biaxially oriented polypropylene film 100 comprises a biaxially oriented film layer 101 comprising propylene polymer. As determined by differential scanning calorimetry, the biaxially oriented polypropylene film has a crystallinity ratio of 38% or more at 165°C or lower.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a biaxially oriented polypropylene film, a food package, and a food package. [Background technology]

[0002] Biaxially oriented polypropylene film (hereinafter also referred to as OPP film) has an excellent balance of performance such as processability, water vapor barrier properties, transparency, mechanical strength, and rigidity, and is used, for example, as a packaging film for packaging food.

[0003] Examples of technologies relating to food packaging films using such OPP films include those described in Patent Document 1 (JP-A No. 2008-73926) and Patent Document 2 (JP-A No. 2004-82499).

[0004] Patent Document 1 describes a biaxially oriented multilayer polypropylene film characterized by having a layer of a propylene-α-olefin random copolymer (C) having a melting point in the range of 125 to 145°C on one side of a biaxially oriented film made of a propylene polymer composition containing 75 to 90% by mass of a propylene homopolymer (A) and 25 to 10% by mass of a tackifier (D), with a layer of a propylene-based polymer (B) having a melting point of 155°C or higher sandwiched therebetween, and a layer of a propylene-based polymer (E) on the other side of the biaxially oriented film. Patent Document 1 describes that the biaxially oriented multilayer polypropylene film can prevent petroleum resins and the like from seeping out onto the film surface, and has excellent lamination strength and moisture resistance.

[0005] Patent Document 2 describes a multilayer resin film that further comprises a polyvinyl alcohol resin layer via an adhesive layer on at least one surface of a biaxially oriented polypropylene resin layer containing 10 to 40% by mass of a highly crystallizable resin and 6 to 15% by mass of a petroleum resin, and that has an oxygen permeability of 600 mL / m at a relative humidity of 85% RH and a temperature of 23°C. 2·day·MPa or less, and the water vapor permeability at a relative humidity of 90%RH and a temperature of 40°C is 3.5g / m 2 The multilayer resin film is characterized by a thickness of 20 μm or less. Patent Document 2 describes that the multilayer resin film has excellent oxygen gas barrier properties and moisture resistance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-73926 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-82499 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, from the viewpoint of environmental issues, there has been a demand for mono-material packaging materials. However, conventional general biaxially oriented polypropylene films sometimes have insufficient thermal dimensional stability from the viewpoint of suppressing thermal wrinkles at the seal portion during bag formation and suppressing thermal expansion during vapor deposition or coating processing. That is, further improvement in thermal dimensional stability is required for biaxially oriented polypropylene films from the viewpoint of suppressing thermal wrinkles at the seal portion during bag formation and suppressing thermal expansion during vapor deposition or coating processing.

[0008] The present invention has been made in view of the above circumstances, and provides a biaxially oriented polypropylene film, a food packaging material, and a food packaging material having improved thermal dimensional stability. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems, and as a result have found that the thermal dimensional stability of biaxially oriented polypropylene films can be improved by adjusting the crystallinity at 165°C or less to a specific range, thereby completing the present invention.

[0010] That is, according to the present invention, there are provided the following biaxially oriented polypropylene film, food packaging material, and food packaging material.

[0011] [1] a biaxially stretched film layer containing a propylene-based polymer; A biaxially oriented polypropylene film having a crystalline ratio of 38% or more at temperatures below 165°C as determined by differential scanning calorimetry. [2] The biaxially oriented polypropylene film according to [1] above, wherein the main melting point of the biaxially oriented polypropylene film is 165°C or higher and 180°C or lower, as determined by differential scanning calorimetry. [3] The biaxially oriented polypropylene film according to [1] or [2], wherein the heat of fusion (ΔH) of the entire biaxially oriented polypropylene film, as determined by differential scanning calorimetry, is 110 J / g or more and 150 J / g or less. [4] The biaxially oriented polypropylene film according to any one of [1] to [3] above, wherein the heat of fusion (ΔH) of the biaxially oriented polypropylene film at 165°C or less, as determined by differential scanning calorimetry, is 40 J / g or more. [5] The biaxially oriented polypropylene film according to any one of [1] to [4] above, wherein the amount of crystals of the biaxially oriented polypropylene film at 165°C or less determined by differential scanning calorimetry is 20% or more. [6] The biaxially oriented polypropylene film according to any one of [1] to [5], wherein the amount of structural units derived from α-olefins other than propylene contained in the biaxially oriented polypropylene film is 0.05 mol % or more, when the total amount of structural units derived from monomers contained in the biaxially oriented polypropylene film is taken as 100 mol %. [7] The biaxially oriented polypropylene film according to any one of [1] to [6] above, further comprising a surface resin layer on at least one surface of the biaxially oriented film layer. [8] The biaxially oriented polypropylene film according to [7] above, wherein the surface resin layer contains homopolypropylene (A). [9] The biaxially oriented polypropylene film according to [8], wherein the content of the homopolypropylene (A) in the surface resin layer is 75% by mass or more and 100% by mass or less, when the entire surface resin layer is taken as 100% by mass.

[10] The biaxially oriented polypropylene film according to any one of [7] to [9] above, wherein the thickness of the surface resin layer is 0.1 μm or more and 10.0 μm or less.

[11] The biaxially oriented polypropylene film according to any one of [1] to

[10] above, wherein the thickness of the biaxially oriented film layer is 5 μm or more and 100 μm or less.

[12] The biaxially oriented polypropylene film according to any one of [1] to

[11] above, wherein the sum (T1+T2) of the tensile modulus of elasticity in the MD direction T1 and the tensile modulus of elasticity in the TD direction T2 of the biaxially oriented polypropylene film is 3,000 MPa or more and 10,000 MPa or less, as measured using a tensile tester in accordance with JIS K7127 (1999) under conditions of a measurement temperature of 23±2°C, 50±5% RH, and a pulling rate of 5 mm / min.

[13] The biaxially oriented polypropylene film according to any one of [1] to

[12] above, which expands in the TD direction when heat-treated at 120°C for 15 minutes in accordance with JIS C2151:2019.

[14] The biaxially oriented polypropylene film according to any one of [1] to

[13] above, which is a food packaging film.

[15] A food packaging product using the biaxially oriented polypropylene film according to any one of [1] to

[14] above.

[16] The food packaging material according to

[15] above, and a food product within the food package. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a biaxially oriented polypropylene film, a food packaging material, and a food packaging material having improved thermal dimensional stability. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view schematically showing an example of the structure of a biaxially oriented polypropylene film of the present embodiment. FIG. [Figure 2] 1 is a cross-sectional view schematically showing an example of the structure of a biaxially oriented polypropylene film of the present embodiment. FIG. [Figure 3] 1 is a cross-sectional view schematically showing an example of the structure of a biaxially oriented polypropylene film of the present embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the drawings are schematic diagrams and do not correspond to the actual dimensional ratios. Note that "~" between numbers in the text indicates "above" to "below" unless otherwise specified.

[0015] <Biaxially oriented polypropylene film> 1 to 3 are cross-sectional views schematically showing an example of the structure of a biaxially stretched polypropylene film 100 according to this embodiment. The biaxially oriented polypropylene film 100 of this embodiment includes a biaxially oriented film layer 101 containing a propylene-based polymer, and has a crystalline ratio at 165° C. or less of 38% or more as determined by differential scanning calorimetry.

[0016] As mentioned above, further improvement in the thermal dimensional stability of biaxially oriented polypropylene films is required from the viewpoint of suppressing thermal wrinkles at the sealed portions during bag making and suppressing thermal elongation during vapor deposition and coating processes. Here, the inventors have found through their studies that the amount of crystalline components below 165°C affects thermal dimensional stability. Based on this finding, the inventors have conducted further studies and discovered that the thermal dimensional stability of the biaxially oriented polypropylene film 100 can be improved by making the crystalline ratio below 165°C 38% or more, thereby arriving at the present invention. That is, the biaxially oriented polypropylene film 100 of this embodiment can improve thermal dimensional stability. Furthermore, since the biaxially oriented polypropylene film 100 of this embodiment has improved thermal dimensional stability, it is possible to suppress heat wrinkles in the sealed portion during bag production, thereby improving bag production properties.

[0017] The crystalline ratio of the biaxially oriented polypropylene film 100 at 165°C or below, as determined by differential scanning calorimetry, is 38% or more, but from the viewpoint of further improving the thermal dimensional stability of the biaxially oriented polypropylene film 100, it is preferably 39% or more, more preferably 40% or more, even more preferably 41% or more, even more preferably 42% or more, and even more preferably 43% or more, and from the viewpoint of further improving the performance balance between the formability and thermal dimensional stability of the biaxially oriented polypropylene film 100, it is preferably 70% or less, more preferably 65% ​​or less, even more preferably 60% or less, even more preferably 55% or less, and even more preferably 50% or less. The crystalline ratio of the biaxially oriented polypropylene film 100 at temperatures of 165° C. or less can be measured by the method described in the examples.

[0018] The main melting point of the biaxially oriented polypropylene film 100, as determined by differential scanning calorimetry, is preferably 165°C or higher, more preferably 168°C or higher, and even more preferably 170°C or higher, from the viewpoint of further improving the thermal dimensional stability of the biaxially oriented polypropylene film 100, and is preferably 180°C or lower, more preferably 178°C or lower, even more preferably 175°C or lower, and even more preferably 173°C or lower, from the viewpoint of further improving the performance balance between the formability and thermal dimensional stability of the biaxially oriented polypropylene film 100. The main melting point of the biaxially stretched polypropylene film 100 can be measured by the method described in the Examples. Herein, the peak temperature of the maximum melting peak in the DSC curve is defined as the main melting point.

[0019] The heat of fusion (ΔH) of the entire biaxially oriented polypropylene film 100, as determined by differential scanning calorimetry, is preferably 100 J / g or more, more preferably 105 J / g or more, even more preferably 110 J / g or more, even more preferably 113 J / g or more, even more preferably 115 J / g or more, and even more preferably 117 J / g or more, from the viewpoint of further improving the thermal dimensional stability of the biaxially oriented polypropylene film 100; and is preferably 150 J / g or less, more preferably 140 J / g or less, even more preferably 130 J / g or less, and even more preferably 128 J / g or less, from the viewpoint of further improving the performance balance between the formability and thermal dimensional stability of the biaxially oriented polypropylene film 100. The heat of fusion (ΔH) of the entire biaxially oriented polypropylene film 100 can be measured by the method described in the Examples. Herein, when multiple melting peaks appear in the DSC curve, the total area of ​​the multiple melting peaks is defined as the heat of fusion (ΔH).

[0020] The heat of fusion (ΔH) of the biaxially oriented polypropylene film 100 at 165°C or less, as determined by differential scanning calorimetry, is preferably 40 J / g or more, more preferably 42 J / g or more, even more preferably 43 J / g or more, even more preferably 45 J / g or more, even more preferably 48 J / g or more, and even more preferably 50 J / g or more, from the viewpoint of further improving the thermal dimensional stability of the biaxially oriented polypropylene film 100; and from the viewpoint of further improving the performance balance between the formability and thermal dimensional stability of the biaxially oriented polypropylene film 100, it is preferably 90 J / g or less, more preferably 85 J / g or less, even more preferably 80 J / g or less, even more preferably 75 J / g or less, even more preferably 70 J / g or less, even more preferably 65 J / g or less, and even more preferably 60 J / g or less. The heat of fusion (ΔH) of the biaxially oriented polypropylene film 100 at 165° C. or less can be measured by the method described in the examples.

[0021] The crystallinity of the biaxially oriented polypropylene film 100, as determined by differential scanning calorimetry, is preferably 40% or more, more preferably 45% or more, even more preferably 50% or more, even more preferably 53% or more, and even more preferably 55% or more, from the viewpoint of further improving the thermal dimensional stability of the biaxially oriented polypropylene film 100; and from the viewpoint of further improving the performance balance between the formability and thermal dimensional stability of the biaxially oriented polypropylene film 100, it is preferably 80% or less, more preferably 75% or less, even more preferably 70% or less, even more preferably 65% ​​or less, even more preferably 62% or less, and even more preferably 60% or less. The crystallinity of the biaxially oriented polypropylene film 100 can be measured by the method described in the examples.

[0022] The crystalline content of the biaxially oriented polypropylene film 100 at temperatures below 165°C, as determined by differential scanning calorimetry, is preferably 20% or more, more preferably 22% or more, even more preferably 23% or more, and even more preferably 24% or more, from the viewpoint of further improving the thermal dimensional stability of the biaxially oriented polypropylene film 100, and is preferably 40% or less, more preferably 38% or less, even more preferably 36% or less, preferably 35% or less, and even more preferably 30% or less, from the viewpoint of further improving the performance balance between the formability and thermal dimensional stability of the biaxially oriented polypropylene film 100. The amount of crystallinity of the biaxially oriented polypropylene film 100 at temperatures below 165° C. can be measured by the method described in the examples.

[0023] The above-mentioned properties of the biaxially oriented polypropylene film 100 determined by differential scanning calorimetry can be adjusted, for example, by adjusting the type and content ratio of the propylene-based polymer contained in the biaxially oriented film layer 101, the thickness and stretching ratio of the biaxially oriented film layer 101, the constituent material and thickness of the surface resin layer 103, etc.

[0024] The sum (T1+T2) of the tensile modulus in the MD direction T1 and the tensile modulus in the TD direction T2 of the biaxially oriented polypropylene film 100, measured in accordance with JIS K7127 (1999) using a tensile tester at a measurement temperature of 23±2°C, 50±5% RH, and a tensile speed of 5 mm / min, is preferably 3000 MPa or more, more preferably 4000 MPa or more, even more preferably 5000 MPa or more, even more preferably 6000 MPa or more, even more preferably 6500 MPa or more, and preferably 10000 MPa or less, more preferably 8000 MPa or less, even more preferably 7500 MPa or less. When the sum (T1 + T2) of the tensile modulus in the MD direction T1 and the tensile modulus in the TD direction T2 is equal to or greater than the lower limit, the biaxially oriented polypropylene film 100 can have a better balance of performance such as thermal dimensional stability, formability, water vapor barrier properties, mechanical properties, transparency, bag formability, and handleability. Furthermore, the stiffness of the biaxially oriented polypropylene film 100 can be improved, which in turn can prevent film positional deviation during heat sealing and prevent sealing defects. In other words, when the sum of the tensile modulus of elasticity in the MD direction T1 and the tensile modulus of elasticity in the TD direction T2 (T1 + T2) is equal to or greater than the above-mentioned lower limit, the biaxially oriented polypropylene film 100 can have a better balance of thermal dimensional stability, formability, water vapor barrier properties, mechanical properties, transparency, bag-making properties, handleability, and packaging suitability. Furthermore, when the sum of the tensile modulus of elasticity in the MD direction T1 and the tensile modulus of elasticity in the TD direction T2 (T1 + T2) is equal to or less than the upper limit, problems such as breakage are less likely to occur during the molding of the biaxially oriented polypropylene film 100, making continuous stretching molding of the film easier and further improving industrial continuous productivity. Such a tensile modulus is a substitute value for quantitatively measuring the stiffness of the film, and can be adjusted, for example, by adjusting the type and content ratio of the propylene-based polymer contained in the biaxially stretched film layer 101, the thickness and stretching ratio of the biaxially stretched film layer 101, the constituent material and thickness of the surface resin layer 103, etc.

[0025] Furthermore, the tensile modulus T1 in the MD direction of the biaxially oriented polypropylene film 100 is preferably 1000 MPa or more, more preferably 1300 MPa or more, even more preferably 1500 MPa or more, even more preferably 1800 MPa or more, even more preferably 2000 MPa or more, and even more preferably 2300 MPa or more, from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100, including thermal dimensional stability, formability, water vapor barrier properties, mechanical properties, transparency, bag formability, handleability, and packaging suitability; and from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100, including thermal dimensional stability, antistatic properties, bag formability, and packaging suitability, it is preferably 4000 MPa or less, more preferably 3500 MPa or less, even more preferably 3000 MPa or less, even more preferably 2800 MPa or less, and even more preferably 2600 MPa or less.

[0026] In order to further improve the balance of thermal dimensional stability and bag formability, it is preferable that the biaxially oriented polypropylene film 100 expands in the TD direction when heat-treated at 120°C for 15 minutes in accordance with JIS C2151:2019. More specifically, the thermal expansion coefficient in the TD direction of the biaxially oriented polypropylene film 100 when heat-treated at 120°C for 15 minutes is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.3% or more, even more preferably 0.4% or more, and even more preferably 0.5% or more, from the viewpoint of further improving the performance balance between thermal dimensional stability and bag formability, and from the viewpoint of further suppressing thermal wrinkles in the sealed portions and obtaining bag products with good thermal wrinkles in the sealed portions, and is preferably 2.0% or less, more preferably 1.5% or less, even more preferably 1.2% or less, even more preferably 1.0% or less, and even more preferably 0.8% or less, from the viewpoint of further improving the performance balance between thermal dimensional stability and bag formability. Generally, a roll of biaxially oriented polypropylene film is unwound in the MD direction, and bag-making, coating, vapor deposition, and the like are carried out while tension is applied. Since no tension is applied in the TD direction, the biaxially oriented polypropylene film is susceptible to thermal shrinkage when heated, and thermal wrinkles are likely to occur in the sealed area. On the other hand, if the thermal expansion coefficient in the TD direction when heated at 120°C for 15 minutes is within the above range, thermal shrinkage in the TD direction is unlikely to occur even when the biaxially oriented polypropylene film 100 is heated, and thermal wrinkles in the sealed area can be further suppressed. The thermal expansion coefficient of the biaxially stretched polypropylene film 100 in the TD direction when heat-treated at 120° C. for 15 minutes is calculated by the following method. First, a 10 cm x 10 cm test piece is cut out from biaxially oriented polypropylene film 100, and this test piece is heat-treated at 120°C for 15 minutes. Next, when the length of the test piece in the TD direction after heat treatment is TD1 [cm], the thermal expansion coefficient in the TD direction [%] is calculated by 100 x (TD1-10) / 10.

[0027] Furthermore, the heat shrinkage rate in the MD direction of the biaxially oriented polypropylene film 100 when heat-treated at 120°C for 15 minutes is, from the viewpoint of further improving the performance balance between thermal dimensional stability and bag formability, and further suppressing thermal elongation of the film during processing, preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, even more preferably 2.5% or less, even more preferably 2.2% or less, and even more preferably 2.0% or less, and may be 0.1% or more, 0.3% or more, or 0.5% or more. Generally, a roll of biaxially oriented polypropylene film is unwound in the MD direction, and bag-making, coating, vapor deposition, and the like are performed while tension is applied. Because tension is applied in the MD direction, if the film has low heat resistance, it is prone to thermal elongation in the MD direction when heated. On the other hand, if the heat shrinkage rate in the MD direction when heated at 120°C for 15 minutes is within the above range, it is possible to further suppress thermal elongation in the MD direction when the biaxially oriented polypropylene film 100 is heated. The heat shrinkage rate in the MD direction of the biaxially stretched polypropylene film 100 when it is heat treated at 120° C. for 15 minutes is calculated by the following method. First, a 10 cm x 10 cm test piece is cut out from biaxially oriented polypropylene film 100, and this test piece is heat-treated at 120°C for 15 minutes. Next, when the length in the MD direction of the test piece after heat treatment is MD1 [cm], the heat shrinkage rate in the MD direction [%] is calculated by 100 x (10 - MD1) / 10.

[0028] The heat shrinkage rate in the TD direction and the heat shrinkage rate in the MD direction when the biaxially oriented polypropylene film 100 is heated at 150°C for 15 minutes are respectively X TD [%] and X MD When set to [%], X TD +X MD From the viewpoint of further improving the balance of thermal dimensional stability and bag formability of the biaxially oriented polypropylene film 100, the stretch ratio is preferably less than 7.0%, more preferably 6.5% or less, and even more preferably less than 6.0%. Also, biaxially oriented polypropylene film 100 x TD [%] and X MD [%] is calculated using the following method. First, a 10 cm x 10 cm test piece is cut out from the biaxially stretched polypropylene film 100, and this test piece is heat-treated at 150 ° C for 15 minutes. Next, when the length in the TD direction of the test piece after heat treatment is TD1 [cm] and the length in the MD direction of the test piece after heat treatment is MD1 [cm], X TD [%] is calculated by 100×(10-TD1) / 10, where X MD [%] is calculated by 100×(10-MD1) / 10.

[0029] The thermal expansion coefficient and thermal shrinkage coefficient of the biaxially oriented polypropylene film 100 can be adjusted, for example, by adjusting the type and content ratio of the propylene-based polymer contained in the biaxially oriented film layer 101, the thickness and stretching ratio of the biaxially oriented film layer 101, the constituent material and thickness of the surface resin layer 103, etc. The thermal expansion coefficient and thermal shrinkage coefficient of the biaxially stretched polypropylene film 100 can be measured in accordance with JIS C2151:2019.

[0030] In order to further improve the balance between the ability to prevent the film from fusing to the seal bar during bag making and the seal appearance in a package produced using the biaxially oriented polypropylene film 100, the heat-seal strength (TD tensile direction) of the portion heat-sealed to the biaxially oriented polypropylene film 100 at 200°C, a pressure of 2.0 kgf, and a sealing time of 1.0 second is preferably 4.0 N / 15 mm or less, more preferably 3.5 N / 15 mm or less, even more preferably 3.0 N / 15 mm or less, even more preferably 2.5 N / 15 mm or less, even more preferably 2.0 N / 15 mm or less, and even more preferably 1.5 N / 15 mm or less. The lower limit of the heat-seal strength of the biaxially oriented polypropylene film 100 at 200°C is not particularly limited, but may be 0.01 N / 15 mm or more, 0.05 N / 15 mm or more, or 0.1 N / 15 mm or more. In this specification, the heat fusion strength is used as an index of the heat fusion resistance of the biaxially oriented polypropylene film surface. It can be determined that the lower the heat fusion strength, the better the heat fusion resistance of the biaxially oriented polypropylene film surface. Here, the heat-sealing strength can be measured by the following method. First, two biaxially oriented polypropylene films 100 are heat-sealed under conditions of 200°C, a pressure of 2.0 kgf, and a sealing time of 1.0 second to obtain a laminated film. Next, the two biaxially oriented polypropylene films 100 are peeled under conditions of 15 mm width, 90-degree peel, a peel speed of 300 mm / min, and tension in the TD direction, and the peel strength at this time is taken as the heat-sealing strength. Such heat fusion strength can be adjusted, for example, by adjusting the type and content ratio of the homopolypropylene (A) and polymer (B) contained in the biaxially oriented film layer 101, the thickness and stretching ratio of the biaxially oriented film layer 101, the constituent material and thickness of the surface resin layer 103, etc.

[0031] The haze of the biaxially oriented polypropylene film 100, measured using a haze meter in accordance with JIS K7136:2000, is preferably 5.0% or less, more preferably 3.0% or less, even more preferably 2.5% or less, even more preferably 2.0% or less, even more preferably 1.5% or less, and even more preferably 1.0% or less, from the viewpoint of further improving the transparency of the biaxially oriented polypropylene film 100. Such haze can be adjusted, for example, by adjusting the type and content ratio of the propylene-based polymer contained in the biaxially stretched film layer 101, the thickness and stretching ratio of the biaxially stretched film layer 101, the constituent material and thickness of the surface resin layer 103, etc.

[0032] Here, food packaging produced using the biaxially oriented polypropylene film 100 exhibits sufficient water vapor barrier properties, and therefore, the biaxially oriented polypropylene film 100 is particularly suitable for use as a food packaging film for packaging foods that require water vapor barrier properties.

[0033] From the viewpoint of stably obtaining food packaging with improved water vapor barrier properties, the water vapor permeability of the biaxially oriented polypropylene film 100, measured by the following method, is preferably 20.0 g / (m 2 24h) or less, more preferably 15.0g / (m 2 24h) or less, more preferably 12.0g / (m 2 24h) or less, more preferably 10.0g / (m 2 ·24h) or less, more preferably 8.0g / (m 2 24h or less. (Measurement method) The biaxially oriented polypropylene film 100 is folded over and heat-sealed on two sides to form a bag. Calcium chloride is then placed inside as the contents. The other side is then heat-sealed to form a bag with a surface area of ​​0.01 m. 2 The resulting bag is then stored for 72 hours at 40°C and 90% RH. The mass of calcium chloride is measured before and after storage, and the difference is used to determine the water vapor permeability (g / (m 2Calculate the time (24h). Such water vapor permeability can be adjusted, for example, by adjusting the type and content ratio of the propylene-based polymer contained in the biaxially stretched film layer 101, the thickness and stretching ratio of the biaxially stretched film layer 101, the constituent material and thickness of the surface resin layer 103, etc.

[0034] The amount of structural units derived from α-olefins other than propylene contained in the biaxially oriented polypropylene film 100, when the total amount of structural units derived from monomers contained in the biaxially oriented polypropylene film 100 is taken as 100 mol%, is preferably 0.05 mol% or more, more preferably 0.1 mol% or more, even more preferably 0.3 mol% or more, and even more preferably 0.5 mol% or more, from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100 among the formability, thermal dimensional stability, and bag formability; and is preferably 50.0 mol% or less, more preferably 30.0 mol% or less, even more preferably 20.0 mol% or less, even more preferably 15.0 mol% or less, even more preferably 10.0 mol% or less, even more preferably 5.0 mol% or less, even more preferably 2.0 mol% or less, and even more preferably 1.0 mol% or less, from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100 among the thermal dimensional stability, water vapor barrier property, bag formability, and transparency. When the amount of structural units derived from α-olefins other than propylene contained in the biaxially oriented polypropylene film 100 is within the above range, the softening effect of the structural units derived from α-olefins suppresses the yield point stress at the start of stretching during the stretching process, improving ease of formability. In addition, the low melting point effect of the structural units derived from α-olefins more efficiently relieves residual stress during the heat setting process during film formation, improving formability and suppressing thickness unevenness, resulting in further improved thermal dimensional stability of the biaxially oriented polypropylene film 100. The amount of structural units derived from α-olefins other than propylene in the biaxially stretched polypropylene film 100 can be measured by the method described in the examples.

[0035] The thickness of the biaxially oriented polypropylene film 100 is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 12 μm or more, and even more preferably 15 μm or more, from the viewpoint of further improving the balance of performance such as thermal dimensional stability, formability, water vapor barrier properties, cost, mechanical properties, transparency, bag formability, handleability, appearance, and lightness, and is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 40 μm or less, even more preferably 30 μm or less, and even more preferably 25 μm or less.

[0036] Each layer constituting the biaxially oriented polypropylene film 100 will be described below.

[0037] [Biaxially stretched film layer] The biaxially stretched film layer 101 (also referred to as a biaxially stretched polypropylene-based film layer) contains a propylene-based polymer. The biaxially stretched film layer 101 is formed, for example, by biaxially stretching a film made of a propylene-based polymer composition containing a propylene-based polymer.

[0038] The biaxially stretched film layer 101 may be a single layer or may have a structure in which a plurality of layers made of a propylene-based polymer composition are laminated, but it is necessary that it is biaxially stretched.

[0039] The thickness of the biaxially oriented film layer 101 is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 12 μm or more, and even more preferably 15 μm or more, from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100, such as thermal dimensional stability, formability, water vapor barrier properties, cost, mechanical properties, transparency, bag-making properties, handleability, appearance, and lightness, and is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 40 μm or less, even more preferably 30 μm or less, and even more preferably 20 μm or less.

[0040] In the biaxially oriented polypropylene film 100, the ratio of the thickness of the biaxially oriented film layer 101 to the total thickness of the biaxially oriented polypropylene film 100 is preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, even more preferably 75% or more, and preferably 100% or less, more preferably 99% or less, even more preferably 95% or less, even more preferably 90% or less.

[0041] (Propylene-based polymer composition) The propylene-based polymer composition of the present embodiment contains a propylene-based polymer. The content of the propylene polymer in the propylene polymer composition of the present embodiment, i.e., the biaxially stretched film layer 101, is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and for example, 100% by mass or less, when the entire propylene polymer composition is taken as 100% by mass, from the viewpoint of further improving the balance of performance of the biaxially stretched polypropylene film 100, such as thermal dimensional stability, environmental compatibility, heat resistance, water vapor barrier property, transparency, cost, mechanical properties, rigidity, bag formability, flowability, moldability, handleability, appearance, and lightness.

[0042] (Propylene polymer) The propylene-based polymer of the present embodiment is a polymer containing structural units derived from propylene, and examples thereof include homopolypropylene (A); at least one polymer (B) selected from the group consisting of random polypropylene (B1) and α-olefin copolymer (B2); and the like.

[0043] (Homopolypropylene (A)) Examples of the homopolypropylene (A) include propylene homopolymers and propylene copolymers having a content of structural units derived from α-olefins other than propylene of 2.0 mol % or less. When the total content of the structural units constituting the homopolypropylene (A) is taken as 100 mol %, the content of structural units derived from propylene in the homopolypropylene (A) is 98.0 mol % or more, preferably 98.5 mol % or more, more preferably 98.7 mol % or more, even more preferably 99.0 mol % or more, even more preferably 99.5 mol % or more, still more preferably 99.8 mol % or more, and is, for example, 100.0 mol % or less.

[0044] The α-olefin other than propylene includes, for example, one or more selected from the group consisting of ethylene and α-olefins having 4 to 20 carbon atoms, preferably one or more selected from the group consisting of ethylene and α-olefins having 4 to 6 carbon atoms, more preferably at least one selected from the group consisting of ethylene and 1-butene, and even more preferably ethylene. The content of structural units derived from α-olefins other than propylene is preferably 2.0 mol% or less, more preferably 1.5 mol% or less, even more preferably 1.3 mol% or less, even more preferably 1.0 mol% or less, even more preferably 0.5 mol% or less, and even more preferably 0.2 mol% or less, when the entire homopolypropylene (A) is taken as 100 mol%. The homopolypropylene (A) in the biaxially stretched film layer 101 may be used alone or in combination of two or more.

[0045] The isotactic mesopentad fraction (mmmm) of the homopolypropylene (A) is preferably 96.0% or more, more preferably 96.5% or more, even more preferably 97.0% or more, even more preferably 97.3% or more, even more preferably 97.5% or more, even more preferably 97.8% or more, and even more preferably 98.0% or more, from the viewpoint of further improving the balance of performance such as thermal dimensional stability, heat resistance, water vapor barrier properties, mechanical properties, rigidity, and bag formability of the biaxially oriented polypropylene film 100. The upper limit of the isotactic mesopentad fraction (mmmm) of the homopolypropylene (A) is not particularly limited, but from the viewpoint of ease of production, it is 99.5% or less, more preferably 99.3% or less, and even more preferably 99.0% or less. The isotactic mesopentad fraction (mmmm) is an index of stereoregularity, 13 It can be determined from a C-nuclear magnetic resonance (NMR) spectrum by a known method. When two or more types of homopolypropylenes are used as the homopolypropylene (A), the isotactic mesopentad fraction of the homopolypropylene (A) can be the isotactic mesopentad fraction of a mixture obtained by melt blending two or more types of homopolypropylene (A) by a known method.

[0046] The melt flow rate (MFR) of the homopolypropylene (A), 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 the balance between fluidity and moldability, and is preferably 20.0 g / 10 min or less, more preferably 10.0 g / 10 min or less, and even more preferably 7.0 g / 10 min or less, from the viewpoint of further stabilizing moldability. When two or more types of homopolypropylenes are used as the homopolypropylene (A), the MFR of the homopolypropylene (A) can be the MFR of a mixture obtained by melt blending two or more types of homopolypropylene (A) by a known method.

[0047] The melting point of the homopolypropylene (A) is preferably 150°C or higher, more preferably 155°C or higher, even more preferably 160°C or higher, and even more preferably 163°C or higher, from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100, such as thermal dimensional stability, heat resistance, water vapor barrier properties, mechanical properties, rigidity, bag formability, fluidity, and moldability, 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. When two or more kinds of homopolypropylenes are used as the homopolypropylene (A), the melting point of the homopolypropylene (A) is the peak temperature of the maximum melting peak.

[0048] The homopolypropylene (A) can be produced by various methods, for example, by using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst.

[0049] (Polymer (B)) The polymer (B) contains at least one selected from the group consisting of random polypropylene (B1) and α-olefin copolymer (B2), and preferably contains random polypropylene (B1).

[0050] The melt flow rate (MFR) of the polymer (B), measured in accordance with ASTM D1238 at 230°C under 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 performance balance between the formability and thermal dimensional stability of the biaxially oriented polypropylene film 100, and is preferably 30.0 g / 10 min or less, more preferably 20.0 g / 10 min or less, even 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. When two or more types of polymers are used as the polymer (B), the MFR of a mixture obtained by melt-blending two or more types of polymers (B) by a known method can be used.

[0051] From the viewpoint of further improving the balance of performance of the biaxially oriented polypropylene film 100, such as thermal dimensional stability, heat resistance, water vapor barrier properties, mechanical properties, rigidity, bag formability, fluidity, and moldability, the melting point of the polymer (B) is preferably 50°C or higher, more preferably 60°C or higher, even more preferably 70°C or higher, even more preferably 80°C or higher, and even more preferably 90°C or higher, and is preferably 155°C or lower, more preferably 150°C or lower, even more preferably 148°C or lower, and even more preferably 145°C or lower. When two or more types of polymers are used as polymer (B), the melting point of polymer (B) is the peak temperature of the maximum melting peak.

[0052] The weight average molecular weight (Mw) of the polymer (B) is preferably 100,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and even more preferably 220,000 or more, from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100 in terms of moldability, thermal dimensional stability, blocking resistance, and sheet payout property; and is preferably 1,000,000 or less, more preferably 800,000 or less, more preferably 600,000 or less, even more preferably 500,000 or less, and even more preferably 450,000 or less, from the viewpoint of further improving the thermal dimensional stability.

[0053] The weight average molecular weight (Mw) / number average molecular weight (Mn) of the polymer (B) is preferably 1.5 or more, more preferably 1.8 or more, from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100 among the formability, thermal dimensional stability, blocking resistance, and sheet payout ability; and from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100 among the formability, thermal dimensional stability, blocking resistance, and sheet payout ability, it is preferably 8.0 or less, more preferably 7.5 or less, even more preferably 7.0 or less, and even more preferably 6.8 or less. When two or more polymers are used as polymer (B), the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the polymer (B) can be determined by the method described in the Examples.

[0054] The content of polymer (B) is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, when the entire biaxially oriented film layer 101 is taken as 100% by mass, from the viewpoint of further improving the performance balance between the formability and thermal dimensional stability of the biaxially oriented polypropylene film 100; and from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100, such as thermal dimensional stability, water vapor barrier property, transparency, mechanical properties, rigidity, bag formability, fluidity, and formability, the content is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, even more preferably 25% by mass or less, even more preferably 22% by mass or less, and even more preferably 20% by mass or less.

[0055] (Random polypropylene (B1)) The random polypropylene (B1) includes a random copolymer of propylene and an α-olefin other than propylene, in which the content of structural units derived from an α-olefin other than propylene is more than 2.0 mol % and not more than 15.0 mol %. The α-olefin other than propylene includes, for example, one or more selected from the group consisting of ethylene and α-olefins having 4 to 20 carbon atoms, preferably one or more selected from the group consisting of ethylene and α-olefins having 4 to 6 carbon atoms, more preferably at least one selected from ethylene and 1-butene, and even more preferably ethylene.

[0056] The content of structural units derived from α-olefins other than propylene in the random polypropylene (B1), when the entire random polypropylene (B1) is taken as 100 mol%, is preferably more than 2.0 mol%, more preferably 2.5 mol% or more, even 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 performance balance of the biaxially oriented polypropylene film 100 among the formability, thermal dimensional stability, and bag formability; and is preferably 15.0 mol% or less, more preferably 12.0 mol% or less, even more preferably 10.0 mol% or less, even more preferably 8.0 mol% or less, and even more preferably 6.5 mol% or less, from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100 among the thermal dimensional stability, water vapor barrier property, bag formability, and transparency. The amount of structural units derived from α-olefins other than propylene can be measured by the method described in the Examples.

[0057] The random polypropylene (B1) preferably contains one or more selected from the group consisting of a propylene-ethylene random copolymer, a propylene-ethylene-1-butene random copolymer, and a propylene-1-butene random copolymer, more preferably contains one or more selected from the group consisting of a propylene-ethylene random copolymer and a propylene-1-butene random copolymer, and even more preferably contains a propylene-ethylene random copolymer. The random polypropylene (B1) in the biaxially stretched film layer 101 may be used alone or in combination of two or more.

[0058] (α-olefin copolymer (B2)) The α-olefin copolymer (B2) is a copolymer of two or more types of α-olefins, and includes, for example, an α-olefin copolymer in which the content of structural units derived from an α-olefin other than propylene exceeds 15.0 mol %. The α-olefin copolymer (B2) includes a random copolymer of propylene and an α-olefin other than propylene, in which the content of structural units derived from an α-olefin other than propylene exceeds 15.0 mol %. The α-olefin other than propylene includes, for example, one or more selected from the group consisting of ethylene and α-olefins having 4 to 10 carbon atoms, preferably one or more selected from the group consisting of α-olefins having 4 to 8 carbon atoms, more preferably at least one selected from 1-butene and 1-octene, and even more preferably 1-butene.

[0059] The content of structural units derived from α-olefins other than propylene in the α-olefin copolymer (B2), when the entire α-olefin copolymer (B2) is taken as 100 mol%, is preferably more than 15.0 mol%, more preferably 20.0 mol% or more, even more preferably 30.0 mol% or more, even more preferably 50.0 mol% or more, even more preferably 70.0 mol% or more, and even more preferably 80.0 mol% or more, from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100 among the thermal dimensional stability, water vapor barrier property, bag formability, and transparency, and is preferably 99.0 mol% or less, more preferably 98.0 mol% or less, even more preferably 95.0 mol% or less, even more preferably 92.0 mol% or less, and even more preferably 90.0 mol% or less, from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100 among the thermal dimensional stability, water vapor barrier property, bag formability, and transparency. The amount of structural units derived from an α-olefin other than propylene in the α-olefin copolymer (B2) can be measured by the method described in the examples.

[0060] The α-olefin copolymer (B2) preferably comprises a random copolymer of propylene and one or more α-olefins selected from the group consisting of ethylene and α-olefins having 4 to 10 carbon atoms, more preferably a random copolymer of propylene and one or two α-olefins selected from the group consisting of 1-butene and 1-octene, and even more preferably a random copolymer of propylene and 1-butene. The α-olefin copolymer (B2) in the biaxially stretched film layer 101 may be used alone or in combination of two or more.

[0061] The polymer (B) can be produced by various methods, for example, by using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst.

[0062] (Other ingredients) To the propylene polymer composition of the present embodiment, various additives such as a tackifier, a heat stabilizer, a weather stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, a slipping agent, a nucleating agent, an antiblocking agent, an antistatic agent, an antifogging agent, a pigment, a dye, and an inorganic or organic filler may be added as needed within a range that does not impair the object of the present embodiment.

[0063] (Method for preparing propylene polymer composition) The propylene polymer composition of the present embodiment 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 heated roll, or the like.

[0064] [Surface resin layer] It is preferable that the biaxially oriented polypropylene film 100 further comprises a surface resin layer 103 on at least one side of the biaxially oriented film layer 101, from the viewpoint of imparting functions such as heat resistance, heat sealing properties, antistatic properties, blocking resistance, printability, and slip properties to the film surface depending on the purpose. The surface resin layer 103 may be provided on both sides of the biaxially stretched film layer 101. By providing the surface resin layer 103 on both sides of the biaxially stretched film layer 101, different functions can be imparted to each surface of the film. In addition, the surface resin layer 103 is preferably provided on the outermost layer of the biaxially oriented polypropylene film 100, depending on the purpose, in order to further improve the functions of the biaxially oriented polypropylene film 100, such as heat resistance, heat sealing properties, antistatic properties, blocking resistance, printability, and slip properties.

[0065] The surface resin layer 103 is preferably provided so as to be in direct contact with the surface of the biaxially oriented film layer 101. This allows the manufacturing process of the biaxially oriented polypropylene film 100 to be simplified.

[0066] In the biaxially oriented polypropylene film 100, the thickness of the surface resin layer 103 is preferably 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.5 μm or more, even more preferably 1.0 μm or more, and even more preferably 1.5 μm or more, from the viewpoint of further improving the heat fusion resistance, antistatic properties, blocking resistance, printability, slip properties, and other properties of the biaxially oriented polypropylene film 100; and from the viewpoint of further improving the performance balance of the biaxially oriented polypropylene film 100, such as heat fusion resistance, thermal dimensional stability, formability, cost, mechanical properties, transparency, environmental compatibility, and light weight, the thickness 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 3.0 μm or less. Here, the thickness of the surface resin layer 103 refers to the thickness of the surface resin layer 103 provided on one side of the biaxially stretched film layer 101. That is, in this embodiment, when the surface resin layer 103 is provided on both sides of the biaxially stretched film layer 101, the above-mentioned thickness of the surface resin layer 103 refers to the thickness of the surface resin layer 103 provided on one side of the biaxially stretched film layer 101.

[0067] In the biaxially oriented polypropylene film 100, the surface resin layer 103 is preferably a single layer, which can further simplify the manufacturing process of the biaxially oriented polypropylene film 100.

[0068] The surface resin 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 biaxially stretched polypropylene film 100 to be produced by a molding method such as co-extrusion, i.e., using a laminated film produced in a single molding operation, thereby further simplifying the manufacturing process of the biaxially stretched polypropylene film 100. Therefore, the surface resin layer 103 is preferably biaxially stretched.

[0069] The surface resin layer 103 may be subjected to a surface treatment in order to further improve the balance between printability and blocking resistance of the biaxially oriented polypropylene film 100. Specifically, the surface may be subjected to a surface activation treatment such as corona treatment, flame treatment, plasma treatment, primer coating treatment, or ozone treatment.

[0070] The surface resin layer 103 is made of, for example, a polyolefin-based resin composition (A) containing a polyolefin. The polyolefin constituting the surface resin layer 103 includes one or more selected from the group consisting of homopolymers or copolymers of α-olefins such as ethylene, propylene, 1-butene, hexene-1, 4-methyl-pentene-1, and 1-octene; high-pressure low-density polyethylene; linear low-density polyethylene (LLDPE); high-density polyethylene; homopolypropylene; random copolymers of propylene and α-olefins having from 2 to 10 carbon atoms; ethylene-vinyl acetate copolymers (EVA); and ionomer resins. Among these, homopolypropylene is preferred as the polyolefin constituting the surface resin layer 103 from the viewpoint of further improving the balance of performance such as heat fusion resistance, thermal dimensional stability, heat resistance, water vapor barrier properties, transparency, mechanical properties, rigidity, bag formability, fluidity, and moldability of the biaxially oriented polypropylene film 100. Here, preferred embodiments of the homopolypropylene constituting the surface resin layer 103 are the same as the homopolypropylene (A) described above. That is, the homopolypropylene constituting the surface resin layer 103 preferably contains the homopolypropylene (A) described above.

[0071] The content of polyolefin in the polyolefin resin composition (A), i.e., the surface resin layer 103, is preferably 75% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, even more preferably 99% by mass or more, and preferably 100% by mass or less, when the entire polyolefin resin composition (A), i.e., the entire surface resin layer 103, is taken as 100% by mass, in order to further improve the performance balance of the biaxially oriented polypropylene film 100, such as heat resistance, thermal dimensional stability, heat resistance, water vapor barrier property, transparency, mechanical properties, rigidity, bag formability, fluidity, and moldability. The content of homopolypropylene (A) in the polyolefin resin composition (A), i.e., the surface resin layer 103, is preferably 75% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, even more preferably 99% by mass or more, and preferably 100% by mass or less, when the entire polyolefin resin composition (A), i.e., the entire surface resin layer 103, is taken as 100% by mass, in order to further improve the performance balance of the biaxially oriented polypropylene film 100, such as heat resistance, thermal dimensional stability, heat resistance, water vapor barrier property, transparency, mechanical properties, rigidity, bag formability, fluidity, and moldability.

[0072] (Other ingredients) If necessary, 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, inorganic or organic fillers, etc. may be added to the polyolefin resin composition (A) constituting the surface resin layer 103, within the scope that does not impair the purpose of this embodiment.

[0073] (Method for preparing polyolefin resin composition (A)) The polyolefin resin composition (A) can be prepared, for example, 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.

[0074] <Method of manufacturing biaxially oriented polypropylene film> The biaxially oriented polypropylene film 100 can be obtained, for example, by co-extrusion molding a propylene-based polymer composition for forming the biaxially oriented film layer 101 and, if necessary, a polyolefin-based resin composition (A) for forming the surface resin layer 103 into a film, and then biaxially stretching the film obtained using a known biaxially oriented film manufacturing method such as simultaneous biaxial stretching, sequential biaxial stretching, or inflation biaxial stretching. The molding apparatus and molding conditions are not particularly limited, and conventionally known molding apparatus and molding conditions can be used. Examples of molding apparatus that can be used include a T-die extruder, a multilayer T-die extruder, an inflation molding machine, and a multilayer inflation molding machine. For example, known OPP film production conditions can be used for the biaxial stretching conditions. More specifically, in the sequential biaxial stretching method, the MD stretching temperature may be 100°C to 145°C, the MD stretch ratio may be 4.5 to 6 times, the TD stretching temperature may be 130°C to 190°C, and the TD stretch ratio may be 9 to 11 times. The biaxially oriented polypropylene film 100 can also be obtained by separately molding the biaxially oriented film layer 101 and, if necessary, the surface resin layer 103, and then laminating and molding these together under heat.

[0075] <Applications of biaxially oriented polypropylene film> The biaxially oriented polypropylene film 100 can also be suitably used as a food packaging film that constitutes a food package.

[0076] The food packaging of this embodiment is a packaging that uses biaxially oriented polypropylene film 100, and is, for example, a packaging bag used for containing food. Furthermore, the food packaging of this embodiment may use biaxially oriented polypropylene film 100 in part or in the entire food packaging, depending on the application.

[0077] The food package of this embodiment includes the food package of this embodiment and food contained in the food package. That is, the food package of this embodiment is the food package of this embodiment that contains food.

[0078] 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 other configurations can also be adopted. The biaxially oriented polypropylene film 100 may further include one or more layers selected from the group consisting of a sealant layer and a coating layer. The biaxially oriented polypropylene film 100 can also be used as a raw material for coating. [Example]

[0079] 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.

[0080] 1. Raw materials The raw materials used in the examples and comparative examples are shown below. (1) Homopolypropylene (A) h-PP1: homopolypropylene (MFR: 3.0 g / 10 min, melting point: 165°C, isotactic mesopentad fraction (mmmm): 98.0%, Mw: 370,000, Mn: 68,000, Mw / Mn: 5.4, content of propylene-derived structural units: 100 mol%) h-PP2: homopolypropylene (MFR: 3.0 g / 10 min, melting point: 159°C, isotactic mesopentad fraction (mmmm): 97.5%, Mw: 469,000, Mn: 56,300, Mw / Mn: 8.3, content of ethylene-derived structural units: 1.2 mol%, content of propylene-derived structural units: 98.8 mol%) (2) Polymer (B) r-PP1: random polypropylene (MFR: 7.0 g / 10 min, melting point: 139°C, Mw: 322,000, Mn: 50,700, Mw / Mn: 6.4, 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: random polypropylene (MFR: 2.4 g / 10 min, melting point: 143°C, Mw: 436,000, Mn: 66,000, Mw / Mn: 6.6, content of ethylene-derived structural units: 4.4 mol%, content of propylene-derived structural units: 95.6 mol%)

[0081] 2. Measurement and evaluation methods (1) Isotactic mesopentad fraction (mmmm) of homopolypropylene (A) The isotactic mesopentad fraction (mesopentad fraction, (mmmm)) was measured using a nuclear magnetic resonance spectrometer (AVANCE III cryo-500, manufactured by Bruker Biospin). 13 Measurement was performed by C-NMR. The sample was dissolved in the following measurement solvent, and the integrated intensity of each signal was evaluated. [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: 50 mg / 0.6 mL Measurement temperature: 120℃ Window function: exponential (BF: 0.5Hz) Chemical shift reference: mmmm(CH3): 21.59 ppm

[0082] (2) MFR of homopolypropylene (A) and polymer (B) Measured in accordance with ASTM D1238 at 230°C under a load of 2.16 kg.

[0083] (3) Melting points of homopolypropylene (A) and polymer (B) The homopolypropylene (A) and the polymer (B) were subjected to a differential scanning calorimeter (product name: Q200DSC manufactured by TA Instruments) under a nitrogen gas flow. The first differential scanning calorimeter (1st run) consisted of a process of increasing the temperature from -30°C to 250°C at a rate of 10°C / min and a process of decreasing the temperature from 250°C to -30°C at a rate of 10°C / min, and the second differential scanning calorimeter (2nd run) consisted of a process of increasing the temperature from -30°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.

[0084] (4) Weight average molecular weight (Mw) and number average molecular weight (Mn) of homopolypropylene (A) and polymer (B) The weight average molecular weight (Mw) and number average molecular weight (Mn) of the homopolypropylene (A) and the polymer (B) were measured by gel permeation chromatography (GPC). GPC was performed using a gel permeation chromatograph (Tosoh Corporation, HLC-8321 GPC / HT model) as follows. The separation columns consisted of two TSKgel GNH6-HT columns and two TSKgel GNH6-HTL columns, each with a diameter of 7.5 mm and a length of 300 mm. The column temperature was 145°C, the mobile phase consisted of o-dichlorobenzene and 0.025% BHT by mass as an antioxidant, and the flow rate was 1.0 mL / min. The sample concentration was 0.1% (w / v), the sample injection volume was 400 μL, and a differential refractometer was used as the detector. The molecular weight was calculated as polypropylene equivalent using monodisperse polystyrene as a standard.

[0085] (5) Measurement of the content of structural units derived from α-olefins other than propylene in homopolypropylene (A) and polymer (B), and the content of structural units derived from α-olefins other than propylene in biaxially oriented polypropylene film The content of structural units derived from α-olefins other than propylene in the homopolypropylene (A) and polymer (B), as well as the content of structural units derived from α-olefins other than propylene contained in the biaxially oriented polypropylene film, was measured using a nuclear magnetic resonance apparatus (AVANCE III cryo-500, manufactured by Bruker Biospin). 13 Measurement was performed by C-NMR. The sample was dissolved in the following measurement solvent and measured, and evaluation was performed based on the integrated intensity of each signal. 13Signals were assigned using C-NMR spectra with reference to 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 each polymer 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: 50 mg / 0.6 mL Measurement temperature: 120℃ Window function: exponential (BF: 0.5Hz) In addition, the content of structural units derived from α-olefins other than propylene contained in the biaxially stretched polypropylene film was measured using the biaxially stretched polypropylene film as a sample.

[0086] (6) Tensile modulus A 15 mm × 15 cm test piece was cut out from the biaxially stretched polypropylene film. The MD tensile modulus (T1) and TD tensile modulus (T2) of the test piece were measured using a tensile tester manufactured by Orientec Co., Ltd. in accordance with JIS K7127 (1999) at a temperature of 23±2°C, 50±5% RH, and a tension speed of 5 mm / min.

[0087] (7) Differential scanning calorimetry of biaxially oriented polypropylene film A test piece of approximately 5.0 mg was cut out from the biaxially stretched polypropylene film. Next, a first differential scanning calorimetry (1st Run) was performed on the sample using a differential scanning calorimeter (product name: Q200DSC, manufactured by TA Instruments) under a nitrogen gas flow. The first run consisted of a heating process from -50°C to 250°C at a heating rate of 5°C / min and a cooling process from 250°C to -50°C at a cooling rate of 5°C / min. From the obtained DSC curve, the main melting point (°C), the heat of fusion ΔH (J / g) of the entire film, and the heat of fusion ΔH (J / g) below 165°C were determined. Here, the peak temperature of the maximum melting peak on the DSC curve was taken as the main melting point. The heat of fusion ΔH (J / g) of the entire film was calculated from the area of ​​the melting peak on the DSC curve in accordance with JIS K 7122:1987 (except that the heating rate was 5°C / min.) When multiple melting peaks appeared on the DSC curve, the sum of the areas of the multiple melting peaks was used as the heat of fusion (ΔH) of the entire film. The heat of fusion ΔH (J / g) at 165° C. or less is the heat of fusion ΔH (J / g) in the range of 165° C. or less out of the heat of fusion ΔH (J / g) of the entire film.

[0088] Next, the crystalline ratio (%) at 165°C or less, the degree of crystallinity (%), the amorphous amount (%), and the crystalline amount at 165°C or less were calculated using the following formulas. The heat of fusion of perfectly crystalline polypropylene used in the calculation was 209 J / g as described in Macromolecular Chemie, Rapid Communication, Vol. 9, page 75 (1988). Crystalline ratio below 165°C (%) = 100 × heat of fusion below 165°C ΔH (J / g) / heat of fusion of entire film ΔH (J / g) Crystallinity (%) = 100 x heat of fusion of the entire film ΔH (J / g) / heat of fusion of fully crystalline polypropylene (209 J / g) Amorphous amount (%) = 100-Crystallinity (%) Amount of crystals below 165°C (%) = Degree of crystallinity (%) × Crystal ratio below 165°C (%) / 100

[0089] (8) Water vapor permeability The biaxially oriented polypropylene film was folded back so that the surface resin layer 1 was on the inside, and the two sides were heat-sealed to form a bag. Calcium chloride was then placed inside as the contents. The other side was then heat-sealed to form a bag with a surface area of ​​0.01 m. 2 The bags were then stored at 40°C and 90% RH for 72 hours. The mass of calcium chloride was measured before and after storage, and the difference was used to determine the water vapor permeability (g / (m 2 ·24h)) were calculated respectively.

[0090] (9) Thermal expansion and shrinkage of biaxially oriented polypropylene film at 120°C The thermal expansion coefficient and thermal shrinkage coefficient of the biaxially stretched polypropylene film at 120°C were measured in accordance with JIS C2151:2019. First, a 10 cm × 10 cm test piece was cut from a biaxially oriented polypropylene film. The test piece was then heat-treated at 120°C for 15 minutes. The test piece was heated in a hot-air circulating thermostatic chamber (manufactured by ADVANTEC, product name: DRM620DE) while suspended without applying any force. After cooling to room temperature, the length of the test piece was measured. The length of the test piece in the TD direction after heat treatment was defined as TD1 [cm], and the thermal expansion coefficient in the TD direction [%] was calculated by 100 × (TD1 − 10) / 10. The length of the test piece in the MD direction after heat treatment was defined as MD1 [cm], and the thermal shrinkage coefficient in the MD direction [%] was calculated by 100 × (10 − MD1) / 10. The above measurement was performed three times, and the average values ​​of the obtained measurements were used as the thermal expansion coefficient and thermal shrinkage coefficient of the biaxially oriented polypropylene film at 120°C, respectively.

[0091] (10) Heat shrinkage of biaxially oriented polypropylene film at 150°C The heat shrinkage of the biaxially stretched polypropylene film at 150°C was measured in accordance with JIS C2151:2019. First, a 10 cm x 10 cm test piece was cut out from a biaxially stretched polypropylene film. Then, the test piece was heat-treated at 150°C for 15 minutes. At this time, the test piece was heated by hanging it without applying any force in a hot air circulation type thermostatic chamber (manufactured by ADVANTEC, product name: DRM620DE). Next, after cooling the test piece to room temperature, the length of the test piece was measured. Next, when the length in the TD direction of the test piece after heat treatment is TD1 [cm] and the length in the MD direction of the test piece after heat treatment is MD1 [cm], X TD [%] is calculated by 100 × (10-TD1) / 10, and X MD [%] was calculated by 100 × (10 - MD1) / 10. The above measurement was carried out three times, and the average value of the obtained measurements was used as the heat shrinkage rate of the biaxially stretched polypropylene film at 150 ° C.

[0092] (11) Hayes The haze of the biaxially stretched polypropylene film was measured in accordance with JIS K7136:2000 using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0093] (12) Heat fusion strength at 200°C Two 15mm-wide biaxially oriented polypropylene films were cut into pieces, and the surface resin layer 1 (heat-resistant adhesive layer) of each was heat-sealed together at 200°C, a pressure of 2.0 kgf, and a sealing time of 1.0 second to obtain a laminated film. The two biaxially oriented polypropylene films were then peeled together at a width of 15mm, at a 90-degree peel angle, at a peel speed of 300 mm / min, and pulled in the TD direction. The peel strength measured at this time was defined as the heat-seal strength.

[0094] (13) Bag-making properties (wrinkles when heat-sealed at 180°C) Two 15 mm wide biaxially oriented polypropylene films were cut into pieces, and the surface resin layer 1 (heat-resistant adhesive layer) was heat-sealed together at 180°C, a pressure of 2.0 kgf, and a sealing time of 1.0 second to obtain a laminated film. The seal area was then visually inspected for heat wrinkles.

[0095] (14) Thermal dimensional stability The thermal dimensional stability of the biaxially oriented polypropylene film was evaluated according to the following criteria. AA (very good): Heat shrinkage rate at 150°C (X MD +X TD ) is less than 6.0% A (Good): Heat shrinkage rate at 150°C (X MD +X TD ) is 6.0% or more but less than 7.0% B (bad): Heat shrinkage rate at 150°C (X MD +X TD ) is 7.0% or more and less than 10.0% C (very bad): Heat shrinkage rate at 150°C (X MD +X TD ) is 10.0% or more

[0096] [Examples 1 to 4 and Comparative Example 1] Polypropylene films were extruded with the compositions shown in Table 1, and then biaxially stretched to produce biaxially stretched polypropylene films, which were then evaluated. The extrusion conditions and biaxial stretching conditions were as follows. Corona treatment was also performed on the surface of the surface resin layer 2 in Table 1. Extrusion molding machine: 60 mmφ multi-layer T-die extrusion molding machine (screw: L / D=27, manufactured by Screw Seiki Co., Ltd.) Extrusion temperature setting: 230-250°C, Processing speed: 20m / min (winding speed) Stretching temperature in MD direction [°C]: See Table 1 Stretching ratio in MD direction [times]: See Table 1 Stretching temperature in TD direction [°C]: See Table 1 Stretching ratio in TD direction [times]: See Table 1 Relaxation rate [%]: See Table 1 Here, the relaxation rate refers to the maximum stretching width in the device settings divided by the tenter outlet width. In addition, the notation "A / B / C" for the stretching temperature in Table 1 means "preheating temperature (temperature at which the raw film is heated before stretching) / stretching temperature (temperature at which stretching is performed) / heat setting temperature (temperature at which heat setting (annealing) is performed after stretching)."

[0097] [Table 1]

[0098] The biaxially oriented polypropylene films of the Examples had improved thermal dimensional stability compared to the biaxially oriented polypropylene films of the Comparative Examples. [Explanation of symbols]

[0099] 100 Biaxially oriented polypropylene film 101 Biaxially oriented film layer 103 Surface resin layer

Claims

1. a biaxially stretched film layer containing a propylene-based polymer; A biaxially oriented polypropylene film having a crystalline ratio of 38% or more at 165°C or less as determined by differential scanning calorimetry.

2. 2. The biaxially oriented polypropylene film according to claim 1, wherein the biaxially oriented polypropylene film has a main melting point of 165°C or higher and 180°C or lower, as determined by differential scanning calorimetry.

3. 3. The biaxially oriented polypropylene film according to claim 1, wherein the heat of fusion (ΔH) of the entire biaxially oriented polypropylene film, as determined by differential scanning calorimetry, is 100 J / g or more and 150 J / g or less.

4. 3. The biaxially oriented polypropylene film according to claim 1, wherein the biaxially oriented polypropylene film has a heat of fusion (ΔH) at 165°C or less of 40 J / g or more as determined by differential scanning calorimetry.

5. 3. The biaxially oriented polypropylene film according to claim 1, wherein the biaxially oriented polypropylene film has a crystal content of 20% or more at 165°C or less.

6. 3. The biaxially oriented polypropylene film according to claim 1, wherein the amount of structural units derived from α-olefins other than propylene contained in the biaxially oriented polypropylene film is 0.05 mol% or more when the total amount of structural units derived from monomers contained in the biaxially oriented polypropylene film is 100 mol%.

7. The biaxially oriented polypropylene film according to claim 1 or 2, further comprising a surface resin layer on at least one side of the biaxially oriented film layer.

8. The biaxially oriented polypropylene film according to claim 7, wherein the surface resin layer contains homopolypropylene (A).

9. 9. The biaxially oriented polypropylene film according to claim 8, wherein the content of the homopolypropylene (A) in the surface resin layer is 75% by mass or more and 100% by mass or less, when the entire surface resin layer is 100% by mass.

10. The biaxially oriented polypropylene film according to claim 7, wherein the thickness of the surface resin layer is 0.1 μm or more and 10.0 μm or less.

11. 3. The biaxially oriented polypropylene film according to claim 1, wherein the thickness of the biaxially oriented film layer is 5 μm or more and 100 μm or less.

12. The tensile modulus T of the biaxially oriented polypropylene film in the MD direction is measured using a tensile tester 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. １ and the tensile modulus in the TD direction T ２ The sum of (T １ +T ２ 3. The biaxially oriented polypropylene film according to claim 1, wherein the elongation stress (E) is 3,000 MPa or more and 10,000 MPa or less.

13. The biaxially oriented polypropylene film according to claim 1 or 2, which expands in the TD direction when heat-treated at 120 ° C. for 15 minutes in accordance with JIS C2151:2019.

14. 3. The biaxially oriented polypropylene film according to claim 1, which is a food packaging film.

15. A food packaging product using the biaxially oriented polypropylene film according to claim 1 or 2.

16. The food packaging body according to claim 15; and a food product within the food package.

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