Biaxially oriented polypropylene film, food packaging and food packaging

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 packaging, and a food packaging. [Background technology]

[0002] Biaxially oriented polypropylene film (hereinafter also referred to as OPP film) has an excellent balance of properties 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 (Japanese Patent Publication No. 2008-73926) and Patent Document 2 (Japanese Patent Publication No. 2004-82499).

[0004] Patent Document 1 describes a biaxially oriented multilayer polypropylene film characterized in that one side of the biaxially oriented film is 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), has a layer made of a propylene-α-olefin random copolymer (C) with a melting point in the range of 125 to 145°C, via a layer made of a propylene-based polymer (B) with a melting point of 155°C or higher, and the other side of the biaxially oriented film has a layer made of a propylene-based polymer (E). Patent Document 1 states that the above-mentioned biaxially oriented multilayer polypropylene film can suppress the seepage of petroleum resin and other substances onto the film surface, and has excellent lamination strength and moisture resistance.

[0005] Patent Document 2 describes a multilayer resin film comprising a polyvinyl alcohol-based resin layer further having an adhesive layer on at least one surface of a biaxially oriented polypropylene-based resin layer containing 10 to 40% by mass of highly crystallized resin and 6 to 15% by mass of petroleum resin, wherein the oxygen permeability at a relative humidity of 85% RH and a temperature of 23°C is 600 mL / m². 2The pressure is less than or equal to day·MPa, and the water vapor transmission rate at a relative humidity of 90%RH and a temperature of 40°C is 3.5g / m³. 2 A multilayer resin film characterized by having a thickness of 20 μm or less is described. Patent Document 2 states that the above-mentioned multilayer resin film has excellent oxygen gas barrier properties and moisture resistance. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2008-73926 [Patent Document 2] Japanese Patent Publication No. 2004-82499 [Overview of the project] [Problems that the invention aims to solve]

[0007] In recent years, from an environmental perspective, there has been a growing demand for monomaterial packaging. However, conventional biaxially oriented polypropylene films sometimes lacked sufficient thermal dimensional stability, both in terms of suppressing thermal wrinkles at the seal during bag making and suppressing thermal expansion during vapor deposition and coating processes. In other words, biaxially oriented polypropylene films require further improvement in thermal dimensional stability, both in terms of suppressing thermal wrinkles at the seal during bag making and suppressing thermal expansion during vapor deposition and coating processes.

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

[0009] The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, they have found that adjusting the crystal ratio at 165°C or below to a specific range can improve the thermal dimensional stability of a biaxially oriented polypropylene film, and thus arrived at the present invention.

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

[0011] [1] comprising a biaxially oriented film layer containing a propylene-based polymer, A biaxially oriented polypropylene film, wherein the crystal ratio at 165°C or lower, as determined by differential scanning calorimetry, is 38% or more. [2] The biaxially oriented polypropylene film according to [1] above, wherein the main melting point of the biaxially oriented polypropylene film, as determined by differential scanning calorimetry, is 165°C or higher and 180°C or lower. [3] The biaxially oriented polypropylene film according to [1] or [2] above, 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) at 165°C or lower of the biaxially oriented polypropylene film, 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 crystal content at 165°C or lower of the biaxially oriented polypropylene film, as determined by differential scanning calorimetry, is 20% or more. [6] The biaxially oriented polypropylene film according to any one of [1] to [5] above, wherein when the total amount of monomer-derived constitutional units contained in the biaxially oriented polypropylene film is 100 mol%, the amount of constitutional units derived from α-olefin other than propylene contained in the biaxially oriented polypropylene film is 0.05 mol% or more. [7] A biaxially oriented polypropylene film according to any one of [1] to [6], 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], wherein the surface resin layer contains homopolypropylene (A). [9] The biaxially oriented polypropylene film according to [8], wherein the content of 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 considered to be 100% by mass.

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

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

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

[12] A biaxially oriented polypropylene film as described in any of [1] to

[11] above, wherein the sum of the tensile modulus T1 in the MD direction and the tensile modulus T2 in the TD direction (T1+T2), measured using a tensile testing machine in accordance with JIS K7127 (1999) at a measurement temperature of 23±2℃, 50±5%RH, and a tensile speed of 5mm / min, is 3000MPa or more and 10000MPa or less.

[13] A biaxially oriented polypropylene film according to any of the above [1] to

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

[14] A biaxially oriented polypropylene film according to any of the above [1] to

[13] , which is a food packaging film.

[15] A food packaging material using a biaxially oriented polypropylene film as described in any of the above [1] to

[14] .

[16] The food packaging described in

[15] above, A food packaging body containing the food inside the aforementioned food packaging body. [Effects of the Invention]

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

[0013] [Figure 1] This is a schematic cross-sectional view showing an example of the structure of the biaxially oriented polypropylene film of this embodiment. [Figure 2] This is a schematic cross-sectional view showing an example of the structure of the biaxially oriented polypropylene film of this embodiment. [Figure 3] This is a schematic cross-sectional view showing an example of the structure of the biaxially oriented polypropylene film of this embodiment. [Modes for carrying out the invention]

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

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

[0016] As mentioned above, biaxially oriented polypropylene films require further improvement in thermal dimensional stability, from the standpoint of suppressing thermal wrinkles in the sealed area during bag making and suppressing thermal expansion during vapor deposition and coating processes. In this study, the inventors found that the amount of crystalline components below 165°C affects the thermal dimensional stability. Based on the above findings, the inventors further investigated and found that the thermal dimensional stability of the biaxially oriented polypropylene film 100 can be improved by setting the crystalline content below 165°C to 38% or more, leading to the present invention. In other words, 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, heat wrinkles in the sealed portion during bag making can be suppressed, and as a result, bag making performance can be improved.

[0017] The crystallinity ratio of the biaxially oriented polypropylene film 100 below 165°C, as determined by differential scanning calorimetry, is 38% or more. However, 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. Furthermore, from the viewpoint of further improving the performance balance between the moldability 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 crystallinity ratio of the biaxially oriented polypropylene film 100 at temperatures below 165°C 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. Furthermore, from the viewpoint of further improving the balance between the moldability and thermal dimensional stability of the biaxially oriented polypropylene film 100, it 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. The principal melting point of the biaxially oriented polypropylene film 100 can be measured by the method described in the examples. Here, in this specification, the peak temperature of the maximum melting peak of the DSC curve is defined as the principal melting point.

[0019] The total heat of fusion (ΔH) of the 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 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 moldability and thermal dimensional stability of the biaxially oriented polypropylene film 100. The total heat of fusion (ΔH) of the biaxially oriented polypropylene film 100 can be measured by the method described in the examples. Here, in this specification, if multiple fusion peaks appear in the DSC curve, the sum of the areas of the multiple fusion peaks is considered to be the heat of fusion (ΔH).

[0020] The heat of fusion (ΔH) of the biaxially oriented polypropylene film 100 at 165°C or below, 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 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, from the viewpoint of further improving the performance balance between the moldability and thermal dimensional stability of the biaxially oriented polypropylene film 100. The heat of fusion (ΔH) of the biaxially oriented polypropylene film 100 at temperatures below 165°C can be measured by the method described in the examples.

[0021] The degree of 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 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, from the viewpoint of further improving the balance between the moldability and thermal dimensional stability of the biaxially oriented polypropylene film 100. The degree of crystallinity of the biaxially oriented polypropylene film 100 can be measured by the method described in the examples.

[0022] The amount of crystals in the biaxially oriented polypropylene film 100 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 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 balance between the moldability and thermal dimensional stability of the biaxially oriented polypropylene film 100. The amount of crystals in 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, as determined by differential scanning calorimetry, can be adjusted, for example, by adjusting the type and content ratio of the propylene polymer contained in the biaxially oriented film layer 101, the thickness and stretching ratio of the biaxially oriented film layer 101, and the constituent materials and thickness of the surface resin layer 103.

[0024] In accordance with JIS K7127 (1999), the sum of the tensile modulus T1 in the MD direction and the tensile modulus T2 in the TD direction of a biaxially oriented polypropylene film 100, measured using a tensile testing machine under the conditions of a measurement temperature of 23±2℃, 50±5%RH, and a tensile speed of 5mm / min, is preferably 3000MPa or more, more preferably 4000MPa or more, even more preferably 5000MPa or more, even more preferably 6000MPa or more, even more preferably 6500MPa or more, and preferably 10000MPa or less, more preferably 8000MPa or less, and even more preferably 7500MPa or less. If the sum of the tensile modulus T1 in the MD direction and the tensile modulus T2 in the TD direction (T1+T2) is equal to or greater than the lower limit, the balance of performance characteristics such as thermal dimensional stability, moldability, water vapor barrier properties, mechanical properties, transparency, bag-making properties, and handling properties of the biaxially oriented polypropylene film 100 can be further improved. Furthermore, the rigidity of the biaxially oriented polypropylene film 100 can be improved, which in turn can suppress misalignment of the film during heat sealing and prevent sealing defects. In other words, if the sum of the tensile modulus T1 in the MD direction and the tensile modulus T2 in the TD direction (T1+T2) is equal to or greater than the above lower limit, the balance of performance of the biaxially oriented polypropylene film 100 in terms of thermal dimensional stability, moldability, water vapor barrier properties, mechanical properties, transparency, bag-making properties, handling properties, and packaging suitability can be improved. Furthermore, if the sum of the tensile modulus T1 in the MD direction and the tensile modulus T2 in the TD direction (T1+T2) is less than or equal to the above upper limit, problems such as cutting will be less likely to occur during the molding of the biaxially oriented polypropylene film 100, making continuous stretch molding of the film easier and further improving industrial continuous productivity. Such tensile modulus is a surrogate 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 polymer contained in the biaxially oriented film layer 101, the thickness and stretching ratio of the biaxially oriented film layer 101, and the constituent materials and thickness of the surface resin layer 103.

[0025] Furthermore, the tensile modulus T1 in the MD direction of the biaxially oriented polypropylene film 100 is preferably 1000 MPa or higher, more preferably 1300 MPa or higher, even more preferably 1500 MPa or higher, even more preferably 1800 MPa or higher, even more preferably 2000 MPa or higher, and even more preferably 2300 MPa or higher, from the viewpoint of further improving the balance of performance of the biaxially oriented polypropylene film 100 in terms of thermal dimensional stability, moldability, water vapor barrier properties, mechanical properties, transparency, bag-making properties, handling properties, and packaging suitability, and is preferably 4000 MPa or lower, more preferably 3500 MPa or lower, even more preferably 3000 MPa or lower, even more preferably 2800 MPa or lower, and even more preferably 2600 MPa or lower.

[0026] From the viewpoint of further improving the balance between thermal dimensional stability and bag-making properties, 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 coefficient of thermal expansion 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 balance between thermal dimensional stability and bag-making performance, and from the viewpoint of further suppressing heat wrinkles in the seal portion and obtaining a bag with good heat wrinkles in the seal portion. Furthermore, from the viewpoint of further improving the balance between thermal dimensional stability and bag-making performance, it 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. In general, a roll of biaxially oriented polypropylene film is fed out in the MD direction, and bag making, coating, and vapor deposition are performed while tension is applied. That is, since there is no tension in the TD direction, the biaxially oriented polypropylene film is susceptible to thermal shrinkage when heated, and heat wrinkles are likely to form 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 less likely to occur even when the biaxially oriented polypropylene film 100 is heated, making it possible to further suppress heat wrinkles in the sealed area. Furthermore, the coefficient of thermal expansion in the TD direction of the biaxially oriented polypropylene film 100 after heat treatment at 120°C for 15 minutes is calculated by the following method. First, a 10cm x 10cm test piece is cut 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 coefficient of thermal expansion [%] in the TD direction is calculated as 100 × (TD1 - 10) / 10.

[0027] Furthermore, the thermal shrinkage rate in the MD direction of the biaxially oriented polypropylene film 100 when heat-treated at 120°C for 15 minutes is 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 also be 0.1% or more, 0.3% or more, or 0.5% or more. In general, a roll of biaxially oriented polypropylene film is fed out in the MD direction, and bag making, coating, and vapor deposition are performed while tension is applied. That is, because tension is applied in the MD direction, if the film has low heat resistance when heated, the film is prone to thermal expansion in the MD direction. On the other hand, if the thermal shrinkage rate in the MD direction when heated at 120°C for 15 minutes is within the above range, it becomes possible to further suppress thermal expansion in the MD direction when the biaxially oriented polypropylene film 100 is heated. Further, the thermal shrinkage rate in the MD direction of the biaxially oriented polypropylene film 100 when heat-treated at 120°C for 15 minutes is calculated by the following method. First, a test piece of 10 cm × 10 cm is cut out from the biaxially oriented polypropylene film 100, and this test piece is heat-treated at 120°C for 15 minutes. Then, when the length of the heat-treated test piece in the MD direction is defined as MD1 [cm], the thermal shrinkage rate [%] in the MD direction is calculated by 100×(10-MD1) / 10.

[0028] In the biaxially oriented polypropylene film 100, when the thermal shrinkage rate in the TD direction and the thermal shrinkage rate in the MD direction upon heat treatment at 150°C for 15 minutes are respectively X TD [%] and X MD [%], X TD +X MD is preferably less than 7.0%, more preferably 6.5% or less, and still more preferably less than 6.0%, from the viewpoint of further improving the performance balance between thermal dimensional stability and bag-making properties of the biaxially oriented polypropylene film 100. Further, X TD [%] and X MD [%] of the biaxially oriented polypropylene film 100 are calculated by the following method. First, a test piece of 10 cm × 10 cm is cut out from the biaxially oriented polypropylene film 100, and this test piece is heat-treated at 150°C for 15 minutes. Then, when the length of the heat-treated test piece in the TD direction is defined as TD1 [cm] and the length of the heat-treated test piece in the MD direction is defined as MD1 [cm], X TD [%] is calculated by 100×(10-TD1) / 10, and X MD [%] is calculated by 100×(10-MD1) / 10.

[0029] The coefficient of thermal expansion and thermal shrinkage rate 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, and the like. Furthermore, the thermal expansion coefficient and thermal contraction coefficient of the biaxially oriented polypropylene film 100 can be measured in accordance with JIS C2151:2019.

[0030] In a package made using biaxially oriented polypropylene film 100, from the viewpoint of further improving the balance between the ability to prevent film fusion to the seal bar during bag making and the appearance of the seal, the heat-seal strength (TD tensile direction) of the portion of the biaxially oriented polypropylene film 100 that has been heat-sealed under the conditions of 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-seal strength is used as an indicator of the heat-seal resistance of the surface of a biaxially oriented polypropylene film. The lower the heat-seal strength, the better the heat-seal resistance of the surface of the biaxially oriented polypropylene film can be determined. Here, the heat-sealing strength can be measured by the following method. First, a laminated film is obtained by heat-sealing two biaxially oriented polypropylene films 100 under the conditions of 200°C, a pressure of 2.0 kgf, and a sealing time of 1.0 second. Next, the two biaxially oriented polypropylene films 100 are peeled off under the conditions of a width of 15 mm, 90-degree peeling, a peeling speed of 300 mm / min, and tensile strength in the TD direction, and the peel strength at that time is defined as the heat-sealing strength. Such heat-sealing strength can be adjusted, for example, by adjusting the types and proportions of 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, and the constituent materials and thickness of the surface resin layer 103.

[0031] In accordance with JIS K7136:2000, the haze of the biaxially oriented polypropylene film 100, as measured using a haze meter, 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 controlled, for example, by adjusting the type and content ratio of the propylene polymer contained in the biaxially oriented film layer 101, the thickness and stretching ratio of the biaxially oriented film layer 101, and the constituent materials and thickness of the surface resin layer 103.

[0032] Here, the food packaging made using the biaxially oriented polypropylene film 100 exhibits sufficient performance in terms of water vapor barrier properties. Therefore, the biaxially oriented polypropylene film 100 can be particularly suitable 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 transmission rate of the biaxially oriented polypropylene film 100, measured by the following method, is preferably 20.0 g / (m²). 2 • 24h) or less, more preferably 15.0 g / (m 2 • 24h) or less, more preferably 12.0 g / (m 2 • 24h) or less, more preferably 10.0 g / (m 2 • 24h) or less, more preferably 8.0 g / (m 2 • Less than 24 hours (Measurement method) A biaxially oriented polypropylene film 100 is folded over, and two sides are heat-sealed to form a bag. Then, calcium chloride is added as the contents. Next, the other side is heat-sealed to create a bag with a surface area of ​​0.01 m². 2 A bag is prepared to achieve the following conditions. Next, the resulting bag is stored for 72 hours at 40°C and 90% RH. The mass of calcium chloride is measured before and after storage, and the water vapor transmission rate (g / m³) is calculated from the difference. 2Calculate (24 hours). Such water vapor permeability can be adjusted, for example, by adjusting the type and content ratio of the propylene polymer contained in the biaxially oriented film layer 101, the thickness and stretching ratio of the biaxially oriented film layer 101, and the constituent materials and thickness of the surface resin layer 103.

[0034] The amount of α-olefin-derived constituent units other than propylene contained in the biaxially oriented polypropylene film 100 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, when the total amount of monomer-derived constituent units contained in the biaxially oriented polypropylene film 100 is taken as 100 mol%, from the viewpoint of further improving the balance of performance of the biaxially oriented polypropylene film 100 in terms of moldability, thermal dimensional stability, and bag-making ability, and from the viewpoint of further improving the balance of performance of the biaxially oriented polypropylene film 100 in terms of thermal dimensional stability, water vapor barrier properties, bag-making ability, and transparency, 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. If the amount of α-olefin-derived structural units other than propylene contained in the biaxially oriented polypropylene film 100 is within the above range, the softening effect of the α-olefin-derived structural units will suppress the yield point stress at the start of the stretching process, improving ease of molding. In addition, the lowering effect of the α-olefin-derived structural units will more efficiently relieve residual stress during the heat setting process when forming the film, improving moldability and suppressing thickness unevenness. As a result, the thermal dimensional stability of the biaxially oriented polypropylene film 100 can be further improved. The amount of α-olefin-derived constituent units other than propylene in the biaxially oriented 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, even more preferably 15 μm or more, and 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, from the viewpoint of further improving the balance of performance such as thermal dimensional stability, moldability, water vapor barrier properties, cost, mechanical properties, transparency, bag-making properties, handling properties, appearance, and lightweight properties.

[0036] The following describes each layer that makes up the biaxially oriented polypropylene film 100.

[0037] [Biaxially oriented film layer] The biaxially oriented film layer 101 (also called the biaxially oriented polypropylene film layer) contains a propylene polymer. The biaxially oriented film layer 101 is formed, for example, by biaxially stretching a film made of a propylene polymer composition containing a propylene polymer.

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

[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, even more preferably 15 μm or more, and 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, from the viewpoint of further improving the balance of performance such as thermal dimensional stability, moldability, water vapor barrier properties, cost, mechanical properties, transparency, bag-making properties, handling properties, appearance, and lightweight properties of the biaxially oriented polypropylene film 100.

[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, and even more preferably 90% or less.

[0041] (Propylene-based polymer composition) The propylene polymer composition of this embodiment contains a propylene polymer. The propylene polymer content in the propylene polymer composition of this embodiment, i.e., the propylene polymer content in the biaxially oriented 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 total propylene polymer composition is considered as 100% by mass. This is done from the viewpoint of further improving the balance of performance such as thermal dimensional stability, environmental compatibility, heat resistance, water vapor barrier properties, transparency, cost, mechanical properties, rigidity, bag-making properties, fluidity, moldability, handling properties, appearance, and lightweight properties of the biaxially oriented polypropylene film 100.

[0042] (Propylene polymer) The propylene-based polymer of this embodiment is a polymer containing structural units derived from propylene, and examples 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 homopolypropylene (A) include propylene homopolymers and propylene copolymers in which the content of structural units derived from α-olefins other than propylene is 2.0 mol% or less. Homopolypropylene (A) is defined as having a content of propylene-derived structural units of 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, even more preferably 99.8 mol% or more, and for example, 100.0 mol% or less, when the total content of structural units constituting homopolypropylene (A) is set to 100 mol%.

[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 total amount of homopolypropylene (A) is considered to be 100 mol%. The homopolypropylene (A) in the biaxially oriented film layer 101 may be used alone or in combination of two or more types.

[0045] The isotactic mesopentad fraction (mmmm) of homopolypropylene (A) is preferably 96.0% or higher, more preferably 96.5% or higher, even more preferably 97.0% or higher, even more preferably 97.3% or higher, even more preferably 97.5% or higher, even more preferably 97.8% or higher, and even more preferably 98.0% or higher, 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-making properties of the biaxially oriented polypropylene film 100. There is no particular upper limit to the isotactic mesopentad fraction (mmmm) of homopolypropylene (A), but from the viewpoint of ease of manufacture, it is 99.5% or lower, more preferably 99.3% or lower, and even more preferably 99.0% or lower. The isotactic mesopentad fraction (mmmm) is an indicator of stereoregularity. 13 It can be determined from the 13C nuclear magnetic resonance (NMR) spectrum using known methods. When using two or more types of homopolypropylene (A), the isotactic mesopentad fraction of homopolypropylene (A) can be the isotactic mesopentad fraction of a mixture obtained by melt-blending two or more types of homopolypropylene (A) using a known method.

[0046] According to ASTM D1238, the melt flow rate (MFR) of homopolypropylene (A), measured under conditions of 230°C and a 2.16 kg load, 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 of fluidity and moldability performance, and 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 using two or more types of homopolypropylene (A) as homopolypropylene (A), the MFR of homopolypropylene (A) can be a mixture obtained by melt-blending two or more types of homopolypropylene (A) using a known method.

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

[0048] Homopolypropylene (A) can be produced by various methods. For example, it can be produced using known catalysts such as Ziegler-Natta catalysts or metallocene catalysts.

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

[0050] In accordance with ASTM D1238, the melt flow rate (MFR) of polymer (B), measured under conditions of 230°C and a 2.16 kg load, 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, even more preferably 2.0 g / 10 min or more, and 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 using two or more polymers as polymer (B), an MFR of a mixture obtained by melt-blending two or more polymers (B) using a known method can be employed.

[0051] The melting point of 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, even more preferably 90°C or higher, and 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, from the viewpoint of further improving the balance of performance such as thermal dimensional stability, heat resistance, water vapor barrier properties, mechanical properties, rigidity, bag-making properties, fluidity and moldability of the biaxially oriented polypropylene film 100. When two or more 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 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 balance of performance of the biaxially oriented polypropylene film 100, including moldability, thermal dimensional stability, blocking resistance, and sheet unwinding, and is preferably 1,000,000 or less, more preferably 800,000 or less, even 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 thermal dimensional stability.

[0053] The weight-average molecular weight (Mw) / number-average molecular weight (Mn) of polymer (B) is preferably 1.5 or higher, more preferably 1.8 or higher, from the viewpoint of further improving the balance of performance of the biaxially oriented polypropylene film 100 in terms of moldability, thermal dimensional stability, blocking resistance, and sheet unwinding, and is preferably 8.0 or lower, more preferably 7.5 or lower, even more preferably 7.0 or lower, and even more preferably 6.8 or lower. When two or more polymers are used as polymer (B), the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polymer (B) can be those of a mixture obtained by melt-blending two or more polymers (B) using a known method. The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polymer (B) can be measured by the method described in the examples.

[0054] From the viewpoint of further improving the balance of moldability and thermal dimensional stability of the biaxially oriented polypropylene film 100, 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 considered as 100% by mass. Furthermore, from the viewpoint of further improving the balance of performance such as thermal dimensional stability, water vapor barrier properties, transparency, mechanical properties, rigidity, bag-making properties, fluidity and moldability of the biaxially oriented polypropylene film 100, the content of polymer (B) 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)) Random polypropylene (B1) includes a random copolymer of propylene and an α-olefin other than propylene, wherein the content of constituent units derived from α-olefins other than propylene is greater than 2.0 mol% and less than or equal to 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 constituent units derived from α-olefins other than propylene in random polypropylene (B1) 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 balance of performance of the biaxially oriented polypropylene film 100 in terms of moldability, thermal dimensional stability, and bag-making properties, when the total amount of random polypropylene (B1) is considered to be 100 mol%, and 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 balance of performance of the biaxially oriented polypropylene film 100 in terms of thermal dimensional stability, water vapor barrier properties, bag-making properties, and transparency. The amount of α-olefin-derived constituent units other than propylene can be measured by the method described in the examples.

[0057] Random polypropylene (B1) preferably comprises one or more selected from the group consisting of propylene-ethylene random copolymer, propylene-ethylene-1-butene random copolymer, and propylene-1-butene random copolymer, more preferably comprises one or more selected from the group consisting of propylene-ethylene random copolymer and propylene-1-butene random copolymer, and even more preferably comprises propylene-ethylene random copolymer. The random polypropylene (B1) in the biaxially oriented film layer 101 may be of a single type or a combination of two or more types.

[0058] (α-olefin copolymer (B2)) α-olefin copolymer (B2) is a copolymer of two or more α-olefins, and includes, for example, an α-olefin copolymer in which the content of structural units derived from α-olefins 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, wherein the content of constituent units derived from α-olefins 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) 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 balance of performance of the biaxially oriented polypropylene film 100 in terms of moldability, thermal dimensional stability, and bag-making ability, when the total amount of the α-olefin copolymer (B2) is considered to be 100 mol%, and 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 balance of performance of the biaxially oriented polypropylene film 100 in terms of thermal dimensional stability, water vapor barrier properties, bag-making ability, 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. The amount of α-olefin-derived structural units 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 comprises a random copolymer of propylene and one or more α-olefins selected from the group consisting of 1-butene and 1-octene, and even more preferably comprises a random copolymer of propylene and 1-butene. The α-olefin copolymer (B2) in the biaxially oriented film layer 101 may be used alone or in combination of two or more types.

[0061] Polymer (B) can be produced by various methods. For example, it can be produced using known catalysts such as Ziegler-Natta catalysts or metallocene catalysts.

[0062] (Other ingredients) The propylene polymer composition of this embodiment may optionally contain various additives such as tackifiers, heat stabilizers, weather stabilizers, antioxidants, ultraviolet absorbers, lubricants, slip agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, and inorganic or organic fillers, to the extent that they do not impair the purpose of this embodiment.

[0063] (Method for preparing a propylene polymer composition) The propylene polymer composition of this embodiment can be prepared by mixing or melting / kneading each component using a dry blender, tumbler mixer, Banbury mixer, single-screw extruder, twin-screw extruder, high-speed twin-screw extruder, hot roll, etc.

[0064] [Surface resin layer] The biaxially oriented polypropylene film 100 is preferably further provided with a surface resin layer 103 on at least one surface of the biaxially oriented film layer 101, from the viewpoint of imparting functions such as heat-resistant adhesion, heat-sealability, antistatic properties, blocking resistance, printability, and slipperiness to the film surface, depending on the purpose. The surface resin layer 103 may be provided on both sides of the biaxially oriented film layer 101. By providing the surface resin layer 103 on both sides of the biaxially oriented film layer 101, different functions can be imparted to each surface of the film. Furthermore, depending on the purpose, the surface resin layer 103 is preferably provided as the outermost layer of the biaxially oriented polypropylene film 100 in order to further improve the functions of the biaxially oriented polypropylene film 100, such as heat fusion resistance, heat sealability, antistatic properties, blocking resistance, printability, and slip resistance.

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

[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 functions of the biaxially oriented polypropylene film 100 such as heat resistance, antistatic properties, blocking resistance, printability, and slip resistance, 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 3.0 μm or less, from the viewpoint of further improving the balance of performance such as heat resistance, thermal dimensional stability, moldability, cost, mechanical properties, transparency, environmental compatibility, and lightweight properties of the biaxially oriented polypropylene film 100. 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 oriented film layer 101. In other words, in this embodiment, when the surface resin layer 103 is provided on both sides of the biaxially oriented film layer 101, the above thickness of the surface resin layer 103 refers to the thickness of the surface resin layer 103 provided on one side of the biaxially oriented film layer 101.

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

[0068] It is preferable that the surface resin layer 103 is formed by biaxial stretching simultaneously with the film layer 101, which is in its pre-biaxial stretching state. This allows for the production of a biaxially stretched polypropylene film 100 using a molding method such as co-extrusion, i.e., a laminated film produced in a single molding process, thereby further simplifying the manufacturing process of the biaxially stretched polypropylene film 100. Therefore, it is preferable that the surface resin layer 103 is biaxially stretched.

[0069] Furthermore, the surface resin layer 103 may be surface-treated to further improve the balance between the printability and blocking resistance of the biaxially oriented polypropylene film 100. Specifically, surface activation treatments such as corona treatment, flame treatment, plasma treatment, primer coating, and ozone treatment may be performed.

[0070] The surface resin layer 103 is composed of, for example, a polyolefin-based resin composition (A) containing a polyolefin. The polyolefin constituting the surface resin layer 103 includes, for example, one or more selected from the group consisting of homopolymers or copolymers of α-olefins such as ethylene, propylene, 1-butene, hexene-1, 4-methylpentene-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 2 to 10 carbon atoms; ethylene-vinyl acetate copolymer (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-making properties, fluidity, and moldability of the biaxially oriented polypropylene film 100. Here, the preferred embodiment of the homopolypropylene constituting the surface resin layer 103 is the same as that of homopolypropylene (A) described above. That is, the homopolypropylene constituting the surface resin layer 103 preferably includes homopolypropylene (A) described above.

[0071] 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-making properties, fluidity, and moldability of the biaxially oriented polypropylene film 100, the polyolefin content in the polyolefin resin composition (A), i.e., the entire 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 total polyolefin resin composition (A), i.e., the entire surface resin layer 103, is considered as 100% by mass. 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-making properties, fluidity, and moldability of the biaxially oriented polypropylene film 100, the content of homopolypropylene (A) in the polyolefin resin composition (A), i.e., the entire 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 total polyolefin resin composition (A), i.e., the entire surface resin layer 103, is considered as 100% by mass.

[0072] (Other ingredients) The polyolefin resin composition (A) constituting the surface resin layer 103 may optionally contain various additives such as tackifiers, heat stabilizers, weather stabilizers, antioxidants, ultraviolet absorbers, lubricants, slip agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, and inorganic or organic fillers, to the extent that they do 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 melting / kneading each component using a dry blender, tumbler mixer, Banbury mixer, single-screw extruder, twin-screw extruder, high-speed twin-screw extruder, hot roll, etc.

[0074] <Method for manufacturing biaxially oriented polypropylene film> The biaxially oriented polypropylene film 100 can be obtained, for example, by co-extruding a propylene polymer composition for forming a biaxially oriented film layer 101 and a polyolefin resin composition (A) for forming a surface resin layer 103 as needed into a film, and then biaxially oriented the resulting film 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 include T-die extruders, multi-layer T-die extruders, inflation molding machines, or multi-layer inflation molding machines. For biaxial stretching conditions, for example, known manufacturing conditions for OPP film can be adopted. More specifically, in the sequential biaxial stretching method, for example, the stretching temperature in the MD direction should be 100°C to 145°C, the stretching ratio in the MD direction should be in the range of 4.5 to 6 times, the stretching temperature in the TD direction should be 130°C to 190°C, and the stretching ratio in the TD direction should be in the range of 9 to 11 times. Furthermore, the biaxially oriented polypropylene film 100 can also be obtained by separately molding a biaxially oriented film layer 101 and, if necessary, a surface resin layer 103, and then laminating and heat-molding these layers.

[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 packaging body.

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

[0077] The food packaging of this embodiment includes the food packaging of this embodiment and the food contained within the food packaging. In other words, the food packaging of this embodiment is a food packaging of this embodiment in which food is contained.

[0078] The embodiments of the present invention have been described above with reference to the drawings, but 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 sealant layers and coating layers. Furthermore, the biaxially oriented polypropylene film 100 can also be used as a raw material for coating. [Examples]

[0079] This embodiment will be described in detail below with reference to examples and comparative examples. However, this embodiment is not limited in any way 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: 3.0g / 10 min, melting point: 165℃, isotactic mesopentad fraction (mmmm): 98.0%, Mw: 370,000, Mn: 68,000, Mw / Mn: 5.4, propylene-derived component content: 100 mol%) h-PP2: Homopolypropylene (MFR: 3.0g / 10 min, Melting point: 159℃, Isotactic mesopentad fraction (mmmm): 97.5%, Mw: 469,000, Mn: 56,300, Mw / Mn: 8.3, Ethylene-derived component content: 1.2 mol%, Propylene-derived component content: 98.8 mol%) (2) Polymer (B) • r-PP1: Random polypropylene (MFR: 7.0g / 10 min, melting point: 139℃, Mw: 322,000, Mn: 50,700, Mw / Mn: 6.4, ethylene-derived component content: 3.2 mol%, 1-butene-derived component content: 2.9 mol%, propylene-derived component content: 93.9 mol%) • r-PP2: Random polypropylene (MFR: 2.4g / 10min, melting point: 143℃, Mw: 436,000, Mn: 66,000, Mw / Mn: 6.6, ethylene-derived component content: 4.4 mol%, propylene-derived component content: 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 (Bruker BioSpin, AVANCE III cryo-500). 13 Measurements were performed using 1C-NMR. The sample was dissolved in the following measurement solvent and measured, and the integrated intensity of each signal was used for evaluation. [Measurement conditions] Nucleus for measurement: 13 C(125MHz) Measurement mode: Single-pulse proton broadband decoupling Pulse width: 45° Points: 64k Repeat time: 5.5 seconds Solvent used for measurement: orthodichlorobenzene / deuterated 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) Measurements were taken in accordance with ASTM D1238, under conditions of 230°C and a 2.16 kg load.

[0083] (3) Melting points of homopolypropylene (A) and polymer (B) For homopolypropylene (A) and polymer (B), a differential scanning calorimeter (product name: Q200DSC, manufactured by TA Instruments Corporation) was used to perform the following differential scanning calorimeter measurements under a nitrogen atmosphere: a first run consisting of heating from -30°C to 250°C at a heating rate of 10°C / min and cooling from 250°C to -30°C at a cooling rate of 10°C / min; and a second run consisting of heating from -30°C to 250°C at a heating rate of 10°C / min. The peak temperature of the maximum melting peak in the DSC curve during the 2nd run was defined 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 homopolypropylene (A) and polymer (B) were measured by gel permeation chromatography (GPC). The GPC method was performed using a gel permeation chromatograph (Tosoh Corporation, HLC-8321 GPC / HT type) as follows. The separation columns consisted of two TSKgel GNH6-HT 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% by mass of BHT as an antioxidant, transferred at a rate of 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. Molecular weight was determined as polypropylene equivalent, based on monodisperse polystyrene.

[0085] (5) Measurement of the content of α-olefin-derived structural units other than propylene in homopolypropylene (A) and polymer (B), and the content of α-olefin-derived structural units other than propylene in biaxially oriented polypropylene film. The content of α-olefin-derived structural units other than propylene in homopolypropylene (A) and polymer (B), and the content of α-olefin-derived structural units other than propylene in biaxially oriented polypropylene film were measured using a nuclear magnetic resonance spectrometer (Bruker BioSpin, AVANCE III cryo-500). 13 Measurements were performed by 13C-NMR. The sample was dissolved in the following measurement solvent and measured, and the integrated intensity of each signal was evaluated. 13Based on 13C NMR spectroscopy, the signals were assigned using references such as Macromolecules (1982) Ethylene-1-Butene Copolymers. 1. Commoner 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. The content of ethylene-derived constituent units (mol%), propylene-derived constituent units (mol%), and 1-butene-derived constituent units (mol%) in each polymer were then quantified. [Measurement conditions] Nucleus for measurement: 13 C(125MHz) Measurement mode: Single-pulse proton broadband decoupling Pulse width: 45° Points: 64k Repeat time: 5.5 seconds Solvent used for measurement: orthodichlorobenzene / deuterated benzene (4:1) Sample concentration: 50 mg / 0.6 mL Measurement temperature: 120℃ Window function: exponential (BF: 0.5Hz) Furthermore, the content of α-olefin-derived structural units other than propylene in biaxially oriented polypropylene film was measured using biaxially oriented polypropylene film as the sample.

[0086] (6) Tensile modulus A 15mm x 15cm test specimen was cut from a biaxially oriented polypropylene film. Then, using a tensile testing machine manufactured by Orientec Co., Ltd., the tensile modulus T1 in the MD direction and the tensile modulus T2 in the TD direction of the test specimen were measured in accordance with JIS K7127 (1999) under the conditions of a measurement temperature of 23±2℃, 50±5%RH, and a tensile speed of 5mm / min.

[0087] (7) Differential scanning calorimetry of biaxially oriented polypropylene film A test piece of approximately 5.0 mg was cut from a biaxially oriented polypropylene film. Next, a first differential scanning calorimetry (1st Run) was performed on the sample using a differential scanning calorimetry meter (product name: Q200DSC, manufactured by TA Instruments Corporation). This involved heating the sample from -50°C to 250°C at a heating rate of 5°C / min, and then cooling it from 250°C to -50°C at a cooling rate of 5°C / min. From the obtained DSC curve, the principal melting point (°C), the total heat of fusion ΔH (J / g) of the film, and the heat of fusion below 165°C ΔH (J / g) were determined. Here, the peak temperature of the maximum melting peak in the DSC curve was defined as the principal melting point. The total heat of fusion ΔH (J / g) of the film was calculated from the melting peak area of ​​the DSC curve, in accordance with JIS K 7122:1987 (with a heating rate of 5°C / min). If multiple melting peaks appeared on the DSC curve, the sum of the areas of the multiple melting peaks was used as the total heat of fusion (ΔH) of the film. The heat of fusion ΔH (J / g) below 165℃ represents the heat of fusion within the range of 165℃ or below, out of the total heat of fusion ΔH (J / g) of the entire film.

[0088] Next, the crystallinity ratio (%), crystallinity (%), amorphous content (%), and crystalline content below 165°C were determined using the following formulas. The heat of fusion of the perfect polypropylene crystal used in the calculation was 209 J / g, as described in Macro Molecular Chemie, Rapid Communication, Vol. 9, No. 75 (1988). Crystallization ratio (%) below 165℃ = 100 × Heat of fusion below 165℃ ΔH (J / g) / Total heat of fusion of the film ΔH (J / g) Crystallinity (%) = 100 × total heat of fusion of the film ΔH (J / g) / heat of fusion of perfectly crystalline polypropylene (209 J / g) Amorphous amount (%) = 100-Crystallinity (%) Crystallinity below 165℃ (%) = Degree of crystallinity (%) × Ratio of crystals below 165℃ (%) / 100

[0089] (8) Water vapor transmission A biaxially oriented polypropylene film was folded so that the surface resin layer 1 was on the inside, and two sides were heat-sealed to form a bag. Then, calcium chloride was added as the contents. Next, the other side was heat-sealed to create a bag with a surface area of ​​0.01 m². 2 A bag was fabricated to achieve the following conditions. Next, the resulting bag was stored for 72 hours at 40°C and 90% RH. The mass of calcium chloride was measured before and after storage, and the water vapor transmission rate (g / m³) was calculated from the difference. 2 The values ​​for each 24 hours were calculated.

[0090] (9) Thermal expansion coefficient and thermal contraction coefficient of biaxially oriented polypropylene film at 120°C The thermal expansion coefficient and thermal contraction coefficient of biaxially oriented polypropylene film at 120°C were measured in accordance with JIS C2151:2019. First, a 10cm x 10cm test specimen was cut from a biaxially oriented polypropylene film. Next, the test specimen was heat-treated at 120°C for 15 minutes. During this time, the test specimen was suspended without any force applied in a hot air circulating constant temperature bath (ADVANTEC, product name: DRM620DE). After the test specimen was cooled to room temperature, its length was measured. Then, the length of the test specimen in the TD direction after heat treatment was defined as TD1 [cm], and the thermal expansion coefficient [%] in the TD direction was calculated as 100 × (TD1 - 10) / 10. Similarly, the length of the test specimen in the MD direction after heat treatment was defined as MD1 [cm], and the thermal shrinkage coefficient [%] in the MD direction was calculated as 100 × (10 - MD1) / 10. The above measurements were performed three times, and the average of the obtained measurements was adopted as the thermal expansion coefficient and thermal shrinkage coefficient of the biaxially oriented polypropylene film at 120°C, respectively.

[0091] (10) Thermal shrinkage rate of biaxially oriented polypropylene film at 150°C The thermal shrinkage rate of biaxially oriented polypropylene film at 150°C was measured in accordance with JIS C2151:2019. First, a 10cm x 10cm test specimen was cut from a biaxially oriented polypropylene film. Next, the test specimen was heat-treated at 150°C for 15 minutes. During this time, the test specimen was suspended without any force applied in a hot air circulating constant temperature bath (ADVANTEC, product name: DRM620DE). After the test specimen was cooled to room temperature, its length was measured. Then, the length of the test specimen in the TD direction after heat treatment was defined as TD1 [cm], and the length of the test specimen in the MD direction after heat treatment was defined as MD1 [cm]. TD [%] is calculated by 100 × (10 - TD1) / 10, X MD The percentage [%] was calculated using the formula 100 × (10 - MD1) / 10. The above measurement was performed three times, and the average of the obtained values ​​was adopted as the heat shrinkage rate of the biaxially oriented polypropylene film at 150°C.

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

[0093] (12) Heat fusion strength at 200°C A laminated film was obtained by heat-sealing the surface resin layer 1 (heat-resistant fusion layer) of two biaxially oriented polypropylene films, each cut to a width of 15 mm, at 200°C, a pressure of 2.0 kgf, and a sealing time of 1.0 second. Next, the two biaxially oriented polypropylene films were peeled apart under the conditions of 15 mm width, 90-degree peeling, peeling speed of 300 mm / min, and tensile strength in the TD direction, and the peel strength at that time was defined as the heat-fusion strength.

[0094] (13) Bag-making properties (presence or absence of wrinkles when heat-sealed at 180°C) A laminated film was obtained by heat-sealing the surface resin layer 1 (heat-resistant fusion layer) of two biaxially oriented polypropylene films, each cut to a width of 15 mm, at 180°C, a pressure of 2.0 kgf, and a sealing time of 1.0 second. Next, the presence or absence of heat wrinkles in the sealed area was visually observed.

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

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

[0097] [Table 1]

[0098] The biaxially oriented polypropylene film of the example showed improved thermal dimensional stability compared to the biaxially oriented polypropylene film of the comparative example. [Explanation of Symbols]

[0099] 100 Biaxially Oriented Polypropylene Film 101 Biaxially oriented film layer 103 Surface resin layer

Claims

1. The film comprises a biaxially oriented film layer containing a propylene polymer, A biaxially oriented polypropylene film having a crystal ratio of 38% or more below 165°C, as determined by differential scanning calorimetry, The amount of α-olefin-derived constituent units other than propylene contained in the biaxially oriented polypropylene film is 0.3 mol% or more and 50.0 mol% or less, when the total amount of monomer-derived constituent units contained in the biaxially oriented polypropylene film is taken as 100 mol%. The main melting point of the biaxially oriented polypropylene film, as determined by differential scanning calorimetry, is 165°C or higher and 180°C or lower. A biaxially oriented polypropylene film having a crystallinity of 40% or more and 80% or less, as determined by differential scanning calorimetry.

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

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

4. The biaxially oriented polypropylene film according to claim 1, wherein the amount of crystals at temperatures below 165°C is 20% or more.

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

6. The biaxially oriented polypropylene film according to claim 5, wherein the surface resin layer comprises homopolypropylene (A).

7. The biaxially oriented polypropylene film according to claim 6, wherein the content of homopolypropylene (A) in the surface resin layer is 75% by mass or more and 100% by mass or less when the total mass of the surface resin layer is taken as 100% by mass.

8. The biaxially oriented polypropylene film according to claim 5, wherein the thickness of the surface resin layer is 0.1 μm or more and 10.0 μm or less.

9. 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.

10. The tensile modulus T in the MD direction of the biaxially oriented polypropylene film is measured in accordance with JIS K7127 (1999) using a tensile testing machine 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 T in the TD direction ２ The sum of (T １ +T ２ The biaxially oriented polypropylene film according to claim 1, wherein the pressure is 3,000 MPa or more and 10,000 MPa or less.

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

12. A biaxially oriented polypropylene film according to claim 1, which is a food packaging film.

13. A food packaging material using the biaxially oriented polypropylene film described in claim 1.

14. A food packaging body according to claim 13, A food packaging body containing the food inside the aforementioned food packaging body.

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