Polypropylene film, laminates, packaging materials and bundles

Abstract

The purpose of this invention is to provide a polypropylene film that is structurally stable to heat during vapor deposition when used for packaging purposes, exhibits moderate slippage without the use of anti-blocking agents or particles, and thus possesses excellent water vapor barrier and oxygen barrier properties, particularly when laminating transparent vapor-deposited layers. This polypropylene film is characterized by having at least two layers (layer A and layer B) primarily composed of polypropylene resin, wherein layer B comprises a thermoplastic resin incompatible with the polypropylene resin, and when the skewness Ssk of layer A and layer B, measured by non-contact three-dimensional surface shape measurement, is set as Ssk(A) and Ssk(B) respectively, Ssk(B) is 5 or more, and Ssk(A) is less than 5.

Description

Technical Field

[0001] This invention relates to polypropylene films, laminates, packaging materials, and bundles that are particularly suitable for packaging applications. Background Technology

[0002] Polypropylene film, due to its excellent transparency, mechanical properties, and electrical properties, is used in various applications such as packaging, tapes, cable packaging, and electrical insulation (e.g., capacitors). In packaging applications where gas barrier properties are required, laminated films formed by depositing a thin film of aluminum (hereinafter sometimes referred to as "Al") onto the polypropylene film have become widely used. However, films obtained through Al deposition are opaque, making them unsuitable for applications requiring visibility of the contents. Furthermore, while recycling of packaging plastics has become more active in recent years, films containing Al deposition layers suffer from insufficient recyclability, making them difficult to distinguish visually from Al foil laminates and prone to discoloration after recycling.

[0003] As described above, there has been a trend to replace conventional Al vapor-deposited layers with transparent vapor-deposited layers such as alumina (hereinafter, sometimes referred to as AlOx). Using these transparent vapor-deposited layers can improve the transparency and recyclability of packaging materials. However, since transparent vapor-deposited layers are generally thinner and more brittle than Al vapor-deposited layers, problems exist such as peeling during the formation of the vapor-deposited layer or in subsequent processes like bag manufacturing, or the formation of defects such as pinholes and cracks within the vapor-deposited layer, easily compromising water vapor barrier properties and oxygen barrier properties.

[0004] Furthermore, due to the requirement for appropriate conveyability during vapor deposition and bag making processes, anti-blocking agents and particles are sometimes added to the film surface to create irregularities and impart slip properties. However, in processed films with vapor-deposited layers, the protrusions formed by these anti-blocking agents and particles are hard. Therefore, when transported as rolled products, the vapor-deposited layer is ground down, resulting in defects and damage such as pinholes and cracks, and the water vapor barrier and oxygen barrier properties are easily compromised.

[0005] As a suitable polypropylene film for packaging applications, conventional methods have included controlling the molecular weight of the polypropylene resin to achieve high rigidity (e.g., Patent Document 1) to improve the planar orientation of the polypropylene film, and using highly crystalline raw materials and subjecting them to high-ratio stretching along the length direction, or further longitudinal stretching along the length direction after biaxial stretching, to improve the planar orientation and thus enhance water vapor barrier properties (e.g., Patent Document 2). Furthermore, as a packaging material, methods have included adding particles to create an uneven, slip-resistant surface (e.g., Patent Document 3) to achieve suitable transportability during vapor deposition and bag making (and adding particles to the film surface to create a smooth texture), and laminated films with particles added to the film surface to achieve a smooth texture by controlling the thickness of each layer (e.g., Patent Document 4). On the other hand, as a polypropylene film for bonding and demolding, methods have included dispersing a high-melting-point resin different from the polypropylene resin on the surface of the polypropylene film to achieve a smooth texture without adding particles (e.g., Patent Document 5).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2014-055283

[0009] Patent Document 2: Japanese Patent Application Publication No. 2001-040111

[0010] Patent Document 3: Japanese Patent Application Publication No. 2020-040361

[0011] Patent Document 4: International Publication No. 2018 / 181011

[0012] Patent Document 5: International Publication No. 2018 / 147334 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] However, the polypropylene films described in Patent Documents 1 and 2 are single-layer structures, making it impossible to control the surface unevenness on both sides of the film surface, resulting in insufficient control over the height of the fibrillated fibers. Therefore, especially when a transparent vapor-deposited layer is laminated, problems arise such as insufficient adhesion of the vapor-deposited layer, inadequate film homogeneity, and reduced water vapor and oxygen barrier properties. The polypropylene films described in Patent Documents 3 and 4 contain particles in the heat-sealing layer, leading to defects such as damage, scratches, pinholes, and cracks when vapor-depositing is performed on the opposite surface. Furthermore, the film in Patent Document 5 creates unevenness on both surfaces by dispersing a high-melting-point resin (different from the polypropylene resin) on the polypropylene film surface in two layers, but it lacks sufficient control over the front and back sides. Additionally, it lacks a technology for heat stabilization when setting the vapor-deposited layer on the surface, resulting in problems such as insufficient adhesion of the vapor-deposited film, inadequate film homogeneity, and reduced water vapor and oxygen barrier properties.

[0015] Therefore, the objective of this invention is to provide a polypropylene film that, when used for packaging purposes, is structurally stable to the heat during vapor deposition, has moderate slippage without the use of anti-blocking agents or particles, and thus exhibits excellent water vapor barrier and oxygen barrier properties, particularly when laminating transparent vapor-deposited layers.

[0016] Problem-solving methods

[0017] In order to solve the above-mentioned problems, the inventors have repeatedly conducted in-depth research and thus invented the following first polypropylene film and second polypropylene film of the present invention.

[0018] The first polypropylene film of the present invention is characterized in that it has at least two layers (layer A and layer B) with polypropylene resin as the main component, wherein layer B contains a resin incompatible with polypropylene resin, and when the skewness Ssk of layer A and layer B, as determined by non-contact three-dimensional surface shape measurement, is set to Ssk(A) and Ssk(B) respectively, Ssk(B) is 5 or more and Ssk(A) is less than 5.

[0019] The second polypropylene film of the present invention has at least two layers (layer A and layer B) with polypropylene resin as the main component, wherein layer B contains a thermoplastic resin incompatible with polypropylene resin. When the skewness Ssk of layer A, measured by non-contact three-dimensional surface shape measurement, is set as Ssk(A), and the surface roughness Sa of layer A and layer B are set as Sa(A) and Sa(B), respectively, Ssk(A) is less than 5, and Sa(A) and Sa(B) satisfy Equation 1.

[0020] Equation 1: Sa(B) / Sa(A)>1.1.

[0021] Invention Effects

[0022] According to the present invention, by means of thermal stability during vapor deposition, moderate sliding properties are achieved without the use of anti-blocking agents or particles, thereby obtaining polypropylene films with excellent water vapor barrier and oxygen barrier properties, especially when laminating transparent vapor-deposited layers. Detailed Implementation

[0023] The polypropylene film of the present invention will now be described in detail. It should be noted that, in the present invention, the length direction refers to the direction in which the film travels during the manufacturing process of the polypropylene film, and when the polypropylene film is wound into a roll, it refers to the winding direction of the roll. Furthermore, the width direction refers to the direction orthogonal to the length direction within the film surface.

[0024] The first polypropylene film of the present invention is characterized in that it has at least two layers (layer A and layer B) with polypropylene resin as the main component, wherein layer B contains a resin incompatible with polypropylene resin, and when the skewness Ssk of layer A and layer B, as determined by non-contact three-dimensional surface shape measurement, is set to Ssk(A) and Ssk(B) respectively, Ssk(B) is 5 or more and Ssk(A) is less than 5.

[0025] The second polypropylene film of the present invention is characterized in that it has at least two layers (layer A and layer B) with polypropylene resin as the main component, wherein layer B contains a thermoplastic resin incompatible with polypropylene resin, and when the skewness Ssk of layer A, measured by non-contact three-dimensional surface shape measurement, is set as Ssk(A), and the surface roughness Sa of layer A and layer B are set as Sa(A) and Sa(B), respectively, Ssk(A) is less than 5, and Sa(A) and Sa(B) satisfy Equation 1.

[0026] Equation 1: Sa(B) / Sa(A)>1.1.

[0027] Hereinafter, the first and second polypropylene films of the present invention will sometimes be referred to as the present invention or the polypropylene film of the present invention. It should be noted that, as described below, Ssk(A), Ssk(B), Sa(A), and Sa(B) are parameters related to the shape and roughness of the surface. Therefore, layers A and B are both located on the outermost surface.

[0028] In this invention, a polypropylene film refers to a sheet-shaped molded body containing 80% to less than 100% by mass, preferably 80% to less than 99.9% by mass, of a polypropylene resin when all constituent components are considered as 100% by mass. A polypropylene resin refers to a resin in which 90% to less than 100% of the structural units constituting the resin are propylene units when all structural units constituting the resin are considered as 100 mol%. "A layer with polypropylene resin as the main component" refers to a layer containing more than 50% to less than 100% by mass of a polypropylene resin when all constituent components are considered as 100% by mass. It should be noted that the term "main component" can be interpreted in the same way below. "Having at least two layers (layer A, layer B) with polypropylene resin as the main component" refers to a scheme having multiple layers with polypropylene resin as the main component, and at least one layer having a different composition from the other layers.

[0029] One method to impart a smooth surface to polypropylene film is by adding anti-blocking agents or particles. In this method, the anti-blocking agents or particles form protrusions on the film surface, thus imparting processability during vapor deposition and bag making. However, when forming rolls from such laminates with vapor-deposited layers on the film surface, the protrusions formed by the anti-blocking agents or particles are hard. This can sometimes lead to defects and damage to the vapor-deposited film, such as grinding of the opposite layer, pinholes, and cracks, as well as compromised water vapor barrier and oxygen barrier properties.

[0030] In addition to adding anti-blocking agents and particles, a method based on crystallization phase change is generally preferred as a way to impart slip properties. More specifically, this involves setting the temperature at which the molten resin composition is cured on a casting (cooling) drum after melt extrusion in the film-forming process to a high temperature, for example, 60°C or higher, thereby forming β-crystal spherulites. In the stretching process, the thermally unstable β-crystal phase is transformed into α-crystals, thereby forming an uneven surface on the film. However, for the polypropylene film of the present invention, considering the formation of a uniform and homogeneous vapor-deposited film and the acquisition of excellent water vapor barrier and oxygen barrier properties, the surface of the film on which vapor deposition is performed is preferably a smooth surface, therefore, the casting temperature is preferably low. Furthermore, sometimes a polyolefin resin with low crystallinity and low melting point is used on the surface of the heat-sealing layer, in which case it is sometimes difficult to apply the aforementioned method based on crystallization phase change.

[0031] Therefore, considering the above aspects, from the perspective of imparting a smooth feel, it is important that the polypropylene film of the present invention has at least two layers (layer A and layer B) with polypropylene resin as the main component, and layer B contains a thermoplastic resin that is incompatible with polypropylene resin.

[0032] By blending polypropylene resins with thermoplastic resins incompatible with polypropylene resins, the surface of the polypropylene film (B layer) can be endowed with surface irregularities utilizing its domain structure. Furthermore, in the film manufacturing process, by setting the curing temperature on the cooling drum after melt extrusion to 10°C or higher and 40°C or lower, preferably 10°C or higher and 35°C or lower, more preferably 10°C or higher and 30°C or lower, and particularly preferably 10°C or higher and 25°C or lower, minute α-crystalline spherulites or mesocrystalline phase structures can be preferentially formed, suppressing the formation of irregularities originating from the aforementioned β-crystals. It should be noted that the term "thermoplastic resin incompatible with polypropylene resins" is sometimes referred to as "incompatible resin" below.

[0033] As the incompatible resin, polymethylpentene resins are preferred, for example. Here, in layer B, which contains both polypropylene resin and the incompatible resin, by making the α-crystalline spherulites small or by forming all or part of the polypropylene resin component as an intermediate phase, the interfacial delamination between the incompatible resin domains and the polypropylene resin that occurs during stretching can be suppressed. By suppressing interfacial delamination, surface protrusions can be formed without causing whitening of the polypropylene film, reducing the likelihood of uneven vapor deposition due to wrinkles during vapor deposition and conveying wrinkles during bag making, thus achieving good processing adaptability.

[0034] In the B layer of the polypropylene film constituting the present invention, the content of the incompatible resin is preferably 0.1% by mass or more and 10% by mass or less in 100% by mass of the total layer. More preferably, it is 0.5% by mass or more and 6% by mass or less, further preferably 1% by mass or more and 4% by mass or less, and most preferably 1% by mass or more and 2% by mass or less. By making the content of the incompatible resin in the B layer 0.1% by mass or more, surface protrusions can be formed efficiently on the surface of the B layer, thereby improving the slip properties of the B layer surface and reducing conveying wrinkles during vapor deposition and bag making. On the other hand, by making the content of the incompatible resin in the B layer 10% by mass or less, the formation of excessive domains in the B layer can be suppressed, and the reduction in transparency caused by excessive voids generated at the resin interfaces during stretching can be mitigated. It should be noted that there is no particular limitation on the content (mass%) of incompatible resin in layer A. However, considering that Ssk(A) is less than Ssk(B) as described later, it is preferable to be lower than the content (mass%) of incompatible resin in layer B. Alternatively, layer A may not contain incompatible resin.

[0035] In the polypropylene film of the present invention, polymethylpentene resins are particularly preferred as incompatible resins, considering their high affinity with polypropylene resins and the ability to reduce domain size. Furthermore, the melting point of polymethylpentene resins is preferably 185°C to 240°C, more preferably 220°C to 240°C, considering extrusion stability when blended with polypropylene and the surface texture imparted by the domain island structure. Based on these characteristics, in the polypropylene film of the present invention, polymers with 4-methylpentene-1 as the main constituent unit (containing 80 mol% to 100 mol% of the constituent units in 100 mol% of all constituent units) are preferred. Examples of preferred polymers include the "TPX" (registered trademark) MX series, "TPX" (registered trademark) DX series, and "TPX" (registered trademark) RT series sold by Mitsui Chemicals Co., Ltd. under the "TPX" (registered trademark) series. Specifically, considering the high affinity with polypropylene resins and the ability to reduce domain size, "TPX" (registered trademark) MX002, MX004, DX310, DX845, and RT31 are preferred.

[0036] In the first polypropylene film of the present invention, considering both slipperiness and barrier properties, it is important that when the skewness Ssk of layer A and layer B, measured by non-contact three-dimensional surface shape measurement, is set to Ssk(A) and Ssk(B) respectively, Ssk(B) is 5 or more and Ssk(A) is less than 5. Similarly, from the same perspective, in the second polypropylene film of the present invention, it is also important that Ssk(A) is less than 5.

[0037] Here, skewness Ssk (sometimes simply called Ssk.) is a parameter representing the degree of deviation of the surface protrusion shape as determined by non-contact three-dimensional surface shape measurement. Ssk represents the cubic average of Z(x, y) in a dimensionless reference surface formed by the cube of the root-mean-square height Sq, signifying the degree of deviation and indicating the symmetry of peaks and valleys centered on the mean surface. When Ssk < 0, it means a downward skewness relative to the mean line, i.e., more valleys compared to peaks. Conversely, when Ssk > 0, it means an upward skewness relative to the mean line, i.e., more peaks compared to valleys. And when Ssk = 0, it means no deviation relative to the mean line.

[0038] Ssk(Ssk(A), Ssk(B), and Ssk(D) described later) can be measured using a known non-contact three-dimensional surface shape measuring instrument. For example, a scanning white light interferometer microscope VS1540 from Hitachi High Tech Sciences Co., Ltd. can be used. It should be noted that the details of the measurement and analysis conditions when using this measuring instrument are shown in the examples.

[0039] In the first polypropylene film of the present invention, by setting Ssk(B) to 5 or more, peaks are appropriately formed on the surface of layer B, resulting in good sliding properties between the polypropylene films or between the polypropylene film and the conveyor roller. Furthermore, by setting Ssk(A) to less than 5, fewer peaks and moderately formed valleys are formed on the surface of layer A. Therefore, the layer (layer D described later), which contains more than 50% by mass and less than 100% by mass of metals and / or inorganic compounds, formed by vapor deposition, will have fewer and more uniformly distributed protrusions. Thus, defects such as pinholes and cracks in layer D can be reduced, resulting in high barrier properties.

[0040] Furthermore, in the second polypropylene film of the present invention, by making Ssk(A) less than 5, the same effect obtained in the first polypropylene film by making Ssk(A) less than 5 can be obtained.

[0041] From the above perspective, in the first polypropylene film, Ssk(B) is preferably 7 or more, more preferably 10 or more. There is no particular upper limit, but 25 is set for feasibility. From the perspective of achieving adequate operability to mitigate uneven vapor deposition caused by wrinkles during vapor deposition and to reduce wrinkles during bag making, 20 is preferred. On the other hand, from the perspective of suppressing water vapor and oxygen permeability of the laminate with layer D and achieving sufficient barrier properties, Ssk(A) is preferably 0 or less, more preferably -5 or less. There is no particular lower limit, but -20 is set for feasibility.

[0042] Furthermore, in the second polypropylene film of the present invention, for the same reason, Ssk(A) is preferably 0 or less, more preferably -5 or less. There is no particular limitation on the lower limit, but it is set to -20 from the perspective of feasibility.

[0043] In the first polypropylene film of the present invention, as a method for controlling Ssk(B) within the above-mentioned range, for example, a method can be listed that adjusts the stretching conditions based on making the blending amount of polypropylene resin and the resin incompatible with polypropylene resin within a preferred range. Regarding the stretching conditions, conditions can be adopted in which the stretching ratio in the length direction is 4.0 times or more, preferably 4.5 times or more, using a successive biaxial stretching method. Alternatively, conditions can be adopted in which the stretching temperature in the length direction is 125°C or less, preferably 120°C or less, more preferably 115°C or less, and even more preferably 105°C or less. It should be noted that these stretching conditions can be used alone or in combination.

[0044] On the other hand, in the first and second polypropylene films of the present invention, as a method for controlling Ssk(A) within the above-mentioned range, for example, a method can be listed where the film-forming conditions and stretching conditions are adjusted based on using a polypropylene resin with high crystallinity (more specifically, a polypropylene resin with a meso-pentameric component ratio of 0.93 or more) and a melting point of 151°C or more (preferably 160°C or more) as the A-layer raw material. As film-forming conditions, it is preferable to use conditions where the surface of the A-layer of the molten sheet falls onto the surface of the cooling drum during film forming, and the cooling and solidification temperature is 35°C or less, preferably 30°C or less. As stretching conditions, it is preferable to use conditions where the stretching ratio in the length direction is 4.0 times or more, preferably 4.5 times or more, using a successive biaxial stretching method, and the stretching temperature in the length direction is 125°C or less, preferably 120°C or less, more preferably 115°C or less, and even more preferably 105°C or less. It should be noted that these film-forming conditions and stretching conditions can be used individually or in combination.

[0045] In the polypropylene film of the present invention, the propylene unit fraction of the resin component constituting layer A is preferably 97.0 mol% or more and 100.0 mol% or less, and is at least the propylene unit fraction of the resin component constituting the entire polypropylene film. Here, "propylene unit fraction of the resin component constituting layer A" refers to the fraction (mol%) of propylene units in layer A when all structural units of the resin component constituting layer A are considered as 100 mol%. Furthermore, "propylene unit fraction of the resin component constituting the entire polypropylene film" refers to the fraction (mol%) of propylene units in the polypropylene film when all structural units of the resin component constituting the polypropylene film are considered as 100 mol%. It should be noted that the propylene unit fraction of the resin component can be obtained through known methods... 13 The determination was performed using C-NMR.

[0046] By ensuring that the propylene unit fraction in layer A is 97.0 mol% or higher, the movement and relaxation of molecular chains on its surface can be suppressed, resulting in a structure that is highly thermally stable during vapor deposition. Therefore, when laminating layers D (represented by the vapor-deposited layer) to form a laminate, it can achieve good water vapor barrier and oxygen barrier properties. From the above perspective, the lower limit of the propylene unit fraction in layer A is preferably 99.0 mol%, more preferably 99.5 mol%. It should be noted that a propylene unit fraction of 99.5 mol% or higher in layer A means that although it may sometimes contain a small amount of impurities, the molecular chains of the polypropylene resin constituting layer A are essentially composed only of polypropylene units. Such polypropylene resin is also called homopolymer polypropylene resin.

[0047] There are no particular limitations on the method for ensuring that the propylene unit fraction in layer A is 97.0 mol% or more and 100.0 mol% or less, or within the aforementioned preferred range. For example, a method using a polypropylene resin in layer A with a propylene unit fraction of 97.0 mol% or more and 100.0 mol% or less can be cited. In this case, by increasing the propylene unit fraction of the polypropylene resin, or by increasing the proportion of the polypropylene resin in layer A, the propylene unit fraction in layer A can be increased.

[0048] In the polypropylene film of the present invention, the melting point of the polypropylene resin, which is the main component of layer A, is preferably 151°C or higher, more preferably 155°C or higher, even more preferably 160°C or higher, further preferably 162°C or higher, particularly preferably 164°C or higher, and most preferably 166°C or higher. By setting the melting point of the polypropylene resin, which is the main component of layer A, to 151°C or higher, layer A maintains high crystallinity, thus reducing the deformation of the polypropylene film caused by heat during vapor deposition.

[0049] In the second polypropylene film of the present invention, considering both slipperiness and barrier properties, it is important that the surface roughness Sa of layer A and layer B, respectively, satisfies Equation 1. Furthermore, from the same perspective, in the first polypropylene film of the present invention, Sa(A) and Sa(B) preferably satisfy Equation 2.

[0050] Equation 1: Sa(B) / Sa(A)>1.1

[0051] Equation 2: Sa(B) / Sa(A)>1.0.

[0052] Here, surface roughness Sa refers to a parameter representing the average absolute value of the height difference between points relative to the average surface area measured by non-contact three-dimensional surface shape measurement. In this measurement, a measuring instrument similar to that used for Ssk can be used. Sa(B) / Sa(A) > 1.1 (the second polypropylene film of the present invention) or Sa(B) / Sa(A) > 1.0 (the first polypropylene film of the present invention) indicates that the surface of layer B is rougher than the surface of layer A, and the surface of layer A is smoother than the surface of layer B. By making the surface of layer B rougher than the surface of layer A, good sliding properties can be achieved when winding the polypropylene film. On the other hand, making the surface of layer A sufficiently smooth allows for uniform thickness of layer D when laminating it, suppressing defects such as pinholes and cracks in layer D. Therefore, the laminate containing layer D can have good water vapor barrier properties and oxygen barrier properties.

[0053] From the above perspective, in the polypropylene film of the present invention, the relationship of Formula 1 is preferably Sa(B) / Sa(A) > 1.2, more preferably Sa(B) / Sa(A) > 1.5, and even more preferably Sa(B) / Sa(A) > 1.8. Considering the balance between slipperiness and barrier properties, the upper limit of Sa(B) / Sa(A) in the polypropylene film of the present invention is preferably 4.0, more preferably 3.5. By making Sa(B) / Sa(A) 4.0 or less, the B layer does not become too rough, the number of protrusions can be suppressed, and thus defects such as pinholes and cracks caused by damage to the D layer due to vapor deposition or other processes can be reduced, maintaining the barrier properties of the laminate. It should be noted that, as a method for making Sa(B) / Sa(A) in the first polypropylene film of the present invention a value greater than 1.0 or the above-mentioned preferred range, and as a method for making Sa(B) / Sa(A) in the second polypropylene film of the present invention a value greater than 1.1 or the above-mentioned preferred range, the same method as the method for adjusting Ssk(A) and Ssk(B) can be used.

[0054] From the perspective of suitability for packaging applications, the thickness of the polypropylene film of the present invention is preferably greater than 10 μm and less than 60 μm. By making the thickness greater than 10 μm, the film is less prone to breakage due to relaxation and tension during vapor deposition and transportation. From the above perspective, the lower limit of the thickness is more preferably 12 μm, further preferably 14 μm, and particularly preferably 19 μm. On the other hand, by setting the thickness to 60 μm or less, not only can good operability be achieved, but manufacturing costs can also be suppressed. From the above perspective, the upper limit of the thickness is more preferably 50 μm, and further preferably 40 μm.

[0055] It should be noted that the thickness of the polypropylene film can be measured using a contact micrometer in an atmosphere of 23°C and 65% RH. For example, an electronic micrometer manufactured by Anritsu Co., Ltd. (Type K-312A) can be used as a contact micrometer.

[0056] There are no particular limitations on the methods used to achieve a thickness greater than 10 μm and less than 60 μm, or within the aforementioned preferred range. For example, methods such as adjusting the discharge rate during melt extrusion of the polypropylene resin composition, adjusting the rotation speed of the casting drum during the cooling and solidification of the molten sheet, adjusting the die lip gap of the die discharging the molten sheet, adjusting the stretch ratio in the length direction, and adjusting the stretch ratio in the width direction can be used. More specifically, the thickness can be reduced by decreasing the discharge rate, increasing the rotation speed of the casting drum, decreasing the die lip gap, and increasing the stretch ratio in the length and width directions.

[0057] Furthermore, in the polypropylene film of the present invention, the thickness of the A layer is preferably 0.3 μm or more and 10 μm or less. By setting it to the above range, even if the surface of the A layer of the polypropylene film is at a low temperature, stretching becomes easier, thus making it easier to achieve high orientation and smoothness. Therefore, when a laminate is formed by laminating the D layer formed by vapor deposition or the like, the thickness of the vapor-deposited film is made uniform, thereby improving the quality of the vapor-deposited film and the water vapor barrier and oxygen barrier properties of the laminate. Considering the above aspects, the thickness of the A layer is more preferably 0.5 μm or more and 5.0 μm or less, and even more preferably 0.8 μm or more and 3.0 μm or less. It should be noted that the method for adjusting the thickness of the A layer can also be the same as the method for making the thickness greater than 10 μm and 60 μm or less or within the above preferred range.

[0058] The thickness of layer A can be measured by preparing an ultrathin section using a microtome, with the cross-section of the polypropylene film along its length-thickness direction as the observation plane, and then determining the thickness based on the cross-sectional photographs obtained using a transmission electron microscope. It should be noted that this method can be used to measure the thickness of any of the layers constituting the polypropylene film or laminate, not just layer A.

[0059] For the polypropylene film of the present invention, considering the need to provide adequate slipability to avoid uneven vapor deposition caused by wrinkles during vapor deposition and wrinkles during bag making, the static friction coefficient (μs) when one surface of the film is overlapped with the opposite surface is preferably 0.3 or more and 1.0 or less. By making μs 0.3 or more, the slipability of the film will not become excessive, and unwinding during film making, vapor deposition, and bag making can be reduced. By making μs 1.0 or less, the reduction of film slipability can be suppressed, thus improving operability and reducing uneven vapor deposition caused by wrinkles during vapor deposition and wrinkles during bag making. Considering the above aspects, μs is more preferably 0.3 or more and 0.8 or less, and more preferably 0.4 or more and 0.6 or less. It should be noted that the static friction coefficient (μs) can be measured according to JIS K 7125 (1999) at 25°C and 65% RH. As a measuring device, for example, a sliding tester manufactured by Toyo Seiki Co., Ltd. can be used (other measuring conditions are shown in the examples).

[0060] As a method to control the static friction coefficient (μs) within the aforementioned range, one example is adjusting the stretching conditions based on a preferred blending amount of polypropylene resin and a resin incompatible with polypropylene resin. Regarding the stretching conditions, a stretching ratio in the length direction of 4.0 times or more, preferably 4.5 times or more, can be achieved using a successive biaxial stretching method. Alternatively, a stretching temperature in the length direction of 125°C or less, preferably 120°C or less, more preferably 115°C or less, and even more preferably 105°C or less, can be used. It should be noted that these stretching conditions can be used individually or in combination.

[0061] For the polypropylene film of the present invention, the sum of the thermal shrinkage rates in the length and width directions after heat treatment at 125°C for 10 minutes is preferably 4.0% or less, more preferably 3.5% or less, further preferably 3.0% or less, and most preferably 2.5% or less. The lower limit is not particularly limited and is approximately -2.0%. When the sum of the thermal shrinkage rates in the length and width directions of the film is 4.0% or less, when a laminate is formed by depositing a D layer, etc., defects such as pinholes and cracks caused by damage to the D layer can be reduced, and the oxygen barrier properties and water vapor barrier properties of the laminate are improved.

[0062] As a method to control the sum of the thermal shrinkage rates in the length and width directions after heat treatment at 125°C for 10 minutes to be below 4.0% or within the aforementioned preferred range, methods include using polypropylene raw materials with a high proportion of racemic five-unit components and low cold xylene-soluble matter (CXS), and appropriately performing heat-fixing and relaxation treatments on the film after biaxial stretching. Additionally, increasing the ratio of incompatible resins in layer B to the previously described preferred range is also effective.

[0063] It should be noted that in the determination of heat shrinkage rate, when it is unclear from the appearance of the film which direction is the length direction and which is the width direction, a rectangular film sample is taken, and the tensile strength (MPa) is measured using a tensile testing machine. The direction that gives the maximum tensile strength is considered the width direction, and the direction orthogonal to it is considered the length direction. Specifically, the following steps are used to determine the width and length directions. First, a rectangular sample with dimensions of 20 mm or more (measurement direction) × 10 mm is randomly taken from the film. The measurement length is set to 20 mm, the tensile speed is set to 300% / min, and the measurement environment is set to 23°C and 65%RH. The tensile strength (MPa) is measured using a tensile testing machine (e.g., Original Tech "Tensilon" (registered trademark) UCT-100). Next, the measurement direction is set to the direction rotated 15° to the right within the film surface, and the same measurement is performed. This measurement is repeated until 12 directions are measured. Finally, by comparing the measured values, the direction in which the maximum fracture strength (MPa) was measured is considered the width direction, and the direction orthogonal to it is considered the length direction.

[0064] In addition, when the tensile strength cannot be determined using a tensile testing machine due to insufficient sample size, the crystal orientation of the α-crystal (110) plane of the polypropylene film is determined using wide-angle X-rays as follows, and the length and width directions are inferred based on the following criteria. That is, X-rays (CuKα rays) are incident perpendicularly to an arbitrarily selected film surface, and the crystal peaks in the 2θ = approximately 14° (α-crystal (110) plane) are scanned in the circumferential direction. The direction with the highest diffraction intensity in the obtained diffraction intensity distribution is regarded as the width direction, and the direction orthogonal to it is regarded as the length direction.

[0065] The polypropylene film of this invention exhibits excellent structural stability to the heat during vapor deposition, particularly when laminated with a transparent vapor-deposited layer, demonstrating good water vapor and oxygen barrier properties. Therefore, it is suitable for packaging applications. There are no particular limitations on the packaging materials that the polypropylene film of this invention can be used to package, including items that are easily deteriorated by water vapor and oxygen, such as food, pharmaceuticals, and flowers.

[0066] Furthermore, the mesopentagonal component ratio of the polypropylene resin used as the main component in the A layer of the polypropylene film of the present invention is preferably 0.93 or higher. More preferably, it is 0.95 or higher, even more preferably 0.96 or higher, and particularly preferably 0.97 or higher. The mesopentagonal component ratio is an indicator of the stereoregularity of the crystalline phase of the polypropylene resin, and is determined by nuclear magnetic resonance (NMR). In the polypropylene film of the present invention, by using a polypropylene resin with a mesopentagonal component ratio of 0.93 or higher as the main component of the A layer, the crystallinity of the A layer is increased, which has the effect of improving the thermal stability of the polypropylene film (especially the A layer). Therefore, when the polypropylene film is used for packaging purposes, deformation caused by heat during vapor deposition is suppressed, the D layer, represented by the vapor-deposited film, is easily and uniformly laminated, and defects such as pinholes and cracks in the D layer are also suppressed. Therefore, the water vapor barrier and oxygen barrier properties of the laminated body containing the D layer can be improved. It should be noted that there is no specific upper limit on the proportion of the meso-five-unit component of the polypropylene resin, which is the main component of layer A.

[0067] In the polypropylene film of the present invention, the polypropylene resin used as the main component in layer A preferably has a polypropylene component (CXS, also known as cold xylene solubles) dissolved in xylene less than 4.0% by mass when the polypropylene film is completely dissolved in xylene and then precipitated at room temperature. Here, cold xylene solubles (CXS) are considered to be components that are difficult to crystallize due to low stereoregularity, low molecular weight, etc. By keeping CXS below 4.0% by mass, the dimensional stability of the polypropylene film at high temperatures is improved. Therefore, when a laminate is formed by forming layer D through vapor deposition or other processes, defects such as pinholes and cracks caused by damage to layer D can be reduced, and the oxygen barrier and water vapor barrier properties of the laminate are improved. Considering the above aspects, CXS is preferably 2.0% by mass or less, more preferably 1.5% by mass or less. To make the CXS content less than 4.0% by mass or within the above-preferred range, methods such as improving the catalytic activity when obtaining the polypropylene resin used, or washing the obtained polypropylene resin with a solvent or propylene monomer itself can be used. Furthermore, there is no particular lower limit for CXS; 0.1% by mass is practical. This is because maintaining CXS above 0.1% by mass can mitigate the deterioration of stretchability during film formation and reduce the occurrence of film rupture. It should be noted that CXS quantification can be performed as follows: dissolve 0.5g of the sample in 100ml of xylene at 135℃, allow it to cool naturally, recrystallize it in a constant temperature water bath at 20℃ for 1 hour, and then filter it. Quantitative evaluation of the polypropylene components dissolved in the filtrate is then performed using liquid chromatography.

[0068] The polypropylene resin used in the A layer of the polypropylene film of the present invention can be one type or a mixture of two or more types. When the D layer is laminated by vapor deposition, an adhesive polypropylene resin can be added to improve the interfacial adhesion between the D layer and the A layer. However, to reduce deformation caused by heat during vapor deposition when manufacturing the polypropylene film, the melting point of the polypropylene resin as the main component is preferably 151°C or higher, more preferably 155°C or higher, more preferably 160°C or higher, further preferably 162°C or higher, particularly preferably 164°C or higher, and most preferably 166°C or higher. By ensuring that the melting point of the polypropylene resin as the main component of the A layer is 160°C or higher, the A layer can maintain high crystallinity, thus reducing deformation of the polypropylene film caused by heat during vapor deposition. In other words, when the D layer is laminated by vapor deposition, defects such as pinholes and cracks in the D layer are reduced, and the water vapor barrier and oxygen barrier properties of the laminate with the D layer are improved.

[0069] Furthermore, the A layer of the polypropylene film of the present invention may arbitrarily contain organic particles, inorganic particles, heat stabilizers, crystallizing nucleating agents, chlorine scavengers, lubricants, antistatic agents, anti-blocking agents, fillers, viscosity modifiers, anti-coloring agents, antioxidants, etc., as needed. However, when a laminate is formed by laminating the D layer by means of vapor deposition, the lower the content of these components in the A layer, the better, considering the improvement of the uniformity of the vapor-deposited layer or the suppression of defects such as pinholes. Specifically, of all components constituting the A layer, it is preferably 3% by mass or less, and more preferably 1% by mass or less.

[0070] In the polypropylene film of the present invention, from the perspective of film-forming properties, the melt flow rate (MFR) of any one of layers A, B, and C (described later) measured at 230°C and 21.18N load is preferably 1 to 20 g / 10 min, more preferably 2 to 10 g / 10 min, and even more preferably 2 to 5 g / 10 min. To ensure that the melt flow rate (MFR) measured under these conditions is as described above, methods such as controlling the average molecular weight and molecular weight distribution can be used.

[0071] The layer structure of the polypropylene film of the present invention is not particularly limited as long as it has a layer A and a layer B, with layer A located on at least one outermost surface and layer B located on the outermost surface opposite to it. That is, it can be configured as two two-layer structures consisting of layer A and layer B, or it can be configured as having other layers between layer A and layer B. As an example of having other layers between layer A and layer B, it is preferable to have a layer (layer C) with polypropylene resin as the main component between layer A and layer B.

[0072] By configuring this structure, the components contained in layer C (described later) can be prevented from seeping to the surface of layer A on one side of the laminated vapor deposition layer, making it easier to uniformly laminate the vapor deposition layer. As the simplest example of this scheme, three three-layer structures of layer A / layer C / layer B can be listed, but other layers can also exist between layer A and layer C or between layer B and layer C.

[0073] The C layer of the polypropylene film of the present invention is not particularly limited in composition as long as it is mainly composed of polypropylene resin, and may also include polypropylene resin with long-chain branched structure, petroleum resin, crystallizing nucleating agent, etc. Furthermore, without impairing the purpose of the present invention, various additives may be included, such as antioxidants, heat stabilizers, chlorine scavengers, lubricants, antistatic agents, fillers, viscosity modifiers, and anti-coloring agents. The C layer of the polypropylene film of the present invention particularly preferably includes petroleum resin among the above-mentioned components. Here, petroleum resin refers to petroleum resin that does not have polar groups composed of hydroxyl, carboxyl, halogen, sulfonyl, or their modified forms; specifically, it is a resin mainly composed of cyclopentadiene or higher olefin hydrocarbons made from petroleum-based unsaturated hydrocarbons.

[0074] By including petroleum resin in the C layer, the uniform stretchability during film formation is improved, and the stretching temperature in the longitudinal direction can be kept below 120°C. Therefore, the heat resistance of the polypropylene film is easily improved, and the static friction coefficient is also easily controlled appropriately. Furthermore, by including petroleum resin in the C layer, the void volume of the amorphous portion of the polypropylene resin can be reduced, thereby improving the water vapor barrier properties of the polypropylene film. Considering the above aspects, when all components of the C layer are considered to be 100% by mass, the amount of petroleum resin added to the C layer is preferably 2% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less, and even more preferably 5% by mass or more and 10% by mass or less.

[0075] Furthermore, considering water vapor barrier properties and productivity, the softening point of the petroleum resin is preferably 90°C or higher and 140°C or lower, more preferably 100°C or higher and 130°C or lower. By setting it to the above range, in addition to improving the water vapor barrier properties of the polypropylene film, it is also easy to improve the uniform stretchability during film formation. Specifically, examples of such petroleum resins include T-REZ HA125 (softening point 125°C) manufactured by JXTG ENERGY Co., Ltd., and "Arukon" (registered trademark) P125 (manufactured by Arukawa Chemical Industry Co., Ltd., softening point 125°C), etc.

[0076] The polypropylene film of the present invention has a structure in which layer A is located on one outermost surface and layer B is located on another outermost surface. In this case, layer B sometimes performs the function of heat sealing. Heat sealing refers to the state (or process) in which the film is melted and pressed together by heating when filling or packaging contents to form a bag. Heat sealability refers to the property of the film sides that are melted and pressed together by heating.

[0077] In the polypropylene film of the present invention, layer B is preferably a heat-sealable layer. Here, a heat-sealable layer refers to a layer whose heat-sealing strength, as measured by the method described later, is 2 N / 25.4 mm or higher.

[0078] As the B layer in the polypropylene film of the present invention, from the perspective of imparting low-temperature and high-speed heat-sealing properties, it is preferable to include a polypropylene resin with low crystallinity and low melting point compared with the polypropylene resin that is the main component of the A layer. Specifically, ethylene-propylene random copolymer, ethylene-propylene-butene random copolymer, propylene-butene random copolymer, etc. can be preferred.

[0079] From the perspective of providing low-temperature and high-speed sealing performance, the melting point of layer B is preferably above 100°C and below 150°C, more preferably above 110°C and below 148°C, and even more preferably above 120°C and below 145°C. It should be noted that the melting point of layer B can be read as the lowest temperature peak among the endothermic peaks generated by melting when analyzing the layer B of the polypropylene film using differential scanning calorimetry (DSC). It should also be noted that, from the perspective of providing moderate slippage without adding particles or lubricating materials, it is important that the layer B of the polypropylene film of the present invention contains resins incompatible with polypropylene resins as described above. However, various additives, such as antioxidants, heat stabilizers, chlorine scavengers, antistatic agents, fillers, viscosity modifiers, and anti-coloring agents, can be included within the scope of the present invention without prejudice to its purpose.

[0080] There are no particular limitations on the method of laminating the B layer. Examples include feed block methods based on melt co-extrusion during film production, multi-manifold methods, extrusion lamination, and dry lamination. Considering production efficiency and cost, melt co-extrusion lamination is preferred. There are no particular limitations on the thickness of the B layer of the polypropylene film. The lower limit of the B layer thickness relative to 100% of the overall thickness of the polypropylene film is preferably 0.5%, more preferably 1%. On the other hand, the upper limit of the B layer thickness relative to 100% of the overall thickness of the polypropylene film is preferably 80%, more preferably 60%, further preferably 40%, and particularly preferably 10%.

[0081] It should be noted that the polypropylene resin used in each of the A, B, and C layers of the polypropylene film of the present invention may include polypropylene resin derived from biomass. When the polypropylene film contains polypropylene resin derived from biomass, if the total polypropylene resin constituting each layer is considered as 100% by mass, its content is preferably 5% by mass or more, more preferably 10% by mass or more. Furthermore, the biomass content of the polypropylene derived from biomass is preferably 10% or more. Additionally, when the polypropylene film of the present invention contains resin components other than polypropylene resins, these components may be derived from biomass. It should be noted that the polypropylene film of the present invention may also contain polypropylene recovered through mechanical or chemical recycling. This can also reduce the environmental impact.

[0082] <Laminated Body>

[0083] Next, the laminate of the present invention will be described. The laminate of the present invention is characterized in that, when the layer comprising a total of more than 50% by mass and less than 100% by mass of metals and / or inorganic compounds is designated as layer D, the aforementioned layer D is in contact with the aforementioned layer A of the polypropylene film of the present invention, and the thickness of the aforementioned layer D is 50 nm or less.

[0084] The laminate of the present invention comprises the polypropylene film of the present invention and a layer (D layer) containing a total of more than 50% by mass and less than 100% by mass of a metal and / or inorganic compound. By configuring it in this way, high water vapor barrier properties and oxygen barrier properties can be achieved. Here, "a layer containing more than 50% by mass of an inorganic compound or metal" means, when all components constituting the layer are considered as 100% by mass, a layer containing only metals more than 50% by mass, a layer containing only inorganic compounds more than 50% by mass, or a layer containing both metals and inorganic compounds, with their total exceeding 50% by mass. The inorganic compound or metal used as the D layer is suitable from the perspectives of improving adhesion to the polypropylene film, improving gas barrier properties when laminated to the polypropylene film, and reducing environmental impact; for example, aluminum, alumina, silicon oxide, cerium oxide, calcium oxide, diamond-like carbon film, or mixtures thereof are suitable.

[0085] From the perspective of improving recyclability and barrier properties when the laminate is reused as a resin or film, and reducing its rupture resistance, the thickness of layer D in the laminate of the present invention is 50 nm or less, preferably 40 nm or less, more preferably 30 nm or less, and even more preferably 20 nm or less. There is no particular limitation on the lower limit; from the perspective of barrier performance, it is set to 1 nm.

[0086] As a method for forming a laminate by forming a D layer on the polypropylene film of the present invention, methods such as coating, vapor deposition, and lamination can be included. From the perspective of not being dependent on humidity and being able to exhibit excellent gas barrier properties in the thin film, vapor deposition is preferred. As a vapor deposition method, physical vapor deposition methods such as vacuum vapor deposition, EB vapor deposition, sputtering, and ion plating, as well as various chemical vapor deposition methods such as plasma CVD, can be used. From the perspective of productivity, vacuum vapor deposition is particularly preferred.

[0087] From the perspective of preserving the contents when used as packaging material, the water vapor transmission rate of the laminate of the present invention is preferably 2.0 g / m³. 2 / day or less, preferably 1.0g / m 2 Below / day, further preferably 0.5g / m 2 / day or less. By setting it to this range, especially when used for food packaging, the deterioration caused by the absorption or release of moisture by the contents can be reduced.

[0088] Furthermore, considering the preservation of the contents when used as packaging material, the oxygen permeability of the laminate of the present invention is preferably 40 cc / m³. 2 Less than / day, preferably 30cc / m 2 Less than / day, further preferred is 20cc / m 2 Less than / day, optimally 10cc / m 2 / day or less. By setting it to this range, especially when used for food packaging, the deterioration caused by oxidation of the contents can be reduced.

[0089] In the laminate of the present invention, it is preferable that when the skewness Ssk of the D layer, measured using a non-contact three-dimensional surface roughness meter, is set to Ssk(D), Ssk(D) is less than 5. By setting Ssk(D) to less than 5, fewer peaks are formed and valleys are formed appropriately, resulting in fewer protrusions on the D layer after vapor deposition, thus achieving a state where the vapor-deposited layer is formed with a uniform height. Therefore, defects such as pinholes and cracks are reduced, and the laminate exhibits high barrier properties. Considering the above aspects, Ssk(D) is preferably 0 or less, more preferably -5 or less, and even more preferably -6 or less. There is no particular limitation on the lower limit, but it is set to -20 from the perspective of maintaining barrier properties.

[0090] Methods for controlling Ssk(D) within the aforementioned range include, for example, using a highly crystalline polypropylene resin as a raw material (more specifically, using a polypropylene resin with a meso-pentameric component ratio of 0.93 or higher), setting the cooling and solidification temperature of the molten sheet to 30°C or lower during film formation, using a successive biaxial stretching method to achieve a length-direction stretching ratio of 4.0 times or higher, preferably 4.5 times or higher, setting the length-direction stretching temperature to 125°C or lower, preferably 120°C or lower, more preferably 115°C or lower, and even more preferably 110°C or lower, and setting the metal layer thickness to 50 nm or lower when forming the D layer on the polypropylene film surface. It should be noted that these methods can be used individually or in combination.

[0091] Packaging materials, bundles

[0092] The packaging material and bundle of the present invention will now be described. The packaging material of the present invention is characterized by having at least one of the polypropylene film of the present invention and the laminate of the present invention. The packaging material of the present invention exhibits excellent structural stability to heat during vapor deposition, particularly good water vapor barrier and oxygen barrier properties when laminating a transparent vapor-deposited layer. Therefore, although it is easily degraded by water vapor and oxygen, it is suitable for packaging.

[0093] The characteristic of the bundle of the present invention is that it uses the packaging material of the present invention to package the contents. The contents are not particularly limited, but considering the excellent transparency, water vapor barrier, and oxygen barrier properties of the packaging material of the present invention, it is preferable to use a substance that is visible from the outside and easily deteriorated by water vapor and oxygen. It should be noted that the bundle of the present invention is obtained by covering the contents with the packaging material of the present invention, and its shape is not particularly limited. For example, a bundle obtained by heat-sealing the packaging material of the present invention into a bag shape and placing the contents therein can be cited. Specific examples of such bundles include snacks, retort pouch foods, etc.

[0094] <Manufacturing Method>

[0095] The manufacturing method of the polypropylene film of the present invention will be described below. In the manufacturing of the polypropylene film of the present invention, firstly, molten polypropylene resin or a polypropylene resin composition is melt-extruded onto a support to form an unstretched polypropylene film. Next, the unstretched polypropylene film is stretched along its length direction, and then stretched along its width direction, undergoing successive biaxial stretching. Then, heat treatment and relaxation treatment are performed to produce a biaxially oriented polypropylene film. A more detailed description will follow, but the polypropylene film and its manufacturing method of the present invention should not be construed as limited thereto.

[0096] First, polypropylene resin or a composition of polypropylene resin, which serves as the raw material for layers A, B, and C, is melt-extruded from individual single-screw extruders set at an extrusion temperature of 220°C to 280°C, preferably 230°C to 270°C, and then passed through a filter to remove impurities. Next, these molten resins are combined in a feed block or the like in a manner that creates a desired layer structure (e.g., layer a / layer c / layer b, where the unstretched layer A is designated as layer a, the unstretched layer B as layer b, and the unstretched layer C as layer c, for example, layer a / layer c / layer b). Then, the mixture is extruded from a slit-shaped die at a temperature of 200°C to 260°C, more preferably 210°C to 240°C. Here, considering that the resin is fully melted during melt extrusion to prevent the molecular chains from being broken due to shearing caused by screw rotation, and thus the membrane structure will not relax even at high temperatures, thereby achieving stability, it is preferable to set the temperature before the filter to be high, the temperature after the filter to be lower than the temperature before the filter, and the die temperature just before discharge to be a multi-stage low-temperature setting that can achieve further low-temperature reduction.

[0097] Next, the molten resin sheet extruded from the slit-shaped die is cooled and solidified on a casting drum (cooling drum) with a surface temperature controlled at 10°C to 40°C, preferably 10°C to 35°C, more preferably 10°C to 30°C, and most preferably 10°C to 25°C, to obtain an unstretched polypropylene film. At this time, co-extrusion lamination is preferably performed with the drum surface side, where the molten sheet extruded from the die initially contacts the A layer, as the A layer. By setting the above temperature range and structure, the mesophase fraction of the surface portion of the unstretched polypropylene film, especially the drum surface side (A layer side), can be increased, giving the unstretched polypropylene film a mesophase structure, making it easier to control the skewness Ssk between the A layer and the B layer and the surface roughness Sa within the desired range. Therefore, the surface of the A layer of the obtained polypropylene film becomes smooth, and the thickness uniformity and adhesion of the D layer formed by vapor deposition or the like are improved. Furthermore, as a method for sealing the molten sheet and the casting drum, any of the following methods can be used: electrostatic application, sealing using the surface tension of water, air knife method, pressure roller method, underwater casting method, air chamber method, etc. Multiple methods can also be combined. The air knife method, which provides good film planarity and easy control of skewness Ssk and surface roughness Sa, is preferred. Additionally, when using the air knife method, to prevent film vibration, it is preferable to appropriately adjust the position of the air knife to allow air to flow downstream of the film forming process.

[0098] The mesophase refers to the intermediate phase between crystalline and amorphous materials, which is specifically formed when solidifying from a molten state at a very rapid cooling rate. Generally, it is known that if polypropylene resin is cooled and solidified, it will crystallize and grow spherulites. However, it is believed that if an unstretched polypropylene film with such spherulites is stretched, differences in tensile stress will occur within the spherulites, between the crystalline and amorphous materials, etc., resulting in localized stretching unevenness, leading to uneven thickness and structure. On the other hand, the mesophase does not take the spherulite form, therefore it does not exhibit stretching unevenness, resulting in higher stretching uniformity. Consequently, the film exhibits high thickness uniformity, low surface roughness, and is easier to homogenize. Furthermore, when an unstretched film contains a mesophase structure, the stretching temperature in the longitudinal direction (longitudinal stretching) can be set lower than that of an unstretched polypropylene film without a mesophase.

[0099] In particular, in laminated polypropylene films comprising an A layer containing a highly stereoregular polypropylene resin and a B layer containing both polypropylene resin and a thermoplastic resin incompatible with the polypropylene resin, the stretchability of highly stereoregular polypropylene, which is difficult to stretch at low temperatures, can be improved by making the A layer an intermediate phase. Therefore, even when the stretching temperature in the longitudinal direction is set at a low temperature, for example, below 120°C, film-forming properties can be improved, and the surface of the A layer can be made smooth.

[0100] Next, the unstretched polypropylene film is biaxially stretched to achieve biaxial orientation. First, the unstretched polypropylene film is preheated between rollers at a lower limit of preferably 70°C, more preferably 80°C, and an upper limit of preferably 150°C, more preferably 130°C, and even more preferably 110°C. Then, the unstretched polypropylene film is longitudinally stretched along its length at a stretch ratio of 2.0 times or more and 15 times or less, preferably 4.0 times or more and 10 times or less, more preferably 4.5 times or more and 8.0 times or less, and even more preferably 4.5 times or more and 6.0 times or less, under an environment where the lower limit is preferably 70°C, more preferably 80°C, and the upper limit is preferably 125°C or less, more preferably 120°C or less, even more preferably 115°C or less, and particularly preferably 105°C or less. After cooling to room temperature, a uniaxially oriented film is obtained.

[0101] Next, with the two ends of the uniaxially oriented film held in a clamp in the width direction, it is fed into a tenter frame and stretched (transverse stretching) in the width direction. The temperature at this time (stretching temperature in the width direction) is 150–175°C, preferably 155–170°C. Furthermore, the stretching ratio in the width direction is preferably 8.5 times or more and 20.0 times or less, more preferably 9.0 times or more and 16.0 times or less, and even more preferably 10.0 times or more and 12.0 times or less. By making the stretching ratio in the width direction 8.5 times or more, a high orientation can be imparted in the width direction while maintaining a high orientation state in the length direction, increasing the in-plane molecular chain tension. Therefore, especially when used for packaging, it can improve the thermal structural stability of the film during vapor deposition, resulting in good water vapor barrier and oxygen barrier properties by forming a uniform vapor-deposited film. Furthermore, by making the stretching ratio in the width direction 20.0 times or less, film breakage during film formation can be prevented, resulting in good productivity.

[0102] Furthermore, in the manufacture of the polypropylene film of the present invention, it is preferable that the area stretch ratio is 42.5 times or more and 100 times or less. The area stretch ratio can be calculated by multiplying the stretch ratio in the length direction by the stretch ratio in the width direction. The lower limit of the area stretch ratio is more preferably 45.0 times, and even more preferably 53.0 times.

[0103] In the manufacture of the polypropylene film of the present invention, heat treatment and relaxation treatment are preferably performed after transverse stretching. The heat treatment and relaxation treatment involve relaxing the film by 2% to 20% along its width direction while the film is held taut by the clamps of a tenter frame at both ends. The treatment is performed at a temperature of 140°C to 170°C, more preferably 152°C to 168°C, and even more preferably 154°C to 165°C. This heat treatment and relaxation treatment improves the film's thermal structural stability, and when a laminate is formed by vapor deposition to create a D-layer, thermal damage such as pinholes and cracks in the D-layer can be suppressed. As a result, the laminate obtained from the polypropylene film exhibits good water vapor barrier and oxygen barrier properties.

[0104] In the relaxation process, considering the improvement of the film's thermal structural stability, the relaxation rate is preferably 2% or more and 20% or less, more preferably 4% or more and 18% or less, and even more preferably 6% or more and 15% or less. When the relaxation rate is less than 2%, the thermal dimensional stability of the film sometimes becomes insufficient. Therefore, when forming a laminate by vapor deposition to form a D layer, the film may deform, resulting in defects such as pinholes and cracks in the D layer. Consequently, the water vapor barrier and oxygen barrier properties of the laminate with the D layer may be compromised. On the other hand, when the relaxation rate exceeds 20%, the film becomes too relaxed inside the tenter frame, resulting in wrinkles in the film after deposition, sometimes leading to reduced mechanical properties and uneven vapor deposition.

[0105] After the aforementioned heat treatment and relaxation treatment, the film is guided outwards from the tenter frame, and the clamps at both ends of the film width direction are released in a room temperature atmosphere. The film edges are then cut during the winding process. Next, for the surface to be vapor-deposited (typically the surface of layer A), to ensure good adhesion of the vapor-deposited layer, corona discharge treatment or plasma treatment is preferably performed in an atmosphere, or in an atmosphere of oxygen, nitrogen, hydrogen, argon, carbon dioxide, silane gas, or mixtures thereof. Particularly preferred is treatment in nitrogen or a nitrogen-containing mixture. The resulting polypropylene film of the present invention is then wound into a roll to obtain the final product roll.

[0106] Example

[0107] The present invention will be described in more detail below with examples, but the present invention is not limited to the methods shown below. It should be noted that the evaluation of each item is carried out using the following methods.

[0108] <Methods for determining characteristic values ​​and methods for evaluating effects>

[0109] The method for measuring the characteristic values ​​and the method for evaluating the effects in this invention are described below.

[0110] (1) Thickness of polypropylene film

[0111] The thickness of a polypropylene film was measured at 10 random locations using a contact-type electronic micrometer (K-312A type) manufactured by Anritsu Co., Ltd., under an atmosphere of 23°C and 65% RH. The arithmetic mean of the thicknesses at these 10 locations was taken as the thickness of the polypropylene film (unit: μm).

[0112] (2) Skewness Ssk(A), Ssk(B) and Ssk(D)

[0113] The skewness Ssk was measured using a VS1540 scanning white light interferometer from Hitachi Hightech Systems Co., Ltd., which is a non-contact three-dimensional surface shape measuring instrument. In the analysis, the accompanying software was used to remove fluctuation components from the captured image through polynomial fourth-order approximate surface correction. Then, after processing with a median (3×3) filter, interpolation was performed (for pixels where height data was unavailable, height data calculated from surrounding pixels was used as a supplement). During the measurement, measurements were taken at five arbitrary points on each of the film surface: surface B (B layer surface), surface A (A layer surface), and surface D (D layer surface) in the case of laminates containing inorganic compound layers or metal layers. The average value was calculated. The measurement conditions are described below.

[0114] <Measurement Conditions>

[0115] Manufacturer: Hitachi High-tech Co., Ltd.

[0116] Device Name: Scanning White Light Interference Microscope VS1540

[0117] Measurement conditions: 10× objective lens

[0118] 1× lens tube

[0119] 1× zoom lens

[0120] 530nm white wavelength filter

[0121] Measurement mode: Wave

[0122] Measurement software: VS-Measure version 10.0.4.0

[0123] Analysis software: VS-Viewer version 10.0.3.0

[0124] Measurement area: 0.561 × 0.562 mm 2 .

[0125] (3) Surface roughness Sa Sa(A) and Sa(B)

[0126] The measurement was performed using the same apparatus, conditions, mode, software, analytical software, and area as (2) skewness (Ssk). For surfaces A and B of the membrane, measurements were taken at any 5 points within each surface, and the average value was calculated.

[0127] (4) The thickness of each layer in the polypropylene film, namely layers A, B, and C, and layer D, which is equivalent to an inorganic compound layer or a metal layer.

[0128] In the case of a membrane or a laminate containing inorganic compound layers or metal layers, the laminate is embedded in epoxy resin, and ultrathin sections are prepared using a microtome with the length-thickness cross-section of the membrane as the observation plane. Transmission electron microscopy is used to photograph the cross-section of the ultrathin sections at 20,000x magnification to confirm the thickness of each layer at the center of the membrane's width direction. The thickness units of layers A, B, and C are specified as "μm", and the thickness unit of layer D is specified as "nm".

[0129] (5) Static friction coefficient (μs)

[0130] The static friction coefficient (μs) of the sample was determined using a sliding tester manufactured by Toyo Seiki Co., Ltd., according to JIS K 7125 (1999) at 25°C and 65% RH. It should be noted that the film length direction must be aligned during the measurement, and one surface of the film must be superimposed on its opposite surface. The test was performed five times, and the average value was calculated as the static friction coefficient (μs) of the sample.

[0131] (6) The sum of the thermal shrinkage rates in the length and width directions at 125°C for 10 minutes

[0132] For the polypropylene film, the heat shrinkage rate was measured separately in the length and width directions using the following method. A sample with the measurement direction as the longer side was cut into a rectangle with a length of 70 mm and a width of 10 mm. Marks were made 10 mm from both ends to ensure a test length of 50 mm. The interval between the marks was measured using a Nikon V-16A universal projector and taken as the test length (l0). Next, the test piece was sandwiched between paper and heated in an oven at 125°C for 10 minutes under zero load. After cooling at room temperature, the dimensions (l1) were measured in the same manner. The heat shrinkage rate was calculated from the obtained l0 and l1 using the following formula. The average value of 5 pieces was taken as the heat shrinkage rate in each direction, and the sum was calculated.

[0133] Thermal shrinkage rate = {(l0-l1) / l0} × 100 (%).

[0134] (7) Melting point of polypropylene resin

[0135] Using a differential scanning calorimeter (Seiko Instrument EXSTAR DSC6220), under a nitrogen atmosphere, a 3 mg sample of polypropylene resin was heated from 30 °C to 260 °C at a rate of 20 °C / min. Then, after holding at 260 °C for 5 minutes, it was cooled to 30 °C at a rate of 20 °C / min. This process was repeated, holding at 30 °C for 5 minutes, and then heating back up to 260 °C at a rate of 20 °C / min. The peak temperature of the endothermic curve obtained during this heating was taken as the melting point of the polypropylene resin. It should be noted that when multiple peak temperatures were observed, the highest temperature was taken as the melting point of the polypropylene resin.

[0136] (8) Heat sealability

[0137] A polypropylene film (B layer) was laminated with a 12 μm thick stretched PET film (Tore Co., Ltd. "Lumira" (registered trademark) type S10), and heat-sealed using a flatbed heat sealer under the following conditions to create a laminate. A T-type peel test was performed on the interface between the polypropylene film and the stretched PET film using an Original Tech Co., Ltd. ("Tensilon" (registered trademark)) to determine the heat seal strength. It should be noted that the laminate for the peel test was sampled as a strip with a width of 20 mm and a length of 150 mm, and the heat seal strength was measured at a stretching speed of 300 mm / min. This test was performed three times, and the average value was calculated as the heat seal strength (N / 25.4 mm). A heat seal strength of 2 N / 25.4 mm or higher was considered acceptable (○), and a strength lower than 2 N / 25.4 mm was considered unacceptable (×).

[0138] <Heat-sealing conditions>

[0139] • Pressing pressure: 0.4 N / mm 2

[0140] • Suppression time: 1 second

[0141] Heater temperature: 120℃.

[0142] (9) Adhesion of the vapor-deposited layer

[0143] A film roll is placed in a vacuum evaporation apparatus equipped with a film moving device to form a 1.00×10⁻⁶ film roll. -2 After being subjected to a high-pressure decompression state (Pa), the aluminum metal is heated and evaporated by moving a cooling metal drum at 20°C, forming a vapor-deposited film layer on layer A. At this time, the vapor-deposited film is controlled to be approximately 40 nm thick. After vapor deposition, the vacuum vapor deposition apparatus is restored to atmospheric pressure, the wound film is rewound, and it is cured at 40°C for 2 days while still in a wound state, resulting in a laminate with an Al (aluminum) vapor-deposited layer laminated on the film. Next, a Nichiban-manufactured "Cerop" (registered trademark) is attached to the surface of the vapor-deposited layer of the obtained laminate using a rubber roller with a load of 2 kg. The laminate is then peeled using a peel tester at a peel angle of 180° and a peel speed of 3000 m / min. The surface of the laminate after the transparent tape is peeled off is visually inspected, and the adhesion of the vapor-deposited layer is judged according to the following standards: ○ indicates good adhesion, △ indicates a level with no practical problems.

[0144] (Judgment Criteria)

[0145] ◎: The vapor-deposited layer has not been completely peeled off.

[0146] ○: Most of the vapor-deposited layer was not peeled off, but a very small portion was.

[0147] △: A very small portion of the vapor-deposited layer was not peeled off, but most of it was.

[0148] ×: The entire vapor-deposited layer has been peeled off.

[0149] (10) Water vapor transmission rate (water vapor barrier property) after Al vapor deposition or AlOx vapor deposition

[0150] The Al-deposited laminate was obtained by the method described in (9). For the AlOx-deposited laminate, a film roll was placed in a vacuum evaporation apparatus equipped with a film moving device to form a 1.00 × 10⁻⁶ film roll. -2 After being subjected to a high-pressure decompression state (Pa), the film is moved by a cooling metal drum at 20°C, allowing oxygen to be introduced while AlOx reacts and evaporates, forming a vapor-deposited layer on layer A. At this point, the vapor-deposited layer is controlled to be approximately 20 nm in size. After vapor deposition, the vacuum vapor deposition apparatus is restored to atmospheric pressure, the wound film is rewound, and it is aged at 40°C for 2 days while still in a wound state, resulting in a laminate with an AlOx vapor-deposited layer laminated on a polypropylene film.

[0151] For laminates subjected to Al or AlOx vapor deposition, water vapor transmission rate measurements were performed using a PERMATRAN-W3 / 30 water vapor transmission rate measuring device manufactured by MOCON / Modern Controls at 40°C and 90% RH. Each sample was measured five times, and the average value was calculated as the water vapor transmission rate of the film (unit: g / m). 2 ( / day). Based on the obtained water vapor transmission rate, the water vapor barrier properties of the laminate are judged according to the following criteria. ○ indicates good water vapor barrier properties, and △ indicates a level that poses no practical problems.

[0152] ◎:0.5g / m 2 / day or less.

[0153] ○: Greater than 0.5g / m 2 / day and 1.0g / m 2 / day or less.

[0154] △: Greater than 1.0g / m 2 / day and 2.0g / m 2 / day or less.

[0155] ×: Greater than 2.0g / m 2 / sky.

[0156] (11) Oxygen permeability (oxygen barrier properties) after Al vapor deposition or AlOx vapor deposition

[0157] Laminates with Al vapor-deposited layers or AlOx vapor-deposited layers were obtained using the methods described in (9) and (10). For each laminate, the oxygen permeability was measured using an Oxtran2 / 20 oxygen permeability measuring device manufactured by MOCON / Modern Controls at 23°C and 0% RH. The measurement was performed five times for each sample, and the average value was calculated as the oxygen permeability of the film (unit: cc / m). 2 ( / day). Based on the obtained oxygen permeability, the oxygen barrier properties of the laminate are judged according to the following criteria. ○ indicates good oxygen barrier properties, and △ indicates a level that poses no practical problems.

[0158] ◎:10cc / m 2 / day or less.

[0159] ○: Greater than 10cc / m 2 / day and 20cc / m 2 / day or less.

[0160] △: Greater than 20cc / m 2 / day and 40cc / m 2 / day or less.

[0161] ×: Greater than 40cc / m 2 / sky.

[0162] <Components used in the manufacture of polypropylene films in each embodiment and comparative example>

[0163] The following components were used in the manufacture of the polypropylene films in each embodiment and comparative example. It should be noted that, unless otherwise specified, MFR refers to the value measured at 230°C and a load of 21.18 N.

[0164] (Layer A uses polypropylene resin)

[0165] A1: Homopolymer polypropylene resin (Plain Polymer Co., Ltd. "F133A" (racemic pentamematic component ratio: 0.97, melting point: 167℃, MFR: 3.0 g / 10 min, CXS: 1.5% by mass, propylene unit fraction: 99.5 mol% or more))

[0166] A2: Homopolymer polypropylene resin (Plain Polymer Co., Ltd. "F113G" (racemic pentamematic component ratio: 0.94, melting point: 162℃, MFR: 2.9g / 10min, CXS: 3.8% by mass, propylene unit fraction: 99.5 mol% or more))

[0167] A3: Ethylene-propylene random copolymer (Polypro Co., Ltd. of Japan, “WFW4M” (melting point: 135℃, MFR: 7.0g / 10min, metallocene, propylene content: 95.0%))

[0168] A4: Homopolymer polypropylene resin (manufactured by Repsol (melting point: 153℃, MFR: 3.0 g / 10 min, CXS: 1.5% by mass, propylene unit fraction ≥ 99.5 mol%)).

[0169] (Masterbatch for Layer A)

[0170] AM1: A masterbatch made by mixing and extruding A2 (90 parts by mass), polymethylpentene resin 2 (10 parts by mass), and antioxidant (0.1 parts by mass) in an extruder set to 260°C, followed by water cooling and slicing of the filament.

[0171] (Layer B uses polypropylene resin)

[0172] B1: Ethylene-propylene random copolymer (Polypro Co., Ltd. of Japan, “WFW5T” (melting point: 130℃, MFR: 3.5g / 10min, metallocene)).

[0173] B2: Homopolymer polypropylene resin (same as A1).

[0174] (Masterbatch for layer B)

[0175] BM1: A masterbatch made by mixing and extruding B1 (90 parts by mass), polymethylpentene resin 1 (10 parts by mass), and antioxidant (0.1 parts by mass) in an extruder set to 260°C, followed by water cooling and slicing of the filament.

[0176] BM2: A masterbatch made by mixing and extruding B1 (90 parts by mass), polymethylpentene resin 2 (10 parts by mass), and antioxidant (0.1 parts by mass) in an extruder set to 260°C, followed by water cooling and slicing of the filament.

[0177] BM3: A masterbatch made by mixing and extruding B2 (90 parts by mass), polymethylpentene resin 1 (10 parts by mass), and antioxidant (0.1 parts by mass) in an extruder set to 260°C, followed by water cooling and slicing of the filament.

[0178] (C layer uses polypropylene resin)

[0179] C1: Homopolymer polypropylene resin (Basell "HA3105" (melting point: 165℃, MFR: 3.0 g / 10 min, CXS: 2.5% by mass, propylene unit fraction: ≥99.5 mol%))

[0180] C2: Homopolymer polypropylene resin ("FY6H" manufactured by Polypro Co., Ltd. of Japan (meta-race five-unit component ratio: 0.92, melting point: 161℃, MFR: 3.3g / 10min, CXS: 4.1% by mass, propylene unit fraction ≥ 99.5 mol%)).

[0181] (Masterbatch for layer C)

[0182] CM1: A masterbatch made by mixing and extruding C1 (70 parts by mass), petroleum resin 1 (30 parts by mass), and antioxidant (0.1 parts by mass) in an extruder set to 240°C, followed by water cooling and slicing of the filament.

[0183] CM2: A masterbatch made by mixing and extruding C2 (70 parts by mass), petroleum resin 1 (30 parts by mass), and antioxidant (0.1 parts by mass) in an extruder set to 240°C, followed by water cooling and slicing of the filament.

[0184] (Resins other than polypropylene resins)

[0185] Polymethylpentene resin 1: Mitsui Chemicals Co., Ltd. "TPX" (registered trademark) (DX845, melting point 232℃, MFR: 9g / 10min (measured at 260℃))

[0186] Polymethylpentene resin 2: Mitsui Chemicals Co., Ltd. "TPX" (registered trademark) (MX004, melting point 228℃, MFR: 25g / 10min (measured at 260℃))

[0187] Petroleum resin 1: T-REZ HA125 (manufactured by JXTG Energi Co., Ltd.).

[0188] (Additives, etc.)

[0189] Antioxidant: Irganox (registered trademark) 1010 (manufactured by BASF Japan Co., Ltd.)

[0190] P1: Silica particles (SFP-20MHE (Silane Coupling Surface Treatment) manufactured by Denka Kogyo Co., Ltd.) (Average particle size: 0.3μm).

[0191] (Example 1)

[0192] A1 is used as the raw material for layer A. A mixture of B1 and BM1 in a mass ratio of 80:20 is used as the raw material for layer B. A mixture of C1 and CM1 in a mass ratio of 75:25 is used as the raw material for layer C. These raw materials are fed to individual single-screw extruders and melt-extruded at 260°C. After removing impurities using a sintered filter with an 80μm opening, the extrusion rate is adjusted using a feed block to laminate the polymer in a 3-layer configuration (A / C / B) with a lamination ratio of 1 / 23 / 1, allowing the melt-laminated polymer to exit from the T-die. Then, on a casting drum maintained at 20°C, an air knife is used to press the exited molten sheet so that the A-layer side contacts the drum surface, allowing for cooling and solidification to obtain an unstretched sheet. Next, the unstretched sheet is preheated to 105°C in stages using multiple roller sets and stretched 5.2 times its original length directly between rollers with a circumferential speed difference to produce a uniaxially oriented film. Next, the obtained uniaxially oriented film is fed into a tenter frame. While the film is held at both ends in the width direction by clamps, it is stretched 10.5 times its original length at 165°C. Then, while allowing a 10% relaxation in the width direction, it is heat-treated at 155°C. The film is then guided to the outside of the tenter frame, the clamps at both ends in the width direction are released, and the film surface (casting drum contact side: layer A) is then heat-treated at 25 W·min / m. 2 The process intensity was adjusted to a corona discharge treatment under a mixed gas atmosphere of carbon dioxide and nitrogen with a carbon dioxide concentration ratio of 15% by volume. Finally, the resulting biaxially oriented polypropylene film with a thickness of 25 μm was wound into a roll. This resulted in a laminate in which an Al vapor-deposited layer was provided on the A-layer side of the film in this embodiment as the D-layer. The characteristics of the obtained biaxially oriented polypropylene film and the laminate are shown in Table 1.

[0193] (Example 2)

[0194] A biaxially oriented polypropylene film was manufactured using the same method as in Example 1, resulting in a laminate with an AlOx vapor-deposited layer as the D layer on the A layer side. The properties of the obtained biaxially oriented polypropylene film and laminate are shown in Table 1.

[0195] (Examples 3-10, Comparative Examples 2-4)

[0196] By changing the raw materials and film-forming conditions as shown in Table 1, except for the method used in Example 2, biaxially oriented polypropylene films and laminates were obtained. The properties of the obtained biaxially oriented polypropylene films and laminates are shown in Table 1.

[0197] (Comparative Example 1)

[0198] As the raw material for layer A, A1 is fed into a single-screw extruder and melt-extruded at 250°C. After removing impurities using a sintered filter with an 80μm opening, the molten polymer is discharged from the T-die. Then, on a casting drum maintained at 30°C, the ejected molten sheets are sealed together using an air knife and cooled to solidify, resulting in an unstretched sheet. Next, this unstretched sheet is preheated to 135°C in stages using multiple roller sets and stretched 4.5 times its original length directly between rollers with a circumferential speed difference to produce a uniaxially oriented film. The resulting uniaxially oriented film is then fed into a tenter frame and stretched 8.2 times its original length at 160°C while the film is held at both ends in the width direction by clamps. It is then heat-treated at 168°C while being relaxed by 6.7% in the width direction. The film is then guided to the outside of the tenter frame, the clamps at both ends in the width direction are released, and the film surface (cast drum contact side: layer A) is then heat-treated at 25 W·min / m. 2 The process intensity was adjusted to a corona discharge treatment in a mixed gas atmosphere of carbon dioxide and nitrogen with a carbon dioxide concentration of 15% by volume. Finally, the resulting biaxially oriented polypropylene film with a thickness of 25 μm was wound into a roll. The properties of the obtained biaxially oriented polypropylene film and laminate are shown in Table 1.

[0199] (Comparative Example 5)

[0200] As the raw material for layer A, a mixture of A2 and AM1 in an 80:20 (mass ratio) was used. As the raw material for layer B, a mixture of A2 and AM2 in an 80:20 (mass ratio), using the same raw material as layer A, was used. C1 was used as the raw material for layer C. These raw materials were fed separately to each single-screw extruder and melt-extruded at 260°C. After removing impurities using a sintered filter with an 80 μm opening, the extrusion rate was adjusted using a feed block to laminate three layers (A / C / B) in a 1 / 22 / 1 ratio, causing the melt-laminated polymer to exit from the T-die. The film-forming conditions were changed as shown in Table 1, except that a biaxially oriented polypropylene film and laminate were obtained using the same method as in Example 2. The characteristics of the obtained biaxially oriented polypropylene film and laminate are shown in Table 1.

[0201]

[0202] Comparative Example 1 has a single-layer structure, therefore the layer constituting the film is treated as layer A. Comparative Examples 2 and 3 do not contain thermoplastic resins incompatible with polypropylene resins, so the layer with B1 as the main component is considered layer B. The percentage of propylene units in layer A of Comparative Example 5 is calculated by considering the percentage of propylene units in A2 as 100 mol%.

[0203] Industrial availability

[0204] The polypropylene film of this invention is structurally stable to heat during vapor deposition, exhibits moderate slippage without the use of anti-blocking agents or particles, and thus provides excellent water vapor barrier and oxygen barrier properties, particularly when laminating transparent vapor-deposited layers. Therefore, it is suitable for packaging applications.

Claims

1. A polypropylene film, characterized in that, It has at least two layers, namely layer A and layer B, with polypropylene resin as the main component. Layer B contains a thermoplastic resin that is incompatible with polypropylene resin. When the skewness Ssk of layer A and layer B, which is determined by non-contact three-dimensional surface shape measurement, is set as Ssk(A) and Ssk(B) respectively, Ssk(B) is 5 or more and Ssk(A) is less than 5. The thermoplastic resin incompatible with polypropylene resin contained in layer B is polymethylpentene resin.

2. A polypropylene film having at least two layers, A and B, primarily composed of a polypropylene resin, wherein layer B comprises a thermoplastic resin incompatible with the polypropylene resin, wherein the skewness Ssk of layer A, measured by non-contact three-dimensional surface shape measurement, is set as Ssk(A), and the surface roughness Sa of layer A and layer B are set as Sa(A) and Sa(B), respectively, wherein Ssk(A) is less than 5, and Sa(A) and Sa(B) satisfy Equation 1. Formula 1: Sa(B) / Sa(A)>1.1, The B layer contains a thermoplastic resin that is incompatible with polypropylene resins, namely a polymethylpentene resin.

3. The polypropylene film according to claim 1 or 2, wherein the percentage of propylene units in the resin component constituting layer A is 97.0 mol% or more and 100.0 mol% or less, and is the percentage of propylene units in the resin component constituting the entire polypropylene film.

4. The polypropylene film according to claim 1 or 2, wherein the polypropylene resin, which is the main component of layer A, has a melting point of 151°C or higher.

5. The polypropylene film according to claim 1, wherein when the surface roughness Sa of layer A and layer B is set to Sa(A) and Sa(B) respectively, Sa(A) and Sa(B) satisfy equation 2. Formula 2: Sa(B) / Sa(A)>1.

0.

6. The polypropylene film according to claim 1 or 2, wherein layer B is a heat-sealable layer.

7. The polypropylene film according to claim 1 or 2, wherein a layer C, mainly composed of polypropylene resin, is provided between layer A and layer B.

8. The polypropylene film according to claim 7, wherein, The C layer contains petroleum resin.

9. The polypropylene film according to claim 1 or 2, for packaging purposes.

10. A laminate, characterized in that, When a layer comprising a total of more than 50% by mass and less than 100% by mass of metals and / or inorganic compounds is designated as layer D, layer D is in contact with layer A of the polypropylene film according to any one of claims 1 to 9, and the thickness of layer D is less than 50 nm.

11. In the laminate according to claim 10, when the skewness Ssk of layer D, measured by a non-contact three-dimensional surface roughness meter, is set to Ssk(D), Ssk(D) is less than 5.

12. A packaging material comprising at least one of a polypropylene film according to any one of claims 1 to 9 and a laminate according to claim 10 or 11.

13. A bundle body, characterized in that, The contents are packaged in the packaging material as described in claim 12.

Images