Light-shielding packaging material and light-shielding packaging body

Abstract

To provide a light-shielding packaging material that has excellent resistance to bag drop during low-temperature storage and excellent light-shielding properties. [Solution] A light-shielding packaging material comprising: a base film and a light-shielding sealant film having a first layer containing a propylene homopolymer (A), a propylene-ethylene random copolymer (B), and an ethylene-α-olefin copolymer elastomer (C), wherein the content of the ethylene-α-olefin copolymer elastomer (C) is 17.5 parts by mass or more with respect to 100 parts by mass of the total amount of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B); or a light-shielding packaging material comprising the base film, the sealant film having the first layer, and a light-shielding layer.

Description

【Technical Field】 【0001】 The present disclosure relates to a light-shielding packaging material and a light-shielding package. Specifically, the present disclosure relates to a light-shielding packaging material having excellent drop bag resistance and excellent light-shielding properties during low-temperature storage, and a light-shielding package obtained using the packaging material. 【Background Art】 【0002】 Since polypropylene-based non-stretched films are excellent in rigidity and heat resistance and are inexpensive, they may be used as sealant films in various packaging materials such as food packaging. 【0003】 In Patent Document 1, a polypropylene-based non-stretched film containing a crystalline propylene polymer having a melting point of 120 to 165°C, an ethylene-α-olefin copolymer, and a copolymer of ethylene and at least one selected from α-olefins having 3 to 20 carbon atoms, cyclic olefins or cyclic polyenes has been proposed. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2003-119298 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 The aforementioned polypropylene-based unoriented film sealant film is laminated with conventionally used biaxially oriented polyamide film (ONy film) substrates, biaxially oriented polyester film (PET film) substrates, and biaxially oriented polypropylene film (OPP) substrates for monomaterial packaging materials to form the packaging material. However, depending on the type of substrate used, sufficient resistance to bag drop may not be obtained when the packaging material is stored at low temperatures. In order to create a more practical packaging material, it is preferable that the polypropylene-based unoriented film used as a sealant film also has excellent resistance to bag drop. 【0006】 Furthermore, packaging materials may require light-blocking properties to protect the contents from external light. In such cases, it is necessary to incorporate a light-blocking layer within the packaging material. 【0007】 This disclosure is made in view of the above circumstances and aims to provide a light-shielding packaging material that has excellent resistance to bag drop during low-temperature storage and excellent light-shielding properties. This disclosure also aims to provide a light-shielding package that can be obtained using the said packaging material. [Means for solving the problem] 【0008】 One aspect of this disclosure includes, for example, the following: [1] A base film and A light-shielding packaging material comprising a light-shielding sealant film having a first layer containing a propylene homopolymer (A), a propylene-ethylene random copolymer (B), and an ethylene-α-olefin copolymer elastomer (C), wherein the content of the ethylene-α-olefin copolymer elastomer (C) is 17.5 parts by mass or more per 100 parts by mass of the total amount of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B). [2] Base film and A sealant film comprising a first layer containing a propylene homopolymer (A), a propylene-ethylene random copolymer (B), and an ethylene-α-olefin copolymer elastomer (C), wherein the content of the ethylene-α-olefin copolymer elastomer (C) is 17.5 parts by mass or more per 100 parts by mass of the total amount of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B), A light-shielding packaging material comprising a light-shielding layer. [3] The light-shielding packaging material according to [1], further comprising a light-shielding layer. [4] The light-shielding sealant film comprises a layer containing an inorganic pigment, as described in [1] or [3]. [5] The packaging material according to any one of [1] to [4], wherein the base film comprises a propylene polymer. [6] The light-shielding packaging material according to any one of [1] to [5], wherein the base film has an inorganic oxide layer on at least one surface. [7] A light-shielding package made from any one of the light-shielding packaging materials described in [1] to [6]. [Effects of the Invention] 【0009】 According to this disclosure, it is possible to provide a light-shielding packaging material that has excellent resistance to bag drop during low-temperature storage and excellent light-shielding properties. Furthermore, according to this disclosure, it is possible to provide a light-shielding package obtained using the said packaging material. 【0010】 The sealant film of this disclosure also has heat resistance that can withstand retort processing, such as sterilization and disinfection under retort conditions of 128°C. [Brief explanation of the drawing] 【0011】 [Figure 1] Figure 1 is a cross-sectional view of a sealant film according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a cross-sectional view of a sealant film according to one embodiment of the present disclosure. [Figure 3] Figure 3 is a cross-sectional view of a sealant film according to an embodiment of the present disclosure. [Figure 4] Figure 4 is a cross-sectional view of a light-shielding packaging material according to an embodiment of the present disclosure. [Figure 5] Figure 5 is a cross-sectional view of a light-shielding packaging material according to an embodiment of the present disclosure. [Figure 6] Figure 6 is a cross-sectional view of a light-shielding packaging material according to an embodiment of the present disclosure. 【Mode for Carrying Out the Invention】 【0012】 <Sealant Film> The sealant film may be a film having a first layer as described below, may be a film having a first layer and a second layer, or may be a film having a first layer, a second layer, and a third layer. The sealant film may or may not have light-shielding properties. When the sealant film has light-shielding properties, that is, when it is a light-shielding sealant film, at least one of these layers is a layer containing an inorganic pigment. 【0013】 The sealant film is an unstretched film and can be mainly composed of a polypropylene-based material, so it can be called a polypropylene-based unstretched film. 【0014】 <Sealant Film 100> Figure 1 is a cross-sectional view of a sealant film 100 according to an embodiment of the present disclosure. The sealant film 100 includes a first layer 10 containing a propylene homopolymer (A), a propylene-ethylene random copolymer (B), and an ethylene-α-olefin copolymer elastomer (C). The sealant film 100 may be a light-shielding sealant film. 【0015】 (Propylene Homopolymer (A)) The propylene homopolymer (A) can be obtained, for example, by a method of homopolymerizing propylene using a Ziegler-Natta type catalyst, a metallocene catalyst, or a half-metallocene catalyst. By containing the propylene homopolymer (A) in the sealant film, excellent heat resistance can be imparted to the first layer. As a result, for example, after performing a pressure heat treatment under retort conditions of 128°C, it is difficult for fusion to occur on the inner surface of the packaging bag. 【0016】 As the propylene homopolymer (A), those having a melting start temperature of 150°C or higher and a melting point of 155°C or higher when measured by differential scanning calorimetry (JIS K 7121) can be used. Since both the melting start temperature and the melting point are within this range, more excellent heat resistance can be imparted to the first layer. As a result, for example, after performing a pressure heat treatment under retort conditions of 128°C, it is even more difficult for fusion to occur on the inner surface of the packaging bag. The conditions for differential scanning calorimetry are as follows. [Differential Scanning Calorimetry Conditions] When the temperature is raised from 25°C to 230°C at a rate of 10°C / min, the intersection of the straight line obtained by extending the baseline on the low-temperature side of the DSC curve to the high-temperature side and the tangent line drawn so as to contact the curve on the low-temperature side of the melting peak and have the maximum slope is defined as the melting start temperature, and the temperature at the apex of the melting peak is defined as the melting point. 【0017】 As the propylene homopolymer (A), those having a melt flow rate (MFR: ISO 1133) (temperature 23°C, load 2.16 kg) in the range of 2.0 to 7.0 g / 10 minutes can be used. When the melt flow rate is at least the lower limit value, the extruder load during molding processing is reduced, it is difficult for the processing speed to decrease, and excellent productivity is easily maintained. Also, when the melt flow rate is at most the upper limit value, the first layer is likely to have excellent impact resistance. 【0018】 [[ID=了15]] (Propylene-Ethylene Random Copolymer (B)) Propylene-ethylene random copolymer (B) can be obtained by copolymerizing ethylene as a comonomer in a main monomer consisting of propylene, for example, using a Ziegler-Natta type catalyst, a metallocene catalyst, or a half-metallocene catalyst. The inclusion of propylene-ethylene random copolymer (B) in the first layer makes it easier to obtain excellent low-temperature sealing properties while maintaining heat resistance. 【0019】 As the propylene-ethylene random copolymer (B), a material with a melting point in the range of 132 to 150°C, as measured by differential scanning calorimetry (JIS K 7121), can be used. Using a material with a melting point within this range makes it easier to obtain excellent low-temperature sealing properties while maintaining heat resistance. The conditions for differential scanning calorimetry are as follows. [Differential scanning calorimetry conditions] The melting point is defined as the temperature at the peak of the melting curve when the temperature is increased from 25°C to 230°C at a rate of 10°C / min. 【0020】 The ethylene content of the propylene-ethylene random copolymer (B) may be 6% by mass or less. Keeping the ethylene content below the upper limit allows for maintaining low-temperature sealing properties while preventing excessive reduction in heat resistance. This makes it easier to suppress fusion on the inner surface of the packaging bag after, for example, pressurized heat treatment under retort conditions at 128°C. From this viewpoint, the ethylene content may be 5.5% by mass or less, or even 4.5% by mass or less. While there is no particular lower limit to the ethylene content, it can be set to 3% by mass from the viewpoint of low-temperature sealing properties. 【0021】 The ethylene content of propylene-ethylene random copolymer (B) can be measured according to the quantitative method for ethylene content (IR method) described on pages 412-413 of the Polymer Analysis Handbook (May 10, 2013, 3rd printing), edited by the Polymer Analysis Symposium of the Japan Society for Analytical Science. 【0022】 (Ethylene-α-olefin copolymer elastomer (C)) The ethylene-α-olefin copolymer elastomer (C) can be obtained by copolymerizing ethylene and α-olefin using, for example, a Ziegler-Natta type catalyst, a metallocene catalyst, or a half-metallocene catalyst. The inclusion of the ethylene-α-olefin copolymer elastomer (C) in the first layer provides excellent low-temperature sealing properties. Furthermore, the inclusion of the ethylene-α-olefin copolymer elastomer (C) in the first layer facilitates excellent resistance to bag drop and pinholes during low-temperature storage. 【0023】 As the ethylene-α-olefin copolymer elastomer (C), an ethylene-α-olefin copolymer elastomer having structural units derived from ethylene and structural units derived from α-olefins with 4 to 20 carbon atoms can be used. This makes it easy to obtain excellent low-temperature sealing properties. The ethylene-α-olefin copolymer elastomer (C) may be a random copolymer. 【0024】 Examples of α-olefins having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-hexadecene, 1-eicosene, 4-methyl-1-pentene, and 4-methyl-1-hexene. The α-olefin having 4 to 20 carbon atoms is preferably 1-butene or 1-hexene. The ethylene-α-olefin copolymer elastomer (C) may have two or more structural units derived from these α-olefins having 4 to 20 carbon atoms. 【0025】 As the ethylene-α-olefin copolymer elastomer (C), one can be used in which the content of structural units derived from ethylene is in the range of 75 to 97% by mass, preferably 80 to 95% by mass, based on 100% by mass of the total amount of ethylene-α-olefin copolymer elastomer (C) (total amount of structural units). Having a content of structural units derived from ethylene above the lower limit makes it easier to maintain excellent heat resistance. Furthermore, having a content of structural units derived from ethylene below the upper limit makes it easier to obtain excellent low-temperature sealing properties. 【0026】 As an ethylene-α-olefin copolymer elastomer (C), the density (JIS K 7112) is 860-950 kg / m³. 3 Materials within this range can be used. A density above the lower limit suppresses the tackiness of the film. Furthermore, a density below the upper limit facilitates achieving good low-temperature sealing properties. 【0027】 As the ethylene-α-olefin copolymer elastomer (C), one can be used with a melt flow rate (MFR: ISO 1133) (temperature 190°C, load 2.16 kg) in the range of 0.5 to 15 g / 10 min, preferably 0.5 to 10 g / 10 min or 0.5 to 5 g / 10 min. A melt flow rate above the lower limit reduces the extruder load during molding, making it easier to maintain excellent productivity without a decrease in processing speed. Furthermore, a melt flow rate below the upper limit ensures good compatibility with propylene homopolymer (A) and propylene-ethylene random copolymer (B), making it easier to maintain heat resistance. 【0028】 The first layer contains 17.5 parts by mass or more of ethylene-α-olefin copolymer elastomer (C) per 100 parts by mass of the total amount of propylene homopolymer (A) and propylene-ethylene random copolymer (B). Having an ethylene-α-olefin copolymer elastomer (C) content above the lower limit allows for both superior low-temperature sealing properties and excellent resistance to bag drop during low-temperature storage, compared to cases where the content is below the lower limit. The upper limit of the ethylene-α-olefin copolymer elastomer (C) content can be set as appropriate, but from the viewpoint of heat resistance, it can be 43 parts by mass or less. From the above viewpoint, the lower limit of the content may be 20 parts by mass, 22 parts by mass, or 24 parts by mass, and the upper limit may be 40 parts by mass, 33 parts by mass, or 26 parts by mass. 【0029】 In the first layer, the mass ratio (A) / (B) of the propylene homopolymer (A) to the propylene-ethylene random copolymer (B) may be in the range of 0.05 to 0.30. A mass ratio (A) / (B) above the lower limit makes it easier to maintain excellent heat resistance. Furthermore, a mass ratio (A) / (B) below the upper limit makes it easier to obtain excellent low-temperature sealing properties. From this viewpoint, the mass ratio (A) / (B) may be 0.07 to 0.25, or 0.10 to 0.20. 【0030】 The content of propylene homopolymer (A), propylene-ethylene random copolymer (B), and ethylene-α-olefin copolymer elastomer (C) in the first layer may be 70% by mass or more, 95% by mass or more, 99.9% by mass or more, based on the total mass of the first layer, and may be 100% by mass (the first layer substantially consisting of these components) in particular if light shielding properties are not required. 【0031】 <Sealant Film 101> Figure 2 is a cross-sectional view of a sealant film 101 according to one embodiment of the present disclosure. The sealant film 101 comprises a first layer 10 which is a heat-seal layer, and a second layer 1 which contains a propylene-ethylene block copolymer (D) and an ethylene-propylene copolymer elastomer (E). By providing the second layer, the sealant film can easily obtain excellent cold shock resistance. The sealant film 101 may be a light-shielding sealant film. 【0032】 (Propylene-ethylene block copolymer (D)) Propylene-ethylene block copolymer (D) is a copolymer that can be obtained by first producing a propylene polymer (D1) and then producing an ethylene-propylene copolymer (D2) by gas-phase polymerization in the second step. Propylene-ethylene block copolymer (D) is not a block copolymer in which the propylene polymer ends and the ethylene-propylene copolymer ends are bonded together, but rather a type of blended copolymer. The inclusion of propylene-ethylene block copolymer (D) in the second layer makes it easier to obtain excellent cold shock resistance. 【0033】 As the propylene-ethylene block copolymer (D), one with a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) in the range of 0.5 to 2.5 g / 10 min can be used. A melt flow rate above the lower limit reduces the extruder load during molding, making it easier to maintain good productivity without a decrease in processing speed. A melt flow rate below the upper limit makes it easier for the second layer to obtain excellent cold shock resistance. 【0034】 The propylene-ethylene block copolymer (D) may contain 90-60% by mass of the propylene polymer (D1) and 10-40% by mass of the ethylene-propylene copolymer (D2). Having each component within this range makes it easier to obtain excellent cold shock resistance. From this viewpoint, the propylene-ethylene block copolymer (D) may contain 87.5-65% by mass of the propylene polymer (D1) and 12.5-35% by mass of the ethylene-propylene copolymer (D2), or it may contain 85-70% by mass of the propylene polymer (D1) and 15-30% by mass of the ethylene-propylene copolymer (D2). 【0035】 The ethylene content of the ethylene-propylene copolymer (D2) is not particularly limited, but it can be in the range of 20 to 40% by mass. Keeping the ethylene content below the upper limit suppresses the tackiness of the product, making it less susceptible to contamination by tack during manufacturing and easier to maintain excellent productivity. Keeping the ethylene content above the lower limit makes it easier to obtain excellent cold shock resistance. 【0036】 (Ethylene-propylene copolymer elastomer (E)) Ethylene-propylene copolymer elastomer (E) can be obtained by slurry polymerization in the presence of an inert hydrocarbon such as hexane, heptane, or kerosene, or a liquefied α-olefin solvent such as propylene, or by gas-phase polymerization without a solvent. Specifically, ethylene-propylene copolymer elastomer (E) can be obtained using a known multi-stage polymerization method. That is, it is a polymerizable high-rubber-containing polypropylene resin obtained by polymerization of propylene and / or a propylene-α-olefin polymer in a first-stage reactor, followed by copolymerization of propylene and α-olefin in a second-stage reaction. By including ethylene-propylene copolymer elastomer (E) in the second layer, it is easier to obtain even better cold shock resistance. 【0037】 As the ethylene-propylene copolymer elastomer (E), one with a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) in the range of 0.5 to 3.5 g / 10 min can be used. A melt flow rate above the lower limit reduces the extruder load during molding, making it easier to maintain good productivity without a decrease in processing speed. A melt flow rate below the upper limit ensures good compatibility between the propylene-ethylene block copolymer (D) and the ethylene-propylene copolymer elastomer (E), making it easier to obtain cold shock resistance. 【0038】 As the ethylene-propylene copolymer elastomer (E), one can be used in which the mass ratio of propylene content to ethylene content (propylene content / ethylene content) is in the range of 1.5 to 4. Within this range, it is easier to obtain even better cold shock resistance. 【0039】 The second layer may contain 90 to 50 parts by mass of propylene-ethylene block copolymer (D) and 10 to 50 parts by mass of ethylene-propylene copolymer elastomer (E), when the total amount of propylene-ethylene block copolymer (D) and ethylene-propylene copolymer elastomer (E) is 100 parts by mass. A content of 50 parts by mass or more of propylene-ethylene block copolymer (D) makes it easier to maintain excellent heat resistance. From this viewpoint, the content may be 60 parts by mass or more, or 70 parts by mass or more. A content of 90 parts by mass or less of propylene-ethylene block copolymer (D), that is, a content of at least 10 parts by mass of ethylene-propylene copolymer elastomer (E), allows for excellent cold shock resistance. From this viewpoint, the content of propylene-ethylene block copolymer (D) may be 87.5 parts by mass or less, or 85 parts by mass or less. From the above perspective, the content of ethylene-propylene copolymer elastomer (E) may be 12.5 to 40 parts by mass, or 15 to 30 parts by mass. 【0040】 The mass ratio (E) / (D) of the ethylene-propylene copolymer elastomer (E) to the propylene-ethylene block copolymer resin (D) in the second layer is preferably 0.10 to 1.00 from the viewpoint of superior heat resistance and cold shock resistance. The mass ratio (E) / (D) may be 0.20 or higher, 0.30 or higher, or 0.40 or higher from the viewpoint of even superior cold shock resistance. The mass ratio (E) / (D) may be 0.80 or lower, 0.60 or lower, or 0.50 or lower from the viewpoint of even superior heat resistance. 【0041】 In the second layer, the content of propylene-ethylene block copolymer resin (D) and ethylene-propylene copolymer elastomer (E) may be 70% by mass or more, 95% by mass or more, 99.9% by mass or more, based on the total mass of the second layer, and may be 100% by mass (the second layer substantially consisting of these components) in cases where light shielding properties are not particularly required. 【0042】 <Sealant Film 102> Figure 3 is a cross-sectional view of a sealant film 102 according to one embodiment of the present disclosure. The sealant film 102 comprises, in this order, a first layer 10 which is a heat-seal layer, a second layer 1, and a third layer 2 containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B). The provision of the third layer makes it easier to suppress distortion and curling of the film. The sealant film 102 may be a light-shielding sealant film. 【0043】 There are no particular restrictions on the mixing ratio (mass ratio) of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B) in the third layer, but it is preferable that the ratio be the same as that of the first layer from the viewpoint of suppressing film curling after film formation. From the same viewpoint, the third layer may also contain the propylene homopolymer (A), the propylene-ethylene random copolymer (B), and the ethylene-α-olefin copolymer elastomer (C), and may have the same composition as the first layer. 【0044】 <Light-blocking sealant layer> When the sealant film is a light-shielding sealant film, the layer containing the inorganic pigment can be called the light-shielding sealant layer, and as described above, at least one of the first, second, and third layers is the light-shielding sealant layer. The light-shielding sealant layer can also have the property of concealing the contents. By using a light-shielding sealant layer, a packaging material with superior recyclability can be made compared to the case where aluminum foil is used. 【0045】 (Inorganic pigment (F)) Examples of inorganic pigments (F) include light-shielding materials such as titanium dioxide, carbon black, iron oxide, titanium yellow, azo pigments, phthalocyanine pigments, and mixtures thereof. The color of the inorganic pigment (F) is not particularly limited, but using dark-colored light-shielding materials such as carbon black and iron oxide makes it easier to improve light-shielding properties. 【0046】 The inorganic pigment (F) is, for example, particulate and dispersed in a light-shielding sealant layer. The average particle size of the inorganic pigment may be 0.10 to 0.50 μm, or it may be 0.15 to 0.40 μm or 0.20 to 0.30 μm. The average particle size of the inorganic pigment is measured by laser diffraction / scattering. 【0047】 The content of inorganic pigment (F) in the light-shielding sealant layer is preferably 0.10 to 30% by mass. From the viewpoint of superior light-shielding properties, the content of inorganic pigment (F) in the light-shielding sealant layer may be 1% by mass or more, 5% by mass or more, or 7% by mass or more, based on the total mass of the light-shielding sealant layer. From the viewpoint of superior cold shock resistance, the content of inorganic pigment (F) in the light-shielding sealant layer may be 23% by mass or less, 20% by mass or less, 15% by mass or less, 12% by mass or less, or 8% by mass or less, based on the total mass of the light-shielding sealant layer. 【0048】 The propylene resin content in the light-shielding sealant layer is preferably 70 to 99.9% by mass, based on the total mass of the light-shielding sealant layer, from the viewpoint of maintaining light-shielding properties and the functions of each layer (heat sealability, bag drop resistance, cold shock resistance, etc.). The propylene resin content in the light-shielding sealant layer can be measured according to Raman spectroscopy. 【0049】 <Thickness of sealant film and sealant layer> The thickness of the sealant film is not particularly limited, as long as it is within a range that can be used as a film for packaging materials, for example. However, if the film is too thick, it will result in a cost disadvantage, so the film thickness can be 100 μm or less, and may be between 50 and 70 μm. The thickness of the sealant film may be the thickness of the first layer 10 in the sealant film 100. 【0050】 The ratio of the thickness of the first layer in sealant films 101 and 102 may be 8 to 30% of the total thickness of the sealant film. A ratio of the first layer thickness above the lower limit facilitates the development of excellent heat seal strength, while a ratio below the upper limit facilitates the acquisition of cold impact resistance for the film, thus facilitating practical application. From this perspective, the ratio of the first layer thickness may be 10 to 25%. 【0051】 The thickness of the second layer in sealant films 101 and 102 may be 20 μm or more. This maintains the cold impact resistance of the film and makes it less likely to tear even during low-temperature storage. From this viewpoint, the thickness of the second layer may be 25 μm or more, or 30 μm or more. There is no particular upper limit to the thickness of the second layer, but since this would be a cost disadvantage, it can be set to 50 μm or 40 μm. 【0052】 The ratio of the total thickness of the first and third layers in the sealant film 102 may be 16-42% based on the thickness of the sealant film. When the ratio of the total thickness of the first and third layers is above the lower limit, excellent heat seal strength is easily achieved, and when it is below the upper limit, cold impact resistance of the film is easily obtained, making it easy to achieve practical use. From this viewpoint, the ratio of the total thickness of the first and third layers may be 20-35%. 【0053】 <Method for manufacturing sealant film> The method for manufacturing the sealant film is not particularly limited, and known methods can be used. For example, methods for thermoforming each of the first to third layers include melt-kneading methods using general mixers such as single-screw extruders, twin-screw extruders, and multi-screw extruders, and methods in which the solvent is removed by heating after dissolving or dispersing each component. When considering workability, a single-screw extruder or a twin-screw extruder can be used. When using a single-screw extruder, examples of screws include full-flight screws, screws with mixing elements, barrier-flight screws, and fluted screws, and these can be used without particular restriction. As for twin-screw mixers, co-rotating twin-screw extruders and opposite-rotating twin-screw extruders can be used, and the screw shape can be full-flight screws, kneading disc types, etc., without particular restriction. 【0054】 In the above method, after melting the raw materials for each layer, the layers can be formed and laminated by depositing them into a film using a T-die via a feed block or multi-manifold. 【0055】 The resulting sealant film may be subjected to surface modification treatments as needed to improve its suitability for subsequent processes. For example, surface modification treatments may be performed on the printed surface or the surface in contact with the substrate film to improve printability or lamination suitability. Examples of surface modification treatments include treatments that generate functional groups by oxidizing the film surface, such as corona discharge treatment, plasma treatment, and flame treatment, as well as wet process modification treatments that form an easily adhesive layer by coating. 【0056】 <Light blocking packaging material> The light-shielding packaging material may comprise a base film and the sealant film, or it may comprise a base film, the sealant film, and a light-shielding layer. In the former case, the sealant film is a light-shielding sealant film, and in the latter case, the sealant film may or may not be a light-shielding sealant film. By using the light-shielding layer described later, a packaging material with superior recyclability compared to the case where aluminum foil is used can be obtained. Light-shielding packaging materials may further include other layers, such as an adhesive layer to bond the individual films (layers) together, and an inorganic oxide layer formed on the base film to improve gas barrier properties. The sealant film is placed in the packaging material so that the heat-sealable layer (e.g., the first layer) faces the contents. 【0057】 From the viewpoint of monomaterialization of materials, the above sealant film can be laminated with a biaxially oriented polypropylene film (OPP) substrate or the like to create a packaging material with superior recyclability. In this case, the propylene resin content in the light-shielding packaging material may be 90% by mass or more based on the total mass of the packaging material. 【0058】 <Light blocking packaging material 200~202> Figures 4-6 are cross-sectional views of a light-shielding packaging material according to one embodiment of the present disclosure. The light-shielding packaging material 200 is formed by laminating a sealant film 100 and a base film 4 with an adhesive layer 3 in between. The light-shielding packaging material 201 is formed by laminating a sealant film 101 and a base film 4 with an adhesive layer 3 in between. The light-shielding packaging material 202 is formed by laminating a sealant film 102 and a base film 4 via an adhesive layer 3. 【0059】 If the light-shielding packaging material includes a light-shielding layer, the light-shielding layer (not shown) can be provided, for example, on the surface of the sealant film facing the base film, or on the surface of the base film facing the sealant film. To improve adhesion with the light-shielding layer, the surfaces of both films may be subjected to various pre-treatments such as corona treatment, plasma treatment, or flame treatment, or a coating layer such as an easy-adhesion layer may be provided. 【0060】 (Base film) Examples of base films include polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin films such as polyethylene and polypropylene, polystyrene films, polyamide films, polycarbonate films, polyacrylonitrile films, polyimide films, and films made by combining two or more of these films. The base film may contain a propylene polymer or may consist solely of a propylene polymer. Examples of propylene polymers include homopolypropylene and propylene copolymer. Examples of propylene copolymers include propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer. 【0061】 The base film may contain trace amounts of additives such as antistatic agents, ultraviolet absorbers, plasticizers, and lubricants. The base film may be subjected to surface treatments such as plasma treatment to improve adhesion with the laminated layer. The base film may also have an inorganic oxide layer (e.g., a metal oxide vapor-deposited layer) on at least one surface of the constituent film. 【0062】 The base film may be a stretched film or an unstretched film, but from the viewpoint of gas barrier properties, a stretched film is preferred. Here, examples of stretched films include uniaxially oriented films and biaxially oriented films, but biaxially oriented films are preferred because they improve the heat resistance of the packaging material. 【0063】 The thickness of the base film is not particularly limited, but it should be, for example, 0.1 mm or less. In particular, the thickness of the base film is preferably 40 μm or less, more preferably 35 μm or less, and especially preferably 30 μm or less. When the thickness of the base film is 0.1 mm or less, the flexibility of the packaging material can be further improved, and the durability can be further improved. Furthermore, from the viewpoint of improving strength, the thickness of the base film is preferably 10 μm or more, and more preferably 12 μm or more. 【0064】 (light shielding layer) The light-shielding layer may be a metal vapor-deposited layer formed by depositing a metal such as aluminum. This makes it easier to obtain high light-shielding properties. The thickness of the metal vapor-deposited layer can be 10 to 100 nm from the viewpoint of light-shielding properties, etc. 【0065】 Methods for forming metal vapor-deposited layers include, for example, physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition, thermochemical vapor deposition, and photochemical vapor deposition. 【0066】 The light-shielding layer may be a printed layer (light-shielding printed layer) formed by gravure printing or flexographic printing using light-shielding ink. The printed layer may be formed over the entire surface of the substrate film or sealant film, or it may be formed only in a portion of the film. In the latter case, the printed layer may be a patterned printed layer, thereby providing light-shielding properties only in the desired location. Furthermore, since the printed layer is easily separated from the film using deinking technology, having the light-shielding layer as a printed layer is advantageous from the viewpoint of recyclability. The thickness of the printed layer can be 1 to 2 μm from the viewpoint of light-shielding properties, etc. 【0067】 Examples of light-blocking inks include white ink, black ink, silver ink, and sepia ink. The light-blocking ink may also be a biomass ink containing biomass-derived materials. 【0068】 When using flexographic printing, it is preferable to use water-based ink as a light-blocking ink from an environmental perspective. 【0069】 (adhesive layer) For example, the adhesive layer material can be polyester-isocyanate resin, urethane resin, polyether resin, or an acid-modified polyolefin. 【0070】 The packaging material can be manufactured by known lamination methods such as dry lamination, which involves bonding a sealant film and a base film with an adhesive layer in between. The dry lamination method may be a non-solvent dry lamination method using a solvent-free adhesive. However, the packaging material may also be manufactured by a method in which the sealant film is directly extruded onto the base material and laminated. 【0071】 (Inorganic oxide layer) Examples of inorganic oxides included in the inorganic oxide layer include aluminum oxide, silicon oxide, magnesium oxide, and tin oxide. From the viewpoint of transparency and barrier properties, the inorganic oxide may be selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide. Furthermore, from the viewpoint of excellent tensile stretchability during processing, it is preferable to use a silicon oxide layer for the inorganic oxide layer. By using an inorganic oxide layer, high barrier properties can be obtained with a very thin layer that does not affect the recyclability of the packaging material. 【0072】 The O / Si ratio of the inorganic oxide layer is preferably 1.7 or higher. When the O / Si ratio is 1.7 or higher, the content of metallic Si is suppressed, making it easier to obtain good transparency. Furthermore, the O / Si ratio is preferably 2.0 or lower. When the O / Si ratio is 2.0 or lower, the crystallinity of SiO is increased, which prevents the inorganic oxide layer from becoming too hard, and good tensile strength can be obtained. In addition, even after forming into a packaging bag, the base film may shrink due to the heat during boiling or retorting, but with an O / Si ratio of 2.0 or lower, the inorganic oxide layer can easily follow the above shrinkage, and a decrease in barrier properties can be suppressed. From the viewpoint of obtaining these effects more fully, the O / Si ratio of the inorganic oxide layer is preferably 1.75 or higher and 1.9 or lower, and more preferably 1.8 or higher and 1.85 or lower. 【0073】 The O / Si ratio of the inorganic oxide layer can be determined by X-ray photoelectron spectroscopy (XPS). For example, the measurement can be performed using an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., product name: JPS-90MXV) with a non-monochromatic MgKα (1253.6 eV) X-ray source and an X-ray output of 100 W (10 kV-10 mA). For quantitative analysis to determine the O / Si ratio, relative sensitivity factors of 2.28 for O1s and 0.9 for Si2p can be used. 【0074】 The thickness of the inorganic oxide layer is preferably between 10 nm and 50 nm. A thickness of 10 nm or more provides sufficient water vapor barrier properties. A thickness of 50 nm or less suppresses crack formation due to deformation caused by internal stress in the thin film, thereby suppressing a decrease in water vapor barrier properties. However, a thickness exceeding 50 nm is undesirable from an economic standpoint because it tends to increase costs due to increased material usage and longer film formation times. From the same viewpoint as above, a thickness of 20 nm or more and 40 nm is more preferable. 【0075】 Inorganic oxide layers can be formed, for example, by vacuum deposition. Vacuum deposition can utilize either physical vapor deposition or chemical vapor deposition. Examples of physical vapor deposition include, but are not limited to, vacuum evaporation, sputtering, and ion plating. Examples of chemical vapor deposition include, but are not limited to, thermal CVD, plasma CVD, and photoCVD. 【0076】 In the vacuum deposition methods described above, resistance heating vacuum deposition, EB (Electron Beam) heating vacuum deposition, induction heating vacuum deposition, sputtering, reactive sputtering, dual magnetron sputtering, and plasma chemical vapor deposition (PECVD) are particularly preferred. However, considering productivity, vacuum deposition is currently the most superior method. For the heating means in vacuum deposition, it is preferable to use one of the following methods: electron beam heating, resistance heating, or induction heating. 【0077】 When an inorganic oxide layer is formed on the surface of a base film, and a light-shielding layer is further provided on the base film, it is preferable that the light-shielding layer is a printed layer formed using light-shielding ink. 【0078】 <Light-shielding packaging> Light-shielding packaging is made from the above-mentioned light-shielding packaging material, and there are no particular restrictions on the method of making the packaging. For example, the above-mentioned light-shielding packaging material (laminated) can be used in flat bags, three-sided bags, gusseted bags, standing pouches, spouted pouches, beaked pouches, etc., using sealant film as the sealing material. Light-shielding packaging may be provided with easy-cutting means such as notches or perforations. 【0079】 Specifically, a steam-permeable pouch is one example of a pouch. Steam-permeable pouches are manufactured, for example, as follows: First, a front sheet and a back sheet made of body sheet material are prepared. Next, a bottom sheet (which may be the same as or different from the front and back sheets) is inserted between the bottom of the front sheet and the back sheet up to the folded-over portion to form a gusset. Subsequently, the inner surfaces of each sheet are heat-sealed to form seals such as a bottom seal, a right side seal, and a left side seal, thereby obtaining a steam-permeable pouch with a square bottom shape. Next, the upper part of the body sheet is heat-sealed at the upper sealing section. However, since this section is used as the filling opening for the contents, it is left as an unsealed opening before filling and heat-sealed after filling. In the example described above, a steam-permeable pouch was constructed using three packaging materials: a front sheet, a back sheet, and a body sheet. However, the number of packaging materials that make up a steam-permeable pouch is not particularly limited. [Examples] 【0080】 The present disclosure will be described in detail below using examples and comparative examples, but the present disclosure is not limited to the following examples. 【0081】 <Manufacturing of packaging materials> As materials to be used for the first and third layers, the following propylene homopolymer (A), propylene-ethylene random copolymer (B), and ethylene-α-olefin copolymer elastomer (C) were prepared. 【0082】 (Propylene homopolymer (A)) A propylene homopolymer having a melting onset temperature of 153°C, a melting point of 159°C, and a melt flow rate (MFR: ISO 1133) of 3.0 g / 10 min (at 230°C and 2.16 kg load), as measured by differential scanning calorimetry (JIS K 7121). 【0083】 (Propylene-ethylene random copolymer (B)) A propylene-ethylene random copolymer with a melting point of 147°C and an ethylene content of 3.4% by mass, as measured by differential scanning calorimetry (JIS K 7121). 【0084】 The ethylene content was measured according to the quantitative method for ethylene content (IR method) described on pages 412-413 of the Polymer Analysis Handbook (May 10, 2013, 3rd printing), edited by the Polymer Analysis Symposium of the Japan Society for Analytical Science. 【0085】 (Ethylene-α-olefin copolymer elastomer (C)) Tuffmer A-1085S (trade name, manufactured by Mitsui Chemicals, Inc.), an ethylene-1-butene copolymer elastomer, was used. The melt flow rate (MFR: ISO 1133) (temperature 190°C, load 2.16 kg) was 1.2 g / 10 min, and the density was 885 kg / m³. 3 The content of structural units derived from ethylene was 84% ​​by mass. 【0086】 For the second layer, we prepared the following materials: propylene-ethylene block copolymer (D), ethylene-propylene copolymer elastomer (E), and titanium dioxide (F). 【0087】 (Propylene-ethylene block copolymer (D)) A propylene-ethylene block copolymer with a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) of 1.8 g / 10 min, containing 81.5% by mass of propylene polymer and 18.5% by mass of ethylene-propylene copolymer, with an ethylene content of 36.2% by weight in the ethylene-propylene copolymer. 【0088】 (Ethylene-propylene copolymer elastomer (E)) An ethylene-propylene copolymer elastomer having a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) of 0.6 g / 10 min and a mass ratio of propylene content to ethylene content of 2.7. 【0089】 (Titanium dioxide (F)) Titanium oxide PEONY HP WHITE series (model number: L-11232-MPT) manufactured by DIC Corporation. 【0090】 (Example 1) For the formation of the first and third layers, a resin mixture was prepared by mixing 11.8 parts by mass of propylene homopolymer (A) and 88.2 parts by mass of propylene-ethylene random copolymer (B) in pellet form. To this resin mixture, 17.6 parts by mass of ethylene-α-olefin copolymer elastomer (C) was added for every 100 parts by mass of the total amount of propylene homopolymer (A) and propylene-ethylene random copolymer (B). For the formation of the second layer, a resin mixture was prepared by mixing ethylene-propylene copolymer elastomer (E) and propylene-ethylene block copolymer (D) in pellet form, such that the mass ratio (E) / (D) of E and D was 0.43. Titanium dioxide (F) was added to this resin mixture in an amount of 7.5% by mass based on the total mass of the second layer. Each resin mixture was supplied to an extruder heated to 250°C, kneaded in a molten state, and laminated in a T-die extruder with a feed block so that the first and third layers were 10 μm thick each, and the second layer was 40 μm thick, to produce a sealant film. In this case, the second layer is a light-shielding sealant layer. 【0091】 A 12 μm thick polyethylene terephthalate (PET) film, a 15 μm thick nylon (ONY) film, and a fabricated sealant film were laminated in this order using a two-component curing urethane adhesive by dry lamination to create a packaging material. 【0092】 (Example 2) A 1μm thick light-shielding layer (light-shielding printed layer) was formed on a 12μm thick PET film by gravure printing using light-shielding ink, with printed layers in the order of white / white / gray from the PET film side. White ink (Riogran 651: manufactured by Toyo Ink Co., Ltd.) and gray ink (Riogran 651 / 92: manufactured by Toyo Ink Co., Ltd.) were used as light-shielding inks. This resulted in a PET film with a light-shielding layer. The packaging material was prepared in the same manner as in Example 1, except that this PET film with a light-shielding layer was used instead of the PET film without a light-shielding layer. In this case, the side of the PET film with the light-shielding layer was placed facing the nylon film. 【0093】 (Example 3) A resin mixture prepared for forming the first layer was supplied to an extruder heated to 250°C, kneaded in a molten state, and extruded using a T-die extruder with a feed block to produce a sealant film with a first layer thickness of 60 μm. The packaging material was prepared in the same manner as in Example 2, except that this sealant film was used. 【0094】 (Comparative Example 1) The film was prepared in the same manner as in Example 1, except that the mixing ratio of each raw material compound was changed as shown in Table 1. 【0095】 (Comparative Example 2) The film was prepared in the same manner as in Example 3, except that the mixing ratio of each raw material compound was changed as shown in Table 1, and the above-mentioned PET film without a light-shielding layer was used instead of the PET film with a light-shielding layer. 【0096】 <Various evaluations> The packaging materials obtained in each example were evaluated as follows. The results are shown in Table 1. 【0097】 [Evaluation of resistance to bag drop] In each example, the first layers of the sealant film of the packaging material were placed facing each other, and heat-sealed using a heat sealer manufactured by Tester Industries Co., Ltd. under the conditions of a sealing pressure of 0.2 MPa, a sealing time of 1 second, a sealing width of 5 mm, and a sealing temperature of 150°C. A packaging bag was then created in which three sides were heat-sealed, leaving one short side unsealed. The size of the packaging bag was 180 mm x 130 mm. After filling the resulting packaging bag with 150 mL of water, the unheated side was heat-sealed to create a water-filled bag. This water-filled bag was retorted at 127°C for 50 minutes and then stored at a low temperature of 5°C for 72 hours. Next, with the water-filled bags standing vertically to the floor, the test was conducted by dropping them from a height of 100 cm 100 times, ensuring that the heat-sealed short side touched the floor first. A total of 10 bags were tested, and the percentage of bags that did not break (survival rate) was evaluated. A survival rate of 60% or higher was considered to indicate good resistance to dropping bags during low-temperature storage. 【0098】 [Low-temperature sealing performance evaluation] The first layers of the sealant film of the packaging materials obtained in each example were placed facing each other, and heat-sealed using a heat sealer manufactured by Tester Industries Co., Ltd. under the conditions of a sealing pressure of 0.2 MPa, a sealing time of 1 second, and a sealing width of 5 mm. The sealing temperature was adjusted in 2°C increments between 140°C and 160°C. Subsequently, the heat-sealed packaging materials at each temperature were cut into 15 mm wide x 80 mm sections, and T-shaped peeling was performed using a tensile testing machine manufactured by Shimadzu Corporation at a tensile speed of 300 mm / min to measure the heat seal strength of the heat-sealed portion. The temperature at which the heat seal strength reached 15 N / 15 mm or higher was defined as the heat seal rise temperature, and it was judged that the lower the heat seal rise temperature, the better the low-temperature sealing performance. 【0099】 [Heat resistance evaluation] In each example, the first layers of the sealant film of the packaging material were placed facing each other, and heat-sealed using a heat sealer manufactured by Tester Industries Co., Ltd. under the following conditions: sealing pressure of 0.05 MPa, sealing time of 30 seconds, sealing width of 10 mm, and sealing temperature of 128 °C. Subsequently, the heat-sealed packaging material was cut into 15 mm wide x 80 mm sections, and T-shaped peeling was performed using a tensile testing machine manufactured by Shimadzu Corporation at a tensile speed of 300 mm / min to measure the heat-sealing strength of the heat-sealed portion. A lower heat-sealing strength was considered to indicate better heat resistance. 【0100】 [Light-blocking performance evaluation] The total light transmittance (TT[%]) of the packaging materials obtained in each example was measured. The measurements were performed using a HAZE Meter NDH7000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7361-1 (ISO 13468-1) "Plastics - Test method for total light transmittance of transparent materials". A lower total light transmittance was considered to indicate better light shielding properties. 【0101】 [Table 1] [Explanation of symbols] 【0102】 1...Second layer, 2...Third layer, 3...Adhesive layer, 4...Base film, 10...First layer, 100~102...Sealant film, 200~202...Light-shielding packaging material.

Claims

[Claim 1] A base film and A light-shielding packaging material comprising a light-shielding sealant film having a first layer containing a propylene homopolymer (A), a propylene-ethylene random copolymer (B), and an ethylene-α-olefin copolymer elastomer (C), wherein the content of the ethylene-α-olefin copolymer elastomer (C) is 17.5 parts by mass or more with respect to 100 parts by mass of the total amount of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B). [Claim 2] A base film and A sealant film comprising a first layer containing a propylene homopolymer (A), a propylene-ethylene random copolymer (B), and an ethylene-α-olefin copolymer elastomer (C), wherein the content of the ethylene-α-olefin copolymer elastomer (C) is 17.5 parts by mass or more per 100 parts by mass of the total amount of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B), A light-shielding packaging material comprising a light-shielding layer. [Claim 3] The light-shielding packaging material according to claim 1, further comprising a light-shielding layer. [Claim 4] The light-shielding packaging material according to claim 1, wherein the light-shielding sealant film comprises a layer containing an inorganic pigment. [Claim 5] The light-shielding packaging material according to claim 1 or 2, wherein the base film contains a propylene polymer. [Claim 6] The light-shielding packaging material according to claim 1 or 2, wherein the base film has an inorganic oxide layer on at least one surface. [Claim 7] A light-shielding package made from the light-shielding packaging material described in claim 1 or 2.

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