Sealant films, packaging materials and packaging bodies

Abstract

To provide a sealant film that is a polypropylene film but is superior in both heat resistance and low-temperature sealability.SOLUTION: A sealant film includes a first layer, which comprises a propylene homopolymer (A), a propylene / ethylene random copolymer (B), and a propylene / α-olefin copolymer elastomer (C). The content of the propylene / α-olefin copolymer elastomer (C) is 5.0-25.0 pts.mass relative to 100 pts.mass of the total amount of the propylene homopolymer (A) and the propylene / ethylene random copolymer (B).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a sealant film, a packaging material, and a package. Specifically, the present invention relates to a sealant film that is a polypropylene-based film, has excellent heat resistance and low-temperature sealability, and can be suitably used for severe treatments such as boiling water treatment and retort treatment as a packaging material, and also relates to a packaging material and a packaging bag obtained by using the sealant film.

Background Art

[0002] Since the non-stretched polypropylene-based film is excellent in rigidity and heat resistance and is inexpensive, it may be used as a sealant film in various packaging materials such as food packaging.

[0003] In Patent Document 1, a polypropylene-based 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.

[0004] In Patent Document 2, a polypropylene-based film characterized by comprising a crystalline propylene-α-olefin random copolymer and an ethylene-α-olefin random copolymer has been proposed.

[0005] In Patent Document 3, a polypropylene-based composite film composed of three layers has been proposed, wherein the intermediate layer is made of a propylene-ethylene block copolymer and both surface layers are made of a propylene-based random copolymer.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] When polypropylene-based unoriented films are used as sealant films, they are required to have heat resistance that can withstand retort processing, such as high-temperature processing at 135°C under high pressure conditions for sterilization and disinfection. In recent years, with the aim of improving the recyclability of packaging materials, research has been progressing on monomaterial packaging materials using biaxially oriented polypropylene film (OPP) as a base material and polypropylene-based unoriented film. However, biaxially oriented polypropylene film has a lower melting point compared to biaxially oriented polyamide film (ONy) and biaxially oriented polyester film (PET), which have been used as base materials in the past, making it impossible to perform heat sealing at high temperatures during bag manufacturing. Therefore, polypropylene-based unoriented films are increasingly required to have low-temperature sealing properties so that proper heat sealing can be performed even at lower heat sealing temperatures. However, with conventional unoriented polypropylene films, it is currently difficult to achieve both excellent heat resistance and low-temperature sealing properties.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a sealant film that, while being a polypropylene film, is capable of achieving both excellent heat resistance and low-temperature sealing properties. The present invention also aims to provide packaging materials and packaging bodies that can be obtained using the sealant film. [Means for solving the problem]

[0009] As a result of diligent research to solve the above problems, the inventors discovered that it is important to include a predetermined amount of propylene-α-olefin copolymer elastomer (C) in a resin composition containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B), and thus completed the present invention.

[0010] A sealant film according to one aspect of the present invention comprises a first layer containing a propylene homopolymer (A), a propylene-ethylene random copolymer (B), and a propylene-α-olefin copolymer elastomer (C), wherein the content of the propylene-α-olefin copolymer elastomer (C) is 5.0 to 25.0 parts by mass per 100 parts by mass of the total amount of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B).

[0011] The above sealant film can achieve both excellent heat resistance and low-temperature sealing properties. Such effects cannot be obtained when using a resin composition containing a crystalline propylene polymer, 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 (for example, Patent Document 1 above), when using a resin composition consisting of a crystalline propylene-α-olefin random copolymer and an ethylene-α-olefin random copolymer (for example, Patent Document 2 above), or when using a propylene-based random copolymer in the surface layer (for example, Patent Document 3 above). These effects are particularly suitable for polypropylene-based monomaterial retort packaging applications.

[0012] In one embodiment, it is preferable that the mass ratio of the propylene homopolymer (A) content to the propylene-ethylene random copolymer (B) content is in the range of 0.12 to 0.95. This makes it easier to obtain better low-temperature sealing performance while maintaining heat resistance.

[0013] In one embodiment, the sealant film may comprise the first layer described above and a second layer containing a propylene-ethylene block copolymer (D) and an ethylene-propylene copolymer elastomer (E). This makes it easier for the film to obtain excellent cold shock resistance.

[0014] In one embodiment, the sealant film may comprise the first layer, the second layer, and a third layer containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B) in this order. This makes it easier to suppress distortion and warping of the film.

[0015] In one embodiment, the second layer may contain 90-50% by mass of propylene-ethylene block copolymer (D) and 10-50% by mass of ethylene-propylene copolymer elastomer (E). This makes it easier for the film to obtain better cold impact resistance.

[0016] In one embodiment, the thickness of the second layer may be 20 μm or more. This makes it easier for the film to obtain better cold impact resistance.

[0017] A packaging material according to one aspect of the present invention comprises the above-mentioned sealant film and a resin film having a metal oxide vapor deposition layer.

[0018] A packaging material according to one aspect of the present invention comprises the above-mentioned sealant film and a biaxially oriented polypropylene film.

[0019] A packaging according to one aspect of the present invention is made from the above-mentioned packaging material. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a sealant film that, while being a polypropylene-based film, can achieve a high level of balance between excellent heat resistance and low-temperature sealing properties. Furthermore, according to the present invention, it is possible to provide packaging materials and packaging bodies obtained using the sealant film.

[0021] The sealant film of the present invention has heat resistance that can withstand retort treatment for sterilization and disinfection at a high temperature of 135°C, which is a high retort condition, and even when used with a biaxially stretched polypropylene film (OPP) substrate (even if it is a packaging material made of the same material as polypropylene), it has excellent low-temperature sealability that enables heat sealing.

Brief Description of the Drawings

[0022] [Figure 1] Figure 1 is a cross-sectional view of a sealant film according to an embodiment of the present invention. [Figure 2] Figure 2 is a cross-sectional view of a sealant film according to an embodiment of the present invention. [Figure 3] Figure 3 is a cross-sectional view of a sealant film according to an embodiment of the present invention. <(0000100)>Figure 4 is a cross-sectional view of a packaging material according to an embodiment of the present invention. [Figure 5] Figure 5 is a cross-sectional view of a packaging material according to an embodiment of the present invention. [Figure 6] Figure 6 is a cross-sectional view of a packaging material according to an embodiment of the present invention.

Mode for Carrying Out the Invention

[0023] <Sealant Film 100> Figure 1 is a cross-sectional view of a sealant film 100 according to an embodiment of the present invention. The sealant film 100 includes a first layer 10 containing a propylene homopolymer (A), a propylene-ethylene random copolymer (B), and a propylene-α-olefin copolymer elastomer (C).

[0024] (Propylene Homopolymer (A)) The propylene homopolymer (A) can be obtained by homopolymerizing propylene using, for example, a Ziegler-Natta type catalyst, a metallocene catalyst, or a half-metallocene catalyst. The inclusion of the propylene homopolymer (A) in the sealant film provides excellent heat resistance to the first layer. This makes it less likely for fusion to occur on the inner surface of the packaging bag after, for example, high-pressure heat treatment at 135°C.

[0025] As the propylene homopolymer (A), a material can be used that has a melting onset temperature of 150°C or higher and a melting point of 155°C or higher, as measured by differential scanning calorimetry (JIS K 7121). Having both the melting onset temperature and melting point within this range provides superior heat resistance to the first layer. This makes it less likely for fusion to occur on the inner surface of the packaging bag after, for example, high-pressure heat treatment at 135°C. The conditions for differential scanning calorimetry are as follows. [Differential scanning calorimetry conditions] When the temperature is increased from 25°C to 230°C at a rate of 10°C / min, the point at which the straight line extending the baseline on the low-temperature side of the DSC curve toward the high-temperature side intersects with a tangent line drawn so as to be tangent to the curve on the low-temperature side of the melting peak and have the maximum slope is defined as the melting onset temperature, and the temperature at the peak of the melting peak is defined as the melting point.

[0026] As the propylene homopolymer (A), one with a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) in the range of 2.0 to 7.0 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. Furthermore, a melt flow rate below the upper limit makes it easier for the first layer to have excellent impact resistance.

[0027] (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.

[0028] 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.

[0029] 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 pressurized heat treatment at 135°C high-retort conditions. 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.

[0030] 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.

[0031] (Propylene-α-olefin copolymer elastomer (C)) The propylene-α-olefin copolymer elastomer (C) can be obtained by copolymerizing propylene and α-olefin using, for example, a Ziegler-Natta type catalyst, a metallocene catalyst, or a half-metallocene catalyst. The inclusion of the propylene-α-olefin copolymer elastomer (C) in the first layer provides excellent low-temperature sealing properties. Furthermore, the inclusion of the propylene-α-olefin copolymer elastomer (C) in the first layer facilitates excellent cold impact resistance, blocking resistance, scratch resistance, and bending whitening resistance.

[0032] As the propylene-α-olefin copolymer elastomer (C), a propylene-α-olefin copolymer elastomer having structural units derived from propylene 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 propylene-α-olefin copolymer elastomer (C) may be a random copolymer.

[0033] 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 propylene-α-olefin copolymer elastomer (C) may have two or more structural units derived from these α-olefins having 4 to 20 carbon atoms.

[0034] As the propylene-α-olefin copolymer elastomer (C), one can be used in which the content of structural units derived from propylene is in the range of 65 to 97% by mass, preferably 70 to 90% by mass, based on 100% by mass of the total amount of propylene-α-olefin copolymer elastomer (C) (total amount of structural units). Having a propylene-derived structural unit content above the lower limit makes it easier to maintain excellent heat resistance. Furthermore, having a propylene-derived structural unit content below the upper limit makes it easier to obtain excellent low-temperature sealing properties.

[0035] As for the propylene-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.

[0036] As the propylene-α-olefin copolymer elastomer (C), one can be used with a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) in the range of 0.5 to 15 g / 10 min, preferably in the range of 1 to 10 g / 10 min or 3 to 8 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.

[0037] The first layer contains 5.0 to 25.0 parts by mass of propylene-α-olefin copolymer elastomer (C) per 100 parts by mass of the total amount of propylene homopolymer (A) and propylene-ethylene random copolymer (B). By keeping the content of propylene-α-olefin copolymer elastomer (C) within the above range, it is easy to obtain low-temperature sealing properties while maintaining excellent heat resistance. From this viewpoint, the content may be 5.0 to 15.0 parts by mass or 5.0 to 10.0 parts by mass.

[0038] 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 0.12 to 0.95. Maintaining a mass ratio (A) / (B) above the lower limit makes it easier to maintain excellent heat resistance. Furthermore, maintaining 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 0.14 to 0.94, or 0.30 to 0.93.

[0039] <Sealant Film 101> Figure 2 is a cross-sectional view of a sealant film 101 according to one embodiment of the present invention. 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.

[0040] (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.

[0041] 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.

[0042] 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).

[0043] 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.

[0044] (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.

[0045] 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 impact resistance.

[0046] 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.

[0047] The second layer may contain 90-50% by mass of propylene-ethylene block copolymer (D) and 10-50% by mass of ethylene-propylene copolymer elastomer (E). A content of 50% 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% by mass or more, or 70% by mass or more. A content of 90% by mass or less of propylene-ethylene block copolymer (D), that is, a content of at least 10% 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% by mass or less, or 85% by mass or less. From the above viewpoints, the content of ethylene-propylene copolymer elastomer (E) may be 12.5-40% by mass or 15-30% by mass.

[0048] <Sealant Film 102> Figure 3 is a cross-sectional view of a sealant film 102 according to one embodiment of the present invention. 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.

[0049] 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 is the same as that of the first layer from the viewpoint of suppressing film curling after film formation.

[0050] Sealant films are unoriented films and can be composed primarily of polypropylene-based materials; therefore, they can be called polypropylene-based unoriented films.

[0051] The thickness of the sealant film is not particularly limited, as long as it is within the range suitable for use as a film for packaging materials, for example. However, since excessively thick film results in cost disadvantages, the film thickness can be 100 μm or less, and may be between 50 and 70 μm.

[0052] 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%.

[0053] 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 when stored at low temperatures. From this viewpoint, the thickness of the second layer may be 25 μm or more, or even 30 μm or more. There is no particular upper limit to the thickness of the second layer, but it can be set to 50 μm to avoid cost disadvantages.

[0054] 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%.

[0055] <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.

[0056] 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.

[0057] 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 printing surface or the surface in contact with the substrate to improve printability when using a single film or to improve lamination suitability when using a laminate. 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.

[0058] <Packaging material> The packaging material comprises the sealant film described above. The packaging material may comprise only the sealant film, or it may further comprise other layers. The sealant film is provided in the packaging material such that the first layer, which is a heat-seal layer, faces the contents.

[0059] <Packaging material 200~202> Figures 4-6 are cross-sectional views of packaging materials according to one embodiment of the present invention. Packaging material 200 is formed by laminating a sealant film 100 and a base material 4 via an adhesive layer 3. Packaging material 201 is formed by laminating a sealant film 101 and a base material 4 via an adhesive layer 3. Packaging material 202 is formed by laminating a sealant film 102 and a base material 4 via an adhesive layer 3.

[0060] Examples of substrates include resin films such as biaxially oriented polyamide film (ONy), biaxially oriented polyester film (PET), and biaxially oriented polypropylene film (OPP), resin films having a metal oxide vapor deposition layer on the surface of these resin films (transparent vapor-deposited films), printing paper, and metal foil (AL foil). The substrate may be a single layer of any of these, or a laminate comprising two or more of these. If the substrate is a laminate, each layer may be laminated with an adhesive layer in between.

[0061] From the viewpoint of gas barrier properties of the packaging material, the base material can be a resin film having a metal oxide vapor deposition layer; that is, the packaging material can comprise a sealant film and a resin film having a metal oxide vapor deposition layer. Examples of metal oxides constituting the metal oxide vapor deposition layer include silicon oxide and aluminum oxide. From the viewpoint of protecting the metal oxide vapor deposition layer, the resin film may be laminated with the metal oxide vapor deposition layer facing the sealant layer. The resin film may have metal oxide vapor deposition layers on both sides.

[0062] From the viewpoint of the recyclability of the packaging material, the base material can be a biaxially oriented polypropylene film, that is, the packaging material can comprise a sealant film and a biaxially oriented polypropylene film. A packaging material obtained using a biaxially oriented polypropylene film as the base material can be called a monocrystalline packaging material.

[0063] From the viewpoint of gas barrier properties and recyclability of the packaging material, the base material can be a laminate of a resin film having a metal oxide vapor deposition layer and a biaxially oriented polypropylene film. That is, the packaging material can comprise a sealant film, a resin film having a metal oxide vapor deposition layer, and a biaxially oriented polypropylene film in this order. In particular, from the viewpoint of recyclability of the packaging material, the resin film having a metal oxide vapor deposition layer may be a biaxially oriented polypropylene film having a metal oxide vapor deposition layer.

[0064] For example, the adhesive layer material can be polyester-isocyanate resin, urethane resin, polyether resin, or an acid-modified polyolefin.

[0065] The packaging material can be manufactured by a conventional dry lamination method, in which a sealant film and a substrate are bonded together via an adhesive layer, as described above. However, the packaging material may also be manufactured by a method in which the sealant film is directly extruded onto the substrate and laminated.

[0066] The composition of the packaging material can be adjusted as appropriate according to the required characteristics of the packaging, such as barrier properties to meet the shelf life of the packaged food, size and impact resistance to accommodate the weight of the contents, visibility of the contents, and recyclability.

[0067] <Package> The packaging can be made from the above-mentioned packaging material, and there are no particular restrictions on the method of making the packaging. For example, the above-mentioned packaging material (laminated material) can be used for flat bags, three-sided bags, gusseted bags, standing pouches, spouted pouches, beaked pouches, etc., using sealant film as the sealing material.

[0068] <Summary of this embodiment> [Invention 1] It contains a propylene homopolymer (A), a propylene-ethylene random copolymer (B), and a propylene-α-olefin copolymer elastomer (C), A sealant film comprising a first layer in which the content of the propylene-α-olefin copolymer elastomer (C) is 5.0 to 25.0 parts by mass per 100 parts by mass of the total amount of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B). [Invention 2] The sealant film according to Invention 1, wherein the mass ratio of the content of the propylene homopolymer (A) to the content of the propylene-ethylene random copolymer (B) is 0.12 to 0.95. [Invention 3] The first layer mentioned above, A sealant film according to invention 1 or 2, comprising a second layer containing a propylene-ethylene block copolymer (D) and an ethylene-propylene copolymer elastomer (E). [Invention 4] The first layer mentioned above, The aforementioned second layer, A sealant film according to Invention 3, comprising, in this order, a third layer containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B). [Invention 5] The sealant film according to invention 3 or 4, wherein the second layer contains 90-50% by mass of the propylene-ethylene block copolymer (D) and 10-50% by mass of the ethylene-propylene copolymer elastomer (E). [Invention 6] A sealant film according to any one of inventions 3 to 5, wherein the thickness of the second layer is 20 μm or more. [Invention 7] A packaging material comprising a sealant film according to any one of inventions 1 to 6, and a resin film having a metal oxide vapor deposition layer. [Invention 8] A packaging material comprising a sealant film according to any one of inventions 1 to 6 and a biaxially oriented polypropylene film. [Invention 9] A package made from the packaging material described in Invention 7 or 8. [Examples]

[0069] The present invention will be described in detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0070] <Preparation of sealant film> (Example 1) The following propylene homopolymers (A), propylene-ethylene random copolymers (B), and propylene-α-olefin copolymer elastomers (C) were prepared.

[0071] (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).

[0072] (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).

[0073] 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.

[0074] (Propylene-α-olefin copolymer elastomer (C)) Tuffmer XM-7090 (trade name, manufactured by Mitsui Chemicals, Inc.), a propylene-1-butene copolymer elastomer, was used. The melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) was 7.0 g / 10 min, and the density was 885 kg / m³. 3 The content of structural units derived from propylene was 89% by mass.

[0075] After mixing 47.4 parts by mass of propylene homopolymer (A) and 52.6 parts by mass of propylene-ethylene random copolymer (B) in pellet form, a resin mixture was prepared by mixing 5.3 parts by mass of propylene-α-olefin copolymer elastomer (C) with 100 parts by mass of the total amount of propylene homopolymer (A) and propylene-ethylene random copolymer (B). The resin mixture was then supplied to an extruder heated to 250°C, kneaded in a molten state, and a film was formed with a thickness of 60 μm using a T-die extruder with a feed block to produce the sealant film of Example 1.

[0076] (Examples 2-5 and Comparative Examples 1-5) 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.

[0077] (Example 6) For the second layer, we prepared the following materials: propylene-ethylene block copolymer (D) and ethylene-propylene copolymer elastomer (E).

[0078] (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.

[0079] (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.

[0080] For the formation of the first layer, 47.4 parts by mass of propylene homopolymer (A) and 52.6 parts by mass of propylene-ethylene random copolymer (B) were mixed in pellet form. Then, a resin mixture was prepared by mixing 5.3 parts by mass of propylene-α-olefin copolymer elastomer (C) with 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 70% by mass of propylene-ethylene block copolymer (D) and 30% by mass of ethylene-propylene copolymer elastomer (E) in pellet form. 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 layer had a thickness of 15 μm and the second layer had a thickness of 45 μm, thereby producing the sealant film of Example 6.

[0081] (Example 7) The film was prepared in the same manner as in Example 6, except that the mixing ratio of each raw material compound was changed as shown in Table 2.

[0082] (Example 8) For the formation of the first and third layers, a resin mixture was prepared by mixing 47.4 parts by mass of propylene homopolymer (A) and 52.6 parts by mass of propylene-ethylene random copolymer (B) in pellet form. For the resin mixture for forming the first layer only, 5.3 parts by mass of propylene-α-olefin copolymer elastomer (C) was added to 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 70% by mass of propylene-ethylene block copolymer (D) and 30% by mass of ethylene-propylene copolymer elastomer (E) in pellet form. 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 the sealant film of Example 8.

[0083] (Example 9) The film was prepared in the same manner as in Example 8, except that the mixing ratio of each raw material compound was changed as shown in Table 2.

[0084] (Comparative Examples 6-7) The film was prepared in the same manner as in Example 6, except that the mixing ratio of each raw material compound was changed as shown in Table 2.

[0085] (Comparative Examples 8-9) The film was prepared in the same manner as in Example 8, except that the mixing ratio of each raw material compound was changed as shown in Table 2.

[0086] <Various evaluations> The following evaluations were performed on the films obtained in each case. The results are shown in Tables 1 and 2.

[0087] [Low-temperature sealing performance evaluation] The films obtained in each example (the first layer if the film is a laminate) 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. After that, the heat-sealed films at each temperature were cut into 15 mm wide x 80 mm strips, and the heat seal strength of the heat-sealed portion was measured by T-shaped peeling at a tensile speed of 300 mm / min using a tensile testing machine manufactured by Shimadzu Corporation. The temperature at which the heat seal strength reached 15 N / 15 mm or more 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.

[0088] [Heat resistance evaluation] The films obtained in each example (the first layer if the film is a laminate) 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 135 °C. After that, the heat-sealed films were cut into 15 mm wide x 80 mm strips, 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. If the heat-sealing strength was 2.0 N / 15 mm or less, it was judged that the heat resistance was good.

[0089] [Table 1]

[0090] [Table 2] [Industrial applicability]

[0091] The sealant film of the present invention, while being a polypropylene-based film, can achieve a high level of both heat resistance and low-temperature sealing performance. Therefore, the sealant film of the present invention can be suitably used in polypropylene-based monomaterial packaging materials (retort packaging materials). [Explanation of Symbols]

[0092] 1...Second layer, 2...Third layer, 3...Adhesive layer, 4...Base material, 10...First layer, 100~102...Sealant film, 200~202...Packaging material.

Claims

1. A first heat-seal layer containing a propylene homopolymer (A), a propylene-ethylene random copolymer (B), and a propylene-α-olefin copolymer elastomer (C), wherein the content of the propylene-α-olefin copolymer elastomer (C) is 5.0 to 25.0 parts by mass relative to 100 parts by mass of the total amount of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B), A sealant film comprising a second layer containing a propylene-ethylene block copolymer (D) and an ethylene-propylene copolymer elastomer (E).

2. The sealant film according to claim 1, wherein the mass ratio of the content of the propylene homopolymer (A) to the content of the propylene-ethylene random copolymer (B) is 0.12 to 0.

95.

3. The first layer mentioned above, The aforementioned second layer, The sealant film according to claim 1, comprising, in this order, a third layer containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B).

4. The sealant film according to claim 1, wherein the second layer contains 90 to 50% by mass of the propylene-ethylene block copolymer (D) and 10 to 50% by mass of the ethylene-propylene copolymer elastomer (E).

5. The sealant film according to claim 3, wherein the second layer contains 90 to 50% by mass of the propylene-ethylene block copolymer (D) and 10 to 50% by mass of the ethylene-propylene copolymer elastomer (E).

6. The sealant film according to claim 1, wherein the thickness of the second layer is 20 μm or more.

7. The sealant film according to claim 3, wherein the thickness of the second layer is 20 μm or more.

8. A packaging material comprising a sealant film according to any one of claims 1 to 7 and a resin film having a metal oxide vapor deposition layer.

9. A packaging material comprising a sealant film according to any one of claims 1 to 7 and a biaxially oriented polypropylene film.

10. A package made from the packaging material described in claim 8.

11. A package made from the packaging material described in claim 9.

Images