Laminated film and its manufacturing method

Abstract

Provided is a laminated film that is excellent in heat seal strength, low-temperature sealability, and recyclability. [Solution] A laminated film comprising a base layer, an intermediate layer, and a heat-sealing layer laminated in this order, wherein the base layer and the intermediate layer are stretched polypropylene films, the heat-sealing layer is an unstretched polypropylene film, the resin composition (A) constituting the intermediate layer satisfies the following requirement (a1), and the resin composition (B) constituting the heat-sealing layer satisfies the following requirements (b1) and (b2). (a1) The durometer D hardness (HDD) measured in accordance with JIS K 7215:1986 is 10 to 78. (b1) The durometer D hardness (HDD) measured in accordance with JIS K 7215:1986 is 10 to 78. (b2) The melting point is 110 to 150°C.

Description

[Technical Field]

[0001] The present invention relates to a laminated film having excellent seal strength and low-temperature sealability, and a method for producing the same. [Background technology]

[0002] Polypropylene film has a variety of excellent properties, including transparency, rigidity, and heat resistance, and is therefore widely used as a packaging film for food, clothing, medical care, pharmaceuticals, stationery, miscellaneous goods, industrial materials, and other industrial applications. In particular, films dry-laminated with polyethylene and biaxially oriented polyamide film, biaxially oriented polyester film, or biaxially oriented polypropylene film are the mainstream on the market, and are used for food packaging and as exterior packaging for lithium-ion batteries. Meanwhile, with growing environmental awareness, interest has been growing in so-called monomaterial packaging, which uses the same material to create packaging materials and is recyclable. While polypropylene film has the characteristics of having a higher melting point and rigidity than polyethylene film, its applications are limited due to its inferior heat seal strength, low-temperature heat sealability, impact resistance, puncture resistance, and tear strength, as well as its poor resistance to bag drop at low temperatures.

[0003] For example, Patent Document 1 discloses a retort sealant film that is composed of a core layer made of 100 parts by weight of a polypropylene elastomer and 0 to 150 parts by weight of a polypropylene resin, and a heat seal layer laminated on at least one side of the core layer and made of a mixture of 30 to 70 parts by weight of a polypropylene resin and 70 to 30 parts by weight of a polypropylene elastomer, and is shown to have excellent impact resistance and low-temperature sealability.

[0004] Patent Documents 2 and 3 disclose packaging materials that include at least a biaxially oriented polypropylene film and a polypropylene-based unoriented film, in which the polypropylene-based unoriented film contains a propylene homopolymer and a propylene-ethylene random copolymer, and show that the balance between heat resistance and low-temperature sealability can be improved.

[0005] Meanwhile, laminate films having three or more layers, including a layer made of a polypropylene-based resin, are also known. Patent Document 4 discloses a laminate comprising a gas barrier laminate film having a gas barrier layer made of a stretched polypropylene resin substrate and an inorganic thin film, and a sealant film. It is shown that the laminate is made of resins with low environmental impact and has necessary properties such as gas barrier properties and heat sealability. Patent Document 5 discloses a laminate comprising a sealant film and a substrate film that meet specific requirements, the sealant film having a heat-sealable layer and an adjacent layer, and containing 70% by mass or more of a propylene (co)polymer and / or a 1-butene (co)polymer when the total mass of the two types of films is taken as 100% by mass. It is shown that the laminate has a high content of propylene copolymer and has excellent low-temperature heat sealability and heat seal strength. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-150491 [Patent Document 2] Japanese Patent Application Publication No. 2023-161216 [Patent Document 3] Japanese Patent Application Publication No. 2023-161210 [Patent Document 4] International Publication No. 2025 / 070687 [Patent Document 5] Japanese Patent Publication No. 2020-192696 Summary of the Invention [Problem to be solved by the invention]

[0007] The sealant film of Patent Document 1, the packaging materials of Patent Documents 2 and 3, and the laminate of Patent Document 4 were inferior in low-temperature heat sealing and had room for improvement in heat sealing strength. The laminate of Patent Document 5 had good low-temperature heat sealing, but had room for improvement in heat sealing strength.

[0008] An object of the present invention is to provide a laminated film that is excellent in heat seal strength, low-temperature sealability and recyclability. [Means for solving the problem]

[0009] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, they discovered that in a laminate film formed by laminating a base layer, an intermediate layer, and a heat-sealing layer in this order, the base layer and the intermediate layer are oriented polypropylene films, the heat-sealing layer is an unoriented polypropylene film, and the intermediate layer and the heat-sealing layer each use resin compositions that satisfy specific requirements, the resulting laminate film has excellent heat-sealing strength, low-temperature sealing property, and recyclability, and thus completed the present invention. The present invention relates to the following [1] to

[10] .

[0010] [1] A laminated film comprising a base layer, an intermediate layer, and a heat-sealing layer laminated in this order, wherein the base layer and the intermediate layer are stretched polypropylene films, the heat-sealing layer is an unstretched polypropylene film, the resin composition (A) constituting the intermediate layer satisfies the following requirement (a1), and the resin composition (B) constituting the heat-sealing layer satisfies the following requirements (b1) and (b2). (a1) The durometer D hardness (HDD) measured in accordance with JIS K 7215:1986 is 10 to 78. (b1) The durometer D hardness (HDD) measured in accordance with JIS K 7215:1986 is 10 to 78. (b2) The melting point is 110 to 150°C. [2] The resin composition (A) contains a propylene polymer (C) and a propylene thermoplastic elastomer (D), and the content of the propylene polymer (C) is 10 to 100% by weight and the content of the propylene thermoplastic elastomer (D) is 0 to 90% by weight, relative to 100% by weight of the total of the propylene polymer (C) and the propylene thermoplastic elastomer (D); the resin composition (B) contains a propylene polymer (E) and a propylene thermoplastic elastomer (F), and the content of the propylene polymer (E) is 10 to 100% by weight and the content of the propylene thermoplastic elastomer (F) is 0 to 90% by weight, relative to 100% by weight of the total of the propylene polymer (E) and the propylene thermoplastic elastomer (F); The laminated film according to [1], wherein the propylene polymer (C) satisfies the following requirements (c1) to (c5), the propylene thermoplastic elastomer (D) satisfies the following requirements (d1) to (d4), the propylene polymer (E) satisfies the following requirements (e1) to (e5), and the propylene thermoplastic elastomer (F) satisfies the following requirements (f1) to (f4). (c1) and (e1) The MFR measured in accordance with JIS K 7210-1:2014 (230°C, 2.16 kg load) is 1 to 50 g / 10 min. (c2) and (e2) The flexural modulus, measured in accordance with JIS K 7171:2022 at a test speed of 2 mm / min, is greater than 500 MPa and less than or equal to 1,300 MPa. (c3) and (e3) The content of units derived from propylene is more than 88.0% by weight and not more than 99.9% by weight. (c4) and (e4) The content of units derived from ethylene and α-olefins having 4 to 20 carbon atoms is 0.1% by weight or more and less than 12.0% by weight. (c5) and (e5) have a melting point of 110 to 155°C. (d1) and (f1) The MFR measured in accordance with JIS K 7210-1:2014 (230°C, 2.16 kg load) is 1 to 30 g / 10 min. (d2) and (f2) The flexural modulus measured in accordance with JIS K 7171:2022 at a test speed of 2 mm / min is 5 to 200 MPa. (d3) and (f3) The content of units derived from propylene is 60.0 to 92.0% by weight. (d4) and (f4) The content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms is 8.0 to 40.0% by weight. [3] The laminated film according to [2], wherein the propylene-based thermoplastic elastomer (D) satisfies the following requirements (d3') and (d4'), and the propylene-based thermoplastic elastomer (F) satisfies the following requirements (f3') and (f4'). The content of units derived from (d3') and (f3') propylene is 60.0 to 88.0% by weight. (d4') and (f4') The content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms is 12.0 to 40.0% by weight. [4] The laminated film according to [2] or [3], wherein in the resin composition (B), the content of the propylene polymer (E) is 50 to 95% by weight, and the content of the propylene thermoplastic elastomer (F) is 5 to 50% by weight, relative to 100% by weight of the total of the propylene polymer (E) and the propylene thermoplastic elastomer (F). [5] The laminated film according to any one of [1] to [4], wherein the thicknesses of the intermediate layer and the heat seal layer are 1 to 10 μm and 10 to 400 μm, respectively. [6] The laminated film according to any one of [1] to [5], wherein the sealing temperature at which the heat seal strength reaches 20 N / 15 mm as measured under the following conditions is 140° C. or lower. <Measurement of the sealing temperature at which the heat seal strength reaches 20N / 15mm> After storing the laminated film at an ambient temperature of 23°C for 7 days, it was cut into strips measuring 180 mm (MD) x 80 mm (TD), folded in half in the MD so that the heat-sealable layers were in contact with each other, and heat-sealed at a width of 10 mm at a position 20-30 mm from the fold under the following sealing conditions. The resulting partially heat-sealed sample was cut into strips with a width of 15 mm in the TD to obtain test pieces. The resulting test pieces were pulled at both ends in a 180° peel direction using a Schopper-type tensile tester at a rate of 500 mm / min, and the maximum force required to peel the heat-sealed portions was measured and used as the heat-seal strength. Sealing conditions: Sealing pressure: 2.0 kg / cm 2 (0.196 MPa), sealing time: 1.0 second, sealing temperature: 90°C to 170°C in 10°C increments. In the seal curve obtained from the seal temperature and heat seal strength, the data between any two points measured at 10°C intervals is approximated with a linear function to determine the seal temperature at which the heat seal strength reaches 20N / 15mm. [7] The laminated film according to any one of [1] to [6], wherein the average number of times the bag is dropped to break is six or more in a bag drop impact test measured under the following conditions: <Dropped bag impact test> Two 120mm x 150mm sheets are cut from the laminated film, and the heat-sealed layers of each sheet are overlapped. Then, three sides are sealed using an impulse sealer under the following sealing conditions to create a 120mm x 150mm sample bag. 100ml of water is poured into the sample bag, and the open side is sealed using an impulse sealer under the following sealing conditions to create a water seal test piece. After storing the water seal test piece in a 0°C atmosphere for one day, it is dropped 50 times consecutively from a height of 1.5m onto a metal plate. The maximum number of times the bag does not break is recorded as the number of bag breakage drops. The test is repeated five times, and the average number of bag breakage drops is calculated. The sealing conditions are as follows: a Fuji Impulse poly sealer (product name: PC-300), seal width: 2 mm, scale: 10 (sealing time: 1.6 seconds). [8] A food packaging film, a heavy-duty packaging film, or a liquid packaging film, which is made of the laminate film according to any one of [1] to [7]. [9] A method for producing a laminate film according to any one of [1] to [7], comprising: step 1 of co-extruding a base layer and an intermediate layer to obtain a laminate; step 2 of stretching the laminate obtained in step 1 to obtain a stretched film; and step 3 of bonding a heat seal layer onto the intermediate layer of the stretched film obtained in step 2.

[10] The method for producing a laminated film according to [9], wherein the step 3 is a step of bonding the intermediate layer and the heat seal layer by a dry lamination method. [Effects of the Invention]

[0011] The present invention provides a laminated film that is excellent in heat seal strength, low-temperature sealability, and recyclability. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing a process flow when one horizontal polymerization vessel is used in the production of propylene polymers 1 and 2 according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The laminated film is composed of a base layer, an intermediate layer, and a heat-sealing layer laminated in this order, the base layer and the intermediate layer being stretched polypropylene films, the heat-sealing layer being an unstretched polypropylene film, the resin composition (A) constituting the intermediate layer satisfying the following requirement (a1), and the resin composition (B) constituting the heat-sealing layer satisfying the following requirements (b1) and (b2). (a1) The durometer D hardness (HDD) measured in accordance with JIS K 7215:1986 is 10 to 78. (b1) The durometer D hardness (HDD) measured in accordance with JIS K 7215:1986 is 10 to 78. (b2) The melting point is 110 to 150°C. By laminating the substrate layer, intermediate layer, and heat-sealing layer of the present invention in this order, a laminate film with excellent heat-sealing strength, low-temperature sealing property, and recyclability can be obtained. The inventors have discovered that a laminate film having an intermediate layer that meets specific requirements between the substrate layer and the heat-sealing layer exhibits significantly improved heat-sealing strength compared to conventional laminate films without an intermediate layer. This intermediate layer is flexible and is believed to effectively disperse stress generated when peeling the laminate film after heat sealing. As a result, stress is prevented from concentrating on the substrate layer, suppressing cracking in the substrate layer and the resulting breakage of the substrate layer. It is believed that this improves the heat-sealing strength of the laminate film as a whole. The laminate film of the present invention has high heat-sealing strength, making it suitable for heavy-duty packaging applications that conventional polypropylene laminate films could not. Furthermore, given the recent market trend toward environmentally conscious film, there is a need for reduced resin content in the film industry. Since the laminate film maintains high heat-sealing strength even when the heat-sealing layer is thin, the thickness of the heat-sealing layer can be made thinner than before, reducing the amount of resin used. Furthermore, the heat-sealing initiation temperature can be lowered, allowing the set temperature of the sealing mold to be lowered, thereby saving energy. Furthermore, since the base layer, intermediate layer, and heat seal layer of the present invention are all polypropylene monomaterial films, they have excellent recyclability, particularly material recyclability. In this specification, a polypropylene monomaterial film refers to a film in which almost all of the raw materials constituting the film are polypropylene, specifically a film in which all of the resins constituting the film are polymers containing 50% by weight or more of polymerization units derived from propylene. In this specification, a polypropylene film refers to a film in which all of the resins constituting the film are polymers containing 50% by weight or more of polymerization units derived from propylene. In polypropylene monomaterial films and polypropylene films, the content of propylene-derived polymerization units relative to 100% by weight of all resins constituting the film is preferably 50% by weight or more, more preferably 60% by weight or more.

[0014] In this specification, the base layer, intermediate layer, heat seal layer, resin compositions (A) and (B), propylene polymer (C), propylene thermoplastic elastomer (D), propylene polymer (E), and propylene thermoplastic elastomer (F) are polymers each containing 50% by weight or more of polymerized units derived from propylene. Each component, production method, and application will be described below.

[0015] <Middle class> The intermediate layer is a stretched polypropylene film, and the resin composition (A) constituting the intermediate layer satisfies the following requirement (a1). When the resin composition (A) satisfies the following requirement (a1), the intermediate layer can disperse the stress generated in the laminate film during heat seal strength measurement. As a result, cracks and breakage of the base layer can be suppressed, and the heat seal strength can be improved. (a1) The durometer D hardness (HDD) measured in accordance with JIS K 7215:1986 is 10 to 78.

[0016] <<Resin composition (A)>> The resin composition (A) satisfies the following requirement (a1). (a1) The durometer D hardness (HDD) measured in accordance with JIS K 7215:1986 is 10 to 78. From the viewpoint of improving the heat seal strength of the laminated film, the durometer D hardness (HDD) of the resin composition (A) is 10-78, preferably 20-75, and more preferably 30-70.

[0017] It is preferable that the resin composition (A) further satisfies the following requirements (a2) to (a6).

[0018] (a2) The melting point is 110 to 150°C. From the viewpoint of flexibility of the intermediate layer, the melting point of the resin composition (A) is preferably from 110 to 150°C, and more preferably from 110 to 140°C.

[0019] In this specification, the melting point and heat of fusion ΔHm are measured as follows: Using a differential scanning calorimeter (DSC), a 5.0 mg sample is heated to 200°C, held at 200°C for 5 minutes, and then cooled to 40°C at a rate of 10°C / min. The sample is then heated at a rate of 10°C / min, and the top temperature of the endothermic peak is taken as the melting peak temperature (melting point / Tm), and the peak area of ​​this peak is taken as ΔHm (J / g).

[0020] (a3) The flexural modulus measured in accordance with JIS K 7171:2022 at a test speed of 2 mm / min is 10 to 1,300 MPa. From the viewpoint of improving the heat seal strength of the laminated film, the flexural modulus of the resin composition (A) is preferably 10 to 1,300 MPa, more preferably 100 to 1,200 MPa, even more preferably 200 to 1,100 MPa, and particularly preferably 300 to 1,000 MPa.

[0021] (a4) The Young's modulus in the machine direction (MD) measured in accordance with JIS K 7127:1999 at a tensile speed of 1 mm / min is 10 to 700 MPa. From the viewpoint of improving the heat seal strength of the laminated film, the Young's modulus of the resin composition (A) is preferably from 10 to 700 MPa, more preferably from 100 to 650 MPa, and even more preferably from 200 to 600 MPa.

[0022] (a5) The heat of fusion ΔHm is 5 to 100 J / g. From the viewpoint of improving the heat seal strength of the laminated film, the heat of fusion ΔHm of the resin composition (A) is preferably 5 to 100 J / g, more preferably 10 to 95 J / g, and even more preferably 20 to 90 J / g.

[0023] (a6) Density measured at 23°C in accordance with JIS K 7112-2:2023 is 0.850 to 0.899 g / cm 3 is. From the viewpoint of improving the heat seal strength of the laminated film, the density of the resin composition (A) is 0.850 to 0.899 g / cm 3 It is preferable that the density is 0.860 to 0.898 g / cm 3 More preferably, it is 0.870 to 0.897 g / cm 3 It is more preferable that:

[0024] From the viewpoint of improving heat seal strength, the resin composition (A) contains a propylene-based polymer (C) and, if necessary, a propylene-based thermoplastic elastomer (D). The content of the propylene-based polymer (C) is preferably 10 to 100% by weight, and the content of the propylene-based thermoplastic elastomer (D) is preferably 0 to 90% by weight, based on 100% by weight of the total of the propylene-based polymer (C) and the propylene-based thermoplastic elastomer (D). The content of the component (C) relative to 100% by weight of the total of the components (C) and (D) is more preferably 40 to 90% by weight, even more preferably 50 to 85% by weight, and particularly preferably 60 to 80% by weight. Similarly, the content of the component (D) relative to 100% by weight of the total of the components (C) and (D) is more preferably 10 to 60% by weight, even more preferably 15 to 50% by weight, and particularly preferably 20 to 40% by weight.

[0025] <<<Propylene polymer (C)>>> The propylene polymer (C) is a copolymer of propylene and ethylene or an α-olefin having 4 to 20 carbon atoms in a content of 0.1% by weight or more, and preferably satisfies the following requirements (c1) to (c5). The ethylene and the α-olefin having 4 to 20 carbon atoms, which are copolymerization components with propylene, may be one type or a combination of two or more types. The copolymerization component is preferably ethylene or an α-olefin having 4 to 10 carbon atoms. Specific examples of the copolymerization component include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 3-methyl-1-butene, 4-methyl-1-pentene, 2-methyl-1-pentene, and 2-methyl-1-hexene, with ethylene or 1-butene being particularly preferred. The propylene polymer (C) may be a blend of two or more of a propylene homopolymer and a random copolymer of propylene with ethylene or an α-olefin having 4 to 20 carbon atoms. The blend may be either a melt blend obtained by melt-kneading these polymers produced separately, or a polymer blend obtained as a multistage polymer produced by the multistage polymerization method described below. The propylene polymer (C) may be used alone or in combination of two or more kinds.

[0026] In this specification, the content of units derived from ethylene in a propylene-ethylene copolymer is a value calculated based on the following formula. Content of ethylene-derived units (%) = Weight of ethylene-derived units / (Weight of units derived from propylene + Weight of units derived from ethylene) x 100 The content of units derived from each monomer in other copolymers such as propylene-ethylene-1-butene copolymer can also be calculated in the same manner as above.

[0027] (c1) The MFR measured in accordance with JIS K 7210-1:2014 (230°C, 2.16 kg load) is 1 to 50 g / 10 min. The propylene polymer (C) preferably has a melt flow rate (MFR) of 1 to 50 g / 10 min, measured in accordance with JIS K 7210-1:2014 (230°C, 2.16 kg load). The MFR is more preferably 2 to 40 g / 10 min, and even more preferably 3 to 30 g / 10 min. When the propylene polymer (C) has an MFR in the range of 1 to 50 g / 10 min, it has good compatibility with the propylene thermoplastic elastomer (D) and exhibits good film processability. Methods for controlling the MFR value are well known, and the MFR value can be easily adjusted by adjusting the temperature and pressure, which are polymerization conditions for the propylene polymer (C), or by controlling the amount of a chain transfer agent such as hydrogen added during polymerization.

[0028] (c2) The flexural modulus measured in accordance with JIS K 7171:2022 at a test speed of 2 mm / min is greater than 500 MPa and less than 1,300 MPa. The propylene polymer (C) preferably has a flexural modulus of more than 500 MPa and not more than 1,300 MPa, as measured at a test speed of 2 mm / min in accordance with JIS K 7171:2022. The upper limit of the flexural modulus is more preferably not more than 1,200 MPa, and even more preferably not more than 1,000 MPa. By setting the flexural modulus within this range, the flexibility of the intermediate layer can be maintained and the heat seal strength can be improved. The method for controlling the flexural modulus is well known, and it can be easily adjusted by controlling the content ratio of ethylene and / or α-olefin having 4 to 20 carbon atoms to be copolymerized.

[0029] (c3) The content of units derived from propylene is more than 88.0% by weight and not more than 99.9% by weight. The content of propylene-derived units in the propylene polymer (C) is preferably more than 88.0 wt% and not more than 99.9 wt%. By setting the content of propylene-derived units within the above range, the flexibility of the mid layer can be maintained. The content of propylene-derived units is more preferably more than 88.5 wt% to 98.0 wt%, and even more preferably more than 89.0 wt% to 97.0 wt%.

[0030] (c4) The content of units derived from ethylene and α-olefins having 4 to 20 carbon atoms is 0.1% by weight or more and less than 12.0% by weight. The content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms in the propylene polymer (C) is preferably 0.1% by weight or more and less than 12.0% by weight. By setting the content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms within the above range, the flexibility of the mid layer can be maintained. The content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms is more preferably 2.0% by weight to less than 11.5% by weight, and even more preferably 3.0% by weight to less than 11.0% by weight. The content of units derived from ethylene in the propylene polymer (C) is preferably 0.1 to 7.0% by weight, more preferably 1.0 to 5.0% by weight. The content of units derived from 1-butene in the propylene polymer (C) is preferably 0 to 11.0% by weight, more preferably 0 to 10.0% by weight. The total content of units derived from ethylene and 1-butene in the propylene polymer (C) is preferably 0.1% by weight or more and less than 12.0% by weight, more preferably 2.0 to less than 11.5% by weight, and even more preferably 3.0 to less than 11.0% by weight.

[0031] (c5) The melting point is 110 to 155°C. The melting point of the propylene polymer (C) is preferably 110 to 155° C., more preferably 115 to 145° C., and even more preferably 120 to 140° C. By adjusting the melting point to within the range of 110 to 155° C., it is possible to improve the heat seal strength and low-temperature sealability. Methods for controlling the melting point are well known, and the melting point can be easily adjusted by controlling the content ratio of ethylene and / or α-olefin having 4 to 20 carbon atoms to be copolymerized.

[0032] From the viewpoint of imparting flexibility to the intermediate layer, the propylene-based polymer (C) is preferably a propylene-ethylene copolymer or a propylene-ethylene-1-butene copolymer satisfying the above requirements (c1) to (c5), and more preferably a propylene-ethylene-1-butene copolymer.

[0033] <<<Propylene-based thermoplastic elastomer (D)>>> The propylene-based thermoplastic elastomer (D) is a copolymer of propylene and ethylene or an α-olefin having 4 to 20 carbon atoms, and preferably satisfies the following requirements (d1) to (d4). The ethylene and α-olefin having 4 to 20 carbon atoms, which are copolymerization components with propylene, may be one type or a combination of two or more types. The copolymerization component is preferably ethylene or an α-olefin having 4 to 10 carbon atoms. Specific examples of the copolymerization component include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 3-methyl-1-butene, 4-methyl-1-pentene, 2-methyl-1-pentene, and 2-methyl-1-hexene, with ethylene or 1-butene being particularly preferred. Examples of the propylene-based thermoplastic elastomer (D) include random copolymer rubbers of propylene with ethylene or an α-olefin having 4 to 20 carbon atoms, and specific examples include propylene-ethylene copolymers and propylene-ethylene-1-butene copolymers. The propylene-based thermoplastic elastomer (D) may be used alone or in combination of two or more kinds.

[0034] (d1) The MFR measured in accordance with JIS K 7210-1:2014 (230°C, 2.16 kg load) is 1 to 30 g / 10 min. The propylene-based thermoplastic elastomer (D) preferably has an MFR of 1 to 30 g / 10 min, as measured in accordance with JIS K 7210-1:2014 (230°C, 2.16 kg load). The MFR is more preferably 2 to 20 g / 10 min, and even more preferably 2 to 10 g / 10 min. When the propylene-based thermoplastic elastomer (D) has an MFR within the range of 1 to 30 g / 10 min, a film with good moldability and appearance can be obtained. Methods for controlling the MFR value are well known, and the MFR value can be easily adjusted by adjusting the temperature and pressure, which are polymerization conditions for the propylene-based thermoplastic elastomer (D), or by controlling the amount of a chain transfer agent such as hydrogen added during polymerization.

[0035] (d2) The flexural modulus measured in accordance with JIS K 7171:2022 at a test speed of 2 mm / min is 5 to 200 MPa. The propylene-based thermoplastic elastomer (D) preferably has a flexural modulus of 5 to 200 MPa as measured at a test speed of 2 mm / min in accordance with JIS K 7171:2022. The flexural modulus is more preferably 5 to 150 MPa, and even more preferably 5 to 100 MPa. When the flexural modulus is within the above range, the flexibility of the intermediate layer is improved, and the heat seal strength and bag drop resistance are also improved. The method for controlling the flexural modulus is well known, and it can be easily adjusted by controlling the content ratio of ethylene and / or α-olefin having 4 to 20 carbon atoms to be copolymerized.

[0036] (d3) The content of units derived from propylene is 60.0 to 92.0% by weight. The content of propylene-derived units in the propylene-based thermoplastic elastomer (D) is preferably 60.0 to 92.0% by weight. By setting the content of propylene-derived units within the above range, the flexibility of the intermediate layer can be improved, and the heat seal strength can be improved. The content of propylene-derived units is more preferably 60.0 to 88.0% by weight, even more preferably 60.0 to 87.0% by weight, and particularly preferably 64.0 to 85.0% by weight.

[0037] (d3) can also be expressed as (d3') below. (d3') The content of units derived from propylene is 60.0 to 88.0% by weight.

[0038] (d4) The content of units derived from ethylene and α-olefins having 4 to 20 carbon atoms is 8.0 to 40.0% by weight. The content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms in the propylene-based thermoplastic elastomer (D) is preferably 8.0 to 40.0% by weight. By setting the content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms within the above range, the flexibility of the intermediate layer can be improved, and the heat seal strength can be improved. The content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms is more preferably 12.0 to 40.0% by weight, even more preferably 13.0 to 40.0% by weight, and particularly preferably 15.0 to 36.0% by weight. The content of units derived from ethylene in the propylene-based thermoplastic elastomer (D) is preferably 6.0 to 20.0% by weight, more preferably 8.0 to 18.0% by weight. The content of units derived from 1-butene in the propylene-based thermoplastic elastomer (D) is preferably 0 to 23.0% by weight, more preferably 0 to 18.0% by weight. The total content of units derived from ethylene and 1-butene in the propylene-based thermoplastic elastomer (D) is preferably 8.0 to 40.0% by weight, more preferably 12.0 to 40.0% by weight, even more preferably 13.0 to 40.0% by weight, and particularly preferably 15.0 to 36.0% by weight.

[0039] (d4) can also be expressed as (d4') below. (d4') The content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms is 12.0 to 40.0% by weight.

[0040] <<<Other ingredients>>> The intermediate layer may contain other components within the range that does not impair the effects of the present invention. Such optional components include resins other than components (C) and (D), and antioxidants, ultraviolet absorbers, crystal nucleating agents, clarifying agents, lubricants, antiblocking agents, antistatic agents, antifogging agents, neutralizing agents, light stabilizers, metal deactivators, colorants, dispersants, peroxides, fillers, and fluorescent brighteners that are commonly used in polyolefin resin materials.

[0041] The proportion of other components relative to the total of components (C) and (D) (100% by weight) is preferably 10% by weight or less, more preferably 0.1 to 9% by weight, and even more preferably 0.5 to 8% by weight.

[0042] <Heat seal layer> The heat seal layer is an unstretched polypropylene film, and the resin composition (B) constituting the heat seal layer satisfies the following requirements (b1) and (b2): When the resin composition (B) satisfies the following requirements (b1) and (b2), the heat seal strength, low-temperature sealability, and drop-bag resistance of the resulting laminated film can be improved. (b1) The durometer D hardness (HDD) measured in accordance with JIS K 7215:1986 is 10 to 78. (b2) The melting point is 110 to 150°C.

[0043] <<Resin composition (B)>> The resin composition (B) satisfies the following requirements (b1) and (b2). (b1) The durometer D hardness (HDD) measured in accordance with JIS K 7215:1986 is 10 to 78. From the viewpoint of improving the heat seal strength of the laminated film, the durometer D hardness (HDD) of the resin composition (B) is 10-78, preferably 20-75, and more preferably 30-70.

[0044] (b2) The melting point is 110 to 150°C. From the viewpoint of improving the heat seal strength, low-temperature sealability and drop-bag resistance of the laminated film, the melting point of the resin composition (B) is 110 to 150°C, preferably 110 to 140°C, more preferably 110 to 135°C, and even more preferably 110 to 130°C.

[0045] It is preferable that the resin composition (B) further satisfies the following requirements (b3) to (b6).

[0046] (b3) The flexural modulus measured in accordance with JIS K 7171:2022 at a test speed of 2 mm / min is 10 to 1,300 MPa. From the viewpoint of improving the heat seal strength of the laminated film, the flexural modulus of the resin composition (B) is preferably 10 to 1,300 MPa, more preferably 100 to 1,000 MPa, even more preferably 200 to 900 MPa, and particularly preferably 300 to 800 MPa.

[0047] (b4) The Young's modulus in the machine direction (MD) measured in accordance with JIS K 7127:1999 at a tensile speed of 1 mm / min is 10 to 700 MPa. From the viewpoint of improving the heat seal strength of the laminated film, the Young's modulus of the resin composition (B) is preferably from 10 to 700 MPa, more preferably from 100 to 600 MPa, and even more preferably from 200 to 500 MPa.

[0048] (b5) The heat of fusion ΔHm is 5 to 100 J / g. From the viewpoint of improving the heat seal strength of the laminated film, the heat of fusion ΔHm of the resin composition (B) is preferably 5 to 100 J / g, more preferably 10 to 90 J / g, and even more preferably 20 to 70 J / g.

[0049] (b6) Density measured at 23°C in accordance with JIS K 7112-2:2023 is 0.850 to 0.899 g / cm 3 is. From the viewpoint of improving the heat seal strength of the laminated film, the density of the resin composition (B) is 0.850 to 0.899 g / cm 3 It is preferable that the density is 0.860 to 0.895 g / cm 3 More preferably, it is 0.870 to 0.893 g / cm 3 It is more preferable that:

[0050] From the viewpoint of improving heat seal strength and low-temperature sealability, the resin composition (B) contains a propylene-based polymer (E) and, if necessary, a propylene-based thermoplastic elastomer (F). The content of the propylene-based polymer (E) is preferably 10 to 100% by weight, and the content of the propylene-based thermoplastic elastomer (F) is preferably 0 to 90% by weight, based on 100% by weight of the total of the propylene-based polymer (E) and the propylene-based thermoplastic elastomer (F). Furthermore, from the viewpoint of improving not only the heat seal strength and low-temperature sealability but also the bag drop resistance, the content of the component (E) is more preferably 50 to 95% by weight, even more preferably 55 to 90% by weight, and particularly preferably 60 to 80% by weight, based on 100% by weight of the total of the components (E) and (F). Similarly, the content of component (F) relative to the total of components (E) and (F) (100% by weight) is more preferably 5 to 50% by weight, even more preferably 10 to 45% by weight, and particularly preferably 20 to 40% by weight.

[0051] <<<Propylene polymer (E)>>> The propylene polymer (E) is a copolymer of propylene and ethylene or an α-olefin having 4 to 20 carbon atoms in a content of 0.1% by weight or more, and preferably satisfies the following requirements (e1) to (e5). The ethylene and the α-olefin having 4 to 20 carbon atoms, which are copolymerization components with propylene, may be one type or a combination of two or more types. The copolymerization component is preferably ethylene or an α-olefin having 4 to 10 carbon atoms. As the ethylene and the α-olefin having 4 to 20 carbon atoms, those exemplified for the propylene polymer (C) can be used. The propylene polymer (E) may be a blend of two or more of a propylene homopolymer and a random copolymer of propylene with ethylene or an α-olefin having 4 to 20 carbon atoms. The blend may be either a melt blend obtained by melt-kneading these polymers produced separately, or a polymer blend obtained as a multistage polymer produced by the multistage polymerization method described below. The propylene polymer (E) may be used alone or in combination of two or more kinds.

[0052] (e1) The MFR measured in accordance with JIS K 7210-1:2014 (230°C, 2.16 kg load) is 1 to 50 g / 10 min. The propylene polymer (E) preferably has a melt flow rate (MFR) of 1 to 50 g / 10 min, measured in accordance with JIS K 7210-1:2014 (230°C, 2.16 kg load). The MFR is more preferably 2 to 40 g / 10 min, and even more preferably 3 to 30 g / 10 min. When the propylene polymer (E) has an MFR in the range of 1 to 50 g / 10 min, it has good compatibility with the propylene thermoplastic elastomer (F), resulting in good film processability. Methods for controlling the MFR value are well known, and the MFR value can be easily adjusted by adjusting the temperature and pressure, which are polymerization conditions for the propylene polymer (E), or by controlling the amount of a chain transfer agent such as hydrogen added during polymerization.

[0053] (e2) The flexural modulus measured in accordance with JIS K 7171:2022 at a test speed of 2 mm / min is greater than 500 MPa and less than 1,300 MPa. The propylene polymer (E) preferably has a flexural modulus of more than 500 MPa and not more than 1,300 MPa, as measured in accordance with JIS K 7171:2022 at a test speed of 2 mm / min. The upper limit of the flexural modulus is more preferably 1,200 MPa or less, and even more preferably 1,100 MPa or less. By making the flexural modulus more than 500 MPa, the formability of the heat-sealable layer can be improved. By making the flexural modulus not more than 1,300 MPa, the flexibility of the heat-sealable layer can be maintained while improving the heat-seal strength, low-temperature heat-sealability, transparency, impact resistance, puncture strength, tear strength, and low-temperature bag drop resistance. The method for controlling the flexural modulus is well known, and it can be easily adjusted by controlling the content ratio of ethylene and / or α-olefin having 4 to 20 carbon atoms to be copolymerized.

[0054] (e3) The content of units derived from propylene is more than 88.0% by weight and not more than 99.9% by weight. The content of the propylene-derived units in the propylene polymer (E) is preferably more than 88.0 wt% and not more than 99.9 wt%. By setting the content of the propylene-derived units within the above range, the flexibility of the heat seal layer can be maintained. The content of the propylene-derived units is more preferably more than 88.5 wt% to 98.0 wt%, and even more preferably more than 89.0 wt% to 97.0 wt%.

[0055] (e4) The content of units derived from ethylene and α-olefins having 4 to 20 carbon atoms is 0.1% by weight or more and less than 12.0% by weight. The content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms in the propylene polymer (E) is preferably 0.1% by weight or more and less than 12.0% by weight. By setting the content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms within the above range, the flexibility of the heat seal layer can be maintained. The content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms is more preferably 2.0% by weight to less than 11.5% by weight, and even more preferably 3.0% by weight to less than 11.0% by weight. The content of units derived from ethylene in the propylene polymer (E) is preferably from 0.1 to 7.0% by weight, more preferably from 1.0 to 5.0% by weight. The content of units derived from 1-butene in the propylene polymer (E) is preferably from 0 to 11.0% by weight, more preferably from 0 to 10.0% by weight. The total content of units derived from ethylene and 1-butene in the propylene polymer (E) is preferably 0.1% by weight or more and less than 12.0% by weight, more preferably 2.0 to less than 11.5% by weight, and even more preferably 3.0 to less than 11.0% by weight.

[0056] (e5) The melting point is 110 to 155°C. The melting point of the propylene polymer (E) is preferably 110 to 155° C., more preferably 115 to 145° C., and even more preferably 120 to 140° C. By adjusting the melting point to within the range of 110 to 155° C., good low-temperature heat sealability can be achieved. Methods for controlling the melting point are well known, and the melting point can be easily adjusted by controlling the content ratio of ethylene and / or α-olefin having 4 to 20 carbon atoms to be copolymerized.

[0057] From the viewpoint of imparting flexibility and low-temperature heat-sealability to the heat-sealable layer, the propylene-based polymer (E) is preferably a propylene-ethylene copolymer or a propylene-ethylene-1-butene copolymer satisfying the above requirements (e1) to (e5), and more preferably a propylene-ethylene-1-butene copolymer.

[0058] <<<Propylene-based thermoplastic elastomer (F)>>> The propylene-based thermoplastic elastomer (F) is a copolymer of propylene and ethylene or an α-olefin having 4 to 20 carbon atoms, and preferably satisfies the following requirements (f1) to (f4). The ethylene and α-olefin having 4 to 20 carbon atoms, which are copolymerization components with propylene, may be one type or a combination of two or more types. The copolymerization component is preferably ethylene or an α-olefin having 4 to 10 carbon atoms. As the ethylene and α-olefin having 4 to 20 carbon atoms, those exemplified for the propylene-based thermoplastic elastomer (D) can be used. Examples of the propylene-based thermoplastic elastomer (F) include random copolymer rubbers of propylene and ethylene or an α-olefin having 4 to 20 carbon atoms, and specific examples include propylene-ethylene copolymers and propylene-ethylene-1-butene copolymers. The propylene-based thermoplastic elastomer (F) may be used alone or in combination of two or more kinds.

[0059] (f1) The MFR measured in accordance with JIS K 7210-1:2014 (230°C, 2.16 kg load) is 1 to 30 g / 10 min. The propylene-based thermoplastic elastomer (F) preferably has an MFR of 1 to 30 g / 10 min, measured in accordance with JIS K 7210-1:2014 (230°C, 2.16 kg load). The MFR is more preferably 2 to 20 g / 10 min, and even more preferably 2 to 10 g / 10 min. When the propylene-based thermoplastic elastomer (F) has an MFR within the range of 1 to 30 g / 10 min, a film with good moldability and appearance can be obtained. Methods for controlling the MFR value are well known, and the MFR value can be easily adjusted by adjusting the temperature and pressure, which are polymerization conditions for the propylene-based thermoplastic elastomer (F), or by controlling the amount of a chain transfer agent such as hydrogen added during polymerization.

[0060] (f2) The flexural modulus measured in accordance with JIS K 7171:2022 at a test speed of 2 mm / min is 5 to 200 MPa. The propylene-based thermoplastic elastomer (F) preferably has a flexural modulus of 5 to 200 MPa as measured at a test speed of 2 mm / min in accordance with JIS K 7171:2022. The flexural modulus is more preferably 5 to 150 MPa, and even more preferably 5 to 100 MPa. A flexural modulus of 5 MPa or more suppresses surface stickiness during molding of the heat-sealable layer, while a flexural modulus of 200 MPa or less improves the flexibility of the heat-sealable layer and improves the heat-seal strength, low-temperature heat-sealability, transparency, impact resistance, puncture strength, tear strength, and low-temperature bag drop resistance. The method for controlling the flexural modulus is well known, and it can be easily adjusted by controlling the content ratio of ethylene and / or α-olefin having 4 to 20 carbon atoms to be copolymerized.

[0061] (f3) The content of units derived from propylene is 60.0 to 92.0% by weight. The content of propylene-derived units in the propylene-based thermoplastic elastomer (F) is preferably 60.0 to 92.0% by weight. By setting the content of propylene-derived units within this range, the flexibility of the heat-sealable layer can be improved, and the heat-seal strength, low-temperature heat-sealability, transparency, impact resistance, puncture strength, tear strength, and low-temperature bag drop resistance can be improved. The content of propylene-derived units is more preferably 60.0 to 88.0% by weight, even more preferably 60.0 to 87.0% by weight, and particularly preferably 64.0 to 85.0% by weight.

[0062] (f3) can also be expressed as (f3') below. (f3') The content of units derived from propylene is 60.0 to 88.0% by weight.

[0063] (f4) The content of units derived from ethylene and α-olefins having 4 to 20 carbon atoms is 8.0 to 40.0% by weight. The content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms in the propylene-based thermoplastic elastomer (F) is preferably 8.0 to 40.0% by weight. By setting the content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms within the above range, the flexibility of the heat seal layer can be improved, and the heat seal strength, low-temperature heat sealability, transparency, impact resistance, puncture strength, tear strength, and low-temperature bag drop resistance can be improved. The content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms is more preferably 12.0 to 40.0% by weight, even more preferably 13.0 to 40.0% by weight, and particularly preferably 15.0 to 36.0% by weight. The content of units derived from ethylene in the propylene-based thermoplastic elastomer (F) is preferably 6.0 to 20.0% by weight, more preferably 8.0 to 18.0% by weight. The content of units derived from 1-butene in the propylene-based thermoplastic elastomer (F) is preferably 0 to 23.0% by weight, more preferably 0 to 18.0% by weight. The total content of units derived from ethylene and 1-butene in the propylene-based thermoplastic elastomer (F) is preferably 8.0 to 40.0% by weight, more preferably 12.0 to 40.0% by weight, even more preferably 13.0 to 40.0% by weight, and particularly preferably 15.0 to 36.0% by weight.

[0064] (f4) can also be expressed as (f4') below. (f4') The content of units derived from ethylene and α-olefins having 4 to 20 carbon atoms is 12.0 to 40.0% by weight.

[0065] <<<Other ingredients>>> The heat seal layer may contain other components as long as they do not impair the effects of the present invention. Examples of such optional components include resins other than components (E) and (F), antioxidants, ultraviolet absorbers, crystal nucleating agents, clarifying agents, lubricants, antiblocking agents, antistatic agents, antifogging agents, neutralizing agents, light stabilizers, metal deactivators, colorants, dispersants, peroxides, fillers, and fluorescent brighteners that are commonly used in polyolefin resin materials.

[0066] The proportion of other components relative to the total of components (E) and (F) (100% by weight) is preferably 10% by weight or less, more preferably 0.1 to 9% by weight, and even more preferably 0.5 to 8% by weight.

[0067] (Origin of ingredients) In order to respond to recent demands for reducing environmental impact, making effective use of resources, and building a sustainable society, the resins or raw materials constituting the resin compositions (A) and (B) are not necessarily limited to unused materials (hereinafter referred to as "virgin materials"). That is, recycled plastics (also called recycled resins or regenerated resins) can be used for at least a part or all of the resins constituting the resin compositions (A) and (B). Specifically, the resins constituting the resin compositions (A) and (B) are not limited to being composed of virgin materials only, and recycled plastics alone may be used, or virgin materials and recycled plastics may be mixed in any ratio. Even when recycled plastics are used, the desired effects of the present invention can be achieved.

[0068] Here, recycled plastic broadly refers to resin materials that have been recycled using recycled plastic waste materials that have been used once or generated during the manufacturing process, regardless of their manufacturing method or origin. Typical methods for production include, but are not limited to, the following. Furthermore, it does not matter whether or not the origin or recycling method has been certified by a third party. (1) Material recycling (mechanical recycling): This is a method of regenerating used plastic products while substantially maintaining their polymer structure through physical processes such as crushing, washing, drying, deodorizing, sorting, removing foreign matter, melt-kneading, and re-pelletizing. Used plastic products can be either post-consumer recycled (PCR) materials recovered from products used by consumers, or post-industrial recycled (PIR) materials recovered from the manufacturing process of offcuts, non-standard products, etc. (2) Chemical recycling (feedstock recycling): This is a method of decomposing used plastic products into monomers, oligomers, synthetic gas, and produced oils through chemical means such as thermal decomposition, gasification, and depolymerization, and then polymerizing these to obtain recycled plastics. This method also includes cases where raw materials derived from used plastics and raw materials derived from fossil fuels are mixed and used in specific manufacturing facilities and processes, and the proportion derived from recycled plastics is allocated using the mass balance method. Any of the above recycled plastics may be in any form, such as pellets, powder, flakes, etc. Any of the recycled plastics can be used to produce resin compositions (A) and (B) using the same production process and conditions as for virgin materials, and steps such as drying and deodorization may be added as necessary.

[0069] Furthermore, raw materials derived from biomass (hereinafter referred to as "biomass raw materials") can be used for at least a part or all of the raw materials for the resins constituting the resin compositions (A) and (B). Specifically, the raw materials for the resins constituting the resin compositions (A) and (B) are not limited to being composed solely of components derived from fossil fuels (hereinafter also referred to as "fossil raw materials"), and only biomass raw materials may be used, or fossil raw materials and biomass raw materials may be mixed in any ratio. The intended effects of the present invention can be achieved even when biomass raw materials are used.

[0070] Here, biomass feedstock broadly refers to renewable natural resources, such as plants, animals, fungi, yeast, algae, and bacteria, and their residues. Regardless of the source, biomass feedstocks can be obtained by any conventionally known method. This also includes cases where biomass and fossil feedstocks are mixed in a specific manufacturing facility or process, and the proportion of biomass feedstock is allocated using the mass balance method. Furthermore, the presence or absence of third-party certification of the origin and regeneration method is not an issue.

[0071] If the manufacturing conditions such as polymerization catalyst and polymerization temperature are the same, the molecular structure of the resin obtained by using biomass raw materials will be: 14 Except for the proportion of C isotopes, the resins are equivalent to those obtained from fossil raw materials. Therefore, the performance of resins obtained from biomass raw materials is also substantially the same as that of resins obtained from fossil raw materials. In other words, the resins constituting the resin compositions (A) and (B) can be produced from the above biomass raw materials using production equipment and production conditions that have been used for conventional fossil raw materials.

[0072] (Method for producing propylene polymers (C) and (E)) The polymerization catalyst for producing the propylene polymers (C) and (E) may be a Ziegler-Natta catalyst and / or a metallocene catalyst, but other catalysts may also be used. Ziegler-Natta catalysts are described in Section 2.3.1 (pp. 20-57) of "Polypropylene Handbook," edited by Edward P. Moore Jr., translated and supervised by Tetsuo Yasuda and Nobu Sakuma, published by the Industrial Research Institute (1998). Ziegler-Natta catalysts include (1) titanium trichloride catalysts consisting of titanium trichloride and organoaluminum halide, combined with magnesium chloride and titanium halide, (2) magnesium-supported catalysts consisting of a solid catalyst component containing an electron-donating compound and an organoaluminum and organosilicon compound, and (3) catalysts combining an organoaluminum compound component with an organosilicon-treated solid catalyst component formed by contacting a solid catalyst component with an organoaluminum and organosilicon compound.

[0073] The metallocene catalyst is a catalyst comprising (i) a transition metal compound of Group 4 of the periodic table containing a ligand having a cyclopentadienyl skeleton (a so-called metallocene compound), (ii) a co-catalyst capable of activating the metallocene compound to a stable ionic state by reacting with the metallocene compound, and, if necessary, (iii) an organoaluminum compound, and any known catalyst can be used. The metallocene compound is preferably a bridged metallocene compound capable of stereoregular polymerization of propylene, and more preferably a bridged metallocene compound capable of isoregular polymerization of propylene.

[0074] (i) As the metallocene compound, for example, those disclosed in JP-A-60-35007, JP-A-61-130314, JP-A-63-295607, JP-A-1-275609, JP-A-2-41303, JP-A-2-131488, JP-A-2-76887, JP-A-3-163088, JP-A-4-300887, JP-A-4-211694, JP-A-5-43616, JP-A-5-209013, JP-A-6-239914, JP-T-7-504934, and JP-A-8-85708 can be preferably used.

[0075] Specifically, methylenebis(2-methylindenyl)zirconium dichloride, ethylenebis(2-methylindenyl)zirconium dichloride, ethylene 1,2-(4-phenylindenyl)(2-methyl-4-phenyl-4H-azulenyl)zirconium dichloride, isopropylidene(cyclopentadienyl)(fluorenyl)zirconium dichloride, isopropylidene(4-methylcyclopentadienyl)(3-t-butylindenyl)zirconium dichloride, dimethylsilylene(2-methyl-4-t-butyl-cyclopentadienyl)(3'-t-butyl-5'-methyl-cyclopentadienyl)zirconium dichloride, dimethylsilylenebis(indenyl) methylsilylenebis(4,5,6,7-tetrahydroindenyl)zirconium dichloride, dimethylsilylenebis[1-(2-methyl-4-phenylindenyl)]zirconium dichloride, dimethylsilylenebis[1-(2-ethyl-4-phenylindenyl)]zirconium dichloride, dimethylsilylenebis[4-(1-phenyl-3-methylindenyl)]zirconium dichloride, dimethylsilylene(fluorenyl)t-butylamido zirconium dichloride, methylphenylsilylenebis[1-(2-methyl-4,(1-naphthyl)-indenyl)]zirconium dichloride, dimethylsilylenebis[1-(2-methyl-4,5-benzoindenyl)] zirconium dichloride, dimethylsilylenebis[1-(2-methyl-4-phenyl-4H-azulenyl)] zirconium dichloride, dimethylsilylenebis[1-(2-ethyl-4-(4-chlorophenyl)-4H-azulenyl)] zirconium dichloride, dimethylsilylenebis[1-(2-ethyl-4-naphthyl-4H-azulenyl)] zirconium dichloride, diphenylsilylenebis[1-(2-methyl-4-(4-chlorophenyl)-4H-azulenyl)] zirconium dichloride Examples of zirconium compounds include dimethylsilylenebis[1-(2-ethyl-4-(3-fluorobiphenyl)-4H-azulenyl)]zirconium dichloride, dimethylsilylenebis[1-(2-ethyl-4-(3-fluorobiphenyl)-4H-azulenyl)]zirconium dichloride, dimethylgermylenebis[1-(2-ethyl-4-(4-chlorophenyl)-4H-azulenyl)]zirconium dichloride, and dimethylgermylenebis[1-(2-ethyl-4-phenylindenyl)]zirconium dichloride.

[0076] In the above, compounds in which zirconium is replaced with titanium, hafnium, etc. can also be used. It is also preferable to use a mixture of a zirconium compound and a hafnium compound. Chloride can also be replaced with other halogen compounds, hydrocarbon groups such as methyl, isobutyl, and benzyl, amide groups such as dimethylamide and diethylamide, alkoxide groups such as methoxy and phenoxy, and hydride groups. Among these, metallocene compounds in which an indenyl group or an azulenyl group is bridged with a silicon or germyl group are particularly preferred.

[0077] The metallocene compound may be supported on an inorganic or organic carrier. The carrier is preferably a porous inorganic or organic compound, and specific examples include inorganic compounds such as ion-exchangeable layered silicates, zeolites, SiO, AlO, silica alumina, MgO, ZrO, TiO, BO, CaO, ZnO, BaO, and ThO; organic compounds such as porous polyolefins, styrene-divinylbenzene copolymers, and olefin-acrylic acid copolymers; and mixtures thereof.

[0078] (ii) Preferred examples of the co-catalyst capable of reacting with a metallocene compound to activate it to a stable ionic state include organoaluminum oxy-compounds (e.g., aluminoxane compounds), ion-exchangeable layered silicates, Lewis acids, boron-containing compounds, ionic compounds, and fluorine-containing organic compounds.

[0079] (iii) Preferred examples of organoaluminum compounds include trialkylaluminums such as triethylaluminum, triisopropylaluminum, and triisobutylaluminum, dialkylaluminum halides, alkylaluminum sesquihalides, alkylaluminum dihalides, alkylaluminum hydrides, and organoaluminum alkoxides.

[0080] The propylene polymers (C) and (E) may be produced by any method known in the art, such as a slurry polymerization method, a bulk polymerization method, or a gas phase polymerization method, without any particular limitation. Furthermore, the propylene polymers (C) and (E) may also be produced by a multistage polymerization method within the scope of the invention.

[0081] (Production method of propylene-based thermoplastic elastomers (D) and (F), etc.) Examples of the propylene-based thermoplastic elastomers (D) and (F) that can be used include the propylene-1-butene copolymers described in JP 2004-099909 A; the propylene-ethylene-1-butene copolymers described in JP 2004-315830 A, JP 2007-169666 A, and JP 2010-163626 A; and the propylene-α-olefin copolymers described in JP 2022-152305 A and JP 2022-152304 A.

[0082] (Method for calculating the content of units derived from ethylene and α-olefins having 4 to 20 carbon atoms) The content ratio of units derived from ethylene and α-olefins having 4 to 20 carbon atoms in the propylene polymers (C) and (E) and the propylene thermoplastic elastomers (D) and (F) is 13It can be calculated from the integrated intensity of the spectrum obtained by C-NMR measurement. For example, in the case of a propylene-ethylene-1-butene copolymer, the ethylene and 1-butene contents (wt%) can be calculated from the following (Equation 1) and (Equation 2), respectively. Ethylene content (mol%) = IE × 100 / (IE + IP + IB) Ethylene content (wt%) = [Ethylene content (mol%) × Molecular weight of ethylene] / [Ethylene content (mol%) × Molecular weight of ethylene + Propylene content (mol%) × Molecular weight of propylene + 1-butene content (mol%) × Molecular weight of 1-butene] (Equation 1) 1-Butene content (mol%) = IB × 100 / (IE + IP + IB) 1-butene content (wt%) = [1-butene content (mol%) × molecular weight of 1-butene] / [ethylene content (mol%) × molecular weight of ethylene + propylene content (mol%) × molecular weight of propylene + 1-butene content (mol%) × molecular weight of 1-butene] (Equation 2) where IE, IP, and IB are the integrated intensities of carbon derived from ethylene, propylene, and 1-butene, respectively.

[0083] <Base material layer> The substrate layer is a stretched polypropylene film. The substrate layer functions as a layer that provides a predetermined strength to the laminate film. By using a stretched polypropylene film for the substrate layer, the strength of the laminate film is improved, and in combination with the intermediate layer and the heat seal layer, it can be suitably used as a mono-material packaging material, and the laminate film can be made recyclable. The substrate layer may be a uniaxially stretched polypropylene film or a biaxially stretched polypropylene film, but from the viewpoint of versatility, a biaxially stretched polypropylene film is preferred.

[0084] Examples of polypropylene constituting the base layer include propylene homopolymers, random copolymers of propylene and ethylene or α-olefins having 4 to 20 carbon atoms, and block copolymers of propylene and ethylene or α-olefins having 4 to 20 carbon atoms. The base layer may be composed of one type of polypropylene, or may be composed of two or more types of polypropylene. From the viewpoint of the strength and secondary processability of the laminated film, the base layer preferably contains 80% by weight or more, more preferably 90% by weight or more, and even more preferably 95% by weight or more, of units derived from propylene. It is particularly preferable that the base layer is a propylene homopolymer.

[0085] The base layer may contain other components as long as they do not impair the effects of the present invention. Examples of such optional components include those exemplified as other components for the intermediate layer and the heat-seal layer. Similarly to the resins constituting the intermediate layer and the heat-seal layer, the resin constituting the base layer is not limited to being made solely of virgin material; it may be made solely of recycled plastic and / or biomass raw materials, or a mixture of virgin material and recycled plastic and / or biomass raw materials in any ratio.

[0086] (Method for producing substrate layer and intermediate layer) For the base layer and intermediate layer, the unstretched polypropylene film can be produced by a conventionally known method. For example, raw material resins are heated, melted, and kneaded in an extruder, and then extruded into a film or sheet from a T-die to obtain an unstretched polypropylene film. When multiple raw material resins are used, the raw material resins may be dry-blended or melt-kneaded in advance and processed into pellets, etc., which are then extruded into a film or sheet from a T-die to obtain the base layer and intermediate layer. The obtained unstretched polypropylene film can be stretched to obtain a stretched polypropylene film. The method for producing the laminate of the stretched polypropylene film for the base layer and the intermediate layer is not particularly limited, and examples thereof include a method in which the base layer and the stretched polypropylene film for the intermediate layer are produced separately and then bonded together by dry lamination or the like, and a method in which a laminate of unstretched polypropylene film having the base layer and the intermediate layer laminated thereon is produced by coextrusion or the like and then the laminate is stretched.

[0087] As the stretching method, a known method can be used, for example, a tubular method, a tenter type stretching method, a pantograph type batch stretching method, etc.

[0088] The stretching direction is not particularly limited, but is usually the longitudinal direction and / or the transverse direction. In the case of uniaxial stretching, either longitudinal uniaxial stretching or transverse uniaxial stretching may be used, and examples thereof include a method utilizing the difference in roll peripheral speed. The stretching temperature is preferably 90 to 140°C, more preferably 100 to 130°C. The stretching ratio is preferably 3 to 12 times, more preferably 4 to 12 times.

[0089] In the case of biaxial stretching, either sequential biaxial stretching or simultaneous biaxial stretching may be used. An example of the stretching method is a method in which a sheet obtained by a T-die method is roll-stretched 3.0 to 6.0 times in the machine direction (MD) and then stretched 8.0 to 12.0 times in the transverse direction (TD) by a tenter method. Another example of the stretching method is the so-called tubular stretching method, in which a tubular unstretched sheet obtained by air-cooling or water-cooling from a circular die is heated to below the melting temperature, and then stretched in a bubble shape with air to 3.0 to 7.0 times in the machine direction (MD) and 3.0 to 7.0 times in the transverse direction (TD). In the case of biaxial stretching, the stretching temperature is preferably 100 to 170°C, more preferably 110 to 160°C.

[0090] The stretched polypropylene film can be subjected to a surface treatment to improve printability, lamination properties, etc. Examples of the surface treatment method include corona discharge treatment, plasma treatment, flame treatment, acid treatment, etc., and there are no particular limitations. Corona discharge treatment, plasma treatment, or flame treatment is preferred because it allows continuous treatment and can be easily carried out before the winding step in the film production process.

[0091] (Method for producing heat seal layer) The heat-seal layer can be produced by a conventionally known method. For example, the raw resin is heated, melted, and kneaded in an extruder, and then extruded through a T-die into a film or sheet to obtain the heat-seal layer. The melt-kneaded raw resin may be processed into pellets or the like, and these may be extruded through a T-die into a film or sheet to obtain the heat-seal layer. The heat-seal layer may be subjected to corona treatment or the like.

[0092] <Laminated film> The laminated film is formed by laminating a base layer, an intermediate layer, and a heat seal layer in this order. From the viewpoints of formability and film physical properties, the thickness of the intermediate layer is preferably 1 to 10 μm, more preferably 1 to 5 μm, and even more preferably 1 to 3 μm. From the viewpoint of heat seal strength, the thickness of the heat seal layer is preferably 10 to 400 μm, more preferably 20 to 150 μm, and even more preferably 30 to 100 μm. From the viewpoints of formability and film physical properties, the thickness of the base layer is preferably 9 to 475 μm, more preferably 15 to 80 μm, and even more preferably 20 to 70 μm. The total thickness of the laminated film is preferably from 17 to 500 μm, more preferably from 35 to 200 μm, and even more preferably from 50 to 150 μm.

[0093] The laminate film may contain layers other than the substrate layer, intermediate layer, and heat seal layer, provided that the effects of the present invention are not impaired. Examples of such layers include a scratch-resistant layer, a printed layer, an adhesive layer, a barrier layer, a gas-permeable layer, a gas-adsorbing layer, and a vapor-deposited layer using aluminum, silica, or the like.

[0094] [Physical properties of laminated film] The sealing temperature at which the laminated film reaches a heat seal strength of 20 N / 15 mm, measured under the following conditions, is preferably 140°C or lower, more preferably 80°C to 135°C, and even more preferably 90°C to 130°C. Setting the sealing temperature to 140°C or lower can improve low-temperature sealability. As a result, it is possible to increase production speed by shortening the sealing time and lower the temperature setting of the seal bar, which makes it less likely for the laminated film to shrink during bonding and improves secondary processability. The sealing temperature can be achieved by changing the type and blending ratio of the resins constituting the heat seal layer, changing the types of resins in the base layer and intermediate layer, or adjusting the thickness ratios of the base layer, intermediate layer, and heat seal layer. <Measurement of the sealing temperature at which the heat seal strength reaches 20N / 15mm> After storing the laminated film at an ambient temperature of 23°C for 7 days, it was cut into strips measuring 180 mm (MD) x 80 mm (TD), folded in half in the MD so that the heat-sealable layers were in contact with each other, and heat-sealed at a width of 10 mm at a position 20-30 mm from the fold under the following sealing conditions. The resulting partially heat-sealed sample was cut into strips with a width of 15 mm in the TD to obtain test pieces. The resulting test pieces were pulled at both ends in a 180° peel direction using a Schopper-type tensile tester at a rate of 500 mm / min, and the maximum force required to peel the heat-sealed portions was measured and used as the heat-seal strength. Sealing conditions: Sealing pressure: 2.0 kg / cm 2 (0.196 MPa), sealing time: 1.0 second, sealing temperature: 90°C to 170°C in 10°C increments. In the seal curve obtained from the seal temperature and heat seal strength, the data between any two points measured at 10°C intervals is approximated with a linear function to determine the seal temperature at which the heat seal strength reaches 20N / 15mm.

[0095] The laminate film preferably has a haze of less than 10% as measured in accordance with JIS K 7136:2000. By making the haze less than 10%, the transparency of the laminate film can be improved. The haze is more preferably 0.5 to 9%, and even more preferably 1 to 8%. If the haze is less than 0.5%, the unevenness of the laminate film surface will be small, which may cause excessive adhesion between films (blocking), resulting in poor secondary processability.

[0096] The laminated film preferably has a puncture strength measured in accordance with JIS Z 1707:2019 of 10 N or more, more preferably 11 N or more, and even more preferably 12 N or more. The upper limit of the puncture strength is not particularly limited, but is usually 20 N or less. If the puncture strength is less than 10 N, cracks may occur in the laminated film and the bag may break during secondary processing or distribution in the market.

[0097] In a bag drop impact test measured under the following conditions, the average number of times the laminate film breaks after being dropped is preferably 6 or more, more preferably 10 or more, and even more preferably 20 or more. The average number of times the bag breaks after being dropped is rounded down to an integer. <Dropped bag impact test> Two 120mm x 150mm sheets are cut from the laminated film, and the heat-sealed layers of each sheet are overlapped. Then, three sides are sealed using an impulse sealer under the following sealing conditions to create a 120mm x 150mm sample bag. 100ml of water is poured into the sample bag, and the open side is sealed using an impulse sealer under the following sealing conditions to create a water seal test piece. After storing the water seal test piece in a 0°C atmosphere for one day, it is dropped 50 times consecutively from a height of 1.5m onto a metal plate. The maximum number of times the bag does not break is recorded as the number of bag breakage drops. The test is repeated five times, and the average number of bag breakage drops is calculated. The sealing conditions are as follows: a Fuji Impulse poly sealer (product name: PC-300), seal width: 2 mm, scale: 10 (sealing time: 1.6 seconds).

[0098] <Laminated film manufacturing method> The method for bonding the base layer, intermediate layer, and heat-sealing layer is not particularly limited, and any conventionally known method can be used. For example, an adhesive layer can be provided by extrusion, dry lamination, or the like, to bond the base layer and intermediate layer and the intermediate layer and the heat-sealing layer together. The order in which the base layer and intermediate layer are bonded together and the intermediate layer and the heat-sealing layer are bonded together is not particularly limited, but from the viewpoint of productivity, it is preferable to bond the intermediate layer and the heat-sealing layer together after obtaining a laminate in which the base layer and intermediate layer are bonded together. Among these, from the viewpoints of obtaining high adhesive strength, fast processing speed, and high productivity, a manufacturing method including step 1 of co-extruding a base layer and an intermediate layer to obtain a laminate, step 2 of stretching the laminate obtained in step 1 to obtain a stretched film, and step 3 of bonding a heat seal layer onto the intermediate layer of the stretched film obtained in step 2 is preferred. Furthermore, dry lamination, extrusion lamination, etc. can be used as the bonding method in step 3. From the viewpoint of being able to laminate a wide variety of materials and impart a wide variety of functionality, step 3 is preferably a step of bonding the intermediate layer and the heat seal layer by dry lamination.

[0099] In the dry lamination method, an adhesive may be applied to an intermediate layer and then a heat seal layer may be laminated thereto, or an adhesive may be applied to a heat seal layer and then an intermediate layer may be laminated thereto. The adhesive may be produced from an adhesive composition prepared by mixing a first composition containing a base agent and a solvent with a second composition containing a curing agent and a solvent. Specifically, the adhesive includes a cured product produced by reaction of the base agent and the curing agent in the adhesive composition.

[0100] An example of an adhesive is polyurethane. Polyurethane is a cured product of a polyol and an isocyanate compound produced by reacting a polyol as a base material with an isocyanate compound as a curing agent. Examples of polyurethane include polyether polyurethane and polyester polyurethane. Polyether polyurethane is a cured product produced by reacting a polyether polyol as a base material with an isocyanate compound as a curing agent. Polyester polyurethane is a cured product produced by reacting a polyester polyol as a base material with an isocyanate compound as a curing agent. Examples of isocyanate compounds that can be used include aromatic isocyanate compounds such as tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), and xylylene diisocyanate (XDI); aliphatic isocyanate compounds such as hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI); and adducts or polymers of the above-mentioned various isocyanate compounds.

[0101] The thickness of the adhesive layer is not particularly limited, but is preferably in the range of 0.01 to 5 μm, more preferably in the range of 0.03 to 3 μm, and particularly preferably in the range of 0.05 to 2 μm. When the thickness of the adhesive layer is equal to or greater than the above lower limit, more sufficient interlayer adhesive strength can be obtained.

[0102] <Applications of laminated film> The laminated film has excellent heat seal strength and low-temperature sealability, and can therefore be suitably used as a food packaging film, a heavy-duty packaging film, or a liquid packaging film, particularly as a rice bag or for individual packaging of frozen foods. [Example]

[0103] The present invention will be described in detail below using examples, but the present invention is not limited to these examples. The raw materials used in the examples and the evaluation methods of the obtained films are as follows.

[0104] 1. Evaluation Method (1) MFR The MFR of the raw resin was measured in accordance with JIS K 7210-1:2014 (230°C, 2.16 kg load).

[0105] (2) Melting point (Tm) and heat of fusion (ΔHm) For the raw resins, resin composition (A), and resin composition (B), a differential scanning calorimeter (DSC) was used. A 5.0 mg sample was heated to 200°C, held at 200°C for 5 minutes, and then cooled to 40°C at a rate of 10°C / min. The sample was then heated at a rate of 10°C / min. The top temperature of the endothermic peak was taken as the melting point (Tm), and the peak area of ​​this peak was taken as the heat of fusion (ΔHm). ΔHm is expressed in J / g.

[0106] (3) Flexural modulus For the raw resins, resin composition (A), and resin composition (B), injection-molded test specimens measuring 4.0 mm thick, 10.0 mm wide, and 80 mm long were prepared. Dumbbell-shaped tensile test specimens (Type A) were molded using a Toshiba Machine IS80G injection molding machine at a molding temperature of 200°C and a mold temperature of 40°C. The flexural modulus of the test specimens thus obtained was measured in accordance with JIS K 7171:2022 (ISO178) at a test speed of 2 mm / min. The flexural modulus is measured in MPa.

[0107] (4) Durometer D hardness (HDD) The raw material resins, resin composition (A), and resin composition (B) were molded into test specimens (4 mm thick) using an IS80G injection molding machine manufactured by Toshiba Machine Co., Ltd. at a molding temperature of 200°C and a mold temperature of 40°C. The hardness of these test specimens was measured using a Type D durometer in accordance with JIS K 7215:1986.

[0108] (5) Young's modulus (MD) Test specimens were prepared for the raw resins, resin composition (A), and resin composition (B), as follows. For resin composition (A) and resin composition (B), the propylene-based polymer and propylene-based thermoplastic elastomer constituting each composition were mixed in a blender to a predetermined ratio, then melt-extruded at 230°C to form pellets. The pellets were used as they were for the raw resins. The resulting pellets were melt-extruded through a T-die attached to an extruder with a 35 mm diameter at a resin temperature of 240°C and a width of 320 mm to form an unstretched film with a thickness of 50 μm. Strip-shaped test specimens measuring 150 mm in the machine direction (MD) and 15 mm in the transverse direction (TD) were cut from the resulting unstretched film. Using the test specimens thus obtained, the MD Young's modulus (tensile modulus) was measured in accordance with JIS K 7127:1999, with a chuck distance of 100 mm and a crosshead speed of 1 mm / min. The Young's modulus is expressed in MPa.

[0109] (6) Density The raw resins, resin composition (A), and resin composition (B) were molded into test specimens using an IS80G injection molding machine manufactured by Toshiba Machine Co., Ltd. at a molding temperature of 200°C and a mold temperature of 40°C. Using these test specimens, the density was measured at 23°C in accordance with JIS K7112-2:2023.

[0110] (7) Ethylene and 1-butene content The ethylene and 1-butene contents in the propylene polymer and propylene thermoplastic elastomer used as raw materials were 13 The sample preparation and NMR measurement conditions were as follows: 200 mg of a propylene-based polymer or propylene-based thermoplastic elastomer was dissolved in an NMR sample tube with an inner diameter of 10 mm together with 2.4 ml of o-dichlorobenzene / deuterated bromide benzene (C6D5Br) = 4 / 1 (volume ratio) and hexamethyldisiloxane as a chemical shift reference substance. NMR measurements were performed using a Bruker Biospin AV400 NMR instrument equipped with a 10 mm diameter cryoprobe. 13 The C-NMR measurement was performed at a sample temperature of 120°C, a pulse angle of 90°, a pulse interval of 15 seconds, and an accumulation count of 512. The ethylene content (wt%) and 1-butene content (wt%) of the propylene polymer and the propylene thermoplastic elastomer are 13 The integrated intensities of the spectra obtained by C-NMR measurement were used to calculate the values ​​using the following (Equation 1) and (Equation 2), respectively. Ethylene content (mol%) = IE × 100 / (IE + IP + IB) Ethylene content (wt%) = [Ethylene content (mol%) × Molecular weight of ethylene] / [Ethylene content (mol%) × Molecular weight of ethylene + Propylene content (mol%) × Molecular weight of propylene + 1-butene content (mol%) × Molecular weight of 1-butene] (Equation 1) 1-Butene content (mol%) = IB × 100 / (IE + IP + IB) 1-butene content (wt%) = [1-butene content (mol%) × molecular weight of 1-butene] / [ethylene content (mol%) × molecular weight of ethylene + propylene content (mol%) × molecular weight of propylene + 1-butene content (mol%) × molecular weight of 1-butene] (Equation 2) where IE, IP, and IB are the integrated intensities of carbon derived from ethylene, propylene, and 1-butene, respectively.

[0111] (8) Maximum heat seal strength (unit: N / 15 mm) The laminated films obtained in the Examples and Comparative Examples were stored at an ambient temperature of 23°C for 7 days, then cut into strips measuring 180 mm (MD) x 80 mm (TD). The strips were folded in half in the MD so that the heat-sealable layers were in contact with each other, and heat-sealed at a width of 10 mm at a position 20-30 mm from the fold under the following sealing conditions. The resulting partially heat-sealed samples were cut into strips with a width of 15 mm in the TD to obtain test pieces. The resulting test pieces were pulled at both ends in a 180° peel direction at a rate of 500 mm / min using a Shopper-type tensile tester (manufactured by Tester Sangyo Co., Ltd.), and the maximum force required to peel the heat-sealed portions was measured and recorded as the heat-seal strength. The sealing conditions are: sealing pressure: 2.0 kg / cm 2 (0.196 MPa), sealing time: 1.0 second, sealing temperature: in the range of 90°C to 170°C in 10°C increments. After obtaining a seal curve from the sealing temperature and heat seal strength, the average value of the heat seal strength between 140°C and 170°C was taken as the maximum heat seal strength. A maximum heat seal strength of 40 N / 15 mm or more was determined to be excellent in heat seal strength.

[0112] (9) Heat seal initiation temperature (unit: °C) In the seal curve obtained by the method for obtaining the maximum heat seal strength in the range of 90°C to 170°C, the data between any two points measured at 10°C intervals was approximated with a linear function, and the seal temperature at which the heat seal strength reached 20 N / 15 mm was determined to be the heat seal initiation temperature. The lower this temperature, the faster the heat seal strength rises, and the better the low-temperature heat sealability of the film can be said to be. A heat seal initiation temperature of 140°C or lower was determined to have excellent low-temperature heat sealability.

[0113] (10) Drop-bag impact test (drop-bag resistance at low temperatures) Two 120mm x 150mm sheets were cut from the laminated film obtained in the Examples and Comparative Examples. The heat-sealed layers of each sheet were then overlapped, and three sides were sealed using an impulse sealer under the following sealing conditions to create a 120mm x 150mm sample bag with a 116mm opening. 100mL of water was poured into the opening of the sample bag, and one side of the opening was sealed using an impulse sealer under the following sealing conditions to create a water-sealing test piece. After storing the water-sealing test piece in a 0°C atmosphere for one day, it was dropped 50 times consecutively onto a metal plate from a height of 1.5m. The maximum number of times the bag did not break was recorded as the bag-breaking drop count. The test was repeated five times, and the average number of bag-breaking drops was calculated. The average number of bag-breaking drops was rounded down to an integer, and this was used as an index of bag-drop resistance at low temperatures. The sealing conditions were a Fuji Impulse poly sealer (product name: PC-300) with a seal width of 2 mm and a scale of 10 (sealing time: 1.6 seconds). Bags that broke and fell 20 times or more on average were judged to have excellent resistance to bag breakage.

[0114] (11) Film Thickness The thickness of the laminated films obtained in the examples and comparative examples was measured using a thickness gauge (manufactured by Mitutoyo Corporation).

[0115] (12) Haze (Transparency) (unit: %) The haze of the laminated films obtained in the examples and comparative examples was measured in accordance with JIS K 7136: 2000. A haze of less than 10% was determined to be excellent in transparency.

[0116] (13) Piercing strength (unit: N) For the laminated films obtained in the examples and comparative examples, test specimens were fixed with the base layer facing up in accordance with JIS Z 1707:2019, and a semicircular needle with a diameter of 1.0 mm and a tip radius of 0.5 mm was pierced at a rate of 50±5 mm per minute to measure the maximum stress until the needle penetrated, which was taken as the puncture strength (N). A puncture strength of 10 N or more was considered to be excellent.

[0117] (14) Recyclability When all of the layers constituting the laminated films obtained in the Examples and Comparative Examples were polypropylene films, the recyclability was evaluated as "good", and when not, it was evaluated as "bad".

[0118] 2.Raw materials Production Example 1: Production of Propylene Polymer-1 Propylene-ethylene-1-butene copolymer was produced using a Ziegler-Natta catalyst as follows.

[0119] [Preparation of catalyst component (A)] As component (A1), THC-C-125 purchased from Toho Titanium Co., Ltd. was used. Analysis of component (A1) revealed that it contained 1.9 mass% Ti, 20.2 mass% Mg, and 63.7 mass% Cl. Next, a 20 L autoclave equipped with a stirrer was thoroughly purged with nitrogen, and 100 g of the slurry of component (A1) was introduced as component (A1). Purified n-heptane was introduced to adjust the concentration of component (A1) to 25 g / L. 50 ml of silicon tetrachloride was added, and the reaction was carried out at 90°C for 1 hour. The reaction product was washed thoroughly with purified n-heptane. Thereafter, purified n-heptane was introduced to adjust the liquid level to 4 L. To the slurry of the reaction product of component (A1) thus obtained was added a diluted n-heptane solution of triethylaluminum containing 30 ml of dimethyldivinylsilane as the vinylsilane compound (component (A2)), 30 ml of diisopropyldimethoxysilane as the organosilicon compound (component (A3)), and 80 g of triethylaluminum as the organoaluminum compound (component (A4)), and the reaction was carried out at 40°C for 2 hours. The reaction product was thoroughly washed with purified n-heptane, and a portion of the resulting slurry was sampled and dried. Analysis revealed that the resulting catalyst component (A) contained 0.88 mass % of Ti, 8.0 mass % of diisopropyldimethoxysilane, and 63.7 mass % of chlorine.

[0120] [Prepolymerization] Using the component (A) obtained above, prepolymerization was carried out according to the following procedure. Purified n-heptane was introduced into the above slurry of component (A) to adjust the concentration of component (A) to 20 g / L. After the slurry was cooled to 10°C, a solution of triethylaluminum diluted in n-heptane containing 10 g of triethylaluminum was added, and 280 g of propylene was fed over 4 hours. After the propylene supply was completed, the reaction was continued for another 30 minutes. Next, the gas phase was thoroughly purged with nitrogen, and the reaction product was thoroughly washed with purified n-heptane. The resulting slurry was taken out of the autoclave and dried in a vacuum to obtain a prepolymerized component (A). After this prepolymerization, component (A) contained 2.0 g of polypropylene per 1 g of the solid component. The component (A) after prepolymerization was slurried with n-hexane, and then charged into the catalyst feed tank in an amount to be used for about one week of continuous operation, with no additional charging during operation.

[0121] [Polymerization process] Propylene polymer-1 was produced according to the process flow shown in Figure 1. Hereinafter, the process flow shown in Figure 1 will be described. A horizontal polymerization vessel 5 (L / D=4.3, internal volume 100 L) equipped with a stirring blade was continuously fed, via pipe 1, with 0.14 g / h of the above-mentioned prepolymerized component (A) and a propylene polymerization catalyst prepared by using triethylaluminum as an organoaluminum compound (component (B)) so that the Al / Mg molar ratio relative to Mg in the prepolymerized component (A) was 10. The reaction temperatures were set at 58°C, 61°C and 64°C from the upstream side for each of the three equal volumes of the horizontal polymerizer 5. While maintaining the reaction pressure at 1.90 MPa and the stirring speed at 28 rpm, hydrogen gas and ethylene were continuously supplied from circulation pipe 2 and 1-butene was continuously supplied from pipe 3 so as to maintain the hydrogen concentration in the gas phase in the polymerization reactor at the hydrogen / (ethylene + propylene + 1-butene) molar ratio shown in Table 1, the ethylene concentration at the ethylene / (ethylene + propylene + 1-butene) molar ratio shown in Table 1, and the 1-butene concentration at the 1-butene / (ethylene + propylene + 1-butene) molar ratio shown in Table 1, thereby adjusting the MFR, ethylene content, and 1-butene content of the polymer.

[0122] The heat of reaction (heat of polymerization) was removed by the heat of evaporation of the raw material liquefied propylene supplied through pipe 3. The unreacted gas discharged from the polymerization reactor was cooled and condensed outside the reactor system through pipe 4 and refluxed to the polymerization reactor 5 through pipe 3. The produced polymer was continuously withdrawn from the polymerizer 5 through a pipe 6 so that the polymer retention level was 50% by volume of the reaction volume. At this time, a portion of the polymer was intermittently sampled from the pipe 6, and the unreacted monomers were removed from the propylene-ethylene-1-butene copolymer, which was then used as a sample for measuring the MFR, ethylene content and 1-butene content. The production rate of the propylene-ethylene-1-butene copolymer was 10 kg / h, and the catalytic activity of the propylene polymerization catalyst calculated from the catalyst feed rate per hour (0.14 g / h) and the production rate (10 kg / h) was approximately 79,000 g / g-catalyst. The production conditions, monomer content, and various physical properties of propylene polymer-1 are shown in Table 1.

[0123] Production Example 2: Production of Propylene Polymer-2 Propylene polymer-2 was obtained under the same conditions as in Production Example 1, except that the catalyst feed amount, hydrogen concentration, ethylene concentration, and 1-butene concentration were changed to the conditions shown in Table 1. The production conditions, monomer content, and various physical properties of propylene polymer-2 are shown in Table 1.

[0124] [Table 1]

[0125] [Propylene polymers (C) and (E)] Propylene polymers 1 and 2 obtained in Production Examples 1 and 2 were used.

[0126] [Propylene-based thermoplastic elastomers (D) and (F)] Propylene-based thermoplastic elastomer-1: Vistamaxx (registered trademark) VM6102 (propylene-ethylene copolymer), manufactured by ExxonMobil Corporation MFR = 3.0 g / 10 min, Tm = 108 °C, ΔHm = 7 J / g, flexural modulus = 11 MPa, density = 0.862 g / cm 3 , propylene content = 84 wt%, ethylene content = 16 wt%

[0127] [Propylene homopolymer] Propylene homopolymer-1: Novatec (registered trademark) FL203D (propylene homopolymer produced by Ziegler-Natta catalyst), manufactured by Japan Polypropylene Corporation MFR = 3.0 g / 10 min, Tm = 162 °C, ΔHm = 107 J / g, flexural modulus = 1,400 MPa, HDD = 80, Young's modulus (MD) = 760 MPa, density = 0.905 g / cm 3

[0128] [Other ingredients] Linear low-density polyethylene-1: manufactured by Japan Polyethylene Co., Ltd., trade name: Harmolex (registered trademark) NC564A MFR = 3.5 g / 10 min, Tm = 124 °C, ΔHm = 124 J / g, flexural modulus = 160 MPa, HDD = 53, Young's modulus (MD) = 141 MPa, density = 0.918 g / cm 3

[0129] Example 1 1. Preparation of a laminate of the base layer and intermediate layer The base layer was made of pellets containing 100% by weight of propylene homopolymer-1, and the intermediate layer was made of pellets containing 100% by weight of propylene polymer-1. Using an extruder, each layer was co-extruded at a resin temperature of 230°C and a width of 300 mm to obtain a laminate of the base layer and intermediate layer, with a thickness of 920 μm and 80 μm, respectively. The resulting laminate was biaxially stretched using a JPP tenter (a biaxial stretching machine manufactured by Mitsubishi Heavy Industries, Ltd.) at a chill roll speed of 3 m / min, longitudinal and transverse stretching speeds of 15 m / min, a longitudinal stretching ratio of 5 times, and a transverse stretching ratio of 8 times. The intermediate layer of the resulting stretched film was subjected to corona treatment at a voltage of 0.6 kV to obtain a biaxially stretched polypropylene film consisting of the base layer and intermediate layer. The biaxially stretched polypropylene film had a base layer thickness of 23 μm and an intermediate layer thickness of 2 μm.

[0130] 2. Preparation of Sealant Film A total of 100 parts by weight of 75 parts by weight of propylene polymer-2 and 25 parts by weight of propylene thermoplastic elastomer-1 were mixed in a blender and then melt-extruded at 230°C to form pellets. The resulting pellets were melt-extruded through a T-die attached to an extruder with a 35 mm diameter at a resin temperature of 240°C and a width of 320 mm to form a film, which was then corona-treated on one side to produce a 50 μm-thick unstretched sealant film. This was used as the heat-seal layer.

[0131] 3. Preparation of Laminated Film A solution of a 1:1 mixture of a urethane adhesive (Unoflex (registered trademark) J-24, manufactured by Sanyo Chemical Industries, Ltd.) and a diluent (NC401 solvent C, manufactured by Toyo Ink Co., Ltd.) was applied to the corona-treated surface of the biaxially oriented polypropylene film using the dry lamination method, and dried to form an adhesive layer. This was then bonded to the corona-treated surface of the sealant film to obtain a laminated film. The laminated film was evaluated for maximum heat seal strength, heat seal initiation temperature, drop resistance at low temperatures, film thickness, haze, puncture strength, and recyclability. The composition of the laminated film of Example 1 and the evaluation results are shown in Table 2.

[0132] Example 2 Except for using pellets of 100% by weight of propylene polymer-2 as the intermediate layer, a laminated film was obtained in the same manner as in Example 1. The composition and evaluation results of the laminated film of Example 2 are shown in Table 2.

[0133] Example 3 A laminated film was obtained in the same manner as in Example 1, except that the intermediate layer was made by thoroughly mixing 75% by weight of propylene polymer-2 and 25% by weight of propylene thermoplastic elastomer-1 in a blender, melt-extruding the mixture at 230°C, and pelletizing the mixture. The composition and evaluation results of the laminated film of Example 3 are shown in Table 2.

[0134] Example 4 Except for using pellets containing 100% by weight of propylene polymer-2 as the heat seal layer, a laminated film was obtained in the same manner as in Example 3. The composition and evaluation results of the laminated film of Example 4 are shown in Table 2.

[0135] Comparative Example 1 Except for using pellets of 100% by weight of propylene homopolymer-1 as the intermediate layer, a laminated film was obtained in the same manner as in Example 1. The composition and evaluation results of the laminated film of Comparative Example 1 are shown in Table 2.

[0136] Comparative Example 2 Except for using pellets of 100% by weight of propylene homopolymer-1 as the intermediate layer, a laminated film was obtained in the same manner as in Example 4. The composition and evaluation results of the laminated film of Comparative Example 2 are shown in Table 2.

[0137] Comparative Example 3 Except for using pellets of 100% by weight of linear low-density polyethylene-1 as the heat seal layer, a laminated film was obtained in the same manner as in Comparative Example 1. The composition and evaluation results of the laminated film of Comparative Example 3 are shown in Table 2.

[0138] Comparative Example 4 A laminated film was obtained in the same manner as in Example 4, except that E5102 (biaxially oriented polyethylene terephthalate film, thickness 25 μm) manufactured by Toyobo Co., Ltd. was used instead of the biaxially oriented polypropylene film consisting of a base layer and an intermediate layer. The composition and evaluation results of the laminated film of Comparative Example 4 are shown in Table 2.

[0139] Comparative Example 5 A laminated film was obtained in the same manner as in Example 1, except that E5102 (biaxially oriented polyethylene terephthalate film, thickness 25 μm) manufactured by Toyobo Co., Ltd. was used instead of the biaxially oriented polypropylene film consisting of a base layer and an intermediate layer. The composition and evaluation results of the laminated film of Comparative Example 5 are shown in Table 2.

[0140] Comparative Example 6 A laminated film was obtained in the same manner as in Comparative Example 3, except that E5102 (biaxially oriented polyethylene terephthalate film, thickness 25 μm) manufactured by Toyobo Co., Ltd. was used instead of the biaxially oriented polypropylene film consisting of a base layer and an intermediate layer. The composition and evaluation results of the laminated film of Comparative Example 6 are shown in Table 2.

[0141] [Table 2]

[0142] As is clear from Table 1, the laminate films of Examples 1 to 4 had a heat-sealing initiation temperature of 140°C or lower, excellent low-temperature heat-sealing properties, a high maximum heat-sealing strength of 40 N / 15 mm or higher, and excellent recyclability. Among them, Examples 1 to 3, in which the resin composition (B) constituting the heat-sealing layer contains 50 to 95% by weight of the propylene polymer (E) and the propylene thermoplastic elastomer (F) in a total of 100% by weight, are excellent in low-temperature heat-sealing properties, maximum heat-sealing strength, and bag-drop resistance at low temperatures, are preferred.

[0143] On the other hand, Comparative Examples 1 to 3, in which the intermediate layer was a propylene homopolymer, and Comparative Example 4, in which a commercially available biaxially oriented polyethylene terephthalate film was used instead of a biaxially oriented polypropylene film, exhibited inferior maximum heat seal strength. Furthermore, Comparative Examples 3 to 6 are not made of a mono-material, and therefore are inferior in recyclability. The laminate film of the present invention has the same maximum heat seal strength as laminate films using a biaxially oriented polyethylene terephthalate film as the base layer, such as Comparative Examples 5 and 6, but is made of a mono-material, so is excellent in recyclability and can be suitably used as a variety of packaging films. [Industrial Applicability]

[0144] The laminated film can be suitably used as a packaging film for general foods, frozen foods, heavy goods, and liquids. [Explanation of symbols]

[0145] 1: Catalyst component supply piping (piping) 2: Raw material mixed gas supply pipe (circulation pipe) 3: Raw material propylene, 1-butene supply piping (piping) 4: Unreacted gas extraction piping (piping) 5: Polymerization vessel (horizontal polymerization vessel) 6: Downstream end of reactor (piping)

Claims

1. A laminated film comprising a base layer, an intermediate layer, and a heat seal layer laminated in this order, the base layer and the intermediate layer are stretched polypropylene films, and the heat seal layer is an unstretched polypropylene film; A laminated film, wherein a resin composition (A) constituting an intermediate layer satisfies the following requirement (a1), and a resin composition (B) constituting a heat seal layer satisfies the following requirements (b1) and (b2). (a1) The durometer D hardness (HDD) measured in accordance with JIS K 7215:1986 is 10 to 78. (b1) The durometer D hardness (HDD) measured in accordance with JIS K 7215:1986 is 10 to 78. (b2) The melting point is 110 to 150°C.

2. the resin composition (A) contains a propylene polymer (C) and a propylene thermoplastic elastomer (D), and the content of the propylene polymer (C) is 10 to 100% by weight and the content of the propylene thermoplastic elastomer (D) is 0 to 90% by weight, relative to 100% by weight of the total of the propylene polymer (C) and the propylene thermoplastic elastomer (D); the resin composition (B) contains a propylene polymer (E) and a propylene thermoplastic elastomer (F), and the content of the propylene polymer (E) is 10 to 100% by weight and the content of the propylene thermoplastic elastomer (F) is 0 to 90% by weight, relative to 100% by weight of the total of the propylene polymer (E) and the propylene thermoplastic elastomer (F); The laminate film according to claim 1, wherein the propylene polymer (C) satisfies the following requirements (c1) to (c5): the propylene thermoplastic elastomer (D) satisfies the following requirements (d1) to (d4): the propylene polymer (E) satisfies the following requirements (e1) to (e5): and the propylene thermoplastic elastomer (F) satisfies the following requirements (f1) to (f4): (c1) and (e1) have an MFR of 1 to 50 g / 10 min measured in accordance with JIS K 7210-1:2014 (230°C, 2.16 kg load). (c2) and (e2) The flexural modulus, measured in accordance with JIS K 7171:2022 at a test speed of 2 mm / min, is greater than 500 MPa and not greater than 1,300 MPa. (c3) and (e3) The content of units derived from propylene is more than 88.0% by weight and not more than 99.9% by weight. (c4) and (e4) The content of units derived from ethylene and α-olefins having 4 to 20 carbon atoms is 0.1% by weight or more and less than 12.0% by weight. (c5) and (e5) have a melting point of 110 to 155°C. (d1) and (f1) have an MFR of 1 to 30 g / 10 min measured in accordance with JIS K 7210-1:2014 (230°C, 2.16 kg load). (d2) and (f2) The flexural modulus measured in accordance with JIS K 7171:2022 at a test speed of 2 mm / min is 5 to 200 MPa. (d3) and (f3) The content of units derived from propylene is 60.0 to 92.0% by weight. (d4) and (f4) The content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms is 8.0 to 40.0% by weight.

3. The propylene-based thermoplastic elastomer (D) satisfies the following requirements (d3') and (d4'), and the propylene-based thermoplastic elastomer (F) satisfies the following requirements (f3') and (f4'). The laminated film according to claim 2. (d3') and (f3') The content of units derived from propylene is 60.0 to 88.0% by weight. (d4') and (f4') The content of units derived from ethylene and an α-olefin having 4 to 20 carbon atoms is 12.0 to 40.0% by weight.

4. 3. The laminate film according to claim 2, wherein, in the resin composition (B), a content of the propylene polymer (E) is 50 to 95% by weight and a content of the propylene thermoplastic elastomer (F) is 5 to 50% by weight, relative to 100% by weight of the total of the propylene polymer (E) and the propylene thermoplastic elastomer (F).

5. 2. The laminated film according to claim 1, wherein the thickness of the intermediate layer and the heat seal layer are 1 to 10 μm and 10 to 400 μm, respectively.

6. 2. The laminated film according to claim 1, wherein the sealing temperature at which a heat seal strength of 20 N / 15 mm is reached, measured under the following conditions, is 140° C. or lower. <Measurement of the sealing temperature at which the heat seal strength reaches 20 N / 15 mm> After storing the laminated film at an ambient temperature of 23°C for 7 days, it was cut into strips measuring 180 mm (MD) x 80 mm (TD), folded in half in the MD so that the heat-sealable layers were in contact with each other, and heat-sealed at a position 20-30 mm from the fold, over a 10 mm width, under the following sealing conditions. The resulting partially heat-sealed sample was cut into strips with a 15 mm width in the TD to obtain test pieces. The resulting test pieces were pulled at both ends in a 180° peel direction using a Schopper-type tensile tester at a rate of 500 mm / min, and the maximum force required to peel the heat-sealed portions was measured and used as the heat-seal strength. The sealing conditions were: sealing pressure: 2.0 kg / cm ２ (0.196 MPa), sealing time: 1.0 second, sealing temperature: in the range of 90°C to 170°C in 10°C increments. In the seal curve obtained from the seal temperature and heat seal strength, the data between any two points measured at 10°C intervals is approximated by a linear function to determine the seal temperature at which the heat seal strength reaches 20 N / 15 mm.

7. 2. The laminated film according to claim 1, wherein the average number of times the bag breaks when dropped is six or more times in a bag drop impact test measured under the following conditions. <Dropped bag impact test> Two 120 mm x 150 mm sheets were cut from the laminated film, and the heat-sealed layers of each sheet were then overlapped. Three sides were sealed using an impulse sealer under the following sealing conditions to prepare a 120 mm x 150 mm sample bag. 100 ml of water was poured into the sample bag, and the open side was sealed using an impulse sealer under the following sealing conditions to prepare a water-sealing test piece. After storing the water-sealing test piece in an atmosphere at 0°C for one day, it was dropped 50 times consecutively onto a metal plate from a height of 1.5 m. The maximum number of times the bag did not break was recorded as the number of bag-breaking drops. The test was repeated five times, and the average number of bag-breaking drops was calculated. The sealing conditions were as follows: a poly sealer (trade name: PC-300) manufactured by Fuji Impulse Co., Ltd., seal width: 2 mm, scale: 10 (sealing time: 1.6 seconds).

8. A food packaging film, a heavy-duty packaging film, or a liquid packaging film, which comprises the laminate film according to any one of claims 1 to 7.

9. 8. A method for producing a laminate film according to claim 1, comprising: step 1 of co-extruding a base layer and an intermediate layer to obtain a laminate; step 2 of stretching the laminate obtained in step 1 to obtain a stretched film; and step 3 of adhering a heat seal layer onto the intermediate layer of the stretched film obtained in step 2.

10. 10. The method for producing a laminated film according to claim 9, wherein the step 3 is a step of bonding the intermediate layer and the heat seal layer by a dry lamination method.

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