Laminated film and method for producing the same, and packaging material

Abstract

To provide a laminated film having excellent recyclability while ensuring sufficient heat-sealing and laminating properties and a method for producing the same, and a packaging material.SOLUTION: A laminated film comprises a base film, a sealant film, and a heat seal layer provided between the base film and the sealant film, wherein the base film is drawn, the sealant film and the heat seal layer remain undrawn, and the base film, heat seal layer, and sealant film all include an identical type of polyolefin resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminated film, a method for producing the same, a laminate, and a packaging material. [Background technology]

[0002] Generally, plastic films have properties such as being lightweight, chemically stable, easy to process, flexible and strong, and capable of mass production. For these reasons, plastic films are used in a wide variety of applications. Applications of plastic films are diverse, including, for example, packaging materials for food products and medicines, intravenous drip packs, shopping bags, posters, tapes, optical films for LCD televisions, protective films, window films for application to windows, greenhouses, building materials, and the like. For these applications, appropriate plastic materials are selected according to the application.

[0003] For example, in packaging materials, laminated films are widely used, in which a resin film with excellent strength and heat resistance, such as a polyester film or a nylon film, is used as a base film, and a resin film with excellent flexibility and low-temperature heat-sealing properties, such as polyethylene or polypropylene, is laminated on top of the base film as a sealant film. By using multiple different plastics as the base film and sealant film, a packaging bag can be obtained in which, when heat-sealed with the sealant film side facing inward, the inside is sufficiently fused and the outside is free of deformation such as wrinkles.

[0004] On the other hand, in recent years, there has been a demand for the realization of a sustainable society, and recycling of packaging materials is also desired. From this perspective, technologies are being developed to separate laminated films made of multiple materials into individual resin materials, as described in Patent Document 1. However, such methods require precise removal of impurities to ensure successful recycling, which poses the problem of requiring a lot of time, energy, and cost. Technologies that take recyclability into consideration are also being considered. For example, Patent Document 2 below proposes a polyethylene laminate for packaging materials in which an oriented polyethylene film and a heat-sealable polyethylene layer are laminated with an adhesive layer containing a solventless adhesive. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 132683 [Patent Document 2] Japanese Patent Application Laid-Open No. 2019-189333 Summary of the Invention [Problem to be solved by the invention]

[0006] The laminate described in Patent Document 2 is made up of a combination of resin films of the same type, eliminating the need to separate each resin material during recycling. However, the laminate does not take into consideration the possibility that the adhesive layer, which is used to ensure sufficient lamination, may become a foreign substance if the laminate is recycled without separating the layers.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a laminated film that has sufficient heat-sealing properties and lamination properties and is also highly recyclable, a method for producing the same, and a packaging material. [Means for solving the problem]

[0008] The present disclosure relates to the following [1] to [5]. [1] A laminated film comprising a base film, a sealant film, and a heat-sealing layer provided between the base film and the sealant film, wherein the base film is stretched, the sealant film and the heat-sealing layer are not stretched, and the base film, the heat-sealing layer, and the sealant film contain the same type of polyolefin resin. [2] The laminated film according to [1], wherein the base film has a laminated structure of two or more layers, and the base film includes a first layer in contact with the heat-sealing layer and a second layer having a melting point higher than the melting point of the first layer. [3] The laminated film according to [1] or [2], wherein the polyolefin resin is a polypropylene-based resin, and the planar orientation M calculated by the following method is 0.5 or more and 0.9 or less on the surface BS2 of the base film opposite to the side in contact with the heat-sealing layer, and is -0.3 or more and 0.3 or less on the surface HS2 of the sealant film opposite to the side in contact with the heat-sealing layer. Calculation method for plane orientation M: The plane orientation M is calculated from the equation M = (0.6887ε - 0.4395) / (0.4962ε + 0.2198) using ε, expressed as ε = (α + β) / (γ + δ), based on the following absorbance peak intensities α, β, γ, and δ measured using polarized ATR-FTIR. (1) The incident light was fixed to S-polarized light, and the sample angle was rotated by 15 degrees. In the measured spectrum, -1 The arrangement of the sample in which the absorbance peak intensity is the largest is defined as the slow axis arrangement, and the absorbance peak intensity in the slow axis arrangement is defined as α, (2) When the incident light is S-polarized and rotated 90 degrees from the slow axis arrangement, the 997 cm -1 The absorbance peak intensity is defined as β. (3) The incident light is P-polarized, and the slow axis arrangement is 997 cm -1 The absorbance peak intensity is γ, (4) When the incident light is P-polarized and rotated 90 degrees from the slow axis arrangement, the 997 cm -1 The absorbance peak intensity is defined as δ. [4] A packaging material comprising the laminated film according to any one of [1] to [3]. [5] A method for producing a laminated film comprising a base film, a sealant film, and a heat-sealing layer provided between the base film and the sealant film, the method comprising: step A of extruding and stretching a resin composition containing a polypropylene-based resin to obtain a base film; step B of extruding and stretching a resin composition containing a polypropylene-based resin to obtain a sealant film; and step C of bonding the base film and the sealant film by sandwich lamination with a molten resin of the resin composition containing a polypropylene-based resin interposed therebetween; in step A, stretching is performed so that the planar orientation M, calculated by the method described below, is 0.5 or more and 0.9 or less on the surface of the base film; and in step B, extrusion is performed so that the planar orientation M, calculated by the method described below, is -0.3 or more and 0.3 or less on the surface of the sealant film. Calculation method for plane orientation M: The plane orientation M is calculated from the equation M = (0.6887ε - 0.4395) / (0.4962ε + 0.2198) using ε, expressed as ε = (α + β) / (γ + δ), based on the following absorbance peak intensities α, β, γ, and δ measured using polarized ATR-FTIR. (1) The incident light was fixed to S-polarized light, and the sample angle was rotated by 15 degrees. In the measured spectrum, -1 The arrangement of the sample in which the absorbance peak intensity is the largest is defined as the slow axis arrangement, and the absorbance peak intensity in the slow axis arrangement is defined as α, (2) When the incident light is S-polarized and rotated 90 degrees from the slow axis arrangement, the 997 cm -1 The absorbance peak intensity is defined as β. (3) The incident light is P-polarized, and the slow axis arrangement is 997 cm -1 The absorbance peak intensity is γ, (4) When the incident light is P-polarized and rotated 90 degrees from the slow axis arrangement, the 997 cm -1 The absorbance peak intensity is defined as δ. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a laminated film that has sufficient heat-sealing properties and lamination properties and also has excellent recyclability, and a method for producing the same. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a laminated film according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing another example of the laminated film of the present embodiment. [Figure 3] FIG. 2 is a cross-sectional view schematically showing another example of the laminated film of the present embodiment. [Figure 4] FIG. 3 is a cross-sectional view schematically showing another example of the laminate of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that each drawing is a schematic view, and the size and shape of each part are appropriately exaggerated for ease of understanding. Also, for ease of explanation, the same reference numerals are used to denote corresponding parts in each drawing.

[0012] [Laminated film] The laminated film of this embodiment comprises a base film, a sealant film, and a heat-sealing layer disposed between the base film and the sealant film, wherein the base film is stretched, the sealant film and the heat-sealing layer are not stretched, and the base film, the heat-sealing layer, and the sealant film contain the same type of polyolefin resin.

[0013] The laminate film of this embodiment, having the above-described configuration, can have excellent recyclability while maintaining sufficient heat-sealing and laminating properties. The inventors speculate as follows about the reason for this effect. First, the laminate film of this embodiment has a structure in which a heat-sealing layer is provided between a substrate film and a sealant film. Since these films contain the same type of polyolefin resin, the film can be produced by sandwich lamination, in which the substrate film and the sealant film are heat-sealed to form a three-layer structure, without using adhesives or anchor coats that would impair recyclability. In this sandwich lamination (sometimes referred to as sand lamination), the substrate film and the sealant film are heat-sealed with the same type of polyolefin resin, and the sealant film and the heat-sealing layer are unstretched. This is thought to enable sufficient lamination strength to be obtained while maintaining sufficient heat-sealing properties.

[0014] Furthermore, the laminated film of this embodiment can obtain sufficient lamination strength without using an adhesive or anchor coat, thereby solving the following problem of the adhesive layer becoming a foreign body when the layers are recycled without being separated. It has been found that, because the adhesive is three-dimensionally crosslinked, it is likely to become a foreign body when reused through recycling. It has also been found that even when the adhesive content in the film is low, it is difficult to finely disperse the crosslinked adhesive, making it likely to become a foreign body. Such foreign body particles can lead to fisheyes and reduced physical properties.

[0015] Fig. 1 is a cross-sectional view schematically showing an example of the laminated film of this embodiment. The laminated film 10 shown in Fig. 1 has a structure in which a base film 20 and a sealant film 40 are laminated via a heat-sealing layer 30. The base film 20, the heat-sealing layer 30, and the sealant film 40 contain the same type of polyolefin resin, and the base film 20 is stretched, while the sealant film 40 and the heat-sealing layer 30 are unstretched.

[0016] As described above, the laminated film 10 can be produced by sandwich lamination without using adhesives or anchor coats that impair recyclability, and can be recycled without separating the individual layers.

[0017] When the main surface of the laminated film 10 on the sealant film 40 side is the front surface and the main surface on the base film 20 side is the back surface, the front surface can be heat-sealed suitably.

[0018] <Base film> The base film 20 may be uniaxially stretched or biaxially stretched. From the viewpoint of strength, the base film may be biaxially stretched, and from the viewpoint of productivity, the base film may be sequentially biaxially stretched.

[0019] The stretching ratio in the machine direction (MD) of the base film 20 may be 2 to 10, or may be 3 to 7. The stretching ratio in the cross direction (TD) of the base film 20 may be 3 to 15, or may be 5 to 12. When the MD and TD of the base film 20 are within the above ranges, the strength and transparency of the base film and the heat resistance of the laminate film 10 can be improved. Here, heat resistance refers to the property of preventing shrinkage and wrinkles from occurring on the back side of the laminate film when the front side is heat-sealed.

[0020] The material constituting the base film 20 is a polyolefin resin. Examples of polyolefin resins include polyethylene-based resins and polypropylene-based resins. The base film 20 may be made of different resins (e.g., polyethylene-based resin and polypropylene-based resin), but from the viewpoint of improving recyclability, it may also be made of a single resin (e.g., polyethylene-based resin or polypropylene-based resin).

[0021] Examples of polyethylene-based resins include polyethylene-based resins including low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) obtained by copolymerizing α-olefin and ethylene, medium-density polyethylene (MDPE), high-density polyethylene (HDPE), etc. The base film 20 may contain a single polyethylene-based resin, or may contain multiple polyethylene-based resins with different melting points, MFRs, etc.

[0022] The melting point of the polyethylene resin may be 90 to 140°C, which is the melting point of a typical polyethylene, or may be 100 to 140°C.

[0023] The MFR (melt flow rate) of the polyethylene resin may be 0.01-50, 0.05-20, or 0.1-10.

[0024] Examples of polypropylene resins include homopolypropylene (PP), block polypropylene, random polypropylene, and propylene-α-olefin copolymers. The base film 20 may contain a single polypropylene resin or multiple polypropylene resins with different melting points, MFRs, etc.

[0025] The melting point of the polypropylene resin may be 110 to 165°C, which is the melting point of general polypropylene, or may be 130 to 165°C.

[0026] The MFR (melt flow rate) of the polypropylene resin may be 0.01-50, 0.05-20, or 0.1-10.

[0027] When the material constituting the base film 20 is polypropylene or a polypropylene-based resin containing a polypropylene resin copolymerized with an α-olefin, the planar orientation M calculated by the following method may be 0.5 to 0.9, 0.6 to 0.9, or 0.7 to 0.85, on the surface BS2 of the base film 20 opposite the side in contact with the heat-sealable layer of the base film. When the planar orientation M of the base film 20 is in the above range, the strength and transparency of the base film are easily obtained. Furthermore, when the planar orientation M of the base film 20 is in the above range, it is easy to improve the heat resistance of the laminate film.

[0028] (Calculation method of plane orientation M) The planar orientation M is calculated from the equation M = (0.6887ε - 0.4395) / (0.4962ε + 0.2198), where ε is expressed as ε = (α + β) / (γ + δ), based on the following absorbance peak intensities α, β, γ, and δ measured at 23°C using polarized ATR-FTIR. (1) The incident light was fixed to S-polarized light, and the sample angle was rotated by 15 degrees. In the measured spectrum, -1 The arrangement of the sample in which the absorbance peak intensity is the largest is defined as the slow axis arrangement, and the absorbance peak intensity in the slow axis arrangement is defined as α, (2) When the incident light is S-polarized and rotated 90 degrees from the slow axis arrangement, the 997 cm -1 The absorbance peak intensity is defined as β. (3) The incident light is P-polarized, and the slow axis arrangement is 997 cm -1 The absorbance peak intensity is γ, (4) When the incident light is P-polarized and rotated 90 degrees from the slow axis arrangement, the 997 cm -1 The absorbance peak intensity is defined as δ.

[0029] Incidentally, a conventional method for evaluating orientation is the dichroic ratio method, in which polarized light is incident on a film, the light totally reflected by the film surface is detected to measure the absorption spectrum, and the orientation is evaluated from the ratio of absorbance in the slow axis direction in the film plane to that in the fast axis direction perpendicular to it. However, this conventional method only uses S-polarized light, and the obtained orientation is limited to the slow axis direction in the film plane and the fast axis direction perpendicular to it, so it does not include information about the thickness direction of the film.

[0030] On the other hand, the plane orientation M of the present invention can measure the direction of molecular vibration by irradiating a sample with S-polarized light, which vibrates perpendicular to the incident plane, and P-polarized light, which vibrates parallel to the incident plane.

[0031] Specifically, the film is positioned with its fast axis aligned with the light's propagation direction, and S-polarized light is irradiated onto the film to obtain orientation information related to the slow axis. Irradiating the film with P-polarized light provides orientation information related to the fast axis and the depth direction, i.e., the film's thickness. Next, the sample is rotated 90 degrees and S-polarized light is irradiated onto the film to obtain orientation information related to the fast axis. Irradiating the film with P-polarized light provides orientation information related to the slow axis and the thickness direction. From this orientation information, molecular orientation information can be determined for the slow axis, fast axis, and thickness directions. Furthermore, because it is possible to specifically analyze molecular orientation on the sample surface down to a depth of approximately 1 μm, the infrared light's penetration depth, it is possible to analyze molecular orientation on the sample surface regardless of sample thickness.

[0032] In polypropylene resins, the 997cm -1 The peak at 997 cm is attributed to the hybrid vibration of C-CH3 rocking, C-CH3 stretching, and CH bending, and is a band that absorbs parallel vibrations to the molecular chain, i.e., parallel polarized light. For this reason, in the spectrum measured by fixing the incident light to S-polarized light and rotating the sample angle by 15 degrees, -1It can be seen that the sample orientation where the absorbance peak intensity is greatest is the orientation in which the molecular chains are generally oriented in the film plane direction (hereinafter referred to as the slow axis orientation). The ratio of the absorbance peak intensity α at this time to the absorbance peak intensity β when the orientation is rotated 90 degrees from the slow axis orientation is the dichroic ratio, which indicates the degree of orientation in the plane direction.

[0033] If the polarization of the incident light is P-polarized, the information includes not only the component in the plane direction of the film but also the component in the thickness direction. Therefore, by comparing this with information from S-polarized light, which can measure only the component in the plane direction of the film, it is possible to evaluate the degree of orientation in the thickness direction.

[0034] As a result of various investigations, the range of the plane orientation M on the surface BS2 described above was determined to be the range of the absorbance peak intensity α and the absorbance peak intensity β described above, and the 997 cm -1 The absorbance peak intensity γ of 997 cm in the configuration rotated 90 degrees from the slow axis configuration -1 This is based on the finding that the planar orientation M calculated from the above formula using the absorbance peak intensity δ of the substrate film is correlated with the strength and transparency of the substrate film and the heat resistance of the laminate film.

[0035] The planar orientation M of one surface of the base film 20 can be controlled by the take-up speed in the process of producing an unstretched film, which is an intermediate of the base film 20, the stretching temperature in the stretching process, the stretching ratio in the stretching process, etc. The planar orientation M tends to increase as the take-up speed in the process of producing an unstretched film increases, as the stretching temperature in the stretching process decreases, and as the stretching ratio increases.

[0036] The base film 20 may have a laminated structure of two or more layers, for example, the base film 20 may be multi-layered with resins of the same type but different melting points, MFRs (melt flow rates), and the like.

[0037] FIG. 2 is a diagram showing an example of a laminate film having a laminated structure of two or more substrate layers. The substrate film 20 shown in FIG. 2 may include a first layer 21 in contact with the heat-sealing layer 30 and a second layer 22 having a melting point higher than that of the first layer 21. In this case, when the substrate film 20 is bonded to the sealant film 40 via the heat-sealing layer 30 by sand lamination, the heat-sealing can be more easily achieved, thereby improving the lamination strength of the laminate film. That is, in sand lamination, the first layer 21 can function as a sand lamination contact region that is in close contact with the heat-sealing layer 30, and the second layer 22 can function as a non-contact region that is not in contact with the heat-sealing layer 30. In this case, the melting point Tm1 of the resin constituting the first layer 21 is preferably lower than the melting point Tm2 of the resin constituting the second layer 22. From the viewpoint of achieving both lamination properties and heat resistance, it is preferably lower by 5°C or more than the melting point Tm2. Here, the melting point Tm1 being lower than the melting point Tm2 may mean that the peak temperature of the heat of fusion is low, or that the ratio of the low-melting point component in the resin constituting the first layer 21 is higher than the ratio of the low-melting point component in the resin constituting the second layer 22. Examples of the low-melting point component include polyethylene-based resins with a melting point of 90 to 130°C and polypropylene-based resins with a melting point of 110 to 155°C.

[0038] Various additives may be mixed into the base film 20 as long as they do not impair the properties of the present invention. Examples include antiblocking agents, crosslinking agents, nucleating agents, fillers, reinforcing agents, slip agents, lubricants, plasticizers, antioxidants, heat stabilizers, weathering agents, light stabilizers, UV absorbers, antistatic agents, flame retardants, flame retardant assistants, anti-fogging agents, pigments, dyes, dispersants, neutralizing agents, natural oils, synthetic oils, waxes, modifying resins, etc. Two or more of these may be used in combination.

[0039] The thickness of the base film 20 may be 8 μm or more and 80 μm or less, or 12 μm or more and 50 μm or less, which can improve the strength and transparency of the base film 20 and the heat resistance of the laminate film 10.

[0040] The base film 20 can be obtained by melting a polyolefin resin, forming it into a film by a melt extrusion molding method such as a T-die molding method or an inflation molding method, and then stretching it. When the base film 20 is multilayered with a first layer 21 and a second layer 22, it can be produced, for example, by using a die via a feed block or a multi-manifold.

[0041] <Thermal adhesive layer> The material constituting the heat-sealing layer 30 is the same type of polyolefin resin as that of the sealant film 40 and the base film 20. The heat-sealing layer 30 may contain the above-mentioned polyethylene-based resin, or may contain a plurality of polyethylene-based resins with different melting points, MFR, etc., or may contain the above-mentioned polypropylene-based resin, or may contain a plurality of polypropylene-based resins with different melting points, MFR, etc. From the viewpoint of increasing the number of film combinations that can be sandwich-laminated and broadening the process conditions for sandwich lamination, the heat-sealing layer 30 may contain a polypropylene resin copolymerized with an α-olefin in the case of a polypropylene-based resin, or may contain linear low-density polyethylene (LLDPE) copolymerized with α-olefin and ethylene in the case of a polyethylene-based resin.

[0042] The heat-sealable layer 30 may contain various additives as long as they do not impair the properties of the present invention. Examples of such additives include antiblocking agents, crosslinking agents, nucleating agents, fillers, reinforcing agents, slip agents, lubricants, plasticizers, antioxidants, heat stabilizers, weathering agents, light stabilizers, UV absorbers, antistatic agents, flame retardants, flame retardant assistants, anti-fogging agents, pigments, dyes, dispersants, neutralizing agents, natural oils, synthetic oils, waxes, and modifying resins. Two or more of these may be used in combination.

[0043] The thickness of the heat-sealing layer 30 may be 2 μm or more and 50 μm or less, 5 μm or more and 40 μm or less, or 10 μm or more and 30 μm or less. When the thickness of the heat-sealing layer 30 is in such a range, it becomes easy to obtain a laminated film with sufficient productivity by maintaining the process speed of sand lamination while ensuring lamination properties.

[0044] <Sealant film> The sealant film 40 is unstretched. In other words, it is not oriented. This allows low-temperature heat sealing properties to be obtained. By providing the laminate film 10 with such a sealant film 40, heat sealing at low temperatures becomes possible, and shrinkage and wrinkles can be less likely to occur. Furthermore, the laminate film 10 can also have excellent flexibility.

[0045] The material constituting the sealant film 40 is the same type of polyolefin resin as that of the heat-sealing layer 30 and the base film 20. The sealant film 40 may contain the above-mentioned polyethylene-based resin, or may contain a plurality of polyethylene-based resins with different melting points, MFR, etc., or may contain the above-mentioned polypropylene-based resin, or may contain a plurality of polypropylene-based resins with different melting points, MFR, etc. From the viewpoints of heat sealability and flexibility, the sealant film 40 may contain a polypropylene resin copolymerized with an α-olefin in the case of a polypropylene-based resin, or may contain linear low-density polyethylene (LLDPE) copolymerized with α-olefin and ethylene in the case of a polyethylene-based resin.

[0046] When the constituent material of the sealant film 40 is a polypropylene-based resin including polypropylene or a polypropylene resin copolymerized with an α-olefin, from the standpoint of heat sealability and flexibility, the surface orientation M calculated by the above-mentioned method may be -0.3 or more and 0.3 or less, -0.2 or more and 0.2 or less, or -0.1 or more and 0.1 or less on the surface of the sealant film 40 that is not in contact with the heat-sealing layer 30.

[0047] When using a T-die molding method, the plane orientation M of the sealant film 40 can be controlled by the take-up speed, air gap, etc. The faster the take-up speed and the smaller the air gap, the greater the plane orientation M tends to be. Here, the air gap refers to the distance from the T-die to the sand lamination section.

[0048] The sealant film 40 may contain various additives as long as they do not impair the properties of the present invention. Examples include antiblocking agents, crosslinking agents, nucleating agents, fillers, reinforcing agents, slip agents, lubricants, plasticizers, antioxidants, heat stabilizers, weathering agents, light stabilizers, UV absorbers, antistatic agents, flame retardants, flame retardant assistants, anti-fogging agents, pigments, dyes, dispersants, neutralizing agents, natural oils, synthetic oils, waxes, and modifying resins. Two or more of these may be used in combination.

[0049] The thickness of the sealant film 40 may be 20 μm or more and 200 μm or less, 30 μm or more and 180 μm or less, or 40 μm or more and 150 μm or less, from the viewpoint of the strength of the laminated film 10 and the heat sealing strength during heat sealing.

[0050] The sealant film 40 can be obtained by melting a polyolefin resin and forming it into a film by a melt extrusion molding method such as a T-die molding method or an inflation molding method.

[0051] The sealant film 40 may have a laminated structure of two or more layers, for example, it may be made up of multiple layers of resins of the same type but different melting points and MFRs.

[0052] Fig. 3 is a diagram showing an example of a laminated film in which the sealant film has a laminated structure of two or more layers. The sealant film 40 shown in Fig. 3 is multilayered, with a substrate-side layer 43 on the side of the base film 20 and the heat-sealing layer 30, a heat-sealing layer 41 on the side opposite the base film 20 and the heat-sealing layer 30, and an intermediate layer 42 between the base-side layer 43 and the heat-sealing layer 41. In this case, the sealant film 40 having a laminated structure can be produced, for example, by using a feed block or a die via a multi-manifold.

[0053] By making the sealant film 40 multilayered, it is possible to achieve both high levels of lamination and impact resistance. By providing impact resistance, even when a heavy item is filled in a packaging bag made of the laminated film 10, the bag can protect the contents without breaking when dropped, allowing for a wider range of contents to be selected.

[0054] The heat seal layer 41, the intermediate layer 42, and the substrate-side layer 43 may each contain the above-mentioned polyethylene-based resin, or may contain multiple polyethylene-based resins with different melting points, MFRs, etc., or may contain the above-mentioned polypropylene-based resin, or may contain multiple polypropylene-based resins with different melting points, MFRs, etc.

[0055] <Laminated film manufacturing method> The method for producing a laminated film of the present embodiment is a method for producing a laminated film comprising a base film, a sealant film, and a heat-sealing layer provided between the base film and the sealant film, and comprises the following steps: Step A of extruding a resin composition containing a polypropylene-based resin and stretching it to obtain a base film; Step B of extruding a resin composition containing a polypropylene-based resin to obtain a sealant film; and Step C of bonding the base film and the sealant film together by sandwich lamination, with a molten resin composition containing a polypropylene-based resin interposed between them.

[0056] In step A, biaxial stretching may be performed so that the planar orientation M calculated by the above-mentioned method is 0.5 to 0.9, 0.6 to 0.9, or 0.7 to 0.85 on the surface of the substrate film, from the viewpoints of the strength and transparency of the substrate film and the heat resistance of the laminate film. The planar orientation M can be adjusted by the above-mentioned method.

[0057] In step B, from the viewpoint of improving heat sealability and flexibility, extrusion film formation may be performed so that the planar orientation M calculated by the above-mentioned method is −0.3 to 0.3, −0.2 to 0.2, or −0.1 to 0.1 on the surface of the sealant film. The planar orientation M can be adjusted by the above-mentioned method.

[0058] In step C, a three-layer structure consisting of a base film, a heat-sealable layer, and a sealant film can be produced by heat-sealing the base film and the sealant film in a sandwich shape with the melt of the resin composition containing a polypropylene-based resin at the center.

[0059] In step C, the temperature of the laminating section may be 30 to 150°C higher, or 80 to 120°C higher, than the melting point of the first layer of the base film. By setting the temperature of the laminating section within the above range, the adhesion between the heat-sealing layer and the base film is ensured, and deformation of the base film or sealant film or odors due to oxidation of the resin during sand lamination are less likely to occur.

[0060] In step C, from the viewpoints of lamination properties, sand lamination process speed, and productivity, the discharge temperature and take-up speed of the molten resin composition containing the polypropylene-based resin may be adjusted so that the thickness of the heat-sealing layer 30 is 2 μm or more and 50 μm or less, 5 μm or more and 40 μm or less, or 10 μm or more and 30 μm or less.

[0061] <Laminate> The laminated film of this embodiment may be a laminate in which a vapor-deposited adhesion layer containing a thermoplastic resin, a vapor-deposited layer, and a protective layer are laminated in this order on a base film of the laminated film, and the vapor-deposited adhesion layer and the vapor-deposited adhesion layer are in direct contact with each other.

[0062] FIG. 4 is a cross-sectional view schematically illustrating an example of a laminate according to this embodiment. The laminate 100 shown in FIG. 4 includes a laminate film 10, a vapor-deposited adhesion layer 44, a vapor-deposited layer 50, and a protective layer 60 laminated in this order. The laminate 100 has the above-described structure, which improves gas barrier properties. The vapor-deposited adhesion layer 44 contains a thermoplastic resin, which can be finely dispersed through a kneading process during recycling of the laminate, making it less likely to become a foreign substance. This improves adhesion to the vapor-deposited layer without significantly impairing the recyclability of the laminate.

[0063] The vapor-deposited adhesion layer 44 functions as a region (vapor-deposited adhesion region) that improves adhesion to the vapor-deposited layer 50. The material constituting the vapor-deposited adhesion layer 44 is a thermoplastic resin, and the above-mentioned polyolefin resin or a resin having a polar group can be used. Examples of resins having a polar group include polyamide resin, polyester resin, ethylene-vinyl alcohol copolymer (EVOH), and polyvinyl alcohol (PVA).

[0064] When the vapor-deposited adhesion layer 44 contains a resin having a polar group, an adhesive resin may be used between the vapor-deposited adhesion layer 44 and the second layer 22. In this case, from the viewpoint of recyclability, the mass proportion of the vapor-deposited adhesion layer 44 in the laminate 100 may be 20 mass % or less, 10 mass % or less, or 5 mass % or less, based on the total mass of the laminate.

[0065] From the viewpoint of recyclability of the laminate, the vapor-deposited adhesive layer 44 may contain the same type of polyolefin resin as the polyolefin resin contained in the base film.

[0066] Filler particles may be added to the vapor-deposited adhesion layer 44. In this case, it is preferable that the surface of the vapor-deposited adhesion layer 44 that comes into contact with the vapor-deposited layer 50 is smooth before the vapor-deposited layer 50 is formed. Furthermore, the surface of the vapor-deposited adhesion layer 44 that comes into contact with the vapor-deposited layer 50 may be subjected to a surface treatment such as plasma treatment as a pretreatment before the vapor-deposited layer 50 is formed.

[0067] From the viewpoint of recyclability, the thickness of the vapor-deposited adhesive layer 44 may be 0.2 μm or more and 5.0 μm or less, or 0.5 μm or more and 3.0 μm or less.

[0068] The deposition layer 50 can be formed by a conventionally known method, for example, a physical vapor deposition method (PVD method) such as vacuum deposition, sputtering, or ion plating, or a chemical vapor deposition method (CVD method) such as plasma chemical vapor deposition, thermal chemical vapor deposition, or photochemical vapor deposition.

[0069] Materials constituting the vapor-deposited layer 50 include metals such as aluminum, and inorganic oxides such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, and barium oxide. Aluminum oxide or silicon oxide is particularly preferred because of its excellent productivity and excellent oxygen and water vapor barrier properties in heat resistance and moist heat resistance. The vapor-deposited layer may be formed of one type of material, or two or more appropriately selected materials.

[0070] The thickness of the vapor-deposited layer 50 may be from 0.001 μm to 0.2 μm, or from 0.005 μm to 0.1 μm. By setting the thickness of the vapor-deposited layer 50 within the above range, it is possible to impart sufficient gas barrier properties while sufficiently minimizing the impact on recyclability, and cracks and the like are less likely to occur in the vapor-deposited layer.

[0071] The protective layer 60 may contain, as constituent materials, at least one of a metal alkoxide, its hydrolysate, and its reaction product, and a coating agent, and may further contain at least one of a silane coupling agent and its hydrolysate.

[0072] Examples of metal alkoxides and their hydrolysates include compounds represented by the general formula M(OR), such as tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum [Al(OC3H7)3]. n and hydrolysates thereof. Only one of these may be contained, or two or more of them may be contained in appropriate combination.

[0073] A water-soluble polymer can be used as the coating agent. Examples of water-soluble polymers include polyvinyl alcohols, polysaccharides such as starch, methyl cellulose, and carboxymethyl cellulose, and various polymers such as acrylic polyols. To further improve the oxygen gas barrier properties, the protective layer may contain a polyvinyl alcohol polymer.

[0074] The protective layer 60 can be formed by a conventionally known method, for example, a wet coating method such as a casting method, a dipping method, a roll coating method, a gravure coating method, a screen printing method, a reverse coating method, a spray coating method, a kit coating method, a die coating method, a metaling bar coating method, a chamber doctor combined coating method, or a curtain coating method.

[0075] The thickness of the protective layer 60 may be from 0.05 μm to 1 μm, or from 0.1 μm to 0.5 μm. By setting the thickness of the protective layer 60 within the above range, it is possible to impart sufficient oxygen barrier properties while sufficiently minimizing the impact on recyclability, making it easy to form a uniform coated surface, and reducing the drying load and manufacturing costs.

[0076] The laminate of this embodiment can be produced by producing the laminate film of this embodiment by the method described above, and then providing a vapor-deposited adhesive layer, a vapor-deposited layer, and a protective layer in this order on the substrate film side of the laminate film by the method described above. When the laminate includes a substrate film having a first layer and a second layer, the first layer, the second layer, and the vapor-deposited adhesive layer may be multilayered using, for example, a feed block or a die via a multi-manifold.

[0077] <Packaging material> The packaging material of this embodiment includes the laminate film of this embodiment or the laminate of this embodiment.

[0078] For example, a packaging bag can be produced by folding a packaging material including the laminate film 10 in half, overlapping the laminate film 10 so that the sealant film 40 is on the inside, and heat-sealing the edges. Alternatively, a packaging bag can be produced by overlapping two sheets of the laminate film 10 so that the sealant films 40 face each other, and heat-sealing the edges.

[0079] The laminated film 10 can also be laminated with other substrates, thereby improving heat resistance and strength, and providing other functional layers.

[0080] A packaging bag can be produced from a packaging material including the laminate 100 by folding the laminate 100 in half, overlapping the laminate 100 so that the sealant film 40 is on the inside, and heat-sealing the edges. Alternatively, a packaging bag can be produced by overlapping two laminates 100 so that the sealant films 40 face each other, and heat-sealing the edges.

[0081] Examples of heat sealing types include side seal type, two-sided seal type, three-sided seal type, four-sided seal type, envelope seal type, palm seal type (pillow seal type), pleated seal type, flat bottom seal type, square bottom seal type, gusset type, etc. By appropriately selecting these, packaging bags of various types can be produced.

[0082] The packaging material of this embodiment can be used to produce, for example, a self-standing packaging bag (standing pouch). The manufacturing method for the self-standing packaging bag is not particularly limited. Heat sealing can be performed by any known method, such as bar sealing, rotary roll sealing, belt sealing, impulse sealing, high frequency sealing, or ultrasonic sealing.

[0083] According to the packaging material of this embodiment, by including the laminated film of this embodiment, it is possible to produce a packaging bag with high recyclability. [Example]

[0084] Examples prepared by the present inventors will be described in detail below in comparison with comparative examples, but the present invention is not limited to the following examples.

[0085] Example 1 A 1 mm thick unstretched sheet was extruded using Prime Polymer's homopolypropylene resin F-300SP (melting point 161°C). This sheet was then biaxially stretched at 5x MD and 10x TD magnifications to produce a 20 μm thick substrate film (biaxially stretched PP). Prime Polymer's homopolypropylene resin F-300SP (melting point 161°C) was extruded to produce a 60 μm thick sealant film (unstretched PP). These films were sandwich-laminated using Prime Polymer's random polypropylene resin F-744NP (melting point 133°C) as the resin material for the heat-sealable layer to produce a laminated film. The heat-sealable layer (sand-laminated PP) was formed by adjusting the extrusion temperature and take-up speed to achieve a lamination temperature of 230°C and a thickness of 20 μm.

[0086] Example 2 A uniaxially oriented polyethylene film PE3K-H (25 μm thick) manufactured by Futamura Chemical Co., Ltd. was prepared as the base film (uniaxially oriented PE). A 100 μm thick sealant film (unstretched PE) was produced by extrusion molding using linear low-density polyethylene resin SP2040 (melting point 116°C) manufactured by Prime Polymer Co., Ltd. These films were sandwich-laminated to produce a laminated film using linear low-density polyethylene resin SP2040 (melting point 116°C) manufactured by Prime Polymer Co., Ltd. as the resin material for the heat-sealable layer. The heat-sealable layer (sand-laminated PE) was formed by adjusting the extrusion temperature and take-up speed so that the laminating temperature was 200°C and the thickness was 20 μm.

[0087] (Comparative Example 1) A 100 μm thick single-layer film (unstretched PP) was produced by extrusion molding using homopolypropylene resin F-300SP (melting point 161°C) manufactured by Prime Polymer Co., Ltd.

[0088] (Comparative Example 2) A 20 μm thick substrate film (biaxially oriented PP) and a 60 μm thick sealant film (unoriented PP) were prepared in the same manner as in Example 1. These films were dry-laminated using an ester-based adhesive (main agent: Takelac A-626 manufactured by Mitsui Chemicals, Inc.; curing agent: Takenate A-50 manufactured by Mitsui Chemicals, Inc.; solvent: NC401 solvent manufactured by Toyo Ink Co., Ltd.; mixing ratio: main agent / curing agent / solvent = 8 / 1 / 7) to prepare a laminated film. At this time, the sealant film and substrate film were subjected to corona treatment, and the surface tension was set to 44 dyne.

[0089] (Comparative Example 3) A laminated film was produced in the same manner as in Example 1, except that the resin material for forming the heat-sealing layer was a linear low-density polyethylene resin SP2040 (melting point 116°C) manufactured by Prime Polymer Co., Ltd., and the heat-sealing layer (sand PE) was formed so that the laminated part temperature was 230°C and the thickness was 20 μm.

[0090] Comparative Example 4 A laminated film was produced in the same manner as in Example 2, except that random polypropylene resin F-744NP (melting point 133°C) manufactured by Prime Polymer Co., Ltd. was used as the resin material for forming the heat-sealing layer, and the heat-sealing layer (sand PP) was formed so that the laminated part temperature was 200°C and the thickness was 20 μm.

[0091] (Comparative Example 5) A laminated film was produced in the same manner as in Comparative Example 2, except that a polyethylene terephthalate film E5100 (thickness 12 μm) manufactured by Toyobo Co., Ltd. was used as the base film (biaxially stretched PET).

[0092] (Comparative Example 6) A laminated film was produced in the same manner as in Example 1, except that a polyethylene terephthalate film E5100 (thickness 12 μm) manufactured by Toyobo Co., Ltd. was used as the base film (biaxially stretched PET).

[0093] [Evaluation of plane orientation M] The following absorbance peak intensities α, β, γ, and δ were measured at 23°C using polarized ATR-FTIR. Using ε, which is expressed as ε = (α + β) / (γ + δ), the planar orientation M was calculated from the formula M = (0.6887ε - 0.4395) / (0.4962ε + 0.2198). (1) The incident light was fixed to S-polarized light, and the sample angle was rotated by 15 degrees. In the measured spectrum, -1 The sample arrangement in which the absorbance peak intensity is the largest is defined as the slow axis arrangement, and the absorbance peak intensity in the slow axis arrangement is defined as α. (2) 997cm when the incident light is S-polarized and rotated 90 degrees from the slow axis orientation -1 The absorbance peak intensity is defined as β. (3) The incident light is P-polarized and the slow axis is 997 cm -1 The absorbance peak intensity is γ, (4) 997 cm when the incident light is P-polarized and rotated 90 degrees from the slow axis orientation -1 The absorbance peak intensity is defined as δ.

[0094] In the case of a laminated film comprising a sealant film, a heat-sealing layer, and a base film, the plane orientation M was measured for the surface HS2 (first surface) of the sealant film opposite to the side in contact with the heat-sealing layer, and the surface BS2 (second surface) of the base film opposite to the side in contact with the heat-sealing layer. In the case of a laminated film using an adhesive instead of a heat-sealing layer, the plane orientation M was measured for the surfaces corresponding to the first and second surfaces. In the case of a monolayer film, the plane orientation M was measured for both main surfaces of the monolayer film. In Example 2 and Comparative Examples 4 to 6, the plane orientation M was not measured, and therefore was marked as "-".

[0095] The polarized ATR prism was made of ZnSe, and measurements were carried out using a single-reflection ATR with a 45-degree incidence angle.

[0096] [Evaluation of heat sealability] Using a Tester Sangyo heat sealer (model number TP-701-B), two films were stacked with the sealant film on the inside and heat-sealed at a sealing pressure of 0.2 MPa, a sealing time of 1 second, and a seal width of 10 mm. The heat-sealing temperature was increased in increments of +5°C from the melting point of the sealant film resin, starting from -10°C. The sample was then cut into 15mm wide x 80mm pieces perpendicular to the sealed area and subjected to a T-peel test using a Shimadzu Corporation tensile testing machine (model number AGS-500NX). The tensile speed was 100mm / min. In this case, the temperature conditions under which there were no problems with the appearance after heat sealing and the average measured strength was 20 N / 15 mm or more were marked with "○", the temperature conditions under which there were no problems with the appearance after heat sealing and the average measured strength was 10 N / 15 mm or more and less than 20 N / 15 mm were marked with "△", and the only temperature conditions under which there were poor appearances after heat sealing or the average measured strength was less than 10 N / 15 mm were marked with "×".

[0097] [Evaluation of lamination] The laminated film was cut into a 15 mm wide x 100 mm piece, and a cutter was placed on the edge of the film to peel off the interface between the heat-sealing layer or adhesive and the base film. A T-peel test was then performed using a Shimadzu Corporation tensile tester (model number AGS-500NX). The pulling speed was 100 mm / min. A test in which the interface between the heat-sealing layer or adhesive and the base film could not be peeled off at all and measurement was impossible was marked with a "◎", a test in which the average measured strength was 2 N / 15 mm or more was marked with a "○", and a test in which the average measured strength was less than 2 N / 15 mm was marked with an "×". Films without a heat-sealing layer or adhesive were ineligible for evaluation and were marked with a "-".

[0098] [Recyclability evaluation] The laminated film was compressed, cut, and formed into granules to obtain a recycled material. This recycled material was extruded to produce an unstretched film with a thickness of 60 μm, and the appearance was visually inspected. Films with no significant fisheyes were marked with an "O" and those with significant fisheyes were marked with an "X."

[0099] (Overall judgment) If all of the above evaluations of heat sealability, lamination property, and recyclability were "○", the overall evaluation was rated as "○", and if even one of them was "×", the overall evaluation was rated as "×".

[0100] Table 1 shows a list of the film configurations and evaluation results in Examples 1 and 2 and Comparative Examples 1 to 6.

[0101] [Table 1]

[0102] Example 3 A sealant film having a thickness of 60 μm was produced by extrusion molding using random polypropylene resin F-744NP (melting point 133° C.) manufactured by Prime Polymer Co., Ltd. A laminated film was produced in the same manner as in Example 1, except that this sealant film was used.

[0103] Example 4 A 1 mm thick multilayer unstretched sheet was produced by coextrusion molding using homopolypropylene resin F-300SP (melting point 161°C) and random polypropylene resin F-744NP (melting point 133°C) manufactured by Prime Polymer Co., Ltd., and subsequently stretched at MD 5x and TD 10x to produce a 20 μm thick film, which served as the substrate film. In this case, the F-300SP resin layer served as the second layer, and the F-744NP resin layer served as the first layer, with a layer ratio of 18:2. A laminated film was produced in the same manner as in Example 1, except that this substrate film was used.

[0104] Example 5 A sealant film having a thickness of 60 μm was produced by extrusion molding using random polypropylene resin F-744NP (melting point 133° C.) manufactured by Prime Polymer Co., Ltd. A laminated film was produced in the same manner as in Example 4, except that this sealant film was used.

[0105] [Evaluation of plane orientation M] The planar orientation M was evaluated in the same manner as above.

[0106] [Evaluation of heat sealability] The heat sealability was evaluated in the same manner as above.

[0107] [Evaluation of lamination] The lamination properties were evaluated in the same manner as above.

[0108] [Recyclability evaluation] The recyclability was evaluated in the same manner as above.

[0109] (Overall judgment) If the heat sealability and lamination properties were evaluated as "◎" and the recyclability was evaluated as "〇", the overall evaluation was given as "◎", if even one of them was "×", the overall evaluation was given as "×", and if the result was anything other than that, the overall evaluation was given as "〇".

[0110] The film configurations and evaluation results for Examples 1 and 3 to 5 are listed in Table 2. The abbreviations in Table 2 are as follows: PP1: Homopolypropylene resin F-300SP (melting point 161°C) (Prime Polymer Co., Ltd.) PP2: Random polypropylene resin F-744NP (melting point 133°C) (Prime Polymer Co., Ltd.)

[0111] [Table 2]

[0112] Example 6 A sealant film with a thickness of 60 μm was produced by extrusion molding using a raw material obtained by dry-blending block polypropylene resin PC480A (melting point 165°C) manufactured by SunAllomer Co., Ltd. and polypropylene resin Q100F (melting point 140°C) manufactured by LyondellBasell Industries in a weight ratio of 80 / 20. A laminated film was produced in the same manner as in Example 4, except for using this sealant film.

[0113] Example 7 A 60 μm thick sealant film was produced by coextrusion molding using homopolypropylene resin F-300SP (melting point 161°C) and random polypropylene resin F-744NP (melting point 133°C) manufactured by Prime Polymer Co., Ltd. In this case, F-744NP was used as the heat seal layer and substrate-side layer, and F-300SP was used as the intermediate layer, with the layer ratio of the heat seal layer, intermediate layer, and substrate-side layer being 10 / 40 / 10. A laminated film was produced in the same manner as in Example 4, except for using this sealant film.

[0114] Example 8 A laminated film was produced in the same manner as in Example 7, except that random polypropylene resin F-744NP (melting point 133°C) manufactured by Prime Polymer Co., Ltd. was used as the resin for forming the heat seal layer and the substrate-side layer, and a raw material obtained by dry-blending block polypropylene resin PC480A (melting point 165°C) manufactured by SunAllomer Co., Ltd. and polypropylene resin Q100F (melting point 142°C) manufactured by LyondellBasell Industries in a weight ratio of 80 / 20 was used as the resin for forming the intermediate layer.

[0115] [Evaluation of plane orientation M] The planar orientation M was evaluated in the same manner as above.

[0116] [Evaluation of heat sealability] Heat sealing was carried out in the same manner as above.

[0117] [Evaluation of lamination] The lamination properties were evaluated in the same manner as above.

[0118] [Recyclability evaluation] The recyclability was evaluated in the same manner as above.

[0119] (Impact resistance evaluation) Two pieces of laminated film measuring 150 mm x 100 mm were cut out and stacked with the sealant film facing inward. A three-sided bag was obtained by heat-sealing two long sides and one short side using a heat sealer (model number TP-701-B) manufactured by Tester Sangyo. The heat sealing was performed under conditions that resulted in a heat sealability rating of "Good." The resulting three-sided bag was filled with 150 mL of water, and the remaining unsealed side was sealed under the same conditions as above, producing 10 impact resistance test samples for each example, each measuring 140 mm x 90 mm.

[0120] The impact resistance test samples were dropped 10 times from a height of 1 m onto a concrete floor at 23°C with the long side perpendicular to the ground. After 10 drops, samples with 5 or more films that did not develop holes or leak contents were rated as "Good", and samples with 4 or fewer films that did not leak contents were rated as "Good".

[0121] (Overall judgment) If the heat sealability and lamination properties were rated as "◎" and the recyclability and impact resistance properties were rated as "〇", the overall judgment was "◎", if the heat sealability and lamination properties were rated as "◎", the recyclability was rated as "〇", and the impact resistance property was rated as "△", the overall judgment was "〇", and if even one property was rated as "×", the overall judgment was "×".

[0122] The film configurations and evaluation results of Examples 4 to 8 are listed in Table 3. The abbreviations in Table 3 are as follows: PP1: Homopolypropylene resin F-300SP (melting point 161°C) (Prime Polymer Co., Ltd.) PP2: Random polypropylene resin F-744NP (melting point 133°C) (Prime Polymer Co., Ltd.) PP3: Block polypropylene resin PC480A (melting point 165°C) (manufactured by SunAllomer Co., Ltd.) and polypropylene resin Q100F (melting point 140°C) (manufactured by LyondellBasell Industries)

[0123] [Table 3]

[0124] Example 9 Using the conditions of Example 5 as the standard conditions, the stretching ratio when producing the substrate film was reduced and the stretching temperature was increased, thereby controlling the planar orientation of the substrate film to be smaller.

[0125] Example 10 Using the conditions of Example 5 as the standard conditions, the planar orientation of the substrate film was controlled to be smaller by increasing the stretching temperature during production of the substrate film.

[0126] Example 11 Using the conditions of Example 5 as the standard conditions, the stretching temperature during production of the substrate film was lowered to control the planar orientation of the substrate film in a direction to increase it.

[0127] Example 12 Using the conditions of Example 5 as the standard conditions, the take-up speed during production of the sealant film was reduced to control the planar orientation of the sealant film in a direction to reduce it.

[0128] Example 13 Using Example 5 as the standard conditions, the film take-up speed during production of the sealant film was increased to control the plane orientation of the sealant film in a direction toward increasing it.

[0129] Example 14 Using Example 5 as the standard conditions, the film take-up speed during production of the sealant film was increased and the air gap was reduced, thereby controlling the planar orientation of the sealant film to be greater.

[0130] [Evaluation of plane orientation M] The planar orientation M was evaluated in the same manner as above.

[0131] [Evaluation of heat sealability] Heat sealing was carried out in the same manner as above.

[0132] [Evaluation of lamination] The lamination properties were evaluated in the same manner as above.

[0133] [Recyclability evaluation] The recyclability was evaluated in the same manner as above.

[0134] (Overall judgment) If the heat sealability and lamination properties were evaluated as "◎" and the recyclability was evaluated as "〇", the overall evaluation was given as "◎", if even one of the properties was evaluated as "×", the overall evaluation was given as "×", and if the evaluation results were any other than those, the overall evaluation was given as "〇".

[0135] The film configurations and evaluation results of Examples 5 and 9 to 14 are listed in Table 4. The abbreviations in Table 4 are as follows: PP1: Homopolypropylene resin F-300SP (melting point 161°C) (Prime Polymer Co., Ltd.) PP2: Random polypropylene resin F-744NP (melting point 133°C) (Prime Polymer Co., Ltd.)

[0136] [Table 4]

[0137] (Evaluation results) As shown in Table 1, the laminated films of Examples 1 and 2, in which a stretched base film containing the same type of polyolefin resin and an unstretched sealant film are laminated with a heat-sealing layer containing the same type of polyolefin resin, are evaluated as "Good" in terms of heat sealability, lamination property, and recyclability.

[0138] Furthermore, as shown in Tables 2 and 3, the laminate films of Examples 3 to 8, in which the base film includes a first layer in contact with the heat-sealing layer and a second layer having a melting point higher than that of the first layer, were evaluated as having lamination properties of "Excellent." The base film is a stretched film, which is less likely to form a strong laminate than an unstretched film. However, in sand lamination, it is believed that a strong laminate is formed by melting and adhering the surface of the first layer, which has a lower melting point, with the molten resin.

[0139] Furthermore, as shown in Table 3, the laminate films of Examples 6 and 8, in which the sealant film contains an impact-resistant block polypropylene resin, were rated "Good" for impact resistance, and other evaluations were also favorable. Packaging bags using such laminate films with excellent impact resistance are suitable for filling heavy items, as the packaging bag is not damaged even when subjected to impacts during transportation or when dropped, and the contents are protected. Note that the laminate films of Examples 4, 5, and 7, which were rated "Good" for impact resistance, still function as packaging bags, and the overall evaluation was "Good."

[0140] Furthermore, as shown in Table 4, when the planar orientation M of the sealant film surface (front surface), i.e., the surface HS2 of the sealant film that is not in contact with the heat-sealing layer, is -0.3 or more and 0.3 or less, and the planar orientation M of the base film surface (back surface), i.e., the surface BS2 of the base film that is not in contact with the heat-sealing layer, is 0.5 or more and 0.9 or less, the heat-sealability was evaluated as "Good." Note that Example 5, in which the planar orientation M of the base film surface (back surface) was less than 0.5, and Example 10, in which the planar orientation M of the sealant film surface (front surface) exceeded 0.3, were evaluated as having "Good" heat-sealability, but because the heat-sealing temperature conditions could be determined, the overall evaluation was "Good." [Explanation of symbols]

[0141] 10...Laminated film, 20...Base film, 21...First layer, 22...Second layer, 30...Heat-sealable layer, 40...Sealant film, 41...Heat-seal layer, 42...Intermediate layer, 43...Base material side layer, 44...Vapor-deposited adhesion layer, 50...Vapor-deposited layer, 60...Protective layer, 100...Laminate.

Claims

1. The film comprises a base film, a sealant film, and a heat-sealing layer provided between the base film and the sealant film, the substrate film is stretched, The sealant film and the heat-sealing layer are not stretched, The base film, the heat-sealing layer, and the sealant film are made of the same polyolefin resin.

2. the substrate film has a laminated structure of two or more layers, The laminated film according to claim 1 , wherein the base film includes a first layer in contact with the heat-sealing layer and a second layer having a melting point higher than that of the first layer.

3. the polyolefin resin is a polypropylene-based resin, The plane orientation M calculated by the following method is the surface BS of the substrate film opposite to the side in contact with the heat-sealing layer. ２ and the surface HS of the sealant film opposite to the side in contact with the heat-sealing layer is 0.5 or more and 0.9 or less. ２ The laminated film according to claim 1, wherein the σ is -0.3 or more and 0.3 or less. Calculation method of plane orientation M: The plane orientation M is calculated from the equation M=(0.6887ε−0.4395) / (0.4962ε+0.2198) using ε expressed as ε=(α+β) / (γ+δ) based on the following absorbance peak intensities α, β, γ, and δ measured using polarized ATR-FTIR. (1) The incident light was fixed to S-polarized light, and the sample angle was rotated by 15 degrees. In the measured spectrum, －１ The arrangement of the sample in which the absorbance peak intensity is the largest is defined as the slow axis arrangement, and the absorbance peak intensity in the slow axis arrangement is defined as α, (2) 997 cm when the incident light is S-polarized and rotated 90 degrees from the slow axis arrangement －１ The absorbance peak intensity is defined as β. (3) When the incident light is P-polarized and the slow axis is arranged as described above, the wavelength is 997 cm －１ The absorbance peak intensity is γ, (4) 997 cm when the incident light is P-polarized and rotated 90 degrees from the slow axis arrangement －１ The absorbance peak intensity is defined as δ.

4. A packaging material comprising the laminate film according to any one of claims 1 to 3.

5. A method for producing a laminated film comprising a base film, a sealant film, and a heat-sealing layer provided between the base film and the sealant film, A step A of extruding a resin composition containing a polypropylene-based resin and stretching the extrudate to obtain a substrate film; A step B of extruding a resin composition containing a polypropylene-based resin to obtain a sealant film; a step C of bonding the base film and the sealant film by sandwich lamination with a molten resin composition containing a polypropylene-based resin interposed therebetween; Equipped with In the step A, the substrate film is stretched so that the planar orientation M calculated by the following method is 0.5 or more and 0.9 or less on the surface of the substrate film, In the step B, extrusion film formation is performed so that the planar orientation M calculated by the following method is −0.3 or more and 0.3 or less on the surface of the sealant film. Calculation method of plane orientation M: The plane orientation M is calculated from the equation M=(0.6887ε−0.4395) / (0.4962ε+0.2198) using ε expressed as ε=(α+β) / (γ+δ) based on the following absorbance peak intensities α, β, γ, and δ measured using polarized ATR-FTIR. (1) The incident light was fixed to S-polarized light, and the sample angle was rotated by 15 degrees. In the measured spectrum, －１ The arrangement of the sample in which the absorbance peak intensity is the largest is defined as the slow axis arrangement, and the absorbance peak intensity in the slow axis arrangement is defined as α, (2) 997 cm when the incident light is S-polarized and rotated 90 degrees from the slow axis arrangement －１ The absorbance peak intensity is defined as β. (3) When the incident light is P-polarized and the slow axis is arranged as described above, the wavelength is 997 cm －１ The absorbance peak intensity is γ, (4) 997 cm when the incident light is P-polarized and rotated 90 degrees from the slow axis arrangement －１ The absorbance peak intensity is defined as δ.

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