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

Abstract

To provide a laminated film having excellent recyclability while ensuring sufficient heat-sealing and laminating properties (particularly low-temperature laminating property) and a method for producing the same, and a laminate and a packaging material.SOLUTION: A laminated film includes a base film and a heat seal layer laminated in direct contact with the base film, wherein both the base film and the heat seal layer include an identical type of polyolefin resin, the melting point of the heat seal layer is lower than that of the base film, and both the base film and the heat seal layer are drawn.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 polyester film or nylon film, is used as a base film, and a resin film with excellent flexibility and low-temperature heat-sealability, such as polyethylene or polypropylene, is laminated on top of it as a sealant film (or heat-seal layer).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] In addition, as a method for producing a laminated film without using an adhesive, there is also a method such as extrusion lamination, in which a resin is heated to a high temperature and a base film and a resin film are bonded together. However, with this method, if the extrusion lamination temperature is too high, the resin is likely to deteriorate, and if the extrusion lamination temperature is too low, it is difficult to obtain sufficient lamination strength, resulting in a decrease in lamination properties. Therefore, it is also desirable for the laminated film to have low-temperature lamination properties, so that it can maintain sufficient lamination strength even when produced by melting the resin at a lower temperature.

[0008] 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 (particularly low-temperature lamination properties) and also has excellent recyclability, a method for producing the same, and a laminate and packaging material. [Means for solving the problem]

[0009] The present disclosure relates to the following [1] to [6] [1] A laminated film comprising a base film and a heat seal layer laminated in direct contact with the base film, wherein the base film and the heat seal layer contain the same type of polyolefin resin, the melting point of the heat seal layer is lower than the melting point of the base film, and the base film and the heat seal layer are stretched. [2] The laminate film according to [1], 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 the side that contacts the heat seal layer, and is −0.3 or more and 0.3 or less on the surface HS2 of the heat seal layer opposite the side that contacts the base 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. [3] The laminated film according to [1] or [2], wherein the heat seal layer is made of a polyolefin resin composition containing a high-melting point component having a melting point of 155°C or more but less than 165°C and a low-melting point component having a melting point of 120°C or more but less than 150°C, and the content of the low-melting point component in the polyolefin resin composition is 20 to 80 parts by mass when the total mass of the high-melting point component and the low-melting point component is 100 parts by mass. [4] A laminate comprising a vapor-deposited adhesive layer containing a thermoplastic resin and a vapor-deposited layer laminated in this order on the base film of the laminated film according to any one of [1] to [3], and the vapor-deposited layer and the vapor-deposited adhesive layer are in direct contact with each other. [5] A packaging material comprising the laminate film according to any one of [1] to [3] or the laminate according to [4]. [6] A method for producing a laminated film, comprising: a step of co-extruding a first resin composition containing a polypropylene-based resin and a second resin composition containing a polypropylene-based resin and having a melting point M2 lower than the melting point M1 of the first resin composition, and stretching the resultant at a temperature equal to or higher than the melting point M2 and equal to or lower than the melting point M1 to form a laminated film in which a base film made of the first resin composition and a heat-seal layer made of the second resin composition are laminated together; in the step, the stretching is performed so that the planar orientation M, calculated by the following method, is 0.5 to 0.9 on a surface BS2 of the base film opposite to the side that contacts the heat-seal layer, and is -0.3 to 0.3 on a surface HS2 of the heat-seal layer opposite to the side that contacts the base 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]

[0010] According to the present invention, it is possible to provide a laminate film that has sufficient heat-sealing properties and lamination properties (particularly low-temperature lamination properties) and also has excellent recyclability, a method for producing the same, a laminate, and a packaging material. [Brief explanation of the drawings]

[0011] [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. 1 is a cross-sectional view schematically illustrating an example of a laminate according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that each figure 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 figure.

[0013] [Laminated film] The laminated film of this embodiment comprises a base film and a heat seal layer laminated in direct contact with the base film, the base film and the heat seal layer containing the same type of polyolefin resin, the melting point of the heat seal layer being lower than the melting point of the base film, and the base film and the heat seal layer being stretched.

[0014] The laminate film of this embodiment, having the above-described configuration, can exhibit excellent recyclability while maintaining sufficient heat-sealing and laminating properties (particularly low-temperature laminating properties). The inventors speculate as follows about the reasons for this effect. First, the laminate film of this embodiment is stretched, and has a structure in which the substrate film containing the same polyolefin resin and the heat-sealing layer are in direct contact with each other. This allows the laminate film to be produced by stretching an unstretched sheet obtained by co-extrusion molding without using an adhesive or anchor coat. In this case, it is believed that sufficient lamination strength can be obtained even when the resin temperature during extrusion is low, while avoiding the problems associated with extrusion lamination described above. Furthermore, the inventors believe that the melting point of the heat-sealing layer being lower than the melting point of the substrate film makes it easier to achieve both heat-sealing and laminating properties (particularly low-temperature laminating properties), which is also one of the reasons for the above-described effect.

[0015] Furthermore, the laminated film of the present embodiment can achieve sufficient lamination strength without using an adhesive or anchor coat, thereby solving the following problem of the adhesive layer becoming a foreign object when the layers are recycled without being separated. Specifically, it has been found that adhesives are typically crosslinked three-dimensionally, and therefore are prone to becoming foreign objects when reused as recycled materials. It has also been found that even when the adhesive content in a film is low, it is difficult to finely disperse crosslinked adhesives, and they are prone to becoming foreign objects. Such foreign objects can lead to fisheyes and reduced physical properties.

[0016] Fig. 1 is a cross-sectional view schematically showing an example of the laminate film of this embodiment. In the laminate film 10 shown in Fig. 1, a base film 20 and a heat seal layer 30 are laminated in direct contact with each other without the use of an adhesive. The base film 20 and the heat seal layer 30 contain the same type of polyolefin resin, and the base film 20 and the heat seal layer 30 are stretched.

[0017] To further improve the low-temperature lamination properties of the base film 20 and the heat-seal layer 30, the surface BS1 of the base film 20 that contacts the heat-seal layer 30 and the surface HS1 of the heat-seal layer 30 that contacts the base film 20 may not be subjected to surface treatments such as corona treatment or ozone treatment. The above-mentioned surface treatments may hinder heat fusion between resins of the same type, and tend to significantly reduce the laminate strength, particularly in heat fusion between polyolefin resins. Furthermore, the laminate film of this embodiment can be produced, for example, by co-extrusion molding the base film and the heat-seal layer, and sufficient laminate strength can be obtained for the reasons described above.

[0018] When the main surface of the laminated film 10 facing the heat seal layer 30 (HS2 in FIG. 1) is the front surface and the main surface of the laminated film 10 facing the base film 20 (BS2 in FIG. 1) is the back surface, the front surface can be heat-sealed suitably.

[0019] <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.

[0020] The stretching ratio in the machine direction (MD) of the base film 20 may be 2 to 10 times, or may be 3 to 7 times. The stretching ratio in the cross direction (TD) may be 3 to 15 times, or may be 5 to 12 times. When the MD and TD of the base film 20 are within the above ranges, the strength and transparency of the base film are easily obtained. Furthermore, when the MD and TD of the base film 20 are within the above ranges, the heat resistance of the laminate film 10 can be improved. Here, heat resistance refers to the property of preventing shrinkage or wrinkles from occurring on the back side of the laminate film when the front side (heat seal layer) of the laminate film is heat-sealed.

[0021] 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).

[0022] 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.

[0023] 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.

[0024] The MFR (melt flow rate) of the polyethylene resin may be 0.01-50, 0.05-20, or 0.1-10.

[0025] 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.

[0026] 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.

[0027] The MFR (melt flow rate) of the polypropylene resin may be 0.01-50, 0.05-20, or 0.1-10.

[0028] 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 that contacts the heat-sealable layer of the base film. When the planar orientation M of the base film 20 is within the above range, the strength and transparency of the base film are easily obtained. Furthermore, when the planar orientation of the base film 20 is within the above range, the heat resistance of the laminate film can be improved and the occurrence of wrinkles during heat sealing can be easily suppressed.

[0029] (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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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,-1 It 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.

[0034] 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.

[0035] 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.

[0036] 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 sheet, which is an intermediate of the base film 20, and the stretch ratio in the stretching process. The planar orientation M tends to increase as the take-up speed in the process of producing an unstretched sheet increases and the stretch ratio in the stretching process increases.

[0037] The base film 20 may have a laminated structure of two or more layers. For example, it may be multi-layered with resins of the same type but with different main chain structures, melting points, MFRs, additives, etc. Specifically, a homo-type polypropylene layer may impart strength and heat resistance, while a block-type polypropylene layer may impart impact resistance, etc.

[0038] The melting point of the multilayered substrate film means the melting point averaged from the melting points of the individual resin components contained in the substrate film and their composition ratios (mass ratios).

[0039] 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.

[0040] The thickness of the base film 20 may be 8 μm or more and 80 μm or less, or 10 μm or more and 50 μm or less. When the thickness of the base film 20 is within the above range, the strength and transparency of the base film are easily obtained. Furthermore, when the thickness of the base film 20 is within the above range, the heat resistance of the laminate film can be improved. Here, heat resistance refers to the property that shrinkage and wrinkles are unlikely to occur on the back side when the front side (heat seal layer) of the laminate film is heat-sealed.

[0041] <Heat seal layer> The heat seal layer 30 is stretched. The heat seal layer 30 and the base film 20 may be laminated as melts to form a film, as in a co-extrusion method, and then stretched simultaneously in a multilayer state. By stretching the layers simultaneously in a multilayer state, the manufacturing process can be simplified and manufacturing costs can be reduced compared to methods in which the layers are bonded together with an adhesive or by extrusion lamination.

[0042] The material constituting the heat seal layer 30 is the same type of polyolefin resin as that of the base film 20. The heat seal layer 30 may contain the above-mentioned polyethylene resin, or may contain a plurality of polyethylene resins with different melting points, MFR, etc., or may contain the above-mentioned polypropylene resin, or may contain a plurality of polypropylene resins with different melting points, MFR, etc. From the viewpoint of low-temperature heat sealability and flexibility, the heat seal layer 30 may contain a polypropylene resin copolymerized with an α-olefin as the polypropylene resin, or may contain linear low-density polyethylene (LLDPE) copolymerized with α-olefin and ethylene as the polyethylene resin.

[0043] The melting point of the heat seal layer 30 is lower than that of the base film 20. Here, the melting point refers to the melting point averaged from the melting points of the resin components contained in the heat seal layer and their composition ratios (mass ratios). The difference in melting point between the heat seal layer 30 and the base film 20 may be 5°C or more, 10°C or more, 15°C or more, 20°C or more, or 25°C or more. When the difference in melting point between the heat seal layer 30 and the base film 20 is within the above range, shrinkage and wrinkling due to heat during heat sealing can be prevented.

[0044] Furthermore, when the heat seal layer is made of polypropylene resin, for example, the melting point of the heat seal layer may be 120° C. or higher, 130° C. or higher, or 135° C. or higher, or 165° C. or lower, 150° C. or lower, or 140° C. or lower. The lower the melting point of the heat seal layer 30, the more sufficient heat sealability can be obtained even at low temperatures.

[0045] When the heat seal layer 30 contains two or more resins, it may contain a component with a high melting point (high melting point component) and a component with a low melting point (low melting point component). The high melting point component may be a component with a melting point of 155°C or higher but lower than 165°C, and the low melting point component may be a component with a melting point of 120°C or higher but lower than 150°C. By containing a high melting point component and a low melting point component in the heat seal layer 30, it is possible to ensure adhesive strength during heat sealing while preventing the heat seal layers from adhering to each other in unintended areas. Furthermore, by containing a high melting point component and a low melting point component in the heat seal layer 30, it is possible to improve resistance to retort treatment and enhance the retort suitability of the laminate film.

[0046] When the heat seal layer 30 contains two or more resins, the content of the low-melting point component may be 20 to 80 parts by mass, 30 to 70 parts by mass, or 40 to 60 parts by mass, where the total mass of the high-melting point component and the low-melting point component is 100 parts by mass. When the content of the low-melting point resin is 20 parts by mass or more, heat sealability is easily achieved. Furthermore, when the content of the low-melting point resin is 80 parts by mass or less, adhesion between the heat seal layers at unintended locations is easily prevented while ensuring adhesive strength during heat sealing. From the viewpoint of heat sealability, the content of the low-melting point component may be 30 to 80 parts by mass, 40 to 80 parts by mass, or 50 to 80 parts by mass, where the total mass of the high-melting point component and the low-melting point component is 100 parts by mass.

[0047] Although the heat seal layer 30 is stretched, it is preferable that it is not oriented. Orientation increases heat resistance, which impairs low-temperature heat sealability. Therefore, it is preferable to produce the film without orientation. Being in an unoriented state allows heat sealing at the lowest possible temperature, thereby preventing shrinkage and wrinkling. Furthermore, the flexibility of the laminated film 10 can be improved.

[0048] When the heat-seal layer 30 contains a polypropylene-based resin, the planar orientation M calculated by the above 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 HS2 of the heat-seal layer opposite the side that contacts the base film. When the planar orientation M of the heat-seal layer 30 is within the above range, the low-temperature heat-sealability and flexibility of the heat-seal layer can be improved.

[0049] The planar orientation M of the surface of the heat seal layer 30 that is not in contact with the base film 20 can be controlled by changing the composition ratio of the resin contained in the heat seal layer 30, the stretching temperature in the stretching step, etc. The M orientation tends to increase as the composition ratio of the resin contained in the heat seal layer 30 contains more high-melting point components, and the planar orientation M tends to increase as the stretching temperature in the stretching step is lower.

[0050] The heat seal layer 30 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.

[0051] The thickness of the heat seal layer 30 may be 10 μm or more and 150 μm or less, 20 μm or more and 120 μm or less, or 30 μm or more and 100 μm or less. When the thickness of the heat seal layer 30 is within the above range, the strength of the laminated film 10 and the heat seal strength during heat sealing can be improved.

[0052] Other substrates and functional layers can also be laminated onto the laminate film 10. This can improve heat resistance and strength, and can also impart other functions.

[0053] The laminated film of this embodiment can be used as a film for packaging materials.

[0054] <Laminated film manufacturing method> Since the laminated film 10 is formed by laminating the heat seal layer 30 and the base film 20 without using an adhesive, in order to ensure sufficient laminate strength, the heat seal layer 30 and the base film 20 are laminated in the molten state to form a film, and the resulting laminate (unstretched sheet) is stretched uniaxially or biaxially.

[0055] Examples of film-forming methods include laminating the materials by coextrusion, and laminating the heat-sealable layer by pouring a molten resin composition for forming the heat-sealable layer onto a substrate film melted on a hot plate. From the viewpoint of production cost, the film may be produced by roll-to-roll coextrusion. This simplifies the production process, prevents the inclusion of impurity materials, and improves recyclability.

[0056] From the viewpoint of strength and productivity, the stretching may be sequential biaxial stretching. The stretching temperature may be a temperature equal to or higher than the melting point of the heat-seal layer 30 and equal to or lower than the melting point of the base film 20. By stretching in this temperature range, the surface heat-seal layer 30 is stretched without being oriented, while the base film 20 is oriented. This makes it possible to achieve both improved strength and heat resistance due to the base film 20 and low-temperature heat-sealability due to the heat-seal layer 30. Furthermore, if the stretching temperature is equal to or higher than the melting point of the heat-seal layer 30, orientation of the heat-seal layer 30 is suppressed, making it easier to achieve low-temperature heat-sealability, and sufficient softening of the base film 20 makes it easier to prevent film breakage. On the other hand, if the stretching temperature is equal to or lower than the melting point of the base film 20, softening and melting of the entire film is suppressed, making it easier to stretch the unstretched sheet.

[0057] In the laminate film of the present embodiment, when the base film and the heat seal layer contain a polypropylene-based resin as the same type of polyolefin resin, the laminate film may be produced by the following method.

[0058] The method for producing a laminated film of this embodiment includes the steps of co-extruding a first resin composition containing a polypropylene-based resin and a second resin composition containing a polypropylene-based resin and having a melting point M2 lower than the melting point M1 of the first resin composition, and stretching the resulting composition at a temperature equal to or higher than the melting point M2 and equal to or lower than the melting point M1 to form a laminated film in which a substrate film made of the first resin composition and a heat-sealable layer made of the second resin composition are laminated. The stretching may be uniaxial or biaxial.

[0059] In the above step, from the viewpoint of improving the strength and transparency of the substrate film and the heat resistance of the laminate film, the stretching may be performed so that the planar orientation M calculated by the above 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. The planar orientation M can be adjusted by the above method.

[0060] In the above step, from the viewpoint of improving the low-temperature heat sealability and flexibility of the heat seal layer, the stretching may be performed so that the planar orientation M calculated by the above method is −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 heat seal layer opposite the side that contacts the base film. The planar orientation M can be adjusted by the above method.

[0061] The stretching temperature may be at least 40°C, at least 10°C, or at least 1°C lower than the melting point M1 of the first resin composition, from the viewpoint of preventing the base film from softening and breaking, and may be at least 1°C, at least 10°C, or at least 40°C higher than the melting point M2 of the second resin composition, from the viewpoint of ensuring that the heat seal layer is sufficiently melted and is less likely to cause problems such as sticking to the stretching device.

[0062] <Laminate> The laminate of this embodiment has a vapor-deposited adhesive layer containing a thermoplastic resin and a vapor-deposited layer laminated in this order on the base film of the laminate film of this embodiment, so that the vapor-deposited layer and the vapor-deposited adhesive layer are in direct contact with each other. The laminate of this embodiment may further have a protective layer laminated on the side of the vapor-deposited layer opposite to the vapor-deposited adhesive layer side.

[0063] Fig. 2 is a cross-sectional view schematically showing an example of the laminate of this embodiment. The laminate 100 shown in Fig. 2 has a heat seal layer 30, a base film 20, a vapor-deposited adhesive layer 32, a vapor-deposited layer 40, and a protective layer 50 laminated in this order. The laminate 100 has the above-mentioned structure, and thus can improve gas barrier properties.

[0064] By including the laminate film 10 of this embodiment, the laminate 100 can have sufficient heat sealability and lamination strength.

[0065] The vapor-deposited adhesion layer 32 functions as a region (vapor-deposited adhesion region) that improves adhesion to the vapor-deposited layer 40. The material that constitutes the vapor-deposited adhesion layer 32 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).

[0066] By including a thermoplastic resin, the vapor-deposited adhesion layer 32 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. Furthermore, the vapor-deposited adhesion layer 32 containing a thermoplastic resin can also be manufactured integrally with a substrate film or the like by co-extrusion. In this case, the thermoplastic resin may be the same type of resin as the polyolefin resin contained in the substrate film.

[0067] In order to improve the recyclability of the laminate 100, the content of the thermoplastic resin in the vapor-deposited adhesion layer 32 may be 20 mass% or less, 10 mass% or less, or 5 mass% or less, based on the total mass of the laminate.

[0068] From the viewpoint of recyclability of the laminate, the vapor-deposited adhesive layer 32 may contain the same type of polyolefin resin as the polyolefin resin contained in the base film.

[0069] Filler particles may be added to the vapor-deposited adhesion layer 32. In this case, it is preferable that the surface of the vapor-deposited adhesion layer 32 that comes into contact with the vapor-deposited layer 40 is smooth before the vapor-deposited layer 40 is formed. Furthermore, the surface of the vapor-deposited adhesion layer 32 that comes into contact with the vapor-deposited layer 40 may be subjected to a surface treatment such as plasma treatment as a pretreatment before the vapor-deposited layer 40 is formed.

[0070] From the viewpoint of recyclability, the thickness of the vapor-deposited adhesive layer 32 may be 0.2 μm or more and 5 μm or less, or 0.5 μm or more and 3 μm or less.

[0071] The deposition layer 40 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.

[0072] Materials constituting the vapor-deposited layer 40 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.

[0073] The thickness of the vapor-deposited layer 40 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 40 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.

[0074] The protective layer 50 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.

[0075] 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.

[0076] 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.

[0077] The protective layer 50 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.

[0078] The thickness of the protective layer 50 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 50 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.

[0079] The laminate of this embodiment can be produced by producing the laminate film of this embodiment using the method described above, and then providing a vapor-deposited adhesion layer, a vapor-deposited layer, and a protective layer in this order on the substrate film side of the laminate film using the methods described above.

[0080] The laminate of this embodiment can be used as a film for packaging materials.

[0081] <Packaging material> The packaging material of this embodiment includes the laminate film of this embodiment or the laminate of this embodiment.

[0082] 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 heat seal layer 30 of the laminate film 10 is on the inside, and heat sealing the edges. Alternatively, a packaging bag can be produced by overlapping two laminate films 10 so that the heat seal layers 30 face each other, and heat sealing the edges.

[0083] A packaging bag can be produced by folding the packaging material including the laminate 100 in half, overlapping the laminate 100 so that the heat seal layer 30 is on the inside, and heat sealing the edges. Alternatively, a packaging bag can be produced by overlapping two sheets of the laminate 100 so that the heat seal layers 30 face each other, and heat sealing the edges.

[0084] 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.

[0085] 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.

[0086] According to the packaging material of this embodiment, by including the laminate film of this embodiment, a package having high recyclability can be produced. Furthermore, according to the packaging material of this embodiment, by including the laminate film of this embodiment, a package having retort suitability can be produced. [Example]

[0087] 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.

[0088] Example 1 A 2mm-thick unstretched sheet was produced by co-extrusion molding using polypropylene resin F-300SP (Prime Polymer Co., Ltd., melting point 161°C) as the resin for forming the base film and polypropylene resin F-744NP (Prime Polymer Co., Ltd., melting point 133°C) as the resin for forming the heat-seal layer. The thickness ratio of each layer was base film:heat-seal layer = 2:3, and the resin temperature during extrusion was 230°C. The unstretched sheet was then biaxially stretched at MD 5x and TD 8x at 157°C after a 2-minute preheating period to produce a 50µm-thick laminated film.

[0089] Example 2 A 250 μm thick unstretched sheet was produced by coextrusion molding using linear low-density polyethylene resin Evolue SP3530 (Prime Polymer Co., Ltd., melting point 123°C) as the resin for forming the base film and linear low-density polyethylene resin Evolue SP1540 (Prime Polymer Co., Ltd., melting point 113°C) as the resin for forming the heat-seal layer. The thickness ratio of each layer was base film:heat-seal layer = 2:3, and the resin temperature during extrusion was 230°C. The unstretched sheet was then uniaxially stretched at an MD ratio of 5x at 120°C after a 2-minute preheating period to produce a 50 μm thick laminated film.

[0090] (Comparative Example 1) Polypropylene resin F-300SP (Prime Polymer Co., Ltd.) was used as the resin for forming the base film, and an 800 μm thick unstretched sheet was produced by extrusion molding. The resin temperature during extrusion was 230°C. Subsequently, the sheet was biaxially stretched at MD 5x and TD 8x magnifications at a temperature of 157°C after a preheating time of 2 minutes to produce a 20 μm thick base film. A 30 μm thick heat seal layer was bonded to this base film by extrusion lamination to obtain a 50 μm thick laminated film. Polypropylene resin F-744NP (Prime Polymer Co., Ltd.) was used as the resin for extrusion lamination, and the resin temperature during extrusion was 230°C.

[0091] (Comparative Example 2) Polypropylene resin F-300SP (manufactured by Prime Polymer Co., Ltd.) was used as the resin for forming the base film, and an unstretched sheet with a thickness of 800 μm was produced by extrusion molding. The resin temperature during extrusion was 230°C. The unstretched sheet was then biaxially stretched at 5x MD and 8x TD at 157°C for 2 minutes after preheating to produce a base film with a thickness of 20 μm.

[0092] On the other hand, a polypropylene resin F-744NP (manufactured by Prime Polymer Co., Ltd.) was used as a resin for forming the heat seal layer, and an unstretched film having a thickness of 30 μm was produced by extrusion molding.

[0093] The substrate film and unstretched film obtained above were bonded together by dry lamination using Takelac A-525 (manufactured by Mitsui Chemicals, Inc.) and Takenate A-52 (manufactured by Mitsui Chemicals, Inc.) as adhesives to obtain a laminated film with a thickness of 50 μm.

[0094] (Comparative Example 3) A 100 μm thick unstretched film was produced by extrusion molding using linear low-density polyethylene resin Evolue SP3530 (manufactured by Prime Polymer Co., Ltd.) as the resin for forming the base film. The resin temperature during extrusion was 230°C. The unstretched film was then uniaxially stretched at an MD5x magnification at a temperature of 120°C after a preheating time of 2 minutes to produce a 20 μm thick base film. This base film was then extrusion laminated with a 30 μm thick heat seal layer to obtain a 50 μm thick laminated film. A linear low-density polyethylene resin Evolue SP1540 (manufactured by Prime Polymer Co., Ltd.) was used as the resin for extrusion lamination, and the resin temperature during extrusion was 230°C.

[0095] Comparative Example 4 A 100 μm thick unstretched film was produced by extrusion molding using linear low-density polyethylene resin Evolue SP3530 (manufactured by Prime Polymer Co., Ltd.) as the resin for forming the base film. The resin temperature during extrusion was 230°C. The unstretched film was then uniaxially stretched at a MD stretching ratio of 5x at a temperature of 120°C for 2 minutes, after which a 20 μm thick base film was produced.

[0096] On the other hand, a linear low-density polyethylene resin Evolue SP1540 (manufactured by Prime Polymer Co., Ltd.) was used as the resin for forming the heat seal layer, and an unstretched film having a thickness of 30 μm was produced by extrusion molding. The resin temperature during extrusion was 230° C.

[0097] The substrate film and unstretched film obtained above were bonded together by dry lamination using adhesives LX-500 (manufactured by DIC Graphics Inc.) and KW-75 (manufactured by DIC Graphics Inc.) to obtain a laminated film with a thickness of 50 μm.

[0098] (Comparative Example 5) A 50 μm thick laminated film was obtained in the same manner as in Comparative Example 4, except that a 12 μm thick biaxially stretched polyethylene terephthalate film E5100 (manufactured by Toyobo Co., Ltd.) was used as the base film.

[0099] (Comparative Example 6) A laminated film having a thickness of 50 μm was obtained in the same manner as in Comparative Example 1, except that the same polypropylene resin F-300SP (manufactured by Prime Polymer Co., Ltd.) as that of the base film was used as the resin for forming the heat seal layer.

[0100] [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 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.

[0101] In a laminate film having a base film and a heat-sealing layer, the plane orientation M was measured for the surface HS2 (first surface) of the heat-sealing layer opposite to the side in contact with the base film, and the surface BS2 (second surface) of the base film opposite to the side in contact with the heat-sealing layer. In a laminate film having an adhesive layer between the base film and the heat-sealing layer, the surface of the heat-sealing layer opposite to the base film was designated the first surface, and the surface of the base film opposite to the heat-sealing layer was designated the second surface, and the plane orientation M was measured for these surfaces.

[0102] The polarized ATR prism was ZnSe, and measurements were carried out using a single-reflection ATR with a 45-degree incidence angle. Materials other than polypropylene were excluded from this evaluation and were marked with a "-".

[0103] [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."

[0104] [Evaluation of low-temperature 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 seal layer 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. Cases where the interface between the heat seal layer and the base film could not be peeled at all and where the average measured strength was 2 N / 15 mm or more were marked "Good," and cases where the average measured strength was less than 2 N / 15 mm were marked "Poor."

[0105] [Evaluation of heat sealability] Using a Tester Sangyo heat sealer (model number TP-701-B), two laminated films were stacked with the heat seal layer facing inward, and heat-sealed at 140°C only on the seal bar, with a sealing pressure of 0.15 MPa, a sealing time of 1 second, and a seal width of 5 mm. A heat seal strength of 10 N / 15 mm or more and no visible wrinkles were evaluated as "Good." A heat seal strength of 8 N / 15 mm or more but less than 10 N / 15 mm, or slight wrinkles that were not a problem for practical use, were evaluated as "Poor." A heat seal strength of less than 8 N / 15 mm or wrinkles that were a problem for practical use were evaluated as "Poor."

[0106] [Evaluation of retort suitability] The laminated film was cut into 180mm x 150mm pieces and heat-sealed using a Tester Sangyo heat sealer (model TP-701-B) at a sealing temperature of 145°C (top and bottom), a sealing pressure of 0.15 MPa, a sealing time of 1 second, and a 5mm seal width. Two sheets of laminated film were placed on top of each other with the heat-sealed layer facing inward, and heat-sealed to obtain pouch-shaped bags. Before sealing the final edge, 150cc of water was poured into the pouch. The pouch was then retorted at 121°C for 30 minutes using a Hisaka Seisakusho high-temperature, high-pressure cooking sterilizer (model RCS-60 / 10RSPXTG). The interior of the pouch was visually inspected for fusion after retort processing. The heat seal strength of the heat-sealed portion of the pouch after retort processing was also measured at 145°C and a width of 15mm. At this time, bags with no fusion inside and a heat seal strength of 10N / 15mm or more were rated "Good", bags with no fusion inside and a heat seal strength of 5N / 15mm or more but less than 10N / 15mm were rated "Good", bags with fusion inside or a heat seal strength of less than 5N / 15mm were rated "Poor", and bags with fusion inside or a heat seal strength of less than 5N / 15mm were rated "Poor".

[0107] (Overall judgment) If all of the above evaluations of recyclability, low-temperature lamination, heat sealability, and retort suitability were "good," the overall judgment was "◎." If only the retort suitability evaluation was "poor" or "good," the overall judgment was "good." If only the heat sealability evaluation was "good," the overall judgment was "good." If there was even one "poor" other than the retort suitability evaluation, the overall judgment was "good."

[0108] Table 1 shows the film configurations and evaluation results for Examples 1 and 2 and Comparative Examples 1 to 6.

[0109] [Table 1]

[0110] Example 3 As for the stretching conditions, the planar orientation M was controlled by increasing the stretching temperature in Example 1. Otherwise, a laminated film having a thickness of 50 μm was obtained in the same manner as in Example 1.

[0111] Example 4 As for the stretching conditions, the planar orientation M was controlled by lowering the stretching temperature in Example 1. Otherwise, a laminated film having a thickness of 50 μm was obtained in the same manner as in Example 1.

[0112] Example 5 As for the stretching conditions, the stretching temperature in Example 1 was further lowered than in Example 4 to control the plane orientation M. Otherwise, the same procedure as in Example 1 was carried out to obtain a laminated film having a thickness of 50 μm.

[0113] Example 6 As for the stretching conditions, the planar orientation M was controlled by lowering the stretching ratio in Example 1. Otherwise, a laminated film having a thickness of 50 μm was obtained in the same manner as in Example 1.

[0114] Example 7 As for the stretching conditions, the stretching ratio was set between that of Example 1 and Example 6 to control the plane orientation M. Otherwise, the same procedure as in Example 1 was carried out to obtain a laminated film having a thickness of 50 μm.

[0115] Example 8 As for the stretching conditions, the planar orientation M was controlled by increasing the stretch ratio in Example 1. Otherwise, a laminated film having a thickness of 50 μm was obtained in the same manner as in Example 1.

[0116] Example 9 A laminated film having a thickness of 50 μm was obtained in the same manner as in Example 1, except that an unstretched sheet was prepared using a material that was previously dry-blended in a mass ratio of 80:20 between polypropylene resin F-744NP (manufactured by Prime Polymer Co., Ltd., melting point 133°C) and polypropylene resin F-300SP (manufactured by Prime Polymer Co., Ltd., melting point 161°C) as the resin for forming the heat seal layer.

[0117] Example 10 A laminated film having a thickness of 50 μm was obtained in the same manner as in Example 1, except that an unstretched sheet was prepared using a material that was previously dry-blended in a mass ratio of 50:50 between polypropylene resin F-744NP (manufactured by Prime Polymer Co., Ltd., melting point 133°C) and polypropylene resin F-300SP (manufactured by Prime Polymer Co., Ltd., melting point 161°C) as the resin for forming the heat seal layer.

[0118] Example 11 A laminated film having a thickness of 50 μm was obtained in the same manner as in Example 1, except that an unstretched sheet was prepared using a material that was previously dry-blended in a mass ratio of 20:80 between polypropylene resin F-744NP (manufactured by Prime Polymer Co., Ltd., melting point 133°C) and polypropylene resin F-300SP (manufactured by Prime Polymer Co., Ltd., melting point 161°C) as the resin for forming the heat seal layer.

[0119] [Evaluation of plane orientation M] The planar orientation M was evaluated in the same manner as above.

[0120] [Recyclability evaluation] The recyclability was evaluated in the same manner as above.

[0121] [Evaluation of low-temperature lamination] The low-temperature lamination property was evaluated in the same manner as above.

[0122] [Evaluation of heat sealability] The heat sealability was evaluated in the same manner as above.

[0123] [Evaluation of retort suitability] The retort suitability was evaluated in the same manner as above.

[0124] (Overall judgment) If all of the above evaluations of recyclability, low-temperature lamination, heat sealability, and retort suitability were "good," the overall judgment was "◎." If only the retort suitability evaluation was "poor" or "good," the overall judgment was "good." If only the heat sealability evaluation was "good," the overall judgment was "good." If there was even one "poor" other than the retort suitability evaluation, the overall judgment was "good."

[0125] The laminated film configurations and evaluation results of Examples 3 to 11 are shown in Table 2.

[0126] [Table 2]

[0127] (Evaluation results) As shown in Table 1, in Examples 1 and 2, in which the base film and heat-seal layer contained the same type of polyolefin resin, the melting point of the heat-seal layer was lower than that of the base film, and the base film and heat-seal layer were laminated in direct contact and stretched, the recyclability, low-temperature lamination, and heat-sealability were confirmed to be "Good." On the other hand, in Comparative Examples 2, 4, and 5, in which an adhesive was used in the adhesive layer, fisheyes occurred frequently, and the recyclability was rated "Poor." Furthermore, in Comparative Examples 1 and 3, in which an unstretched material was used in the heat-seal layer, the lamination strength was insufficient, resulting in weak interfacial strength, and the low-temperature lamination was rated "Poor." In Comparative Example 6, in which the heat-seal layer and the base film had the same melting point, the heat-seal strength was not sufficient, and the heat-sealability was rated "Poor."

[0128] From the results in Table 2, as in Examples 3, 4, 7, and 8, when the planar orientation M of the surface of the heat seal layer opposite the side that contacts the base film was -0.3 or more and 0.3 or less, and the planar orientation M of the surface of the base film opposite the side that contacts the heat seal layer was 0.5 or more and 0.9 or less, the heat sealability was "○". On the other hand, in Example 5, where the planar orientation M of the heat seal layer surface (front surface) exceeded 0.3, the heat sealability was "△". This is thought to be because the heat seal layer was slightly oriented and the heat resistance was slightly increased. Furthermore, in Example 6, where the planar orientation M of the base film surface (rear surface) was less than 0.5, thin wrinkles occurred during heat sealing at a level that was not a problem in practical use, and the heat sealability was "△". This is thought to be because the heat resistance of the base film was slightly insufficient. From these results, it can be seen that it is preferable for the plane orientation M of the heat seal layer surface (front surface) to be between -0.3 and 0.3, and for the plane orientation M of the base film surface (back surface) to be between 0.5 and 0.9, but even if they are outside this range, the heat sealability will only be slightly reduced, and this will not be a problem in practical use.

[0129] Furthermore, from the results in Table 2, in Examples 9, 10, and 11, in which the heat seal layer was a blend of a low-melting point resin and a high-melting point resin, the inclusion of the high-melting point resin prevented the inside of the bag from fusing after retort treatment, and the heat sealability did not deteriorate, resulting in good retort resistance. In Example 11, in which the content of the low-melting point resin was 20 parts by mass per 100 parts by mass of the total mass of the high-melting point resin and the low-melting point resin, the heat sealability was rated "Fair," but was within a range that could be used in practice. [Explanation of symbols]

[0130] 10...Laminated film, 20...Base film, 30...Heat seal layer, 32...Vapor-deposited adhesive layer, 40...Vapor-deposited layer, 50...Protective layer, 100...Laminate.

Claims

1. The film has a base film and a heat seal layer laminated in direct contact with the base film, the base film and the heat seal layer contain the same type of polyolefin resin, the melting point of the heat seal layer is lower than the melting point of the base film; A laminated film in which the base film and the heat seal layer are stretched.

2. 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 seal layer. ２ and the surface HS of the heat seal layer opposite to the side in contact with the base film 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.

3. the heat seal layer is made of a polyolefin resin composition containing a high-melting point component having a melting point of 155°C or more and less than 165°C and a low-melting point component having a melting point of 120°C or more and less than 150°C, The content of the low melting point component in the polyolefin resin composition is 20 to 80 parts by mass when the total mass of the high melting point component and the low melting point component is 100 parts by mass. The laminate film according to claim 1.

4. The laminated film according to claim 1, wherein a vapor-deposited adhesive layer containing a thermoplastic resin and a vapor-deposited layer are laminated in this order on the substrate film, The vapor-deposited layer and the vapor-deposited adhesive layer are in direct contact with each other.

5. A packaging material comprising the laminate film according to claim 1 or the laminate according to claim 4.

6. a first resin composition containing a polypropylene-based resin; and a polypropylene-based resin composition having a melting point M １ Lower melting point M ２ and a second resin composition having the melting point M ２ The melting point M １ and forming a laminated film in which a base film made of the first resin composition and a heat seal layer made of the second resin composition are laminated by stretching the film at a temperature below 100° C., In the above step, the plane orientation M calculated by the following method is a value obtained by dividing the surface BS of the substrate film opposite to the side in contact with the heat seal layer by 1 / 2 mm. ２ and the surface HS of the heat seal layer opposite to the side in contact with the base film is 0.5 or more and 0.9 or less. ２ The method for producing a laminated film comprises stretching the film so that the stretching temperature 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.

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