Layered film and packing bag

Abstract

[Problem] To provide a carbon-neutral heat-sealed laminate film that has exceptional heat resistance, impact resistance, and flexing pinhole resistance and that uses a biomass-derived raw material. [Solution] Provided is a laminate film having at least a base material layer and a sealant layer. The base material layer is a biaxially stretched polyamide film in which a B layer is laminated on at least one surface of an A layer; the A layer contains 70-99 mass% (inclusive) of a polyamide 6 resin, and 1-30 mass% (inclusive) of a polyamide resin that includes a biomass-derived raw material; the B layer contains 70-100 mass% (inclusive) of a polyamide 6 resin; and the sealant layer is an unstretched polyolefin film containing 70-95 mass%(inclusive) of a polypropylene resin, and 5-30 mass% (inclusive) of a straight-chain low-density polyethylene resin for which at least part of a raw material is derived from biomass.

Description

Laminated films and packaging bags

[0001] The present invention relates to a laminated film suitable for use in packaging bags and the like.

[0002] Biaxially stretched films made of aliphatic polyamides, such as polyamide 6, are excellent in impact resistance and pinhole resistance due to bending, and are widely used as various packaging materials.

[0003] In recent years, in order to build a recycling-oriented society, the use of biomass as a raw material instead of fossil fuels has been attracting attention in the materials field. Biomass is an organic compound photosynthesized from carbon dioxide and water, and by using it, it is converted back into carbon dioxide and water, making it a so-called carbon-neutral raw material. In other words, it is a raw material that can suppress the increase of carbon dioxide, a greenhouse gas, because the amount of carbon dioxide emitted and absorbed in the environment is the same. The practical application of biomass plastics made from these biomass raw materials has rapidly progressed, and biaxially oriented polyamide films made from biomass-derived raw materials have also been proposed (see, for example, Patent Document 1).

[0004] When used as a packaging material, the biaxially oriented polyamide film is laminated with a sealant film or the like to form a laminate film, which is then processed into a packaging bag, etc. As the sealant film, an unstretched linear low-density polyethylene film, an unstretched polypropylene film, etc. are used, but from the viewpoint of carbon neutrality, a sealant film containing polyethylene polymerized using a biomass-derived raw material has been proposed (see, for example, Patent Document 2).

[0005] International Publication No. 2020 / 170714 Japanese Patent Application Laid-Open No. 2018-001612

[0006] An object of the present invention is to provide a heat-sealable laminated film that is excellent in heat resistance, impact resistance, and pinhole resistance due to bending, and is carbon-neutral and uses raw materials derived from biomass.

[0007] The present invention has the following configuration: [1] A laminate film having at least a base layer and a sealant layer, wherein the base layer is a biaxially oriented polyamide film, and the biaxially oriented polyamide film has a layer B laminated on at least one surface of a layer A, the layer A containing 70% to 99% by mass of a polyamide 6 resin having ε-caprolactam as a lactam unit derived from a fossil fuel and 1% to 30% by mass of a polyamide resin containing a biomass-derived raw material, and the layer B containing 70% to 100% by mass of a polyamide 6 resin having ε-caprolactam as a lactam unit derived from a fossil fuel, and the sealant layer is an unstretched polyolefin film containing 70% to 95% by mass of a polypropylene-based resin and 5% to 30% by mass of a linear low-density polyethylene resin at least part of which is biomass-derived. [2] The laminate film according to [1], wherein the sealant layer is laminated on the Layer B side of the base layer. [3] The laminate film according to [1] or [2], wherein the carbon-14 content in the base layer is 1% or more and 30% or less of the total carbon in the base layer. [4] The laminate film according to any one of [1] to [3], wherein the polyamide resin in the base layer, at least a part of which is derived from biomass, is at least one polyamide resin selected from the group consisting of polyamide 11, polyamide 410, polyamide 610, and polyamide 1010. [5] The laminate film according to any one of [1] to [4], wherein the carbon-14 content in the sealant layer is 3% or more and 30% or less of the total carbon in the sealant layer.[6] The laminate film according to any one of [1] to [5], wherein the sealant layer has a seal layer, a core layer, and a laminate layer, wherein the resin composition constituting the seal layer comprises 94% by mass or more and 100% by mass or less of a propylene-α-olefin random copolymer and 0% by mass or more and 3% by mass or less of a linear low-density polyethylene, wherein the resin composition constituting the core layer comprises 25% by mass or more and 97% by mass or less of a propylene-α-olefin random copolymer and 3% by mass or more and 40% by mass or less of a linear low-density polyethylene, and wherein the resin composition constituting the laminate layer comprises 25% by mass or more and 70% by mass or less of a propylene-α-olefin random copolymer and 3% by mass or more and 50% by mass or less of a linear low-density polyethylene, and wherein the laminate layer, core layer, and seal layer are present in the sealant layer in this order from the surface in contact with the base layer. [7] The laminate film according to any one of [1] to [6], wherein the carbon-14 content in the laminate film is 2% or more and 30% or less of the total carbon in the laminate film. [8] A packaging bag using the laminate film according to any one of [1] to [7].

[0008] According to the present invention, by laminating a sealant film containing a biomass-derived material onto a biaxially oriented polyamide film containing polyamide 6 and a polyamide resin polymerized from specific biomass-derived materials, a heat-sealable laminated film that is excellent in heat resistance, impact resistance, and flex pinhole resistance and is also carbon-neutral can be obtained.

[0009] [Substrate Layer] The substrate layer of the present invention is preferably composed of a biaxially oriented polyamide film. In a preferred embodiment of the present invention, the biaxially oriented polyamide film is a biaxially oriented polyamide film in which Layer B is laminated on at least one side of Layer A.

[0010] [Layer A] Layer A is preferably composed of a polyamide resin composition containing at least 70% by mass or more and 99% by mass or less of polyamide 6 resin and 1% by mass or more and 30% by mass or less of polyamide resin containing a biomass-derived raw material.

[0011] By including 70% by mass or more of polyamide 6 resin in Layer A, a biaxially oriented polyamide film having excellent mechanical strength such as impact strength and gas barrier properties against oxygen and the like can be obtained. By including 1% by mass or more and 30% by mass or less of a polyamide resin containing a biomass-derived material in Layer A, the biaxially oriented polyamide film is not only a carbon-neutral biaxially oriented polyamide film made from a biomass-derived material, but also has improved pinhole resistance due to bending. Conventionally used polyamide elastomers and polyolefin elastomers as flex pinhole resistance improvers tend to improve pinhole resistance due to bending but deteriorate pinhole resistance due to friction. In the present invention, by including 1% by mass or more and 30% by mass or less of a polyamide resin containing a biomass-derived material, a biaxially oriented polyamide film having excellent pinhole resistance due to bending and friction can be obtained.

[0012] The upper limit of the content of the polyamide resin containing a biomass-derived raw material in Layer A is preferably 30% by mass, more preferably 20% by mass. If the content of the polyamide resin containing a biomass-derived raw material exceeds 30% by mass, the molten film may become unstable when cast, making it difficult to obtain a homogeneous unstretched film.

[0013] Polyamide 6 used in layer A is usually produced by ring-opening polymerization of ε-caprolactam. The polyamide 6 obtained by ring-opening polymerization is treated with hot water to remove the lactam monomer, then dried and melt-extruded in an extruder.

[0014] The relative viscosity of polyamide 6 is preferably 1.8 or more and 4.5 or less, more preferably 2.6 or more and 3.2 or less. A relative viscosity of 1.8 or more allows the film to have the necessary impact strength. A relative viscosity of 4.5 or less makes it easy to melt-extrude the raw material resin from an extruder and form an unstretched film.

[0015] As polyamide 6, in addition to polyamide 6 polymerized from commonly used monomers derived from fossil fuels, polyamide 6 chemically recycled from used polyamide 6 products such as waste plastic products, waste tire rubber, fibers, fishing nets, etc. As a method for obtaining chemically recycled polyamide 6 from used polyamide 6 products, for example, a method can be used in which used polyamide products are collected, depolymerized to obtain ε-caprolactam, which is then purified and then polymerized into polyamide 6.

[0016] Additionally, it is possible to use mechanically recycled polyamide 6. Mechanically recycled polyamide 6 is a raw material obtained by recovering waste materials, such as non-standard, unshippable film and offcuts (edge ​​trimmings) that are generated during the production of biaxially oriented polyamide film, and pelletizing them by melt extrusion or compression molding.

[0017] <Polyamide at least part of which is derived from biomass as a raw material> Examples of polyamides at least part of which is derived from biomass as a raw material used in the present invention include polyamide 11, polyamide 410, polyamide 610, polyamide 1010, polyamide MXD10, and polyamide 11-6T copolymer resins.

[0018] Polyamide 11 is a polyamide resin having a structure in which monomers having 11 carbon atoms are bonded via amide bonds. Polyamide 11 is typically obtained using aminoundecanoic acid or undecane lactam as the monomer. Aminoundecanoic acid, in particular, is a monomer obtained from castor oil, making it desirable from the perspective of carbon neutrality. The structural units derived from these monomers having 11 carbon atoms preferably account for 50 mol% or more of the total structural units in polyamide 11, more preferably 80 mol% or more, and even 100 mol%. Polyamide 11 is typically produced by the ring-opening polymerization of the aforementioned undecane lactam. The polyamide 11 obtained by ring-opening polymerization is typically subjected to removal of the lactam monomer with hot water, drying, and melt-extrusion in an extruder. The relative viscosity of polyamide 11 is preferably 1.8 or more and 4.5 or less, more preferably 2.4 or more and 3.2 or less. A relative viscosity of 1.8 or more allows for the necessary impact strength of the film to be obtained. When the relative viscosity is 4.5 or less, it becomes easy to melt-extrude the raw material resin from an extruder and form an unstretched film.

[0019] Polyamide 410 is a polyamide resin having a structure in which a monomer having four carbon atoms is copolymerized with a diamine having ten carbon atoms. Typically, sebacic acid and tetramethylenediamine are used in polyamide 410. From an environmental perspective, sebacic acid made from castor oil, a vegetable oil, is preferred. The sebacic acid used here is preferably obtained from castor oil from the standpoint of environmental protection, particularly from the standpoint of carbon neutrality.

[0020] Polyamide 610 is a polyamide resin having a structure obtained by polymerizing a diamine having six carbon atoms and a dicarboxylic acid having ten carbon atoms. Hexamethylenediamine and sebacic acid are typically used. Of these, sebacic acid is a monomer obtained from castor oil, and is therefore desirable from the perspective of carbon neutrality. The combined total of the structural units derived from these monomers having six carbon atoms and the structural units derived from monomers having ten carbon atoms in PA610 is preferably 50 mol % or more, more preferably 80 mol % or more, and may even be 100 mol % of all structural units.

[0021] Polyamide 1010 is a polyamide resin having a structure obtained by polymerizing a diamine having 10 carbon atoms and a dicarboxylic acid having 10 carbon atoms. Polyamide 1010 typically utilizes 1,10-decanediamine (decamethylenediamine) and sebacic acid. Decamethylenediamine and sebacic acid are monomers obtained from castor oil, and are therefore desirable from the perspective of carbon neutrality. The combined total of the structural units derived from these diamines having 10 carbon atoms and the structural units derived from dicarboxylic acids having 10 carbon atoms in polyamide 1010 is preferably 50 mol% or more, more preferably 80 mol% or more, and may even be 100 mol% of all structural units.

[0022] The lower limit of the content of the polyamide at least partly derived from biomass in Layer A is not particularly limited, but is preferably 1% by mass, more preferably 3% by mass. The upper limit of the content is 30% by mass, more preferably 20% by mass. If the content of the polyamide at least partly derived from biomass exceeds 30% by mass, the molten film may become unstable when cast, making it difficult to obtain a homogeneous unstretched film.

[0023] <Secondary Materials and Additives> Layer A may contain various additives such as other thermoplastic resins, lubricants, heat stabilizers, antioxidants, antistatic agents, anti-fogging agents, UV absorbers, dyes, and pigments, as needed.

[0024] <Other Thermoplastic Resins> Layer A may contain thermoplastic resins other than the polyamide 6 and polyamide resins at least partially derived from biomass, as long as the objectives of the present invention are not impaired. Examples include polyamide-based resins such as polyamide 12 resin, polyamide 66 resin, polyamide 6-12 copolymer resin, polyamide 6-66 copolymer resin, and polyamide MXD6 resin. If necessary, thermoplastic resins other than polyamide-based resins, such as polyester-based polymers such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, and polyolefin-based polymers such as polyethylene and polypropylene, may also be contained. It is preferable that the raw materials for these thermoplastic resins are derived from biomass, as this does not affect the increase or decrease in terrestrial carbon dioxide and reduces the environmental impact.

[0025] [Layer B] Layer B is preferably composed of a polyamide resin composition containing 70% by mass or more and 100% by mass or less of polyamide 6 resin. By containing 70% by mass or more of polyamide 6 resin, a biaxially stretched polyamide film having excellent mechanical strength such as impact strength and gas barrier properties against oxygen and the like can be obtained. As the polyamide 6 resin, the same polyamide 6 resin as used in Layer A can be used.

[0026] Layer B can contain various additives such as other thermoplastic resins, lubricants, heat stabilizers, antioxidants, antistatic agents, anti-fogging agents, ultraviolet absorbers, dyes, pigments, etc. depending on the functions to be imparted to the surface of Layer B. When Layer B is used on the outside of a packaging bag, it needs to be resistant to abrasion and pinholes, so it is not preferable to contain soft resins such as polyamide elastomers or polyolefin elastomers or substances that generate a large number of voids.

[0027] Layer B may contain a thermoplastic resin other than the polyamide 6, as long as it does not impair the object of the present invention. Examples include polyamide-based resins such as polyamide MXD6 resin, polyamide 11 resin, polyamide 12 resin, polyamide 66 resin, polyamide 6-12 copolymer resin, and polyamide 6-66 copolymer resin. If necessary, thermoplastic resins other than polyamide-based resins, such as polyester-based polymers such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, and polyolefin-based polymers such as polyethylene and polypropylene, may also be contained.

[0028] <Lubricant> Layer B preferably contains fine particles or an organic lubricant such as a fatty acid amide as a lubricant to improve the slipperiness of the film and make it easier to handle. The fine particles can be appropriately selected from inorganic fine particles such as silica, kaolin, and zeolite, and polymeric organic fine particles such as acrylic and polystyrene-based fine particles. From the viewpoint of transparency and slipperiness, it is preferable to use silica fine particles. The average particle diameter of the fine particles is preferably 0.5 μm or more and 5.0 μm or less, and more preferably 1.0 μm or more and 3.0 μm or less. An average particle diameter of 0.5 μm or more can achieve good slipperiness. On the other hand, an average particle diameter of 5.0 μm or less can suppress poor appearance due to the surface roughness of the film.

[0029] When the silica fine particles are used, the pore volume of the silica is preferably in the range of 0.5 ml / g to 2.0 ml / g, more preferably 0.8 ml / g to 1.6 ml / g. A pore volume of 0.5 ml / g or more can suppress deterioration of film transparency due to the generation of voids, while a pore volume of 2.0 ml / g or less makes it easy to form surface protrusions due to the fine particles.

[0030] Layer B may contain a fatty acid amide and / or a fatty acid bisamide to improve slipperiness. Examples of fatty acid amides and / or fatty acid bisamides include erucic acid amide, stearic acid amide, ethylene bisstearic acid amide, ethylene bisbehenic acid amide, and ethylene bisoleic acid amide. The content of the fatty acid amide and / or fatty acid bisamide is preferably 0.01% by mass or more and 0.40% by mass or less, and more preferably 0.05% by mass or more and 0.30% by mass or less. A fatty acid amide and / or fatty acid bisamide content of 0.01% by mass or more can impart slipperiness, and a content of 0.40% by mass or less can maintain wettability.

[0031] To improve the slip property, a polyamide resin such as polyamide MXD6 resin, polyamide 12 resin, polyamide 66 resin, polyamide 6.12 copolymer resin, or polyamide 6.66 copolymer resin may be added to layer B.

[0032] <Antioxidant> An antioxidant can be contained in Layer A and Layer B of the biaxially stretched polyamide film of the present invention. Phenol-based antioxidants are preferred. The phenol-based antioxidant is preferably a fully hindered phenolic compound or a partially hindered phenolic compound. Examples of the phenol-based antioxidant include tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, stearyl-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane. The inclusion of a phenol-based antioxidant improves the film-forming operability of the biaxially stretched polyamide film. In particular, when recycled films are used as raw materials, the resin is prone to thermal degradation, which can lead to operational problems in film production and increased production costs. In contrast, the inclusion of an antioxidant suppresses thermal degradation of the resin and improves operational efficiency.

[0033] The base layer in the present invention is a biaxially stretched polyamide film in which Layer B is laminated on at least one side of Layer A. Specific examples of the structure include a two-layer structure of Layer A / Layer B and a three-layer structure of Layer B / Layer A / Layer B.

[0034] The thickness of the base material layer is not particularly limited, but when used as a packaging material, it is usually preferably 100 μm or less, and may be 5 μm or more and 50 μm or less, or may be 8 μm or more and 30 μm or less.

[0035] The biaxially stretched polyamide film of the base layer preferably has a heat shrinkage rate of 0.6% or more and 3.0% or less in both the MD and TD directions at 160°C for 10 minutes, more preferably 0.6% or more and 2.5% or less. If the heat shrinkage rate exceeds 3.0%, curling or shrinkage may occur when heat is applied in subsequent processes such as lamination or printing. Furthermore, the lamination strength with the sealant film may be weakened. Although it is possible to reduce the heat shrinkage rate to less than 0.6%, the film may become mechanically fragile and productivity may be further reduced.

[0036] The impact strength of the biaxially stretched polyamide film is preferably 0.7 J / 15 μm or more, more preferably 0.9 J / 15 μm or more.

[0037] The haze value of the biaxially stretched polyamide film is preferably 10% or less, more preferably 7% or less, and even more preferably 5% or less. A small haze value provides transparency and gloss, making it particularly suitable for packaging bags. Since the addition of fine particles to improve the slipperiness of the film increases the haze value, when the film has two or more layers, it is preferable to add fine particles only to layer B, as this reduces the haze value.

[0038] The dynamic friction coefficient of the biaxially stretched polyamide film is preferably 1.0 or less, more preferably 0.7 or less, and even more preferably 0.5 or less. A small dynamic friction coefficient of the film improves the slipperiness and makes the film easier to handle. If the dynamic friction coefficient of the film is too small, it may be too slippery and difficult to handle, so the dynamic friction coefficient is preferably 0.15 or more.

[0039] Biaxially oriented polyamide film conforms to ASTM D6866-18 radiocarbon １４ The content of carbon derived from biomass as determined by C measurement, i.e., the biomass ratio, is preferably 1% or more and 30% or less of the total carbon in the polyamide film. １４ Because it contains a certain percentage of carbon (105.5 pMC), plants that grow by absorbing carbon dioxide from the atmosphere, such as corn, １４ The carbon content is also known to be about 105.5 pMC. １４ It is also known that almost no carbon is contained in the film. １４ By measuring the proportion of C, the proportion of carbon derived from biomass can be calculated.

[0040] [Method for Producing Biaxially Stretched Polyamide Film] The biaxially oriented polyamide film of the substrate layer can be produced by a known production method, and a typical production example will be described below.

[0041] First, the resin composition forming layer A and the resin composition forming layer B are melt-extruded using an extruder, and layers A and B are laminated using a feed block or multi-manifold, extruded into a film form from a T-die, cast onto a cooling roll and cooled to obtain an unstretched film.

[0042] The melting temperature of the resin is preferably 220°C or higher and 350°C or lower. If the melting temperature is lower than the above range, unmelted material may be generated, resulting in defects and other poor appearance. If the melting temperature is higher than the above range, resin deterioration may be observed, resulting in a decrease in molecular weight and a deterioration in appearance. The die temperature is preferably 250°C or higher and 350°C or lower. The chill roll temperature is preferably -30°C or higher and 80°C or lower, and more preferably 0°C or higher and 50°C or lower. To obtain an unstretched film by casting a film-like molten material extruded from a T-die onto a rotating cooling drum and cooling it, methods such as using an air knife or an electrostatic adhesion method in which a static charge is applied can be applied. The latter method is particularly preferred. It is also preferable to cool the surface of the cast unstretched film opposite the chill roll. For example, it is preferable to combine methods such as contacting the surface of the unstretched film opposite the chill roll with a cooling liquid in a tank, applying a liquid that evaporates using a spray nozzle, or spraying a high-speed fluid to cool it.

[0043] The unstretched film thus obtained is stretched biaxially to obtain a biaxially stretched polyamide film. The stretching method may be either simultaneous biaxial stretching or sequential biaxial stretching. In either case, multi-stage stretching such as one-stage stretching or two-stage stretching can be used as the MD stretching method. As will be described later, multi-stage MD stretching such as two-stage stretching is preferred over single-stage stretching in terms of physical properties and uniformity of physical properties in the MD and TD directions, i.e., isotropy. Roll stretching is preferred for MD stretching in the sequential biaxial stretching method.

[0044] The lower limit of the MD stretching temperature is preferably 50°C, more preferably 55°C, and even more preferably 60°C. If the temperature is less than 50°C, the resin does not soften and stretching may become difficult. The upper limit of the MD stretching temperature is preferably 120°C, more preferably 115°C, and even more preferably 110°C. If the temperature exceeds 120°C, the resin may become too soft and stable stretching may not be possible.

[0045] The lower limit of the stretching ratio in the MD direction is preferably 2.2 times, more preferably 2.5 times, and even more preferably 2.8 times. When stretching is performed in multiple stages, the above stretching ratio is the total stretching ratio obtained by multiplying the ratios in each stage. If it is less than 2.2 times, the thickness accuracy in the MD direction may decrease, and the crystallinity may become too low, resulting in a decrease in impact strength. The upper limit of the stretching ratio in the MD direction is preferably 5.0 times, more preferably 4.5 times, and most preferably 4.0 times. If it exceeds 5.0 times, subsequent stretching may become difficult.

[0046] Furthermore, when stretching in the MD direction is performed in multiple stages, the above-mentioned stretching is possible in each stretching, but the stretching ratios must be adjusted so that the product of all stretching ratios in the MD direction is 5.0 or less. For example, in the case of two-stage stretching, it is preferable to perform the first-stage stretching at a ratio of 1.5 to 2.1 times, and the second-stage stretching at a ratio of 1.5 to 1.8 times.

[0047] The film stretched in the MD direction is stretched in the TD direction using a tenter, heat-set, and then relaxed. The lower limit of the stretching temperature in the TD direction is preferably 50°C, more preferably 55°C, and even more preferably 60°C. If the temperature is lower than 50°C, the resin does not soften, and stretching may become difficult. The upper limit of the stretching temperature in the TD direction is preferably 190°C, more preferably 185°C, and even more preferably 180°C. If the temperature exceeds 190°C, crystallization may occur, making stretching difficult.

[0048] The lower limit of the stretching ratio in the TD direction is preferably 2.8 times, more preferably 3.2 times, even more preferably 3.5 times, and particularly preferably 3.8 times. When stretching is performed in multiple stages, the above stretching ratio is the total stretching ratio obtained by multiplying the ratios of each stage. If it is less than 2.8 times, the thickness accuracy in the TD direction may decrease, and the impact strength may decrease due to a decrease in crystallinity. The upper limit of the stretching ratio in the TD direction is preferably 5.5 times, more preferably 5.0 times, even more preferably 4.7 times, particularly preferably 4.5 times, and most preferably 4.3 times. If it exceeds 5.5 times, productivity may decrease.

[0049] The lower limit of the heat setting temperature is preferably 210°C, more preferably 212°C. If the heat setting temperature is too low, the heat shrinkage rate becomes too large, which tends to deteriorate the appearance after lamination or reduce the laminate strength. The upper limit of the heat setting temperature is preferably 220°C, more preferably 218°C. If the heat setting temperature is too high, the impact strength tends to decrease.

[0050] The heat setting time is preferably 0.5 seconds or more and 20 seconds or less, and more preferably 1 second or more and 15 seconds or less. The heat setting time can be set appropriately depending on the heat setting temperature and the wind speed in the heat setting zone. By setting the heat setting conditions within the above range of time, crystallization and orientation relaxation can be achieved in the desired state.

[0051] Relaxation treatment after heat setting is effective in controlling the thermal shrinkage rate. The temperature for the relaxation treatment can be selected within the range from the heat setting temperature to the glass transition temperature Tg of the resin, but is preferably at least "heat setting temperature (°C) - 10°C" and not more than "glass transition temperature (°C) + 10°C." The lower limit of the relaxation rate in the relaxation treatment is preferably 0.5%, more preferably 1%. The upper limit of the relaxation rate is preferably 20%, more preferably 15%, and even more preferably 10%.

[0052] Furthermore, the biaxially stretched polyamide film of the base layer can be subjected to heat treatment or humidity conditioning treatment to improve dimensional stability depending on the application. In addition, to improve the adhesion of the film surface, corona treatment, coating treatment, flame treatment, etc., can be performed, and printing and vapor deposition of metals, inorganic oxides, etc. are also possible. As the vapor deposition film formed by vapor deposition, vapor deposition films of aluminum, silicon oxide, aluminum oxide alone or a mixture thereof are preferably used. Furthermore, by coating a protective layer or the like on these vapor deposition films, oxygen barrier properties, etc. can be improved.

[0053] [Sealant Layer] The sealant layer of the present invention is preferably composed of an unstretched polyolefin film. In a preferred embodiment of the present invention, the unstretched polyolefin film contains 70% by mass or more and 95% by mass or less of a polypropylene-based resin and 5% by mass or more and 30% by mass or less of a linear low-density polypropylene-based resin at least partly derived from biomass.

[0054] The unstretched polyolefin film preferably has a laminated structure, more preferably including a seal layer, a core layer, and a laminate layer. The seal layer and the laminate layer are layers located on the surface side of the unstretched polyolefin film, and the core layer is preferably located between them. The laminate layer is a layer suitable for bonding a biaxially oriented polyamide film, and is preferably laminated to the biaxially oriented polyamide film via an adhesive resin. The seal layer is a layer suitable for producing packaging bags by heat sealing. By adopting the above layer structure, it is possible to incorporate a larger amount of biomass-derived linear low-density polyethylene resin while maintaining the properties of the unstretched polypropylene film, which is a sealant layer with excellent heat resistance.

[0055] <Sealing layer> In the present invention, the polypropylene resin composition constituting the sealing layer preferably contains a propylene-α-olefin random copolymer. The content of the propylene-α-olefin random copolymer in the polypropylene resin composition constituting the sealing layer is preferably 94% by mass or more, more preferably 97% by mass or more, even more preferably 99% by mass or more, and particularly preferably 100% by mass. By making it 94% by mass or more, sufficient heat sealing strength can be obtained.

[0056] In the present invention, the polypropylene-based resin composition constituting the seal layer can contain a propylene homopolymer. The inclusion of the propylene homopolymer can improve slipperiness. From the viewpoint of heat seal strength, the content of the propylene homopolymer is preferably 3% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0% by mass.

[0057] In the present invention, the seal layer may contain linear low-density polyethylene. By including linear low-density polyethylene, pinhole resistance during bending can be improved. From the viewpoint of heat seal strength, the content of linear low-density polyethylene is preferably 3% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0% by mass.

[0058] <Core Layer> In the present invention, the polypropylene resin composition constituting the core layer preferably contains a propylene-α-olefin random copolymer. The inclusion of a propylene-α-olefin random copolymer can improve heat seal strength. From the viewpoint of heat seal strength, the content of the propylene-α-olefin random copolymer is preferably 25% by mass or more, more preferably 40% by mass or more, even more preferably 60% by mass or more, particularly preferably 75% by mass or more, and particularly preferably 80% by mass or more. From the viewpoint of flex pinhole resistance, the content is preferably 97% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

[0059] In the present invention, the polypropylene resin composition constituting the core layer may contain a propylene homopolymer. The content of the propylene homopolymer is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less, from the viewpoints of heat seal strength and bag rupture resistance.

[0060] In the present invention, the core layer may contain linear low-density polyethylene. By including linear low-density polyethylene, pinhole resistance during bending can be improved. The content of linear low-density polyethylene is preferably 3% by mass or more, more preferably 8% by mass or more, even more preferably 12% by mass or more, and particularly preferably 15% by mass or more. From the viewpoint of heat resistance, the content is preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less.

[0061] <Laminate Layer> In the present invention, the polypropylene resin composition constituting the laminate layer preferably contains a propylene-α-olefin random copolymer. The inclusion of the propylene-α-olefin random copolymer can improve heat seal strength. The content of the propylene-α-olefin random copolymer is preferably 20% by mass or more, more preferably 40% by mass or more, and even more preferably 70% by mass or more. From the viewpoint of flex pinhole resistance, the content is preferably 90% by mass or less, more preferably 80% by mass or less.

[0062] In the present invention, the polypropylene resin composition constituting the laminate layer may contain a propylene homopolymer. The content of the propylene homopolymer is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less, from the viewpoints of heat seal strength and bag rupture resistance.

[0063] In the present invention, the laminate layer may contain linear low-density polyethylene. The inclusion of linear low-density polyethylene can improve pinhole resistance during bending. The content of linear low-density polyethylene is preferably 3% by weight or more, more preferably 8% by weight or more, even more preferably 15% by weight or more, particularly preferably 20% by weight or more, and most preferably 25% by weight or more. From the viewpoint of heat resistance and heat seal strength, the content is preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 30% by weight or less.

[0064] In the unstretched polyolefin film of the present invention, the difference in the content of linear low-density polyethylene between the seal layer and the core layer is preferably 1% by mass or more and 28% by mass or less, more preferably 1% by mass or more and 23% by mass or less, even more preferably 1% by mass or more and 18% by mass or less, and particularly preferably 1% by mass or more and 15% by mass or less. By keeping the difference in content at 28% by mass or less, high interlayer strength at the interface between the seal layer and the core layer can be maintained, and high heat seal strength can be obtained.

[0065] In the unstretched polyolefin film of the present invention, the difference in the content of linear low-density polyethylene between the core layer and the laminate layer is preferably 1% by mass or more and 28% by mass or less, more preferably 1% by mass or more and 23% by mass or less, even more preferably 1% by mass or more and 18% by mass or less, and particularly preferably 1% by mass or more and 15% by mass or less. By keeping the difference in content at 28% by mass or less, high interlayer strength at the interface between the core layer and the laminate layer can be maintained, and high heat seal strength can be obtained.

[0066] In the unstretched polyolefin film of the present invention, the content of linear low-density polyethylene in the core layer is preferably greater than that in the seal layer, and the content of linear low-density polyethylene in the laminate layer is preferably greater than that in the core layer. This makes it easier for the linear low-density polyethylene to be uniformly dispersed in the film, which is advantageous in terms of flex pinhole resistance. Furthermore, the high proportion of polypropylene-based resin in the resin near the heat-seal surface allows for high heat-seal strength.

[0067] By using a propylene-α-olefin random copolymer with a low melting point for the seal layer and a propylene-α-olefin random copolymer with a high melting point for the core layer and laminate layer, it is possible to improve the heat seal strength while also improving the heat resistance and flex pinhole resistance.

[0068] <Propylene-α-olefin random copolymer> The propylene-α-olefin random copolymer of the present invention can be a copolymer of propylene and at least one α-olefin other than propylene having from 2 or 4 to 20 carbon atoms. Examples of such an α-olefin monomer having from 2 or 4 to 20 carbon atoms include ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, and octene-1.

[0069] From the viewpoint of heat sealing property, the propylene-α-olefin random copolymer preferably contains ethylene as the α-olefin. At least one type of α-olefin is sufficient, and two or more types can be mixed and used as needed. A particularly preferred copolymer is a propylene-ethylene-butene random copolymer in which the main monomer is propylene and a certain amount of ethylene and butene are copolymerized.

[0070] The lower limit of the melt flow rate MFR of the propylene-α-olefin random copolymer is preferably 0.6 g / 10 min, more preferably 1.0 g / 10 min, and even more preferably 1.2 g / 10 min. The upper limit of the melt flow rate of the random copolymer is preferably 12.0 g / 10 min, more preferably 9.0 g / 10 min, and even more preferably 8.0 g / 10 min.

[0071] <Propylene Homopolymer> The melt flow rate (MFR) (measured at 230°C under a load of 2.16 kg) of the propylene homopolymer is not particularly limited, but is preferably 1.0 g / 10 min or more and 10.0 g / 10 min or less, and more preferably 2.0 g / min or more and 8.0 g / min or less. If it is less than 1.0 g / 10 min, the viscosity may be too high, making extrusion through a T-die difficult. Conversely, if it exceeds 10.0 g / 10 min, problems such as stickiness of the film and poor impact strength (impact strength) of the film may occur. As the propylene homopolymer, isotactic polypropylene is preferred, which has high crystallinity and suppresses deterioration of the heat shrinkage rate.

[0072] <Linear Low-Density Polyethylene> Linear low-density polyethylene can be produced by a production method such as a high-pressure method, a solution method, or a gas-phase method. Examples of linear low-density polyethylene include copolymers of ethylene and at least one α-olefin having 3 or more carbon atoms. Examples of the α-olefin having 3 or more carbon atoms include propylene, butene-1, hexene-1, octene-1, and 4-methyl-1-pentene. Examples of copolymers of ethylene and an α-olefin include ethylene-hexene-1 copolymer, ethylene-butene-1 copolymer, and ethylene-octene-1 copolymer, with ethylene-hexene copolymer being preferred from the viewpoint of flex pinhole resistance.

[0073] The linear low-density polyethylene may include biomass-derived linear low-density polyethylene polymerized using ethylene derived from plants such as sugarcane and ethylene derived from fossil fuels such as petroleum or plants as part of the raw materials. Biomass-derived linear low-density polyethylene is said to be effective in reducing carbon dioxide emissions and suppressing global warming from the viewpoint of carbon neutrality. When the biomass-derived linear low-density polyethylene contains biomass-derived ethylene, the content of biomass-derived ethylene is preferably 50% by mass or more, more preferably 80% by mass or more. A content of 50% by mass or more provides a good carbon dioxide reduction effect. The upper limit is preferably 98% by mass, more preferably 96% by mass. Since copolymerization of an α-olefin other than ethylene is preferred from the viewpoint of flex pinhole resistance, 98% by mass or less is preferred.

[0074] The lower limit of the melt flow rate MFR (measured at 190°C and 2.18 kg) of the linear low-density polyethylene is preferably 1.0 g / 10 min, more preferably 2.0 g / 10 min. The upper limit is preferably 7.0 g / min, more preferably 5.0 g / min. By setting the MFR within the above range, compatibility with polypropylene-based resins is good and high seal strength can be obtained.

[0075] The lower limit of the density of the linear low-density polyethylene is preferably 910 kg / m ３ and more preferably 913 kg / m ３910 kg / m ３ By setting the value to 935 kg / m or more, good blocking resistance can be obtained. ３ and more preferably 930 kg / m ３ 935 kg / m ３ When the thickness is equal to or less than 100 mm, good resistance to bag breakage can be obtained.

[0076] <Additives> The unstretched polyolefin film may contain an appropriate amount of an antiblocking agent, an antioxidant, an antistatic agent, an antifogging agent, a neutralizing agent, a nucleating agent, a colorant, other additives, an inorganic filler, etc. in any layer as needed, within the scope of not impairing the object of the present invention.

[0077] The polyolefin resin composition constituting the unstretched polyolefin film may contain an antiblocking agent. While one type of antiblocking agent may be used, blending two or more types of inorganic particles with different particle sizes and shapes will result in the formation of complex protrusions even on the unevenness of the film surface, thereby achieving a more advanced antiblocking effect. The antiblocking agent to be added is not particularly limited, but inorganic particles such as spherical silica, amorphous silica, zeolite, talc, mica, alumina, hydrotalcite, and aluminum borate, as well as organic particles such as polymethyl methacrylate and ultra-high molecular weight polyethylene, can be added.

[0078] The antiblocking agent contained in the polypropylene resin composition constituting the sealing layer is preferably 0.30% by mass or less, more preferably 0.25% by mass or less, relative to the polyolefin resin of the layer to which it is added. By setting it to 0.30% by mass or less, it is possible to reduce the detachment of the antiblocking agent. Furthermore, it is preferably 0.05% by mass or more, more preferably 0.10% by mass or more. By setting it to 0.05% by mass or more, good antiblocking properties can be obtained.

[0079] The antiblocking agent contained in the polypropylene resin composition constituting the laminate layer is preferably added in an amount of 0.30% by mass or less, more preferably 0.25% by mass or less, even more preferably 0.10% by mass or less, and particularly preferably 0.05% by mass or less, based on the polyolefin resin of the layer to which it is added. By adding an amount of 0.30% by mass or less, it is possible to reduce the shedding of the antiblocking agent on the surface of the laminate layer.

[0080] The polyolefin resin composition constituting the unstretched polyolefin film may contain an organic lubricant. The inclusion of an organic lubricant improves the film's lubricity and anti-blocking effect, improving the film's handleability. This is believed to be due to the organic lubricant bleeding out and its presence on the film surface, thereby exhibiting its lubricating and release effects. Organic lubricants preferably have a melting point above room temperature. Examples of organic lubricants include fatty acid amides and fatty acid esters. Specific examples include oleic acid amide, erucic acid amide, behenic acid amide, ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, and ethylene bisoleic acid amide. While these may be used alone, combining two or more types is preferred, as this maintains the lubrication and anti-blocking effects even in harsh environments. The content of the organic lubricant in the polypropylene resin composition is preferably 0.15% by mass or less, more preferably 0.10% by mass or less. By keeping the content at 0.15% by mass or less, blocking is less likely to occur even when the film is stored in a location exposed to high temperatures, such as a warehouse in summer. The content is preferably 0.02% by mass or more, and more preferably 0.025% by mass or more. By setting the content to 0.02% by mass or more, good slip properties can be obtained.

[0081] The polyolefin resin composition constituting the unstretched polyolefin film may contain an antioxidant. Examples of the antioxidant include phenolic antioxidants, phosphite antioxidants, a combination of these, and antioxidants having both phenolic and phosphite skeletons in one molecule. Examples of the neutralizing agent include calcium stearate.

[0082] [Unstretched Polyolefin Film] The lower limit of the thickness of the unstretched polyolefin film of the sealant layer is preferably 15 μm, more preferably 20 μm, and even more preferably 25 μm. If it is 15 μm or more, heat seal strength and bag rupture resistance are easily obtained. The upper limit of the film thickness is preferably 80 μm, more preferably 70 μm, even more preferably 60 μm, and particularly preferably 50 μm. If it is 80 μm or less, the film has a moderate stiffness and is easy to process, making it suitable for producing packaging bags.

[0083] The haze value of the unstretched polyolefin film is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. When it is 20% or less, visibility of the package is easily obtained. Linear low-density polyethylene is highly crystalline and tends to increase haze, but if it is added within the above preferred range, the increase in haze can be suppressed. The lower limit is preferably 1%, more preferably 2%. When it is 1% or more, the film surface is not extremely uneven, so blocking of the inner surface of the package is unlikely to occur.

[0084] The static friction coefficient of the unstretched polyolefin film is preferably 0.70 or less, more preferably 0.50 or less, and even more preferably 0.40 or less. If it is 0.70 or less, the opposite surfaces will slide easily when filling the package with food or when opening it, making it easy to open. The lower limit is preferably 0.10 or more, more preferably 0.20 or more, and particularly preferably 0.30 or more. If it is 0.10 or more, the rolled film will not easily collapse when transported.

[0085] The impact strength of the unstretched polyolefin film is preferably 0.20 J / 15 μm or more, more preferably 0.25 J / 15 μm or more, and even more preferably 0.30 J / 15 μm or more. By making it 0.20 J / 15 μm or more, the drop-breakage resistance of the package can be improved. The upper limit of the impact strength is not particularly limited, but is preferably 1.0 J / 15 μm or less. The impact strength is largely dependent on the thickness and molecular orientation of the film. Furthermore, impact strength and drop-breakage resistance do not necessarily correlate.

[0086] The pin puncture strength of the unstretched polyolefin film is preferably 1.0 N / μm or more, more preferably 1.5 N / μm or more, and even more preferably 1.7 N / μm or more. When it is 1.0 N / μm or more, the pinhole resistance of the laminate is good.

[0087] The planar orientation coefficient of the unstretched polyolefin film is preferably 0.000 or more, more preferably 0.001 or more. The upper limit of the planar orientation of the film is preferably 0.010 or less, more preferably 0.008 or less, and even more preferably 0.006 or less. By setting it to 0.010 or less, a film with a uniform thickness can be obtained.

[0088] The heat-sealing initiation temperature of the unstretched polyolefin film is preferably 110°C or higher, more preferably 120°C or higher. At 110°C or higher, the film has a stiff feel and is easy to handle. The upper limit of the heat-sealing initiation temperature is 150°C, more preferably 140°C, and even more preferably 130°C. At 150°C or lower, packages can be produced at high speed, which is economically advantageous. The heat-sealing initiation temperature is greatly affected by the melting point of the seal layer.

[0089] The wet tension of the surface of the unstretched polyolefin film is preferably 30 mN / m or more, more preferably 35 mN / m or more. If it is 30 mN / m or more, the laminate strength is less likely to decrease. The upper limit of the wet tension is preferably 55 mN / m, more preferably 50 mN / m. If it is 55 mN / m or less, blocking between films is less likely to occur when the polyolefin resin film is wound around a roll.

[0090] Unstretched polyolefin film is radiocarbon resistant to ASTM D6866-18. １４ The content of biomass-derived carbon as determined by C measurement, i.e., the biomass ratio, is preferably 3% or more and 30% or less of the total carbon in the unstretched polyolefin film.

[0091] [Method for producing unstretched polyolefin film] The unstretched polyolefin film of the present invention can be produced by, for example, an inflation method or a T-die method, but the T-die method is preferred in order to improve transparency. The inflation method uses air as a cooling medium, while the T-die method uses a cooling roll, making it an advantageous production method for increasing the cooling rate. By increasing the cooling rate, crystallization of the unstretched sheet can be suppressed, which is advantageous in terms of transparency. For these reasons, the T-die method is preferred for producing a non-oriented sheet.

[0092] A typical production example is described below. The raw materials of the polypropylene resin compositions for the seal layer, core layer, and laminate layer are mixed and melt-mixed and extruded in separate extruders. The molten laminated sheet of the seal layer, core layer, and laminate layer is cast from a T-die onto a chill roll to obtain a non-oriented sheet. The lower limit of the chill roll temperature is preferably 15°C, more preferably 20°C. If the temperature is lower than this, condensation may occur on the chill roll, resulting in insufficient adhesion. The upper limit of the chill roll temperature is preferably 60°C, more preferably 50°C. If the temperature exceeds this range, transparency may deteriorate.

[0093] [Laminated Film] The laminated film of the present invention has a substrate layer and a sealant layer, but the laminated film can also be constructed by interposing an adhesive layer, a printed layer, a metal layer, etc. between the substrate layer and the sealant layer. Known lamination methods such as dry lamination and extrusion lamination can be used as the lamination method, but any lamination method may be used. Specific examples are shown below.

[0094] Examples of layer structures of the laminated film of the present invention are: ONY / adhesive / CPP, ONY / adhesive / Al / adhesive / CPP, PET / adhesive / ONY / adhesive / CPP, PET / adhesive / ONY / adhesive / Al / adhesive / CPP, PET / adhesive / Al / adhesive / ONY / adhesive / CPP, ONY / adhesive / PET / adhesive / CPP, ONY / PE / CPP, ONY / adhesive / EVOH / adhesive / CPP, ONY / adhesive / aluminum-deposited PET / adhesive / CPP, CPP / adhesive / ONY / adhesive / LLDPE, ONY / adhesive / aluminum-deposited CPP. The abbreviations used in the above layer structures are as follows: / : indicates the boundary of layers ONY: biaxially oriented polyamide film PET: oriented polyethylene terephthalate film LLDPE: linear low-density polyethylene film CPP: unoriented polypropylene film PE: extrusion laminate or unoriented low-density polyethylene film Al: aluminum foil EVOH: ethylene-vinyl alcohol copolymer resin Adhesive: adhesive layer that bonds films together Aluminum vapor deposition: indicates that aluminum is vapor-deposited

[0095] [Properties of Laminated Film] The flex resistance of the laminated film of the present invention can be measured by pinhole evaluation. The number of pinholes after bending the laminated film 1000 times at 1°C is preferably 20 or less, more preferably 15 or less, and particularly preferably 10 or less. If the number is 20 or less, pinholes are less likely to occur due to bending impact during transportation of the packaging bag.

[0096] The puncture strength of the laminated film of the present invention is preferably 10 N or more, more preferably 12 N or more, and even more preferably 14 N or more. If the puncture strength is 10 N or more, pinholes are unlikely to occur when the protrusions come into contact with the packaging material.

[0097] The heat seal strength of the laminated film of the present invention is preferably 20 N / 15 mm or more, more preferably 25 N / 15 mm or more, and even more preferably 30 N / 15 mm or more. When it is 20 N / 15 mm or more, bag rupture resistance is easily obtained. When the heat seal strength is 60 N / 15 mm, it is very excellent, and when it is 35 N / 15 mm, it is sufficient.

[0098] The laminated film of the present invention is radiocarbon compliant according to ASTM D6866-18. １４ The content of carbon derived from biomass as determined by C measurement, i.e., the biomass ratio, is preferably 2% or more and 30% or less of the total carbon in the laminated film.

[0099] [Packaging Bag] In a preferred embodiment, the laminate film of the present invention is processed into a packaging bag intended to protect contents, such as food and beverages, from natural dust, gases, and the like. The packaging bag is produced by bonding the inner surfaces of the laminate film together using a heated heat seal bar or ultrasonic waves to form a bag. For example, two rectangular laminates are stacked with the sealant layer side facing inward, and the four edges are heat-sealed to form a four-side sealed bag. The laminate film of the present invention can be processed into packaging bags such as bottom-sealed bags, side-sealed bags, three-side sealed bags, pillow bags, stand-up pouches, gusseted bags, and square-bottom bags.

[0100] The drop-break resistance of the package of the present invention is preferably 15 times or more, more preferably 20 times or more, and even more preferably 22 times or more. If it is 15 times or more, the package containing food is less likely to break even when dropped. A drop-break resistance of about 30 times is sufficient. The drop-break resistance of the package is affected by the flex pinhole resistance, puncture strength, and heat seal strength of the laminate, and it is best to set these properties within preferred ranges.

[0101] The film was evaluated by the following measurement methods. Unless otherwise specified, the measurements were carried out in a measurement room at an environment of 23° C. and a relative humidity of 65%.

[0102] (1) Film Thickness The obtained film was cut into 100 mm lengths in the longitudinal direction, and conditioned for at least 2 hours in an environment at a temperature of 23°C and a relative humidity of 65%. The film was then divided into 10 equal sections in the width direction (for narrow films, the sections were divided to ensure a width that allowed thickness measurement), and the thickness was measured using a thickness measuring device manufactured by Tester Sangyo Co., Ltd. The average value was divided by the number of films stacked, and the film thickness was determined as the film thickness. The thickness of Layer A in the biaxially stretched polyamide film was calculated based on the ratio of the resin extrusion amounts of Layer A and Layer B.

[0103] (2) Haze Value The haze value of the film was measured using a direct reading haze meter manufactured by Toyo Seiki Seisakusho Co., Ltd. in accordance with JIS K7105.

[0104] (3) Biomass Degree The biomass degree of the film was determined by the radiocarbon method shown in ASTM D6866-18 Method B (AMS). １４ C measurement.

[0105] (4) Heat Shrinkage Ratio The heat shrinkage ratio of the film was measured in both the MD and TD directions using the following formula in accordance with the dimensional change test method described in JIS C2318, except that the test temperature was 160°C and the heating time was 10 minutes: Heat shrinkage ratio = [(length before treatment - length after treatment) / length before treatment] x 100 (%)

[0106] (5) Impact Strength The impact strength of the film was measured using a film impact tester manufactured by Toyo Seiki Seisakusho, Ltd. The measured value was converted to a value per 15 μm thickness and expressed in units of J / 15 μm.

[0107] (6) Planar Orientation Degree A sample was taken from the center position in the width direction of the film. The refractive index (nx) in the MD direction of the film and the refractive index (ny) in the TD direction of the sample were measured using an Abbe refractometer with sodium D line as a light source according to JIS K 7142-1996 Method A, and the planar orientation degree was calculated using the formula (1). Formula (1): Planar orientation degree (ΔP) = (nx + ny) / 2 - nz

[0108] (7) Puncture Strength The puncture strength of the film was measured in accordance with "2. Test Method for Strength, etc." in "Specifications and Standards for Foods, Food Additives, etc., Part 3: Apparatus and Containers / Packaging" (Ministry of Health and Welfare Notification No. 20, 1982) under the Food Sanitation Act. A needle with a tip diameter of 0.7 mm was pierced into the film at a puncture speed of 50 mm / min, and the strength at which the needle penetrated the film was measured, and the puncture strength was expressed in units of N. When the puncture strength is expressed in units of N / μm, the puncture strength was calculated by dividing the puncture strength of the film in units of N by the thickness of the film in units of μm.

[0109] (8) Wet Tension The wet tension of the film surface was measured in accordance with JIS-K6768 Plastics - Films and Sheets - Wet Tension Test Method.

[0110] (9) Heat-sealing initiation temperature The heat-sealing initiation temperature of unstretched polyolefin film was measured in accordance with JIS Z 1713-2009. The film was cut into rectangular test pieces measuring 50 mm in the TD direction and 250 mm in the MD direction. The seal layer portions of two test pieces were overlapped, and a thermal gradient tester (heat-sealing tester) manufactured by Toyo Seiki Seisakusho Co., Ltd. was used. The heat-sealing pressure was 0.2 MPa and the heat-sealing time was 1.0 sec. The test pieces were then heat-sealed under conditions of increasing temperature at 5°C increments. After heat-sealing, test pieces were cut into 15 mm widths. The heat-sealed test pieces were opened 180°, and the unsealed portion was clamped with a zipper and the sealed portion was peeled off. The temperature at which the heat-sealing strength reached 4.9 N was then determined. The tester used was a universal material testing machine 5965 manufactured by Instron Instruments. The test speed was 200 mm / min. Measurement was carried out with N=5, and the average value was calculated.

[0111] (10) Heat Seal Strength The heat seal strength was measured in accordance with JIS Z1707. The specific procedure is as follows: Two laminated films were used with a heat sealer to bond the seal layers of unstretched polyolefin films together. The heat sealing conditions were an upper bar temperature of 120°C, a lower bar temperature of 30°C, a pressure of 0.2 MPa, and a time of 2 seconds. The adhesive sample was cut out to have a seal width of 15 mm. The peel strength was measured at a tensile speed of 200 mm / min using a tensile tester "AGS-KNX" (manufactured by Shimadzu Corporation). The peel strength is expressed as the strength per 15 mm: unit N / 15 mm.

[0112] (11) Bending Pinhole Resistance The laminated film was cut into a length of 280 mm in the MD direction and 260 mm in the TD direction. The film was cut into a cylindrical shape with a diameter of 89 mm and a height of 260 mm, with the unstretched polyolefin film facing inward, and fixed with cellophane tape. The sample was attached to a thermostatically controlled Gelbo Flex Tester manufactured by Tester Sangyo Co., Ltd., and subjected to a bending load of 1,000 times at 1°C. The sample was removed, and the number of pinholes was counted.

[0113] The number of pinholes was measured using the following method. The unstretched polyolefin film was placed on filter paper (No. 50, manufactured by Advantec Co., Ltd.) with the unstretched side facing downwards, and the four corners were fixed with Cellotape (registered trademark). Ink (Pilot ink (product number INK-350-Blue) diluted five times with pure water) was applied to the test film and spread over the entire surface using a rubber roller. After wiping off any unnecessary ink, the test film was removed and the number of ink dots on the filter paper was counted. Measurements were made with N=3, and the average value was calculated.

[0114] (12) Drop-Rupture Resistance Using the laminated film, four-sided sealed bags with internal dimensions of 170 mm length and 120 mm width were prepared, containing 200 ml of saturated saline solution. The heat-sealing conditions were a pressure of 0.2 MPa for 1 second, a seal bar width of 10 mm, and a heat-sealing temperature of 160°C. After bag production, the four-sided sealed bag was cut off, leaving a seal width of 5 mm. The bag was then left in a +5°C environment for 8 hours, and then dropped from a height of 1.2 m onto a flat concrete floor so that the surface was horizontal. The bag was repeatedly dropped until it ruptured, and the number of repeated drops was measured. This test was repeated for 20 samples, and the average value was calculated.

[0115] [Production Example 1] <Preparation of biaxially stretched polyamide film: ONY> (ONY1) Using an apparatus consisting of two extruders and a 380 mm wide co-extrusion T-die, layers were laminated in a B layer / A layer / B layer configuration by the feed block method, and the molten resin was extruded from the T-die into a film, which was then cast onto a cooling roll controlled to a temperature of 20°C and electrostatically adhered to obtain an unstretched film with a thickness of 200 μm.

[0116] The resin compositions of Layer A and Layer B were as follows: Layer A: 97 parts by mass of polyamide 6 (manufactured by Toyobo Co., Ltd., relative viscosity 2.8, melting point 220°C); and 3.0 parts by mass of polyamide 11 (manufactured by Shuseisha Co., Ltd., relative viscosity 2.5, melting point 186°C). Layer B: 95 parts by mass of polyamide 6 (manufactured by Toyobo Co., Ltd., relative viscosity 2.8, melting point 220°C); 5.0 parts by mass of polyamide MXD6 (manufactured by Mitsubishi Gas Chemical Co., Ltd., relative viscosity 2.1, melting point 237°C); 0.54 parts by mass of porous silica fine particles (manufactured by Fuji Silysia Chemical Ltd., average particle size 2.0 μm, pore volume 1.6 ml / g); and 0.15 parts by mass of fatty acid bisamide (ethene bisstearamide, manufactured by Kyoeisha Chemical Co., Ltd.).

[0117] The feed block configuration and the extrusion rate of the extruder were adjusted so that the final total thickness of the biaxially oriented polyamide film would be 15 μm, the thickness of layer A would be 12 μm, and the thicknesses of layers B, which would be placed on both sides of layer A, would each be 1.5 μm.

[0118] The resulting unstretched film was introduced into a roll-type stretching machine, and using the difference in peripheral speed of the rolls, it was stretched 1.73 times in the MD direction at 80°C, and then further stretched 1.85 times at 70°C. Subsequently, this uniaxially stretched film was continuously introduced into a tenter-type stretching machine, preheated at 110°C, and then stretched 1.2 times in the TD direction at 120°C, 1.7 times at 130°C, and 2.0 times at 160°C. It was then heat-set at 218°C, followed by a 7% relaxation treatment at 218°C. The surface to be dry-laminated with the sealant layer was then corona-discharge-treated to obtain a biaxially stretched polyamide film. The evaluation results of the resulting biaxially stretched polyamide film are shown in Table 1.

[0119] (ONY2 to ONY13) Biaxially stretched polyamide films were obtained in the same manner as ONY1, except that the raw material resin compositions of Layer A and Layer B, the heat setting temperature, and other film-forming conditions were changed as shown in Table 1. The evaluation results of the obtained biaxially stretched polyamide films are shown in Table 2. However, in ONY14, the molten resin could not be stably extruded from the T-die into a film shape, and a homogeneous unstretched film could not be obtained, so biaxial stretching was not possible.

[0120] The polyamide resins containing at least a portion of biomass-derived raw materials, polyamide 410, polyamide 610, and polyamide 1010, were as follows: Polyamide 410: (ECOPaXX Q150-E, manufactured by DSM, melting point 250°C) Polyamide 610: (RilsanS SMNO, manufactured by Arkema, melting point 222°C) Polyamide 1010: (RilsanT TMNO, manufactured by Arkema, melting point 202°C)

[0121]

[0122]

[0123]

[0124] [Production Example 2] <Preparation of Unstretched Polyolefin Film: CPP> (CPP1) Raw materials were prepared based on the resin composition and proportions of each layer shown in Table 2. The preparations for each layer shown in Table 2 were taken as 100 parts by weight. To the sealing layer, 360 ppm of behenic acid amide was added as an organic lubricant, and 2000 ppm of silica with an average particle size of 4 μm was added as a masterbatch. To the core layer, 2700 ppm of behenic acid amide was added as an organic lubricant.

[0125] (Raw materials used in the sealing layer) PP-1: Propylene-ethylene-butene random copolymer FL6745A (MFR 6.0 g / 10 min, melting point 130°C) manufactured by Sumitomo Chemical Co., Ltd. LL-1: Ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g / min, density 916 kg / m) manufactured by Braskem ３ , melting point 126°C) Silica particles: amorphous silica KMP130-4 (average particle size 4 μm) manufactured by Shin-Etsu Chemical Co., Ltd. Organic lubricant: behenic acid amide BNT-22H manufactured by Nippon Fine Chemical Co., Ltd.

[0126] (Raw materials used in the core layer) PP-2: propylene-ethylene-butene random copolymer FL8115A (MFR 7.0 g / 10 min, melting point 148°C) manufactured by Sumitomo Chemical Co., Ltd. PP-3: propylene homopolymer FLX80E4 (MFR 7.5 g / 10 min, melting point 164°C) manufactured by Sumitomo Chemical Co., Ltd. LL-1: ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g / min, density 916 kg / m) manufactured by Braskem ３ , melting point 126°C) LL-2: Ethylene-hexene copolymer (fossil fuel-derived linear low-density polyethylene) FV405 (MFR 4.0 g / min, density 923 kg / m) manufactured by Sumitomo Chemical Co., Ltd. ３ , melting point 118°C) LDPE-1: Ethylene-hexene copolymer (plant-derived low-density polyethylene) SLH818 (MFR 8.1 g / min, density 918 kg / m) manufactured by Braskem ３ ) Organic lubricant: Behenic acid amide BNT-22H manufactured by Nippon Fine Chemical Co., Ltd.

[0127] (Raw materials used in the laminate layer) PP-2: Propylene-ethylene-butene random copolymer FL8115A (MFR 7.0 g / 10 min, melting point 148°C) manufactured by Sumitomo Chemical Co., Ltd. PP-3: Propylene homopolymer FLX80E4 (MFR 7.5 g / 10 min, melting point 164°C) manufactured by Sumitomo Chemical Co., Ltd. LL-1: Ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g / min, density 916 kg / m) manufactured by Braskem ３ , melting point 126°C) LL-2: Ethylene-hexene copolymer (fossil fuel-derived linear low-density polyethylene) FV405 (MFR 4.0 g / min, density 923 kg / m) manufactured by Sumitomo Chemical Co., Ltd. ３ , melting point 118°C) LDPE-1: Ethylene-hexene copolymer (plant-derived low-density polyethylene) SLH818 (MFR 8.1 g / min, density 918 kg / m) manufactured by Braskem ３ These raw materials were mixed uniformly in the proportions shown in Table 2 to obtain a mixed raw material for producing an unstretched polyolefin film.

[0128] The mixed raw materials for the core layer were extruded in a three-stage single-screw extruder with a screw diameter of 90 mm, and the mixed raw materials for the seal layer and laminate layer were extruded in three-stage single-screw extruders with diameters of 65 mm and 45 mm, respectively, in the order of seal layer / core layer / laminate layer, and extruded using a T-slot die at an outlet temperature of 230° C. The thickness ratios of the seal layer / core layer / laminate layer were 25% / 50% / 25%, respectively.

[0129] The molten resin sheet emerging from the die was cooled on a cooling roll at 35°C to obtain an unstretched polyolefin film having a thickness of 30 μm. During cooling on the cooling roll, both ends of the film on the cooling roll were fixed with air nozzles, and the entire width of the molten resin sheet was pressed against the cooling roll with an air knife. At the same time, a vacuum chamber was activated to prevent air entrapment between the molten resin sheet and the cooling roll. Both ends of the air nozzle were installed in series in the direction of film travel. The die was surrounded by a sheet to prevent wind from hitting the molten resin sheet. The direction of the suction port of the vacuum chamber was aligned with the direction of travel of the extruded sheet.

[0130] The surface of the film laminate layer was subjected to corona treatment (power density 20 W min / m ２ The film was formed at a film forming speed of 20 m / min. The edge portions of the formed film were trimmed and the film was wound into a roll.

[0131] (CPP2 to CPP14) For CPP1, the raw materials shown in Table 2 were used and an unstretched polyolefin film having the thickness shown in Table 2 was obtained in the same manner. However, for CPP12, the raw materials shown in Table 2 were used and an extruder for the core layer only was used and an unstretched polyolefin film having a single layer thickness of 30 μm was obtained in the same manner. The evaluation results of the films CPP1 to CPP14 are shown in Table 2.

[0132]

[0133]

[0134]

[0135] [Examples and Comparative Examples] <Preparation of Laminated Films> The biaxially oriented polyamide films and unstretched polyolefin films obtained in Production Examples 1 and 2 were dry-laminated using an ester-based adhesive applied to the biaxially oriented polyamide film at a coating weight of 3.0 g / m2. The ester-based adhesive was obtained by mixing 33.6 parts by weight of a base agent (TM569, manufactured by Toyo-Morton Co., Ltd.), 4.0 parts by weight of a curing agent (CAT10L, manufactured by Toyo-Morton Co., Ltd.), and 62.4 parts by weight of ethyl acetate. The film was wound up and kept at 40°C for 3 days, after which the laminated film was evaluated. Laminated films were prepared using the combinations of biaxially oriented polyamide films and unstretched polyolefin films shown in Table 3 and evaluated. The results are shown in Table 3.

[0136]

[0137] As shown in Table 3, the laminated films of the Examples had good heat seal strength, pinhole resistance due to bending, and resistance to bag breakage due to dropping, even when the biomass content was increased.

[0138] On the other hand, the laminated films using biaxially oriented polyamide films containing no material for improving pinhole resistance in Comparative Examples 1 and 2 and the biaxially oriented polyamide film containing too little polyamide 11 in Comparative Example 3 exhibited poor pinhole resistance. In Comparative Example 4, the thickness and thickness ratio of Layer A were small, resulting in poor pinhole resistance. In Comparative Example 5, the amount of polyamide MXD6 in Layer B was high and the amount of polyamide 6 resin was low, resulting in poor pinhole resistance. In Comparative Example 6, linear low-density polyethylene was not added to the core layer or laminate layer, resulting in poor pinhole resistance. In Comparative Examples 7 and 8, the difference in linear low-density polyethylene content between the seal layer and the core layer was large, resulting in poor heat seal strength. In Comparative Example 9, the heat seal strength was poor due to the high content of linear low-density polyethylene in the seal layer. In Comparative Example 10, the linear low-density polyethylene was contained in a large amount throughout the entire film, resulting in a large amount near the surface of the film, and the heat seal strength was poor. In Comparative Example 11, the core layer contained linear low-density polyethylene, but the laminate layer did not contain linear low-density polyethylene, resulting in poor flex pinhole resistance. In Comparative Example 12, high-pressure low-density polyethylene (LDPE) was added as the polyethylene, resulting in poor heat seal strength.

Claims

1. A laminated film having at least a base layer and a sealant layer, the base layer is a biaxially oriented polyamide film, the biaxially oriented polyamide film has a B layer laminated on at least one surface of an A layer, the A layer contains 70% by mass or more and 99% by mass or less of a polyamide 6 resin having ε-caprolactam derived from a fossil fuel as a lactam unit, and 1% by mass or more and 30% by mass or less of a polyamide resin containing a biomass-derived raw material, and the B layer contains 70% by mass or more and 100% by mass or less of a polyamide 6 resin having ε-caprolactam derived from a fossil fuel as a lactam unit, The sealant layer is an unstretched polyolefin film, and the unstretched polyolefin film is a laminated film containing 70% by mass or more and 95% by mass or less of a polypropylene-based resin and 5% by mass or more and 30% by mass or less of a linear low-density polyethylene resin, at least a part of which is derived from biomass as a raw material.

2. The laminated film according to claim 1 , wherein the sealant layer is laminated on the layer B side of the base layer.

3. 2. The laminate film according to claim 1, wherein the content of carbon-14 in the substrate layer is 1% or more and 30% or less of the total carbon in the substrate layer.

4. 2. The laminate film according to claim 1, wherein the polyamide resin in the base layer, at least a part of which is derived from biomass, is at least one polyamide resin selected from the group consisting of polyamide 11, polyamide 410, polyamide 610, and polyamide 1010.

5. 2. The laminated film according to claim 1, wherein the content of carbon-14 in the sealant layer is 3% or more and 30% or less of the total carbon in the sealant layer.

6. the sealant layer comprises a seal layer, a core layer and a laminate layer; The resin composition constituting the seal layer contains 94% by mass or more and 100% by mass or less of a propylene-α-olefin random copolymer and 0% by mass or more and 3% by mass or less of a linear low-density polyethylene, the resin composition constituting the core layer contains 25% by mass or more and 97% by mass or less of a propylene-α-olefin random copolymer and 3% by mass or more and 40% by mass or less of a linear low-density polyethylene, the resin composition constituting the laminate layer contains 25% by mass or more and 70% by mass or less of a propylene-α-olefin random copolymer and 3% by mass or more and 50% by mass or less of a linear low-density polyethylene; The laminate film according to claim 1 , wherein the sealant layer includes a laminate layer, a core layer, and a seal layer in this order from the surface in contact with the base layer.

7. 2. The laminate film according to claim 1, wherein the carbon-14 content in the laminate film is 2% or more and 30% or less of the total carbon in the laminate film.

8. A packaging bag using the laminated film according to any one of claims 1 to 7.