Polyamide resin film and packaging material

Abstract

To provide a polyamide-based resin film which is excellent in impact resistance, transparency and oxygen gas barrier property.SOLUTION: A polyamide-based resin film has at least one or more layers of a layer (A) containing an aliphatic polyamide resin (a) as a main component, a layer (B) containing the aliphatic polyamide resin (a), and an aromatic polyamide resin (b) and / or a thermoplastic elastomer, and a layer (C) containing the aromatic polyamide resin (b) and a polyamide-based elastomer (e) having a molecular structure of polyamide 11 as a hard segment, wherein the layer (A), the layer (B) and the layer (C) are arranged in this order, and when the total of the resins constituting the layer (C) is 100 mass%, 1.0 mass% or more and 20.0 mass% or less of the polyamide-based elastomer (e) is contained.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyamide resin film and a packaging product using the film. [Background technology]

[0002] Polyamide resins are resin materials that are used in a variety of applications due to their excellent mechanical properties such as impact resistance and strength, heat resistance, and moldability such as biaxial orientation. Furthermore, although polyamide resins have superior gas barrier properties against oxygen and other gases compared to general-purpose plastics such as polyolefin resins, they are known to have insufficient gas barrier properties to meet the level required for long-term storage of contents such as food and pharmaceutical packaging. Therefore, polyamide resin films that combine mechanical properties, moldability, gas barrier properties, etc., by multi-layering them with layers of resins with high gas barrier properties, such as saponified ethylene-vinyl acetate copolymer (EVOH) and metaxylylenediadipamide (MXD6 nylon), have become widely used.

[0003] On the other hand, layers made of saponified ethylene-vinyl acetate copolymers or metaxylylenediadipamide have high gas barrier properties but are highly rigid and lack flexibility, so in order to meet the flexibility and toughness required of polyamide resin films, techniques have been developed to mix polyamide elastomers into the layers (e.g., Patent Documents 1 to 3). Among these, polyamide elastomers, copolymers (PA12-PTMG) primarily composed of polylauryllactam and polyoxytetramethylene glycol, have been used from the perspective of improving flex pinhole resistance.

[0004] However, the crystallization rate of the molecular structure of polyamide 12, which is formed by the ring-opening polycondensation of the hard segment polylauryllactam, in PA12-PTMG is slow, and the spherulite structure tends to become coarse. Therefore, further improvement of the impact resistance of the gas barrier resin layer, and ultimately of the polyamide-based resin film, was a challenge. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 8-224844 [Patent Document 2] Japanese Patent Application Publication No. 11-254615 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-187246 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above circumstances, an object of the present invention is to provide a polyamide resin film that is excellent in impact resistance, transparency, and oxygen gas barrier property. [Means for solving the problem]

[0007] As a result of extensive research into achieving the above object, the present inventors have found that the above-mentioned problems can be solved by the following invention.

[0008] [1] A polyamide-based resin film having at least one layer each of a layer (A) containing an aliphatic polyamide resin (a) as a main component, a layer (B) containing the aliphatic polyamide resin (a) and an aromatic polyamide resin (b) and / or a thermoplastic elastomer, and a layer (C) containing the aromatic polyamide resin (b) and a polyamide-based elastomer (e) having a molecular structure of polyamide 11 as a hard segment, wherein the layers are arranged in the order of layer (A), layer (B), and layer (C), and the polyamide-based elastomer (e) is contained in an amount of 1.0% by mass or more and 20.0% by mass or less when the total amount of resins constituting layer (C) is taken as 100% by mass.

[0009] [2] The polyamide resin film according to [1], wherein the layer (A) or the layer (B) contains the polyamide elastomer (e).

[0010] [3] The polyamide resin film according to [1] or [2], wherein the aliphatic polyamide resin (a) is at least one selected from the group consisting of polyamide 6, polyamide 11, and polyamide 1010.

[0011] [4] The polyamide resin film according to any one of [1] to [3], which is biaxially stretched.

[0012] [5] A packaging body made using the polyamide resin film according to any one of [1] to [4]. [Effects of the Invention]

[0013] According to the present invention, a polyamide resin film having excellent impact resistance, transparency, and oxygen gas barrier properties can be provided. Due to these characteristics, the polyamide resin film of the present invention can be suitably used as packaging for food products, medicines, clothing, industrial parts, etc., including packaging for liquid-filled products such as soups and seasonings. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below. The "polyamide resin film of the present invention" may be referred to as the "film of the present invention." In the present invention, "mainly composed" means that the solid content is 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. Furthermore, when it is written as "X to Y" (X and Y are any numbers), unless otherwise specified, it means "X or more and Y or less," as well as "preferably greater than X" and "preferably smaller than Y."

[0015] <Layer(A)> The polyamide resin film of the present invention has at least one layer (A) containing an aliphatic polyamide resin (a) as a main component. The layer (A) may be a single layer or multiple layers. In the case of multiple layers, the resin compositions of the layers (A) may be different. (Aliphatic polyamide resin (a)) The aliphatic polyamide resin (a) used in layer (A) refers to a polyamide resin produced by ring-opening polymerization of various known lactams, or a polyamide resin produced by condensation polymerization of known aliphatic diamines and aliphatic dicarboxylic acids, such as polyamide 4, polyamide 6, polyamide 7, polyamide 11, polyamide 12, polyamide 46, polyamide 410, polyamide 510, polyamide 66, polyamide 69, polyamide 610, polyamide 611, polyamide 6 / 66, polyamide 6 / 610, polyamide 6 / 611, polyamide 612, polyamide 6 / 612, polyamide 810, polyamide 910, polyamide 1010, and polyamide 1012.

[0016] Among these, polyamide 6, polyamide 66, and polyamide 6 / 66 are preferred, with polyamide 6 being more preferred, from the standpoint of film-forming properties and versatility. Furthermore, from the viewpoint of reducing the environmental burden, resins having the molecular structure of polyamide or polyamide 11 containing biomass-derived diamine having 10 carbon atoms and / or dicarboxylic acid having 10 carbon atoms are preferred, with polyamide 11, polyamide 410, polyamide 510, polyamide 610, polyamide 810, polyamide 910, polyamide 1010, and polyamide 1012 being preferred. Of these, polyamide 11 and polyamide 1010 are more preferred because they both have a bio-based carbon content close to 100% and have higher impact resistance and lower water absorption than polyamide 6, polyamide 66, etc. These may be used alone or in combination of two or more. Bio-based carbon content is defined in ISO 16620-2 and is the percentage of carbon mass derived from biomass components out of the total carbon mass in a product.

[0017] When a mixture of polyamide 6 and polyamide 11 and / or polyamide 1010 is used as the aliphatic polyamide resin (a), the mixing ratio of polyamide 6 to polyamide 11 and / or polyamide 1010 is preferably 1-99:1-99 (polyamide 6:polyamide 11 and / or polyamide 1010), where the total is 100% by mass, more preferably 50-99:1-50 in terms of improving biaxial stretchability, and more preferably 1-50:50-99 in terms of improving environmental load reduction, impact resistance, and low water absorption. When polyamide 6 is used in combination with polyamide 11 and polyamide 1010, the mixing ratio of polyamide 11 to polyamide 1010 is preferably 10-90:10-90, and more preferably 15-85:15-85, in terms of interlayer adhesion between adjacent layers, where the total of polyamide 11 and polyamide 1010 is 100% by mass. When a mixture of only two types of polyamide 11 and polyamide 1010 is used as the aliphatic polyamide resin (a), the mixing ratio of polyamide 11 to polyamide 1010 is preferably 1-99:1-99, and more preferably 5-95:5-95, in terms of interlayer adhesion with adjacent layers, provided that the total of both is 100% by mass.

[0018] As the polyamide 6, a known resin obtained by ring-opening polymerization of ε-caprolactam can be used. In terms of film formability, the relative viscosity of polyamide 6 measured under the conditions of JIS K6920-2:2009, 96% sulfuric acid, is preferably 1.0 to 5.0, more preferably 2.0 to 4.5, and particularly preferably 2.5 to 4.0. Within this range, stable co-extrusion film formation with layers (B), (C), etc. is facilitated, and flow unevenness due to viscosity differences between layers is reduced, which is preferable. The melting point of polyamide 6 is preferably 200 to 250° C., more preferably 210 to 240° C. If the melting point of polyamide 6 is within this range, it will have excellent heat resistance and extrusion moldability, and will be easy to mold into a biaxially stretched film. The glass transition temperature of polyamide 6 is generally around 50° C., preferably 45 to 60° C. If the glass transition temperature of polyamide 6 is within this range, it has excellent film-forming properties and stretchability, and can be easily molded into a biaxially stretched film.

[0019] Polyamide 11 is obtained by condensation polymerization of 11-aminoundecanoic acid obtained from castor oil, has a bio-based carbon content of nearly 100%, and is compatible with known resins. Polyamide 1010 is obtained by a polycondensation reaction of sebacic acid, which is made from castor oil, and 1,10-decanediamine, which is obtained by amminating sebacic acid. It has a bio-based carbon content of nearly 100%, and known resins can be used. Polyamide 11 and polyamide 1010 have longer hydrocarbon chains than polyamide 6, resulting in a lower concentration of amide bond groups per unit mass and, therefore, lower water absorption. Furthermore, because the concentration of amide bond groups per unit mass is lower than that of polyamide 6, the proportion of hydrogen bonds between polyamide resins during film formation, particularly when biaxially stretched, is reduced, reducing the elasticity of the film and potentially increasing its impact resistance. Therefore, using polyamide 11 and / or polyamide 1010 in layer (A) is effective in reducing the environmental impact of polyamide-based resin films and improving their low water absorption and impact resistance.

[0020] Furthermore, since polyamide 11 and polyamide 1010 have high compatibility with polyamide 6, when polyamide 6 is mixed with polyamide 11 and / or polyamide 1010 as polyamide resin (a), a fine sea / island structure can be designed in the form of an immiscible mixture with polyamide 6. Therefore, it is preferable that void formation at the sea / island phase interface during biaxial stretching is suppressed and a biaxially stretched polyamide-based resin film with excellent transparency can be obtained. From the viewpoint of heat resistance, polyamide 11 and polyamide 1010 preferably have a melting point of 180°C or higher, more preferably 185°C or higher. The glass transition temperature is preferably 30°C to 60°C, more preferably 35°C to 50°C. Furthermore, from the viewpoint of impact resistance of the film, a density of 1100 kg / m 3 Preferably less than 1080 kg / m 3 The following is more preferred:

[0021] The layer (A) may contain an aliphatic polyamide resin (a) as a main component, and may contain other resin components, such as an aromatic polyamide (b) and a thermoplastic elastomer, which will be described later. Examples of thermoplastic elastomers include styrene-based elastomers, vinyl chloride-based elastomers, olefin-based elastomers, polyester-based elastomers, polyamide-based elastomers, urethane-based elastomers, and acid-modified products thereof. Among them, polyamide-based elastomers are preferred because they have high compatibility with the aliphatic polyamide resin (a) and can improve the pinhole resistance of the film and transparency. In particular, polyamide-based elastomers (e) containing the molecular structure of polyamide 11 described below as a hard segment are preferred. The content of the thermoplastic elastomer is preferably from 0 to 50% by mass, and more preferably from 1 to 30% by mass, when the total amount of the resin components constituting the layer (A) is taken as 100% by mass.

[0022] <Layer (B)> The polyamide resin film of the present invention has at least one layer (B) containing an aliphatic polyamide resin (a) and an aromatic polyamide resin (b) and / or a thermoplastic elastomer. The layer (B) may be a single layer or multiple layers. In the case of multiple layers, the resin compositions of the layers (B) may be different. The aliphatic polyamide resin (a) used in layer (B) can be selected from the same types as the aliphatic polyamide resin (a) used in layer (A). From the viewpoints of co-extrudability, interlayer adhesion, and transparency, it is preferable to use the same type of aliphatic polyamide resin (a) used in layer (A), and more preferably to use one or more selected from the group consisting of polyamide 6, polyamide 11, and polyamide 1010. When polyamide 6, polyamide 11, and polyamide 1010 are used, the mixing ratio is the same as that of layer (A).

[0023] (Aromatic polyamide resin (b)) Examples of the aromatic polyamide resin (b) include polymetaxylylene adipamide (polyamide MXD6), metaxylylene / paraxylylene adipamide copolymers, and copolymers thereof copolymerized with aliphatic diamines, alicyclic diamines, aromatic diamines other than metaxylylene and paraxylylene, aromatic dicarboxylic acids, lactams, ω-aminocarboxylic acids, aromatic aminocarboxylic acids, etc. Among these, polymetaxylylene adipamide (polyamide MXD6) is preferred from the viewpoints of gas barrier properties and moldability.

[0024] Polymetaxylylene adipamide (polyamide MXD6) refers to a polymerization product of primarily metaxylylene diamine and adipic acid. When the diamine components constituting polymetaxylylene adipamide are taken as 100 mol %, metaxylylene diamine accounts for 70 mol % or more, preferably 80 mol % or more, and more preferably 90 mol % or more. It may contain up to 30 mol % of an isomer of orthoxylylene diamine, paraxylylene diamine, or an aliphatic diamine having 6 to 12 carbon atoms, but from the viewpoints of gas barrier properties and heat resistance, it is preferable that these are not included. When the dicarboxylic acid components constituting polymetaxylylene adipamide (polyamide MXD6) are taken as 100 mol %, adipic acid accounts for 70 mol % or more, preferably 80 mol % or more, and more preferably 90 mol % or more. The film may contain 30 mol% or less of an aliphatic dicarboxylic acid having 7 to 12 carbon atoms, an aromatic dicarboxylic acid such as terephthalic acid or isophthalic acid, or a cyclic aliphatic dicarboxylic acid such as 1,4-cyclohexanedicarboxylic acid, but from the viewpoint of gas barrier properties and stretchability, it is preferable that these are not contained.

[0025] When a mixture of aliphatic polyamide resin (a) and aromatic polyamide resin (b) is used in layer (B), the affinity between layer (A) containing aliphatic polyamide resin (a) as a main component and layer (C) containing aromatic polyamide resin (b) is increased, thereby improving interlayer adhesion, and the mechanical properties of layer (A) and the gas barrier properties of layer (C) can be effectively reflected in the film. The mixing ratio of the aliphatic polyamide resin (a) to the aromatic polyamide resin (b) is preferably 60-99:1-40, more preferably 70-95:5-30, and even more preferably 80-90:10-20, when the total of both is 100% by mass. When the layer (B) is a layer made of an aliphatic polyamide resin (a) and an aromatic polyamide resin (b), the transparency of the resulting film can be further improved.

[0026] Layer (B) may contain a thermoplastic elastomer to improve impact resistance and flex resistance. The types of thermoplastic elastomers usable in layer (B) are the same as those usable in layer (A), and among these, polyamide elastomer (e) is preferred. The content of the thermoplastic elastomer is preferably 0 to 50% by mass, more preferably 3 to 30% by mass, and even more preferably 5 to 20% by mass, when the total of the resin components constituting the layer (B) is 100% by mass.

[0027] <Layer(C)> The polyamide resin film of the present invention has at least one layer (C) containing an aromatic polyamide resin (b) and a polyamide elastomer (e) having a hard segment with a molecular structure of polyamide 11. The layer (C) may be a single layer or multiple layers. In the case of multiple layers, the resin composition of each layer (C) may be different. The aromatic polyamide resin (b) used in layer (C) can be selected from the same types as the aromatic polyamide resin (b) used in layer (B). From the viewpoints of co-extrudability, interlayer adhesion, and transparency, it is preferable to use the same type of aromatic polyamide resin (b) used in layer (B).

[0028] (Polyamide elastomer (e)) The polyamide elastomer (e) is composed of a hard segment having a molecular structure of polyamide 11 and a soft segment. Because the hard segments are polyamide, they are highly compatible with the aliphatic polyamide resin (a) and aromatic polyamide resin (b) that make up each layer. Because they are finely dispersed within these resins, they can fully function as an elastomer, improving impact resistance, while also providing good transparency. Furthermore, because the hard segments have a polyamide 11 molecular structure, they can achieve even higher impact resistance than other polyamide molecular structures. Therefore, by blending a polyamide elastomer (e) with aromatic polyamide resin (b), which exhibits high gas barrier properties and rigidity due to the arrangement of aromatic rings and molecular chain orientation through amide bonds, the impact resistance of layer (C) and the polyamide resin film can be effectively improved. Furthermore, because the molecular structure of polyamide 11 is derived from biomass, it also contributes to reducing environmental impact.

[0029] Examples of the soft segment of the polyamide elastomer (e) include polyoxyethylene glycol, polyoxytetramethylene glycol, and polyoxypropylene glycol, with polyoxytetramethylene glycol being preferred from the viewpoint of flexibility. The polyamide elastomer (e) may be an acid-modified product. Suitable polyamide elastomers (e) include block copolymers of polyamide 11 and polyoxytetramethylene glycol and acid-modified products thereof. From the viewpoint of heat resistance, the polyamide elastomer (e) preferably has a melting point of 120° C. to 180° C. The melting point tends to be higher as the composition ratio of the hard segment increases, and lower as the composition ratio decreases.

[0030] The copolymerization composition ratio of the hard segment in the polyamide elastomer (e) is preferably 10% by mass or more and 90% by mass or less, more preferably 20% by mass or more and 80% by mass or less, and even more preferably 30% by mass or more and 70% by mass or less. A high copolymerization composition ratio of the hard segment tends to increase the bio-based carbon content, while a low copolymerization composition ratio tends to increase elasticity. Since layer (C) contains the highly elastic aromatic polyamide resin (b), a high copolymerization composition ratio of the hard segment of the polyamide elastomer (e) improves compatibility, and a high copolymerization composition ratio of the hard segment of the polyamide elastomer (e) improves the impact resistance of the polyamide resin film. Therefore, the copolymerization composition ratio is preferably 40% by mass or more and 70% by mass or less, more preferably 45% by mass or more and 70% by mass or less, and even more preferably 50% by mass or more and 70% by mass or less. When the polyamide elastomer (e) is used in the layers (A) and (B), the copolymerization composition ratio of the hard segment of the polyamide elastomer (e) is preferably 10% by mass or more and 70% by mass or less, and the lower limit is more preferably 20% by mass or more, and even more preferably 30% by mass or more.

[0031] Layer (C) contains 1.0 to 20.0% by mass of polyamide elastomer (e), assuming the total amount of resins constituting layer (C) to be 100% by mass. It is preferably 2.0 to 15.0% by mass, and more preferably 3.0 to 12.0% by mass. This range enhances the flexibility of layer (C) containing the highly rigid aromatic polyamide resin (b), improves the impact resistance of the polyamide resin film, and also provides gas barrier properties. It also suppresses an increase in haze due to the influence of mixing and dispersion with the aromatic polyamide resin (b), improving the transparency of the polyamide resin film.

[0032] The layer (C) only needs to contain the aromatic polyamide resin (b) and the polyamide elastomer (e), and may also contain other resin components, such as other thermoplastic elastomers. Examples of other thermoplastic elastomers include styrene-based elastomers, vinyl chloride-based elastomers, olefin-based elastomers, polyester-based elastomers, urethane-based elastomers, and acid-modified products thereof.

[0033] (additives) Each layer constituting the film of the present invention may contain additives, etc., within the range that does not impair the effects of the present invention. Examples of additives include heat stabilizers, antioxidants, ultraviolet absorbers, weathering agents, lubricants, fillers, nucleating agents, plasticizers, antiblocking agents, antifogging agents, flame retardants, dyes, pigments, stabilizers, coupling agents, and impact modifiers.

[0034] <Layer configuration> The film of the present invention has at least one layer each of layer (A) containing an aliphatic polyamide resin (a) as a main component, layer (B) containing the aliphatic polyamide resin (a) and an aromatic polyamide resin (b) and / or a thermoplastic elastomer, and layer (C) containing the aromatic polyamide resin (b) and a polyamide-based elastomer (e), and the layers are arranged in the order of layer (A), layer (B), and layer (C). The phrase "arranged in the order of Layer (A), Layer (B), and Layer (C)" means that the polyamide resin film of the present invention has at least a three-layer structure of "A / B / C," and other layer structures are not particularly limited. Each layer may be composed of multiple layers, and the three-layer structure of "A / B / C" also includes "A / A / B / C," "A / B / B / C," and "A / B / C / C."

[0035] Examples of layer configurations include a three-layer configuration of [A / B / C], a four-layer configuration of [A / B / C / A], [A / B / C / B], a five-layer configuration of [A / B / C / B / A], [A / B / C / A / B], and a seven-layer configuration of [A / A / B / C / B / A / A], [A / B / B / C / B / B / A], etc. From the viewpoint of film formation stability, layer configurations such as [A / B / C / B / A], [A / A / B / C / B / A / A], which are symmetrical with layer (C) as the center, and [A / B / C / B / A], [A / A / B / C / B / A / A], [A / B / B / C / B / B / A] are preferred. Furthermore, other layers (D) may be disposed between the layers as long as the effects of the present invention are not impaired. The component of layer (D) is not particularly limited, but examples thereof include polyolefin resins, polyester resins, and thermoplastic elastomers.

[0036] The total thickness of the film of the present invention is not particularly limited, but from the viewpoints of processability, transparency, and handleability, the lower limit is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 12 μm or more. From the viewpoints of productivity and handleability, the upper limit is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 25 μm or less. If the total thickness is within the above range, the film will have good mechanical properties as a polyamide-based biaxially stretched film and excellent gas barrier properties.

[0037] From the viewpoint of toughness and gas barrier properties as a polyamide resin film, it is preferable that the thickness ratio of layer (A) to the total film thickness (100%) is 25 to 90%, the thickness ratio of layer (B) to 10 to 75%, and the thickness ratio of layer (C) to 10 to 75%. When there are multiple layers (A), (B), and (C), the ratio is considered as the ratio of the total thickness of each layer to the total thickness.

[0038] The thickness of each of Layer (A), Layer (B), and Layer (C) is not particularly limited, but is preferably 1 to 15 μm, more preferably 2 to 10 μm, and even more preferably 3 to 8 μm. When there are multiple Layers (A), Layers (B), and Layers (C), the thicknesses may be different for each layer or the same for each layer.

[0039] The film of the present invention can be subjected to surface treatments or finishes such as printing, coating, and vapor deposition. It can also be used by laminating it with other resin layers such as polyolefins and polyesters, other films or adhesive layers, metal foils, paper, etc. Known lamination methods can be used, such as dry lamination, wet lamination, sand lamination, and extrusion lamination. During lamination, the surface of the film of the present invention can also be subjected to surface treatments such as corona discharge and anchor coating.

[0040] When the film of the present invention is used as a packaging material, from the viewpoint of maintaining the quality of the contents and preventing spoilage, the gas barrier properties and moisture resistance can be further improved by vapor-depositing aluminum, silicon oxide, alumina, diamond-like carbon, or the like on one or both sides of the film, or by applying a gas barrier coating agent such as a polyvinyl alcohol (PVA)-based resin or a polyvinylidene chloride (PVDC)-based resin.

[0041] <Manufacturing method> The film of the present invention may have a film configuration having at least one layer each of Layer (A), Layer (B), and Layer (C), and can be produced by a known method. The production steps are, for example, in the following order. The raw materials, such as the aliphatic polyamide resin (a), the aromatic polyamide resin (b), and the polyamide elastomer (e), are preferably dried in advance to a moisture content of 0.1% by mass or less in order to prevent the generation of water vapor or oligomers that may inhibit film formation when the materials are thermally melted and extruded. The resins are fed into extruders for each layer, and the molten resins are joined in a feed block, or a multi-manifold flat die, or an annular die, and then co-extruded as a multilayer film, which is then rapidly cooled to obtain a flat or annular unstretched film.

[0042] To obtain a biaxially stretched film, an unstretched film is biaxially stretched in the film's machine direction (longitudinal direction, MD) and its transverse direction (transverse direction, TD) using a known method such as tenter-type sequential biaxial stretching, tenter-type simultaneous biaxial stretching, or tubular-type simultaneous biaxial stretching. For example, in the case of the tenter-type sequential biaxial stretching method, the unstretched film can be produced by heating the film to a temperature range of 40 to 100°C, stretching it in the machine direction using a roll-type machine-type stretching machine, and then stretching it in the transverse direction using a tenter-type transverse stretching machine at a temperature range of 100 to 230°C. In addition, in the case of the tenter-type simultaneous biaxial stretching method or the tubular-type simultaneous biaxial stretching method, the film can be produced by simultaneously stretching it in both the machine and transverse directions at a temperature range of 40 to 230°C. The stretching ratio is preferably 2.0 to 5.0 times, more preferably 3.0 to 5.0 times, in each of the machine direction (machine direction, MD) and width direction (transverse direction, TD) of the film. A stretching ratio within this range promotes stretch orientation of the film, resulting in good mechanical properties such as film strength, and also makes the film less likely to break during stretching, resulting in good productivity.

[0043] Furthermore, to improve the dimensional stability of the film, the biaxially stretched film can be heat-set. The heat-setting temperature is preferably 200° C. to 225° C., more preferably 205° C. to 220° C. This makes it possible to obtain a biaxially stretched film with good dimensional stability at room temperature. In order to alleviate the stress of crystallization shrinkage due to heat setting, a relaxation treatment can be carried out in the width direction during heat setting in the range of 0 to 15%, preferably 3 to 10%. After the relaxation treatment, the film can be re-stretched in the width direction by 2 to 9%, preferably 3 to 7%, and more preferably 4 to 7% at a temperature of 140 to 200° C. If the re-stretching temperature is within the above range, an appropriate stress is obtained during stretching, resulting in uniform stretching and making it easier to achieve a uniform transverse shrinkage rate in the width direction.

[0044] <Film properties> (shock resistance) The films of the present invention exhibit excellent impact resistance. The impact resistance of the film of the present invention can be evaluated by the puncture impact strength when the penetration portion opens a hole in a film test piece. It is desirable for the puncture impact strength to be high under both low-temperature and room-temperature conditions; however, the value tends to be lower under low-temperature conditions (-20°C) than under room-temperature conditions (23°C) because brittle fracture is more likely to occur there. The puncture impact strength under room-temperature conditions (23°C) is preferably 1.25 J or more, more preferably 1.30 J or more, and even more preferably 1.35 J or more. The puncture impact strength under low-temperature conditions (-20°C) is preferably 1.00 J or more, more preferably 1.05 J or more, and even more preferably 1.10 J or more. If the puncture impact strength is within the relevant range, the film has excellent impact resistance and is favorable in that it is less likely to develop holes when used as a packaging material. Furthermore, the package is less likely to break during low-temperature transportation and storage. The impact resistance of the film of the present invention can be measured using an impact tester, for example, a Hydroshot impact tester HTM-1 manufactured by Shimadzu Corporation, where a test piece is fixed with a clamp and the test can be performed under the conditions of a test speed of 3 m / sec, a punching jig having a diameter of 1 / 2 inch, a striker tip diameter of 1 / 2 inch, and a punching table having a diameter of 50 mm.

[0045] (Bending pinhole resistance) The film of the present invention is likely to exhibit sufficient pinhole resistance due to bending by using the polyamide elastomer (e) in the layer (C). The pinhole resistance can be evaluated by performing a bending test under specific temperature and relative humidity conditions using a Gelbo flex tester and counting the number of pinholes that occur. For example, the number of pinholes is 10.0 / 481 cm under an environment of 23°C temperature and 50% relative humidity. 2 The following is preferable: 5.0 pieces / 481cm 2 The lower the ambient temperature, the less flexibility the film loses, so it is desirable to have fewer pinholes under low temperature conditions. 2 If the film is below this level, pinholes are less likely to occur due to bending of the film when the package is transported or stored, or due to collisions between packages, and oxidation deterioration of the contents due to a decrease in gas barrier properties is also more easily prevented.

[0046] (tensile stress at break, tensile elongation at break) The tensile breaking stress is preferably 150 MPa or more, more preferably 200 MPa or more, in both the machine direction (MD) and the cross direction (TD), and at both temperatures of -20°C and 23°C. There is no particular upper limit, but it is about 500 MPa. A film with a tensile breaking stress within this range maintains the rigidity of the film when contents are packaged, and is less likely to develop pinholes or breaks due to bending or impact. The tensile breaking elongation is preferably 35% or more, and more preferably 40% or more, in both the machine direction (MD) and cross direction (TD) of the film, and at both temperatures of -20°C and 23°C. The lower the temperature, the more difficult the film is to stretch, and the lower its puncture resistance when packaging frozen foods, so a tensile breaking elongation of 35% or more at -20°C is useful. There is no particular upper limit to the tensile breaking elongation, but it is about 150%. The tensile elongation at break and the tensile stress at break are measured in accordance with JIS K7127:1999, at a test speed of 200 mm / min, at temperatures of -20°C and 23°C.

[0047] (transparency) The film of the present invention preferably has a haze of 10.0% or less, more preferably 8.0% or less, and even more preferably 5.0% or less. When the haze is in this range, the film has excellent transparency, and the film has good design properties and good visibility of the contents when used as a packaging film. The haze is measured in accordance with JIS K7136:2000.

[0048] (Oxygen gas barrier properties) The film of the present invention has an oxygen permeability of 10.0 cc / m under conditions of 23°C and 50% relative humidity. 2 / 24h / atm or less is preferable, and 9.0cc / m 2 / 24h / atm or less is more preferable, and 8.0cc / m 2 It is more preferable that the oxygen permeability is 10.0 cc / m / 24h / atm or less, and it is desirable that the value is even lower. 2 / 24h / atm or less is preferable because the packaging film can maintain sufficient oxygen gas barrier properties to prevent deterioration of the contents and keep them fresh. The oxygen gas barrier property is measured in accordance with JIS K7126-1 Method B:2006.

[0049] (bio-based carbon content) When a biomass-derived aliphatic polyamide resin (a) is used, and the polyamide 11 skeleton of the polyamide elastomer (e) is biomass-derived, the bio-based carbon content of the film can be calculated from the composition ratio of each layer and the ratio of each layer thickness to the total film thickness. From the perspective of recent environmental issues, the higher the bio-based carbon content of the film, the more desirable it is, with 0.5% or more being preferred, 1.0% or more being more preferred, 2.0% or more being even more preferred, and 5.0% or more being particularly preferred. The biobased carbon content is determined in accordance with ISO 16620-2:2019. The biobased carbon content of a film can also be calculated from the biobased carbon content of the raw materials, the layer composition ratio, and the layer thickness ratio.

[0050] <Package> The polyamide-based resin film of the present invention can be laminated with a sealant film or the like by a known lamination method to form a package such as a bag or a tube, or the polyamide-based resin film of the present invention can be used to form a lid or a base material, which can then be combined to form a package such as a container. [Example]

[0051] The present invention will be specifically explained below using examples, but the present invention is not limited to these. <Ingredients> The abbreviations, components, physical properties, etc. of the resins used in the examples and comparative examples are as follows: The melting point and glass transition temperature of the resin are values measured in accordance with JIS K7121:2012. The bio-based carbon content of the resin was determined in accordance with ISO 16620-2:2019.

[0052] (Aliphatic polyamide resin (a)) PA6: Polyamide 6, relative viscosity 3.4, glass transition temperature 48°C, melting point 215°C, bio-based carbon content 0%

[0053] (Aromatic polyamide resin (b)) MXD6: Polymetaxylylene adipamide (Polyamide MXD6), 0% bio-based carbon content

[0054] (Polyamide elastomer) EL1: Polyamide 11-polytetramethylene glycol block copolymer, polyamide 11 copolymer composition ratio 31% by mass, bio-based carbon content 31%, melting point 146°C EL2: Polyamide 11-polytetramethylene glycol block copolymer, polyamide 11 copolymer composition ratio 46% by mass, bio-based carbon content 46%, melting point 148°C EL3: Polyamide 11-polytetramethylene glycol block copolymer, polyamide 11 copolymer composition ratio 65% by mass, bio-based carbon content 65%, melting point 167°C EL4: Polyamide 12-polytetramethylene glycol block copolymer, polyamide 12 copolymer composition ratio 46% by mass, bio-based carbon content 0%, melting point 160°C

[0055] (Saponified ethylene-vinyl acetate copolymer) EVOH: ethylene composition ratio 25% by mass, bio-based carbon content 0%, melting point 195°C

[0056] <Film production, film layer structure> (Examples 1 to 7, Comparative Examples 1 to 3) The raw materials for each layer were blended in the mass ratios shown in Table 1. The resin composition for layer (A) was fed into an extruder with a screw diameter of 40 mm, the resin composition for layer (B) was fed into an extruder with a screw diameter of 32 mm, and the resin composition for layer (C) was fed into an extruder with a screw diameter of 32 mm. Each was melted at 250°C, distributed using a distribution block, and multilayered in a coextrusion T-die to extrude the molten film, which was then quenched on a cooling roll at 30 to 40°C to produce an unstretched multilayer film. The resulting unstretched multilayer film was stretched 3.0 times in the machine direction at 56°C using a roll-type longitudinal stretching machine, then stretched 4.9 times in the width direction at 120°C using a tenter-type transverse stretching machine, and subsequently heat-set at 215°C and relaxed 8% in the width direction. The film was then cooled to room temperature, and both ends corresponding to the gripping portions of the clips were trimmed. The trimmed film was wound into a roll to obtain a biaxially stretched multilayer film with a layer structure of [Layer (A) 3.5 μm / Layer (B) 2.0 μm / Layer (C) 4.0 μm / Layer (B) 2.0 μm / Layer (A) 3.5 μm] and a total thickness of 15.0 μm. The thickness of each layer was measured by cutting the film vertically and observing it under a microscope. The bio-based carbon content of the film was calculated from the bio-based carbon content of the raw material, the layer composition ratio, and the layer thickness ratio. The biaxially stretched multilayer film obtained was subjected to the following evaluations, and the results are summarized in Table 1.

[0057] <Evaluation> (shock resistance) In accordance with JIS P8134:1998, a Shimadzu Hydroshot impact tester HTM-1 was used. The test specimen was clamped and measured at a test speed of 3 m / sec, with a punching tool 1 / 2 inch in diameter, a striker tip diameter of 1 / 2 inch in diameter, and a punching stand of 50 mm in diameter. Evaluations were conducted at two conditions: 23°C and -20°C. ○: 1.25J or more (23℃) and 1.00J or more (-20℃) ×: Less than 1.25J (23℃) or less than 1.00J (-20℃)

[0058] (Transparency (haze)) The haze (unit: %) was measured in accordance with JIS K7136:2000.

[0059] (Oxygen gas barrier properties) Oxygen permeability (unit: cc / m) at 23°C and 50% RH in accordance with JIS K7126-1 B Method: 2000 2 / 24h / atm) and evaluated according to the following criteria. ○: 10.0cc / m 2 / 24h / atm or less ×:10.0cc / m 2 / 24h / atm

[0060] [Table 1]

[0061] In Examples 1 to 7, 1.0% by mass or more of EL1, EL2, and EL3 corresponding to polyamide elastomer (e) were blended relative to 100% by mass of the total resin constituting Layer (C), and the impact resistance tended to be better than that of Comparative Example 1, which blended EL4 having the molecular structure of polyamide 12 as a hard segment. In particular, the impact resistance at room temperature (23°C) was relatively high, at 1.25 J or more. With regard to transparency, in Examples 1 to 7, the haze was 10.0% or less, which is within a range that does not pose a problem in practice, and in Examples 1, 2, and 5, which contained PA6 and MXD6 in layer (B), the haze was even better, at 5.0% or less. Furthermore, compared with Comparative Example 1, which used EL4 in layer (C), Examples 1 and 5, which used EL3 and EL2, had low haze and somewhat good transparency. In addition, in Examples 1 to 7, the oxygen permeability was 10.0 cc / m because the layer (C) contained MXD6, an aromatic polyamide resin. 2 / 24h / atm or less, demonstrating good oxygen gas barrier properties. [Industrial Applicability]

[0062] The film of the present invention is a polyamide resin film with excellent impact resistance, transparency, and oxygen gas barrier properties, and is therefore suitable for packaging food products, medical and clothing products, industrial parts, etc. It is particularly useful for packaging liquid-filled products such as soups and seasonings. Furthermore, the use of biomass-derived resin raw materials greatly contributes to reducing environmental impact.

Claims

1. a layer (A) containing an aliphatic polyamide resin (a) as a main component; a layer (B) containing the aliphatic polyamide resin (a) and polymetaxylylene adipamide (polyamide MXD6) and / or a thermoplastic elastomer; and a film having at least one layer (C) containing the polymetaxylylene adipamide (polyamide MXD6) and at least one layer (C) containing a polyamide-based elastomer (e) having a molecular structure of polyamide 11 as a hard segment, The layers are arranged in the order of the layer (A), the layer (B), and the layer (C), a polyamide-based resin film containing the polyamide-based elastomer (e) in an amount of 1.0% by mass or more and 20.0% by mass or less, where the total amount of resins constituting the layer (C) is 100% by mass;

2. The polyamide-based resin film according to claim 1 , wherein the layer (A) or the layer (B) contains the polyamide-based elastomer (e).

3. 3. The polyamide resin film according to claim 1, wherein the aliphatic polyamide resin (a) is at least one selected from the group consisting of polyamide 6, polyamide 11, and polyamide 1010.

4. The polyamide resin film according to any one of claims 1 to 3, which is biaxially stretched.

5. A packaging material comprising the polyamide resin film according to any one of claims 1 to 4.

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