Polyamide-based resin film and package

Abstract

To provide a polyamide-based resin film having a layer containing an aliphatic polyamide resin and a layer containing a barrier resin (ethylene-vinyl acetate copolymer saponified product), which has sufficient boil resistant characteristics when being used as a film for packaging and a package.SOLUTION: A polyamide-based resin film includes at least two layers of a layer (A) containing 40 mass% or more of a predetermined aliphatic polyamide resin (a) and a layer (B) containing a predetermined barrier resin (b).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] BACKGROUND ART Films made of polyamide resins are resin materials 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, while 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 be insufficient in terms of gas barrier properties 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 combining layers of resins with high gas barrier properties, such as saponified ethylene-vinyl acetate copolymer (EVOH) and metaxylylene adipamide (polyamide MXD6), have come into widespread use. In particular, resin films combined with saponified ethylene-vinyl acetate copolymer (hereinafter referred to as EVOH) are widely used, primarily for food packaging, due to their high gas barrier properties.

[0003] Patent Document 1 discloses a polyamide film that has a polyamide 6 resin layer and an EVOH layer and combines gas barrier properties with strength. However, saponified ethylene-vinyl acetate copolymer (EVOH) has a high affinity for water, and is prone to absorbing water, particularly when used for boiling in hot water, which causes the adjacent polyamide 6 resin layer to whiten and deteriorates its appearance, which is problematic.

[0004] Patent Document 2 discloses a polyamide film having an EVOH layer containing an aliphatic polyamide and fatty acid magnesium, but the aliphatic polyamide and the EVOH react to gel, which tends to deteriorate the appearance and reduce long-term productivity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-79620 [Patent Document 2] WO2015 / 063587 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-based resin film having a layer containing an aliphatic polyamide resin and a layer containing a barrier resin (saponified ethylene-vinyl acetate copolymer), which has sufficient boil resistance when used as a packaging film or packaging material. [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 object can be achieved by combining a layer (A) containing a predetermined amount of a specific aliphatic polyamide resin (a) with a layer (B) containing a barrier resin (b) (a saponified ethylene-vinyl acetate copolymer), and have thus completed the present invention.

[0008] [1] A polyamide-based resin film having at least two layers: a layer (A) containing 40% by mass or more of an aliphatic polyamide resin (a), and a layer (B) containing a barrier resin (b), A polyamide resin film that satisfies the following (1) and (2): (1) The aliphatic polyamide resin (a) is at least one selected from the group consisting of polyamides having a molecular structure obtained by polycondensation of diamines having 10 or more carbon atoms and / or dicarboxylic acids having 10 or more carbon atoms, and polyamides having a molecular structure obtained by ring-opening polymerization of caprolactam having 10 or more carbon atoms. (2) The barrier resin (b) is a saponified ethylene-vinyl acetate copolymer.

[0009] [2] The polyamide resin film according to [1], which has a water absorption rate of 3.5% or less as measured in accordance with JIS K7209 (2000). [3] The polyamide resin film according to [1] or [2], wherein the layer (A) is disposed on both sides of the layer (B), and the film has at least three layers.

[0010] [4] The water vapor transmission rate is 60.0 g / (m 2 The polyamide resin film according to any one of [1] to [3], wherein the temperature is 500°C or lower (24 hr·atm). [5] The polyamide resin film according to any one of [1] to [4], which is biaxially stretched.

[0011] [6] A packaging body made using the polyamide resin film according to any one of [1] to [5]. [Effects of the Invention]

[0012] According to the present invention, a polyamide resin film can be provided that has sufficient gas barrier properties and boil resistance when used as a packaging film or packaging material. Due to these characteristics, the polyamide resin film of the present invention can be suitably used as packaging materials for food, medicine, clothing, industrial parts, etc. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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," the "layer (A) containing the aliphatic polyamide resin (a)" may be referred to as the "layer (A)," and the "layer (B) containing the barrier resin (b)" may be referred to as the "layer (B)."

[0014] In this specification, the term "major component" refers to a component that accounts for the largest percentage by mass when the total of the target substance is 100% by mass, and is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more.

[0015] 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."

[0016] In this specification, the term "film" encompasses a wide range of materials from thick sheets to thin films.

[0017] [Polyamide resin film] The polyamide-based resin film of the present invention is a polyamide-based resin film having at least two layers: a layer (A) containing 40 mass % or more of an aliphatic polyamide resin (a) and a layer (B) containing a barrier resin (b), and is a polyamide-based resin film that satisfies (1) and (2). (1) The aliphatic polyamide resin (a) is at least one selected from the group consisting of polyamides having a molecular structure obtained by polycondensation of diamines having 10 or more carbon atoms and / or dicarboxylic acids having 10 or more carbon atoms, and polyamides having a molecular structure obtained by ring-opening polymerization of caprolactam having 10 or more carbon atoms. (2) The barrier resin (b) is a saponified ethylene-vinyl acetate copolymer.

[0018] <Layer (A) Containing Aliphatic Polyamide Resin (a)> The polyamide resin film of the present invention has at least one layer (A) containing an aliphatic polyamide resin (a), and the layer (A) contains 40% by mass or more of the aliphatic polyamide resin (a) when the total mass of the layer (A) is taken as 100% by mass.

[0019] (Aliphatic polyamide resin (a)) The aliphatic polyamide resin (a) in the present invention must be at least one selected from polyamides having a molecular structure obtained by polycondensation of diamines having 10 or more carbon atoms and / or dicarboxylic acids having 10 or more carbon atoms, and polyamides having a molecular structure obtained by ring-opening polymerization of caprolactam having 10 or more carbon atoms.

[0020] Aliphatic polyamide resin (a) has a longer hydrocarbon chain and fewer amide bonds than polyamides having a molecular structure obtained by polycondensation of diamines having less than 9 carbon atoms and / or dicarboxylic acids having less than 9 carbon atoms, and polyamides having a molecular structure obtained by ring-opening polymerization of caprolactam having less than 9 carbon atoms, and therefore has lower water absorption and moisture permeability, making it preferable in terms of boiling resistance. Therefore, when a polyamide resin film is formed having at least two layers, namely, layer (A) and layer (B) containing a barrier resin (saponified ethylene-vinyl acetate copolymer), the film tends to be less susceptible to deterioration in appearance, such as whitening of the barrier resin (saponified ethylene-vinyl acetate copolymer) after boiling treatment.

[0021] For example, from the viewpoint of high mechanical properties, polyamide 11, polyamide 12, polyamide 4,10, polyamide 5,10, polyamide 6,10, polyamide 10,10, and polyamide 10,12 are preferred, and polyamide 10,10, polyamide 11, and polyamide 12 are more preferred. Furthermore, from the viewpoint of also having impact resistance, polyamide 10,10 and polyamide 11 are even more preferred.

[0022] The aliphatic polyamide resin (a) preferably has a melting point of 170° C. or higher, more preferably 180° C. or higher, from the viewpoint of heat resistance of the film. The aliphatic polyamide resin (a) has a density of 1200 kg / m 3 Preferably less than 1150 kg / m 3 The following is more preferred:

[0023] As described above, the aliphatic polyamide resin (a) in the present invention may be a polyamide resin produced by ring-opening polymerization of various known lactams having a predetermined number of carbon atoms, or may be a polyamide resin produced by condensation polymerization of known aliphatic diamines having a predetermined number of carbon atoms and aliphatic dicarboxylic acids having a predetermined number of carbon atoms. The layer (A) containing the aliphatic polyamide resin (a) may be one layer or multiple layers, and in the case of multiple layers, the resin composition of each layer may be different.

[0024] (Polyamide 10,10) Polyamide 10,10 can be a known resin obtained by polycondensation of sebacic acid and decanediamine. From the viewpoint of film formability, the relative viscosity measured under 96% sulfuric acid conditions according to JIS K6920-2 (2009) 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, when a laminated film is formed with other layers, such as layer (B) containing saponified ethylene-vinyl acetate copolymer (b), it is easy to stably co-extrude the film and there is little uneven flow due to viscosity differences between the layers, which is preferable.

[0025] The melting point of polyamide 10,10 is preferably 170° C. to 250° C., more preferably 180° C. to 240° C. If the melting point of polyamide 10,10 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 density of polyamide 10,10 is 1200 kg / m3, which is the most important factor in terms of impact resistance of the film. 3 Preferably less than 1150 kg / m 3 The following is more preferred:

[0026] (Polyamide 11) Polyamide 11 can be a known resin obtained by ring-opening polymerization of 11-aminoundecanoic acid. From the viewpoint of film formability, the relative viscosity measured under 96% sulfuric acid conditions according to JIS K6920-2 (2009) 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, when a laminated film is formed with other layers, such as layer (B) containing saponified ethylene-vinyl acetate copolymer (b), it is easy to stably co-extrude the film and there is little uneven flow due to viscosity differences between the layers, which is preferable.

[0027] The melting point of polyamide 11 is preferably 170 to 250° C., more preferably 180 to 240° C. If the melting point of polyamide 11 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 density of polyamide 11 is 1200 kg / m3 in terms of impact resistance of the film. 3 Preferably less than 1150 kg / m 3 The following is more preferred:

[0028] (Composition of Layer (A)) When the total mass of the layer (A) is taken as 100 mass %, the layer (A) contains 40 mass % or more of the aliphatic polyamide resin (a). Layer (A) preferably contains an aliphatic polyamide resin (a) as a main component resin, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass or more. By ensuring that the film has a high transparency, gas barrier properties, low water absorption and moisture permeability, and good boil resistance, it is useful for preventing deterioration and spoilage of the contents and improving long-term storage stability when used in packaging materials.

[0029] (Other polyamide resins) The layer (A) containing the aliphatic polyamide resin (a) may further contain other polyamide resins within the range that does not impair the effects of the present invention. Examples of the polyamide resin include aliphatic polyamide resins other than polyamide resins having a molecular structure obtained by polycondensation of diamines having 10 or more carbon atoms and / or dicarboxylic acids having 10 or more carbon atoms, and aliphatic polyamide resins, aromatic polyamide resins, and semi-aromatic polyamide resins, other than aliphatic polyamide resins having a molecular structure obtained by ring-opening polymerization of caprolactam having 10 or more carbon atoms.

[0030] Examples of aliphatic polyamide resins other than the aliphatic polyamide resin (a) include ring-opening polymers of cyclic lactams, polycondensates of aminocarboxylic acids, polycondensates of dicarboxylic acids and diamines, etc. Specific examples include a homopolymer of ε-caprolactam known as polyamide 6, polyhexamethylene adipamide known as polyamide 66, and a copolymer thereof, such as polyamide 6-66.

[0031] Furthermore, examples of the aromatic polyamide resin include resins containing, in the molecular chain, 70 mol% or more of polyamide structural units composed of xylylene diamine and an α,ω-aliphatic dicarboxylic acid having from 6 to 12 carbon atoms. Specific examples include aromatic polyamide resins such as homopolymers such as polymetaxylylene adipamide, polymetaxylylene pimelamide, polymetaxylylene azelamide, polyparaxylylene azelamide, and polyparaxylylene decanamide, as well as metaxylylene / paraxylylene adipamide copolymers, metaxylylene / paraxylylene pimelamide copolymers, metaxylylene / paraxylylene azelamide copolymers, and metaxylylene / paraxylylene sepacamide copolymers. The semi-aromatic polyamide resin may be a semi-aromatic polyamide resin composed of a dicarboxylic acid component containing terephthalic acid as the main component and a diamine component containing an aliphatic diamine as the main component. These polyamide resins may be used singly or in combination of two or more.

[0032] (Other ingredients) The layer (A) containing the aliphatic polyamide resin (a) may further contain a thermoplastic elastomer, additives, etc., within the range that does not impair the effects of the present invention.

[0033] Examples of the thermoplastic elastomer include polyamide elastomers, polyester elastomers, polystyrene elastomers, and polyolefin elastomers. These are resins that have a molecular skeleton of polyamide, polyester, polystyrene, or polyolefin as a hard segment and a polyalkylene ether glycol or rubber component as a soft segment, and exhibit elasticity. Here, polyamide elastomers refer to those with a soft segment content of 50% by mass or more. Furthermore, when polyamide-based elastomers, polyester-based elastomers, and polyolefin-based elastomers are modified with an unsaturated carboxylic acid such as maleic anhydride or its derivatives or anhydrides, they have a high affinity with aliphatic polyamide resins, have good dispersibility and miscibility, and the pinhole resistance and transparency of the film are improved, which is preferable. Suitable thermoplastic elastomers include, for example, block copolymers of polyamide 11 or polyamide 12 with polyoxytetramethylene glycol and acid-modified products thereof, block copolymers of polybutylene terephthalate with polyoxytetramethylene glycol and acid-modified products thereof, and styrene-isobutylene-styrene block copolymers (SIBS). When the total mass of the layer (A) is taken as 100% by mass, the content of the thermoplastic elastomer is preferably 10% by mass or less from the viewpoints of film formability, high transparency, and low water absorption.

[0034] Examples of additives that may be included include heat stabilizers, antioxidants, ultraviolet absorbers, weathering agents, lubricants, fillers, nucleating agents, plasticizers, antiblocking agents, anti-fogging agents, flame retardants, dyes, pigments, stabilizers, coupling agents, and impact resistance improvers. The content of the additives is preferably 5% by mass or less relative to 100% by mass of the total of the constituent components of the layer (A) from the viewpoints of film formability, high transparency, and low water absorption.

[0035] <Layer (B) Containing Barrier Resin (b)> The film of the present invention has a layer (B) containing a barrier resin (b), which can impart gas barrier properties and is useful for preventing deterioration and spoilage of contents and improving long-term storage stability when used as a packaging material. When the total mass of the layer (B) is taken as 100 mass %, the layer (B) preferably contains the barrier resin (b) as a main component or more. Layer (B) more preferably contains 60% by mass or more of the barrier resin (b), further preferably 70% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass or more.

[0036] (Saponified ethylene-vinyl acetate copolymer) In the present invention, the barrier resin (b) constituting layer (B) is preferably a saponified ethylene-vinyl acetate copolymer. The saponified ethylene-vinyl acetate copolymer is a copolymer obtained by saponifying a copolymer of ethylene and vinyl acetate with an alkali catalyst or the like. In addition to ethylene structural units and vinyl alcohol structural units (including unsaponified vinyl ester structural units), the copolymer may further contain structural units derived from the following comonomers. Examples of the comonomers include α-olefins such as propylene, isobutene, α-octene, α-dodecene, and α-octadecene; hydroxyl-containing α-olefins such as 3-butene-1-ol, 4-pentene-1-ol, and 3-butene-1,2-diol, as well as hydroxyl-containing α-olefin derivatives such as esters and acylates thereof; unsaturated carboxylic acids or salts thereof, partial alkyl esters, complete alkyl esters, nitriles, amides, or anhydrides; unsaturated sulfonic acids or salts thereof; vinylsilane compounds; vinyl chloride; and styrene.

[0037] Furthermore, it is also possible to use EVOH-based resins that have been post-modified by urethanization, acetalization, cyanoethylation, oxyalkylenation, etc. These EVOHs may be used alone or in combination of two or more.

[0038] The ethylene content in the saponified ethylene-vinyl acetate copolymer is not particularly limited, but from the viewpoint of film formation stability, it is generally preferably 5 mol% or more, more preferably 10 mol% or more, and particularly preferably 20 mol% or more. From the viewpoint of gas barrier properties, the upper limit of the ethylene content is preferably 48 mol% or less, more preferably 38 mol% or less, and even more preferably 35 mol% or less. Furthermore, the saponified ethylene-vinyl acetate copolymer has a saponification degree of preferably 96% or more, more preferably 98% or more. In the film of the present invention, when the ethylene content and saponification degree in the saponified ethylene-vinyl acetate copolymer are within the above ranges, an excellent balance between film formability and gas barrier properties is achieved, making the film suitable for molding processes such as coextrusion with layer (A) and biaxial stretching.

[0039] (Other ingredients) The layer (B) may contain additives and the like to the extent that the effects of the present invention are not impaired. Examples of additives that may be included include heat stabilizers, antioxidants, ultraviolet absorbers, weathering agents, lubricants, fillers, nucleating agents, plasticizers, antiblocking agents, anti-fogging agents, flame retardants, dyes, pigments, stabilizers, coupling agents, and impact resistance improvers. The content of the additives is preferably 5% by mass or less relative to 100% by mass of the total of the constituent components of the layer (B) from the viewpoints of film formability, high transparency, and low water absorption.

[0040] <Layer configuration> The polyamide resin film of the present invention may have at least two layers: a layer (A) containing an aliphatic polyamide resin (a) and a layer (B) containing a barrier resin (b). When multiple layers (A) are provided, the layers (A) may have the same composition or different compositions. For example, in the case of a layer structure such as layer (A1) / layer (A2) / layer (B), it is preferable that layer (A2) contains a resin common to layer (A1) and / or layer (B) in order to improve the interlayer adhesion between layer (A1) and layer (B). When a plurality of layers (B) are disposed, the layers (B) may have the same composition or different compositions.

[0041] In addition to the layer (A) and the layer (B), another layer (C) may be present. The components of the other layer (C) are not particularly limited, but when layer (C) is disposed between layer (A) and layer (B), it is preferable to use an adhesive resin, such as an acid-modified polyolefin resin, to improve interlayer adhesion. When layer (C) is disposed on the surface of the film, it is preferable to provide a layer made of polyamide 6, polyamide 6,6, polyamide 6,66, polyamide MXD6, polyester, etc., to improve the pinhole resistance and friction / abrasion resistance of the film.

[0042] The order of the layers is not particularly limited, but for example, a two-layer structure such as [A / B], a three-layer structure such as [A / B / A], [A / B / C], [A / C / B], or a five-layer structure such as [A / A / B / A / A], [A / C / B / C / A], [C / A / B / A / C], or [A / B / C / B / A] is preferred in terms of film formation stability. Among these, a structure in which low-water-absorbent layers (A) are disposed on both sides of layer (B), such as [A / B / A], [A / A / B / A / A], [A / C / B / C / A], or [C / A / B / A / C], is preferred in terms of preventing water absorption by layer (B) and improving the gas barrier properties of the film, and imparting sufficient impact resistance to the film, including layer (B).

[0043] The total thickness of the film of the present invention is not particularly limited, but from the viewpoints of processability, transparency, and handleability, it is preferably 5 to 50 μm, more preferably 10 to 30 μm, and even more preferably 12 to 25 μm. 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.

[0044] From the viewpoint of the mechanical properties and oxygen gas barrier properties of the film, it is preferable that the thickness ratio of layer (A) to the total film thickness (100%) is 25 to 90%, and that of layer (B) to 10 to 75%. When there are multiple layers (A) and / or layers (B), the thickness ratio refers to the ratio of the total thickness of layer (A) or layer (B) to the total thickness.

[0045] 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. Furthermore, 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 deposition of aluminum, silicon oxide, alumina, diamond-like carbon, etc., or by applying a gas barrier coating agent such as a polyvinyl alcohol (PVA)-based resin or a polyvinylidene chloride (PVDC)-based resin.

[0046] <Manufacturing method> The film of the present invention may have a film configuration having at least two layers, namely, a layer (A) containing an aliphatic polyamide resin (a) and a layer (B) containing a barrier resin (b), and can be produced by a known method. When using raw material polyamides and gas barrier resins that have absorbed water, water vapor and oligomers are generated during the thermal melting and extrusion process, hindering film formation. Therefore, when preparing the raw materials, it is preferable to dry the resin in advance to reduce the moisture content to 0.1% by mass or less. 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.

[0047] 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 80 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 80 to 230°C.

[0048] The stretching ratio is preferably 2.0 to 6.0 times, more preferably 2.5 to 5.5 times, in each of the machine direction (machine direction, MD) and width direction (transverse direction, TD) of the film. When the stretching ratio in each of the biaxial stretching directions is 2.0 times or more, stretching orientation proceeds and mechanical properties such as film strength become good, and when the stretching ratio is 5.5 times or less, the film is less likely to break during stretching and productivity is good.

[0049] Furthermore, to improve the dimensional stability of the film, the biaxially stretched film can be heat-set. The heat-setting temperature is preferably 150° C. to 200° C., more preferably 170° C. to 195° 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 190° 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.

[0050] <Film properties> (Low water absorption) The polyamide resin film of the present invention preferably has low water absorption, and the water absorption rate is preferably 3.5% or less, more preferably 3.2% or less, and even more preferably 3.0% or less. Biaxially stretched films are preferred because they have a lower water absorption rate than unstretched films due to the progress of crystalline orientation of the resin. Water absorption is determined by the following water absorption test. A circular film specimen with a diameter of 100 mm is stored at 23°C and a relative humidity of 50% for at least 24 hours, and then its mass (s) is weighed. The film specimen is then immersed in distilled water at 23°C for 24 hours, after which the water adhering to the surface is wiped off and the mass (e) of the film specimen is weighed, and the water absorption (%) is calculated using the following formula 1. Four film specimens are tested and the average value is calculated. {(e)-(s)} / (s)×100(%) (Formula 1)

[0051] (Impact resistance (puncture impact strength and elongation)) The impact resistance of the film of the present invention can be evaluated by the puncture impact strength when a hole is made in a film test piece. The puncture impact strength at either the measurement temperature of 23°C or -20°C is preferably 0.65 J or more, more preferably 0.70 J or more, and it is even more preferable that the puncture impact strength at both temperatures of 23°C and -20°C is within the above range. If the puncture impact strength is within this 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 elongation (mm) measured as described above is preferably greater than 15.0 mm at either the measurement temperature, 23°C, or -20°C, more preferably 16.0 mm or more, and even more preferably 17.0 mm or more, and it is particularly preferable that the elongation at both 23°C and -20°C is within the above range. The impact resistance of the film of the present invention is measured by the impact puncture strength test of JIS P8134 (1998). The stand of the device is set on a solid foundation so as not to lose work load, and the pendulum has an arm in a 90-degree arc, with a penetrating part attached to the tip of the arm, allowing it to oscillate freely.

[0052] (tensile strength at break, tensile elongation at break) The tensile strength at break in both the machine direction (MD) and the transverse direction (TD) of the film, under both temperature conditions of -20°C and 23°C, is preferably 120 MPa or more, more preferably 150 MPa or more. There is no particular upper limit, but it is about 500 MPa or less. A film with a tensile breaking strength in this range maintains the rigidity of the film when packaging contents, and is less likely to develop pinholes or break due to bending. The tensile breaking elongation is preferably 20% or more, and more preferably 25% 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 20% or more under -20°C conditions 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 strength at break can be measured according to JIS K7127 (1999), at a test speed of 200 mm / min, at temperatures of -20°C and 23°C.

[0053] (transparency) The film of the present invention preferably has a haze of less than 4.0%, more preferably 3.0% or less, and even more preferably 2.0% or less, with the lower the haze the better. When the haze value is within this range, the film has excellent transparency, and is excellent in design and visibility of contents when used as a packaging film. The haze is measured based on JIS K7136 (2000).

[0054] (oxygen permeability) The film of the present invention has an oxygen permeability of 5.00 cc / (m 2 ·24h·atm) or less, and 3.00cc / (m 2 ·24h·atm) or less is more preferable, and 2.50cc / (m 2 ·24h·atm) or less is particularly preferable, and 2.00cc / (m 2It is most preferable that the value is less than 24h atm. Oxygen permeability is 5.00cc / (m 2 24h·atm) or less is preferable because it can maintain sufficient oxygen gas barrier properties as a packaging film to prevent deterioration of the contents and keep them fresh.

[0055] (Water vapor permeability) The film of the present invention has a water vapor transmission rate of 60.0 g / (m 2 ·24h·atm) or less, and 55.0g / (m 2 ·24h·atm) or less is more preferable, and 50.0g / (m 2 ·24h·atm) or less, and 45.0g / (m 2 It is particularly preferable that the water vapor transmission rate is 60.0 g / (m 2 24h·atm) or less is preferable because it can maintain sufficient oxygen gas barrier properties as a packaging film to prevent deterioration of the contents and keep them fresh.

[0056] (Penetration strength) The puncture strength of the film of the present invention is preferably 7.0 N or more, more preferably 8.0 N or more, and even more preferably 9.0 N or more, and higher values ​​are preferred, under temperature conditions of 23° C. and −20° C. A puncture strength of 7.0 N or more is preferred because the film has excellent impact resistance and tends to be less prone to punctures when used as a packaging material.

[0057] (tear strength) The tear strength of the film of the present invention, as measured by JIS K7128 (1998) trouser tear strength test, is preferably 0.6 N / mm or more, more preferably 0.7 N / mm or more, and even more preferably 0.8 N / mm or more, and higher values ​​are preferred. A tear strength of 0.6 N / mm or more is preferred because the film tends to be less prone to tearing.

[0058] (Boiling resistance evaluation) The haze of the film of the present invention after treatment in hot water at 98°C for 30 minutes and then cooling for 15 minutes is preferably 4.0% or less, more preferably 3.5% or less, even more preferably 3.0% or less, and preferably even lower. A haze of 4.0% or less is preferable because the transparency of the film after boiling is good.

[0059] [Packaging] The film of the present invention can be laminated with a sealant film or the like by a known lamination method and formed into a package such as a bag, a tube, or a container combining a lid and a base. The method for forming the various packaging bodies is not particularly limited and any known method can be used, for example, pillow molding. [Example]

[0060] 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:

[0061] (Aliphatic polyamide resin) PA6: Polyamide 6 (manufactured by UBE, relative viscosity 3.4, melting point 220°C, density 1140 kg / m 3 ) PA10,10: Polyamide 10,10 (Polypla, manufactured by Evonik, melting point 199°C, density 1040 kg / m 3 ) PA11: Polyamide 11 (manufactured by ARKEMA, melting point 185°C, density 1030 kg / m 3 )

[0062] (barrier resin) EVOH: Ethylene-vinyl acetate copolymer saponification product (manufactured by Mitsubishi Chemical Corporation, ethylene content 32 mol%, melting point 183°C, density 1190 kg / m 3 )

[0063] <Film production, film layer structure> The resin composition for layer (A), which was prepared by blending the above-mentioned raw materials in the mass ratios shown in Table 1, was fed into a φ40 mm single-screw extruder, and the resin composition for layer (B), which was prepared by blending the above-mentioned raw materials in the mass ratios shown in Table 1, was fed into a φ32 mm single-screw extruder. In the examples, both layers (A) and (B) were melted at 220°C, while in the comparative examples, layer (A) was melted at 250°C and layer (B) was melted at 220°C. The melts were then distributed using a distribution block, multilayered in a multilayer T-die set at 260°C, melt-extruded, and quenched on a cooling roll at 30°C to produce an unstretched polyamide-based resin film (180 μm) having a layer (A) / layer (B) / layer (A) configuration. 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 5.0 times in the width direction at 120°C using a tenter-type transverse stretching machine. Subsequently, the film was heat-set at 185°C for the Examples and 215°C for the Comparative Examples, and then 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 polyamide resin film with a layer structure [Layer (A) 5.5 μm / Layer (B) 4.0 μm / Layer (A) 5.5 μm] and a total thickness of 15.0 μm. The thickness of each layer was confirmed by microscopic observation of a vertical cross-section of the film.

[0064] <Evaluation> The polyamide resin films obtained in the examples and comparative examples were evaluated as follows, and the results are summarized in Table 1. (1) Transparency (haze (%)) Haze (unit: %) was measured in accordance with JIS K7136 (2000) and evaluated according to the following criteria. 3.0% or less 〇 Over 3.0% and under 4.0% △ 4.0% or more ×

[0065] (2) Tensile strength at break (MPa), tensile elongation at break (%) Based on JIS K7127 (1999), the tensile breaking strength (unit: MPa) and tensile breaking elongation (unit: %) in the machine direction (MD) and transverse direction (TD) were measured at a test speed of 200 mm / min and at temperatures of -20°C and 23°C.

[0066] (3) Impact resistance (puncture impact strength (J) and elongation (mm)) The puncture impact strength (unit: J) and elongation (unit: mm) were measured using the impact hole opening strength test of JIS P8134 (1998). The stand of the device was set on a solid foundation to prevent loss of work, and the pendulum had an arm in a 90-degree arc, with a penetrating part attached to the tip of the arm, allowing it to oscillate freely. The puncture impact strength was measured under two temperature conditions: 23°C and -20°C.

[0067] (4) Piercing strength (N) Based on JIS Z1707 (2019), the puncture strength (N) was measured at -20°C and 23°C.

[0068] (5) Tear strength Tear strength (unit: N / mm) was measured in both MD and TD according to JIS K7128 (1998) Trouser Tear Strength.

[0069] (6) Water absorption (water absorption rate (%)) The obtained polyamide resin film was cut into circular film test pieces with a diameter of 100 mm, which were stored for at least 24 hours under conditions of 23°C and 50% relative humidity, and the mass (s) was weighed. The film test pieces were then immersed in distilled water at 23°C for 24 hours, after which the water adhering to the surface was wiped off and the mass (e) of the film test piece was weighed, and the water absorption rate (unit: %) was calculated using the following formula (1). Four film test pieces were tested, and the average value was calculated and evaluated according to the following criteria. {(e)-(s)} / (s)×100(%) (Formula 1) 〇: 3.0% or less, △: more than 3.0% but less than 3.5%, ×: More than 3.5%

[0070] (7) Oxygen permeability Using an oxygen permeability measuring device (OX-Tran2 / 21: manufactured by MOCON), oxygen permeability (cc / m) at 23°C and 0% RH was measured in accordance with JIS K7126-1 (2006). 2 The thermal conductivity (24hr·atm) was measured and evaluated according to the following criteria. 〇: 2.0cc / (m 2 ·24hr · atm) or less, △: 2.0cc / (m 2 ·24hr·atm), 5.0cc / (m 2 ·24hr · atm) or less, ×:5.0cc / (m 2 ·24hr · ATM),

[0071] (8) Water vapor permeability Using a water vapor transmission rate measuring device (OX-Tran2 / 21: manufactured by MOCON), the water vapor transmission rate (g / m) at 40°C and 90% RH was measured in accordance with JIS K7129-B (2008). 2 The thermal conductivity (24hr·atm) was measured and evaluated according to the following criteria. 〇: 45.0g / (m 2 ·24hr · atm) or less, △: 45.0 g / (m 2 ·24hr·atm), 60.0g / (m 2 ·24hr · atm) or less, ×:60.0g / (m 2 ·24hr · atm) super,

[0072] (9) Boil resistance The obtained polyamide resin film was cut into a 15 cm square, clamped between an aluminum frame and secured with clips, treated in 98°C hot water for 30 minutes, and then allowed to cool for 15 minutes. The condition of the film was then checked, and the appearance was visually inspected and the haze (unit: %) was measured in accordance with JIS K7136 (2000), and evaluated according to the following criteria. (Haze) 〇: 3.0% or less, △: Over 3.0% and 4.0% or less, ×: More than 4.0% (visual evaluation) 〇: No bleaching is observed. △: Some bleaching is observed. ×: Whitening is observed throughout the specimen.

[0073] [Table 1]

Claims

1. A polyamide-based resin film having at least two layers, namely, a layer (A) containing 40% by mass or more of an aliphatic polyamide resin (a) and a layer (B) containing a barrier resin (b), A polyamide resin film that satisfies the following (1) and (2): (1) The aliphatic polyamide resin (a) is at least one selected from the group consisting of polyamides having a molecular structure obtained by polycondensation of diamines having 10 or more carbon atoms and / or dicarboxylic acids having 10 or more carbon atoms, and polyamides having a molecular structure obtained by ring-opening polymerization of caprolactam having 10 or more carbon atoms. (2) The barrier resin (b) is a saponified ethylene-vinyl acetate copolymer.

2. 2. The polyamide resin film according to claim 1, which has a water absorption rate of 3.5% or less as measured in accordance with JIS K7209 (2000).

3. The polyamide resin film according to claim 1 , wherein the layer (A) is disposed on both sides of the layer (B), and the polyamide resin film has at least three layers.

4. The water vapor permeability under conditions of 40°C and 90% relative humidity is 60.0 g / (m ２ 2. The polyamide resin film according to claim 1, wherein the compressive strength is 24 hr·atm or less.

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

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

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