Polyamide resin films and packaging

Abstract

To provide a polyamide resin film that has excellent film formability and low water absorbency to resist elongation and dimensional change due to water absorption even under the high humidity environment, and offers excellent transparency and impact resistance.SOLUTION: A polyamide resin film has at least two layers of a layer (A) containing a predetermined aliphatic polyamide resin (a1) and a predetermined aromatic polyamide resin (a2) and a layer (B) containing a barrier resin (b).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyamide resin film that can be suitably used as a packaging material for food and pharmaceuticals, and to a packaging body made using the film. [Background technology]

[0002] Films made from polyamide resins are resin materials used in a variety of applications due to their excellent mechanical properties such as impact resistance and strength, as well as heat resistance and moldability, including biaxial stretching. Furthermore, while polyamide resins offer superior oxygen barrier properties compared to general-purpose plastics such as polyolefin resins, they are known to be insufficient for the level of barrier properties required for long-term preservation of contents in food and pharmaceutical packaging. Therefore, polyamide resin films that combine mechanical properties, moldability, and barrier properties by layering them with resins that have high barrier properties, such as ethylene-vinyl acetate copolymer saponified (EVOH) or polymetaxylylene adipamide (MXD6 polyamide), have become widely used.

[0003] On the other hand, biaxially oriented films using polyamide resins generally use polyamide 6 as the main component due to its versatility and productivity. However, due to the relatively high water absorption properties of polyamide 6, there is a potential problem that water absorption elongation and dimensional changes are likely to occur in high-humidity environments, which can cause problems in secondary processes of packaging material production, such as printing, lamination, boiling, and retorting. Furthermore, there is a need for polyamide biaxially oriented films with excellent low water absorption, including the ability to prevent water absorption in the barrier resin layer.

[0004] Patent Document 1 discloses a technology for a polyamide resin film that has good dimensional stability against water and excellent flexural fatigue resistance, which includes polyamide 6T, polyamide 6T / 6, polyamide MXD, polyamide 12, etc., as a low-hygroscopic polyamide resin, and a flexural fatigue resistance modifier. However, the inclusion of the flexural fatigue resistance modifier tends to reduce transparency, and the impact resistance of the film was insufficient depending on the usage environment.

[0005] Furthermore, with the recent increase in environmental awareness, there is a growing interest in using biomass as a raw material for plastics. Polyamides such as polyamide 10,10, obtained by condensing sebacic acid and 1,10-decanediamine, which are derived from castor oil, and polyamide 11, obtained by polymerizing 11-aminoundecanoic acid, have been industrialized. These are attracting attention as low-hygroscopic polyamide resins due to their low water absorption, which is caused by having fewer amide bonds compared to polyamide 6. However, the technology described in Patent Document 1 similarly suffered from insufficient transparency and, depending on the usage environment, insufficient impact resistance of the film. Furthermore, due to the long linear chains between amide bonds and high crystallinity, stretching was difficult, and film-forming properties tended to be poor compared to polyamide 6 and other materials. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2010-121136 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The problem that this invention aims to solve is to provide a polyamide resin film that has low water absorption, is less prone to water absorption elongation and dimensional changes even in high humidity environments, has good film-forming properties, and exhibits good transparency and impact resistance. [Means for solving the problem]

[0008] As a result of diligent research to achieve the above objective, the inventors have completed the following invention.

[0009] [1] A polyamide resin film having at least two layers: a layer (A) containing an aliphatic polyamide resin (a1) and an aromatic polyamide resin (a2), and a layer (B) containing a barrier resin (b), A polyamide resin film that satisfies the following conditions (1) and (2). (1) The aliphatic polyamide resin (a1) is at least one selected from polyamides containing 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 caprolactams having 10 or more carbon atoms. (2) The aromatic polyamide resin (a2) is at least one selected from polyamides having a molecular structure of a diamine with 6 or more carbon atoms and terephthalic acid and / or isophthalic acid, or polyamides having a molecular structure of an aminocarboxylic acid with 6 or more carbon atoms and terephthalic acid and / or isophthalic acid.

[0010] [2] The polyamide resin film according to [1], wherein the aliphatic polyamide resin (a1) is at least one selected from polyamide 6,10, polyamide 10,10, polyamide 11, and polyamide 12.

[0011] [3] The polyamide resin film according to either [1] or [2], wherein the aromatic polyamide resin (a2) has a molecular structure derived from a cycloalkane.

[0012] [4] The polyamide resin film according to any one of [1] to [3], wherein the barrier resin (b) is polymeta-xylylene adipamide and / or ethylene-vinyl acetate copolymer saponified product.

[0013] [5] A polyamide resin film described in any one of items [1] to [4], having a water absorption rate of 3.8% or less as measured in accordance with JIS K7209 (2000).

[0014] [6] The polyamide resin film according to any one of [1] to [5], having at least three layers in the order of the layer (A) / the layer (B) / the layer (A).

[0015] [7] The polyamide resin film according to any one of [1] to [6], which is biaxially stretched.

[0016] [8] A package using the polyamide resin film according to any one of [1] to [7]. [Advantages of the Invention]

[0017] According to the present invention, it is possible to provide a polyamide resin film having low water absorption, excellent film-forming properties, good transparency and impact resistance. Due to these characteristics, the polyamide resin film of the present invention is suitable for use in a relatively high-humidity environment and can be preferably used as a package for food products, pharmaceutical and clothing products, industrial parts, etc. [Embodiments for Carrying out the Invention]

[0018] Hereinafter, the present invention will be described in detail. In addition, 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 (a1) and the aromatic polyamide resin (a2)" 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)". In the case of a layer containing both the polyamide resin (the aliphatic polyamide resin (a1) and the aromatic polyamide resin (a2)) and the barrier resin (b), when the content of the polyamide resin in the layer is 50% by mass or more, it is defined as the layer (A), and when the content of the polyamide resin is less than 50% by mass, it is defined as the layer (B). The polyamide resin film may absorb moisture (water) in the air or may package a food containing water and absorb the water. In the description of the present invention, hygroscopicity and water absorption are used synonymously. When described as "X to Y" (where X and Y are arbitrary numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", as well as the meanings of "preferably greater than X" and "preferably less than Y".

[0019] <Polyamide resin film> The polyamide resin film of the present invention is a polyamide resin film having at least two layers, namely a layer (A) containing an aliphatic polyamide resin (a1) and an aromatic polyamide resin (a2) and a layer (B) containing a barrier resin (b), and is a polyamide resin film satisfying the following (1) and (2). (1) The aliphatic polyamide resin (a1) is at least one selected from polyamides containing 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 aromatic polyamide resin (a2) is at least one selected from polyamides having a molecular structure of diamines having 6 or more carbon atoms and terephthalic acid and / or isophthalic acid, or polyamides having a molecular structure of aminocarboxylic acids having 6 or more carbon atoms and terephthalic acid and / or isophthalic acid

[0020] (Layer (A) containing aliphatic polyamide resin (a1) and aromatic polyamide resin (a2)) ·Aliphatic polyamide resin (a1) The aliphatic polyamide resin (a1) in the present invention is at least one selected from polyamides containing 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.

[0021] Layer (A) may contain an aliphatic polyamide resin (c) other than the aliphatic polyamide resin (a1) described above. Examples of aliphatic polyamide resin (c) include polyamide 6, polyamide 6,6, etc. However, from the viewpoint of reducing the water absorption of the polyamide resin film, the content of aliphatic polyamide resin (c) is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, particularly preferably 5% by mass or less, and most preferably none, based on 100% by mass of the entire layer (A). Furthermore, layer (A) may be a single layer or multiple layers. In the case of multiple layers, the resin composition of each layer may be different.

[0022] The molecular structure of aliphatic polyamide resin (a1) has a longer alkyl chain than polyamide 6, which is commonly used in polyamide resin films. Therefore, aliphatic polyamide resin (a1) is highly hydrophobic, reducing the water absorption of the film and, consequently, reducing dimensional changes due to water absorption. Note that "polyamide containing diamines with 10 or more carbon atoms and / or dicarboxylic acids with 10 or more carbon atoms" means that it contains residues obtained by condensation polymerization of diamines with 10 or more carbon atoms and / or dicarboxylic acids with 10 or more carbon atoms. "Polyamide having a molecular structure obtained by ring-opening polymerization of caprolactam with 10 or more carbon atoms" means, for example, in addition to polyamide 11 and polyamide 12 shown below, it also includes copolymers of polyamide 11 or polyamide 12 with polyalkylene ether glycol. These may be used individually or in combination of two or more.

[0023] Examples of polyalkylene ether glycols in copolymers of polyamide 10 or polyamide 11 with polyalkylene ether glycol include polyoxyethylene glycol, polyoxytetramethylene glycol, and polyoxypropylene glycol, with polyoxytetramethylene glycol being preferred from the viewpoint of resistance to flexural pinholes. Furthermore, in order to contribute the molecular structural properties of polyamide 10 or polyamide 11 to the film, the copolymerization composition ratio of polyamide 10 or polyamide 11 is preferably 65% ​​by mass or more, and more preferably 70% by mass or more. By setting the copolymerization composition ratio of polyamide 10 or polyamide 11 within this range, the contribution of long-chain alkyl chains increases, resulting in excellent low water absorption.

[0024] From the viewpoint of low water absorption, the aliphatic polyamide resin (a1) is preferably polyamide 10, polyamide 11, polyamide 4,10, polyamide 5,10, polyamide 6,10, polyamide 8,10, polyamide 9,10, polyamide 10,10, or polyamide 10,12, and more preferably polyamide 6,10, polyamide 10,10, polyamide 11, or polyamide 12. Furthermore, polyamide 10,10 and polyamide 11 are even more preferred because they also possess impact resistance.

[0025] The aliphatic polyamide resin (a1) is at least one selected from polyamides containing diamines and / or dicarboxylic acids having 10 or more carbon atoms, and polyamides having a molecular structure obtained by ring-opening polymerization of caprolactams having 10 or more carbon atoms, thereby providing the film with excellent low water absorption and sufficient impact resistance. The molecular structure of aliphatic polyamide resin (a1) has longer hydrocarbon chains compared to polyamide 6, a typical polyamide resin, resulting in a lower concentration of amide bonds per unit mass and thus low water absorption. Furthermore, because aliphatic polyamide resin (a1) has a lower concentration of amide bonds per unit mass compared to polyamide 6, the proportion of hydrogen bonds between polyamide resins in film formation, especially when biaxially stretched, is reduced, decreasing the elasticity of the film and increasing its impact resistance.

[0026] Furthermore, in terms of reducing environmental impact, which is a social issue in recent years, polyamide 10, polyamide 11, polyamide 4,10, polyamide 5,10, polyamide 6,10, polyamide 8,10, polyamide 9,10, polyamide 10,10, polyamide 10,12, polyamide 10T, polyamide 11T, and polyamide 11-polyoxytetramethylene glycol are preferred among aliphatic polyamide resins (a1) that contain biomass-derived components. Among these, polyamide 11 and polyamide 10,10 are preferred because they are 100% biomass-derived resins. Polyamide 10,10 is obtained by copolymerization of sebacic acid and 1,10-decanediamine obtained by amination of sebacic acid. Polyamide 11 is obtained by ring-opening polymerization of 11-aminoundecanoic acid obtained from castor oil.

[0027] The aliphatic polyamide resin (a1) preferably has a melting point of 180°C or higher, and more preferably 185°C or higher, in terms of the heat resistance of the film. The upper limit of the melting point is not particularly limited, but is usually 270°C or lower. Aliphatic polyamide resin (a1) has a density of 1200 kg / m³ in terms of the impact resistance of the film. 3 The following is preferable: 1180 kg / m 3 The following are preferable.

[0028] The biomass content of the aliphatic polyamide resin (a1) is preferably 50% or more, more preferably 80% or more, even more preferably 90% or more, particularly preferably 95% or more, and most preferably 100%.

[0029] The aliphatic polyamide resin (a1) preferably has a relative viscosity of 2.5 to 5.5, more preferably 2.8 to 4.5, and even more preferably 3.0 to 4.0, as measured under conditions of 96% H2SO4 as a solvent, a sample concentration of 1.0 mass%, and a temperature of 25°C, in accordance with JIS K6920-2 (2009). Using an aliphatic polyamide resin (a1) with a relative viscosity within the above range tends to improve the impact resistance of the film. Furthermore, when two or more aliphatic polyamide resins (a1) are mixed and used, their relative viscosities may be the same or different. The relative viscosity is determined by measuring the relative viscosity of each aliphatic polyamide resin (a1) being mixed and taking the weighted average value.

[0030] • Aromatic polyamide resin (a2) The aromatic polyamide resin (a2) is at least one selected from polyamides having a molecular structure of a diamine with 6 or more carbon atoms and terephthalic acid and / or isophthalic acid, or polyamides having a molecular structure of an aminocarboxylic acid with 6 or more carbon atoms and terephthalic acid and / or isophthalic acid. Furthermore, "polyamide having a molecular structure of a diamine with 6 or more carbon atoms and terephthalic acid and / or isophthalic acid" means a polyamide having a molecular structure obtained by condensation polymerization of a diamine and terephthalic acid and / or isophthalic acid, and "polyamide having a molecular structure of an aminocarboxylic acid with 6 or more carbon atoms and terephthalic acid and / or isophthalic acid" means a polyamide having a molecular structure obtained by condensation polymerization of an aminocarboxylic acid and terephthalic acid and / or isophthalic acid.

[0031] From the viewpoint of suppressing the crystallinity of aliphatic polyamide resins (a1) with long carbon chains, using aromatic polyamide resins (a2) with sterically hindered skeletons derived from terephthalic acid or isophthalic acid can reduce the degree of crystallinity and improve stretchability (film-forming properties). Furthermore, it is preferable that the aromatic polyamide resin (a2) has a molecular structure derived from cycloalkanes. This increases the crystallinity suppression effect described above, making it possible to obtain a homogeneous polyamide resin film with excellent transparency.

[0032] As described above, the aromatic polyamide resin (a2) preferably contains both terephthalic acid and / or isophthalic acid, as this tends to further suppress crystallization and improve the stretchability (film-forming properties) of the polyamide resin (a1), and also improve its mechanical strength.

[0033] The number of carbon atoms in the aminocarboxylic acid constituting the aromatic polyamide resin (a2) is preferably 10 or more, and more preferably 11 or more, from the viewpoint of low water absorption.

[0034] • Other ingredients Layer (A) may contain other resins, thermoplastic elastomers, additives, etc., as long as it does not impair the effects of the present invention. Other resins that may be added include polyamide resins other than aliphatic polyamide resin (a1) and aromatic polyamide resin (a2), as well as aramid resins. Other examples include polyolefin resins, polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polyester resins, polycarbonate resins, polyacetal resins, acrylic resins, ethylene vinyl acetate copolymers, polymethylpentene resins, polyvinyl alcohol resins, cyclic olefin resins, polylactic acid resins, polybutylene succinate resins, polyacrylonitrile resins, polyethylene oxide resins, cellulose resins, polyimide resins, polyurethane resins, polyphenylene sulfide resins, polyphenylene ether resins, polyvinyl acetal resins, polybutadiene resins, polybutene resins, polyamide-imide resins, polyamide-bismaleimide resins, polyarylate resins, polyetherimide resins, polyetheretherketone resins, polyetherketone resins, polyethersulfone resins, polyketone resins, polysulfone resins, and fluorine resins. The content of other resins is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and most preferably 10% by mass or less, relative to the total mass of layer (A) of 100% by mass.

[0035] Examples of thermoplastic elastomers include polyamide elastomers, polyester elastomers, polystyrene elastomers, and polyolefin elastomers. These are resin types that exhibit elasticity by having a molecular backbone of polyamide, polyester, polystyrene, or polyolefin as a hard segment, and containing polyalkylene ether glycol or rubber components as a soft segment within it. Here, polyamide elastomers refer to those in which the soft segment makes up 50% by mass or more. Furthermore, polyamide elastomers, polyester elastomers, and polyolefin elastomers are preferable when they are modified with unsaturated carboxylic acids such as maleic anhydride, their derivatives, or anhydrides, as this increases their affinity with aliphatic polyamide resins (a1) and aromatic polyamide resins (a2), resulting in good dispersion and miscibility, and tends to improve the pinhole resistance and transparency of the film. Suitable thermoplastic elastomers include, for example, block copolymers of polyamide 11 or polyamide 12 with polyoxytetramethylene glycol and their acid-modified products, block copolymers of polybutylene terephthalate with polyoxytetramethylene glycol and their acid-modified products, and styrene-isobutylene-styrene block copolymers (SIBS). When the total mass of layer (A) is 100% by mass, the thermoplastic elastomer content is preferably 10% by mass or less from the viewpoint of film-forming properties, high transparency, and low water absorption.

[0036] Additives may include, for example, heat stabilizers, antioxidants, UV absorbers, weathering agents, lubricants, fillers, nucleating agents, plasticizers, anti-blocking agents, anti-fogging agents, flame retardants, dyes, pigments, stabilizers, coupling agents, impact resistance modifiers, and the like. From the viewpoint of film-forming properties, high transparency, and low water absorption, the additive content is preferably 5% by mass or less relative to the total mass of the constituent components of layer (A).

[0037] • Composition of layer (A) In the film of the present invention, when the total mass of layer (A) is 100% by mass, layer (A) preferably contains 1 to 99% by mass, more preferably 30 to 95% by mass, even more preferably 50 to 92% by mass, and particularly preferably 60 to 90% by mass of aliphatic polyamide resin (a1). Furthermore, layer (A) contains an aromatic polyamide resin (a2), preferably in an amount of 1 to 99% by mass. More preferably, it contains 5 to 70% by mass, even more preferably 8 to 50% by mass, and particularly preferably 10 to 40% by mass.

[0038] If multiple layers (A) exist, the composition of each layer (A) may be the same or different. This configuration makes it possible to achieve good film-forming properties while enabling low water absorption, impact resistance, and reduced environmental impact of the polyamide resin film.

[0039] When layer (A) contains both an aliphatic polyamide resin (a1) and an aromatic polyamide resin (a2), they tend to form an immiscible dispersion, with the component with a higher composition ratio forming the "sea" (matrix) and the component with a lower composition ratio forming the "islands" (domains), thus easily creating a sea / island structure. When a sea / island structure is formed, if the composition ratio of the component with the lower composition ratio between the aliphatic polyamide resin (a1) and the aromatic polyamide resin (a2) is 40% by mass or less, the domain diameter tends to be smaller, which reduces film haze and is preferable in terms of film transparency. Furthermore, void generation originating from the sea / island phase interface is easily suppressed, which is also effective for stable film formation.

[0040] (Layer (B) containing barrier resin (b)) The film of the present invention can be given barrier properties by providing a layer (B) containing a barrier resin (b), which is useful in preventing deterioration and spoilage of contents when used as packaging material and improving long-term storage. As the barrier resin, known resins can be used, such as polyvinyl alcohol (PVA) resins, ethylene-vinyl acetate copolymer saponified (EVOH) resins, semi-aromatic polyamides containing structural units derived from metaxylylenediamine such as polymetaxylylene adipamide (polyamide MXD6), and polyvinylidene chloride (PVDC) resins. Among these, ethylene-vinyl acetate copolymer saponified (EVOH) resins and semi-aromatic polyamides containing structural units derived from metaxylylenediamine are preferred in terms of oxygen barrier properties and moldability, and semi-aromatic polyamides containing structural units derived from metaxylylenediamine are more preferred in terms of interlayer adhesion with the layer (A) containing the aliphatic polyamide resin.

[0041] • Ethylene-vinyl acetate copolymer saponified The ethylene-vinyl acetate copolymer saponified product (EVOH) used in the present invention is a copolymer obtained by saponifying a copolymer of ethylene and vinyl acetate with an alkaline catalyst or the like, and in addition to ethylene structural units and vinyl alcohol structural units (including unsaponified vinyl ester structural units), it 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 group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, and 3-buten-1,2-diol, and hydroxyl group-containing α-olefin derivatives such as their esters and acylated products; unsaturated carboxylic acids or their salts, partially alkyl esters, fully alkyl esters, nitriles, amides, or anhydrides; unsaturated sulfonic acids or their salts; vinylsilane compounds; vinyl chloride; styrene, etc. Furthermore, EVOH-based resins that have been post-modified by urethaneization, acetalization, cyanoethylation, oxyalkyleneization, etc., can also be used. These EVOHs may be used individually or as a mixture of two or more types. The ethylene content in the ethylene-vinyl acetate copolymer saponified product is not particularly limited, but from the viewpoint of film formation stability, it is generally preferred to be 5 mol% or more, more preferably 10 mol% or more, and particularly preferred to be 20 mol% or more. From the viewpoint of 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 30 mol% or less. Furthermore, the degree of saponification of the ethylene-vinyl acetate copolymer saponified product is preferably 96% or more, and more preferably 98% or more. In the film of the present invention, by having the ethylene content and degree of saponification in the ethylene-vinyl acetate copolymer saponified product within the above ranges, an excellent balance between film formation properties and barrier properties is obtained, making it suitable for molding processes such as co-extrusion with layer (A) and biaxial stretching.

[0042] • Semi-aromatic polyamide containing structural units derived from metaxylylenediamine Examples of semi-aromatic polyamides containing structural units derived from metaxylylenediamine used in the present invention include, for example, polymetaxylylene adipamide (polyamide MXD6), metaxylylene / paraxylylene adipamide copolymers, and copolymers obtained by copolymerizing these with aliphatic diamines, alicyclic diamines, aromatic diamines other than metaxylylenediamine and paraxylylenediamine, aromatic dicarboxylic acids, lactams, ω-aminocarboxylic acids, aromatic aminocarboxylic acids, etc. Among these, polymetaxylylene adipamide (polyamide MXD6) is preferred from the viewpoint of barrier properties and moldability.

[0043] Polymeta-xylylene adipamide (polyamide MXD6) primarily refers to the polymerization product of meta-xylylenediamine and adipic acid. When the diamine component constituting polymeta-xylylene adipamide is taken as 100 mol%, 70 mol% or more, preferably 80 mol% or more, and more preferably 90 mol% or more, is meta-xylylenediamine. It may also contain isomers such as orthoxylylenediamine and para-xylylenediamine, or aliphatic diamines with 6 to 12 carbon atoms in amounts of 30 mol% or less, but from the viewpoint of barrier properties and heat resistance, it is preferable that these are not included. When the dicarboxylic acid component constituting polymeta-xylylene adipamide (polyamide MXD6) is taken as 100 mol%, 70 mol% or more, preferably 80 mol% or more, and more preferably 90 mol% or more, is adipic acid. The material may contain 30 mol% or less of aliphatic dicarboxylic acids having 7 to 12 carbon atoms, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, and cyclic aliphatic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, but it is preferable that these are not included from the viewpoint of barrier properties and extensibility.

[0044] • Other ingredients The layer (B) containing the barrier resin (b) may contain other resins or thermoplastic elastomers, etc., as long as the effects of the present invention are not impaired. For example, when a thermoplastic elastomer is included, the flexibility of layer (B) tends to be improved, and the pinhole resistance of the film tends to be improved. The same types of thermoplastic elastomers that can be included in layer (A) described above can be used as the thermoplastic elastomer. When layer (B) is considered to be 100% by mass, the thermoplastic elastomer content is preferably 20% by mass or less, and more preferably 1 to 15% by mass. A thermoplastic elastomer content of 20% by mass or less is preferable in terms of film productivity because it suppresses a decrease in the barrier properties and transparency of the film, and also suppresses gel formation during film manufacturing.

[0045] (Layer composition) The film of the present invention may have at least two layers, layer (A) and layer (B). When multiple layers (A) are arranged, the layers (A) may have the same composition or different compositions. In the case of a layer configuration such as layer (A1) / layer (A2) / layer (B), it is preferable to include a resin common to layer (A1) and / or layer (B) in layer (A2) in order to improve the interlayer adhesion between layer (A1) and layer (B). For example, it is preferable that layer (A2) contains an aliphatic polyamide resin (a1) and / or an aromatic polyamide resin (a2) and a barrier resin (b) (e.g., polyamide MXD6). Even when multiple layers (B) are arranged, they may be layers (B) of the same composition or layers (B) of different compositions.

[0046] In addition to layers (A) and (B), there may also be another layer (C). The components of the other layer (C) are not particularly limited, but when layer (C) is placed between layer (A) and layer (B), it is preferable to use an adhesive resin to improve interlayer adhesion, such as an acid-modified polyolefin resin. When layer (C) is placed on the surface layer 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.

[0047] While there are no particular limitations on the order of the layers, for example, a two-layer configuration of [A / B], a three-layer configuration of [A / B / A], [A / B / C], [A / C / B], [C / A / B], or a five-layer configuration of [A / A / B / A / A], [A / C / B / C / A], [C / A / B / A / C], or [A / B / C / B / A] is preferable in terms of film formation stability. In particular, configurations such as [A / B / A], [A / A / B / A / A], [A / C / B / C / A], and [C / A / B / A / C], in which layers (A) having low water absorption are placed on both sides of layer (B), that is, having at least three layers in the order of layer (A) / layer (B) / layer (A) (other layers (e.g., layer (C)) may be placed between layer (A) and layer (B) as long as this order is followed), are preferred in that they prevent water absorption by layer (B) and improve the barrier properties of the film, and provide sufficient impact resistance to the film, including layer (B). In the above layer configuration, layer (A) is referred to as "A", layer (B) as "B", and layer (C) as "C".

[0048] Hereinafter, aliphatic polyamide resin (a1) will be abbreviated as resin (a1), polyamide MXD6 as MXD6, polyamide 6 as PA6, aromatic polyamide resin (a2) as resin (a2), ethylene-vinyl acetate copolymer saponified product as EVOH, and thermoplastic elastomer as elastomer, and the layer composition will be illustrated. A preferred layer configuration for [A / B / A] is, for example, the following: ·[Resin (a1) + Resin (a2)] / [EVOH] / [Resin (a1) + Resin (a2)] • [Resin (a1) + Resin (a2)] / [MXD6 + Elastomer] / [Resin (a1) + Resin (a2)]

[0049] A preferred layer configuration for [A / A / B / A / A] is, for example, the following: • [Resin (a1) + Resin (a2)] / [Resin (a1) + Resin (a2) + MXD6] / [MXD6 + Elastomer] / [Resin (a1) + Resin (a2) + MXD6] / [Resin (a1) + Resin (a2)] • [Resin (a1) + Resin (a2)] / [Resin (a1) + MXD6] / [MXD6 + Elastomer] / [Resin (a1) + MXD6] / [Resin (a1) + Resin (a2)] • [Resin (a1) + Resin (a2)] / [Resin (a1) + Resin (a2) + MXD6 + Elastomer] / [MXD6 + Elastomer] / [Resin (a1) + Resin (a2) + MXD6 + Elastomer] / [Resin (a1) + Resin (a2)]

[0050] The total thickness of the film of the present invention is not particularly limited, but from the viewpoint of processability, transparency, and handling, 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 film and will also have excellent barrier properties.

[0051] From the standpoint of the mechanical properties and oxygen barrier properties of the film, the thickness ratio of layer (A) to the total film thickness of 100% is preferably 25-90%, and the thickness ratio of layer (B) is preferably 10-75%. If there are multiple layers (A) and / or layers (B), the ratio is the ratio of the total thickness of layer (A) or layer (B) to the total thickness. The thickness of each 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. If there are multiple layers (A), layer (B), and layer (C), each layer may have a different thickness or the same thickness.

[0052] The film of the present invention can be subjected to surface treatments and processing such as printing, coating, and vapor deposition. Furthermore, it can be used in lamination with other resin layers such as polyolefins and polyesters, other films, adhesive layers, metal foils, paper, etc. Known lamination methods can be used, such as dry lamination, wet lamination, sand lamination, and extrusion lamination. Additionally, surface treatments such as corona discharge and anchor coating may be applied to the surface of the film of the present invention during lamination. Furthermore, when the film of the present invention is used as packaging material, barrier properties and moisture resistance can be further improved from the viewpoint of maintaining the quality of the contents and preventing spoilage by vapor deposition of aluminum, silicon oxide, alumina, diamond-like carbon, etc., or by applying a barrier coating agent such as polyvinyl alcohol (PVA) resin or polyvinylidene chloride (PVDC) resin.

[0053] <Method for manufacturing the film of the present invention> The film of the present invention may have a film structure comprising at least a layer (A) containing an aliphatic polyamide resin (a1) and an aromatic polyamide resin (a2), and a layer (B) containing a barrier resin (b), and can be manufactured by known methods. When using various polyamides (aliphatic polyamide resins (a1), aromatic polyamide resins (a2)) and barrier resins (b) as raw materials, if the resin has absorbed water, it will melt when heated and extrude, generating water vapor and oligomers which will inhibit film formation. Therefore, when preparing the raw materials, it is preferable to dry the resin beforehand to reduce the moisture content to 0.1% by mass or less. These resins are fed into separate extruders for each layer, the molten resins are combined in a feed block, a flat die, or an annular die of a multi-manifold, and then co-extruded as a multilayer film. After rapid cooling, a flat or annular unstretched film can be obtained.

[0054] The polyamide resin film of the present invention may be used as an unstretched film, but may also be a stretched film stretched in at least one direction, or a biaxially oriented film stretched in both longitudinal and transverse directions. For example, when producing a biaxially oriented film, an unstretched film is biaxially stretched in the film's flow direction (longitudinal direction, MD) and the width direction perpendicular to it (transverse direction, TD) using known methods such as tenter-type sequential biaxial stretching, tenter-type simultaneous biaxial stretching, or tubular-type simultaneous biaxial stretching. For example, in the tenter-type sequential biaxial stretching method, the unstretched film is heated to a temperature range of 40 to 100°C, stretched longitudinally using a roll-type longitudinal stretcher, and then stretched transversely using a tenter-type transverse stretcher within a temperature range of 80 to 230°C to produce the film. In the case of tenter-type simultaneous biaxial stretching or tubular-type simultaneous biaxial stretching methods, for example, the film can be produced by stretching in both the longitudinal and transverse directions simultaneously within a temperature range of 40 to 230°C. The stretching ratio is preferably 2.0 to 5.0 times in the film's flow direction (longitudinal direction, MD) and width direction (transverse direction, TD), and more preferably 2.5 to 4.5 times in each direction. A stretching ratio of 2.0 times or more in each biaxial stretching direction promotes stretch orientation, resulting in good mechanical properties such as film strength. Furthermore, a stretching ratio of 5.0 times or less in each direction makes the film less likely to break during stretching, resulting in good productivity.

[0055] Furthermore, to improve the dimensional stability of the film, the biaxially oriented film can be heat-set. The heat-set temperature is preferably 170°C to 225°C, and more preferably 180°C to 220°C. This makes it possible to obtain a biaxially oriented film with good dimensional stability at room temperature. To alleviate the stress caused by crystallization shrinkage due to thermal fixation, a relaxation treatment can be performed during thermal fixation in the width direction by 0 to 15%, preferably 3 to 10%. Furthermore, after the relaxation treatment, the material can be re-stretched at a temperature of 140°C to 200°C by a range of 2 to 9%, preferably 3 to 7%, and more preferably 4 to 7% in the width direction. If the re-stretching temperature is within the above range, an appropriate stress is obtained during stretching, resulting in uniform stretching and a more even lateral shrinkage rate in the width direction.

[0056] <Various physical properties of the film of the present invention> (Low water absorption) The water absorption rate of the film of the present invention is preferably 3.8% or less, more preferably 3.5% or less, and even more preferably 3.3% or less. By setting it to 3.8% or less, it becomes easier to suppress changes in film dimensions due to moisture, and the dimensional stability of the film can be improved. When it is a biaxially oriented film, crystal orientation also becomes less likely to progress, making it easier to improve dimensional stability. The water absorption rate is determined by the following water absorption test. The film of the present invention is prepared as a circular film test piece with a diameter of 100 mm, and stored for 24 hours or more under conditions of 23°C and 50% relative humidity, and its mass (s) is weighed. Next, the film test piece is immersed in distilled water at 23°C for 24 hours, and after wiping off the water adhering to the surface, the mass (e) of the film test piece is weighed, and the water absorption rate is calculated using the formula 1 below. Four film test pieces are tested, and the average value is determined. {(e)-(s)} / (s)×100(%) (Formula 1)

[0057] (Impact resistance) The impact resistance of the film of the present invention can be evaluated in accordance with the impact puncture strength test of JIS P8134 (1998). The puncture impact strength at -20°C and 23°C when the penetration point punctures a film test piece is preferably 0.3 J or higher, and more preferably 0.4 J or higher, at both -20°C and 23°C. Within the range of the puncture impact strength, the film has excellent impact resistance and can be said to be good because it is less likely to be punctured when used as packaging material.

[0058] (Tensile fracture stress, tensile fracture elongation) The tensile breaking stress is preferably 150 MPa or higher, and more preferably 200 MPa or higher, in both the flow direction (MD) and width direction (TD), and at both temperature conditions of -20°C and 23°C. There is no particular upper limit, but it is around 500 MPa. With a tensile breaking stress within this range, when packaging contents, the rigidity of the film is maintained, and pinholes and breakage due to bending are less likely to occur. The tensile elongation at break is preferably 35% or more, and more preferably 40% or more, in both the film's flow direction (MD) and width direction (TD), and at both -20°C and 23°C temperatures. Since films become less stretchable at lower temperatures and their puncture resistance weakens in frozen food packaging, a tensile elongation of 35% or more at -20°C is beneficial. There is no particular upper limit to the tensile elongation at break, but it is generally around 150%. Tensile elongation at fracture and tensile stress at fracture are measured according to JIS K7127 (1999), at a test speed of 200 mm / min, and at temperatures of -20°C and 23°C.

[0059] (transparency) The film of the present invention preferably has a haze of 10.0% or less, more preferably 8.0% or less, and the lower the haze value, the better. Within this range of haze value, the film has excellent transparency, good design, and good visibility of the contents when used as a packaging film. Haze is measured according to JIS K7136(2000).

[0060] (Barrier properties) The film of the present invention has an oxygen permeability of 20 cc / m² under conditions of 23°C and 50% relative humidity. 2 It is preferable that the pressure be 24 hours / atm or less, and 15 cc / m 2 It is even more preferable that the oxygen permeability is 20 cc / m³ or less, and even lower is desirable. 2 If the oxygen level is 24h / atm or lower, it is preferable as a packaging film because it can maintain sufficient oxygen barrier properties to prevent deterioration of the contents and keep them fresh.

[0061] (Biomass content) When a biomass-derived aliphatic polyamide resin (a1) and / or aromatic polyamide resin (a2) are used in layer (A), the biomass content of the film can be calculated from the composition ratio of the layer and the layer thickness ratio to the total film thickness. From the perspective of recent environmental concerns, it is desirable to increase the biomass content of the film, for example, 1% or more is preferable, 5% or more is more preferable, 10% or more is even more preferable, and the higher the better.

[0062] (Piercing strength) The puncture strength of the film of the present invention is preferably 5.0 g or more, more preferably 6.0 g or more, and even more preferably 7.0 g or more, at both -20°C and 23°C. Within the specified range of puncture strength, the film exhibits excellent resistance to punctures and good durability as a packaging film. The puncture strength is measured according to JIS Z1707 (2019).

[0063] <Package> The film of the present invention can be laminated with a sealant film or the like by a known lamination method and formed into packaging bodies such as bags, tubes, or containers that combine a lid and a bottom material. [Examples]

[0064] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. <Ingredients> The abbreviations, components, and physical properties of the resins used in the examples and comparative examples are as follows.

[0065] (Aliphatic polyamide resin (a1)) PA6: Polyamide 6, relative viscosity 3.4, melting point 220°C, density 1140 kg / m³ 3 , Biomass content 0% PA10,10: Polyamide 10,10, relative viscosity 3.4, melting point 190°C, density 1030 kg / m³ 3 100% biomass PA11: Polyamide 11, relative viscosity 3.4, melting point 220°C, density 1140 kg / m³ 3 100% biomass (Aromatic polyamide resin (a2)) a2-1: Rilsan Clear G120 (ARKEMA): Polyamide containing 11-aminoundecanoic acid / 4,4'-methylenebis(2-methylcyclohexylamine) / terephthalic acid / isophthalic acid-derived components, biomass content 44% a2-2: Selar PA3426 (manufactured by DuPont): Hexamethylenediamine / polyamide containing terephthalic acid and isophthalic acid-derived components, 0% biomass content.

[0066] (Thermoplastic elastomer) PA12-PTMG: Polyamide 12-polytetramethylene ether glycol (PTMG) block copolymer, PTMG copolymer composition ratio 70% by mass (Barrier resin) MXD6: Polymethaxylyleneadipamide

[0067] <Film production, film layer structure> (Examples 1-3, Comparative Examples 1-3) The resin compositions for layers (A1) and (A2), prepared by blending the raw materials in the mass ratios shown in Table 1, were fed into separate φ40 mm extruders, and the resin composition for layer (B) was fed into a φ32 mm extruder. Both layers were melted at 250°C, distributed in a distribution block, and multilayered in a co-extrusion T-die. The molten film was then extruded and rapidly cooled on a cooling roll at 30°C to produce an unstretched polyamide resin film. The obtained unstretched polyamide resin film was stretched 3.0 times in the flow direction at 56°C using a roll-type longitudinal stretcher, then stretched 4.9 times in the width direction at 120°C using a tenter-type transverse stretcher, and subsequently heat-set at 215°C, followed by 8% relaxation in the width direction. After cooling to room temperature, both ends corresponding to the gripping portion of the clip were trimmed, and the trimmed film was wound into a roll to obtain a polyamide resin film (width 530 mm) with a layer structure [layer (A1) 3.4 μm / layer (A2) 2.6 μm / layer (B) 3.0 μm / layer (A2) 2.6 μm / layer (A1) 3.4 μm] and a total thickness of 15.0 μm. The thickness of each layer was measured by microscopic observation after cross-sectioning the film perpendicularly.

[0068] <Rating> The obtained polyamide resin films were evaluated as described below, and the results are summarized in Table 1. Regarding film-forming properties, in Examples 1-3, the crystallinity was reduced by using a specific aromatic polyamide resin (a2) in addition to the aliphatic polyamide resin (a1), which is polyamide 10,10 or polyamide 11. This suppressed the formation of spherulites that inhibit film stretching, thus improving film-forming properties. In Comparative Example 1, polyamide 6 was used as the aliphatic polyamide resin (a1), and therefore the crystallinity was relatively low, so there were no problems with film-forming properties. Furthermore, in Comparative Examples 2 and 3, since only polyamide 10,10 and polyamide 11 were used as the aliphatic polyamide resin (a1), the crystallinity was high, making it easy for spherulites that inhibit film stretching to form, resulting in poor film formation.

[0069] (1) Film thickness variations The thickness of the polyamide resin film was measured at 10 points, each equally divided along the width (530 mm), and evaluated based on the difference between the maximum and minimum values ​​according to the following criteria. For thickness measurement, we used the Mitutoyo ID-F125. 10μm or less:◎ More than 10μm and less than 20μm:〇 More than 20μm: ×

[0070] (2) Water absorption (water absorption rate (%)) A 100 mm diameter circular polyamide resin film was used as a test specimen, and its mass (s) was weighed after being stored for 24 hours or more under conditions of 23°C and 50% relative humidity. After immersing the film specimen in distilled water at 23°C for 24 hours, the water adhering to the surface was wiped off, and the mass (e) of the film specimen was weighed. The water absorption rate (in %) was calculated using formula 1 below. Four film specimens were tested, and the average value was calculated. {(e)-(s)} / (s)×100 (Formula 1) Water absorption was evaluated according to the following criteria. 2.0% or less: ◎ More than 2.0% and less than 3.8%:〇 More than 3.8%:×

[0071] (3) Impact resistance (puncture impact strength (J)) The puncture impact strength (unit: J) was measured by the impact opening strength test of JIS P8134 (1998). The base of the device was installed on a firm foundation so that there was no loss of work. The pendulum had an arm in an arc of 90 degrees, and a penetrating part was attached to the tip of the arm, which could vibrate freely.

[0072] (4) Tensile breaking stress (MPa), tensile breaking elongation (%) Based on JIS K7127 (1999), the tensile breaking stress (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 under temperature conditions of -20°C and 23°C.

[0073] (5) Transparency (haze (%)) The haze (unit: %) was measured in accordance with JIS K7136 (2000). [[ID=!13]]

[0074] (6) Biomass content (%) The biomass content (%) was calculated from the biomass content of the raw material polyamide resin, the layer composition ratio, and the layer thickness ratio.

[0075] (7) Puncture strength (g) The puncture strength was measured based on JIS Z1707 (2019).

[0076] (8) Barrier property (oxygen transmission rate) Using an oxygen transmission rate measuring device (OX-Tran2 / 21: manufactured by MOCON), the oxygen transmission rate (cc / m 2 ·24hr·atm) at 23°C and 50% RH was measured in accordance with JIS K7126-1 (2006). 15 cc / m 2 ·24hr·atm or less: ◎ 15 cc / m 2 ·24hr·atm over 20 cc / m 2 ·24hr·atm or less: 〇 20 cc / m 2 ·24hr·atm over: ×

[0077] It should be noted that in the above translation, there is a possible incorrect tag "!13" in the original text which might be a typo. I've translated it as it is but it should be checked in the original context. [Table 1]

[0078] In the polyamide resin films of Examples 1 to 3, layers (A1) and (A2) contained a predetermined aliphatic polyamide resin (a1) and a predetermined aromatic polyamide resin (a2). Compared to Comparative Example 1, the film water absorption rate was lower, and the impact resistance, expressed as puncture impact strength, was sufficient for a polyamide film. Furthermore, the tensile breaking stress and tensile breaking elongation were also good. In addition, the film-forming properties were improved compared to Comparative Examples 2 and 3, and the thickness uniformity was also good. [Industrial applicability]

[0079] The film of the present invention is a polyamide resin film with excellent low water absorption, sufficient impact resistance, and film-forming properties, and can be suitably used for packaging food products, pharmaceuticals, clothing, industrial parts, etc. In particular, it is useful for applications under high humidity conditions and for packaging contents containing moisture. Furthermore, by using biomass-derived resin raw materials, it greatly contributes to reducing the environmental burden.

Claims

1. A polyamide resin film having at least two layers: a layer (A) containing an aliphatic polyamide resin (a1) and an aromatic polyamide resin (a2), and a layer (B) containing a barrier resin (b), The barrier resin (b) is polymetaxylylene adipamide, A polyamide resin film that satisfies the following conditions (1) and (2). (1) The aliphatic polyamide resin (a1) is at least one selected from polyamides containing a diamine having 10 or more carbon atoms and / or a dicarboxylic acid having 10 or more carbon atoms, and polyamides having a molecular structure obtained by ring-opening polymerization of a caprolactam having 10 or more carbon atoms. (2) The aromatic polyamide resin (a2) is a polyamide having a molecular structure of an aminocarboxylic acid with 6 or more carbon atoms and terephthalic acid and / or isophthalic acid, and is selected from at least one polyamide having a molecular structure derived from a cycloalkane.

2. The polyamide resin film according to claim 1, wherein the aliphatic polyamide resin (a1) is at least one selected from polyamide 6, 10, polyamide 10, 10, polyamide 11, and polyamide 12.

3. A polyamide resin film according to claim 1 or 2, wherein the water absorption rate measured in accordance with JIS K7209 (2000) is 3.8% or less.

4. A polyamide resin film according to any one of claims 1 to 3, having at least three layers in the order of layer (A) / layer (B) / layer (A).

5. A polyamide resin film according to any one of claims 1 to 4, which is formed by biaxial stretching.

6. A packaging body made using a polyamide resin film according to any one of claims 1 to 5.

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