TWI868331B - Biaxially oriented polyamide films, laminated films and packaging bags - Google Patents

Abstract

The purpose of the present invention is to provide a biaxially stretched polyamide film, which has excellent impact resistance, bending pinhole resistance and friction pinhole resistance, and can reduce environmental load. The biaxially stretched polyamide film of the present invention comprises 70% to 99% by weight of polyamide 6 and 1% to 30% by weight of polyamide, at least part of which is derived from biomass, as a polyamide resin, and the polyamide 6 comprises 5% to 100% by weight of polyamide 6 obtained by chemical regeneration when the polyamide 6 is set to 100% by weight.

Description

Biaxially oriented polyamide films, laminated films and packaging bags

The present invention relates to a biaxially stretched polyamide film having excellent impact resistance, bending pinhole resistance and friction pinhole resistance, and using a raw material derived from biomass (organic resources derived from plants and other organisms) and polyamide 6 obtained by chemically regenerating waste polyamide products. The biaxially stretched polyamide film of the present invention can be preferably used as a food packaging film, etc.

Previously, biaxially stretched films made of aliphatic polyamides represented by polyamide 6 have excellent impact resistance and bending pinhole resistance and have been widely used as various packaging material films.

As a means of improving the above-mentioned bending pinhole resistance, a film in which a polyamide-based elastomer is mixed with an aliphatic polyamide is known (for example, refer to Patent Document 1). The film has good bending pinhole resistance and impact resistance in a low temperature environment, and is not easy to produce pinholes caused by bending fatigue in a low temperature environment. However, it is known that due to the thermal degradation of the polyamide-based elastomer added during film production, degraded products called resin deposits are easily generated at the die lip outlet, which will become a cause of deterioration of the accuracy of film thickness. In addition, there is a problem that the degraded products will produce defective products due to their own falling, which will reduce the production efficiency during continuous film production.

Pinholes are not only caused by bending, but also by friction (abrasion). The improvement methods for pinholes caused by bending and pinholes caused by friction are often opposite. For example, there is a tendency as follows: if the flexibility of the film is increased, it becomes less likely to produce bending pinholes, but the degree of flexibility becomes corresponding, and it becomes easier to produce pinholes caused by friction. In response to this, it is proposed to provide a surface coating on the outer surface of a biaxially stretched polyamide film to produce a laminate for packaging with excellent bending resistance and friction pinhole resistance (for example, refer to patent document 2). However, this method has little effect on preventing the generation of friction pinholes. In addition, a coating step becomes necessary.

In recent years, in order to build a circular society, the use of biomass as a raw material to replace fossil fuels in the field of materials has attracted attention. Biomass is an organic compound formed by photosynthesis of carbon dioxide and water. By using this organic compound, carbon dioxide and water can be used again as a raw material for so-called carbon neutrality (since the amount of carbon dioxide emitted and absorbed in the environment is the same, the increase of carbon dioxide as a greenhouse gas can be suppressed). Recently, the practical application of bioplastics using these biomass as raw materials has developed rapidly, and attempts have also been made to produce polyesters as general polymer materials from these biomass raw materials.

In order to reduce the amount of plastic waste, it is required to use recycled materials. There are the following methods to recycle polyamide 6: thermal recycling method, which is to recover it in the form of heat energy by incineration; material recycling method, which is to re-mold it after melting and reuse it; and chemical recycling method, which is to chemically depolymerize it and reduce it to the raw materials of polyamide, so as to reuse it in polyamide production.

Among these methods, the chemical regeneration method can decompose polyamide 6 into the raw material caprolactam and then recover it, thereby reusing it as a raw material for polyamide 6, so it can be said to be an industrially useful regeneration method.

For example, Patent Document 3 discloses a recycling method, which is to recycle the used polyamide clothing products, depolymerize and recover ε-caprolactam, purify and polymerize them, and regenerate polyamide fibers or polyamide molded products by melt spinning or molding. According to this technology, it is possible to realize recycling of recycled clothing products by returning them to raw materials for reuse. In addition, by decomposing and refining the recycled clothing products, high-quality raw materials (raw material monomers) can be obtained with high purity, so that high-quality polyamide 6 products can be obtained by recycling and reuse, thereby realizing repeated recycling. In addition, it is also possible to greatly reduce the recovery and sorting operations of recycled clothing products.

The polyamide resin obtained by the chemical regeneration method has been mainly used as a raw material for fibers and molded products, but has not yet been put into practical use as a film for food packaging. [Prior Art Literature] [Patent Literature]

[Patent document 1] Japanese Patent Publication No. 11-254615. [Patent document 2] Japanese Patent Publication No. 2001-205761. [Patent document 3] Japanese Patent Publication No. 7-310204.

[The problem that the invention wants to solve]

The present invention is created in view of the above-mentioned problems of the prior art. The purpose of the present invention is to provide a biaxially stretched polyamide film with excellent impact resistance, bending pinhole resistance and friction pinhole resistance, and can reduce environmental load. [Means for solving the problem]

That is, the present invention includes the following structures. [1] A biaxially stretched polyamide film comprising 70% to 99% by weight of polyamide 6 and 1% to 30% by weight of a polyamide of which at least a portion of the raw material is derived from biomass as a polyamide resin, wherein the polyamide 6 comprises 5% to 100% by weight of polyamide 6 obtained by chemical regeneration, based on 100% by weight of polyamide 6. [2] A biaxially stretched polyamide film as described in [1], wherein the polyamide 6 comprises, in addition to polyamide 6 obtained by chemical regeneration, 5 to 50 parts by weight of polyamide 6 obtained by physical regeneration when the polyamide 6 is 100 parts by weight. [3] A biaxially stretched polyamide film as described in [1] or [2], characterized in that the content of carbon derived from biomass determined by radiocarbon (C ¹⁴ ) is 1% to 15% relative to the total carbon in the biaxially stretched polyamide film. [4] A biaxially stretched polyamide film as described in any one of [1] to [3], wherein at least a portion of the raw materials are derived from a biomass-derived polyamide resin, which is at least one polyamide resin selected from the group consisting of polyamide 11, polyamide 410, polyamide 610, and polyamide 1010. [5] The biaxially stretched polyamide film as described in any one of [1] to [4] is a layer having at least one area layer on at least one surface of the biaxially stretched polyamide film, and the area layer contains 70 mass % to 100 mass % of polyamide 6, and the polyamide 6 contains 5 mass % to 100 mass % of polyamide 6 obtained by chemical regeneration when the polyamide 6 is set to 100 mass %. [6] A biaxially stretched polyamide film as described in [5], wherein the polyamide 6 comprises, when the polyamide 6 is 100 parts by weight, 5 to 50 parts by weight of polyamide 6 obtained by physical regeneration in addition to polyamide 6 obtained by chemical regeneration. [7] A biaxially stretched polyamide film as described in [5] or [6], wherein the thickness of the laminated layer is 7% to 50% of the thickness of the entire film. [8] A biaxially stretched polyamide film as described in any one of [1] to [7], characterized in that: the following (a) and (b) are satisfied: (a) the number of pinhole defects when the torsional bending test is carried out 1000 times at a temperature of 1°C using a Gelbo FLex tester is 10 or less; (b) the distance until pinholes are generated in the friction pinhole resistance test is 2900 cm or more. [9] A biaxially stretched polyamide film as described in any one of [1] to [8], characterized in that: the haze is less than 10% and the dynamic friction coefficient is less than 1.0. [10] A biaxially stretched polyamide film as described in any one of [1] to [8], characterized in that the lamination strength of the biaxially stretched polyamide film and the polyethylene sealant film after bonding is 4.0N/15mm or more. [11] A laminated film, wherein a sealant film is laminated on at least one side of the biaxially stretched polyamide film as described in any one of [1] to [10]. [12] A packaging bag using the laminated film as described in [11]. [Effect of the invention]

The biaxially stretched polyamide film of the present invention uses polyamide 6 resin as a main component, is mixed with a polyamide resin polymerized from a raw material derived from a specific biomass, and adopts specific film-making conditions, thereby obtaining a polyamide film that exhibits impact resistance, bending pinhole resistance, friction pinhole resistance, adhesion to a sealant film, and is carbon neutral.

The biaxially stretched polyamide membrane of the present invention can further obtain a polyamide membrane capable of reducing environmental load by using or blending polyamide 6 obtained by chemically regenerating waste polyamide products.

Furthermore, according to the present invention, polyamide derived from biomass has an effect on improving the bending pinhole resistance, so it is not necessary to add polyamide elastomer. Therefore, it is possible to suppress the adhesion of deteriorated products generated by polyamide elastomer to the inner surface of the mold and to suppress the adhesion of resin deposits to the die lip outlet. As a result, it is possible to prevent the deterioration of the uneven thickness of the film and realize long-term continuous production.

[Biaxially stretched polyamide film] The biaxially stretched polyamide film of the present invention is characterized in that it contains 70% to 99% by mass of polyamide 6 and 1% to 30% by mass of a polyamide of which at least a part is derived from biomass as a raw material as a polyamide resin. Furthermore, the polyamide 6 is characterized in that when the polyamide 6 is set to 100 parts by mass, 5 parts to 100 parts by mass of polyamide 6 obtained by chemical regeneration is included. By including 70% or more of polyamide 6, the biaxially stretched polyamide film composed of polyamide 6 can obtain excellent mechanical strength such as impact strength and gas barrier properties such as oxygen, which are originally possessed.

The biaxially stretched polyamide film of the present invention has improved bending pinhole resistance and abrasion pinhole resistance by including 1% to 30% by mass of a polyamide resin of which at least a portion of the raw materials are derived from biomass. In the case of polyamide elastomers or polyolefin elastomers used as improvers for bending pinhole resistance, although the bending pinhole resistance is improved, the abrasion pinhole resistance is deteriorated. By including a polyamide resin of which at least a portion of the raw materials are derived from biomass, a biaxially stretched polyamide film having excellent bending pinhole resistance and abrasion pinhole resistance can be obtained. In addition, a carbon-neutral film having little effect on the increase or decrease of carbon dioxide on the ground can be obtained.

The polyamide 6 used in the biaxially stretched polyamide film of the present invention is preferably polyamide 6 obtained by chemical regeneration in an amount of 5 to 100 parts by weight based on 100 parts by weight of the total polyamide 6. Examples of the chemically regenerated raw materials include, but are not limited to, waste plastic products, waste tire rubber, fiber, fishing nets and other waste polyamide 6 products. By using the chemically regenerated polyamide 6, a polyamide film capable of reducing environmental load can be obtained.

[Polyamide 6] The polyamide 6 resin used in the present invention is usually produced by ring-opening polymerization of ε-caprolactam. The polyamide 6 resin obtained by ring-opening polymerization is usually melt-extruded by an extruder after removing the caprolactam monomer with hot water, drying, and then performing the melt extrusion.

The relative viscosity of the polyamide 6 resin is preferably 1.8 to 4.5, more preferably 2.6 to 3.2. When the relative viscosity is less than 1.8, the impact strength of the film is insufficient. When it is greater than 4.5, the load of the extruder becomes large and it is difficult to obtain an unstretched film before stretching.

As the polyamide 6 used in the biaxially stretched polyamide film of the present invention, in addition to the commonly used polyamide 6 obtained by polymerization of monomers derived from fossil fuels, polyamide 6 obtained by chemically regenerating waste polyamide 6 products such as waste plastic products, waste tire rubber, fiber, and fishing nets can also be used. As a method for obtaining polyamide 6 obtained by chemically regenerating waste polyamide 6 products, for example, the following method can be used: after the used polyamide products are recovered, they are depolymerized to obtain ε-caprolactam, and the ε-caprolactam is purified and then polymerized into polyamide 6.

[Depolymerization conditions] In the depolymerization of the chemically regenerated polyamide 6 used in the production of the biaxially stretched polyamide membrane of the present invention, the polyamide 6 product is usually depolymerized by heating. The depolymerization may or may not use a catalyst.

The depolymerization pressure may be any of reduced pressure, normal pressure, and increased pressure. The depolymerization temperature is usually 100°C to 400°C, preferably 200°C to 350°C, and more preferably 220°C to 300°C. If the temperature is low, the polyamide 6 product cannot be melted, so the depolymerization speed is slow. If the temperature is high, unnecessary monomers of polyamide 6 (i.e., caprolactam) may decompose, and the purity of the recovered caprolactam may be reduced.

When a catalyst is used in the above depolymerization, an acid catalyst or an alkaline catalyst is generally used. Examples of the acid catalyst include phosphoric acid, boric acid, sulfuric acid, organic acid, organic sulfonic acid, solid acid, and salts of these acids. Examples of the alkaline catalyst include alkali metal hydroxides, alkali metal salts, alkali earth metal hydroxides, alkali earth metal salts, organic bases, solid bases, and the like. Preferred examples include phosphoric acid, boric acid, organic acids, alkali metal hydroxides, alkali metal salts, and the like. More preferably, phosphoric acid, sodium phosphate, potassium phosphate, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, etc. may be listed.

The amount of the acid catalyst used in the above depolymerization is usually 0.01% to 50% by weight relative to the polyamide 6 fiber component, preferably 0.01% to 20% by weight, and more preferably 0.5% to 10% by weight. If the amount of the catalyst used is small, the reaction speed will be slow, and if the amount of the catalyst used is large, the side reactions will increase, and the catalyst cost will increase, which will be disadvantageous in terms of economy.

The above depolymerization can be carried out in the absence of water (dry method) or in the presence of water (wet method). In the case of wet depolymerization, the amount of water used is 0.1 to 50 times by weight relative to the polyamide 6 product components such as fiber. It is preferably 0.5 to 20 times by weight, and more preferably 1 to 10 times by weight. If the amount of water used is small, the reaction rate becomes slow, and if the amount of water used is large, the concentration of the recovered caprolactam aqueous solution becomes low, which becomes disadvantageous in obtaining caprolactam. When performing wet depolymerization, the generated caprolactam is distilled out from the reaction device together with water, thereby obtaining a recovered caprolactam aqueous solution. After the depolymerization reaction is completed, caprolactam can be extracted by distillation under reduced pressure. Alternatively, it can be extracted continuously as the reaction proceeds. In the case of dry depolymerization, the generated caprolactam is distilled out from the reaction device by distillation under reduced pressure to obtain recovered caprolactam. After the depolymerization reaction is completed, caprolactam can be extracted by distillation under reduced pressure. Alternatively, it can be extracted continuously as the reaction proceeds.

Furthermore, as a method for obtaining high-purity caprolactam, it can be combined with the following purification methods: a method of subjecting the recovered caprolactam to precise distillation, a method of adding a trace amount of sodium hydroxide and performing reduced-pressure distillation, a method of performing activated carbon treatment, a method of performing ion exchange treatment, a method of performing recrystallization, etc.

The biaxially stretched polyamide film of the present invention may further use polyamide 6 obtained by physically regenerating waste generated from the production step of the biaxially stretched polyamide film.

The polyamide 6 obtained by physical regeneration mentioned above refers to, for example, the raw material obtained by granulating the film that is out of specification and cannot be shipped when manufacturing biaxially stretched polyamide film or the scraps generated in the form of cut ends (scraps) by melt extrusion or compression molding.

The lower limit of the proportion of the physically regenerated polyamide 6 added to the biaxially stretched polyamide film of the present invention is not particularly limited. As the upper limit, the total amount of polyamide 6 is set to 100 parts by mass, preferably 50 parts by mass, more preferably 40 parts by mass, and more preferably 30 parts by mass. If the proportion of the physically regenerated polyamide added exceeds the upper limit, the appearance of the film may be damaged, for example, the coloring of the film may become stronger or the haze value may become higher. Alternatively, the amount of degraded products may increase during the production of the film, which may deteriorate the film-forming properties.

[Polyamide resins in which at least a portion of the raw materials are derived from biomass] Polyamide resins in which at least a portion of the raw materials used in the present invention are derived from biomass include, for example, polyamide 11, polyamide 410, polyamide 610, polyamide 1010, polyamide MXD10 resin, polyamide 11-6T copolymer resin, etc.

Polyamide 11 is a polyamide resin having a structure in which monomers having 11 carbon atoms are bonded via amide bonds. Usually, polyamide 11 is obtained using aminoundecanoic acid or undecalactamide as a monomer. In particular, aminoundecanoic acid is a monomer obtained from castor oil, and is therefore more ideal from the perspective of carbon neutrality. The structural units derived from these monomers having 11 carbon atoms in polyamide 11 are preferably 50 mol% or more of all structural units, more preferably 80 mol% or more, and may also be 100 mol%. Polyamide 11 is usually produced by ring-opening polymerization of the aforementioned undecalactamide. The polyamide 11 obtained by ring-opening polymerization is usually melt-extruded by an extruder after removing the lactamide monomer with hot water, drying, and then melt-extruded by an extruder. The relative viscosity of the polyamide 11 is preferably 1.8 to 4.5, and more preferably 2.4 to 3.2. When the relative viscosity is less than 1.8, the impact strength of the film is insufficient. When it is greater than 4.5, the load of the extruder becomes large and it is difficult to obtain an unstretched film before stretching.

Polyamide 610 is a polyamide resin having a structure formed by polymerization of a diamine having 6 carbon atoms and a dicarboxylic acid having 10 carbon atoms. Usually, hexamethylenediamine and sebacic acid are used. Sebacic acid is a monomer obtained from castor oil, so it is more ideal from the perspective of carbon neutrality. The structural units derived from these monomers having 6 carbon atoms and the structural units derived from the monomers having 10 carbon atoms in PA610 are preferably more than 50 mol% of all structural units, more preferably more than 80 mol%, and can also be 100 mol%.

Polyamide 1010 is a polyamide resin having a structure formed by polymerization of a diamine having 10 carbon atoms and a dicarboxylic acid having 10 carbon atoms. Usually, polyamide 1010 uses 1,10-decanediamine (decamethylenediamine) and sebacic acid. Decamethylenediamine and sebacic acid are monomers obtained from castor oil, and therefore are more ideal from the perspective of carbon neutrality. The structural units derived from these diamines having 10 carbon atoms and the structural units derived from the dicarboxylic acid having 10 carbon atoms in PA1010 preferably account for more than 50 mol% of all structural units, more preferably more than 80 mol%, and can also be 100 mol%.

Polyamide 410 is a polyamide resin having a structure formed by copolymerization of a monomer having 4 carbon atoms and a diamine having 10 carbon atoms. Polyamide 410 is usually made from sebacic acid and tetramethylene diamine. As sebacic acid, castor oil, which is a vegetable oil, is preferably used as a raw material from the perspective of environmental protection. As the sebacic acid used here, from the perspective of environmental protection (especially carbon neutrality), sebacic acid obtained from castor oil is more desirable.

The lower limit of the content of the polyamide resin in which at least a part of the raw materials in the biaxially stretched polyamide film of the present invention is derived from biomass is not particularly limited, and is preferably 1 mass%, and more preferably 3 mass% or more. The upper limit of the content is 30 mass%, and more preferably 20 mass%. If the content of the polyamide resin in which at least a part of the raw materials is derived from biomass exceeds 30 mass%, there is a situation where the molten film becomes unstable when casting the molten film, and it is difficult to obtain a homogeneous unstretched film.

[Subsidiary materials, additives] The biaxially stretched polyamide film of the present invention may contain various additives such as other thermoplastic resins, lubricants, heat stabilizers, antioxidants, antistatic agents or antifogging agents, ultraviolet absorbers, dyes, pigments, etc. as needed.

[Other thermoplastic resins] The biaxially stretched polyamide film of the present invention may contain thermoplastic resins in addition to the above-mentioned polyamide 6 and polyamide resins of which at least a part of the raw materials are derived from biomass, within the scope of not impairing the purpose of the present invention. For example, polyamide resins such as polyamide 12 resin, polyamide 66 resin, polyamide 6-polyamide 12 copolymer resin, polyamide 6-polyamide 66 copolymer resin, and polyamide MXD6 resin can be listed. If necessary, it may also contain thermoplastic resins other than polyamides, such as polyester polymers such as polyethylene terephthalate, polybutylene terephthalate, and poly-2,6-naphthalate, and polyolefin polymers such as polyethylene and polypropylene. If the raw materials of these thermoplastic resins are derived from biomass, they will not affect the increase or decrease of carbon dioxide on the ground, and thus can reduce the environmental load, which is preferred.

[Lubricant] In order to improve the lubricity and facilitate handling, the biaxially stretched polyamide film of the present invention preferably contains an organic lubricant such as microparticles or fatty acid amide as a lubricant. The biaxially stretched polyamide film of the present invention has the effect of reducing the breakage of the packaging bag due to friction by improving the lubricity.

As the aforementioned microparticles, inorganic microparticles such as silica, kaolin, zeolite, and polymer organic microparticles such as acrylic acid, polystyrene, etc. can be appropriately selected and used. In addition, in terms of transparency and slip, it is preferred to use silica microparticles. The preferred average particle size of the aforementioned microparticles is 0.5μm to 5.0μm, and more preferably 1.0μm to 3.0μm. If the average particle size does not reach 0.5μm, a large amount of addition is required to obtain good slip. On the other hand, if it exceeds 5.0μm, the surface roughness of the film tends to become too large and the appearance deteriorates.

When the aforementioned silicon dioxide particles are used, the pore volume of the silicon dioxide is preferably in the range of 0.5 ml/g to 2.0 ml/g, and more preferably in the range of 0.8 ml/g to 1.6 ml/g. If the pore volume is less than 0.5 ml/g, voids are easily generated, which deteriorates the transparency of the film. If the pore volume exceeds 2.0 ml/g, it tends to be difficult to form surface protrusions generated by the particles.

In the biaxially stretched polyamide film of the present invention, fatty acid amide and/or fatty acid diamide may be contained for the purpose of improving the slip properties. Examples of fatty acid amide and/or fatty acid diamide include erucic acid amide, stearic acid amide, ethyl distearic acid amide, ethyl dioleic acid amide, etc. The content of fatty acid amide and/or fatty acid diamide in the biaxially stretched polyamide film of the present invention is preferably 0.01% by mass to 0.40% by mass, and more preferably 0.05% by mass to 0.30% by mass. If the content of fatty acid amide and/or fatty acid diamide is less than the above range, the slip properties tend to deteriorate. On the other hand, if it exceeds the above range, the wettability tends to deteriorate.

In the biaxially stretched polyamide film of the present invention, for the purpose of improving the sliding property, polyamide resins such as polyamide MXD6 resin, polyamide 12 resin, polyamide 66 resin, polyamide 6-polyamide 12 copolymer resin, and polyamide 6-polyamide 66 copolymer resin may be added. In particular, polyamide MXD6 resin is preferred, and the addition amount is preferably 1% by mass to 10% by mass.

[Antioxidant] The biaxially stretched polyamide film of the present invention may contain an antioxidant. As the antioxidant, a phenolic antioxidant is preferred. The phenolic antioxidant is preferably a completely hindered phenolic compound or a partially hindered phenolic compound. For example, tetrakis-[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate stearyl, 3,9-bis[1,1-dimethyl-2-[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane, etc. The inclusion of a phenolic antioxidant improves the film-making operability of a biaxially stretched polyamide film. In particular, when a recycled film is used as a raw material, thermal degradation of the resin is easily caused, which tends to cause poor film-making operability and increase production costs. In contrast, the inclusion of an antioxidant can inhibit thermal degradation of the resin and improve operability.

[Surface layer] In the present invention, one or more surface layers composed of the same or different resin compositions can be laminated on one or both sides of the biaxially stretched polyamide film. By laminating at least one surface layer, the surface properties can be improved.

The surface layer is preferably a layer composed of a resin composition containing 70 mass % to 100 mass % of polyamide 6. Preferably, the polyamide 6 is 80 mass % or more. More preferably, the polyamide 6 is 90 mass % or more. The upper limit is 100 mass %, preferably 99 mass %, and more preferably 97 mass %. By containing 70 mass % or more of polyamide 6, a biaxially stretched polyamide film having excellent mechanical strength such as impact strength or gas barrier properties such as oxygen can be obtained.

Furthermore, it is preferred that 5 to 100 parts by mass of polyamide 6 obtained by chemical regeneration be included in 100 parts by mass of polyamide 6. In addition to polyamide 6 obtained by chemical regeneration, polyamide 6 obtained by physical regeneration may also be used in combination. It is preferred that when polyamide 6 is 100 parts by mass, the proportion of polyamide 6 obtained by physical regeneration is 0 to 50 parts by mass. If the proportion of physically regenerated polyamide exceeds the above upper limit, the appearance of the film may be impaired, for example, the coloring of the film may become stronger or the haze value may become higher. Alternatively, the amount of degraded products may increase during the production of the film, thereby deteriorating the film forming properties.

The surface layer may contain various additives such as other thermoplastic resins, lubricants, heat stabilizers, antioxidants, antistatic agents or antifogging agents, ultraviolet absorbers, dyes, pigments, etc., depending on the functions given to the surface of the surface layer. When the surface layer is used on the outside of the packaging bag, it is not suitable to contain soft resins such as polyamide elastomers or polyolefin elastomers or substances that produce a large number of voids because friction pinhole resistance is necessary.

The surface layer may contain a thermoplastic resin other than the above-mentioned polyamide 6 within the scope of not impairing the purpose of the present invention. For example, polyamide resins such as polyamide MXD6 resin, polyamide 11 resin, polyamide 12 resin, polyamide 66 resin, polyamide 6-polyamide 12 copolymer resin, polyamide 6-polyamide 66 copolymer resin, etc. may be listed. If necessary, thermoplastic resins other than polyamide resins may be contained, such as polyester polymers such as polyethylene terephthalate, polybutylene terephthalate, and poly-2,6-naphthalate, and polyolefin polymers such as polyethylene and polypropylene.

In order to improve the slipperiness of the film, the surface layer preferably contains fine particles or an organic lubricant as a lubricant. By improving the slipperiness, the handling of the film is improved, and the breakage of the packaging bag due to friction is reduced.

As the aforementioned fine particles, inorganic fine particles such as silica, kaolin, and zeolite, and polymer organic fine particles such as acrylic and polystyrene can be appropriately selected and used. In addition, from the perspective of transparency and slipperiness, silica fine particles are preferably used.

The preferred average particle size of the aforementioned microparticles is 0.5 μm to 5.0 μm, more preferably 1.0 μm to 3.0 μm. If the average particle size is less than 0.5 μm, a large amount of addition is required to obtain good lubricity. On the other hand, if it exceeds 5.0 μm, the surface roughness of the film tends to become too large and the appearance tends to deteriorate.

When the aforementioned silica particles are used, the pore volume of the silica is preferably in the range of 0.5 ml/g to 2.0 ml/g, and more preferably in the range of 0.8 ml/g to 1.6 ml/g. If the pore volume is less than 0.5 ml/g, voids are easily generated, which deteriorates the transparency of the film. If the pore volume exceeds 2.0 ml/g, it tends to be difficult to form surface protrusions generated by the particles.

As the aforementioned organic lubricant, fatty acid amide and/or fatty acid diamide may be contained. Examples of fatty acid amide and/or fatty acid diamide include erucic acid amide, stearic acid amide, ethyl distearic acid amide, ethyl dioleic acid amide, etc. The content of fatty acid amide and/or fatty acid diamide added to the surface layer is preferably 0.01 mass % to 0.40 mass %, and more preferably 0.05 mass % to 0.30 mass %. If the content of fatty acid amide and/or fatty acid diamide does not reach the above range, the sliding property tends to deteriorate. On the other hand, if it exceeds the above range, the wettability tends to deteriorate.

In the surface layer, in order to improve the slipperiness of the film, a polyamide resin other than polyamide 6 may be added, such as polyamide MXD6 resin, polyamide 11, polyamide 12 resin, polyamide 66 resin, polyamide 6-polyamide 12 copolymer resin, polyamide 6-polyamide 66 copolymer resin, etc. Polyamide MXD6 resin is particularly preferred, and it is preferred to add 1% to 10% by mass. If it is less than 1% by mass, the effect of improving the slipperiness of the film is small. In the case of more than 10% by mass, the effect of improving the slipperiness of the film is saturated. Polyamide MXD6 resin is produced by polycondensation of meta-xylylenediamine and adipic acid. The relative viscosity of polyamide MXD6 is preferably 1.8 to 4.5, more preferably 2.0 to 3.2. When the relative viscosity is less than 1.8 or greater than 4.5, it is sometimes difficult to use an extruder to mix with the polyamide resin.

When microparticles, organic lubricants, or polyamide resins such as polyamide MXD6 resin are added to the surface layer for the purpose of improving the lubricity of the film, it is preferable to reduce the amount of these components added to the biaxially stretched polyamide film serving as the substrate, because a film having excellent transparency and excellent lubricity can be obtained.

In addition, in order to improve the adhesion, a polyamide resin other than polyamide 6 may be added to the surface layer. In this case, copolymerized polyamide resins such as polyamide 6-polyamide 12 copolymer resin and polyamide 6-polyamide 66 copolymer resin are preferred.

As a method of adding auxiliary materials or additives such as lubricants or antioxidants to the biaxially stretched polyamide film and the surface layer of the present invention, the lubricants or antioxidants can be added during the polymerization of the resin or during the melt extrusion using an extruder. A high-concentration masterbatch can also be prepared and added to the polyamide resin during film production. This can be done by such a known method.

[Biaxially stretched polyamide film] The thickness of the biaxially stretched polyamide film of the present invention is not particularly limited. When used as a packaging material, it is usually less than 100 μm. Generally, a film with a thickness of 5 μm to 50 μm is used, and in particular, a film with a thickness of 8 μm to 30 μm is used.

When at least one surface layer of the biaxially stretched polyamide film of the present invention is used as one or more surface layers to form a laminated film, if the thickness of the surface layer accounts for a large portion of the total thickness of the film, the bending pinhole resistance is reduced. The thickness of the laminated layer is preferably 7% to 50%, more preferably 7% to 30%, relative to the thickness of the entire film.

The number of pinhole defects of the biaxially stretched polyamide film of the present invention when the torsional bending test is performed 1000 times at a temperature of 1°C using a Gelber-Francis tester based on the measurement method described in the embodiment is 10 or less. More preferably, it is 5 or less. The fewer the number of pinhole defects after the bending test, the better the bending pinhole resistance. If the number of pinholes is 10 or less, a packaging bag that is not prone to pinholes even when a load is applied to the packaging bag during transportation can be obtained.

Furthermore, the distance until pinholes are generated in the friction pinhole resistance test of the biaxially stretched polyamide film of the present invention described in the examples is 2900 cm or more. It is more preferably 3100 cm or more, and even more preferably 3300 cm or more. The longer the distance until pinholes are generated, the better the friction pinhole resistance is. If the distance until pinholes are generated is 2900 cm or more, a packaging bag that is not prone to pinholes even when the packaging bag rubs against a corrugated cardboard box during transportation can be obtained.

The biaxially stretched polyamide film of the present invention is characterized in that it is excellent in both the above-mentioned properties of bending pinhole resistance and friction pinhole resistance. The biaxially stretched polyamide film of the present invention having these properties is not prone to pinholes during transportation, and is therefore extremely useful as a packaging film.

The thermal shrinkage rate of the film of the present invention at 160°C for 10 minutes is in the range of 0.6% to 3.0% in both the travel direction (hereinafter referred to as MD direction) and the width direction (hereinafter referred to as TD direction), preferably 0.6% to 2.5%. When the thermal shrinkage rate exceeds 3.0%, curling or shrinkage may occur when heat is applied in subsequent steps such as lamination or printing. In addition, the lamination strength with the sealant film may be weakened. Although the thermal shrinkage rate can be reduced to less than 0.6%, the mechanical properties may become brittle. In addition, productivity deteriorates, so it is not good.

Excellent impact resistance is a characteristic of the biaxially stretched polyamide film, so the impact strength of the biaxially stretched polyamide film of the present invention is preferably 0.7 J/15 μm or more, and more preferably 0.9 J/15 μm or more.

The haze value of the biaxially stretched polyamide film of the present invention is preferably 10% or less. It is more preferably 7% or less, and even more preferably 5% or less. If the haze value is small, the transparency and gloss are good, so when used in packaging bags, beautiful printing can be achieved to improve the product value. If microparticles are added to improve the slipperiness of the film, the haze value will increase. Therefore, when the film is two or more layers, the microparticles can be added only to the surface layer to reduce the haze value.

The dynamic friction coefficient of the biaxially stretched polyamide film of the present invention is preferably 1.0 or less. It is more preferably 0.7 or less, and even more preferably 0.5 or less. If the dynamic friction coefficient of the film is small, the sliding property becomes good and the film becomes easy to handle. If the dynamic friction coefficient of the film is too small, it becomes too slippery and difficult to handle. Therefore, the dynamic friction coefficient of the biaxially stretched polyamide film of the present invention is preferably 0.15 or more.

The biaxially stretched polyamide film of the present invention preferably contains 1% to 15% of the carbon derived from biomass (also called biomass degree) relative to the total carbon in the polyamide film as determined by radiocarbon (C ¹⁴ ) according to ASTM D6866-16. It is known that carbon dioxide in the atmosphere contains C ¹⁴ at a fixed ratio (105.5 pMC), so the C ¹⁴ content in plants that absorb carbon dioxide in the atmosphere, such as corn, is also about 105.5 pMC. In addition, it is also known that fossil fuels contain almost no C ¹⁴ . Therefore, by measuring the ratio of C ¹⁴ contained in the total carbon atoms in the polyester, the ratio of carbon derived from biomass can be calculated.

The lamination strength of the biaxially stretched polyamide film of the present invention after being bonded with the polyethylene-based sealant described in the embodiment is 4.0N/15mm or more. The biaxially stretched polyamide film is usually processed into a packaging bag after being laminated with a sealant film. If the above-mentioned lamination strength is 4.0N/15mm or more, when the biaxially stretched polyamide film of the present invention is used to make packaging bags with various layered structures, the strength of the sealing part can be fully obtained, and a strong packaging bag that is not easy to break can be obtained. In order to set the lamination strength to 4.0N/15mm or more, the biaxially stretched polyamide film of the present invention can be subjected to corona treatment, coating treatment, flame treatment, etc.

[Film production method] The biaxially stretched polyamide film of the present invention can be produced by a known production method. For example, a stepwise biaxial stretching method and a synchronous biaxial stretching method can be listed. The stepwise biaxial stretching method can increase the film production speed, which is advantageous in terms of production cost and is therefore preferred.

The method for producing the biaxially stretched polyamide film of the present invention is described. First, the raw resin is melt-extruded using an extruder, extruded from a T-die into a film, cast on a cooling roll for cooling, and an unstretched film is obtained.

When a biaxially stretched polyamide film is produced by laminating at least one surface layer of a film serving as a substrate, it is preferred to use a co-extrusion method such as a feeder or a multi-manifold to obtain a laminated unstretched film. In addition to the co-extrusion method, dry lamination method, extrusion lamination method, etc. can also be selected. When lamination is performed using the co-extrusion method, the polyamide resin composition used in each layer is preferably such that the difference in melt viscosity is minimized.

The melting temperature of the resin is preferably 220°C to 350°C. If it is less than 220°C, unmelted materials may be produced, resulting in defects and other appearance defects. If it exceeds 350°C, resin degradation may be observed, resulting in a decrease in molecular weight and a poor appearance. The mold temperature is preferably 250°C to 350°C.

The cooling roller temperature is preferably -30°C to 80°C, and more preferably 0°C to 50°C. In order to cast the film-like melt extruded from the T-die on a rotating cooling drum for cooling to obtain an unstretched film, for example, a method using an air knife or an electrostatic sealing method of applying an electrostatic charge can be preferably applied. The latter is particularly preferably used.

In addition, it is preferred that the cast unstretched film is also cooled on the opposite side of the cooling roll. For example, it is preferred to use the following methods together: a method of making the cooling liquid in the tank contact the opposite side of the cooling roll of the unstretched film, a method of applying a liquid evaporated by a spray nozzle, a method of cooling by blowing a high-speed fluid, etc. The unstretched film obtained in this way is stretched in biaxial directions to obtain the biaxially stretched polyamide film of the present invention.

As a stretching method, it can be any of a synchronous biaxial stretching method and a stepwise biaxial stretching method. In either case, as a stretching method in the MD direction, a multi-stage stretching method such as a one-stage stretching method or a two-stage stretching method can be used. As described later, in terms of physical properties and the uniformity (isotropy) of physical properties in the MD direction and the TD direction, multi-stage stretching in the MD direction such as a two-stage stretching method is preferred rather than a one-stage stretching method. The stretching in the MD direction in the stepwise biaxial stretching method is preferably a roller stretching method.

The lower limit of the stretching temperature in the MD direction is preferably 50°C, more preferably 55°C, and even more preferably 60°C. If it is less than 50°C, the resin may not soften and may be difficult to stretch. The upper limit of the stretching temperature in the MD direction is preferably 120°C, more preferably 115°C, and even more preferably 110°C. If it exceeds 120°C, the resin may become too soft and may not be stably stretched.

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

In addition, when the stretching in the MD direction is performed in multiple stages, the stretching as described above can be performed by utilizing the stretching in each stage, but the stretching ratio must be adjusted so that the product of the stretching ratios in all MD directions becomes 5.0 or less. For example, in the case of two-stage stretching, it is preferred to set the stretching ratio in the first stage to 1.5 to 2.1 times and the stretching ratio in the second stage to 1.5 to 1.8 times.

The film stretched in the MD direction is stretched in the TD direction using a tenter, and heat-fixed and relaxed (also called a relaxation treatment) are performed. The lower limit of the stretching temperature in the TD direction is preferably 50°C, more preferably 55°C, and more preferably 60°C. If it is less than 50°C, the resin may not soften and stretching may become difficult. The upper limit of the stretching temperature in the TD direction is preferably 190°C, more preferably 185°C, and more preferably 180°C. If it exceeds 190°C, crystallization may occur and stretching may become difficult.

The lower limit of the stretching ratio in the TD direction (when stretching is performed in multiple stages, the total stretching ratio obtained by multiplying the ratios of each stage) is preferably 2.8, more preferably 3.2, still more preferably 3.5, and particularly preferably 3.8. If it is less than 2.8, the thickness accuracy in the TD direction may be reduced, and the crystallinity may be too low to reduce the impact strength. The upper limit of the stretching ratio in the TD direction is preferably 5.5, more preferably 5.0, still more preferably 4.7, particularly preferably 4.5, and most preferably 4.3. If it exceeds 5.5, the productivity may be significantly reduced.

The selection of the heat setting temperature is an important factor in the present invention. As the heat setting temperature increases, the film crystallization and orientation relaxation occur, which can improve the impact strength and reduce the thermal shrinkage rate. On the other hand, when the heat setting temperature is low, the crystallization and orientation relaxation are insufficient and the thermal shrinkage rate cannot be fully reduced. In addition, if the heat setting temperature becomes too high, the resin will deteriorate and the film toughness such as impact strength will be quickly lost.

The lower limit of the heat setting temperature is preferably 210°C, more preferably 212°C. If the heat setting temperature is low, the thermal shrinkage rate becomes too large, the appearance after lamination becomes poor, and the lamination strength tends to decrease. The upper limit of the heat setting temperature is preferably 220°C, more preferably 218°C. If the heat setting temperature is too high, the impact strength tends to decrease.

The heat fixation time is preferably 0.5 to 20 seconds. Preferably, it is 1 to 15 seconds. The heat fixation time can be set to an appropriate time by matching the heat fixation temperature or the wind speed in the heat fixation area. If the heat fixation conditions are too weak, crystallization and orientation relaxation become insufficient, causing the above-mentioned problems. If the heat fixation conditions are too strong, the film toughness is reduced.

Relaxation after heat setting is an effective way to control the thermal shrinkage rate. The temperature for relaxation can be selected from the range of heat setting temperature to the glass transition temperature (Tg) of the resin, but it is best to be from the heat setting temperature -10℃ to Tg + 10℃. If the relaxation temperature is too high, the shrinkage rate will be too fast and cause strain, etc., so it is not good. On the contrary, if the relaxation temperature is too low, it will not be relaxed, and it will only be relaxed without reducing the thermal shrinkage rate, and the dimensional stability will deteriorate.

The lower limit of the relaxation rate in the relaxation treatment is preferably 0.5%, more preferably 1%. If it is less than 0.5%, the thermal shrinkage may not be sufficiently reduced. The upper limit of the relaxation rate is preferably 20%, more preferably 15%, and even more preferably 10%. If it exceeds 20%, sagging may occur in the tenter, making production difficult.

Furthermore, the biaxially stretched polyamide film of the present invention may be subjected to heat treatment or moisture conditioning treatment in order to improve dimensional stability according to the application. In addition, in order to improve the adhesion of the film surface, it may be subjected to corona treatment, coating treatment or flame treatment, or printing processing, evaporation processing of metal or inorganic oxide, etc. may be performed. In addition, as the evaporated film formed by evaporation processing, an aluminum evaporated film, a single or mixed evaporated film of silicon oxide or aluminum oxide can be preferably used. Furthermore, by coating a protective layer on these evaporated films, etc., it is possible to improve oxygen barrier properties, etc.

[Laminated film and bag] The biaxially stretched polyamide film of the present invention is laminated with a sealant film to form a laminated film, and then processed into bottom-sealed bags, side-sealed bags, three-side sealed bags, pillow-type bags, self-supporting bags, gusseted bags, gusseted bottom bags and other packaging bags. As the sealant film, there can be listed unstretched linear low-density polyethylene film, unstretched polypropylene film, ethylene-vinyl alcohol copolymer film and the like.

The layer structure of the laminated film of the present invention using the biaxially stretched polyamide film of the present invention is not particularly limited as long as the laminated film contains the biaxially stretched polyamide film of the present invention. In addition, the film used in the laminated film may be a raw material derived from petrochemicals or a raw material derived from biomass. In terms of reducing environmental load, polylactic acid, polyethylene terephthalate, polybutylene succinate, polyethylene, polyethylene furandicarboxylate, etc. polymerized using raw materials derived from biomass are preferred.

Examples of the layer structure of the laminated film of the present invention include: ONY/adhesive/LLDPE, ONY/adhesive/CPP, ONY/adhesive/Al/adhesive/CPP, ONY/adhesive/Al/adhesive/LLDPE, ONY/PE/Al/adhesive/LLDPE, ONY/adhesive/Al/PE/LLDPE, PET/adhesive/ONY/adhesive/LLDPE, PET/adhesive/ONY/PE/LLDPE, PET/adhesive/ONY/adhesive/Al/adhesive/LLDPE, PE T／Adaptor／Al／Adaptor／ONY／Adaptor／LLDPE、PET／Adaptor／Al／Adaptor／ONY／PE／LLDPE、PET／PE／Al／PE／ONY／PE／LLDPE、PET／Adaptor／ONY／Adaptor／CPP、PET／Adaptor／ONY／Adaptor／Al／Adaptor／CPP、PET／Adaptor／Al／Adaptor／ONY／Adaptor／CPP、ONY／Adaptor／PET／Adaptor／LLDPE、ONY／Adaptor／PET／PE／LLDPE、ONY／Adaptor Adhesive / PET / Adhesive / CPP, ONY / Adhesive / Al / Adhesive / PET / Adhesive / LLDPE, ONY / Adhesive / Al / v / PET / PE / LLDPE, ONY / PE / LLDPE, ONY / PE / CPP, ONY / PE / Al / PE, ONY / PE / Al / PE / LLDPE, OPP / Adhesive / ONY / Adhesive / LLDPE, ONY / Adhesive / EVOH / Adhesive / LLDPE, ONY / Adhesive / EVOH / Adhesive / CPP, ONY / Adhesive / Aluminum Dioxide PET/adhesive/LLDPE, ONY/adhesive/aluminum-deposited PET/adhesive/ONY/adhesive/LLDPE, ONY/adhesive/aluminum-deposited PET/PE/LLDPE, ONY/PE/aluminum-deposited PET/PE/LLDPE, ONY/adhesive/aluminum-deposited PET/adhesive/CPP, PET/adhesive/aluminum-deposited PET/adhesive/ONY/adhesive/LLDPE, CPP/adhesive/ONY/adhesive/LLDPE, ONY/adhesive/aluminum-deposited LLDPE, ONY/adhesive/aluminum-deposited CPP, etc. In addition, the abbreviations used in the above layer structures are as follows. /: indicates the boundary of the layer; ONY: biaxially stretched polyamide film; PET: stretched polyethylene terephthalate film; LLDPE: unstretched linear low-density polyethylene film; CPP: unstretched polypropylene film; OPP: stretched polypropylene film; PE: extrusion laminated or unstretched low-density polyethylene film; Al: aluminum foil; EVOH: ethylene-vinyl alcohol copolymer; adhesive: adhesive layer for bonding the films to each other; aluminum vapor deposition: indicates that aluminum is vapor deposited. [Example]

Next, the present invention is described in more detail by way of examples, but the present invention is not limited to the following examples. In addition, the evaluation of the membrane is performed by the following measurement method. Unless otherwise specified, the measurement is performed in a measurement room at 23°C and a relative humidity of 65%.

(1) Film haze value Measured in accordance with JIS K7105 using a direct-reading haze meter manufactured by Toyo Seiki Seisakusho Co., Ltd. (2) Film thickness The film was divided into 10 equal parts along the TD direction (for narrow films, the film was divided into equal parts so that the width could be measured). Ten films with a length of 100 mm in the MD direction were overlapped and cut out. The films were conditioned for more than 2 hours at a temperature of 23°C and a relative humidity of 65%. The thickness of each sample was measured at the center using a thickness tester manufactured by TESTER SANGYO, and the average value of the measured thicknesses was set as the thickness.

(3) Biomass of the membrane The obtained biomass of the membrane was measured by radiocarbon (C ¹⁴ ) measurement as shown in ASTM D6866-16 Method B (AMS). (4) Thermal shrinkage of the membrane The test temperature was set to 160°C and the heating time was set to 10 minutes. In addition, the thermal shrinkage was measured according to the dimensional change test method described in JIS C2318 by the following formula. Thermal shrinkage = [(length before treatment - length after treatment) / length before treatment] × 100 (%) (5) Impact strength of the membrane was measured using a membrane impact tester manufactured by Toyo Seiki Seisaku-sho Co., Ltd. The measured value is converted to J (joule) / 15 μm per thickness of 15 μm. (6) Dynamic friction coefficient of film The dynamic friction coefficient between the outer surfaces of the film roll was evaluated according to JIS-C2151 under the following conditions. The test piece size was 130 mm in width and 250 mm in length, and the test speed was 150 mm/min.

(7) Film resistance to bending pinholes The number of bending fatigue pinholes was measured by the following method using a Gelb-Francis tester manufactured by Rigaku Kogyo Co., Ltd. The film produced in the embodiment was coated with a polyester adhesive, and then a 40 μm thick linear low-density polyethylene film (L-LDPE film: L4102 manufactured by Toyobo Co., Ltd.) was dry-laminated and aged for 3 days at 40°C to produce a laminated film. The obtained laminated film was cut into 12 inches × 8 inches and made into a cylinder with a diameter of 3.5 inches. One end of the cylindrical film was fixed to the fixed head side of the Gelber-Francis tester, and the other end was fixed to the movable head side. The initial holding interval was set to 7 inches. The bending fatigue test was performed 1000 times at a speed of 40 times/minute, and the number of pinholes generated in the laminated film was counted. The bending fatigue test was applied with a 440-degree twist in the first 3.5 inches of the stroke, and then the total stroke was completed with a straight horizontal movement in the next 2.5 inches. In addition, the measurement was performed in an environment of 1°C. Place the L-LDPE film side of the test film on filter paper (Advantec, No.50) with the four corners fixed with CELLOTAPE (registered trademark). Apply ink (ink made by PILOT (product number INK-350-blue) diluted 5 times with pure water) on the test film and use a rubber roller to spread it on one side. After wiping off the unnecessary ink, remove the test film and count the number of dots of ink attached to the filter paper.

(8) Friction pinhole resistance of the film A friction test was performed using a fastness tester (Toyo Seiki Seisaku-sho, Ltd.) by the following method to measure the distance of pinhole generation. The same laminated film as that produced in the above-mentioned evaluation of bending pinhole resistance was folded into four parts to produce a test sample with sharp corners. The inner surface of the corrugated cardboard was rubbed using a fastness tester with an amplitude of 25 cm, an amplitude speed of 30 times/minute, and a weight of 100 g. The corrugated cardboard used was K280×P180×K210(AF)=(surface material backing×core material×inner material backing (type of flute of corrugated cardboard)). The distance of pinhole generation was calculated according to the following procedure. The longer the distance at which pinholes are generated, the better the friction pinhole resistance is. First, perform a friction test with an amplitude of 100 times and a distance of 2500cm. If no pinholes are generated, increase the amplitude by 20 times and increase the distance by 500cm to perform a friction test. Also, if no pinholes are generated, increase the amplitude by 20 times and increase the distance by 500cm to perform a friction test. Repeat this operation and mark the distance at which pinholes are generated with × and set it as level 1. If pinholes are generated with an amplitude of 100 times and a distance of 2500cm, reduce the amplitude by 20 times and reduce the distance by 500cm to perform a friction test. In addition, when pinholes are generated, the friction test is performed by further reducing the amplitude by 20 times and reducing the distance by 500 cm. This operation is repeated and the distance where no pinholes are generated is marked with ○ and set as level 1. Next, as level 2, when the last ○ in level 1 is ○, the friction test is performed by increasing the amplitude by 20 times. If no pinholes are generated, it is marked with ○, and if pinholes are generated, it is marked with ×. When the last ○ in level 1 is ×, the friction test is performed by reducing the amplitude by 20 times. If no pinholes are generated, it is marked with ○, and if pinholes are generated, it is marked with ×. Furthermore, for levels 3 to 20, when the previous level was ○, the number of amplitudes was increased by 20 times and the friction test was performed. If no pinhole was generated, ○ was marked, and if a pinhole was generated, × was marked. When the previous level was ×, the number of amplitudes was reduced by 20 times and the friction test was performed. If no pinhole was generated, ○ was marked, and if a pinhole was generated, × was marked. Repeat this operation and mark ○ or × for levels 3 to 20. For example, the results shown in Table 1 were obtained. The calculation method of the distance where pinholes are generated is explained using Table 1 as an example. Count the number of tests of ○ and × for each distance. Set the distance with the most tests as the center value and set the coefficient to zero. When the distance is longer than the central value, the coefficient is set to +1, +2, +3, etc. every 500cm. When the distance is shorter than the central value, the coefficient is set to -1, -2, -3, etc. every 500cm. In all tests from level 1 to level 20, the number of tests without holes and the number of tests with holes are compared. For the following A and B situations, the friction pinhole generation distance is calculated using various formulas. A: In all tests, the number of tests without holes is greater than the number of tests with holes. Friction pinhole generation distance = central value + 500 × (Σ (coefficient × number of tests without holes) / number of tests without holes) + 1/2) B: In all tests, the number of tests without holes does not reach the number of tests with holes. Friction pinhole generation distance = central value + 500 × (Σ (coefficient × number of tests with holes) / number of tests with holes) - 1/2)

[Table 1]

(9) Lamination strength relative to polyethylene sealant A laminated film prepared in the same manner as described in the description of the evaluation of bending pinhole resistance was cut into short strips of 15 mm in width and 200 mm in length. One end of the laminated film was peeled off at the interface between the biaxially oriented polyamide film and the linear low-density polyethylene film. The lamination strength was measured three times in the MD direction and the TD direction using an Autograph (manufactured by Shimadzu Corporation) at a temperature of 23°C, a relative humidity of 50%, a tensile speed of 200 mm/min, and a peeling angle of 90°. The average value of the three times was used for evaluation.

(10) Film Stability during Casting The steps of extruding the molten resin from a T-die into a film, casting it onto a cooling roller for cooling, and obtaining an unstretched film were visually observed, and the film stability was evaluated as follows. A: The film was stable and a homogeneous unstretched film was obtained. B: The film was slightly unstable, and the width of the unstretched film varied, but biaxial stretching was possible. C: The film was unstable and the unstretched film was not homogeneous, so a biaxially stretched film was not obtained. In addition, an evaluation of B or above is considered practical. (11) Generation cycle of thermal degradation products generated at the die lip outlet After cleaning the die lip, film production was started and the time until thermal degradation products were generated at the die lip was observed.

(12) Relative viscosity of raw material polyamide 0.25 g of polyamide was dissolved in 96% sulfuric acid in a 25 ml volumetric flask to a concentration of 1.0 g/dl, and the relative viscosity of the obtained polyamide solution was measured at 20°C. (13) Melting point of raw material polyamide The measurement was performed in a nitrogen atmosphere using a SSC5200 differential scanning calorimeter manufactured by Seiko Instruments in accordance with JIS K7121, under the conditions of sample weight: 10 mg, heating start temperature: 30°C, and heating rate: 20°C/min, and the endothermic peak temperature (Tmp) was determined as the melting point.

[Polyamide 6] Polyamide 6 used in the examples and comparative examples is as follows. Polyamide 6 (a-1) Relative viscosity 2.8, melting point 220°C, manufactured by Toyobo Co., Ltd.

Polyamide 6 (a-2) obtained by chemical regeneration Relative viscosity 2.7, melting point 221℃ Polyamide 6 fiber recovered from waste and 75 mass% phosphoric acid aqueous solution as a depolymerization catalyst are added to a depolymerization device and heated to 260℃ under a nitrogen atmosphere. Superheated water vapor is blown into the depolymerization device while the reaction starts. The ε-caprolactam and water vapor continuously distilled from the depolymerization device are cooled, and the ε-caprolactam distillate is recovered. The recovered distillate is concentrated by an evaporator, and the concentrated ε-caprolactam is repolymerized to obtain a chemically regenerated polyamide resin.

Polyamide 6 (a-3) obtained by physical regeneration Relative viscosity: 2.6, melting point: 221°C The standard outer film produced by the stretched film produced in Example 1 and the scraps produced by cutting the end material (scraps) were recovered and crushed, and kneaded by an extruder with a cylinder temperature of 270°C. After granulation, it was dried at 100°C under reduced pressure to obtain polyamide 6 obtained by physical regeneration.

[Example 1-1] Using an apparatus consisting of an extruder and a 380 mm wide T-die, the following molten resin composition was extruded from the T-die into a film, cast on a cooling roll adjusted to 20°C and electrostatically bonded to obtain an unstretched film with a thickness of 200 μm. [Resin composition] Polyamide 6 (a-1): 92 parts by mass Polyamide 6 (a-2): 5 parts by mass Polyamide 11 (produced by Arkema, relative viscosity 2.5, melting point 186°C): 3 parts by mass Porous silica particles (produced by Fuji Silysia Chemical Co., Ltd., average particle size 2.0 μm, pore volume 1.6 ml/g): 0.45% by mass Fatty acid diamide (ethyl distearate amide produced by Kyoeisha Chemical Co., Ltd.): 0.15% by mass

The obtained unstretched film was introduced into a roll stretching machine, and stretched 1.73 times in the MD direction at 80°C by using the circumferential speed difference of the rolls, and then further stretched 1.85 times at 70°C. Then, the uniaxially stretched film was continuously introduced into a tenter-type stretching machine, preheated at 110°C, stretched 1.2 times in the TD direction at 120°C, stretched 1.7 times at 130°C, stretched 2.0 times at 160°C, heat-fixed at 218°C, and then 7% relaxation treatment was performed at 200°C, and then the surface of the side dry-laminated with the linear low-density polyethylene film was subjected to a corona discharge treatment to obtain a biaxially stretched polyamide film. The evaluation results of the obtained biaxially stretched film are shown in Table 2.

[Example 1-2 to Example 1-12] Except for changing the film-making conditions such as the raw material resin composition and the heat setting temperature as shown in Table 2, a biaxially stretched film was obtained by the same method as Example 1-1. The evaluation results of the obtained biaxially stretched film are shown in Table 2. In the examples and comparative examples, the following polyamide was used as the polyamide resin at least part of which was derived from biomass as the raw material. Polyamide 410: (manufactured by DSM, ECOPaXX Q150-E, melting point 250°C) Polyamide 610: (manufactured by Arkema, RilsanS SMNO, melting point 222°C) Polyamide 1010: (manufactured by Arkema, RilsanT TMNO, melting point 202°C)

[Table 2] Embodiment 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8 1-9 1-10 1-11 1-12 Composition Polyamide 6(a-1) Quality 92 7 37 7 5 30 45 15 5 5 5 5 Polyamide 6(a-2) Quality 5 90 30 60 90 30 10 30 60 60 60 60 Polyamide 6(a-3) Quality 0 0 30 30 0 30 30 30 30 30 30 30 Polyamide 11 Quality 3 3 3 3 5 10 15 25 5 - - - Polyamide 410 Quality - - - - - - - - - 5 - - Polyamide 610 Quality - - - - - - - - - - 5 - Polyamide 1010 Quality - - - - - - - - - - - 5 Microparticles Quality% 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 Fatty acid amides Quality% 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 MD stretching temperature ℃ 80 80 80 80 80 80 80 80 80 80 80 80 MD stretch ratio - 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.0 3.2 3.2 3.2 TD stretching temperature ℃ 130 130 130 130 130 130 130 130 130 130 130 130 TD stretch ratio - 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 3.3 4.0 4.0 4.0 TD heat fixation temperature ℃ 218 218 218 218 218 218 218 218 210 218 218 218 TD relaxation temperature ℃ 218 218 218 218 218 218 218 218 210 218 218 218 TD relaxation rate % 7 7 7 7 7 7 7 7 7 7 7 7 thickness μm 15 15 15 15 15 15 15 15 15 15 15 15 Biomass % 2.7 2.7 2.7 2.7 4.5 9.0 13.5 22.5 4.5 4.4 4.6 4.5 Fog % 2.6 2.5 2.6 2.6 2.8 2.8 3.2 4.9 2.9 3.4 3.4 3.3 Impact strength J/15μm 1.2 1.3 1.2 1.1 1.3 1.1 1.2 1.1 1.4 1.2 1.2 1.2 Pinhole resistance Piece 3 4 2 3 3 5 4 4 4 5 5 6 Friction-resistant pinhole cm 3260 3170 3060 3150 3160 3100 3210 3160 3300 3520 3190 3250 Thermal shrinkage MD % 0.9 1.0 0.9 1.1 1.0 0.9 1.1 1.2 1.6 1.2 1.3 1.3 TD % 0.9 0.9 1.1 0.9 1.0 1.1 1.2 1.3 0.9 1.4 1.5 1.5 Laminated strength MD N/mm 6.9 6.7 7.1 6.8 6.7 7.4 7.2 7.0 3.1 6.9 6.8 7.0 TD N/mm 6.6 6.5 6.2 6.6 6.1 7.0 6.7 6.8 3.0 6.8 6.7 6.7 Film stability during casting - A A A A A A A B A A A A Thermal degradation product generation cycle Hours 36 - - - - - - - - - - -

As shown in Table 2, the film of the example obtained a film having good bending pinhole resistance and friction pinhole resistance. In addition, the film has low haze and good transparency, strong impact strength, and high lamination strength relative to sealant film, and is excellent as a packaging film.

[Comparative Example 1-1 to Comparative Example 1-5] Except for changing the film-making conditions such as the raw material resin composition and the heat setting temperature as shown in Table 3, biaxially stretched films were obtained by the same method as in Example 1-1. The evaluation results of the obtained biaxially stretched films are shown in Table 3. However, in Comparative Example 1-4, the molten resin could not be stably extruded from the T-die into a film, and a homogeneous unstretched film was not obtained, so biaxial stretching could not be performed.

[Table 3] Comparison Example 1-1 1-2 1-3 1-4 1-5 Composition Polyamide 6(a-1) Quality 100 100 100 65 97 Polyamide 6(a-2) Quality 0 0 0 0 0 Polyamide 6(a-3) Quality 0 0 0 0 0 Polyamide 11 Quality - - 0.5 35 - Polyamide elastomer Quality - - - - 3 Microparticles Quality% 0.45 0.45 0.45 0.45 0.45 Fatty acid amides Quality% 0.15 0.15 0.15 0.15 0.15 MD stretching temperature ℃ 80 80 80 - 80 MD stretch ratio - 3.2 3.2 3.2 - 3.2 TD stretching temperature ℃ 130 130 130 - 130 TD stretch ratio - 4.0 4.0 4.0 - 4.0 TD heat fixation temperature ℃ 218 210 218 - 210 TD relaxation temperature ℃ 218 210 218 - 210 TD relaxation rate % 7 7 7 - 7 thickness μm 15 15 15 15 15 Biomass % 0.0 0.0 0.5 31.5 0.0 Fog % 2.2 2.2 2.4 - 2.3 Impact strength J/15μm 0.9 1.2 0.9 - 1.2 Pinhole resistance Piece 20 12 18 - 3 Friction-resistant pinhole cm 2520 3310 2630 - 2780 Thermal shrinkage MD % 0.8 1.0 0.8 - 1.1 TD % 0.8 1.1 0.9 - 1.3 Laminated strength MD N/mm 7.1 3.2 6.8 - 4.3 TD N/mm 6.9 3.3 6.6 - 4.0 Film stability during casting - A A A C A Thermal degradation product generation cycle Hours - - - - 18

As shown in Table 3, the biaxially stretched polyamide films of Comparative Examples 1-1 and 1-2 (not containing a material for improving the bending pinhole resistance) and the biaxially stretched polyamide film of Comparative Example 1-3 (the content of polyamide 11 is too low) have poor bending pinhole resistance. Since the content of polyamide 11 is too high in Comparative Example 1-4, the molten resin cannot be stably extruded from the T-die into a film, and a homogeneous unstretched film is not obtained, and a biaxially stretched polyamide film is not obtained. In Comparative Example 1-5, the polyamide elastomer used previously is used as a material for improving the bending pinhole resistance, and the bending pinhole resistance is good, but the friction pinhole resistance is poor. In addition, there are the following disadvantages: when long-term production is carried out, deteriorated products are easily attached to the mold, and long-term continuous production cannot be achieved.

[Example 2-1] Using an apparatus consisting of two extruders and a 380 mm wide co-extrusion T-die, the molten resin was extruded from the T-die into a film by lamination in a B layer/A layer/B layer structure using a feed block method, and then cast on a cooling roll adjusted to 20°C and electrostatically bonded to obtain an unstretched film with a thickness of 200 μm. In addition, regarding the thickness of the biaxially stretched polyamide film, the feed block structure and the extruder discharge amount were adjusted so that the total thickness was 15 μm, the thickness of the substrate layer (A layer) was 12 μm, and the thickness of the inner and outer surface layers (B layers) were 1.5 μm each.

The resin compositions of the A layer and the B layer used in Example 2 are as follows. [Resin composition constituting the A layer] Polyamide 6 (a-1): 92 parts by mass Polyamide 6 (a-2) obtained by chemical regeneration: 5 parts by mass Polyamide 11 (manufactured by Jisheng Corporation, relative viscosity 2.5, melting point 186°C): 3 parts by mass [Resin composition constituting the B layer] Polyamide 6 (a-1): 90 parts by mass Polyamide 6 (a-2) obtained by chemical regeneration: 5 parts by mass Polyamide MXD6 (manufactured by Mitsubishi Gas Chemical Co., Ltd., relative viscosity 2.1, melting point 237°C): 5 parts by mass Porous silica particles (Fuji Silysia Chemical Co., Ltd., average particle size 2.0μm, pore volume 1.6ml/g): 0.54 mass% Fatty acid diamide (ethyl distearate amide manufactured by Kyoeisha Chemical Co., Ltd.): 0.15 mass%

The obtained unstretched film was introduced into a roll stretching machine, and stretched 1.73 times in the MD direction at 80°C by using the circumferential speed difference of the rolls, and then further stretched 1.85 times at 70°C. Then, the uniaxially stretched film was continuously introduced into a tenter stretching machine, preheated at 110°C, stretched 1.2 times in the TD direction at 120°C, stretched 1.7 times at 130°C, stretched 2.0 times at 160°C, heat fixed at 218°C, and then 7% relaxation treatment was performed at 218°C, and then the surface of the side dry-laminated with the linear low-density polyethylene film was subjected to corona discharge treatment to obtain a biaxially stretched polyamide film. The evaluation results of the obtained biaxially stretched film are shown in Table 4.

[Example 2-2 to Example 2-12] Except for changing the film-making conditions such as the resin composition of layer A and layer B and the heat setting temperature as shown in Table 4, a biaxially stretched film was obtained by the same method as in Example 2-1. The evaluation results of the obtained biaxially stretched film are shown in Table 4.

[Table 4] Embodiment 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-11 2-12 A layer Polyamide 6(a-1) Quality 92 7 35 10 5 15 55 35 5 5 5 5 Polyamide 6(a-2) Quality 5 90 30 50 80 30 10 30 60 50 50 50 Polyamide 6(a-3) Quality 0 0 30 30 0 30 30 30 30 30 30 30 Polyamide 11 Quality 3 3 5 10 15 25 5 5 5 - - - Polyamide 410 Quality - - - - - - - - - 15 - - Polyamide 610 Quality - - - - - - - - - - 15 - Polyamide 1010 Quality - - - - - - - - - - - 15 B layer Polyamide 6(a-1) Quality 90 5 65 47 15 65 80 70 35 45 45 45 Polyamide 6(a-2) Quality 5 90 30 50 80 30 10 30 60 50 50 50 Polyamide MXD6 Quality 5 5 5 3 5 5 10 0 5 5 5 5 Microparticles Quality% 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.65 0.54 0.54 0.54 0.54 Fatty acid amides Quality% 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.20 0.15 0.15 0.15 0.15 Overall thickness μm 15 15 15 15 15 15 15 15 15 15 15 15 Core layer thickness % 80 80 80 80 80 80 80 80 80 80 80 80 Laminated resin composition - B/A/B B/A/B B/A/B B/A/B B/A/B B/A/B B/A/B B/A/B B/A/B B/A/B B/A/B B/A/B MD stretching temperature ℃ 80 80 80 80 80 80 80 80 80 80 80 80 MD stretch ratio - 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.0 3.2 3.2 3.2 TD stretching temperature ℃ 130 130 130 130 130 130 130 130 130 130 130 130 TD stretch ratio - 4.0 4.0 4.0 4.0 4.0 4.0 3.8 3.8 3.3 4.0 4.0 4.0 TD heat fixation temperature ℃ 218 218 218 218 218 218 218 218 210 218 218 218 TD relaxation temperature ℃ 218 218 218 218 218 218 218 218 210 218 218 218 TD relaxation rate % 7 7 7 7 7 7 7 7 7 7 7 7 Biomass % 0.5 0.5 0.9 1.8 2.7 4.5 0.9 0.9 0.9 2.7 2.7 2.7 Fog % 2.4 2.5 2.7 2.9 3.0 4.9 2.9 3.8 2.7 3.5 3.3 3.4 Dynamic friction coefficient - 0.65 0.68 0.64 0.75 0.70 0.68 0.61 0.79 0.64 0.65 0.66 0.63 Impact strength J/15μm 1.10 1.13 1.34 1.03 1.31 1.09 1.21 1.21 1.46 1.25 1.14 1.22 Pinhole resistance Piece 5 4 4 4 4 4 3 4 4 5 5 6 Friction-resistant pinhole cm 3290 3200 3430 3130 3160 3400 3160 3230 3070 3460 3150 3160 Thermal shrinkage MD % 0.9 1.0 0.9 0.9 1.0 1.3 0.9 0.9 1.3 1.2 1.3 1.4 TD % 1.0 1.1 1.0 1.1 1.2 1.3 1.0 1.0 1.4 1.4 1.5 1.5 Laminated strength MD N/mm 7.1 6.6 6.7 7.2 7.0 6.9 7.3 6.2 3.1 6.9 6.8 6.9 TD N/mm 6.6 6.7 6.6 7.3 7.2 6.8 7.4 6.1 3.0 6.8 6.6 7.0 Film stability during casting - A A A A A A A A A A A A Thermal degradation product generation cycle Hours 37 - - - - - - - - - - -

As shown in Table 4, the film of the example obtained a film having good bending pinhole resistance and friction pinhole resistance. In addition, the haze was low and the transparency was good, the impact strength was strong, and the lamination strength was high relative to the sealant film, and it was excellent as a packaging film.

[Comparative Example 2-1 to Comparative Example 2-7] Except for changing the film-making conditions such as the resin composition of the A layer and the B layer and the heat setting temperature as shown in Table 5, a biaxially stretched film was obtained by the same method as in Example 2-1. The evaluation results of the obtained biaxially stretched films are shown in Table 5. However, in Comparative Example 2-4, the molten resin could not be stably extruded from the T-die into a film, and a homogeneous unstretched film was not obtained, so biaxial stretching could not be performed.

[Table 5] Comparison Example 2-1 2-2 2-3 2-4 2-5 2-6 2-7 A layer Polyamide 6(a-1) Quality 100 100 99.5 65 95 95 97 Polyamide 6(a-2) Quality - - - - - - - Polyamide 6(a-3) Quality - - - - - - - Polyamide 11 Quality - - 0.5 35 5 5 - Polyamide elastomer Quality - - - - - - 3 B layer Polyamide 6(a-1) Quality 100 100 95 95 95 65 97 Polyamide 6(a-2) Quality - - - - - - - Polyamide MXD6 Quality - - 5 5 5 35 - Polyamide elastomer Quality - - - - - - 3 Microparticles Quality% 0.54 0.54 0.54 0.54 0.54 0.54 0.54 Fatty acid amides Quality% 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Overall thickness μm 15 15 15 15 15 15 15 Core layer thickness % 80 80 80 80 20 80 80 Laminated resin composition - B/A/B B/A/B B/A/B B/A/B B/A/B B/A/B B/A/B MD stretching temperature ℃ 80 80 80 - 80 80 80 MD stretch ratio - 3.2 3.2 3.2 - 3.2 3.2 3.2 TD stretching temperature ℃ 130 130 130 - 130 130 130 TD stretch ratio - 4.0 4.0 4.0 - 4.0 4.0 4.0 TD heat fixation temperature ℃ 218 210 218 - 218 218 210 TD relaxation temperature ℃ 218 210 218 - 218 218 210 TD relaxation rate % 7 7 7 - 7 7 7 Biomass % 0.0 0.0 0.1 6.3 0.9 0.9 3.0 Fog % 2.2 2.3 2.3 - 3.0 3.1 2.3 Dynamic friction coefficient - 1.08 1.10 0.66 - 0.67 0.61 0.76 Impact strength J/15μm 0.85 1.18 0.95 - 1.20 0.80 1.20 Pinhole resistance Piece twenty three 11 14 - twenty one 20 3 Friction-resistant pinhole cm 2920 3090 3010 - 3200 2900 2630 Thermal shrinkage MD % 0.8 1.3 0.7 - 1.0 0.9 1.1 TD % 0.7 1.4 0.9 - 0.9 1.0 1.3 Laminated strength MD N/mm 7.0 3.3 6.8 - 6.6 6.2 4.2 TD N/mm 6.9 3.1 6.6 - 6.5 6.3 4.0 Film stability during casting - A A A C A A A Thermal degradation product generation cycle Hours - - - - - - 17 The biaxially stretched polyamide films of Comparative Examples 2-1 and 2-2 (not containing a material for improving the bending pinhole resistance) and the biaxially stretched polyamide film of Comparative Example 2-3 (the content of polyamide 11 is too low) have poor bending pinhole resistance. Since the content of polyamide 11 is too high in Comparative Example 2-4, the molten resin cannot be stably extruded from the T-die into a film, and a homogeneous unstretched film is not obtained, and a biaxially stretched polyamide film is not obtained. In Comparative Example 2-5, since the thickness and thickness ratio of the A layer are small, the film has poor bending pinhole resistance. In Comparative Example 2-6, since the amount of polyamide MXD6 in the B layer is large and the amount of polyamide 6 resin is small, the film has poor pinhole resistance to bending and pinhole resistance to friction. Comparative Example 2-7 uses the previously used polyamide elastomer as a material for improving the pinhole resistance to bending, and the result is good pinhole resistance to bending, but poor pinhole resistance to friction. In addition, there are the following disadvantages: when long-term production is carried out, deteriorated products are easily attached to the mold, and long-term continuous production cannot be achieved.

[Example 3 and Example 4] The biaxially stretched polyamide film prepared in Example 1-2 and Example 2-2 is used to prepare a laminated film having the following structures (1) to (9), and the laminated film (1) to (9) is used to prepare a three-side sealed type and a pillow type packaging bag. A packaging bag with good appearance and not easy to break in a drop impact test can be produced. (1) Biaxially stretched polyamide film layer/printing layer/polyurethane adhesive layer/linear low-density polyethylene film sealant layer. (2) Biaxially stretched polyamide film layer/printing layer/polyurethane adhesive layer/unstretched polypropylene film sealant layer. (3) Biaxially stretched PET film layer/printing layer/polyurethane adhesive layer/biaxially stretched polyamide film layer/polyurethane adhesive layer/unstretched polypropylene film sealant layer. (4) Biaxially stretched PET film layer/printing layer/polyurethane adhesive layer/biaxially stretched polyamide film layer/polyurethane adhesive layer/linear low-density polyethylene film sealant layer. (5) Biaxially stretched polyamide film layer/anchored coating layer/inorganic film layer/inorganic film protective layer/printed layer/polyurethane adhesive layer/linear low-density polyethylene film sealant layer. (6) Linear low-density polyethylene film sealant layer/polyurethane adhesive layer/biaxially stretched polyamide film layer/anchored coating layer/inorganic film layer/polyurethane adhesive layer/linear low-density polyethylene film sealant layer. (7) Linear low-density polyethylene film layer/polyurethane adhesive layer/biaxially stretched polyamide film layer/anchor coating layer/inorganic film layer/polyurethane adhesive layer/linear low-density polyethylene film layer/low-density polyethylene/paper/low-density polyethylene/linear low-density polyethylene film sealant layer. (8) Biaxially stretched polyamide film layer/anchor coating layer/inorganic film layer/inorganic film protective layer/printing layer/polyurethane adhesive layer/non-stretched polypropylene film sealant layer. (9) Biaxially stretched PET film layer/inorganic film layer/inorganic film protective layer/printing layer/polyurethane adhesive layer/biaxially stretched polyamide film layer/polyurethane adhesive layer/easy-to-peel non-stretched polypropylene film sealant layer. [Industrial Availability]

The biaxially stretched polyamide film of the present invention is excellent in impact resistance, bending pinhole resistance, and friction pinhole resistance, so it can be preferably used for packaging materials such as food packaging. Furthermore, since the resin is polymerized from biomass raw materials originally existing on the ground, it is a carbon-neutral film, which can reduce the environmental load in terms of reducing the impact on the increase and decrease of carbon dioxide on the ground. Furthermore, since it contains polyamide 6 obtained by chemically regenerating waste polyamide products, previously discarded plastic products can be reused, thereby reducing the environmental load and helping to reduce the amount of plastic waste discharged.

1: Head of the fastness tester 2: Corrugated cardboard 3: Paper backing for holding the sample 4: Film sample folded in 4 parts 5: Friction amplitude direction

[Figure 1] is a schematic diagram of the friction pinhole resistance evaluation device.

Claims (10)

A biaxially stretched polyamide film comprises 70 to 99% by weight of polyamide 6 and 1 to 30% by weight of a polyamide resin at least part of which is derived from biomass; the polyamide 6 comprises 5 to 100 parts by weight of a biomass-derived polyamide obtained by chemical regeneration, based on 100 parts by weight of the polyamide 6. Polyamide 6; and, one or more layers are laminated on both sides of the aforementioned biaxially stretched polyamide film, and the aforementioned laminated layers contain 70% to 100% by mass of polyamide 6, and the aforementioned polyamide 6 contains 5% to 100% by mass of polyamide 6 obtained by chemical regeneration when the polyamide 6 is set to 100 parts by mass. The biaxially stretched polyamide film as described in claim 1, wherein the aforementioned polyamide 6, when the polyamide 6 is set to 100 parts by mass, includes, in addition to the polyamide 6 obtained by chemical regeneration, 0 to 50 parts by mass of polyamide 6 obtained by physical regeneration. A biaxially stretched polyamide film as claimed in claim 1 or 2, wherein the content of carbon derived from biomass determined by radiocarbon C ¹⁴ is 1% to 15% relative to the total carbon in the biaxially stretched polyamide film. The biaxially stretched polyamide film as described in claim 1 or 2, wherein at least a portion of the raw materials are derived from biomass-derived polyamide resins, which are at least one polyamide resin selected from the group consisting of polyamide 11, polyamide 410, polyamide 610, and polyamide 1010. The biaxially stretched polyamide film as described in claim 1, wherein the thickness of the aforementioned laminated layer is 7% to 50% relative to the thickness of the entire film. The biaxially stretched polyamide film described in claim 1 or 2 satisfies the following (a) and (b): (a) The number of pinhole defects when the torsional bending test is performed 1000 times at a temperature of 1°C using a Gelber-Francis tester is 10 or less; (b) The distance until pinholes are generated in the friction pinhole resistance test is 2900 cm or more. The biaxially stretched polyamide film described in claim 1 or 2 has a haze of less than 10% and a dynamic friction coefficient of less than 1.0. The biaxially stretched polyamide film as described in claim 1 or 2, wherein the lamination strength of the biaxially stretched polyamide film and the polyethylene sealant film after lamination is 4.0N/15mm or more. A laminated film having a sealant film laminated on at least one side of a biaxially stretched polyamide film as described in any one of claims 1 to 8. A packaging bag using the laminated film as described in claim 9.