TW202142607A - Biaxially stretched polyamide film, laminate film, and packaging body - Google Patents

Abstract

PROBLEM: To provide a biaxially stretched polyamide film having excellent piercing strength, impact resistance and friction pinhole resistance, and capable of reducing the environmental load by using polyamide 6 chemically recycled from a discharged polyamid product as a raw material. SOLUTION: A biaxially stretched polyamide film comprising a polyamide resin composition containing 70% by mass or more of polyamide 6 and 4 to 90% by mass of chemically recycled polyamide 6.

Description

Biaxially stretched polyamide film, laminate and packaging bag

The present invention relates to a biaxially stretched polyamide film that has excellent puncture strength, impact resistance and friction resistance and pinhole resistance, and uses polyamide 6 obtained by chemical recycle of waste polyamide products as raw materials It can reduce the environmental load. The biaxially stretched polyamide film of the present invention can be preferably used for food packaging films and the like.

In recent years, with the increasing demand for the construction of a recycling-oriented society, the desire to move away from fossil fuels in the field of materials is the same as that of energy. In addition, in recent years, marine plastic pollution has become a major problem. If the plastic in marine debris flows into the sea, it will become fragments due to ultraviolet rays or physical abrasion, and become tiny plastic particles (microplastics). As marine organisms prey on such particles, they may be exposed to the chemical substances contained or adsorbed in the particles, and may also affect the upper predators through the food chain. This situation has become a global problem. Most of the above-mentioned marine plastic waste comes from drifting on land, most of which are plastic containers and packaging that you want to discard after use. On the other hand, it also includes fishing lines or fishing nets. In this context, in order to reduce plastic waste, these plastic wastes are recycled and effectively used, which is effective in reducing marine plastic waste.

On the other hand, in the past, biaxially stretched films composed of aliphatic polyamides represented by polyamide 6 have been widely used as various packaging material films because of their excellent impact resistance and bending pinhole resistance. Regarding the polyamide films used for these packaging purposes, it is also one of the reasons for the plastic waste mentioned above, so the use of recycled materials is required.

As a method of regenerating nylon 6 (also known as polyamide 6), there are thermal recycle method (thermal recycle method) in which it is incinerated and recovered as heat energy, material regeneration method in which it is remolded and reused after melting, and And it is chemically depolymerized and recovered to the raw material of nylon and reused in the chemical regeneration method of nylon manufacturing. In addition, nylon is also known as polyamide.

Among these, the chemical regeneration method decomposes nylon 6 into the raw material of caprolactam and then recovers it, so that it can be reused as a raw material of nylon 6, so it can be described as an industrially useful regeneration method.

For example, Patent Document 1 discloses the following regeneration method: after recycling finished nylon clothing products, depolymerizing and recovering, refining, and polymerizing ε-caprolactam, it is formed by melt spinning and forming. Nylon fiber or nylon molded product. According to the above technology, the recycled clothing products can be restored to the raw materials for reuse. In addition, by decomposing and refining recycled clothing products, high-purity and good-quality raw materials (raw monomers) can be obtained. Therefore, good-quality nylon 6 products can be obtained by recycling and reuse, and repeated recycling can also be achieved. Furthermore, the recycling and screening operations of recycled clothing products are greatly reduced.

The nylon resin regenerated by the above-mentioned chemical regeneration method has been mainly used as a raw material for fibers or molded products, but has not been actually used as a film for food packaging. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Laid-Open No. 7-310204.

[The problem to be solved by the invention]

The present invention is created in view of the above-mentioned prior art. The purpose of the present invention is to provide a biaxially stretched polyamide film which has excellent puncture strength, impact resistance and friction resistance and pinhole resistance, and uses polyamide 6 obtained by chemical regeneration of waste polyamide products as raw materials. It can reduce the environmental load. [Means to solve the problem]

That is, the present invention includes the following configurations. [1] A biaxially stretched polyamide film, characterized in that it is composed of a polyamide resin composition, the polyamide resin composition containing 70% by mass or more of polyamide 6, and containing 4% to 90% by mass Mass% of polyamide 6 obtained by chemical regeneration. [2] The biaxially stretched polyamide film as described in [1], wherein the biaxially stretched polyamide film contains 5% to 60% by mass of polyamide 6 obtained by mechanical recycle. [3] A biaxially stretched polyamide film, in which at least a single area layer of the substrate layer (layer A) has a surface layer (layer B), characterized in that the layer A is as described in [1] or [2] In the biaxially stretched polyamide film, the B layer is composed of a polyamide resin composition containing more than 70% by mass of polyamide 6. [4] The biaxially stretched polyamide film as described in [3], characterized in that: layer A contains 5 mass% to 80 mass% of polyamide 6 obtained by mechanical regeneration, and layer B contains 0 mass% to 30% by mass of polyamide 6 mechanically regenerated. [5] The biaxially stretched polyamide film as described in any one of [1] to [4], characterized in that the biaxially stretched polyamide film satisfies the following (a) and (b): ( a) The puncture strength is 0.65N/μm or more; (b) The impact strength is 0.9J/15μm or more. [6] The biaxially stretched polyamide film as described in any one of [1] to [5], wherein the biaxially stretched polyamide film satisfies the following (c): (c) rubbing resistance pinhole test The distance from the middle to the occurrence of pinholes is 2900 cm or more. [7] The biaxially stretched polyamide film as described in any one of [1] to [6], wherein the biaxially stretched polyamide film satisfies the following (d) and (e): (d) The haze is 2.6% or less; (e) The dynamic friction coefficient is 1.0 or less. [8] The biaxially stretched polyamide film as described in any one of [1] to [7], characterized in that: the laminated strength of the biaxially stretched polyamide film and the polyethylene-based sealant film after being laminated It is 4.0N/15mm or more. [9] A laminated film comprising a sealant film laminated on the biaxially stretched polyamide film described in any one of [1] to [8]. [10] A packaging bag using the laminated film as described in [9]. [Efficacy of invention]

The biaxially stretched polyamide film of the present invention is obtained by using polyamide 6 as the main component, blending polyamide 6 obtained by chemical regeneration of waste polyamide products, and adopting specific film forming conditions. A biaxially stretched polyamide film with excellent puncture strength, impact resistance, bending pinhole resistance, and friction pinhole resistance, and can reduce environmental load. Furthermore, by blending the mechanically regenerated polyamide 6 into the raw material, a biaxially stretched polyamide film that can further reduce the environmental load can be obtained.

Hereinafter, the biaxially stretched polyamide film of the present invention will be described in detail. The biaxially stretched polyamide film of the present invention is composed of a polyamide resin composition containing more than 70% by mass of polyamide 6, and 4% to 90% by mass of the aforementioned polyamide 6 is chemically regenerated The obtained biaxially stretched polyamide film of polyamide 6 (layer A); and at least the single area layer as the base layer of the aforementioned A layer is composed of polyamide 6 containing 70% by mass or more of polyamide 6 The biaxially stretched polyamide film of the surface layer (layer B) formed by the resin composition.

[A layer (biaxially stretched polyamide film or substrate layer)] The layer A in the present invention contains more than 70% by mass of polyamide 6, and the biaxially stretched polyamide film composed of polyamide 6 can obtain excellent mechanical strength such as impact strength and resistance to oxygen. Other gas barrier properties. The layer A in the present invention is a layer composed of a polyamide resin composition containing at least 70% by mass or more of polyamide 6, and 4% to 90% by mass of the aforementioned polyamide 6 is self-disposable Plastic products, waste tires, rubber, fibers, fishing nets and other waste polyamide 6 products are composed of polyamide 6 chemically regenerated. The A layer in the present invention contains 4% to 90% by mass of polyamide 6 obtained from waste plastic products, waste tire rubber, fibers, fishing nets, and other waste polyamide 6 products that are chemically regenerated to provide a double The axially stretched polyamide film uses the raw material obtained by regenerating polyamide products that have been discarded as garbage in the past to reduce the environmental load. In addition, by selecting a specific stretching method, a biaxially stretched polyamide film with excellent puncture resistance, impact resistance, and friction pinhole resistance can be obtained.

[Polyamide 6] The polyamide 6 used in the present invention is usually produced by ring-opening polymerization of ε-caprolactam. Polyamide 6 obtained by ring-opening polymerization is usually used to remove the internal amide monomer with hot water, then dried, and then melt-extruded using an extruder. The relative viscosity of the polyamide 6 used in the present invention 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 the relative viscosity is greater than 4.5, the load of the extruder becomes large, and it becomes difficult to obtain an unstretched film before stretching.

[Polyamide 6 obtained by chemical regeneration] As the above-mentioned polyamide 6 used in layer A, in addition to the commonly used polyamide 6 obtained by polymerization of monomers derived from fossil fuels, it can also be used from waste plastic products, waste tire rubber, fiber, Polyamide 6 obtained by chemical regeneration of waste polyamide 6 products such as fishing nets.

As a method for obtaining polyamide 6 obtained by chemical regeneration of waste polyamide 6 products, for example, the method disclosed in Patent Document 1 listed above can be used. That is, the following method can be used: after the finished product of nylon (polyamide) is recovered, it is depolymerized and ε-caprolactam is recovered, refined, and polymerized.

[Disaggregation conditions] In the depolymerization of the chemically regenerated polyamide 6 used in the production of the A layer, the polyamide 6 fiber is usually depolymerized by heating. Depolymerization can use catalyst or not. In addition, depolymerization can be carried out in the absence of water (dry type), or in the presence of water (wet type).

The depolymerization pressure of the chemically regenerated polyamide 6 used in the production of the A layer can be any of reduced pressure, normal pressure, and increased pressure. The temperature of depolymerization 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, since the polyamide 6 product will not melt, the depolymerization speed will slow down. If the temperature is high, it may cause unnecessary decomposition of the monomer of polyamide 6 (that is, caprolactam), which may reduce the purity of the recovered caprolactam.

When a catalyst is used in the depolymerization of the polyamide 6 obtained by chemical regeneration used in the production of the A layer, an acid catalyst or an alkali catalyst is usually used. Examples of acid catalysts include phosphoric acid, boric acid, sulfuric acid, organic acids, organic sulfonic acids, solid acids, and salts of these acids. In addition, examples of alkali catalysts include alkali metal hydroxides, alkali metal salts, Alkaline earth metal hydroxides, alkaline earth metal salts, organic alkalis, solid alkalis, etc. Preferred are phosphoric acid, boric acid, organic acid, alkali metal hydroxide, alkali metal salt, and the like. More preferred are phosphoric acid, sodium phosphate, potassium phosphate, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, and the like.

The amount of the acid catalyst used in the above-mentioned depolymerization is generally preferably 0.01% by mass to 50% by mass relative to the polyamide 6 fiber component. It is more preferably 0.01% by mass to 20% by mass, and still more preferably 0.5% by mass to 10% by mass. If the amount of catalyst used is small, the reaction speed becomes slow, and if the amount of catalyst used is large, side reactions increase, and the cost of the catalyst increases, which becomes economically disadvantageous.

The above-mentioned depolymerization can be carried out in the absence of water (dry type) or in the presence of water (wet type). In the case of wet depolymerization, the amount of water used is preferably 0.1 to 50 times by mass relative to the polyamide 6 product components such as fibers. More preferably, it is 0.5 to 20 mass times, and still more preferably 1 to 10 mass times. If the amount of water used is small, the reaction speed becomes slow, and if the amount of water used is large, the concentration of the recovered caprolactamine aqueous solution becomes low, which becomes disadvantageous in terms of obtaining caprolactam.

The recovery method of caprolactam recovered by the above-mentioned method can be adopted without particular limitation. For example, in the case of dry depolymerization, the produced caprolactam is distilled from the reaction device by vacuum distillation to obtain recovered caprolactam. After the depolymerization reaction is completed, the caprolactam can also be taken out by distillation under reduced pressure. Alternatively, it may be taken out continuously as the reaction progresses. In the case of wet depolymerization, the produced caprolactamide is distilled out from the reaction device together with water to obtain an aqueous solution of recovered caprolactamide. After the depolymerization reaction is completed, the caprolactam can also be taken out by distillation under reduced pressure. Alternatively, it may be taken out continuously as the reaction progresses. Furthermore, as a method for obtaining high-purity caprolactam, the following purification methods can be combined: a method of precision distillation of the recovered caprolactam, a method of adding a small amount of sodium hydroxide for vacuum distillation, and a method of reactivation The method of carbon treatment, the method of ion exchange treatment, the method of recrystallization, etc.

[Polyamide 6 obtained by mechanical regeneration] Polyamide 6 can be further added to the A layer (obtained by mechanically regenerating waste materials generated in the manufacturing step or processing step of the biaxially stretched polyamide film).

The so-called polyamide 6 obtained by mechanical regeneration is, for example, recycled nonstandard (nonstandard) films that cannot be shipped or used as cut sapwood (offcuts) produced during the manufacture of biaxially stretched polyamide films. The produced scraps are raw materials obtained by pelletizing them by melt extrusion or compression molding.

The lower limit of the addition amount of the mechanically regenerated polyamide 6 added to the A layer is preferably 10% by mass, more preferably 15% by mass, and still more preferably 20% by mass. If the addition amount of polyamide 6 obtained by mechanical regeneration does not reach the above-mentioned lower limit, the regeneration ratio in the film becomes low. The upper limit of the addition amount of the mechanically regenerated polyamide 6 added to the A layer is preferably 50% by mass, more preferably 40% by mass, and still more preferably 30% by mass. If the added amount of mechanically regenerated polyamide exceeds the above upper limit, the coloration of the film may become stronger or the haze value may increase, and the appearance of the film may be impaired. Or, there is a possibility that deterioration products increase in the process of manufacturing the film, which may deteriorate the film-forming properties.

[Auxiliary materials, additives] The biaxially stretched polyamide film or substrate layer (layer A) of the present invention may contain other thermoplastic resins, slip agents, heat stabilizers, antioxidants, antistatic agents or antifogging agents, and ultraviolet absorbers as needed. Various additives such as agents, dyes, and pigments.

[Other thermoplastic resins] In the biaxially stretched polyamide film or substrate layer (layer A) of the present invention, within the scope of not impairing the purpose of the present invention, except for the above-mentioned polyamide 6 and at least a part of the raw materials are derived from biopolymers. In addition to the amide resin, a thermoplastic resin may also be included. For example, polyamide-based resins such as polyamide 12, polyamide 66, polyamide 6-polyamide 12 copolymer, polyamide 6-polyamide 66 copolymer, and polyamide MXD6 can be cited. It can also contain thermoplastic resins other than polyamide-based resins, such as polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate and other polyester-based polymerizations. Polyolefin polymers such as polyolefins, polyethylene, polypropylene, etc. 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 surface, so the environmental load can be reduced, which is preferable.

[Slip agent] In the biaxially stretched polyamide film or base layer (layer A) of the present invention, in order to make the sliding properties good and easy to handle, it is preferable to contain organic lubricants such as fine particles or fatty acid amides as a lubricant. The biaxially stretched polyamide film of the present invention has good sliding properties, and also has the effect of reducing bag breakage caused by friction.

As the aforementioned fine particles, inorganic fine particles such as silica, kaolin, and zeolite, and polymer-based organic fine particles such as acrylic and polystyrene may be appropriately selected and used. In addition, in terms of transparency and sliding properties, it is preferable to use silica fine particles. The preferred average particle size of the aforementioned fine particles 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 in order to obtain good sliding properties. On the other hand, if the average particle diameter exceeds 5.0 μm, the surface roughness of the film becomes too large and the appearance tends to deteriorate.

In the case of using the aforementioned silica particles, the pore volume of silica is preferably in the range of 0.5 ml/g to 2.0 ml/g, more preferably 0.8 ml/g to 1.6 ml/g. If the pore volume is less than 0.5 ml/g, voids are likely to be generated and the transparency of the film is deteriorated. If the pore volume exceeds 2.0 ml/g, it tends to be difficult to form surface protrusions caused by fine particles.

The biaxially stretched polyamide film or base layer (layer A) in the present invention may contain fatty acid amide and/or fatty acid bisamide for the purpose of improving sliding properties. Examples of fatty acid amides and/or fatty acid bisamides include: erucamide, stearic acid amide, ethylene bisstearate, ethylene bisbehenate, and ethylene bisstearate. Oleic acid amide and so on. The content of fatty acid amide and/or fatty acid bisamide in the biaxially stretched polyamide film of the present invention is preferably 0.01% to 0.40% by mass, and more preferably 0.05% to 0.30% by mass. If the content of fatty acid amide and/or fatty acid bisamide does not fall within the above range, the sliding 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 or substrate layer (layer A) of the present invention, for the purpose of improving sliding properties, polyamide MXD6, polyamide 12, polyamide 66, polyamide can be added Polyamide resins such as 6-polyamide 12 copolymer and polyamide 6-polyamide 66 copolymer. Especially preferred is polyamide MXD6, and it is preferred to add 1% by mass to 10% by mass.

[Antioxidants] The biaxially stretched polyamide film or substrate layer (layer A) in the present invention may contain an antioxidant. As the antioxidant, a phenol-based antioxidant is preferred. The phenolic antioxidant is preferably a fully hindered phenolic compound or a partially hindered phenolic compound. Examples include: tetra-[methylene-3-(3',5'-di-tertiary butyl-4'-hydroxyphenyl) propionate] methane, β-(3,5-di-tertiary butyl) 4-hydroxyphenyl) stearyl propionate, 3,9-bis[1,1-dimethyl-2-[β-(3-tert-butyl-4-hydroxy-5-methylbenzene) Yl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane and the like. By containing the above-mentioned phenolic antioxidant, the film forming workability of the biaxially stretched polyamide film is improved. In particular, when a recycled film is used as a raw material, it is likely to cause thermal degradation of the resin, which results in poor film forming operations and a tendency to increase production costs. In this regard, by containing an antioxidant, the thermal degradation of the resin can be suppressed and the workability can be improved.

[Layer B (surface layer)] The layer B in the present invention is a layer containing 70% by mass or more of polyamide 6. The layer B in the present invention contains 70% by mass or more of polyamide 6, so that a biaxially stretched polyamide film with excellent mechanical strength such as impact strength and gas barrier properties against oxygen and the like can be obtained. As the above-mentioned polyamide 6, polyamide 6 obtained by polymerization of new raw materials, polyamide 6 obtained by chemical regeneration, and mechanically regenerated as the polyamide 6 used in the aforementioned layer A can be used. The resulting polyamide 6. The layer B in the present invention may contain other thermoplastic resins, slip agents, heat stabilizers, antioxidants, antistatic agents or antifogging agents, ultraviolet absorbers, dyes, and pigments according to the functions imparted to the surface of the layer B And other additives. When layer B is used on the outside of the packaging bag, it is not suitable to contain soft resins such as polyamide-based elastomers or polyolefin-based elastomers or materials that generate a large number of voids because of the need for resistance to friction and pinholes. In addition, when it is desired to improve the resistance to abrasion and pinholes, the content of the polyamide 6 obtained by mechanical regeneration is preferably less than 30% by mass, and more preferably 15% by mass or less.

The layer B in the present invention may contain a thermoplastic resin in addition to the above-mentioned polyamide 6 within a range that does not impair the purpose of the present invention. Examples include: polyamide MXD6, polyamide 11, polyamide 12, polyamide 66, polyamide 6-polyamide 12 copolymer, polyamide 6-polyamide 66 copolymer, and other polyamides Amine resin. It can also contain thermoplastic resins other than polyamide-based resins, such as polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate and other polyester-based polymerizations. Polyolefin polymers such as polyolefins, polyethylene, polypropylene, etc.

In the layer B in the present invention, in order to improve the sliding properties of the film, it is preferable to contain fine particles or an organic lubricant as a lubricant. By making the sliding property good, the operability of the film is improved, and the bag breakage caused by friction is reduced.

As the above-mentioned fine particles, inorganic fine particles such as silica, kaolin, and zeolite, and polymer organic fine particles such as acrylic and polystyrene are suitably selected and used. In addition, in terms of transparency and sliding properties, it is preferable to use silica fine particles.

The above-mentioned fine particles preferably have an average particle size of 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 in order to obtain good sliding properties. On the other hand, if it exceeds 5.0 μm, the surface roughness of the film becomes too large and the appearance tends to deteriorate.

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

As the above-mentioned organic lubricant, it may contain fatty acid amide and/or fatty acid bisamide. Examples of fatty acid amides and/or fatty acid bisamides include: erucamide, stearic acid amide, ethylene bisstearate, ethylene bisbehenate, and ethylene bisstearate. Oleic acid amide and so on. The content of the fatty acid amide and/or the fatty acid bisamide added to the layer B 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 bisamide does not fall within the above range, the sliding properties tend to deteriorate. On the other hand, if the content of fatty acid amide and/or fatty acid bisamide exceeds the above range, the wettability tends to deteriorate.

In the layer B of the present invention, for the purpose of improving the sliding properties of the film, polyamide resins other than polyamide 6 can be added, such as polyamide MXD6, polyamide 11, polyamide 12, and polyamide resin. Amine 66, polyamide 6-polyamide 12 copolymer, polyamide 6-polyamide 66 copolymer, etc. Especially preferred is polyamide MXD6, and it is preferred to add 1% by mass to 10% by mass. If the polyamide resin other than polyamide 6 is less than 1% by mass, the sliding property improvement effect of the film is small. When the polyamide resins other than polyamide 6 are more than 10% by mass, the film's sliding property improvement effect is saturated. Polyamide MXD6 resin is produced by polycondensation of metaxylylenediamine and adipic acid. The relative viscosity of the above-mentioned 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 knead the polyamide resin.

In addition, in the layer B, for the purpose of improving adhesiveness, polyamide-based resins other than polyamide 6 may be added. In this case, copolymerized polyamide resins such as polyamide 6-polyamide 12 copolymer and polyamide 6-polyamide 66 copolymer are preferred.

As a method of adding auxiliary materials or additives such as lubricants and antioxidants to the A layer and/or B layer of the biaxially stretched polyamide film of the present invention, it can be used during resin polymerization or during melt extrusion using an extruder Add to. It is also possible to make a high-concentration masterbatch and add the masterbatch to the polyamide resin during film production. It can be carried out by such a well-known method.

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

In the thickness structure of each layer of the biaxially stretched polyamide film of the present invention, in the case of imparting slidability to the B layer and the case of imparting rubbing pinhole resistance, in order to exhibit these functions, the thickness of the B layer is preferable It is 0.5μm to 8μm. In addition, in order to increase the regeneration rate, it is preferable to set the thickness of the A layer to 50% to 93%, especially 70% to 93%, of the total thickness of the A layer and the B layer.

[Method for manufacturing biaxially stretched polyamide film] The biaxially stretched polyamide film of the present invention can be manufactured by the following manufacturing method. For example, the stepwise biaxial stretching method and the synchronous biaxial stretching method can be cited. The gradual biaxial stretching method can increase the film production speed, and therefore is advantageous in terms of manufacturing cost, and is therefore preferred. The manufacturing method of the biaxially stretched polyamide film in the present invention will be further described. First, the raw material resin is melt-extruded using an extruder, extruded from a T-die into a film, and cast on a cooling roll for cooling to obtain an unstretched film. The melting temperature of the resin is preferably 200°C to 300°C. If the temperature is less than 200°C, unmelted materials may be produced, which may cause defects such as defects in appearance. If it exceeds 300°C, resin degradation may be observed, resulting in a decrease in molecular weight and poor appearance. When the surface layer (layer B) is laminated on the base layer (layer A), it is preferable to obtain an unstretched film by a co-extrusion method using a feed block, a multi-manifold, or the like.

The temperature of the cooling roll 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 adhesion method using electrostatic charge can be preferably applied. In particular, the latter can be preferably used.

In addition, it is preferable that the cast unstretched film is also cooled on the opposite side of the cooling roll. For example, it is preferable to use the following methods together: a method in which the cooling liquid in the tank is brought into contact with the opposite side of the cooling roll of the unstretched film, a method in which a liquid is applied to evaporate by a spray nozzle, and a method in which a high-speed fluid is sprayed for cooling Wait. The unstretched film thus obtained is stretched in a biaxial direction to obtain a biaxially stretched polyamide film.

As an extension method in the MD (Machine Direction) direction, multi-stage extension such as one-stage extension or two-stage extension can be used. As will be described later, in terms of physical properties and the uniformity (isotropy) of physical properties in the MD direction and the TD (Transverse Direction) direction, multi-stage MD direction extension such as two-stage extension is preferred, rather than One-stage extension. The extension in the MD direction in the stepwise biaxial extension method is preferably roll extension.

The lower limit of the stretching temperature in the MD direction is preferably 50°C, more preferably 55°C, and still more preferably 60°C. If it does not reach 50°C, the resin may not be softened 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 still more preferably 110°C. If it exceeds 120°C, the resin may become too soft and cannot be stretched stably.

The lower limit of the stretching magnification in the MD direction (in the case of stretching in multiple stages, the total stretching magnification obtained by multiplying the magnifications of each stage) is preferably 2.2 times, more preferably 2.5 times, and still 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 and the impact strength may decrease. 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, the subsequent extension may become difficult.

In addition, in the case of stretching in the MD direction in multiple stages, the stretching in each stage can be used to perform the stretching as described above, but regarding the magnification, the stretching must be adjusted so that the product of the stretching magnification in all MD directions becomes 5.0 or less Magnification. For example, in the case of two-stage extension, it is preferable to set the extension in the first stage to 1.5 times to 2.1 times, and to set the extension in the second stage to 1.5 times to 1.8 times.

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

The lower limit of the stretching magnification in the TD direction (in the case of stretching in multiple stages, the total stretching magnification obtained by multiplying the magnifications of each stage) is preferably 2.8, more preferably 3.2 times, and even more preferably 3.5 times, especially The best is 3.8 times. If it is less than 2.8, the thickness accuracy in the TD direction may decrease, and the crystallinity may become too low, and the impact strength may decrease. The upper limit of the stretching ratio in the TD direction is preferably 5.5 times, more preferably 5.0 times, still more preferably 4.7, particularly preferably 4.5, and most preferably 4.3 times. If it exceeds 5.5 times, productivity may decrease significantly.

The selection of the heat-fixing temperature is an important element in the present invention. As the heat-fixing temperature is increased, the crystallization and alignment of the film will be relaxed, which can increase the impact strength and reduce the heat shrinkage rate. On the other hand, when the heat fixation temperature is low, crystallization and alignment relaxation are insufficient, and the heat shrinkage rate cannot be sufficiently reduced. In addition, if the heat-fixing temperature becomes too high, deterioration of the resin will occur, and the toughness of the film such as impact strength will be quickly lost.

The lower limit of the heat fixing temperature is preferably 180°C, more preferably 200°C. If the heat-fixing temperature is low, the heat shrinkage rate becomes too large, and the appearance after lamination decreases, and the lamination strength tends to decrease. The upper limit of the heat fixing temperature is preferably 230°C, more preferably 220°C. If the heat fixing temperature is too high, the impact strength tends to decrease.

The time of heat fixation is preferably 0.5 second to 20 seconds. Furthermore, it is 1 second to 15 seconds. The heat fixation time can be set as an appropriate time by matching with the heat fixation temperature or the wind speed in the heat fixation area. If the heat fixing conditions are too weak, crystallization and alignment relaxation become insufficient, causing the above-mentioned problems. If the heat setting conditions are too strong, the film strength and toughness will decrease.

Relaxation treatment after heat fixation is a way to effectively control the heat shrinkage rate. The temperature for performing the relaxation treatment can be selected from the heat-fixing treatment temperature to the glass transition temperature (Tg) of the resin, but the heat-fixing treatment temperature is preferably -10°C to Tg+10°C. If the relaxation temperature is too high, the shrinkage speed will be too fast to cause strain, etc., so it is unsatisfactory. Conversely, if the relaxation temperature is too low, the relaxation treatment cannot be performed, and only sagging occurs, but the thermal shrinkage rate does not decrease, and the dimensional stability deteriorates.

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

In order to increase the bonding strength with respect to the sealant film or the printed layer, corona treatment or flame treatment may be applied to the surface of the laminated stretched polyamide film. With regard to the biaxially stretched polyamide film of the present invention obtained in this way, even when friction occurs with corrugated cardboard and other handling packages during the transportation of bag-made products, it is possible to suppress scratches on the film due to the friction. The broken bag. In addition, bag breakage caused by bending fatigue caused by contact between the bags can be suppressed. In addition, since the water-resistant adhesive strength between the polyamide film and the sealant film is high, it exhibits high bag breaking resistance.

[Characteristics of biaxially stretched polyamide film] The biaxially stretched polyamide film of the present invention is preferably based on the measurement method described in the examples. The torsion and bending test using a Gelbo-Flex testing machine is performed 1000 times at a temperature of 1°C. The number of pinhole defects at the time was less than 20. More preferably, there are less than ten. The smaller the number of pinhole defects after the bending test, the better the bending pinhole resistance. If the number of pinholes is 10 or less, it is possible to obtain a packaging bag that is less likely to produce pinholes even when a load is applied to the packaging bag during transportation.

Furthermore, it is preferable that the biaxially stretched polyamide film of the present invention has a distance of 2000 cm or more until pinholes are generated in the rubbing resistance pinhole test. It is more preferably 2900 cm or more, and still more preferably 3000 cm or more. The longer the distance of pinholes, the better the resistance to rubbing pinholes. If the distance of pinholes is 2900cm or more, it is possible to obtain a packaging bag that is not prone to pinholes even when the bag is rubbed against a corrugated cardboard box during transportation. . In the present invention, by optimizing the raw material composition of the A layer and the B layer, a biaxially stretched polyamide film having excellent both the above-mentioned bending pinhole resistance and rubbing pinhole resistance can be obtained. Since the biaxially stretched polyamide film of the present invention having these characteristics is not prone to pinholes during transportation, it is extremely useful as a film for packaging.

The biaxially stretched polyamide film of the present invention preferably has a heat shrinkage rate of 0.6% to 5.0% in both the traveling direction (hereinafter referred to as MD direction) and the width direction (hereinafter referred to as TD direction) at 160°C for 10 minutes. The range is more preferably 0.6% to 3.0%. When the heat shrinkage rate exceeds 5.0%, curling or shrinkage may sometimes occur when heat is applied in subsequent steps such as laminating or printing. In addition, the lamination strength with the sealant film may become weak. Although the thermal shrinkage rate can be less than 0.6%, it may become mechanically brittle. In addition, the productivity deteriorates, so it is unsatisfactory.

The excellent impact resistance is the characteristic of the biaxially stretched polyamide film. Therefore, the easily-adhesive polyamide film of the present invention preferably has an impact strength of 0.7J/15μm or more. The better impact strength is 0.9J/15μm or more. The impact strength is better, but it is difficult to exceed 1.5J/15μm. The puncture strength of the easily adhesive polyamide film of the present invention is preferably 0.65 N/μm or more. The better puncture resistance strength is 0.70N/μm or more. The puncture strength is better, but it is difficult to exceed 1.0N/μm. The easy-adhesive polyamide film of the present invention preferably has a surface alignment coefficient of 0.045 or more. A more preferable surface alignment coefficient is 0.050 or more. When the surface alignment coefficient is large, the impact strength and puncture strength are better. However, in order to be greater than 0.080, the extension ratio must be further increased, and it is easy to break during the extension step, so it is difficult to exceed 0.080.

The haze value of the biaxially stretched polyamide film of the present invention is preferably 10% or less. It is more preferably 5% or less, and still more preferably 2.6% or less. If the haze value is small, the transparency and gloss are good, so when it is used in packaging bags, it can achieve beautiful printing and increase the product value. If fine particles are added in order to improve the sliding properties of the film, the haze value will increase. Therefore, it is preferable to add fine particles only to the B layer of the surface layer or more in the B layer of the surface layer to reduce the content of the A layer Therefore, a film with good sliding properties and a small haze value can be obtained.

The laminate strength after the biaxially stretched polyamide film of the present invention and the polyethylene-based sealant described in the examples are bonded is preferably 4.0 N/15 mm or more. The biaxially stretched polyamide film of the present invention is usually processed into packaging bags 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 laminated structures, the strength of the seal portion can be sufficiently obtained, and the A strong packaging bag that is not easy to break. In order to set the lamination strength to 4.0N/15mm or more, the biaxially stretched polyamide film of the present invention may be subjected to corona treatment, coating treatment, flame treatment, and the like.

Furthermore, the biaxially stretched polyamide film of the present invention may be subjected to heat treatment or humidity control in order to have good dimensional stability due to its application. In addition, in order to improve the adhesiveness of the film surface, corona treatment, coating treatment, flame treatment, etc., or printing processing, metal or inorganic oxide vapor deposition processing, etc. may be performed. In addition, as the vapor-deposited film formed by the vapor-deposition process, an aluminum vapor-deposited film, a silicon oxide or an aluminum oxide's single or a mixture vapor-deposited film can be preferably used. Furthermore, by coating a protective layer or the like on these vapor-deposited films, oxygen barrier properties, hydrogen barrier properties, and the like can be improved.

The biaxially stretched polyamide film laminated sealant film of the present invention is processed into a laminated film and then processed into bottom sealed bags, side sealed bags, three-sided sealed bags, pillow bags, stand-up bags, gusset bags, Packaging bags such as corner bottom bags. Examples of the sealant film include unstretched linear low-density polyethylene films, unstretched polypropylene films, ethylene-vinyl alcohol copolymer resin films, and the like. The layer structure of the laminated film using the biaxially stretched polyamide film of the present invention is not particularly limited as long as the laminated film has the easily adhesive polyamide film of the embodiment of the present invention. In addition, the film used in the laminated film can be either a petrochemical-derived material or a biomass-derived material. In terms of reducing the environmental load, it is better to use a biomass-derived material for polymerization. Polylactic acid, polyethylene terephthalate, polybutylene succinate, polyethylene, polyethylene furandicarboxylate, etc.

As an example of the layer structure of the laminated film of the present invention, if the boundary of the layers is represented by "/", for example: ONY/connect/LLDPE, ONY/connect/CPP, ONY/connect/Al/connect/CPP, ONY /Connect/Al/Connect/LLDPE, ONY/PE/Al/Connect/LLDPE, ONY/Connect/Al/PE/LLDPE, PET/Connect/ONY/Connect/LLDPE, PET/Connect/ONY/PE/LLDPE, PET /Connect/ONY/Connect/Al/Connect/LLDPE, PET/Connect/Al/Connect/ONY/Connect/LLDPE, PET/Connect/Al/Connect/ONY/PE/LLDPE, PET/PE/Al/PE/ONY /PE/LLDPE, PET/Connect/ONY/Connect/CPP, PET/Connect/ONY/Connect/Al/Connect/CPP, PET/Connect/Al/Connect/ONY/Connect/CPP, ONY/Connect/PET/Connect /LLDPE, ONY/connect/PET/PE/LLDPE,ONY/connect/PET/connect/CPP,ONY//Al//PET//LLDPE, ONY/connect/Al/connect/PET/PE/LLDPE, ONY/ PE / LLDPE, ONY / PE / CPP, ONY / PE / Al / PE, ONY / PE / Al / PE / LLDPE, OPP / connection / ONY / connection / LLDPE, ONY / connection / EVOH / connection / LLDPE, ONY / Connect / EVOH / Connect / CPP, ONY / Connect / Aluminum or inorganic oxide vapor deposition PET / Connect / LLDPE, ONY / Connect / Aluminum vapor deposition PET / Connect / ONY / Connect / LLDPE, ONY / Connect / Aluminum vapor deposition PET ／PE／LLDPE, ONY／PE／Aluminum Evaporated PET／PE／LLDPE, ONY／Aluminum Evaporated PET／CPP，PET／Aluminum Evaporated PET／OnY／Ony／LLDPE，CPP／ Connect / ONY / connect / LLDPE, ONY / connect / aluminum vapor deposition LLDPE, ONY / connect / aluminum vapor deposition CPP, etc. In addition, each abbreviation used in the above-mentioned layer structure is as follows. ONY: the biaxially stretched polyamide film of the present invention; 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 resin; Connection: Adhesive layer to bond the films to each other; Aluminum or inorganic oxide vapor deposition Evaporated with aluminum or inorganic oxide. [Example]

Next, the present invention will be explained in more detail with examples, but the present invention is not limited to the following examples. In addition, the evaluation of the film was performed by the following measurement method. Unless otherwise stated, the measurement is performed in a measurement room at 23°C and a relative humidity of 65%.

(1) Regeneration ratio of membrane The regeneration ratio of the biaxially stretched polyamide membrane is calculated by calculating the ratio of the raw material obtained by chemical regeneration and the raw material obtained by mechanical regeneration relative to the raw material of the whole membrane and expressed in %. (2) Film thickness Divide into 10 equal parts along the TD direction of the film (for a film with a narrow width, divide into equal parts so that the width can ensure the width of the measurable thickness), overlap 10 pieces of the film with a thickness of 100mm in the MD direction and cut out. Adjust for more than 2 hours in an environment with a temperature of 23°C and a relative humidity of 65%. The thickness measurement at the center of each sample was performed using a thickness measuring instrument manufactured by TESTER Sangyo, and the average value of the measured thickness was defined as the thickness.

(3) Haze value of the film A direct-reading haze meter manufactured by Toyo Seiki Seisakusho Co., Ltd. was used for measurement in accordance with JIS-K-7105. (4) Coefficient of dynamic friction of the film According to JIS-C2151, the coefficient of dynamic friction between the outer surfaces of the film rolls was evaluated under the following conditions. In addition, it was performed under the following conditions: the size of the test piece was 130 mm in width, 250 mm in length, and the test speed was 150 mm/min.

(5) Impact strength of the film A film impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd. was used for the measurement. The measured value is converted for every 15 μm thickness and expressed in J (Joule)/15 μm. (6) Surface orientation of the film For the sample, the JIS K 7142-1996 A method was used to measure the refractive index in the longitudinal direction (Nx), the refractive index in the width direction (Ny), and the refractive index in the thickness direction of the film using an Abbe refractometer using sodium D-ray as a light source. (Nz), the surface orientation coefficient is calculated by the calculation formula of formula (1). Surface orientation coefficient (ΔP)=(Nx＋Ny)/2－Nz (1) (7) Puncture strength of membrane The obtained polyester film was sampled into a 5 cm square, and the digital force gauge "ZTS-500N" manufactured by IMADA Co., Ltd., the electric measuring table "MX2-500N" and the puncture jig "TKS-250N" were used, according to JIS Z1707 measures the puncture strength of the membrane. The unit is expressed in N/μm.

(8) Film resistance to bending and pinholes The number of bending fatigue pinholes was measured by the following method using a Galbo-Frank tester manufactured by Rigaku Kogyo Co., Ltd. After coating the polyester-based adhesive on the film produced in the example, a linear low-density polyethylene film (L-LDPE film: L4102 manufactured by Toyobo Co., Ltd.) with a thickness of 40 μm was dry-laminated at 40°C. Aging was carried out for 3 days in an environment to form a laminated film. The obtained laminated film was cut into 12 inches × 8 inches, and made into a cylindrical shape with a diameter of 3.5 inches. The other end is fixed on the side of the movable head, and the initial holding interval is set to 7 inches. Perform 1000 bending fatigue tests at a speed of 40 times/min, and count the number of pinholes generated in the laminated film. The bending fatigue test is performed at the first 3.5 inches of the stroke and a twist of 440 degrees is applied, and then 2.5 Inch to end the total stroke with a straight horizontal movement. In addition, the measurement was performed in an environment of 1°C. The test film was placed on a filter paper (Advantec, No. 50) with the L-LDPE film side of the test film as the lower surface, and the four corners were fixed with CELLOTAPE (registered trademark). The ink (the ink made by PILOT (product number INK-350-blue) is diluted 5 times with pure water) is applied on the test film, and the ink is spread on one side using a rubber roller. After the unnecessary ink is wiped off, the test film is removed, and the number of ink dots attached to the filter paper is counted.

(9) Friction and pinhole resistance of the film Using a fastness tester (Toyo Seiki Co., Ltd.), a friction test was performed by the following method to measure the pinhole generation distance. Fold the same laminate film in four as the laminate film produced in the above-mentioned bending pinhole resistance evaluation to make a test sample with sharp corners. Using a fastness tester, amplitude: 25 cm, amplitude speed: 30 times /Min, weight: 100g weight, friction on the inner surface of the corrugated cardboard. The corrugated cardboard system uses K280×P180×K210(AF)=(surface material pad×core material×inner surface material pad (type of flute of corrugated cardboard)). The pinhole generation distance is calculated according to the following procedure. The longer the pinhole generation distance, the better the rubbing pinhole resistance. First, a friction test was carried out at a distance of 2500 cm with an amplitude of 100 times. When there is no pinhole, increase the number of amplitude 20 times and increase the distance by 500cm to perform the friction test. If there is still no pinhole, increase the number of amplitude 20 times and increase the distance by 500cm to perform the friction test. Repeat this operation to mark the distance where the pinhole is generated and set it as level 1. When pinholes are generated at a distance of 2500cm at 100 times of amplitude, the friction test is performed by reducing the number of times of amplitude by 20 times and the distance of 500cm. When pinholes still occur, the friction test is performed by reducing the number of amplitudes by 20 times and reducing the distance by 500cm. This operation is repeated and the distance where no pinhole is generated is marked with ○ and set to level 1. Next, as level 2, in the case where level 1 is ○ at the end, the friction test is performed by increasing the number of amplitudes by 20 times. If no pinholes are generated, mark ○, and if pinholes are generated, mark ×. In the case of x at the end in level 1, the friction test is performed by reducing the number of amplitudes by 20 times. If no pinholes are generated, mark ○, and if pinholes are generated, mark ×. Furthermore, as level 3 to level 20, when the previous level was ○, the friction test was performed by increasing the amplitude frequency by 20 times. If no pinholes were generated, ○ was marked, and if pinholes were generated, × was marked. When the previous level was ×, the friction test was performed by reducing the amplitude frequency by 20 times. If no pinholes were generated, mark ○, and if pinholes were generated, mark ×. This operation is repeated to mark ○ or × for level 3 to level 20. For example, the results shown in Table 1 were obtained. Take Table 1 as an example to illustrate how to find the pinhole distance. Count the number of trials of ○ and × for each distance. Set the distance with the largest number of trials to the central value, and set the coefficient to zero. When the distance is longer than the central value, set the coefficients to +1, +2, +3 every 500cm. When the distance is shorter than the central value, set the coefficients to -1, -2,-every 500cm. 3... In all the tests from level 1 to level 20, compare the number of tests with no holes and the number of tests with holes. For the cases of A and B below, use various formulas to calculate the friction pinhole generation distance. A: In all the tests, the number of tests without holes is more than the number of tests with holes. The distance of the friction pinhole generation = central value + 500 × (Σ (factor × number of tests without holes) / number of tests without holes) + 1/2) B: In all tests, the number of tests without holes did not reach the number of tests with holes. The distance generated by the friction pinhole = central value + 500 × (Σ (factor × number of tests with holes) / number of tests with holes)-1/2)

[Table 1] A: In all tests, the number of tests without holes (O) is more than the number of tests with holes (X). The distance generated by the friction pinhole = central value + 500 × (Σ (factor × the number of tests without a hole) / the number of tests without a hole) + 1/2) The distance generated by the friction pinhole = 3500 + 500 × (-4/10 + 1/2) = 3550 Amplitude frequency Amplitude distance 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Number of O Number of X coefficient Number*Coefficient 180 4500 160 4000 X X X X X X 0 6 1 0 140 3500 X X O O X X O O O O 6 4 0 0 120 3000 O O O O 4 0 -1 -4 100 2500 count 10 10 A -4 B: In all tests, the number of tests without holes (X) does not reach the number of tests with holes (O). The distance generated by the friction pinhole = the central value + 500 × (Σ (factor × the number of tests with the hole) / the number of tests with the hole)-1/2) The distance generated by the friction pinhole = 3000 + 500 × (3/11-1/2) = 2886 Amplitude frequency Amplitude distance 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Number of O Number of X coefficient Number * Coefficient 160 4000 140 3500 X X X X 0 4 1 4 120 3000 X X O O X X O O X X 4 6 0 0 100 2500 O O O O O X 5 1 -1 -1 80 2000 count 9 11 B 3

(10) Heat shrinkage rate of film Except that the test temperature was set to 160°C and the heating time was set to 10 minutes, the thermal shrinkage rate was measured by the following formula in accordance with the dimensional change test method described in JIS C2318. Thermal shrinkage ratio=[(length before treatment-length after treatment)/length before treatment]×100(%)

(11) Laminating strength with polyethylene sealant The laminated film produced in the same manner as the method described in the description of the bending pinhole resistance evaluation was cut into short strips with a width of 15 mm × a length of 200 mm, and one end of the laminated film was placed on the biaxially stretched polyamide The interface between the film and the linear low-density polyethylene film was peeled off using Autograph (manufactured by Shimadzu Corporation) at a temperature of 23°C, a relative humidity of 50%, a stretching speed of 200mm/min, and a peeling angle of 90°. The laminate strength was measured three times in the MD direction and the TD direction, and the average value of the three times was evaluated.

(12) Relative viscosity of raw material polyamide 0.25 g of polyamide was dissolved in a 25 ml volumetric flask with 96% sulfuric acid in 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 In accordance with JIS K7121, the SSC5200 differential scanning calorimeter manufactured by Seiko Instruments is used for measurement in a nitrogen atmosphere under the conditions of sample weight: 10 mg, heating start temperature: 30°C, and heating rate: 20°C/min. The endothermic peak temperature (Tmp) was calculated as the melting point.

[Polyamide 6(a-1) obtained by re-polymerizing raw materials from petrochemicals] As polyamide 6(a-1) obtained by repolymerizing raw materials derived from petrochemicals, polyamide 6 with a relative viscosity of 2.8 and a melting point of 220°C manufactured by Toyobo Co., Ltd. was used. [Production of polyamide 6(a-2) obtained by chemical regeneration] The polyamide 6 fiber recovered from the waste and the 75% by mass phosphoric acid aqueous solution as a depolymerization catalyst are added to the depolymerization device and heated to 260°C under a nitrogen atmosphere. The reaction is started while blowing the superheated steam into the depolymerization device, the epsilon-caprolactam and water vapor continuously distilled from the depolymerization device are cooled, and the epsilon-caprolactam distillate is recovered. The recovered distillate is concentrated by an evaporator, and the obtained ε-caprolactam is repolymerized to obtain chemically regenerated polyamide 6. Polyamide 6(a-2) has a relative viscosity of 2.7 and a melting point of 221°C.

[Manufacturing of polyamide 6(a-3) obtained by mechanical regeneration] The non-standard film produced from the stretched film obtained by the method shown in Example 1 described later and the scraps produced as cutting sapwood (offcuts) are recovered and crushed, and the cylinder temperature is 270°C. The extruder is kneaded and pelletized, and then dried at 100° C. under reduced pressure to obtain polyamide 6 obtained by mechanical regeneration. Polyamide 6(a-3) has a relative viscosity of 2.6 and a melting point of 221°C.

[Example 1] Using a device consisting of one extruder and a single-layer T-die with a width of 380mm, the molten resin of the following polyamide resin composition was extruded from the T-die into a film, and the temperature was adjusted to 20°C. The roll was cooled and electrostatically adhered to obtain an unstretched film with a thickness of 200 μm. The polyamide resin composition is composed of 95 parts by mass of polyamide 6(a-1), 5.0 parts by mass of polyamide 6(a-2), and porous silica particles (manufactured by FUJI SILYSIA CHEMICAL Co., Ltd., Polyamide resin composition composed of 0.45 parts by mass (average particle size 2.0μm, pore volume 1.6ml/g) and 0.15 parts by mass of fatty acid bis-amide (ethylene distearate manufactured by Kyoeisha Chemical Co., Ltd.) Things. In addition, the thickness of the biaxially stretched polyamide film was adjusted so that the total thickness became 15 μm, and the discharge amount of the extruder was adjusted. The obtained unstretched film was introduced into a roll stretcher, and after being stretched 1.73 times in the MD direction at 80°C using the difference in the peripheral speed of the rolls, it was further stretched 1.85 times at 70°C. Then, the uniaxially stretched film was continuously introduced into a tenter stretcher, and after preheating at 110°C, it was stretched 1.2 times at 120°C in the TD direction, 1.7 times at 130°C, and 2.0 times at 160°C. After heat-fixing treatment at 218°C, 7% relaxation treatment was performed at 218°C, and then the surface on the side dry-laminated with the linear low-density polyethylene film was subjected to corona discharge treatment to obtain a biaxially stretched polyamide film. Table 2 shows the evaluation results of the obtained biaxially stretched polyamide film.

[Example 2 to Example 6, and Reference Example 1] As shown in Table 1, the film forming conditions such as the polyamide resin composition, the stretching ratio, and the heat-fixing temperature were changed, and a biaxially stretched film was obtained by the same method as in Example 1, except that the film forming conditions were changed. Table 2 shows the evaluation results of the obtained biaxially stretched film.

[Example 7] In order to perform simultaneous biaxial stretching of the unstretched sheet of the polyamide resin composition shown in Table 1, it was sent to a warm water tank adjusted to 50°C for 2 minutes of immersion treatment to adjust the moisture content to about 4%, and then used It was held in the jig of the tentering-type synchronous biaxial stretching machine, and subjected to corona discharge treatment under the film forming conditions such as the stretching magnification and the heat-fixing temperature shown in Table 1 to obtain a biaxially stretched film. The evaluation results of the obtained biaxially stretched film are shown in Table 2.

[Table 2] Example Reference example 1 2 3 4 5 6 7 1 composition Polyamide 6(a-1) (from petrochemical raw material) quality% 84.5 9.9 49.7 24.9 74.6 0 24.9 100 Polyamide 6(a-2) (chemical regeneration) quality% 5.0 89.5 39.8 24.9 24.9 89.5 24.9 - Polyamide 6(a-3) (mechanical regeneration) quality% 0 0 9.9 49.7 0 9.9 49.7 - Microparticles quality% 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 Fatty acid amide quality% 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Overall thickness μm 15 15 15 15 15 15 15 15 Extension method - Step by step Step by step Step by step Step by step Step by step Step by step Synchronize Step by step MD extension temperature °C 80 80 80 80 80 80 180 80 MD stretch magnification - 3.2 3.2 3.2 3.2 3.2 3.2 3.3 3.15 TD extension temperature °C 130 130 130 130 130 130 180 130 TD extension ratio - 4.0 4.0 4.0 4.0 4.0 4.0 3.3 4.0 TD thermal fixation temperature °C 218 218 218 218 218 218 210 218 TD relaxation temperature °C 218 218 218 218 218 218 210 218 TD relaxation rate % 7 7 7 7 7 7 5 7 Regeneration ratio % 5 89 50 75 25 99 75 0 Haze % 2.7 2.9 3.1 3.1 2.7 3.0 3.1 2.5 Dynamic friction coefficient - 0.69 0.67 0.65 0.63 0.70 0.67 0.69 0.68 Impact strength J/15μm 1.23 1.22 1.24 1.21 1.23 1.22 1.10 1.23 Surface orientation coefficient - 0.060 0.059 0.058 0.056 0.052 0.058 0.049 0.062 Puncture strength N/μm 0.80 0.79 0.81 0.81 0.78 0.77 0.73 0.78 Bending resistance to pinholes Piece 18 19 18 17 20 19 18 20 Resistance to rubbing pinholes cm 2600 2400 2500 2300 2600 2400 2200 2500 Heat shrinkage MD % 0.9 1.0 0.9 1.1 1.2 1.1 1.5 0.8 TD % 0.9 1.0 1.1 1.3 1.3 1.3 1.2 0.8 Lamination strength MD N/mm 6.9 6.7 7.4 7.1 7.1 7.1 7.9 7.0 TD N/mm 6.5 6.4 6.9 7.0 6.9 6.8 7.8 6.9

As shown in Table 2, the biaxially stretched polyamide film using the chemically regenerated polyamide 6(a-2) or the chemically regenerated polyamide 6(a-2) shown in the examples And the biaxially stretched polyamide film of polyamide 6(a-3) obtained by mechanical regeneration has good impact resistance, puncture strength, and bending pinhole resistance. Compared with the biaxially stretched polyamide 6(a-1) obtained by re-polymerizing raw materials derived from petrochemicals as the raw material of Reference Example 1, it is possible to obtain Biaxially stretched polyamide film with the same characteristics. In addition, the haze is low, the transparency is good, and the lamination strength with the sealant film is also high, and it is excellent as a packaging film.

[Example 8] Using a device composed of 2 extruders and a 380mm wide co-extrusion T-die, the molten resin is extruded from the T-die into a film by using the feed block method to laminate with the B-layer/A-layer/B-layer composition Shape, cast on a cooling roll whose temperature is adjusted to 20°C and make it electrostatically close to obtain an unstretched film with a thickness of 200μm. The resin compositions of the A layer and the B layer are as follows. ・Resin composition constituting layer A: a polyamide resin composition composed of 95 parts by mass of polyamide 6(a-1) and 5 parts by mass of polyamide resin (a-2). ・The resin composition constituting the B layer: 95 parts by mass of polyamide 6(a-1), 5.0 parts by mass of polyamide 6(a-2), and porous silica particles (FUJI SILYSIA CHEMICAL Co., Ltd. Manufactured, the average particle size is 2.0μm, the pore volume is 1.6ml/g) 0.45 parts by mass and 0.15 parts by mass of fatty acid diamide (ethylene bisstearate manufactured by Kyoeisha Chemical Co., Ltd.) Resin composition. In addition, the thickness of the biaxially stretched polyamide film is adjusted so that the total thickness becomes 15 μm, the thickness of the base layer (layer A) becomes 12 μm, and the thickness of the front and back surface layers (layer B) becomes 1.5 μm each. The composition of the feed block and the discharge volume of the extruder. The obtained unstretched film was introduced into a roll stretcher, and after being stretched 1.73 times in the MD direction at 80°C using the difference in the peripheral speed of the rolls, it was further stretched 1.85 times at 70°C. Then, the uniaxially stretched film was continuously introduced into a tenter stretcher, and after preheating at 110°C, it was stretched 1.2 times at 120°C in the TD direction, 1.7 times at 130°C, and 2.0 times at 160°C. After heat-fixing treatment at 218°C, 7% relaxation treatment was performed at 218°C, and then the surface on the side dry-laminated with the linear low-density polyethylene film was subjected to corona discharge treatment to obtain a biaxially stretched polyamide film. Table 3 shows the evaluation results of the obtained biaxially stretched polyamide film.

[Example 9 to Example 14] As shown in Table 3, the film forming conditions such as the polyamide resin composition, the stretching ratio, and the heat setting temperature were changed, and except for that, the same method as in Example 8 was used to obtain a biaxially stretched polyamide film. Table 3 shows the evaluation results of the obtained biaxially stretched polyamide film.

[Example 15] As shown in Table 3, film forming conditions such as the polyamide resin composition, stretching ratio, and heat setting temperature were changed. Except for this, an unstretched film was produced in the same manner as in Example 8, and the same method as in Example 7 was used. Perform simultaneous biaxial stretching to obtain a biaxially stretched polyamide film. Table 3 shows the evaluation results of the obtained biaxially stretched polyamide film.

[table 3] Example Reference example 8 9 10 11 12 13 14 15 2 3 4 Substrate layer A layer Polyamide 6(a-1) (from petrochemical raw material) quality% 95 10 50 25 75 0 50 25 100 25 25 Polyamide 6(a-2) (chemical regeneration) quality% 5 90 40 25 25 90 40 25 0 25 25 Polyamide 6(a-3) (mechanical regeneration) quality% 0 0 10 50 0 10 10 50 0 50 50 Surface layer B layer Polyamide 6(a-1) (from petrochemical raw materials) quality% 94.4 9.9 59.6 74.6 74.6 9.9 89.5 74.6 99.4 0 49.7 Polyamide 6(a-2) (chemical regeneration) quality% 5.0 89.5 39.8 24.9 24.9 89.5 0 24.9 0 0 0 Polyamide 6(a-3) (mechanical regeneration) quality% 0 0 0 0 0 0 9.9 0 0 99.4 49.7 Microparticles quality% 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 Fatty acid amide quality% 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Overall thickness μm 15 15 15 15 15 15 15 15 15 15 15 Substrate layer thickness % 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 Extension method - Step by step Step by step Step by step Step by step Step by step Step by step Step by step Synchronize Step by step Step by step Step by step MD extension temperature °C 80 80 80 80 80 80 80 130 80 80 80 MD stretch magnification - 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.0 3.2 3.2 3.2 TD extension temperature °C 130 130 130 130 130 130 130 130 130 130 130 TD extension ratio - 4.0 4.0 4.0 4.0 4.0 4.0 4.0 3.0 4.0 4.0 4.0 TD thermal fixation temperature °C 218 218 218 218 218 218 218 218 218 218 218 TD relaxation temperature °C 218 218 218 218 218 218 218 218 218 218 218 TD relaxation rate % 7 7 7 7 7 7 7 7 7 7 7 Regeneration ratio % 5 90 48 65 25 98 40 65 0 80 70 Haze % 2.3 2.5 2.6 2.6 2.3 2.6 2.8 2.6 2.2 3.2 3.0 Dynamic friction coefficient - 0.69 0.67 0.67 0.66 0.68 0.65 0.67 0.67 0.68 0.69 0.69 Impact strength J/15μm 1.21 1.20 1.23 1.20 1.20 1.21 1.23 1.00 1.23 1.20 1.21 Surface orientation coefficient - 0.060 0.059 0.058 0.056 0.052 0.058 0.058 0.049 0.062 0.056 0.061 Puncture strength N/μm 0.82 0.80 0.81 0.83 0.81 0.79 0.81 0.71 0.78 0.80 0.81 Pinhole resistance Piece 17 18 16 15 18 17 16 18 20 10 14 Resistance to rubbing pinholes cm 3140 3020 3050 3020 3100 3000 2950 3060 3120 2780 2850 Heat shrinkage MD % 1.0 1.1 0.9 1.0 1.1 1.0 1.1 1.3 0.8 1.0 1.1 TD % 0.9 1.0 1.0 1.2 1.1 1.2 1.0 1.4 0.8 1.2 1.2 Lamination strength MD N/mm 6.8 6.9 7.3 7.5 7.0 7.2 7.0 7.8 7.0 7.2 6.9 TD N/mm 6.6 6.5 7.0 7.1 6.8 6.8 6.8 7.7 6.9 6.8 6.7

As shown in Table 3, the biaxially stretched polyamide film using the polyamide 6 obtained by chemical regeneration (a-2) or the polyamide 6 obtained by chemical regeneration (a-2) as shown in the examples And the biaxially stretched polyamide film of polyamide 6(a-3) obtained by mechanical regeneration has good impact resistance, puncture strength, and friction pinhole resistance. Compared with the biaxially stretched polyamide 6(a-1) obtained by re-polymerizing raw materials derived from petrochemicals as the raw material of Reference Example 2, it is possible to obtain Biaxially stretched polyamide film with the same characteristics. In addition, the haze is low, the transparency is good, and the lamination strength with the sealant film is also high, and it is excellent as a packaging film.

In addition, in Reference Example 3 and Reference Example 4, a large amount of mechanically regenerated polyamide 6 was used in the surface layer (layer B). In this case, compared with the film in which the content of the mechanically regenerated polyamide 6 in the surface layer of Example 8 to Example 15 is 10% by mass or less, its transparency (haze) and resistance to rubbing pinholes Poor sex.

[Example 15] The biaxially stretched polyamide film produced in Example 11 was used to produce the laminates of the following (1) to (9), and the laminates (1) to (9) were used to produce the three-sided sealing type and Pillow-shaped packaging bags. It can produce packaging bags that have good appearance and are not easily broken in the drop impact test. (1) Biaxially stretched polyamide film layer/printing layer/polyurethane-based adhesive layer/linear low-density polyethylene film sealant layer. (2) Biaxially stretched polyamide film layer/printing layer/polyurethane-based adhesive layer/non-stretched polypropylene film sealant layer. (3) Biaxially stretched PET film layer/printing layer/polyurethane-based adhesive layer/biaxially stretched polyamide film layer/polyurethane-based adhesive layer/non-stretched polypropylene film sealing Agent layer. (4) Biaxially stretched PET film layer/printing layer/polyurethane-based adhesive layer/biaxially stretched polyamide film layer/polyurethane-based adhesive layer/linear low-density polymer Vinyl film sealant layer. (5) Biaxially stretched polyamide film layer/anchor coat layer/inorganic film layer/inorganic film protective layer/printing layer/polyurethane-based adhesive layer/linear low-density polymer Vinyl film sealant layer. (6) Linear low-density polyethylene film sealant layer / polyurethane adhesive layer / biaxially stretched polyamide film layer / anchor coating layer / inorganic film layer / polyurethane System adhesive layer/straight-chain 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 Agent 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-based adhesive layer/non-extended 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 Agent layer/easy peel type non-extended polypropylene film sealant layer. [Industry Availability]

The biaxially stretched polyamide film of the present invention has excellent puncture strength, impact resistance, bending pinhole resistance, and friction pinhole resistance, so it can be preferably used for packaging materials such as food packaging. Furthermore, the use of polyamide 6 that is chemically regenerated from waste polyamide products can help reduce environmental load. Furthermore, by blending the mechanically regenerated polyamide 6 into the raw material, a biaxially stretched polyamide film that can further reduce the environmental load can be obtained.

1: The head of the fastness testing machine 2: Corrugated cardboard 3: Backing paper for sample retention 4: Fold the film sample with 4 folds 5: Friction amplitude direction

[Fig. 1] It is a schematic diagram of an evaluation device for rubbing resistance and pinhole properties.

Claims (10)

A biaxially stretched polyamide film, composed of a polyamide resin composition, the aforementioned polyamide resin composition containing more than 70% by mass of polyamide 6, and containing 4% to 90% by mass of chemically regenerated The resulting polyamide 6. The biaxially stretched polyamide film according to claim 1, wherein the aforementioned biaxially stretched polyamide film contains 5 to 60% by mass of polyamide 6 obtained by mechanical regeneration. A biaxially stretched polyamide film, in which at least the single-area layer of the A layer as the base layer has the B layer as the surface layer, and the A layer is the biaxially stretched polyamide as described in claim 1 or 2. The film and layer B are composed of a polyamide resin composition containing more than 70% by mass of polyamide 6. The biaxially stretched polyamide film as described in claim 3, wherein the A layer as the base layer contains 5% to 80% by mass of the mechanically regenerated polyamide 6, and the B layer as the surface layer contains 0% to 30% by mass of polyamide 6 obtained by mechanical regeneration. The biaxially stretched polyamide film according to any one of claims 1 to 4, wherein the aforementioned biaxially stretched polyamide film satisfies the following (a) and (b): (a) The puncture strength is 0.65N/μm or more; (b) The impact strength is 0.9J/15μm or more. The biaxially stretched polyamide film according to any one of claims 1 to 4, wherein the aforementioned biaxially stretched polyamide film satisfies the following (c): (c) The distance until pinholes are generated in the rubbing resistance pinhole test is 2900 cm or more. The biaxially stretched polyamide film according to any one of claims 1 to 4, wherein the aforementioned biaxially stretched polyamide film satisfies the following (d) and (e): (d) Haze is below 2.6%; (e) The coefficient of dynamic friction is 1.0 or less. The biaxially stretched polyamide film according to any one of claims 1 to 4, wherein the laminated strength of the aforementioned biaxially stretched polyamide film and the polyethylene-based sealant film after being laminated is 4.0N/15mm or more . A laminated film is a biaxially stretched polyamide film laminated with a sealant film as described in any one of claims 1 to 8. A packaging bag that uses a laminated film as described in claim 9.

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