阅读说明：本技术 双轴拉伸聚酰胺树脂膜及其制造方法 (Biaxially stretched polyamide resin film and method for producing same ) 是由 野田敦子 结城究 田中信广 西谷千惠美 阪仓洋 于 2007-12-17 设计创作，主要内容包括：在使用了聚酰胺树脂的双轴拉伸膜的制造工序中的任意阶段,进行使膜与pH6.5～9.0、温度20～70℃的水接触0.5～10分钟的单体除去工序。由此得到的膜的己内酰胺单体的提取量为0.1质量％以下。(In any stage of the production process of the biaxially stretched film using a polyamide resin, a monomer removal step of bringing the film into contact with water having a pH of 6.5 to 9.0 and a temperature of 20 to 70 ℃ for 0.5 to 10 minutes is performed. The caprolactam monomer extraction amount of the film thus obtained is 0.1 mass% or less.)

1. A biaxially stretched polyamide resin film comprising a polyamide resin layer, characterized in that: the polyamide resin is a polyamide resin having caproamide as a repeating unit, wherein the amount of caprolactam monomer extracted is 0.001 to 0.1 mass%, and a sealing material resin layer is laminated on the polyamide resin layer.

2. The biaxially stretched polyamide resin film according to claim 1, wherein: a vapor deposition layer is laminated on the polyamide resin layer.

3. The biaxially stretched polyamide resin film according to claim 1, wherein: a gas barrier coating is laminated on the polyamide resin layer.

4. The biaxially stretched polyamide resin film according to claim 3, wherein: the gas barrier coating is formed of a polyvinylidene chloride-based copolymer.

5. The biaxially stretched polyamide resin film according to claim 3, wherein: the adhesion strength between the polyamide resin layer and the gas barrier coating is 0.8N/cm or more.

6. The biaxially stretched polyamide resin film according to claim 3, wherein: the thickness of the gas barrier coating is 0.5-3.5 μm.

7. The biaxially stretched polyamide resin film according to claim 1, wherein: an easy-adhesion layer made of a polyurethane resin or a polyurethane-urea resin is laminated on the polyamide resin layer.

8. A packaging material, characterized in that: comprising the biaxially stretched polyamide resin film according to any one of claims 1 to 7.

Technical Field

The present invention relates to a biaxially stretched polyamide resin film and a method for producing the same, and more particularly to a biaxially stretched polyamide resin film which can be used for a polyamide resin packaging container body particularly suitable for a medical container such as an infusion bag by laminating a polyolefin resin sheet such as polyethylene or polypropylene serving as a sealing material, and a method for producing the same.

Background

Biaxially stretched polyamide resin films using nylon 6, nylon 66, or the like are excellent in mechanical properties such as tensile strength, puncture strength, pinhole strength, impact strength, and the like, and are excellent in gas barrier properties and heat resistance. Therefore, a laminated film in which a sealing material made of a polyolefin film is laminated to a biaxially stretched polyamide resin film as a surface substrate by a method such as dry lamination or extrusion lamination has been used in a wide range of fields including packaging materials for sterilization treatment such as boiling and retort treatment.

These biaxially stretched polyamide resin films are generally used as surface substrates and are often not in direct contact with the contents. Therefore, the behavior of caprolactam monomer (hereinafter sometimes simply referred to as "monomer") in biaxially stretched polyamide resin films has not been so far described.

However, in recent years, the demand for the problem of deterioration of packaged articles or contents has become increasingly stringent, and improvements have been demanded. In particular, in medical applications where subtle composition changes of contents are prohibited, monomers having a small molecular weight contained in the polyamide resin film are transferred to the contents through the sealing material during heating such as sterilization treatment, and thus cannot be ignored.

In order to cope with such a problem, for example, nylon 11 or nylon 12 having a large molecular weight of a monomer unit constituting a polyamide resin, or a copolyamide resin having these as a main component has been proposed (JP 4-325159 a). Further, a copolymerized polyamide resin of 1, 6-hexamethylenediamine and sebacic acid has been proposed (JP 2001-328681A). However, they are special polyamides, and are expensive and have low versatility. Therefore, it is strongly desired to use a membrane having a low monomer content and high versatility of nylon 6 or nylon 66.

Even if unreacted monomers or oligomers are removed from the polyamide resin in the chip stage before film molding, the monomers or oligomers are regenerated when the polyamide resin chips are remelted by a melt extruder or the like, and as a result, the monomers remain in the film, and the quality thereof is degraded. In particular, polyamides mainly comprising caproamides as repeating units have the characteristic that monomers are relatively easily formed as compared with polyamides comprising dicarboxylic acids and diamines.

In general, if the end group concentration of the polyamide resin is high, the amount of monomer regenerated during remelting tends to increase. Therefore, polyamides have been developed in which the above-mentioned problems are reduced by adding a compound that reacts with a terminal carboxyl group or a terminal amino group of the polyamide. Specifically, a method of reacting an organic glycidyl ester with a carboxyl group and an amino group of polyamide is disclosed (JP 10-219104A). However, in this method, when the organic glycidyl ester is dry-blended with the polyamide chips and then melt-kneaded in an extruder, the organic glycidyl ester reacts with the terminal group of the polyamide. Therefore, in this method, it is difficult to uniformly mix them in the dry blending step before film molding. As a result, the composition varies, and it is difficult to obtain a polyamide having a uniform terminal group concentration, and the dry blending step itself is not suitable for a film having a large melt extrusion amount. In addition, the amount of monomer extracted after melt molding is still as much as 0.35 to 0.5 mass%, and the amount of monomer reduced is insufficient.

On the other hand, a method of capping the terminal amino group of a polyamide resin with a dicarboxylic anhydride is disclosed (JP 2005-187665A). However, the amount of the monomer to be regenerated at the time of melting is still as much as 0.27 to 0.75% by mass, and it is difficult to sufficiently reduce the monomer extracted from the polyamide resin film.

On the other hand, in recent years, there has been a movement to limit the discharge from factories and enterprises of organic compounds (generally, abbreviated as "VOC") that evaporate at normal temperature and pressure and are easily volatilized into the air. For example, in japan, according to the revised air pollution prevention act, a political directive specifying the type and scale of a facility to be controlled is implemented on 6/1/2005. In addition, government and provincial directives such as emission standard values, declared matters, and measurement methods were published in 6/10/2005 and executed in 1/4/2006.

Further investigation is needed as to whether venting caprolactam monomer to the atmosphere has an adverse effect. However, in the production of a polyamide resin film, printing of the film, lamination processing or bag processing using the film, it has become the responsibility and obligation of manufacturers to reduce the amount of caprolactam monomer discharged from the film into the atmosphere.

Therefore, it is strongly desired to reduce the amount of caprolactam monomer extracted from the film and to recover caprolactam monomer at the time of film production.

Disclosure of Invention

The present invention solves the above problems, and an object thereof is to provide: a biaxially stretched polyamide resin film which can be used in a polyamide resin packaging container body suitable for a medical container such as an infusion bag or the like without fear of deterioration of a packaged article or contents because the amount of caprolactam monomer released from the film is greatly reduced without impairing the original excellent properties, and a method for producing the same.

The biaxially stretched polyamide resin film of the present invention for achieving the above object is a biaxially stretched film using a polyamide resin, characterized in that: the extraction amount of caprolactam monomer is 0.1 mass% or less.

In the biaxially stretched polyamide resin film of the present invention, the polyamide resin is preferably a polyamide resin having caproamide as a repeating unit.

According to the biaxially stretched polyamide resin film of the present invention, a vapor-deposited layer is preferably laminated on the polyamide resin layer.

According to the biaxially stretched polyamide resin film of the present invention, a gas barrier coating layer is preferably laminated on the polyamide resin layer. In this case, it is preferable that: the gas barrier coating is formed by polyvinylidene chloride copolymer, the adhesion strength of the polyamide resin layer and the gas barrier coating is more than 0.8N/cm, and the thickness of the gas barrier coating is 0.5-3.5 mu m.

According to the biaxially stretched polyamide resin film of the present invention, a sealing material resin layer is preferably laminated on the polyamide resin layer.

According to the biaxially stretched polyamide resin film of the present invention, an easy-adhesion layer made of a polyurethane resin or a polyurethane-urea resin (also referred to as a melamine-urea resin) is preferably laminated on the polyamide resin layer.

The method for producing a biaxially stretched polyamide resin film of the present invention is characterized by comprising: in any stage of the production process of the biaxially stretched film using a polyamide resin, a monomer removal step of bringing the film into contact with water having a pH of 6.5 to 9.0 and a temperature of 20 to 70 ℃ for 0.5 to 10 minutes is performed.

According to the method for producing a biaxially stretched polyamide resin film of the present invention, it is preferable that: the method comprises the steps of treating an unstretched polyamide film in a monomer removal step, and simultaneously biaxially stretching the film after the moisture content of the film is adjusted to 2 to 10 mass% in a moisture adjustment step.

The packaging material of the present invention is characterized in that: comprising the above biaxially stretched polyamide resin film.

According to the present invention, the monomer removal step is performed on the polyamide resin film, whereby the amount of monomer released from the film can be significantly reduced without impairing the original excellent properties of the polyamide resin film. Therefore, according to the present invention, a biaxially stretched polyamide resin film which can be used for a polyamide resin packaging container body suitable for a medical container such as an infusion bag without fear of deterioration of the packaged material or the contents can be obtained.

Detailed Description

The present invention will be described in detail below.

The biaxially stretched polyamide resin film of the present invention is required to have a polyamide resin layer and to have a monomer extraction amount of 0.1 mass% or less. The amount of monomer extracted is preferably 0.05% by mass or less, and more preferably 0.02% by mass or less.

If the monomer extraction amount exceeds 0.1 mass%, even when the polyamide resin film is laminated with a sealing material to form a laminate film and the polyamide resin film is arranged on the side not in contact with the content to form a packaging bag, if the content is an aqueous substance, the monomer contained in the film may be transferred to the content through the sealing material.

The smaller the amount of monomer extracted, the better, but the more the amount of monomer extracted is reduced, the longer the monomer removal step in film formation, and the worse the production efficiency. Therefore, the lower limit is approximately 0.001 mass%.

The monomer extraction amount of the polyamide resin film in the present invention is calculated by the following measurement method in the view of the situation close to the sterilization treatment of the actual packaging bag. That is, about 0.5g of a membrane cut in a 0.5cm square was precisely weighed, extracted in a boiling water bath (100 ℃) for 2 hours using 10ml of distilled water, and the amount of monomer extracted from the membrane was determined by liquid chromatography (e.g., Hewlett packard, HP1100HPLC system). More specific methods for the measurement are described later.

Examples of the raw material of the biaxially stretched polyamide resin film in the present invention include nylon 6, nylon 66, nylon 46, nylon 69, nylon 610, nylon 612, nylon 11, nylon 12, poly (m-xylylene adipamide) (nylon MXD6), and a mixture or copolymer thereof. The biaxially stretched polyamide resin film of the present invention may be a multilayer film of films formed from the above-mentioned polyamide raw materials.

Nylon 6, which is excellent in cost performance, is particularly preferable from the viewpoint of productivity and performance. When nylon 6 is used as the film material, 30 mass% or less of other polyamide components in the above polyamide types may be contained in the form of copolymerization, blending, multilayer, or the like.

In order to suppress the formation of monomers during melting, it is more preferable that these polyamide resins contain organic glycidyl esters, dicarboxylic anhydrides, monocarboxylic acids such as benzoic acid, diamines, and the like as an end-capping agent.

The relative viscosity of the polyamide resin is not particularly limited, but is preferably 1.5 to 5.0 as measured at a temperature of 25 ℃ and a concentration of 1g/dl using 96% sulfuric acid as a solvent. More preferably 2.5 to 4.5, and still more preferably 3.0 to 4.0. When the relative viscosity is less than 1.5, the mechanical properties of the film tend to be significantly reduced. Further, if it exceeds 5.0, the film formability of the film is easily inhibited.

If necessary, 1 or 2 or more of various additives such as pigments, antioxidants, ultraviolet absorbers, preservatives, antistatic agents, antiblocking agents, and inorganic fine particles may be added to these polyamide resins within a range that does not adversely affect the performance of the film.

These polyamide resins may contain 1 or 2 or more kinds of various inorganic lubricants or organic lubricants for the purpose of improving the smoothness of the film. Examples of the lubricant include clay, talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, magnesium aluminosilicate, glass balloon (glass balloon), carbon black, zinc oxide, antimony trioxide, zeolite, hydrotalcite, layered silicate, and ethylene bis stearamide.

The polyamide resin film of the present invention is produced by the following method.

In general, for example, a polyamide resin composition is heated and melted by an extruder, extruded into a film form through a T-die, cooled and solidified on a rotating cooling drum by a known casting method such as an air knife casting method or an electrostatic casting method, to obtain an unstretched film, and the unstretched film is subjected to a stretching treatment. Since the stretchability may be lowered in a subsequent step if the unstretched film is oriented, the unstretched film is preferably in a substantially amorphous and unoriented state.

The stretching treatment includes sequential biaxial stretching in which stretching treatment is performed in the transverse direction after stretching in the longitudinal direction, and simultaneous biaxial stretching in which stretching treatment is performed simultaneously in the transverse direction and the longitudinal direction. The longitudinal stretching in the successive biaxial stretching may be performed a plurality of times. In any drawing method, in order to obtain a plane orientation coefficient of 0.05 or more, it is preferable to perform a drawing process so that the surface magnification becomes 9 times or more.

The stretching method is not particularly limited, but a simultaneous biaxial stretching method is preferable because it is efficient, and the method can perform melt film formation, a monomer removal step, a moisture adjustment step, a stretching step, a thermosetting step, and a cooling step, which will be described later, in one step.

The film subjected to the sequential biaxial stretching or simultaneous biaxial stretching is heat-set at a temperature of 150 to 220 ℃ in a tenter after the stretching treatment, and if necessary, the film is subjected to a relaxation treatment in the longitudinal direction and/or transverse direction in a range of 0 to 10%, preferably 2 to 6%.

In order to produce the polyamide resin film of the present invention, it is necessary to provide a monomer removal step at any stage of the above-described film forming step. In any stage, the amount of caprolactam generated in the polyamide resin increases when the polyamide resin is melted, and therefore the monomer removal step is preferably performed after the polyamide resin is melted and molded into a film shape. The monomer removal step may be performed in any of the steps of the unstretched film, the step after longitudinal stretching, and the step after biaxial stretching, and is preferably performed in the step of the unstretched film in which crystallization and orientation of the film have not been performed, because the efficiency of monomer removal is high and the monomer is not discharged to the atmosphere in the stretching step.

The monomer removal step was performed as follows: the polyamide membrane is brought into contact with water having a pH of 6.5 to 9.0 and a temperature of 20 to 70 ℃ in a monomer removal tank under tension for 0.5 to 10 minutes.

In the monomer removal step, the temperature of the water in the monomer removal tank is required to be 20 to 70 ℃, preferably 30 to 65 ℃, and more preferably 40 to 55 ℃. If the water temperature in the monomer removal tank is less than 20 ℃, it is difficult to remove the monomer in a short time. When the temperature exceeds 70 ℃, wrinkles are likely to occur in the unstretched film when the monomer removal step is performed at the stage of the unstretched film, stretching becomes uneven, the quality of the stretched film is lowered, and problems such as easy breakage of the film during stretching, easy peeling of the film at the edges of the film due to nipping, and the like are likely to occur, and the workability is deteriorated.

The pH of the water in the monomer removal tank is required to be 6.5 to 9.0. Preferably 7.0 to 8.5, and more preferably 7.5 to 8.0. If the pH is less than 6.5, oxidative degradation of the polyamide resin film progresses. If the pH exceeds 9.0, the water is not preferable in terms of safety because the alkaline water adheres to the membrane and is therefore easily accessible to the operator.

The time for which the polyamide resin film is contacted with water in the monomer removing step is required to be in a range of 0.5 to 10 minutes, depending on the temperature and pH of water. Preferably 0.5 to 5 minutes, and more preferably 1 to 3 minutes. If the time is less than 0.5 minute, it is difficult to sufficiently remove the monomer, and if it exceeds 10 minutes, the process is excessively prolonged, and the moisture content of the film during stretching is increased, which is not preferable.

The water temperature, pH, and contact time of water and the membrane in the monomer removal step are closely related to each other. The higher the water temperature is, the more effective the monomer removal is, but if the water temperature is increased, wrinkles are likely to occur in the unstretched film. If the water temperature is set to a low temperature, it takes time to remove the monomer, and the production efficiency is deteriorated. By setting the pH to the weak base side of 6.5 to 9.0, the problematic monomer can be selectively removed by a relatively short treatment even at low temperatures.

In order to avoid problems during stretching when stretching is performed after the monomer removal step, it is preferable that the unstretched polyamide film is treated in the monomer removal step to remove the monomer, and then the polyamide resin film is stretched after the moisture content of the polyamide resin film is adjusted to 2 to 10 mass%, preferably 4 to 8 mass%, in the moisture adjustment step. When the moisture content is lower than 2 mass%, the tensile stress increases, and problems such as film breakage tend to occur. Conversely, when the moisture content is higher than 10 mass%, the thickness unevenness of the unstretched film increases, and the thickness unevenness of the obtained stretched film also increases. In the moisture control step, when the moisture content of the film is generally low, the film is passed through a moisture control bath at a temperature of 40 to 90 ℃, more preferably 50 to 80 ℃, and the passage time is controlled to control the moisture content of the film. Pure water is generally used in the water conditioning tank, but a dye, a surfactant, a plasticizer, and the like may be added to the treatment liquid as needed. In addition, the moisture can be adjusted by spraying water vapor.

On the other hand, when the moisture content of the film is higher than 10 mass%, the moisture content is lowered by, for example, bringing the film into contact with a roll having a water-absorbing layer.

According to the present invention, a biaxially stretched polyamide resin film having excellent gas barrier properties with few processing defects can be obtained by forming a structure in which a vapor deposition layer is laminated on a polyamide resin layer. The deposition layer uses a compound containing an inorganic substance or an organic substance. As the inorganic substance, a metal such as aluminum or an inorganic oxide of aluminum, silicon, magnesium, titanium or the like is used.

Examples of the method for forming the inorganic layer include a vacuum evaporation method, a sputtering method, a Chemical Vapor Deposition (CVD) method, a Physical Vapor Deposition (PVD) method, and the like. The vacuum evaporation method is particularly excellent in practicality.

When the polyamide resin layer is subjected to vapor deposition, the polyamide resin layer may be subjected to corona treatment, plasma treatment, coating treatment with an inorganic or organic compound, or the like in advance in order to improve adhesion between the polyamide resin layer and the vapor deposition layer.

In the case of vacuum deposition, aluminum (Al) or aluminum oxide (Al) is used as a deposition material₂O₃) Silicon (Si), silicon dioxide (SiO)₂) Or a combination thereof. Examples of the method for heating the raw material include resistance heating, high-frequency induction heating, electron beam heating, and laser heating. Further, an ion-assisted method in which oxygen gas is used together with or in addition to oxygen gas during heating may be employed.

The thickness of the evaporation layer is preferably about 1-1000 nm. If the thickness is 1nm or less, the gas barrier property cannot be exhibited, and if the thickness is 1000nm or more, the plasticization of the whole film obtained by the processing is lost, and the practicability is lowered.

According to the present invention, a gas barrier coating layer may be laminated on at least one surface of the polyamide resin layer. As the gas barrier coating, polyvinylidene chloride-based copolymer (PVDC) is suitable. But is not particularly limited.

The PVDC is a polymer containing vinylidene chloride units in an amount of 60 mass% or more, preferably 70 to 97 mass%, and is used in the form of a latex and applied to at least one surface of the polyamide resin layer. The average particle diameter of PVDC in the latex is preferably 0.05-0.5 μm, and particularly preferably 0.07-0.3 μm. Various additives such as an antiblocking agent, a crosslinking agent, a water repellent agent, an antistatic agent and the like may be used in combination in the PVDC within a range not to impair the effects of the present invention.

The thickness of the gas barrier coating layer using PVDC is preferably in the range of 0.5 to 3.5. mu.m, more preferably in the range of 0.7 to 3.0. mu.m, and still more preferably in the range of 1.0 to 2.5. mu.m. If the coating layer is thinner than 0.5 μm, it is difficult to exhibit sufficient gas barrier properties. On the other hand, if the coating layer is thicker than 3.5 μm, not only the effect is saturated but also the physical properties of the film are sometimes impaired.

The adhesion strength between the polyamide resin layer as the base film and the gas barrier coating layer is preferably 0.8N/cm or more, more preferably 1.0N/cm or more, and still more preferably 2.0N/cm or more. If the adhesive strength is lower than this value, the polyamide resin layer and the gas barrier coating layer may peel off during boiling treatment or retort treatment, or sufficient sealing strength may not be obtained.

In the formation of the gas barrier coating layer, the gas barrier coating layer is formed in a stage where the amount of the monomer after the monomer removal step and before the stretching is small, and this is important in improving the adhesion to the substrate film.

The coating method is not particularly limited, and various coating methods such as a gravure roll method, a reverse roll method, an air knife method, a reverse gravure method, a wire bar method, a reverse roll method, or a combination thereof, or various spray methods can be used.

Just before coating, the polyamide resin layer may be subjected to corona discharge treatment or the like.

The biaxially stretched polyamide resin film having a structure in which a gas barrier layer is laminated, which is obtained in this way, has excellent strength and mechanical properties as a polyamide film, excellent gas barrier properties, and excellent adhesion between the polyamide resin layer and the coating layer, and is therefore suitable for use as a packaging material.

According to the present invention, a structure in which a sealing material resin layer is laminated on a polyamide resin layer can also be formed. Since heat sealability can be imparted by laminating a sealing material resin layer on the polyamide resin layer, the polyamide resin film can be used as a package.

The sealing material layer may use a resin having good thermal adhesiveness. For example, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-acrylic acid/methacrylic acid copolymer, ethylene-acrylic acid/methacrylic acid ester copolymer, acid-modified polyethylene/polypropylene-based resin, polyvinyl acetate-based resin, and the like can be used. These resins may be used alone, or they may be used after being copolymerized or melt-mixed with other resins or components, or they may be used after being modified. These resin components may be used for a single layer, or at least one or more resin components may be used for a plurality of layers. Particularly preferred are polyolefin resins such as polyethylene, polypropylene, and polyethylene/polypropylene copolymers.

The polyamide resin layer may be an outermost layer and the sealant layer may be an innermost layer, and an aluminum foil layer, a gas barrier resin layer, another thermoplastic resin layer, another polyamide resin layer, or the like may be laminated therebetween without impairing the effect of the present invention. The method of lamination is not particularly limited, and examples thereof include a dry lamination method, a wet lamination method, a solvent-free dry lamination method, an extrusion lamination method, and the like.

The film having the sealing material layer laminated thereon is preferably used as a package such as a pouch or a lid for a tray package by heat-sealing the sealing material layer side. Examples of the form of the bag include a three-side sealed bag, a four-side sealed bag, a pillow bag, a stand-up bag, and a box package.

Examples of the method for forming the sealing material layer include a method of forming a film of the sealing material layer and laminating the film on the polyamide resin layer, a co-extrusion method of simultaneously extrusion-laminating the polyamide resin layer and the sealing material layer, and a method of applying a resin for forming the sealing material layer on the polyamide resin layer with an applicator. When the sealing material layer is once formed into a film, the film may be unstretched or stretched at a low magnification, and practically, an unstretched film is preferable. As a method for forming the film, a tenter method in which the film is heated and melted by an extruder and extruded from a T-die, and cooled and solidified by a cooling roll or the like, a tube method in which the film is extruded from a circular die and cooled and solidified by water cooling or air cooling, or the like can be used.

As a method of laminating a sealing material layer formed in a film form on a polyamide resin layer, a general production method can be used. For example, a lamination method such as a dry lamination method, a wet lamination method, a solvent-free dry lamination method, and an extrusion lamination method can be used. The extrusion lamination method is particularly preferably used.

Alternatively, a lamination method using an adhesive such as urethane may be employed. In this case, it is preferable to laminate both the polyamide resin layer and the sealing material layer with an adhesive after corona discharge treatment or easy adhesion treatment.

When the polyamide resin layer and the sealing material layer are laminated in this manner and the obtained film is used as a package, it is possible to reduce the deposition of monomers from the polyamide resin layer onto the film surface when the package is subjected to a sterilization treatment using dry heat treatment or wet heat treatment. Therefore, the film is particularly suitable for use as a packaging body for food packaging or the like subjected to sterilization treatment such as boiling treatment or retort treatment.

According to the present invention, an easy-adhesion layer made of a polyurethane resin or a polyurethane-urea resin may be provided on at least one surface of the polyamide resin layer.

The polyurethane resin used for the polyurethane resin is a reaction product of a polyol and a polyisocyanate.

Examples of the polyol used as a raw material of the polyurethane include polyethylene glycol, polypropylene glycol, polyethylene glycol-propylene glycol, poly-1, 4-butanediol, 1, 6-hexanediol, 1, 4-butanediol, 1, 5-pentanediol, diethylene glycol, triethylene glycol, polycaprolactone, poly-1, 6-hexanediol adipate, poly-1, 6-hexanediol sebacate, poly-1, 4-butanediol adipate, poly-1, 4-butanediol sebacate, trimethylolpropane, trimethylolethane, pentaerythritol, and glycerin.

Examples of the polyisocyanate compound include hexamethylene diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate, an adduct of tolylene diisocyanate and trimethylolpropane, and an adduct of hexamethylene diisocyanate and trimethylolethane.

The polyurethane resin is not particularly limited, and an aqueous polyurethane resin can be suitably used in view of a problem of solvent remaining in the film and less environmental pollution. The aqueous urethane resin may be an ionomer type self-emulsifying urethane resin. Examples of the water-dispersed polyurethane resin include those obtained by neutralizing a terminal carboxyl group with a cation such as amine, ammonia or sodium, or with an anion such as carboxylic acid or halogen.

A polyurethane-urea resin (melamine-urea resin) is a compound in which a polyhydroxy compound, a polyisocyanate, and a polyamine or an aminoalcohol are appropriately reacted to have urea groups in the compound.

The polyol or polyisocyanate compound used in the polyurethane-urea resin may be the same as that used in the polyurethane resin.

Examples of the polyamine include low molecular weight diamines such as ethylenediamine, 1, 2-propylenediamine, 1, 6-hexamethylenediamine, hydrazine, 1, 2-diaminoethane, 1, 2-diaminopropane, 1, 3-diaminopentane, 1, 6-diaminohexane, diaminotoluene, bis (4-aminophenyl) methane, bis (4-amino-3-chlorophenyl) methane, bis (aminomethyl) benzene, bis (2-amino-2-propyl) benzene, 1-amino-3-aminomethyl-3, 5, 5-trimethylcyclohexane, bis (4-aminocyclohexyl) methane, diaminocyclohexane and bis (aminomethyl) cyclohexane, and low molecular weight diamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and the like, Low molecular weight amines having 3 or more amino groups such as 2, 2' -diaminodiethylamine, and the like.

Examples of the aminoalcohol include compounds having at least 1 amino group and at least 1 hydroxyl group such as 2-hydroxyethylhydrazine, N- (2-hydroxyethyl) -1, 2-diaminoethane, hydroxyethyldiethylenetriamine, and 3-aminopropanediol. The melamine-urea resin is also not particularly limited in its form, as is the case with the polyurethane resin, and an aqueous polyurethane-urea resin can be suitably used in view of a problem of a residual solvent in a film and less environmental pollution.

In order to improve the adhesion to the polyamide resin layer and the solvent resistance, it is preferable to use a curing agent in combination with the polyurethane resin or the polyurethane-urea resin. Examples of the curing agent include isocyanate compounds, melamine compounds, epoxy compounds,Oxazoline compounds, carbodiimide compounds, aziridine compounds, and the like. These compounds may be used alone or in combination without impairing the pot life and performance, but melamine compounds are suitably used from the viewpoint of curability and pot life. Among them, methylolated melamine is suitably used, and in order to control reactivity and impart storage stability, a melamine compound obtained by alkoxylating a methylol group is preferably used.

The step and the order of providing the easy adhesion layer are not particularly limited. There are an in-line coating method in which an unstretched polyamide resin sheet, which has not been oriented in a film forming step, is subjected to an easy-adhesion coating treatment and then stretched and heat-set, and an off-line coating method in which a polyamide resin layer, which has been stretched and heat-set, is coated. Among them, the on-line coating method is preferable in terms of production efficiency and quality.

The coating method is not particularly limited, and the same method as the method for forming the barrier coating layer may be used.

In order to impart functionality to the biaxially stretched polyamide resin film of the present invention, for example, antistatic treatment for controlling generation of static electricity may be performed, and various functional coating liquids other than the above-described barrier coating liquid may be applied.

The thickness of the biaxially stretched polyamide resin film of the present invention is not particularly limited, and is preferably in the range of 10 to 30 μm when used for packaging.

The obtained biaxially stretched polyamide resin film may be subjected to physicochemical treatments such as corona discharge treatment, plating treatment, cleaning treatment, and dyeing treatment as required.