Biaxially oriented polyamide film

Abstract

[Problem] To provide a biaxially stretched polyamide film that has excellent resistance to pinholes caused by bending and pinholes caused by repeated contact, excellent resistance to punctures, and furthermore, can suppress the occurrence of foreign substances during film formation. [Solution] A biaxially stretched polyamide film in which a functional layer (layer B) is laminated on at least one side of a substrate layer (layer A), wherein the substrate layer (layer A) comprises at least (a) 70 to 99 mass% of polyamide 6 resin and (b) 1 to 20 mass% of an aliphatic or aromatic aliphatic polyester resin, and the functional layer (layer B) comprises at least 70 mass% of polyamide 6 resin.

Description

Technology Field

[0001] The present invention relates to a biaxially stretched polyamide film having excellent impact resistance, bending pinhole resistance, and friction pinhole resistance. The biaxially stretched polyamide film of the present invention is suitably used as a food packaging film, etc. Background Technology

[0002] Conventionally, biaxially stretched films containing aliphatic polyamides, such as polyamide 6, have excellent impact resistance and bending pinhole resistance, and are widely used as various packaging material films.

[0003] In addition, for liquid filling packaging such as soups and seasonings, a biaxially stretched polyamide film is used in which various elastomers (rubber components) are mixed with aliphatic polyamide to further improve flexural pinhole resistance and impact resistance, and the film is made more flexible to improve flexural pinhole resistance.

[0004] A film in which a polyamide-based elastomer is mixed with an aliphatic polyamide is known as a means to improve the above-mentioned bending pinhole resistance (see, for example, Patent Document 1). This film has good bending pinhole resistance and impact resistance under low-temperature environments, and it is difficult for pinholes to occur due to bending fatigue even under low-temperature environments. However, in the case of a film in which a polyamide-based elastomer is mixed with an aliphatic polyamide, the polyamide-based elastomer added during film manufacturing undergoes thermal degradation, so it is easy to generate a degraded material called a lump at the lip exit of the die. The degraded material falls off on its own, causing defective products and reducing production efficiency during continuous film production.

[0005] Pinholes can occur not only due to bending but also due to friction (scratching). The methods for improving pinholes caused by bending and those caused by friction are often contradictory. For example, increasing the flexibility of a film makes it less likely for bending pinholes to occur, but the more flexible it becomes, the more likely it is for friction pinholes to form. In response to this, a packaging laminate has been proposed that improves the occurrence of pinholes caused by bending or friction by providing a surface coating agent on the outer surface of a biaxially stretched polyamide film (see, for example, Patent Document 2). However, this method has little effect in preventing friction pinholes. In addition, a coating process is required.

[0006] Furthermore, for example, Patent Documents 3 and 4 disclose a stretched film comprising a polyamide resin composition containing 1 to 10 mass% of a polyester-based thermoplastic elastomer. According to this technology, the flexural strength is excellent even in low-temperature environments, but there is still room for improvement regarding the problem that, even in these technologies, a deteriorated product called a lump is likely to be formed at the lip exit of the die because the elastomer component with low heat resistance is present in the surface layer. Prior art literature

[0007] Japanese Patent Publication No. Hei 11-254615 Japanese Patent Publication No. 2001-205761 International Publication No. 2019 / 131752 Japanese Patent Publication No. 2019-147964 Japanese Patent Publication No. Hei 10-29264 The problem to be solved

[0008] The present invention was conceived in consideration of the problems of the prior art. The objective of the present invention is to provide a biaxially stretched polyamide film that has excellent resistance to pinholes caused by bending and pinholes caused by repeated contact, excellent resistance to punctures, and furthermore, can suppress the occurrence of foreign substances during film formation. In addition to the above, the invention provides a polyamide film with excellent water-resistant adhesive strength with a sealant film and further suppresses the occurrence of foreign substances during film formation, or a biaxially stretched polyamide film with excellent gas barrier properties. means of solving the problem

[0009] The present invention includes the following configurations.

[0010] [1] A biaxially stretched polyamide film having a functional layer (layer B) laminated on at least one side of a substrate layer (layer A), wherein the substrate layer (layer A) comprises at least (a) 70 to 99 mass% of polyamide 6 resin and (b) 1 to 20 mass% of an aliphatic or aromatic aliphatic polyester resin, and the functional layer (layer B) comprises at least 70 mass% of polyamide 6 resin.

[0011] [2] The biaxially stretched polyamide film described in [1], characterized in that the above (b) aliphatic or aromatic aliphatic polyester resin is at least one polyester resin selected from the group consisting of polybutylene succinate, polybutylene succinate adipate and polybutylene adipate terephthalate.

[0012] [3] A biaxially stretched polyamide film as described in [1] or [2], characterized in that the above-described layer (layer A) contains a polyamide resin in which at least part of the raw material is derived from biomass.

[0013] [4] A biaxially stretched polyamide film as described in [3], characterized in that at least one polyamide resin selected from the group consisting of polyamide 11, polyamide 410, polyamide 610 and polyamide 1010, at least one of which is a polyamide resin in which at least part of the raw material is derived from biomass.

[0014] [5] A biaxially stretched polyamide film as described in any one of [1] to [4], characterized in that the biaxially stretched polyamide film satisfies (a) to (c) below.

[0015] (a) The number of flexural fatigue pinholes is 5 or fewer when performing 1,000 flexural tests using a Gelbo Flex Tester at a temperature of 1°C.

[0016] (b) Distance to pinhole occurrence in the friction-resistant pinhole test is 2,900 cm or more

[0017] (c) The puncture strength of the film is 0.67 N / ㎛ or higher

[0018] [6] A biaxially stretched polyamide film having a coating layer on at least one side of the biaxially stretched polyamide film described in any one of [1] to [5], the coating layer comprising one or more resins selected from the group consisting of polyester resin, polyurethane resin, polyacrylic resin and acrylic graft copolymer polyester resin, with a solid content of 0.01 to 3 g / m².

[0019] [7] A polyamide film having an inorganic thin film layer on at least one side of a biaxially stretched polyamide film described in any one of [1] to [6].

[0020] [8] A laminated film in which a sealant film is laminated onto a biaxially stretched polyamide film as described in any one of [1] to [7].

[0021] [9] Packaging pouch using the laminated film described in [8]. Effects of the invention

[0022] The biaxially stretched polyamide film of the present invention has excellent impact resistance, bending pinhole resistance, and friction pinhole resistance by arranging a layer blended with a specific polyester resin, with polyamide 6 resin as the main component, in the inner layer of the film.

[0023] In addition, since the elastomer component does not degrade inside the die during the film forming process, the adhesion of degraded materials to the inner surface of the die or the adhesion of lumps to the die lip exit can be suppressed over a long period of time. Non-uniformity in film thickness caused by the adhesion of degraded materials to the inner surface of the die or the die lip exit can be suppressed. Furthermore, since the number of times production is stopped to clean the die lip can be reduced, the biaxially stretched polyamide film of the present invention enables continuous production over a long period of time. Brief explanation of the drawing

[0024] Figure 1 is a schematic diagram of a friction-resistant pinhole evaluation device. Specific details for implementing the invention

[0025] Hereinafter, the biaxially stretched polyamide film of the present invention will be described in detail.

[0026] The biaxially stretched polyamide film of the present invention is a biaxially stretched polyamide film in which a functional layer (B) is laminated on at least one side of layer A (substrate layer). Details of each layer will be described below.

[0027] [Floor A (Recording Floor)]

[0028] The substrate layer (layer A) comprises a resin composition comprising at least (a) 70 to 99 mass% of polyamide 6 resin and (b) 1 to 20 mass% of an aliphatic or aromatic aliphatic polyester resin.

[0029] A biaxially stretched polyamide film is obtained by including 70 mass% or more of polyamide 6 resin in the substrate layer (Layer A), thereby having mechanical strength such as excellent impact strength and gas barrier properties such as oxygen. The polyamide 6 used in the substrate layer (Layer A) is typically manufactured by ring-opening polymerization of ε-caprolactam. The polyamide 6 obtained by ring-opening polymerization is typically melt-extruded from an extruder after removing the lactam monomer with hot water and drying.

[0030] The relative viscosity of polyamide 6 is preferably 1.8 to 4.5, and more preferably 2.6 to 3.2. If the relative viscosity is less than 1.8, the impact strength of the film is insufficient. If it is greater than 4.5, the load on the extruder increases, making it difficult to obtain an unoriented film before stretching.

[0031] A biaxially stretched polyamide film with excellent flexural pinhole resistance is obtained by including 1 to 20 mass% of an aliphatic or aromatic aliphatic polyester resin in the substrate layer (Layer A). It is preferable that the aliphatic or aromatic aliphatic polyester resin included in the substrate layer (Layer A) has a glass transition temperature (Tg) of -30°C or lower. By using a polyester copolymer having a glass transition temperature of -30°C or lower, excellent pinhole resistance can be exhibited even under a freezing environment. Among these, polybutylene succinate and polybutylene succinate adipate are preferred as aliphatic polyester resins, and polybutylene adipate terephthalate is preferred as an aromatic aliphatic polyester resin in that it has flexible properties.

[0032] The lower limit of the aliphatic or aromatic aliphatic polyester resin included in the substrate layer (Layer A) is preferably 1 mass%, more preferably 2 mass%, and most preferably 3 mass%. If the amount of the aliphatic or aromatic aliphatic polyester resin added to the substrate layer (Layer A) is less than 1 mass%, the effect of improving bending resistance and pinhole resistance is not obtained. The upper limit of the aliphatic or aromatic aliphatic polyester resin included in the substrate layer (Layer A) is preferably 20 mass%, and more preferably 15 mass%. If the amount of the aliphatic or aromatic aliphatic polyester resin added to the substrate layer (Layer A) exceeds 20 mass%, the film becomes excessively flexible, which not only lowers puncture strength and impact strength but also makes the film prone to stretching, making it prone to pitch misalignment during processing such as printing.

[0033] The substrate layer (Layer A) can further improve flexural pinhole resistance by further including a specific polyamide resin containing raw materials derived from biomass. The upper limit of the content of the polyamide resin, of which at least a portion of the raw materials included in the substrate layer (Layer A) is preferably 30 mass%, and more preferably 20 mass%. If the content of the polyamide resin, of which at least a portion of the raw materials is derived from biomass, exceeds 30 mass%, the molten film becomes unstable when casting the molten film, making it difficult to obtain a homogeneous unoriented film.

[0034] As polyamide resins for which at least part of the raw material is derived from biomass and which can be used in the substrate layer (layer A), polyamide 11, polyamide 610, polyamide 1010, and polyamide 410 are preferred in terms of availability.

[0035] The above polyamide 11 is a polyamide resin having a structure in which monomers having 11 carbon atoms are bonded through amide bonds. Typically, polyamide 11 is obtained using aminoundecanoic acid or undecanolactam as monomers. In particular, aminoundecanoic acid is preferred from the perspective of environmental protection (especially from the perspective of carbon neutrality) because it is a monomer obtained from castor oil. It is preferable that constituent units derived from these monomers having 11 carbon atoms constitute 50% or more of the total constituent units in polyamide 11, and may be 100%. The above polyamide 11 is typically prepared by ring-opening polymerization of the aforementioned undecanolactam. The polyamide 11 obtained by ring-opening polymerization is typically melt-extruded from an extruder after removing the lactam monomer with hot water and drying. The relative viscosity of polyamide 11 is preferably 1.8 to 4.5, and more preferably 2.4 to 3.2. If the relative viscosity is less than 1.8, the impact strength of the film is insufficient. If it is greater than 4.5, the load on the extruder increases, making it difficult to obtain an unoriented film before stretching.

[0036] The above polyamide 610 is a polyamide resin having a structure in which a monomer having 6 carbon atoms and a monomer having 10 carbon atoms are bonded through an amide bond. Typically, polyamide 610 is obtained by copolymerizing a diamine and a dicarboxylic acid, and hexamethylenediamine and sebacic acid are used, respectively. Among these, sebacic acid is preferred from the perspective of environmental protection (especially from the perspective of carbon neutrality) because it is a monomer obtained from castor oil. It is preferable that the total of the constituent units derived from the monomer having 6 carbon atoms and the constituent units derived from the monomer having 10 carbon atoms within the polyamide 610 is 50% or more of the total constituent units, and may be 100%.

[0037] The above polyamide 1010 is a polyamide resin having a structure in which a diamine having 10 carbon atoms and a dicarboxylic acid having 10 carbon atoms are copolymerized. Typically, 1,10-decanediamine (decamethylenediamine) and sebacic acid are used in polyamide 1010. Decamethylenediamine and sebacic acid are monomers obtained from castor oil, so they are desirable from the perspective of environmental protection (especially from the perspective of carbon neutrality). It is preferable that the total of the constituent units derived from these diamines having 10 carbon atoms and the constituent units derived from the dicarboxylic acid having 10 carbon atoms within polyamide 1010 is 50% or more of the total constituent units, and may be 100%.

[0038] The above polyamide 410 is a polyamide resin having a structure in which a monomer having 4 carbon atoms and a diamine having 10 carbon atoms are copolymerized. Typically, sebacic acid and tetramethylenediamine are used for polyamide 410. As for sebacic acid, it is preferable to use castor oil derived from vegetable oil as a raw material for environmental reasons. For the sebacic acid used here, it is preferable to obtain it from castor oil from the perspective of environmental protection (particularly from the perspective of carbon neutrality).

[0039] The substrate layer (Layer A) may contain various additives as needed, such as other thermoplastic resins, lubricants, heat stabilizers, antioxidants, antistatic agents or anti-fog agents, ultraviolet absorbers, dyes, and pigments.

[0040] The substrate layer (layer A) may include a thermoplastic resin other than polyamide 6 resin to the extent that it does not impair the purpose of the present invention. Examples include polyamide-based resins such as polyamide 12 resin, polyamide 66 resin, polyamide 6·12 copolymer resin, polyamide 6·66 copolymer resin, polyamide MXD6 resin, polyamide MXD10 resin, and polyamide 11·6T copolymer resin.

[0041] If necessary, thermoplastic resins other than polyamide-based ones may be included, for example, polyester-based polymers such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, and polyolefin-based polymers such as polyethylene and polypropylene.

[0042] [Functional Layer (Layer B)]

[0043] The functional layer (layer B) is characterized by containing 70 to 100 mass% or more of polyamide 6 resin.

[0044] The functional layer (layer B) contains 70 mass% or more of polyamide 6 resin, thereby obtaining a biaxially stretched polyamide film having mechanical strength such as excellent impact strength or gas barrier properties such as oxygen. As for the polyamide 6 resin, the same polyamide 6 resin used in the substrate layer (layer A) can be used.

[0045] The functional layer (B layer) may contain various additives, such as other thermoplastic resins, lubricants, heat stabilizers, antioxidants, antistatic agents or anti-fog agents, UV absorbers, dyes, and pigments, depending on the function of having them on the surface of the functional layer (B layer). When the functional layer (B layer) is used on the outer side of a packaging bag, friction pinhole resistance is required; therefore, it is not desirable to contain flexible resins such as polyamide-based elastomers or polyolefin-based elastomers, or materials that generate a large amount of voids.

[0046] The functional layer (layer B) may include a thermoplastic resin in addition to the polyamide 6 resin, to the extent that the purpose of the present invention is not impaired. Examples include polyamide-based resins such as polyamide MXD6 resin, polyamide 11 resin, polyamide 12 resin, polyamide 66 resin, polyamide 6·12 copolymer resin, and polyamide 6·66 copolymer resin. If necessary, thermoplastic resins other than polyamide-based resins may be included, such as polyester-based polymers such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, and polyolefin-based polymers such as polyethylene and polypropylene.

[0047] In the functional layer (layer B), it is desirable to include fine particles or organic lubricants as a lubricant to improve the film's slipperiness. By improving the slipperiness, the handling of the film is improved, and damage to the packaging bag due to friction is reduced.

[0048] As the above-mentioned fine particles, inorganic fine particles such as silica, kaolin, and zeolite, and polymeric organic fine particles such as acrylic and polystyrene-based ones can be appropriately selected and used. In addition, it is preferable to use silica fine particles in terms of transparency and slipperiness.

[0049] The preferred average particle size of the above fine particles is 0.5 to 5.0 μm, and more preferably 1.0 to 3.0 μm. If the average particle size is less than 0.5 μm, a large amount of additive is required to obtain good slipperiness. On the other hand, if it exceeds 5.0 μm, the surface roughness of the film tends to become excessively large, and the appearance tends to deteriorate.

[0050] When using the above silica microparticles, the pore volume of the silica is preferably in the range of 0.5 to 2.0 ml / g, and more preferably in the range of 0.8 to 1.6 ml / g. If the pore volume is less than 0.5 ml / g, voids are prone to occur, and the transparency of the film deteriorates. If the pore volume exceeds 2.0 ml / g, it tends to be difficult to form protrusions on the surface caused by the microparticles.

[0051] As the above organic lubricant, fatty acid amide and / or fatty acid bisamide may be included. Examples of fatty acid amide and / or fatty acid bisamide include erucicamide, stearamide, ethylenebisstearamide, ethylenebisbehenamide, ethylenebisoleamide, etc. The content of fatty acid amide and / or fatty acid bisamide added to the functional layer (layer B) is preferably 0.01 to 0.40 mass%, and more preferably 0.05 to 0.30 mass%. If the content of fatty acid amide and / or fatty acid bisamide is below the above range, the slipperiness tends to deteriorate. On the other hand, if it exceeds the above range, the wettability tends to deteriorate.

[0052] In the functional layer (layer B), a polyamide-based resin other than polyamide 6, such as polyamide MXD6 resin, polyamide 11, polyamide 12 resin, polyamide 66 resin, polyamide 6·12 copolymer resin, polyamide 6·66 copolymer resin, etc., may be added for the purpose of improving the slipperiness of the film. Polyamide MXD6 resin is particularly preferred, and it is preferable to add 1 to 10 mass%. If the amount is less than 1 mass%, the effect of improving the slipperiness of the film is small. If the amount is greater than 10 mass%, the effect of improving the slipperiness of the film becomes saturated.

[0053] Polyamide MXD6 resin is prepared by the polycondensation of methaxylylenediamine and adipic acid. The relative viscosity of polyamide MXD6 is preferably 1.8 to 4.5, and more preferably 2.0 to 3.2. If the relative viscosity is less than 1.8 or greater than 4.5, it may be difficult to mix with the polyamide resin in an extruder.

[0054] In addition, a polyamide-based resin other than polyamide 6 may be added to the functional layer (layer B) to improve adhesion. In this case, copolymerized polyamide resins such as polyamide 6·12 copolymer resin and polyamide 6·66 copolymer resin are preferred.

[0055] As a method for adding auxiliary materials or additives, such as lubricants and antioxidants, to the substrate layer (Layer A) and functional layer (Layer B) of the biaxially stretched polyamide film of the present invention, they may be added during resin polymerization or melt extrusion in an extruder. Alternatively, a high-concentration masterbatch may be prepared and added to the polyamide resin during film production. This can be done by such known methods.

[0056] The thickness of the biaxially stretched polyamide film of the present invention is not particularly limited, but when used as a packaging material, it is typically 100 μm or less, and generally, a thickness of 5 to 50 μm is used, and in particular, a thickness of 8 to 30 μm is used.

[0057] In the thickness configuration of the substrate layer (Layer A) and the functional layer (Layer B) of the biaxially stretched polyamide film of the present invention, if the thickness of the functional layer (Layer B) occupies most of the total thickness of the film, the flexural pinhole resistance is reduced. Therefore, in the present invention, it is preferable to set the thickness of the substrate layer (Layer A) to 50 to 93%, particularly 60 to 93%, of the total thickness of the substrate layer (Layer A) and the functional layer (Layer B).

[0058] In the case where a polyamide resin in which at least part of the raw material is derived from biomass is used in the biaxially stretched polyamide film of the present invention, it is preferable that the content of carbon derived from biomass, as measured by radiocarbon (C14), is 1 to 15% of the total carbon in the polyamide film.

[0059] The biaxially stretched polyamide film of the present invention has five or fewer pinhole defects when a twisting bending test using a Gelbo Flex Tester according to the measurement method described in the example is performed 1,000 times at a temperature of 1°C. More preferably, it has three or fewer. The fewer the number of pinhole defects after the bending test, the better the bending pinhole resistance. If the number of pinholes is five or fewer, a packaging bag is obtained in which pinholes are unlikely to occur even when a load is applied to the packaging bag during transportation, etc.

[0060] In addition, the biaxially stretched polyamide film of the present invention has a distance of 2,900 cm or more to the occurrence of a pinhole in a friction pinhole test by the measurement method described in the examples. More preferably, it is 3,100 cm or more, and even more preferably, 3,300 cm or more. The longer the distance to the occurrence of a pinhole, the better the friction pinhole resistance. If the distance to the occurrence of a pinhole is 2,900 cm or more, a packaging bag is obtained in which it is difficult for a pinhole to occur even if the packaging bag rubs against a corrugated cardboard box, etc., during transportation, etc.

[0061] The biaxially stretched polyamide film of the present invention is characterized by having excellent properties of both flexural pinhole resistance and frictional pinhole resistance. The biaxially stretched polyamide film of the present invention having these properties is very useful as a packaging film because it is difficult for pinholes to occur during transportation.

[0062] The film of the present invention preferably has a thermal shrinkage rate at 160°C for 10 minutes in the range of 0.6 to 3.0% in both the flow direction (hereinafter abbreviated as MD direction) and the width direction (hereinafter abbreviated as TD direction), and more preferably 0.6 to 2.5%. If the thermal shrinkage rate exceeds 3.0%, curling or shrinkage may occur when heat is applied in subsequent processes such as lamination or printing. In addition, the laminate strength with the sealant film may be weakened. Although it is possible to reduce the thermal shrinkage rate to less than 0.6%, it may become mechanically soft. In addition, productivity may deteriorate.

[0063] Since excellent impact resistance is a characteristic feature of the biaxially stretched polyamide film, the impact strength of the biaxially stretched polyamide film of the present invention is preferably 0.7 J / 15 μm or higher. A more preferred impact strength is 0.9 J / 15 μm or higher.

[0064] It is preferable that the puncture strength of the film of the present invention be 0.67 N / ㎛ or higher. By making the puncture strength 0.67 N / ㎛ or higher, even when filled with solid contents, it is possible to prevent the contents from being inserted into the pocket and causing a hole in the pocket, or the pocket from being punctured by external factors during transport.

[0065] It is preferable that the haze value of the biaxially stretched polyamide film of the present invention be 10% or less. More preferably, it is 7% or less, and even more preferably 5% or less. Since a low haze value results in good transparency and gloss, when used in packaging bags, it enables attractive printing, thereby increasing product value. Since adding fine particles to improve the slipperiness of the film increases the haze value, it is better to add the fine particles only to the functional layer (layer B) of the surface layer to keep the haze value low.

[0066] The biaxially stretched polyamide film of the present invention preferably has a laminate strength of 4.0 N / 15 mm or more after being bonded with the polyethylene-based sealant film described in the examples. The biaxially stretched polyamide film is typically laminated with a sealant film and then processed into a packaging bag. If the laminate strength is 4.0 N / 15 mm or more, when a packaging bag is manufactured using the biaxially stretched polyamide film of the present invention in various laminate configurations, sufficient strength is obtained in the seal portion, and a packaging bag that is resistant to tearing is obtained. To achieve a laminate strength of 4.0 N / 15 mm or more, the biaxially stretched polyamide film of the present invention may undergo corona treatment, coating treatment, flame treatment, etc.

[0067] [Method for producing biaxially stretched polyamide film]

[0068] The biaxially stretched polyamide film of the present invention can be manufactured by known manufacturing methods. Examples include sequential biaxial stretching and simultaneous biaxial stretching. Sequential biaxial stretching is preferred because it increases the film formation speed, making it advantageous in terms of manufacturing costs.

[0069] A method for producing a biaxially stretched polyamide film according to the present invention will be described.

[0070] First, the raw resin is melt-extruded using an extruder, extruded into a film from a T-die, cast onto a cooling roll, and cooled to obtain an unoriented film. In the present invention, to obtain an unoriented film in which a substrate layer (Layer A) and a functional layer (Layer B) are laminated, a co-extrusion method using a feed block or a multi-manifold is preferred. In addition to the co-extrusion method, a dry lamination method, an extrusion lamination method, etc., may also be selected. When laminating by the co-extrusion method, it is preferable that the polyamide resin composition used for the substrate layer (Layer A) and the functional layer (Layer B) has a small difference in melt viscosity between the substrate layer (Layer A) and the functional layer (Layer B).

[0071] The melting temperature of the resin is preferably 220 to 350°C. If the temperature is lower than this range, unmelted material may occur, resulting in appearance defects such as defects; if it exceeds this range, degradation of the resin may be observed, leading to a decrease in molecular weight and a decrease in appearance. The die temperature is preferably 250 to 350°C. The cooling roll temperature is preferably -30 to 80°C, and more preferably 0 to 50°C. To obtain an unoriented film by casting the film-like melt extruded from the T-die onto a rotary cooling drum and cooling it, methods such as using an air knife or applying an electrostatic charge may be preferably applied. The latter is particularly preferred. Additionally, it is preferable to cool the opposite side of the cooling roll of the cast unoriented film. For example, it is preferable to use a combination of methods such as contacting the cooling liquid in a tank with the opposite side of the cooling roll of the unoriented film, applying a liquid vaporized through a spray nozzle, or cooling by spraying a high-speed fluid. The unoriented film obtained in this way is stretched in a biaxial direction to obtain the biaxially stretched polyamide film of the present invention.

[0072] As for the stretching method, either simultaneous biaxial stretching or sequential biaxial stretching may be used. Sequential biaxial stretching is preferable because it increases the film formation speed, making it advantageous in terms of manufacturing costs. In either case, multi-stage stretching, such as single-stage stretching or two-stage stretching, may be used as the stretching method in the MD direction. As described below, multi-stage stretching in the MD direction, such as two-stage stretching, rather than single-stage stretching, is preferable in terms of physical properties and the uniformity (isotropy) of physical properties in the MD and TD directions. For the stretching in the MD direction in the sequential biaxial stretching method, roll stretching is preferred.

[0073] The lower limit of the stretching temperature in the MD direction is preferably 50°C, more preferably 55°C, and even more preferably 60°C. If the temperature is below 50°C, the resin does not soften, and stretching may become difficult. The upper limit of the stretching temperature in the MD direction is preferably 120°C, more preferably 115°C, and even more preferably 110°C. If the temperature exceeds 120°C, the resin becomes excessively flexible, and stable stretching may become impossible.

[0074] The lower limit of the elongation ratio in the MD direction (in the case of multi-stage elongation, the total elongation ratio obtained by multiplying each ratio) is preferably 2.2 times, more preferably 2.5 times, and even more preferably 2.8 times. If it is less than 2.2 times, in addition to the thickness precision in the MD direction decreasing, the degree of crystallization may become excessively low, resulting in a decrease in impact strength. The upper limit of the elongation ratio in the MD direction is preferably 5.0 times, more preferably 4.5 times, and most preferably 4.0 times. If it exceeds 5.0 times, subsequent elongation may become difficult.

[0075] In addition, when performing multi-stage stretching in the MD direction, stretching as described above is possible in each stretching step, but regarding the ratio, it is necessary to adjust the stretching ratio so that the product of the overall stretching ratios in the MD direction is 5.0 or less. For example, in the case of two-stage stretching, it is preferable that the first stage stretching be 1.5 to 2.1 times and the second stage stretching be 1.5 to 1.8 times.

[0076] A film stretched in the MD direction is stretched in the TD direction using a tenter, heat-set, and subjected to a relaxation treatment (also called a relaxation treatment). The lower limit of the stretching temperature in the TD direction is preferably 50°C, more preferably 55°C, and even more preferably 60°C. If the temperature is below 50°C, the resin does not soften, and stretching may become difficult. The upper limit of the stretching temperature in the TD direction is preferably 190°C, more preferably 185°C, and even more preferably 180°C. If the temperature exceeds 190°C, crystallization may occur, and stretching may become difficult.

[0077] The lower limit of the elongation ratio in the TD direction (in the case of multi-stage elongation, the total elongation ratio obtained by multiplying each ratio) is preferably 2.8, more preferably 3.2, even more preferably 3.5, and particularly preferably 3.8. If it is less than 2.8, in addition to the thickness precision in the TD direction decreasing, the degree of crystallization may become excessively low, resulting in a decrease in impact strength. The upper limit of the elongation ratio in the TD direction is preferably 5.5, more preferably 5.0, even more preferably 4.7, particularly preferably 4.5, and most preferably 4.3. If it exceeds 5.5, productivity may decrease significantly.

[0078] The selection of the heat-setting temperature is an important factor in the present invention; as the heat-setting temperature is increased, the crystallization and orientation relaxation of the film proceed, the impact strength is improved, and the thermal shrinkage rate can be reduced. On the other hand, if the heat-setting temperature is low, the crystallization and orientation relaxation are insufficient, and the thermal shrinkage rate cannot be sufficiently reduced. Furthermore, if the heat-setting temperature becomes excessively high, the degradation of the resin proceeds, and the toughness of the film, such as impact strength, is rapidly lost.

[0079] The lower limit of the heat-setting temperature is preferably 210°C, and more preferably 212°C. If the heat-setting temperature is too low, the thermal shrinkage rate becomes excessively high, which degrades the appearance after lamination and tends to reduce the laminate strength. The upper limit of the heat-setting temperature is preferably 220°C, and more preferably 218°C. If the heat-setting temperature is too high, the impact strength tends to decrease. The heat-setting time is preferably 0.5 to 20 seconds. Furthermore, it is 1 to 15 seconds. The heat-setting time can be set to an appropriate time by considering the heat-setting temperature or the wind speed in the heat-setting zone. If the heat-setting conditions are too weak, crystallization and orientation relaxation become insufficient, leading to the aforementioned problems. If the heat-setting conditions are too strong, the film toughness decreases.

[0080] Performing a relaxation treatment after heat-setting treatment is effective for controlling the thermal shrinkage rate. The relaxation treatment temperature can be selected from the range from the heat-setting treatment temperature to the Tg of the resin, but preferably, it is preferably between the heat-setting treatment temperature - 10°C and Tg + 10°C. If the relaxation temperature is excessively high, the shrinkage rate becomes excessively fast, which is undesirable as it causes deformation. Conversely, if the relaxation temperature is excessively low, the relaxation treatment does not occur, and the material merely loosens without reducing the thermal shrinkage rate, resulting in poor dimensional stability. The lower limit of the relaxation rate for the relaxation treatment is preferably 0.5%, and more preferably 1%. If it is less than 0.5%, the thermal shrinkage rate may not be sufficiently reduced. The upper limit of the relaxation rate is preferably 20%, more preferably 15%, and even more preferably 10%. If it exceeds 20%, loosening occurs within the tenter, which may make production difficult.

[0081] In addition, the biaxially stretched polyamide film of the present invention may be subjected to heat treatment or humidity control treatment to improve dimensional stability depending on the application. Furthermore, to improve the adhesion of the film surface, corona treatment, coating treatment, flame treatment, etc., may be performed, or printing processing, deposition processing of metals or inorganic oxides, etc., may be performed.

[0082] [Coating layer (C)]

[0083] Another embodiment of the biaxially stretched polyamide film of the present invention is a film having a coating layer (C) on at least one side of a biaxially stretched polyester film to impart ease of adhesion to the film. The coating layer (C) may comprise one or more resins selected from the group consisting of polyester resin, polyurethane resin, polyacrylic resin, and acrylic graft copolymer polyester resin, with a solid content of 0.01 to 3 g / m². It is preferable that the coating layer (C) be prepared by applying and drying a coating solution before winding the film onto a mill roll in the film manufacturing process. The coating solution may be applied to an unoriented film, a uniaxially stretched film, and / or a biaxially stretched film. When the film is manufactured by a sequential biaxial stretching method, the coating solution is typically applied to and dried on a uniaxially stretched film. When manufacturing a film by simultaneous biaxial stretching, typically, a coating solution is applied to the non-axially stretched film and dried.

[0084] In the present invention, the coating layer (C) is prepared by applying and drying a coating solution before winding the film onto a mill roll during the film manufacturing process. Therefore, to ensure safety and hygiene during manufacturing, it is preferable to use a water-based dispersion of resin as the coating solution.

[0085] Polyester resin used in coating layer (C)

[0086] When a polyester resin is used as the coating layer (C), a copolymerized polyester resin may be selected as the polyester resin. A copolymerized polyester resin is a polycondensation product of a dicarboxylic acid component, a diol component, and other ester-forming components. As for the dicarboxylic acid component contained as a constituent in the copolymerized polyester resin, examples include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenylenedicarboxylic acid, and 5-sodium sulfoisophthalic acid; aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, and sebacic acid; and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid and 1,2-cyclohexanedicarboxylic acid.

[0087] Examples include unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and tetrahydrophthalic acid.

[0088] In addition to the above dicarboxylic acid component, salts of 5-sulfoisophthalic acid, sulfoterephthalic acid, 4-sulfoisophthalic acid, 4-sulfonaphthalene-2,6-dicarboxylic acid, and 5(4-sulfophenoxy)isophthalic acid may be used to impart water dispersibility. Among these, it is preferable to use 5-sodium sulfoisophthalic acid in a range of 1 to 10 mol%.

[0089] Examples of diol components contained in copolymerized polyester resins include aliphatic diols such as ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, and polyethylene glycol; alicyclic diols such as 1,4-cyclohexanedimethanol; aromatic diols such as 4,4'-bis(hydroxyethyl)bisphenol A; and furthermore, bis(polyoxyethylene glycol)bisphenol ether.

[0090] Polyurethane resin used in the coating layer

[0091] When a polyurethane resin is used as the coating layer (C), the polyurethane resin may be, for example, obtained by reacting an organic polyisocyanate with a polyol having two or more active hydrogens.

[0092] Examples of polyols include polyols having unsaturated double bonds, such as saturated polyester polyols; polyether polyols (e.g., polyethylene glycol, polytetramethylene glycol, etc.); amino alcohols (e.g., ethanolamine, diethanolamine, triethanolamine, etc.); unsaturated polyester polyols (e.g., obtained by polycondensing an unsaturated polycarboxylic acid alone or a mixture of it and a saturated polycarboxylic acid, and a mixture of a saturated polyalcohol and an unsaturated polyalcohol), polybutadiene polyols (e.g., 1,2-polybutadiene polyol, 1,4-polybutadiene polyol, etc.), and acrylic polyols (acrylic polyols having hydroxyl groups in their side chains, obtained by copolymerizing various acrylic monomers with acrylic acid monomers having hydroxyl groups).

[0093] Examples of organic polyisocyanates include aromatic polyisocyanates (e.g., diphenylmethane diisocyanate, toluene diisocyanate, etc.), aliphatic polyisocyanates (e.g., hexamethylene diisocyanate, etc.), alicyclic polyisocyanates (e.g., isophorone diisocyanate, etc.), aromatic and aliphatic polyisocyanates (e.g., xylylene diisocyanate), and polyisocyanates obtained by reacting these isocyanates with low molecular weight polyols.

[0094] Polyacrylic resin used in the coating layer

[0095] When a polyacrylic resin is used as the coating layer (C), examples of polyacrylic resins include acrylic polymers obtained by polymerizing acrylic acid or methacrylic acid, or their salts or esters.

[0096] Examples of acrylic acid ester-based and methacrylic acid ester-based monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, and glycidyl methacrylate. Examples of salts of acrylic acid and methacrylic acid include sodium acrylate, sodium methacrylate, potassium acrylate, potassium methacrylate, ammonium acrylate, and ammonium methacrylate.

[0097] In addition to these essential components, acrylic acid monomers such as acrylamide, methacrylamide, aminoethyl methacrylate, aminomethyl methacrylate, N-methylolacrylamide, and N-methoxymethylacrylamide may be added.

[0098] In addition to the above, monomers such as vinyl chloride, vinyl acetate, styrene, vinyl ether, butadiene, isoprene, and sodium vinylsulfonic acid may also be used as copolymer components in the polyacrylic resin. Furthermore, it is desirable for the acrylic polymer to include hydrophilic components such as acrylate components, methacrylate components, acrylic acid components, acrylamide components, 2-hydroxyethyl acrylic acid components, and N-methylolacrylamide components as copolymer components to enhance the functionality of the coating film. Additionally, it may be a copolymer having functional groups in the molecular side chains. Furthermore, this acrylic polymer may be obtained by using a hard component such as methyl methacrylate or ethyl methacrylate as the main component and copolymerizing a soft component such as an acrylic acid ester as the copolymer component.

[0099] Acrylic graft copolymer polyester resin used in the coating layer

[0100] An acrylic graft copolymer polyester resin may be used as the coating layer (C), and in the present invention, an acrylic graft copolymer polyester aqueous dispersion may be cited as a preferred example. It comprises particles of grafted polyester and water, an aqueous solvent, or an organic solvent, and exhibits a translucent to milky white appearance. This grafted polyester has a main chain containing polyester and a graft portion (side chain) formed by a polymer of radical polymerizable monomers containing radical polymerizable monomers having hydrophilic groups.

[0101] The average particle size of grafted polyester particles in an acrylic graft copolymer polyester aqueous dispersion, measured by laser light scattering, is 500 nm or less, preferably 10 nm to 500 nm, and more preferably 10 nm to 300 nm. If the average particle size exceeds 500 nm, the strength of the coating film after application decreases.

[0102] The content of acrylic graft copolymer polyester particles in the acrylic graft copolymer polyester aqueous dispersion is typically 1 mass% to 50 mass%, preferably 3 mass% to 30 mass%.

[0103] The particles in the acrylic graft copolymer polyester aqueous dispersion that can be used in the present invention may have a core-shell structure in which the polyester main chain is the core in the aqueous dispersion medium.

[0104] The coating film obtained from the above acrylic graft copolymer polyester aqueous dispersion has excellent adhesion to polyamide films. In addition, because it has excellent anti-blocking properties, it can be used without problems even on film substrates with relatively low glass transition points. Furthermore, when formed into a laminate, it also has very good adhesion to adhesives used when laminating printing inks or sealant layers. The resulting laminated film (also called a laminate film) can have significantly improved durability during retort processing or boiling water processing. In addition, if a flexible grafted polyester is used in the copolymer polyester aqueous dispersion, the glass transition temperature of the grafted polyester is 30°C or lower, preferably 10°C or lower, the durability of the laminate is further improved.

[0105] (Polyester main chain of acrylic graft copolymer polyester)

[0106] In the present invention, the polyester that can be used as the main chain of the grafted polyester is suitably a saturated or unsaturated polyester synthesized from at least a dicarboxylic acid component and a diol component, and the resulting polyester may be a single polymer or a mixture of two or more polymers. Furthermore, a polyester that is not dispersed or dissolved in water by itself is preferred. The weight average molecular weight of the polyester that can be used in the present invention is 5,000 to 100,000, preferably 5,000 to 50,000. If the weight average molecular weight is less than 5,000, the physical properties of the coating film, such as the subsequent processability of the dried coating film, are degraded. In addition, if the weight average molecular weight is less than 5,000, the polyester serving as the main chain is prone to water solubilization, so the resulting grafted polyester cannot form the core-shell structure described later. If the weight average molecular weight of the polyester exceeds 100,000, water oxidation becomes difficult. From the perspective of water oxidation, 100,000 or less is desirable. The glass transition point is 30°C or less, preferably 10°C or less.

[0107] The above dicarboxylic acid component is preferably a dicarboxylic acid mixture comprising at least one aromatic dicarboxylic acid, at least one aliphatic and / or alicyclic dicarboxylic acid, and at least one radical polymerizable dicarboxylic acid having an unsaturated double bond.

[0108] As aromatic dicarboxylic acids, terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, etc. may be used. In addition, sodium 5-sulfoisophthalate may also be used as needed.

[0109] As aliphatic dicarboxylic acids, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedionic acid, dimer acid, and their acid anhydrides can be used.

[0110] As cycloaliphatic dicarboxylic acids, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, and their acid anhydrides can be used.

[0111] As radical polymerizable dicarboxylic acids containing unsaturated double bonds, α,β-unsaturated dicarboxylic acids such as fumaric acid, maleic acid, maleic anhydride, itaconic acid, and citraconic acid may be used, and as alicyclic dicarboxylic acids containing unsaturated double bonds, 2,5-norbornene dicarboxylic acid anhydride, tetrahydrophthalic anhydride, etc. Among these, fumaric acid, maleic acid, and 2,5-norbornene dicarboxylic acid (endo-bicyclo-(2,2,1)-5-heptene-2,3-dicarboxylic acid) are preferred.

[0112] The above diol component consists of at least one of an aliphatic glycol having 2 to 10 carbon atoms, alicyclic glycol having 6 to 12 carbon atoms, and an ether-linked glycol.

[0113] As an aliphatic glycol having 2 to 10 carbon atoms, ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol, etc. may be used.

[0114] As a cycloaliphatic glycol having 6 to 12 carbon atoms, 1,4-cyclohexanedimethanol, etc., can be used.

[0115] As ether-linked glycols, diethylene glycol, triethylene glycol, dipropylene glycol, and glycols obtained by adding 1 mole to several moles of ethylene oxide or propylene oxide to two phenolic hydroxyl groups of bisphenols, for example, 2,2-bis(4-hydroxyethoxyphenyl)propane, may be used. Polyethylene glycol, polypropylene glycol, and polytetramethylene glycol may also be used as needed.

[0116] In addition to the above dicarboxylic acid component and diol component, polycarboxylic acids and / or polyols with three or more functionalities can be copolymerized.

[0117] As polycarboxylic acids with three or more functions, (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid, (anhydrous) benzophenone tetracarboxylic acid, trimesic acid, ethylene glycol bis(anhydrotrimellitate), glycerol tris(anhydrotrimellitate), etc. can be used.

[0118] As polyols with three or more functionalities, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, etc. can be used.

[0119] Polycarboxylic acids and / or polyols having three or more functions may be used in a range of 0 to 5 mol%, preferably 0 to 3 mol%, with respect to the total polycarboxylic acid component including the dicarboxylic acid component or the total polyol component including the diol component.

[0120] (Graft portion of acrylic graft copolymer polyester)

[0121] The graft portion of the grafted polyester that can be used in the present invention may be a polymer derived from a monomer mixture comprising at least one radical polymerizable monomer having a hydrophilic group or a group that can be later changed to a hydrophilic group.

[0122] The weight-average molecular weight of the polymer constituting the graft portion is 500 to 50,000, preferably 4,000 to 50,000. If the weight-average molecular weight is less than 500, the grafting rate decreases, so hydrophilicity is not sufficiently imparted to the polyester; furthermore, it is generally difficult to control the weight-average molecular weight of the graft portion to be less than 500. The graft portion forms a hydration layer of the dispersed particles. In order to have a hydration layer of sufficient thickness on the particles and to obtain a stable dispersion, it is preferable that the weight-average molecular weight of the graft portion derived from the radical polymerizable monomer be 500 or more. As described above, the upper limit of the weight-average molecular weight of the graft portion of the radical polymerizable monomer is preferably 50,000 in terms of polymerization in solution polymerization. Control of molecular weight within this range can be achieved by appropriately selecting the amount of polymerization initiator, monomer dropping time, polymerization time, reaction solvent, and monomer composition, and, if necessary, appropriately combining a chain transfer agent or a polymerization inhibitor. The glass transition point is 30°C or lower, preferably 10°C or lower.

[0123] As hydrophilic groups possessed by radical polymerizable monomers, carboxyl groups, hydroxyl groups, sulfonic acid groups, amide groups, quaternary ammonium salts, phosphate groups, etc., may be used. As groups capable of being converted into hydrophilic groups, acid anhydrides, glycidyl, chlor, etc., may be used. The dispersibility of the grafted polyester in water can be controlled by the hydrophilic groups introduced into the polyester by grafting. Among the above hydrophilic groups, carboxyl groups are preferred for controlling the dispersibility of the grafted polyester in water because the amount introduced into the grafted polyester can be accurately determined using acid values ​​known in the relevant art.

[0124] Examples of carboxyl group-containing radical polymerizable monomers include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, etc. Additionally, maleic anhydride, itaconic anhydride, methacrylic anhydride, etc., which readily generate carboxylic acids upon contact with water / amine, may be used. Preferred carboxyl group-containing radical polymerizable monomers are acrylic anhydride, methacrylic anhydride, and maleic anhydride.

[0125] In addition to the above-mentioned radical polymerizable monomer containing a hydrophilic group, it is preferable to copolymerize a radical polymerizable monomer that does not contain at least one hydrophilic group. If only the monomer containing a hydrophilic group is used, grafting onto the polyester main chain does not occur smoothly, making it difficult to obtain a good copolymerized polyester aqueous dispersion. Only by copolymerizing a radical polymerizable monomer that does not contain at least one hydrophilic group can highly efficient grafting be performed.

[0126] As a radical polymerizable monomer that does not contain a hydrophilic group, one or more combinations of monomers having an ethylenically unsaturated bond and also not containing a hydrophilic group as described above are used. Examples of such monomers include acrylic acid esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, and hydroxypropyl acrylate; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, and hydroxylpropyl methacrylate; acrylic acid or methacrylic acid derivatives such as acrylamide, N-methylolacrylamide, and diacetoneacrylamide; and nitriles such as acrylonitrile and methacrylonitrile. Examples include vinyl esters such as vinyl acetate, vinyl propionate, and vinyl benzoate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone; N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride; and aromatic vinyl compounds such as styrene, α-methylstyrene, t-butylstyrene, vinyltoluene, and vinyl naphthalene. These monomers may be used individually or in combination of two or more.

[0127] The ratio of the monomer containing hydrophilic groups to the monomer not containing hydrophilic groups is determined by considering the amount of hydrophilic groups introduced into the grafted polyester, but typically, as a mass ratio (monomer containing hydrophilic groups:monomer not containing hydrophilic groups), it is in the range of 95:5 to 5:95, preferably 90:10 to 10:90, and more preferably 80:20 to 40:60.

[0128] When a carboxyl group-containing monomer is used as the hydrophilic group-containing monomer, the total acid value of the grafted polyester is 600 to 4000 eq. / 10 6 g, preferably 700 to 3000 eq. / 10 6 g, most preferably 800 to 2500 eq. / 10 6 It is g. The acid value is 600 eq. / 10 6 When the value is g or less, it is difficult to obtain a copolymer polyester aqueous dispersion with small particle size when the grafted polyester is dispersed in water, and furthermore, the dispersion stability of the copolymer polyester aqueous dispersion decreases. The acid value is 4000 eq. / 10 6 If g or more, the water resistance of the easy-adhesion layer formed by the copolymer polyester water-based dispersion is reduced.

[0129] The mass ratio of the polyester main chain to the graft portion (polyester:radical polymerizable monomer) in the acrylic graft copolymer polyester is in the range of 40:60 to 95:5, preferably 55:45 to 93:7, and more preferably 60:40 to 90:10.

[0130] If the mass ratio of the polyester main chain is 40 mass% or less, the excellent performance of the matrix polyester described above—namely, high processability, excellent water resistance, and excellent adhesion to various substrates—cannot be fully exhibited, and conversely, the undesirable performance of the acrylic resin—namely, low processability, gloss, and water resistance—is added. If the mass ratio of the polyester is 95 mass% or more, the amount of hydrophilic groups in the graft portion that impart hydrophilicity to the grafted polyester is insufficient, and a good aqueous dispersion cannot be obtained.

[0131] <Crosslinking agent added to the application solution>

[0132] The above coating solution can be used as is to form a coating layer, but by further incorporating a crosslinking agent (curing resin) and performing curing, high water resistance can be imparted to the coating layer.

[0133] As a crosslinking agent, phenolformaldehyde resins, which are condensates of alkylated phenols, cresols, etc., and formaldehyde; amino resins, such as adducts of formaldehyde with urea, melamine, benzoguanamine, etc., and alkyl ether compounds containing the adduct and an alcohol having 1 to 6 carbon atoms; polyfunctional epoxy compounds; polyfunctional isocyanate compounds; block isocyanate compounds; polyfunctional aziridine compounds; oxazoline compounds, etc. may be used.

[0134] The coating layer used in the present invention may also contain additives such as antistatic agents, inorganic lubricants, and organic lubricants to impart antistatic and slip properties, to the extent that the effects of the present invention are not impaired. When applying antistatic agents, inorganic lubricants, organic lubricants, etc. to the film surface, it is preferable to include them in the coating layer to prevent detachment of these additives.

[0135] As a method for applying a coating agent to a polyamide film substrate to form a coating layer, known coating methods such as gravure, reverse, die, bar, and dip methods may be used.

[0136] The amount of coating agent applied is 0.01 to 3 g / m² as a solid content relative to the polyamide film after biaxial stretching. Preferably, it is applied to be 0.04 to 0.5 g / m². If the amount of coating is 0.01 g / m² or less, sufficient adhesion strength between the coating layer and other layers is not obtained. If it is 3 g / m² or more, blocking occurs, which is a practical problem.

[0137] The coating layer can be prepared by applying a coating agent to a biaxially stretched polyamide film substrate, or by applying a coating agent to an unoriented or uniaxially stretched polyamide film substrate, drying, and, if necessary, further performing heat setting after uniaxial or biaxial stretching. By performing drying and heat setting at a drying temperature of 150°C or higher, preferably 200°C or higher, after applying the coating agent, the coating film becomes hard and the adhesion between the easy-to-adhere layer and the polyamide film substrate is improved.

[0138] When stretching is performed after coating, drying after coating requires controlling the moisture content of the coating film to a range of 0.1 to 2% so as not to impair the stretchability of the coating film. After stretching, drying and heat-setting at 200°C or higher makes the coating film rigid and dramatically improves the adhesion between the coating layer and the polyamide film substrate.

[0139] [Inorganic thin film layer (D)]

[0140] The biaxially stretched polyamide film of the present invention can provide gas barrier properties by providing an inorganic thin film layer on at least one side of the film.

[0141] An inorganic thin film layer and a method for forming the same, according to an embodiment of the present invention, are described.

[0142] The inorganic thin film layer is a thin film containing a metal or an inorganic oxide. While there are no particular restrictions on the material forming the inorganic thin film layer as long as it can be formed into a thin film, inorganic oxides such as silicon oxide (silica), aluminum oxide (alumina), and mixtures of silicon oxide and aluminum oxide are preferably used from the perspective of transparency and gas barrier properties. In particular, a composite oxide of silicon oxide and aluminum oxide is preferred in terms of achieving both flexibility and density of the inorganic thin film layer. In this composite oxide, the mixing ratio of silicon oxide and aluminum oxide is preferably such that Al is in the range of 20 to 70 mass% in terms of the mass ratio of the metal powder. If the Al concentration is less than 20 mass%, the water vapor barrier properties may be reduced. On the other hand, if it exceeds 70 mass%, the inorganic thin film layer tends to become rigid, and the film may be destroyed during secondary processing such as printing or lamination, which may lead to a decrease in gas barrier properties. Also, silicon oxide mentioned here refers to various silicon oxides such as SiO or SiO2 or mixtures thereof, and aluminum oxide refers to various aluminum oxides such as AlO or Al2O3 or mixtures thereof.

[0143] The film thickness of the inorganic thin film layer is typically 1 to 100 nm, preferably 5 to 50 nm. If the film thickness of the inorganic thin film layer is less than 1 nm, it may be difficult to obtain satisfactory gas barrier properties, while if it is made excessively thicker than 100 nm, the corresponding improvement in gas barrier properties is not obtained, and it becomes disadvantageous in terms of flexibility and manufacturing costs.

[0144] There are no particular limitations on the method for forming an inorganic thin film layer, and known deposition methods such as physical vapor deposition (PVD) methods like vacuum deposition, sputtering, and ion plating, or chemical vapor deposition (CVD) methods may be appropriately employed. Below, a typical method for forming an inorganic thin film layer is described using silicon oxide and aluminum oxide-based thin films as examples. For example, when employing a vacuum deposition method, a mixture of SiO2 and Al2O3, or a mixture of SiO2 and Al, is preferably used as the deposition material. Typically, particles are used as these deposition materials; in this case, the size of each particle is preferably such that the pressure does not change during deposition, and the preferred particle diameter is 1 mm to 5 mm. For heating, methods such as resistance heating, high-frequency induction heating, electron beam heating, and laser heating may be employed. In addition, it is also possible to employ reactive deposition using means such as the introduction of oxygen, nitrogen, hydrogen, argon, carbon dioxide, water vapor, etc., as reaction gases, ozone addition, or ion assist. In addition, film deposition conditions can be arbitrarily changed, such as by applying a bias to the substrate (the laminated film provided for deposition) and heating or cooling the substrate. These deposition materials, reaction gases, bias of the substrate, heating and cooling, etc., can be changed in the same way when employing the sputtering method or the CVD method.

[0145] [Laminated film with laminated sealant film]

[0146] The biaxially stretched polyamide film of the present invention is processed into a laminated film in which a sealant film, etc. is laminated, and then processed into a packaging bag. Examples of sealant films include an unoriented linear low-density polyethylene (LLDPE) film, an unoriented polypropylene (CPP) film, an ethylene-vinyl alcohol copolymer resin (EVOH) film, etc.

[0147] Examples of the layer composition of the laminated film of the present invention include, for example, ONY / adhesive / LLDPE, ONY / adhesive / CPP, ONY / adhesive / Al / adhesive / CPP, ONY / adhesive / Al / adhesive / LLDPE, ONY / PE / Al / adhesive / LLDPE, ONY / adhesive / Al / PE / LLDPE, PET / adhesive / ONY / adhesive / LLDPE, PET / adhesive / ONY / PE / LLDPE, PET / adhesive / ONY / adhesive / Al / adhesive / LLDPE, PET / adhesive / Al / adhesive / ONY / adhesive / LLDPE, PET / adhesive / Al / adhesive / ONY / PE / LLDPE, PET / PE / Al / PE / ONY / PE / LLDPE, PET / adhesive / ONY / adhesive / CPP, PET / Adhesive / ONY / Adhesive / Al / Adhesive / CPP, PET / Adhesive / Al / Adhesive / ONY / Adhesive / CPP, ONY / Adhesive / PET / Adhesive / LLDPE, ONY / Adhesive / PET / PE / LLDPE, ONY / Adhesive / PET / Adhesive / CPP, ONY / Adhesive / Al / Adhesive / PET / Adhesive / LLDPE, ONY / Adhesive / Al / Adhesive / PET / PE / LLDPE, ONY / PE / LLDPE, ONY / PE / CPP, ONY / PE / Al / PE, ONY / PE / Al / PE / LLDPE, OPP / Adhesive / ONY / Adhesive / LLDPE, ONY / Adhesive / EVOH / Adhesive / LLDPE, ONY / Adhesive / EVOH / Adhesive / CPP, ONY / Adhesive / Aluminum Deposition Examples include PET / adhesive / LLDPE, ONY / adhesive / aluminum deposited PET / adhesive / ONY / adhesive / LLDPE, ONY / adhesive / aluminum deposited PET / PE / LLDPE, ONY / PE / aluminum deposited PET / PE / LLDPE, ONY / adhesive / aluminum deposited PET / adhesive / CPP, PET / adhesive / aluminum deposited PET / adhesive / ONY / adhesive / LLDPE, CPP / adhesive / ONY / adhesive / LLDPE, ONY / adhesive / aluminum deposited LLDPE, ONY / adhesive / aluminum deposited CPP, etc.

[0148] In addition, each abbreviation used in the above layer composition is as follows.

[0149] / : Indicates the boundary of the layer.

[0150] ONY: Biaxially stretched polyamide film, or biaxially stretched polyester film having a coating layer

[0151] PET: Stretched polyethylene terephthalate film

[0152] LLDPE: Unoriented linear low-density polyethylene film

[0153] CPP: Unoriented polypropylene film

[0154] OPP: Stretched polypropylene film

[0155] PE: Extruded laminate or unoriented low-density polyethylene film

[0156] Al: Aluminum foil

[0157] EVOH: Ethylene-vinyl alcohol copolymer resin

[0158] Adhesive: An adhesive layer that bonds films together.

[0159] Aluminum deposition: Indicates that aluminum has been deposited.

[0160] Examples of layer configurations of a laminated film using a biaxially stretched polyamide film having an inorganic thin film layer (D) of the present invention include, for example, ONY / inorganic thin film layer / adhesive / CPP, PET / adhesive / ONY / inorganic thin film layer / adhesive / LLDPE, PET / adhesive / ONY / inorganic thin film layer / PE / LLDPE, PET / adhesive / ONY / inorganic thin film layer / adhesive / CPP, ONY / inorganic thin film layer / adhesive / PET / adhesive / LLDPE, ONY / inorganic thin film layer / adhesive / PET / PE / LLDPE, ONY / inorganic thin film layer / adhesive / PET / adhesive / CPP, ONY / inorganic thin film layer / PE / LLDPE, ONY / inorganic thin film layer / PE / CPP, OPP / adhesive / ONY / inorganic thin film layer / adhesive / LLDPE, ONY / inorganic Examples include thin film layer / adhesive / EVOH / adhesive / LLDPE, ONY / inorganic thin film layer / adhesive / EVOH / adhesive / CPP, CPP / adhesive / ONY / inorganic thin film layer / adhesive / LLDPE, etc.

[0161] In addition, each abbreviation used in the above layer composition is as follows.

[0162] / : Represents the boundary of a layer

[0163] ONY / Inorganic thin film layer: Biaxially stretched polyamide film having an inorganic thin film layer (D)

[0164] PET: Stretched polyethylene terephthalate film

[0165] LLDPE: Unoriented linear low-density polyethylene film

[0166] CPP: Unoriented polypropylene film

[0167] OPP: Stretched polypropylene film

[0168] PE: Extruded laminate or unoriented low-density polyethylene film

[0169] EVOH: Ethylene-vinyl alcohol copolymer resin

[0170] Adhesive: An adhesive layer that bonds films together.

[0171] Examples

[0172] Next, the present invention will be explained in more detail by way of examples, but the present invention is not limited to the following examples. In addition, the film was evaluated by the following measurement method. Unless otherwise specified, measurements were performed in a measurement room with an environment of 23°C and 65% relative humidity.

[0173] (1) Film haze value

[0174] A direct reading haze meter manufactured by Toyo Seki Seisakusho Co., Ltd. was used, and measurements were taken in accordance with JIS-K-7105.

[0175] (2) Thickness of the film

[0176] The film was divided into 10 equal parts in the TD direction (for narrow films, it was divided into equal parts to ensure a width sufficient for thickness measurement), 10 sheets of 100mm film were stacked and cut in the MD direction, and conditioned for at least 2 hours under an environment of 23℃ temperature and 65% relative humidity. The thickness of the center of each sample was measured using a tester acid-based thickness gauge, and the average value was taken as the thickness.

[0177] (3) Biomass of the film is also measured

[0178] The biomass of the obtained film was determined by radiocarbon (C14) measurement as described in ASTM D6866-16 Method B (AMS).

[0179] (4) Thermal shrinkage rate of the film

[0180] Except for the test temperature being 160℃ and the heating time being 10 minutes, the thermal shrinkage rate was measured by the following formula in accordance with the dimensional change test method described in JIS C2318.

[0181] Thermal shrinkage rate = [(Length before treatment - Length after treatment) / Length before treatment] × 100 (%)

[0182] (5) Impact strength of the film

[0183] Measurements were taken using a film impact tester manufactured by Toyo Seki Seisakusho Co., Ltd. The measured values ​​were expressed as J (Joule) / 15㎛, converted per 15㎛ thickness.

[0184] (6) The kinetic friction coefficient of the film

[0185] In accordance with JIS-C2151, the coefficient of kinetic friction between the outer surfaces of the film winding was evaluated under the following conditions. In addition, the test specimen size was 130 mm in width and 250 mm in length, and the test speed was 150 mm / min.

[0186] (7) Film piercing strength

[0187] Measurements were taken in accordance with “2. Test Methods for Strength, etc.” of “Standards for Food, Additives, etc. No. 3: Utensils and Containers / Packaging” (Ministry of Health, Labour and Welfare Notification No. 20 of 1982) under the Food Sanitation Act. A needle with a tip diameter of 0.7 mm was pierced into the film at a piercing speed of 50 mm / min, and the strength at which the needle penetrated the film was measured and defined as the piercing strength. The measurement was performed at room temperature (23℃), and the value obtained by dividing the piercing strength of the film (unit N) by the actual thickness of the film was defined as the piercing strength (unit N / ㎛).

[0188] (8) Surface orientation of the film

[0189] The sample was obtained from the center position in the width direction of the film. For the sample, the refractive index in the long side direction (nx) and the refractive index in the width direction (ny) of the film were measured using an Abbe refractometer with sodium D rays as a light source according to JIS K 7142-1996 A method, and the plane orientation coefficient was calculated by the calculation formula of Equation (1).

[0190] Planar orientation coefficient (ΔP) = (nx + ny) / 2 - nz (1)

[0191] (9) Elasticity of the film

[0192] After allowing the obtained biaxially stretched polyamide film to stand for 2 hours in a room adjusted to 23°C and 50% RH, samples were obtained by cutting the film into a rectangular shape with a length of 150 mm (distance between gauges 100 mm) in the MD and TD measurement directions and a length of 15 mm perpendicular to the measurement direction. A tensile test was performed at a test speed of 200 mm / min using a tensile testing machine (Shimadzu Seisakusho AG-1) equipped with a 1 kN load cell and a sample holder. The elastic modulus was calculated from the gradient of the obtained load-elongation curve. Measurements were performed on 3 samples, and the average value for each was calculated.

[0193] (10) Film's bending resistance and pinhole resistance

[0194] Using a Gelbo Flex Tester manufactured by Rigaku High School, the number of bending fatigue pinholes was measured by the following method.

[0195] After applying a polyester-based adhesive to the film prepared in the example, a linear low-density polyethylene film (L-LDPE film: manufactured by Toyobo Co., Ltd., L4102) with a thickness of 40 μm was dry-laminated, and the film was aged for 3 days under an environment of 40°C to form a laminate film. The obtained laminate film was cut into 12-inch × 8-inch pieces and formed into a cylinder with a diameter of 3.5 inches. One end of the cylindrical film was fixed to the fixed head side and the other end to the movable head side of a Gelbo Flex Tester, and the initial gripping distance was set to 7 inches. Flex fatigue was performed 1,000 times at a speed of 40 times / minute, with 440 twists applied during the first 3.5 inches of the stroke, followed by a linear horizontal motion for the next 2.5 inches to complete the entire stroke, and the number of pinholes generated in the laminate film was counted. Additionally, the measurement was performed under an environment of 1°C. The L-LDPE film side of the test film was placed on filter paper (Advantech, No. 50) with the lower side facing down, and the four corners were secured with cellophane tape (registered trademark). Ink (Pilot ink (part number INK-350-Blue) diluted 5 times with pure water) was applied onto the test film and spread across one side using a rubber roller. After wiping off the excess ink, the test film was removed, and the number of ink dots on the filter paper was counted.

[0196] (11) Film's frictional pinhole resistance

[0197] Using a durability tester (Toyoseki Seisakusho), a friction test was performed according to the following method, and the pinhole occurrence distance was measured.

[0198] A test sample was prepared by folding a laminate film identical to the one produced in the above bending pinhole resistance evaluation into four equal parts and sharpening the angles, and it was rubbed against the inner surface of a corrugated cardboard using a fastness tester with an amplitude of 25 cm, an amplitude speed of 30 times / min, and a weight of 100 g. The corrugated cardboard used was K280×P180×K210(AF)=(surface material liner×center core material×back material liner (type of flute)).

[0199] The pinhole occurrence distance was calculated according to the following procedure. The longer the pinhole occurrence distance, the better the friction pinhole resistance.

[0200] First, a friction test was performed at a distance of 2,500 cm with an amplitude of 100. If no pinhole was formed, the friction test was performed with the amplitude increased by 20 and the distance by 500 cm. Additionally, if no pinhole was formed, the friction test was performed with an amplitude increased by another 20 and the distance by 500 cm. This process was repeated, and at the distance where a pinhole was formed, an × was marked and the level was set to 1. If a pinhole was formed at a distance of 2,500 cm with an amplitude of 100, the friction test was performed with the amplitude reduced by 20 and the distance by 500 cm. Additionally, if a pinhole was formed, the friction test was performed with an amplitude reduced by another 20 and the distance by 500 cm. This process was repeated, and at the distance where no pinhole was formed, an ○ was marked and the level was set to 1.

[0201] Next, as Level 2, if the last result in Level 1 was ○, the number of amplitudes was increased by 20 and a friction test was performed; ○ was marked if no pinhole was formed, and × was marked if a pinhole was formed. If the last result in Level 1 was ×, the number of amplitudes was reduced by 20 and a friction test was performed; ○ was marked if no pinhole was formed, and × was marked if a pinhole was formed.

[0202] Also, for levels 3 to 20, if the result was ○ at the previous level, increase the amplitude count by 20 and perform a friction test; mark ○ if no pinhole is formed, and × if a pinhole is formed. If the result was × at the previous level, decrease the amplitude count by 20 and perform a friction test; mark ○ if no pinhole is formed, and × if a pinhole is formed. Repeat this process to mark ○ or × at levels 3 to 20.

[0203] For example, results as shown in Table 1 were obtained. Using Table 1 as an example, the method for calculating the pinhole occurrence distance will be explained.

[0204] Count the number of ○ and × tests for each distance.

[0205] The distance with the highest number of tests was set as the median, and the coefficient was set to zero. For distances longer than that, the coefficient was set to +1, +2, +3… for every 500 cm, and for distances shorter than that, the coefficient was set to -1, -2, -3… for every 500 cm.

[0206] In all tests from level 1 to 20, the number of un-drilled tests and the number of drilled tests were compared, and the friction pinhole occurrence distance was calculated for the following cases A and B using respective formulas.

[0207] A; In all tests, if the number of unperforated tests is greater than or equal to the number of perforated tests

[0208] Friction Pinhole Distance = Median + 500 × (Σ(Coefficient × Number of Undrilled Tests) / Number of Undrilled Tests) + 1 / 2)

[0209] B: In all tests, if the number of unperforated tests is less than the number of perforated tests

[0210] Friction Pinhole Distance = Median + 500 × (Σ(Coefficient × Number of Tests) / Number of Tests) - 1 / 2)

[0211]

[0212] (12) Lamination strength with polyethylene sealant

[0213] A laminate film prepared in the same manner as described in the description of the evaluation of bending pinhole resistance was cut into a rectangle with a width of 15 mm × a length of 200 mm, and one end of the laminate film was peeled at the interface between a biaxially stretched polyamide film and a linear low-density polyethylene film. Using a (manufactured by Shimadzu Seisakusho Co., Ltd., Autograph), the laminate strength was measured three times each in the MD direction and the TD direction under conditions of a temperature of 23°, relative humidity of 50%, tensile speed of 200 mm / min, and peel angle of 90°, and evaluated as the average value.

[0214] (13) Water resistance laminate strength (laminate strength under water adhesion conditions)

[0215] When measuring the laminate strength of (12), water was flowed through the peeling interface of the rectangular laminate film using a dropper to measure the laminate strength. The measurement was taken three times each in the MD direction and the TD direction and evaluated as the average value.

[0216] (13) Cycle of thermal degradation products generated at the die lip outlet

[0217] After cleaning the lip of the die, film formation was started, and the time until thermal degradation occurred on the lip of the die was observed.

[0218] A: Even after film formation for more than 36 hours, there is no generation of thermal degradation products and no adhesion of foreign substances to the film.

[0219] B: Thermally degraded material adheres to the ribs of the die for 24 to 36 hours.

[0220] C: Within 24 hours, thermal degradation products adhere to the ribs of the die, and foreign matter occurs on the film.

[0221] (14) Relative viscosity of raw polyamide

[0222] The relative viscosity of a polyamide solution prepared by dissolving 0.25 g of polyamide in 96% sulfuric acid in a 25 ml volumetric flask to a concentration of 1.0 g / dl was measured at 20°C.

[0223] (15) Melting point of raw polyamide

[0224] In accordance with JIS K7121, a differential scanning calorimeter of the SSC5200 type manufactured by Seiko Instruments was used to measure in a nitrogen atmosphere with a sample weight of 10 mg, a heating initiation temperature of 30℃, and a heating rate of 20℃ / min, and the endothermic peak temperature (Tmp) was determined as the melting point.

[0225] [Example 1-1]

[0226] Using a device consisting of two extruders and a co-extrusion T-die with a width of 380 mm, molten resin of the following resin composition was extruded into a film from the T-die by laminating a functional layer (Layer B) / substrate layer (Layer A) / functional layer (Layer B) using a feed block method, cast onto a cooling roll controlled to a temperature of 20°C, and electrostatically bonded to obtain an unoriented film with a thickness of 200 μm.

[0227] The resin composition of the base layer (Layer A) and the functional layer (Layer B) is as follows.

[0228] A resin composition constituting a substrate layer (layer A): a polyamide resin composition comprising 89.5 parts by mass of polyamide 6 (manufactured by Toyobo Corporation, relative viscosity 2.8, melting point 220°C), and 10.5 parts by mass of polybutylene terephthalate adipate (manufactured by BASF, trade name "Ecoflex"), glass transition temperature -31.3°C, melting point 120°C.

[0229] A resin composition constituting a functional layer (layer B): a resin composition comprising 95 parts by mass of polyamide 6 (manufactured by Toyobo Corporation, relative viscosity 2.8, melting point 220°C), 5.0 parts by mass of polyamide MXD6 (manufactured by Mitsubishi Gas Chemical Co., Ltd., relative viscosity 2.1, melting point 237°C), 0.54 parts by mass of porous silica fine particles (manufactured by Fuji Silicia Chemical Co., Ltd., average particle size 2.0 μm, pore volume 1.6 ml / g), and 0.15 parts by mass of fatty acid bisamide (ethylenebisstearic acidamide manufactured by Kyoesha Chemical Co., Ltd.).

[0230] In addition, the configuration of the feed block and the discharge amount of the extruder were adjusted so that the total thickness of the biaxially stretched polyamide film is 15㎛, the thickness of the substrate layer (layer A) is 9㎛, and the thickness of the functional layer (layer B) is 3㎛ on the front and back respectively.

[0231] The obtained unoriented film was guided to a roll-type stretcher, and using the difference in peripheral speed of the rolls, it was stretched 1.73 times in the MD direction at 80°C, and then stretched further 1.85 times at 70°C. Subsequently, this uniaxially stretched film was continuously guided to a tenter-type stretcher, preheated at 110°C, and then stretched 1.2 times at 120°C, 1.7 times at 130°C, and 2.0 times at 160°C in the TD direction. After heat-setting treatment at 218°C, a 7% relaxation treatment was performed at 218°C, and then the surface of the side to be dry-laminated with a linear low-density polyethylene film was corona discharge-treated to obtain a biaxially stretched polyamide film. The evaluation results of the obtained biaxially stretched film are shown in Table 2.

[0232] [Examples 1-2 to 1-11]

[0233] The film formation conditions, such as the resin composition of the substrate layer (Layer A) and the functional layer (Layer B) and the heat-setting temperature, were changed as shown in Table 2, and a biaxially stretched film was obtained in the same manner as in Example 1. The evaluation results of the obtained biaxially stretched film are shown in Table 2.

[0234] In addition, the aliphatic or aromatic aliphatic polyester resins used were each as follows.

[0235] ㆍPBAT: Polybutylene Adipate Terephthalate (BASF, Ecoflex)

[0236] ㆍPBS: Polybutylene succinate (Manufactured by Showa Kobun Corporation, Bionole 1001)

[0237] ㆍPBSA: Polybutylene succinate adipate (Manufactured by Showa Kobun Corporation, Bionole 3001)

[0238] ㆍPAE: Polyamide elastomer (Arkema, Nylon 12 / Polytetramethylene Glycol Copolymer, Pebax SA01)

[0239] ㆍPEE: Maleic anhydride modified polyester elastomer (Mitsubishi Chemical Corporation, Tepabloc)

[0240] In addition, the following polyamide resins were used, each having at least a portion of its raw material derived from biomass.

[0241] ㆍPolyamide 11: (Straight fiber product, relative viscosity 2.5, melting point 186℃, biomass 100%)

[0242] ㆍPolyamide 410: (DSM, ECOPaXX Q150-E, melting point 250℃, biomass 70%)

[0243] ㆍPolyamide 610: (Arkemas, RilsanS SMNO, melting point 222℃, biomass 63%)

[0244] ㆍPolyamide 1010: (Arkemas, RilsanT TMNO, melting point 202℃, biomass 100%)

[0245] [Table 2A]

[0246]

[0247] [Table 2B]

[0248]

[0249] As shown in Table 2, the film of the example was obtained as a film with good resistance to both bending pinholes and friction pinholes. In addition, it had low haze and good transparency, high impact strength and puncture strength, and high laminate strength with sealant film, making it excellent as a packaging film. Furthermore, even during long-term film formation, no deterioration material adhered to the lip of the die, and it was possible to form a stable film.

[0250] [Comparative Example 1]

[0251] According to the resin composition and conditions shown in Table 3, a biaxially stretched polyamide film was produced in the same manner as in Example 1-1. The raw materials used in the resin composition were the same as in Example 1. In addition, for Comparative Examples 1-5, a biaxially stretched polyamide film was produced by the following method.

[0252] [Comparative Example 1-5]

[0253] Using a device consisting of one extruder and a single-layer T-die with a width of 380 mm, molten resin of the following resin composition was extruded into a film from the T-die, cast onto a cooling roll with a temperature controlled to 20°C, and electrostatically bonded to obtain an unoriented film with a thickness of 180 μm.

[0254] Resin composition constituting the layer: a polyamide resin composition comprising 97 parts by mass of polyamide 6 (manufactured by Toyobo Corporation, relative viscosity 2.8, melting point 220°C), and 3.0 parts by mass of maleic anhydride-modified polyester elastomer (manufactured by Mitsubishi Chemical, Primaloy AP GQ131). 0.09 parts by mass of porous silica microparticles (manufactured by Fuji Silicia Chemical Co., Ltd., average particle size 2.0 μm, pore volume 1.6 ml / g). 300 ppm of ethylenebisstearamide.

[0255] Next, the obtained unoriented film was longitudinally stretched 3.0 times by a roll stretcher at 65°C, then transversely stretched 4.0 times by a tenter stretcher in an atmosphere of 110°C, and further heat-treated in an atmosphere of 210°C by the same tenter to prepare a single layer polyamide-based film with a thickness of 15 μm.

[0256] The physical properties and various evaluation results of the biaxially stretched polyamide film produced in Comparative Example 1 are shown in Table 3.

[0257]

[0258] As shown in Table 3, the biaxially stretched polyamide film of Comparative Example 1-1, which does not contain a material that modifies flexural pinhole resistance, showed reduced flexural pinhole resistance. In Comparative Example 1-2, because there was an excessive amount of material that modifies flexural pinhole resistance, although the flexural pinhole resistance was excellent, the film's haze value was high, and the film's impact strength, puncture strength, and friction pinhole resistance were reduced. In Comparative Examples 1-3, 1-4, and 1-5, because the surface layer also contained a material that modifies flexural pinhole resistance, the friction pinhole resistance was reduced. Additionally, deterioration occurred on the lip of the die during the extrusion process.

[0259] [Example 2]

[0260] Using the biaxially stretched polyamide film produced in Example 1-1, a laminate with the following compositions (1) to (9) was produced, and three-way seal type and pillow type packaging pouches were produced using the laminates (1) to (9). It was possible to produce packaging pouches that had a good appearance and were difficult to tear in drop impact tests.

[0261] (1) Biaxially oriented polyamide film layer / printing layer / polyurethane-based adhesive layer / linear low-density polyethylene film sealant layer.

[0262] (2) Biaxially oriented polyamide film layer / printing layer / polyurethane-based adhesive layer / non-oriented polypropylene film sealant layer.

[0263] (3) Biaxially stretched PET film layer / printing layer / polyurethane-based adhesive layer / biaxially stretched polyamide film layer / polyurethane-based adhesive layer / non-oriented polypropylene film sealant layer

[0264] (4) Biaxially stretched PET film layer / printing layer / polyurethane-based adhesive layer / biaxially stretched polyamide film layer / polyurethane-based adhesive layer / linear low-density polyethylene film sealant layer

[0265] (5) Biaxially oriented polyamide film layer / anchor coat layer / inorganic thin film layer / inorganic thin film protective layer / printing layer / polyurethane adhesive layer / linear low-density polyethylene film sealant layer

[0266] (6) Linear low-density polyethylene film sealant layer / polyurethane adhesive layer / biaxially stretched polyamide film layer / anchor coat layer / inorganic thin film layer / polyurethane adhesive layer / linear low-density polyethylene film sealant layer

[0267] (7) Linear low-density polyethylene film layer / polyurethane adhesive layer / biaxially oriented polyamide film layer / anchor coat layer / inorganic thin film layer / polyurethane adhesive layer / linear low-density polyethylene film layer / low-density polyethylene / paper / low-density polyethylene / linear low-density polyethylene film sealant layer

[0268] (8) Biaxially oriented polyamide film layer / anchor coat layer / inorganic thin film layer / inorganic thin film protective layer / printing layer / polyurethane adhesive layer / non-oriented polypropylene film sealant layer

[0269] (9) Biaxially stretched PET film layer / inorganic thin film layer / inorganic thin film protective layer / printing layer / polyurethane-based adhesive layer / biaxially stretched polyamide film layer / polyurethane-based adhesive layer / easy-peel type non-oriented polypropylene film sealant layer

[0270] [Example 3] (Biaxially stretched polyamide film having a coating layer)

[0271] Using a device consisting of two extruders and a co-extrusion T-die with a width of 380 mm, the resin composition shown in Table 4 was laminated in a composition of functional layer (Layer B) / substrate layer (Layer A) / functional layer (Layer B) by the feed block method, and the molten resin was extruded from the T-die into a film, cast onto a cooling roll controlled to a temperature of 20°C, and electrostatically bonded to obtain an unoriented film with a thickness of 200 μm. The raw materials used in the resin composition were the same as those in Example 1 and Comparative Example 1.

[0272] The obtained unoriented film was guided to a roll-type stretcher, and using the difference in peripheral speed of the rolls, it was stretched 1.73 times in the MD direction at 80°C, and then stretched further 1.85 times at 70°C. Subsequently, the following coating solution (A) was applied to this uniaxially stretched film using a roll coater, and then dried with hot air at 70°C. The uniaxially stretched film was then guided to a tenter-type stretcher, preheated at 110°C, stretched 1.2 times at 120°C, 1.7 times at 130°C, and 2.0 times at 160°C in the TD direction, heat-set at 218°C, and then subjected to a 7% relaxation treatment at 218°C. Next, the surface of the side to be dry-laminated with a linear low-density polyethylene film was corona discharge-treated to obtain a biaxially stretched polyamide film. However, in Examples 3-4, the following coating solution (B): a water-based dispersion of polyurethane resin was used as the coating solution.

[0273] The physical properties and various evaluation results of the biaxially stretched polyamide film produced in Example 3 are shown in Table 4.

[0274] [Table 4A]

[0275]

[0276] [Table 4B]

[0277]

[0278] As shown in Table 4, the film of the example was obtained as a film with good resistance to both bending pinholes and friction pinholes. In addition, it had low haze and good transparency, high impact strength and puncture strength, and high water-resistant laminate strength with sealant film, making it excellent as a packaging film. Furthermore, even during long-term film formation, no deterioration material adhered to the lip of the die, and it was possible to form a stable film.

[0279] [Comparative Example 3]

[0280] According to the resin composition and conditions shown in Table 5, a biaxially stretched polyamide film having a coating layer was produced in the same manner as in Example 3.

[0281] In addition, for Comparative Examples 3 to 8, biaxially stretched polyamide films were produced by the following method.

[0282] Using an apparatus consisting of one extruder and a single-layer T-die with a width of 380 mm, molten resin of the resin composition described in Table 5 was extruded from the T-die into a film, cast onto a cooling roll controlled to a temperature of 20°C, and electrostatically bonded to obtain an unoriented film with a thickness of 180 μm. Next, the obtained unoriented film was longitudinally stretched 3.0 times in the MD direction by a roll-type stretcher at 65°C. Subsequently, the following coating liquid (A) was applied to this uniaxially stretched film using a roll coater, and then dried with hot air at 70°C. The uniaxially stretched film was then guided to a tenter-type stretcher and transversely stretched 4.0 times by a tenter stretcher in an atmosphere of 110°C, and further heat-treated in an atmosphere of 210°C by the same tenter to produce a single-layer polyamide-based film with a thickness of 15 μm.

[0283] Coating solution (A): Water-based dispersion of acrylic graft copolymer polyester

[0284] 466 parts by mass of dimethyl terephthalate, 466 parts by mass of dimethyl isophthalate, 401 parts by mass of neopentyl glycol, 443 parts by mass of ethylene glycol, and 0.52 parts by mass of tetra-n-butyl titanate were added to a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux condenser, and an ester exchange reaction was carried out at 160 to 220°C for 4 hours. Next, 23 parts by mass of fumaric acid were added, and the temperature was increased from 200°C to 220°C over 1 hour to carry out an esterification reaction. Next, the temperature was increased to 255°C, the reaction system was gradually depressurized, and the reaction was carried out under a reduced pressure of 0.2 mmHg for 1 hour and 30 minutes while stirring to obtain a polyester. The obtained polyester was pale yellow transparent, had a glass transition temperature of 60°C, and a weight average molecular weight of 12,000. The composition obtained by NMR measurement, etc. was as follows.

[0285] ㆍDicarboxylic acid components

[0286] Terephthalic acid 48 mol%

[0287] Isophthalic acid 48 mol%

[0288] Fumaric acid 4 mol%

[0289] Dior ingredients

[0290] Neopentyl glycol 50 mol%

[0291] Ethylene glycol 50 mol%

[0292] In a reactor equipped with a stirrer, a thermometer, a reflux device, and a quantitative dispensing device, 75 parts by mass of the polyester resin, 56 parts by mass of methyl ethyl ketone, and 19 parts by mass of isopropyl alcohol were added and heated and stirred at 65°C to dissolve the resin. After the resin was completely dissolved, a mixture of 17.5 parts by mass of methacrylic acid and 7.5 parts by mass of ethyl acrylate and a solution of 1.2 parts by mass of azobisdimethylvaleronitrile dissolved in 25 parts by mass of methyl ethyl ketone were added dropwise to the polyester solution at a rate of 0.2 ml / min, and stirring was continued for 2 hours after the addition was finished. After taking an analytical sample (5 g) from the reaction solution, 300 parts by mass of water and 25 parts by mass of triethylamine were added to the reaction solution, and the mixture was stirred for 1 hour to prepare a dispersion of grafted polyester. Afterwards, the temperature of the obtained dispersion was raised to 100°C, and methyl ethyl ketone, isopropyl alcohol, and excess triethylamine were removed by distillation to obtain a copolymer polyester aqueous dispersion.

[0293] The obtained dispersion was white, had an average particle size of 300 nm, and a Type B viscosity of 50 centipoise at 25°C. 1.25 g of heavy water was added to 5 g of this dispersion to adjust the solid content to 20 mass%, and then DSS was added, and 125 MHz 13 C-NMR was measured. The full width at half maximum (FWHM) of the signal at the carbonyl carbon of the polyester main chain (160 to 175 ppm) was ∞ (no signal detected), and the FWHM of the signal at the carbonyl carbon of the methacrylic acid in the graft portion (181 to 186 ppm) was 110 Hz. The solution sampled at the end of the grafting reaction was dried under vacuum at 100°C for 8 hours, and the acid value, the grafting efficiency of the polyester (measured by NMR), and the molecular weight of the graft portion by hydrolysis were measured for the solid. The acid value of the solid was 2300 eq. / 10 6 It was g. 1In the H-NMR measurement, no signal derived from fumaric acid (δ=6.8-6.9 ppm, doublet) was detected, confirming that the graft efficiency of the polyester was 100%. The molecular weight of the grafted portion was a weight-average molecular weight of 10,000.

[0294] After that, the aqueous dispersion obtained as described above was diluted with water to a solid content concentration of 5 mass% to obtain a coating solution (A).

[0295] Coating solution (B): Water-based dispersion of polyurethane resin

[0296] Preparation of a polyurethane and an aqueous dispersion; adipic acid was used as the dicarboxylic acid component; and 60 mol% of 1,4-butanediol (glycol component) and 40 mol% of a propylene oxide (1 mol) adduct of bisphenol A were used as the glycol component to obtain a polyester (polyester polyol) with a Tg of -5°C. A urethane polymer was obtained by reacting this polyester with toluene diisocyanate. Using this as a prepolymer, 1,6-hexanediol was reacted to extend the chain and simultaneously react the aminocarboxylate at the terminals to obtain a water-insoluble and water-dispersible polyurethane. This was dispersed in hot water while stirring to obtain a 25% aqueous dispersion.

[0297] A coating solution (B) was obtained by adding the above-mentioned water-based dispersion of polyurethane to an equal mixture of ion-exchanged water and isopropyl alcohol and diluting it so that the solid content was 5 mass%.

[0298] The physical properties and various evaluation results of the biaxially stretched polyamide film produced in Comparative Example 3 are shown in Table 5.

[0299]

[0300] As shown in Table 5, the biaxially stretched polyamide film of Comparative Example 3-1, which does not contain a material that modifies flexural pinhole resistance, showed reduced flexural pinhole resistance. In Comparative Example 3-2, because there was an excessive amount of material that modifies flexural pinhole resistance, although the flexural pinhole resistance was excellent, the film's haze value was high, and the film's impact strength, puncture strength, and friction pinhole resistance were reduced. In Comparative Examples 3-3, 3-4, and 3-5, because the surface layer also contained a material that modifies flexural pinhole resistance, the friction pinhole resistance was reduced. Additionally, deterioration occurred on the lip of the die during the extrusion process.

[0301] [Example 4] (Biaxially stretched polyamide film having an inorganic thin film layer)

[0302] Film formation conditions, such as the resin composition of the substrate layer (Layer A) and the functional layer (Layer B) and the heat-setting temperature, were changed as shown in Table 6, and a biaxially stretched film was obtained in the same manner as in Example 1-1. The raw materials used in the resin composition were the same as those in Example 1 and Comparative Example 1.

[0303] A composite oxide thin film layer of silicon dioxide and aluminum oxide was formed on the corona-treated surface of the subsequently obtained biaxially stretched polyamide film using the following method.

[0304] <Formation of an Inorganic Thin Film Layer of Silicon Dioxide and Aluminum Oxide Composite Oxide (SiO2 / Al2O3)>

[0305] An inorganic thin film layer of a composite oxide of silicon dioxide and aluminum oxide was formed on the corona-treated surface of the obtained biaxially stretched polyamide film using electron beam deposition. The deposition method involves setting the film on the unwinding side of a continuous vacuum deposition machine and winding the film by driving it through a cooling metal drum. At this time, the continuous vacuum deposition machine is 10 -4The pressure was reduced to below Torr, and particulate SiO2 (99.9% purity) and Al2O3 (99.9% purity) of approximately 3 mm to 5 mm were used as deposition sources in an alumina crucible from the bottom of a cooling drum. The thickness of the obtained inorganic thin film layer (SiO2 / Al2O3 composite oxide layer) was 13 nm. In addition, the composition of this composite oxide layer was SiO2 / Al2O3 (mass ratio) = 60 / 40.

[0306] However, in Examples 4-5, an inorganic thin film layer of aluminum oxide was formed as an inorganic thin film layer by the following method.

[0307] <Formation of an Aluminum Oxide (Al2O3) Inorganic Thin Film Layer>

[0308] An inorganic thin film layer of aluminum oxide was formed on the corona-treated surface of the obtained biaxially stretched polyamide film by electron beam deposition. The method for depositing aluminum oxide involves setting the film on the unwinding side of a continuous vacuum deposition machine and winding the film by driving it through a cooling metal drum. At this time, the continuous vacuum deposition machine is 10 -4 The pressure was reduced to below Torr, and 99.99% pure metallic aluminum was loaded into an alumina crucible from the bottom of a cooling drum, the metallic aluminum was heated and evaporated, and oxygen was supplied into the vapor to cause an oxidation reaction while depositing it on a film, thereby forming an aluminum oxide film with a thickness of 30 nm.

[0309] The physical properties and various evaluation results of the biaxially stretched polyamide film produced in Example 4 are shown in Table 6.

[0310] [Table 6A]

[0311]

[0312] [Table 6B]

[0313]

[0314] [Table 6C]

[0315]

[0316] As shown in Table 6, the film of the example was obtained as a film with good resistance to both bending pinholes and friction pinholes. In addition, a film with low haze, good transparency, and high gas barrier properties was obtained. Furthermore, it had high impact strength and puncture strength, making it excellent as a packaging film. In addition, even during long-term film formation, no deterioration material adhered to the lip of the die, and it was possible to form a stable film.

[0317] [Comparative Example 4]

[0318] The film formation conditions, such as the resin composition of the substrate layer (Layer A) and the functional layer (Layer B) and the heat-setting temperature, were changed as shown in Table 7, and a biaxially stretched film was obtained in the same manner as in Comparative Example 1. Next, a composite oxide thin film layer of silicon dioxide and aluminum oxide was formed on the corona-treated surface of the obtained biaxially stretched polyamide film. In addition, in Comparative Example 4-3, an inorganic thin film layer was not formed.

[0319] The physical properties and various evaluation results of the biaxially stretched polyamide film produced in Comparative Example 4 are shown in Table 7.

[0320]

[0321] As shown in Table 7, the biaxially stretched polyamide film of Comparative Example 4-1, which did not contain a material that modifies flexural pinhole resistance, exhibited reduced flexural pinhole resistance. In Comparative Example 4-2, the film's flexural pinhole resistance was reduced because the material that modifies flexural pinhole resistance was excessively small. In Comparative Example 4-3, since an inorganic thin film layer was not formed, the oxygen permeability was high, making it unsuitable as a gas barrier film. In Comparative Example 4-4, because the material that modifies flexural pinhole resistance was excessively large, the flexural pinhole resistance was excellent, but the film's impact strength, puncture strength, and friction pinhole resistance were reduced. In Comparative Example 4-5, the friction pinhole resistance was reduced because the functional layer serving as the surface layer contained a material that modifies flexural pinhole resistance. Additionally, deterioration occurred on the lip of the die during the extrusion process. In Comparative Examples 4-6 and 4-7, conventional polyamide elastomers and polyester elastomers were used as materials to modify flexural pinhole resistance, so although flexural pinhole resistance was excellent, the impact strength, puncture strength, and friction pinhole resistance of the film were poor. Industrial applicability

[0322] The biaxially stretched polyamide film of the present invention is suitable for use as a packaging material, such as food packaging, as it simultaneously exhibits excellent impact resistance, bending pinhole resistance, and friction pinhole resistance. In addition, since the elastomer component does not deteriorate inside the die, the adhesion of deteriorated material to the inner surface of the die or the adhesion of lumps to the die lip exit can be suppressed over a long period of time, thereby reducing the frequency of stopping production to clean the die lip and enabling continuous production for a long time. Explanation of the symbols

[0323] 1: Head part of the fastness tester 2: Cardboard 3: Backing paper for sample retention 4: Film sample folded into four equal parts 5: Rubbing amplitude direction

Claims

Claim 1 A biaxially stretched polyamide film having a functional layer (layer B) laminated on at least one side of a substrate layer (layer A), wherein the substrate layer (layer A) comprises, as a resin, (a) 70 to 99 mass% of polyamide 6 resin, (b) 1 to 20 mass% of an aliphatic or aromatic aliphatic polyester resin, and only a polyamide-based resin other than the polyamide 6 resin of (a) that may be included, and when the substrate layer (layer A) comprises a polyamide-based resin other than the polyamide 6 resin of (a), the polyamide-based resin other than the polyamide 6 resin of (a) is a polyamide-based resin selected from polyamide 11, polyamide 410, polyamide 610, polyamide 1010, polyamide 12 resin, polyamide 66 resin, polyamide 6·12 copolymer resin, polyamide 6·66 copolymer resin, polyamide MXD6 resin, polyamide MXD10 resin, and polyamide 11·6T copolymer resin. A biaxially stretched polyamide film characterized by being a resin, wherein the functional layer (layer B) comprises at least 70 mass% of polyamide 6 resin. Claim 2 A biaxially stretched polyamide film according to claim 1, characterized in that the (b) aliphatic or aromatic aliphatic polyester resin is at least one polyester resin selected from the group consisting of polybutylene succinate, polybutylene succinate adipate, and polybutylene adipate terephthalate. Claim 3 A biaxially stretched polyamide film according to claim 1 or 2, characterized in that the substrate layer (layer A) contains a polyamide resin in which at least a portion of the raw material is derived from biomass. Claim 4 A biaxially stretched polyamide film according to claim 3, characterized in that the polyamide resin, of which at least part of the raw material is biomass-derived, is at least one polyamide resin selected from the group consisting of polyamide 11, polyamide 410, polyamide 610, and polyamide 1010. Claim 5 A biaxially stretched polyamide film according to claim 1 or 2, characterized in that the biaxially stretched polyamide film satisfies the following (a) to (c): (a) 5 or fewer bending fatigue pinholes when a bending test using a Gelboflex tester is performed 1,000 times at a temperature of 1°C; (b) 2,900 cm or more to pinhole occurrence in a friction-resistant pinhole test; (c) puncture strength of the film is 0.67 N / ㎛ or more. Claim 6 A biaxially stretched polyamide film having, on at least one side of the biaxially stretched polyamide film described in claim 1 or 2, a coating layer comprising one or more resins selected from the group consisting of polyester resin, polyurethane resin, polyacrylic resin, and acrylic graft copolymer polyester resin, having a solid content of 0.01 to 3 g / m². Claim 7 A polyamide film having an inorganic thin film layer on at least one side of the biaxially stretched polyamide film described in claim 1 or 2. Claim 8 A laminated film having a sealant film laminated to a biaxially oriented polyamide film described in claim 1 or 2. Claim 9 A packaging bag using the laminated film described in paragraph 8.

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