JP5348535B2 - Laminated biaxially oriented polyamide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially stretched laminated polyamide-based film which shows excellence in an impact resistance, a sticking resistance and a flex fatigue resistance, particularly a flex fatigue resistance under a low temperature environment, shows an excellent effect in bag breakage prevention and the like during transportation and storage of goods when the film is used for a packaging material for food packaging and the like, and is suitable for various packaging applications, particularly a filling and packaging bag of aqueous stuff, particularly soup, source and the like. <P>SOLUTION: The biaxially stretched laminated polyamide-based film includes a layer A of a polymer mixture composed of 97 to 70 wt.% of an aliphatic polyamide polymer, 3 to 20 wt.% of an aliphatic polyamide copolymer, and if desired 0.5 to 10 wt.% of a thermoplastic elastomer, and a layer B of a polymer mixture composed of 99.5 to 90 wt.% of an aliphatic polyamide polymer and 0.5 to 10.0 wt.% of a thermoplastic elastomer, the layer B being laminated on at least one surface of the layer A. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention is excellent in impact resistance and bending fatigue resistance, in particular, bending fatigue resistance and piercing resistance in a low temperature environment, when used as a packaging material for food packaging, etc. The present invention relates to a laminated biaxially stretched polyamide film suitable for various packaging applications, which is effective in preventing bag breakage, etc., and can maintain its strength sufficiently even when the film thickness is reduced.

  Conventionally, unstretched films and stretched films made of aliphatic polyamides typified by nylon 6 and nylon 66 are excellent in impact resistance and bending fatigue resistance, and are widely used as various packaging material films.

  In addition, in order to further improve flexural fatigue resistance and impact resistance for liquid-filled packaging such as soups and seasonings, various elastomers (rubber components) are mixed with aliphatic polyamide in a single layer configuration to make them more flexible. Stretched polyamide films for pinholes are widely used.

  Among the above pinhole-resistant films, a film in which a polyolefin-based elastomer is mixed with an aliphatic polyamide is known (for example, see Patent Document 1). This film has good bending fatigue resistance and impact resistance at room temperature, but the bending fatigue resistance and impact resistance become poor in a low temperature environment, and pinholes are likely to occur due to bending fatigue during product transportation. There is a problem. If a pinhole occurs in the packaging material of a product, it may cause contamination due to leakage of the content, decay of the content, generation of mold, etc., leading to a decrease in product value.

  A film in which a polyamide-based elastomer is mixed with an aliphatic polyamide is known (see, for example, Patent Document 2). This film has good bending fatigue resistance and impact resistance under a low temperature environment, and pinholes are hardly generated due to bending fatigue even under a low temperature environment.

  However, in the film of this structure, when the film thickness is thin, in addition to the contact with the projections, the pinhole is likely to penetrate due to the impact on the bag surface, and the bag is resistant to breakage due to insufficient film strength and slipperiness. Tend to decrease. Therefore, in a water-filled packaging bag having a thin film configuration, pinholes due to friction and puncture, compression, and breakage due to impact are likely to occur.

  Furthermore, the thickness of the polyethylene resin layer for heat sealing is increased for the purpose of improving the handleability at the time of bag making and improving the workability at the time of filling the contents into the bag. In addition, a bag-made product having a polyamide film / polyethylene resin configuration in which a harder polyethylene resin is selected has been proposed (see Patent Document 3). However, in this bag-made product, the pinhole is easily opened because the bag-made product is stiff. Therefore, the polyamide-type film used for these requires further pinhole resistance.

  Thus, as a degree of correspondence to the expanded required characteristics in the current pinhole resistant polyamide film, the polyolefin elastomer mixed polyamide film is inferior in bending fatigue resistance and impact strength in a low temperature environment, Polyamide-based elastomer-mixed polyamide-based films tend to have good bending fatigue resistance and impact strength even in low-temperature environments, but the thin film structure satisfies satisfactory bag breaking strength, impact strength, puncture strength, and pinhole resistance. There was a problem that sex could not be achieved.

JP-A-56-147847 JP-A-11-254615 JP-A-10-218204

  The present invention was devised in view of the problems of such a conventional pinhole-resistant polyamide film, and its purpose is to break the bag, impact resistance, puncture resistance, and bending fatigue resistance, In particular, it has excellent bending fatigue resistance under low-temperature environments, and when used as a packaging material for food packaging, etc., it has excellent effects such as bag breakage prevention during transportation and storage of products. An object of the present invention is to provide a laminated biaxially stretched polyamide film suitable for a water-filled packaging bag such as a sauce.

  That is, the present invention relates to an A comprising a mixed polymer of 97 to 70% by weight of an aliphatic polyamide polymer, 3 to 20% by weight of an aliphatic copolymer polyamide polymer, and optionally 0.5 to 10% by weight of a thermoplastic elastomer. A layer B comprising a mixed polymer of 99.5 to 90% by weight of an aliphatic polyamide polymer and 0.5 to 10.0% by weight of a thermoplastic elastomer is laminated on at least one surface of the layer. Is a laminated biaxially stretched polyamide film.

In a preferred embodiment of the laminated biaxially stretched polyamide film of the present invention, the film has the following features (1) to (9).
(1) The thermoplastic elastomer constituting the A layer is at least one elastomer selected from the group consisting of polyamide elastomers, polyolefin elastomers, and ionomer polymers.
(2) The total thickness of the film is 9-25 μm.
(3) The thickness of the A layer is 70 to 93% of the total thickness of the A layer and the B layer, and the thickness of the B layer is 1 μm or more.
(4) Even with the film configuration as in (2) or (3) above, the impact strength is 0.7 J or more, the piercing strength is 10 N or more, and the number of flex fatigue pinholes at 5 ° C. is 5. The breaking strength is 45 N / 15 mm or more.
(5) Inorganic fine particles having a pore volume of 0.6 to 1.0 ml with respect to the B layer 0.005 to 1.0% by weight and inorganic fine particles having a pore volume of 1.1 to 1.6 ml 01 to 0.5% by weight is added, and the average particle size of the inorganic fine particles is 0.5 to 5.0 μm.
(6) The polyamide polymer constituting the A layer and / or the B layer contains 0.01 to 0.40% by weight of fatty acid amide and / or fatty acid bisamide.
(7) When the above configuration (5) or (6) is adopted, the static friction coefficient at 23 ° C. and 65% RH is 0.90 or less.
(8) The mixed polymer constituting the layer A contains 0.01 to 0.1% by weight of an antioxidant.
(9) The laminated biaxially stretched polyamide film is used as a packaging material with the B layer as the outermost layer.

  The laminated biaxially stretched polyamide film of the present invention is softened by the A layer containing an aliphatic copolymer polyamide polymer in the aliphatic polyamide polymer, and troubles such as breakage are unlikely to occur even at a high stretch ratio. It is possible to improve the breaking strength of the film, and further contribute to the expression of impact resistance, puncture resistance and bending fatigue resistance by dispersing thermoplastic elastomer as a pinhole resistant material, especially in low temperature environment Gives bending fatigue resistance. In addition, the B layer made of a mixed polymer of an aliphatic polyamide polymer and a thermoplastic elastomer has excellent flex pinhole resistance, and excellent slipperiness and transparency by adding inorganic particles with a defined pore volume High impact strength, puncture resistance, and bending fatigue resistance due to the synergistic effect of each characteristic, which contributes to the development of wear resistance and bag breakage prevention by receiving friction and bending impacts on packaging bags. Performance, wear resistance, and bag breakage prevention.

  Due to the above characteristics, when used as packaging materials for food packaging, liquid packaging, etc., it is pierced by impact, vibration, friction, bending fatigue, friction fatigue during transportation, especially during low temperature transportation and storage. It is effective in preventing bag breakage due to the bag, and also in preventing bag breakage even when the bag-made product is dropped during transportation and storage. Furthermore, blocking and slipping failure at the time of bag making and filling of the product into the bag-made product can be prevented, stable workability can be given, and it can be effectively used as various packaging materials. In particular, the laminated biaxially stretched polyamide-based film of the present invention can have characteristics that function effectively as a bag packaged product even when a thinned structure of less than 15 μm is required.

Hereinafter, the laminated biaxially stretched polyamide film of the present invention will be described in detail.
The laminated biaxially stretched polyamide film of the present invention is configured by laminating a B layer made of a specific mixed polymer on at least one surface of an A layer made of a specific mixed polymer.

  The A layer of the present invention comprises a mixed polymer of 97 to 70% by weight of an aliphatic polyamide polymer, 3 to 20% by weight of an aliphatic copolymerized polyamide polymer, and optionally 0.5 to 10% by weight of a thermoplastic elastomer. . The layer A has a structure in which an aliphatic copolymer polyamide polymer is finely dispersed as a flexibility imparting agent and a toughness imparting agent in an aliphatic polyamide polymer excellent in impact resistance and bending fatigue resistance. Contributes to improved impact strength, puncture resistance, and bending fatigue resistance, and has a structure in which thermoplastic elastomer as a pinhole material is dispersed, further improving bending fatigue resistance, especially It contributes to improvement of bending fatigue resistance under low temperature environment. Here, when the amount of the aliphatic copolymer polyamide polymer constituting the layer A is less than 3% by weight, if the amount of the thermoplastic elastomer is small, it is highly required to exceed the existing pinhole-resistant stretched polyamide film. Impact resistance, puncture resistance, and bending fatigue resistance cannot be obtained. On the other hand, when the mixing amount exceeds 20% by weight, impact strength, puncture resistance, and bending fatigue resistance are saturated. Furthermore, when the amount of the thermoplastic elastomer mixed is increased, an effect of improving the bending fatigue resistance can be obtained. However, when the amount exceeds 10% by weight, the transparency becomes poor and the bending fatigue resistance is saturated.

  The aliphatic polyamide polymer constituting the A layer of the present invention is not particularly limited as long as it can be used as a film molding material and is suitable for forming the above structure. For example, an aliphatic polyamide homopolymer such as nylon 6, nylon 6,6, nylon 11, nylon 12, nylon 6,10 or the like can be used.

  As the aliphatic copolymer polyamide polymer mixed in the A layer, a monomer copolymerizable with the above aliphatic polyamide homopolymer is 10% by weight or less, preferably 1 to 10% by weight of copolymer, for example, Representative of aliphatic copolymer polyamide polymers such as nylon 6/6/6 copolymer, nylon 6/12 copolymer, nylon 6/6/10 copolymer, nylon 6/6/6/10 copolymer, etc. A small amount of aromatics, which are mainly composed of aliphatic polyamides, or ε-caprolactam, and copolymerized with nylon salts of hexamethylenediamine and isophthalic acid or nylon salts of metaxylylenediamine and adipic acid. Polyamide copolymers containing can be used.

  The thermoplastic elastomer mixed in the A layer is a thermoplastic material as a substance having rubber-like elasticity, and is not particularly limited as long as it is suitable for forming the above structure. Examples thereof include polyamide elastomers, polyolefin elastomers, polystyrene elastomers, polyurethane elastomers, polyester elastomers, polyvinyl chloride elastomers, ionomer polymers, and the like, and mixtures of these elastomers. A thermoplastic elastomer can be used individually or in combination of 2 or more types.

  In the present invention, the thermoplastic elastomer may be modified as long as the object of the present invention is not impaired. For example, the modified body of the thermoplastic elastomer illustrated above may be used. Examples of the modification in the thermoplastic elastomer include modification by copolymerization or graft modification, modification by imparting a polar group, and the like. The application of the polar group may be performed by graft modification. Examples of such a polar group include an epoxy group, a carboxyl group, an acid anhydride group, a hydroxyl group, an amino group, and an oxo group. A polar group can be provided by one kind or a combination of plural kinds. Accordingly, the modified products to which polar groups have been added include, for example, epoxy-modified products, carboxy-modified products, acid anhydride-modified products, hydroxy-modified products, and amino-modified products of thermoplastic elastomers.

  As the thermoplastic elastomer of the present invention, polyamide elastomers, polyolefin elastomers and ionomer polymers can be suitably used.

  Examples of the polyamide-based elastomer include a polyamide-based block copolymer composed of a hard segment composed of a polyamide component and a soft segment composed of a polyoxyalkylene glycol component. The hard segment polyamide component is a group consisting of (1) lactam, (2) ω-amino aliphatic carboxylic acid, (3) aliphatic diamine and aliphatic dicarboxylic acid, or (4) aliphatic diamine and aromatic dicarboxylic acid. Specific examples include lactams such as ε-caprolactam, aliphatic diamines such as aminoheptanoic acid, aliphatic dicarboxylic acids such as adipic acid, and aromatic dicarboxylic acids such as terephthalic acid. Examples of the polyoxyalkylene glycol constituting the soft segment of the polyamide-based block copolymer include polyoxytetramethylene glycol, polyoxyethylene glycol, polyoxy-1,2-propylene glycol and the like.

  The melting point of the polyamide-based block copolymer is determined by the kind and ratio of the hard segment composed of the polyamide component and the soft segment composed of the polyoxyalkylene glycol component, but is usually in the range of 120 ° C to 180 ° C. Things are used.

  By using a polyamide block copolymer as a component of a laminated biaxially stretched polyamide film, it is effective in improving the bending fatigue resistance of the laminated biaxially stretched polyamide film, particularly in a low temperature environment. is there.

  The polyolefin elastomer is not particularly limited, and examples thereof include a block copolymer having a polyolefin as a hard segment and various rubber components as a soft segment. Examples of the polyolefin constituting the hard segment include ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene and 1-dodecene. , 1-tetradecene, 1-hexadecene, 1-octadecene, and the like, homopolymers or copolymers such as α-olefins having about 2 to 20 carbon atoms. Polyolefins can be used alone or in combination of two or more. Preferred olefins include ethylene and propylene. Examples of the rubber component constituting the soft segment include ethylene-propylene rubber (EPR), ethylene-propylene-diene rubber (EPDM), polybutadiene, polyisoprene, natural rubber (NR), nitrile rubber (NBR; acrylonitrile). Butadiene rubber), styrene-butadiene rubber (SBR), chloroprene rubber (CR), butyl rubber (IIR), hydrogenated NBR (H-NBR), acrylonitrile-isoprene rubber (NIR), acrylonitrile-isoprene-butadiene rubber (NBIR), etc. Is mentioned. These rubber components include, for example, acid-modified rubbers such as carboxylated rubber containing unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and maleic anhydride as comonomers, other modified rubbers, and hydrogenated products. Etc. are also included. These rubber components can be used alone or in combination of two or more.

The ionomer polymer is not particularly limited, and includes a block copolymer formed by using polyolefin as a hard segment, various rubber components acid-modified with an unsaturated carboxylic acid as a soft segment, and further neutralized with metal ions. Can be mentioned. As a preferable ionomer polymer, a copolymer resin composed of ethylene and methacrylic acid or a copolymer resin composed of ethylene, methacrylic acid and an acrylate ester is neutralized with a metal ion containing Na ⁺ , K ⁺ and Zn ^2+. The ionomer polymer which is formed is mentioned.

  The mixed polymer constituting the A layer may be a mixture of the above-mentioned aliphatic polyamide polymer of the virgin raw material and the aliphatic copolymer polyamide polymer and, if desired, a thermoplastic elastomer. It may be prepared by adding a non-standard film generated when producing a laminated biaxially stretched polyamide film, a scrap material generated as a cut end material (ear trim), and its recycled resin and virgin raw material.

  The mixed polymer constituting the A layer preferably contains 0.01 to 0.1% by weight of an antioxidant. When the content of the antioxidant exceeds the above range, whitening due to precipitation on the surface of the laminated biaxially stretched polyamide film, adhesion failure at the time of laminating with polyethylene or polypropylene sealant, and below the above range When a recovered / recycled raw material such as scrap material and regenerated resin is used as the mixed polymer of the A layer, a film forming operability may be deteriorated due to thermal deterioration of the recovered / recycled raw material.

  As the antioxidant, a phenolic antioxidant is preferable. The phenolic antioxidant is preferably a completely hindered phenolic compound or a partially hindered phenolic compound. For example, tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, stearyl-β- (3,5-di-t-butyl-4-hydroxy Phenyl) propionate, 3,9-bis [1,1-dimethyl-2- [β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8,10- And tetraoxaspiro [5,5] undecane.

  By including the phenolic antioxidant in the mixed polymer of the A layer, film forming operability of the laminated biaxially stretched polyamide film is improved. In particular, in a recovered / recycled raw material mixing system using scrap film, recycled resin, etc., heat deterioration is likely to occur due to recovery and regeneration of the thermoplastic elastomer, resulting in poor film production due to this, resulting in decreased operating efficiency. There is a tendency to increase production costs due to an increase in production costs and an increase in raw material costs for maintaining operability due to a decrease in the amount of recovered recycled materials used. In contrast, the antioxidant is contained in the mixed polymer of the A layer of the polyamide biaxially stretched film containing the recovered and recycled raw materials, thereby suppressing thermal degradation of various polymers including thermoplastic elastomers. And realizes stable film forming operability. For this reason, according to the present invention, it is possible to reduce the production cost by improving the operability and reducing the raw material cost by increasing the amount of the recovered recycled raw material.

  The B layer of the present invention comprises a mixed polymer of 99.5 to 90% by weight of an aliphatic polyamide polymer and 0.5 to 10% by weight of a thermoplastic elastomer. Such a B layer has excellent bending-resistant pinhole properties, receives the impact of bending applied to the packaging bag, and contributes to the expression of bag breaking prevention. If the content of the thermoplastic elastomer is within the above range, the bending fatigue resistance can be improved while maintaining good transparency.

  As the aliphatic polyamide polymer and thermoplastic elastomer constituting the B layer, the above-described aliphatic polyamide polymer and thermoplastic elastomer of the A layer can be used in the same manner.

  The laminated biaxially stretched polyamide film of the present invention in which the B layer configured as described above is laminated on at least one surface (for example, one side or both sides) of the A layer configured as described above, Even if the total thickness is less than 15 μm, even 9 to 15 μm, especially 10 to 14 μm, the impact strength is 0.7 J or more, the piercing strength is 10 N or more, and bending fatigue at 5 ° C. The number of pinholes can be 5 or less, and the breaking strength can be 45 N / 15 mm or more. The laminated biaxially stretched polyamide film of the present invention preferably has a haze of 6% or less. If the haze exceeds 6%, the transparency is not sufficiently improved, and it becomes difficult to use in applications where transparency is required. More preferably, it is 5% or less, More preferably, it is 4% or less. The haze value is preferably as small as possible, but may be 1% or more. Even if it is 2% or more, it can be said to be a preferable range.

  The laminated biaxially stretched polyamide film of the present invention is composed of inorganic fine particles having a pore volume of 0.6 to 1.0 ml and inorganic fine particles having a pore volume of 1.1 to 1.6 ml with respect to layer B. Thus, it is preferable to add inorganic fine particles having two or more kinds of pore volumes. The range of the pore volume of the inorganic fine particles is preferably 0.5 to 2.0 ml / g, more preferably 0.8 to 1.5 ml / g. If the pore volume is less than 0.5 ml / g, voids are likely to occur and the transparency of the film deteriorates. If the pore volume exceeds 2.0 ml / g, the slipperiness of the film deteriorates, It is not preferable. By using inorganic fine particles having two or more kinds of pore volumes in this way, transparency and excellent slipperiness are maintained even in high humidity environments, receiving friction and bending impacts on the packaging bag, and wear resistance. This can contribute to the development of safety and bag-breaking prevention properties.

  The inorganic fine particles can be appropriately selected from inorganic lubricants such as silica, kaolin, and zeolite, and polymer organic lubricants such as acrylic and polystyrene. From the viewpoint of transparency and slipperiness, it is preferable to use silica fine particles.

  The average particle diameter of the inorganic fine particles is preferably 0.5 to 5.0 μm, more preferably 1.0 to 3.0 μm. If the average particle diameter is less than 0.5 μm, a large amount of addition is required to obtain good slipperiness, and if it exceeds 5.0 μm, the surface roughness of the film becomes too large to satisfy practical properties. Therefore, it is not preferable.

  The pore volume means the pore volume (ml / g) contained per gram of inorganic fine particles. Such silica fine particles are generally obtained by pulverizing and classifying synthetic silica, but it is also possible to use porous silica fine particles obtained directly as spherical fine particles at the time of synthesis. Such silica fine particles are aggregates formed by agglomerating primary particles, and the gap between the primary particles and the primary particles forms pores.

  The pore volume can be adjusted by changing the synthesis conditions of the inorganic fine particles. The smaller the pore volume, the better the slipperiness can be given with a small amount of addition. When inorganic fine particles having a small pore volume are used, high protrusions are formed on the film surface in the stretching step of the blended polyamide resin, but many voids are generated, and the transparency of the film may be impaired. On the other hand, when inorganic fine particles having a large pore volume are used, a large amount can be added while maintaining transparency. However, the height of the surface protrusions to be formed is low, and it is necessary to add a large amount of inorganic fine particles in order to maintain suitable slipperiness even under high humidity conditions. Therefore, when the above-mentioned two or more types of inorganic fine particles are added to the B layer, high surface protrusions and low surface protrusions coexist while maintaining transparency, and excellent slipperiness in a high humidity environment can be obtained. Can do. The transparency of the biaxially stretched film varies depending on the stretching conditions (temperature and magnification) or the subsequent relaxation treatment conditions (relaxation rate and temperature), and it is desirable to appropriately control these conditions.

  As a method of adding the inorganic fine particles to the B layer, it is added at the time of polymerization of the resin or at the time of melt extrusion with an extruder to form a master batch, and this master batch is added to the polyamide polymer at the time of film production and used. It can carry out by the well-known method.

  The average particle size of the inorganic fine particles is a value measured as follows. After dispersing inorganic fine particles in ion-exchanged water stirred at a predetermined rotational speed (about 5000 rpm) using a high-speed stirrer, and adding the dispersion to isotone (saline), further dispersing with an ultrasonic disperser, The particle size distribution was determined by the call counter method, and the particle size at 50% of the weight cumulative distribution was calculated as the average particle size.

  The content of the inorganic fine particles in the B layer is 0.03 to 2.5% by weight, more preferably 0.08 to 1.5% by weight. If the content of the inorganic fine particles is less than the above range, the slipperiness of the biaxially stretched film under high humidity is not sufficiently improved, and if the content exceeds the above range, the amount of loss in the extraction process increases. In addition, the transparency of the film is unacceptably deteriorated. Further, inorganic fine particles having a pore volume of 0.6 to 1.0 ml and inorganic fine particles having a pore volume of 1.1 to 1.6 ml are respectively 0.005 to 0.5% by weight, 0% in the B layer. It is preferable to contain 0.01 to 2.0 weight%.

  In addition to the above essential components, the laminated biaxially stretched polyamide-based film of the present invention has various other additives within a range not impairing the above-described properties, such as a lubricant, an anti-blocking agent, a thermal stabilizer, an antioxidant, It is also possible to contain an antistatic agent, a light resistance agent, an impact resistance improvement agent and the like. In particular, it is preferable to add an organic lubricant having an effect of lowering the surface energy to such an extent that no problem occurs in adhesiveness and wettability, because the stretched film can be further improved in slipperiness and transparency.

  In the present invention, a fatty acid amide and / or a fatty acid bisamide can be contained in the polyamide polymer constituting the A layer and / or the B layer for the purpose of imparting slipperiness. Examples of the fatty acid amide and / or fatty acid bisamide include erucic acid amide, stearic acid amide, ethylene bis stearic acid amide, ethylene bis oleic acid amide and the like.

  In this case, the content of fatty acid amide and / or fatty acid bisamide in the polyamide polymer is preferably 0.01 to 0.40% by weight, more preferably 0.05 to 0.2% by weight. If the content of fatty acid amide and / or fatty acid bisamide is less than the above range, the slipperiness is poor, and the processing suitability in printing or laminating becomes poor. Spots may be produced, which is undesirable in terms of quality.

  The laminated biaxially stretched polyamide film of the present invention contains inorganic fine particles in the B layer as described above, or contains a fatty acid amide and / or a fatty acid bisamide in the polyamide polymer constituting the A layer and / or the B layer. Thus, a static friction coefficient at 23 ° C. and 65% RH of 0.90 or less can be achieved.

  The total thickness of the laminated biaxially stretched polyamide film of the present invention is not particularly limited, but when used as a packaging material, it is usually 100 μm or less, and generally has a thickness of 5 to 50 μm. . However, the laminated biaxially stretched polyamide-based film of the present invention is characterized in that it exhibits the above-described effects even when it has a thin film structure as described above.

  When the laminated biaxially stretched polyamide-based film of the present invention is processed into a packaging material (bag-made product), it is preferable to have a laminate configuration in which the B layer surface is the outermost surface of the bag-made product. If friction with the transport packaging such as corrugated cardboard occurs during the transportation of bag-made products, the friction causes the film to scrape and break the bag, or pierce by contact between the bags, increasing bending fatigue and breaking the bag. . In the configuration of the present invention, the B layer having good slipperiness reduces the bag breaking factor due to friction, and exhibits high bag breaking prevention performance.

  In this case, when the thickness of the B layer occupies a considerable portion of the total thickness of the film, high slipperiness is ensured, but transparency is greatly reduced. On the other hand, when the thickness of the A layer almost occupies the total thickness of the film, although the flexibility, impact strength, puncture resistance, and bending fatigue resistance are excellent, slipping and wear resistance cannot be ensured. Therefore, in the present invention, the thickness of the A layer is preferably 70 to 93%, particularly 80 to 93% of the total thickness of the A layer and the B layer. In addition, when the thickness of the B layer is at least 1 μm or more, preferably 3 μm or less, it is possible to effectively express both bending fatigue resistance and wear resistance.

  There are no particular restrictions on the method of mixing the various polyamide polymers constituting the A layer and the B layer, the thermoplastic elastomer, etc. Usually, a chip-shaped polymer is mixed using a V-type blender and then melted. A molding method is used.

  For the polyamide polymer constituting the A layer and the B layer of the laminated biaxially stretched polyamide film of the present invention, other thermoplastic resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6- Polyester polymers such as naphthalate, polyolefin polymers such as polyethylene and polypropylene, and the like may be contained within a range that does not impair the characteristics.

  Further, various additives such as an antistatic agent, an antifogging agent, an ultraviolet absorber, a dye, and a pigment are contained in one or both of the A layer and / or the B layer made of a polyamide polymer as necessary. be able to.

  The laminated biaxially stretched polyamide film of the present invention can be produced by a known production method. For example, the polymer constituting each layer is melted by using a separate extruder and manufactured by coextrusion from one die, and the polymer constituting each layer is separately melt-extruded into a film and then laminated. Arbitrary well-known methods, such as the method of laminating and the method of combining these, can be adopted. Examples of the stretching method include a flat sequential biaxial stretching method, a flat simultaneous axial stretching method, and a tubular method. Using a known method, the film is stretched 2 to 5 times in the longitudinal direction and 3 to 6 times in the transverse direction, and heat-fixed as necessary. Thus, the transparency, oxygen gas barrier properties and processability of the laminated film can be improved.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to a following example. The film was evaluated by the following measurement method.

(1) Impact strength A film impact tester manufactured by Toyo Seiki Seisakusho was used, and the measurement was performed in an environment of a temperature of 23 ° C and a relative humidity of 65%.

(2) Number of bending fatigue pinholes Using a gelbo flex tester manufactured by Rigaku Corporation, the number of bending fatigue pinholes was measured by the following method.
After applying a polyester adhesive to the film produced in the example, a 40 μm-thick linear low-density polyethylene film (L-LDPE film: L4102, manufactured by Toyobo Co., Ltd.) is dry-laminated for 3 days in an environment of 40 ° C. Aging was performed to obtain a laminated film. The obtained laminate film is cut into 12 inches × 8 inches and formed into a cylindrical shape with a diameter of 3.5 inches. One end of the cylindrical film is on the fixed head side of the gelboflex tester and the other end is on the movable head side. The initial gripping interval was 7 inches. The first 3.5 inches of stroke gives a twist of 440 degrees, and then 2.5 inches, bending fatigue that completes the whole stroke by linear horizontal movement is performed 500 times at a speed of 40 times / min. The number of pinholes that occurred was counted. The measurement was performed in an environment of 5 ° C. The L-LDPE film side of the test film was placed on the filter paper (Advantech, No. 50) with the L-LDPE film side as the bottom surface, and the four corners were fixed with cello tape (registered trademark). Ink (pilot ink (product number INK-350-blue) diluted 5 times with pure water) was applied onto a test film and spread over one surface using a rubber roller. After wiping off unnecessary ink, the test film was removed, and the number of ink spots on the filter paper was counted.

(3) Puncture strength Measured in accordance with “2. Strength test method” of “Standards for Foods, Additives, etc. 3: Equipment and Containers and Packaging” (Ministry of Health and Welfare Notification No. 20 of 1982) in the Food Sanitation Law did. A needle having a tip diameter of 0.7 mm was pierced into the film at a piercing speed of 50 mm / min, and the strength when the needle penetrated the film was measured to obtain the piercing strength. The measurement is performed at room temperature (23 ° C.), and the unit is [N].

(4) Haze A direct reading haze meter manufactured by Toyo Seiki Seisakusho Co., Ltd. was used and measured according to JIS-K-7105.
Haze (%) = [Td (diffuse transmittance%) / Tt (total light transmittance%)] × 100

(5) Coefficient of static friction The coefficient of static friction between the film smooth surfaces was measured in an environment of 23 ° C. and 65% RH in accordance with JIS-K-7125.

(6) Breaking strength A film to be measured was cut into a strip of 180 mm × 15 mm in the flow direction (MD direction) and the width direction (TD direction), and used as a test piece. Using a tensile tester (manufactured by Shimadzu Corporation, Autograph (trade name) model name AG-5000A), the tensile breaking strength was measured in each of the MD and TD directions under the conditions of a tensile speed of 200 mm / min and a chuck distance of 100 mm. Measurement was performed, and the average value in the MD direction and the TD direction was used as data.

Example 1
An unstretched sheet having the following constitution was obtained using a two-type, three-layer coextrusion T-die facility. In the configuration of B layer / A layer, the total thickness of the unstretched sheet is 160 μm, and the thickness ratio of the A layer to the total thickness is 88%.
Composition constituting layer A: 87 parts by weight of nylon 6 (manufactured by Toyobo Co., Ltd., T814), 10 parts by weight of an aliphatic copolymer polyamide polymer composed of nylon 6 and nylon 12 (7034B by Ube Industries, Ltd.), and nylon It consists of 3.0 parts by weight of a polyamide-based elastomer (PEBAX 4033SN01, manufactured by Arkema Co., Ltd.) having 12 as a polyamide component, and further contains 0.1 parts by weight of a phenolic antioxidant (manufactured by Ciba Specialty Chemicals, Irganox 1010). A mixed polymer composition.
Composition constituting layer B: Nylon 6 (T814, Toyobo Co., Ltd.) 96.85 parts by weight, polyamide elastomer (Arkema, PEBAX4033SN01) 3.0 parts by weight, pore volume 0.6-1.0 ml A polymer composition comprising 0.08 parts by weight of silica particles, 0.5 parts by weight of silica particles having a pore volume of 1.1 to 1.6 ml, and 0.15 parts by weight of fatty acid amide.

  The obtained unstretched sheet was stretched 3.4 times in the longitudinal direction and then stretched 4.0 times in the transverse direction to produce a biaxially stretched film having a thickness of 12 μm. A corona discharge treatment was performed on the surface of the B layer on the side to be dry laminated with a density polyethylene film (L-LDPE film: L4102, manufactured by Toyobo Co., Ltd.). The obtained biaxially stretched film was measured for haze, coefficient of static friction, breaking strength, impact strength, piercing strength, and bending fatigue pinhole number. The results are shown in Table 1 together with the details of the layer structure.

(Examples 2-6 and Comparative Examples 1-2)
A biaxially stretched film was obtained in the same manner as in Example 1 except that the layer configuration was changed as shown in Table 1. The obtained biaxially stretched film was measured for haze, coefficient of static friction, breaking strength, impact strength, piercing strength, and bending fatigue pinhole number. The results are shown in Table 1 together with the details of the layer structure.

  The laminated biaxially stretched polyamide film of the present invention has been described based on a plurality of examples. However, the present invention is not limited to the configurations described in the above examples, and the configurations described in the respective examples. The configuration can be changed as appropriate without departing from the spirit of the invention, for example, by appropriately combining them.

  The laminated biaxially stretched polyamide film of the present invention has characteristics such as impact resistance, puncture resistance, bending fatigue resistance, and abrasion resistance, and is particularly excellent in packaging materials such as food packaging. It can use suitably for a use. In particular, when a thinned configuration is required, it can be used extremely beneficially.

Claims (10)

A laminated biaxially oriented polyamide film for packaging material having a total thickness of 9 μm or more and less than 15 μm, comprising 97 to 70% by weight of aliphatic polyamide polymer, 3 to 20% by weight of aliphatic copolymer polyamide polymer, and heat On at least one surface of the layer A composed of a mixed polymer of 0.5 to 10% by weight of a plastic elastomer, 99.5 to 90% by weight of an aliphatic polyamide polymer and 0.5 to 10.0% by weight of a thermoplastic elastomer A laminated biaxially stretched polyamide film for packaging material , wherein a B layer made of a mixed polymer is laminated and the B layer is used as the outermost layer of the packaging material . The laminated biaxially stretched polyamide-based film for packaging material according to claim 1, wherein the laminated constitution is a two-layer constitution of A layer / B layer . The laminated biaxially stretched polyamide-based film for packaging material according to claim 1, wherein the laminated constitution is a three-layer constitution of B layer / A layer / B layer . The packaging according to any one of claims 1 to 3, wherein the thermoplastic elastomer constituting the A layer is at least one elastomer selected from the group consisting of polyamide elastomers, polyolefin elastomers, and ionomer polymers. A laminated biaxially oriented polyamide film for materials . The laminated biaxially stretched polyamide-based film for packaging material according to any one of claims 1 to 4, wherein the B layer has a total thickness of 1 µm to 3 µm . Impact strength of not less than 0.7 J, piercing strength of not less than 10 N, the bending fatigue number of pins holes 5 ° C. is 5 or less, according to claim 1, breaking strength, characterized in that at 45N / 15 mm or more The laminated biaxially stretched polyamide film for packaging material according to any one of -5 . 0.005 to 0.5% by weight of inorganic fine particles having a pore volume of 0.6 to 1.0 ml with respect to the B layer and 0.01 to 2 of inorganic fine particles having a pore volume of 1.1 to 1.6 ml The laminated biaxially stretched polyamide-based film for packaging materials according to any one of claims 1 to 6 , wherein 0.0% by weight is added and the average particle size of the inorganic fine particles is 0.5 to 5.0 µm. . The packaging according to any one of claims 1 to 7 , wherein the polyamide polymer constituting the A layer and / or the B layer contains 0.01 to 0.40% by weight of fatty acid amide and / or fatty acid bisamide. A laminated biaxially oriented polyamide film for materials . The laminated biaxially stretched polyamide film for packaging materials according to claim 7 or 8 , wherein the static friction coefficient at 23 ° C and 65% RH is 0.90 or less. The laminated biaxially stretched polyamide-based film for packaging materials according to any one of claims 1 to 9 , wherein the mixed polymer constituting the A layer contains 0.01 to 0.1 wt% of an antioxidant. .