JP5326559B2 - Polyamide-based laminated biaxially stretched film - Google Patents

Description

  The present invention is excellent in oxygen gas barrier properties, impact resistance, and bending fatigue resistance, and when used as a packaging material for food packaging, the contents are prevented from being altered and the contents are protected from vibration and impact during transportation of the product. The present invention relates to a polyamide-based laminated biaxially stretched film suitable for various packaging applications.

  Conventionally, a film made of a polyamide polymer containing xylylenediamine as a constituent component has characteristics such as excellent oxygen gas barrier properties and heat resistance and strong film strength as compared with films made of other polymer components.

  However, when this film is used for a packaging material that requires resistance to bending fatigue, there is a problem that pinholes are likely to occur due to bending processes during processing of vacuum packaging and the like and during transportation of goods. It was. 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.

  On the other hand, 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 materials.

  This film has excellent film properties such as impact resistance and bending fatigue resistance, but has a problem of poor oxygen gas barrier properties.

  Furthermore, in order to solve these problems, a method has been proposed in which a polyamide polymer containing xylylenediamine and an aliphatic polyamide are melt-extruded with separate extruders, laminated, and biaxially stretched. (For example, see Patent Documents 1 to 4).

  However, the techniques described in these patent documents are also not satisfactory in terms of having both good product preservation and protection against impact and bending during transportation. In the method of Patent Document 2, in order to obtain a film satisfying good oxygen gas barrier properties and bending fatigue resistance, a large amount of polyamide polymer containing xylylenediamine must be used, and packaging and distribution costs are reduced. It was not a desirable method when reduction was required. Patent Document 3 discloses a gas barrier property and a bending fatigue resistance in which a resin layer made of an aliphatic polyamide and a bending fatigue resistance improver is laminated on at least one side of a gas barrier resin layer made of a polyamide mainly composed of xylylenediamine. Although a film satisfying the properties is disclosed, it is described that the ratio of the gas barrier resin layer must be 40% or more in order to satisfy the gas barrier properties. The present inventors evaluated the bending fatigue resistance under severe conditions using the film of Patent Document 3, but they were not satisfied. Patent Document 4 discloses a bag breakage prevention property and a bending fatigue resistance in which a resin layer made of a mixed polyamide of an aliphatic polyamide and a semi-aromatic polyamide is laminated on at least one surface of a resin layer made of an aliphatic polyamide and a thermoplastic elastomer. Although compatible films have been disclosed, a gas barrier film having bending fatigue resistance could not be obtained using this method. In addition, there is a concern in the method described in the above patent document in terms of preventing the deterioration of contents against vibration, impact, friction, etc. during transportation of packaging materials, which is particularly important in the form of food distribution today. It remained.

The present inventors have previously solved the above-mentioned various problems and proposed a useful polyamide-based laminated biaxially stretched film (Japanese Patent Application No. 2007-278468). However, when a long film having a width of 1000 mm or more is to be produced industrially in large quantities, there remains a concern for obtaining a film having stable physical properties over the entire width of the film.
JP-A-6-255054 Japanese Patent Laid-Open No. 2003-11307 JP 2001-341253 A JP 2006-205711 A

  The present invention solves the problems of the above-mentioned conventional polyamide-based laminated biaxially stretched films, is excellent in oxygen gas barrier properties, impact resistance and bending fatigue resistance, which are film quality required as a packaging film, and various packaging Polyamides suitable for packaging applications that prevent deterioration and discoloration of the contents when used as a material, and also prevent product breakage due to vibration and shock during transportation and protect the quality of the contents It aims at providing a system lamination biaxially stretched film industrially stably.

In order to achieve the above object, the following configuration is adopted in the present invention.
1. Metaxylylene having metaxylylenediamine or mixed xylylenediamine composed of metaxylylenediamine and paraxylylenediamine as the main diamine component and an α, ω-aliphatic dicarboxylic acid component having 6 to 12 carbon atoms as the main dicarboxylic acid component A slit roll having a length of 50 m or more formed by laminating a resin layer (B layer) mainly composed of an aliphatic polyamide resin on at least one surface of a resin layer (A layer) mainly composed of a group-containing polyamide polymer. A polyamide-based laminated biaxially stretched film, which is the difference between the refractive index in the direction that forms an angle of 45 degrees with the winding direction of the film and the refractive index in the direction that forms an angle of 135 degrees with the winding direction. Is from 0.003 to 0.013, and satisfies the following requirements (1) to (4):
(1) Whether the proportion of the metaxylylene group-containing polyamide polymer in the resin layer (A layer) containing the metaxylylene group-containing polyamide polymer as a main component is 99% by weight or more and a thermoplastic elastomer is not added Or less than 1% by weight;
(2) A laminate film of the polyamide-based laminated biaxially stretched film and a polyethylene film having a thickness of 40 μm is subjected to 40 cycles per minute using a gelboflex tester in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50%. The number of pinholes in the case of performing 2000 cycles of bending test continuously at a speed is 10 or less;
(3) The oxygen permeability at a temperature of 23 ° C. and a relative humidity of 65% is 150 ml / m ² · MPa · day or less;
(4) In a film having a length of 800 mm in the width direction of the film, Δnz, which is a difference in refractive index nz in the thickness direction of the film at both end portions in the width direction, is in the range of 0.0001 to 0.0020.
2. The polyamide-based laminated biaxially stretched film according to the first aspect, wherein the polyamide-based laminated biaxially stretched film satisfies the following formula (I):
Pa <1 / [t (0.015x + 0.15)] (I)
(Where x is the content (% by weight) of the metaxylylene group-containing polyamide polymer in the film, Pa is the oxygen permeability (ml / m ² · MPa · day) of the film at a temperature of 23 ° C. and a relative humidity of 65%, t Indicates the thickness (mm) of the film.)
3. A thermoplastic elastomer is added to the resin layer (B layer) containing the aliphatic polyamide resin as a main component so as to have a mixing ratio of 0.5 wt% or more and 8.0 wt% or less. The polyamide-based laminated biaxially stretched film according to the first or second aspect.
4). The polyamide-based laminated biaxially stretched film according to any one of the first to third aspects, wherein the thickness of the A layer is 10% to 30% of the total thickness of the A layer and the B layer.
5. The polyamide-based laminated biaxially stretched film according to any one of the first to fourth aspects, wherein the film has a thickness of 8 to 50 µm.

  The polyamide-based laminated biaxially stretched film of the present invention has excellent oxygen gas barrier properties and good impact resistance and bending fatigue resistance, and is effective in preventing deterioration and discoloration of contents in food packaging and the like. Furthermore, the contents can be protected from bending fatigue due to impact or vibration during transportation, and can be effectively used as various packaging materials.

  Hereinafter, the polyamide-based laminated biaxially stretched film of the present invention will be described in detail.

  The A layer of the polyamide-based laminated biaxially stretched film of the present invention has metaxylylenediamine or mixed xylylenediamine composed of metaxylylenediamine and paraxylylenediamine as a main diamine component, α having 6 to 12 carbon atoms, The main component is a metaxylylene group-containing polyamide polymer having ω-aliphatic dicarboxylic acid as a main dicarboxylic acid component. When mixed xylylenediamine is used as the diamine component, the paraxylylenediamine is preferably 30 mol% or less in the total xylylenediamine, and the structural unit composed of xylylenediamine and an aliphatic dicarboxylic acid is It is preferably at least 70 mol% or more in the molecular chain.

  Examples of the metaxylylene group-containing polyamide polymer include, for example, polymetaxylylene adipamide, polymetaxylylene pimeramide, polymetaxylylene veramide, polymetaxylylene azelamide, polymetaxylylene sebamide, polymetaxylylene decane Homopolymers such as diamide, and metaxylylene / paraxylylene adipamide copolymer, metaxylylene / paraxylylene pimeramide copolymer, metaxylylene / paraxylylene veramide copolymer, metaxylylene / paraxylylene One of the components of azeramide copolymer, metaxylylene / paraxylylene sebacamide copolymer, metaxylylene / paraxylylene decanediamide copolymer, etc., and homopolymers or copolymers thereof. Such as hexamethylenediamine Aliphatic diamines, cycloaliphatic diamines such as piperazine, aromatic diamines such as para-bis- (2-aminoethyl) benzene, aromatic dicarboxylic acids such as terephthalic acid, lactams such as ε-caprolactam, and aminoheptanoic acids and a copolymer obtained by copolymerizing an aromatic aminocarboxylic acid such as ω-aminocarboxylic acid and para-aminomethylbenzoic acid.

  The B layer of the polyamide-based laminated biaxially stretched film of the present invention contains an aliphatic polyamide resin as a main component. Examples of the aliphatic polyamide resin include nylon 6 using ε-caprolactam as a main raw material. Examples of other aliphatic polyamide resins include polyamide resins obtained by polycondensation of lactams having three or more members, ω-amino acids, dibasic acids and diamines. Specific examples of lactams include enantolactam, capryllactam, and lauryllactam in addition to the above-described ε-caprolactam, and examples of ω-amino acids include 6-aminocaproic acid, 7-amino. Examples include heptanoic acid, 9-aminononanoic acid, and 11-aminoundecanoic acid. Examples of dibasic acids include adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecadioic acid, hexadecadioic acid, eicosandioic acid, eicosadienedioic acid, 2 2,4-trimethyladipic acid. Furthermore, as diamines, ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, pentamethylenediamine, undecamethylenediamine, 2,2,4 (or 2,4,4) -trimethylhexamethylenediamine, cyclohexane Examples thereof include diamine and bis- (4,4′-aminocyclohexyl) methane. Also, it contains a small amount of aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, xylylene dicarboxylic acid, or a small amount of aromatic diamine such as metaxylylene diamine. it can. Polymers obtained by polycondensation of these or copolymers thereof, such as nylon 6, 7, 11, 12, 6.6, 6.9, 6.11, 6.12, 6T, 6I, MXD6 (Metaxylene dipanamid 6), 6 / 6.6, 6/12, 6 / 6T, 6 / 6I, 6 / MXD6, and the like can be used. In addition, when the polyamide-based laminated biaxially stretched film of the present invention is manufactured, the above polyamide resins can be used alone or in admixture of two or more.

  Of the above aliphatic polyamide resins, those having a relative viscosity in the range of 2.0 to 3.5 are particularly preferred in the present invention. The relative viscosity of the polyamide-based resin affects the toughness and spreadability of the resulting biaxially stretched film. If the relative viscosity is less than 2.0, the impact strength tends to be insufficient. This is because, if it exceeds 3.5, the biaxial stretchability tends to deteriorate with increasing stretching stress. In addition, the relative viscosity in this invention means the value at the time of measuring at 25 degreeC using the solution which melt | dissolved 0.5g of polymers in 50 ml of 97.5% sulfuric acid.

  The polyamide-based laminated biaxially stretched film of the present invention comprises A / B (two types and two layers), B / A / B (two types and three layers), or B / A / C (three types and three layers, aliphatic polyamide resin). It is preferable from the viewpoint of curling that the B layer and the C layer as the main components are different resin layers, and a B / A / B configuration having a symmetrical layer configuration is particularly preferable. In the following description, among the layers constituting the laminated film, the layer that is not located on the outermost side and is made of a resin mainly composed of a metaxylylene group-containing polyamide polymer (that is, B / A / B, Or A layer in the case of a B / A / C layer structure), and a thin layer in the case of a two-type two-layer structure (that is, A in the case of an A / B layer structure of a thick B layer and a thin A layer) Layer) is called the core layer. In addition, the outermost layer (that is, the B / C layer in the case of the B / A / B or B / A / C layer structure) and the two-kind / two-layer structure mainly composed of an aliphatic polyamide resin The thick layer (that is, the B layer in the case of the A / B layer structure of the thick B layer and the thin A layer) is called a skin layer.

  As for the thickness ratio of each layer of the polyamide-based laminated biaxially stretched film, the lower limit of the thickness ratio of the A layer is preferably 10% or more, more preferably 15% or more, and particularly preferably 18% or more. The upper limit of the thickness ratio of the A layer is preferably 30% or less, more preferably 25% or less, and particularly preferably 23% or less. The lower limit of the thickness ratio of the B layer or the B layer and the C layer is preferably more than 70%, more preferably more than 75%, and particularly preferably more than 77%. The upper limit of the thickness ratio of the B layer or the B layer and the C layer is preferably less than 90%, more preferably less than 85%, and particularly preferably less than 82%. In the case of the B / A / B configuration of two types and three layers, the thickness ratio of the B layer of the surface layer means the sum of the thickness ratios of both surface layers, and in the case of the B / A / C configuration of the three types and three layers, the surface layer The thickness ratio of the B layer and the C layer means the sum of the thickness ratios of both surface layers. If the thickness ratio of the A layer exceeds 30%, the bending fatigue resistance tends to deteriorate and pinholes tend to increase, such being undesirable. On the other hand, if the thickness ratio of the A layer is less than 10%, the gas barrier property tends to deteriorate, which is not preferable.

  Moreover, as resin which forms a skin layer, an aliphatic polyamide resin is made into a main component, and a thermoplastic elastomer can be added as needed. The lower limit of the amount of the thermoplastic elastomer added to the aliphatic polyamide resin is preferably 0.5% by weight or more, more preferably 1.0% by weight or more, and 2.0% by weight or more. Is particularly preferred. The upper limit is preferably 8.0% by weight or less, more preferably 7.0% by weight or less, and particularly preferably 6.0% by weight or less. When the added amount of the thermoplastic elastomer is less than 0.5% by weight, the effect of improving the bending fatigue resistance may not be obtained. On the other hand, if the amount of the thermoplastic elastomer added exceeds 8.0% by weight, it may not be suitable for packaging applications such as foods that require high transparency (haze). Furthermore, the resin forming the skin layer can be filled with a resin other than thermoplastic elastomer and aliphatic polyamide resin, if necessary, and can be filled with a lubricant, an anti-blocking agent, a thermal stabilizer, an oxidation agent. It is also possible to fill with an inhibitor, an antistatic agent, a light resistance agent, an impact resistance improver and the like.

  Examples of the thermoplastic elastomer used in the present invention include polyamides such as blocks or random copolymers of polyamide resins such as nylon 6 and nylon 12 and PTMG (polytetramethylene glycol) and PEG (polyethylene glycol). -Based elastomers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, copolymers of ethylene and butene, polyolefin elastomers such as copolymers of styrene and butadiene, and olefin resins such as ethylene ionomers These ionomers can be suitably used.

  On the other hand, the resin forming the core layer needs to contain a metaxylylene-containing polyamide polymer. In particular, it is preferable to contain 100% by weight of a metaxylylene-containing polyamide polymer. If necessary, other resins such as polyamide resins and thermoplastic elastomers can be mixed. However, when a resin other than the metaxylylene-containing polyamide polymer is mixed in the resin forming the core layer, it contains metaxylylene. It is necessary to obtain a good gas barrier property by setting the content ratio of the polyamide polymer to 99% by weight or more and the content ratio of the other resin to less than 1% by weight. In particular, when a thermoplastic elastomer is mixed, the content ratio needs to be less than 1% by weight. In this way, a skin layer mainly composed of a relatively soft aliphatic polyamide resin is provided outside the core layer mainly composed of a hard metaxylylene-containing polyamide polymer, and the skin layer is filled with a thermoplastic elastomer. By doing so, it is possible to exhibit a good gas barrier property due to the metaxylylene-containing polyamide polymer and at the same time to exhibit a good bending fatigue resistance improving effect due to the thermoplastic elastomer and the polyamide-based resin.

  The resin forming the core layer can be filled with a lubricant, an anti-blocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent, an impact resistance improving agent, and the like as necessary. .

  The polyamide-based laminated biaxially stretched film of the present invention is a laminate film laminated with a polyethylene film having a thickness of 40 μm, in an atmosphere of a temperature of 23 ° C. and a relative humidity of 50%, using a gelbo flex tester in the following manner. It is preferable that the number of pinholes when the bending test of 2000 cycles is continuously performed at a rate of 40 cycles per minute is 10 or less. Of course, 0 is most preferable.

The outline of the method for measuring the number of pinholes is as follows. A film that has been laminated to a polyolefin film or the like and cut to a predetermined size (20.3 cm × 27.9 cm) is conditioned at a predetermined temperature for a predetermined time, and then the rectangular test film is wound around. A cylindrical shape of a predetermined length is used. Then, both ends of the cylindrical film are fixed to the outer periphery of the disk-shaped fixed head and the outer periphery of the disk-shaped movable head of the gelboflex tester, respectively, and the movable heads are parallel to the direction of the fixed head. Rotate a predetermined angle (440 °) while approaching a predetermined length (7.6 cm) along the axis, and then proceed straight ahead for a predetermined length (6.4 cm) without rotating, then reverse their movements A one-cycle bending test in which the movable head is returned to the initial position by being executed in the direction is continuously repeated for a predetermined cycle (2000 cycles) at a predetermined speed (40 cycles per minute). Thereafter, the number of pinholes generated in a predetermined range (497 cm ² ) excluding the fixed head of the tested film and the portion fixed to the outer periphery of the movable head is measured.

  When the number of pinholes is in the above-mentioned range, the polyamide-based laminated biaxially stretched film of the present invention has a bag breakage or a minute hole due to vibration or impact when transporting a gas barrier packaging material using the film. The effect of preventing leakage of contents and deterioration of quality due to can be expressed effectively. The number of pinholes is more preferably 8 or less, and the number of pinholes is particularly preferably 6 or less.

  As means for reducing the number of pinholes in the polyamide-based laminated biaxially stretched film of the present invention to 10 or less, the resin layer (A layer) containing a metaxylylene group-containing polyamide polymer as a main component is made as thin as possible, This can be achieved by appropriately including a thermoplastic elastomer in the resin layer (B layer) containing a main group polyamide resin as a main component.

The polyamide-based laminated biaxially stretched film of the present invention preferably has an oxygen permeability of 150 ml / m ² · MPa · day or less at a temperature of 23 ° C. and a relative humidity of 65%.

When the oxygen permeability is in the above range, the polyamide-based laminated biaxially stretched film of the present invention is effective in preventing deterioration of the quality of the contents when the gas barrier packaging material using the film is stored for a long period of time. Can be expressed. The oxygen permeability is more preferable if 130ml ^/ m 2 · MPa · day or less, particularly preferably as long 110ml ^/ m 2 · MPa · day or less. The lower limit of the oxygen permeability in the present invention is substantially about 60 ml / m ² · MPa · day from the limit of gas barrier properties of the metaxylylene group-containing polyamide polymer itself.

As a means for reducing the oxygen permeability of the polyamide-based laminated biaxially stretched film of the present invention to 150 ml / m ² · MPa · day or less, as described above, a resin layer containing a metaxylylene group-containing polyamide polymer as a main component ( This can be achieved by increasing the proportion of the metaxylylene group-containing polyamide polymer in layer A) as much as possible and adjusting the thickness ratio of layer A as appropriate within a range of 10 to 30% of the total film thickness.

The polyamide-based laminated biaxially stretched film of the present invention is x (wt%) representing the content of the metaxylylene group-containing polyamide polymer in the film, t (mm) representing the thickness of the film, and Pa (ml representing oxygen permeability). / M ² · MPa · day) preferably satisfies the relationship of the following formula (I) in order to satisfy gas barrier properties, pinhole resistance, and laminate adhesion at a high level. By satisfying the relationship of the formula (I), it is possible to obtain an economically excellent film having a high gas barrier property with a small MXD6 content in the film and having a small decrease in bending fatigue resistance.
Pa <1 / [t (0.015x + 0.15)] (I)
X is preferably in the range of 5 to 50 (% by weight), and t is preferably in the range of 0.008 to 0.050 (mm) (8 to 50 μm).

  When a resin with a high gas barrier property such as a metaxylylene group-containing polyamide polymer is mixed with another resin with a relatively low gas barrier property such as an aliphatic polyamide resin, two types of resins are dispersed and homogenized. As it progresses, it works to inhibit the formation of an effective gas barrier structure. As the mixing ratio increases and the degree of mixing and homogenization increases, the gas barrier property tends to decrease. In addition, when the gas barrier resin single layer and the other resin single layer are laminated in a state where they are not completely mixed, the laminated film has the best gas barrier property. In this case, in reality, a minute fluctuation occurs at the interface between the two types of resin layers, and the gas barrier property may slightly decrease.

  The present inventors have found that a polyamide-based laminated film satisfying the relationship of formula (I) effectively exhibits gas barrier properties at a small amount of gas barrier resin. That is, in the polyamide-based resin laminated biaxially stretched film of the present invention that satisfies the relationship of the formula (I), a thin layer of the metaxylylene group-containing polyamide expresses an effective gas barrier property and also maintains flexibility. Less impact resistance.

  If the relationship of formula (I) is not satisfied, for example, the content of the metaxylylene group-containing polyamide polymer must be increased in order to compensate for the decrease in gas barrier properties, and if the content of the metaxylylene group-containing polyamide polymer is increased, pin resistance In order to compensate for the decrease in pinhole resistance due to poor hole properties, the amount of thermoplastic elastomer added must be increased.

  As a means for satisfying the relationship of the formula (I), melt extrusion, in which other resin is not contained in the layer A mainly composed of a metaxylylene group-containing polyamide polymer or the ratio of the other resin is minimized. This can be achieved by means such as adjusting the blending method and kneading conditions so that resins of different times do not mix as much as possible.

  The object of the present invention is to preserve the contents of packaging materials using polyamide film and to protect against impact, bending and vibration during transportation. This is realized by using a film.

  The polyamide-based laminated biaxially stretched film of the present invention has excellent elastic recovery in normal temperature and low temperature environments, excellent properties such as impact resistance and bending fatigue resistance, and good suitability for printing and laminating. Yes, it is a laminated biaxially stretched film suitable as various packaging materials.

  The thickness of the polyamide-based laminated biaxially stretched film of the present invention is not particularly limited, but when used as a packaging material, a thickness of 8 to 50 μm is generally preferable, and a thickness of 10 to 30 μm is more preferable.

  The polyamide-based laminated biaxially stretched film of the present invention is formed by a sequential biaxial stretching method in which roll / tenter stretching is combined. In general, it is known that in the formation of a polyamide film by a sequential biaxial stretching method, distortion of the orientation main axis called bowing occurs. As a result, the center portion of the (so-called mill roll) film once produced in a wide width has little bowing, but the bowing becomes larger toward the end portion. When manufacturing a narrow film, the difference in physical properties due to this bowing is not so much of a problem, but when manufacturing a long film with a width of 1000 mm or more, it is slitted because of this large bowing. Various physical property differences occur between both end portions of the film of the roll, which causes problems in practical use of the film. As a result of investigating the cause of variation in oxygen permeability between both ends of the film, the present inventors have found that there is a difference in nz which is the refractive index in the film thickness direction. By minimizing, a biaxially stretched film with little variation in oxygen permeability was obtained at both ends of a large bowed film.

  The polyamide-based laminated biaxially stretched film of the present invention has a width direction Δnab (that is, an angle of 45 degrees with respect to the winding direction of the wound film) of the film once slit from the mill roll once manufactured to a wide width. The absolute value of the difference between the refractive index in the forming direction and the refractive index in the direction forming an angle of 135 degrees with the winding direction) is limited to 0.003 or more and 0.013 or less. That is, in a film where Δnab is less than 0.003, no physical property difference occurs due to the distortion in the width direction described above. Further, in a film having a large distortion such that Δnab exceeds 0.013, it is difficult to adjust Δnz so as to satisfy the requirements of the present invention. Here, Δnab uses the maximum value among the values of Δnab at both ends of a film having a length in the width direction of 800 mm.

  The polyamide-based laminated biaxially stretched film of the present invention is a film in which Δnab is 0.003 or more and 0.013 or less. It is necessary that Δnz, which is the difference in rate nz, is in the range of 0.0001 to 0.0020. Δnz is preferably 0.0015 or less, and most preferably 0.0010 or less. When Δnz exceeds 0.0020, the oxygen permeability of the film is not stably expressed. Further, the lower limit of Δnz is 0.0001 or more from the limit of measurement.

  It is industrially useful that the width of the slit roll of the polyamide-based laminated biaxially stretched film of the present invention is 800 mm or more.

  The polyamide-based laminated biaxially stretched film of the present invention can be produced by the following production method.

  The raw resin is melt-extruded from two extruders by a co-extrusion method, merged by a feed block, extruded from a T-die into a film shape, supplied onto a cooling roll, cooled, and B layer / A layer / B layer 2 An unstretched sheet having a seed three-layer structure is obtained. At that time, the resin melting temperature in each extruder is arbitrarily selected within the range of the melting point of the resin constituting each layer + 10 ° C. to 50 ° C. In the case of an A layer made of a metaxylylene group-containing polyamide polymer, from the point of uniformity of film thickness and prevention of deterioration of the resin, a B layer made of an aliphatic polyamide resin in the range of 245 to 290 ° C., preferably 255 to 280 ° C. In the case of, the range of 230-280 ° C, preferably 250 ° C-270 ° C is preferred.

  In addition, a well-known method can be applied to rapidly cool an unstretched sheet while the sheet-like melt is brought into close contact with the rotary cooling drum. For example, a method using an air knife or an electrostatic charge is applied to the sheet-like melt. A method of imprinting is preferably applicable. In those methods, the latter is preferably used.

  As a method for cooling the air surface of the sheet-like material, a known method can be applied. For example, a method in which the cooling liquid in the tank is brought into contact with the sheet surface, and a liquid evaporated by a spray nozzle is applied to the sheet air surface. You may use together the method of apply | coating, and the method of spraying and cooling a high-speed fluid. The unstretched sheet thus obtained is stretched in the biaxial direction to obtain a film.

  In the present invention, when an unstretched sheet having a laminated structure is formed into a film by a sequential biaxial stretching method, the stretched film is stretched so that the value of Δnz is minimized, but is stretched by the following method. Is preferred. That is, by stretching the molecular orientation in the plane direction in a well-balanced manner on the surface of the polyamide resin layer after biaxial stretching, even if bowing distortion occurs, the physical property difference between the end and the center can be minimized. The technical idea is that (1) in order to prevent excessive orientation of the polyamide resin layer during stretching in the longitudinal direction, crystallization during preheating is suppressed, stretching is performed in multiple stages, and orientation by one stretching is reduced. (2) In order to make the molecular orientation of the polyamide resin layer by stretching in the longitudinal direction uniform in the width direction, the necking is suppressed and the high-temperature flow stretching is performed. It turns out that it can be obtained by combining, and can be achieved by various different processes and conditions.

  In order to obtain a film having a suitable Δnz range of the polyamide-based resin laminated biaxially stretched film of the present invention, for example, the film can be formed by the following stretching method.

  In the case of stretching in the longitudinal direction, first, the unstretched sheet is preheated by three or more continuous heating rolls. At this time, the temperature of the first stage preheating roll is set to 1 to 8 ° C. higher than the glass transition temperature (TgB) of the polyamide resin of the B layer (for example, 51 to 58 ° C.). The temperature of the second stage preheating roll is in the range of + 3 ° C. to −3 ° C. (for example, 62 to 68 ° C.) centering on the intermediate temperature between the glass transition temperature (TgA) and TgB of the A-layer metaxylylene group-containing polyamide resin, The temperature of the 3rd stage preheating roll shall be TgA-8 degreeC-TgA-3 degreeC (for example, 72-77 degreeC). Next, the preheated unstretched sheet is stretched by the rotation speed ratio of the two rolls. At this time, it is preferable to stretch in two stages. The first stage stretching temperature is preferably in the range of TgA to TgA + 30 ° C. (for example, 80 to 110 ° C.), and the stretching ratio is preferably in the range of 1.7 to 2.1 times. The second stage stretching temperature is preferably lower than TgA, higher than TgB (for example, 50 to 70 ° C.), and the stretching ratio is preferably in the range of 1.4 to 1.8 times. The total of the draw ratios in the longitudinal direction is preferably 2.8 to 3.5 times. If the total draw ratio is less than 2.8 times, the film thickness unevenness and flatness deteriorate, and if it exceeds 3.5 times, the haze increases or the film breaks during the subsequent stretching in the width direction. Since the frequency increases, it is not preferable.

  In the case of stretching in the width direction, the stretching temperature needs to be 80 to 210 ° C, preferably 100 to 200 ° C. If the stretching temperature in the width direction is less than 80 ° C., the film tends to break, which is not preferable. Moreover, when it exceeds 210 degreeC, since the uneven thickness of the obtained film worsens, it is not preferable. The draw ratio in the width direction is 3.0 to 5.0 times, preferably 3.5 to 4.5 times. When the draw ratio in the width direction is less than 3.0 times, the thickness unevenness of the obtained film is deteriorated, which is not preferable. If the draw ratio in the width direction exceeds 5.0 times, the frequency of breaking increases in the drawing, which is not preferable.

  Subsequently, heat setting is performed. The temperature in the heat setting treatment step is preferably 180 ° C. or higher and 230 ° C. If the temperature of the heat setting treatment is less than 180 ° C., the planarity and dimensional stability are not sufficient, which is not preferable. If the temperature of the heat setting treatment exceeds 230 ° C., the impact resistance is not sufficient, which is not preferable.

  It is effective to control the heat shrinkage rate by narrowing the guide rail of the gripping tool by the heat setting process and performing the relaxation process. The temperature for the relaxation treatment can be selected in the range from the heat setting treatment temperature to the Tg of the resin, and preferably the heat setting treatment temperature is -10 ° C to Tg + 10 ° C. The width relaxation rate is preferably 1 to 10%. If it is less than 1%, there is no effect, and if it exceeds 10%, the flatness of the film deteriorates or the film flutters in the tenter, which is not preferable.

  In addition, the polyamide-based laminated biaxially stretched film of the present invention includes a lubricant, an anti-blocking agent, a thermal stabilizer, an antioxidant, an antistatic agent, a light-proofing agent, and an impact resistance-improving agent as long as the properties are not impaired. It is also possible to contain various additives such as. In particular, it is preferable to contain various inorganic particles for the purpose of improving the slipperiness of the biaxially stretched film. Moreover, it is preferable to add an organic lubricant such as ethylenebisstearic acid that exhibits the effect of reducing the surface energy because the slipping property of the film constituting the film roll becomes excellent.

  Furthermore, the polyamide-based laminated biaxially stretched film of the present invention can be subjected to heat treatment or humidity control treatment in order to improve dimensional stability depending on the application. In addition, in order to improve the adhesion of the film surface, corona treatment, coating treatment, flame treatment, etc., and processing such as printing, vapor deposition and the like can be performed.

  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.

[Relative viscosity (RV)]
0.25 g of a sample was dissolved in 25 ml of 96% sulfuric acid, 10 ml of this solution was used, the number of seconds dropped at 20 ° C. was measured with an Ostwald viscosity tube, and the relative viscosity was calculated from the following formula.
RV = t / t0
However, t0: The number of seconds for dropping the solvent, t: The number of seconds for dropping the sample solution.

[Δnab]
After leaving the test piece of the film in an atmosphere of 23 ° C. and 65% RH for 2 hours or more, using an “Abbe refractometer 4T type” manufactured by Atago Co., Ltd. The refractive index (na) in the direction that forms an angle and the refractive index (nb) in the direction that forms an angle of 135 degrees with the winding direction of the wound film were measured. Then, the absolute value of the difference between the two refractive indexes was calculated as Δnab. The test pieces were taken out from a slit roll film having a length of 50 m in the winding direction, and 10 films taken at 800 mm length in the width direction of the film at intervals of 5 m were measured at both ends in the film width direction. Each sample was taken from a position within 50 mm from the edge, each Δnab was measured, and the average value of the values of Δnab at both end edges was averaged for the ten films collected, which was Δnab of the present invention.

[Δnz]
After the film specimen was left for 2 hours or more in an atmosphere of 23 ° C. and 65% RH, the refractive index (nz) in the thickness direction of the film was measured using an “Abbe refractometer 4T type” manufactured by Atago Co., Ltd. did. And the absolute value of the difference of nz of a film both-ends edge was computed as (DELTA) nz. The test pieces were taken out from a slit roll film having a length of 50 m in the winding direction, and 10 films taken at 800 mm length in the width direction of the film at intervals of 5 m were measured at both ends in the film width direction. Each sample was taken from a position within 50 mm from the edge, each refractive index (nz) was measured, and Δnz was calculated. The average value of Δnz of the collected 10 films was used as Δnz of the present invention.

[Oxygen permeability (gas barrier property)]
The film was subjected to oxygen substitution for 2 days in an atmosphere of humidity 65% RH and temperature 23 ° C., and then an oxygen permeability measuring device (OX-TRAN) according to JIS-K-7126 (Method B). 2/20: manufactured by MOCOM).

[Oxygen permeability variation]
About the film produced in the Example, a total of 10 test pieces for oxygen permeability were collected at equal intervals from the full width of the 800 mm wide film roll, and the atmosphere was a humidity of 65% RH and a temperature of 23 ° C. for 2 days. After oxygen substitution, the oxygen permeability was measured using an oxygen permeability measuring device (OX-TRAN 2/20: manufactured by MOCOM) according to JIS-K-7126 (Method B). Of the obtained oxygen permeability values, the difference between the maximum value and the minimum value (Δ oxygen permeability) was determined. The evaluation method is as follows, and it was determined that there was no practical problem if it was ○ or more.
○: [Δ oxygen permeability] ≦ 10 (ml / m ² · MPa · day)
Δ: 10 <[Δ oxygen permeability] ≦ 20 (ml / m ² · MPa · day)
×: [Δ oxygen permeability]> 20 (ml / m ² · MPa · day)

[Production of laminate film]
The film produced in the example was further slit into a slit roll having a width of 400 mm, and a polyester two-component adhesive (manufactured by Toyo Morton Co., Ltd., TM590 / CAT56 = 13/2 (parts by weight)) was applied in an amount of 3 g / m. After coating at ² , a linear low density polyethylene film (L-LDPE film: L6102 manufactured by Toyobo Co., Ltd.) having a thickness of 40 μm was dry-laminated and aged for 3 days in a 40 ° C. environment to obtain a laminated film.

[Pinhole resistance]
The laminate film was cut into a size of 20.3 cm (8 inches) × 27.9 cm (11 inches), and the rectangular test film (laminate film) after the cutting was subjected to a condition of a temperature of 23 ° C. and a relative humidity of 50%. Below, it was conditioned for more than 24 hours. Thereafter, the rectangular test film is wound to form a cylindrical shape having a length of 20.32 cm (8 inches). Then, one end of the cylindrical film is fixed to the outer periphery of a disk-shaped fixing head of a gelbo flex tester (manufactured by Rigaku Kogyo Co., Ltd., NO.901 type) (conforming to the standard of MIL-B-131C). The other end of the tester was fixed to the outer periphery of a tester disk-shaped movable head opposed to the fixed head by 17.8 cm (7 inches) apart. Then, the movable head is rotated 440 ° while approaching the fixed head in the direction of 7.6 cm (3.5 inches) along the axis of both heads opposed in parallel, and then 6.4 cm (without rotation) 2.5-inch) A one-cycle bending test in which the movement is performed in the reverse direction and the movable head is returned to the initial position is performed continuously for 2000 cycles at a rate of 40 cycles per minute. Repeated. Thereafter, the cylindrical test sample is removed from the head, and the fixed portion of the rectangular film with the bonded portion cut open and the portion fixed to the outer periphery of the movable head are removed. 17.8 cm (7 inches) × 27.9 cm (11 inches) The number of pinholes generated in the inner portion was measured by the following method (that is, the number of pinholes per 497 cm ² (77 square inches) was measured). 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.

[Storage stability test]
(A) Production of packaging bag Using the laminate film, a linear low-density polyethylene film side was superposed on the inside to produce a three-side sealed bag having an inner dimension of 15 cm in width and 19 cm in length.
(B) Preparation of Coloring Solution To 2000 parts by weight of water, 7 parts by weight of agar and 0.04 parts by weight of methylene blue were added and dissolved in 95 ° C. hot water. Furthermore, 1.2 parts by weight of hydrosulfite (Na ₂ S ₂ O ₄ ) was added and mixed under a nitrogen atmosphere to obtain a colorless solution.
(C) In a nitrogen atmosphere, put 250 ml of the colored solution prepared in (b) above into the three-side sealed bag prepared in (a) above, seal the top of the bag while venting the gas in the bag, The inner dimensions were 15 cm wide and 15 cm long.
(D) The obtained bag is allowed to stand at room temperature for 3 hours, and after agar is hardened, it is stored under conditions of 40 ° C. and 90% humidity, and the coloration state of the methylene blue agar solution in the bag after 2 weeks is confirmed. Observed. The evaluation method is as follows, and if it is more than ○, it was regarded as practically no problem.
◎: No discoloration ○: Very slightly discolored blue △: Discolored slightly blue ×: Discolored blue

[Vibration durability test]
Using the methylene blue color-packed packaging bag prepared in the above (a) to (d), a shaking test was performed by the following method. Twenty packaging bags to be used for the test were put in a cardboard box, placed in a shaking test apparatus, and shaken for 24 hours at 23 ° C. in a horizontal direction with a stroke width of 5 cm and a shaking frequency of 120 times / minute. . Subsequently, it preserve | saved on the conditions of 40 degreeC and humidity 90%, and the color development state of the methylene blue agar solution in the bag after 3 days was observed. The evaluation method is as follows, and if it is more than ○, it was regarded as practically no problem.
◎: No discoloration ○: Very slightly discolored blue △: Discolored slightly blue ×: Discolored blue

[Example 1]
An unstretched sheet having the following constitution was obtained using a two-type, three-layer coextrusion T-die facility. In the constitution of B layer / A layer / B layer, the total thickness of the unstretched sheet is 190 μm, and the thickness ratio of each layer to the total thickness is B layer / A layer / B layer = 40% / 20% / 40%, A The extrusion resin temperature of the layer is 270 ° C., and the extrusion resin temperature of the B layer is 260 ° C. Composition constituting layer A: A composition comprising polymetaxylylene adipamide (Mitsubishi Gas Chemical Co., Ltd., RV = 2.65) = 100 wt%. Composition constituting layer B: Nylon 6 (Toyobo Co., Ltd., RV = 2.8) is 95% by weight and a polyamide elastomer (nylon 12 / polytetramethylene glycol copolymer, Arkema Co., Ltd.) as a thermoplastic elastomer. A composition comprising 5% by weight of Pebax 4033, RV = 2.0).

  The obtained unstretched sheet is introduced into a roll stretching machine, the first stage preheating temperature is 55 ° C., the second stage preheating temperature is 65 ° C., the third stage preheating temperature is 75 ° C., and the first stage stretching. Stretching in the machine direction at a temperature of 95 ° C, a stretching ratio of 1.9 times, a second stage stretching temperature of 65 ° C, a stretching ratio of 1.7 times (total stretching ratio of 3.2 times), and then a tenter The film was stretched 3.7 times in the transverse direction at a stretching temperature of 120 ° C. Further, the film was heat-fixed at a temperature of 215 ° C. and subjected to a thermal relaxation treatment of 5% to prepare a biaxially stretched film having a thickness of 15 μm. Further, after removing both ears with a trimmer, a corona discharge treatment was performed on the surface of layer B on the side of dry lamination with a linear low density polyethylene film (L-LDPE film: Toyobo Co., Ltd., L6102) having a thickness of 40 μm. A mill roll having a width of about 4000 mm was obtained. A slit roll having a width of 800 mm was collected from one end of the mill roll. The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Example 2]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer B: Composition comprising 98% by weight of nylon 6 and 2% by weight of polyamide-based elastomer.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Example 3]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer B: A composition comprising 99% by weight of nylon 6 and 1% by weight of polyamide elastomer.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Example 4]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer B: Composition comprising 98% by weight of nylon 6 and 2% by weight of polyamide-based elastomer.
The thickness ratio of each layer to the total thickness is B layer / A layer / B layer = 41% / 18% / 41%.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Example 5]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer B: a composition comprising 97% by weight of nylon 6 and 3% by weight of polyamide elastomer.
The ratio of the thickness of each layer to the total thickness is B layer / A layer / B layer = 39% / 22% / 39%.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Example 6]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
The thickness ratio of each layer to the total thickness is B layer / A layer / B layer = 43% / 14% / 43%.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Example 7]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer B: Composition comprising 98% by weight of nylon 6 and 2% by weight of polyamide-based elastomer.
The thickness ratio of each layer to the total thickness is B layer / A layer / B layer = 36% / 28% / 36%.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Example 8]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer B: A composition comprising 99% by weight of nylon 6 and 1% by weight of polyamide elastomer.
The thickness ratio of each layer to the total thickness is B layer / A layer / B layer = 43% / 14% / 43%.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Example 9]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer B: A composition comprising 93% by weight of nylon 6 and 7% by weight of polyamide elastomer.
The thickness ratio of each layer to the total thickness is B layer / A layer / B layer = 36% / 28% / 36%.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Example 10]
Of the approximately 4000 mm wide mill roll of the biaxially stretched film obtained in Example 1, the 800 mm wide slit roll was removed from the end on one side, and an 800 mm wide slit roll was further collected inside.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Comparative Example 1]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer B: Composition comprising 100% by weight of nylon 6.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Comparative Example 2]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
The thickness ratio of each layer to the total thickness is B layer / A layer / B layer = 30% / 40% / 30%.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Comparative Example 3]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer A: a composition comprising 80% by weight of polymetaxylylene adipamide and 20% by weight of nylon 6.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Comparative Example 4]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer A: a composition comprising 80% by weight of polymetaxylylene adipamide and 20% by weight of nylon 6.
The thickness ratio of each layer to the total thickness is B layer / A layer / B layer = 20% / 60% / 20%.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Comparative Example 5]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer A: a composition comprising 80% by weight of polymetaxylylene adipamide and 20% by weight of nylon 6.
The thickness ratio of each layer to the total thickness is B layer / A layer / B layer = 30% / 40% / 30%.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Comparative Example 6]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer A: A composition comprising 90% by weight of polymetaxylylene adipamide and 10% by weight of polyamide elastomer.
Composition constituting layer B: Composition comprising 100% by weight of nylon 6.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Comparative Example 7]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer A: A composition comprising 90% by weight of polymetaxylylene adipamide and 10% by weight of nylon 6.
Composition constituting layer B: A composition comprising 93% by weight of nylon 6 and 7% by weight of polyamide elastomer.
The thickness ratio of each layer to the total thickness is B layer / A layer / B layer = 15% / 70% / 15%.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Comparative Example 8]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer A: A composition comprising 96% by weight of nylon 6 and 4% by weight of polyamide elastomer.
Composition constituting layer B: a composition comprising 97% by weight of nylon 6 and 3% by weight of polymetaxylylene adipamide.
The thickness ratio of each layer to the total thickness is B layer / A layer / B layer = 15% / 70% / 15%.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Comparative Example 9]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the following changes were made in the description of Example 1.
Composition constituting layer A: A composition comprising 96% by weight of nylon 6 and 4% by weight of polyamide elastomer.
Composition constituting layer B: a composition comprising 90% by weight of polymetaxylylene adipamide and 10% by weight of nylon 6.
The thickness ratio of each layer to the total thickness is B layer / A layer / B layer = 15% / 70% / 15%.

  The obtained biaxially stretched film was measured for oxygen permeability and the number of pinholes. Moreover, the storage stability of the packaging bag produced from the obtained film and the vibration durability test were done. The results are shown in Table 1.

[Comparative Example 10]
An unstretched film having the same composition and the same layer structure as in Example 1 was biaxially stretched by the following method to obtain a film. The film was stretched 3.2 times in the machine direction at a preheating and stretching temperature of 85 ° C., and then stretched 3.7 times in the transverse direction at a preheating and stretching temperature of 120 ° C. by a tenter. Further, the film was heat-fixed at a temperature of 215 ° C. and subjected to a thermal relaxation treatment of 5% to prepare a biaxially stretched film having a thickness of 15 μm. Further, after removing both ears with a trimmer, a linear low density polyethylene film (L-LDPE film: L6102 manufactured by Toyobo Co., Ltd., 40 μm) was subjected to a corona discharge treatment on the B layer surface on the dry laminate side. A mill roll having a width of 4000 mm was obtained. A slit roll having a width of 800 mm was collected from one end of the mill roll.

  The obtained biaxially stretched film was measured for oxygen permeability, pinhole number, and peel strength. Moreover, the packaging bag produced from the obtained film was tested for storage stability, vibration durability, and bag breaking resistance. The results are shown in Table 1.

  The polyamide-based laminated biaxially stretched film of the present invention has excellent oxygen gas barrier properties and good impact resistance and bending fatigue resistance, and is effective in preventing deterioration and discoloration of contents in food packaging and the like. Furthermore, the contents can be protected from bending fatigue due to impact or vibration during transportation, and can be effectively used as various packaging materials.

Claims (5)

Metaxylylene having metaxylylenediamine or mixed xylylenediamine composed of metaxylylenediamine and paraxylylenediamine as the main diamine component and an α, ω-aliphatic dicarboxylic acid component having 6 to 12 carbon atoms as the main dicarboxylic acid component A slit roll having a length of 50 m or more formed by laminating a resin layer (B layer) mainly composed of an aliphatic polyamide resin on at least one surface of a resin layer (A layer) mainly composed of a group-containing polyamide polymer. A polyamide-based laminated biaxially stretched film, which is the difference between the refractive index in the direction that forms an angle of 45 degrees with the winding direction of the film and the refractive index in the direction that forms an angle of 135 degrees with the winding direction. Is from 0.003 to 0.013, and satisfies the following requirements (1) to (4): None:
(1) Whether the proportion of the metaxylylene group-containing polyamide polymer in the resin layer (A layer) containing the metaxylylene group-containing polyamide polymer as a main component is 99% by weight or more and a thermoplastic elastomer is not added Or less than 1% by weight;
(2) A laminate film of the polyamide-based laminated biaxially stretched film and a polyethylene film having a thickness of 40 μm is subjected to 40 cycles per minute using a gelboflex tester in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50%. The number of pinholes in the case of performing 2000 cycles of bending test continuously at a speed is 10 or less;
(3) The oxygen permeability at a temperature of 23 ° C. and a relative humidity of 65% is 150 ml / m ² · MPa · day or less;
(4) In a film having a length of 800 mm in the width direction of the film, Δnz, which is a difference in refractive index nz in the thickness direction of the film at both end portions in the width direction, is in the range of 0.0001 to 0.0015 . The polyamide-based laminated biaxially stretched film according to claim 1, wherein the polyamide-based laminated biaxially stretched film satisfies the following formula (I).
Pa <1 / [t (0.015x + 0.15)] (I)
(Where x is the content (% by weight) of the metaxylylene group-containing polyamide polymer in the film, Pa is the oxygen permeability (ml / m ² · MPa · day) of the film at a temperature of 23 ° C. and a relative humidity of 65%, t Indicates the thickness (mm) of the film.)   A thermoplastic elastomer is added to the resin layer (B layer) containing the aliphatic polyamide resin as a main component so as to have a mixing ratio of 0.5 wt% or more and 8.0 wt% or less. The polyamide-based laminated biaxially stretched film according to claim 1 or 2. The thickness of A layer is 10% or more and 30% or less of the total thickness of A layer and B layer, and the thickness of a film is 8-50 micrometers , The polyamide in any one of Claims 1-3 characterized by the above-mentioned. Laminated biaxially stretched film. A method of manufacturing a polyamide-based multilayer biaxially oriented film according to any one of 請 Motomeko 1-4, m-xylylenediamine or m-xylylenediamine and mixtures xylylenediamine a main diamine consisting para-xylylenediamine, A resin mainly comprising a metaxylylene group-containing polyamide polymer having a C 6-12 α, ω-aliphatic dicarboxylic acid component as a main dicarboxylic acid component, and a resin mainly containing an aliphatic polyamide resin; As a main diamine component, metaxylylenediamine or mixed xylylenediamine composed of metaxylylenediamine and paraxylylenediamine, and an α, ω-aliphatic dicarboxylic acid component having 6 to 12 carbon atoms Mainly composed of a metaxylylene group-containing polyamide polymer as the main dicarboxylic acid component A step of obtaining an unstretched sheet in which a resin layer (B layer) mainly composed of an aliphatic polyamide resin is laminated on at least one surface of the resin layer (A layer), and the obtained unstretched sheet in the longitudinal direction and It includes a step of obtaining a biaxially stretched film by biaxially stretching in the width direction, and continuously stretching the unstretched sheet with three or more heating rolls before stretching the unstretched sheet in the longitudinal direction. Feature method.