JP4665999B2 - 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.

  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.

  In the conventional film described above, when the former film made of a polyamide polymer having xylylenediamine as a constituent component is used for a packaging material that requires bending fatigue resistance, a processing step for performing vacuum packaging or the like, There was a problem that pinholes were easily generated due to bending fatigue during transportation. 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, the film made of the latter aliphatic polyamide 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 a separate extruder, 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 that a gas barrier resin layer composed of a polyamide having xylylenediamine as a main component is laminated with a resin layer composed of an aliphatic polyamide and a bending fatigue resistance improving agent on at least one surface. Although a film satisfying the bending fatigue property is disclosed, it is described that in order to satisfy the gas barrier property, the ratio of the gas barrier resin layer must be 40% or more. The present inventors evaluated the bending fatigue resistance under severe conditions using the film of Patent Document 3, but 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 still a concern in the method described in the above publication in terms of preventing 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 was a thing.
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.

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 two-layer / three-layer B / A / B configuration in which a resin layer (B layer) mainly composed of an aliphatic polyamide resin is laminated on both surfaces of a resin layer (A layer) mainly composed of a group-containing polyamide polymer. A polyamide-based laminated biaxially stretched film, wherein the thickness of the A layer is 10% to 25% of the total thickness of the A layer and the B layer, and the thickness of the B layer is the total thickness of the A layer and the B layer A polyamide-based laminated biaxially stretched film characterized by being 75% or more and 90% or less as a sum of thickness ratios of both surface layers with respect to the above, and satisfying the following requirements (1) to (3).
(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 (2) A laminate film of the polyamide-based laminated biaxially stretched film and a polyethylene film having a thickness of 40 μm is added to a gel gel in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50%. The number of pinholes when a flex test of 2000 cycles is continuously performed at a rate of 40 cycles per minute using a flex tester is 10 or less. (3) Oxygen at a temperature of 23 ° C. and a relative humidity of 65% 1. The transmittance is 150 ml / m ² · MPa · day or less. 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) mainly composed of the aliphatic polyamide resin 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.

  Such a 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 used effectively as various packaging materials.

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

  The main diamine component is metaxylylenediamine or mixed xylylenediamine composed of metaxylylenediamine and paraxylylenediamine, which is used to constitute layer A of the polyamide-based laminated biaxially stretched film of the present invention. In the metaxylylene group-containing polyamide polymer containing ˜12 α, ω-aliphatic dicarboxylic acid as the main dicarboxylic acid component, paraxylylenediamine is preferably 30% or less of the total xylylenediamine, and xylylenediamine It is preferable that the structural unit composed of the carboxylic acid and the aliphatic dicarboxylic acid is at least 70 mol% or more in the molecular chain.

  Examples of the metaxylylene group-containing polyamide polymer used in the present invention include, for example, polymetaxylylene adipamide, polymetaxylylene pimeramide, polymetaxylylene veramide, polymetaxylylene azelamide, polymetaxylylene sebacamide. , Homopolymers such as polymetaxylylene decanediamide, and the like, and metaxylylene / paraxylylene adipamide copolymer, metaxylylene / paraxylylene pimeramide copolymer, metaxylylene / paraxylylene veramide copolymer, Copolymers such as metaxylylene / paraxylylene azelamide copolymer, metaxylylene / paraxylylene sebacamide copolymer, metaxylylene / paraxylylene decanediamide copolymer, and homopolymers or copolymers of these Part of the coalescence component Aliphatic diamines such as methylene diamine, alicyclic 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, amino Examples thereof include a copolymer obtained by copolymerizing an ω-aminocarboxylic acid such as heptanoic acid and an aromatic aminocarboxylic acid such as para-aminomethylbenzoic acid.

  Moreover, as an aliphatic polyamide resin used for comprising B layer of the polyamide-type laminated biaxially stretched film of this invention, the nylon 6 which uses the epsilon caprolactam as a main raw material can be mentioned, for example. Examples of other polyamide resins include polyamide resins obtained by polycondensation of lactams having three or more members, ω-amino acids, dibasic acids and diamines. Specifically, as lactams, in addition to the aforementioned ε-caprolactam, enantolactam, capryllactam, lauryllactam, and ω-amino acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9- Examples include aminononanoic acid and 11-aminoundecanoic acid. 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. And 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 produced, 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 that the main B layer and the C layer have a different resin layer). From the viewpoint of curling, the B / A / B configuration which is a symmetrical layer configuration is particularly preferable. In the following description, among the layers constituting the laminated film, a central layer (that is, B / A / B, or the outermost layer made of a resin mainly composed of a metaxylylene group-containing polyamide polymer) A layer in the case of a B / A / C layer structure) and a thin layer in the case of a two-kind two-layer structure (that is, an A layer in the case of an A / B layer structure of a thick B layer and a thin A layer) ) Is called the core layer. In addition, the outermost layer (ie, the B / C layer in the case of the B / A / B or B / A / C layer structure) mainly composed of an aliphatic polyamide resin and a two-kind two-layer structure A thick layer in a certain case (that is, a B layer in the case of an A / B layer configuration of a thick B layer and a 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 70% or more, more preferably 75% or more, and particularly preferably 77% or more. The upper limit of the thickness ratio of the B layer or the B layer and the C layer is preferably 90% or less, more preferably 85% or less, and particularly preferably 82% or less. 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.

  The resin forming the skin layer is mainly an aliphatic polyamide resin, and a thermoplastic elastomer can be added as necessary. 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 particularly preferably 2.0% by weight or more. preferable. 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 a polyamide such as a block or random copolymer of a polyamide-based resin such as nylon 6 or nylon 12 and PTMG (polytetramethylene glycol) or 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. 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 for obtaining a good gas barrier property that the content ratio of the polyamide polymer is 99% by weight or more, preferably 100% by weight and the content ratio of the other resin is 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 obtained by laminating 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 by the following method. It is preferable that the number of pinholes in the case of performing 2000 cycles of bending test continuously at a rate of 40 cycles per minute is 10 or less. Of course, the most preferable number is zero.

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 a means for reducing the number of pinholes in the polyamide-based laminated biaxially stretched film of the present invention to 10 or less, as described above, the resin layer (A layer) containing the metaxylylene group-containing polyamide polymer as a main component is made as thin as possible. In addition, this can be achieved by appropriately containing a thermoplastic elastomer in the resin layer (B layer) containing an aliphatic 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 · 24H · MPa 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 · 24H · MPa or less, particularly preferably as long 110ml ^/ m 2 · 24H · MPa or less. The lower limit of the oxygen permeability in the present invention is substantially about 60 ml / m ² · 24H · MPa from the limit of gas barrier properties of the metaxylylene group-containing polyamide polymer itself.

As described above, as a means for setting the oxygen permeability of the polyamide-based laminated biaxially stretched film of the present invention to 150 ml / m ² · 24H · MPa or less, 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 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, and 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, the polyamide-based resin laminated biaxially stretched film of the present invention that satisfies the relationship of the formula (I) expresses an effective gas barrier property with a thin layer of the metaxylylene group-containing polyamide, and also maintains flexibility. There is little damage to impact resistance.

  If the relationship of formula (I) is deviated, for example, the content of the metaxylylene group-containing polyamide polymer must be increased to compensate for the decrease in gas barrier properties, and if the content of the metaxylylene group-containing polyamide polymer is increased, pinhole resistance In order to compensate for the deterioration of pinhole resistance, the amount of thermoplastic elastomer added must be increased.

  As a means for satisfying the relationship of formula (I), the other layer is not contained in the layer A mainly composed of a metaxylylene group-containing polyamide polymer, or the ratio of the other resin is reduced as much as possible. It is possible to achieve this by means such as adjusting the blending method and kneading conditions so that the different resins are not mixed 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 can be produced by the following 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. A method of laminating, a method of combining these, and the like can be employed, and a method in which the polymer constituting each layer is melted using a separate extruder and manufactured by coextrusion from one die is preferable. As the stretching method, it can be produced by using a flat sequential biaxial stretching method, a flat simultaneous biaxial stretching method, a tubular method or the like, and the flat sequential biaxial stretching method is preferable. Here, production of a film by a melt coextrusion method and a flat sequential biaxial stretching method will be described as an example.

  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 film 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 to 280 ° C, preferably 250 ° C to 270 ° C is preferable. The obtained unstretched sheet is guided to a roll-type longitudinal stretching machine, and the difference in speed between the rolls is used in the range of 65 to 100 ° C, preferably 80 to 90 ° C in the longitudinal direction. The film is stretched to 0 times, preferably 3.0 to 4.0 times, and then introduced into a tenter-type transverse stretching machine, and the temperature is in the range of 80 to 140 ° C, preferably in the range of 100 to 130 ° C, 3.0 to After transverse stretching to 6.0 times, preferably 3.5 to 4.0 times, heat setting in the range of 180 to 230 ° C., preferably 200 to 220 ° C., and in the range of 0 to 8%, preferably 2 to 2 A relaxation treatment is applied in the range of 6% to obtain a polyamide-based laminated biaxially stretched film.

  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 the following examples. 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.

[Oxygen permeability (gas barrier property)]
The film was subjected to oxygen substitution for 2 days in an atmosphere of humidity 65% RH and temperature 25 ° C., and then an oxygen permeability measuring device (OX-TRAN) according to JIS-K-7126 (Method B). 2/20: manufactured by MOCOM).

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

[Pinhole resistance]
The laminated film was cut into a size of 20.3 cm (8 inches) × 27.9 cm (11 inches), and the rectangular test film (laminated 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 disk-shaped movable head of a tester facing the fixed head at a distance of 17.8 cm (7 inches). 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 (manufactured by Toyobo Co., Ltd., RV = 2.8) is 95% by weight, and is a polyamide block copolymer (nylon 12 / polytetramethylene glycol copolymer) as a thermoplastic elastomer. A composition of Pebax 4033, RV = 2.0, manufactured by Arkema Inc., 5% by weight.

  The obtained unstretched sheet was stretched 3.3 times in the machine direction at a stretching temperature of 85 ° C. by a roll, and then stretched 3.7 times in the transverse direction by a tenter 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, a corona discharge treatment was performed on the surface of the layer B on the side to be dry laminated with 40 μm of a linear low density polyethylene film (L-LDPE film: L6102 manufactured by Toyobo Co., Ltd.). 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 it was changed as follows in the description of Example 1.
Composition constituting layer B: A composition comprising 98% by weight of nylon 6 and 2% by weight of a polyamide-based block copolymer.

  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 it was changed as follows in the description of Example 1.
Composition constituting layer B: A composition comprising 99% by weight of nylon 6 and 1% by weight of a polyamide-based block copolymer.

  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 it was changed as follows in the description of Example 1.
Composition constituting layer B: A composition comprising 98% by weight of nylon 6 and 2% by weight of a polyamide-based block copolymer.
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 it was changed as follows in the description of Example 1.
Composition constituting layer B: A composition comprising 97% by weight of nylon 6 and 3% by weight of a polyamide-based block copolymer.
The thickness ratio 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 it was changed as follows 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.

[ Reference Example 1 ]
A biaxially stretched film was obtained in the same manner as in Example 1 except that it was changed as follows in the description of Example 1.
Composition constituting layer B: A composition comprising 98% by weight of nylon 6 and 2% by weight of a polyamide-based block copolymer.
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 7]
A biaxially stretched film was obtained in the same manner as in Example 1 except that it was changed as follows in the description of Example 1.
Composition constituting layer B: A composition comprising 99% by weight of nylon 6 and 1% by weight of a polyamide-based block copolymer.
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.

[ Reference Example 2 ]
A biaxially stretched film was obtained in the same manner as in Example 1 except that it was changed as follows in the description of Example 1.
Composition constituting layer B: A composition comprising 93% by weight of nylon 6 and 7% by weight of a polyamide-based block copolymer.
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.

[Comparative Example 1]
A biaxially stretched film was obtained in the same manner as in Example 1 except that it was changed as follows 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 it was changed as follows in the description of Example 1.
The ratio of the thickness 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 it was changed as follows 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 it was changed as follows 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 it was changed as follows 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 ratio of the thickness 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 it was changed as follows in the description of Example 1.
Composition constituting layer A: a composition comprising 90% by weight of polymetaxylylene adipamide and 10% by weight of a polyamide block copolymer.
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 it was changed as follows 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 a polyamide-based block copolymer.
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 it was changed as follows in the description of Example 1.
Composition constituting layer A: a composition comprising 96% by weight of nylon 6 and 4% by weight of a polyamide-based block copolymer.
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 it was changed as follows in the description of Example 1.
Composition constituting layer A: a composition comprising 96% by weight of nylon 6 and 4% by weight of a polyamide-based block copolymer.
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.

  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 (3)

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 on both surfaces of the resin layer composed mainly of group-containing polyamide polymer (a layer), a B / a / B structure of two three-layer formed by laminating a resin layer composed mainly of an aliphatic polyamide resin (B layer) A polyamide-based laminated biaxially stretched film, wherein the thickness of the A layer is 10% to 25% of the total thickness of the A layer and the B layer, and the thickness of the B layer is the total thickness of the A layer and the B layer A polyamide-based laminated biaxially stretched film characterized by being 75% or more and 90% or less as a sum of thickness ratios of both surface layers with respect to the above, and satisfying the following requirements (1) to (3).
(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 (2) A laminate film of the polyamide-based laminated biaxially stretched film and a polyethylene film having a thickness of 40 μm is added to a gel gel in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50%. The number of pinholes when a flex test of 2000 cycles is continuously performed at a rate of 40 cycles per minute using a flex tester is 10 or less. (3) Oxygen at a temperature of 23 ° C. and a relative humidity of 65% The transmittance is 150 ml / m ² · MPa · day or less. 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) mainly composed of the aliphatic polyamide resin 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.