JP2009154294A - Biaxially oriented laminated polyamide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyamide-based biaxially oriented laminated film which is excellent in adhesive strength, especially waterproof adhesive strength, and effective for preventing a bag forming article for drink from being broken when the article is transported or falls. <P>SOLUTION: In the biaxially oriented laminated polyamide film, on at least one side of a layer A obtained by adding 0.01-0.1 wt.% a phenolic antioxidant into mixed polyamide polymers comprising 29.9-71.49 wt.% of a polyamide polymer containing meta-xylilene groups in which mixed xylilene diamines are made main diamine components, and a 6-12C α, ω-aliphatic dicarboxylic acid component is made a main dicarboxylic acid component, 20-50 wt.% of a polyamide polymer not containing a meta-xylilene group, and 8.5-20 wt.% of a polyamide block copolymer, a layer B formed from mixed polyamide polymers comprising 50-90 wt.% of an aliphatic polyamide polymer and 10-50 wt.% of a polyamide copolymer of nylon 6 and nylon 12 or nylon 66 is laminated, and the layer A and the layer B are biaxially oriented. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is excellent in oxygen gas barrier properties, impact resistance and bending fatigue resistance, and bending fatigue resistance in a low-temperature environment, especially when used as a packaging material for food packaging, etc. The present invention relates to a polyamide-based laminated biaxially stretched film that is effective in preventing bag breakage during transportation, maintains high transparency, gives excellent printability to products, and is suitable for various packaging applications.

  Conventionally, a film made of a polyamide polymer containing xylylenediamine as a constituent component has excellent oxygen gas barrier properties, 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, the former film made of a polyamide polymer containing xylylenediamine as a constituent component is used for a packaging material requiring bending fatigue resistance. There was a problem that pinholes were likely to occur 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 is excellent in impact resistance, bending fatigue resistance, etc., 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. (Patent Document 1).
JP-A-4-270655

  However, even in these methods, it has a satisfactory oxygen gas barrier property, and furthermore, it has a satisfactory level in terms of having film properties necessary as a packaging film such as impact resistance and bending fatigue resistance. Not reached.

In order to solve the above problems, a mixed polyamide polymer and a fat obtained by adding 8.5 to 20% by weight of a polyamide block copolymer containing nylon 12 as a hard segment component to a polyamide polymer containing xylylenediamine as a constituent component A method has been proposed in which a group polyamide or the like is melt-extruded from separate extruders, laminated and biaxially stretched (Patent Document 2).
Japanese Patent Laid-Open No. 2003-11307

  Addition of a large amount of nylon 12 polyamide block copolymer causes whitening in the film, resulting in poor transparency, giving the product after bag-making a cloudy appearance, and as a result, buyers can check the contents of the bag-made product. Is difficult to confirm, and the product image deteriorates due to the cloudy appearance. Therefore, a mixed polyamide polymer in which 8.5 to 20% by weight of a polyamide block copolymer having nylon 6 as a hard segment component is added to a polyamide polymer having xylylenediamine as a constituent component is separately extruded from an aliphatic polyamide. A method of melt extrusion from a machine, lamination and biaxial stretching was proposed. As a result, it has become possible to provide a film excellent in oxygen gas barrier properties and impact resistance, bending fatigue resistance at low temperatures, and transparency.

  This polyamide biaxially stretched film is usually used as a packaging material after being laminated on polyethylene, polypropylene or the like. These combinations are effective for many packaging applications, in particular a laminate construction of polyamide biaxially oriented film and low density polyethylene film is used as a typical food packaging material.

  However, when nylon 6 is used for the layer of the laminate surface, there is a problem that the laminate strength is weak and the laminate is peeled off when it is used for a water soup bag such as a liquid soup bag. And as a method of improving the lamination strength, there is a method to increase the adhesive strength by coating the film surface. However, this method increases the cost of the film forming process and increases the cost, and the coating is likely to cause streaks and scratches. was there.

  The present invention solves the problems of the above-mentioned polyamide-based laminated biaxially stretched film, provides a polyamide-based laminated biaxially stretched film excellent in adhesive strength, particularly water-resistant adhesive strength, and transports bag products for water use Another object of the present invention is to provide a polyamide-based laminated biaxially stretched film that is also effective in preventing bag breakage when dropped.

  In order to achieve the above object, the polyamide-based laminated biaxially stretched film of the present invention comprises metaxylylenediamine or mixed xylylenediamine composed of metaxylylenediamine and paraxylylenediamine as a main diamine component, and has 6 to 6 carbon atoms. A metaxylylene group-containing polyamide polymer having 12 α, ω-aliphatic dicarboxylic acid components as a main dicarboxylic acid component, 29.9 to 71.49% by weight, and 20 to 50% by weight of a polyamide polymer not containing a metaxylylene group, Fat mixed on at least one surface of layer A formed by adding 0.01 to 0.1% by weight of a phenolic antioxidant to a polyamide-based polymer mixed with 8.5 to 20% by weight of a polyamide-based block copolymer Polyamide of 50 to 90% by weight of an aromatic polyamide polymer and nylon 6 and nylon 12 or nylon 66 B layer comprising a mixed polyamide polymer of the polymer 10 to 50 wt% is laminated, A layer and B layer is characterized by comprising a biaxially stretched, a polyamide-based multilayer biaxially stretched film.

In this case, the polyamide block copolymer is
(a) (1) Lactam
(2) ω-amino aliphatic carboxylic acid (3) aliphatic diamine and aliphatic dicarboxylic acid
(4) A polyamide block copolymer comprising a hard segment composed of a polyamide component selected from the group of aliphatic diamine and aromatic dicarboxylic acid, and (b) a soft segment composed of a polyoxyalkylene glycol component. It can be.

  Moreover, in this case, 0.01 to 0.40 part by weight of aliphatic amide and / or aliphatic bisamide can be contained in 100 parts by weight of the polyamide-based mixed polymer constituting the A layer and / or the B layer. .

  Furthermore, in this case, the thickness of the A layer can be in the range of 20 to 87% of the total thickness of the A layer and the B layer.

  Such a polyamide-based laminated biaxially stretched film of the present invention has excellent oxygen gas barrier properties and impact resistance and bending fatigue resistance, in particular, bending fatigue resistance in a low temperature environment, and is suitable for food packaging and the like. Effective in preventing alteration and discoloration of contents. Furthermore, it has excellent adhesive strength, particularly water-resistant adhesive strength, and is very effective in preventing bag breakage due to impact and vibration during transportation of soup packaging bags, water packaging bags, etc., and dropping during transportation and storage. Furthermore, the contents can be protected from bending fatigue due to impact and vibration during low temperature transportation. Furthermore, blocking and slipping failure during bag making and bag filling products can be prevented, stable workability can be given, and it can be effectively used as various packaging materials. It is also effective for preventing bag breakage even when the bag-made product is transported or dropped during storage.

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

  Metaxylylenediamine used in the present invention or mixed xylylenediamine composed of metaxylylenediamine and paraxylylenediamine as a main diamine component, and an α, ω-aliphatic dicarboxylic acid having 6 to 12 carbon atoms as a main dicarboxylic acid In the metaxylylene group-containing polyamide polymer as an acid component, the content of paraxylylenediamine units is preferably 30% or less in the total xylylenediamine, and is composed of xylylenediamine and an aliphatic dicarboxylic acid. The structural unit is preferably 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 Some hexagonal ingredients Cycloaliphatic diamines such as tylenediamine, aromatic diamines such as para-bis- (2-aminoethyl) benzene, aromatic dicarboxylic acids such as terephthalic acid, lactams such as ε-caprolactam, ω-amino such as aminoheptanoic acid Examples thereof include a copolymer obtained by copolymerizing a carboxylic acid, an aromatic aminocarboxylic acid such as para-aminomethylbenzoic acid, and the like.

  Examples of polyamide polymers that do not contain a metaxylylene group that can be used to form the layer A of the polyamide-based laminated biaxially stretched film of the present invention include nylon 6, nylon 6,6, nylon 12, nylon 6 · Aliphatic polyamide copolymers such as aliphatic polyamides such as 10, nylon 6/6 · 6 copolymers, nylon 6/6 · 10 copolymers, nylon 6/6/6 · 10 copolymers, etc. And mixed polymers thereof.

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

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

  Using polyamide block copolymer as a component of polyamide laminated biaxially stretched film is effective in improving the bending fatigue resistance of polyamide laminated biaxially stretched film, especially in low temperature environments. is there.

  The mixed polyamide polymer constituting the A layer is a homogeneous mixture of the above-mentioned metaxylylene group-containing polyamide polymer, a polyamide not containing a metaxylylene group, and a polyamide-based block copolymer. This mixed polymer may be a mixture of the above-mentioned metaxylylene group-containing polyamide polymer of the virgin raw material, a polyamide that does not contain a metaxylylene group, and a polyamide-based block copolymer, and the polyamide-based laminate 2 of the present invention. It may be prepared by adding a non-standard film generated when producing an axially stretched film, a scrap material generated as a cut end material (ear trim), and its recycled resin and virgin raw material.

  In the present invention, the antioxidant added to the mixed polymer of layer A is preferably a phenolic antioxidant.

  In the present invention, the phenolic antioxidant added to the mixed polymer of layer A is preferably a completely hindered phenolic compound or a partially hindered phenolic compound. Examples include tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, stearyl-β- (3,5-di-t-butyl-4 -Hydroxyphenyl) propionate, 3,9-bis [1,1-dimethyl-2- [β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8, And 10-tetraoxaspiro [5,5] undecane.

  By adding the above-mentioned phenolic antioxidant to the mixed polymer of the A-layer of the polyamide-based laminated biaxially stretched film, the film forming operability of the polyamide-based laminated biaxially stretched film is improved. In particular, in the recovery and recycling raw material addition system using film waste material, recycled resin, etc., heat deterioration due to recovery and regeneration of the polyamide block copolymer is likely to occur, resulting in film formation operation failure due to this, and thus This leads to an increase in production costs due to an increase in production costs due to a decrease in efficiency and an increase in raw material costs for maintaining operability due to a decrease in the amount of recovered recycled materials used. On the other hand, by adding the above-mentioned phenolic antioxidant to the mixed polymer of the A-layer of the polyamide-based biaxially stretched film containing the recovered and regenerated raw materials, various heavy weights including the polyamide-based block copolymer can be obtained. Suppresses thermal degradation of coalescence and realizes stable film forming operability. From this, it is possible to reduce the production cost by improving the operability and reducing the raw material cost by increasing the amount of the recovered and recycled raw material.

  It is effective to reduce the crystallinity of the surface layer of the polyamide laminated film in order to overcome the above-mentioned problem that the adhesive strength, particularly the water-resistant adhesive strength is weak, and the aliphatic polyamide copolymer is applied to the surface of the polyamide film. It contains.

  Examples of the aliphatic polyamide polymer constituting the B layer of the polyamide-based laminated biaxially stretched film of the present invention include aliphatic polyamide homopolymers such as nylon 6, nylon 6,6, nylon 12, and nylon 6/10. Can be used.

  The polyamide copolymer resin constituting the B layer is nylon 6/6/6 copolymer, nylon 6/12, nylon 6/6/10 copolymer, nylon 6/6/6/10 copolymer. The main component is aliphatic polyamide represented by aliphatic polyamide copolymer such as ε-caprolactam, nylon salt of hexamethylenedimine and isophthalic acid, nylon salt of metaxylylenediamine and adipic acid, etc. And a polyamide copolymer containing a small amount of an aromatic copolymer.

  In particular, the aliphatic polyamide copolymer mixed with the aliphatic polyamide such as nylon 6 includes a copolymer of nylon 6 and nylon 12, or a copolymer of nylon 6 and nylon 6 · 6. A nylon 12 copolymer is preferred.

When a polymer having a different structure is mixed with a single polymer, if the structural difference is small compared to the original polymer, the degree of crystallinity does not decrease so much, so the adhesive strength does not increase so much. If the difference is too large, the compatibility with the original polymer is deteriorated, and there is an adverse effect that the appearance of the film and cohesive failure due to impact at the time of dropping the product are likely to occur.
Although there is no restriction | limiting in particular about the ratio of nylon 12 and nylon 6 in a polyamide copolymer, Nylon 12: Nylon 6 = 10-30: 90-70 (weight ratio) is preferable from a cost or the ease of a synthesis | combination. The layer containing the aliphatic polyamide copolymer is not particularly limited with respect to the content of the copolymer, but the effect of improving the adhesiveness is increased from the case of 10% by weight or more. However, if it exceeds 50% by weight, delamination may occur between the center layer and the surface layer or in the surface layer, and this is disadvantageous in terms of cost, so the content of the copolymer is preferably 10 to 50% by weight. .
However, even if the copolymer content is the same, if the film forming conditions such as the stretching temperature, the stretching ratio, and the heat setting temperature are different, the degree of reduction in crystallinity also differs.

  By eliminating the various elastomers used as rubber components from the polyamide polymer that constitutes layer B, and using the mixed polyamide polymer, cohesive failure inside the film due to impact when the bag is dropped is prevented. And the bag-breaking prevention effect at the time of the fall of the bag making product after filling the contents is brought about.

  The mixed polymer constituting the A layer of the present invention is composed of 29.9 to 71.49% by weight of a metaxylylene group-containing polyamide polymer and 20 to 50% by weight of a polyamide polymer not containing a metaxylylene group, and does not contain a metaxylylene group. Part or all of the polyamide polymer is a polyamide block copolymer, and the ratio of the polyamide block copolymer contained in the mixed polymer of the A layer is 8.5 to 20% by weight. That is, in order to impart oxygen barrier properties to the polyamide-based laminated biaxially stretched film, 29.9 to 71.49% by weight of a metaxylylene group-containing polyamide polymer is required in the polymer constituting the A layer. In order to balance the impact resistance and the bending fatigue resistance, in particular, the bending fatigue resistance in a low temperature environment, it is necessary to contain a polyamide polymer containing no metaxylylene group in the range of 20 to 50% by weight. Furthermore, as a polyamide polymer not containing a metaxylylene group, it is necessary that the polyamide block copolymer occupies a proportion of 8.5 to 20% by weight in the mixed polyamide polymer constituting the A layer.

  When the ratio of mixing the metaxylylene group-containing polyamide polymer and the polyamide polymer not containing the metaxylylene group and the ratio of mixing the polyamide block copolymer not containing the metaxylylene group exceed the upper limit of the above range, an oxygen barrier If the mixing ratio is below the lower limit of the above range, impact resistance and bending fatigue resistance under low temperature environment will be poor, and the film quality improvement effect will be insufficient. It lacks suitability as a packaging material. The lower limit of the mixing amount of the metaxylylene group-containing polyamide polymer in the polymer constituting the A layer is preferably 35% by weight, and the upper limit is preferably 71% by weight. The lower limit of the mixing amount of the polyamide polymer not containing a metaxylylene group is preferably 22%, and the upper limit is preferably 47% by weight. The lower limit of the mixing amount of the polyamide-based block copolymer is preferably 25%, and the upper limit is preferably 45% by weight.

  The mixed polyamide polymer constituting the layer A of the polyamide-based laminated biaxially stretched film of the present invention must contain a phenolic antioxidant in the range of 0.01 to 0.1% by weight. Stable film-forming operability by reducing defective film-forming operability due to thermal degradation of recovered / recycled raw materials when using recovered / recycled raw materials such as scrap and recycled resin as mixed polyamide polymer of layer A In order to realize this, an antioxidant is required in the mixed polyamide polymer in an amount of 0.01 to 0.1% by weight.

  If the ratio of the antioxidant mixed in the mixed polymer of layer A exceeds the upper limit of the above range, whitening due to precipitation on the surface of the polyamide-based laminated biaxially stretched film, adhesion during lamination with polyethylene and polypropylene sealants When the lower limit of the above range is exceeded, the film-forming operation due to thermal deterioration of the recovered and recycled raw material when the recovered and recycled raw material such as scrap material and recycled resin is used as the mixed polymer of the A layer. It is impossible to reduce inferiority and to give stable film forming operability. The lower limit of the mixing amount of the antioxidant is preferably 0.02% by weight.

  Examples of the aliphatic amide and / or fatty acid bisamide contained in the mixed polyamide polymer constituting the A layer and / or the B layer of the polyamide-based laminated biaxially stretched film of the present invention include erucic acid amide, stearic acid amide, ethylene Examples thereof include bis stearic acid amide and ethylene bis oleic acid amide.

  In this case, the content of the fatty acid amide and / or the fatty acid bisamide contained in the polyamide polymer constituting the A layer and / or the B layer is preferably 0.00 with respect to 100 parts by weight of the mixed polyamide polymer. It is 01-0.40 weight part, More preferably, it is 0.05-0.2 weight part. When the content of the fatty acid amide and / or the fatty acid bisamide is less than 0.01 parts by weight with respect to 100 parts by weight of the mixed polyamide polymer, the slipperiness is poor and the processing suitability in printing, laminating, etc. becomes poor, and 0.40 Exceeding parts by weight may cause unevenness on the surface due to bleeding on the film surface over time, which is undesirable in terms of quality.

  In the polyamide-based laminated biaxially stretched film of the present invention, the thickness ratio of the A layer composed of the metaxylylene group-containing polyamide polymer and the polyamide polymer not containing the metaxylylene group is A layer and B layer (both of the A layer) When the B layer is laminated on the surface, the total thickness is preferably 20 to 87% of the total thickness. If the thickness ratio of the A layer exceeds 87%, the impact resistance and the bending fatigue resistance are not sufficient, and cohesive failure occurs when the bag-making product is dropped. If it is less than 20%, the oxygen barrier property is insufficient. The lower limit of the thickness ratio of the A layer is more preferably 22%, and the upper limit is more preferably 85%.

  The polyamide-based laminated biaxially stretched film of the present invention has excellent elastic recovery in normal temperature and low temperature environments, and has excellent impact resistance and bending fatigue resistance, as well as processing such as printing, laminating and bag making. This is a laminated biaxially stretched film suitable for 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, it is usually 100 μm or less and generally has a thickness of 12 to 50 μm.

  The method of mixing the metaxylylene group-containing polyamide polymer constituting the A layer and the polyamide polymer not containing the metaxylylene group is not particularly limited, but usually a chip-like polymer is mixed using a V-type blender or the like. Thereafter, a method of melting and molding is used.

  The polyamide polymer constituting the A-layer and B-layer of the polyamide-based laminated biaxially stretched film of the present invention may be replaced with other thermoplastic resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate. You may make it contain in the range which does not injure the characteristic, such as polyester polymers, such as polyolefin polymers, such as polyethylene and a polypropylene.

  In addition, various additives such as antistatic agents, antifogging agents, ultraviolet absorbers, dyes, pigments, and the like are included in one or both of the A layer and / or the B layer made of a polyamide polymer, if necessary. be able to.

  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. Arbitrary known methods such as a method of laminating and a combination thereof can be used, and as a stretching method, a flat sequential biaxial stretching method, a flat simultaneous axial stretching method, a tubular method, or the like is used. Then, the film is stretched 2 to 5 times at a stretching temperature of 75 to 90 ° C in the longitudinal direction and 3 to 6 times at a stretching temperature of 120 to 140 ° C in the lateral direction, and heat-set at 180 to 230 ° C if necessary. In addition, it is preferable to perform the relaxation treatment at the time of heat setting at 2 to 10%. Thus, the transparency, oxygen gas barrier property and processability of the laminated film can be improved.

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

・ Oxygen permeability (mL / m ²・ d ・ Mpa)
OX-TRAN 2/20 manufactured by Modern Control was used, and measurement was performed under the conditions of a temperature of 23 ° C. and a relative humidity of 65%.

(2) Impact strength Using a film impact tester manufactured by Toyo Seiki Seisakusho, the impact strength was measured in an environment of a temperature of 23 ° C. and a relative humidity of 65%.

(3) Bending fatigue resistance (number of pinholes)
Using a gelbo flex tester manufactured by Rigaku Corporation, the bending fatigue resistance was measured by the following method.

  After applying a polyester adhesive to the film produced in the example, 40 μm of a linear low density polyethylene film (L-LDPE film: Toyobo Co., Ltd., L6102) is dry-laminated and aged in an environment at 40 ° C. for 3 days. A laminated film was obtained. The obtained laminate film is cut into 12 inches × 8 inches to form a cylindrical shape with a diameter of 3.5 inches, and one end of the cylindrical film is fixed to the fixed head side of the gelboflex tester and the other end is fixed to the movable head side. The initial gripping interval was 7 inches.

  At the first 3.5 inches of the stroke, a twist of 440 degrees was given, and then 2.5 inches, a bending fatigue was performed 500 times at a speed of 40 times / min. The number of pinholes that occurred was counted. The measurement was performed in an environment of 5 ° C.

(4) Laminate strength After applying a polyester adhesive to the film produced in the example, a linear low density polyethylene film (L-LDPE: manufactured by Toyobo Co., Ltd., L6102: thickness 40 μm) is dry laminated, and the environment at 40 ° C. The laminate film was aged for 3 days to obtain a laminate film. In order to measure the laminate strength, the laminate film was cut into a strip of 15 mm x 150 mm in the longitudinal direction, and one end was peeled off at the interface between a polyamide-based laminated biaxially stretched film and a linear low-density polyethylene film, Tensilon (Toyo Baldwin) The laminate strength was measured using STM-T-50BP (manufactured by STM-T-50BP) while maintaining water perpendicular to the tensile direction and adhering water to the interface between the polyamide-based laminated biaxially stretched film and the linear low density polyethylene film.

(5) Crystallinity parameter A film cut sample (20 mm x 90 mm) is set so that the polarization direction is perpendicular to the reflecting surface and the polarization direction is parallel to the MD direction, and a polarized ATR spectrum (Ge45 °) is obtained from PerkinElmer. Measured with a FT-IR spectrometer PARAGON1000. From the obtained spectrum, the absorbance ratio (absorption of 1199 cm-1 / absorption of 1172 cm-1) between 1199 cm-1 and 1172 cm-1 was determined.

(Example 1) An unstretched sheet having the following constitution was obtained using a two-type, three-layer co-extrusion T-die facility. In the configuration of B layer / A layer / B layer, the total thickness of the unstretched sheet is 190 μm, and the thickness ratio of the A layer to the total thickness is 67%. Composition constituting layer A: polymetaxylylene adipamide (Mitsubishi Gas Chemical Co., Ltd .: S6007) 70% by weight and nylon 6 (Toyobo Co., Ltd .: T814) 17.9% by weight and nylon 6 hard segment A mixed polymer composition comprising 12% by weight of a polyamide block copolymer (Arkema: Pebax MH1657) having polyethylene glycol as a soft segment and 0.1% by weight of a phenolic antioxidant. Composition constituting layer B: nylon 6 (Toyobo Co., Ltd .: T814) is 89.85% by weight, nylon 6 / nylon 12 polyamide copolymer (Ube Industries, Ltd .: 7024B) is 10.0% by weight, and A polymer composition comprising 0.15% by weight of ethylenebisstearic acid amide.

  The obtained unstretched sheet was stretched in the longitudinal direction by roll stretching at a stretching temperature of 80 ° C. and 3.5 times, and then stretched by a tenter in the transverse direction at a stretching temperature of 130 ° C. in the transverse direction and then 210 ° A 15 μm biaxially stretched film was produced by cooling after heat-fixing with 5.0% lateral relaxation treatment, and a linear low density polyethylene film (L-LDPE film: manufactured by Toyobo Co., Ltd., L4102) Corona discharge treatment was performed on the surface of layer B on the side to be dry laminated with 40 μm. The obtained biaxially stretched film was measured for oxygen permeability, impact strength, number of pinholes, and waterproof laminate strength. 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 description in Example 1 was changed as follows.
Composition constituting layer B: Nylon 6 is 79.85% by weight, nylon 6 / nylon 12 polyamide copolymer (Ube Industries, Ltd .: 7024B) is 20.0% by weight, and ethylene bis-stearic acid amide is 0.8%. A polymer composition comprising 15% by weight.

  The obtained biaxially stretched film was measured for oxygen permeability, impact strength, number of pinholes, and waterproof laminate strength. 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 description in Example 1 was changed as follows.
Composition constituting layer B: 59.85% by weight of nylon 6, 40.0% by weight of nylon 6 / nylon 12 polyamide copolymer (Ube Industries, Ltd .: 7024B), and 0.02% of ethylenebisstearic acid amide. A polymer composition comprising 15% by weight.

  The obtained biaxially stretched film was measured for oxygen permeability, impact strength, number of pinholes, and waterproof laminate strength. 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 description in Example 1 was changed as follows.
Composition constituting layer B: A polymer composition comprising 99.85% by weight of nylon 6 and 0.15% by weight of ethylenebisstearic acid amide.

  The obtained biaxially stretched film was measured for oxygen permeability, impact strength, number of pinholes, and waterproof laminate strength. The results are shown in Table 1.

  The polyamide-based laminated biaxially stretched film of the present invention has excellent oxygen gas barrier properties, impact resistance, flex fatigue resistance, and flex fatigue resistance under a low temperature environment. It is effective in preventing alteration and discoloration, and can protect the contents from bending fatigue due to impact and vibration during transportation, particularly during low temperature transportation, and can be used effectively as various packaging materials. Further, stable operability can be given even in operability during production.

Claims (4)

  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 Mixed polyamide polymer of 29.9 to 71.49% by weight of a group-containing polyamide polymer, 20 to 50% by weight of a polyamide polymer not containing a metaxylylene group, and 8.5 to 20% by weight of a polyamide block copolymer In addition, on at least one surface of the layer A to which 0.01 to 0.1% by weight of an antioxidant is added, 50 to 90% by weight of an aliphatic polyamide polymer and nylon 6 and nylon 12 or nylon 6 and nylon 66 are added. B layer made of mixed polyamide polymer consisting of 10-50% by weight of polyamide copolymer with Is, in a polyamide based multilayer biaxially stretched film, characterized in that A and B layers is biaxially stretched. The polyamide block copolymer contained in the A layer in the film according to claim 1,
(a) a polyamide-based block copolymer comprising a hard segment composed of a polyamide component composed of ε-caprolactam and (b) a soft segment composed of a polyoxyalkylene glycol component, a polypropylene glycol component or a polyethylene glycol component. The polyamide-based laminated biaxially stretched film according to claim 1, wherein:   It is characterized by further containing 0.01 to 0.40 parts by weight of aliphatic amide and / or aliphatic bisamide with respect to 100 parts by weight of the mixed polyamide polymer constituting the A layer and / or the B layer. The polyamide-based laminated biaxially stretched film according to claim 1 or 2.   The polyamide-based laminated biaxially stretched film according to claim 1, 2, or 3, wherein the thickness of the A layer is in the range of 20 to 87% of the total thickness of the A layer and the B layer.