JP2010269557A - Biaxially oriented polyamide laminate film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially oriented polyamide laminate film which has proper interlaminar bond strength and can obtain physical strength characteristics such as impact-resistance strength, or tensile strength and sufficient bond strength to a sealant film. <P>SOLUTION: In the biaxially oriented polyamide laminate film, lamination is executed in the order of polyamide A/polyamide B/polyamide C/polyamide B/polyamide A and heat-setting is executed so as to obtain 0.5-5.0% of the longitudinal and lateral hot-water shrinkage factor at 95°C for five minutes after the longitudinal and lateral 2-5 magnified stretching under the state polyamide A is mixed layer containing 70-99 wt.% of polyamide 6 and 30-1 wt.% of polyamide 6-66 which is the copolymer of polyamide 6 and polyamide 66 in a state that the polyamide 66 ratio is 10-25 wt.%, polyamide B is mixed layer containing 50-95 wt.% of polyamide 6 and 50-5 wt.% of aromatic polyamide and polyamide C containing the aromatic polyamide. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a biaxially oriented polyamide laminated film useful as a packaging material for steam sterilization exceeding 100 ° C., particularly for packaging of foods and medical products.

  Conventionally, a laminated film made of polyamide such as polyamide 6 and polymetaxylylene adipamide has been used as a packaging material having both excellent mechanical properties of polyamide 6 and excellent oxygen gas barrier properties of polymetaxylylene adipamide. Yes.

For example, Patent Document 1 proposes a configuration of an aliphatic polyamide layer / (aliphatic polyamide + aromatic polyamide) layer / aromatic polyamide layer / (aliphatic polyamide + aromatic polyamide) layer / aliphatic polyamide layer. .
Patent Document 2 discloses (crystalline polyamide + amorphous polyamide) / (crystalline polyamide + polyamide copolymer) / barrier layer / (crystalline polyamide + polyamide copolymer) / (crystalline polyamide + amorphous polyamide). ) Is proposed.
Patent Document 3 proposes a polyamide-based multilayer film having a three-layer structure of (polyamide 6 + polyamide 6-66 + aromatic polyamide) layer / barrier layer / (polyamide 6 layer + polyamide 6-66 + aromatic polyamide).
Patent Document 4 discloses (polyamide 6 + crystalline aromatic polyamide) / (polyamide 6 + polyamide 6-66 + aromatic polyamide) / saponified ethylene-vinyl acetate copolymer / (polyamide 6 + polyamide 6-66 + aromatic polyamide) / ( Polyamide 6 + crystalline aromatic polyamide) has been proposed.

JP 2005-212389 A JP 2005-288923 A JP 2008-94016 A JP 2008-188774 A

  However, in the above document, there is no proposal of a laminated film that has sufficient physical strength such as impact strength and tensile strength and has sufficient laminate strength with a sealant film such as unstretched polypropylene (hereinafter CPP). It was. Conventionally, laminated films for use in steam sterilization and laminated with CPP or the like have been insufficient in impact strength because they are sufficiently heat-set with emphasis on laminate strength. On the other hand, when the impact strength was regarded as important, sufficient heat fixation was not performed and the laminate strength was insufficient.

  Accordingly, an object of the present invention is to provide a biaxially stretched polyamide laminated film having physical strength such as impact strength and tensile strength and sufficient laminate strength with a sealant film such as CPP.

The present inventors have found that the above problems are solved by the following inventions (1) to (9).
(1) Polyamide A / Polyamide B / Polyamide C / Polyamide B / Polyamide A are laminated in this order and stretched 2 to 5 times in both the machine direction and the transverse direction. A biaxially stretched polyamide laminated film, which is heat-fixed to 0.5 to 5.0% in both lateral directions.
Polyamide A: Mixed layer polyamide containing 70 to 99% by weight of polyamide 6 and 30 to 1% by weight of polyamide 6-66 which is a copolymer of polyamide 6 and polyamide 66 and the ratio of polyamide 66 is 10 to 25% by weight B: Mixed layer polyamide containing 50 to 95% by weight of polyamide 6 and 50 to 5% by weight of aromatic polyamide C: Layer mainly containing aromatic polyamide (2) The thickness of the polyamide A layer is 2 to 5 μm The biaxially stretched polyamide laminated film according to (1).
(3) The biaxially stretched polyamide laminated film according to (1) or (2), wherein the delamination strength between polyamide B / polyamide C is 200 to 500 gf / 15 mm width.
(4) The biaxially stretched polyamide laminated film according to any one of (1) to (3), wherein the polyamide A contains 0.01 to 0.5% by weight of a hindered phenol antioxidant.
(5) The hindered phenol antioxidant is N, N′-hexane-1,6-diylbis [3- (3,5-di-t-butyl) -4-hydroxyphenylpropionamide] (1 The biaxially stretched polyamide laminated film according to any one of (1) to (4).
(6) The biaxially stretched polyamide laminated film according to any one of (1) to (5), wherein the aromatic polyamide contained in polyamide B and polyamide C is polymetaxylylene adipamide.
(7) The biaxially stretched polyamide laminated film according to any one of (1) to (6), wherein the puncture impact strength (under 23 ° C. and 50% RH condition) is 1.2 J / sheet or more.
(8) In a laminate in which an unstretched polypropylene film is dry-laminated on the biaxially stretched polyamide laminated film according to any one of (1) to (7), the laminate strength is 500 to 1500 gf / 15 mm width. A biaxially oriented polyamide laminated film laminate characterized by the following.
(9) The biaxially oriented polyamide laminated film laminate according to (8), which is used as a packaging material for steam sterilization at 105 ° C to 135 ° C.

  The biaxially stretched polyamide laminated film of the present invention has physical strength such as impact strength and tensile strength, and can have sufficient laminate strength with a sealant film such as CPP. Moreover, it has an appropriate oxygen barrier property and interlayer adhesive strength, and can be used for packaging applications such as foods and medical products.

  Moreover, the biaxially stretched polyamide laminated film laminate of the present invention has sufficient film strength even in steam sterilization at 100 ° C. or higher due to the excellent impact strength of the laminated film and sufficient adhesive strength with the sealant film. be able to. In addition, it is possible to prevent bag breakage due to peeling of the dry laminate portion at the seal portion and peeling between layers of the biaxially stretched polyamide laminated film, so that the contents can be stored safely.

Hereinafter, the biaxially stretched polyamide laminated film of the present invention (hereinafter sometimes referred to as “laminated film”) will be described in detail.
The laminated film of the present invention is laminated in the order of polyamide A / polyamide B / polyamide C / polyamide B / polyamide A. Thus, since each layer has a symmetrical configuration with polyamide C as the center, a film without curl can be obtained.

  The laminated film of the present invention is laminated as described above, and the hot water shrinkage rate at 95 ° C. for 5 minutes after being stretched 2 to 5 times in both the longitudinal direction and the transverse direction is 0.5 in both the longitudinal direction and the transverse direction. It is a film heat-fixed so that it may become -5.0%. Thereby, even when performing a boil or a retort process, it is hard to heat-shrink and it is hard to impair a physical characteristic and an external appearance. Here, the draw ratio in the machine direction and the transverse direction is preferably 2.2 to 4.5 times, more preferably 2.5 to 4.0 times.

  The thickness of the laminated film of the present invention is preferably 8 to 25 μm. This is because the thickness is preferably 8 μm or more in consideration of the strength of the laminated film, and is preferably 25 μm or less in consideration of cost. In this respect, the thickness is more preferably 10 to 22 μm, still more preferably 12 to 20 μm.

  The delamination strength between polyamide B / polyamide C of the laminated film of the present invention is preferably 200 to 500 gf / 15 mm width, more preferably 230 to 450 gf / 15 mm width, still more preferably 250 to 400 gf / 15 mm width. . If the sealant layer is less than 200 gf / 15 mm wide, it may peel off between the layers during boil / retort or transportation when the contents are packed in a bag and then used for packing. Is not preferable. On the other hand, if there is an interlayer adhesive strength exceeding 500 gf / 15 mm width, the adhesive strength between polyamide A / polyamide B may peel off between the layers during boil / retort or transport, resulting in a problem of bag breaking. Is not preferable. In general, since the polyamide A layer alone is thin, the measurement is difficult because the polyamide A layer is cut when measuring the delamination strength. Therefore, the strength between polyamide B / polyamide C is used as a guide.

  The laminated film of the present invention preferably has a puncture impact strength of 1.2 J / sheet or more. If the orientation is suppressed with emphasis on the laminate strength, the puncture impact strength will be weakened, but if the puncture impact strength is less than 1.2 J / sheet, the strength required for the biaxially stretched polyamide laminated film is preferably insufficient. Absent. The puncture impact strength is more preferably 1.3 J / sheet or more, further preferably 1.4 J / sheet or more, and most preferably 1.5 J / sheet or more.

  The polyamide A is a mixture containing 70 to 99% by weight of polyamide 6 and 30 to 1% by weight of polyamide 6-66 which is a copolymer of polyamide 6 and polyamide 66 and the ratio of polyamide 66 is 10 to 25% by weight. Is a layer. The laminated film of the present invention is a polyamide 6 which is excellent in impact strength as a main material of polyamide A as a surface layer, and is a film which is excellent in strength even if it is thin by stretching in the biaxial direction of the longitudinal direction and the transverse direction. Can do. In addition, by including polyamide 6-66 in the polyamide A, it is possible to improve the dry laminate strength with unstretched polypropylene (hereinafter referred to as CPP) while maintaining the impact strength of the film.

  In the polyamide A of the present invention, the blending ratio of the polyamide 6 is 70 to 99% by weight, preferably 75 to 97% by weight, and more preferably 80 to 95% by weight. If the content of polyamide 6 in the polyamide A is less than 70%, the impact strength of the laminated film becomes insufficient. Polyamide 6 is used in biaxially stretched polyamide films because it has high toughness and is inexpensive. However, when the polyamide A is composed only of polyamide 6, heat is required to obtain a strong laminate strength. It was necessary to increase the fixing temperature and relax the degree of plane orientation of polyamide 6, which led to a decrease in film strength. Therefore, in the present invention, the polyamide A has a melting point lower than that of the polyamide 6 and very good compatibility with the polyamide 6 is blended with 30 to 1% by weight of a polyamide 6-66 copolymer nylon. The orientation of the polyamide 6-66 dispersed in the polyamide A is relaxed without reducing the orientation of the polyamide 6 even if the value is lowered, so that the degree of plane orientation of the polyamide A is lowered and the laminate strength can be strongly maintained. become able to.

  In the polyamide A of the present invention, the blending ratio of the polyamide 6-66 is 30 to 1% by weight, preferably 25 to 3% by weight, and more preferably 20 to 5% by weight. If the blending ratio of the polyamide 6-66 in the polyamide A exceeds the above specific value, there are too many portions where the orientation after heat setting does not work, and the impact strength decreases, which is not preferable. On the other hand, if it is less than 1% by weight, the effect of relaxing the plane orientation is low, which is not preferable.

  The polyamide 66 copolymerization ratio in the polyamide 6-66 needs to be 10 to 25% by weight, preferably 12 to 23% by weight, and more preferably 14 to 21% by weight. When the polyamide 66 copolymerization ratio in the polyamide 6-66 is less than 10%, the melting point is not sufficiently lower than that of the polyamide 6 and the effect of relaxing the plane orientation is lowered. Conversely, if the polyamide 66 copolymerization ratio in the polyamide 6-66 exceeds 25% by weight, the melting point becomes too low, and stickiness tends to occur during longitudinal stretching with a roll or heat sealing after laminating with a sealant. Absent. In particular, since the laminated film of the present invention is a film suitable for steam sterilization at 100 ° C. or higher, a film having a high melting point such as CPP having high heat resistance is often used as a sealant, and the heat seal temperature is high, so that the stickiness is also high. It tends to occur.

  The polyamide A preferably contains a hindered phenol-based antioxidant in an amount of 0.01 to 0.5% by weight, more preferably 0.03 to 0.2% by weight. If the content of the hindered phenolic antioxidant in the polyamide A layer is less than 0.01% by weight, the biaxially stretched polyamide laminated film treated with hot water is deteriorated by oxidation, and the tensile strength at break is extremely reduced. There is a case. On the other hand, if the content of the hindered phenolic antioxidant exceeds 0.5% by weight, the hindered phenolic antioxidant bleeds out on the surface of the polyamide A layer, and printing ink or adhesive is deposited. May be worse. In addition, when used by being laminated with another plastic film such as a sealant film via an adhesive, if the antioxidant bleeds out, peeling occurs at the interface between the adhesive and the laminated film, which is not preferable.

  As a method for preparing polyamide A containing the hindered phenolic antioxidant, a method of adding the antioxidant at the start of polymerization of the polyamide, during or after polymerization, and a method of dry blending each at a predetermined ratio Any of these may be used.

  In addition, the effect of the addition of the hindered phenol antioxidant can be confirmed by measuring the tensile strength in the TD direction before and after the sterilization in the presence of oxygen. The tensile strength retention is preferably 70% or more, more preferably 80%, and still more preferably 90% or more.

  The hindered phenol-based antioxidant is not specified as long as it can be suitably used for a generally known polyamide-based resin. Specifically, N, N′-hexane-1,6-diylbis [3- ( 3,5-di-tert-butyl) -4-hydroxyphenylpropionamide], 3,5-di-tert-butyl-4-hydroxy-benzylphosphonate-diethyl ester, 1,3,5-trimethyl-2 , 4,6-Tris (3,5-di-t-butyl-4-hydroxy-benzyl) benzene, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate ], Tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylylene-di-phosphonite, triethylene glycol-bis-3- (3-t- Til-4-hydroxy-5-methyl-phenyl) propionate and the like, in particular N, N′-hexane-1,6-diylbis [3- (3,5-di-t-butyl) -4-hydroxyphenylpropionate Onamide] is preferable because of its high effect of preventing oxidative degradation of polyamide.

  The polyamide A may contain a small amount of aromatic polyamide and softness modifier contained mainly in the polyamides B and C resulting from recycling, such as tenter ears. However, the content of the resin component other than polyamide 6 and polyamide 6-66 in the polyamide A is preferably 20% by weight or less, more preferably 15% by weight or less, and still more preferably 10% by weight of the polyamide A layer. % Or less.

  In the laminated film of the present invention, the polyamide A layer containing 0.01 to 0.5% by weight of a hindered phenolic antioxidant forms at least one outer layer, and the thickness of the polyamide A layer is 2 to 5 μm. Is preferred. If the thickness of the polyamide A layer is less than 2 μm, the antioxidant effect of the entire film becomes insufficient, and the film strength may decrease due to oxidative degradation of the polyamide 6 during steam sterilization or the like, which is not preferable. On the other hand, if the thickness of the polyamide A layer exceeds 5 μm, many expensive antioxidant-added layers are used and the whole film becomes expensive, which is not preferable. The thickness of the polyamide A layer is more preferably 2.2 to 4.8 μm, still more preferably 2.5 to 4.5 μm.

  The polyamide B is a mixed layer containing 50 to 95% by weight of polyamide 6 and 50 to 5% by weight of aromatic polyamide. This is a constitution in which polyamide 6 which is the main component of the polyamide A and aromatic polyamide which is the main component of the polyamide C are blended, and the polyamide A which is a strength layer and the polyamide C which is a gas barrier layer are This is because, when the biaxial stretching is performed by coextrusion, a sufficient interlayer adhesive strength cannot be obtained, and it is necessary to use it as an adhesive layer.

  The aromatic polyamide contained in the polyamide B needs to be 50 to 5% by weight, preferably 40 to 7% by weight, more preferably 30 to 8% by weight, and further preferably 25 to 10% by weight. It is. If it is 5% by weight or less, the interlayer adhesive strength with the polyamide C becomes insufficient. On the other hand, if it is 50% by weight or more, the interlayer adhesive strength with the polyamide A becomes insufficient, and the aromatic polyamide component increases. Since bending pinhole property falls, it is not preferable. The ratio of the aromatic polyamide contained in the polyamide B is preferably as small as possible within the range in which the interlayer adhesion strength with the polyamide C is not problematic, in view of strength such as bending pinhole resistance.

  The polyamide B may contain a small amount of polyamide 6-66 and a softness modifier contained in polyamides A and C mainly caused by recycling such as tenter ears. However, the content of the resin component other than polyamide 6 and aromatic polyamide in the polyamide B is preferably 20% by weight or less of the polyamide B layer, more preferably 15% by weight or less, and still more preferably 10% by weight. % Or less.

  The polyamide C is a layer mainly containing an aromatic polyamide, and the aromatic polyamide is preferably contained in the polyamide C in an amount of 50 to 100% by weight. The aromatic polyamide is not particularly limited as long as it is a polyamide having an aromatic ring, but a polyamide constituent unit composed of xylylenediamine and an α, ω aliphatic dicarboxylic acid having 6 to 12 carbon atoms in the molecular chain is 70. What contains more than mol% is used suitably. This is because high gas barrier properties can be obtained by containing 70 mol% or more of xylylenediamine and an α, ω aliphatic dicarboxylic acid having 6 to 12 carbon atoms in the molecular chain as the structural unit of the aromatic polyamide.

  Specific examples of the polyamide component composed of the above xylylenediamine and an α, ω aliphatic dicarboxylic acid having 6 to 12 carbon atoms include polymetaxylylene adipamide, polymetaxylylene pimeramide, polymetaxylylene azease. Homopolymers such as ramides, polyparaxylylene azeramides, polyparaxylylene decanamides, metaxylylene / paraxylylene adipamide copolymers, metaxylylene / paraxylylene pimeramide copolymers, metaxylylene / paraxylylene Mention may be made of copolymers such as lenazeramide copolymers and metaxylylene / paraxylylene sebacamide copolymers.

  Other aromatic polyamide constituents include nylon salts of diamines and dicarboxylic acids and ring-opening polymers of lactams such as ε-caprolactam, and self-forming ω-aminocarboxylic acids such as ε-aminocarboxylic acid. Examples include polycondensates. Specific examples of diamines as components of the nylon salt include aliphatic diamines such as hexamethylene diamine and 2,2,4-trimethylhexamethylene diamine, piperazine bispropylamine, and neopentyl glycol bispropylamine. Examples of dicarboxylic acids include aliphatic dicarboxylic acids such as adipic acid, azelaic acid and sebacic acid, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, and the like. And cyclic aliphatic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid.

  In the present invention, it is most preferable to use polymetaxylylene adipamide as the polyamide C because it is excellent in terms of gas barrier properties, stretchability, coextrusion suitability with polyamide 6, and film strength.

  In each layer of the laminated film of the present invention, a softening modifier can be added for bending pinhole modification. Examples of the softening modifier include polyolefins, polyamide elastomers, and polyester elastomers.

  The polyolefins contain 50 mass% or more of polyethylene units and polypropylene units in the main chain, and those modified by grafting with maleic anhydride or the like can also be used. In addition, as the structural unit other than the polyethylene unit and the polypropylene unit of the polyolefin, vinyl acetate, or a partially saponified product thereof, acrylic acid, methacrylic acid, acrylic ester, methacrylic ester, or partial metal neutralization thereof. Products (ionomers), 1-alkenes such as butene, alkadienes, styrene and the like, and those containing a plurality of these structural units can also be used.

  The polyamide elastomers belong to a polyamide block copolymer such as polyether amide and polyether ester amide. Examples of the amide component include polyamide 6, polyamide 66, polyamide 12, and the like. Examples of the ether component include polyoxytetramethylene glycol, polyoxyethylene glycol, polyoxy-1,2-propylene glycol, and the like. From the standpoint of compatibility, thermal stability during extrusion, and flexibility-modifying effect, a copolymer containing polyoxytetramethylene glycol and polylauryl lactam (polyamide 12) as main components is most preferable. Moreover, what contains a small amount of dicarboxylic acid units, such as dodecane dicarboxylic acid, adipic acid, a terephthalic acid, as an arbitrary component can also be used.

  Examples of the polyester elastomers include polyether ester elastomers combining polybutylene terephthalate and polyoxytetramethylene glycol, and polyester ester elastomers combining polybutylene terephthalate and polycaprolactone.

  These softening modifiers can be used alone or in admixture of two or more. It is particularly preferable to add 1 to 5% by weight to the polyamide C, which is a hard aromatic polyamide.

  All the raw material polyamides used in the present invention have a high hygroscopic property. Therefore, when the raw materials are melted and extruded, water vapor and oligomers may be generated to inhibit film formation. Therefore, these raw materials are dried in advance to have a moisture content of 0.1% by mass or less. It is preferable. In these raw material resins, in addition to the softening modifier, various additives such as a lubricant, an antistatic agent, an antioxidant, an antiblocking agent, a stabilizer, a dye, a pigment, and inorganic fine particles are laminated film. It can be added in a range that does not affect the properties.

Next, the manufacturing method of the laminated film of this invention is demonstrated concretely.
The laminated film of the present invention can be produced by a conventionally known method. For example, using a polyamide A, a polyamide B, or a polyamide C as raw materials, an unstretched film (hereinafter referred to as “amorphous”) that is substantially amorphous. (Sometimes referred to as “laminated unstretched film”). This laminated unstretched film can be produced, for example, by melting the above raw materials with 3 to 5 extruders, extruding them with a flat die or a round die, and then rapidly cooling them to form a flat or tube-like laminated unstretched film. The coextrusion method is used.

  Next, the laminated unstretched film thus obtained is usually stretched 2 to 5 times in the biaxial direction of the film flow direction (longitudinal direction) and the direction perpendicular thereto (transverse direction). As the biaxial stretching method, known stretching methods such as tenter sequential biaxial stretching, tenter simultaneous biaxial stretching, and tubular simultaneous biaxial stretching can be employed. For example, in the case of the tenter-type sequential biaxial stretching method, the laminated unstretched film is heated to a temperature range of about 50 to 110 ° C., and stretched 2 to 5 times in the longitudinal direction by a roll-type longitudinal stretching machine. The film is stretched 2 to 5 times in the transverse direction within a temperature range of about 60 to 140 ° C by a tenter type transverse stretching machine. In the case of the tenter simultaneous biaxial stretching or the tubular simultaneous biaxial stretching method, for example, the film is stretched 2 to 5 times in the longitudinal and lateral directions in a temperature range of about 60 to 130 ° C.

  The biaxially stretched laminated film that has been biaxially stretched by the above method is subsequently heat-set by heat treatment to impart dimensional stability at room temperature. The heat treatment temperature should be selected within the range of 110 ° C. as the lower limit and 2 ° C. lower than the melting point of the polyamide 6 constituting the polyamide A layer as the upper limit. Can be obtained. The biaxially stretched laminated film that has been sufficiently heat-set by the heat treatment operation can be cooled and wound by a conventional method. Moreover, in order to improve adhesive strength with another base film, surface treatments, such as a corona discharge treatment, can be given to the single side | surface or both surfaces of a laminated | multilayer film.

  The improvement in strength due to stretching is due to the orientation of polyamide 6 molecules. However, if stretched, heat shrinks during printing, laminating with a sealant film, and processing such as bag making. Is done. In the case of the film of the present invention after stretching, in the case of the film of the present invention, the shrinkage rate is suppressed by applying heat to near the melting point of the polyamide 6 as the main raw material as in the above-described heat treatment operation. It is necessary that the hot water shrinkage ratio is 0.5 to 5.0% in both the vertical and horizontal directions. When the hot water shrinkage rate is 0.5% or less, since the heat setting temperature is not excessively applied, the polyamide 6 is in a molten state and the orientation is restored. On the other hand, if heat fixation is insufficient and the shrinkage rate in either the vertical or horizontal direction exceeds 5.0%, it is not preferable because it shrinks during post-processing and has a high possibility of affecting the dimensions and appearance. . Moreover, when heat setting is inadequate, the plane orientation of a film will become strong and a film will peel easily in the thickness direction. That is, when laminating with a sealant film, the strength in the direction of peeling off the sealant film is weakened, so that the lamination strength of the laminate surface is difficult to be obtained. In particular, in the case of a multi-layer film of 5 layers as in the present invention, the thickness of each layer is reduced, and the strength of each layer is reduced, so that peeling is likely to occur, which greatly affects the laminate strength. In order to increase the laminate strength, it is effective to increase the heat setting temperature and relax the plane orientation, but this is not preferable because the orientation of the polyamide 6 becomes weak and the film strength is lowered. The hot water shrinkage is preferably 0.8 to 4.0%, more preferably 1.0 to 3.0%.

  The biaxially stretched polyamide film of the present invention thus obtained is usually used by being laminated on another base film such as a polyolefin-based sealant film such as polypropylene or polyethylene.

  In the present invention, it is preferable to dry laminate CPP as the sealant film. When used as a packaging material for steam sterilization, it is preferable to dry laminate CPP in terms of heat resistance. However, when a biaxially stretched laminated polyamide film having a sufficiently high impact strength is dry laminated, the laminate strength with CPP is low. The problem of weakening is likely to occur. If the biaxially stretched polyamide laminated film of the present invention is used, it becomes easy to secure a dry laminate strength with CPP of 500 gf / 15 mm width or more.

  In the present invention, the laminate strength with the CPP is preferably 500 to 1500 gf / 15 mm width, more preferably 600 to 1500 gf / 15 mm width, and still more preferably 700 to 1500 gf / 15 mm width. If an adhesive with a laminate strength exceeding 1500 gf / 15 mm width is used, heat resistance is insufficient, and it is easy to break the bag during steam sterilization. It is not preferable. The laminate having the laminate strength can be effectively used as a packaging material for steam sterilization at 105 to 135 ° C. If the steam sterilization temperature is less than 105 ° C., the sterilization of the bacteria is insufficient, and the contents are likely to be discolored or spoiled, which is not preferable. On the other hand, when the temperature is higher than 135 ° C., the CPP of the sealant film cannot maintain a sufficient strength, and there is a possibility that a seal breakage may occur. The temperature range of steam sterilization is more preferably 110 ° C to 130 ° C, still more preferably 115 ° C to 130 ° C.

  The biaxially stretched polyamide laminated film laminate of the present invention has sufficient film strength even in steam sterilization at 100 ° C. or higher due to the excellent impact strength of the laminated film and sufficient laminate strength with the sealant film, Since it becomes possible to prevent bag breakage due to peeling of the dry laminate portion at the seal portion and peeling between layers of the biaxially stretched polyamide laminated film, the contents can be stored safely. In particular, since the packaging material for steam sterilization at 105 ° C. to 135 ° C. requires high film strength and dry laminate strength, the biaxially stretched polyamide film laminate of the present invention is preferably used.

  In addition, the method for laminating the laminated film of the present invention and CPP is not particularly limited, and a known method is used, and examples thereof include a dry laminating method, an extrusion laminating method, a poly sand laminating method, and the like. Is preferred.

EXAMPLES Hereinafter, although the content and effect of this invention are demonstrated in detail by an Example, this invention is not limited to the following examples.
In the following examples, the obtained film was evaluated by the following method.

(1) Hot water shrinkage A film specimen is cut into a width of 120 mm and a length of 120 mm, and a line of about 100 mm is drawn on the sample in the longitudinal (MD) direction and the transverse (TD) direction. This sample is allowed to stand for 24 hours in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50%, and the reference line is measured. The measured length is defined as a length F before heat setting by heat treatment. After immersing this sample film in hot water at 95 ° C. for 5 minutes, the attached water was completely wiped off and allowed to dry for about 5 hours in an atmosphere of a temperature of 23 ° C. and a relative humidity of 50%. The reference line is measured to obtain a length G after heat setting by heat treatment.
The heat shrinkage rate is calculated by [(F−G) / F] × 100 (%).
By the above method, each shrinkage rate of MD and TD was measured at n = 5, and the average value was defined as the hot water shrinkage rate.

(2) Delamination strength Measured with a tensile tester [manufactured by Shimadzu Corporation, Autograph AG-I]. The measurement conditions were as follows: an evaluation sample having a width of 15 mm was used, and T-type peeling was performed at a peeling speed of 20 mm / min.

(3) Puncture impact strength (J / one film)
A test piece having a width of 150 mm and a flow direction of 150 mm was cut out from the laminated film obtained by the method described in each of the following examples, and the sample was conditioned at 23 ° C. × 50% RH for 10 hours or more to obtain a measurement sample. The measurement was performed using a puncture type film impact tester manufactured by Toyo Seiki Seisakusho, a humidity control sample was set, and puncture point 1/2 inch, no weight, and E scale were used. The n number of 20 was measured under the condition of 23 ° C. and 50% RH, and the average value (J / one film) was defined as the impact strength.

(4) Tensile strength retention after steam sterilization in the TD direction The tensile strength before steam sterilization was measured with a tensile tester [manufactured by Shimadzu Corporation, Autograph AG-I]. The measurement conditions were such that the sample for evaluation was cut out in a width of 10 mm in the TD direction, the distance between chucks was 50 mm, and the peeling speed was 50 mm / min.
Steam sterilization is performed by cutting out a square sample film with a length of 200 mm on one side, and having a square-shaped opening with a length of 100 mm on one side of the sample film. It fixed with the formwork provided with. Place this sample film on the bottom of a pressurized retort tank (Hirayama Seisakusho, "Super Accelerated Life Tester PL-30AeRIII") in advance, and place water on the top so that the sample film does not submerge. After putting in and capping, it was heated to 135 ° C. with air remaining. After maintaining in this state for 30 minutes, the temperature was lowered to 80 ° C., and then the lid was opened to wipe off the moisture of the sample film, and then the humidity was adjusted for 24 hours in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50%. About the sample film which performed steam sterilization treatment, the tensile strength of TD direction was measured by the method similar to the breaking strength before said retort treatment. The tensile strength retention after steam sterilization was calculated as the ratio (%) of the tensile strength after the hot water treatment when the tensile strength before the hot water treatment was taken as 100.

(5) Laminate strength An unstretched polypropylene film (Toray Synthesis Co., Ltd.) using a urethane two-component adhesive (AD900 / RT5, manufactured by Toyo Morton Co., Ltd.) on the film obtained by the method described in each example below. A laminated film was prepared by dry laminating (ZK-93, thickness 70 μm) manufactured by Co., Ltd. Next, this laminated film was aged at 40 ° C. for 3 days, and then laminated with a biaxially stretched polyamide laminated film and an unstretched polypropylene film with a tensile tester [manufactured by Shimadzu Corporation, Autograph AG-I]. The strength was measured. The measurement conditions used a laminate film having a width of 15 mm, and measured the laminate strength in the TD direction at a T-type peeling and a peeling speed of 20 mm / min.

Example 1
As the polyamide A constituting the outermost polyamide layer, polyamide 6 (Mitsubishi Engineering Plastics Co., Ltd., Novamid 1022C6, melting point 224 ° C.) 89.9% by weight, polyamide 6-66 copolymer (Mitsubishi Engineering Plastics ( Co., Ltd., Novamid 2420, melting point 192 ° C., 66 ratio 20% by weight), 10% by weight, hindered phenol antioxidant (manufactured by Ciba Japan, Irganox 1098, N, N′-hexane-1,6) -Mixing 0.1 wt% of diylbis [3- (3,5-di-t-butyl) -4-hydroxyphenylpropionamide] into an extruder with a diameter of 65 mm and polyamide 6 (Mitsubishi Engineering Plastics) 85% by weight of Novamid 1022C6, melting point 224 ° C) A blend of 15% by weight of MXD6 (Mitsubishi Gas Chemical Co., Ltd., MX nylon 6007, melting point 237 ° C.) as an aromatic polyamide was added to a φ50 mm extruder and aromatic polyamide MXD6 (Mitsubishi Gas Chemical Co., Ltd.) as polyamide C. Manufactured using MX-Nylon 6007, melting point 237 ° C.) 95% by weight, and 5% by weight of a polyamide elastomer (Arkema, PEBAX4033) as a bending pinhole resistance improving material, Further, the polyamide A and the polyamide B were divided into half in each distribution block and introduced into the die, and laminated in a multi-manifold coextrusion T-die having five manifolds and extruded as a melt having a five-layer structure. , Rapidly cooled on a cooling roll at 30 ℃, unstretched product of about 150μm thickness Film was obtained (polyamide A layer / polyamide layer B / polyamide C layer / polyamide layer B / polyamide layer A).

Next, after heating and heating the unstretched laminated film to 50 ° C., the film was stretched three times in the longitudinal direction using a roll-type longitudinal stretching machine under this temperature condition, and further heated to 120 ° C. The film was stretched 3.5 times in the transverse direction using a stretching machine. The obtained biaxially stretched film was heat-set by heat-treating it at 215 ° C. for 6 seconds to obtain a laminated film having a thickness of 15 μm. The average thickness (μm) of each layer of polyamide A layer / polyamide B layer / polyamide C layer / polyamide B layer / polyamide A layer was 3.5 / 2.0 / 4.0 / 2.0 / 3.5. . The film was measured and the results shown in Table 1 were obtained.

(Example 2)
A film was produced in the same manner as in Example 1 except that the blending ratio of polyamide A was set to 94.9: 5: 0.1.
(Example 3)
A film was prepared in the same manner as in Example 1 except that the blending ratio of polyamide A was set to 79.9: 5: 0.1.
Example 4
A film was prepared and measured in the same manner as in Example 1 except that polyamide 6-66 copolymer (manufactured by Mitsubishi Engineering Plastics Co., Ltd., Novamid 2020, melting point 200 ° C., 66 ratio 15% by weight) was used as polyamide A. The results shown in Table 1 were obtained.
(Example 5)
A film was produced in the same manner as in Example 1 except that the blending ratio of polyamide B was 90:10, and the measurement was performed to obtain the results shown in Table 1.
(Example 6)
A film was prepared in the same manner as in Example 1 except that the blending ratio of polyamide B was set to 75:25.
(Example 7)
A film was prepared and measured in the same manner as in Example 1 except that the heat treatment temperature for heat setting was 218 ° C., and the results shown in Table 1 were obtained.
(Example 8)
A film was produced in the same manner as in Example 1 except that the heat treatment temperature for heat setting was set to 212 ° C., and measurement was performed to obtain the results shown in Table 1.
(Comparative Example 1)
A film was produced in the same manner as in Example 1 except that polyamide A was changed to polyamide 6 (manufactured by Mitsubishi Engineering Plastics Co., Ltd., Novamid 1022C6, melting point 224 ° C.).
(Comparative Example 2)
A film was prepared in the same manner as in Example 1 except that the polyamide A was changed to 64.9: 35: 0.1, and the measurement was performed to obtain the results shown in Table 1.
(Comparative Example 3)
A film was prepared in the same manner as in Example 1 except that polyamide B was changed to 97: 3, and measurement was performed to obtain the results shown in Table 1.
(Comparative Example 4)
A film was produced in the same manner as in Example 1 except that the polyamide B was changed to 45:55, and measurement was performed to obtain the results shown in Table 1.
(Comparative Example 5)
A film was prepared in the same manner as in Example 1 except that the heat treatment temperature for heat setting was set to 222 ° C., and measurement was performed to obtain the results shown in Table 1.
(Comparative Example 6)
A film was prepared and measured in the same manner as in Example 1 except that the heat treatment temperature for heat setting was set to 205 ° C., and the results shown in Table 1 were obtained.

  From Table 1, the biaxially stretched polyamide laminated film of the present invention obtained a film satisfying all of the interlaminar adhesive strength, physical strength such as impact strength and tensile strength, and sufficient laminate strength with the sealant film. Examples 1-8). In contrast, Comparative Example 1 in which polyamide 6 does not contain polyamide 6-66 is inferior in tensile strength retention and laminate strength after steam sterilization in the TD direction, and comparative example 2 in which the blending ratio of polyamide 6 in polyamide A is small. Was inferior in puncture impact strength. Further, Comparative Example 3 in which the blending ratio of the aromatic polyamide in the polyamide B is small and Comparative Example 4 in which the blending ratio of the polyamide 6 in the polyamide B is small are greatly inferior in the delamination strength and the heat treatment temperature for heat setting is too high. No. 5 was inferior in puncture impact, and Comparative Example 6 in which the heat treatment temperature for heat setting was too low was inferior in laminate strength.

  Thereby, the biaxially stretched polyamide laminate film of the present invention has an appropriate interlayer adhesion strength, and has sufficient laminate strength between the physical strength characteristics such as impact strength and tensile strength and the sealant film. I understand.

Claims (9)

Polyamide A / Polyamide B / Polyamide C / Polyamide B / Polyamide A are laminated in this order, and hot water shrinkage at 95 ° C. for 5 minutes after being stretched 2 to 5 times in both the longitudinal and transverse directions is longitudinal and transverse. A biaxially stretched polyamide laminated film characterized in that both are heat-set to 0.5 to 5.0%.
Polyamide A: 70 to 99% by weight of polyamide 6;
A mixed layer polyamide B containing 30 to 1% by weight of polyamide 6-66, which is a copolymer of polyamide 6 and polyamide 66 and the ratio of polyamide 66 is 10 to 25% by weight. Polyamide 6: 50 to 95% by weight, aromatic Layer polyamide C containing 50 to 5% by weight of aromatic polyamide: layer mainly containing aromatic polyamide The biaxially stretched polyamide laminated film according to claim 1, wherein the polyamide A layer has a thickness of 2 to 5 µm. The biaxially stretched polyamide laminated film according to claim 1 or 2, wherein the delamination strength between polyamide B and polyamide C is 200 to 500 gf / 15 mm width. The biaxially stretched polyamide laminated film according to any one of claims 1 to 3, wherein the polyamide A contains a hindered phenol-based antioxidant in an amount of 0.01 to 0.5% by weight. The hindered phenol-based antioxidant is N, N'-hexane-1,6-diylbis [3- (3,5-di-t-butyl) -4-hydroxyphenylpropionamide]. Biaxially stretched polyamide laminated film. The biaxially oriented polyamide laminated film according to any one of claims 1 to 5, wherein the aromatic polyamide contained in polyamide B and polyamide C is polymetaxylylene adipamide. The biaxially stretched polyamide laminated film according to any one of claims 1 to 6, wherein the puncture impact strength (under 23 ° C and 50% RH condition) is 1.2 J / sheet or more. A biaxially laminated laminate film obtained by dry laminating an unstretched polypropylene film to the biaxially stretched polyamide laminate film according to any one of claims 1 to 7, wherein the laminate strength is 500 to 1500 gf / 15 mm width. Stretched polyamide laminated film laminate. The biaxially oriented polyamide laminated film laminate according to claim 8, which is used as a packaging material for steam sterilization at 105 ° C to 135 ° C.