JP5393121B2 - Polyamide multilayer film - Google Patents

Description

  The present invention relates to a polyamide-based multilayer film that has excellent pinhole resistance and gas barrier properties due to bending and has a beautiful appearance.

  A film made of a polyamide-based resin is used in various fields as a film having toughness. Among them, multilayer films including barrier layers such as saponified ethylene-vinyl acetate copolymers are widely used as films having excellent barrier properties.

  When such a multilayer film is used, for example, as a packaging film for foods distributed in the market, pinholes may be generated in its transportation, transportation, and the like. Due to this pinhole, the excellent gas barrier properties of the multilayer film were hindered. For this reason, further improvement of toughness, especially improvement of pinhole resistance is desired from the market.

In response to such demands from the market, attempts have been made to improve the flexibility of the packaging film by blending a soft component in the polyamide layer in order to suppress the occurrence of pinholes, softening the polyamide layer. However, by adding a soft component, the gloss of the surface is lowered and the design as a packaging film is lowered. For this reason, there has been a strong demand for a film that has improved flexibility and does not deteriorate barrier properties and gloss.
JP 2008-188776 A

  The main object of the present invention is to provide a polyamide-based multilayer film that has excellent pinhole resistance and gas barrier properties due to bending and has a beautiful appearance.

  As a result of intensive studies in view of the above problems, the present inventors have found that a polyamide layer (A layer) containing an aliphatic polyamide, 55 to 95% by weight of a saponified ethylene-vinyl acetate copolymer, a soft polymer. The polyamide-based multilayer film in which the above-mentioned problems have been solved by laminating an oxygen barrier layer (B layer) containing 5 to 45% by weight and a polyamide layer (C layer) containing an aliphatic polyamide in this order. It was found that it can be obtained. The present invention has been completed based on such findings. That is, the present invention relates to the following polyamide multilayer film.

Item 1. A polyamide-based multilayer film in which a polyamide layer (A layer), an oxygen barrier layer (B layer), and a polyamide layer (C layer) are laminated in this order,
(A) the layer contains an aliphatic polyamide;
The layer (B) contains 55 to 95% by weight of saponified ethylene-vinyl acetate copolymer and 5 to 45% by weight of a soft polymer,
(C) Polyamide-type multilayer film characterized by the layer containing aliphatic polyamide.

  Item 2. Item 2. The polyamide-based multilayer film according to Item 1, wherein the layer (A) contains 75 to 100% by weight of aliphatic polyamide and 0 to 25% by weight of aromatic polyamide.

  Item 3. Item 3. The polyamide-based multilayer film according to Item 1 or 2, which is a multilayer film obtained by biaxial stretching 2.5 to 4.5 times in the MD direction and 2.5 to 5 times in the TD direction.

  Item 4. Any one of Items 1 to 3, wherein the thickness of the (A) layer and the (C) layer is 4 μm or more, the thickness of the (B) layer is 2 to 24 μm, and the total film thickness of the polyamide-based multilayer film is 10 to 80 μm. The polyamide-based multilayer film described in 1.

  Item 5. Item 5. The polyamide multilayer film according to any one of Items 1 to 4, further comprising a seal layer on one surface.

  Item 6. Item 6. The packaging material obtained by bonding both ends of the polyamide-based multilayer film according to any one of items 1 to 5 so as to form a cylindrical shape, and further bonding one end of the opening of the cylindrical material. bag.

  Item 7. Item 7. A packaging bag according to Item 6, which is for food packaging.

  Item 8. Resin composition for polyamide layer (A layer) containing aliphatic polyamide, oxygen barrier layer (B layer) containing 55 to 95% by weight of saponified ethylene-vinyl acetate copolymer and 5 to 45% by weight of soft polymer ) And a polyamide layer (C layer) resin composition containing an aliphatic polyamide are laminated by coextrusion so as to be in this order, stretched biaxially and horizontally, and heat-treated. A method for producing a polyamide-based multilayer film.

  The polyamide-based multilayer film of the present invention is excellent in pinhole resistance and gas barrier properties and has a beautiful appearance. The polyamide-based multilayer film of the present invention having such excellent characteristics is suitably used as a packaging film.

1. Polyamide-based multilayer film The polyamide-based multilayer film of the present invention is a polyamide-based multilayer film in which a polyamide layer (A layer), an oxygen barrier layer (B layer) and a polyamide layer (C layer) are laminated in this order,
(A) the layer contains an aliphatic polyamide;
The layer (B) contains 55 to 95% by weight of saponified ethylene-vinyl acetate copolymer and 5 to 45% by weight of a soft polymer,
The layer (C) contains an aliphatic polyamide.

  That is, the oxygen barrier layer (B layer) having flexibility, that is, bending resistance, is sandwiched between the polyamide layer (A layer) and the polyamide layer (C layer) to have a three-layer laminated structure. Therefore, it has excellent pinhole resistance and gas barrier properties and a beautiful appearance.

  Hereinafter, each structure of the polyamide-type multilayer film of this invention is explained in full detail. Hereinafter, the polyamide-based multilayer film may be simply abbreviated as a multilayer stretched film.

(1) (A) layer In this invention, the (A) layer contains aliphatic polyamide as a main component.

(1-1) Aliphatic polyamide Examples of the aliphatic polyamide include aliphatic nylon and copolymers thereof. Specifically, polycapramide (nylon-6), poly-ω-aminoheptanoic acid (nylon-7), poly-ω-aminononanoic acid (nylon-9), polyundecanamide (nylon-11), polylauryllactam ( Nylon-12), polyethylenediamine adipamide (nylon-2,6), polytetramethylene adipamide (nylon-4,6), polyhexamethylene adipamide (nylon-6,6), polyhexamethylene Bacamide (nylon-6,10), polyhexamethylene dodecamide (nylon-6,12), polyoctamethylene adipamide (nylon-8,6), polydecamethylene adipamide (nylon-10,8) , Caprolactam / lauryl lactam copolymer (nylon-6 / 12), caprolactam / ω-aminononanoic acid copolymer Body (nylon-6 / 9), caprolactam / hexamethylenediammonium adipate copolymer (nylon-6 / 6,6), lauryllactam / hexamethylenediammonium adipate copolymer (nylon-12 / 6,6), Ethylenediamine adipamide / hexamethylene diammonium adipate copolymer (nylon-2,6 / 6,6), caprolactam / hexamethylene diammonium adipate / hexamethylene diammonium sebacate copolymer (nylon-6 / 6,6) / 6,10), ethyleneammonium adipate / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon-6 / 6,6 / 6,10), etc. Even if you mix the aliphatic polyamide There.

  Preferred aliphatic polyamides include nylon-6, nylon-6,6, nylon-6 / 6,6 (copolymer of nylon 6 and nylon 6,6), more preferably nylon-6, nylon. -6/6, 6 and more preferably nylon-6. As the two or more kinds of aliphatic polyamides, a combination of nylon-6 and nylon-6 / 6,6 (weight ratio of about 50:50 to 95: 5) is preferable.

(1-2) The aromatic polyamide (A) layer may further contain an aromatic polyamide.

  As the aromatic polyamide, for example, an aromatic diamine such as metaxylenediamine and paraxylenediamine and a dicarboxylic acid such as adipic acid, suberic acid, sebacic acid, cyclohexanedicarboxylic acid, terephthalic acid, and isophthalic acid, or a derivative thereof can be used. Examples thereof include crystalline aromatic polyamides obtained by a condensation reaction. A crystalline aromatic polyamide such as polymetaxylene adipamide (MXD-nylon) is preferable. Specific examples include S-6007 and S-6011 (both manufactured by Mitsubishi Gas Chemical Co., Inc.).

  Alternatively, amorphous aromatic polyamide (amorphous) obtained by polycondensation reaction of aliphatic diamines such as hexamethylenediamine and trimethylhexamethylenediamine with dicarboxylic acids such as terephthalic acid, isophthalic acid, adipic acid and azelaic acid or derivatives thereof Nylon). Preferred is a copolymer of hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid. Specific examples include Sealer PA (manufactured by Mitsui DuPont Polychemical Co., Ltd.), Novamid X21 (manufactured by Mitsubishi Engineering Plastics Co., Ltd.), and the like.

  When the aromatic polyamide is contained in the layer (A) in the multilayer stretched film of the present invention, a preferable combination of the aliphatic polyamide and the aromatic polyamide is a combination of nylon-6 and MXD-nylon, a combination of nylon-6 and amorphous aromatic. A combination of a group polyamide (amorphous nylon) is exemplified.

(1-3) Content In the layer (A) in the multilayer stretched film of the present invention, the content of the aliphatic polyamide is 75 to 100% by weight, preferably 80 to 99% by weight; the content of the aromatic polyamide is 0 to 0%. It is preferable to adjust so that it is contained in an amount of 25% by weight, preferably 1 to 20% by weight. By adjusting the respective contents within this range, more excellent stretchability can be imparted.

  In addition to the aliphatic polyamide and the aromatic polyamide, the layer (A) in the multilayer stretched film of the present invention contains a soft polymer within a range that does not impair the effects of the present invention in order to suppress the generation of pinholes. You can also.

  Examples of such soft polymers include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-butene copolymer, polypropylene, Polyolefin resins such as ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers; modified polyolefin resins obtained by graft-modifying unsaturated carboxylic acids to polyolefin resins; ionomer resins; polyether amides, polyether ester amides Polyamide elastomers such as polyester amides; Acrylic or methacrylic elastomers such as methyl acrylate, ethyl acrylate, methyl methacrylate or ethyl methacrylate and ethylene copolymers; Hard segment made of polystyrene And bets, polybutadiene, polyisoprene, polyisobutylene, copolymers of polybutadiene and polyisoprene, or elastomers such as formed styrene elastomer and a soft segment composed of hydrogenated products thereof; or a mixture thereof can be used. Specifically, Admer NF587 manufactured by Mitsui Chemicals, Inc. can be used as the modified polyolefin, and SIBSTAR-073T manufactured by Kaneka Corporation can be used as the styrene-isobutylene block copolymer.

(2) (B) Layer In the present invention, the (B) layer contains 55 to 95% by weight of saponified ethylene-vinyl acetate copolymer and 5 to 45% by weight of a soft polymer.

(2-1) Saponified ethylene- vinyl acetate copolymer The saponified ethylene-vinyl acetate copolymer is obtained by saponifying a copolymer of ethylene and vinyl acetate with an alkali catalyst or the like. The saponified ethylene-vinyl acetate copolymer used in the present invention is not particularly limited by the saponification method.

  The ethylene-vinyl acetate copolymer saponified product is not particularly limited, but has an ethylene content of 55 mol% or less, preferably 20 to 50 mol%, more preferably 25 to 45 mol%. A saponification degree is 90 mol% or more, Preferably 95 mol% or more can be illustrated. Specifically, Soarnol manufactured by Nippon Synthetic Chemical Industry Co., Ltd. or Eval manufactured by Kuraray Co., Ltd. can be used. In addition, ethylene content and a saponification degree can be calculated | required by NMR method etc., for example.

  In the present invention, the saponified ethylene-vinyl acetate copolymer may be used alone or in combination of two or more. In addition, when using 2 or more types, ethylene content and saponification degree can be calculated | required from the compounding weight ratio. By blending two or more types of ethylene-vinyl alcohol copolymers having different compositions, the moldability and oxygen barrier property can be further improved.

(2-2) Soft polymer As the soft polymer, one having a lower elastic modulus than the saponified ethylene-vinyl acetate copolymer can be used, for example, high density polyethylene, low density polyethylene, linear low density polyethylene. Polyolefin resins such as ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-butene copolymer, polypropylene, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer; Modified polyolefin resins obtained by graft-modifying unsaturated carboxylic acids on them; ionomer resins; polyamide elastomers such as polyether amides, polyether ester amides, and polyester amides; methyl acrylate, ethyl acrylate, methyl methacrylate, or ethyl methacrylate And ethylene Acrylic or methacrylic elastomer such as polymer; composed of a hard segment made of polystyrene and a soft segment made of polybutadiene, polyisoprene, polyisobutylene, a copolymer of polybutadiene and polyisoprene, or a hydrogenated product thereof. An elastomer such as a styrene-based elastomer; or a mixture thereof can be used. Specifically, Admer NF587 manufactured by Mitsui Chemicals, Inc. can be used as the modified polyolefin, and SIBSTAR-073T manufactured by Kaneka Corporation can be used as the styrene-isobutylene block copolymer.

  Furthermore, it is preferable that the oxygen absorption capacity is imparted to the soft polymer without lowering the barrier property. Examples of the soft polymer to which oxygen absorbing ability is imparted include those in which an oxygen absorbent is dispersed in the soft polymer, and those having an oxygen absorbing ability in the soft polymer itself.

  Examples of the oxygen absorbent dispersed in the soft polymer include ascorbic acid and iron-based metal powder.

  Examples of the soft polymer having oxygen absorption ability include rubbers containing conjugated double bonds and cyclohexene groups. For example, natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), butadiene-isoprene co-polymers. Single or copolymer of conjugated dienes such as polymer rubber (BIR); styrene-butadiene rubber (SBR), isoprene-isobutylene copolymer rubber (IIR), ethylene-propylene-diene copolymer rubber (EPDM), Copolymers of conjugated dienes such as styrene-isoprene block copolymers and monomers copolymerizable therewith, cyclized products thereof, and the like.

(2-3) Content In the layer (B) in the multilayer stretched film of the present invention, the content of the saponified ethylene-vinyl acetate copolymer is 55 to 95% by weight, preferably 65 to 90% by weight; The content is adjusted so as to be 5 to 45% by weight, preferably 10 to 35% by weight. When the content of the saponified ethylene-vinyl acetate copolymer is less than 55% by weight and the content of the soft polymer is more than 45% by weight, the layers (B), (A) and (C) The interlaminar strength of the material becomes low, causing problems in practical use. On the other hand, when the content of the saponified ethylene-vinyl acetate copolymer is more than 95% by weight and the content of the soft polymer is less than 5% by weight, the improvement in flex resistance becomes insufficient, and the pinhole resistance Sex cannot be imparted.

  The saponified ethylene-vinyl acetate copolymer and the soft polymer may be dry-blended at the time of manufacture, or a resin in which the saponified ethylene-vinyl acetate copolymer and the soft polymer are dispersed is purchased. May be used.

  In addition, in the layer (B) in the multilayer stretched film of the present invention, in addition to the saponified ethylene-vinyl acetate copolymer and the soft polymer, the effects of the present invention are not impaired in order to suppress the generation of pinholes. A soft component can be included in the range.

(3) (C) Layer In the present invention, the (C) layer contains aliphatic polyamide as a main component. As the (C) layer, those described in the description of the (A) layer can be used. Moreover, the same thing as a (A) layer may be used and the thing different from a (A) layer may be used.

(4) Layer constitution The polyamide-based multilayer film of the present invention comprises an aliphatic polyamide-containing polyamide layer (A layer), an ethylene-vinyl acetate copolymer saponified product of 55 to 95% by weight, and a soft polymer of 5 to 45%. An oxygen barrier layer (B layer) containing wt% and a polyamide layer (C layer) containing an aliphatic polyamide are laminated in this order. By doing so, the polyamide-based multilayer film of the present invention is excellent in pinhole resistance and gas barrier properties and has a beautiful appearance.

  In each layer of the polyamide-based multilayer film of the present invention, different types of polymers may be mixed as long as the object of the present invention is not impaired. In addition, antioxidants, heat stabilizers, lubricants, ultraviolet rays Additives such as an absorbent, a light stabilizer, an antiblocking agent, an antistatic agent, and a nucleating agent may be added.

  As described above, the (A) layer and the (C) layer may be the same or different from each other, but are preferably the same from the viewpoint of convenience in the production of a polyamide-based multilayer film described later. .

  The total film thickness of the polyamide-based multilayer film of the present invention having the layer structure as described above can be appropriately set according to the application and is not particularly limited, but is usually about 10 to 80 μm, preferably about 12 to 60 μm. is there.

  The thickness of each layer is usually about 4 μm, preferably about 4 to 28 μm, more preferably about 5 to 25 μm for the (A) layer and the (C) layer. When the thickness of the (A) layer and the (C) layer is 4 μm or more, excellent functions such as pinhole resistance can be imparted to the polyamide-based multilayer film of the present invention.

  Further, the thickness of the layer (B) is usually about 2 to 24 μm, preferably about 2 to 20 μm. When the thickness of the (B) layer is 2 to 24 μm, sufficient barrier properties and pinhole resistance due to bending can be imparted to the polyamide-based multilayer film of the present invention.

  The thickness ratio of each layer is preferably 0.5 to 10.0 for the (A) layer and the (C) layer when the (B) layer is 1, and is 0.7 to 7.0. More preferably.

  Moreover, you may provide a sealing layer, an adhesive resin layer, etc. as needed in the outer layer or each interlayer of the polyamide-type multilayer film of this invention.

2. Production Method The production method of the polyamide-based multilayer film of the present invention is not particularly specified. For example, the raw materials of each layer are melt-kneaded with an extruder set at a cylinder temperature of 170 to 270 ° C., and T Coextrusion is carried out on a chill roll in which cooling water circulates from a die to obtain a flat multilayer film.

  The obtained film may be uniaxially stretched or biaxially stretched (simultaneous biaxial stretching and sequential biaxial stretching). The stretching ratio is, for example, longitudinal stretching (MD) 2.5 to 4.5 times and transverse stretching (TD) 2.5 to 5.0 times.

  For example, in the case of sequential biaxial stretching, longitudinal stretching is performed 2.5 to 4.5 times with a roll stretching machine at 50 to 80 ° C., and further 2.5 to 5.0 with a tenter stretching machine in an atmosphere at 50 to 150 ° C. The film can be stretched by a factor of 2 and then heat-treated in an atmosphere of 100 to 240 ° C. with the same tenter. The multilayer stretched film of the present invention may be simultaneously biaxially stretched and sequentially biaxially stretched, and the obtained multilayer stretched film can be subjected to corona discharge treatment on both surfaces or one surface if necessary.

  The “pinhole resistance due to bending” of the polyamide-based multilayer film of the present invention is evaluated using a gelbo flex tester described in Examples described later. In the multilayer film of the present invention, the number of pinholes generated in the evaluation of the resistance to 1,000 pinholes under 5 ° C. conditions is 10 or less, preferably 8 or less, more preferably 5 or less.

About the "oxygen barrier property" of the polyamide-type multilayer film of this invention, it evaluates by the method as described in the below-mentioned Example. Specifically, the oxygen permeability measured in accordance with ASTM D 3985 under the condition of 20 ° C. × 65% RH is 100 ml / m ² · day · MPa or less, preferably 50 ml / m ² · day · MPa or less. It is.

  About the "appearance" of the polyamide-type multilayer film of this invention, it evaluates by the method as described in the below-mentioned Example. Specifically, the gloss measured according to JIS Z 8741 is 180% or more, preferably 190% or more.

  Furthermore, the polyamide-based multilayer film of the present invention also has excellent interlayer strength. Specifically, the film is cut out with a width of 10 mm, and a T-shaped peel test is performed at a speed of 200 mm / min under the condition of 23 ° C. × 65% RH at the interface between the (A) layer and the (B) layer. In this case, the peel strength (N / 10 mm) is 0.6 N / 10 mm or more, preferably 0.8 N / 10 mm or more.

  Since the polyamide-based multilayer film of the present invention is excellent in resistance to pinholes due to bending, it is suitable for packaging heavy items, particularly foods such as baskets and wieners. It is also suitable for packaging frozen foods that are transported at low temperatures. Furthermore, since the polyamide-based multilayer film of the present invention has high transparency, it is easy to visually check the contents (food) when it is used as food packaging, and when printed on the polyamide-based multilayer film of the present invention. It looks good and has excellent design.

  When the polyamide-based multilayer film of the present invention is used as a packaging bag, for example, both ends of the film are bonded to form a cylindrical shape, and further, one end of the opening of the cylindrical material is bonded. Thus, a packaging bag is manufactured. As a method for bonding, a known method can be adopted.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not limited to these Examples.

The raw material resins used in the following Examples and Comparative Examples are shown below.
Aliphatic polyamide: UBE nylon 1022FDX04, Ube Industries, Ltd. crystalline aromatic polyamide: MX-nylon S6011, Mitsubishi Gas Chemical Co., Ltd. amorphous aromatic polyamide: Sealer PA3426, Mitsui DuPont Polychemical Co., Ltd. Saponified ethylene-vinyl acetate copolymer: Soarnol DC3203, Soft polymer 1 manufactured by Nippon Synthetic Chemical Industry Co., Ltd. (styrene-isobutylene block copolymer): SIBSTAR-073T, Soft polymer 2 manufactured by Kaneka Corporation (Polyisoprene cyclized product)
Soft polymer 3 (modified polyolefin): Admer NF587, manufactured by Mitsui Chemicals, Inc.

[Example 1]
Aliphatic polyamide (100% by weight) was used as a resin for the polyamide layer (A) and the polyamide layer (C).

  Further, a saponified ethylene-vinyl acetate copolymer (90% by weight) and a soft polymer 1 (10% by weight) were blended to obtain a resin composition for the oxygen barrier layer (B).

  The resin constituting each layer is coextruded onto a chill roll in which cooling water circulates from a T die so that the order of (A) layer / (B) layer / (C) layer is obtained, and a flat three-layer film Got. This three-layer film was longitudinally stretched 3.0 times by a roll stretcher at 65 ° C., then stretched 4.0 times by a tenter stretcher in an atmosphere at 110 ° C., and further in an atmosphere at 210 ° C. by the same tenter. And a film having a thickness of 15 μm was obtained. The thickness of each layer was 6/3/6 (μm).

[Example 2]
Aliphatic polyamide (90% by weight) and crystalline aromatic polyamide (10% by weight) were blended to obtain a resin composition for the polyamide layer (A) and the polyamide layer (C).

  Further, a saponified ethylene-vinyl acetate copolymer (70% by weight) and a soft polymer 2 (30% by weight) were blended to obtain a resin composition for the oxygen barrier layer (B).

  In the same manner as in Example 1, a A / B / C three-layer film having a thickness of 15 μm was obtained. The thickness of each layer was 5/5/5 (μm).

[Example 3]
Aliphatic polyamide (92% by weight) and amorphous aromatic polyamide (8% by weight) were blended to obtain a resin composition for the polyamide layer (A) and the polyamide layer (C).

  Further, a saponified ethylene-vinyl acetate copolymer (80% by weight) and a soft polymer 1 (20% by weight) were blended to obtain a resin composition for the oxygen barrier layer (B).

  In the same manner as in Example 1, a A / B / C three-layer film having a thickness of 15 μm was obtained. The thickness of each layer was 5/5/5 (μm).

[Example 4]
Aliphatic polyamide (97% by weight) and crystalline aromatic polyamide (3% by weight) were blended to obtain a resin composition for the polyamide layer (A) and the polyamide layer (C).

  Further, a saponified ethylene-vinyl acetate copolymer (60% by weight) and a soft polymer 1 (40% by weight) were blended to obtain a resin composition for the oxygen barrier layer (B).

  In the same manner as in Example 1, a three-layer film having an A / B / C thickness of 25 μm was obtained. The thickness of each layer was 9/7/9 (μm).

[Example 5]
Aliphatic polyamide (85% by weight) and crystalline aromatic polyamide (15% by weight) were blended to obtain a resin composition for the polyamide layer (A) and the polyamide layer (C).

  Further, a saponified ethylene-vinyl acetate copolymer (70% by weight) and a soft polymer 2 (30% by weight) were blended to obtain a resin composition for the oxygen barrier layer (B).

  In the same manner as in Example 1, a three-layer film having an A / B / C thickness of 25 μm was obtained. The thickness of each layer was 5/15/5 (μm).

[Example 6]
Aliphatic polyamide (89% by weight) and amorphous aromatic polyamide (11% by weight) were blended to obtain resin compositions for the polyamide layer (A) and the polyamide layer (C).

  Further, a saponified ethylene-vinyl acetate copolymer (80% by weight) and a soft polymer 2 (20% by weight) were blended to obtain a resin composition for the oxygen barrier layer (B).

  In the same manner as in Example 1, a three-layer film having an A / B / C thickness of 45 μm was obtained. The thickness of each layer was 15/15/15 (μm).

[Comparative Example 1]
Aliphatic polyamide (95% by weight) and crystalline aromatic polyamide (5% by weight) were blended to obtain a resin composition for the polyamide layer (A) and the polyamide layer (C).

  Further, saponified ethylene-vinyl acetate copolymer (100% by weight) was used as a resin for the oxygen barrier layer (B).

  In the same manner as in Example 1, a A / B / C three-layer film having a thickness of 15 μm was obtained. The thickness of each layer was 5/5/5 (μm).

[Comparative Example 2]
Aliphatic polyamide (88% by weight) and amorphous aromatic polyamide (12% by weight) were blended to obtain resin compositions for the polyamide layer (A) and the polyamide layer (C).

  Further, a saponified ethylene-vinyl acetate copolymer (98% by weight) and a soft polymer 1 (2% by weight) were blended to obtain a resin composition for the oxygen barrier layer (B).

  In the same manner as in Example 1, a A / B / C three-layer film having a thickness of 15 μm was obtained. The thickness of each layer was 6/3/6 (μm).

[Comparative Example 3]
Aliphatic polyamide (93% by weight) and crystalline aromatic polyamide (7% by weight) were blended to obtain a resin composition for the polyamide layer (A) and the polyamide layer (C).

  Further, a saponified ethylene-vinyl acetate copolymer (40% by weight) and a soft polymer 1 (60% by weight) were blended to obtain a resin composition for the oxygen barrier layer (B).

  In the same manner as in Example 1, a three-layer film having an A / B / C thickness of 20 μm was obtained. The thickness of each layer was 7/6/7 (μm).

[Comparative Example 4]
Aliphatic polyamide (100% by weight) was used as a resin for the polyamide layer (A) and the polyamide layer (C).

  Further, a saponified ethylene-vinyl acetate copolymer (80% by weight) and a crystalline aromatic polyamide (20% by weight) were blended to obtain a resin composition for the oxygen barrier layer (B).

  In the same manner as in Example 1, a A / B / C three-layer film having a thickness of 15 μm was obtained. The thickness of each layer was 5/5/5 (μm).

[Comparative Example 5]
A resin composition for a polyamide layer (A) and a polyamide layer (C) comprising an aliphatic polyamide (88% by weight), a crystalline aromatic polyamide (7% by weight), and a soft polymer 3 (5% by weight). It was.

  Further, saponified ethylene-vinyl acetate copolymer (100% by weight) was used as a resin for the oxygen barrier layer (B).

  In the same manner as in Example 1, a A / B / C three-layer film having a thickness of 15 μm was obtained. The thickness of each layer was 5/5/5 (μm).

[Comparative Example 6]
UBE nylon (80% by weight) and amorphous aromatic polyamide (20% by weight) were blended to obtain a resin composition for the polyamide layer (A) and the polyamide layer (C).

  Further, saponified ethylene-vinyl acetate copolymer (100% by weight) was used as a resin for the oxygen barrier layer (B).

  In the same manner as in Example 1, a three-layer film having an A / B / C thickness of 25 μm was obtained. The thickness of each layer was 5/15/5 (μm).

[Comparative Example 7]
UBE nylon (85% by weight) and crystalline aromatic polyamide (15% by weight) were blended to obtain a resin composition for the polyamide layer (A) and the polyamide layer (C).

  Further, saponified ethylene-vinyl acetate copolymer (100% by weight) was used as a resin for the oxygen barrier layer (B).

  In the same manner as in Example 1, a three-layer film having an A / B / C thickness of 45 μm was obtained. The thickness of each layer was 15/15/15 (μm).

[Test Example 1]
The polyamide-based multilayer films obtained in Examples 1 to 6 and Comparative Examples 1 to 7 were evaluated for flex resistance, oxygen barrier properties, appearance, and interlayer strength. The results are shown in Tables 1 and 2.

[Flexibility]
The measurement was performed using a gelbo flex tester manufactured by RIKEN. A film formed into a cylindrical shape with a folding diameter of 150 mm and a length of 300 mm is attached to a gelbo flex tester, and a bending linear motion of 15.0 cm at a twist angle of 440 ° is repeated 1000 times under a condition of 5 ° C. The number of pinholes was examined using the penetrant. The number of pinholes was measured at a location of 300 cm ² in the center of the sample. The number of pinholes was measured for three samples, and the average value is shown in Table 1.

[Oxygen barrier properties]
The oxygen permeability (gas barrier property) was measured using an OX-TRAN 200 model manufactured by MODERN CONTROL, and the oxygen permeability at 20 ° C. × 65% RH was measured according to JIS K 7126.

[appearance]
The glossiness was measured according to JIS Z 8741.

[Interlayer strength]
A film was cut out with a width of 10 mm, and a T-shaped peel test was performed at a speed of 200 mm / min at the interface between the (A) layer and the (B) layer under the condition of 23 ° C. × 65% RH.

  From Table 1, it turned out that the film of Examples 1-6 has the outstanding characteristic in any test. On the other hand, none of the films of Comparative Examples 1 to 7 could satisfy all the characteristics.

  In particular, Comparative Example 1, 2, 4 having a barrier layer made of a saponified ethylene-vinyl acetate copolymer, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2008-188976). It was found that the pinhole resistance by bending is remarkably superior to the films of 6 and 7.

  In addition, it turned out that the film of the comparative example 3 has a low interlayer intensity | strength of (A) layer and (C) layer, and (B) layer, and is unpreferable practically. Further, the film of Comparative Example 5 is a polyamide-based multilayer film having a barrier layer made of a saponified ethylene-vinyl acetate copolymer. By adding modified polyolefin to the (A) layer and the (C) layer, the film is bent. Although pinhole resistance has been improved, it has been found that the glossiness is deteriorated, which is not preferable for use in packaging bags.

Claims (8)

A polyamide-based multilayer film in which a polyamide layer (A layer), an oxygen barrier layer (B layer), and a polyamide layer (C layer) are laminated in this order,
(A) the layer contains an aliphatic polyamide;
The layer (B) contains 55 to 95% by weight of saponified ethylene-vinyl acetate copolymer and 5 to 45% by weight of a soft polymer,
(C) the layer contains an aliphatic polyamide ,
The soft polymer is at least one selected from the group consisting of a conjugated diene homopolymer cyclization product, a conjugated diene copolymer cyclization product, and a cyclization product of a conjugated diene and a copolymerizable monomer. A polyamide-based multilayer film, characterized in that The polyamide-based multilayer film according to claim 1, wherein the layer (A) contains 75 to 100% by weight of aliphatic polyamide and 0 to 25% by weight of aromatic polyamide. The polyamide-based multilayer film according to claim 1 or 2, which is a multilayer film obtained by biaxially stretching 2.5 to 4.5 times in the MD direction and 2.5 to 5 times in the TD direction. The thickness of the (A) layer and the (C) layer is 4 μm or more, the thickness of the (B) layer is 2 to 24 μm, and the total film thickness of the polyamide-based multilayer film is 10 to 80 μm. A polyamide-based multilayer film according to claim 1. Furthermore, the polyamide-type multilayer film in any one of Claims 1-4 which has a sealing layer in one surface. A packaging obtained by bonding both ends of the polyamide-based multilayer film according to any one of claims 1 to 5 so as to form a cylindrical shape, and further bonding one end of an opening of the cylindrical material. Bags. The packaging bag according to claim 6, which is for food packaging. Resin composition for polyamide layer (A layer) containing aliphatic polyamide, oxygen barrier layer (B layer) containing 55 to 95% by weight of saponified ethylene-vinyl acetate copolymer and 5 to 45% by weight of soft polymer ) And a polyamide layer (C layer) resin composition containing an aliphatic polyamide are laminated by coextrusion so as to be in this order, stretched biaxially and horizontally, and heat-treated. And
The soft polymer is at least one selected from the group consisting of a conjugated diene homopolymer cyclization product, a conjugated diene copolymer cyclization product, and a cyclization product of a conjugated diene and a copolymerizable monomer. der Ru method for producing a polyamide-based multilayer film.