JP2019166725A - Polyamide-based multilayer stretched film - Google Patents

Abstract

To provide a polyamide-based multilayer stretched film excellent in pinhole resistance by bending.SOLUTION: A polyamide-based multilayer stretched film has at least layer A which contains a polyamide-based resin and contains 3 wt.% or less of a component other than the polyamide-based resin, layer B containing 85-99 wt.% of a polyamide-based resin and 1-15 wt.% of a polyester-based elastomer, and C layer containing a barrier resin.SELECTED DRAWING: None

Description

  The present invention relates to a polyamide-based multilayer stretched film.

  Conventionally, films containing nylon resin are widely used in various directions as films having gas barrier properties, toughness and the like. For example, a film composed of three layers of polyamide layer / barrier layer / polyamide layer is widely used for packaging.

  This film is used, for example, as a packaging film for food or the like distributed in the market, but pinholes may be generated during its transportation and transportation. Due to this pinhole, the excellent gas barrier properties of the film were hindered. Therefore, further improvement in toughness, especially improvement in pinhole resistance is desired from the market.

  Film pinholes may be caused by bending or may be caused by repeated contact wear.

  In general, if the nylon resin layer is hard, pinholes due to repeated contact wear are difficult to form, but pinholes due to bending tend to occur. On the other hand, if the nylon resin layer is soft, pinholes due to bending are less likely to occur, but pinholes are more likely to occur due to repeated contact wear.

  Therefore, a film excellent in pinhole resistance against either bending or repeated contact is strongly desired.

  In order to solve this problem, the present applicant has already developed a polyamide-based film having at least a polyamide layer containing a polyamide and an anti-bending agent (Patent Document 1).

  However, there is a demand for further improvement, and development of a polyamide-based multilayer stretched film that is superior in pinhole resistance due to bending and repeated contact is desired.

JP 2017-2114

  An object of this invention is to provide the polyamide-type multilayer stretched film excellent in the pinhole resistance by a bending | flexion and repeated contact.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that in a polyamide-based multilayer stretched film, a layer A containing a polyamide-based resin, a layer B containing a polyamide-based resin and a polyester-based elastomer, and a barrier resin It has been found that the polyamide-based multilayer stretched film has an excellent pinhole resistance due to bending and repeated contact by having at least a C layer containing.

  That is, the present invention provides the following polyamide-based multilayer stretched film.

Item 1.
Including a polyamide-based resin, a layer A containing 3% by weight or less of components other than the polyamide-based resin, a B-layer containing a polyamide-based resin 85 to 99% by weight and a polyester-based elastomer 1 to 15% by weight, and a barrier resin A polyamide-based multilayer stretched film having at least a C layer.

Item 2.
Item 2. The polyamide multilayer stretched film according to Item 1, wherein the A layer contains an aliphatic polyamide and an aromatic polyamide.

Item 3.
Item 3. The polyamide-based multilayer stretched film according to Item 1 or 2, wherein the barrier resin is an ethylene-vinyl alcohol copolymer or an aromatic polyamide.

  The polyamide-based multilayer stretched film of the present invention is excellent in pinhole resistance due to bending and repeated contact.

  The polyamide-based multilayer stretched film of the present invention is excellent in transparency.

The schematic diagram of the measuring apparatus used for evaluation of the pinhole which generate | occur | produces by repeated contact is shown. An example of a cone-shaped aluminum jig is shown.

(1) Polyamide-based multilayer stretched film The polyamide-based multilayer stretched film of the present invention includes a polyamide-based resin, and includes a layer A in which components other than the polyamide-based resin are 3% by weight or less, 85-99% by weight of the polyamide-based resin, and polyester At least a B layer containing 1 to 15% by weight of a base elastomer and a C layer containing a barrier resin.

  The polyamide-based multilayer stretched film of the present invention has excellent pinhole resistance due to bending and repeated contact.

  The polyamide-based multilayer stretched film of the present invention is further excellent in transparency.

  Hereinafter, the polyamide film of the present invention will be described in detail.

(1-1) Polyamide-based multilayer stretched film A layer (PA layer 1)
The A layer of the polyamide-based multilayer stretched film of the present invention contains a polyamide-based resin, and components other than the polyamide-based resin are 3% by weight or less.

Polyamide resin The polyamide resin is not particularly limited, and aliphatic polyamides, aromatic polyamides, and the like can be preferably used.

  The A layer preferably contains an aliphatic polyamide in that it is excellent in pinhole resistance due to bending and repeated contact.

Examples of the aliphatic polyamide include aliphatic nylon and copolymers thereof.

  Polycapramide (nylon-6), poly-ω-aminoheptanoic acid (nylon-7), poly-ω-aminononanoic acid (nylon-9), polyundecanamide (nylon-11), polylauryllactam (nylon-12), etc. It is better to use

  Polyethylenediamine adipamide (nylon-2,6), polytetramethylene adipamide (nylon-4,6), polyhexamethylene adipamide (nylon-6,6), polyhexamethylene sebamide (nylon- 6,10), polyhexamethylene dodecamide (nylon-6,12), polyoctamethylene adipamide (nylon-8,6), polydecamethylene adipamide (nylon-10,8), etc. This is true.

  Caprolactam / lauryl lactam copolymer (nylon-6 / 12), caprolactam / ω-aminononanoic acid copolymer (nylon-6 / 9), caprolactam / hexamethylenediammonium adipate copolymer (nylon-6 / 6,6 ), Lauryl lactam / hexamethylenediammonium adipate copolymer (nylon-12 / 6,6) and the like are preferable.

  Ethylenediamine adipamide / hexamethylenediammonium adipate copolymer (nylon-2,6 / 6,6), caprolactam / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon-6,6 / 6) 10), ethyleneammonium adipate / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon-6 / 6,6 / 6,10) and the like are preferable.

  One kind of the above-mentioned aliphatic polyamide may be used, or two or more kinds of the above-mentioned aliphatic polyamides may be mixed and used.

  Preferred aliphatic polyamides include nylon-6, nylon-6,6, nylon-6 / 6,6 (a copolymer of nylon 6 and nylon 6,6). Nylon-6 and nylon-6 / 6,6 are more preferable, and nylon-6 is particularly preferable.

  As the two or more kinds of aliphatic polyamides, a combination of nylon-6 and nylon-6 / 6,6 is preferable. Nylon-6 is preferably contained in a weight ratio of about 50 to 95, and nylon-6 / 6,6 is preferably contained in a weight ratio of about 50 to 5.

The aromatic polyamide polyamide resin may further contain an aromatic polyamide.

  As an aromatic polyamide, a polycondensation reaction of an aromatic diamine such as meta-xylene diamine and para-xylene diamine with a dicarboxylic acid such as adipic acid, suberic acid, sebacic acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid or a derivative thereof. Examples thereof include crystalline aromatic polyamides obtained.

  The aromatic polyamide is preferably a crystalline aromatic polyamide such as polymetaxylylene adipamide (MX-nylon). Specific examples of the crystalline aromatic polyamide include S-6001, S-6007, and S-6121 (all manufactured by Mitsubishi Gas Chemical Co., Ltd.).

  Examples of the aromatic polyamide include amorphous aromatic polyamide (amorphous nylon) obtained by a polycondensation reaction between an aliphatic diamine such as hexamethylenediamine and a dicarboxylic acid such as terephthalic acid or isophthalic acid or a derivative thereof.

  The amorphous aromatic polyamide is preferably a hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid copolymer. A specific example of the amorphous aromatic polyamide is Sealer PA (Mitsui / DuPont Polychemical Co., Ltd.).

Preferred Composition of Polyamide Resin The content of the aliphatic polyamide (such as nylon 6) in the polyamide resin is preferably about 80 to 100% by weight, more preferably 80 to 99% by weight, where the amount of polyamide is 100% by weight. About%. By setting the content of the aliphatic polyamide in the polyamide within the above range, the pinhole resistance of the polyamide film can be improved.

  When the polyamide-based resin contains an aliphatic polyamide and an aromatic polyamide, the polyamide-based film of the present invention can exhibit more excellent stretch film forming properties.

  Preferred combinations of aliphatic polyamide and aromatic polyamide include nylon-6 and crystalline aromatic polyamide (MX-nylon, etc.), nylon-6 and amorphous aromatic polyamide (amorphous nylon). Is mentioned.

  The content of aromatic polyamide (such as MX-nylon or amorphous nylon) in the polyamide-based resin is preferably about 0 to 20% by weight, more preferably about 1 to 20% by weight, where the amount of polyamide is 100% by weight. It is.

Preferred Relative Viscosity of Polyamide Resin Polyamide resin having a relative viscosity of 2.0 to 4.5 measured under the conditions of 96% H ₂ SO ₄ , 1.0 g / 100 ml, and a temperature of 25 ° C. by a measuring method based on JIS K6920. It is preferable to use 2.5 to 4.5. The relative viscosity (JIS K6920) of the polyamide resin is more preferably 3.0 to 4.2. When the relative viscosity of the polyamide satisfies this range, the pinhole resistance due to bending of the polyamide multilayer stretched film is good.

  When two or more types of polyamide resins are used in combination, the relative viscosity of the polyamide resin is determined by measuring the relative viscosities of the respective polyamides to be mixed, and calculating the weighted average value. Viscosity.

Components other than polyamide resin
From the viewpoint of pinhole resistance due to repeated contact, the layer A preferably contains 3% by weight or less of components other than the polyamide-based resin. If the component other than the polyamide-based resin exceeds 3% by weight, it is not preferable because pinhole resistance deteriorates due to repeated contact.

  In the polyamide-based multilayer stretched film of the present invention, the above-mentioned “A layer containing a polyamide-based resin and containing 3% by weight or less of components other than the polyamide-based resin”, in other words, the A layer is 97% by weight or more of the polyamide-based resin Is to include. Therefore, the polyamide-based multilayer stretched film of the present invention may be expressed as “A layer containing polyamide-based resin of 97% by weight or more”.

  The layer A may contain other additives as necessary within the range not impairing the effects of the present invention. As other additives, an antiblocking agent, a lubricant, a nucleating agent, an antioxidant and the like can be preferably used.

(1-2) Polyamide-based multilayer stretched film B layer (PA layer 2)
The B layer of the polyamide-based multilayer stretched film of the present invention contains a polyamide-based resin 85 to 99% by weight and a polyester-based elastomer 1 to 15% by weight. The polyamide-based multilayer stretched film of the present invention is particularly excellent in pinhole resistance (bending resistance) due to bending due to the B layer.

Polyamide resin The polyamide resin is not particularly limited, and aliphatic polyamides, aromatic polyamides, and the like can be preferably used. Aliphatic polyamides are preferred because of their superior pinhole resistance.

Examples of the aliphatic polyamide include aliphatic nylon and copolymers thereof.

  Polycapramide (nylon-6), poly-ω-aminoheptanoic acid (nylon-7), poly-ω-aminononanoic acid (nylon-9), polyundecanamide (nylon-11), polylauryllactam (nylon-12), etc. It is better to use

  Polyethylenediamine adipamide (nylon-2,6), polytetramethylene adipamide (nylon-4,6), polyhexamethylene adipamide (nylon-6,6), polyhexamethylene sebamide (nylon- 6,10), polyhexamethylene dodecamide (nylon-6,12), polyoctamethylene adipamide (nylon-8,6), polydecamethylene adipamide (nylon-10,8), etc. This is true.

  Caprolactam / lauryl lactam copolymer (nylon-6 / 12), caprolactam / ω-aminononanoic acid copolymer (nylon-6 / 9), caprolactam / hexamethylenediammonium adipate copolymer (nylon-6 / 6,6 ), Lauryl lactam / hexamethylenediammonium adipate copolymer (nylon-12 / 6,6) and the like are preferable.

  Ethylenediamine adipamide / hexamethylenediammonium adipate copolymer (nylon-2,6 / 6,6), caprolactam / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon-6,6 / 6) 10), ethyleneammonium adipate / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon-6 / 6,6 / 6,10) and the like are preferable.

  One kind of the above-mentioned aliphatic polyamide may be used, or two or more kinds of the above-mentioned aliphatic polyamides may be mixed and used.

  Preferred aliphatic polyamides include nylon-6, nylon-6,6, nylon-6 / 6,6 (a copolymer of nylon 6 and nylon 6,6). Nylon-6 and nylon-6 / 6,6 are more preferable, and nylon-6 is particularly preferable.

  The B layer contains a polyamide-based resin of 85 to 99 weight, and two or more aliphatic polyamides can be used in combination as the polyamide-based resin.

  As the two or more types of aliphatic polyamides in the B layer, a combination of an aliphatic polyamide resin (nylon-6 or the like) and a polyamide copolymer (nylon-6 / 6, 6 or the like) is preferable. For example, in layer B, an aliphatic polyamide resin (nylon-6, etc.) is contained in a weight ratio (wt%) of about 50 to 94, and a polyamide copolymer (nylon-6 / 6, 6 etc.) is contained in a weight ratio. It is preferable to contain about 5-40.

The aromatic polyamide polyamide resin may be used by mixing the aliphatic polyamide and the aromatic polyamide. The polyamide-based resin may contain an aromatic polyamide as an optional component.

  When the polyamide-based resin contains an aliphatic polyamide and an aromatic polyamide, the polyamide-based multilayer stretched film of the present invention can exhibit more excellent stretch film-forming properties.

  As an aromatic polyamide, a polycondensation reaction of an aromatic diamine such as meta-xylene diamine and para-xylene diamine with a dicarboxylic acid such as adipic acid, suberic acid, sebacic acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid or a derivative thereof. Examples thereof include crystalline aromatic polyamides obtained.

  The aromatic polyamide is preferably a crystalline aromatic polyamide such as polymetaxylylene adipamide. Specific examples of the crystalline aromatic polyamide include S-6001, S-6007, and S-6121 (all manufactured by Mitsubishi Gas Chemical Co., Ltd.).

  As the aromatic polyamide, amorphous aromatic polyamide (amorphous nylon) obtained by polycondensation reaction of an aliphatic diamine such as hexamethylene diamine and a dicarboxylic acid such as terephthalic acid or isophthalic acid or a derivative thereof is used. Can be mentioned.

  The aromatic polyamide is preferably a hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid copolymer. A specific example of the amorphous aromatic polyamide is Sealer PA (Mitsui / DuPont Polychemical Co., Ltd.).

  Preferable combinations of aliphatic polyamide and aromatic polyamide include a combination of nylon-6 and crystalline aromatic polyamide, and a combination of nylon-6 and amorphous aromatic polyamide (amorphous nylon).

  The content of the aliphatic polyamide in the polyamide-based resin of the B layer is preferably about 80 to 100% by weight, more preferably about 90 to 100% by weight, where the amount of polyamide is 100% by weight. By setting the content of the aliphatic polyamide in the polyamide within the above range, the pinhole resistance of the polyamide film can be improved.

  When the polyamide-based resin of layer B contains an aliphatic polyamide and an aromatic polyamide, the content of the aromatic polyamide in the polyamide is preferably 0 to 20% by weight, with the amount of polyamide as 100% by weight as an optional component. 0 to 10% by weight is more preferable.

Preferred Relative Viscosity of Polyamide Resin A polyamide resin having a relative viscosity of 2.5 to 4.5 measured under the conditions of 96% H ₂ SO ₄ , 1.0 g / 100 ml, and a temperature of 25 ° C. by a measuring method based on JIS K6920. It is preferable to use it. The relative viscosity (JIS K6920) of the polyamide resin is more preferably 3.0 to 4.5, and still more preferably 3.2 to 4.2. When the relative viscosity of the polyamide satisfies this range, the pinhole resistance due to bending of the polyamide multilayer stretched film is good.

  When two or more types of polyamide resins are used in combination, the relative viscosity of the polyamide resin is determined by measuring the relative viscosities of the respective polyamides to be mixed, and calculating the weighted average value. Viscosity.

Polyester Elastomer The B layer of the polyamide-based multilayer stretched film of the present invention contains 1 to 15% by weight of a polyester-based elastomer, which functions as a bending-resistant agent and can impart pinhole resistance due to bending.

  The polyester elastomer is a thermoplastic elastomer and is a thermoplastic material as a substance having rubber-like elasticity.

  In addition to the polyester elastomer, a polyamide elastomer, a polyolefin elastomer, a polystyrene elastomer, a polyurethane elastomer, a polyvinyl chloride elastomer, an ionomer polymer, or the like can be used in combination.

  Since the pinhole resistance due to bending of the polyamide-based multilayer stretched film of the present invention can be further improved, a polyester-based elastomer is used, and a polyamide-based elastomer and a polyolefin-based elastomer can be used optionally. More preferably, a polyamide-based elastomer is used in combination.

  In addition to the polyester elastomer, other thermoplastic elastomers can be used alone or in combination of two or more.

  The polyester elastomer may be modified as long as the pinhole resistance due to bending of the polyamide multilayer stretched film of the present invention is not lowered. A modified polyester elastomer may also be used.

  Examples of the modification in the polyester elastomer include modification by copolymerization or graft modification, modification by imparting a polar group, and the like.

  The application of the polar group may be performed by graft modification. Examples of such a polar group include an epoxy group, a carboxyl group, an acid anhydride group, a hydroxyl group, an amino group, and an oxo group. The polar group can be imparted by one type or a combination of a plurality of types. Accordingly, the modified body to which a polar group is added includes, for example, an epoxy-modified body, a carboxy-modified body, an acid anhydride-modified body, a hydroxy-modified body, an amino-modified body and the like of a polyester elastomer.

  Examples of polyester elastomers include modified polyester elastomers. The modified polyester elastomer is obtained by modifying a saturated polyester thermoplastic elastomer containing a polyalkylene ether glycol segment with an unsaturated carboxylic acid or a derivative thereof.

  Specifically, it is obtained by modifying a saturated polyester thermoplastic elastomer having a polyalkylene ether glycol segment content of 58 to 73% by weight with an unsaturated carboxylic acid or a derivative thereof in the presence of a radical generator. It is a modified polyester elastomer. Since a reactive group is introduced by graft reaction and terminal addition reaction of unsaturated carboxylic acid or its derivative, chemical bondability and hydrogen bondability with various resins are improved.

  The saturated polyester thermoplastic elastomer is a block copolymer composed of a soft segment containing a polyalkylene ether glycol segment and a hard segment containing a polyester, and the content of the polyalkylene ether glycol segment is the polyester elastomer. It is about 58 to 73% by weight.

  As the polyalkylene ether glycol constituting the soft segment, for example, polyethylene glycol, poly (1,2 and 1,3-propylene ether) glycol, poly (tetramethylene ether) glycol, poly (hexamethylene ether) glycol and the like are preferably used. be able to. The number average molecular weight of the polyalkylene ether glycol is preferably about 400 to 6000.

  As unsaturated carboxylic acid or its derivative (s), unsaturated carboxylic acid, such as acrylic acid, maleic acid, fumaric acid, its acid anhydride, its ester, or its metal salt is mentioned, for example.

  Examples of the radical generator include peroxides such as t-butyl hydroperoxide and cumene hydroperoxide, and azo compounds such as 2,2′-azobisisobutyronitrile (AIBN).

  It is preferable that the unsaturated carboxylic acid or its derivative contains 0.01 to 30 parts by weight and the radical generator contains 0.001 to 3 parts by weight with respect to 100 parts by weight of the saturated polyester thermoplastic elastomer.

  The method for preparing the modified polyester elastomer is not particularly limited. For example, it can be prepared by the method described in JP-A-2002-155135.

  The melt flow rate (MFR) of the resulting modified polyester elastomer is preferably 40 to 300 g / 10 min. MFR shall be a value measured under the conditions of 230 ° C and 2.16 kg by a measurement method in accordance with JIS K7210.

  As the polyester elastomer, maleic anhydride-modified polyester elastomer is particularly preferable. Specific examples of commercially available modified polyester elastomers include Tefa Block-GQ131 (manufactured by Mitsubishi Chemical Corporation).

  A polyamide-based elastomer preferable as an optional thermoplastic elastomer includes a polyamide-based block copolymer composed of a hard segment composed of a polyamide component and a soft segment composed of a polyoxyalkylene glycol component.

  The hard segment polyamide component comprises (1) lactam, (2) ω-aminoaliphatic carboxylic acid, (3) aliphatic diamine and aliphatic dicarboxylic acid, or (4) aliphatic diamine and aromatic dicarboxylic acid. Selected from. Specific examples of the hard-segment polyamide component 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. it can.

  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 block copolymer is determined by the kind and ratio of the hard segment constituted by the polyamide component and the soft segment constituted by the polyoxyalkylene glycol component. Usually, the thing of the range of 120-180 degreeC is preferable.

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

  Examples of the polyolefin-based elastomer include a resin obtained by graft-modifying or copolymerizing an unsaturated carboxylic acid or an anhydride thereof with a polyolefin resin.

  The polyolefin resins that can be used as the base polymer for polyolefin elastomers are ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene. Α-olefin homopolymers such as, these two or more random copolymers, these two or more block copolymers, copolymers of ethylene and vinyl acetate, ethylene and ethyl (meth) acrylate Examples thereof include polymers selected from ethylene / polar monomer copolymers such as copolymers.

  More specifically, examples of the polyolefin resin that can be used as the base polymer include high-density polyethylene, medium-density polyethylene, high-pressure low-density polyethylene, and linear low-density polyethylene (co-polymer of ethylene and an α-olefin having 3 or more carbon atoms). Polymer), polypropylene (homopolymer, random polymer, block copolymer, etc.), poly-1-butene, poly-4-methyl-1-pentene, ethylene-vinyl acetate copolymer, etc. .

  These may be produced with any catalyst system. For example, in the said linear low density polyethylene, what was manufactured with the metallocene catalyst or the multisite catalyst can be used.

  The polyolefin-based elastomer can be obtained by grafting an unsaturated carboxylic acid to a polyolefin resin that is a base polymer, and can also be obtained by copolymerization modification of an olefin and a small amount of an unsaturated carboxylic acid.

  Examples of unsaturated carboxylic acids or anhydrides used for grafting or copolymerization modification include acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, itaconic anhydride, norbornene-2, 3-dicarboxylic anhydride Can do.

  In particular, an acid anhydride is preferable, and maleic anhydride is particularly preferable.

  The polyolefin elastomer is preferably a maleic anhydride-modified ethylene copolymer. Examples of maleic anhydride-modified ethylene copolymers include maleic anhydride graft-modified ethylene copolymers and maleic anhydride-ethylene copolymers. Partially saponified ethylene-vinyl acetate copolymers were modified with maleic anhydride. A thing can be used suitably.

Content of polyamide resin and polyester elastomer
The content of the polyamide-based resin in the B layer is 85 to 99% by weight, where the weight of the entire B layer is 100% by weight. When the polyamide-based resin in the B layer satisfies this content range, the pinhole resistance due to bending is good. The content of the polyamide-based resin in the B layer is preferably 90 to 98% by weight.

  The content of the polyester elastomer in the B layer is 1 to 15% by weight, where the weight of the entire B layer is 100% by weight. When the polyester elastomer in the B layer satisfies this content range, the pinhole resistance due to bending is good. The content of the polyester-based elastomer in the B layer is preferably 2 to 10% by weight.

  The B layer may contain other additives as necessary within a range not impairing the effects of the present invention. As other additives, an antiblocking agent, a lubricant, a nucleating agent, an antioxidant and the like can be preferably used.

  The polyamide-based multilayer stretched film of the present invention is particularly excellent in pinhole resistance (bending resistance) due to bending due to the B layer.

(1-3) Polyamide-based multilayer stretched film C layer (barrier layer)
The C layer of the polyamide-based multilayer stretched film of the present invention contains a barrier resin.

  The barrier resin is preferably an ethylene-vinyl alcohol copolymer (EVOH) and / or an aromatic polyamide. The barrier resin is preferably EVOH and / or polymetaxylylene adipamide (MX-nylon), more preferably EVOH.

  The polyamide-based multilayer stretched film of the present invention includes the C layer, so that the gas barrier property of the polyamide-based multilayer stretched film is excellent. For the C layer, EVOH and polymetaxylylene adipamide may be used alone or in combination.

  The ethylene-vinyl alcohol copolymer (EVOH) is not particularly limited. EVOH has an ethylene content of preferably 55 mol% or less, more preferably 20 to 50 mol%, still more preferably 25 to 44 mol%.

  EVOH has a saponification degree of the vinyl acetate component of preferably 90 mol% or more, more preferably 95 mol% or more.

  EVOH includes a small amount of an α-olefin such as propylene, isobutene, α-octene, α-dodecene, α-octadecene, etc., as long as the effects of the present invention are not adversely affected; Salts, partially alkyl esters, fully alkyl esters, nitriles, amides, anhydrides); may contain comonomers such as unsaturated sulfonic acids or salts thereof.

  The melt index (MI) of EVOH is preferably 0.5 to 50 g / 10 min (210 ° C., 2,160 g load), more preferably 1 to 35 g / 10 min (210 ° C., 2,160 g load). When the MI satisfies this range, the viscosity does not hinder melt extrusion, and the film forming property is good.

  Examples of commercially available EVOH include DC3203FB and DT2904RB (both manufactured by Nippon Synthetic Chemical Co., Ltd.).

  Aromatic polyamides such as polymetaxylylene adipamide (MX-nylon) can be preferably used.

  Examples of the aromatic polyamide include S-6001, S-6007, and S-6121 (all manufactured by Mitsubishi Gas Chemical Co., Ltd.).

  The C layer may further contain other components such as a modified ethylene vinyl acetate copolymer and a methacrylic acid copolymer ionomer as long as the barrier layer does not adversely affect the effects of the present invention. When the C layer contains other components, the content of this component is usually preferably 15 parts by weight or less, more preferably 7.5 parts by weight or less, with respect to a total of 100 parts by weight of EVOH and / or MX-nylon. It is.

(1-4) Layer structure of polyamide-based multilayer stretched film The polyamide-based multilayer stretched film of the present invention includes a layer A containing a polyamide-based resin, a polyamide-based resin 85 to 99% by weight, and a polyester-based elastomer 1 to 15% by weight. It has at least a B layer and a C layer containing a barrier resin.

  The embodiment of the polyamide-based multilayer stretched film of the present invention preferably has a layer structure in which layers are laminated in the order of A layer / B layer / C layer. The aspect of the polyamide-based multilayer stretched film of the present invention is as follows: A layer (PA layer 1) / B layer (PA layer 2) / C layer (barrier layer) / B layer (PA layer 2) / A layer (PA layer 1) For example, a layer structure in which five or more layers are stacked is also possible.

  The total thickness of the polyamide-based multilayer stretched film of the present invention is preferably about 10 to 50 μm, more preferably about 10 to 30 μm.

  The thickness of the A layer (PA layer 1) is preferably about 0.5 to 30 μm, more preferably about 0.5 to 20 μm. The thickness of the A layer may be considered as the total thickness of the layers on both sides.

  The thickness of the B layer (PA layer 2) is preferably about 0.5 to 30 μm, more preferably about 0.5 to 20 μm. The thickness of layer B may be considered as the total thickness of the layers on both sides.

  The thickness of the C layer (barrier layer) is preferably about 0.5 to 20 μm, more preferably about 0.5 to 15 μm.

  In the case of 5 layers (A layer / B layer / C layer / B layer / A layer), the thickness of each layer is preferably about 0.5 to 29.5 μm for A layer (PA layer 1), and B layer (PA layer 2) About 0.5 to 29.5 μm is preferable, and the C layer (barrier layer) is preferably about 0.5 to 20 μm. The A layer is more preferably about 0.5 to 19.5 μm thick, the B layer is more preferably about 0.5 to 19.5 μm thick, and the C layer is more preferably about 0.5 to 15 μm thick. Each thickness of the A layer and the B layer may be considered as the total thickness of the layers on both sides.

(2) Method for producing polyamide-based multilayer stretched film The method for producing the polyamide-based multilayer stretched film of the present invention is not particularly limited. A conventionally known production method for forming a laminate can be preferably employed.

  In order to produce the polyamide-based multilayer stretched film of the present invention, a resin composition for forming an A layer (PA layer 1), a B layer (PA layer 2), and a C layer (barrier layer), for example, A layer / Co-extrusion is carried out on a chill roll in which cooling water circulates from a T die so that the order of B layer / C layer / B layer / A layer is obtained. Thereby, a flat polyamide-type multilayer stretched film can be produced.

  The obtained polyamide-based multilayer stretched film may be uniaxially stretched or biaxially stretched (simultaneous biaxial stretching, sequential biaxial stretching). The draw ratio is preferably about 2.5 to 4.5 times longitudinal stretch (MD), preferably about 2.5 to 5.0 times transverse stretch (TD).

  In the case of sequential biaxial stretching, the polyamide-based multilayer stretched film is stretched longitudinally 2.5 to 4.5 times with a roll stretcher at 50 to 80 ° C, and stretched 2.5 to 5.0 times with a tenter stretcher in an atmosphere at 80 to 140 ° C. It is recommended that the heat treatment be performed in an atmosphere of 180 to 220 ° C. using the same tenter.

  The polyamide-based multilayer stretched film of the present invention may be uniaxially stretched or biaxially stretched (simultaneous biaxial stretching, sequential biaxial stretching), and the obtained polyamide-based multilayer stretched film may have both surfaces or pieces if necessary. The surface can also be subjected to corona discharge treatment.

(3) Performance and application of polyamide-based multilayer stretched film
Pinhole resistance by bending “ Pinhole resistance by bending” is evaluated using a gelbo flex tester on the film as described in the examples below. In the polyamide-based multilayer stretched film of the present invention, the number of pinholes generated in the evaluation of the resistance to pinholes bent 1000 times at 5 ° C. is preferably 5 or less.

Pinhole resistance due to abrasion “ Pinhole resistance due to abrasion ” is evaluated by the method described in Examples below. The number of sliding times until a pinhole is formed is preferably 250 times or more.

The haze value “haze value” is measured according to JIS K7136 (2000) with respect to the film as described in Examples below. The haze value is defined as the ratio (ratio) of diffuse transmittance to total light transmittance. In the polyamide-based multilayer stretched film of the present invention, the haze value (%) is preferably 7% or less.

  The polyamide-based multilayer stretched film of the present invention is excellent in pinhole resistance due to bending and abrasion, and is also excellent in transparency, and is therefore suitable for packaging heavy objects. The polyamide-based multilayer stretched film of the present invention is particularly suitable for packaging foods such as straws and winners.

  The polyamide-based multilayer stretched film of the present invention can also be suitably used for packaging frozen foods that are transported at low temperatures.

  Below, this invention is demonstrated in detail using an Example and a comparative example.

  The present invention is not limited to these examples.

(1) Raw materials used in Examples Table 1 shows raw materials used in Examples and Comparative Examples.

(2) Examples 1 and 2 and Comparative Examples 1 to 3
A resin composition for forming A layer (PA layer 1), B layer (PA layer 2), and C layer (barrier layer) using the raw materials shown in Table 1 and the formulation shown in Table 2 Prepared.

  The resin composition for forming the A layer was further added with 900 ppm of silica having an average particle diameter of 3 μm as an antiblocking agent and 300 ppm of ethylenebisstearic acid amide as a lubricant.

  The resin compositions of Examples and Comparative Examples were respectively supplied to an extruder at 250 ° C., and overlapped with a feed block so that the order of A layer / B layer / C layer / B layer / A layer was 250 ° C. From the T die, it was extruded into a sheet shape on a chill roll through which cooling water circulates, and a 5-layer film having a layer configuration of A layer / B layer / C layer / B layer / A layer was produced.

  Subsequently, the obtained film was longitudinally stretched 3.0 times by a roll stretching machine at 65 ° C, and then stretched 4.0 times by a tenter stretching machine in an atmosphere at 110 ° C.

  Further, the same tenter was heat-treated in an atmosphere at 210 ° C. to prepare a polyamide-based multilayer stretched film having a thickness of A / B / A having a thickness ratio shown in Table 2 having a thickness of 15 μm.

  The performance of the polyamide-based multilayer stretched films of Examples and Comparative Examples was evaluated.

(3) Pinhole resistance by bending the film (flexibility test)
The pinhole resistance due to bending of the polyamide-based multilayer stretched film was measured using a gelbo flex tester manufactured by RIKEN.

  A polyamide-based multilayer stretched film made into a cylindrical shape with a folding diameter of 150 mm and a length of 300 mm was attached to a gelbo flex tester. About this, after giving a twist of 440 ° at the first 88.9cm, and then repeating the bending linear motion of 63.5cm in a linear horizontal motion 1000 times at a test speed of 40 times / min under the condition of 5 ° C, The number of pinholes was examined using the penetrant.

The number of pinholes was measured at 300 cm ^{2 at} the center of the sample. The number of pinholes was measured for three samples, and the average value was taken as the measurement result.

  In the sample film, it was determined that the number of pinholes was 5 or less.

(4) Pinhole resistance due to film abrasion (Abrasion resistance test)
A film is attached to a jig made of aluminum with a cone shape using tape or the like, and the apex of the cone-shaped jig is placed on the cardboard through the film (for KOKUYO Campus, for fine pus, 430g / m ² ). The vertex R was set to a sliding direction R = 0.1 to 1.0 mm and a direction R perpendicular to the sliding direction R = 0.1 to 1.0 mm. Next, a load of 63 g was placed on the jig. Under a humidity of 65%, slide the jig parallel to the cardboard at a speed of 2700 mm / min and a moving distance of 45 mm. The number of times was measured. For example, if it was opened at 300 times and not opened at 250 times, it was set at 300 times.

  The occurrence of pinholes was determined based on whether or not the penetrating solution was dropped onto the film where the top of the jig had hit and permeated on white paper.

  In the sample film, 250 times or more was considered acceptable.

  FIG. 1 shows a schematic diagram of a measuring apparatus, and FIG. 2 shows an example of a conical aluminum jig.

(5) Haze value of film (transparency test)
The haze value of the polyamide-based multilayer stretched film was measured according to JIS K7136 (2000). As a measuring instrument, a haze meter (NDH-5000 manufactured by Nippon Denshoku Industries Co., Ltd.) was used.

  The haze value is defined as the ratio (ratio) of the diffuse transmittance to the total light transmittance, and can be obtained as follows. Each sample was measured three times and the average value was calculated.

Haze value (%) = (diffuse transmittance) / (total light transmittance) × 100
In the sample film, a haze value of 7% or less was regarded as acceptable.

(6) Evaluation results of polyamide-based multilayer stretched film Table 2 shows the results of the bending resistance test and the transparency test.

  The polyamide-based multilayer stretched film of the present invention is exemplified in Examples 1 and 2, and the layer A contains a polyamide-based resin (PA-1 and MXD6), and components other than the polyamide-based resin are 3% by weight or less, and B The layer contains 85 to 99% by weight of a polyamide resin (PA-1 and PA-2) and 1 to 15% by weight of a polyester elastomer (PEE), and the C layer contains a barrier resin (EVOH).

  Due to these characteristics, the polyamide-based multilayer stretched film of the present invention is excellent in pinhole resistance due to bending, pinhole resistance due to repeated contact, and transparency.

  On the other hand, Comparative Examples 1 and 2 are cases where the polyamide resin in the B layer is less than 85 wt% and the polyamide resin in the B layer exceeds 99 wt%. In other words, Comparative Examples 1 and 2 are cases where the polyester elastomer in the B layer is less than 1% by weight and the polyester elastomer in the B layer is more than 15% by weight. The films of Comparative Examples 1 and 2 were not good in pinhole resistance and transparency due to bending.

  Further, since the film of Comparative Example 3 contained 4% by weight of polyester elastomer (PEE) in the A layer, the pinhole property due to repeated contact was not sufficient.

Claims (3)

  Including a polyamide-based resin, a layer A containing 3% by weight or less of components other than the polyamide-based resin, a B-layer containing a polyamide-based resin 85 to 99% by weight and a polyester-based elastomer 1 to 15% by weight, and a barrier resin A polyamide-based multilayer stretched film having at least a C layer.   The polyamide-based multilayer stretched film according to claim 1, wherein the layer A contains an aliphatic polyamide and an aromatic polyamide.   The polyamide-based multilayer stretched film according to claim 1 or 2, wherein the barrier resin is an ethylene-vinyl alcohol copolymer or an aromatic polyamide.