JP2023009104A - Polyamide-based multilayer stretched film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyamide-based multilayer stretched film having high resistance to pinholes due to bending.

SOLUTION: A polyamide-based multilayer stretched film has at least a layer A which contains a polyamide-based resin with the content of other components being 3 wt.% or less, a layer B containing 85-99 wt.% of a polyamide-based resin and 1-15 wt.% of a polyester-based elastomer, and a C layer containing a barrier resin.

SELECTED DRAWING: None

COPYRIGHT: (C)2023,JPO&INPIT

Description

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

BACKGROUND ART Conventionally, films containing nylon resins have been widely used in various fields as films having gas barrier properties, toughness, and the like. For example, a film consisting 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 products distributed in the market, and pinholes may be formed during transportation. These pinholes hinder the excellent gas barrier properties of the film. Therefore, there is a demand from the market for further improvement in toughness, particularly improvement in pinhole resistance.

Pinholes in films are caused by flexing and wear due to repeated contact.

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

Therefore, there is a strong demand for a film that is highly resistant to pinholes, whether it is bent or repeatedly contacted.

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 a flex-resistant agent (Patent Document 1).

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

Japanese Patent Application Laid-Open No. 2017-2114

An object of the present invention is to provide a polyamide-based multilayer stretched film having excellent resistance to pinholes due to bending and repeated contact.

As a result of intensive research to solve the above problems, the present inventors have found that in a multilayer stretched polyamide-based 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 By having at least the C layer containing, this polyamide-based multilayer stretched film is excellent in pinhole resistance due to bending and repeated contact, and has completed the present invention.

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

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

Section 2.
3. The multilayer stretched polyamide-based film according to item 1, wherein the layer A contains an aliphatic polyamide and an aromatic polyamide.

Item 3.
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 multilayer stretched polyamide-based 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) Multi-layer stretched polyamide-based film The multi-layer stretched polyamide-based film of the present invention comprises an A layer containing a polyamide-based resin and containing 3% by weight or less of components other than the polyamide-based resin, 85 to 99% by weight of the polyamide-based resin, and polyester. It has at least a layer B containing 1 to 15% by weight of a system elastomer and a layer C containing a barrier resin.

The multilayer stretched polyamide-based 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 further excellent in transparency.

The polyamide-based film of the present invention will be described in detail below.

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

Polyamide-based resin The polyamide-based 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 more excellent in pinhole resistance due to bending and repeated contact.

Aliphatic Polyamides Aliphatic polyamides include aliphatic nylons and copolymers thereof.

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

Polyethylene diamine adipamide (nylon-2,6), polytetramethylene adipamide (nylon-4,6), polyhexamethylene adipamide (nylon-6,6), polyhexamethylene sebacamide (nylon- 6,10), polyhexamethylene dodecamide (nylon-6,12), polyoctamethyleneadipamide (nylon-8,6), polydecamethyleneadipamide (nylon-10,8), etc. This is good.

Caprolactam/lauryllactam copolymer (nylon-6/12), caprolactam/ω-aminononanoic acid copolymer (nylon-6/9), caprolactam/hexamethylenediammonium adipate copolymer (nylon-6/6,6 ), lauryllactam/hexamethylenediammonium adipate copolymer (nylon-12/6,6), etc. are preferably used.

Ethylenediamine adipamide/hexamethylenediammonium adipate copolymer (nylon-2,6/6,6), caprolactam/hexamethylenediammonium adipate/hexamethylenediammonium sebacate copolymer (nylon-6,6/6 ,10), ethylene ammonium adipate/hexamethylenediammonium adipate/hexamethylenediammonium sebacate copolymer (nylon-6/6,6/6,10), etc. are preferably used.

One of the above aliphatic polyamides may be used, or a mixture of two or more of the above aliphatic polyamides may be used.

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

A combination of nylon-6 and nylon-6/6,6 is preferred as the two or more aliphatic polyamides. It is preferable to contain nylon-6 in a weight ratio of about 50 to 95 and nylon-6/6,6 in a weight ratio of about 50 to 5.

Aromatic polyamide Polyamide-based resin may further contain aromatic polyamide.

As an aromatic polyamide, a polycondensation reaction of 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 The resulting crystalline aromatic polyamide is mentioned.

As aromatic polyamide, preferably poly-meta-xylylene adipamide (MX-nylon)
and other crystalline aromatic polyamides. Specific examples of crystalline aromatic polyamides include S-6001, S-6007, and S-6121 (all manufactured by Mitsubishi Gas Chemical Company, Inc.).

Examples of aromatic polyamides include amorphous aromatic polyamides (amorphous nylons) obtained by polycondensation reaction of aliphatic diamines such as hexamethylenediamine and dicarboxylic acids such as terephthalic acid and isophthalic acid or derivatives 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 Polychemicals Co., Ltd.).

Preferred composition of polyamide resin The content of aliphatic polyamide (nylon 6, etc.) in the polyamide resin is preferably about 80 to 100% by weight, more preferably 80 to 99% by weight, with the amount of polyamide being 100% by weight. %. By setting the content of the aliphatic polyamide in the polyamide within the above range, the pinhole resistance of the polyamide-based 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 stretching film-forming properties.

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

Aromatic polyamide in polyamide resin (MX-nylon or amorphous nylon, etc.)
The content of is preferably about 0 to 20% by weight, more preferably about 1 to 20% by weight, based on 100% by weight of the polyamide.

Preferred relative viscosity of polyamide resin As a polyamide resin, 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 according to the measurement method in accordance with JIS K6920. 2.5
It is more preferable to use those of ~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 multi-layer stretched polyamide-based film has good pinhole resistance due to bending.

When using a mixture of two or more polyamide resins, the relative viscosity of the polyamide resin is
The relative viscosity of each polyamide to be mixed is measured, and the value obtained by weighted average is taken as the relative viscosity of the mixed polyamide.

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

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

The A layer may contain other additives as necessary within a range that does not impair the effects of the present invention. As other additives, antiblocking agents, lubricants, nucleating agents, antioxidants and the like can be preferably used.

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

Polyamide-based resin The polyamide-based 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.

Aliphatic Polyamides Aliphatic polyamides include aliphatic nylons and copolymers thereof.

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

Polyethylene diamine adipamide (nylon-2,6), polytetramethylene adipamide (nylon-4,6), polyhexamethylene adipamide (nylon-6,6), polyhexamethylene sebacamide (nylon- 6,10), polyhexamethylene dodecamide (nylon-6,12), polyoctamethyleneadipamide (nylon-8,6), polydecamethyleneadipamide (nylon-10,8), etc. This is good.

Caprolactam/lauryllactam copolymer (nylon-6/12), caprolactam/ω-aminononanoic acid copolymer (nylon-6/9), caprolactam/hexamethylenediammonium adipate copolymer (nylon-6/6,6 ), lauryllactam/hexamethylenediammonium adipate copolymer (nylon-12/6,6), etc. are preferably used.

Ethylenediamine adipamide/hexamethylenediammonium adipate copolymer (nylon-2,6/6,6), caprolactam/hexamethylenediammonium adipate/hexamethylenediammonium sebacate copolymer (nylon-6,6/6 ,10), ethylene ammonium adipate/hexamethylenediammonium adipate/hexamethylenediammonium sebacate copolymer (nylon-6/6,6/6,10), etc. are preferably used.

One of the above aliphatic polyamides may be used, or a mixture of two or more of the above aliphatic polyamides may be used.

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

The B layer contains 85 to 99 weights of polyamide resin, and as the polyamide resin, two or more aliphatic polyamides may be used in combination.

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

As the aromatic polyamide -polyamide resin, the aliphatic polyamide and the aromatic polyamide may be mixed and used. 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 multilayer stretched polyamide-based film of the present invention can exhibit more excellent stretching film-forming properties.

As an aromatic polyamide, a polycondensation reaction of 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 The resulting crystalline aromatic polyamide is mentioned.

The aromatic polyamide is preferably a crystalline aromatic polyamide such as poly-meta-xylylene adipamide. Specific examples of crystalline aromatic polyamides include S-6001, S-6007, and S-6121 (all manufactured by Mitsubishi Gas Chemical Company, Inc.).

Further, as the aromatic polyamide, there is an amorphous aromatic polyamide (amorphous nylon) obtained by a polycondensation reaction of an aliphatic diamine such as hexamethylenediamine and a dicarboxylic acid such as terephthalic acid or isophthalic acid or a derivative thereof. 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 Polychemicals Co., Ltd.).

Preferred 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 when 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-based film can be improved.

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

Preferred relative viscosity of polyamide resin As a polyamide resin, 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 is used according to the measurement method in accordance with JIS K6920. It is preferable to use The relative viscosity (JIS K6920) of the polyamide resin is more preferably 3.0 to 4.5, still more preferably 3.2 to 4.2. When the relative viscosity of the polyamide satisfies this range, the multi-layer stretched polyamide-based film has good pinhole resistance due to bending.

When using a mixture of two or more polyamide resins, the relative viscosity of the polyamide resin is
The relative viscosity of each polyamide to be mixed is measured, and the value obtained by weighted average is taken as the relative viscosity of the mixed polyamide.

Polyester-Based Elastomer Layer B 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.

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

In addition to polyester-based elastomers, polyamide-based elastomers, polyolefin-based elastomers, polystyrene-based elastomers, polyurethane-based elastomers, polyvinyl chloride-based elastomers, ionomer polymers, and the like can optionally be used in combination.

A polyester-based elastomer can be used, preferably a polyamide-based elastomer or a polyolefin-based elastomer, because it can further improve the resistance to pinholes due to bending of the polyamide-based multilayer stretched film of the present invention. More preferably, a polyamide-based elastomer is used together.

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

The polyester-based elastomer may be modified to the extent that the resistance to pinholes due to bending of the polyamide-based multilayer stretched film of the present invention is not lowered. A modified polyester elastomer may also be used.

Modifications in polyester-based elastomers include, for example, modification by copolymerization and graft modification, modification by addition of polar groups, and the like.

A polar group may be imparted by graft modification. Such polar groups include, for example, epoxy groups, carboxyl groups, acid anhydride groups, hydroxyl groups, amino groups, oxo groups and the like. One type of polar group or a combination of multiple types can be provided. Accordingly, the modified product having a polar group includes, for example, an epoxy modified product, a carboxy modified product, an acid anhydride modified product, a hydroxy modified product, an amino modified product, and the like of a polyester elastomer.

Examples of polyester elastomers include modified polyester elastomers. Modified polyester elastomers are obtained by modifying saturated polyester thermoplastic elastomers containing polyalkylene ether glycol segments with unsaturated carboxylic acids or derivatives 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. Modified polyester elastomer. Since a reactive group is introduced by the graft reaction and terminal addition reaction of the unsaturated carboxylic acid or its derivative, the chemical bondability and hydrogen bondability with various resins are improved.

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

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, etc. are preferably used. be able to. The number average molecular weight of the polyalkylene ether glycol is preferably about 400-6000.

Examples of unsaturated carboxylic acids or derivatives thereof include unsaturated carboxylic acids such as acrylic acid, maleic acid and fumaric acid, acid anhydrides thereof, esters thereof, and metal salts thereof.

Radical generators include peroxides such as t-butyl hydroperoxide and cumene hydroperoxide, and azo compounds such as 2,2'-azobisisobutyronitrile (AIBN).

Preferably, 0.01 to 30 parts by weight of the unsaturated carboxylic acid or its derivative and 0.001 to 3 parts by weight of the radical generator are contained with respect to 100 parts by weight of the saturated polyester thermoplastic elastomer.

The method for preparing the modified polyester-based 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 minutes. MFR shall be the value measured under the conditions of 230°C and 2.16 kg according to the measurement method in accordance with JIS K7210.

A maleic anhydride-modified polyester elastomer is particularly preferable as the polyester-based elastomer. Specific examples of commercially available modified polyester-based elastomers include Tefablock-GQ131 (manufactured by Mitsubishi Chemical Corporation).

Preferred polyamide-based elastomers as the optional thermoplastic elastomer include polyamide-based block copolymers composed of hard segments composed of a polyamide component and soft segments composed of a polyoxyalkylene glycol component.

The polyamide component of the hard segment is a group consisting of (1) a lactam, (2) an ω-aminoaliphatic carboxylic acid, (3) an aliphatic diamine and an aliphatic dicarboxylic acid, or (4) an aliphatic diamine and an aromatic dicarboxylic acid. is selected from Specific examples of the polyamide component of the hard segment 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. can.

Examples of polyoxyalkylene glycols constituting soft segments of polyamide-based block copolymers include polyoxytetramethylene glycol, polyoxyethylene glycol, and polyoxy-1,2-propylene glycol.

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

By using a polyamide block copolymer as a component of a laminated biaxially oriented polyamide film, it is effective in improving the resistance to bending fatigue of the laminated biaxially oriented polyamide film, especially in a low temperature environment. be.

Examples of polyolefin elastomers include resins obtained by graft-modifying or copolymerizing polyolefin resins with unsaturated carboxylic acids or their anhydrides.

Polyolefin resins that can be used as base polymers for polyolefin elastomers include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-
Homopolymers of α-olefins such as decene, 1-dodecene, 4-methyl-1-pentene, these 2
Ethylene/polar monomer copolymers such as random copolymers of more than one species, block copolymers of two or more of these, copolymers of ethylene and vinyl acetate, copolymers of ethylene and ethyl (meth)acrylate, etc. and the like.

More specifically, polyolefin resins that can be used as the base polymer include high-density polyethylene, medium-density polyethylene, high-pressure low-density polyethylene, linear low-density polyethylene (ethylene and 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. .

They may be produced with any catalyst system. For example, in the linear low-density polyethylene, those produced with a metallocene catalyst or a multi-site catalyst can be used.

A polyolefin elastomer can be obtained by grafting an unsaturated carboxylic acid to a polyolefin resin, which is a base polymer, or by copolymerizing and modifying an olefin and a small amount of an unsaturated carboxylic acid.

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

Acid anhydrides are particularly preferred, and maleic anhydride is particularly preferred.

The polyolefin elastomer is preferably a maleic anhydride-modified ethylene copolymer. Maleic anhydride-modified ethylene copolymers include maleic anhydride graft-modified ethylene copolymers and maleic anhydride-ethylene copolymers, which are obtained by modifying a partially saponified ethylene-vinyl acetate copolymer with maleic anhydride. can be preferably used.

Content of polyamide resin and polyester elastomer
The content of the polyamide-based resin in the B layer is 85 to 99% by weight when the weight of the entire B layer is 100% by weight.
is. When the polyamide-based resin in the layer B 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 90-98% by weight.

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

The B layer may contain other additives as necessary within a range that does not impair the effects of the present invention. As other additives, antiblocking agents, lubricants, nucleating agents, antioxidants and the like can be preferably used.

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

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

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

Since the multi-layer stretched polyamide-based film of the present invention contains the layer C, the multi-layer stretched polyamide-based film has excellent gas barrier properties. For the C layer, EVOH and poly-meta-xylylene adipamide may be used alone or in combination.

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

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

EVOH may further contain a small amount of α-olefins such as propylene, isobutene, α-octene, α-dodecene, α-octadecene; unsaturated carboxylic acids or derivatives thereof (e.g., salts, partial alkyl esters, full alkyl esters, nitriles, amides, anhydrides); unsaturated sulfonic acids or salts thereof.

The melt index (MI) of EVOH is preferably 0.5 to 50 g/10 minutes (210°C, 2,160 g load), more preferably 1 to 35 g/10 minutes (210°C, 2,160 g load). When the MI satisfies this range, the viscosity is such that melt extrusion is not hindered, and the film formability is good.

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

Aromatic polyamides such as poly-meta-xylylene adipamide (MX-nylon) can be preferably used.

Examples of aromatic polyamide include S-6001, S-6007, S-6121 (all manufactured by Mitsubishi Gas Chemical Company, Inc.).

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

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

An embodiment of the polyamide-based multilayer stretched film of the present invention preferably has a layer structure in which the layers are laminated in the order of A layer/B layer/C layer. Embodiments of the polyamide-based multilayer stretched film of the present invention include the A layer (PA
Layer 1) / B layer (PA layer 2) / C layer (barrier layer) / B layer (PA layer 2) / A layer (PA layer 1), etc. A layer structure consisting of 5 or more layers is also possible. .

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

The thickness of the A layer (PA layer 1) is preferably about 0.5-30 μm, more preferably about 0.5-20 μm. The thickness of layer A 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 0.5-30 μm, more preferably about 0.5-20 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 0.5-20 μm, more preferably about 0.5-15 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 the A layer (PA layer 1) and about 0.5 to 29.5 μm for the B layer (PA layer 2). It is preferably about 0.5 to 29.5 μm, and the C layer (barrier layer) is preferably about 0.5 to 20 μm. The A layer more preferably has a thickness of about 0.5 to 19.5 μm, the B layer more preferably has a thickness of about 0.5 to 19.5 μm, and the C layer more preferably has a thickness of about 0.5 to 15 μm. 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 multilayer stretched polyamide film The method for producing the multilayer stretched polyamide film of the present invention is not particularly limited. A manufacturing method for forming a conventionally known laminate can be preferably employed.

In order to produce the polyamide-based multilayer stretched film of the present invention, the resin composition for forming the A layer (PA layer 1), B layer (PA layer 2) and C layer (barrier layer), for example, A layer / The layers are co-extruded from a T-die onto a chill roll through which cooling water circulates, in the order of B layer/C layer/B layer/A layer. As a result, a flat multilayer stretched polyamide-based film can be produced.

The resulting 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 in machine direction (MD), preferably about 2.5 to 5.0 times in transverse direction (TD).

In the case of sequential biaxial stretching, the multi-layer stretched polyamide film is longitudinally stretched 2.5-4.5 times with a roll stretching machine at 50-80°C, and transversely stretched 2.5-5.0 times with a tenter stretching machine at 80-140°C. It is recommended to heat-treat in an atmosphere of 180 to 220°C with 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 be stretched on both surfaces or on one side, if necessary. A corona discharge treatment can also be applied to the surface.

(3) Performance and application of multilayer stretched polyamide film
Resistance to Pinholes Due to Bending " Pinhole resistance due to bending" is evaluated using a gelbo flex tester on a film as described in Examples below. In the multilayer stretched polyamide-based film of the present invention, the number of pinholes generated in the evaluation of pinhole resistance after bending 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 times of sliding until a pinhole is formed is preferably 250 or more.

Haze value "Haze value" is, as described in the examples below, for the film, JIS K7136 (2000
). Haze value is defined as the ratio (percentage) of diffuse transmittance to total light transmittance. The haze value (%) of the polyamide-based multilayer stretched film of the present invention is preferably 7% or less.

The multi-layer stretched polyamide-based film of the present invention is suitable for packaging heavy objects because it has excellent pinhole resistance due to bending and abrasion and also has excellent transparency. The multi-layer stretched polyamide-based film of the present invention is particularly suitable for packaging foods such as mochi (rice cakes) and wiener sausages.

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

Below, the present invention will be described in more detail using examples and comparative examples.

The 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 1-3
Using the raw materials shown in Table 1 above, resin compositions for forming the A layer (PA layer 1), B layer (PA layer 2), and C layer (barrier layer) are prepared according to the formulation shown in Table 2. prepared.

Further, 900 ppm of silica having an average particle size of 3 μm as an antiblocking agent and 300 ppm of ethylenebisstearic acid amide as a lubricant were added to the resin composition for forming the A layer.

The resin compositions of Examples and Comparative Examples were supplied to extruders at 250°C, respectively, and stacked in a feed block in the order of A layer/B layer/C layer/B layer/A layer. A sheet was extruded from a T-die onto a chill roll through which cooling water circulated to prepare a five-layer film having a layer structure of A layer/B layer/C layer/B layer/A layer.

Next, the obtained film was longitudinally stretched by a factor of 3.0 with a roll stretcher at 65°C, and then transversely stretched by a factor of 4.0 by a tenter stretcher in an atmosphere of 110°C.

Further, the same tenter was used to heat-treat in an atmosphere of 210° C. to produce a 3-layer stretched polyamide-based film having a layer structure of A layer/B layer/A layer with a thickness ratio shown in Table 2 and 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 due to film bending (bending resistance test)
The pinhole resistance due to bending of the polyamide-based multilayer stretched film was measured using a Gelboflex tester manufactured by Rikagaku Kogyo Co., Ltd.

A multi-layer stretched polyamide-based film bagged into a tube having a folding diameter of 150 mm and a length of 300 mm was attached to a gelbo flex tester. For this, a 440° twist was applied at the first 88.9 cm, followed by repeated flexing linear motion with linear horizontal motion for 63.5 cm at a test speed of 40 times/at 5°C.
After 1000 repetitions at min, the penetrant was used to check the number of pinholes.

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

A sample film having 5 or less pinholes was regarded as acceptable.

(4) Pinhole resistance due to film abrasion (wear resistance test)
Attach the film to a cone-shaped aluminum jig using tape, etc., and attach the apex of the cone-shaped jig to a piece of cardboard (Kokuyo Campus, Itame, 430 g/m ² ). The R of the apex was 0.1 to 1.0 mm in the sliding direction and 0.1 to 1.0 mm in the direction perpendicular to the sliding direction. next,
A load of 63 g was placed on the jig. Under the condition of 65% humidity, the jig is slid parallel to the cardboard at a speed of 2700mm/min and the moving distance is 45mm. The number of times was measured. For example, if it opens at 300 times and does not open at 250 times, then 300
times.

The occurrence of pinholes was determined by dropping the penetrating liquid onto the film where the apex of the jig was in contact and whether or not the penetrating liquid penetrated on the white paper.

In the sample film, 250 times or more was regarded as passing.

FIG. 1 shows a schematic diagram of the measuring device, and FIG. 2 shows an example of a cone-shaped aluminum jig.

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

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

Haze value (%) = (diffuse transmittance) / (total light transmittance) x 100
A sample film having a haze value of 7% or less was regarded as acceptable.

(6) Results of Evaluation of Multilayer Stretched Polyamide 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, the A layer contains a polyamide-based resin (PA-1 and MXD6), the content of components other than the polyamide-based resin is 3% by weight or less, and the B
The layers contain 85-99% by weight polyamide resins (PA-1 and PA-2) and 1-15% by weight polyester elastomer (PEE), and the C layer contains a barrier resin (EVOH).

Due to these characteristics, the multilayer stretched polyamide 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, in Comparative Examples 1 and 2, the polyamide-based resin of the layer B is less than 85% by weight and the polyamide-based resin of the layer B exceeds 99% by weight. In other words, in Comparative Examples 1 and 2, when the polyester-based elastomer of the B layer is less than 1% by weight, the polyester-based elastomer of the B layer is 15% by weight.
% by weight. The films of Comparative Examples 1 and 2 were not good in pinhole resistance due to bending and transparency.

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

Claims (3)

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

Images