JP2010042586A - Polyamide-based multilayered oriented film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyamide-based multilayered oriented film which is superior in bending resistance, heat dimensional stability, aroma retention property, anti-curling property, or the like. <P>SOLUTION: The polyamide-based multilayered oriented film is obtained by biaxially orienting a multilayered laminated body having at least three layers of a polyester layer (A), a polyamide layer (B) and a polyamide layer (C)in this order. The layer (A) contains crystalline polyester, the layer (B) contains aliphatic polyamide, and the layer (C) contains aromatic polyamide. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polyamide-based multilayer stretched film having excellent dimensional stability, fragrance retention, and curl resistance while maintaining excellent toughness.

  Conventionally, a polyamide-based multilayer stretched film containing a nylon resin has been widely used in various fields as a film having gas barrier properties, toughness, pinhole resistance and the like.

  Although this polyamide-based multilayer stretched film has excellent properties as described above, for example, when it is used for a packaging film for food or the like, there is a problem that the odor of the contents leaks. This is not preferable because it leads to deterioration of contents and a decrease in commercial value. Therefore, the packaging film is required to have high fragrance retention. Furthermore, when used as a packaging film for more severe boil processing or retort processing, higher thermal dimensional stability is required.

Polyamide-based multilayer stretched films are distributed in the market as packaging films for foods, etc., but pinholes may occur due to wear during transportation, transportation, etc. The excellent gas barrier properties of the multilayer film due to the pinholes Was the result of inhibition. Therefore, a multilayer film having excellent bending resistance has been desired from the market.
JP-A-8-118569

  The main object of the present invention is to provide a polyamide-based multilayer stretched film excellent in bending resistance, thermal dimensional stability, aroma retention, curling resistance, and the like.

  As a result of intensive studies, the inventors have biaxially stretched a multilayer laminate having at least three layers of a polyester layer (A layer), a polyamide layer (B layer), and a polyamide layer (C layer) in this order. It has been found that the above-mentioned problems can be solved by the polyamide-based multilayer stretched film obtained by the above method. The present invention has been completed as a result of further research based on such knowledge.

That is, the present invention provides the following polyamide-based multilayer stretched film.
Item 1. A polyamide-based multilayer stretched film obtained by biaxially stretching a multilayer laminate having at least three layers of a polyester layer (A layer), a polyamide layer (B layer) and a polyamide layer (C layer) in this order,
(A) layer contains crystalline polyester,
(B) the layer contains an aliphatic polyamide,
(C) The polyamide-based multilayer stretched film, wherein the layer contains an aromatic polyamide.
Item 2. The crystalline polyester contained in the layer (A) is at least one selected from the group consisting of polyethylene terephthalate (PET), isophthalic acid copolymerized polyethylene terephthalate, sulfoisophthalic acid copolymerized polyethylene terephthalate, and mixtures thereof. 2. The polyamide-based multilayer stretched film according to 1.
Item 3. In item 1 or 2, the aliphatic polyamide of layer (B) is at least one selected from the group consisting of nylon-6, a copolymer of nylon-6 and nylon-6,6, and a mixture thereof. The polyamide-based multilayer stretched film described.
Item 4. Item 4. The polyamide-based multilayer stretched film according to Items 1 to 3, wherein the aromatic polyamide is polymetaxylene adipamide.
Item 5. Item 5. The polyamide-based multilayer stretched film according to any one of Items 1 to 4, wherein the total film thickness is 10 to 50 µm.
Item 6. A packaging film obtained by laminating a sealing layer on the (C) layer side of the polyamide-based multilayer stretched film according to Item 1.
Item 7. Item 7. A packaging bag obtained by making the packaging film of Item 6 into a bag shape and heat-sealing the sealing layer surfaces.
Item 8. Item 8. A package formed by filling the packaging bag according to Item 7.

  The polyamide-based multilayer stretched film of the present invention has excellent flex resistance, thermal dimensional stability, fragrance retention, and curl resistance. The multilayer film of the present invention having such excellent characteristics is suitably used as a packaging film.

I. Polyamide-based multilayer film The polyamide-based multilayer stretched film of the present invention is a biaxial multilayer laminate having at least three layers of a polyester layer (A layer), a polyamide layer (B layer), and a polyamide layer (C layer) in this order. A polyamide-based multilayer stretched film obtained by stretching,
(A) layer contains crystalline polyester,
(B) the layer contains an aliphatic polyamide,
The layer (C) contains an aromatic polyamide.

  Hereinafter, each structure of the multilayer stretched film of this invention is explained in full detail.

(1) (A) Layer In the present invention, the (A) layer imparts functions such as dimensional stability, aroma retention, and heat resistance to the multilayer stretched film.

  The layer (A) contains crystalline polyester as a main component. The crystalline polyester is not particularly limited as long as it can provide functions such as dimensional stability, fragrance retention, and heat resistance. For example, it is possible to use a resin obtained by polycondensation of a dicarboxylic acid and a diol. it can.

  Examples of the dicarboxylic acid include o-phthalic acid, terephthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, octyl succinic acid, cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid, fumaric acid, maleic acid, and itaconic acid. , Decamethylene carboxylic acid, their anhydrides and lower alkyl esters, 5-sulfoisophthalic acid, 2-sulfoisophthalic acid, 4-sulfoisophthalic acid, 3-sulfophthalic acid, dialkyl 5-sulfoisophthalate, 2-sulfoisophthalic acid Examples thereof include dialkyl, dialkyl 4-sulfoisophthalate, dialkyl 3-sulfoisophthalate, and sulfo group-containing dicarboxylic acids such as sodium salts and potassium salts thereof.

  Examples of the diol include ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, dipropylene glycol, triethylene glycol, and tetraethylene glycol. 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, neopentyl glycol (2,2-dimethylpropane-1,3-diol), 1,2-hexanediol, 2,5 -Aliphatic diols such as hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol; 2,2-bis (4 -Hydroxycyclohexyl) propane, 2,2-bis (4-hydroxycyclohex) E) Alkylene oxide adducts of propane, alicyclic diols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol, 1,3-dihydroxybutanesulfonic acid, 1,4-dihydroxybutanesulfonic acid, etc. A sulfone group containing diol etc. are mentioned.

  Among these, in particular, the component derived from dicarboxylic acid is terephthalic acid and the component derived from diol is ethylene glycol, polyethylene terephthalate (PET); the components derived from dicarboxylic acid are terephthalic acid (99 to 80 mol%) and isophthalic acid ( 1-20 mol%), isophthalic acid copolymerized polyethylene terephthalate in which the component derived from diol is ethylene glycol; the component derived from dicarboxylic acid is terephthalic acid (99.5-90 mol%) and 5-sodium sulfoisophthalic acid ( 0.5 to 10 mol%), a sulfoisophthalic acid copolymerized polyethylene terephthalate having a component derived from diol of ethylene glycol is preferred from the viewpoint of dimensional stability, aroma retention, heat resistance, etc., more preferably terephthalic. Polyethylene consisting of acid and ethylene glycol It is a terephthalate (PET).

  Such crystalline polyester is commercially available. For example, Belpet-EFG6C, Belpet PIFG5 (both manufactured by Bell Polyester Products Co., Ltd.) and the like are used as the crystalline polyester constituting the layer (A). be able to.

  The crystalline polyester used in the layer (A) may be only one kind, or two or more kinds may be blended as necessary. Alternatively, it is possible to provide two or more layers (A) (for example, an embodiment 3 described later). This also makes it possible to impart adhesion to the (B) layer.

  Further, the layer (A) may contain a resin compatible with the crystalline polyester, if necessary, but the content of the crystalline polyester relative to the total weight of the components constituting the (A) layer is 50 % By weight or more, preferably 70% by weight or more.

  Non-crystalline polyester etc. can be illustrated as resin compatible with crystalline polyester. An amorphous polyester is a polyester in which the heat of fusion is not observed in the differential scanning calorimetry based on JIS K7121. Although it will not specifically limit if it is polyester which has such a characteristic, As a specific example, the component derived from dicarboxylic acid is terephthalic acid, the component derived from diol is ethylene glycol (20-80 mol%) and cyclohexane dimethanol (80 Polyester consisting of terephthalic acid (20 to 80 mol%) and isophthalic acid (80 to 20 mol%) as a component derived from dicarboxylic acid, and a polyester composed of ethylene glycol as a component derived from diol is suitable. It is. Such an amorphous polyester is commercially available. For example, Eastar Copolyester 6763 (manufactured by Eastman Chemical) or the like can be used as the amorphous polyester.

  Moreover, a well-known inorganic or organic additive etc. can be suitably mix | blended with a (A) layer as needed in the range which does not impair the effect of this invention. As an inorganic or organic additive, an antiblocking agent, a nucleating agent, a water repellent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a colorant, a pigment, a dye, and the like can be appropriately blended.

(2) (B) Layer In the present invention, the (B) layer imparts functions such as flex resistance and impact resistance to the multilayer stretched film of the present invention. The layer (B) contains an 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 / hexamethylenediammonium adipate copolymer (nylon-2,6 / 6,6), caprolactam / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon-6,6 / 6) 10), ethyleneammonium adipate / hexamethylene diammonium adipate / hexamethylene diammonium sebacate copolymer (nylon-6 / 6, 6/6, 10), etc., among which two or more fats Can be mixed with polyamid polyamide .

  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 particularly 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.

  The layer (B) may be composed of the above-mentioned polyamide-based resin, but the aromatic polyamide is contained in an amount of 1 to 50% by weight as necessary so as not to impair the characteristics of the aliphatic polyamide. You may adjust so that.

  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, an 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 can be used. Preferred is a copolymer of hexamethylene diamine-terephthalic acid-hexamethylene diamine-isophthalic acid. Specific examples include Sealer PA (Mitsui / DuPont Polychemical Co., Ltd.) and the like.

  As the layer (B) of the present invention, preferred combinations of aliphatic polyamide and aromatic polyamide include a combination of nylon-6 and MXD-nylon, and a combination of nylon-6 and amorphous aromatic polyamide (amorphous nylon). .

  Moreover, a well-known bending resistance improvement agent, an inorganic or organic additive, etc. can be mix | blended. Examples of the bending resistance improver include polyolefins, polyester elastomers, polyamide elastomers, and the like, and can be appropriately blended in the range of about 0.5 to 10% by weight. Examples of inorganic or organic additives include nucleating agents, antioxidants, heat stabilizers, lubricants such as metal soaps, and antistatic agents.

(3) (C) Layer In the present invention, the (C) layer imparts a curl resistance function to the multilayer stretched film. The layer (C) contains a predetermined amount of 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.).

  Further, the layer (C) may further contain an aliphatic polyamide. This makes it possible to improve pinhole resistance. As the aliphatic polyamide, those described in the column of the layer (C) can be used. When the aliphatic polyamide is contained in the layer (C), the content of the aliphatic polyamide is 1 to 70% by weight, preferably 1 to 50% by weight, more preferably 1 to 40% by weight.

  The layer (C) may be composed of the above-mentioned polyamide-based resin, but if necessary, blends a known flex resistance improver, an inorganic or organic additive, etc. as long as the effects of the present invention are not impaired. can do. Examples of the bending resistance improver include polyolefins, polyester elastomers, polyamide elastomers, and the like, and can be appropriately blended in the range of about 0.5 to 10% by weight. Examples of inorganic or organic additives include antiblocking agents, nucleating agents, water repellents, antioxidants, heat stabilizers, lubricants such as metal soaps, antistatic agents, and the like. For example, if it is an antiblocking agent, a silica, a talc, a kaolin etc. can be mix | blended suitably in the range of about 100-5000 ppm.

(4) Adhesive layer In the present invention, an adhesive layer may be formed for the purpose of adhering the (A) layer and the (B) layer. By interposing the adhesive layer, the interlaminar strength after adhesion of both is dramatically improved. The adhesive layer is formed between the (A) layer and the (B) layer of the multilayer stretched film of the present invention. For example, an acid-modified resin graft-modified with an unsaturated carboxylic acid or a derivative thereof can be used.

  Examples of the acid-modified resin graft-modified with unsaturated carboxylic acid or a derivative thereof include modified polyolefin and modified styrene elastomer.

  The modified polyolefin is obtained by a known production method, for example, obtained by heating and mixing an unsaturated carboxylic acid or a derivative thereof and a polyolefin in the presence of a radical generator.

  Examples of unsaturated carboxylic acids or derivatives thereof include unsaturated carboxylic acids such as maleic acid and fumaric acid, acid anhydrides, esters or metal salts thereof (for example, sodium salts, potassium salts, calcium salts).

  Examples of the polyolefin include olefin homopolymers, mutual copolymers, and copolymers with other copolymerizable monomers (for example, other vinyl monomers). Specifically, for example, polyethylene (for example, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), etc.), polypropylene, polybutene, a copolymer thereof, an ionomer resin, an ethylene-acrylic acid copolymer. And ethylene-vinyl acetate copolymer.

  As the modified polyolefin, maleic anhydride-modified polyolefin is preferable. Examples thereof include maleic anhydride-modified polyolefin resins (for example, Mitsui Chemicals, Inc. Admer SF731, SE800 and Mitsubishi Chemical Corporation Modic).

  The modified styrene elastomer can be obtained by a known production method, for example, by heating and mixing an unsaturated carboxylic acid or a derivative thereof and a styrene elastomer in the presence of a radical generator.

  Examples of the styrene elastomer include a hydrogenated product of a styrene-butadiene copolymer and a hydrogenated product of a styrene-isoprene copolymer.

  Examples of unsaturated carboxylic acids or derivatives thereof include unsaturated carboxylic acids such as maleic acid and fumaric acid, acid anhydrides, esters or metal salts thereof (for example, sodium salts, potassium salts, calcium salts). .

  The modified styrene elastomer is preferably a hydrogenated styrene-butadiene copolymer modified with maleic anhydride. Specifically, styrene-butadiene copolymer hydrogenated products modified with maleic anhydride (for example, Kraton FG1901 manufactured by Kraton Polymer, Tuftec M1913 manufactured by Asahi Kasei Chemicals, etc.) are exemplified.

(5) Layer Configuration The polyamide-based multilayer stretched film of the present invention has at least three layers of (A) layer, (B) layer, and (C) layer in this order. In addition, an adhesive layer, a gas barrier layer, a seal layer, and the like can be provided as necessary.

  Moreover, although the multilayer stretched film of this invention may consist of the said 3 layer structure, it may have a structure of 4 layers or more as needed.

  Specific layer configurations include (A) layer / (B) layer / (C) layer, (A) layer / adhesive layer / (B) layer / (C) layer, (A) layer / (B) layer / Gas barrier layer / (B) layer / (C) layer, (A) layer / adhesive layer / B) layer / gas barrier layer / (B) layer / (C) layer, (A) layer / (B) layer / (C ) Layer / seal layer, (A) layer / adhesive layer / (B) layer / (C) layer / seal layer, and the like.

  Here, the gas barrier layer is a layer having a low gas permeability such as oxygen, nitrogen, and carbon dioxide. Specific examples include ethylene-vinyl alcohol copolymers and aromatic polyamides.

  The ethylene-vinyl alcohol copolymer is obtained by saponification of an ethylene-vinyl acetate copolymer. The ethylene content of the ethylene-vinyl alcohol copolymer is 20 to 70 mol%, preferably 25 to 50 mol%. When the ethylene content is less than 20 mol%, the thermal stability is poor and the moldability is deteriorated, and foreign matters such as gels are easily generated in extrusion melt molding, and the film is easily broken in stretch molding. When the ethylene content exceeds 70 mol%, sufficient barrier properties cannot be obtained. In the ethylene-vinyl alcohol copolymer, other known components that do not significantly deteriorate the gas barrier properties may be copolymerized or blended. The ethylene-vinyl alcohol copolymer may be a blend of ethylene-vinyl alcohol copolymers having different compositions. Examples of commercially available ethylene-vinyl alcohol copolymers include “EVAL” (manufactured by Kuraray Co., Ltd.), “Soarnol” (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), and the like.

  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 S6007 and S6011 (both manufactured by Mitsubishi Gas Chemical Co., Inc.).

  The sealing layer may be a resin film having sealing properties. For example, LLDPE (linear low density polyethylene), LDPE (low density polyethylene), CPP (unstretched polypropylene), EVA (ethylene vinyl acetate co-polymer). A layer composed of a polyolefin such as a polymer may be employed.

  The total film thickness of the polyamide-based multilayer stretched 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 6 to 50 μm, preferably about 10 to 30 μm. It is. The thickness of each layer is usually 1 μm or more, preferably about 1 to 15 μm, more preferably about 2 to 12 μm for the (A) layer. When the thickness of the (A) layer is 1 μm or more, excellent functions such as dimensional stability, aroma retention, and heat resistance can be imparted to the multilayer stretched film of the present invention. The thickness of the layer (B) is 4 μm or more, preferably about 4 to 35 μm, more preferably about 6 to 20 μm. When the thickness of the (B) layer is 4 μm or more, excellent functions such as flex resistance and impact resistance can be imparted to the multilayer stretched film of the present invention. Furthermore, the thickness of (C) layer is 1 micrometer or more, Preferably it is about 1-10 micrometers, More preferably, it is about 1-5 micrometers. When the thickness of the (C) layer is 1 μm or more, excellent functions such as curling resistance and laminate suitability can be imparted to the multilayer stretched film of the present invention.

The preferable aspect of the multilayer stretched film of this invention is illustrated below.
Example 1. (A) Layer is made of polyethylene terephthalate (film thickness 2-12 μm); (B) Layer is made of nylon-6 (film thickness 7-20 μm); (C) Layer is made of MXD nylon and nylon-6, MXD The nylon content is 60 to 80% by weight, and the nylon-6 content is 20 to 40% by weight (film thickness 1 to 5 μm).

II. Manufacturing Method The manufacturing method of the polyamide-based stretched multilayer film of the present invention is, for example, co-extruded on a chill roll in which cooling water circulates from a T die so that the layers are in the order of each layer, thereby obtaining a flat multilayer film. The obtained film was longitudinally stretched 2.5 to 4.5 times by a roll stretching machine at 50 to 100 ° C., for example, and further stretched to 2.5 to 5 times by a tenter stretching machine in an atmosphere at 90 to 150 ° C., and then the same tenter. Can be obtained by heat treatment in an atmosphere of 100 to 240 ° C. The multilayer stretched film of the present invention may be subjected to simultaneous biaxial stretching and sequential biaxial stretching, and the obtained multilayer stretched film can be subjected to corona discharge treatment on both surfaces or one surface if necessary.

  Examples of the corona discharge treatment include a method in which corona discharge is generated by applying a high voltage of several thousand volts between a grounded metal roll and a knife-like electrode placed at intervals of several millimeters. The film is passed between the electrode and the roll during discharge at high speed. At this time, the surface of the film is subjected to corona discharge treatment, and the affinity for adhesives, inks, paints and the like is improved. Here, the degree of processing can be set by controlling the discharge current. The surface tension after the corona discharge treatment has a value measured according to the method of JIS K 6768 of 46 mN / m or more, more preferably 50 mN / m or more.

III. Features of the polyamide-based multilayer stretched film The polyamide-based multilayer stretched film of the present invention produced as described above has excellent bending resistance, thermal dimensional stability, aroma retention, and curl resistance. It is suitably used as a packaging film.

[Flexibility]
The polyamide-based multilayer stretched film of the present invention is excellent in abrasion resistance due to bending.
Specifically, the number of pinholes generated in a gelboflex test at normal temperature (23 ° C.) × 1,000 times is 10/300 cm ² or less, and further 5/300 cm ² or less. . Evaluation of pinholes by bending is as described in Test Example 1.

[Thermal dimensional stability]
The polyamide-based multilayer stretched film of the present invention has excellent thermal dimensional stability.
The thermal dimensional stability was evaluated by retorting a sample of MD × TD = 100 mm × 100 mm (121 ° C. × 30 minutes) and measuring the shrinkage after the treatment. Under such measurement conditions, the shrinkage of the polyamide based multilayer stretched film of the present invention is 3.0% or less, preferably 2.5% or less.

[Scent retention]
The multilayer stretched film of the present invention has excellent fragrance retention. The evaluation method of fragrance retention is as described in Test Example 1.

[Curl resistance]
The polyamide-based multilayer stretched film of the present invention has excellent curl resistance.
Curl resistance is evaluated at 23 ° C x 50% RH for 24 hours, with layer (A) on top, and MD x TD = 10cm x 10cm square diagonal cut on the mat. The area of the mat that can be confirmed by curling the film when observed from directly above was measured. The area of the mat was measured with an image analysis software NIH Image (National Institute of Health) after taking an image taken with a digital camera into a PC. Under such measurement conditions, the polyamide-based multilayer stretched film of the present invention has an area of 30 cm ² or less, preferably 20 cm ² or less, more preferably 10 cm ² or less.

  Since the polyamide-based multilayer stretched film of the present invention has the above characteristics, it is suitably used as a packaging film. When the polyamide multilayer stretched film of the present invention is used as a packaging film, a sealing film is laminated on one surface of the film to produce a packaging film. This is formed into a bag shape with the outermost layer facing outward, and the sealing layer surfaces are heat-sealed and processed into a bag shape to produce a packaging bag.

  Since the polyamide-based multilayer stretched film of the present invention has the above characteristics, it is suitably used as a packaging film. When the polyamide-based multilayer stretched film of the present invention is used as a packaging film, a sealing film is laminated on the (C) layer side of the film to produce a packaging film. This is formed into a bag shape with the outer layer ((A) layer) facing outward, and the sealing layer surfaces are heat sealed to form a bag shape to produce a packaging bag.

  The obtained packaging bag is filled with the contents to obtain a package. There are no restrictions on the type of contents to be packaged, but in particular, water-based foods such as soup, rice cakes, and pickles, heavy foods such as rice cakes, winners, and seasonings, shampoos, rinses, and body soaps for refilling. The effects of the present invention are remarkably exhibited when packaging heavy liquids such as detergents, packaging with large bags such as rice and ice, and odors such as soy sauce and vinegar. Examples of the form of the packaging bag include bag-like forms such as a three-side seal form, an envelope form, a closet form, and a flat bottom form, a standing pouch, a spout pouch, and a refill pouch.

  Furthermore, since the multilayer film of the present invention has high transparency, it is easy to visually check the contents when packaged.

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

[Example 1]
(A) Crystalline polyester "Belpet-EFG6C" (manufactured by Bell Polyester Products) is used as layer (A), and aliphatic polyamide resin nylon-6 "UBE nylon-1022B" (Ube Industries, Ltd.) as layer (B) (C) layer, aromatic polyamide MXD nylon “S6007” (Mitsubishi Gas Chemical Co., Ltd.) 70% by weight, aliphatic polyamide resin nylon-6 “UBE nylon-1022B” (Ube Industries, Ltd.) (Product made) A resin blended with 30% by weight was used.

  The resin constituting each layer is co-extruded on a chill roll in which cooling water circulates from a T die so that the order is (A) layer / (B) layer / (C) layer, and a flat four-layer film Got. This three-layer film was longitudinally stretched 2.7 times by a 65 ° C. roll stretcher, then stretched 4.0 times by a tenter stretcher at 110 ° C. atmosphere, and further in a 210 ° C. atmosphere by the same tenter. And a three-layer film having a thickness of 15 μm was obtained. The thickness of each layer is as shown in Table 1.

[Example 2]
The (A) layer, the (B) layer, and the (C) layer were used in the same manner as in Example 1. Further, the modified polyolefin “Admer SF731” (Mitsui Chemicals, Inc.) was used as an adhesive layer between the (B) layer and the (C) layer. A multilayer stretched film was produced in the same manner as in Example 1 except that the product manufactured by Kogyo Co.) was used. The thickness of each layer is as shown in Table 1 below.

[Example 3]
Polyethylene terephthalate “Belpet-EFG6C” (manufactured by Bell Polyester Products Co., Ltd.) is used as the (A-1) layer, and sulfoisophthalic acid copolymerized polyethylene terephthalate (a component derived from dicarboxylic acid is used as the terephthalic acid) as the (A-2) layer. An acid (95 mol%), 5-sodium sulfoisophthalic acid (5 mol%), and a crystalline polyester whose intrinsic component is ethylene glycol (intrinsic viscosity: 0.50 dl / g)) were used. As the layer (B), aliphatic polyamide nylon-6 “UBE nylon-1022B” (manufactured by Ube Industries) was used. As the layer (C), aromatic polyamide MXD nylon “S6007” (manufactured by Mitsubishi Gas Chemical Co., Inc.) was used. Using these resins, a multilayer stretched film was produced in the order of (A-1) layer / (A-2) layer / (B) layer / (C) layer. The thickness of each layer is as shown in Table 1 below.

[Examples 4 to 6]
The multilayer stretched films of Examples 4 to 6 were produced in the same manner as in Example 2 except that the thickness of each layer was changed as described in Table 1 below.

[Example 7]
(A) Layer of sulfoisophthalic acid copolymerized polyethylene terephthalate (component derived from dicarboxylic acid is terephthalic acid (97 mol%) and 5-sodium sulfoisophthalic acid (3 mol%), component derived from diol is ethylene glycol Crystalline polyester (Intrinsic viscosity: 0.55 dl / g)), Nylon-6 “UBE nylon-1022B” (manufactured by Ube Industries, Ltd.) 90% by weight as an aromatic polyamide resin for layer (B), aromatic polyamide Resin blended with 10% by weight of amorphous nylon “Sealer PA” (Mitsui / DuPont Polychemical Co., Ltd.) as the resin, and aromatic polyamide MXD nylon “S6007” (Mitsubishi Gas Chemical Co., Ltd.) as the (C) layer ) Using a resin blended with 90% by weight, aliphatic polyamide resin nylon-6 “UBE nylon-1022B” (manufactured by Ube Industries), 10% by weight, Was produced multilayer stretched film in the same manner as Example 1. The thickness of each layer is as shown in Table 1 below.

[Example 8]
Nylon-6 “UBE nylon-1022B” (made by Ube Industries) as the (B) layer aliphatic polyamide resin, and aromatic polyamide MXD nylon “S6007” (made by Mitsubishi Gas Chemical Co., Ltd.) as the (C) layer Using a resin blended with 70% by weight, 30% by weight of aliphatic polyamide resin nylon-6 “UBE nylon-1022B” (manufactured by Ube Industries), a multilayer stretched film in the same manner as in Example 7. Manufactured. The thickness of each layer is as shown in Table 1 below.

[Comparative Example 1]
A multilayer stretched film was produced in the same manner as in Example 1 except that the thickness of each layer was changed as described in Table 1 below.

[Comparative Example 2]
MXD nylon “S6007” (Mitsubishi Gas Chemical Co., Ltd.) 10 wt%, aromatic polyamide resin nylon-6 “UBE nylon-1022B” (Ube Industries, Ltd.) 90 wt. %, A multilayer stretched film was produced in the same manner as in Example 1 except that the blended resin was used. The thickness of each layer is as shown in Table 1 below.

[Comparative Example 3]
Using the same components as in Example 1, a multilayer stretched film laminated in the order of (A) layer / (C) layer / (B) layer was produced. The manufacturing method followed the conditions described in Example 1 above. The thickness of each layer is as shown in Table 1 below.

[Test Example 1]
The multilayer stretched films obtained in Examples 1 to 8 and Comparative Examples 1 to 3 were evaluated for flex resistance, laminate strength, thermal dimensional stability, aroma retention, and curl resistance. The results are shown in Table 2.

[Flexibility test]
Evaluation of the pinhole property by bending (bending resistance) was performed using a gelbo flex tester manufactured by RIKEN. In this method, a multilayer stretched film made into a cylindrical shape with a fold diameter of 150 mm and a length of 300 mm is attached to a gelboflex tester, and a 62.5 cm linear horizontal motion at a twist angle of 440 ° under normal temperature (23 ° C) conditions. After repeating 1000 times, the number of pinholes is examined using an osmotic solution. Note that the number of pinholes was measured at a location of 300 cm ^{2 in} the center portion of the sample that was twisted and bent. The number of pinholes is measured for three samples and the average value is shown as a result.

[Thermal dimensional stability test]
The thermal dimensional stability was evaluated by retorting a sample of MD × TD = 100 mm × 100 mm (121 ° C. × 30 minutes) and measuring the shrinkage after the treatment.

[Aroma retention test]
Small sachets (3 cm × 8 cm) were prepared with each film, filled with 5 ml each of vinegar (rice vinegar, brewed vinegar) and sealed. This was sealed in a glass jar. The vinegar odor after 3 days was evaluated by sensory evaluation according to the evaluation criteria (n = 6). Numerical values in Table 2 represent average values.

Sensory Evaluation Criteria 5: No odor at all 4: Slightly odor 3: Slight odor 2: Odor 1: Strong odor [Curl resistance test]
After storing for 24 hours in a 23 ° C x 50% RH atmosphere, layer (A) was placed on top, and a cross was cut into the diagonal line of MD x TD = 10 cm x 10 cm on the mat and observed from directly above The area of the mat that could be confirmed by the curling of the film was measured. The area of the mat was measured by taking an image taken with a digital camera into a computer and using image analysis software NIH Image (National Institute of Health). When the measured area value was 30 cm ² or less, the film had good curl resistance.

  As shown in Table 2, Examples 1 to 8 all exhibited excellent flex resistance, thermal dimensional stability, aroma retention, and curl resistance.

  In contrast, the multilayer stretched film of Comparative Example 1 in which the thickness of the (B) layer was 2 μm was inferior in bending resistance. In addition, the multilayer stretched film of Comparative Example 2 in which the composition of the layer (C) was 90% by weight of aliphatic polyamide and 10% by weight of aromatic polyamide was inferior in curl resistance. The multilayer stretched film of Comparative Example 3 in which the order of the (B) layer and the (C) layer was exchanged also had poor curl resistance.

  From the above results, it is a multilayer stretched film laminated in the order of (A) layer / (B) layer / (C) layer, wherein (A) layer is made of crystalline polyester and (B) layer is made of aliphatic polyamide. The multilayer film containing the aromatic polyamide in the (C) layer was shown to have excellent bending resistance, thermal dimensional stability, aroma retention, and curl resistance. Moreover, in the multilayer stretched film whose thickness of each layer is (A) layer 3-12 micrometers; (B) layer 6-13 micrometers; (C) layer 2-4 micrometers, it was shown that said outstanding effect is show | played. .

Claims (8)

A polyamide-based multilayer stretched film obtained by biaxially stretching a multilayer laminate having at least three layers of a polyester layer (A layer), a polyamide layer (B layer) and a polyamide layer (C layer) in this order,
(A) layer contains crystalline polyester,
(B) the layer contains an aliphatic polyamide,
(C) The polyamide-based multilayer stretched film, wherein the layer contains an aromatic polyamide.   The crystalline polyester contained in the layer (A) is at least one selected from the group consisting of polyethylene terephthalate (PET), isophthalic acid copolymerized polyethylene terephthalate, sulfoisophthalic acid copolymerized polyethylene terephthalate, and mixtures thereof. Item 2. The polyamide-based multilayer stretched film according to Item 1.   The aliphatic polyamide of the layer (B) is at least one selected from the group consisting of nylon-6, a copolymer of nylon-6 and nylon-6,6, and a mixture thereof. The polyamide-based multilayer stretched film described in 1.   The polyamide-based multilayer stretched film according to claim 1, wherein the aromatic polyamide is polymetaxylene adipamide.   The polyamide-based multilayer stretched film according to any one of claims 1 to 4, having a total film thickness of 10 to 50 µm.   A packaging film obtained by laminating a sealing layer on the (C) layer of the polyamide-based multilayer stretched film according to claim 1.   A packaging bag obtained by making the packaging film according to claim 6 into a bag shape and heat-sealing the sealing layer surfaces.   A package formed by filling the packaging bag according to claim 7 with contents.