JP2002166512A - Polyamide film excellent in bending fatigue resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyamide film excellent in bending fatigue resistance, bag tearing resistance and transparency being film characteristics necessary as a packaging film, capable of preventing the contamination or leakage of content caused by the generation of a pinhole or the tearing of a bag when used as various packaging materials, good in the printing of the film or processability in lamination or the like, and suitable for a packaging use. SOLUTION: The polyamide film is obtained by laminating an A-layer comprising a mixed polymer consisting of 80-99 wt.% of an aliphatic polyamide and 20-1 wt.% of an elastomer and the B-layer laminated on at least one surface of the A-layer and comprising a polyamide polymer different from that of the A-layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide film having excellent bending fatigue resistance, and particularly to printing and laminating when used as a packaging material for food packaging and the like, which is excellent in bending fatigue resistance and bag breaking resistance. The present invention relates to a polyamide film having good workability in, for example, and excellent bending fatigue resistance suitable for various packaging applications.

[0002]

2. Description of the Related Art Conventionally, an unstretched film or stretched film made of a polyamide polymer represented by nylon 6 or nylon 66 is superior in strength and gas barrier properties as compared with films of polyester and polyolefin.
Widely used as various packaging materials such as food packaging.

[0003]

However, in the case of a packaging material using an unstretched film or stretched film made of the above-mentioned polyamide-based polymer, the processing steps such as vacuum packaging have been diversified with the diversification of uses such as food packaging. However, there is a problem that a pinhole is generated or a bag is broken due to local destruction of a film due to bending fatigue at a time, vibration or impact during transportation of foods such as frozen foods and retort foods.

[0004] In addition, the occurrence of pinholes and breaks in the packaging material causes contamination and decay due to leakage of the contents, which poses a problem in the processing and transportation of the product. Quality improvement is required.

In order to solve the above problems, a method of improving film properties by mixing a flexible polymer such as an ionomer with a polyamide polymer (Japanese Patent Laid-Open No.
No. 6-147847).

However, even in these methods,
Flexural fatigue resistance and bag breakage resistance required for polyamide-based films have been satisfied, and the film has not yet reached a level with sufficient film properties for use as various packaging materials.

The present invention solves the above-mentioned problems of the conventional polyamide film having excellent bending fatigue resistance, and further provides the film characteristics required as a packaging film, such as bending fatigue resistance and bag breaking resistance. Excellent transparency, prevents contamination and leakage of contents due to pinholes and tearing of bags when used as various packaging materials, and has good workability in film printing and lamination. It is an object of the present invention to provide a polyamide-based film suitable for:

[0008]

In order to achieve the above object, the polyamide film having excellent flex fatigue resistance according to the present invention comprises a mixture of 80 to 99% by weight of an aliphatic polyamide and 20 to 1% by weight of an elastomer. An A layer composed of the unified
It is characterized in that the layer A is laminated on at least one surface of the layer, and the layer B is composed of a different kind of polyamide polymer.

The polyamide film having excellent flex fatigue resistance according to the present invention having the above constitution is excellent in flex fatigue resistance and bag breakage resistance, and generates pinholes during film processing and transportation of goods. Prevention of cracks and tears reduces the rejection rate, and is excellent in transparency, good in workability in processing such as printing and lamination, and can be effectively used as various packaging materials.

In this case, the thickness of the layer A can be 40 to 95% of the thickness of the layers A and B.

In this case, the elastomer is composed of (a) a polyamide component selected from the group consisting of lactam ω-amino aliphatic carboxylic acid aliphatic diamine, aliphatic dicarboxylic acid, aliphatic diamine and aromatic dicarboxylic acid. It can be a polyamide block copolymer comprising a hard segment and (b) a soft segment composed of a polyoxyalkylene glycol component.

Further, the polyamide film having excellent bending fatigue resistance according to the present invention is characterized in that an adhesive property modification layer is laminated on at least one surface of the film.

The polyamide-based film having the above-mentioned structure has an adhesiveness-improving layer formed on at least one surface to improve the adhesiveness, particularly the water-resistant adhesiveness which is a weak point of the polyamide-based film. In addition, it is also effective in suppressing quality deterioration such as adhesiveness and gas barrier property due to boil treatment and retort treatment.

Further, the polyamide film of the present invention having excellent bending fatigue resistance is characterized in that a gas barrier layer is laminated on the film.

The polyamide-based film having the above-described structure has a gas barrier layer formed on at least one surface, so that the gas-barrier property of the polyamide-based film is further improved, and various types of packaging requiring high-gas barrier property are required. It can be used for materials.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a polyamide film having excellent bending fatigue resistance according to the present invention will be described.

In the present invention, the aliphatic polyamide 80
The layer A is made of a mixed polymer of 〜99% by weight and the elastomer 20 エ ラ ス ト マ ー 1% by weight, and the layer B is laminated on at least one surface of the layer A, so that bending fatigue resistance and bag crush resistance are achieved. And a polyamide film having excellent film properties and excellent flex fatigue resistance.

The aliphatic polyamide used in the present invention includes nylon 6, nylon 6.6, nylon 12,
Nylon 6/10 is a typical example, but in addition to these, nylon 6/6/6, nylon 6 /
6.10, nylon 6.6 / 6/10, a small amount of nylon salt of ε-caprolactam as a main component, nylon salt of hexamethylenediamine and isophthalic acid, or nylon salt of metaxylylenediamine and adipic acid. Can be used.

Examples of the elastomer used in the present invention include polyamide-based block copolymers such as polyetheramide, polyetheresteramide, and polyesteramide, and ethylene and methyl acrylate, ethyl acrylate, methyl methacrylate, and methacrylic. Acrylic or methacrylic elastomers such as copolymers with acrylates or methacrylates such as ethyl acrylate, and styrene-based elastomers can be used.

When these elastomers are used as constituents of the polyamide film of the present invention, a polyamide block copolymer consisting of a hard segment constituted by a polyamide component and a soft segment constituted by a polyoxyalkylene glycol component is used. In this case, the polyamide component of the hard segment is preferably selected from the group consisting of lactam, ω-amino aliphatic carboxylic acid, aliphatic diamine and aliphatic dicarboxylic acid or aliphatic diamine and aromatic dicarboxylic acid, Examples include lactams such as ε-caprolactam, ω-aminoaliphatic carboxylic acids such as aminoheptanoic acid, aliphatic diamines such as hexamethylenediamine, aliphatic dicarboxylic acids such as adipic acid, and aromatic dicarboxylic acids such as terephthalic acid. In That.

The polyoxyalkylene glycol constituting the soft segment of the polyamide-based block copolymer includes, for example, polyoxytetramethylene glycol, polyoxyethylene glycol, polyoxy-1,2-propylene glycol and the like. it can.

The mixed polymer constituting the layer A is mixed at a ratio of 80 to 99% by weight of the aliphatic polyamide and 20 to 1% by weight of the elastomer. When the amount of the elastomer is less than 1% by weight, the effect of improving the bending fatigue resistance is not improved. If the amount is too small and exceeds 20% by weight, a problem occurs in the transparency of the film. A preferable mixing ratio of the elastomer which balances the bending fatigue resistance and the transparency of the film is 2 to 10% by weight.

The method of mixing the aliphatic polyamide and the elastomer is not particularly limited, but usually, a method of mixing both chips in a blender using a blender and then melting and molding the mixture is used.

In the present invention, the polyamide polymer constituting the layer B is a polyamide polymer different from the above-mentioned layer A, and nylon 6, nylon 6.6, nylon 12,
Aliphatic polyamides such as nylon 6,10, nylon 6
Aliphatic polyamide copolymers such as 6.6 / 6 copolymer, nylon 6/6/10 copolymer, nylon 6.6 / 6/10 copolymer, etc .; Polyamide copolymer containing a small amount of aromatics obtained by copolymerizing a nylon salt of methylenediamine and isophthalic acid or a nylon salt of m-xylylenediamine and adipic acid; Metaxylylene group-containing polyamide polymers and aromatic polyamides having α, ω-aliphatic dicarboxylic acids of the formulas 6 to 10 as a main dicarboxylic acid component, and mixed polymers thereof can be used.

The polymer forming the layer A and / or the layer B according to the present invention may contain other thermoplastic resins, if necessary, for example, polyester polymers such as polyethylene terephthalate and polybutylene terephthalate, polyethylene and polypropylene. May be contained in a range that does not impair the properties thereof.

Also, an antistatic agent, an inorganic lubricant, an organic lubricant,
Various additives such as an antifogging agent, an antiblocking agent, a heat stabilizer, an ultraviolet absorber, a dye, and a pigment can be added to one or both of the A layer and the B layer as needed.

By modifying the surface of the polyamide film of the present invention, the adhesive performance can be improved. The means for such surface modification is not particularly limited, and examples thereof include a corona discharge treatment, a flame treatment, a low-temperature plasma treatment, a glow discharge treatment and the like, but the most practical is the surface of the polyamide-based film. This is a method of forming an adhesive property modification layer on the substrate.

Examples of the adhesive property modification layer formed on at least one surface of the polyamide film of the present invention include polyester resins, polyacryl resins, polyurethane resins, etc., and polyester resins are particularly preferable. Among them, it is preferable to use a graft copolymer resin obtained by modifying a copolymerized polyester with an acrylic acid component, a maleic anhydride component, or the like.

The copolymerized polyester in this case includes
A typical example is a crystalline or amorphous thermoplastic resin having a high molecular weight by esterification, and can be obtained, for example, by subjecting a dicarboxylic acid or a tricarboxylic acid and a glycol to a polycondensation reaction. .

The components used for such polycondensation include acid components such as terephthalic acid, isophthalic acid, adipic acid, trimellitic acid, fumaric acid and sebacic acid, and ethylene glycol, neopentyl glycol, butanediol and propylene glycol. And glycol components such as ethylene glycol-modified bisphenol A, but are not limited thereto. Components that are graft-copolymerized with the copolymerized polyester include, but are not limited to, acrylic acid, acrylic esters, maleic anhydride, and styrene. Further, these graft copolymer resins may be used alone or in combination with other resins. Furthermore, it is also possible to use isocyanate, epoxy, acrylic, melamine, etc. together as a curing agent.

The preferred thickness of the adhesive property-modifying layer laminated on at least one surface of the polyamide film is from 0.01 to 0.01.
It is 10 μm, more preferably 0.02 to 5 μm. When the thickness is less than 0.01 μm, the effect of improving the adhesiveness is small,
Excessively thicker than 10 μm causes operational difficulties in production processes such as coating.

As a method for forming the adhesive property modification layer, for example,
Any method such as a roll coating method, a reverse coating method, a roll brushing method, a spray coating method, an air knife coating method, a gravure coating method, an impregnation method, and a curtain coating method can be adopted, and the production of a polyamide film There are an in-line method in which coating is sometimes performed, and an off-line method in which coating is performed in a step different from the production of a polyamide-based film. Which method or method is determined depending on the quality and productivity required for the polyamide-based film.

Further, the gas barrier layer laminated on at least one surface of the polyamide film of the present invention includes:
A coating layer such as a vinylidene chloride copolymer latex,
Aluminum vapor-deposited layers, silicon oxide, aluminum oxide, magnesium oxide, inorganic vapor-deposited layers composed of a mixture of these, and the like. Among these, which method is used depends on the polyamide required as a packaging material for goods. It is selected from the gas barrier quality of the base film.

The thickness of the polyamide film of the present invention is not particularly limited, but when it is used as a packaging material, it is usually 100 μm or less, and generally 5 to 50 μm.
m is used.

Further, in the polyamide film of the present invention, the thickness ratio of the layer A composed of a mixed polymer of 80 to 99% by weight of the aliphatic polyamide and 20 to 1% by weight of the elastomer (the layer B is formed on both surfaces of the layer A). When the layers are stacked, the total thickness ratio) is set to 40 to 95% of the thickness of the A layer and the B layer. If the thickness ratio of the A layer is more than 95%, the bag-breaking resistance is insufficient, and if it is less than 40%, the bending fatigue resistance becomes insufficient.

The polyamide film of the present invention has excellent properties in bending fatigue resistance and bag breaking resistance under normal temperature and low temperature environments, and also has excellent transparency. The film has a good appearance and is suitable as various packaging materials.

The polyamide film of the present invention can be produced by a known production method. For example, a method in which the polymers constituting each layer are melted using separate extruders and co-extruded from one die. A known method such as a method of separately extruding the polymer constituting each layer into a film shape and then laminating them by a lamination method and a method of combining these can be employed.

Further, in the present invention, each layer of the polyamide film may be either an unstretched film layer or a stretched film layer. However, in order to improve the transparency and processability of the polyamide film, it is preferable to use a uniaxial film. Alternatively, it is preferable to stretch in the biaxial direction. As the stretching method in this case, a known method such as a flat sequential biaxial stretching method, a flat simultaneous biaxial stretching method, and a tubular method can be used.

[0039]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. In addition, the evaluation of the film was performed by the following measuring methods.

(1) Haze Using a direct-reading haze meter manufactured by Toyo Seiki Seisaku-sho,
It measured based on IS-K-7105. Haze (%) = [Td (diffuse transmittance%) / Tt (total light transmittance%)] × 100

(2) Impact Strength The impact strength was measured using a film impact tester manufactured by Toyo Seiki Seisakusho under an environment of a temperature of 23 ° C. and a relative humidity of 65%.

(3) Bending Fatigue Resistance (Number of Pinholes) Using a Gelboflex tester manufactured by Rigaku Corporation, bending fatigue resistance was measured by the following method. After applying a polyester-based adhesive to the film prepared in the example, 40 μm of a linear low-density polyethylene film (L-LDPE film: L6102 manufactured by Toyobo Co., Ltd.) was dry-laminated, and aged at 40 ° C. for 3 days. The resulting laminate film was obtained. The laminated film of 12 inches × 8 inches is formed into a cylindrical shape having a diameter of 3.5 inches. One end of the cylindrical film is fixed to the fixed head side of the gelbo flex tester, and the other end is fixed to the movable head side. Was 7 inches. 4 in the first 3.5 inches of the stroll
A twist of 40 degrees was given, and then a 2.5-inch bending fatigue was performed 1,000 times at a speed of 40 times / min to complete the entire horizontal streak, and the number of pinholes generated in the laminated film was counted. . The measurement was performed at 5 ° C.
In a low temperature environment.

(4) Laminating strength The film prepared in the example and the linear low-density polyethylene film (L-LDPE film: L61 manufactured by Toyobo Co., Ltd.)
02) 40 μm was dry-laminated in the same manner as above to obtain a laminated film. For measuring the lamination strength, 15 mm width x 15 in the longitudinal direction of the laminated film
A cut sample having a length of 0 mm was prepared, and the lamination strength of the film prepared in the example and the L-LDPE film was measured.

(5) Relative viscosity The relative viscosity was measured using an Ubbelohde viscometer at a concentration of 1 gram / 1 deciliter and a temperature of 20 ° C. using 96% sulfuric acid.

(Example 1) An unstretched sheet having the following structure was obtained using a co-extrusion T-die equipment of two types and three layers. B
In the configuration of layer / layer A / layer B, the total thickness of the unstretched sheet is 180 μm, and the total thickness ratio of layer A to the total thickness is 84%. Composition constituting layer A: a polymer composed of 97.0% by weight of nylon 6 (relative viscosity = 2.8) and 3.0% by weight of a polyamide-based block copolymer (manufactured by Daicel Huls, diamide). Composition. Composition constituting layer B: Nylon 6 (relative viscosity = 2.8) from 70.0% by weight, nylon 6 / 6.6 copolymer (Ube Industries, Ltd., product number 5023) from 30.0% by weight Polymer composition comprising: The obtained unstretched sheet is stretched 3.15 times in the machine direction and then 3.8 times in the cross direction to obtain 1 sheet.
A biaxially stretched film of 5 μm was prepared, and a corona discharge treatment was performed on the layer B on the side to be dry-laminated with a linear low density polyethylene film (L-LDPE film: L6102, manufactured by Toyobo Co., Ltd.) of 40 μm. The haze, impact strength, number of pinholes, and lamination strength of the obtained biaxially stretched film were measured. Table 1 shows the results.

Example 2 A biaxially stretched film was obtained in the same manner as in Example 1 except that the description in Example 1 was changed as follows. Composition constituting layer A: Nylon 6 (relative viscosity = 2.
A polymer composition comprising 87.0% by weight of 8) and 3.0% by weight of a polyamide-based block copolymer (manufactured by Daicel Huls, diamide). Composition constituting layer B: Nylon 6 (relative viscosity = 2.
8) A polymer composition comprising 97.5% by weight and polymethaxylylene adipamide (relative viscosity = 2.1) 2.5% by weight. Haze, impact strength, of the obtained biaxially stretched film,
The number of pinholes and the lamination strength were measured. Table 1 shows the results.

(Example 3) An adhesive property modification layer was laminated on the film surface of one side of the B layer of the polyamide-based film prepared in Example 2, and a corona discharge treatment was further performed. The adhesion modification layer was coated with a graft copolymer resin (manufactured by Toyobo Co., Ltd., Tg-20 ° C., acid value 2000 eq./ton) having a thickness of 0.05 μm comprising a polyester and an acrylic acid component. The coating was performed on the film after the stretching in the longitudinal direction was completed, and then the film was stretched in the transverse direction. The haze, impact strength, number of pinholes, and lamination strength of the obtained biaxially stretched film were measured. Table 1 shows the results.

Comparative Example 1 A secondary stretched film was obtained in the same manner as in Example 1 except that the description in Example 1 was changed as follows. The following polymer compositions were used for both the A layer and the B layer. Composition for forming layer A to layer B: nylon 6 (relative viscosity =
2.8) was 97.0% by weight, and a polyamide-based block copolymer (Daiamide, manufactured by Daicel Huels Co., Ltd.) was 3.0.
A polymer composition consisting of% by weight. The haze, impact strength, number of pinholes, and lamination strength of the obtained biaxially stretched film were measured. Table 1 shows the results.

Comparative Example 2 A secondary stretched film was obtained in the same manner as in Example 1 except that the description in Example 1 was changed as follows. The following polymer compositions were used for both the A layer and the B layer. Composition constituting layers A and B: 97.5% by weight of nylon 6 (relative viscosity = 2.8) and 2.5% by weight of polymethaxylylene adipamide (relative viscosity = 2.1) Polymer composition. The haze, impact strength, number of pinholes, and lamination strength of the obtained biaxially stretched film were measured. Table 1 shows the results.

[0050]

[Table 1]

[0051]

According to the polyamide film having excellent bending fatigue resistance of the present invention, it is excellent in bending fatigue resistance and bag breakage resistance. By preventing the breakage, the defect rate is reduced, the transparency is excellent, the processing suitability at the time of processing such as printing and laminating is good, and it can be effectively used as various packaging materials.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masatoshi Okutani 344 Maehata, Kizu-shi, Inuyama-shi, Aichi Prefecture Inside the Inuyama Plant of Toyobo Co., Ltd. 4F100 AK46B AK46C AK48A AK48J AL02A AL05A AL09A AR00D AR00E BA02 BA03 BA04 BA05 BA06 BA07 BA25 GB15 JD02A JD02E JK20 JK20A JL11D YY00A

Claims (5)

[Claims] 1. A different type of polyamide comprising an A layer composed of a mixed polymer of 80 to 99% by weight of an aliphatic polyamide and 20 to 1% by weight of an elastomer, and an A layer laminated on at least one surface of the A layer. A polyamide film excellent in bending fatigue resistance, characterized by being laminated with a layer B composed of a series polymer. 2. The thickness of the A layer is 4 times the thickness of the A layer and the B layer.
The polyamide-based film having excellent flex fatigue resistance according to claim 1, wherein the content is 0 to 95%. 3. A hard segment, wherein the elastomer comprises (a) a polyamide component selected from the group consisting of: lactam ω-aminoaliphatic carboxylic acid aliphatic diamine, aliphatic dicarboxylic acid, aliphatic diamine and aromatic dicarboxylic acid. 3. The polyamide film having excellent flex fatigue resistance according to claim 1, wherein the polyamide film is a polyamide block copolymer comprising (b) a soft segment composed of a polyoxyalkylene glycol component. 4. The film according to claim 1, wherein an adhesion modifying layer is laminated on at least one surface of the film.
Or a polyamide film excellent in bending fatigue resistance according to 3. 5. The polyamide film having excellent bending fatigue resistance according to claim 1, wherein a gas barrier layer is laminated on the film.