JP2003012407A - Polyamide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antibacterial film suitable for wrapping materials. SOLUTION: This polyamide film contains a polymer having more excellent flex resistance than that of a polyamide resin in a layer comprising the polyamide resin in which an inorganic antibacterial agent is dispersed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to packaging of foods, medical products, medicines, etc., which are easily deteriorated by bacteria or the like, or
TECHNICAL FIELD The present invention relates to an antibacterial polyamide film suitable for packaging a cold insulating agent.

[0002]

2. Description of the Related Art Conventionally, polyamide films have been used as various packaging materials either alone or laminated with other types of films. In particular, as a package for a cooling agent, it has been used heavily because of its excellent pinhole resistance, flexibility at low temperatures, and drop bag puncture resistance. On the other hand, the demand for antibacterial properties has been increasing in recent years, and antibacterial films have been receiving attention. There are many proposals for films using antibacterial agents (Japanese Patent Laid-Open No. Hei 2
-247239, JP-A-9-57923,
JP-A-2000-85069).

[0003]

In the antibacterial polyamide film, the addition of an antibacterial agent such as silver ion makes the film opaque, or the film tends to break when stretched to increase the film strength and is stable. It was difficult to produce. Further, when an organic antibacterial agent is used, the dispersibility in the polyamide resin is good and breakage during stretching is small, but bleeding of the antibacterial agent from the film is large and the antibacterial effect is likely to decrease. Therefore, in view of the above situation, an object of the present invention is to provide an antibacterial polyamide stretched film having excellent antibacterial properties and having film physical properties such as toughness.

[0004]

The inventors of the present invention have completed the present invention as a result of extensive studies to solve the above problems. Therefore, the gist of the present invention is
The base material layer has a layer made of a polyamide resin in which an inorganic antibacterial agent is dispersed on at least one surface, and the polyamide resin layer contains a polymer having higher flex resistance than the polyamide resin. A laminated polyamide film or a layer made of a polyamide resin in which an inorganic antibacterial agent is dispersed contains a polymer having higher flex resistance than the polyamide resin.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
As the polyamide resin of the present invention, ε-caprolactam homopolymer (nylon-6), polyhexamethylene adipamide (nylon-66) and polymetaxylylene adipamide (MXD) are preferable, but in some cases, A polymer obtained by copolymerizing a compound copolymerizable therewith may be used. The amount of the copolymerizable compound is preferably about 20 mol% or less. Compounds copolymerizable with caprolactam, hexamethylene adipamide, metaxylylene adipamide, etc. include aliphatic or aromatic or alicyclic diamines, and aliphatic or aromatic or alicyclic dicarboxylic acids. Examples include nylon salts. Examples of the diamines include ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, octamethylenediamine, decamethylenediamine, and the like, heterocyclic rings or heteroatom-containing diamines such as piperazine bispropylamine and neopentylglycol bispropylamine. Etc. Examples of dicarboxylic acids are adipic acid, sebacic acid, cork acid, glutaric acid, azelaic acid, β-methyladipic acid, decamethylenedicarboxylic acid, dodecamethylenedicarboxylic acid, pimelic acid, terephthalic acid, isophthalic acid, 1,4-cyclohexanedicarboxylic acid. Etc.

The above polyamide resin includes a lubricant,
Various additives such as antistatic agents, antioxidants, antiblocking agents, stabilizers, dyes, pigments and inorganic fine particles can be added within a range that does not affect the properties of the film.

A polymer having excellent flex resistance means that the film functions as a flex resistance improver, and an unstretched film composed of the polymer itself is cut into a specific size. When the number of pinholes in the film after the repeated bending test with a flex tester is measured, it means a polymer of 10/77 inch ² or less. The specific measuring method is shown in the examples described later.

Specific examples of the polymer having excellent bending resistance include, for example, polyolefins, modified polyolefins, mixtures of modified polyolefins and polyolefins, polyamide elastomers, ionomer polymers, etc., and mixtures thereof. Can be used, but is not limited to these. Specific examples of the polyolefins are homopolymers of olefins such as ethylene and propylene, and mixtures thereof, or copolymers and mixtures thereof, and examples thereof include high-density polyethylene, low-density polyethylene, and linear low-density polyethylene. Polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-butene copolymer, polypropylene, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-vinyl acetate copolymer, etc. Is mentioned.

Modified polyolefins are also included in polyolefins. The modified polyolefins are those obtained by graft-polymerizing unsaturated carboxylic acids with polyolefins as the main skeleton. Specific examples of the polyolefin as the main skeleton, ethylene, homopolymers of olefins such as propylene, and mixtures thereof, or copolymers and mixtures thereof, for example, high-density polyethylene, low-density polyethylene, Linear low density polyethylene,
Examples thereof include ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-butene copolymer, polypropylene and the like. Specific examples of the unsaturated carboxylic acids, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, carboxylic acids such as citraconic acid, maleic anhydride, citraconic anhydride, acid anhydrides such as itaconic anhydride Or a metal salt of an acid such as potassium acrylate or potassium methacrylate. These unsaturated carboxylic acids are not limited to one kind, and two or more kinds may be mixed and used.

The content of unsaturated carboxylic acids in the modified polyolefin is usually less than 4% by weight, preferably 0.1 to 2% by weight. If it exceeds 4% by weight, not only the production cost becomes high, but also the effect of improving the flex resistance of the obtained film is saturated, so the content of unsaturated carboxylic acids in the modified polyolefin is 4% by weight. It is not necessary to exceed the content.

The ionomer polymer is made of an olefin and an α, β-ethylenically unsaturated monomer having a carboxyl moiety, which is considered to be an acid equivalent, and the carboxylic acid has a valence of 1 to 3. What is neutralized with the metal ions of. Specific examples of the olefin include polyethylene or ethylene and usually 3 to 8 carbon atoms.
Is a copolymer of at least one α-olefin with a diolefin, for example, 1,4-hexadiene. Specific examples of the α, β-ethylenically unsaturated monomer having a carboxyl moiety include methacrylic acid, acrylic acid, maleic acid, maleic anhydride, fumaric acid and the like. The metal ions include zinc ions, sodium ions, lithium ions, potassium ions, magnesium ions and the like. The ionomer polymer is produced by a direct synthesis method in which an α-olefin and an olefin monomer having a carboxyl moiety are polymerized, a grafting method in which a monomer having a carboxyl moiety is added to an olefin skeleton, or the like.

Examples of the ethylene-acrylic ester copolymer or ethylene-methacrylic ester copolymer elastomer include copolymers with methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate and the like.

Examples of the polyamide elastomer include polyether amide, polyether ester amide and polyester amide. Further, a small amount of a dicarboxylic acid such as dodecanedicarboxylic acid, adipic acid or terephthalic acid may be used as an optional component.

The content of the polymer having excellent bending resistance is usually in the range of 0.1 to 5% by weight based on the polyamide resin.
If it is less than 0.1% by weight, the effect of improving the flexural pinhole resistance is small, and if it exceeds 5% by weight, the transparency of the obtained film tends to be impaired.

The inorganic antibacterial agent is generally an antibacterial agent such as soluble glass, zeolite, silica, titanium oxide, amorphous aluminosilicate, zirconium phosphate, aluminum phosphate, hydroxyapatite, etc. It has been known for a long time that silver, copper, zinc, mercury, lead, tin, chromium, bismuth, cadmium, thallium, and other ions are supported, and soluble glass containing silver ions is known. Particularly preferred.

[0016] The soluble glass containing silver ions is a mixture of silica glass, phosphoric acid glass, boric acid glass and the like with a silver compound. Ag content is Ag
From the viewpoint of antibacterial effect, economical efficiency, etc., it is usually preferable that the amount of O is about 0.1 to 5% by weight. Soluble glass is a general term for glasses having a melting rate controlled by the composition of the glass, and silver ions from the compounded silver compound can be eluted for a long period of time even though the amount is very small. Then, an antibacterial effect is obtained by such silver ions.

In the present invention, the above inorganic antibacterial agent is dispersed in a polyamide resin. The dispersion amount is not particularly limited as long as the desired antibacterial effect is obtained, but is usually 0.0
It is 1 to 1% by weight. If the amount is too small, the antibacterial effect becomes poor, and if the amount is too large, the film may be easily broken during stretching, and the transparency of the film may be deteriorated even if the film is not broken.

As the inorganic antibacterial agent, resin pellets of the above polyamide resin may be blended as they are by dry blending, but generally, a masterbatch having a high concentration of the inorganic antibacterial agent is prepared and A method of forming a film by using a dry blend with a polyamide resin is preferable.

The polyamide resin in which the inorganic antibacterial agent is dispersed can be directly formed into a film, but a method of forming a film by melt-passing through a filter in advance is preferable.

The polyamide resin in which the antibacterial glass particles are dispersed is introduced into a die and formed into a film, which is discharged from the die. The discharged film is rapidly cooled and becomes a substantially non-oriented film. . The unoriented film is
By a stretching method such as roll type uniaxial stretching, tenter type uniaxial stretching, tenter type sequential biaxial stretching, tenter type simultaneous biaxial stretching, tubular type simultaneous biaxial stretching, etc., usually at least 1.5 times or more, preferably in at least one direction. Stretch 2 to 5 times. In particular, a film obtained by biaxial stretching is preferably used because of its strength, transparency, thickness uniformity, and ease of handling.
By stretching in this way, the film strength and transparency are improved, but the antibacterial activity is hardly reduced in spite of the decrease in the concentration of the antibacterial agent per area of the film surface. Although the reason for this is not clearly known, it is presumed that the antibacterial agent is expressed when the head easily comes out from the film surface. Further, the antibacterial property can be further improved by corona-treating the antibacterial agent-containing layer arranged on the outer side. Usually, it is known that the inside of the packaging film base material is subjected to corona discharge treatment to facilitate the attachment of the adhesive during printing or lamination, but in the film obtained by the present invention, an outer antibacterial material-containing layer is further added. Similar corona discharge treatment tends to increase the antibacterial activity.

The antibacterial polyamide film of the present invention may be any film containing an antibacterial agent-containing layer in the surface layer. In this sense, the antibacterial polyamide film of the present invention is not limited to a single-layer polyamide film having only an antibacterial agent-containing layer, but may have a multi-layered structure as long as the surface has an antibacterial agent layer. Rather, by including the antibacterial agent only in one surface layer, the total amount of the antibacterial agent can be reduced, which is preferable from the viewpoint of transparency and economy. When the layer structure is A layer made of polyamide resin containing an antibacterial agent and B layer which is a base material layer made of polyamide resin not containing an antibacterial agent,
Although there are constitutions such as A, A / B, A / B / A and the like, the layer B may be composed of two or more layers, and the polyamide resin of each layer may be different. Further, a C layer other than the polyamide resin may be added thereto. The B layer, which is the base material layer, may be other than the polyamide resin.

In the antibacterial polyamide film of the present invention, the thickness of the antibacterial agent-containing layer is usually 2 to 40 μm, and the total thickness of the film is preferably 10 to 40 μm. When the total thickness is less than 10 μm, the strength as a film is not sufficient, and a film which is satisfactory for packaging cannot be obtained. When it exceeds 40 μm, the film becomes hard, and when a sealant layer is further stuck,
The entire film becomes very thick, making it unsuitable for flexible packaging applications.

The above-mentioned antibacterial polyamide film of the present invention can be further laminated with a heat-welding resin layer called LLDPE, CPP, EVA, ionomer or other so-called sealant to form a laminated film. In such a laminated film, the antibacterial agent-containing layer is usually the outermost layer, and the inner layer on the side opposite to the outermost layer is a sealant layer, for example, after heat-sealing into a bag shape, a cold insulating material in the bag, By filling with a heat storage material or the like, a cold storage material pack and a heat storage material pack having an outer surface antibacterial property can be obtained. By cooling or heating it sufficiently, it can be used for keeping cold foods such as fresh foods and pharmaceuticals, or for keeping heat, or for cooling muscles during sports and warming during warming up. It is possible to prevent the growth of bacteria and the like on the surfaces of the material pack and the heat storage material pack. It is effective for long-term storage of contents by using it as a content-retaining material other than a heat insulating material and a heat storage material, for example, a part of a bag in which an oxygen absorbent or a desiccant is enclosed.

[0024]

EXAMPLES The present invention will now be described in more detail with reference to the examples, but the present invention is not limited to the examples as long as the gist thereof is not exceeded. The film evaluation method in the examples is as follows. (1) Antibacterial activity Each film was tested for antibacterial activity against Staphylococcus aureus by the antibacterial product technology council test method “Antibacterial Product Evaluation Test Method for Antibacterial Products (Fiscal 1998 Revised Edition) Film Adhesion Method”.
As a result, an increase / decrease value difference was calculated as follows, and an increase / decrease value difference of 2 or more was judged to be antibacterial. Increase / decrease value difference = logC−logD where C: average value of viable cell count of control sample (ONY film containing no antibacterial agent) after 24 hours (unprocessed test section) D: viable cell of test sample after 24 hours Average number (antibacterial processing test zone)

(2) Bending resistance (number of pinholes / 77 inch ² ) Conditioned by leaving a film cut into a size of 8 inches × 11 inches at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours or more. Gelvo Flex Tester (Rigaku Kogyo Co., Ltd., No.901 type (MIL-B-1
The bending test was repeated as described below, and the number of pinholes was measured.

The rectangular test film is wound into a cylindrical shape having a length of 8 inches, one end of the wound cylindrical film is on the outer circumference of the disk-shaped fixed head of the tester, and the other end is the disk of the tester. Fixed to the outer periphery of the movable head, and the movable head is parallel to the fixed head along the axis of both heads that face each other in parallel (the fixed head and the movable head face each other at a distance of 7 inches). Rotate 440 ° while approaching for 0.5 inch, then straight forward for 2.5 inch without rotating, and then reverse these operations to return the movable head to the initial position. The bending test for one cycle was continuously performed for 3000 cycles at a speed of 40 cycles per minute, and then fixed to the outer periphery of the fixed head and the movable head of the tested film. Number pinholes occurring in the film in seven inches × 11 inches excluding the portion, pinholes tester (Sanko Electronic Laboratory Ltd., TRD-type) by 1KV
The voltage was applied and measured.

Example 1 55% by weight as P2O5 and 30% by weight as ZnO,
5% by weight as B2O3, 5% by weight as CaO, A
3% by weight as g2O, 1% by weight as Na2O, Ce
The respective glass raw materials were uniformly pulverized and mixed in the crucible so that O2 was 1% by weight. Then, it was heated using a glass melting furnace to prepare molten glass, and this molten glass was poured into water and granulated. Then crush it in a mortar,
Further, finely pulverized with a vibrating ball mill. The obtained powder was dispersed in methanol, and the particle size distribution was measured by a light scattering method.
8% had a particle size of 7 μm or less. The particles prepared above were used as antibacterial agent A. Nylon 6 resin pellets (Mitsubishi Engineering Plastics Co., Ltd.) and an antibacterial agent (nylon 6 masterbatch containing antibacterial agent particles A10%) were dry blended at a weight ratio of 95: 5 and a resin mixture ().
Nylon 6 resin and polyamide elastomer X (manufactured by Daicel Hüls) were mixed at a weight ratio of 99: 1, and the resin () was extruded from separate 65 mmφ extruders and led to a two-layer manifold, and at the T-die outlet, And was extruded into a film.

The above laminated film was brought into close contact with a cooling roll kept at 35 ° C. by an electrostatic contact method and then rapidly cooled to give a layer of about 100 μm, a layer of 40 μm, and a total thickness of 14
A 0 μm non-oriented laminated film was obtained. The non-oriented laminated film was guided to a longitudinal stretching machine composed of a plurality of rolls, and longitudinally stretched under the conditions of a stretching temperature of 50 ° C., an average deformation rate of 13000% / min, and a stretching ratio of 3. Subsequently, the longitudinally stretched film was transferred to a tenter type horizontal stretching machine, both ends thereof were held by tenter clips, and the stretching temperature was 100 ° C. and the average deformation rate was 3
The transverse stretching was performed under the conditions of 000% / min and a stretching ratio of 3.4 times. Subsequently, the laterally stretched film was heat treated at 200 ° C. while being held by a tenter clip. The heat-treated film was cut and removed from both ears of the film and wound up with a winder. The obtained laminated biaxially stretched film had a total thickness of 15 μm (layer about 11 μm / layer about 4 μm
m). Table 1 shows the performance measurement results of the obtained film.

Example 2 The same laminated biaxially stretched film as in Example 1 was obtained except that the following description was made in Example 1. Nylon 6 resin pellets (Mitsubishi Engineering Plastics),
MXD resin pellets (manufactured by Mitsubishi Gas Chemical Co., Inc.) and antibacterial agents (nylon 6 masterbatch containing 10% antibacterial agent particles A) were added at a weight ratio of 75: 20: 5 with 0.6% polyamide elastomer X (manufactured by Daicel Hüls). The dry blended resin mixture (), MXD resin (manufactured by Mitsubishi Gas Chemical Co., Inc.) and polyamide elastomer (97: 3) were blended at a weight ratio of 97: 3, and the resin mixture () was extruded from each 65 mmφ extruder, and two inlets and three manifolds were used. And the resin () to the central manifold, and the raw material () is branched into two by the flow path and guided to the manifold of two layers on both outer sides, and laminated in three layers of // at the T die outlet. And extruded into a film. The above laminated film was brought into close contact with a cooling roll kept at 35 ° C. by an electrostatic contact method,
By rapidly cooling, a non-oriented laminated film having a raw material layer of about 55 μm, a raw material layer of 40 μm, a raw material layer of about 55 μm, and a total thickness of 150 μm was obtained. The above-mentioned non-oriented laminated film is guided to a longitudinal stretching machine composed of a plurality of rolls and stretched at a stretching temperature of 6
Longitudinal stretching was performed under the conditions of 0 ° C., average deformation rate of 13000% / min, and stretching ratio of 3. Subsequently, the longitudinally stretched film is transferred to a tenter type horizontal stretching machine, both ends thereof are held by tenter clips, and the stretching temperature is 120 ° C. and the average deformation rate is 30.
The transverse stretching was performed under the conditions of 00% / min and a stretching ratio of 3.6 times. Subsequently, the laterally stretched film was heat treated at 200 ° C. while being held by a tenter clip. The heat-treated film was cut and removed from both ears of the film and wound up with a winder. The total thickness was 15 μm.

Example 3 A result produced under the same conditions as in Example 2 except that MXD resin was not used as the resin under the conditions of Example 2 and the polyamide elastomer X was changed to modified polyolefin O (manufactured by Nippon Polychem). Is shown in Table 1. Example 4 Table 1 shows results produced under the same conditions as in Example 2 except that the modified polyamide elastomer X was changed to modified ethylene-vinyl acetate copolymer P (manufactured by Japan Polychem) under the conditions of Example 2. Example 5 In the same manner as in Example 1, the polyamide elastomer X in the resin mixture was changed to 2% ethylene-ethyl acrylate copolymer Y (Mitsui DuPont Chemical Co., Ltd.) to produce a monolayer film. Shown in. Example 6 Except that the polyamide elastomer X was changed to an ionomer Z (manufactured by Mitsui DuPont Chemicals) under the conditions of Example 2,
Table 1 shows the results produced under the same conditions as in Example 2. Example 7 Table 1 shows the results of producing a film under the same conditions as in Example 5 except that Nylon 6 was changed to Nylon 66 (Leona manufactured by Asahi Kasei Kogyo KK) under the conditions of Example 5. Example 8 In Example 5, the antibacterial agent was changed to 0.3%,
Table 1 shows the results of producing a film by changing the ethylene-ethyl acrylate copolymer Y2% to the polyamide elastomer X1%. 56% by weight as B2O3, P2O
5 to 11% by weight, Ag2O to 3% by weight, Na2O to 4% by weight, and MgO to 26% by weight,
The respective glass raw materials were uniformly pulverized and mixed in the crucible. Then, it was heated using a glass melting furnace to prepare molten glass, and this molten glass was poured into water and granulated. Further, it was coarsely pulverized in a mortar and then finely pulverized by a vibrating ball mill. The obtained powder was dispersed in methanol, and the particle size distribution was measured by a light scattering method. As a result, 98% of the number of particles accumulated from fine particles was 10 μm or less. The particles prepared above were used as antibacterial agent B. Example 9 Results produced under the same conditions as in Example 8 except that the amount of the antibacterial agent was changed to 0.05% in Example 8 and the polyamide elastomer X1% was changed to ethylene-ethyl acrylate copolymer Y4%. Is shown in Table 1. Example 10 Polyamide elastomer X1% in Example 8 was treated with ethylene-
Table 1 shows the results produced under the same conditions as in Example 8 except that the vinyl acetate copolymer Q (manufactured by Nippon Polychem) was changed to 3%.
Shown in.

Comparative Example 1 Under the conditions of Example 5, the results of producing a film in the same manner as in Example 5 except that the antibacterial agent and the ethylene-ethyl acrylate copolymer Y were not used are shown in Table 1. Comparative Example 2 Table 1 shows the results of producing a film in the same manner as in Example 5 except that the ethylene-ethyl acrylate copolymer Y was not used under the conditions of Example 5. Comparative Example 3 Table 1 shows the results of producing a film under the same conditions as in Example 8 except that the polyamide elastomer X was not used. Comparative Example 4 Table 1 shows the results of producing a film in the same manner as in Example 2 except that the polyamide elastomer X was not used in Example 2.

[0032]

[Table 1]

[0033]

The antibacterial polyamide film of the present invention is
It has excellent physical properties of polyamide such as transparency, bending resistance, and toughness, and has excellent antibacterial properties. Therefore, it is suitable for packaging foods, medical products, chemicals, etc., which are easily deteriorated by bacteria or the like, or for packaging ice packs. In particular, in a laminated film obtained by laminating a sealant layer to the antibacterial polyamide film of the present invention, as a bag, a cold insulating material pack having an external antibacterial property, a heat storage material pack,
It can be used as a preservative pack.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08K 3/00 C08K 3/00 C08L 23/00 C08L 23/00 23/08 23/08 23/26 23 / 26 77/00 77/00 F-term (reference) 4F100 AA01B AA18 AA25 AB24B AG00B AK01B AK03B AK46B AK68B AK70B AK71B AL09B AR00C AT00A BA07 BA10A BA10B BA10C CA30B DE01B GB15 GB23 JC00 JK07A01B12C01 JK04B01C12 DH06 4J002 BB002 BB072 BB232 BF032 CL001 CL002 DL006 FB076 GG02

Claims (12)

[Claims] 1. A base material layer having, on at least one surface thereof, a polyamide resin in which an inorganic antibacterial agent is dispersed, and
A laminated polyamide film characterized in that the polyamide resin layer contains a polymer having more excellent flex resistance than the polyamide resin. 2. A polyamide film comprising a layer of a polyamide resin having an inorganic antibacterial agent dispersed therein, and a polymer having more excellent flex resistance than the polyamide resin. 3. The polyamide film according to claim 1, wherein the polymer having excellent flex resistance is polyolefin. 4. The polyamide film according to claim 1, wherein the polymer having excellent flex resistance is an ionomer. 5. A polymer having excellent bending resistance is an ethylene-acrylic ester copolymer elastomer or ethylene-
The polyamide film according to claim 1 or 2, which is a methacrylic ester copolymer elastomer. 6. The polyamide film according to claim 1, wherein the polymer having excellent flex resistance is an ethylene-vinyl acetate copolymer. 7. The polyamide film according to claim 1, wherein the polymer having excellent flex resistance is a polyamide elastomer. 8. The polyamide film according to claim 1, which contains 0.1 to 5% by weight of a polymer having excellent flex resistance. 9. The polyamide film according to claim 1, wherein the inorganic antibacterial agent is soluble glass particles containing silver ions. 10. A polyamide laminated film obtained by providing a sealant layer on the polyamide film according to claim 1, wherein the sealant layer is provided on the opposite side to a layer made of a polyamide resin in which an inorganic antibacterial agent is dispersed. Laminated film 11. A polyamide laminated film obtained by providing a sealant layer on the polyamide film according to claim 2. 12. A film for packaging a cold insulating material comprising the laminated film according to claim 10 or 11.