JP7568294B2 - Polyamide laminate film and its manufacturing method - Google Patents

Description

The present invention relates to a polyamide-based laminate film used for packaging or covering food, electronic components, etc.

Polyamide films have excellent toughness and are widely used in a variety of applications, from food packaging to industrial applications. Resin films, including polyamide films, are processed using printers, laminators, etc., depending on the intended use. In these processing machines, the resin film is transported by running between rolls whose surfaces are made of metal or rubber. Since the rolls and the resin film are in direct contact with each other, if the friction coefficient of the contact surface of the resin film is large, a difference will occur between the transport speed of the resin film and the rotation speed of the rolls. As a result, scratches will appear on the surface of the resin film, and the running of the resin film may become unstable. For this reason, a method has been proposed in which the resin film contains an inorganic filler and the surface of the resin film is roughened to reduce the contact surface with the rolls and reduce friction.

However, in recent years, there has been a demand to increase the running speed of resin films in order to improve productivity, and conventional physical methods of roughening the film surface alone are not enough to reduce friction, and excessive roughening can impair printability. Furthermore, simply roughening the film surface causes the problem of an increase in the coefficient of friction in high humidity conditions.

In response to this, a method has been proposed in which inorganic particles and long-chain fatty acid bisamide are incorporated into a polyamide film (Patent Document 1). However, although the incorporation of an aliphatic amide can suppress an increase in the dynamic friction coefficient under high humidity conditions, it is difficult to control the amount of bleed-out, which raises concerns about roll contamination and reduced printability.

On the other hand, a biaxially oriented polyamide film has been proposed in which a coating layer containing wax with a long-chain alkyl group and spherical fine particles is laminated on a polyamide film (Patent Document 2). With this film, by providing a coating layer containing slip agents and particles, a predetermined effect can be obtained with a smaller amount than when they are contained in a resin film. However, when the particle diameter of the spherical fine particles is small compared to the thickness of the coating layer, the effect of adding them is small. On the other hand, when the particle diameter of the spherical fine particles is large, there is a high risk that the fine particles will slip or fall off. In addition, when high-definition printing is required, if the surface roughness is high, printing defects may occur, and printing accuracy may decrease.

As such, in conventional technology, making a film more slippery sacrifices its printability, while improving printability creates the problem of making the film less slippery, making it difficult to improve both at once.

In recent years, one of the uses of polyamide films in the industrial field is as an exterior material for lithium-ion batteries. Even in such applications, the slipperiness of the film becomes an issue.

Traditionally, metal cans have been the mainstream exterior material for lithium-ion batteries. However, drawbacks of metal can types include a low degree of freedom in shape and difficulty in reducing weight. For this reason, it has been proposed to use a laminate consisting of a base layer (polyamide film), a metal foil layer (aluminum foil layer), and a sealant layer as the exterior. Such laminates are more flexible and have a high degree of freedom in shape than metal cans, and can be made thinner to reduce weight and easily miniaturized, making them widely used.

The laminate is then processed into a desired shape by cold forming to obtain various products such as containers. One of the physical properties of the film that affects the moldability during cold forming is the slipperiness of the film. For example, when a laminate having a polyamide film as the outermost layer is cold formed, the polyamide film comes into contact with the forming die, and if the polyamide film is not slippery (i.e., has a large coefficient of friction), wrinkles may form on the surface of the laminate when the forming die is pressed in, or the laminate may delaminate. Moreover, it is difficult to uniformly form the entire laminate, and uneven thickness occurs, raising concerns about the occurrence of pinholes. In particular, when cold forming is performed under high humidity, these problems become even more pronounced. In this respect, it is also required that the slipperiness of the film does not depend on humidity.

JP 2002-348465 A JP 2015-168125 A

For these reasons, there is a demand for a polyamide film that has excellent slip properties regardless of humidity, and therefore excellent cold forming and various processability, and that can also be used to apply high-resolution printing, but such a film has not yet been developed.

Therefore, the main object of the present invention is to provide a polyamide-based laminate film that combines high slip properties and good printability.

As a result of extensive research into solving the above problems, the inventors discovered that the above objective could be achieved by adopting a specific layer structure including a polyamide film and a specific resin layer, and thus completed the present invention.

That is, the present invention relates to the following polyamide-based laminate film and a method for producing the same.
1. A laminated film comprising a polyamide film and a polyurethane resin layer containing a polyurethane resin and an organic lubricant laminated on at least one surface of the film,
(1) The glass transition temperature of the polyurethane resin is 50° C. or higher,
(2) The arithmetic mean height (Ra) of the surface of the polyurethane resin layer is 0.010 to 0.060 μm, and the dynamic friction coefficient of the surface of the polyurethane resin layer in an environment of 20° C.×90% RH is 0.40 or less.
A polyamide-based laminate film characterized by:
2. The polyamide-based laminate film according to item 1, wherein the dynamic friction coefficient of the surface of the polyurethane resin layer in an environment of 23° C.×50% RH is 0.30 or less.
3. The polyamide-based laminate film according to item 1, wherein the polyurethane resin layer has a thickness of 0.005 to 0.150 μm.
4. A food packaging laminate comprising the polyamide-based laminate film according to any one of items 1 to 3.
5. A laminate for cold forming, comprising the polyamide-based laminate film according to any one of items 1 to 3.
6. A method for producing a polyamide-based laminate film comprising a polyamide film and a polyurethane resin layer containing a polyurethane resin and an organic lubricant on at least one surface of the film, comprising the steps of:
(1) a sheet forming step of forming a melt-kneaded material containing a polyamide resin into a sheet shape to obtain an unstretched sheet;
(2) a stretching step of obtaining a biaxially stretched film by MD stretching and TD stretching the unstretched sheet, and (3) a coating step of applying an aqueous coating liquid containing a polyurethane resin and an organic lubricant to one surface of the unstretched sheet, the MD stretched film, the TD stretched film, or the biaxially stretched film.
7. The method according to item 6, wherein the water-based coating liquid is a mixture of a dispersion of a polyurethane resin and a dispersion of an organic lubricant having a particle size of 0.010 μm to 0.500 μm.
8. The stretching step is carried out by simultaneous biaxial stretching and is represented by the following formulas (a) and (b);
(a) 0.80≦X/Y≦0.95
(b) 9.8≦X×Y≦11.6
(wherein X represents the stretch ratio in the MD direction, and Y represents the stretch ratio in the TD direction.)
7. The method according to claim 6, wherein both of the above are satisfied.
9. The stretching step is carried out by sequential biaxial stretching and the following formulas (a) and (b) are satisfied:
(a) 0.85≦X/Y≦0.95
(b) 8.5≦X×Y≦9.5
(wherein X represents the stretch ratio in the MD direction, and Y represents the stretch ratio in the TD direction.)
7. The method according to claim 6, wherein both of the above are satisfied.

According to the present invention, it is possible to provide a polyamide-based laminate film that combines high slipperiness and good printability. In other words, the present invention makes it possible to simultaneously improve slipperiness and printability (particularly ink transfer from the plate), which were considered to be mutually exclusive properties in the prior art.

The polyamide laminate film of the present invention has a low arithmetic mean height (Ra) of the polyurethane resin layer, so that high-definition printing can be performed. At the same time, despite the low Ra, the dynamic friction coefficient at high humidity is small, so that the film exhibits stable slip properties independent of humidity. As a result, the polyamide laminate film of the present invention is suitable for transport by rolls, and can be suitably used in various processing applications.

In particular, since the polyurethane resin layer is composed mainly of an organic polyurethane resin, it has excellent ink adhesion and can exhibit excellent printability. In addition, since the polyurethane resin layer has relatively good flexibility, it can follow dimensional changes in the polyamide film, for example, during boiling or retort treatment. Therefore, when processing such as molding (particularly cold molding) is performed using the polyamide-based laminate film of the present invention, the occurrence of delamination can be effectively suppressed or prevented.

Furthermore, when the polyamide-based laminate film of the present invention is laminated with aluminum foil and subjected to cold forming, it has good conformability to the aluminum foil and has low friction with the forming die, so that it has excellent formability and it is possible to obtain a molded product that does not have delamination or pinholes.

According to the manufacturing method of the polyamide-based laminate film of the present invention, the polyamide-based laminate film of the present invention can be obtained more reliably and with better productivity.

1 is a diagram showing an example of a layer structure of a polyamide-based laminate film of the present invention. 1 is a diagram showing an embodiment of a polyamide-based laminate film of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

1. Polyamide-Based Laminate Film The polyamide-based laminate film of the present invention (the film of the present invention) is a laminate film comprising a polyamide film and a polyurethane resin layer containing a polyurethane resin and an organic lubricant laminated on at least one surface of the film,
(1) The glass transition temperature of the polyurethane resin is 50° C. or higher,
(2) The arithmetic mean height (Ra) of the surface of the polyurethane resin layer is 0.010 to 0.060 μm, and the dynamic friction coefficient of the surface of the polyurethane resin layer in an environment of 20° C.×90% RH is 0.40 or less.
It is characterized by:

A. Layer structure of the film of the present invention As described above, the film of the present invention is basically a laminated film including a polyamide film and a polyurethane resin layer (hereinafter, simply referred to as "polyurethane resin layer") containing a polyurethane resin and an organic lubricant laminated on at least one surface of the film. That is, the film of the present invention is basically a laminated structure in which a polyurethane resin layer is formed adjacent to one or both surfaces of a polyamide film without an adhesive layer therebetween.

Figure 1 shows an example of the layer structure of the film of the present invention. Figure 1A shows a laminate (film of the present invention) 10 in which a polyurethane resin layer 12 is laminated on one side of a polyamide film 11. Figure 1B shows a laminate (film of the present invention) 10' in which polyurethane resin layers 12, 12 are laminated on both sides of a polyamide film 11. In both of these cases, the polyurethane resin layer is disposed as the outermost layer (outermost layer) (layer exposed to the outside). In this way, by exposing the polyurethane resin layer as the outermost layer, for example, when a package (bag, etc.) is produced using the film of the present invention with the polyurethane resin layer facing outward, the contents of the package can be protected from the outside. Therefore, in the film of the present invention, it is desirable that the polyurethane resin layer is disposed as the outermost layer (outermost layer) (layer exposed to the outside) on at least one of the front and back surfaces.

In the film of the present invention, as described above, the polyurethane resin layer is formed directly on the surface of the polyamide film, and as long as at least one polyurethane resin layer is disposed as the outermost layer, other layers may be laminated thereon as necessary. Examples of such layers include a barrier layer (gas barrier layer, water vapor barrier layer, etc.), a printing layer, an adhesive layer, a heat fusion layer (sealant layer, heat seal layer), a primer layer (anchor coat layer), an antistatic layer, a vapor deposition layer, an ultraviolet absorbing layer, an ultraviolet blocking layer, etc.

Figure 2 shows an example of the layer structure of a polyamide-based laminate film in which, in addition to a polyamide film and a polyurethane resin layer, other optional layers are further laminated.

Figure 2A shows a laminate 20 in which a barrier layer 13 and a heat-sealing layer 14 are laminated in this order on one side of the laminate 10 in Figure 1A. In this laminate 20, the barrier layer 13 and the heat-sealing layer 14 are laminated on the side of the polyamide film 11 on which the polyurethane resin layer 12 is not formed, so that the polyurethane resin layer 12 remains exposed as the outermost surface layer.

Figure 2B shows a laminate 20' in which a barrier layer 13 and a heat-sealing layer 14 are laminated in that order on one side of the laminate 10' in Figure 1B. In this laminate 20', the barrier layer 13 and the heat-sealing layer 14 are laminated on one of the polyurethane resin layers 12 of the polyamide film 11, and the other polyurethane resin layer 12 is maintained in an exposed state as the outermost surface layer.

2A or 2B, when the film of the present invention has a heat-sealing layer 14, the heat-sealing layer 14 is disposed as the outermost layer. In other words, when the film of the present invention has a heat-sealing layer 14, it is preferable to adopt a layer structure in which one outermost layer is a polyurethane resin layer 12 and the other outermost layer is a heat-sealing layer 14.

Below, we will explain the polyamide film and polyurethane resin layer that make up the film of the present invention, as well as the optional layers.

A-1. Polyamide film The polyamide film is the substrate (core) of the film of the present invention, and is usually provided in the form of a preformed film. The polyamide film itself may be a publicly known or commercially available one. A film produced by a publicly known production method may also be used.

The polyamide film may be a single layer structure, or a multilayer structure in which two or more polyamide films are laminated. In the case of a multilayer structure, each layer may have the same composition or different compositions.

The polyamide film is mainly composed of polyamide resin, but may contain other components as long as they do not impede the effects of the present invention. In this case, the content of polyamide resin in the polyamide film is not limited, but is usually about 70 to 100% by mass, preferably 90 to 99.5% by mass, and even more preferably 95 to 99% by mass.

The polyamide resin may be any melt-moldable thermoplastic resin that has an amide bond (-CONH-) in its molecule, and any known or commercially available resin may be used. For example, polyamides obtained by polycondensation of lactams, ω-amino acids, or dibasic acids with diamines may be used.

Examples of lactams include ε-caprolactam, enantholactam, capryllactam, and lauryllactam.

Examples of ω-amino acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, and 11-aminoundecanoic acid.

Examples of dibasic acids include adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecadioic acid, hexadecadioic acid, eicosanedionic acid, eicosadienedioic acid, 2,2,4-trimethyladipic acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and xylylenedicarboxylic acid.

Examples of diamines include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, 2,2,4 (or 2,4,4)-trimethylhexamethylenediamine, cyclohexanediamine, bis-(4,4'-aminocyclohexyl)methane, metaxylylenediamine, etc.

In the present invention, these compounds (starting materials) may also be biomass-derived compounds from the standpoint of environmental protection, etc.

As the polymer or copolymer obtained by polycondensing these monomer components, for example, nylon 6, 7, 11, 12, 6.6, 6.9, 6.11, 6.12, 6T, 9T, 10T, 6I, MXD6 (polymetaxylylene adipamide), 6/6.6, 6/12, 6/6T, 6/6I, 6/MXD6, etc. can be used. These can be used alone or in combination of two or more. Among these, aliphatic polyamide resins such as nylon 6 and nylon 6,6 are preferred, and among them, nylon 6 is more preferred because it has an excellent balance between heat resistance and mechanical properties.

In addition, the relative viscosity of the polyamide resin used in the polyamide film is not limited, but is usually preferably about 1.5 to 5.0, and more preferably 2.0 to 4.0. If the relative viscosity is less than 1.5, the mechanical properties of the resulting film tend to be significantly reduced. On the other hand, if the relative viscosity exceeds 5.0, the film formability of the film tends to be impaired. The above relative viscosity is a value measured using an Ubbelohde viscometer for a sample solution (liquid temperature 25°C) in which polyamide is dissolved in 96% sulfuric acid to a concentration of 1.0 g/dl. In the present invention, the relative viscosity of the polyamide film in the finally obtained film of the present invention is also preferably within the above range.

As described above, the polyamide film may contain, in addition to the polyamide resin, other components within the range that does not impair the effects of the present invention. Examples of other components include known or commercially available additives. More specifically, examples include metals (metal ions), pigments, heat stabilizers, antioxidants, weathering agents, flame retardants, plasticizers, release agents, and reinforcing agents (fillers). In particular, hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, alkali metal halides, and the like can be suitably used as heat stabilizers or antioxidants.

The polyamide film may contain a lubricant as required. Specific examples of lubricants include inorganic lubricants such as clay, talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, magnesium aluminosilicate, glass balloons, carbon black, zinc oxide, antimony trioxide, zeolite, hydrotalcite, and layered silicates, and organic lubricants such as erucic acid amide, oleic acid amide, stearic acid amide, ethylene bisstearic acid amide, ethylene bisethylene bisoleic acid amide, hexamethylene bisstearic acid amide, and hexamethylene bisoleic acid amide methylene bisstearic acid amide. These may be used alone or in combination of two or more.

The thickness of the polyamide film is not particularly limited, but is generally preferably 4 to 35 μm, and more preferably 5 to 25 μm. If the thickness is less than 4 μm, the mechanical strength is likely to be insufficient and moldability will decrease. On the other hand, if the thickness exceeds 35 μm, there is a risk of an increase in the amount of raw materials used or a decrease in productivity.

In addition, from the viewpoint of mechanical strength, it is preferable that the polyamide film is stretched. In other words, it is preferable that the film has an oriented structure. In this case, the film may be uniaxially or biaxially stretched, but it is particularly preferable that the film has an oriented structure due to biaxial stretching. The stretch ratio can be appropriately set within the range described below.

In order to improve the adhesion between the layers constituting the laminate when it is made into a laminate, it is preferable that the polyamide film has a surface that has been subjected to a known surface treatment such as corona treatment, plasma treatment, or ozone treatment on at least one side.

A-2. Polyurethane Resin Layer The polyurethane resin layer constituting the film of the present invention is a layer mainly for exhibiting slip properties and printability, and contains a polyurethane resin and an organic lubricant.

Polyurethane resins are polymers obtained, for example, by the reaction of polyfunctional isocyanates with hydroxyl group-containing compounds. More specifically, examples of polyurethane resins include urethane resins obtained by the reaction of polyfunctional isocyanates such as aromatic polyisocyanates, such as tolylene diisocyanate, diphenylmethane isocyanate, and polymethylene polyphenylene polyisocyanate, or aliphatic polyisocyanates, such as hexamethylene diisocyanate and xylene isocyanate, with hydroxyl group-containing compounds, such as polyether polyols, polyester polyols, polyacrylate polyols, and polycarbonate polyols. These polyurethane resins themselves may be publicly known or commercially available.

In addition, various functional groups such as anionic functional groups, cationic functional groups, and nonionic functional groups may be introduced into the polyurethane resin as long as the effects of the present invention are not impaired. In particular, it is preferable that the polyurethane resin contains anionic functional groups from the viewpoint of dispersibility in the coating liquid. Examples of anionic functional groups include carboxyl groups and sulfone groups.

The method of introducing anionic functional groups into a polyurethane resin is not particularly limited, and examples thereof include a) a method of using a diol having an anionic functional group as a polyol component, and b) a method of using a diol having an anionic functional group as a chain extender. Examples of diols having anionic functional groups include aliphatic carboxylic acids such as glyceric acid, dioxymaleic acid, dioxyfumaric acid, tartaric acid, dimethylolpropionic acid, dimethylolbutanoic acid, 2,2-dimethylolvaleric acid, 2,2-dimethylolpentanoic acid, 4,4-di(hydroxyphenyl)valeric acid, and 4,4-di(hydroxyphenyl)butyric acid, as well as aromatic carboxylic acids such as 2,6-dioxybenzoic acid.

It is preferable that the polyurethane resin layer forms a crosslinked structure. The crosslinked structure can be formed by a) a method of forming the crosslinked structure by adding a crosslinking agent that reacts with the polyurethane resin to form a crosslinked structure, or b) a method of using a polyurethane resin that contains reactive groups in the skeleton.

As the crosslinking agent, a crosslinking agent capable of reacting with the terminal group of the polyurethane resin is preferable. This can reduce the polar groups in the polyurethane resin molecule, thereby further improving the slipperiness. Specific examples of the crosslinking agent include isocyanate, oxazoline, carbodiimide, melamine resin, etc. Among these, it is preferable to use melamine resin from the viewpoints of reactivity, economy, etc. A representative example of the melamine resin is tri(alkoxymethyl)melamine. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, etc. These melamine resins can be used alone or in combination.

When a crosslinking agent is used, the amount added can be set appropriately depending on the type of crosslinking agent used, but can usually be set within the range of 1 to 10 parts by weight per 100 parts by weight of polyurethane resin.

The glass transition temperature of the polyurethane resin must be 50°C or higher, particularly from the viewpoint of improving slipperiness, and is preferably 70°C or higher, and more preferably 90°C or higher. If the glass transition temperature is less than 50°C, the dynamic friction coefficient range specified in the present invention may be exceeded, and slipperiness tends to decrease, especially under high humidity. The upper limit of the glass transition temperature is not limited, but can be, for example, about 150°C.

The content of polyurethane resin in the polyurethane resin layer is not particularly limited, but can usually be about 50 to 98% by weight (particularly 70 to 95% by weight), but is not limited to this.

In the present invention, the organic lubricant, when coexisting with a polyurethane resin having a glass transition temperature of 50°C or higher, serves the function of simultaneously enhancing both mutually contradictory properties, namely slipperiness and printability.

Organic lubricants are not particularly limited, and examples include various organic compounds such as hydrocarbons, fatty acids, aliphatic bisamides, and metal soaps, as well as resin-based organic lubricants such as phenol resins, melamine resins, and polymethyl methacrylate resins.

Among these organic lubricants, in the present invention, organic lubricants having a melting point of 50 to 200°C are particularly preferred. Although there are no particular limitations on such organic lubricants, it is preferred to use at least one of polyethylene wax, silicone-acrylic copolymer, silicone-urethane copolymer, and aliphatic amide. These organic lubricants can be in a liquid state, so they do not impair the smoothness of the polyurethane resin layer surface. In addition, since they are added to the polyurethane resin layer, it is possible to obtain the effect as a lubricant with a smaller amount added, and it is also easier to control the amount of bleed-out. Commercially available organic lubricants can also be used.

From the viewpoint of slipperiness, the polyethylene wax is preferably one that is mainly composed of highly crystalline polyethylene, and preferably has a melting point of 90°C or higher, more preferably 100°C or higher, and most preferably 120°C or higher. As long as the melting point is 90°C or higher, it may be polyethylene alone, a polyethylene copolymer, or a mixture of polyethylene and a polyethylene copolymer. The upper limit of the melting point may be, for example, about 150°C.

From the viewpoint of compatibility with polyurethane resins, it is preferable that the silicone-acrylic copolymer and silicone-urethane copolymer have side chains polymerized to the main chain by graft polymerization. If the main chain is a silicone component, the side chain is preferably an acrylic or urethane component, and if the main chain is an acrylic or urethane component, the side chain is preferably a silicone component.

The aliphatic amide preferably has a carbon number of C8 to C20, more preferably C12 to C18, and even more preferably C16 to C18. If it exceeds C20, printability may decrease. If it is less than C8, the effect of improving slipperiness may not be sufficient. Specific examples of such fatty acid amides include saturated fatty acids such as stearic acid (C18) and monoamides of unsaturated fatty acids such as oleic acid (C18). Among these, at least one of stearic acid amide and ethylene bis stearic acid amide is preferred because of its good compatibility with water-based coating fluids.

The organic lubricant may be contained in the polyurethane resin layer, but may be unevenly distributed on the surface of the polyurethane resin layer. When the organic lubricant is unevenly distributed on the surface of the polyurethane resin layer, slipperiness can be reliably imparted with a smaller amount of organic lubricant.

From the viewpoint of improving slipperiness and printability, the content of organic lubricant (solids ratio) is preferably 5 to 30 parts by mass, more preferably 10 to 30 parts by mass, and most preferably 15 to 30 parts by mass, of 100 parts by mass of polyurethane resin. If the organic lubricant content exceeds 0 parts by mass, not only will printability deteriorate, but the effect of reducing the dynamic friction coefficient will also be reduced. If the organic lubricant content falls below 5 parts by mass, printability will be good, but it will be difficult to reduce the dynamic friction coefficient.

The polyurethane resin layer may contain additives other than the organic lubricant as necessary, provided that the properties of the layer are not significantly impaired. For example, additives such as surfactants, defoamers, heat stabilizers, antioxidants, reinforcing materials, pigments, anti-deterioration agents, weather resistance agents, flame retardants, plasticizers, and release agents may be included.

The thickness of the polyurethane resin layer is not particularly limited, but is usually preferably 0.005 to 0.150 μm, more preferably 0.010 to 0.150 μm, and most preferably 0.020 to 0.100 μm. If the thickness of the polyurethane resin layer is less than 0.005 μm, it is difficult to form a polyurethane resin layer of uniform thickness on the polyamide film, making it difficult to obtain sufficient slipperiness. On the other hand, if the thickness of the polyurethane resin layer exceeds 0.150 μm, the slipperiness improving effect of the polyurethane resin layer becomes saturated, which is economically disadvantageous.

A-3. Other layers As described above, in addition to the polyamide film and polyurethane resin layer, the film of the present invention can be laminated with various layers as necessary. That is, the polyamide-based laminate film of the present invention includes a basic structure of a polyamide film and a polyurethane resin layer, and also includes a laminate in which other layers are laminated. Therefore, in this specification, a laminate in which other layers are laminated in addition to the basic structure (the laminate film) is also called a "laminate".

Such a laminate can be suitably used as a packaging laminate, for example, for food packaging, battery packaging (exterior material), etc. In addition, the film of the present invention is also suitable for cold forming (for example, at a forming temperature of 50°C or less) as a laminate for cold forming, and is therefore also applicable to a manufacturing method for a molded product that includes a step of cold forming the film of the present invention. Thus, the present invention includes a polyamide-based laminate film that is particularly used for food packaging or cold forming.

Layers other than the above basic configuration may be similar to those used in known packaging materials. Examples include a barrier layer, a primer layer, a heat-sealing layer, an adhesive layer, a clear layer, a printed layer, etc. These may be similar to known laminates, but it is desirable to set the barrier layer and heat-sealing layer as follows:

The barrier layer has excellent barrier properties (gas barrier properties, especially oxygen barrier properties, etc.), and examples of such layers include inorganic barrier layers such as known metal foils, metal vapor deposition films, and transparent vapor deposition films, as well as various barrier films such as organic coating layers of polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Among these, metal foils such as aluminum foil and copper foil are preferred in terms of versatility, with aluminum foil being particularly preferred.

When a metal foil is used as the barrier layer, the thickness of the metal foil is not particularly limited, but is usually about 5 to 200 μm, more preferably 5 to 150 μm, and most preferably 7 to 50 μm.

In addition, one or both surfaces of the metal foil may be subjected to a surface treatment to improve adhesion, corrosion resistance, etc. Examples of surface treatments include chemical conversion treatments and chromate treatments. In particular, it is preferable that these surface treatments are applied to the surface that contacts the heat-sealing layer.

The heat-sealable layer is not particularly limited as long as it is a heat-sealable layer, and known layers can be used, such as polyvinyl chloride film and polyolefin film. Examples of polyolefins include polyethylene, polypropylene, and polyethylene, as well as copolymers mainly made of polypropylene and acid-modified versions of these. Either a stretched film or a non-stretched film can be used for the heat-sealable layer, and molten resin can be directly laminated.

The thickness of the heat-sealing layer is not particularly limited, but is usually preferably 20 to 200 μm, and more preferably 30 to 100 μm.

When laminating these materials, it is possible to laminate them using, for example, known adhesives, but this is not limited to this.

In the present invention, methods for bonding the polyamide film and the metal foil can be suitably adopted, for example, dry lamination or thermal lamination using a two-component urethane adhesive.

In addition, methods that can be suitably used to bond the metal foil and the heat-sealing layer include, for example, dry lamination, heat lamination, extrusion lamination, and sandwich lamination.

An anchor coat layer, primer layer, etc. may be pre-applied on the surface of the film, metal foil, or heat-sealing layer on which the adhesive layer is formed, as long as this does not impair the effects of the present invention.

In the present invention, when other layers are laminated, and particularly when a polyurethane resin layer is placed as the outermost layer, the film has excellent slip properties and printability, making it suitable for use in a variety of industrial applications, including packaging for food, electronic and electrical parts, etc.

As the film of the present invention, for example, a laminate including a polyurethane resin layer 12/polyamide film 11/metal foil 13/thermal adhesive layer 14 as shown in Figure 2A or Figure 2B, or a laminate including a polyurethane resin layer 12/polyamide film 11/polyurethane resin layer 12/metal foil 13/thermal adhesive layer 14, etc. are effective as packaging materials including, for example, exterior materials for batteries.

B. Characteristics of the Film of the Present Invention The thickness of the film of the present invention is not particularly limited and can be appropriately set depending on, for example, the application, the method of use, etc. For example, when the film of the present invention is used as an exterior material for a battery, the thickness of the laminate 10 or 10' in FIG. 1 can be, for example, in the range of about 10 to 25 μm, and can also be, for example, in the range of 15 to 25 μm, but is not limited thereto.

In the film of the present invention, the dynamic friction coefficient of the polyurethane resin layer surface in a 20°C x 90% RH environment is usually 0.40 or less, preferably 0.35 or less, and more preferably 0.30 or less. In the film of the present invention, the lower limit of the dynamic friction coefficient in a 20°C x 90% RH environment is not particularly limited, but is usually about 0.20. If the dynamic friction coefficient in a 20°C x 90% RH environment is 0.40 or less, excellent processability and printability can be more reliably obtained even under high humidity.

Furthermore, from the viewpoint of improving formability and printability, the film of the present invention has a kinetic friction coefficient of the polyurethane resin layer surface in an environment of 23°C x 50% RH of usually 0.30 or less, preferably 0.25 or less, and more preferably 0.20 or less. The lower limit of the kinetic friction coefficient in an environment of 23°C x 50% RH is not particularly limited, but is usually about 0.10.

In addition, the arithmetic mean height (Ra) of the polyurethane resin layer surface of the film of the present invention calculated from two-dimensional surface roughness measurement must usually be 0.010 to 0.060 μm, preferably 0.010 to 0.055 μm, more preferably 0.020 to 0.050 μm, and most preferably 0.010 to 0.040 μm. If the Ra exceeds 0.060 μm, the unevenness of the resin layer surface will become large, which may result in printing defects and make it difficult to perform high-definition printing.

Furthermore, from the viewpoint of improving slipperiness or printability, the contact angle of water on the surface of the polyurethane resin layer of the film of the present invention is preferably 82° to 98°, more preferably 86° to 98°, and most preferably 90° to 98°. If the contact angle is less than 82°, frictional resistance will increase, and slipperiness may decrease. Furthermore, if the contact angle exceeds 98°, there is a risk of printability decreasing due to a decrease in ink adhesion. Furthermore, since the surface of the polyurethane resin layer of the film of the present invention has few irregularities, variation in the contact angle measurement value can be suppressed.

2. Production of polyamide-based laminate film The film of the present invention is, for example, a method for producing a polyamide-based laminate film comprising a polyamide film and a polyurethane resin layer containing a polyurethane resin and an organic lubricant laminated on at least one surface of the film, the method comprising the steps of:
(1) a sheet forming step of forming a melt-kneaded material containing a polyamide resin into a sheet shape to obtain an unstretched sheet;
The polyamide-based laminate film can be suitably produced by a method for producing the polyamide-based laminate film, which comprises: (2) a stretching step of obtaining a biaxially stretched film by MD stretching and TD stretching the unstretched sheet; and (3) a coating step of applying an aqueous coating liquid containing a polyurethane resin and an organic lubricant onto one surface of the unstretched sheet, the MD stretched film, the TD stretched film, or the biaxially stretched film.

Sheet Molding Step In the sheet molding step, a molten mixture containing a polyamide resin is molded into a sheet to obtain an unstretched sheet.

The unstretched sheet can be obtained by forming a melt-kneaded material containing a polyamide resin into a film. The preparation of the melt-kneaded material itself may be carried out according to a known method. For example, the unstretched sheet can be produced by forming a melt-kneaded material obtained by melting a resin composition containing a polyamide resin into a film (sheet). This can be carried out by using a known or commercially available device. For example, a melt extruder having a T-die can be used. That is, first, a starting material (e.g., a pellet-shaped raw material) is supplied to a hopper, plasticized and melted in the melt extruder, the melt-kneaded material is extruded into a sheet from a T-die attached to the tip of the extruder, and cooled and solidified by a cast roll. At this time, the melt-kneaded material can be pressed against the cast roll by air to obtain an unstretched sheet.

In addition to the polyamide resin, the resin composition may contain various additives as necessary. Examples of additives include those added to polyamide films.

In this case, the average thickness of the unstretched sheet is not particularly limited, but is generally about 15 to 250 μm, and preferably 50 to 235 μm. By setting it within such a range, the stretching process can be carried out more efficiently.

Stretching Step In the stretching step, the unstretched sheet is stretched in the MD and TD to obtain a biaxially stretched film.

It is preferable to preheat the unstretched sheet or uniaxially stretched film prior to the stretching step. The preheating temperature is not limited, but is preferably set within ±50°C of the stretching temperature. Preheating makes it possible to more reliably obtain a biaxially stretched film with good physical properties. The preheating time depends on the preheating temperature, etc., but is usually preferably about 0.5 to 5 seconds.

The preheating method is not particularly limited. For example, a method in which the temperature of the hot air blown onto the film traveling through the preheating zone of the stretching machine is set to within the above temperature range can be suitably adopted.

The method for adjusting the stretching temperature to the above-mentioned range is not limited, but it is preferable to set the temperature of the hot air blown onto the film traveling through the stretching zone of the stretching machine to the above-mentioned temperature range. In this case, it is usually preferable to set the time for which the polyamide film travels through the stretching zone to about 0.5 to 5 seconds.

As for the stretching method, when a biaxially stretched film of the present invention is finally obtained, a simultaneous biaxial stretching method or a sequential biaxial stretching method can be adopted. In addition, classification by stretching device includes, for example, a tubular method, a tenter method, etc., and any of them can be applied. In the present invention, a stretching method by a tenter method is preferable, especially in terms of quality stability and dimensional stability. Therefore, a tenter type simultaneous biaxial stretching method or a tenter type sequential biaxial stretching method can be suitably adopted. Examples of the tenter type biaxial stretching method include a pantograph type tenter, a screw type tenter, and a linear motor type tenter.

In addition, when simultaneous biaxial stretching is adopted as the stretching method, an aqueous coating liquid containing a urethane resin and an organic lubricant is applied to an unstretched sheet, and then the sheet is simultaneously biaxially stretched in the MD and TD directions to obtain the film of the present invention in which a urethane resin layer is formed on a specified biaxially stretched polyamide film.

In addition, when the sequential biaxial stretching method is adopted, an aqueous coating liquid containing a urethane resin and an organic lubricant is applied to a film that has been uniaxially stretched in advance in the MD direction or TD direction, and then the film is stretched in a direction (TD direction or MD direction) approximately perpendicular to the uniaxial stretching direction to obtain the film of the present invention in which a urethane resin layer is formed on a specified biaxially stretched polyamide film.

The stretching ratio is not particularly limited, but usually it is sufficient to stretch to about 2.0 to 4.5 times in both the MD and TD directions. In this case, the stretching ratios in the MD and TD directions may be the same or different. Such stretching can produce a stretched film with good physical properties such as tensile strength and tensile elongation.

In order for the arithmetic mean height (Ra) of the polyurethane resin layer of the polyamide laminate film of the present invention to fall within the range specified in the present invention, it is necessary for the following conditions (a) and (b) to be simultaneously satisfied. In the following formulas (a) and (b), X indicates the stretching ratio in the MD direction, and Y indicates the stretching ratio in the TD direction. Furthermore, X/Y indicates the stretching ratio ratio between the MD stretching ratio (X) and the TD stretching ratio (Y). X×Y indicates the areal stretching ratio.

In the case of carrying out simultaneous biaxial stretching, in particular, (a) 0.80≦X/Y≦0.94
(b) 9.8≦X×Y≦11.6
It is preferable that the following is satisfied.

In the case of carrying out sequential biaxial stretching, in particular, (a) 0.85≦X/Y≦0.95
(b) 8.5≦X×Y≦9.5
It is preferable that the following is satisfied.

The stretching temperature is not limited and can be set appropriately within the range of 225°C or less (preferably 40 to 220°C) depending on, for example, the stretching method, the application of the film of the present invention, the form of use, etc.

The film stretched in the stretching step is preferably further heat-treated. The heat treatment temperature is not particularly limited, but is usually preferably about 190 to 220 ° C, and more preferably 195 to 215 ° C. Heat treatment temperatures below 190 ° C result in a film with a large shrinkage rate, which is not preferable for packaging polyamide films. In addition, when an organic lubricant, crosslinking agent, etc. are added, the former does not bleed out sufficiently, and the latter does not progress in the crosslinking reaction sufficiently, so the effect of adding them may not be fully obtained. On the other hand, if the heat treatment temperature exceeds 220 ° C, the strength of the polyamide film decreases. In addition, if the bleed out of the organic lubricant or the progress of the crosslinking reaction of the crosslinking agent is insufficient in the above heat treatment, an aging treatment may be performed after the stretching is completed. In addition, the heat treatment time can be appropriately set depending on the heat treatment temperature, etc., but it is usually preferable to set it to about 1 to 15 seconds.

The heat treatment method is not particularly limited, and may be, for example, a method of blowing hot air, a method of irradiating infrared rays, a method of irradiating microwaves, etc. Among these, a method of blowing hot air is preferred from the viewpoint of being able to heat uniformly and precisely. For example, heat setting can be performed by blowing hot air set to the above temperature range onto the film traveling through the heat setting zone of the stretching machine.

Coating Step In the coating step, an aqueous coating liquid containing a polyurethane resin and an organic lubricant is applied onto one surface of the unstretched sheet, MD stretched film, TD stretched film or biaxially stretched film.

The aqueous coating liquid can be prepared by dissolving or dispersing the polyurethane resin and organic lubricant in an aqueous medium. By using an aqueous coating liquid, the desired film of the present invention can be obtained efficiently, and it is also advantageous in terms of workability and environmental aspects.

In the present invention, the aqueous medium is water or a mixed solvent whose main component is water (usually a liquid containing 50% or more by mass of water). As the mixed solvent, a mixed solvent of water and a water-soluble organic solvent can be used. Examples of the water-soluble organic solvent include, but are not limited to, alcohols such as methanol, ethanol, and isopropanol, and ketones such as acetone and methyl ethyl ketone (MEK). One or more water-soluble organic solvents can be used. By mixing a water-soluble organic solvent, it is possible to obtain effects such as increasing the wettability of the polyamide film and shortening the drying process. In this respect, even when additives such as a crosslinking agent are used in addition to polyurethane resins, it is preferable that these additives are aqueous (aqueous solution or aqueous dispersion (emulsion)).

When preparing the water-based coating fluid, the order in which the components such as the polyurethane resin, organic lubricant, and aqueous medium are mixed is not limited. For example, the water-based coating fluid can be suitably prepared by adding an organic lubricant to a previously prepared aqueous dispersion or solution of the polyurethane resin. This method is described below as a representative example.

The polyurethane resin used in the water-based coating liquid is not particularly limited, but as described above, it is preferable to use a polyurethane resin into which an anionic functional group has been introduced (anionic polyurethane resin). By using an anionic polyurethane resin, it is possible to disperse the polyurethane resin more uniformly and stably in water. Thus, in the present invention, it is preferable to prepare the coating liquid using the polyurethane resin in the form of an aqueous dispersion.

Furthermore, when dispersing an anionic polyurethane resin in an aqueous medium, it is generally preferable to use a volatile base. The volatile base is not particularly limited, and any known base can be used. More specifically, examples include ammonia, methylamine, ethylamine, dimethylamine, diethylamine, triethylamine, morpholine, and ethanolamine. Among these, triethylamine is more preferable in that the liquid stability of the water-dispersible polyurethane resin is good, and furthermore, the boiling point is relatively low, so that the amount remaining in the primer layer is small.

The aqueous dispersion of such polyurethane resin may be a publicly known or commercially available product. Examples of commercially available products that can be used include anionic water-dispersible polyurethane resins such as "Takelac W-5030", "Takelac WS-4000", and "Takelac WS-4022" manufactured by Mitsui Chemicals Polyurethanes, Inc., and "Hydran AP40F" manufactured by DIC Corporation.

Next, an organic lubricant is added and mixed into the aqueous dispersion of polyurethane resin. The type and amount of organic lubricant may be the same as those described above. In this case, the organic lubricant may be used in the form of a dispersion in a solvent (water or solvent), or may be used alone (powder). In particular, in the present invention, it is preferable to use the organic lubricant in the form of a dispersion (e.g., aqueous dispersion) in which the organic lubricant is dispersed in a solvent. Therefore, it is desirable for the aqueous coating liquid to be a mixture of a dispersion of polyurethane resin and a dispersion of organic lubricant.

In this case, the particle size of the organic lubricant in the dispersion is not particularly limited, but is usually preferably about 0.010 μm to 0.500 μm, more preferably 0.010 μm to 0.400 μm, even more preferably 0.010 μm to 0.200 μm, and most preferably 0.010 μm to 0.100 μm. If the particle size is smaller than 0.010 μm, the organic lubricant will be very finely dispersed in the polyurethane resin layer, improving printability, but reducing the effect of reducing the dynamic friction coefficient. On the other hand, if the particle size exceeds 0.500 μm, the organic lubricant will be more likely to aggregate, reducing printability, although it will still be able to reduce the dynamic friction coefficient.

The particle size of the organic lubricant in the dispersion liquid is the median size obtained by a laser diffraction/scattering method (dispersion medium: water) based on the Mie theory using a laser diffraction particle size distribution measuring device (product name "Mastersizer 3000" manufactured by MalVern Instruments LTD). In this case, the refractive index of the dispersion medium (water) was set to 1.330. The refractive index of the organic lubricant was set to 1.500 for polyethylene wax, 1.59 for silicone-acrylic copolymer, 1.49 for silicone-urethane copolymer, and 1.46 for fatty acid amide.

The mixing of the polyurethane resin and the organic lubricant is not particularly limited as long as the organic lubricant can be uniformly dispersed, and can be carried out using a known or commercially available mixing device such as a mixer or kneader. In particular, in the present invention, heating can be appropriately carried out, and the mixing can be suitably carried out using a dissolving kettle equipped with a stirrer. The mixing temperature is not particularly limited, and can be, for example, about 5 to 40°C.

In addition to the polyurethane resin and organic lubricant, the water-based coating liquid may contain other components within the range that does not impair the effects of the present invention. For example, the various additives exemplified above can be blended.

In the present invention, a surfactant can be added as one of the additives to improve the coatability of the polyamide film. The surfactant is not particularly limited, but examples include anionic surfactants such as polyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, glycerin fatty acid esters, fatty acid metal soaps, alkyl sulfates, alkyl sulfonates, and alkyl sulfosuccinates, as well as nonionic surfactants such as acetylene glycol.

The content of the surfactant is not particularly limited, but it is generally preferred that the surfactant be present in an amount of 0.01 to 1% by mass in the aqueous coating liquid. It is also preferred that the surfactant be one that volatilizes during heat treatment in the manufacturing process of the polyamide-based laminate film.

The solids concentration of the water-based coating liquid can be adjusted as appropriate, for example, depending on the specifications of the coating device and drying/heat treatment device used. However, a coating liquid that is too dilute is likely to cause problems such as a long drying time and an increase in the risk of defects because the coating thickness after drying is too thin, making it difficult to form a uniform coating. On the other hand, a water-based coating liquid that is too concentrated is likely to cause problems with coatability, making it difficult to achieve a uniform coated surface. Therefore, from this perspective, it is generally preferable that the solids concentration of the water-based coating liquid be around 5 to 70 mass%.

The method for applying the aqueous coating liquid to the polyamide film is not particularly limited, and any known method can be used as appropriate. For example, gravure roll coating, reverse roll coating, wire bar coating, air knife coating, curtain coating, doctor knife, die coating, dip coating, bar coating, and combinations of these methods can be used.

The drying process after coating is not particularly limited, and can be performed using known methods such as drying in a dry atmosphere such as an oven, drying by contact with a heated roll, drying in a stretching machine, etc. The drying temperature is not limited, but can usually be set within the range of about 30 to 200°C. The drying time can be set appropriately depending on the drying temperature, etc., but it is generally sufficient to set it within the range of 0.5 to 60 seconds.

The timing of applying the aqueous coating liquid may be any timing as long as the aqueous coating liquid can be applied to one surface of the unstretched sheet, MD stretched film, TD stretched film, or biaxially stretched film. In other words, any method such as in-line coating method or post-coating method (off-line coating method) can be used.

In particular, in the present invention, by adopting the in-line coating method, the film thickness can be made thinner and more uniform than in the offline coating method, and the productivity is also improved, making it possible to manufacture high-quality products at low cost. In particular, when the in-line coating method is adopted, both slipperiness and printability can be improved. Although the reason is not clear, it is thought that the molecular chains of the polyurethane resin are oriented by performing heat treatment simultaneously with stretching in the in-line coating method, and the crosslinking reaction or bleeding out of the organic lubricant is promoted, resulting in better slipperiness and printability. In particular, it is possible for the organic lubricant to be unevenly distributed on the surface of the stretched film by bleeding out on the surface of the stretched film, and it is presumed that even a relatively small amount of organic lubricant can modify the stretched film to have a slippery property.

The in-line coating method is not particularly limited as long as the formation of a coating film using an aqueous coating liquid and the stretching of the film can be carried out substantially simultaneously, and examples include a) a method in which an aqueous coating liquid is applied to an unstretched sheet, followed by sequential or simultaneous biaxial stretching, b) a method in which an aqueous coating liquid is applied to an MD-stretched uniaxially stretched film, followed by TD stretching, and c) a method in which an aqueous coating liquid is applied to a TD-stretched uniaxially stretched film, followed by MD stretching. In contrast, the post-coating method is a method in which a coating film using an aqueous coating liquid is formed on a film after biaxial stretching.

A preferred embodiment of the in-line coating method for simultaneous biaxial stretching is a method including a step of applying an aqueous coating liquid after a sheet forming step in which a polyamide resin is formed into a sheet to obtain an unstretched polyamide sheet. The unstretched polyamide sheet to which the aqueous coating liquid has been applied is preferably simultaneously biaxially stretched under conditions of a stretching temperature of 215°C or less (preferably 190°C to 215°C) and a stretching ratio of 2.5 to 3.8 times in both the MD and TD directions after being dried in a drying step at 50 to 220°C, preferably 80°C to 180°C, more preferably 120°C to 160°C. The unstretched polyamide sheet can be simultaneously biaxially stretched by a known stretching method. Among them, it is preferable to perform the simultaneous biaxial stretching by tenter-type simultaneous biaxial stretching or Lisim simultaneous biaxial stretching method from the viewpoint of economic efficiency such as productivity.

A preferred embodiment of the in-line coating method for sequential biaxial stretching includes a method including the following steps. After a sheet forming step in which a polyamide resin is formed into a sheet to obtain an unstretched sheet, the unstretched sheet is stretched 2.5 to 3.5 times in the sheet flow direction (MD stretching) at a stretching temperature of 40 to 80°C (preferably 50 to 65°C), and then an aqueous coating liquid is applied to the uniaxially stretched polyamide film. The uniaxially stretched film to which the aqueous coating liquid has been applied is stretched 2.5 to 3.5 times in the width direction (TD stretching) at a preheating and stretching temperature of 50 to 220°C (preferably 60 to 130°C), which also serves as a drying step, to produce the film of the present invention. When performing sequential biaxial stretching, it is preferable to use a combination of a roll stretching method and a tenter type stretching method. More specifically, successive biaxial stretching can be suitably performed by performing MD stretching by roll stretching and then performing TD stretching by tenter stretching.

Other steps The method for laminating each layer is not particularly limited, and any of a) a method for forming a coating film using a coating liquid, b) a method for laminating a preformed film, and c) a method for forming a vapor deposition film by a PVD method, a CVD method, etc. can be used. In the case of b), any of a method for laminating via an adhesive and a method for laminating by simultaneous extrusion molding can be used. In particular, when the film of the present invention is used as an exterior material for a battery such as a lithium ion secondary battery, a known method for manufacturing an exterior material can also be used. In this case, it is also possible to laminate using a known adhesive.

For example, when laminating with a barrier layer, a laminate including a urethane resin layer/polyamide film or a laminate including a urethane resin layer/polyamide film/urethane resin layer can be dry laminated or heat laminated to a metal foil for forming the barrier layer using a two-component urethane adhesive or the like.

In addition, known methods (dry lamination, thermal lamination, extrusion lamination, sandwich lamination, etc.) can be used to join the barrier layer and the heat-sealing layer.

An anchor coat layer, primer layer, printing layer, clear layer, etc. may be provided on the surface of the polyamide film, barrier layer, and heat-sealing layer on which the above-mentioned adhesive layer is formed, as necessary, as long as this does not impair the effects of the present invention.

3. Use of polyamide-based laminate film The film (or laminate) of the present invention can be used for various purposes, but is particularly suitable for use as a packaging material. That is, it can be used as a packaging material for packaging contents. The contents are not limited, and can include, for example, foods and beverages, electronic parts, chemical products, cosmetics, medical products (medical devices), and the like.

When used as a packaging material, the form is not particularly limited, and it can be used, for example, as a packaging bag or a packaging container. As a packaging bag, it can be used as various types of bag bodies such as pillow bags, gusset bags, stand bags, etc. The bag body can be formed according to a known method.

Furthermore, the present invention also includes a product (packaged product) whose contents are packaged in the above-mentioned packaging material or packaging bag. In this case, the packaged state may be, for example, a state in which the contents are sealed from the outside by the packaging material or packaging bag.

The following examples and comparative examples are provided to more specifically explain the features of the present invention. However, the scope of the present invention is not limited to the examples. Note that "%" in the following weight or concentration descriptions refers to "% by mass."

1. Materials Used (1) Polyurethane Resin As the polyurethane resin, the following polyurethane water dispersions (a) to (d) were used.
(a) Product name: "HYDRAN AP40F" (manufactured by DIC Corporation, glass transition temperature: 55°C, solid content: 25%)
(b) Product name: "Takelac W-5030" (manufactured by Mitsui Chemicals, Inc., glass transition temperature 85°C, solid content 30%)
(c) Product name: "Takelac WS-4022" (manufactured by Mitsui Chemicals, Inc., glass transition temperature 115°C, solid content 30%)
(d) Product name: "HYDRAN AP-201" (manufactured by DIC Corporation, glass transition temperature: 7°C, solid content: 25%)

(2) Organic Lubricants The following organic lubricants (a) to (g) were used, all of which were in the form of a dispersion liquid.
(a) Product name: "AQUACER 517" (manufactured by BYK Corporation, polyethylene wax, solid content 35%, particle size 0.150 μm, melting point 120° C.)
(b) Product name "Hitec E6400" (manufactured by Toho Chemical Industry Co., Ltd., polyethylene wax, solid content concentration 35%, particle size 0.050 μm, melting point 120° C.)
(c) Product name: "Charine E E-370" (manufactured by Nissin Chemical Industry Co., Ltd., silicone-acrylic copolymer, solid content concentration 50%, particle size 0.450 μm)
(d) Product name: "Simac US-450" (manufactured by Toagosei Co., Ltd., silicone-acrylic copolymer, solid content concentration 30%, particle size 0.350 μm)
(e) Product name: "Chaline E RU-911" (manufactured by Nissin Chemical Industry Co., Ltd., silicone-urethane copolymer, solid content concentration 40%, particle size 0.330 μm)
(f) Product name: "Alflow H-50ES" (manufactured by NOF Corporation, fatty acid amide, solid content concentration 42%, particle size 0.450 μm, melting point 113° C., 147° C.)
(g) Product name: "Slipax E SA-20" (manufactured by Mitsubishi Chemical Corporation, fatty acid amide, solid content concentration 22%, particle size 0.460 μm, melting point 113° C., 147° C.)

(3) Other Additives As other additives, the following (a) and (b) were used.
(a) Product name "Aerosil 200" (manufactured by Nippon Aerosil Co., Ltd., silica particles, primary particle diameter 12 nm)
(b) Product name "MX100W" (manufactured by Nippon Shokubai Co., Ltd., acrylic particles, average particle diameter 150 nm)

2. Examples and Comparative Examples
Example 1
(1) Preparation of Coating Fluid A polyurethane water dispersion "HYDRAN AP40F" and an organic lubricant "AQUACER 515" were mixed in this order into water so that the solid content concentration was 9% by mass, and stirred to obtain a water-based coating fluid A. The "HYDRAN AP40F" and "AQUACER 515" were weighed so that the solid content mass ratio was HYDRAN AP40F/AQUACER 515=100/20.
(2) Production of polyamide-based laminated film (sequential biaxial stretching)
Using an extruder equipped with a T-die, nylon 6 (Unitika Ltd., A1030BRF, relative viscosity 3.1) was extruded from the T-die into a sheet, which was then brought into close contact with a casting roll whose surface temperature was adjusted to 18°C and quenched to obtain an unstretched sheet.
Next, the unstretched sheet was passed through a stretching roll heated to a preheat temperature of 58° C. and a stretching temperature of 61° C., and stretched in the MD direction to a stretch ratio of 2.85 times to obtain an MD stretched film. Next, an aqueous coating solution A having a solid content concentration of 9% by mass was applied to the MD stretched film so that the thickness after drying and stretching was 0.10 μm, and then stretched in the TD direction at a stretch ratio of 3.20 times under conditions of a preheat temperature of 80° C. and a stretching temperature of 120° C. Further, heat treatment was performed under conditions of a heat treatment temperature of 210° C. and a heat treatment time of 3 seconds, and then a 3% relaxation treatment was performed in the TD direction.
The polyamide film surface of the obtained laminated film was subjected to a corona treatment to obtain a polyamide-based laminated film (thickness 15 μm) on which a polyurethane resin layer having a thickness of 0.10 μm was laminated.
(3) Preparation of Laminate A two-component polyurethane adhesive (TM-K55/CAT-10L, manufactured by Toyo-Morton Co., Ltd.) was applied to the corona-treated surface of the obtained polyamide-based laminate film ^to a coating amount of 5 g/m2, and dried for 10 seconds at 80° C. Aluminum foil (thickness 50 μm) was attached to the adhesive-coated surface.
Next, the above adhesive was applied to the aluminum foil surface under the same conditions and dried, and an unstretched polypropylene film (Mitsui Chemicals Tocello, GHC, thickness 50 μm) was laminated as a heat-sealing layer, and aging treatment was performed for 7 days in an atmosphere of 60° C., obtaining a laminate laminated in the order of “polyurethane resin layer/polyamide film/adhesive layer/aluminum foil/heat-sealing layer”.

Examples 2, 5 to 17 and Comparative Examples 1 to 2, 4, and 7
A polyamide-based laminate film was produced in the same manner as in Example 1, except that the conditions shown in Table 1 were used. A coating liquid was prepared in the same manner as in Example 1, except that the types and blending ratios of the polyurethane water dispersion and the organic lubricant were changed as shown in Table 1. Note that the order of addition of the organic lubricants in a coating liquid containing two types of organic lubricants is not limited and can be selected arbitrarily. Furthermore, a laminate was produced in the same manner as in Example 1 using the obtained polyamide-based laminate film.

Example 3
A polyamide-based laminate film was produced in the same manner as in Example 1, except that the stretching method was changed as follows.
Using an extruder equipped with a T-die, nylon 6 (Unitika Ltd., A1030BRF, relative viscosity 3.1) was extruded from the T-die into a sheet, which was then brought into close contact with a casting roll whose surface temperature was adjusted to 18°C and quenched to obtain an unstretched sheet.
Next, this unstretched sheet was coated with aqueous coating solution B having a solid content concentration of 9% by mass using a gravure coater so that the thickness after drying and stretching would be 0.10 μm, and then dried with a hot air dryer, and then introduced into a pantograph-type tenter simultaneous biaxial stretching machine, where it was simultaneously biaxially stretched at a stretch ratio of 3.0 times in the MD direction and 3.3 times in the TD direction under conditions of a preheating stretching temperature of 200° C. Further, it was subjected to a heat treatment under conditions of a heat treatment temperature of 215° C. and a heat treatment time of 3 seconds, and then subjected to a 3% relaxation treatment in the TD direction.
The polyamide film surface of the obtained laminate film was subjected to a corona treatment to obtain a polyamide-based laminate film having a thickness of 15 μm on which a polyurethane resin layer having a thickness of 0.10 μm was laminated. Further, a laminate was produced in the same manner as in Example 1 using the obtained polyamide-based laminate film.

Example 4
A polyamide-based laminate film was obtained in the same manner as in Example 3, except that the simultaneous biaxial stretching machine was changed from a pantograph-type tenter to a linear motor-type tenter and a 1% relaxation treatment was also performed in the MD direction. Furthermore, a laminate was produced in the same manner as in Example 1 using the obtained polyamide-based laminate film.

Comparative Example 3
A polyamide-based laminate film was produced in the same manner as in Example 1, except that the aqueous coating liquid contained 2.0% by mass of silica relative to 100% by mass of the solid content of the polyurethane aqueous dispersion. Further, a laminate was produced in the same manner as in Example 1 using the obtained polyamide-based laminate film.

Comparative Example 5
A polyamide-based laminate film was obtained in the same manner as in Example 1, except that the coating process of the aqueous coating liquid was changed from during the stretching process to after the stretching process. In the coating process, the stretched polyamide film was introduced into a gravure coater, and the aqueous coating liquid R was applied to the film so that the coating thickness was 0.5 μm. The film was then dried through a drying furnace consisting of five zones: Zone 1 (80° C.) → Zone 2 (100° C.) → Zone 3 (120° C.) → Zone 4 (110° C.) → Zone 5 (80° C.). A polyamide-based laminate film was obtained by drying the film through the drying furnace. Furthermore, a laminate was produced in the same manner as in Example 1 using the obtained polyamide-based laminate film.

Comparative Example 6
A polyamide-based laminate film was produced in the same manner as in Example 1, except that the aqueous coating liquid contained 2.0% by mass of acrylic particles relative to 100% by mass of the solid content of the polyurethane aqueous dispersion. Furthermore, a laminate was produced in the same manner as in Example 1 using the obtained polyamide-based laminate film.

Test Example 1
The polyamide-based laminate films or laminates obtained in the respective Examples and Comparative Examples were measured for the following properties, and the results are shown in Table 2.

(1) Dynamic Friction Coefficient The dynamic friction coefficient of the polyurethane resin layer surface in the present invention was measured in accordance with the Japanese Industrial Standard "JIS K7125". The measuring device used was a tabletop material testing machine "STB-1225S" manufactured by A&D Co., Ltd., and a data processing system "TACT", and the measuring environment was 23°C x 50% RH and 20°C x 90% RH. Specifically, a sample of a polyamide-based laminate film was conditioned at 23°C x 50% RH or 20°C x 90% RH for 2 hours, and then the polyurethane resin layers of the polyamide-based laminate film were overlapped with each other under the same temperature and humidity as above, and the measurement was performed. Even in the case of a laminate including the film of the present invention as the outermost layer, the surface of the polyurethane resin layer that is the outermost layer was used as the measuring surface, and the measurement was performed in the same manner as above. In practice, the dynamic friction coefficient is required to be 0.30 or less at 23°C x 50% RH and 0.40 or less at 20°C x 90% RH. The measurement was carried out with n=5, and the average value was taken as the measured value.

(2) Arithmetic mean height (Ra)
The arithmetic mean height measurement (Ra) in the present invention was performed in accordance with the Japanese Industrial Standard "JIS B 0601" using a contact surface roughness measuring instrument "Surfcorder SE500A" manufactured by Kosaka Laboratory Co., Ltd. Specifically, a sample of a polyamide-based laminated film was conditioned at 23°C x 50% RH for 2 hours, and then the surface of the polyurethane resin layer was measured under the same temperature and humidity as above. In the case of a laminate including the film of the present invention as the outermost layer, the surface of the polyurethane resin layer that is the outermost layer was used as the measurement surface. The measurement was performed with n=5, and the average value was used as the measurement value.

(3) Contact angle The contact angle was measured using water with an automatic contact angle meter, model DSA30S, manufactured by KRUSS. Specifically, a polyamide laminate film sample was conditioned at 23°C x 50% RH for 2 hours, and then the measurement was carried out under the same temperature and humidity as above. The measurement was carried out with n=5, and the average value was taken as the measured value.

(4) Printability (ink transfer from the plate)
The printability in the present invention was measured under the same temperature and humidity conditions after conditioning a polyamide laminate film sample at 23°C x 50% RH for 2 hours. A dot pattern was printed on the polyurethane resin layer of the polyamide laminate film using a gravure printing method so that there were 100 dots within 1 cm x 1 cm, and the number of defects in the dot pattern within 1 cm x 1 cm was counted and the average value of three places was calculated to evaluate the printability. As the ink, a commercially available ink (Rio Alpha R39 indigo, manufactured by Toyo Ink Co., Ltd.) was used. With regard to the printability, in practical terms, it is preferable that the number of defects in the dot pattern is 7.0 or less, more preferably 3.5 or less, and most preferably 1.0 or less.

(5) Formability of laminate (Erichsen test)
Based on the Japanese Industrial Standard "JIS Z 2247", a laminate sample that had been conditioned at 23°C x 50% RH for 2 hours was measured at the same temperature and humidity as above using an Erichsen tester (No. 5755 manufactured by Yasuda Seiki Seisakusho Co., Ltd.). A steel ball punch was pressed into the polyurethane resin layer surface of the laminate sample at a predetermined indentation depth to obtain the Erichsen value, and the moldability was evaluated according to the following evaluation criteria. The Erichsen value was measured every 0.5 mm. For practical purposes, the Erichsen value is preferably 5.0 mm or more, more preferably 8.0 mm or more, and most preferably 9.0 mm or more. The measurement was performed with n=5, and the average value was taken as the measured value.

As is clear from the results in Table 2, the polyamide-based laminate films of each Example have a small dynamic friction coefficient of the polyurethane resin layer surface in an environment of 20°C x 90% RH, and are therefore excellent in both printability and formability.
In the polyamide-based laminated films described in Comparative Examples 1 to 3, the glass transition temperature of the polyurethane water dispersion was less than 50°C, so the dynamic friction coefficient of the polyurethane resin layer surface was large. In addition, the polyamide-based laminated film described in Comparative Example 4 did not contain an organic lubricant, and Comparative Example 5 adopted a post-coating method, so sufficient slipperiness was not obtained. In Comparative Example 6, the dynamic friction coefficient of the polyurethane resin layer surface was small by adding acrylic particles, but the arithmetic mean height Ra exceeded the range specified in the present invention, and the printability and moldability were poor. In Comparative Example 7, the glass transition temperature was 50°C or higher, but the dynamic friction coefficient of the polyurethane resin layer surface was high because no organic lubricant was added.

Claims (9)

A laminated film comprising a polyamide film and a polyurethane resin layer laminated on at least one surface of the film, the polyurethane resin layer containing 5 to 30 parts by mass of an organic lubricant per 100 parts by mass of a polyurethane resin,
(1) The glass transition temperature of the polyurethane resin is 90° C. or higher,
(2) The arithmetic mean height (Ra) of the surface of the polyurethane resin layer is 0.010 to 0.022 μm, and the dynamic friction coefficient of the surface of the polyurethane resin layer in an environment of 20° C.×90% RH is 0.27 or less.
A polyamide-based laminate film characterized by: The polyamide-based laminate film according to claim 1, wherein the dynamic friction coefficient of the surface of the polyurethane resin layer in an environment of 23°C x 50% RH is 0.30 or less. The polyamide-based laminate film according to claim 1, wherein the polyurethane resin layer has a thickness of 0.005 to 0.150 μm. A food packaging laminate comprising the polyamide laminate film according to any one of claims 1 to 3. A laminate for cold forming comprising the polyamide laminate film according to any one of claims 1 to 3. A method for producing a polyamide-based laminate film comprising: a polyamide film; and a polyurethane resin layer on at least one surface of the film, the polyurethane resin layer comprising 5 to 30 parts by mass of an organic lubricant per 100 parts by mass of a polyurethane resin having a glass transition temperature of 90° C. or higher; the polyurethane resin layer has a surface arithmetic mean height (Ra) of 0.010 to 0.022 μm; and the polyurethane resin layer has a surface dynamic friction coefficient of 0.27 or less in an environment of 20° C. and 90% RH,
(1) a sheet forming step of forming a melt-kneaded material containing a polyamide resin into a sheet shape to obtain an unstretched sheet;
(2) a stretching step of obtaining a biaxially stretched film by stretching the unstretched sheet in the MD and TD directions, and (3) a coating step of applying an aqueous coating liquid containing a polyurethane resin and an organic lubricant onto one surface of the unstretched sheet, the MD stretched film, or the TD stretched film. The manufacturing method according to claim 6, wherein the aqueous coating liquid is a mixture of a polyurethane resin dispersion and an organic lubricant dispersion having a particle size of 0.010 μm to 0.500 μm. The stretching step is carried out by simultaneous biaxial stretching and is represented by the following formulas (a) and (b):
(a) 0.80≦X/Y≦0.95
(b) 9.8≦X×Y≦11.6
(wherein X represents the stretch ratio in the MD direction, and Y represents the stretch ratio in the TD direction.)
The method according to claim 6, which satisfies both of the above. The stretching step is carried out by sequential biaxial stretching and is represented by the following formulas (a) and (b):
(a) 0.85≦X/Y≦0.95
(b) 8.5≦X×Y≦9.5
(wherein X represents the stretch ratio in the MD direction, and Y represents the stretch ratio in the TD direction.)
The method according to claim 6, which satisfies both of the above.

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