JP7218577B2 - laminated film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laminated film used in the packaging field of foods, medicines, industrial products and the like. Specifically, it is a laminated film comprising a base film, a coating layer, an inorganic thin film layer, and a protective layer, and is capable of exhibiting good gas barrier properties and water-resistant adhesion (laminate strength) even in a high-temperature, high-humidity environment. Regarding.

Packaging materials used for foods, pharmaceuticals, etc. must have the property of blocking gases such as oxygen and water vapor, that is, gas barrier properties, in order to suppress the oxidation of proteins and fats, preserve the taste and freshness, and maintain the efficacy of pharmaceuticals. It has been demanded. It is also important that the barrier performance and adhesion performance do not deteriorate during long-distance transportation and storage in high-temperature and high-humidity environments due to recent climate change in Japan (rising temperatures and heavy rains) and growing demand both in Japan and overseas. It has become.

Conventionally, in food applications that require blocking of various gases such as water vapor and oxygen, metal thin films such as aluminum and inorganic oxides such as silicon oxide and aluminum oxide are coated on the surface of a base film made of plastic. A gas barrier laminate having a thin film is generally used. Among them, those formed with inorganic oxide thin films (inorganic thin film layers) such as silicon oxide, aluminum oxide, and mixtures thereof are widely used because they are transparent and the content can be confirmed.

However, since the gas barrier laminate described above tends to reach high temperatures locally during the formation process, the base material may be damaged, and the low molecular weight portion or the additive portion such as the plasticizer may decompose or degas. As a result, defects, pinholes, and the like may occur in the inorganic thin film layer, and the gas barrier properties may deteriorate. Furthermore, there is also the problem that the inorganic thin film layer cracks and cracks occur during the post-processing of the packaging material such as printing, lamination, bag making, etc., and the gas barrier properties deteriorate.

Attempts have been made to provide a protective layer having gas barrier properties on the inorganic thin film layer as a method for improving the drawbacks of the gas barrier laminate having an inorganic thin film layer formed thereon. For example, there is a method of laminating a gas barrier resin composition comprising a gas barrier resin comprising an ethylene-vinyl alcohol copolymer, an inorganic layered compound and an additive (for example, Patent Document 1). This method greatly improves the drawbacks and gas barrier properties of the inorganic thin film layer.

However, in the above method, the interlaminar adhesion is lowered due to the lack of water resistance in the protective layer. Films with reduced interlaminar adhesion have the problem of delamination due to bending loads and liquid contents, resulting in deterioration of barrier properties and leakage of contents.

In order to solve these problems, the inorganic thin film layer is coated with a water-soluble polymer, an inorganic layered compound and a metal alkoxide or a hydrolyzate thereof, and the inorganic substance containing the inorganic layered compound and the water solution are coated on the inorganic thin film layer by a sol-gel method. A method has been proposed for forming a complex with a soluble polymer (for example, Patent Document 2). According to this method, in addition to excellent barrier properties, it exhibits excellent properties in terms of water resistance. In the case of roll film, the characteristics differ between the outer circumference and inner circumference of the roll), the characteristics differ due to slight differences in drying and heat treatment temperatures in the width direction of the film, and the quality varies depending on the manufacturing environment. There was a problem that a large amount of Furthermore, since the film coated by the sol-gel method has poor flexibility, it has been pointed out that when the film is bent or subjected to impact, pinholes and cracks are likely to occur, and gas barrier properties may deteriorate. .

Against this background, there is a demand for an improvement in which a resin layer can be formed on an inorganic thin film layer by a coating method that does not involve a sol-gel reaction, that is, a coating method that is mainly composed of a resin and involves a cross-linking reaction during coating. rice field. Examples of such improved gas barrier laminates include a gas barrier laminate in which an inorganic thin film is coated with a barrier resin containing a silane coupling agent (for example, Patent Document 3), and a metaxylylene group-containing polyurethane on an inorganic thin film. Coated laminate (
For example, Patent Document 4) can be mentioned.

However, even in the above-described method, when the base material is a polyamide film, the base material absorbs moisture and the film expands and contracts when exposed to a high-temperature and high-humidity environment. Shear stress acts on the interface of the protective layer, causing deterioration of barrier performance and deterioration of adhesion.

In Patent Document 3, improvement of barrier properties before and after hand-kneading has been studied, and good results have been obtained, but performance in a moist and hot environment has not been studied. Moreover, in Patent Document 4, the humidity dependence of the oxygen permeability was examined, and good values were shown, but the performance under a moist and heat environment was not examined.

Japanese Patent No. 5434341 JP-A-2000-43182 Japanese Patent No. 3441594 Japanese Patent No. 4524463

None of the above-mentioned methods has produced a gas barrier film composed of a polyamide base film that is excellent in production stability and economy during production, and that has good barrier properties and water-resistant adhesion even in a high-temperature, high-humidity environment. It was the status quo. An object of the present invention is to provide a gas barrier film comprising a polyamide base film which is excellent in production stability and economic efficiency during production, and which has good barrier properties and water-resistant adhesion even in a high-temperature, high-humidity environment. be.

As a result of intensive studies to solve the above problems, the inventors of the present invention have found that by providing a specific coating layer, an inorganic thin film layer and a protective layer on at least one side of a substrate film, good barrier properties and water-resistant adhesiveness can be obtained. and has sufficient performance even in a high-temperature and high-humidity environment, and completed the present invention.

The laminated film of the present invention, which solves the above problems, has the following aspects.

(1) A polyamide base film has a coating layer on at least one side, the coating layer is made of a coating layer resin composition containing a polyester resin as a constituent, and has an inorganic thin film layer on the coating layer, A laminated film comprising a protective layer containing a urethane resin having a metaxylylene group on the inorganic thin film layer, wherein the protective layer of the laminated film has a surface hardness of 220 to 310 N/mm ² .

(2) The laminated film as described in (1) above, wherein the polyester resin contained in the coating layer is an acrylic-grafted polyester resin.

(3) The laminated film according to any one of (1) and (2) above, wherein the inorganic thin film layer is a layer comprising a composite oxide of silicon oxide and aluminum oxide.

The laminated film comprising the coating layer, the inorganic thin film layer and the protective layer of the present invention has gas barrier properties and excellent water-resistant adhesiveness. There is no problem of deterioration or leakage of contents. In addition, the laminated film of the present invention is designed as a protective layer with a surface hardness that can follow the expansion and contraction of the polyamide base film in a high-temperature and high-humidity environment. It is possible to prevent damage to the film and a decrease in adhesion strength due to delamination. Moreover, since the laminated film of the present invention can be easily produced with fewer processing steps, it is excellent in both economic efficiency and production stability, and can provide a gas barrier film with uniform properties.

The laminated film of the present invention has a coating layer on at least one surface of a polyamide base film, the coating layer is made of a coating layer resin composition containing a polyester resin as a constituent component, and an inorganic thin film layer on the coating layer and a protective layer containing a urethane resin on the inorganic thin film layer, wherein the protective layer of the laminated film has a surface hardness of 220 to 310 N/mm ² .

Hereinafter, the base film and each layer laminated thereon will be described in order.

[Base film]
As the base film used in the present invention, a polyamide base film (hereinafter sometimes referred to as "base film") typified by nylon 4/6, nylon 6, nylon 6/6, nylon 12, etc. is used. . Polyamide base films are superior to other resin base films in terms of bag breakage resistance and pinhole resistance. Examples of the polyamide resin used in the present invention include nylon 6 containing ε-caprolactam as a main raw material. Other polyamide resins include polyamide resins obtained by polycondensation of lactams having three or more membered rings, ω-amino acids, dibasic acids and diamines. Specifically, lactams include enantholactam, capryllactam, and lauryllactam in addition to ε-caprolactam shown above, and ω-amino acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9- Mention may be made of aminononanoic acid, 1,1-aminoundecanoic acid. Dibasic acids include adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecadioic acid, hexadecadioic acid, eicosandioic acid, eicosadienedioic acid, 2 , 2,4-trimethyladipic acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid and xylylenedicarboxylic acid. Furthermore, diamines include ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, pentamethylenediamine, undecamethylenediamine, 2,2,4 (or 2,4,4)-trimethylhexamethylenediamine, and cyclohexane. Diamine, bis-(4,4'-aminocyclohexyl)methane, meta-xylylenediamine and the like can be mentioned. And polymers obtained by polycondensation of these or copolymers thereof, such as nylon 6, 7, 11, 12, 6.6, 6.9, 6.11, 6.12, 6T, 6I, MXD6 (meta-xylene dipanamide 6), 6/6.6, 6/12, 6/6 T, 6/6I, 6/MXD6 and the like can be used. The above polyamide resins may be used alone or in combination of two or more.

As the base film, a film having any thickness can be used according to the desired purpose and application such as mechanical strength and transparency. is recommended, and 8 to 60 μm is desirable when used as a packaging material. The transparency of the substrate film is not particularly limited, but when it is used as a packaging material that requires transparency, it preferably has a light transmittance of 50% or more.

From the viewpoint of imparting mechanical strength, the polyamide base film is preferably a stretched film stretched in at least one direction of the machine direction or the transverse direction. A stretched film is more preferable. As for the stretching method of the biaxially stretched film, any stretching method such as simultaneous biaxial stretching and sequential biaxial stretching can be adopted. As a preferred aspect of the stretching method in sequential biaxial stretching, an unstretched film is stretched in the longitudinal direction at a stretching ratio of 3.0 to 4.5 times at a temperature of 70 ° C. to 90 ° C. with a roll type stretching machine. A method of stretching, then stretching at a stretching ratio of 3.5 to 5.5 times at a temperature of 110° C. to 140° C. with a tenter type stretching machine, and heat treatment at a temperature of 180° C. to 230° C. after stretching will be mentioned. be able to. Further, when an in-line coating method is employed as the step of forming a coating layer, which will be described later, in the step of sequential biaxial stretching, the coating layer is coated on the film after being stretched in the longitudinal direction, and then continuously. The film can be drawn in a tenter-type stretching machine and stretched in the transverse direction and heat-treated.

The base film may be a single-layer film made of a polyamide resin, or a laminated film in which a polyamide resin layer and another plastic film (may be of two or more kinds) are laminated. . As long as there is a polyamide resin layer, the number of layers, the method of stacking, and the like are not particularly limited, and can be arbitrarily selected from known methods depending on the purpose.

Further, in the present invention, a desired surface treatment layer can be provided in advance, if necessary, in order to improve the interlayer adhesion between the inorganic thin film layer and the polyamide base material.
In the present invention, examples of the surface treatment layer include corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen gas or nitrogen gas, glow discharge treatment, oxidation treatment using chemicals, etc. For example, a corona-treated layer, an ozone-treated layer, a plasma-treated layer, an oxidation-treated layer, and the like can be formed and provided. The above-mentioned surface pretreatment is carried out as a method for improving the adhesion between various resin films and vapor-deposited films of metal oxides. For example, on the surface of various resin films, a primer coating layer, an undercoat layer, an anchor coating layer, an adhesive layer, a vapor deposition anchor coating layer, or the like is optionally formed in advance to coat. It can also be layered.

[Coating layer]
The laminated film of the present invention has a coating layer on at least one side of the polyamide base film. From the viewpoints of cost and sanitation, it is preferable to use a polyester resin to improve the adhesion strength between the substrate layer and the inorganic thin film layer by forming the coating layer. Such polyester resins are obtained by polycondensation of dicarboxylic acids or tricarboxylic acids and glycols. Components used in the polycondensation include acid components such as terephthalic acid, isophthalic acid, adipic acid, and trimellitic acid, and glycol components such as ethylene glycol, neopentyl glycol, butanediol, and ethylene glycol-modified bisphenol A. However, it is of course not limited to these. Further, it is preferable to use an acrylic-grafted polyester resin obtained by graft-copolymerizing an acrylic-based monomer as the polyester-based resin in that the curing of the film proceeds and the cohesive force can be improved.

In the present invention, it is preferable that the coating amount of the coating layer is 0.010 to 0.200 g/m ² . As a result, the coating layer can be uniformly controlled, and as a result, the inorganic thin film layer can be densely deposited. In addition, the cohesive force inside the coating layer is improved, and the adhesion between the base film-coating layer-inorganic thin film layer is also enhanced, so that the water-resistant adhesiveness of the coating layer can be enhanced. The coating amount of the coating layer is preferably 0.015 g/m 2 or more, more preferably 0.020 g/m ² or more, still more preferably 0.025 g/m ² or more, and preferably 0.190 g/m ² or less. It is more preferably 0.180 g/m ² or less, still more preferably 0.170 g/m ² or less. If the amount of the coating layer applied exceeds 0.200 g/m ² , the cohesive force inside the coating layer becomes insufficient, and good adhesion may not be achieved. Moreover, since the uniformity of the coating layer is also deteriorated, defects may occur in the inorganic thin film layer, and the gas barrier properties may be deteriorated. Moreover, the manufacturing cost increases, which is economically disadvantageous. On the other hand, if the film thickness of the coating layer is less than 0.010 g/m ² , the base material cannot be sufficiently coated, and there is a possibility that sufficient gas barrier properties and interlayer adhesion cannot be obtained.

The coating layer resin composition may optionally contain various known inorganic and organic additives such as antistatic agents, slip agents, and antiblocking agents within the scope of the present invention. good too.

A method for forming the coating layer is not particularly limited, and a conventionally known method such as a coating method can be employed. Suitable methods among the coating methods include an off-line coating method and an in-line coating method. For example, in the case of the in-line coating method performed in the process of manufacturing the base film, the drying and heat treatment conditions during coating depend on the coating thickness and equipment conditions, but immediately after coating, the film is sent to the stretching process in the perpendicular direction and stretched. It is preferable to dry in the preheating zone or stretching zone of the process, and in such a case, the temperature is usually preferably about 50 to 250°C.

[Inorganic thin film layer]
In the laminated film of the present invention, an inorganic thin film layer is laminated above the coating layer. The inorganic thin film layer is a thin film made of an inorganic oxide. The material for forming the inorganic thin film layer is not particularly limited as long as it can be made into a thin film. ) and other inorganic oxides are preferred. In particular, a composite oxide of silicon oxide and aluminum oxide is preferable from the viewpoint of achieving both flexibility and denseness of the thin film layer. In this composite oxide, the mixing ratio of silicon oxide and aluminum oxide is preferably in the range of 20 to 70% by mass of Al in terms of the metal content. If the Al concentration is less than 20%, the barrier property may be lowered, while if it exceeds 70%, the inorganic thin film layer tends to become hard, and the film breaks during secondary processing such as printing and lamination. There is a risk that the barrier property will be lowered due to the Furthermore, it is not possible to follow the expansion and contraction of the base film under high temperature and high humidity conditions, and there is a risk that the film will crack and the barrier properties will deteriorate. Here, silicon oxide means various silicon oxides such as SiO and SiO ₂ or mixtures thereof, and aluminum oxide means various aluminum oxides such as AlO and Al ₂ O ₃ or mixtures thereof.

The film thickness of the inorganic thin film layer is usually 1 to 100 nm, preferably 5 to 50 nm. If the thickness of the inorganic thin film layer is less than 1 nm, it may be difficult to obtain satisfactory gas barrier properties. It is rather disadvantageous in terms of bending resistance and manufacturing cost.

The method for forming the inorganic thin film layer is not particularly limited, and known vapor deposition such as physical vapor deposition (PVD method) such as vacuum vapor deposition, sputtering, ion plating, or chemical vapor deposition (CVD method). Laws should be adopted accordingly. A typical method for forming an inorganic thin film layer will be described below using a silicon oxide/aluminum oxide thin film as an example. For example, when a vacuum deposition method is employed, a mixture of SiO ₂ and Al ₂ O ₃ or a mixture of SiO ₂ and Al is preferably used as the deposition raw material. Particles are usually used as these vapor deposition raw materials, and in this case, the size of each particle is desirably such that the pressure during vapor deposition does not change, and the preferred particle diameter is 1 mm to 5 mm. For heating, methods such as resistance heating, high-frequency induction heating, electron beam heating, and laser heating can be adopted. It is also possible to introduce oxygen, nitrogen, hydrogen, argon, carbon dioxide gas, water vapor, etc. as reaction gases, or adopt reactive vapor deposition using means such as addition of ozone and ion assist. Furthermore, film formation conditions can be arbitrarily changed, such as applying a bias to the object to be vapor-deposited (laminated film to be vapor-deposited), heating or cooling the object to be vapor-deposited. Such vapor deposition material, reaction gas, bias of the object to be vapor-deposited, heating/cooling, etc. can be changed in the same way when the sputtering method or the CVD method is adopted.

[Protective layer]
The laminated film of the present invention has a protective layer on the inorganic thin film layer. The inorganic thin film layer laminated on the plastic film is not a completely dense film, and is dotted with minute defects. By forming a protective layer by applying a specific protective layer resin composition described later on the inorganic thin film layer, the resin in the protective layer resin composition permeates into the defective portions of the inorganic thin film layer, resulting in An effect of stabilizing the gas barrier property is obtained. In addition, by using a material with gas barrier properties for the protective layer itself, the gas barrier properties of the laminated film are greatly improved.

In the present invention, the protective layer of the laminated film preferably has a surface hardness of 220 to 310 N/mm ² . As a result, the film has the hardness necessary for exhibiting adhesion, and can maintain its performance even when the polyamide base film expands and contracts in a high-temperature, high-humidity environment. The surface hardness is preferably 225 N/mm ² or more, more preferably 230 N/mm ² or more, still more preferably 235 N/mm ² or more, preferably 305 N/mm ² or less, more preferably 300 N/mm ² or less, and further preferably It is preferably 295 N/mm ² or less. If the surface hardness of the laminated film exceeds 310 N/mm ² , the surface becomes too hard and the adhesive during printing or lamination does not permeate, resulting in poor adhesion. In addition, it cannot follow the expansion and contraction of the base film, and there is a possibility that adhesion may be deteriorated under high temperature and high humidity conditions. On the other hand, if the surface hardness is less than 220 N/mm ² , the cohesive force of the protective layer is weak, and the protection of the inorganic thin film layer and the supplementation of defective portions are insufficient, and the barrier performance may be deteriorated. Furthermore, the pigment in the ink may be buried and the ink transferability (printing appearance) may be deteriorated. In order to make the surface hardness of the protective layer within the range described above, it is preferable to blend a urethane resin described later and, if necessary, a cross-linking agent or the like, and adjust the adhesion amount within a predetermined range by the method for forming the protective layer described later. .

In the present invention, it is preferable that the protective layer is applied in an amount of 0.10 to 0.60 g/m ² . This makes it possible to uniformly control the protective layer during coating, resulting in a film with less coating unevenness and defects. In addition, the cohesive force of the protective layer itself is improved, and the adhesion between the inorganic thin film layer and the protective layer is strengthened. The adhesion amount of the protective layer is preferably 0.13 g/m ² or more, more preferably 0.16 g/m ² or more, still more preferably 0.19 g/m ² or more, and preferably 0.57 g/m ² or less. , more preferably 0.54 g/m ² or less, still more preferably 0.51 g/m ² or less. If the coating amount of the protective layer exceeds 0.600 g/m ² , the gas barrier property is improved, but the cohesive force inside the protective layer is insufficient and the uniformity of the protective layer is also reduced, resulting in an uneven coating appearance. Defects may occur, and sufficient gas barrier properties and adhesive properties may not be exhibited. On the other hand, if the film thickness of the protective layer is less than 0.10 g/m ² , sufficient gas barrier properties and interlayer adhesion may not be obtained.

The laminated film of the present invention contains a urethane resin having a metaxylylene group in the protective layer. The urethane resin has good adhesion to the inorganic thin film layer due to the presence of a urethane bond portion having polarity, and the resin easily permeates into the defective portion. In addition, since there is a crystal part with high cohesive force due to hydrogen bonding between urethane bonds, stable gas barrier performance can be obtained. Furthermore, since the highly flexible amorphous part is also present at the same time, the surface hardness can be set within the predetermined range by controlling the ratio of the amorphous part to the crystal part. As the urethane resin, a water-dispersed one having high polarity and good wettability with respect to the inorganic thin film layer is preferable. Moreover, as the curing type of the resin, a thermosetting resin is desirable from the viewpoint of production stability.

(Urethane resin (A))
The urethane resin (A) can be obtained by reacting the polyisocyanate component (B) described below with the polyol component (C) described below by a conventional method. Furthermore, the chain is extended by reacting a low-molecular-weight compound having two or more active hydrogens, such as a diol compound (eg, 1,6-hexanediol) or a diamine compound (eg, hexamethylenediamine, etc.), as a chain extender. is also possible.

(B) Polyisocyanate Component The polyisocyanate component (B) that can be used for synthesizing the urethane resin (A) includes aromatic polyisocyanate, alicyclic polyisocyanate, aliphatic polyisocyanate, and the like. A diisocyanate compound is usually used as the polyisocyanate compound.

Examples of aromatic diisocyanates include tolylene diisocyanate (2,4- or 2,6-tolylene diisocyanate or mixtures thereof) (TDI), phenylene diisocyanate (m-, p-phenylene diisocyanate or mixtures thereof), 4,4 '-diphenyl diisocyanate, 1,5-naphthalene diisocyanate (NDI), diphenylmethane diisocyanate (4,4'-, 2,4'-, or 2,2'-diphenylmethane diisocyanate or mixtures thereof) (MDI) , 4,4′-toluidine diisocyanate (TODI), 4,4′-diphenyl ether diisocyanate, and the like. Examples of araliphatic diisocyanates include xylylene diisocyanate (1,3- or 1,4-xylylene diisocyanate or mixtures thereof) (XDI), tetramethyl xylylene diisocyanate (1,3- or 1,4-tetramethyl xylylene diisocyanate or a mixture thereof) (TMXDI), ω,ω'-diisocyanate-1,4-diethylbenzene, and the like.

Examples of alicyclic diisocyanates include 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (iso Holodiisocyanate, IPDI), methylenebis(cyclohexylisocyanate) (4,4'-, 2,4'- or 2,2'-methylenebis(cyclohexylisocyanate)) (hydrogenated MDI), methylcyclohexane diisocyanate (methyl-2,4- cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate), bis(isocyanatomethyl)cyclohexane (1,3- or 1,4-bis(isocyanatomethyl)cyclohexane or a mixture thereof) (hydrogenated XDI), and the like.

Examples of aliphatic diisocyanates include trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate), hexamethylene Diisocyanate, pendamethylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanatomethyl caffeate, and the like can be mentioned.

(C) Polyol Component As the polyol component (particularly the diol component), low-molecular-weight glycols to oligomers can be used. , 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, neopentyl glycol, heptanediol, octanediol and other linear or branched C2-10 alkylene glycols), (poly)oxy Low molecular weight glycols such as C2-4 alkylene glycol (diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, etc.) are used. Preferred glycol components are C2-8 polyol components [e.g. C2-6 alkylene glycols (especially ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol)], di- or trioxy C2-3 alkylene glycols (diethylene glycol, triethylene glycol, dipropylene glycol, etc.), and particularly preferred diol components are C2-8 alkylene glycols (especially C2 -6 alkylene glycol).

These diol components can be used alone or in combination of two or more. Further optionally, aromatic diols (e.g., bisphenol A, bishydroxyethyl terephthalate, catechol, resorcinol, hydroquinone, 1,3- or 1,4-xylylenediol or mixtures thereof), alicyclic diols ( For example, a low-molecular-weight diol component such as hydrogenated bisphenol A, xylylenediol, cyclohexanediol, cyclohexanedimethanol, etc.) may be used in combination. Furthermore, if necessary, tri- or higher functional polyol components, for example, polyol components such as glycerin, trimethylolethane, and trimethylolpropane, can be used in combination. The polyol component preferably contains at least a C2-8 polyol component (especially C2-6 alkylene glycol). The ratio of the C2-8 polyol component (especially C2-6 alkylene glycol) in 100% by mass of the polyol component can be selected from the range of about 50 to 100% by mass, and is usually preferably 70% by mass or more and 100% by mass or less, It is more preferably 80% by mass or more and 100% by mass or less, still more preferably 90% by mass or more and 100% by mass or less.

In the present invention, it is more preferable to use a urethane resin containing an aromatic or araliphatic diisocyanate component as a main component, from the viewpoint of improving gas barrier properties due to the formation of crystal parts derived from urethane bonds. Among these, it is particularly preferable to contain a meta-xylylene diisocyanate component. By using the above resin, the cohesive force of the urethane bonds can be further increased due to the stacking effect of the aromatic rings, and as a result, good gas barrier properties can be obtained. The proportion of meta-xylylene diisocyanate in the urethane resin is preferably in the range of 30 mol % or more (30 to 100 mol %) in 100 mol % of the polyisocyanate component (E). The proportion of the total amount of aromatic or araliphatic diisocyanates is preferably 40-100 mol %, more preferably 50-100 mol %, still more preferably 60-100 mol %. As such a resin, the "Takelac (registered trademark)" series commercially available from Mitsui Chemicals, Inc. can be suitably used. If the ratio of the total amount of meta-xylylene diisocyanate is less than 30 mol%, good gas barrier properties may not be obtained.

From the viewpoint of improving affinity with the inorganic thin film layer, the urethane resin preferably has a carboxylic acid group (carboxyl group). In order to introduce a carboxylic acid (salt) group into a urethane resin, for example, a polyol compound having a carboxylic acid group such as dimethylolpropionic acid or dimethylolbutanoic acid may be introduced as a copolymerization component. Further, after synthesizing a carboxylic acid group-containing urethane resin, neutralization with a salt-forming agent makes it possible to obtain an aqueous dispersion of the urethane resin. Specific examples of salt-forming agents include ammonia, trialkylamines such as trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine and tri-n-butylamine; -alkylmorpholines, N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These may be used alone or in combination of two or more.

(Characteristics of urethane resin)
The acid value of the urethane resin is preferably within the range of 10-60 mgKOH/g. It is more preferably in the range of 15 to 55 mgKOH/g, still more preferably in the range of 20 to 50 mgKOH/g. When the acid value of the urethane resin is within the above range, the liquid stability is improved when it is made into an aqueous dispersion, and the protective layer can be uniformly deposited on the highly polar inorganic thin film layer, so that the coat appearance is improved. become good.

The urethane resin of the present invention preferably has a glass transition temperature (Tg) of 100° C. or higher, more preferably 110° C. or higher, and still more preferably 120° C. or higher, from the viewpoint of improving barrier properties due to cohesion. However, in order to obtain a surface hardness that develops adhesion, a flexible resin having a Tg of 100° C. or less, which is excellent in flexibility, may be mixed and used. In that case, the addition ratio of the flexible resin is preferably in the range of 0 to 80%. It is more preferably in the range of 10 to 70%, still more preferably in the range of 20 to 60%. When the addition ratio is within the above range, both cohesion and flexibility can be achieved, and barrier properties and adhesion are improved. If the addition ratio exceeds 80%, the film becomes too soft and the barrier performance is lowered.

Various cross-linking agents may be added to the urethane resin of the present invention for the purpose of improving cohesive strength and water-resistant adhesiveness of the film as long as the gas barrier properties are not impaired. Examples of cross-linking agents include silicon-based cross-linking agents, oxazoline compounds, carbodiimide compounds, and epoxy compounds. Among these, a silicon-based cross-linking agent is particularly preferable from the viewpoint of improving the water-resistant adhesiveness to the inorganic thin film layer.

As the silicon-based cross-linking agent, a silane coupling agent is preferable from the viewpoint of cross-linking between an inorganic substance and an organic substance. Examples of silane coupling agents include hydrolyzable alkoxysilane compounds such as halogen-containing alkoxysilanes (2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, chloro C2-4 alkyltri-C1-4 alkoxysilanes such as ethoxysilane), alkoxysilanes having an epoxy group [2-glycidyloxyethyltrimethoxysilane, 2-glycidyloxyethyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane silane, glycidyloxy-C2-4 alkyltri-C1-4 alkoxysilane such as 3-glycidyloxypropyltriethoxysilane, glycidyloxydi-C2-4 such as 3-glycidyloxypropylmethyldimethoxysilane and 3-glycidyloxypropylmethyldiethoxysilane 4-alkyldiC1-4alkoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-(3,4-epoxycyclohexyl)propyltri (Epoxycycloalkyl) C2-4 alkyltriC1-4 alkoxysilanes such as methoxysilane], alkoxysilanes having an amino group [2-aminoethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, etc.] amino C2-4 alkyltriC1-4 alkoxysilanes such as ethoxysilane; aminodi-C2-4 alkyldi-C1-4 alkoxysilanes such as 3-aminopropylmethyldimethoxysilane and 3-aminopropylmethyldiethoxysilane; 2-aminoethyl)amino]ethyltrimethoxysilane, 3-[N-(2-aminoethyl)amino]propyltrimethoxysilane, 3-[N-(2-aminoethyl)amino]propyltriethoxysilane ( 2-aminoC2-4alkyl)aminoC2-4alkyltriC1-4alkoxysilane, 3-[N-(2-aminoethyl)amino]propylmethyldimethoxysilane, 3-[N-(2-aminoethyl)amino ] (Amino-C2-4 alkyl) amino-di-C2-4 alkyl-di-C1-4 alkoxysilanes such as propylmethyldiethoxysilane], alkoxysilanes having a mercapto group (2-mercaptoethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane , 3 - Mercapto-C2-4 alkyltri-C1-4 alkoxysilanes such as mercaptopropyltriethoxysilane, mercapto-di-C2-4 alkyldi-C1-4 alkoxysilanes such as 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, etc.) , alkoxysilanes having a vinyl group (vinyltrimethoxysilane, vinyltri-C1-4 alkoxysilanes such as vinyltriethoxysilane, etc.), alkoxysilanes having an ethylenically unsaturated bond group [2-(meth)acryloxyethyltrimethoxysilane , 2-(meth)acryloxyethyltriethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, etc. (meth)acryloxy C2-4 alkyltri-C1-4 (Meth)acryloxydiC2-4alkyldiC1-4alkoxysilanes such as alkoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, etc.). These silane coupling agents can be used alone or in combination of two or more. Among these silane coupling agents, silane coupling agents having an amino group are preferred.

The silane coupling agent is added to the protective layer in an amount of preferably 0.25 to 3.00% by mass, more preferably 0.5 to 2.75% by mass, and still more preferably 0.75 to 2.50% by mass. is. If the amount added exceeds 3.00% by mass, the film will be cured and the cohesive strength will be improved, but some unreacted portions will be formed, and the adhesion between layers may be reduced. On the other hand, if the amount added is less than 0.25% by mass, sufficient cohesion may not be obtained.

When the protective layer is formed from the protective layer resin composition, a coating solution (coating solution) comprising the polyurethane resin, deionized water, and water-soluble organic solvent may be prepared, applied to the substrate film, and dried. As the water-soluble organic solvent, a single solvent or a mixed solvent selected from alcohols such as ethanol and isopropyl alcohol (IPA), ketones such as acetone and methyl ethyl ketone, and the like can be used. is preferably IPA.

The coating method of the protective layer resin composition is not particularly limited as long as it is a method of coating the film surface to form a layer. For example, ordinary coating methods such as gravure coating, reverse roll coating, wire bar coating and die coating can be employed.

When forming the protective layer, it is preferable to apply the protective layer resin composition and then heat-dry it. is 150-190°C. If the drying temperature is lower than 110° C., the protective layer may be insufficiently dried, or the film formation of the protective layer may not proceed, resulting in reduced cohesive strength and water-resistant adhesiveness, resulting in reduced hand tearability. On the other hand, if the drying temperature exceeds 190° C., the film may be subjected to excessive heat, making the film brittle or shrinking, resulting in poor workability. In particular, by drying at 150° C. or higher, preferably 160° C. or higher, film formation of the protective layer proceeds effectively, and the adhesion area between the resin of the protective layer and the inorganic thin film layer increases, thereby improving water-resistant adhesiveness. can do. In addition to drying, additional heat treatment (for example, 150 to 190° C.) is also effective in advancing the formation of the protective layer.

[Lamination with heat-sealable resin layer]
When the laminated film of the present invention is used as a packaging material, it is necessary to include a heat-sealable resin layer called a sealant. The heat-sealable resin layer is usually provided on the inorganic thin film layer side, that is, on the protective layer side, but may be provided on the outside of the substrate film (the side opposite to the surface on which the coating layer is formed). Formation of the heat-sealable resin layer is usually carried out by an extrusion lamination method or a dry lamination method. The thermoplastic polymer forming the heat-sealable resin layer may be any polymer that can exhibit sufficient sealant adhesiveness, and includes polyethylene resins such as HDPE, LDPE, and LLDPE, polypropylene resins, and ethylene-vinyl acetate copolymers. , ethylene-α-olefin random copolymers, ionomer resins, and the like can be used. The thickness of the heat-sealable resin layer is preferably 20 µm or more, more preferably 25 µm or more, still more preferably 30 µm or more, and preferably 80 µm or less, more preferably 75 µm or less, and still more preferably 70 µm or less. If the thickness is 20 µm or less, the productivity will deteriorate. On the other hand, when the thickness is 80 μm or more, the cost increases and the transparency deteriorates.

[Other layers]
In the laminated film of the present invention, at least one or more printed layers or other plastic substrates and/or paper substrates are laminated between or outside the inorganic thin film layer or base film and the heat-sealable resin layer. may be

As the printing ink for forming the printing layer, water-based and solvent-based resin-containing printing inks can be preferably used. Examples of resins used in printing inks include acrylic resins, urethane resins, polyester resins, vinyl chloride resins, vinyl acetate copolymer resins, and mixtures thereof. Antistatic agents, light shielding agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, lubricants, antifoaming agents, cross-linking agents, anti-blocking agents, antioxidants, and other known agents are used in printing inks. may contain additives. The printing method for forming the printed layer is not particularly limited, and known printing methods such as offset printing, gravure printing, and screen printing can be used. For drying the solvent after printing, a known drying method such as hot air drying, hot roll drying, or infrared drying can be used.

On the other hand, as other plastic substrates and paper substrates, paper, polyester resins, biodegradable resins, and the like are preferably used from the viewpoint of obtaining sufficient rigidity and strength of the laminate. Further, a stretched film such as a biaxially stretched polyester film is preferable in order to obtain a film having excellent mechanical strength.

The laminated film of the present invention preferably has an oxygen permeability of 7 ml/m ² ·d·MPa or less after storage in a high-temperature and high-humidity environment. Furthermore, by controlling the above-mentioned protective layer component and adhesion amount, it is possible to make it preferably 6 ml/m ² ·d·MPa or less, more preferably 5 ml/m ² ·d·MPa or less. When the oxygen permeability is 7 ml/m ² ·d·MPa or more, it becomes difficult to respond to applications requiring high gas barrier properties.

The laminated film of the present invention preferably has a water soak lamination strength of 1.5 N/15 mm or more, more preferably 2.0 N/15 mm or more, and still more preferably 2.5 N/15 mm or more after storage in a high-temperature and high-humidity environment. is. If the lamination strength is less than 1.5 N/15 mm, peeling may occur due to a bending load or liquid content, resulting in deterioration of the barrier property or leakage of the content. Furthermore, there is also a possibility that the hand cutting property may deteriorate.

EXAMPLES Next, the present invention will be described in detail using examples and comparative examples, but the present invention is of course not limited to the following examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass".
The evaluation methods used in the present invention are as follows.

(1) Preparation of laminated laminate for evaluation A polyurethane adhesive (TM569 manufactured by Toyo-Morton Co., Ltd.) is applied to the protective layer surface of the laminated film obtained in Examples and Comparative Examples at 80 ° C. After drying treatment, the thickness becomes 3 μm. After coating, a linear low-density polyethylene film (L4102 manufactured by Toyobo; thickness 40 μm; LL) is dry-laminated on a metal roll heated to 60 ° C., and aged at 40 ° C. for 4 days. A laminated gas barrier laminate for evaluation (hereinafter sometimes referred to as “laminated laminate A”) was obtained.

(2) Evaluation method of oxygen permeability For the laminate A produced in (1) above, according to JIS-K7126 B method, an oxygen permeability measuring device (manufactured by MOCON "OX-TRAN (registered trademark) 1/ 50"), the normal oxygen permeability was measured in an atmosphere of 23° C. and 65% RH. The oxygen permeability was measured in the direction in which oxygen permeates from the substrate film side of the laminate to the heat-sealable resin layer side.

(3) Laminate strength evaluation method
Laminate laminate A prepared above was cut to a width of 15 mm and a length of 200 mm in the width direction (TD direction) and length direction (MD direction) of the base film, respectively. Under the condition of 65%, the laminate strength was measured using a Tensilon Universal Material Tester ("Tensilon UMT-II-500" manufactured by Toyo Baldwin Co., Ltd.). The lamination strength was measured at a tensile speed of 200 mm/min, and water was applied between the laminated film layer and the heat-sealable resin layer obtained in Examples and Comparative Examples, and the layers were peeled off at a peel angle of 90 degrees. The strength was measured when On the other hand, the laminate A produced in (1) was subjected to a wet heat treatment at 80 ° C. × 80% RH × 6 hours, and immediately, a test piece was obtained from the obtained laminate after retort treatment in the same manner as described above. It was cut out and the lamination strength (after wet heat treatment) was measured in the same manner as described above.

(4) Method for Measuring Surface Hardness of Film The surface hardness of the film was measured using a dynamic ultra-micro hardness tester ("DUH-211" manufactured by Shimadzu Corporation). Specifically, the protective layer surface of a single laminated film fixed and held on a glass plate with an adhesive is subjected to a hardness measurement test in a load and unload test using a diamond triangle pyramid indenter (Berkovich type) with an angle between edges of 115°. , the obtained Martens hardness was used as the value of the surface hardness. The test conditions were a test force of 0.1 mN, a load rate of 0.02 mN/sec, and a holding time of 2 seconds.

Each material used for forming the coating layer and the protective layer in each example and comparative example was prepared as follows.

<Preparation of each material used for forming the coating layer or protective layer>
[Polyester resin (A)]
As a polyester resin, "AGN201" (solid content: 25%) manufactured by Takemoto Yushi Co., Ltd., which is a water-dispersible acrylic graft polyester resin containing self-crosslinking maleic anhydride as a graft chain, was prepared.

[Urethane resin (B)]
As the urethane resin, a dispersion of a commercially available meta-xylylene group-containing urethane resin (“Takelac (registered trademark) WPB341” manufactured by Mitsui Chemicals, Inc.; solid content: 30%) was prepared. The acid value of this urethane resin was 25 mgKOH/g, and the glass transition temperature (Tg) measured by DSC was 130°C. The ratio of aromatic or araliphatic diisocyanate to the entire polyisocyanate component measured by 1H-NMR was 85 mol%.

[Silane coupling agent (C)]
As a silane coupling agent, commercially available "(registered trademark) KBM903" manufactured by Shin-Etsu Chemical Co., Ltd.; solid content: 100%) was prepared.

[Urethane resin (D)]
As the urethane resin, a dispersion of commercially available polyester urethane resin (“Takelac (registered trademark) WS6021” manufactured by Mitsui Chemicals, Inc.; solid content: 30%) was prepared. The acid value of this urethane resin was 25 mgKOH/g, and the glass transition temperature (Tg) measured by DSC was 40°C.

[Urethane resin (E)]
As the urethane resin, a commercially available polyester urethane resin dispersion ("Hydran (registered trademark) AP-201" manufactured by DIC; solid content 23%) was prepared. This urethane resin had an acid value of 25 mgKOH/g and a glass transition temperature (Tg) of 10°C as measured by DSC.

[Gas barrier ethylene-vinyl alcohol resin composition coating solution (F)]
<Preparation of ethylene-vinyl alcohol copolymer solution>
In a mixed solvent of 20.996 parts of purified water and 51 parts of n-propyl alcohol (NPA), ethylene-vinyl alcohol copolymer (trade name: Soarnol (registered trademark) V2603, manufactured by Nippon Synthetic Chemical Co., Ltd., ethylene-vinyl acetate copolymer 15 parts of a polymer obtained by saponifying the polymer, an ethylene ratio of 26 mol%, a saponification degree of the vinyl acetate component of about 100% (hereinafter abbreviated as EVOH), and a hydrogen peroxide solution with a concentration of 30%. 13 parts and 0.004 parts of FeSO4 were added, heated to 80°C under stirring, and reacted for about 2 hours. After cooling, catalase was added to 3000 ppm to remove residual hydrogen peroxide, thereby obtaining an almost transparent ethylene-vinyl alcohol copolymer solution (EVOH solution) having a solid content of 15%.
<Preparation of Inorganic Layered Compound Dispersion>
4 parts of montmorillonite (trade name: Kunipia (registered trademark) F, manufactured by Kunimine Industries Co., Ltd.), which is an inorganic layered compound, is added to 96 parts of purified water while stirring, and the pressure is sufficiently set to 50 MPa in a high-pressure dispersing device. Dispersed. Thereafter, the mixture was kept at 40° C. for 1 day to obtain an inorganic layered compound dispersion having a solid content of 4%.
<Additive>
Zirconium chloride (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., trade name; Zircosol (registered trademark) ZC-20, solid content 20%)
<Preparation of coating liquid (F)>
To 62.30 parts of mixed solvent A (solvent containing 40% purified water and 60% n-propyl alcohol), 31.75 parts of the EVOH solution was added and thoroughly stirred and mixed. Furthermore, 5.95 parts of an inorganic layered compound dispersion was added to this solution while stirring at high speed. To 100 parts of this mixed solution, 3 parts of a cation exchange resin is added and stirred for 1 hour at a stirring speed that does not cause crushing of the ion exchange resin to remove cations, followed by cation exchange. Only the resin was filtered off with a strainer. The mixed liquid obtained from the above operation was further subjected to dispersion treatment at a pressure of 50 MPa using a high-pressure dispersing device. 25 parts were added, mixed and stirred, and filtered through a 255-mesh filter to obtain a protective layer coating liquid 3 having a solid content of 5%.

Example 1
(1) Preparation of Coating Liquid 1 Used for Coating Layer Coating liquid 1 was prepared by mixing the following coating agents. Table 1 shows the mass ratio of the polyester resin (A) in terms of solid content.

water 33%
Isopropanol 7%
Polyester resin (A) 60%

(2) Preparation of Coating Solution 2 Used for Protective Layer Coating solution 2 was prepared by mixing the following coating agents. Table 1 shows the mass ratio of the urethane resin (B) in terms of solid content.

Water 41.61%
Isopropanol 40.00%
Urethane resin (B) 18.15%
Silane coupling agent (C) 0.24%

(3) Production of polyamide base film and coating of coating liquid 1 (lamination of coating layer)
Polycaproamide was heated and melted at 260°C with a screw type extruder, extruded into a sheet from a T-die, and then the unstretched sheet was longitudinally stretched 3.3 times at 80°C between a heating roll and a cooling roll. . Then, one side of the obtained uniaxially stretched film was coated with the coating liquid 1 by a fountain bar coating method. Next, the film was guided to a tenter, stretched 4.0 times in the transverse direction at 120°C, and heat-set at 215°C to form a coating layer of 0.075 g/m ² on the biaxially stretched polyamide film with a thickness of 15 µm. A laminated film was obtained.

(4) Formation of Inorganic Thin Film Layer A composite oxide layer of silicon dioxide and aluminum oxide was formed as an inorganic thin film layer on the coating layer forming surface of the film obtained in (3) above by electron beam vapor deposition. As the vapor deposition source, SiO ₂ particles (99.9% purity) and Al ₂ O ₃ (99.9% purity) having a size of about 3 mm to 5 mm were used. Here, the composition of the composite oxide layer was SiO ₂ /Al ₂ O ₃ (mass ratio)=70/30. In addition, the film thickness of the inorganic thin film layer (SiO ₂ /Al ₂ O ₃ composite oxide layer) in the film (inorganic thin film layer/coating layer-containing film) thus obtained was 13 nm. Thus, a vapor-deposited film having a coating layer and an inorganic thin film layer was obtained.

(5) Coating the coating liquid 2 on the deposition film (laminating the protective layer)
The coating solution 2 prepared in (2) above was applied onto the inorganic thin film layer of the deposited film obtained in (4) by gravure roll coating and dried at 170° C. to obtain a protective layer. The coating amount after drying was 0.33 g/m ² (Dry).
As described above, a laminated film having a coating layer/inorganic thin film layer/protective layer on the substrate film was produced. The obtained laminated film was evaluated for surface hardness, oxygen permeability and lamination strength as described above. Table 1 shows the results.

(Examples 2-5, Comparative Examples 1-3)
A laminated film was produced in the same manner as in Example 1, except that in preparing the coating liquid for forming the protective layer, the blending amount, adhesion amount and type of the resin were changed as shown in Table 1. Surface hardness, oxygen permeability and laminate strength were evaluated. Table 1 shows the results.

It was found that the gas barrier laminate film of the present invention comprising a coating layer, an inorganic thin film layer and a protective layer is excellent in gas barrier properties and water-resistant adhesiveness. As a result, peeling does not occur due to bending load or aqueous contents, and there is no problem of deterioration of barrier properties or leakage of contents. In addition, the laminated film of the present invention is designed as a protective layer with a surface hardness that can follow the expansion and contraction of the nylon base film in a high-temperature and high-humidity environment, so damage to the inorganic layer due to shear stress, It is possible to prevent a decrease in adhesion strength due to peeling between layers. Moreover, since the laminated film of the present invention can be easily produced with fewer processing steps, it is excellent in both economic efficiency and production stability, and can provide a gas barrier film with uniform properties.

Claims (3)

At least one side of the polyamide base film has a coating layer, the coating layer is made of a coating layer resin composition containing a polyester resin as a constituent component, and has an inorganic thin film layer on the coating layer, and the inorganic thin film A laminated film having a protective layer containing a urethane resin having a meta-xylylene group and a glass transition temperature of 110° C. or higher on the layer, wherein the protective layer of the laminated film has a surface hardness of 220 to 310 N/mm ² . A laminated film characterized by: 2. The laminated film according to claim 1, wherein the polyester resin contained in the coating layer is an acrylic-grafted polyester resin. 3. The laminated film according to claim 1, wherein said inorganic thin film layer is a layer comprising a composite oxide of silicon oxide and aluminum oxide.