JP2021003889A - Laminated film - Google Patents

Abstract

To provide a polyamide laminated film which has no anisotropy with respect to a measurement surface of gass barrier permeability and is excellent in gas barrier property exhibition on high-humidity condition.SOLUTION: There is provided a laminated film in which a metal oxide layer and a protective layer are laminated in this order on at least one surface of a polyamide base material film through or without through another layer, where the protective layer is obtained from a resin composition for protective layer that contains an urethane resin in which 50 mol% or more of the total of a polyisocyanate component is composed of m-xylene diisocyanate and/or a hydrogenated m-xylene diisocyanate component, as a component.SELECTED DRAWING: None

Description

The present invention relates to a laminated film used in the packaging field of foods, pharmaceuticals, industrial products and the like. Specifically, it is a laminated film provided with a metal oxide layer and a protective layer, which can enhance the interlayer adhesion of the metal oxide layer and has good gas barrier properties and adhesion even when exposed to high humidity or the like ( It relates to a laminated film capable of expressing (lamination strength).

Packaging materials used in 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 oxidation of proteins and fats and oils, maintain taste and freshness, and maintain the efficacy of pharmaceuticals. It has been demanded. Further, gas barrier materials used for electronic devices such as solar cells and organic ELs and electronic parts require higher gas barrier properties than packaging materials such as foods.

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

However, since the above-mentioned gas barrier laminate tends to be locally heated to a high temperature in the forming process, the base material may be damaged, or decomposition or degassing may occur in a low molecular weight portion or an additive portion such as a plasticizer. As a result, defects, pinholes, etc. may occur in the metal oxide layer, and the gas barrier property may be lowered. Further, there is also a problem that the metal oxide layer is cracked and cracked during the post-processing of the packaging material such as printing, laminating, and bag making, and the gas barrier property is lowered. It is considered that this is because the adhesion between the plastic base material and the metal oxide layer was not good, and the metal oxide layer could not follow the deformation of the film base material, so that cracks occurred.

As a method for improving the drawbacks of the gas barrier laminate on which the metal oxide layer is formed, an attempt has been made to provide a layer having a gas barrier property on the metal oxide layer. For example, there is a method of laminating a gas barrier resin composed of an ethylene-vinyl alcohol-based copolymer and a gas barrier resin composition composed of an inorganic layered compound and an additive (see, for example, Patent Document 1). In this method, the drawbacks of the metal oxide layer and the gas barrier property are greatly improved.

However, the above method has a problem that the gas barrier property is remarkably lowered under high humidity conditions. In addition, the gas barrier permeability is anisotropic, and it is not suitable for development in food applications where it is necessary to suppress both the inflow of external water and the outflow of internal water, for example. Therefore, as an example of imparting gas barrier properties under high humidity and gas barrier properties without anisotropy of gas barrier permeability to the laminate, a water-soluble polymer, an inorganic layered compound, and a metal alkoxide or its hydrolysis are provided on the metal oxide layer. A method has been proposed in which a substance is coated to form a composite of an inorganic substance containing an inorganic layered compound and a water-soluble polymer on a metal oxide layer by a solgel method (see, for example, Patent Document 2). According to this method, the gas barrier property under high humidity is also excellent, but the stability of the liquid to be applied to the coating is low, so that the roll film at the start and the end of the coating (for example, industrially distributed roll film) If this is the case, the characteristics will differ between the outer and inner circumferences of the roll, the characteristics will differ due to slight differences in the temperature of drying and heat treatment in the film width direction, and the quality will differ greatly depending on the manufacturing environment. I had a problem such as. 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 impacted, pinholes and cracks are likely to occur and the gas barrier property may be deteriorated. ..

Against this background, it is hoped that a coating method that does not involve a sol-gel reaction, that is, a coating method that mainly uses a resin and that involves a cross-linking reaction at the time of coating, can form a resin layer on the metal oxide layer. It was rare. As the gas barrier laminate with such improvements, a gas barrier laminate in which a barrier resin containing a silane coupling agent is coated on an inorganic thin film is disclosed (for example, Patent Document 3).

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

However, the above-mentioned method cannot satisfy the gas barrier property of oxygen, water vapor, etc., and the current situation is that the gas barrier property cannot be sufficiently maintained.

As a result of diligent studies to solve the above problems, the present inventors have conducted a protective layer made of a polyurethane dispersion composition on a laminated film having at least a metal oxide layer on both sides or one side of the base film. The present invention was completed by finding a laminated film having good gas barrier properties under high humidity and having no anisotropy of gas barrier permeability.

The gas barrier film of the present invention has the following aspects.

(1) A metal oxide layer and a protective layer are laminated in this order on at least one surface of the polyamide base film with or without other layers, and the protective layer is 50 mol% of the total polyisocyanate component. The above is obtained from a resin composition for a protective layer containing a urethane resin composed of a metaxylene diisocyanate and / or a hydrogenated metaxylene diisocyanate component as a component.
The acid value of the urethane resin constituting the protective layer is 10 to 60 mgKOH / g, and the coating amount of the resin composition for the protective layer is 0.05 to 1.0 g / m ² in a dry state. Laminated film.

(2) The laminated film according to (1) above, wherein the oxygen permeability under the condition of 23 ° C. × 90% RH is 10 [ml / m ² · d · MPa] or less.

(3) The water vapor permeability when water vapor permeates from the base film side and the water vapor permeability when water vapor permeates from the protective layer side under the condition of 40 ° C. × 90% RH are both 2 [g / m ^2].・
d] The laminated film according to (1) or (2) below.

(4) Any of the above (1) to (3) having a coating layer formed from a coating liquid containing a water-dispersible acrylic graft polyester resin between the polyamide base film and the metal oxide layer. The laminated film described in.

According to the present invention, a laminated film exhibiting excellent gas barrier properties (barrier properties against oxygen and water vapor) not only under low humidity but also under high humidity and having no anisotropy on the measurement surface of gas barrier permeation is provided. it can.

As a result, the laminated film according to the present invention is also useful as a packaging film for foods, pharmaceuticals, industrial products, etc., which require gas barrier properties.

The laminated film of the present invention is formed by laminating a metal oxide layer and a protective layer on one or both sides of a base film in this order with or without other layers. Hereinafter, the base film and each layer laminated on the base film will be described in order.

[Base film]
Examples of the polyamide resin used in the present invention include nylon 6 containing ε-caprolactam as a main raw material. Further, as another polyamide resin, a polyamide resin obtained by polycondensation of lactam, ω-amino acid, dibasic acid and diamine having three or more members of a ring can be mentioned. Specifically, as lactams, in addition to ε-caprolactam shown above, enantractum, caprilactam, lauryllactam, and as ω-amino acids, 6-aminocaproic acid, 7-aminoheptanoic acid, 9- Aminononanoic acid, 1,1-aminoundecanoic acid can be mentioned. Examples of dibasic acids include adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandionic acid, dodecadionic acid, hexadecadionic acid, eikosandionic acid, eikosadiendioic acid, 2 , 2,4-trimethyladiponic acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, xylylene dicarboxylic acid. Further, as diamines, ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, pentamethylenediamine, undecamethylenediamine, 2,2,4 (or 2,4,4) -trimethylhexamethylenediamine, cyclohexane Examples thereof include diamine, bis- (4,4'-aminocyclohexyl) methane, and metaxylylenediamine. Then, a polymer obtained by polycondensing these or a copolymer thereof, for example, nylon 6, 7, 11, 12, 6.6, 6.9, 6.11, 6.12, 6T, 6I, MXD6. (Metaxylene panamide 6), 6 / 6.6, 6/12, 6 / 6T, 6 / 6I, 6 / MXD6 and the like can be used. In addition, when producing the polyamide resin laminated film roll before vapor deposition of the present invention, the above-mentioned polyamide resin can be used alone or in combination of two or more.

As the base film, a film having an arbitrary film thickness can be used according to a desired purpose and application such as mechanical strength and transparency, and the film thickness is not particularly limited, but is usually 5 to 100 μm. Is recommended, and when used as a packaging material, it is preferably 8 to 60 μm. The transparency of the base film is not particularly limited, but when it is used as a packaging material that requires transparency, it is desirable that the base film has a light transmittance of 50% or more.

The base film may be a single-layer film made of a polyamide resin, or may be a laminated film in which a polyamide resin layer and another plastic film (two or more kinds may be laminated) are laminated. .. The type of the laminated body in the case of forming a laminated film is not particularly limited as long as there is a polyamide resin layer, the number of laminations, the lamination method and the like are not particularly limited, and can be arbitrarily selected from known methods according to the purpose.

Further, in the present invention, in order to improve the interlayer adhesion between the metal oxide layer and the polyamide base material, a desired surface treatment layer can be provided in advance, if necessary.
In the present invention, the surface treatment layer includes, for example, corona discharge treatment, ozone treatment, low temperature plasma treatment using oxygen gas or nitrogen gas, glow discharge treatment, oxidation treatment using chemicals, etc. Etc. can be arbitrarily applied to form, for example, a corona-treated layer, an ozone-treated layer, a plasma-treated layer, an oxidation-treated layer, and the like. The above surface pretreatment is carried out as a method for improving the tight adhesion between various resin films and a metal oxide vapor-deposited film, but as a method for improving the tight adhesion, other methods. For example, a primer coating agent layer, an undercoat agent layer, an anchor coating agent layer, an adhesive layer, a vapor deposition anchor coating agent layer, etc. are arbitrarily formed on the surface of various resin films and coated. It can also be a layer.

[Coating layer]
In order to improve the adhesion strength between the base material layer and the metal oxide vapor deposition layer by forming the coating layer, it is preferable to use a water-based polyester resin from the viewpoint of cost and hygiene. Such a polyester-based resin can be obtained by polycondensing a dicarboxylic acid or a tricarboxylic acid with glycols. Examples of the component used for 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, of course, it is not limited to these. Further, this polyester resin may be obtained by graft-copolymerizing an acrylic monomer.

The preferable thickness of the coating layer is 0.01 to 10 μm, more preferably 0.02 to 5 μm, and if the thickness is less than 0.01 μm, it tends to be difficult to sufficiently exert the effect of improving the adhesion strength, and 10 μm is used. Even if it is made excessively thick, the effect of improving the adhesion is not exhibited any more, which is economically disadvantageous.

[Metal oxide layer]
In the laminated film of the present invention, a metal oxide layer is laminated on the coating layer. The metal oxide layer is a thin film made of an inorganic oxide. The material for forming the metal oxide layer is not particularly limited as long as it can be made into a thin film, but from the viewpoint of gas barrier properties, silicon oxide (silica), aluminum oxide (alumina), and a mixture of silicon oxide and aluminum oxide (composite oxidation). Inorganic oxides such as (things) are preferably mentioned. 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% of Al in terms of the mass ratio of the metal content. If the Al concentration is less than 20%, the barrier property may be lowered, while if it exceeds 70%, the metal oxide layer tends to be hard, and the film may be formed during secondary processing such as printing or laminating. It may be destroyed and the barrier property may be reduced. The silicon oxide referred to here is various silicon oxides such as SiO and SiO ₂ or a mixture thereof, and aluminum oxide is various aluminum oxides such as AlO and Al ₂ O ₃ or a mixture thereof.

The film thickness of the metal oxide layer is usually 1 to 100 nm, preferably 5 to 50 nm. If the film thickness of the metal oxide layer is less than 1 nm, it may be difficult to obtain a satisfactory gas barrier property. On the other hand, even if the thickness exceeds 100 nm, the corresponding improvement effect of the gas barrier property is obtained. It cannot be obtained, which is rather disadvantageous in terms of bending resistance and manufacturing cost.

The method for forming the metal oxide layer is not particularly limited, and is known, for example, a physical vapor deposition method (PVD method) such as a vacuum vapor deposition method, a sputtering method, or an ion plating method, or a chemical vapor deposition method (CVD method). The vapor deposition method may be appropriately adopted. Hereinafter, a typical method for forming the metal oxide layer will be described by taking a silicon oxide / aluminum oxide thin film as an example. For example, when the vacuum vapor deposition method is adopted, a mixture of SiO ₂ and Al ₂ O ₃ or a mixture of SiO ₂ and Al is preferably used as the vapor deposition raw material. Particles are usually used as these vapor deposition raw materials, but at that time, it is desirable that the size of each particle is such that the pressure at the time of vapor deposition does not change, and the particle diameter is preferably 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, water vapor or the like as the reaction gas, or to adopt reactive vapor deposition using means such as ozone addition and ion assist. Further, the film forming conditions can be arbitrarily changed, such as applying a bias to the film to be vapor-deposited (laminated film to be subjected to vapor deposition) or heating or cooling the film to be deposited. Such vapor deposition material, reaction gas, bias of the vapor deposition body, heating / cooling, and the like can be similarly changed when the sputtering method or the CVD method is adopted.

[Protective layer]
The laminated film of the present invention has a protective layer formed from the resin composition for a protective layer described in detail below above the metal oxide layer.
The metal oxide layer is not a completely dense film, but is dotted with minute defects. By applying a specific protective layer resin composition described later on the metal oxide layer to form the protective layer, the resin in the protective layer resin composition permeates the defective portion of the metal oxide layer. As a result, the effect of stabilizing the gas barrier property can be obtained. Furthermore, by covering the metal oxide layer with a protective layer, it is possible to protect the metal oxide layer from rubbing and slipping in the printing process, and also to protect the metal oxide layer from pigments in the ink to provide a barrier property. It becomes possible to maintain it stably. In addition, by using a material having a gas barrier property for the protective layer itself, the gas barrier performance of the laminated film is greatly improved.

(Resin composition for protective layer)
The resin composition for the protective layer is obtained from a urethane resin containing metaxylene diisocyanate and / or hydrogenated metaxylene diisocyanate as a main constituent component of the polyisocyanate component. At this time, good gas barrier properties can be exhibited when the ratio of the metaxylene diisocyanate and / or the hydrogenated metaxylene diisocyanate component to the total polyisocyanate component in the urethane resin is 50 mol% or more.

The urethane resin is obtained by reacting the following polyisocyanate component (A) with the following polyol component (B) by a usual method so that the amount of the metaxylene diisocyanate and / or the hydrogenated metaxylene diisocyanate component is within the above range. Be done. Further, chain extension is performed by reacting a low molecular weight compound having two or more active hydrogens such as a diol compound (for example, 1,6-hexanediol) and a diamine compound (for example, hexamethylenediamine) as a chain extender. Is also possible. Further, the "Takelac (registered trademark) WPB" series commercially available from Mitsui Chemicals, Inc. can also be used as a suitable water-based urethane resin.

(A) Polyisocyanate component The polyisocyanate component (A) that can be used in the synthesis of urethane resin includes aromatic polyisocyanate, alicyclic polyisocyanate, aliphatic polyisocyanate and the like. As the polyisocyanate compound, a diisocyanate compound is usually used.

Examples of the aromatic diisocyanate include tolylene diisocyanate (2,4- or 2,6-toluene diisocyanate or a mixture thereof) (TDI), phenylene diisocyanate (m-, p-phenylene diisocyanate or a mixture thereof), 4,4. '
-Diphenyl diisocyanate, 1,5-naphthalenedi isocyanate (NDI), diphenylmethane diisocinate (4,4'-, 2,4'-, or 2,2'-diphenylmethane diisosinate or a mixture thereof) (MDI), 4 , 4'-Toluidine diisocyanate (TODI), 4,4'-diphenyl ether diisocyanate and the like can be exemplified. Examples of the aromatic aliphatic diisocyanate include xylene diisocyanate (1,3- or 1,4-xylene diisocyanate or a mixture thereof) (XDI), tetramethylxylene diisocyanate (1,3- or 1,4-tetramethylxylene diisocyanate or (TMXDI), ω, ω'-diisocyanate-1,4-diethylbenzene and the like can be exemplified.

Examples of the alicyclic diisocyanate include 1,3-cyclopentenediisocyanate, cyclohexanediisocyanate (1,4-cyclohexanediisocyanate, 1,3-cyclohexanediisocyanate), 3-isocyanatemethyl-3,5,5-trimethylcyclohexylisocyanate (iso). Holodiisocyanate, IPDI), methylenebis (cyclohexylisocyanate) (4,4'-, 2,4'-or 2,2'-methylenebis (cyclohexylisocyanate)) (hydrogenated MDI), methylcyclohexanediisocyanate (methyl-2,4) -Cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate), bis (isocyanatemethyl) cyclohexane (1,3- or 1,4-bis (isocyanatemethyl) cyclohexane or a mixture thereof) (hydrogenated XDI) and the like. it can.

Examples of the aliphatic diisocyanate include trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylenedi isocyanate) and hexamethylene. Examples thereof include diisocyanate, pendamethylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methyl caffeate and the like.

(B) Polyol Compound As the polyol component (particularly the diol component), low molecular weight glycols to oligomers can be used, but from the viewpoint of gas barrier properties, alkylene glycols (for example, ethylene glycol, propylene glycol, trimethylene glycol) are usually used. , 1,3-Butanediol, 1,4-Butanediol, Pentandiol, Hexadiol, Neopentyl glycol, Heptanediol, Octanediol, etc. Linear or branched C _2-10 alkylene glycol), (Poly) Low molecular weight glycols such as Oxy-C _2-4 alkylene glycol (diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, etc.) are used. Preferred glycol components are C _2-8 polyol components [eg, C _2-6 alkylene glycols (particularly ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4-butanediol, 1,6-hexane). Diol, 3-methyl-1,5-pentanediol), etc.], di or trioxy C _2-3 alkylene glycol (diethylene glycol, triethylene glycol, dipropylene glycol, etc.), and a particularly preferable diol component is C _2-8 alkylene. Glycols (particularly C _2-6 alkylene glycol).

These diol components can be used alone or in combination of two or more. Further, if necessary, aromatic diols (eg, bisphenol A, bishydroxyethyl terephthalate, catechol, resorcin, hydroquinone, 1,3- or 1,4-xylene diol or a mixture thereof, etc.), alicyclic diols (eg, for example). A low molecular weight diol component such as hydrogenated bisphenol A, xylylene diol, cyclohexanediol, cyclohexanedimethanol, etc. may be used in combination. Further, if necessary, a trifunctional or higher functional polyol component, for example, a polyol component such as glycerin, trimethylolethane, or trimethylolpropane can be used in combination. The polyol component preferably contains at least a C _2-8 polyol component (particularly, C _2-6 alkylene glycol). The ratio of the C _2-8 polyol component (particularly, C _2-6 alkylene glycol) in 100% by mass of the polyol component can be selected from the range of about 50 to 100% by mass, and usually 70% by mass or more and 100% by mass or less. It is preferable, more preferably 80% by mass or more and 100% by mass or less, and further preferably 90% by mass or more and 100% by mass or less.

(Characteristics of urethane resin)
The acid value of the urethane resin is preferably in the range of 10 to 60 mgKOH / g. It is more preferably in the range of 15 to 55 mgKOH / g, and even 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 protective layer can maintain flexibility while being partially crosslinked, and can further improve the cohesive force and relax the stress of the metal oxide.

When the protective layer is formed by the resin composition for the protective layer, a coating liquid (coating liquid) composed of the polyurethane resin, ion-exchanged water, and a water-soluble organic solvent may be prepared, coated on the base film, and dried. As the water-soluble organic solvent, a single or mixed solvent selected from alcohols such as ethanol and isopropyl alcohol (IPA) and ketones such as acetone and methyl ethyl ketone can be used, and from the viewpoint of coating film processing and odor. Is preferably IPA.

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

The amount of the resin composition for the protective layer applied is not particularly limited, but is preferably in the range of 0.05 to 1.0 g / m ^{2 in} a dry state, and is 0 from the viewpoint of practicality. A range of ¹ to 0.5 g / m ² is more preferable. If it is less than 0.05 g / m ^2, sufficient adhesion and gas barrier properties, protective effect is difficult to obtain, tend to be economically disadvantageous if it exceeds 1.0 g / m ^2.

When forming the protective layer, it is preferable to apply the resin composition for the protective layer and then heat-dry it, and the drying temperature at that time is preferably 110 to 190 ° C, more preferably 130 to 190 ° C, still more preferable. Is 170-190 ° C. If the drying temperature is less than 110 ° C., the protective layer may be insufficiently dried, the cross-linking of the protective layer may not proceed, and the adhesion under normal conditions and the water resistance of the protective layer when retort-treated may decrease. There is a risk of On the other hand, if the drying temperature exceeds 190 ° C., the film may be overheated and the film may become brittle or shrink to deteriorate workability. Further, apart from drying, adding an additional heat treatment (for example, 150 to 190 ° C.) is also effective in advancing the cross-linking of the protective layer.

Regarding the laminated film coated with the resin composition for the protective layer, it is estimated as follows that there is no humidity dependence. In general, urethane resin exhibits gas barrier properties due to the aggregation effect of the hydrogen bond component of the urethane bond. However, under high humidity, the hydrogen bonding force weakens and the cohesive force weakens, so that the gas barrier property deteriorates. The resin composition for a protective layer used in the present invention is a urethane resin containing metaxylene diisocyanate and / or hydrogenated metaxylene diisocyanate as a main component, and is due to a stacking effect of a metaxylene group in addition to hydrogen bond aggregation due to urethane bonds. It is thought that there is also agglomeration. Since the stacking effect of the meta-xylene group is not affected by humidity, it is presumed that the humidity dependence is reduced.

Further, the laminated film coated with the resin composition for the protective layer is a laminated film having no anisotropy with respect to the measurement surface of gas barrier permeation. The following estimation is also made for this. When a protective layer that exhibits gas barrier properties due to the aggregation effect of hydrogen bond components such as urethane bonds is applied on the vapor deposition layer, when oxygen is permeated from the base film side, oxygen permeates in the order of the vapor deposition layer and the protective layer. To do. At this time, moisture is blocked by the thin-film deposition layer, and oxygen passing through the protective layer permeates under a low humidity state, so that the gas barrier property is improved. However, when oxygen permeates from the protective layer side, oxygen permeates in the order of the protective layer and the thin-film deposition layer. At this time, oxygen passing through the protective layer permeates under high humidity, so that the gas barrier property of the protective layer is lowered. For the above reasons, anisotropy occurs with respect to the measurement surface of gas barrier permeation. On the other hand, when a urethane resin containing metaxylene diisocyanate and / or hydrogenated metaxylene diisocyanate as a main component is applied on the vapor-deposited layer, the protective layer is less dependent on humidity, so either the base film side or the protective layer side. It is estimated that even if oxygen is permeated from the surface, anisotropy with respect to the measurement surface of gas barrier permeation does not occur.

[Other layers]
In addition to the base film, the coating layer, the metal oxide layer, and the protective layer, the laminated film of the present invention is provided with various layers provided by the laminated film having a known gas barrier property, if necessary. Can be done.
For example, when the laminated film of the present invention is used as a packaging material, it is preferable to include a thermosetting resin layer called a sealant. The heat-sealable resin layer is usually provided on the metal oxide layer side, but may be provided on the outside of the base film (the surface opposite to the coating layer forming surface). The heat-sealing resin layer is usually formed by an extrusion laminating method or a dry laminating method. The thermoplastic polymer that forms the heat-sealable resin layer may be any one that can sufficiently exhibit sealant adhesiveness, and is a polyethylene resin such as HDPE, LDPE, LLDPE, a polypropylene resin, or an ethylene-vinyl acetate copolymer. , Ethethylene-α-olefin random copolymer, ionomer resin and the like can be used.

Further, in the laminated film of the present invention, at least one layer of a printing layer or another plastic base material and / or a paper base material is provided between or outside the metal oxide layer or the base film and the thermosetting resin layer. The above may be laminated.

As the printing ink forming the printing layer, water-based and solvent-based resin-containing printing inks can be preferably used. Examples of the resin used for the printing ink include acrylic resin, urethane resin, polyester resin, vinyl chloride resin, vinyl acetate copolymer resin, and a mixture thereof. Known printing inks include antistatic agents, light blocking agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, lubricants, defoamers, cross-linking agents, blocking agents, antioxidants, etc. Additives may be included. The printing method for providing the print layer is not particularly limited, and known printing methods such as an offset printing method, a gravure printing method, and a screen printing method can be used. For drying the solvent after printing, known drying methods such as hot air drying, hot roll drying, and infrared drying can be used.

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

The laminated film of the present invention as described above exhibits excellent gas barrier properties not only under low humidity but also under high humidity, and is a laminated film having no anisotropy with respect to the measurement surface of gas barrier permeation. Further, the laminated film can achieve both gas barrier properties and print quality such as design properties without damaging the metal oxide layer even when printing is performed.

Next, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is naturally not limited to the following Examples. Unless otherwise specified, "%" means "% by mass" and "part" means "part by mass".
The evaluation method used in the present invention is as follows.

<Preparation of Laminate Laminated Body A for Evaluation>
On the laminates obtained in Examples and Comparative Examples, a polyurethane adhesive (TM569 manufactured by Toyo Morton Co., Ltd.) was applied to the vapor-deposited surface of the obtained film so that the thickness after drying at 80 ° C. was 3 μm. After that, a 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 to have a laminating gas barrier property for evaluation. A laminated body (hereinafter, also referred to as "laminated laminated body A") was obtained.

<Evaluation method of oxygen permeability>
The laminated laminate A produced above is subjected to an oxygen permeability measuring device (“OX-TRAN (registered trademark) 1/50” manufactured by MOCON) in accordance with the JIS-K7126 B method, at a temperature of 23 ° C. and a humidity of 65. Oxygen permeability was measured in an atmosphere of ~ 90% RH. The oxygen permeability was measured in the direction in which oxygen permeated from the base film side of the laminated laminate to the heat-sealing resin layer (low-density polyethylene) side.

<Evaluation method of water vapor permeability>
Regarding the laminated laminate A produced above, a water vapor permeability measuring device (“PERMATRAN-W (registered trademark) 3/33 MG” manufactured by MOCON) was used in accordance with the JIS-K7129B method, and the temperature was 40 ° C. and the humidity was 90. The water vapor permeability was measured in an atmosphere of% RH. The water vapor permeability was measured in the direction in which water vapor permeated from the base film side of the laminated laminate to the heat-sealing resin layer and in the direction in which water vapor permeated from the heat-sealing resin layer to the base film layer.

<Evaluation method of laminate strength>
The laminate laminate A produced above was cut into a test piece having a width of 15 mm and a length of 200 mm, and under the conditions of a temperature of 23 ° C. and a relative humidity of 65%, a Tencilon universal material tester (“Tencilon UMT-” manufactured by Toyo Boldwin Co., Ltd. The laminate strength (normal state) was measured using "II-500 type"). The lamination strength was measured at a tensile speed of 200 mm / min, and water was applied between the laminated film layer and the thermosetting resin layer obtained in Examples and Comparative Examples to peel them off at a peeling angle of 90 degrees. The strength of the time was measured.

Example 1
(1) Preparation of Coating Liquid 1 Used for Coating Layer As a water-dispersible acrylic graft polyester resin containing self-crosslinking maleic anhydride as a graft chain, "AGN201" (solid content 25%) manufactured by Takemoto Oil & Fat Co., Ltd. was prepared. ..
Each material was mixed at the following blending ratio to prepare a coating liquid 1 (composition for forming a coating layer).
33% water
Isopropanol 7%
Water-dispersible acrylic graft polyester resin 60%

(2) Preparation of Coating Liquid 2 Used for Protective Layer A commercially available dispersion of a urethane-based resin containing a metaxylylene group (“Takelac (registered trademark) WPB341” manufactured by Mitsui Chemicals, Inc .; solid content 25%) was prepared. The acid value (theoretical value) of this urethane resin was 25 mgKOH / g. The ratio of metaxylylene diisocyanate to the total polyisocyanate component measured by ^{1 1} H-NMR was 85 mol%.
Each material was mixed at the following blending ratio to prepare a coating liquid 2 (resin composition for a protective layer).
Water 30%
Isopropanol 30%
Polyurethane dispersion 40%

(3) Production of polyamide base film and coating of coating liquid 1 (lamination of coating layer)
Polycarbonate proamide was heated and melted at 260 ° C. using a screw extruder, extruded into a sheet from a T-die, and then this unstretched sheet was longitudinally stretched 3.3 times at 80 ° C. between a heating roll and a cooling roll. .. Then, the coating liquid 1 was applied to one side of the obtained uniaxially stretched film by the fountain bar coating method. Next, it was guided to a tenter, stretched 4.0 times laterally at 120 ° C., and then heat-fixed at 215 ° C., and a coating layer of 0.750 g / m ² was formed on a biaxially stretched polyamide film (Ny) having a thickness of 15 μm. The formed laminated film was obtained.

(4) Formation of Metal Oxide Layer A composite oxide layer of silicon dioxide and aluminum oxide was formed as a metal oxide layer on the coating layer forming surface of the film obtained in (3) above by an electron beam vapor deposition method. As the vapor deposition source, particulate SiO ₂ (purity 99.9%) and Al ₂ O ₃ (purity 99.9%) 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) = 66/33. Further, the film thickness of the metal oxide layer (SiO ₂ / Al ₂ O ₃ composite oxide layer) in the film (metal oxide layer / coating layer-containing film) thus obtained was 13 nm. In this way, a thin-film film having a coating layer and a metal oxide layer was obtained.

(5) Coating of coating liquid 2 on thin-film deposition film (lamination of protective layer)
The coating liquid 2 prepared in (2) above was applied onto the metal oxide layer of the vapor-deposited film obtained in (4) by the gravure roll coating method, and dried at 190 ° C. to obtain a protective layer. The coating amount after drying was 0.30 g / m ² (Dry).
As described above, a laminated film having a coating layer / metal oxide layer / protective layer on the base film was produced. The obtained laminated film was evaluated for oxygen permeability, water vapor permeability and lamination strength as described above. The results are shown in Table 2.

Example 2
A laminated film was prepared in the same manner as in Example 1 except that the coating layer was not formed, and the oxygen permeability, water vapor permeability, and lamination strength were evaluated. The results are shown in Table 2.

Comparative Example 1
A laminated film was prepared in the same manner as in Example 1 except that the protective layer was not formed, and the oxygen permeability, water vapor permeability, and lamination strength were evaluated. The results are shown in Table 2.

Comparative Example 2
(Preparation of gas barrier resin composition used in Comparative Example 2)
<Preparation of ethylene-vinyl alcohol copolymer solution>
Ethylene-vinyl alcohol copolymer (trade name: Soanol (registered trademark) V2603, manufactured by Nippon Synthetic Chemical Co., Ltd., ethylene-vinyl acetate) in a mixed solvent of 20.996 parts of purified water and 51 parts of n-propyl alcohol (NPA). A polymer obtained by saponifying the polymer, an ethylene ratio of 26 mol%, a degree of saponification of the vinyl acetate component of about 100%, hereinafter abbreviated as EVOH) 15 parts are added, and a hydrogen peroxide solution having a concentration of 30% is further added. 13 parts and 0.004 part of FeSO ₄ were added, and the mixture was heated to 80 ° C. with stirring and reacted for about 2 hours. Then, the mixture was cooled and catalase was added to 3000 ppm to remove residual hydrogen peroxide, whereby a substantially transparent ethylene-vinyl alcohol copolymer solution (EVOH solution) having a solid content of 15% was obtained.

<Preparation of inorganic layered compound dispersion>
Add 4 parts of montmorillonite (trade name: Kunipia (registered trademark) F, manufactured by Kunimine Industries, Ltd.), which is an inorganic layered compound, into 96 parts of purified water with stirring, and set the pressure to 50 MPa with a high-pressure disperser. Distributed. Then, the mixture was kept warm at 40 ° C. for 1 day to obtain an inorganic layered compound dispersion having a solid content of 4%.

<Additives>
Zirconium hydrochloride (manufactured by Daiichi Rare Element Chemical Industry Co., Ltd., trade name; zirconium (registered trademark) ZC-20, solid content 20%)

<Preparation of coating liquid 3 used for protective layer>
31.75 parts of EVOH solution was added to 62.30 parts of the mixed solvent A (solvent composed of 40% purified water and 60% n-propyl alcohol), and the mixture was thoroughly stirred and mixed. Further, 5.95 parts of the inorganic layered compound dispersion was added to this solution while stirring at high speed. Three parts of the cation exchange resin is added to 100 parts of this mixed solution, and the mixture is stirred at a stirring speed such that the ion exchange resin is not crushed for 1 hour to remove cations, and then cation exchange. Only the resin was filtered off with a strainer.
The mixed solution obtained from the above operation was further dispersed in a high-pressure disperser at a pressure of 50 MPa, and then 0.75 parts of zirconium hydrochloride and 0.75 parts of mixed solvent A2 were added to 97 parts of the dispersed mixed solution. Twenty-five parts were added, and the mixture was mixed and stirred, and filtered through a 255 mesh filter to obtain a coating liquid 3 for a protective layer having a solid content of 5%.

A coating layer and a metal oxide layer are formed on the polyamide base film in the same manner as in Example 1, and the protective layer (adhesion amount after drying) is placed on the metal oxide layer by using the protective layer coating liquid 3. 0.30 g / m ² ) was formed to obtain a laminated film. The oxygen permeability, water vapor permeability and laminate strength of the obtained film were evaluated. The results are shown in Table 2.

The laminated film of the present invention is useful in the packaging field of foods, pharmaceuticals, industrial products and the like.

Claims (4)

A metal oxide layer and a protective layer are laminated in this order on at least one side of the polyamide base film with or without other layers, and the protective layer contains 50 mol% or more of the total polyisocyanate component as meta. Obtained from a resin composition for a protective layer containing a urethane resin composed of a xylene diisocyanate and / or a hydrogenated metaxylene diisocyanate component as a component.
The acid value of the urethane resin constituting the protective layer is 10 to 60 mgKOH / g, and the coating amount of the resin composition for the protective layer is 0.05 to 1.0 g / m ² in a dry state. Laminated film. The laminated film according to claim 1, wherein the oxygen permeability under the condition of 23 ° C. × 90% RH is 10 [ml / m ² · d · MPa] or less. The water vapor permeability when water vapor permeates from the base film side and the water vapor permeability when water vapor permeates from the protective layer side under the condition of 40 ° C. × 90% RH are both 2 [g / m ² · d]. The laminated film according to claim 1 or 2 below. The laminated film according to any one of claims 1 to 3, which has a coating layer formed from a coating liquid containing a water-dispersible acrylic graft polyester resin between a polyamide base film and a metal oxide layer.