Resin composition, film and multilayer structure

Abstract

To provide a resin composition that has excellent gas barrier properties, especially oxygen barrier properties, even when exposed to high humidity conditions for a long time.SOLUTION: A resin composition contains a hydrophilic resin an a metallic compound and satisfies the Condition A: the resin composition is put into a 10 wt.% aqueous solution or water dispersion, and the resultant flow-cast film is let stand for one week at 23°C and 80%RH, and a contact angle (°) of water before treatment is defined as α and a contact angle (°) of water after treatment is defined as β, satisfying the following formula (1) of (β-α)≥10.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition, and more particularly to a resin composition from which a film having high gas barrier properties can be obtained even when exposed to high humidity for a long period of time. [Background technology]

[0002] Hydrophilic resins such as polyvinyl alcohol-based resins are excellent in strength, transparency, gas barrier properties, etc., and are therefore formed into films and widely used as various packaging materials, particularly packaging materials for foods, medicines, and other items that require prevention of deterioration due to oxygen. However, hydrophilic resins are susceptible to the influence of humidity because they have many hydroxyl groups, and gas barrier properties are significantly reduced in high humidity environments.

[0003] As an example of a film with improved gas barrier properties, Patent Document 1 discloses a gas barrier film material that contains poorly water-soluble inorganic fine particles having an average particle size of 500 nm or less and a water-soluble or water-dispersible polymer compound, in which the poorly water-soluble inorganic fine particles are ionic crystals synthesized by reacting an inorganic compound containing one or more essential components selected from aluminum, silicon, zinc, zirconium, silver, and tin, or a salt thereof, with one or more compounds selected from organic acids, inorganic acids, and salts thereof.

[0004] In addition, Patent Document 2 discloses a method for producing a water-soluble polymer, at least one of a metal alkoxide, a hydrolyzate thereof, and tin chloride, and a compound represented by the general formula (R 1 Si(OR 2 )3)n(However, R 1 is an organic functional group, R 2 and a compound represented by the formula (I) CH3, C2H5, or C2H4OCH3).

[0005] Furthermore, Patent Document 3 discloses a method for producing a gas barrier laminate, which includes the steps of forming a coating film containing zinc ions, at least one of a metal alkoxide and a hydrolyzate thereof, and a water-soluble polymer on the surface of a substrate film or a laminate containing the same, and forming a gas barrier layer on the surface. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-338821 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-221864 [Patent Document 3] Japanese Patent Application Publication No. 2018-089567 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0007] However, the gas barrier films disclosed in the above Patent Documents 1 to 3 do not have sufficient gas barrier properties under high humidity conditions, and further improvement is required.

[0008] Under these circumstances, an object of the present invention is to provide a resin composition that has excellent gas barrier properties, particularly oxygen barrier properties, even when exposed to high humidity for a long period of time. [Means for solving the problem]

[0009] However, the present inventors have discovered that by forming a coating film from a resin composition containing a hydrophilic resin and a specific metal compound, the gas barrier properties are excellent even when exposed to high humidity for a long period of time.

[0010] That is, a first gist of the present invention is a resin composition containing a hydrophilic resin and a metal compound, which satisfies the following condition (A): Condition (A): The above resin composition is made into a 10 wt % aqueous solution or dispersion, and the resulting cast film is left standing for one week under conditions of 23°C and 80% RH. When the contact angle of water (°) before treatment is α and the contact angle of water (°) after treatment is β, the following formula (1) is satisfied. (β-α)≧10 (1)

[0011] The second aspect of the present invention is a film containing the resin composition according to the first aspect, and the third aspect is a multilayer structure having at least one layer made of the film according to the second aspect. [Effects of the Invention]

[0012] The resin composition of the present invention is a resin composition containing a hydrophilic resin and a metal compound, and satisfies the above-mentioned condition (A). Therefore, a film containing this resin composition exhibits excellent gas barrier properties, particularly oxygen barrier properties, even when exposed to high humidity for a long period of time. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments for carrying out the present invention will be specifically described, but the present invention is not limited to these.

[0014] The resin composition of the present invention contains a hydrophilic resin and a metal compound. Each of the components will be described below.

[0015] <Hydrophilic resin> Specific examples of the hydrophilic resin used in the present invention include water-soluble resins such as vinyl alcohol resins, polysaccharides, acrylic resins, polyether resins, etc. The above hydrophilic resins may be used alone or in combination of two or more.

[0016] Furthermore, the hydrophilic resin preferably has the following properties when formed into a film. A film having a thickness of 30 μm is prepared using the above hydrophilic resin, and when the film is immersed in water at 25° C. for 2 hours, the area change rate is 105% or more. The area change rate can be calculated using the following formula. Area change rate (%) = film area after immersion / film area before immersion × 100 Specific hydrophilic resins will be described in detail below.

[0017] [Vinyl alcohol resin] The vinyl alcohol resins mentioned above exclude resins generally known as ethylene-vinyl alcohol copolymer resins (ethylene content: 20 to 60 mol%), and examples thereof include polyvinyl alcohol (hereinafter referred to as "PVA") resins.

[0018] The PVA resin is usually preferably an unmodified PVA resin, but a modified PVA resin may also be used.

[0019] The unmodified PVA resin can usually be produced by polymerizing a vinyl ester monomer and then saponifying the polymer. The modified PVA resin can be produced by saponifying a polymer of a vinyl ester monomer and another unsaturated monomer, or by post-modifying an unmodified PVA resin.

[0020] Examples of the vinyl ester monomer include aliphatic vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versatate, and vinyl trifluoroacetate, and aromatic vinyl esters such as vinyl benzoate. Among these, aliphatic vinyl esters having 3 to 20 carbon atoms are preferred, more preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms, with vinyl acetate being particularly preferred. These are usually used alone, but multiple types may be used simultaneously as necessary.

[0021] Examples of the other unsaturated monomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, and itaconic acid, or their salts or mono- or di-alkyl esters; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallylsulfonic acid, or their salts; alkyl vinyl ethers; N-acrylamidomethyltrimethylammonium chloride, allyl trimethylammonium chloride, dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, polyisoprene, and the like. Examples of suitable alkoxy groups include polyoxyalkylene (meth)allyl ethers such as polyoxyethylene (meth)allyl ether and polyoxypropylene (meth)allyl ether, polyoxyalkylene (meth)acrylates such as polyoxyethylene (meth)acrylate and polyoxypropylene (meth)acrylate, polyoxyalkylene (meth)acrylamides such as polyoxyethylene (meth)acrylamide and polyoxypropylene (meth)acrylamide, polyoxyethylene (1-(meth)acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, and polyoxypropylene vinylamine. These may be used alone or in combination of two or more. The term "(meth)allyl" as used above means allyl or methallyl, "(meth)acrylate" means acrylate or methacrylate, and "(meth)acrylic" means acrylic or methacrylic, respectively.

[0022] The PVA resin can be obtained by any known polymerization method, saponification method, or post-modification method.

[0023] The amount of the other unsaturated monomer introduced and the amount of modification by post-modification are appropriately set depending on the type of monomer, but are usually 15 mol % or less, particularly 10 mol % or less. If the amount introduced or the amount of modification is too high, the crystallinity of the PVA resin tends to decrease, and the gas barrier properties of the PVA resin when made into a film tend to decrease.

[0024] The average saponification degree of the PVA resin is usually 70 to 100 mol%, preferably 80 to 100 mol%, particularly preferably 85 to 100 mol%, and even more preferably 90 to 99.99 mol%. If the average saponification degree is less than 70 mol%, the oxygen permeability tends to increase under high humidity conditions. The average saponification degree is measured in accordance with JIS K 6726.

[0025] The average degree of polymerization of the PVA resin is usually 100 to 4,000, preferably 200 to 3,000, and particularly preferably 250 to 2,500. If the average degree of polymerization is too low, mechanical properties such as film strength tend to decrease, while if it is too high, handling tends to become difficult, for example, it becomes difficult to make an aqueous solution. The average degree of polymerization is measured in accordance with JIS K 6726.

[0026] Furthermore, two or more PVA-based resins differing in the type of modification, the amount of modification, the average degree of saponification, the average degree of polymerization, etc. may be used in combination.

[0027] [Polysaccharide] Examples of the polysaccharides include starch and cellulose. Examples of the starch include natural starches such as corn starch and potato starch, and modified starches such as etherified starch, esterified starch, crosslinked starch, grafted starch, roasted dextrin, enzyme-modified dextrin, pregelatinized starch, and oxidized starch. Examples of the cellulose include carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl cellulose, nitrocellulose, cationized cellulose, and metal salts thereof such as sodium salts.

[0028] [Acrylic resin] Examples of the acrylic resin include polyacrylamide, polyacrylic acid, and metal salts thereof such as sodium salts.

[0029] [Polyether resin] Examples of the polyether resin include polyethylene glycol and polypropylene glycol.

[0030] Among the above hydrophilic resins, vinyl alcohol resins and polysaccharides are preferred because they have excellent oxygen barrier properties under high humidity conditions, and PVA resins and modified starch are more preferred, and soluble starch and hydroxypropyl methylcellulose are particularly preferred, with unmodified PVA resin being most preferred.

[0031] The hydrophilic resin is preferably the main component of the resin composition of the present invention, and the content of the hydrophilic resin in the entire resin composition is usually 80% by weight or more, preferably 90% by weight or more, and particularly preferably 95% by weight or more, with the upper limit usually being 99.99% by weight.

[0032] <Metal compounds> The metal compound used in the present invention has a structure in which specific structural units are layered at specific interplanar spacings, such as a metal-containing layered compound containing Zn or the like as a metal species.

[0033] The structural unit contains a metal, a hydroxy ligand, and an anionic ligand other than a hydroxy ligand, and is represented by the following chemical formula (1). M a (OH)b A n- (2a-b) / n ···(1) (The above M represents a metal species, and A represents an anionic ligand other than a hydroxy ligand having a valence of n. However, A does not include O (oxo ligand). n is an integer of 1 or more, and a and b are numbers greater than 0, satisfying a / b=0.1 to 10.)

[0034] In the above chemical formula (1), examples of M include Na, K, Ca, Mg, Si, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, and Zn. These metal species may be contained alone or in combination with two or more. Among them, Al, Si, Mg, Ni, Co, and Zn are preferred, Ni, Co, and Zn are particularly preferred, and Zn is particularly preferred, from the viewpoint of excellent oxygen barrier properties under high humidity conditions.

[0035] In the above chemical formula (1), examples of A include RO (alkoxy ligand), ROCO (carboxylic acid ligand), CO3, NO3, SO3, PO4, BO3, F, Br, Cl, etc. (R is an alkyl chain, and C m H 2m+1 It is generally represented by a chemical formula in which m=1 to 20. However, the alkyl chain may have a functional group such as an OH group as long as it does not impair the effects of the present invention. However, O (oxo ligand) is excluded as A. These anionic ligands may be contained alone or in combination of two or more. Among them, from the viewpoint of interaction with the hydrophilic resin, NO3, Cl, RO, and ROCO are preferred, ROCO is particularly preferred, and among these, CHOCO is particularly preferred.

[0036] The metal compound used in the present invention may contain water molecules.

[0037] Furthermore, when measured by wide-angle X-ray diffraction using CuKα radiation, the metal compound typically has a main X-ray diffraction peak at 2θ=2 to 15°, preferably at 2θ=2 to 9°, and particularly preferably at 2θ=3 to 8°.

[0038] The wide-angle X-ray diffraction is measured under the following conditions. [Measurement conditions] Equipment used: D8 DISCOVER (manufactured by Bruker Japan) Detector: 2D detector VANTEC-500 (manufactured by Bruker Japan) Voltage: 50kV ·Current: 100mA Camera length: 100mm ·Measurement method: Reflection method Accumulation time: 30 minutes Wavelength: CuKα line (Kα1 and Kα2 are not separated) Detector position: 2θ=10° ·X-ray incident angle: θ=0.3° ·Conditions for one-dimensionalization in the 2θ direction: 2θ = 0 to 35°, azimuth angle (chi) = -95 to -85° ·One-dimensionalization in the azimuth angle direction: azimuth angle (chi) = -180 to 0° When linearizing in the azimuthal direction, linearization is performed in the azimuthal direction in a range of 1.0° so that the peak with the strongest diffraction intensity is included in the range of 2θ = 2 to 15°. In this case, if a peak is observed in the azimuthal angle range of -180 to 0°, it is determined that a diffraction peak is observed in the range of 2θ = 2 to 15°. For example, if a diffraction peak is observed at 2θ = 6.8°, when linearizing in the azimuthal direction in the range of 2θ = 6.0 to 7.0°, if a peak is observed in the azimuthal angle range of -180 to 0°, it can be determined that a diffraction peak is observed in the range of 2θ = 2 to 15°.

[0039] The interlayer distance (distance between layers) of the metal compound is preferably 0.01 to 50 nm, more preferably 0.1 to 30 nm, from the viewpoint of interaction with the hydrophilic resin molecules and water molecules. The interlayer distance of the metal compound can be calculated from the Bragg equation based on the diffraction position of the strongest peak in the 2θ range of 2 to 15° when analyzed by X-ray diffraction.

[0040] The molecular weight of the layered structural unit peeled off from the metal compound is preferably 100 to 10,000, particularly preferably 200 to 2,000, in order to enable interaction with the hydrophilic resin at the molecular level.

[0041] The layered structural unit is preferably hydrophilic in view of interaction with the molecules of the hydrophilic resin. Furthermore, it is preferable that the layered structural unit does not decompose even when left standing in an environment of 20°C and 90% RH for 1,000 hours.

[0042] Specific examples of the metal compound include layered metal compounds containing Zn as the metal species. Among these, a Zn-containing layered compound represented by the chemical formula [Zn(OH)(CHCO) 2·2H0] is preferred because of its excellent oxygen barrier properties under high humidity conditions.

[0043] In the present invention, it is presumed that the metal compound and the hydrophilic resin interact to increase the polarity of the hydrophilic resin, thereby achieving the effect of excellent oxygen barrier properties under high humidity conditions.

[0044] The content of the metal compound in the resin composition of the present invention in terms of metal is usually 0.01 to 20 parts by weight, preferably 0.1 to 18 parts by weight, and particularly preferably 0.2 to 15 parts by weight, relative to 100 parts by weight of the hydrophilic resin. If the content of the metal compound is too low, the oxygen barrier property under high humidity conditions tends to decrease, while if the content of the metal compound is too high, whitening and reduced transparency tend to occur when the composition is made into a film or the like. When the resin composition contains a plurality of metal compounds of different metal species, the total amount of all the metal compounds contained in the resin composition is defined as the content. The content of the metal compounds can be determined by the standard addition method using ICP-MS.

[0045] The metal compound can be obtained, for example, by (I) a method of reacting a metal-containing compound in the presence of a base, or (II) a method of reacting a metal-containing compound by heating.

[0046] Examples of the metal-containing compound used in each of the above methods include organic acid metal salts and inorganic metal salts.

[0047] Examples of organic acids constituting the organic acid metal salts include monocarboxylic acids such as acetic acid, dicarboxylic acids such as succinic acid, oxalic acid, and tartaric acid, and tricarboxylic or higher carboxylic acids such as citric acid and ethylenediaminetetraacetic acid. These may be used alone or in combination of two or more. The organic acid metal salts may be hydrates or anhydrides. As the organic acid metal salt, a monovalent carboxylic acid metal salt is preferred from the viewpoint of excellent oxygen barrier properties under high humidity conditions, a metal acetate is particularly preferred, and zinc acetate or a hydrate thereof is particularly preferred.

[0048] Examples of the inorganic metal salt include metal fluorides, chlorides, bromides, iodides, and oxoacids. These may be used alone or in combination of two or more. The inorganic metal salt may be a hydrate or an anhydride. As the inorganic metal salt, metal chlorides and oxoacids are preferred because they have excellent oxygen barrier properties under high humidity conditions, and zinc chloride, zinc nitrate, or hydrates thereof are particularly preferred. Each method will be described in detail below.

[0049] [Method (I)] The above method (I) is a method in which a metal-containing compound is reacted in the presence of a base.

[0050] Examples of the base used in the above method (I) include hydroxides of alkali metals or alkaline earth metals. Among them, hydroxides of alkali metals are preferred, and sodium hydroxide is particularly preferred, because they have excellent reactivity with metal-containing compounds.

[0051] In the reaction of the metal-containing compound with the base, the metal-containing compound and the base are usually mixed in a solution and reacted. From the viewpoint of workability, it is preferable to dissolve or disperse the hydrophilic resin in the solution. The method for mixing the metal-containing compound and the base is not particularly limited, and examples thereof include a method of mixing a solution in which a metal-containing compound is dissolved with a solution in which a base is dissolved, and a method of mixing a slurry liquid in which a metal-containing compound is dispersed with a solution in which a base is dissolved. Among these, from the viewpoint of reaction efficiency, a method of mixing a solution in which a metal-containing compound is dissolved with a solution in which a base is dissolved is preferred. Furthermore, when an organic acid metal salt is used as the metal-containing compound, a method of adding a solution in which an organic acid metal salt is dissolved to a solution in which a base is dissolved and mixing them is preferred, and when an inorganic metal salt is used, a method of adding a solution in which a base is dissolved to a solution in which an inorganic metal salt is dissolved and mixing them is preferred.

[0052] The solvent for dissolving the metal-containing compound and the base is not particularly limited as long as it can dissolve the metal-containing compound and the base, and examples thereof include water and lower alcohols having 1 to 5 carbon atoms, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol. These may be used alone or in combination of two or more. Among these, water is preferred from the viewpoint of ease of post-treatment.

[0053] The concentration of the metal-containing compound in the solution in which the metal-containing compound is dissolved is usually 0.5 to 3 mol / L, and preferably 1 to 2 mol / L. The concentration of the base in the solution obtained by dissolving the base in the solvent is usually 0.01 to 100 mol / L, preferably 0.1 to 30 mol / L, and particularly preferably 1 to 10 mol / L. If the concentrations of the metal-containing compound and the base are lower than the above ranges, the reaction tends to proceed insufficiently, whereas if the concentrations of the metal-containing compound and the base are higher than the above ranges, side reactions tend to occur.

[0054] The molar ratio of the metal-containing compound to the base (metal-containing compound:base) is usually 0.5:2 to 2:0.5, preferably 0.8:1.5 to 1.5:0.8, and particularly preferably 0.9:1.2 to 1: 1. If the molar ratio is outside the above range, the reaction tends not to proceed sufficiently.

[0055] The pH when reacting the metal-containing compound with the base is usually 4 to 9, preferably 5 to 8. If the pH is too low below the above range, the reaction tends not to proceed sufficiently. If the pH is too high above the above range, the generated metal-containing compound tends to decompose. The pH is adjusted by adjusting the amounts of the solution in which the metal-containing compound is dissolved and the solution in which the base is dissolved.

[0056] The reaction temperature in the above reaction is usually 15 to 60° C., preferably 20 to 40° C. If the reaction temperature is too low, the reaction tends not to proceed sufficiently, whereas if the reaction temperature is too high, the metal-containing compound tends to be decomposed by heat, making it difficult to obtain the desired metal compound. The reaction time is usually 0.5 to 5 hours, preferably 1 to 3 hours, and the reaction may be carried out under normal pressure.

[0057] [Method (II)] The above method (II) is a method in which a metal-containing compound is heated to cause a reaction.

[0058] The method (II) is usually carried out by heating a solution containing a metal-containing compound while stirring it. From the viewpoint of workability, it is preferable to dissolve or disperse the hydrophilic resin in the solution.

[0059] As the solvent for dissolving the metal-containing compound, the solvents listed in the above method (I) can be used. Among them, water and alcohols are preferred, and water is particularly preferred.

[0060] As for the heating conditions, the solution may be heated to a temperature of usually 20 to 100° C., preferably 50 to 95° C., and particularly preferably 70 to 90° C. If the reaction temperature is too low, the reaction tends not to proceed sufficiently, whereas if the reaction temperature is too high, the metal-containing compound tends to be decomposed by heat, making it difficult to obtain the desired metal compound. The reaction time is usually 0.1 to 100 hours, preferably 0.5 to 30 hours, and particularly preferably 1 to 10 hours, and the reaction may be carried out under normal pressure.

[0061] Metal compounds can be obtained by any of the above methods, but method (II) is preferred from the viewpoint of workability. As described above, the metal compounds obtained by each of the above methods have a structure in which the layered structural units represented by the chemical formula (1) are layered at a specific interplanar spacing. Therefore, when hydrophilic resin molecules or water molecules are present around the metal compound, the layers of the metal compound are peeled off, and these peeled fine layered structural units interact with the hydrophilic resin at the molecular level, which is presumed to result in excellent oxygen barrier properties.

[0062] [Other ingredients] The resin composition of the present invention may contain, to the extent that the effects of the present invention are not impaired, additives generally added to resin compositions, such as heat stabilizers, antioxidants, antistatic agents, colorants, ultraviolet absorbers, lubricants, plasticizers, light stabilizers, surfactants, antibacterial agents, desiccants, antiblocking agents, flame retardants, crosslinking agents, curing agents, foaming agents, crystal nucleating agents, antifogging agents, biodegradable additives, silane coupling agents, oxygen absorbers, etc. These may be used alone or in combination of two or more.

[0063] The resin composition of the present invention can be obtained by mixing a hydrophilic resin, a metal compound, and, if necessary, other components.

[0064] The resin composition of the present invention contains a hydrophilic resin and a metal compound and satisfies the following condition (A). Condition (A): The resin composition is made into a 10 wt % aqueous solution or dispersion, and the resulting cast film is left to stand for one week under conditions of 23°C and 80% RH. When the contact angle of water (°) before the treatment is α and the contact angle of water (°) after the treatment is β, the following formula (1) is satisfied: (β-α)≧10 (1)

[0065] The difference (β-α) between the water contact angle after the treatment and the water contact angle before the treatment is at least 10, preferably at least 15, and more preferably at least 20, in order to provide excellent gas barrier properties, particularly oxygen barrier properties, under high humidity conditions. The water contact angle is determined by dropping 2 μL of purified water onto the cast film under conditions of 23° C. and 50% RH to form a water droplet, and measuring the contact angle between the water droplet and the cast film surface 10 times using a contact angle meter (DropMaster 500, manufactured by KYOWA INTERFACE SCIENCE).

[0066] The contact angle with water after treatment is usually 60° or more, preferably 70° or more, and particularly preferably 75° or more, in order to provide excellent gas barrier properties, particularly oxygen barrier properties, under high humidity conditions.

[0067] <Film containing resin composition> The film containing the resin composition of the present invention is obtained by forming the resin composition into a film.

[0068] Examples of methods for producing the film include a method using a solution (coating liquid) containing the resin composition of the present invention, and a method of melt-molding pellets containing the resin composition of the present invention using an extruder. Among these, a method using a solution (coating liquid) containing the resin composition is preferred. When using the coating liquid, the solid content is usually 0.5 to 30% by weight, preferably 5 to 20% by weight.

[0069] The coating liquid can be prepared, for example, by adding all components to a solvent at once and mixing them, or by dissolving some components in a solvent and adding other components to the solution and mixing them. Among these, from the viewpoint of workability, the method of adding other components to a solution in which a hydrophilic resin is dissolved in a solvent and mixing them is preferred. Furthermore, from the viewpoint of workability, in the methods (I) and (II) for obtaining the above-mentioned metal compound, it is also preferable to dissolve or disperse a hydrophilic resin in a solvent when reacting the metal-containing compound, and use the solution after the reaction as a coating liquid, which is particularly preferable when obtaining the metal compound by method (II). As the solvent, the solvents exemplified for the metal compounds can be used.

[0070] The film can be formed by any known method, such as a melt extrusion method, an endless belt method, a drum method, a coating method, or other casting method. Of these, the casting method is preferred.

[0071] After forming a film by the above-mentioned film-forming method, a film containing the resin composition can be obtained by drying, for example, by heat treatment at 60 to 105° C. for 0.5 to 10 minutes. Furthermore, the above-mentioned film may be subjected to a stretching operation such as uniaxial stretching or biaxial stretching, if necessary.

[0072] The film may be a single-layer film or a multilayer structure. The multilayer structure preferably has at least one layer made of the film. Furthermore, the multilayer structure may be formed by laminating the film or by laminating another base resin.

[0073] The thickness of the film containing the resin composition of the present invention is usually 1 to 200 μm, preferably 1 to 100 μm, and particularly preferably 1 to 50 μm. When the film formed above has a multilayer structure, the total thickness of the film is the sum of the thicknesses of all the films containing the resin composition.

[0074] Examples of the base resin include polyethylene-based resins such as linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-propylene (block and random) copolymers, and ethylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymers; polypropylene-based resins such as polypropylene and propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymers; (unmodified) polyolefin-based resins such as polybutene, polypentene, and polycyclic olefin-based resins (polymers having a cyclic olefin structure in at least one of the main chain and side chain); and polyolefins obtained by dissolving these polyolefins in an unsaturated carboxylic acid or Examples of the base resin include polyolefin resins in the broad sense, including modified olefin resins such as unsaturated carboxylic acid-modified polyolefin resins graft-modified with esters of the base resin; ionomers; ethylene-vinyl acetate copolymers; ethylene-acrylic acid copolymers; ethylene-acrylic acid ester copolymers; polyester resins; polyamide resins (including copolymerized polyamides); polyvinyl chloride; polyvinylidene chloride; acrylic resins; polystyrene; vinyl ester resins; polyester elastomers; polyurethane elastomers; polystyrene elastomers; halogenated polyolefins such as chlorinated polyethylene and chlorinated polypropylene; and aromatic or aliphatic polyketones. These may be used alone or in combination of two or more. These base resins may also be subjected to surface treatments such as corona treatment.

[0075] The film made of the resin composition of the present invention has excellent gas barrier properties even when exposed to high humidity for a long period of time. Although the mechanism by which such an effect is obtained is unclear, it is presumed that the long-term exposure to high humidity causes the hydrophilic resin molecules to plasticize, and the metal compounds dispersed in the film interact with the hydrophilic resin or become localized on the surface of the film. In the present invention, "long-term exposure to high humidity" means exposure to an environment of 20±5° C. and 90±10% RH for 70 hours or more.

[0076] In addition, the oxygen permeability of the film after long-term exposure to the above high humidity was 80cc·3μm / m 2 ·day·atm or less is preferable, and 70cc·3μm / m 2 ·day·atm or less is more preferable, and 55cc·3μm / m 2 ·day·atm or less is more preferable, and 30cc·3μm / m 2 It is particularly preferable that the oxygen permeability is 0 cc·day·atm or less. The oxygen permeability is measured in an environment of 23°C and 80% RH, and the lower limit of the oxygen permeability is usually 0 cc·3 μm / m 2 ·day·atm. The oxygen permeability can be determined by an oxygen permeability measuring device.

[0077] Films containing the resin composition of the present invention have extremely excellent transparency, far superior to films containing inorganic layered compounds or fillers. Specifically, films containing the resin composition of the present invention preferably have a haze of 1% or less, more preferably 0.6% or less, even more preferably 0.3% or less, and particularly preferably 0.2% or less. The haze is a haze value measured in accordance with JIS K7361-1. For example, ten 50 mm x 50 mm test pieces are cut from the film and measured using a haze meter (NDH-4000 manufactured by Nippon Denshoku Industries Co., Ltd.), and the average value of the ten pieces is taken as the haze (%).

[0078] The resin composition of the present invention and a film made of the resin composition are useful as packaging materials, and can be suitably used in particular as packaging materials for foods, medicines, and the like. [Example]

[0079] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention. Note that "parts" below are based on weight.

[0080] Prior to the examples, the following hydrophilic resins were prepared.

[0081] [Hydrophilic resin] [PVA resin] PVA1 (unmodified PVA resin, average degree of polymerization 300, average degree of saponification 99 mol%) PVA2 (modified PVA resin, average degree of polymerization 450, average degree of saponification 98 mol%) PVA3 (unmodified PVA resin, average degree of polymerization 400, average degree of saponification 88 mol%) [Polysaccharide] Starch (water-soluble starch, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., starch (soluble)) Hydroxypropyl methylcellulose (Mitsubishi Chemical Foods Corporation, Hypromellose AW-4)

[0082] Example 1 100 parts of PVA1 and 1 part of Zn acetate (metal equivalent) were added to 900 parts of water, and the mixture was heated to 90°C with stirring to dissolve. The mixture was then stirred for 3 hours while maintaining the temperature at 90°C, and then cooled to room temperature (23°C) to prepare a resin composition solution. The resulting resin composition solution was adjusted to a solids concentration of 10% by weight using water, and then cast into a film. A resin composition film (thickness 3 μm) was obtained by drying at 120°C for 5 minutes in a hot air dryer. Furthermore, the resin composition film was laminated to a thickness of 30 μm or more, and subjected to wide-angle X-ray diffraction according to the method described above, and as a result, a diffraction peak was observed at 2θ=6.2°.

[0083] <Example 2> A resin composition film (thickness 3 μm) was obtained in the same manner as in Example 1, except that PVA1 was changed to PVA2 and the amount of Zn acetate added was changed to 5 parts in terms of metal. Wide-angle X-ray diffraction was also performed in the same manner as in Example 1. As a result, a diffraction peak was observed at 2θ=6.2°.

[0084] Example 3 A resin composition film (thickness: 3 μm) was obtained in the same manner as in Example 2, except that the amount of Zn acetate added was 10 parts in terms of metal. Wide-angle X-ray diffraction was also performed in the same manner as in Example 1. As a result, a diffraction peak was observed at 2θ=6.2°.

[0085] Example 4 A resin composition film (thickness: 3 μm) was obtained in the same manner as in Example 1, except that PVA1 in Example 1 was changed to hydroxypropyl methylcellulose. Wide-angle X-ray diffraction was also performed in the same manner as in Example 1. As a result, a diffraction peak was observed at 2θ=6.2°.

[0086] <Example 5> A resin composition film (thickness: 3 μm) was obtained in the same manner as in Example 1, except that PVA1 in Example 1 was changed to starch. Wide-angle X-ray diffraction was also performed in the same manner as in Example 1. As a result, a diffraction peak was observed at 2θ=6.2°.

[0087] Example 6 A resin composition film (thickness: 3 μm) was obtained in the same manner as in Example 1, except that PVA1 was changed to PVA3 in Example 1. Wide-angle X-ray diffraction was also performed in the same manner as in Example 1. As a result, a diffraction peak was observed at 2θ=6.2°.

[0088] <Comparative Example 1> A PVA1 film (thickness: 3 μm) was obtained in the same manner as in Example 1, except that Zn acetate was not added. Wide-angle X-ray diffraction was also performed in the same manner as in Example 1. As a result, no diffraction peak was observed at 2θ=2 to 15°.

[0089] <Comparative Example 2> A PVA2 film (thickness: 3 μm) was obtained in the same manner as in Example 2, except that Zn acetate was not added. Wide-angle X-ray diffraction was also performed in the same manner as in Example 1. As a result, no diffraction peak was observed at 2θ=2 to 15°.

[0090] <Comparative Example 3> A hydroxypropyl methylcellulose film (thickness: 3 μm) was obtained in the same manner as in Example 4, except that Zn acetate was not added. Wide-angle X-ray diffraction was also performed in the same manner as in Example 1. As a result, no diffraction peak was observed at 2θ=2 to 15°.

[0091] <Comparative Example 4> A starch film (thickness: 3 μm) was obtained in the same manner as in Example 5, except that Zn acetate was not added. Wide-angle X-ray diffraction was also performed in the same manner as in Example 1. As a result, no diffraction peak was observed at 2θ=2 to 15°.

[0092] <Comparative Example 5> A PVA3 film (thickness: 3 μm) was obtained in the same manner as in Example 6, except that Zn acetate was not added. Wide-angle X-ray diffraction was also performed in the same manner as in Example 1. As a result, no diffraction peak was observed at 2θ=2 to 15°.

[0093] [Contact angle] The films of Examples 1 to 6 and Comparative Examples 1 to 5 obtained above were subjected to 2 μL of purified water dropwise deposition onto the film at 23°C and 50% RH to form a water droplet. The contact angle between the water droplet and the film surface was measured 10 times using a contact angle meter (DropMaster 500, manufactured by Kyowa Interface Science Co., Ltd.), and the average value was taken as the water contact angle (α) before treatment. Furthermore, the water contact angle (β) of these films was also measured in the same manner as above after leaving them for one week under high humidity conditions of 23°C and 80% RH. The results are shown in Table 1 below.

[0094] [Oxygen barrier properties] The oxygen permeabilities of the films of Examples 1 to 6 and Comparative Examples 1 to 5, which had been left standing for one week under the high humidity conditions, were measured at 23°C and 80% RH using an oxygen permeability measuring device (OX-TRAN100A, manufactured by MOCON). The results are shown in Table 1 below.

[0095] [Table 1]

[0096] As can be seen from Table 1 above, Examples 1 to 6, which contain a hydrophilic resin and a metal compound and have a difference of 10 or more between the water contact angle (β) after long-term treatment under high humidity and the water contact angle (α) before treatment, had excellent oxygen barrier properties under high humidity. On the other hand, in Comparative Examples 1 to 5, in which the difference between the water contact angles (β) and (α) was less than 10, the oxygen barrier properties were all poor. [Industrial Applicability]

[0097] The resin composition of the present invention is useful as a packaging material, particularly as a packaging material for foods, medicines, etc., because it has excellent gas barrier properties, particularly oxygen barrier properties, under high humidity conditions.

Claims

1. A resin composition comprising a hydrophilic resin and a metal compound, wherein the content of the metal compound in terms of metal is 0.01 to 20 parts by weight per 100 parts by weight of the hydrophilic resin, the hydrophilic resin is a polyvinyl alcohol-based resin, the metal compound is a metal layer compound containing a carboxylic acid ligand as a structural unit, and the resin composition satisfies the following condition (A): Condition (A): The resin composition is made into a 10 wt % aqueous solution or dispersion, and the resulting cast film is allowed to stand for 1 week under conditions of 23°C and 80% RH. When the contact angle of water (°) before treatment is α and the contact angle of water (°) after treatment is β, the following formula (1) is satisfied: （β－α）≧１０ ・・・（１）

2. 2. The resin composition according to claim 1, wherein the metal species of the metal compound is one selected from the group consisting of Ni, Co, and Zn.

3. A film comprising the resin composition according to claim 1 or 2.

4. The oxygen permeability of the film under an environment of 23°C and 80% RH is 80cc.3µm / m 2 4. The film according to claim 3, wherein the film has a viscosity of 0.5 sq. day atm or less.

5. A multilayer structure having at least one layer made of the film of claim 3 or 4.

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