Composition, molded body, film, and layered structure

Abstract

Provided is a composition having excellent gas barrier properties, particularly oxygen barrier properties, under high humidity.　The composition comprises (A) an ethylene-vinyl alcohol copolymer, (B) zinc oxide, and (C) a zinc salt other than the zinc oxide (B). The zinc salt (C) is an inorganic zinc salt and / or a C1-6 organic zinc salt, and the mass ratio [(C) / (B)] of the zinc salt (C) in terms of metal content versus the zinc oxide (B) in terms of metal content exceeds 0.5.

Description

Composition, molded article, film, multilayer structure

[0001] The present invention relates to a composition, a molded article, a film, and a multilayer structure.

[0002] Ethylene-vinyl alcohol copolymers (hereinafter, sometimes referred to as "EVOH resins") are excellent in transparency, gas barrier properties such as oxygen and other gases, aroma retention, solvent resistance, oil resistance, mechanical strength, and the like, and are formed into films, sheets, bottles, and the like, and are widely used as various packaging materials such as food packaging materials, pharmaceutical packaging materials, industrial chemical packaging materials, and agricultural chemical packaging materials.

[0003] However, since EVOH resin has relatively active hydroxyl groups in its molecules, it is highly susceptible to the effects of humidity, and its gas barrier properties deteriorate significantly in high humidity environments.

[0004] As a resin composition using an EVOH resin, Patent Document 1 discloses a resin composition having excellent odor gas barrier properties, which is obtained by incorporating a zinc compound as a deodorizing agent into the EVOH resin.

[0005] Japanese Patent Application Publication No. 10-101881

[0006] However, although the resin composition disclosed in Patent Document 1 provides a resin composition containing an EVOH resin and a zinc compound, the problem is to improve odor gas barrier properties, and therefore the gas barrier properties under high humidity, particularly the oxygen barrier properties under high humidity, are insufficient, and further improvement is required.

[0007] In view of the above, the present invention provides a composition that has excellent gas barrier properties under high humidity, particularly excellent oxygen barrier properties under high humidity.

[0008] However, in view of the above circumstances, the present inventors have conducted extensive research and have found that by incorporating specific amounts of zinc oxide (B) and a specific zinc salt (C) into an EVOH resin (A), gas barrier properties, particularly oxygen barrier properties, under high humidity conditions are improved.

[0009] That is, the present invention has the following aspects. [1] A composition containing an ethylene-vinyl alcohol copolymer (A), zinc oxide (B), and a zinc salt (C) other than the zinc oxide (B), wherein the zinc salt (C) is an inorganic zinc salt and / or an organic zinc salt having 1 to 6 carbon atoms, and wherein the mass ratio of the metal-equivalent content of the zinc salt (C) to the metal-equivalent content of the zinc oxide (B) [(C) / (B)] is greater than 0.5. [2] The composition according to [1], wherein the metal-equivalent content of the zinc oxide (B) is 0.005 to 10 parts by mass per 100 parts by mass of the ethylene-vinyl alcohol copolymer (A). [3] The composition according to [1] or [2], wherein the zinc salt (C) is an inorganic zinc salt. [4] The composition according to any one of [1] to [3], wherein the main X-ray diffraction peak is at 2θ = 2 to 15° when measured by wide-angle X-ray diffraction (XRD) using CuKα radiation. [5] A molded article comprising the composition according to any one of [1] to [4]. [6] A film comprising the composition according to any one of [1] to [4]. [7] A multilayer structure having a layer comprising the composition according to any one of [1] to [4].

[0010] The composition of the present invention has excellent gas barrier properties under high humidity, particularly excellent oxygen barrier properties under high humidity.

[0011] The present invention will be described below based on examples of embodiments for carrying out the present invention, but the present invention is not limited to the embodiments described below.

[0012] In this specification, "x and / or y (x and y are any configuration)" means at least one of x and y, and can mean three things: x only, y only, or x and y. When expressed as "X to Y" (X and Y are any numbers), unless otherwise specified, it also means "X or more and Y or less," as well as "preferably more than X" or "preferably less than Y." When expressed as "X or more" (X is any number) or "Y or less" (Y is any number), it also means "preferably more than X" or "preferably less than Y." With regard to the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range can also be replaced with the values ​​shown in the examples.

[0013] <Composition> A composition according to one embodiment of the present invention (hereinafter sometimes referred to as "the composition") contains an EVOH resin as a main component, and a specific amount of zinc oxide and a specific zinc salt other than the zinc oxide. That is, the base resin of the composition is an EVOH resin, and the content of the EVOH resin in the composition is usually 70% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more. Each component will be described below.

[0014] [EVOH Resin (A)] The EVOH resin (A) used in the present embodiment is a resin obtained by saponifying an ethylene-vinyl ester copolymer, which is a copolymer of ethylene and a vinyl ester monomer, and is a water-insoluble thermoplastic resin.

[0015] The polymerization of ethylene and vinyl ester monomers can be carried out by any known polymerization method, such as solution polymerization, suspension polymerization, or emulsion polymerization, and solution polymerization using methanol as a solvent is generally used. The resulting ethylene-vinyl ester copolymer can also be saponified by a known method.

[0016] The EVOH resin (A) produced in this manner is mainly composed of structural units derived from ethylene and vinyl alcohol structural units, and usually contains a small amount of vinyl ester structural units remaining unsaponified.

[0017] Vinyl acetate is typically used as the vinyl ester monomer because of its commercial availability and the efficiency of impurity removal during production. Other vinyl ester monomers include, for example, aliphatic vinyl esters such as vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, and vinyl versatate, and aromatic vinyl esters such as vinyl benzoate. Aliphatic vinyl esters having typically 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and more preferably 4 to 7 carbon atoms can be used. These can be used alone or in combination of two or more types.

[0018] The content of ethylene structural units in the EVOH resin (A) can be controlled by the ethylene pressure used when copolymerizing the vinyl ester monomer with ethylene, and is usually 20 to 60 mol%, preferably 25 to 50 mol%, and more preferably 25 to 35 mol%. If the content is too low, the gas barrier properties and melt moldability under high humidity conditions tend to decrease, while if the content is too high, the gas barrier properties tend to decrease. The content of ethylene structural units can be measured in accordance with ISO 14663.

[0019] The degree of saponification of the vinyl ester component in the EVOH resin (A) can be controlled by the amount, temperature, time, etc. of the saponification catalyst (usually an alkaline catalyst such as sodium hydroxide is used) used when saponifying the ethylene-vinyl ester copolymer, and is usually 90 to 100 mol%, preferably 95 to 100 mol%, and more preferably 99 to 100 mol%. If the saponification degree is too low, the gas barrier properties, thermal stability, moisture resistance, etc. tend to decrease. The saponification degree of the EVOH resin (A) can be measured in accordance with JIS K6726 (however, the EVOH resin is used as a solution uniformly dissolved in a water / methanol solvent).

[0020] The melt flow rate (MFR) (210°C, 2160 g load) of the EVOH resin (A) is typically 0.5 to 100 g / 10 min, preferably 1 to 50 g / 10 min, and more preferably 3 to 35 g / 10 min. If the MFR is too high, film-forming properties tend to become unstable, while if it is too low, the viscosity tends to become too high, making melt extrusion difficult. The MFR is an indicator of the degree of polymerization of the EVOH resin and can be adjusted by adjusting the amount of polymerization initiator and the amount of solvent used when copolymerizing ethylene and vinyl ester monomers. In this specification, the MFR is determined by measuring the flow rate of a sample through an orifice with a length of 8 mm and a diameter of 2.095 mm under conditions of 210°C and a load of 2160 g using a semi-automatic melt flow rate tester (manufactured by Toyo Seiki Seisakusho, Ltd.).

[0021] The EVOH resin (A) may further contain structural units derived from the following comonomers in an amount that does not impair the effects of the present invention (for example, 10 mol % or less of the EVOH resin, the lower limit being 0 mol %).Examples of the comonomer include olefins such as propylene, 1-butene, and isobutene; hydroxyl group-containing α-olefins such as 3-butene-1-ol, 3-butene-1,2-diol, 4-pentene-1-ol, and 5-hexene-1,2-diol, and derivatives thereof such as esters and acylation products; hydroxyalkylvinylidenes such as 2-methylenepropane-1,3-diol and 3-methylenepentane-1,5-diol; 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, and 1,3-dibutyryloxy-2-methylenepropane. -Hydroxyalkylvinylidene diacetates such as 2-methylenepropane; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, or their salts or mono- or di-alkyl esters in which the alkyl group has 1 to 18 carbon atoms; acrylamide, N-alkylacrylamide in which the alkyl group has 1 to 18 carbon atoms, N,N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or its salt, acrylamidopropyldimethylamine or its acid salt or its quaternary salt, etc. acrylamides such as methacrylamide, N-alkylmethacrylamides in which the alkyl group has 1 to 18 carbon atoms, N,N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid or a salt thereof, methacrylamidepropyldimethylamine or an acid salt or a quaternary salt thereof, and the like; N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, and N-vinylacetamide; vinyl cyanides such as acrylonitrile and methacrylonitrile; alkyl vinyl ethers in which the alkyl group has 1 to 18 carbon atoms, hydrochlorides, and the like. vinyl ethers such as alkoxyalkyl vinyl ether and alkoxyalkyl vinyl ether; halogenated vinyl compounds such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and vinyl bromide; vinyl silanes such as trimethoxyvinylsilane; halogenated allyl compounds such as allyl acetate and allyl chloride; allyl alcohols such as allyl alcohol and dimethoxyallyl alcohol; and comonomers such as trimethyl-(3-acrylamido-3-dimethylpropyl)-ammonium chloride and acrylamido-2-methylpropanesulfonic acid.These may be used alone or in combination of two or more.

[0022] In particular, an EVOH resin (A) having a primary hydroxyl group in the side chain is preferred because it has good secondary moldability while maintaining gas barrier properties. Among these, an EVOH resin (A) copolymerized with a hydroxy group-containing α-olefin is preferred, and an EVOH resin (A) having a 1,2-diol structure in the side chain is particularly preferred.

[0023] In particular, when the EVOH resin (A) has a primary hydroxyl group in the side chain, the content of the structural unit derived from the monomer having the primary hydroxyl group is usually 0.1 to 20 mol %, more preferably 0.5 to 15 mol %, and particularly preferably 1 to 10 mol % of the EVOH resin (A).

[0024] The EVOH resin (A) used in this embodiment may be "post-modified" such as urethanized, acetalized, cyanoethylated, oxyalkylenated, or acylated.

[0025] Furthermore, the EVOH resin (A) used in the present embodiment may be a mixture with a different other EVOH resin. Examples of such other EVOH resins include those having a different degree of saponification, a different degree of polymerization, or a different copolymerization component.

[0026] [Zinc Oxide (B)] As described above, the present composition contains zinc oxide (B). The average particle size of the zinc oxide (B) is preferably 100 nm or less, more preferably 50 nm or less, and particularly preferably 30 nm or less. If the average particle size exceeds 100 nm, transparency tends to decrease and turbidity tends to increase when formed into a film or the like. The lower limit is usually 10 nm. Methods for measuring the average particle size include dynamic light scattering (DLS) and sedimentation velocity methods, and the average particle size can be determined by a predetermined method. The average particle size referred to here is the median diameter.

[0027] The content of the zinc oxide (B) in terms of metal is usually 0.005 to 10 parts by mass, preferably 0.04 to 8 parts by mass, more preferably 0.08 to 5 parts by mass, and particularly preferably 0.1 to 2 parts by mass, relative to 100 parts by mass of the EVOH resin (A). If the content of zinc oxide (B) is too low, the gas barrier property under high humidity conditions tends to decrease, while if it is too high, transparency tends to decrease and turbidity tends to increase when the film is formed. The content of zinc oxide in terms of metal is the content of elemental zinc.

[0028] The metal-equivalent content of the zinc oxide (B) can be quantified by dissolving the composition in a mixed solvent of water / 1-propanol (1 / 1), separating the composition into a soluble fraction and an insoluble fraction, and measuring the zinc in the insoluble fraction by ICP mass spectrometry using an ICP mass spectrometer (Agilent 8800, manufactured by Agilent Technologies).

[0029] [Zinc Salt (C) Other Than Zinc Oxide (B)] As described above, the present composition contains a zinc salt (C) other than the zinc oxide (B), and the zinc salt (C) is an inorganic zinc salt and / or an organic zinc salt having 1 to 6 carbon atoms. The zinc salt (C) can be used alone or in combination of two or more types. Among these, a zinc salt that is soluble when dissolved in a 1 / 1 mixed solvent of water / 1-propanol is preferred, an inorganic zinc salt of zinc or an organic zinc salt having 1 to 6 carbon atoms is more preferred, and an inorganic zinc salt is even more preferred.

[0030] Examples of organic acids constituting the organic zinc salt having 1 to 6 carbon atoms include monocarboxylic acids such as lactic acid, acetic acid, and gluconic acid, dicarboxylic acids such as succinic acid, oxalic acid, and tartaric acid, and tricarboxylic or higher carboxylic acids such as citric acid. These may be used alone or in combination of two or more. The organic zinc salt may also be a hydrate or an anhydride.

[0031] As the organic zinc salt having 1 to 6 carbon atoms, a monovalent zinc carboxylate is preferred, and zinc lactate, zinc acetate, or a hydrate thereof is more preferred, in view of the excellent gas barrier properties under high humidity conditions when formed into a composition.

[0032] Examples of the inorganic zinc salt include zinc halides such as fluoride, chloride, bromide, and iodide, and oxoacid salts such as nitrate, sulfate, phosphate, sulfonate, and carbonate. The inorganic zinc salt may be a hydrate or anhydrous.

[0033] As the inorganic zinc salt, zinc halides and oxoacid salts are preferred, and zinc chloride, zinc nitrate, or hydrates thereof are more preferred, in view of the excellent gas barrier properties under high humidity conditions when formed into a composition.

[0034] The content of the zinc salt (C) in terms of metal is usually 0.01 to 10 parts by mass, preferably 0.04 to 8 parts by mass, more preferably 0.08 to 5 parts by mass, and particularly preferably 0.1 to 2 parts by mass per 100 parts by mass of the EVOH resin (A). If the content of the zinc salt (C) is too low, the gas barrier properties under high humidity conditions tend to decrease, while if it is too high, the moldability of the composition tends to decrease. The content of the zinc salt in terms of metal is the content of elemental zinc.

[0035] The content of the zinc oxide (C) in terms of metal can be quantified by dissolving the composition in a water / alcohol mixed solvent such as water / 1-propanol, separating the composition into a soluble fraction and an insoluble fraction, and measuring the zinc in the soluble fraction by ICP mass spectrometry using an ICP mass spectrometer (Agilent 8800, manufactured by Agilent Technologies).

[0036] The mass ratio [(C) / (B)] of the content of the zinc salt (C) converted into metal to the content of the zinc oxide (B) converted into metal is greater than 0.5, preferably 0.55 to 200, more preferably 0.6 to 10, even more preferably 0.7 to 7, and particularly preferably 0.83 to 5. If such a mass ratio is not satisfied, the gas barrier property under high humidity conditions tends to decrease.

[0037] [Other Thermoplastic Resins] The composition may contain thermoplastic resins other than EVOH resins within a range that does not impair the effects of the present invention (for example, typically 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, with the lower limit being 0% by mass or less, of the composition). Examples of other thermoplastic resins that may be used include known thermoplastic resins, such as polyester resins, polystyrene resins, polyvinyl chloride resins, polycarbonate resins, ionomers, polyvinylidene chloride, polyester elastomers, polyurethane elastomers, chlorinated polyethylene, and chlorinated polypropylene. These may be used alone or in combination of two or more.

[0038] [Other Compounding Agents] The composition may also contain compounding agents (excluding the zinc oxide (B) and the zinc salt (C)) that are generally compounded with EVOH resins, within a range that does not impair the effects of the present invention (for example, 5% by mass or less, with the lower limit being 0% by mass or less). Examples of the compounding agents include inorganic double salts (for example, hydrotalcite, etc.), plasticizers (for example, aliphatic polyhydric alcohols such as ethylene glycol, glycerin, and hexanediol), oxygen absorbers [for example, inorganic oxygen absorbers such as aluminum powder and potassium sulfite; ascorbic acid, its fatty acid esters and metal salts, etc.; gallic acid; polyhydric phenols such as hydroxyl group-containing phenolaldehyde resins; terpene compounds; blends of tertiary hydrogen-containing resins and transition metals (for example, a combination of polypropylene and cobalt); and carbon-carbon unsaturated bond-containing resins and inorganic oxygen absorbers. Polymeric oxygen absorbers such as blends with transition metals (e.g., a combination of polybutadiene and cobalt), photooxidatively degradable resins (e.g., polyketones), anthraquinone polymers (e.g., polyvinyl anthraquinone), and combinations thereof to which photoinitiators (e.g., benzophenone) or antioxidants or deodorizers (e.g., activated carbon) other than those mentioned above may be added, as well as heat stabilizers, light stabilizers, ultraviolet absorbers, colorants, antistatic agents, surfactants (excluding those used as lubricants), antibacterial agents, antiblocking agents, fillers (e.g., inorganic fillers), etc. These compounds may be used alone or in combination of two or more.

[0039] [Method for Producing the Composition] The composition can be produced by mixing the EVOH resin (A), zinc oxide (B), and zinc salt (C) by a known method, such as a solution mixing method, a melt mixing method, etc. These production methods can also be used in any combination.

[0040] Examples of the solution mixing method include a method in which a solution is prepared using a commercially available EVOH resin (A) and zinc oxide (B) and a zinc salt (C) are blended thereto; a method in which a solution is prepared using a commercially available EVOH resin (A) and zinc oxide (B) and a zinc salt (C) are blended thereto, followed by coagulation molding, followed by solid-liquid separation by known means, and drying; and a method in which, during the production process of the EVOH resin (A), zinc oxide (B) and a zinc salt (C) are added to an ethylene-vinyl ester copolymer solution before saponification or a homogeneous solution of the EVOH resin (A) (e.g., a water / alcohol solution), followed by coagulation molding, followed by solid-liquid separation by known means, and drying. Various drying methods can be used as the drying method, including either static drying or fluidized drying. These methods can also be used in combination.

[0041] Examples of the melt-mixing method include a method in which a pellet-shaped EVOH resin (A) is dry-blended with zinc oxide (B) and a zinc salt (C), and the dry-blended product is melt-kneaded; and a method in which zinc oxide (B) and a zinc salt (C) are added to a molten EVOH resin (A), and the mixture is melt-kneaded.

[0042] As described above, in the present invention, the above-mentioned different methods can be combined. Among them, the solution mixing method is preferred in that a resin composition in which the effects of the present invention are more pronounced can be obtained. Furthermore, when the above-mentioned other thermoplastic resins and other compounding agents are used, they may be compounded by a conventional method according to the above-mentioned manufacturing method.

[0043] The gas barrier properties, particularly oxygen barrier properties, of the composition obtained in this manner under high humidity conditions improve over time starting immediately after exposure to high humidity, and once this improvement trend reaches equilibrium, the composition exhibits high oxygen barrier properties. Although the mechanism by which this effect is achieved is unclear, it is presumed that when the composition is exposed to high humidity, zinc oxide (B) and zinc salt (C) react with each other in the EVOH resin (A) plasticized by water molecules, and the resulting layered zinc hydroxide interacts with the EVOH resin molecules, resulting in this effect.

[0044] In the present invention, "under high humidity" means 20±5° C. and 90±10% RH.

[0045] The gas barrier properties, particularly the oxygen barrier properties, of the present composition under high humidity conditions improve over time from immediately after exposure to high humidity, and the time until this improvement trend reaches equilibrium is usually less than 1,000 hours, preferably less than 900 hours, more preferably less than 800 hours, particularly preferably less than 700 hours, and especially preferably less than 600 hours.

[0046] Although the present composition has excellent gas barrier properties under high humidity, in order to further improve the gas barrier properties under high humidity, it is preferable to leave the composition at medium humidity for a certain period of time before exposing it to high humidity. Although the mechanism by which such an effect is obtained is not clear, it is presumed that the effect is obtained because, by leaving the composition at medium humidity for a certain period of time, the interaction between the layered zinc hydroxide formed by subsequent exposure to high humidity and the EVOH resin molecules becomes stronger.

[0047] In the present invention, "medium humidity" means 20±5° C. and 60±15% RH.

[0048] The standing time under medium humidity is usually less than 1000 hours, preferably less than 900 hours, more preferably less than 800 hours, particularly preferably less than 700 hours, and especially preferably less than 600 hours.

[0049] In order to achieve excellent gas barrier properties, particularly oxygen gas barrier properties, under high humidity conditions, the present composition preferably has a main X-ray diffraction peak at 2θ = 2 to 15°, more preferably at 2θ = 4 to 14°, and particularly preferably at 2θ = 6 to 13°, when measured by wide-angle X-ray diffraction (XRD) using CuKα radiation.

[0050] When measured by wide-angle X-ray diffraction (XRD) using CuKα radiation, the main peak of X-ray diffraction observed at 2θ=2 to 15° is preferably a peak derived from the layered zinc hydroxide. In the present invention, the layered zinc hydroxide satisfies the following formula (1): Zn a (OH) b A n- (2a-b) / n ...(1) (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, and a / b=0.1 to 10 is satisfied.)

[0051] The wide-angle X-ray diffraction (XRD) was 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: 50 kV - Current: 100 mA - Camera length: 100 mm - Measurement method: Reflection method - Accumulation time: 20 minutes - Wavelength: CuKα ray (Kα1 and Kα2 not separated) - Detector position: 2θ = 10°, 35° - X-ray incident angle: θ = 0.3° - Conditions for one-dimensionalization in the 2θ direction: 2θ = 0 to 59°, azimuth angle (chi) = -110 to -70°

[0052] As a sample to be used for the wide-angle X-ray diffraction, the composition in the form of a film described below may be used as it is. In addition, when the composition is laminated with another substrate, if the composition layer can be peeled off, the composition layer is peeled off and measurement is performed, and if peeling is not possible, the composition layer may be measured while it is still laminated with the other substrate. Note that, at the time of measurement, the thickness of the peeled composition layer (film) is preferably 30 μm or more, and if the film thickness is insufficient, a film may be laminated.

[0053] The composition thus obtained is prepared into various forms, such as pellets, powder, or liquid, and is provided as a molding material for various molded articles. In particular, in the present invention, when the composition is provided as a liquid molding material, the effects of the present invention tend to be more efficiently obtained, which is preferred.

[0054] [Molded Articles] Examples of shapes of molded articles containing the present composition include films, sheets, tapes, cups, trays, tubes, bottles, pipes, filaments, irregular cross-section extrudates, and various irregularly shaped articles.

[0055] The molding method for the molded article is not particularly limited, and any molding method applicable to general resin compositions can be used. For example, a film-forming method using a solution (coating liquid) of the composition containing the composition, or a melt molding method can be used. Examples of melt molding methods include extrusion molding methods (T-die extrusion, inflation extrusion, blow molding, melt spinning, profile extrusion, etc.) and injection molding.

[0056] [Film / Multilayer Structure] A film containing the present composition is obtained by forming a film from a composition containing the present composition, and preferably from the above composition.

[0057] Examples of methods for forming the film include a method using a solution (coating liquid) of the composition containing the composition, and a method of melt-molding the composition using an extruder. Among these, a method using a solution (coating liquid) of the composition is preferred. When using the coating liquid, the solids concentration is usually 0.5 to 30% by mass, preferably 5 to 20% by mass.

[0058] The coating liquid can be prepared, for example, by charging all components into a solvent at once and mixing them, or by dissolving some components in a solvent and adding the other components to the solution and mixing them. Among these, from the viewpoint of workability, the method of adding the other components to a solution of the EVOH resin (A) dissolved in a solvent and mixing them is preferred.

[0059] The solvent may be a mixed solvent of water and a lower alcohol, specifically, a mixed solvent containing water and at least one lower alcohol having 1 to 5 carbon atoms, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, or 2-butanol.

[0060] The film can be formed by any known method, such as melt extrusion, casting, or coating. Of these, coating is preferred.

[0061] Examples of the coating method include known methods such as bar coating, roll coating, die coating, gravure coating, comma coating, and screen printing.

[0062] After coating, a film made of the composition can be obtained by drying, for example, by heat treatment at 60 to 105° C. for 0.5 to 10 minutes. The film may be stretched uniaxially or biaxially, as necessary.

[0063] The film may be a single-layer structure or a multilayer structure. The multilayer structure preferably has at least one layer made of the film. The multilayer structure may be formed by laminating the film or by laminating another base resin.

[0064] The thickness of the film is usually 1 to 5000 μm, preferably 1 to 100 μm, and more preferably 1 to 50 μm. When the formed film has a multilayer structure, the total thickness of the film is the sum of the thicknesses of all the films made of the composition.

[0065] 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 suitable polyethylene resins include polyolefin resins in the broad sense, including modified olefin resins such as unsaturated carboxylic acid-modified polyolefin resins graft-modified with olefin esters or ionomers, 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. The terms linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, medium-density polyethylene, and high-density polyethylene are commonly used terms to represent types of polyethylene.

[0066] The oxygen permeability of a film made of this composition is 15cc / 20μm / m 2 ・day・atm(cm) 3 ・20 μm / m 2 ·day·atm) or less, and 10cc·20μm / m 2 It is more preferable that the viscosity is 5 cc / day / atm or less, and 5 cc / 20 μm / m 2It is particularly preferable that the oxygen permeability is 0 cc·day·atm or less. The oxygen permeability is measured in an environment of 20°C and 90% RH, and the lower limit of the oxygen permeability is usually 0 cc·20 μm / m 2 ·day·atm. The oxygen permeability can be determined by an oxygen permeability measuring device.

[0067] When the composition is laminated with another substrate, the sample used for the oxygen permeability measurement may be measured after peeling off the composition layer, or may be measured while the composition layer is still laminated with the other substrate. At the time of measurement, the thickness of the composition layer (film) is preferably 5 to 20 μm.

[0068] The present composition and a film made from the present composition are useful as packaging materials, and can be suitably used in particular as packaging materials for food, medicines, and the like.

[0069] 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 invention. In the examples, "parts" and "%" are by mass.

[0070] Prior to the examples, the following ingredients were prepared:

[0071] [EVOH resin (A)] EVOH resin (A1): content of ethylene structural units 25 mol%, degree of saponification 99.6 mol%, MFR 4 g / 10 min (210°C, load 2160 g) [Zinc oxide (B)] Zinc oxide (B1): zinc oxide, average particle size 20 nm (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) [Zinc salt (C)] Zinc chloride (C1): zinc chloride (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) Zinc nitrate (C2): zinc nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) Zinc lactate (C3): zinc lactate trihydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) Zinc salicylate (C4): zinc salicylate trihydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) Zinc stearate (C5): zinc stearate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.)

[0072] Example 1 5 parts of the EVOH resin (A1) were added to 45 parts of a 1 / 1 (volume ratio) water / 1-propanol mixed solvent, and the mixture was heated and stirred at 87°C for 1 hour to completely dissolve the EVOH resin (A1). This solution was allowed to cool to 55°C, and 0.8 parts of the zinc oxide (B1) per 100 parts of the EVOH resin (A1) in terms of metal content and 1 part of the zinc chloride (C1) per 100 parts of the EVOH resin (A1) in terms of metal content were added. The mixture was heated and stirred at 87°C for 2 hours to prepare a coating solution. The resulting coating solution was applied to a corona-treated 12 μm-thick PET substrate using a #24 wire bar and dried at 80°C for 5 minutes. This process was repeated twice to obtain a two-layer film in which a 6 μm-thick EVOH film layer was laminated on the PET substrate.

[0073] Example 2 A two-layer film was obtained in the same manner as in Example 1, except that the amount of zinc oxide (B1) was changed to 1 part per 100 parts of EVOH resin (A1) in terms of metal.

[0074] Example 3 A two-layer film was obtained in the same manner as in Example 1, except that zinc nitrate (C2) was used instead of zinc chloride (C1).

[0075] Example 4 A two-layer film was obtained in the same manner as in Example 1, except that zinc lactate (C3) was used instead of zinc chloride (C1).

[0076] Example 5 A two-layer film was obtained in the same manner as in Example 1, except that the amount of zinc oxide (B1) was changed to 0.005 parts in terms of metal per 100 parts of EVOH resin (A1).

[0077] Comparative Example 1 A two-layer film was obtained in the same manner as in Example 1, except that zinc oxide (B1) was not used, and zinc chloride (C1) was used in an amount of 1 part in terms of metal relative to 100 parts of EVOH resin (A1), and zinc nitrate (C2) was used in an amount of 0.8 parts in terms of metal relative to 100 parts of EVOH resin (A1).

[0078] Comparative Example 2 A two-layer film was obtained in the same manner as in Example 1, except that the amount of zinc oxide (B1) was changed to 1 part in terms of metal relative to 100 parts of the EVOH resin (A1) and the amount of zinc chloride (C1) was changed to 0.5 parts in terms of metal relative to 100 parts of the EVOH resin (A1).

[0079] Comparative Example 3 A two-layer film was obtained in the same manner as in Example 1, except that zinc salicylate (C4) was used instead of zinc chloride (C1).

[0080] Comparative Example 4 A two-layer film was obtained in the same manner as in Example 1, except that zinc stearate (C5) was used instead of zinc chloride (C1).

[0081] The obtained two-layer films containing the compositions of Examples 1 to 5 and Comparative Examples 1 to 4 were subjected to the following oxygen permeability measurement and wide-angle X-ray diffraction (XRD) measurement. The results are shown in Table 1 below.

[0082] [Measurement of oxygen permeability] The two-layer film obtained above was allowed to stand for 2 days under humidity conditions of 23°C and 70% RH, and then the oxygen permeability (cc·20 μm / m) of the composition was measured under conditions of 20°C and 90% RH using an oxygen permeability measuring device (Ox-tran 2 / 21, manufactured by MOCON Corporation). 2 When the oxygen permeability changed over time, the measurement was continued until the value reached equilibrium, and the equilibrium value was used as the measured value. 2 The smaller the value of (day·atm), the better the gas barrier property.

[0083] [Wide-angle X-ray diffraction (XRD) measurement of film] From the two-layer film obtained above, the EVOH film layer was peeled off from the PET film layer, and the resulting film was laminated to a thickness of 30 μm or more to obtain a sample. This sample was subjected to wide-angle X-ray diffraction (XRD) measurement under the following conditions. (Measurement conditions) Equipment used: D8 DISCOVER (manufactured by Bruker Japan) Detector: 2D detector VANTEC-500 (manufactured by Bruker Japan) Voltage: 50 kV Current: 100 mA Camera length: 100 mm Measurement method: Reflection method Integration time: 20 minutes Wavelength: CuKα radiation (Kα1 and Kα2 not separated) Detector position: 2θ = 10°, 35° X-ray incident angle: θ = 0.3° Conditions for one-dimensionalization in 2θ direction: 2θ = 0 to 59°, azimuth angle (chi) = -110 to -70°

[0084]

[0085] The results in Table 1 above show that the compositions of Examples 1 to 5, which contained EVOH resin (A), zinc oxide (B), and the specific zinc salt (C), had superior gas barrier properties compared to the composition of Comparative Example 1, which did not use zinc oxide (B), and Comparative Examples 3 and 4, which did not use the specific zinc salt (C). Furthermore, the compositions of Examples 1 to 5, in which zinc oxide (B) and zinc salt (C) had a specific relationship, had superior gas barrier properties compared to the composition of Comparative Example 2, in which zinc oxide (B) and the specific zinc salt (C) did not have a specific relationship.

[0086] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0087] Because of its excellent gas barrier properties, the present composition is useful as a packaging material for various foods, as well as seasonings such as mayonnaise and dressings, fermented foods such as miso, oily foods such as salad oil, beverages, cosmetics, pharmaceuticals, etc.

Claims

1. A composition containing an ethylene-vinyl alcohol copolymer (A), zinc oxide (B), and a zinc salt (C) other than the zinc oxide (B), wherein the zinc salt (C) is an inorganic zinc salt and / or an organic zinc salt having 1 to 6 carbon atoms, and the mass ratio [(C) / (B)] of the metal-equivalent content of the zinc salt (C) to the metal-equivalent content of the zinc oxide (B) is greater than 0.

5.

2. The composition according to claim 1, wherein the content of the zinc oxide (B) in terms of metal is 0.005 to 10 parts by mass per 100 parts by mass of the ethylene-vinyl alcohol copolymer (A).

3. The composition according to claim 1 or 2, wherein the zinc salt (C) is an inorganic zinc salt.

4. The composition according to claim 1 or 2, which has a main X-ray diffraction peak at 2θ = 2 to 15° when measured by wide-angle X-ray diffraction (XRD) using CuKα radiation.

5. A molded article comprising the composition according to claim 1 or 2.

6. A film comprising the composition of claim 1 or 2.

7. A multi-layer structure having a layer comprising the composition according to claim 1 or 2.